In winter construction or concrete engineering with early strength requirements, early strength agent plays an important role in speeding up the construction schedule and improving the quality of concrete, and its content is generally not more than 5% of the mass of cement. At present, the traditional early strength components are unable to meet the requirements of green and high performance concrete. Most of the previous studies about early strength agent are conducted at room temperature, while the research of early strength agent in low temperature environment (especially 5 ℃) is relatively insufficient, and low temperature early strength effect is relatively limited, the mechanism of low temperature early strength is also not clear. With the further development of engineering construction, it is an important research direction to develop low temperature early strength agent which meets the requirements of low temperature early strength and good workability. Based on the classification summary of the performance characteristics, existing problems and action mechanisms of the common early strength components, this paper introduces the research and application of early strength agent in low temperature, and also point out the development direction of low temperature early strength agent.

Black phosphorus was first successfully synthesized in the bulk form in 1914. After remaining silent for 100 years, the novel 2D-nanomaterial formed by attenuating bulk black phosphorus into the multilayer state, i.e. 2D black phosphorus, was firstly obtained in 2014. This layered 2D semiconductor material consisting of only phosphorus atoms has from then onward been drawing intensive interest in the field of low-dimensional inorganic semiconductor because of its rich variety of special electrical and optical properties such as appropriate tunable direct bandgap, high carrier mobility, high leakage current modulation ratio, relatively high on-off current ratio, good electrical and thermal conductivity and strong in-plane anisotropy. 2D black phosphorus is an intrinsic p-type material with a series of excellent properties, but the production of large-area phosphorene (i.e. monolayer black phosp-horus) film has so far remained unrealized due to the instability of 2D black phosphorus. This article intends to make a review of the research progress on 2D black phosphorus. We here introduce systematically the structure, preparation and properties of 2D black phosphorus, also offer a detailed description of its physical properties (electronic, optical, mechanical, thermal, magnetic) and chemical stability. The paper ends with the rough summary and discussion on the research prospect of this emerging new material with sharp momentum.

Metal-organic frameworks (MOFs)are a kind of porous materials by combining metal nodes with organic ligands by strong bonds. Compared with the traditional adsorption materials, MOFs have various advantages, such as adjustable structural, functional diversity, large specific surface area and high porosity. Another unique advantage is that the pores size can be adjusted, and the specific functional groups and active sites can be modified by in situ synthesis or post-modification to obtain the efficient and selective adsorption of different heavy metals and radionuclides from wastewater, which is of great significance to resource recycling and environmental remediation. In this paper, the latest research progresses and corresponding adsorption mechanisms for the adsorption of heavy metals (As, Cr, Hg, etc.)and radionuclides (U, Tc, etc.)are described in detail. And the methods of improving the adsorption of MOFs are summarized. Furthermore, the challenges and problems of MOFs as the adsorbents of heavy metals and radionuclides are proposed.

Molybdenum disulfide (MoS₂) is two-dimensional layered material with natural tunable band-gap. Very recently, MoS₂ have received much attention owing to its unusual properties and hold great potential for optoelectronic and microelectronic application. In this paper, basic structure and properties of MoS₂ are introduced firstly. Then the common fabrication methods of MoS₂ are analyzed. The applications of MoS₂ in electronic and optoelectronic devices and the prospects for future applications are summarized in the end.

Acute skin injuries and persistent non-healing chronic wounds are common in daily life. Dressings are playing critical roles in wound care because they can protect the wound from external infection and accelerate the healing process. With the characteristics of high porosity, high water content and good biocompatibility, hydrogel dressings have broad application prospects in clinical treatment and tissue engineering.
The synthesis methods of hydrogels include the physical cross-linking method and the chemical cross-linking method. Hydrogels prepared by different synthesis methods or different substrates often have different characteristics. Natural polysaccharide hydrogels are far inferior to artificial polymer hydrogels in terms of mechanical properties and stability, and a single polysaccharide hydrogel material may not be able to meet the diversified needs of wound healing. At present, the focus of research is the hybrid double-crosslinked hydrogel which can improve its mechanical properties, and the multi-functional composite hydrogel with antimicrobial properties and biocompatibility.
This review gives a summary on the the types of polysaccharides used for hydrogels, the preparation methods and classification of hydrogels based on polysaccharides, and the functional composite hydrogel dressings. In addition, it summarizes the animal experiments, clinical applications and commercial products of hydrogel dressings based on polysaccharides. It hopes to provide a certain reference for relevant researchers in this field.

The space charge has been a key factor to affect the electrical properties of solid insulation materials. The existence of space charge can cause uneven electric field distribution in polymer, accelerate the aging of insulating materials, and even lead to the breakdown of materials. This paper summarizes the influence factors of space charge accumulation in solid insulation materials, and points out that the accumulation of space charge is closely related to the applied electric field(effects of electric field, electric field type, pre-applied voltage and polarity reversal, etc.), temperature(high temperature, temperature gradient, low temperature), stress, and structure of the dielectrics(such as crosslinking degree, insulation thickness). The suppressed methods to space charge accumulation were summarized from the aspects of electrode materials, surface modification and doping fillers(morphology, size, type and content). The relevant mechanisms of space charge accumulation and suppression are discussed, and the space charge transport mechanism based on trap theory still needs to be further studied.

As an important part of supercapacitors, electrolyte plays a key role in determining the performance of device. This review briefly discusses about the characteristics and the latest research results of the electrolytes including aqueous, organic liquid, ionic liquid, solid/quasi-solid polymer electrolyte and redox system for supercapacitors. The classification and property of solid/quasi-solid polymer electrolytes are focused, and put forward the development of wide potential window, high ionic conductivity, and stable electrochemical properties of ionic liquids and excellent mechanical strengths and comprehensive properties of gel polymer electrolytes are trends in the field of electrolytes for supercapacitors in the future. Finally, the development prospect of electrolytes for supercapacitors is proposed.

In order to optimize the preparation method, deeply cognize the properties and extend the application of porous metallic materials, the present paper reviews the preparation methods, properties and applications of porous metallic materials. Preparation methods mainly include the electrodeposition method, dealloying method, solid-state sintering process and liquid solidification. Based on the sound absorption properties, separation performance, thermal and electrical conductivities and catalytic performance of porous metallic materials, the applications of porous metallic materials in automotive industry, aerospace industry and biomedical fields are introduced. The paper ends with a brief description of the future development trend of porous metallic materials,i.e. compositing,introducing gradient and diversifying porous structures.

The application market for carbon fiber reinforced resin composite materials (CFRP) is increasing. The wide application and upgrading of CFRP components have brought about the treatment of waste and scrapped products and environmental protection issues. The research on CFRP recycling and reuse technology has caused many manufacturers and the attention of experts and scholars. This article reviews the cha-racteristics, processes and application status of existing CFRP recycling and reuse technologies, analyzes the relationship between the molding process of common CFRP parts and applicable recycling technologies, and discusses the technology, supply, and regulations of CFRP parts recycling technology. Looking forward to the development trend of CFRP recycling technology.

As a new type of green energy material, metal deuteride has excellent deuterium storage performance, and its importance and widespread application in the energy field have been more and more outstanding. Under the high speed of social and practical applications' development, metal deuteride energy materials will play a more and more important role in the country's energy strategy. The metal deuterides is usually prepared by direct compounding in a high-temperature environment. It is highly susceptible to O₂, CO₂, H₂O, etc in the air atmosphere, especially the high humidity (more than 60%) air atmosphere because of the very active surface chemistry. It can cause changes in the performance of metal deuterides, which may cause safety hazards in severe cases, and the scope of use is limited. At present, a variety of metal deuteride materials such as lithium deuteride, titanium deuteride, zirconium deuteride and cerium deuteride have been prepared successively and have certain applications. This article summarizes the research progress of several common metal deuterides preparation and application according to the cha-racteristics, classification and applications of metal deuterides, summarizes the research status and progress of metal deuterides, and puts forward prospects. The purpose is to summarize data and reference for the research and application of deuterated metals.

As halogen-containing flame retardants suffers from toxicity and environmental concerns, phosphorus-containing flame retardants have received increasing attention as alternatives for their environmental friendliness. Since the emergence of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) as a kind of phosphorus-containing flame retardant, numerous efforts have been successively put in optimizing the synthetic approaches and chemical structure of the DOPO derivatives, and recently fruitful achievements have been made. DOPO-derivatives are considered as favorable alternatives for extensive applications in flame retardant polymer materials because of their high thermal stability, excellent water resistance, and versatile flame extinguishing behavior in the gas phase and condensed phase. DOPO derivatives can be used as reactive or additive flame retardants for epoxy resin, polyester and engineering plastics, according to their diverse functional groups. Various DOPO derivatives with P-C, P-N and P-O functional groups have been developed, among which a majority of P-C contained DOPO derivatives act as flame retardants in epoxy resins, while P-N and P-O contained DOPO derivatives are mostly applied in polyurethane foams, engineering plastics and epoxy resins.
The phosphinate derivatives of DOPO are prepared by replacing P-H bond with P-C bond through chemical processes, which mainly include two approaches, namely nucleophilic addition/substitution and molecular rearrangement. In addition, there are primarily two types of P-heteroatoms contained DOPO derivatives, representing by P-O contained phosphonate DOPO-derivatives and P-N contained phosphonamidate DOPO derivatives. In both cases, P-H bond activation of DOPO is crucial step to achieve P-N or P-O bond transformation. According to the literature, Atherton-Todd reaction and using DOP-Cl as starting material constitute the two major reaction pathways for synthesizing DOPO derivatives.
The addition of phosphorus flame retardants is able to endow polymer with satisfactory flame retardant performance. Nevertheless, the introduction of the phosphoric weak bonds of P-O and P-C may exert negative effects on the mechanics of flame retardant polymer. The negative effects of phosphorous groups will be weakened in DOPO derivatives with low loading amount of phosphorus. Therefore, the flame retardant macromole-cular materials with DOPO derivatives are superior in mechanical properties compared with other phosphorus flame retardants.
Understanding the principle of reaction is the key to developing novel DOPO based derivatives. This review offers a retrospection of the research efforts with respect to the synthesis principle and approaches of DOPO derivatives, and flame retardant applications, aiming at provide a refe-rence for the synthesis and application of novel flame retardant of DOPO derivatives. It has been proposed that the impact of DOPO derivatives on the mechanical properties of polymers will be the focus of research in the future.

Recycling of waste indium tin oxide (ITO) is of great importance both for sustainable utilization of indium resource and environmental protection. This review firstly gives a rough estimation of the recycling potential of waste ITO, and subsequently introduces the recent research and developments with respect to the recovery technology of indium from waste ITO, which mainly includes hydrometallurgical and pyrometallurgical techniques, along with a comparative analysis of their respective advantages and disadvantages. Based on the above discussion, the main problems during the recycling process, as well as the corresponding countermeasures are proposed. The paper finally ends with a sketch of the outlook for the field’s future trends, suggesting the significance of the innovation of effective and environment-friendly recycling process.

Thallium and its salts are extremely harmful pollutants to the water environment. The ingestion of infinitesimal Tl in the living organisms is likely to cause lethal effect. With the continuous development and utilization of abundant thallium-contained mineral resources in China, thallium pollution in waters has shown a trend of aggravation, which poses a serious threat to human health and ecological environment. Therefore, it is in urgent need for the treatment and purification of thallium-contained wastewater.
Suffered from the limitation of low processing depth, poor selectivity and impurity ion interference, the traditional technology is not able to treat thallium-contained wastewater effectively. Recently, notable progress has been made in the treatment technology of thallium-contained wastewater at home and abroad. In particular, amazing effect have been obtained in removing thallium in acidic wastewater by strengthened oxidation coagulation method, and the removal rate of thallium is as high as 99.98%.The adsorption method features high adsorption capacity, easy regeneration, high processing depth and so forth. Metal oxides, like hydrated iron oxide, nano-alumina, magnetic Fe₃O₄, hydrated manganese oxide, titanium oxide, titanium nanotubes, are generally considered to be ideal materials to adsorb Tl (Ⅰ) in wastewater, among which hydrated manganese oxide and hydrated iron oxide are most effective with the removal rates of about 98.5%. The treatments by employing biosorbents and modified resin have also achieved fruitful results, which exhibit favorable thallium removal rates of 96.6% and 97%, respectively.
In this article, the research status of thallium removal from wastewater at home and abroad in recent years is reviewed from the methods of precipitation, adsorption, ion exchange and so forth. The governing mechanisms of various methods are analyzed, the corresponding advantages and disadvantages of are discussed, and the direction of improvement is put forward. Finally, the development trend and application prospect of thallium contamination control are predicted.

As the earliest alloy in human history, the invention of bronze opened a new chapter in the history of metal smelting. There are more than 30 practical alloy systems that have been used for industrial sectors so far. Eutectic alloys, such as steel (Fe-C), Al-Si alloy, Ag-Cu alloy, have been widely used because of special properties such as low melting point and good fluidity.
High entropy alloys are known as one of the three major breakthroughs in alloying theory in recent decades. Theoretically, more than 7 000 high entropy alloy systems can be designed from 13 kinds of arbitrarily selected common elements. Compared with traditional alloys that based on one element, the design space of high entropy alloys are much larger. Moreover, it is found that high entropy alloys can form simple microstructures such as a simple face-centered cubic, single body-centered cubic or face-centered cubic and body-centered cubic while conventional alloys gene-rally form complex intermetallic compounds. Hence, high entropy alloys owe high strength, high wear resistance, high corrosion resistance and other excellent properties. Specific performance changes can be achieved by controlling the composition of high entropy alloys to meet different design needs, so high entropy alloys have great research value and application space.
Eutectic high entropy alloys (EHEAs) have composition characteristics of eutectic alloys and high entropy alloys. EHEAs have gained extensive attention in recent years because of the super strength, plasticity, resistance to friction and corrosion. So far, a variety of new eutectic high entropy alloys have been successfully prepared. The scholars have carried out in-depth research on the growth mechanism and strengthening mechanism of the first eutectic high entropy alloy AlCoCrFeNi_2.1 designed by Professor Yiping Lu. EHEAs have gained extensive attention in recent years because of the super strength, plasticity, resistance to friction and corrosion. In this paper, the production of eutectic EHEAs is briefly described, and the achievements are reviewed. Moreover, the composition design, preparation method and studies about EHEAs' properties are mainly introduced, and the prospects for their future development are discussed.

In the last decade, polymeric semiconductors have attracted wide attentions owing to their potential application in organic light-emitting diodes, organic solar cell and organic field-effect transistors. Some polymer materials, especially elastomers, have excellent flexibility, such as strechability, bendability, etc., so polymeric semiconductors are considered as the most promising kind of materials in the future research of flexible electronics. The key point for the flexibility evaluation of polymeric semiconductors is intrinsic mechanical properties, for which, according to relevant works, researchers have already developed some effective approaches to determine, including stretching method, sinusoidal buckling technique, nanoindentation method, and AFM nanomechanical mapping. On the other hand, a variety of ideas for designing flexible polymeric semiconductor materials have emerged and can be classified into supramolecular strategy, "chain flexibilization" strategy, and doping/blending strategy. It is noteworthy that the orthogonal dynamic non-covalent interaction is a fundamental molecular mechanism to induce the flexibility of conjugated polymers. And the tactic based on this mechanism provides a universal method to design flexible semiconductor materials and deserves further studies. This review gives a summary on the intrinsic mechanical properties and design strategies of flexible polymeric semiconductor materials based on the state-of-the-art researches.

High-entropy ceramic materials usually refer to the multi-principal solid solution composed of five or more ceramic components in equal mole or nearly equal mole. In recent years,high-entropy ceramics(HECs) have gained considerable attention due to their single-phase crystal structure and excellent properties. In this paper, we review the research development of high-entropy ceramic materials, such as high-entropy carbide, high-entropy nitride, high-entropy oxide, high-entropy boride, high entropy-silicide and high-entropy sulfide at home and abroad, summarize preparation method, structural properties and application structures and properties of HECs. Furthermore, we also propose our view about the future development and prospect of high-entropy ceramics.

Carbon fiber reinforced silicon carbide (C/SiC) ceramic matrix composites have comprehensive properties such as low density, high strength, high temperature resistance and wear resistance, and have become one of the important thermal structural material systems. At present, it has been successfully applied to aero-engine thermal structural components, aircraft thermal protection systems, braking systems and nuclear structural components. In this paper, the research progress in preparation and application of C/SiC ceramic matrix composites is reviewed. A series of representative preparation methods of C/SiC composites are introduced, with emphasis on the hybridization process combining various preparation methods. The applications of C/SiC composites in the fields of aerospace thermal structure and thermal protection, brake materials and space camera structures are summarized. A more excellent hybrid preparation process and a new composite material system for different application requirements are prospected. The paper is expected to provide a reference for further research on C/SiC ceramic matrix composites in the future.

In recent years, rare earth yttrium has been widely used in various applications, especially in crystalline luminescent materials, due to its excellent physical and chemical properties. And it gradually becomes an important additive in industrial production all over the world. However, China is the world's largest exporter of rare earth yttrium resources, yet the use of rare-earth yttrium processing in industrial production is still at a low level. How to develop and utilize rare earth yttrium resources has gradually become a huge problem on China's industrialization path. In this paper, we have focused on the current research status of Y/Y₂O₃ in related industries, such as luminescent crystals, metallurgy, superconductivity, biomedicine and other important fields, expecting to provide assistance in the design and development of yttrium resources in China.

The consumption of non-renewable energy resources such as coal, oil and natural gas leads to more and more se-rious environment pollution problems, which makes the utilization of clean and renewable energy deserve immediate and intense attention. Photocatalytic hydrogen evolution has been considered to be one of the effective approaches to solve fossil energy shortage and environmental pollution problems. However, the photocatalytic hydrogen evolution reaction system is complicated, in which the co-catalyst have a crucial effect to the photocatalyst’s efficiency and can effectively promote the hydrogen evolution rate during the photocatalytic process, hence the development of cheap and efficient co-catalyst has become one of the research focus. This paper briefly introduces the reaction mechanism of photocatalytic hydrogen evolution and the roles of co-catalysts in the photocatalytic systems, summarizes the variety of co-catalysts and relevant research, and analyzes the characteristics and mechanism of several principal types co-catalysts including metals, transition metal sulfides, transition metal oxides, transition metal hydroxides, phosphides, and composites. The paper ends with a prospective presentation of the future research directions, and is expected to provide reference for the innovation and development of highly efficient photocatalysts applying to hydrogen evolution systems.

Polycarboxylate superplasticizers (PCE) has become an indispensable component of high-performance or ultra-high performance concrete, owing to its low dosage, high water reducing rate (>40%), significant positive effects on the workability, mechanical and durability properties of concrete. PCE. is usually composed of a backbone containing anionic groups (like carboxyl group, sulfonic acid group and phosphate group) and grafted side chains with neutral charge. The anionic groups are adsorbed on the surface of cement particles, providing the electrosta-tic repulsion forces, while the PEO-grafted side chains extend from the cement particle surface into the pore solution to create steric hindrance forces. The synergistic effects of the two forces break down the flocculated clusters and improve the dispersion of cement paste. Diverse modified PCE with different side chains, grafting density, anchoring functional group and length of backbone show various effects and can be employed by concrete with different demand in performance. However, with the continuous raise in requirements of concrete performance and the decrease in quality of raw materials, the performance of PCE may be more sensitive to the mixture proportion parameters (cement type, w/c, etc.) and production conditions such as operating temperature and mixing time. The incompatibility between PCE with carboxyl and polyethylene oxide (PEO) side chains and cementitious materials is increasingly serious. Besides, with the increasing requirements of ultra-high performance concrete, a series of PCE with performances of shrinkage reduction, low viscosity and high slump retention have emerged as the times require.
PCE can be primarily classified into two categories. One is polyester-type PCE, which made from α-methoxy poly (ethylene glycol) methacrylate ester (MPEG-MA) by aqueous free radical copolymerization or esterification/transesterification reaction. The other is polyether-type PCE, which is synthesize by free radical copolymerization in bulk or in aqueous solution with α-allyl-α-methoxy or α-hydroxy poly (ethylene glycol) (APEG) ether and maleic anhydride as key monomers, or copolymerization via isoprenyl oxy poly (ethylene glycol, acrylic acid, and α-methallyl-α-methoxy or α-hydroxy poly (ethylene glycol) ether. Polycarboxylate superplasticizer (PCE) features low dosage and high water reducing rate. Different functional groups of PCE exhibit different effects, for example, carboxylic groups show retarding effect and water reducibility, sulfonic groups exert dispersing effect, and hydroxyl groups retarding and soaking wetting effects, and polyethoxy groups present flowability retention capability. The water reducing rate and ability of delayed hydration inhibition of ester-PCE are slightly lower than that of ether-PCE. The method of free radical polymerization possesses easy process and mild synthesis conditions, nevertheless, it is difficult to control the synthetic products due to the irreversible reaction.While reversible addition-fragmentation chain transfer (RAFT) polymerization can prepare the block PCE with controlled molecular weight and narrow molecular weight distribution. In this article, the development of synthesis techniques of PCE is comprehensively reviewed from the aspects of raw materials, synthesis conditions, synthesis methods and post-processing. The impacts of these factors on the performance of PCE are discussed in detail. Finally, the development trend of PCE is also proposed.

Self-healing technology of concrete play an important role in the field of civil engineering, which can effectively heal cracks, improve the internal structure of concrete materials, optimize the mechanical properties and durability during service life. In this article, the research results and applications of self-healing concrete at home and abroad are systematically introduced, the principles of self-healing technology of concrete are classified and summarized, and the self-healing technologies on account of chemical, physical and biological theories are expounded and compared. The evaluation methods of self-healing effect of concrete and their application scope are analyzed. The problems existing in the study of concrete self-healing are pointed out and the development trend and prospect are proposed.

Soft magnetic composites (SMCs) possess high electrical resistivity and saturation induction, which have found wide application in high speed electric motors, switching power supply and electric industry, with an especially pronounced potential as the candidate materials for magnetic cores. The hotspots in recent years have been focus on new-type soft magnetic composites with high energy efficiency, small volume and favorable adaptability. This paper introduces the manufacturing techniques, structural composition, core materials and coating materials of the soft magnetic composites, elaborates the performance’s dependences on these factors, introduces the application of soft magnetic composite materials in electric motor, and also offers a brief presentation of the recent advances in SMCs.

Geopolymer concrete, a class of newly emerging green building materials prepared from the readily obtainable industrial solid waste, possess a variety of advantages such as low energy consumption & carbon emission and facile production process, as well as excellent compressive strength, acid and alkali resistance, freezing and thawing performance and carbonation resistance. It has displayed notable application potential, and become one of the most promising alternatives to ordinary Portland cement. This paper renders a retrospection of the domestic and overseas research endeavors, a vivid description for the raw materials, mix design, mechanical property, workability and durability of geopolymer concrete, as well as a critical discussion upon the technological problems confronting this novel and prospective engineering material.

Titanium and titanium alloys which hold the advantages of high specific strength, favorable corrosion resistance and low-temperature performance, high thermal strength, etc., have become a kind of critical structural materials in aerospace industry, and moreover, have displayed considerable application potential for aeroengine heat-enduring parts owing to superior high-temperature performance compared with aluminum alloys and magnesium alloys. In 1954, the United States developed the first practical high-temperature titanium alloy Ti-6Al-4V which possesses a long-term use temperature range of 300—350 ℃ and a pleasurable comprehensive performance, and acquired extensive and long-lasting application. With the continuous progress of the aerospace industry, especially the advent of aeroengines, other countries successively developed some higher-working-temperature titanium alloys, among which IMI834, as the world’s first 600 ℃ high temperature titanium alloy, was created in 1984 by the United Kingdom. The typical feature of IMI834 is the addition of 0.06% C into the existing Ti-Al-Sn-Zr-Mo-Si titanium alloy system, expanding the processing window and optimizing the microstructure. After that, the United States obtained a high temperature titanium alloy Ti1100 in 1988, by adjusting the amount of some alloying elements in the original high-temperature titanium alloy Ti-6542S. In 1992, Russia also established its high temperature titanium alloy BT36 by substituting 5% W (a high-melting-point element) for 1% Nb within BT18Y. China’s research of high-temperature titanium alloy started relatively late, initially imitated foreign alloys, and later specia-lized in utilizing rare earth elements to design high-temperature titanium alloys. The Ti60 and Ti600 alloys, developed by IMR (CAS)/BaoTi Group and NIN respectively, both have the working temperature of 600 ℃ and favorable comprehensive performance. In general, the upper temperature limit of high-temperature titanium is difficult to exceed 600 ℃ at present. Sufficient studies have proved that the nearly ineliminable mismatch between thermal strength and thermal stability and the steep-oxidation-resistance-decay-induced severe surface oxidation at above 600 ℃ will result in the deterioration of thermal stability and fatigue properties, and even, the risk of “titanium fire” for those components serving in the high-pressure compressor section of an aeroengine.
    This review is concerned with the worldwide development status of 600 ℃ and above high-temperature titanium alloys. We give introductions for the 600 ℃ high-temperature titanium alloys including Ti1100 (US), IMI834 (UK), BT36 (Russia), and Ti60/TG6/Ti600 (China), as well as the 600 ℃-above ones including Ti65/Ti750 (China). The major nations’ design schemes of high-temperature titanium alloys and the obstacles to raising the upper temperature limit are outlined, and some possible solutions are put forward. The paper ends with a prospective discussion over the future trends of high-temperature titanium alloys, from the perspectives of controlling the size, morphology and content of α₂ phase and adjusting the hot working process.

Energy and environment are the essential conditions for human survival and development, furthermore, the mutual coordination between them is a vital guarantee for social sustainable development. In recent years, the negative impact of fossil fuels on human survival has gra-dually attracted widespread attention from society. The greenhouse effect is mainly attributed to the release of CO₂ from the burning of fossil fuel. Therefore, the development of efficient and environmental-friendly carbon capture and storage technologies in a low-carbon economy environment play a crucial role in energy recycling and environmental protection.
Utilizing the amine solutions for scrubbing and absorbing CO₂ is one of the most commonly technologies for industrial capture and storage (CCS) (e.g., separating CO₂ from flue gas of power plant flue gas), which can significantly reduce the CO₂ emissions, but also increases the plant energy consumption by 25%~40%, hence leading to an increase in additional costs to a large extent. In addition, other disadvantages of amine scrubbing include corrosion of the equipment by the alkaline solution, loss of solvent, degradation of the amine caused by heat production, and difficulty of separation after capturing. Solid materials such as alkali metal ceramics, solid amines, layered double hydroxides or calcium-based adsorbents for high temperature absorption (chemisorption) are another method of capturing CO₂, while the energy consumption and the sensitivity of water molecules and other components limit their scope of application. In addition, it is also a feasible method to selectively separate the mixed gases with different mechanisms by utilizing polymers or inorganic membranes, yet the membranes with high stability, high selectivity, and high throughput are hard to obtain, and it is necessary to ameliorate the membranes’ adsorption and separation and their selectivity. For solid adsorbents, the capture of CO₂ by porous materials at high pressure is dominated by adsorptive interactions, while selective capture at low pressure or low CO₂ concentrations is primarily influenced by the interaction of adsorbents and a chemical affinity to CO₂.
Metal organic frameworks (MOFs) exhibit tremendous potential for gas adsorption, especially for CO₂ capture, due to their high crystallinity, high specific surface area and tunable pore structure. Compared with other solid adsorbents, such as activated carbon, zeolites, MOFs have higher adsorption selectivity. Applying it to the carbon capture and storage technology can dramatically broaden the range of CO₂ adsorbents, increase the adsorption selectivity, meanwhile, effectively reduce the costs. Currently, MOFs are expected to capture CO₂ in power plants, separation of CH₄/CO₂ in natural gas, CO₂ collection from vehicles, and even direct capture from the air. Therefore, the development of MOFs mate-rials capable of efficiently adsorbing and separating CO₂ is of great significance for relieving environmental stress.
This paper summarizes the establishment of CO₂ adsorption model and proposes several methods to improve the adsorption capacity of CO₂, such as increasing the density of open metal sites, doping metal or nitrogen atoms, adjusting their pore size or amino-functionalization, and synthesizing MOFs composite materials, and compared the effects of different methods on the adsorption capacity of CO₂ under low pressure. In addition, they are expected to be applied to the capture of CO₂ in post-combustion flue gas, vehicle exhaust and other small emission sources.

Scanning Kelvin probe force microscopy (SPFKM) is a material measuring and characterizing technique which applies scanning Kelvin probe on the basis of atomic force microscopy (AFM) and has been gaining momentum in recent years. It involves simultaneously the nanometer-level topography measurement and the in-situ high-resolution volta potential mapping, thereby providing a novel insight in investigating the mechanisms of materials’ corrosion behaviours. The present paper sketches out the principles with respect to the two working modes of SKPFM, summarizes the unresolved issues that have emerged in SPFKM’s application, and also renders a comparative discussion between SKPFM and the traditional SKP technique. The review offers an elaborate delineation about the application of SKPFM in corrosion science, and ends with a rough description of the opportunities and challenges.

Skin is the largest organ in human body, and play a crucial role as barrier. When human skin is damaged, skin dressings are usually used to repair the wound. It is of great significance for repair of human skin injury and production of medicine and cosmetics to develop skin dressings that can imitate normal human skin. With the rapid development of skin dressings, various types of skin dressings continue to emerge. In this article, the current research status of skin dressings is elaborated, including wound dressings and artificial skin in terms of their type, structure and property. In addition, four types of skin dressings, namely traditional type, biological type, synthetic type, and composite skin dressings are introduced. The composition and features of the above four types of skin dressings are discussed and compared in detail. Besides, the types of commercial artificial skin is briefly introduced as well. Finally, the future development of skin dressings is proposed.

Steelmaking is a high-consumption and high-emission industry. With the task of peak carbon dioxide emissions and carbon neutrality advocated by the state being put on the agenda, it is urgent to develop a low-carbon economy in the steel industry with high carbon emissions. At present, hydrogen metallurgy technology is highly valued, and it is an important development direction in metallurgy field. This paper mainly summarizes the development status of hydrogen metallurgy technology at home and abroad under the background of peak carbon dioxide emissions and carbon neutrality, and the development trend of China steel industry under the background of hydrogen metallurgy. Based on the theoretical study of thermodynamics and kinetics of metallurgical process, the advantages and disadvantages of reducing iron oxide by H₂(CO) are compared and analyzed, and the reduction advantages of H₂ are defined. At the same time, the technical bottleneck of current hydrogen metallurgy development is discussed, and the future development of hydrogen metallurgy technology is prospected, which provides theoretical basis for the development of hydrogen metallurgy technology.

Weathering steel (WS) is widely used in bridge engineering because of its advantage of uncoated application. And it is an important direction for the development of steel bridge in China in the future. In recent years, the corrosion and fatigue fracture of the welded joints in WS bridges have become increasingly prominent with the application of WS. It seriously affects the service performance of WS bridges to a certain extent. Therefore, it is urgent to carry out the research on the corrosion and mechanical behaviors and the prediction method of properties degradation for the welded joints of WS in bridges. According to the actual service conditions of bridges, WS is often subjected to the coupling effects of corrosion and load. Therefore, it is particularly important to comprehensively and systematically study the corrosion behavior of WS welded joints under the coupling effects of corrosion and load, and quantify the stress corrosion damage and fatigue damage resulting in the deterioration of its mechanical properties. In this study, the research status of corrosion and mechanical behaviors, simulation methods of corrosion evolution, and evaluation methods of mechanical property degradation for WS and its welded joints was reviewed and analyzed. And the urgent issues to be solved with regard to the research on the properties of WS and its welded joints were proposed. In addition, the current progress was introduced. These point out the direction for the related researches on WS bridges, aiming to eliminate the doubts of bridge design and construction units for the long-term performance of WS, and pushing forward the large-scale application progress of WS in bridges in China. This study can play a more active action in the construction and maintenance of WS bridges in the future.

Continuous basalt fibers made by drawing raw basalt ore have been recognized as a kind of high-performance and environmental friendly inorganic mineral fiber, which has a wide range of applications and is of great significance in both industrial development and national defense construction. By reviewing the development of preparation technology for continuous basalt fibers, this paper introduces the crucible and tank kiln method, especially the current common tank kiln production process, as well as the three main influencing factors of tank kiln process including ore raw materials, key equipment and wetting agent. Moreover, this paper briefly introduced the different effects of various elements in basalt fiber on the its properties, and compares the properties and parameters of basalt fiber with other high-performance fibers. It is considered that continuous basalt fiber has excellent comprehensive properties. Combined with the application forms of continuous basalt fiber, its applications are summarized, including the application of geotechnical reinforcement of basalt fiber wire, the application of temperature resistance and heat insulation of wire processed into a variety of fabrics, the application of rock wool and scale, the application of basic profile (composite reinforcement, composite plate, composite pipeline, etc.), and the application of composite materials in many industrial fields or special fields. On the basis of the above, this paper analyzed and prospected the development prospect, crucial fields of application, impact factors of production, preparation technology and industrial expansion of continuous basalt fibers, so that to motivate their engineering level and industrial development in China.

Metal-organic framework compounds (MOFs), an organic-inorganic porous complex mainly formed by self-assembly of metal ions and organic ligands. Metal organic frameworks (MOFs)emerging as a kind of porous of organic-inorganic skeleton materials, have tunable nanospaces, high porosity and high specific surface area, which makes it has a wide range of applications in biomedicine, sensing, gas separation membranes, etc. But MOFs materials have some disadvantages, such as poor stability and low mechanical strength. In order to improve its shortcomings, some researchers have combined MOFs materials with inorganic or organic materials to improve the defects of MOFs meanwhile broa-den the application of MOFs. This review focuses on the synthesis of polymer-based MOFs composites.
In this review, MOFs are classified into the following categories according to the naming, composition and synthesis methods of MOFs: isoreti-cular metal-organic frameworks (IRMOFs), zeoliticimidazolate frameworks (ZIFs), and metarial sofistitute Lavoisier frameworks (MILs), poc-ket-channel frameworks (PCNs), etc. Two preparation methods commonly used in polymer-based MOFs composites are summarized: physical blending and in-situ methods. The composite mode of the polymer and MOFs in the material is non-covalently bonded, including hydrogen bond, van der Waals force, electrostatic action, etc.; covalent bond, which is mainly the combination of amino group and carboxyl group. In the combination of non-covalent bond and covalent bond, there are hydrogen bonds. And the combination of covalent bond can make the polymer and MOFs material better composite, the polymer-based MOFs composite material is more stable and more applicable widely. Finally, the application status of polymer-based MOFs composites in biomedicine, sensing, gas separation membranes, etc. are introduced. The development trend of polymer-based MOFs composites are prospected. It mainly includes the way of composites, the structural control of composites, and the application of composites in other fields. It is hoped that researchers in polymer-based MOFs composites will provide some guidance and reference.

The main task for the nuclear shielding design is to block out neutron and γ-ray. Thereby, the radiation shielding materials which combine the shielding ability from neutron and γ-ray are the best candidates. This paper offers an elaborate description of the types, substrate materials and performances of the currently applied neutron and γ-ray combined shielding material, and furthermore, roughly discusses the respective principal problems of these materials. We emphasize the crucial and urgent problem with respect to the mutual exclusion between shielding effectiveness and other performances (e.g. mechanical performance, heat resistant stability, etc.). Finally the review sketches out the prospect of the neutron and γ-ray combined shielding materials, suggesting that the development of structure/function integrated radiation shielding materials is one of the future trends.

Undoubtedly, crystalline silicon solar modules represented by polycrystalline silicon (poly-Si) and monocrystalline silicon (c-Si) play a dominant role in the current photovoltaic market. At present, poly-Si solar modules with low production cost occupy a large market share, but they show relatively low conversion efficiencies. On the contrary, c-Si solar modules with relatively high production cost occupy a smaller market share compared to poly-Si modules, but they behave higher conversion efficiencies. With the progress of silicon material and c-Si wafer cutting technology, the cost of c-Si solar modules is continuously decreasing. There is a booming demand for high-efficient photovoltaic products in the future market. Accordingly, high efficiency c-Si solar cells and modules will be expected to receive more and more attention.
Aiming at further enhancing the device performance of c-Si solar cells, numerous research efforts have been performed, which mainly focus on improving the quality of Si wafers to reduce bulk defects, seeking novel passivation materials to reduce surface and interface defects, developing advanced anti-reflection technology (novel light trapping structures and materials) to raise incident light utilization, introducing low-resistant contact technology to cut down series resistance, optimizing PN junction fabrication and device designs et al. Since 2014, successive breakthroughs of conversion efficiency of c-Si silicon solar cells have been achieved with a current record of 26.6% reported by Kaneka Corp., Japan. c-Si solar cells with efficiency 25% or above include Passivated Emitter and Rear Locally diffused (PERL) cells, Interdigitated Back Contact (IBC) cells, Silicon Heterojunction (SHJ) cells, Interdigitated Back Contact and Silicon Heterojunction (HBC) cells, Tunneling Oxide layer Passivation Contact (TOPCon) cells and polysilicon on oxide (POLO) cells, etc. By analyzing the key technologies of these typical c-Si solar cells, it can be concluded that the contact recombination of metal grid electrodes and c-Si at the surface becomes the key influencing factors for the device efficiency. For the sake of weaken such recombination, one approach is to reduce the direct contact area between metal and semiconductor, such as Passivated Emitter and Rear Cell(PERC), PERL and Passivated Emitter and Rear Totally-diffused(PERT)solar cells. Another approach is to develop novel carrier-selective passivation contact, such as SHJ and TOPCon cells, which can achieve excellent surface passivation, separate and transport carriers without opening holes. In addition, the combination of interdigitated back contact and other device structures has become an inevitable choice to maximize light utilization, including IBC and HBC cells.
In this paper, the typical high-efficiency c-Si solar cells with conversion efficiencies of 25% or above are firstly summarized. The corresponding device structure, key technology and materials are analyzed in detail, respectively. At last, the development trends and future prospects of high-efficiency c-Si solar cells are performed.

Aerogels are highly porous light-weight solid materials with unique three-dimensional network structures constructed from colloid particles or polymer molecules, and the whole nanoporous network of aerogels is filled with air. The particles and pore size of aerogels are of nanometer magnitude. Thanks to their high specific surface area and porosity, adjustable open pore structure, easiness of chemical modification and diverse types/forms, the aerogels have received considerable attention as adsorbents for gas purification. The adsorption capacity of aerogels can be two orders of magnitude higher than that of activated carbons under the same condition. Currently, SiO₂ aerogels and carbon aerogels are the main research objects in the field of gas adsorption and purification. In addition, metal oxide aerogels and novel aerogels such as SiC aerogels, graphene aerogels and biomass-based aerogels have also been explored for gas adsorption application recently.   The adsorption materials should possess high adsorption capacity and good selectivity for target gases. Although the high specific surface area and porosity of aerogels provide numerous adsorption sites, the adsorption capacity for gases is usually limited only depending on their own physical adsorption and selectivity is unsatisfactory as well. Besides, the adsorption performance of the target gas is often badly affected by the competitive adsorption of the coexisting gas components in practical application. Therefore, aiming to further enhance the adsorption capacity of aerogels and improve the selectivity of target gases, huge researches have carried out around the modification of aerogels and certain progress has been made.   Currently, target gases reported in the aforementioned researches mainly include the major greenhouse gas CO₂ and atmospheric pollutants volatile organic compounds (VOCs). Several methods have been proposed to improve the capacity and selectivity of aerogels. For CO₂ adsorption, aerogels are principally modified by amino-functionalization and nitrogen-doping to introduce basic sites on the surfaces; and for VOCs adsorption, non-polar organic functional groups are commonly introduced to increase their surface hydrophobicity. The modification methods can be divided into the following two types. One is to functionalize the aerogel surface by graf-ting and impregnation after wet gel formation or supercritical drying, and the adsorption capacity and selectivity of aerogel to target gas can be enhanced by introducing specific functional groups or active components. The other is to introduce functionalized precursors in the sol-gel process which gives the aerogel network specific properties at molecular or nano scale, thus effectively balancing the stability of the active component and the adsorption performance of the target gas. Moreover, the specific surface area, pore structure and surface chemical properties of carbon aerogels can be further improved through activation, and finally the adsorption performance of target gas pollutants can be optimized.   This review offers a retrospection of the research efforts for the application of different aerogels in CO₂ and VOCs adsorption. Firstly, the general preparation process and structural characteristics of aerogels are briefly introduced. Then, the adsorption performances and mechanisms of various aerogels are mainly discussed, as well as the summary of primary methods of the aerogel modification. Based on the recent research progress, this review points out the focus of future research including improving the structural stability and adsorption rate of aerogels, designing aerogels capable of adsorbing multiple gases simultaneously, shortening the preparation period and lowering the cost.

Natural diamonds are too rare and precious to satisfy the growing industrial demand. Annual output of artificial diamonds made by industrial synthesis technology has exceeded remarkably that of natural diamonds. Now, because of their extreme hardness, diamonds are mainly used as abrasive materials and super-hard materials in industry, mostly for grinding tools, blades and for drilling, cutting, polishing, etc. In addition to the high hardness, diamonds also display other excellent properties, such as optical properties, electrical properties, catalytic properties, lubrication properties, biocompatibility, etc., and thus are especially suitable for functional materials. Synthetic diamonds have been successfully prepared through three different strategies: Ⅰ. Ultrahigh-pressure and high-temperature process, i.e. the so-called static catalyst approach, which results in single crystal diamonds; Ⅱ. Chemical vapor deposition efficient for producing bulk (or sheet) diamond with large size; Ⅲ. The detonation method that can synthesize ultrafine (usually nanosized) diamond powders. Large single crystal, large-size bulk (sheet) and nanosized powders are currently the most promising, exemplary and state-of-the-art forms for functionalized artificial diamonds.   However, the research and innovation for the functionalization of diamond and its composites are inadequate, especially for nanodiamond that shows a variety of excellent properties, such as high modulus, high hardness, high thermal conductivity, good insulation, unique photoelectric characteristics, low friction coefficient and excellent wear resistance, satisfactory chemical stability and biocompatibility. The original application of nanodiamonds and their composites is to serve as photoelectric materials, and have now been extended to the fields of biological medicine, drug delivery, catalysis, thermal management, lubrication, etc., indicating a rapid, hopeful and high-potential development prospect.   Nanosized diamonds generally tend to agglomerate, which is similar to other nanomaterials. This can be solved or alleviated by stirring-assisted ball milling, ultrasonic treatment, electrospinning, and so on. Moreover, for certain application purpose, chemical modification is also indispensable. For the sake of grafting ideal chemical functional groups onto the surface of nanodiamond, changing, adjusting and designing the chemical activity of their surfaces, and in consequence, further mitigating agglomeration and improving solubility and dispersibility in solvents (or solid matrices), researchers have tentatively adopted various chemical modification approaches including carboxylation, hydrogenation, ammoniation, amidation, acylation and hydroxylation. And the modified nanodiamonds have successfully and swiftly found biomedical application, e.g. biological imaging, molecular imprinting, bio-sensing, cell-targeted drug delivery, tissue engineering and so on. The surface functionalization of the nanodiamonds facilitates the combination of them with polymer matrices by forming covalent bonds, which can promote dispersion and thermal conductivity of the nanodiamond-reinforced composites. Furthermore, functionalized nanodiamonds have also been applied in the fields of photocatalytic mate-rials, friction materials, photoelectric materials, self-cleaning materials, etc.   In this paper, the recent advances of nanodiamonds serving as functional materials is summarized. The modification methods, agglomeration and dispersion of nanodiamonds are introduced, focusing on the above-mentioned application situation. It is expected to provide a reference for the further research.

The use of traditional solvent polyurethane (PU) is likely to cause environmental pollution, which hinders the wide application of PU in functional films, finishes, foaming materials and the like. Blocked solvent-free polyurethane (SFPU), with its advantages of green, environmental protection, low energy consumption, high stability and simple operation, has become a research hotspot in the field of PU in recent years. In particular, SFPU with controllable activity can achieve efficient sealing and unsealing, which promotes the further development of PU materials.
However, due to the difference in the type and structure of the blocking agent, the blocked SFPU prepolymer formed has large deflagration temperature fluctuation and easy yellowing. In addition, the escape of the small molecule blocking agent during deblocking destroys the regularity of the product structure, reducing its mechanical properties. Therefore, in recent years, in addition to studying the effect of monomer on the physicochemical properties of blocked SFPU, the researchers have been trying on the selection of sealants, and have achieved relevant results, which effectively reduce the stability of blocked SFPU materials. It unblocks the temperature. At present, the blocked SFPU can achieve complete deblocking at 120 ℃.
The commonly used blocking agents are mainly alcohols, phenols, terpenes, amines and amides, active methylenes, pyrazoles and triazoles, bisulfites and the like. Among these blocking agents, the blocking agent for the alcohol structure is the earliest, the blocked prepolymer has a lo-wer activity and a higher deblocking temperature, giving the material excellent stability; although the anthraquinone blocking agent is lower. The release of the active isocyanate group at the deblocking temperature facilitates the re-extraction of the exposed isocyanate group and the chain extender, but the yellowing resistance is poor; the less toxic pyrazole and triazole sealer have nitrogen The structure of the five-membered ring is not easy to yellow. The blocked SFPU was initially prepared by a method of directly blocking the isocyanate monomer, but the method has a poor effect of extending the chain and a low film forming property. In recent years, the research work has adopted the method of sealing SFPU prepolymer, that is, synthesizing SFPU prepolymer first, and further blocking the prepolymer, ensuring high molecular weight and good film formation of the blocked SFPU.
In this paper, the research progress of blocked PU is reviewed, including three types of traditional blocked solvent PU, blocked WPU and blocked SFPU. The types and synthesis of blocked PU, common blocking agent and blocked-unblocking are discussed. Reaction mechanism, factors influencing the deblocking temperature, and methods for determining the deblocking temperature. The mechanism of blocked deblocking is divided into elimination-addition mechanism and nucleophilic substitution mechanism; the factors affecting the deblocking temperature are the structure of isocyanate, the structure of the blocking agent, the reaction medium and the catalyst. At the end of this paper, the advantages and disadvantages of the current blocked SFPU are summarized. It is pointed out that solving the three difficulties of blocking agent release, high deblocking temperature and high viscosity when unsealing is the key to be solved in the application process of this technology.

In recent years, microneedles have received a lot of attention from researchers because of its advantages of being painless and minimally invasive, safe and efficient. Microneedles have been widely used in the fields of transdermal drug delivery, medical aesthetics and biological diagnosis. However, traditional microneedles, especially those prepared directly from polymer materials, generally have problems such as low mechanical strength, single drug release mode, poor biological sensing performance and simple functions. The clever combination of nanotechnology and microneedles can effectively improve the above problems, due to the unique nano-size, mechanical strength and photoelectric effects of nanoparticles. This paper reviews nanoparticles for microneedles, including inorganic nanoparticles (metal, inorganic non-metal), organic nanoparticles (polymer, lipid) and drug nanoparticles (nanocrystalline drugs, virus-like particles), and describes the role of nanoparticles in increasing mechanical property, synergistic improvement of drug release and immune enhancement are introduced. Finally, the urgent problems need to be solved in this field and the future research directions are discussed.

According to the lack of clear reference for the selection of grouting materials for roads non-excavation reinforcement, the types and proportions of the commonly used road grouting materials are investigated systematically. Based on the statistical analysis, the ratios of cement based grouting material and geopolymer grouting material are recommended. The effect of the density of polymer grouting material on water absorption and compressive strength is determined. The results show that the recommended water-cement ratio of cement paste grouting material is 0.46-0.67, and the ratio of cement mortar is mcement∶mwater∶msand=1∶(0.46-0.59)∶(0.31-0.73). The recommended range of the sodium silicate modulus, the water-cement ratio and the mass fraction of sodium silicate of the geopolymer grouting material are 2.3-3.1, 0.49-0.67 and 7.27%-9.73%. With the increase of density of solidified polymer grouting material, the compressive strength increases and the water absorption reduces.

The organicmetal halide perovskite solar cells has been developing rapidly in recent years, and the cells’ certified photoelectric conversion efficiency has reached 22.1%. Simultaneously, low cost, short energy payback time and other merits have made the commercial application of organicmetal halide perovskite solar cells into reality. Nevertheless, the perovskite itself is not stable in the circumstances of high humidity, high temperature or light. Especially, the instability of perovskite will be more serious when assembled with other functional layers into the device, because electrode corrosion or deep defects will be easily initiated in this situation. More and more literature has reported various methods to improve the stability of the device, which mainly focuses on two aspects: Ⅰ. controlling the composition of the perovskite material to enhance the stability; Ⅱ. optimizing the device structure of the solar cells to enhance the stability.   As for the component optimization, researchers put efforts in modifying ABX₃ structure, controlling structural dimension and the use of protective layer to improve the stability of perovskite materials themselves. Ⅰ. With the satisfaction of the requirements of Goldschmidt tolerance factor t or octahedral factor μ, the introduction of hydrophobic or temperature-resistant groups like formamidinium or cesium cation into the A site of ABX₃, while incorporation of bromide anion or thiocyanate ion into X site will increase the moisture resistance of perovskite material. What’s more, a combination sites of perovskite Cs_x(MA_0.17FA_0.83)_(100-x)Pb(I_0.83Br_0.17)₃ could not only improve the thermal stability but also enhance the device’s conversion efficiency to 21.1%. Ⅱ. Low-dimensional (mainly two-dimensional) perovskite materials have also been comprehensively studied. For instance, BA_0.05(FA_0.83Cs_0.17)_0.95Pb(I_0.8-Br_0.2)₃ displays excellent stability in high humidity and light circumstances. Ⅲ. Protective layers with favorable hydrophobic properties, excellent charge transport ability such as butylphosphonic acid 4-ammonium chloride or benzylamine can also enhance the stabi-lity of the perovskite material.   As for the device structure optimization, researchers have tried to strengthen the stability of the device through changing electron transporting material (SnO₂, La-doped BaSnO₃, etc.), hole transporting material (CuGaO₂, CuPC etc.) and counter electrode (carbon, copper etc.), respectively. For example, La-doped BaSO₃ has weak UV photocatalytic activity, excellent electron mobility and suitable energy band structure, the device with La-doped BaSO₃ as electron transporting material show unexceptionable light stability. In addition, taking chemical and thermal stable CuPC as the hole transporting material of the device could not only achieve favorable thermal stability but also obtain a conversion efficiency of 17.5%. Considering the counter electrode, carbon electrode shows excellent stability under high humidity and light conditions when it applies to large area devices. Moreover, when copper electrode replace gold or silver electrode, the device acquired a conversion efficiency of more than 20%, and presented an admirable heat and light stability as well.   This review mainly summarizes the current status of the stability study of organometallic halide perovskite solar cells in view of the perovskite absorbing material compositions and device structure. Researches about optimizing the stability of the device from the perovskite composition of ABX₃, structural dimension of perovskite material and the use of other functional layers are summarized. Finally, the development trends of organometallic halide perovskite solar cells are proposed based on the available research.

In recent years, with the rapid development of portable electronic devices and electric vehicles, lithium has been increasingly used in the field of new energy materials. Its exploitation and utilization have caused much attention. Lithium mainly deposits in the hard-rock ores and salt lake brines, and among them, lithium reserves in salt lake brines account for more than 70%. The process of lithium recovery from salt lake brines is simple with low energy consumption compared with that from hard-rock ores since it avoids the complex process of ore treatment and conversion to transfer lithium from solid compounds into a solution. The process does not generate large amounts of acidic or alkaline solid wastes, so that it is clean and environmentally friendly. Lithium recovery from brines has become the main way to produce lithium in the world because it has obvious technical and economic advantages.
In salt lake brines, large amounts of elements such as Na, K, B, Mg present together with Li. Therefore, complicated process is needed to separate and remove impurity ions for the lithium purification and production. It is particularly difficult in the separation of Li from large amount of Mg. As most salt lake brines outside China have low Mg content with a low Mg/Li ratio (Mg/Li(w/w)<20), traditional method of solar evaporation coupled with precipitation could be used for the lithium recovery. The process is simple with low cost. However, almost all salt lake brines have high Mg content with Mg/Li ratio higher than 20 in China, except Zabuye Salt Lake in Tibet area, which is one of carbonate type of brines with very low Mg/Li ratio. As aforementioned traditional method is not suitable for high Mg content brines due to the high reagent consumption, the development of new economical method is highly demanded and it has become a hot research topic. This is particularly true in China.
At present, although a number of processes have been developed and commercially applied in China for the lithium recovery from salt lake brines with high Mg/Li ratios, such as calcination-selective leaching based method, solvent extraction based method, membrane separation based method and adsorption based method. Among them, the method based on calcination followed by selective leaching can achieve comprehensive utilization of various resources in the brine. However, it has serious disadvantages including large amount of water evaporation, high energy consumption, serious equipment corrosion and air pollution by HCl production. Although solvent extraction based method has its obvious advantages, such as continuous operation, high throughput capacity, low capital and operating cost, lithium stripping with strong acidic solution limits its wide applications. In addition, solvent loss by phase entrainment, crud formation etc., also hinders its application. The new advanced extraction system which can solve these problems is urgently needed for this method. Membrane separation based method is another commercially used method with the advantages including simple process, low reagent consumption, clean production without environmental impact. It also has its significant drawbacks such as high capital and operating cost, membrane poisoning and short service life. The alumina-based adsorbent have good selectivity for lithium over other impurities and it has been commercially applied for lithium recovery from high Mg content brines in a large scale in China. However, the adsorption method must be followed by other methods for lithium production. In overview, it is indicated that the methods based on solvent extraction and membrane separation are more prospective for the lithium recovery from salt lake brines containing high Mg concentration, and alumina-based adsorption method is more suitable for the case of low lithium content brines.
Based on the analysis of the properties of brine resources, this paper summarizes the research status and features of typical methods mentioned above for lithium recovery from brines. The advantages and disadvantages of all mentioned methods have been discussed in detail. The review is especially focused on the recovery of lithium from salt lake brines with high Mg/Li ratios. The direction and separation of impurities in the process of lithium extraction was also discussed. In addition, the development trend of clean and efficient production of lithium from salt lake brines was predicted.