High-entropy brings high-entropy effect on thermodynamics, lattice distortion effect on structure, diffusion retardation effect on dynamics and “cocktail” effect on properties in materials. It is a hotspot to improve the properties of ceramics by high-entropy design. However, it still lacks the study of high-entropy structures and their correlation to the properties through transmission electron microscopy (TEM). In this study, high-entropy borides and carbides powders were fabricated by using metal oxides, boron carbide and graphite as raw materials. The high-entropy (TiZrHfNbTa)B2 and (TiZrHfNbTa)C ceramics were then synthesized by spark plasma sintering of the as-fabricated powders. Transmission electron microscope and energy dispersive spectrometry were used to characterize the structure of the two high-entropy ceramics at the nano-scale and atomic-scale. The integrity of crystal structure maintained after solid solution of five transition metal elements which were found to uniformly distribute in the ceramics. However, at atomic scales, concentration oscillations of solid solution elements, atomic dispersion and lattice strain were observed. The solid solution structures at atomic scales as-obtained in this work can help to understand the structure-property relationship of high-entropy ceramics and provide experimental basis for the composition and structure design of high-entropy ceramics.
Environmental barrier coatings (EBCs) have been developed to improve the durability of SiCf/SiC CMC components against harsh combustion environment. Among the most promising EBC candidates, rare-earth (RE) silicates attract attentions for their low thermal expansion coefficient, excellent high temperature water vaper and CMAS corrosion resistance, and good thermal and chemical compatibility with silicon-based ceramics and composites. Herein, we reviewed the optimizations of critical key properties of rare-earth silicates through strategic high entropy design to modify the current performance deficiencies of rare-earth silicates like thermal properties (coefficient of thermal expansion and thermal conductivity), CMAS corrosion resistance and high temperature phase stability. The present advancements demonstrate the merits of high entropy engineering for advanced EBCs for the improvement of crucial properties in engine applications.
As a new emergence material, high-entropy ceramics possess unique properties due to its high configurational entropy. Among these ceramics, high-entropy transition metal carbide ceramics (HETMCC) are expected to be the potential candidates for the thermal protection system of hypersonic aircraft. Compared with single-component ceramics, the comprehensive performance of single-phase HETMCC is greatly improved. At present, the research on HETMCC is still in the initial stage, and the composition design and theoretical analysis of HETMCC are lack of sufficient research support. In addition, it is necessary to further explore the preparation of high purity HETMCC. In terms of the properties of HETMCC, further in-depth research has been conducted. In this paper, the theoretical design and preparation methods of high-entropy ceramics are reviewed. Research progress of the mechanical properties, thermal conductivity, and oxidation resistance properties of HETMCC are introduced in detail. The concerned scientific issues of HETMCC are pointed out and their future development direction are also prospected.
As the extension of high-entropy alloy, entropy engineering has been already extensively used in thermoelectrics because it can guide the optimization of thermoelectric (TE) performance from the aspects of both electrical and thermal transports. Due to the inherent material gene-like feature, entropy can be used as a performance indicator to rapidly screen new multicomponent TE materials. In this review, we first reveal the reason why entropy can be used as the performance indicator of TE materials. The physical mechanisms of enhanced structure symmetry, improved Seebeck coefficient, and suppressed lattice thermal conductivity as a result of the increased configurational entropy are discussed. Then, the applications of entropy engineering in typical TE materials, such as liquid-like materials and IV-VI semiconductors, are outlined, and the approach to screen and identify candidate multicomponent TE materials with high configurational entropy is introduced. Finally, the future directions for entropy engineering are highlighted.
Silicon carbide is widely used because of its excellent physical and chemical properties. The chemical bonding characteristics of SiC make it difficult to be sintered. Therefore, preparation of high-quality SiC ceramics is one of the challenges in SiC research field. In this study, the ternary rare-earth carbide Dy3Si2C2 was proposed as a new sintering additive for SiC ceramics, through the phase transition of Dy-Si-C system at high temperatures to promote the densification of SiC. The Dy3Si2C2 coated SiC powders were synthesized via an in-situ reaction between metal Dy and SiC in high temperature molten salts. The Dy3Si2C2 coated SiC powder was sintered by spark plasma sintering (SPS), at 1800 ℃, 45 MPa. As the result, high-purity SiC ceramic with the density of 99% and thermal conductivity of 162.8 W·m -1·K -1was obtained to form the SiC-Dy3Si2C2 raw material with n(Dy) : n(SiC)=1 : 4. Further study shows that Dy3Si2C2 and SiC undergo a eutectic reaction at high temperatures, which generates liquid phase at the grain boundaries and promotes the densification of SiC ceramics. This study shows that the ternary rare-earth carbides Re3Si2C2 (Re=La, Ce…) has great potential to be used as the sintering additive for SiC.
Hydrolysis is a unique method for hydrogen generation at ambient condition. Widespread attentions have been paid to materials for hydrogen generation via hydrolysis due to several advantages: high theoretical hydrogen capacity, moderate storage and operation condition, safety, etc. In this paper, recent progress and development in this area were reviewed. Three types of materials including borohydride (NaBH4, NH3·BH3), metal (Mg, Al), and metal hydride (MgH2) were introduced. Several issues about them were discussed specifically: mechanism, main problems, designments of catalysts and materials, etc. Based on these discussions, we compared the different materials mentioned above, commented their current performances and practical difficulties. At last, prospects in this field were presented.
An electron irradiation induced fast phase-separation behavior was observed under convention Transmission electron microscopy (TEM) observation of spark plasma sintered AlF3 doped alumina ceramic. Spherical nanocrystalline Al precipitates separated out from original alumina grain surface within several seconds under transmission electron microscopy electron irradiation. By high resolution TEM observation combined with diffraction patterns analysis, it was found that the original alumina grain surface was in highly defected state. After electron irradiation under TEM, the defects on original alumina surface vanished accompanied by the precipitation of nanocrystalline Al particles. By thoroughly analysis of the defect reaction during doping process and the feature of cation sub-lattice of alumina, a defect assisted interstitial atom segregation mechanism was proposed to explain this behavior. According to this mechanism, doped F ions first occupied oxygen vacancy sites with corresponding Al ions at intrinsic interstitial sites. After oxygen vacancies being fully occupied, both F and Al ions tended to settle down at intrinsic octahedron interstitial sites, which resulted in a metastable doping state. Under the act of 1/3 [11ˉ00] partial dislocation of alumina matrix, distorted cation sub-lattice generated double aggregated vacant octahedron sites. When these doublets vacant octahedron sites were occupied by foreign Al ions, stacking faults composed of about three sequences were generated as that observed in high resolution TEM. Meanwhile, the segregated doping Al ions at double aggregated octahedron sites along the stacking faults worked as early stage precipitations. Under electron irradiation, with the ablation of F ions, the unstable segregated Al ions separated out as nano precipitation with the reconstruction of alumina lattice.
Chemotherapy is the main method used for cancer treatment. However, most chemotherapeutic drugs show low selectivity towards tumor cells. When killing tumor cells, chemotherapeutic drugs can also damage normal tissue cells and induce a series of side effects and toxic reactions, such as gastrointestinal reactions, calvities and so on. An effective way to reduce the adverse drug reactions is to construct targeted delivery systems based on the microenvironment properties of tumor tissue. Porous carbon nanomaterials (PCN), with excellent properties such as good structural stability, pores, and easily modified surface, are promising candidate to be used for such strategy. In this paper, the construction and application of the PCN-based targeted antitumor drugs delivery system were reviewed; the structural properties, the design philosophy of PCN suitable for drug loading were summarized; the effective strategies to improve drug loading on PCN for combined drug delivery were discussed both theoretically and experimentally. The mechanism and applications of PCN for tumor microenvironment based targeted delivery system were analyzed from the perspectives of endogenous sensitive stimulations (such as acidity, redox potential and specific enzyme), exogenous sensitive stimulations (such as light and magnetic) and multiple sensitive stimulations (such as double sensitive stimulations, including acidity/redox potential, acidity/magnetic and magnetic/light, and three sensitive stimulation, including acidity/redox potential/light). The biocompatibility and biodegradability of PCN used as anti-tumor drug delivery system was discussed, and the possible solutions were analyzed. The prospects of the application of PCN to be used in tumor drugs were discussed at the end of this review. This review provides theoretical basis and examples towards design and synthesis of porous carbon (PC) materials based anti-tumor drug delivery system, which may help the research and development of targeted and controllable tumor treatment.
The stable and reliable red phosphor with high-photon energy emission (620-650 nm) is critical for the fabrication of the phosphor-converted white light-emitting diode (WLED) with low correlated color temperature and high color rendering index. Mn 4+-activated phosphor is an emerging kind of red-emitting phosphor for WLED. Herein, the energy levels transition and photoluminescence characteristics of the Mn 4+ ion were introduced; then, the preparation, crystal structure and luminescent properties of as-far reported seven kinds of Mn 4+-doped oxyfluoride red phosphors (such as Na2WO2F4:Mn 4+) containing d 0, d 10 or s 0 cations were reviewed. Currently, only in quite rare case of oxyfluoride, Mn 4+ was found to exhibit strong R-line emission, with local coordination remaining as either [MnF6] or [MnO6]. The studies on the chemical stability and quantum efficiency of Mn 4+-doped oxyfluoride phosphors are still insufficient. Finally, we prospected the future development of Mn 4+-doped oxyfluoride phosphor.
Dynamic mechanical analysis (DMA) has the advantage of high sensitivity, excellent cooling system, flexible rotation testing part, multiple deformation mode, and continuous frequency and temperature scanning mode. DMA is able to characterize the strain response under alternating stress, creep, stress relaxation, and thermomechanical properties, which has application in the investigation of plastic, thermoset, composite, high elastomer, coating, alloy and ceramic. This paper briefly introduced the fundamental and method about DMA, the application of DMA in the investigation of ferroelectric-paraelectric phase transformation, low frequency relaxation, ferroelectric fatigue, and ferroelectric composite damping. In the measurement of relaxation behavior of PZT ceramics and single crystals, and BaTiO3 ceramics, DMA tended to be more sensitive than dielectric characterization especially in the low frequency range. DMA has been one of the critical instruments for ferroelecric investigation.
Chromogenic materials are capable of optical change reversibly in response to physical stimuli (e.g., electric field, temperature, illumination, and atmosphere). Among them, electrochromic materials are expected to be widely used in smart windows, screen displays, multi-functional energy storage devices and other fields due to their characteristics such as large adjustment range, fast response rate, high coloring efficiency and good cycle stability. However, compared with semi-solid-state electrochromic devices that are difficult to package and organic electrochromic materials that are prone to denaturation and failure, inorganic all-solid-state electrochromic materials and devices have better comprehensive application. This paper focuses on the typical inorganic all-solid-state electrochromic materials and devices, presents a brief review on the current preparation methods of each structure layer of electrochromic devices and compares its advantages and disadvantages, introduces in detail the main alternative electrochromic materials and its key performance evaluation index, and explains the principle of several representative electrochromic devices, proposes to use transparent flexible electrodes with both high light transmittance, low surface resistance and excellent bending fold to replace the traditional rigid substrate in order to realize multi-field responsible device application development. Finally, the application prospect of inorganic all-solid-state electrochromic devices is prospected from the perspective of performance bottleneck, process difficulty and industrialization opportunity, which provides reference for the industrialization process of electrochromic devices.
Solid-state cooling technology based on the electrocaloric (EC) effect is attracting increasing attention as an important alternative for traditional cooling systems because of its advantages of high efficiency, environmental friendliness, light weight, low cost, and easy miniaturization. Ferroelectric materials are suitable candidates for EC refrigeration due to their large polarization and entropy change through applying or removing an external electric field. Recently, study on the EC effect of lead-free bulk ceramics has become one of hot topics on ferroelectric community due to the requirements of sustainable development. In this review, we firstly introduce the significant history events in EC research and the basic principles of EC refrigeration. Then, design strategy for achieving a large EC temperature change near room temperature and a wide using range is summarized. Subsequently, we systematically review the research status of EC effect in BaTiO3-based, Bi0.5Na0.5TiO3-based and K0.5Na0.5NbO3-based lead-free bulk ceramics and discuss their advantages as well as challenges. Finally, we propose some prospects for the future work on EC effect in lead-free bulk ceramics.
In recent years, ternary layered carbide/nitride MAX phases and their derived two-dimensional nanolaminates MXenes have attracted extensive attention. The crystal structure of MAX phase is composed of Mn+1Xn unit interleaved with layers of A element. MAX phases combine good properties of metal and ceramic, which makes them promising candidates for high temperature structural materials, friction and wear devices, nuclear structural materials, etc. When etching the A-layer atoms of the MAX phase, the two-dimensional nanolaminates with the composition of Mn+1XnTx (Tx is surface termination), i.e. MXene, is obtained. MXenes have wide range of composition, and tunable physical and chemical properties, which endow them great potential in the applications of energy storage devices, electromagnetic shielding materials, and electronic devices, etc. In this paper, the research progress of MAX phase and MXene was introduced in terms of composition and structure, synthesis methods, and properties and application. Furthermore, the research prospects of this large family of materials were discussed.
Two-dimensional materials have attracted broad interest because of their wide variety of properties. They can be used as photocatalysts and electrocatalysts due to their extremely high specific surface area, and have great potential application in the field of environment and renewable energy. This review focuses on the structure and properties of common two-dimensional materials such as 2D carbides and nitrides (MXenes), g-C3N4 and black phosphorus (BP). Furthermore, the latest research on the modification of two-dimensional materials in the area of photocatalysis and electrocatalysis are discussed and commented. Finally, research prospects for two-dimensional materials in the future are predicted.
Ceramic matrix composites (CMCs) are promising candidates for application in aeroengine, aerospace aircraft thermal protection systems, nuclear power system, and other fields. At present, CMCs are developing from structural bearing materials to multi-functional composites. MAX phases are a group of layered ternary ceramics with excellent plastic deformation capacity, high electrical conductivity, good irradiation resistance and ablation resistance. Besides strengthening and toughening CMCs, the introducing MAX phases into CMCs can effectively improve the anti-irradiation, anti-ablation and electromagnetic interference shielding performance, meeting requirements of multi-functional CMCs. This paper reviewed the progress on MAX phases modified CMCs, design mechanism and application prospect.
Graphitic-like carbon nitride (g-C3N4), one of the most significant two-dimensional layered materials, has attracted worldwide attention in multidisciplinary areas such as photocatalysis, energy conversion and environmental pollution management. Its derivative compounds have also attracted multifarious attention owing to the intrinsic characters of their stable physicochemical properties, low cost and environmentally friendly features. This review focus on the design of high-performance g-C3N4-based nanomaterials and their potential for pollutant elimination in environmental pollution cleanup. Over the past few years, signi?cant advances have been achieved to synthesize g-C3N4 and g-C3N4-based nanomaterials, and their properties have been enhanced and characterized in detail. In this review, recent developments in the synthesis and modification of g-C3N4-based nanomaterials are summarized. The applications in heavy metal ions adsorption from wastewaters are gathered and their underlying reaction mechanisms are discussed. Finally, a summary and outlook are also briefly illustrated.
With the development of wearable flexible electronic technology, the demand for flexible sensor with high sensitivity and wide sensing range is gradually increasing. The application of suitable conductive materials with high electrical conductivity and high flexibility as sensitive materials for sensors is the key to obtain high performance sensors. In recent years, MXene materials have become very promising sensitive materials due to their good conductivity, high flexibility, good hydrophilicity, and controllable synthesis. The types of MXene-based flexible force sensors, microstructure design of sensitive materials, sensing performance, and sensing mechanism analysis have been expound and summarized in this paper.
Phase diagrams, also known as equilibrium phase diagrams, serve as a road map for materials design. However, preparation process of coatings (such as Physical Vapor Deposition, PVD) is generally far from equilibrium and results in metastable phases. Thus, the CALPHAD (Calculation of Phase Diagrams) approach faces a challenge in calculating the metastable phase diagrams for PVD coating materials. Here we summarized the development of the modeling methodology for the metastable phase diagrams, where the model with critical surface diffusion distance established in recent years were highlighted. The CALPHAD approach, first-principles calculations coupled with high-throughput magnetron sputtering experiments were used to model the atomic surface diffusion, while only one key combinatorial experiment was performed to obtain the basic data for the computation, and the calculated metastable phase diagrams were confirmed by further experiments. Therefore, the database of the stable and metastable phase diagrams can be established, which will be used to guide the design of the ceramic coating materials by the relationship of composition, processing, microstructure, and performance. This model can also help to achieve the goal to shorten the time and reduce the costs of materials research and development.
As smart electronic products are increasingly applied in our daily life, there is not only an increasing demand for high-performance photovoltaic power generation devices, but also strong need for in-situ energy storage functions in these devices. The integration of energy generating components and energy storage components into one device has become an attractive challenging technology. The basic idea is that by integration design and engineering the assembly of the photoelectric conversion layer and the energy storage layer into one in-situ energy conversion and storage system could not only offer multiple functions, such as self-powered ability, weak light buffer and portability, but reduce sunlight fluctuation effect on energy output. This review summarizes the research progress in novel in-situ integrative photovoltaic-storage tandem cells, classified by silicon solar cell, sensitized solar cell and perovskite solar cell. Evaluation of methodology, operational principle, construction feature, and performance parameter are also discussed and critically reviewed, and the further development of in-situ integrative photovoltaic-storage tandem cell is also prospected.
In recent years, hexagonal boron nitride (h-BN) two-dimensional (2D) atomic crystal has attracted considerable attention due to its unique structure, novel property and potential applications. The synthesis of high quality h-BN determines how far we can go for property research and practical applications. However, the sizes of h-BN domains obtained by mechanical exfoliation were limited to several micrometers. Transition metal substrates are usually used in the CVD growth of 2D h-BN layers, and thus a transfer process is required for fabricating h-BN-based electronic devices. Therefore, it is strongly desirable to directly synthesize 2D h-BN on dielectric substrates. In this article, we review recent process on the direct growth of h-BN by CVD, MOVPE, PVD on different dielectric substrates, including silicon-based substrates, sapphire, quartz, etc. Several approaches, such as, increasing substrate temperature, oxide-assisted nucleation, and surface nitridation were adopted to directly grow h-BN on dielectric substrates. Besides, we also summarized the main applications of 2D h-BN grown on dielectric substrates.
Silver nanowire transparent conductive film is one of the new indium-free electrode materials. It has attracted increasing attention from academia and industry due to its superior optoelectronic properties and excellent flexibility. It has been employed in a wide variety of applications in displays, touch panels, solar cells, smart heaters, electromagnetic interference shielding, and so on. However, silver nanowire transparent conductive film has a serious stability issue in service, for example, break or spheroidization above 300 ℃ under fulfidation, accelerating the degradation under ultraviolet light, pores for mation or even breakdown due to electromigration. In this review, the degradation phenomena is thoroughly introduced, the degradation mechanisms is analyzed, and the remedy strategy of degradation is discussed.
The structure and electrical properties of Ce 3+-doped intergrowth bismuth layer-structured piezoelectric ceramics Na0.5Bi8.5-xCexTi7O27 (NBT-BIT-xCe, 0≤x≤0.1) prepared by conventional solid-state reaction process were systematically studied. In this study, all the ceramic samples were found to possess a single bismuth layer structure, and with the increase of x content, there is an increasing trend towards the lattice distortion of the sample, while the average grain size decreased. As demonstrated by dielectric spectrum and DSC method, two dielectric anomalies of the samples occur, which corresponds to ferroelectric phase transitions of the ceramics. And Ce 3+doping significantly reduces concentration of oxygen vacancy and dielectric loss in materials, improving piezoelectric constant (d33) of ceramic samples. The resultant ceramics with x=0.06 reached the optimal performance, possessing a d33 up to 27.5 pC/N with the Curie temperature of 658.2 ℃ and tanδ=0.39%.
The electrocaloric (EC) effect is strongly related to interaction of polarization and temperature changes, showing great potential in high-efficient solid state refrigeration. This work focuses on the Pb0.3CaxSr0.7-xTiO3 (PCST(x), x = 0.00, 0.05, 0.10, 0.15) ceramics in which the influence of Ca content on dielectric and ferroelectric property under electric field was studied, and the EC temperature change was calculated through indirect method. Substitution of Ca largely modifies the diffused phase transition behaviors of PCST ceramics, which the diffusion exponent of PCST(0.05) increases with electric field up, indicating a promising wide temperature range of large electrocaloric effect. Thus, the largest adiabatic temperature change (1.71 K) is obtained near the room temperature in PCST(0.05) by indirect method. With an electric field of 8 kV/mm, PCST(0.05) ceramic shows good EC effect in a wide temperature range that the adiabatic temperature change is larger than 1 K from 5 ℃ to 70 ℃.
Co-doping of silicon in zinc gallate spinel persistent luminescent phosphor was adopted to enhance the afterglow properties. Firstly, a series of silicon-chromium co-doping zinc gallate spinel samples were prepared by high temperature solid state reaction method. Phosphor with chemical formula of Zn1+xGa2-2xSixO4:Cr 3+ (x = 0, 0.1, 0.15, 0.2, 0.5, 1) was obtained with the raw materials of ZnO, Ga2O3, SiO2, and Cr2O3. The experimental results show that the introduction of suitable concentration of silicon improves the afterglow performance effectively. The strongest afterglow intensity was obtained for sample with x = 0.2, which is 3 times higher than ZnGa2O4:Cr 3+, and the afterglow duration is up to 24 h. Through further trap distribution analysis, it is shown that the introduction of silicon in the ZnGa2O4 host can regulate the distribution of trap depths. Particularly, besides the antisite defects, the co-doping of silicon can induce the formation of aliovalent substitution defects and interstitial defects, as well as tune the band gap value, thereby achieving the purpose of improving the afterglow performance.
Due to its unique physical and chemical property, diamond is widely used in many fields such as detectors and optoelectronic devices. Many scholars’ attention is drew into single crystal diamond because of its potential to significantly increase the functionality of these devices. Presently, single crystal diamonds grown heteroepitaxially on iridium (Ir) substrates reach the largest size and an excellent growth quality. In this paper, substrates with different structures for nucleation and growth processes of epitaxial diamond are introduced. The mechanisms of diamond nucleation by Bias Enhanced Nucleation (BEN) method and growth undergoing an Epitaxial Lateral Overgrowth (ELO) process are described, including technique of Patterned Nucleation and Growth(PNG). Limitations of current study are pointed out, and the future development of heteroepitaxial theory and experiment are also forecasted in this paper.
As a new solid-state lighting source, the white light-emitting diodes (WLEDs) have a greatly promising application in the field of lighting and display. They have superior advantages of high luminous efficacy, fast response speed and long service life, etc. compared with the existing light sources (incandescent lamps, fluorescent lamps, etc.). At present the WLEDs are commonly fabricated by combination of a blue LED chip and YAG: Ce 3+ yellow-emitting phosphor, and combination of a ultraviolet-near ultraviolet excitation chip and red-green-blue (RGB) emitting color phosphors, compared with the above two phosphors, the single-phase phosphors containing white emission have the advantages of a higher luminous efficacy, color rendering. Meanwhile, the single-phase phosphors may effectively solve the reabsorption problem existing in RGB phosphors. There have been a large number of reports on the research of single-phase phosphors, involving a variety of material systems. According to the principle of luminescence, it can be simply divided into three groups: single ion doped system, multi-ion doped system and other systems which do not rely on rare earth ion to light. This paper reviews the research progress of single-matrix WLEDs phosphors, and points out the problems in their development, and forecasts the future development trend.
Visible laser has been widely used in data storage, optical communication, laser display, laser medical treatment, laser printing, and scientific research. With the development of commercial blue light LD, the direct pumping of rare-earth ions doped laser crystals have attracted a lot of interests. Currently, visible ions mainly concentrat on Pr 3+, Dy 3+, Tb 3+, and Sm 3+. Trivalent praseodymium (Pr 3+) is a famous rare-earth ion with extensive laser transitions in visible region such as blue, green, red and orange light. However, there is still a region in yellow emission which is not covered by Pr 3+. Dy 3+ and Tb 3+ have attracted much attention because of their yellow laser transitions. In addition, Sm 3+ and Eu 3+ are also typical visible rare-earth ions. In this paper, we mainly reviewed properties of rare-earth ions doped laser crystals for visible lasers, especially Pr 3+, Dy 3+, Tb 3+ and Sm 3+-doped YAlO3 (YAP), SrAl12O19 (SRA) crystals. A design criterion for Pr 3+ doped oxide materials was summarized. The crystal growth, structure, thermal properties, polarization spectroscopic and laser characteristics were analyzed in detail.
Graphene, which has two-dimensional carbon single atomic layer, attracts great attention due to its superb mechanical, electrical and thermal properties. In addition to its excellent mechanical properties, a large surface area (about 2600 m 2?g -1) makes it an ideal reinforcement for copper-based composites. However, graphene owns a low density (2.2 g?cm -3), while the density of copper is about 8.9 g?cm -3. The traditional powder metallurgy process is difficult to solve the problem of uniform dispersion of graphene in the copper matrix and the poor bonding strength between graphene and copper due to the huge density difference between copper and graphene. With the in-depth exploration in the issue of graphene/copper interface in recent years, some novel preparation processes and strengthening mechanisms were proposed and demonstrated. This review systematically introduces and compares the recently-developed preparation processes of graphene-reinforced copper composites, also summarizes the mechanism of mechanical enhancement in graphene-reinforced copper matrix composites.
Silicon has the highest theoretical lithium insertion specific capacity, more than ten times the theoretical specific capacity of graphite electrode material, and low delithiation potential, with abundant resources and good rate characteristics, high-energy-density lithium-ion battery silicon-based materials have become hot spots in application fields such as electric vehicles and renewable energy storage systems. However, it will cause powdering and structural collapse of the silicon electrode material due to its large volume expansion effect in the process of delithiation and lithium insertion. In addition, the solid electrolyte interface (SEI) layer on the surface of silicon is repeatedly formed in the electrolyte, which increases the polarization and reduces the coulomb efficiency, eventually leading to deterioration of electrochemical performance. In order to solve the above problems and realize the commercial application of silicon electrodes. This paper systematically summarizes the work to solve the volume effect in charge and discharge process through the selection and structural design of silicon-based materials, and deeply analyzes and discusses the preparation methods, electrochemical properties and corresponding mechanisms of representative silicon-based composite materials, focusing on silicon-carbon composites and SiOx (0<x≤2) based anode materials. Finally, the problems of silicon-based anode materials are analyzed and their prospects are prospected.
Thermoelectric materials are a kind of energy conversion materials, which are extensively used in power generation or refrigeration. The key parameter that measure the performance of thermoelectric materials is the figure of merit ZT value, which requires material excellent electrical transport performance and low thermal conductivity. Standard first principles calculations on thermoelectric materials focus on small samples of materials, which is difficult to conclude general rules and propose new candidates. The Materials Genome Initiative speeds up the discovery and design of materials based on big data and high-throughput computational methods, which is promising in novel material screening. In thermoelectrics, first principles high-throughput calculations play an increasingly important role in the predicting and designing new materials. However, there are some drawbacks in the current high-throughput efforts for thermoelectric material screening, such as the demand of efficient high-throughput algorithms for transport properties, suitable tools for analyzing big data, etc. Solving these challenges strongly determines the efficiency and accuracy of high-throughput applications in thermoelectrics. This review summarizes several high-throughput theoretical methods and cases study on electrical and thermal transport properties in thermoelectric materials, and prospects the future trend of the combination of high-throughput and thermoelectric material research.
High-throughput experiments aimed to promptly obtain the relationship among composition-phase-structure-performance with fewer experiments and screen out optimal material systems with optimized compositions. Up to now, high-throughput experiments are successfully applied in superconducting materials, fluorescent materials and giant magnetoresistance materials. Thermoelectric materials are functional materials that can realize the direct conversion between thermal energy and electrical energy and can be potentially applied in the fields of thermoelectric power generation and waste heat utilization. However, traditional preparation and characterization methods for thermoelectric materials have disadvantages of time consuming and low efficiency. Therefore, it is of great theoretical and practical significance to introduce methods and concepts of high-throughput experiments into development and optimization of new thermoelectric materials. In this paper, we summarize and discuss the existing high-throughput experimental preparation and characterization techniques with great application prospects in thermoelectric materials, including high-throughput sample preparation, composition-structure, and electro-thermal transport properties characterization, and then analyze the advantages and limitations of these high-throughput techniques. We hope to provide a reference for future high-throughput optimization and screening of thermoelectric materials.
With rapid development of sustainable energies and energy conversion technologies, application prospect of thermoelectric (TE) materials in power generation and cooling has received increasing attention. The requirement of improving TE materials with high figure of merit becomes much more important. How to obtain the low lattice thermal conductivity is one of the main concerns in TE materials. In this review, the influences of specific heat, phonon group velocity and relaxation time on the lattice thermal conductivity are discussed, respectively. Several typical features of TE materials with intrinsic low lattice thermal conductivity are introduced, such as strong anharmonicity, weak chemical bonds and complex primitive cells. Introducing multiscale phonon scatterings to reduce the lattice thermal conductivity of known TE materials is also presented and discussed, including but not limited to point defect scattering, dislocation scattering, boundary scattering, resonance scattering and electron-phonon scattering. In addition, some theoretical models of the minimum lattice thermal conductivity are analyzed, which has certain theoretical significance for rapid screening of TE materials with low lattice thermal conductivity. Finally, the efficient ways to obtain the low lattice thermal conductivity for TE property optimization are proposed.
Thermoelectric power generation via Seebeck effect features an unique advantage in converting large amount of distributed and low-grade waste heat into electricity. Thermoelectric materials have become a hot topic of research in the field of new energy materials, guided by the high figure of merit ZT. Although various mid-temperature thermoelectric materials were discovered, the industrial application of these materials, especially in power generation applications, progressed very slowly. The staggering interface technology associated with thermoelectric device restricted the advance of thermoelectric conversion technology. In this review, the bottleneck issues of utilizing Bi2Te3-based devices for power generation were used as an example to illustrate the critical interface technologies. The key issues at designing electrode contact interfaces were summarized, including low contact resistance, high bonding strength, and superior thermal chemical stability at high temperature. The recent progress on the metallization and interfacial barrier layer for typical materials of Bi2Te3, PbTe and CoSb3 were also reviewed.
Here we report a novel surface modified bamboo charcoal/TiO2 (SMBC/TiO2) nanocomposites with high adsorption and photocatalytic property. SMBC were prepared by a wet oxidization method of cheap natural bamboo charcoal (BC) with good absorbent and chemical stabilities. After modification, high density of carboxyl groups were generated on the surface of BC, thus SMBC particles can be easily dispersed in water and have stronger interactions with TiO2 nanoparticles, which ensure SMBC uniformly coated on TiO2. And SMBC/TiO2 nanocomposties have much higher specific surface area than BC/TiO2, which could offer higher adsorption capacity. The saturated adsorption capacity of SMBC/TiO2 is approximately 1.6 times, 12.1 times as great as BC/TiO2 and pure TiO2, respectively. The synergetic effect of adsorption and catalysis endow SMBC/TiO2 composites much higher photocatalytic activity than BC/TiO2 and pure TiO2 for MB degradation, and the rate constant for MB photocatalytic degradation of SMBC/TiO2 was almost 7 times and 6 times as large as BC/TiO2 and pure TiO2, respectively.
Sphere-like hierarchical Y zeolite was synthesized by a “steam-assisted conversion (SAC)” procedure. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, solid-state nuclear magnetic resonance (NMR) spectra, and Fourier transform infrared (IR) spectroscopy. Results observed by SEM displayed that the as-synthesized Y zeolite was sphere-like polycrystalline aggregates composed of primary crystals with size of about 50-300 nm. These results exhibited that some polycrystalline aggregates were hollow Y zeolite spheres. Combined with characterization results of FT-IR, 29Si NMR, SEM, and TEM, a mechanism illustrating formation of the hollow Y zeolite polycrystalline spheres was proposed.
Two dimensional (2D) materials have attracted wide attention due to their ultrathin atomic structure, large specific surface area and quantum confinement effect which are remarkably different from their bulk counterparts. Anisotropic materials are unique among reported 2D materials. Their orientation-dependent physical and chemical properties make it possible to selectively improve the performance of materials. As representative examples, Re-based transition metal dichalcogenides (Re-TMDs) have tunable bandgaps in visible spectrum, extremely weak interlayer coupling, and anisotropic properties in optics and electronics, which make them attractive in the application areas of electronics and optoelectronics. In this riviev, the unique crystal structures and intrinsic properties of the Re-based TMDs semiconductors are introduced firstly, and then the synthetic method is introduced, followed by discussion on the unique physical characterizations and optimized means. Finally, prospects and suggestions are put forward for the preparation and research of ReX2.
With the development of nuclear energy, the long-lived radionuclides are inevitably released into the natural environment during the mine process, fuel manufacture, nuclear power usable and spent fuel management, which are dangerous to human health and environmental pollution. Thereby the efficient elimination of radionuclides is an important parameter which affects the development of nuclear power. In recent years, the metal-organic frameworks (MOFs) have attracted worldwide attention in the adsorption of radionuclides from large volume of aqueous solutions, because of their high chemical stability, abundant functional groups and changeable porous structures. In this review, we mainly summarized the recent works of MOFs in the efficient removal of radionuclides, and to understand the interaction mechanism from batch adsorption experiments, model analysis, advanced spectroscopy analysis, and theoretical calculation. The adsorption capacities of MOFs with other materials were also summarized, and the future research opportunities and challenges are given in the perspective.
The technique for Materials Genetic Initiative (MGI) is the key tool for realizing the demand-oriented design of new materials assisted by the artificial intelligence (AI). Accordingly, the development and application of innovative intelligence algorithms are particularly important. Based on the generalization and analyses of the existing nature-inspired algorithms, this work aims at outlining the suggestion to build the nature-inspired algorithms library (NIAL). The potential route in which inspirations are obtained from varieties of disciplines, was used to produce new algorithms in high-throughput ways is introduced. The general procedure for building algorithm library is elaborated, while its advantages and characteristics are anatomized. Finally, the potential of NIAL in new materials development has been envisioned to enhance the standard for the application of AI including MGI.
All-inorganic cesium lead halide CsPbX3 (X = Cl, Br, I) perovskite materials emerged as a rising star in the area of optoelectronics since 2015, due to its excellent photoelectric properties and environmental stability. Substantial progresses were made in the application of many electronic and optoelectronic devices, which attracted wide attention from the scientific community. This paper mainly reviews the latest research progress of cesium lead halide perovskite based planar heterojunction LED, where the structure and working principle of LED devices are briefly introduced. In addition, the classification and summarization of some optimization strategies for improving luminescence performance and working stability of LED devices are emphatically suggested, and the development trend of stable and efficient inorganic perovskite based planar heterojunction LED is finally prospected.