Synthesis and Modulation of Low-Dimensional Transition Metal Chalcogenide Materials via Atomic Substitution

In recent years,low-dimensional transition metal chalcogenide(TMC)materials have garnered growing research attention due to their superior electronic,optical,and catalytic properties compared to their bulk counterparts.The controllable synthesis and manipulation of these materials are crucial for tailoring their properties and unlocking their full potential in various applications.In this context,the atomic substitution method has emerged as a favorable approach.It involves the replacement of specific atoms within TMC structures with other elements and possesses the capability to regulate the compositions finely,crystal structures,and inherent properties of the resulting materials.In this review,we present a comprehensive overview on various strategies of atomic substitution employed in the synthesis of zero-dimensional,one-dimensional and two-dimensional TMC materials.The effects of substituting elements,substitution ratios,and substitution positions on the structures and morphologies of resulting material are discussed.The enhanced electrocatalytic performance and photovoltaic properties of the obtained materials are also provided,emphasizing the role of atomic substitution in achieving these advancements.Finally,challenges and future prospects in the field of atomic substitution for fabricating low-dimensional TMC materials are summarized.

Multiple structure graphite stabilized stearic acid as composite phase change materials for thermal energy storage

This paper used 3 types of graphite with different physical structures as the porous matrix to prepare composite phase change materials(PCMs),and investigated their photo-thermal conversion performance and application in battery thermal management.Multiple structure graphite minerals,including microcrystalline graphite(MG),scale graphite(SG),and expanded graphite(EG)were used as porous matrix,while stearic acid(SA)acts as the phase change material.The vacuum impregnation method was applied to prepare SA/MG,SA/SG,SA/EG,and SA/MG1,and SA/EG1was/were prepared by the ethyl alcohol method.Results show that the thermal conductivities of all composite phase change materials were 10.82 to 22.06 times higher than that of the pure SA.Thermogravimetric(TG)analysis showed that the loadages of SA were 43.61%,18.74%,and 92.66%for SA/MG,SA/SG,and SA/EG respectively.The load rates of SA were 18.98%and 18.88%for SA/MG1 and SA/EG1,respectively.For the 3 types of graphite materials of different dimensions,the BET(Brunauer,Emmett,and Teller)surface area determines the maximum load of SA.The Fourier-transform infrared(FTIR)and X-ray diffraction(XRD)results indicated that there was good compatibility between the SA and the supports.The SA/EG1 has better thermophysical properties in heat energy storage and release process.The thermal infrared images show that SA/EG1 has higher sensitivity to the temperature changes.SA/EG1 has better photo-heat conversion performance than SA/SG and SA/MG1 attributed to the multilayer structure of EG.SA/EG has better thermal management performance in the Li-ion batteries discharge process.

GALVANIC CORROSION BETWEEN GRAPHITE EPOXY COMPOSITE MATERIALS AND LY12CZ ALUMINUM ALLOY

The electrochemical approach was used to show the nature of the galvanic corrosion when graphite epoxy composite materials(GECM)were coupled to LY12CZ aluminum alloy. An open circuit potential difference of one volt was obtained in 3.5% NaCl solution between GECM and LY12CZ. Corrosion current data (zero impedance technique) indicated that there was serious corrosion at GECM/LY12CZ couple.When GECM/LY12CZ couples were exposed to ASTM salt spray and alternate immersion condition, fiber glass cloth and H06-2 epoxy primer paint were effective methods for preventing galvanic corrosion.The slow strain rate test (SSRT) showed that GECM increased the LY12CZ stress corrosion crack growth rate.

Low-dimensional materials for photovoltaic application

The photovoltaic(PV)market is currently dominated by silicon based solar cells.However technological diversification is essential to promote competition,which is the driving force for technological growth.Historically,the choice of PV materials has been limited to the three-dimensional(3D)compounds with a high crystal symmetry and direct band gap.However,to meet the strict demands for sustainable PV applications,material space has been expanded beyond 3D compounds.In this perspective we discuss the potential of low-dimensional materials(2D,1D)for application in PVs.We present unique features of low-dimensional materials in context of their suitability in the solar cells.The band gap,absorption,carrier dynamics,mobility,defects,surface states and growth kinetics are discussed and compared to 3D counterparts,providing a comprehensive view of prospects of low-dimensional materials.Structural dimensionality leads to a highly anisotropic carrier transport,complex defect chemistry and peculiar growth dynamics.By providing fundamental insights into these challenges we aim to deepen the understanding of low-dimensional materials and expand the scope of their application.Finally,we discuss the current research status and development trend of solar cell devices made of low-dimensional materials.

Negative photoconductivity in low-dimensional materials

In recent years,low-dimensional materials have received extensive attention in the field of electronics and optoelectronics.Among them,photoelectric devices based on photoconductive effect in low-dimensional materials have a broad development space.In contrast to positive photoconductivity,negative photoconductivity(NPC)refers to a phenomenon that the conductivity decreases under illumination.It has novel application prospects in the field of optoelectronics,memory,and gas detection,etc.In this paper,we review reports about the NPC effect in low-dimensional materials and systematically summarize the mechanisms to form the NPC effect in existing low-dimensional materials.

Influence of graphite content on sliding wear characteristics of CNTs-Ag-G electrical contact materials

CNTs-Ag-G electrical contact composite material was prepared by means of powder metallurgical method. The influence of the graphite content on sliding wear characteristics of electrical contact levels was examined. In experiments, CNTs content was retained as 1% (mass fraction), and graphite was added at content levels of 8%, 10%, 13%, 15% and 18%, respectively. The results indicate that with the increase of graphite content, the contact resistance of electrical contacts is enhanced to a certain level then remains constant. Friction coefficient decreases gradually with the increase of graphite content. Wear mass loss decreases to the minimum value then increases. With the small content of graphite, the adhesive wear is hindered, which leads to the decrease of wear mass loss, while excessive graphite brings much more worn debris, resulting in the increase of mass loss. It is concluded that wear mass loss reaches the minimum value when the graphite mass fraction is about 13%. Compared with conventional Ag-G contact material, the wear mass loss of CNTs-Ag-G composite is much less due to the obvious increase of hardness and electrical conductivity, decline of friction surface temperature and inhibition of adhesive wear between composites and slip rings.

Heat transport in low-dimensional materials: A review and perspective

Heat transport is a key energetic process in materials and devices. The reduced sample size, low dimension of the problem and the rich spectrum of material imperfections introduce fruitful phenomena at nanoscale. In this review, we summarize recent progresses in the understanding of heat transport process in low-dimensional materials, with focus on the roles of defects, disorder, interfaces, and the quantum- mechanical effect. New physics uncovered from computational simulations, experimental studies, and predictable models will be reviewed, followed by a perspective on open challenges.

Tin oxide-graphite composite for lithium storage material in lithium-ion batteries

A SnO-graphite composite material, which can deliver high capacities and good cycling stability compared with unsupported SnO, was described. This material prepared via chemical co-precipitation reaction in the presence of graphite consists of high dispersion of SnO with a size of about several hundred nanometers in the graphite. The phase structure was analyzed by X-ray diffraction (XRD). The morphology and the element distribution were examined by scanning electron microscopy (SEM) equipped with energy spectrum. The results show that the SnO-graphite composites produced by slowly hydrolysis have higher rechargeable capacities than pure graphite and better cycling performance than SnO.

The influence of composition of asphaltenes of different genesis on the properties of carbon materials manufactured from them by plasma processing

The results of experimental studies of carbon materials, which are formed in the plasma of a direct current (DC) arc discharge initiated in open air from the asphaltenes of different origins, extracted from the natural asphaltite and from the oil of the Sredne-Ugutskoye Oilfield, are presented. The influence of the initial asphaltene composition on the composition and properties of the resulting carbon materials is analyzed. The initial asphaltenes and the samples of the carbon materials are characterized by the methods of X-ray diffraction, differential thermal analysis, X-ray fluorescence analysis, IR-Fourier spectroscopy, laser diffraction, transmission and scanning electron microscopy. The changes in the composition and structure of the asphaltenes are determined before and after their plasma treatment and the hypotheses are put forward concerning the chemical processes causing the changes in the molecular structure of the samples. As a result of plasma treatment of asphaltenes (100 A, 30 s), it was shown that graphitization occurs, as well as oxidation, and a decrease in sulfur content. Moreover, nanotubes and nano-onions have been detected using electron microscopy. Petroleum asphaltenes after plasma treatment give a less thermostable carbon material, but with a lower content of heteroatoms, and with a large amount of sulfur in the composition of sulfoxide structural fragments. This method is shown to be a promising technology for processing the petroleum feedstock enriched with heavy asphaltene components for the manufacture of carbon nanomaterials: nanotubes, nano-onions and polyhedral graphite.

Optical and electrical anisotropy regulation engineering of low-dimensional materials toward polarized detection and imaging applications

Polarized-sensitive image sensors are a kind of photodetector with great development potential due to their enhanced ability to detect and identify the target objects from the aspect of spatial,spectral and polarized information.Recently,low-dimensional anisotropic materials with inherent anisotropic properties,ultrathin thickness,tunable bandgap and feasible integration with complementary metal oxide semiconductor(CMOS)fabrication processes have attracted great interest for their facilitation of polarized photodetector devices miniaturization.Maximizing the polarized detection performance of low-dimensional materials to satisfy realistic needs stimulates the exploration of modulation of anisotropic properties.In this review,we comprehensively introduce the latest research progress in modulating the optical and optoelectronic anisotropy characteristics of low-dimensional materials.The strategy of anisotropy regulation through crystal structure engineering and coupling system is discussed emphatically.Then,the latest progress in image recognition applications using anisotropic low-dimensional materials is reviewed in detail.Finally,we summarize the challenge and propose future opportunities in the practical application of polarized-sensitive imaging photodetectors based on low-dimensional anisotropic materials.

Hybrid 2D/3D Graphitic Carbon Nitride-Based High-Temperature Position-Sensitive Detector

Ultraviolet position-sensitive detectors(PSDs)are expected to undergo harsh environments,such as high temperatures,for a wide variety of applications in military,civilian,and aerospace.However,no report on relevant PSDs operating at high temperatures can be found up to now.Herein,we design a new 2D/3D graphitic carbon nitride(g-C_(3)N_(4))/gallium nitride(GaN)hybrid heterojunction to construct the ultraviolet high-temperature-resistant PSD.The g-C_(3)N_(4)/GaN PSD exhibits a high position sensitivity of 355 mV mm^(-1),a rise/fall response time of 1.7/2.3 ms,and a nonlinearity of 0.5%at room temperature.The ultralow formation energy of-0.917 eV atom^(-1)has been obtained via the thermodynamic phase stability calculations,which endows g-C_(3)N_(4)with robust stability against heat.By merits of the strong built-in electric field of the 2D/3D hybrid heterojunction and robust thermo-stability of g-C_(3)N_(4),the g-C_(3)N_(4)/GaN PSD delivers an excellent position sensitivity and angle detection nonlinearity of 315 mV mm^(-1)and 1.4%,respectively,with high repeatability at a high temperature up to 700 K,outperforming most of the other counterparts and even commercial silicon-based devices.This work unveils the high-temperature PSD,and pioneers a new path to constructing g-C_(3)N_(4)-based harsh-environment-tolerant optoelectronic devices.

Electrochemical Performance of SnO_2/ Graphite Nanocomposites as Anode Material for Lithium-Ion Batteries

SnO2/ graphite nanocomposites with different SnO2 contents were successfully prepared by a co-precipitation method.The nanocomposites, used as the anode material for lithium-ion batteries( LIBs),were characterized by X-ray diffraction( XRD),thermogravimetric analysis( TGA), and transmission electron microscopy( TEM). The SnO2 particles had the average size of about 15 nm and their distribution on graphite matrix much depended on the contents of SnO2 in the nanocomposites. The galvanostatic charge-discharge cycles were used to investigate the effects of SnO2 contents on the electrochemical performance of these composites. The results show that the initial specific capacities increase with the SnO2 contents. However,the cyclic stabilities are determined by the distribution of SnO2 particles in composites. For55% by weight SnO2/ graphite composites, the initial specific capacity is 740 m Ah g- 1and 70% of the initial specific capacity( 518 m Ah·g- 1) can still be retained after 50 charge-discharge cycles.

Preparation and Properties of 1-octadecanol/1,3:2,4-di-(3,4-dimethyl) Benzylidene Sorbitol/Expanded Graphite Form-stable Composite Phase Change Material

A 1-octadecanol（OD）/1,3:2,4-di-（3,4-dimethyl） benzylidene sorbitol（DMDBS）/expander graphite（EG） composite was prepared as a form-stable phase change material（PCM） by vacuum melting method. The results of field emission-scanning electron microscopy（FE-SEM） showed that 1-octadecanol was restricted in the three-dimensional network formed by DMDBS and the honeycomb network formed by EG. X-ray diffraction（XRD） and Fourier transform infrared spectroscopy（FT-IR） results showed that no chemical reaction occurred among the components of composite PCM in the preparation process. The gel-to-sol transition temperature of the composite PCMs containing DMDBS was much higher than the melting point of pure 1-octadecanol. The improvements in preventing leakage and thermal stability limits were mainly attributed to the synergistic effect of the three-dimensional network formed by DMDBS and the honeycomb network formed by EG. Differential scanning calorimeter（DSC） was used to determine the latent heat and phase change temperature of the composite PCMs. During melting and freezing process the latent heat values of the PCM with the composition of 91% OD/3% DMDBS/6% EG were 214.9 and 185.9 kJ·kg-1, respectively. Its degree of supercooling was only 0.1 ℃. Thermal constant analyzer results showed that its thermal conductivity（κ） changed up to roughly 10 times over that of OD/DMDBS matrix.

Formation of NiFe_2O_4/Expanded Graphite Nanocomposites with Superior Lithium Storage Properties

A Ni Fe_2O_4/expanded graphite(Ni Fe_2O_4/EG)nanocomposite was prepared via a simple and inexpensive synthesis method. Its lithium storage properties were studied with the goal of applying it as an anode in a lithium-ion battery. The obtained nanocomposite exhibited a good cycle performance, with a capacity of 601 m Ah g^(-1)at a current of 1 A g^(-1)after 800 cycles. This good performance may beattributed to the enhanced electrical conductivity and layered structure of the EG. Its high mechanical strength could postpone the disintegration of the nanocomposite structure,efficiently accommodate volume changes in the Ni Fe_2O_4-based anodes, and alleviate aggregation of Ni Fe_2O_4 nanoparticles.

Investigation of nanocrystalline structure in selected carbonaceous materials

The structural parameters of nine Indian coals were determined by X-ray diffraction （XRD） and Kaman spectroscopy. The study revealed that the coals contain crystalline carbon of turbostratic structure with amorphous carbon. The stacking height （Lc） and interlayer spacing （rico2） of the crystallite structure of the coals ranged from 1.986 to 2.373 nm and from 0.334 to 0.340 nm, respectively. The degree of graphitization was calculated to range from 42% to 99%, thereby confirming the ordering of the carbon layers with the increase in coal rank. An exponential correlation was observed among the aromaticity （fa）, the lateral size （La）, and the rank （I20/I26）, suggesting that the coal crystallites are nanocrystalline in nature. A very strong correlation was observed between the structural parameters （fa, d002, Lc, the H/C ratio, and I20/I26）, the volatile matter content, and the elemental carbon content, indicating the structures of coals are controlled by the degree of contact metamorphism. The Raman spectra exhibited two prominent bands： the graphitic band （G） and the fn＇st-order characteristic defect band （D）. The deconvolufion resulted in five peaks： G, D1, D2, D3, and D4. The intense D1 band, which appeared at -1350 cm^-1, corresponds to a lattice vibration mode with Alg symmetry. The D2 mode, which appeared at -1610 cm^-1, arises from the structural disorder as a shoulder on the G band.

Technology for recycling and regenerating graphite from spent lithium-ion batteries

With the annual increase in the amount of lithium-ion batteries(LIBs),the development of spent LIBs recycling technology has gradually attracted attention.Graphite is one of the most critical materials for LIBs,which is listed as a key energy source by many developed countries.However,it was neglected in spent LIBs recycling,leading to pollution of the environment and waste of resources.In this paper,the latest research progress for recycling of graphite from spent LIBs was summarized.Especially,the processes of pretreatment,graphite enrichment and purification,and materials regeneration for graphite recovery are introduced in details.Finally,the problems and opportunities of graphite recycling are raised.

Insight into the microstructural evolution of anthracite during carbonization-graphitization process from the perspective of materialization

Materialization of coal is one of effective and clean pathways for its utilization. The microstructures of coal-based carbon materials have an important influence on their functional applications. Herein, the microstructural evolution of anthracite in the temperature range of 1000–2800 ℃ was systematically investigated to provide a guidance for the microstructural regulation of coal-based carbon materials.The results indicate that the microstructure of anthracite undergoes an important change during carbonization-graphitization process. As the temperature increases, aromatic layers in anthracite gradually transform into disordered graphite microcrystals and further grow into ordered graphite microcrystals, and then ordered graphite microcrystals are laterally linked to form pseudo-graphite phase and eventually transformed into highly ordered graphite-like sheets. In particular, 2000–2200 ℃ is a critical temperature region for the qualitative change of ordered graphite crystallites to pseudo-graphite phase,in which the relevant structural parameters including stacking height, crystallite lateral size and graphitization degree show a rapid increase. Moreover, both aromaticity and graphitization degree have a linear positive correlation with carbonization-graphitization temperature in a specific temperature range.Besides, after initial carbonization, some defect structures in anthracite such as aliphatic carbon and oxygen-containing functional groups are released in the form of gaseous low-molecular volatiles along with an increased pore structure, and the intermediates derived from minerals could facilitate the conversion of sp^(3) amorphous carbon to sp^(2) graphitic carbon. This work provides a valuable reference for the rational design of microstructure of coal-based carbon materials.

Facile synthesis of MoS_2/graphite intercalated composite with enhanced electrochemical performance for sodium ion battery

MoS2 is a promising anode material for sodium ion batteries owing to its two-dimensional layered structure and high specific capacity. But it still exhibits a poor cycle stability and limited rate capability for Na＋ storage because of its poor electrical conductivity and structural instability. In this work, MoS2/graphite composite is fabricated by mechanically delaminated and restacked MoS2 and graphite to form two-dimensional composite layers. The graphite sheets will improve electrical conductivity and prevent the aggregation as well as structure collapse of the MoS2 layers during charge-discharge process. The MoS2/graphite composite exhibits excellent Na＋ storage properties. It delivers a high discharge specific capacity of 358.2 mAh/g at a current density of 100 mA]g in the first discharge process and with capacity retention of 68.1% after 800 cycles （retains 244 mAh/g）. The average discharge specific capacities retain 250.9 and 225.4 mAh/g corresponding to the current densities of 100 and 1000 mA]g, showing excellent rate capability. The improved electrochemical performance is attributed to the improved electrical conductivity and structural stability after composition of graphite sheets. The study demonstrates a new research strategy for improving sodium ion storage properties of Mo52.

Piezoresistivity of Carbon Fiber Graphite Cement-based Composites with CCCW

The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites（CFGCC） with carbon fiber content（1% by the weight of cement）,graphite powder contents （0%-50% by the weight of cement） and CCCW（cementitious capillary crystalline waterproofing materials,4% by the weight of cement） were studied.The experimental results showed that the relationship between the resistivity of CFGCC and the concentration of graphite powders had typical features of percolation phenomena.The percolation threshold was about 20%.A clear piezoresistive effect was observed in CFGCC with 1wt% of carbon fibers,20wt% or 30wt% of graphite powders under uniaxial compressive tests,indicating that this type of smart composites was a promising candidate for strain sensing.The measured gage factor （defined as the fractional change in resistance per unit strain） of CFGCC with graphite content of 20wt% and 30wt% were 37 and 22,respectively.With the addition of CCCW,the mechanical properties of CFGCC were improved,which benefited CFGCC piezoresistivity of stability.

Multidimensional(0D-3D)functional nanocarbon:Promising material to strengthen the photocatalytic activity of graphitic carbon nitride

As a prospective visible-light-responsive photochemical material,graphitic carbon nitride(g-C_(3)N_(4))has become a burgeoning research hot topics and aroused a wide interest as a metal-free semiconductor in the area of energy utilization and conversion,environmental protection due to its unique properties,such as facile synthesis,high physicochemical stability,excellent electronic band structure,and sustainability.However,the shortcomings of high recombination rate of charge carriers,relatively low electrical conductivity and visible light absorption impede its practical application.Various strategies,such as surface photosensitization,heteroatom deposition,semiconductor hybridization,etc.,have been applied to overcome the barriers.Among all the strategies,functional nanocarbon materials with various dimensions(0D~3D)attract much attention as modifiers of g-C_(3)N_(4)due to their unique electronic properties,optical properties,and easy functionalization.More importantly,the properties of these functional nanocarbon materials can be tuned by various dimensions and thus there will be a way to overcome the defects of g-C_(3)N_(4)by choosing different dimensional carbon materials.Distinguishing from some present reviews,this review starts with the fundamental physicochemical characteristics of g-C_(3)N_(4)materials,followed by analyzing the advantages of functional nanocarbon materials modifying gC_(3)N_(4).Then,we present a systematic introduction to various dimensional carbon materials.The design philosophy of carbon/g-C_(3)N_(4)composites and the advanced studies are exemplified in detail.Finally,a nichetargeting summary and outlook on the major challenges,opportunities for future research in high-powered carbon/g-C_(3)N_(4)composites was proposed.