Multi-phase nitrides bonded silicon carbide lintel blocks were prepared using industrial SiC(SiC≥98 mass%,3-0.5,≤0.5 and≤0.044 mm),Si powder(Si≥98 mass%,≤0.044 mm),and SiO2 micropowder(SiO2≥96 mass%,d50=0.15 pm)...Multi-phase nitrides bonded silicon carbide lintel blocks were prepared using industrial SiC(SiC≥98 mass%,3-0.5,≤0.5 and≤0.044 mm),Si powder(Si≥98 mass%,≤0.044 mm),and SiO2 micropowder(SiO2≥96 mass%,d50=0.15 pm)as raw materials,and calcium lignosulfonate as the additive,batching,mixing,and molding on a vibration pressure molding machine,drying and then firing at 1420℃for 10 h in high-purity N2.The apparent porosity,the bulk density,the cold modulus of rupture,the hot modulus of rupture,and the linear expansion coefficient of the samples were tested.The phase composition and the microstructure of the samples at different nitriding depths(50,100,and 150 mm)were analyzed by XRD and SEM.The field application effects of the blocks were studied.The results show that:(1)the multi-phase nitrides bonded silicon carbide refractories can dynamically adjust their own phase composition and minimize structural and thermal stresses,improving the service life of key parts of dry quenching furnaces;(2)calcium lignosulfonate can improve the nitriding micro-environment of multi-phase nitrides bonded silicon carbide lintel blocks,successfully increasing the effective nitriding thickness of the blocks to 300 mm;(3)Sinosteel LI RR provides a unique concept in the design of materials and block types as well as the stable and scientific overall structure,promoting the industrialization process of dry quenching furnaces with long service life in China.展开更多
Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunc...Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunctional electrocatalysts for air-cathode oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)processes,the practical application of rechargeable ZABs is seriously hindered.In the effort of developing high active,stable and cost-effective electrocatalysts,transition metal nitrides(TMNs)have been regarded as the candidates due to their high conductivity,strong corrosion-resistance,and bifunctional catalytic performance.In this paper,the research progress in TMNs-based material as ORR and OER electrocatalysts for ZABs is discussed with respect to their synthesis,chemical/physical characterization,and performance validation/optimization.The surface/interface nanoengineering strategies such as defect engineering,support binding,heteroatom introduction,crystal plane orientation,interface construction and small size effect,the physical and chemical properties of TMNs-based electrocatalysts are emphasized with respect to their structures/morphologies,composition,electrical conductivity,specific surface area,chemical stability and corrosion resistance.The challenges of TMNs-based materials as bifunctional air-cathode electrocatalysts in practical application are evaluated,and numerous research guidelines to solve these problems are put forward for facilitating further research and development.展开更多
Ⅲ-nitride semiconductor materials have excellent optoelectronic properties,mechanical properties,and chemical stability,which have important applications in the field of optoelectronics and microelectronics.Two-dimen...Ⅲ-nitride semiconductor materials have excellent optoelectronic properties,mechanical properties,and chemical stability,which have important applications in the field of optoelectronics and microelectronics.Two-dimensional(2D)materials have been widely focused in recent years due to their peculiar properties.With the property of weak bonding between layers of 2D materials,the growth ofⅢ-nitrides on 2D materials has been proposed to solve the mismatch problem caused by heterogeneous epitaxy and to develop substrate stripping techniques to obtain high-quality,low-cost nitride materials for high-quality nitride devices and their extension in the field of flexible devices.In this progress report,the main methods for the preparation of 2D materials,and the recent progress and applications of different techniques for the growth ofⅢ-nitrides based on 2D materials are reviewed.展开更多
Titanium(Ti)nitrides were in situ grown on Ti6Al4V alloy(TA)using a glow discharge plasma nitriding(GDPN).The morphology,chemical composition,phase and mechanical property of the obtained nitrided TA were analyzed usi...Titanium(Ti)nitrides were in situ grown on Ti6Al4V alloy(TA)using a glow discharge plasma nitriding(GDPN).The morphology,chemical composition,phase and mechanical property of the obtained nitrided TA were analyzed using a scanning electron microscope(SEM),energy dispersive spectroscope(EDS),X-ray diffraction(XRD),and nanoindentation tester,respectively.The tribological performances of un-nitrided and nitrided TAs were evaluated using a ball-on-plate wear tester,and the wear mechanism was also discussed in detail.The results show that the nitrided layer with the compound and diffusion layers is formed on the nitrided TA,which is composed of δ-TiN and a-Ti phases.The nanohardness and elastic modulus of nitrided TA are 6.05 and 143.13 GPa,respectively,higher than those of un-nitrided TA.The friction reduction and anti-wear performances of nitrided TA are better than those of un-nitrided TA,and the wear mechanism is primary abrasive wear,accompanying with adhesive wear,which is attributed to the formation of Ti nitrides with the high nanohardness and elastic modulus.展开更多
A TEM investigation was made on the morphology,orientation relationship and habit plane ofthree alloy nitrides,namely CrN,VN and Mo<sub>2</sub>N simultaneously formed within thediffussional nitrided layers...A TEM investigation was made on the morphology,orientation relationship and habit plane ofthree alloy nitrides,namely CrN,VN and Mo<sub>2</sub>N simultaneously formed within thediffussional nitrided layers in an H13 steel nitrided at 580℃.It was.found that the nitrideswere precipitated by continuous clustering and subsequent ordering of both interstitial（N）andsubstitutional（Cr,V,Mo）solutes on {001} habit plane,and that the observed morphologyand crystallography of the nitrides were in good agreement with the predictions from theinvariant line stain model proposed for precipitation transformations.展开更多
Ultrafine particles of Al_(2)O_(3),MoO_(3),TiO_(2)and SiO_(2)were prepared by irradiate high power laser beams on material surface in O_(2)atmosphere as well as TiN in N_(2) atmosphere.X-ray diffractometer analysis id...Ultrafine particles of Al_(2)O_(3),MoO_(3),TiO_(2)and SiO_(2)were prepared by irradiate high power laser beams on material surface in O_(2)atmosphere as well as TiN in N_(2) atmosphere.X-ray diffractometer analysis identified that all oxides and nitrides powder obtained are crystalline except SiO_(2) particles which have amorphous struc-ture.展开更多
Large-scale deployment of Internet of Things (IoT),a revolutionary innovation for a better world,is hampered by the limitation of energy self-sufficiency.Constructing transition metal nitride (TMN)-based micro-superca...Large-scale deployment of Internet of Things (IoT),a revolutionary innovation for a better world,is hampered by the limitation of energy self-sufficiency.Constructing transition metal nitride (TMN)-based micro-supercapacitors is a possible solution by taking advantage of the high conductivity,large specific capacitance,and large tap density of the materials.However,the pseudocapacitive storage mechanism of TMNs is still unclear consequently impeding the design of microdevices.Herein,the functions and mechanism of TMNs with different metal oxynitride (TMNO_(x)) concentrations in pseudocapacitive electrodes are investigated systematically by in situ Raman scattering,ex situ X-ray photoelectron spectroscopy,as well as ion isolation and substitution cyclic voltammetry.It is found that the specific capacitances of TMNs depend on the TMNO_(x) concentrations and the N–M–O site is responsible for the large pseudocapacitance via the Faradic reaction between TMNO_(x) and OH^(-).Our study elucidates the mechanism pertaining to pseudocapacitive charge storage of TMNs and provides insights into the design and optimization of TMNO_(x) as well as other electrode materials for pseudocapacitors.展开更多
Three transition metal-like facet centered cubic structured transition metal nitrides,γ-Mo_(2)N,β-W_(2)N andδ-NbN,are synthesized and applied in the reaction of CO_(2)hydrogenation to CO.Among the three nitride cat...Three transition metal-like facet centered cubic structured transition metal nitrides,γ-Mo_(2)N,β-W_(2)N andδ-NbN,are synthesized and applied in the reaction of CO_(2)hydrogenation to CO.Among the three nitride catalysts,theγ-Mo_(2)N exhibits superior activity to target product CO,which is 4.6 and 76 times higher than the other two counterparts ofβ-W_(2)N andδ-NbN at 600℃,respectively.Additionally,γ-Mo_(2)N exhibits excellent stability on both cyclic heating-cooling and high space velocity steady state operation.The deactivation degree of cyclic heating-cooling evaluation after 5 cycles and long-term stability performance at 773 and 873 K in 50 h are all less than 10%.In-situ XRD and kinetic studies suggest that theγ-Mo_(2)N itself is able to activate both of the reactants CO_(2)and H_(2).Below 400℃,the reaction mainly occurs at the surface ofγ-Mo_(2)N catalyst.CO_(2)and H_(2)competitively adsorbe on the surface of catalyst and CO_(2)is the relatively stronger surface adsorbate.At a higher temperature,the interstitial vacancies of theγ-Mo_(2)N can be reversibly filled with the oxygen from CO_(2)dissociation.Both of the surface and bulk phase sites ofγ-Mo_(2)N participate in the high temperature CO_(2)hydrogenation pathway.展开更多
The samples of microdiamond as an inclusion of Os Ir alloy, coesite, stishovite, high pressure form of Tio2, high pressure nitrides associated with SiC along with boron carbide, have been reported in the past from the...The samples of microdiamond as an inclusion of Os Ir alloy, coesite, stishovite, high pressure form of Tio2, high pressure nitrides associated with SiC along with boron carbide, have been reported in the past from the placer deposits of Luobasa ophiolite of Yarlung Zangbo region of Tibet. For the formation of these ultra high findings, pressure in the range of 4 to 9 Gpa and temperature in the range of 700° C - 1300° C is required. Thus these minerals can either be incorporated into the chromitite in the deep upper mantle or they have an impact origin. In absence of impact crater, Prof. Fang and others have favored the mantle origin but for the formation of nitrides in the deep mantle, the source of N is not clear. However, the event of comet impact provides better explanation for the formation process. It also simplifies the explanation of coexistence of most of these minerals in a single crystal with the shallow origin and the perfect preservation of the coesite as consequence of rapid cooling after the shock metamorphism.展开更多
A series of carbon nitride(CN)materials represented by graphitic carbon nitride(g-C3N4)have been widely used in bioimaging,biosensing,and other fields in recent years due to their nontoxicity,low cost,and high lumines...A series of carbon nitride(CN)materials represented by graphitic carbon nitride(g-C3N4)have been widely used in bioimaging,biosensing,and other fields in recent years due to their nontoxicity,low cost,and high luminescent quantum efficiency.What is more attractive is that the luminescent properties such as wavelength and intensity can be regulated by controlling the structure at the molecular level.Hence,it is time to summarize the related research on CN structural evolution and make a prospect on future developments.In this review,we first summarize the research history and multiple structural evolution of CN.Then,the progress of improving the luminescence performance of CN through structural evolution was discussed.Significantly,the relationship between CN structure evolution and energy conversion in the forms of photoluminescence,chemiluminescence,and electrochemiluminescence was reviewed.Finally,key challenges and opportunities such as nanoscale dispersion strategy,luminous efficiency improving methods,standardization evaluation,and macroscopic preparation of CN are highlighted.展开更多
Artificial photocatalysis offers a promising strategy to sustainably produce hydrogen peroxide(H_(2)O_(2))that is one of the most valuable multifunctional chemicals.Among various photocatalysts,polymeric carbon nitrid...Artificial photocatalysis offers a promising strategy to sustainably produce hydrogen peroxide(H_(2)O_(2))that is one of the most valuable multifunctional chemicals.Among various photocatalysts,polymeric carbon nitride(pCN)has drawn continuous attention in non-sacrificial H_(2)O_(2)production.However,the poor activ-ity of half reactions,ie.,the oxygen reduction reaction(ORR)and water oxidation reaction(WOR),greatly restricts the efficiency of photocatalytic H_(2)O_(2) production.In this highlight,we discuss the significant ad-vances in molecular engineering of carbon nitrides for H_(2)O_(2) photosynthesis and the importance of the deep understanding of the photocatalysis process for rational design and reaction pathways of organic conjugated polymers to address the growing H_(2)O_(2)demand.Furthermore,we summarize the emerging applications of photocatalytic H_(2)O_(2)productions beyond energy and environment.展开更多
The development of non-precious,acid-stable,oxygen reduction reaction(ORR)electrocatalysts can significantly aid the commercialization of proton exchange membrane fuel cells(PEMFCs).We report a survey of the ORR elect...The development of non-precious,acid-stable,oxygen reduction reaction(ORR)electrocatalysts can significantly aid the commercialization of proton exchange membrane fuel cells(PEMFCs).We report a survey of the ORR electrocatalysis on 3d metal substituted(M=Mn,Fe,Co)molybdenum and tungsten nitrides in acidic environments.We find that molybdate catalysts are more active than tungstates,with the specific activity depending on the chemistry of the substituted 3d metal.In both families,more electronegative 3d metals led to higher ORR activity(i.e.,Co>Fe>Mn).We attribute this result to the ability of the more electro negative 3d metal to withdraw electro ns from the Mo-or W-based active sites,effectively oxidizing the metal centers of the catalysts.Based on our observation,future nitride ORR electrocatalysts can be further optimized by oxidizing the Mo sites further by,for example,addi ng eve n more electro negative dopa nt metals or in corporati ng anion vaca ncies.展开更多
Inorganic semiconductor plays a key role for today’s technological progress [1–4]. Comparing with other organic semiconductors [5,6] and two-dimensional(2D) metal sulfides [7–10], Ⅲ-nitrides as direct bandgap semi...Inorganic semiconductor plays a key role for today’s technological progress [1–4]. Comparing with other organic semiconductors [5,6] and two-dimensional(2D) metal sulfides [7–10], Ⅲ-nitrides as direct bandgap semiconductors have achieved enormous success in commercial applications.展开更多
With the increasing demand for energy, various emerging energy storage/conversion technologies have gradually penetrated human life, providing numerous conveniences. The practical application efficiency is often affec...With the increasing demand for energy, various emerging energy storage/conversion technologies have gradually penetrated human life, providing numerous conveniences. The practical application efficiency is often affected by the slow kinetics of hydrogen or oxygen electrocatalytic reactions(hydrogen evolution and oxidation reactions, oxygen evolution and reduction reactions) among the emerging devices. Therefore, the researchers devote to finding cost-effective electrocatalysts. Non-noble metal catalysts have low cost and good catalytic activity, but poor stability, agglomeration, dissolution, and other problems will occur after a long cycle, such as transition metal oxides and carbides. Transition metal nitrides(TMNs) stand out among all kinds of non-noble metal catalysts because of the intrinsic platinum-like electrocatalytic activities, relatively high conductivity, and wide range of tunability. In this review, the applications of TMNs in electrocatalytic fields are summarized based on the number of metals contained in TMNs. The practical application potentials of TMNs in fuel cell, water splitting, zinc-air battery and other electrochemical energy storage/conversion devices are also listed. Finally, the design strategies and viewpoints of TMNs-based electrocatalyst are summarized. The potential challenges of TMNs-based electrocatalyst in the development of electrocatalytic energy devices in the future are prospected.展开更多
Graphitic carbon nitride(g-C_(3)N_(4))is emerging as a promising visible-light photocatalyst while the low crystallinity with sluggish charge separation/migration dynamics significantly restricts its practical applicat...Graphitic carbon nitride(g-C_(3)N_(4))is emerging as a promising visible-light photocatalyst while the low crystallinity with sluggish charge separation/migration dynamics significantly restricts its practical applications.Currently,synthesizing highly crystalline g-C_(3)N_(4) with sufficient surface activities still remains challenging.Herein,different from using alkali molten salts which is commonly reported,we propose an approach for synthesis of highly crystalline g-C_(3)N_(4) with FeCl3/KCl rock/molten mixed salts.The rock salt can serve as the structure-directing template while molten salt provides the required liquid medium for re-condensation.Intriguingly,the synthesized photocatalyst showed further enhanced crystallinity and improved surface area along with high p/p*excitation compared with crystalline C_(3)N_(4) prepared from conventional molten-salt methods.These catalytically advantageous features lead to its superior photocatalytic and piezocatalytic activities with a high reactivity for overall water splitting that is not commonly reported for C_(3)N_(4).This work provides an effective strategy for structural optimization of organic semiconductor based materials and may inspire new ideas for the design of advanced photocatalysts.展开更多
In order to explore the thermal conductivity of polypropylene(PP)/hexagonal boron nitride(BN) composites,PP composites filled with different proportions of BN were prepared through extrution compounding,injection moul...In order to explore the thermal conductivity of polypropylene(PP)/hexagonal boron nitride(BN) composites,PP composites filled with different proportions of BN were prepared through extrution compounding,injection moulding and compression moulding.The composites were filled with BN particles of 5 and 20 μm respectively,and their mass fractions in composites were considered.Percentage of BN was varied from 0 to 25wt% in steps of 5wt%.The effects of BN filler on mechanical properties of the composites were evaluated.The thermal behaviors were studied using DSC and TGA,and the thermal conductivity was also investigated by Laser Flash Device and the Model of 3D Heat Conduction respectively.The experimental results show that impact strength of PP/BN can be enhanced with the addition of BN,but that composites exhibit lower breaking elongation & tensile strength when compared to unfilled ones.It is found that mass fraction of BN influenced the final thermal stability and degree of crystallization of PP matrix,the degree of crystallization of PP with 15wt% of 20 μm BN can be improved by 25% than neat PP.Meanwhile,crystallization temperatures of PP composites are elevated by about 10 ℃.The thermal conductivity results demonstrate that the maximum value of the thermal conductivity is achieved from PP/BN with 20wt% of 20 μm BN,higher than that of pure PP by 95.65%,close to the simulation one.展开更多
To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and ...To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In_(0.15)Ga_(0.85)N five-period multiquantum wells.The lattice-composition-energy relationship was established with the help of energy-dispersive x-ray spectroscopy,and the bandgaps of In_(0.15)Ga_(0.85)N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence spectra.The luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were revealed.Our study establishing the direct relationship between the atomic structure of In_(x)Ga_(1-x)N multiquantum wells and photoelectric properties provides useful information for nitride applications.展开更多
Hexagonal boron nitride nanosheets(BNNSs)exhibit remarkable thermal and dielectric properties.However,their self-assembly and alignment in macroscopic forms remain challenging due to the chemical inertness of boron ni...Hexagonal boron nitride nanosheets(BNNSs)exhibit remarkable thermal and dielectric properties.However,their self-assembly and alignment in macroscopic forms remain challenging due to the chemical inertness of boron nitride,thereby limiting their performance in applications such as thermal management.In this study,we present a coaxial wet spinning approach for the fabrication of BNNSs/polymer composite fibers with high nanosheet orientation.The composite fibers were prepared using a superacid-based solvent system and showed a layered structure comprising an aramid core and an aramid/BNNSs sheath.Notably,the coaxial fibers exhibited significantly higher BNNSs alignment compared to uniaxial aramid/BNNSs fibers,primarily due to the additional compressive forces exerted at the core-sheath interface during the hot drawing process.With a BNNSs loading of 60 wt%,the resulting coaxial fibers showed exceptional properties,including an ultrahigh Herman orientation parameter of 0.81,thermal conductivity of 17.2 W m^(-1)K^(-1),and tensile strength of 192.5 MPa.These results surpassed those of uniaxial fibers and previously reported BNNSs composite fibers,making them highly suitable for applications such as wearable thermal management textiles.Our findings present a promising strategy for fabricating high-performance composite fibers based on BNNSs.展开更多
Photocatalysis driven by abundant yet intermittent solar energy has considerable potential in renewable energy generation and environmental remediation.The outstanding electronic structure and physicochemical properti...Photocatalysis driven by abundant yet intermittent solar energy has considerable potential in renewable energy generation and environmental remediation.The outstanding electronic structure and physicochemical properties of graphitic carbon nitride(g-C_(3)N_(4)),together with unique metal-free characteristic,make them ideal candidates for advanced photocatalysts construction.This review summarizes the up-to-date advances on g-C_(3)N_(4)based photocatalysts from ingenious-design strategies and diversified photocatalytic applications.Notably,the advantages,fabrication methods and limitations of each design strategy are systemically analyzed.In order to deeply comprehend the inner connection of theory–structure–performance upon g-C_(3)N_(4)based photocatalysts,structure/composition designs,corresponding photocatalytic activities and reaction mechanisms are jointly discussed,associated with introducing their photocatalytic applications toward water splitting,carbon dioxide/nitrogen reduction and pollutants degradation,etc.Finally,the current challenges and future perspectives for g-C_(3)N_(4)based materials for photocatalysis are briefly proposed.These design strategies and limitations are also instructive for constructing g-C_(3)N_(4) based materials in other energy and environment-related applications.展开更多
With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent.In this work,“high-temperature...With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent.In this work,“high-temperature solid-phase&diazonium salt decomposition”method is carried out to prepare benzidine-functionalized boron nitride(m-BN).Subsequently,m-BN/poly(pphenylene benzobisoxazole)nanofiber(PNF)nanocomposite paper with nacremimetic layered structures is prepared via sol–gel film transformation approach.The obtained m-BN/PNF nanocomposite paper with 50 wt%m-BN presents excellent thermal conductivity,incredible electrical insulation,outstanding mechanical properties and thermal stability,due to the construction of extensive hydrogen bonds andπ–πinteractions between m-BN and PNF,and stable nacre-mimetic layered structures.Itsλ∥andλ_(⊥)are 9.68 and 0.84 W m^(-1)K^(-1),and the volume resistivity and breakdown strength are as high as 2.3×10^(15)Ωcm and 324.2 kV mm^(-1),respectively.Besides,it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640°C,showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.展开更多
文摘Multi-phase nitrides bonded silicon carbide lintel blocks were prepared using industrial SiC(SiC≥98 mass%,3-0.5,≤0.5 and≤0.044 mm),Si powder(Si≥98 mass%,≤0.044 mm),and SiO2 micropowder(SiO2≥96 mass%,d50=0.15 pm)as raw materials,and calcium lignosulfonate as the additive,batching,mixing,and molding on a vibration pressure molding machine,drying and then firing at 1420℃for 10 h in high-purity N2.The apparent porosity,the bulk density,the cold modulus of rupture,the hot modulus of rupture,and the linear expansion coefficient of the samples were tested.The phase composition and the microstructure of the samples at different nitriding depths(50,100,and 150 mm)were analyzed by XRD and SEM.The field application effects of the blocks were studied.The results show that:(1)the multi-phase nitrides bonded silicon carbide refractories can dynamically adjust their own phase composition and minimize structural and thermal stresses,improving the service life of key parts of dry quenching furnaces;(2)calcium lignosulfonate can improve the nitriding micro-environment of multi-phase nitrides bonded silicon carbide lintel blocks,successfully increasing the effective nitriding thickness of the blocks to 300 mm;(3)Sinosteel LI RR provides a unique concept in the design of materials and block types as well as the stable and scientific overall structure,promoting the industrialization process of dry quenching furnaces with long service life in China.
基金financial support from the National Key Research and Development Program of China(2017YFB0102900)
文摘Zn-air batteries(ZABs),especially the secondary batteries,have engrossed a great interest because of its high specific energy,economical and high safety.However,due to the insufficient activity and stability of bifunctional electrocatalysts for air-cathode oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)processes,the practical application of rechargeable ZABs is seriously hindered.In the effort of developing high active,stable and cost-effective electrocatalysts,transition metal nitrides(TMNs)have been regarded as the candidates due to their high conductivity,strong corrosion-resistance,and bifunctional catalytic performance.In this paper,the research progress in TMNs-based material as ORR and OER electrocatalysts for ZABs is discussed with respect to their synthesis,chemical/physical characterization,and performance validation/optimization.The surface/interface nanoengineering strategies such as defect engineering,support binding,heteroatom introduction,crystal plane orientation,interface construction and small size effect,the physical and chemical properties of TMNs-based electrocatalysts are emphasized with respect to their structures/morphologies,composition,electrical conductivity,specific surface area,chemical stability and corrosion resistance.The challenges of TMNs-based materials as bifunctional air-cathode electrocatalysts in practical application are evaluated,and numerous research guidelines to solve these problems are put forward for facilitating further research and development.
基金Project supported by the State Key Program of the National Natural Science Foundation of China(Grant No.61734008)the National Natural Science Foundation of China(Grant No.62174173)。
文摘Ⅲ-nitride semiconductor materials have excellent optoelectronic properties,mechanical properties,and chemical stability,which have important applications in the field of optoelectronics and microelectronics.Two-dimensional(2D)materials have been widely focused in recent years due to their peculiar properties.With the property of weak bonding between layers of 2D materials,the growth ofⅢ-nitrides on 2D materials has been proposed to solve the mismatch problem caused by heterogeneous epitaxy and to develop substrate stripping techniques to obtain high-quality,low-cost nitride materials for high-quality nitride devices and their extension in the field of flexible devices.In this progress report,the main methods for the preparation of 2D materials,and the recent progress and applications of different techniques for the growth ofⅢ-nitrides based on 2D materials are reviewed.
基金Funded by the Fundamental Research Funds for the Central Universities(Nos.2232018A3-08,2232018D3-04)
文摘Titanium(Ti)nitrides were in situ grown on Ti6Al4V alloy(TA)using a glow discharge plasma nitriding(GDPN).The morphology,chemical composition,phase and mechanical property of the obtained nitrided TA were analyzed using a scanning electron microscope(SEM),energy dispersive spectroscope(EDS),X-ray diffraction(XRD),and nanoindentation tester,respectively.The tribological performances of un-nitrided and nitrided TAs were evaluated using a ball-on-plate wear tester,and the wear mechanism was also discussed in detail.The results show that the nitrided layer with the compound and diffusion layers is formed on the nitrided TA,which is composed of δ-TiN and a-Ti phases.The nanohardness and elastic modulus of nitrided TA are 6.05 and 143.13 GPa,respectively,higher than those of un-nitrided TA.The friction reduction and anti-wear performances of nitrided TA are better than those of un-nitrided TA,and the wear mechanism is primary abrasive wear,accompanying with adhesive wear,which is attributed to the formation of Ti nitrides with the high nanohardness and elastic modulus.
文摘A TEM investigation was made on the morphology,orientation relationship and habit plane ofthree alloy nitrides,namely CrN,VN and Mo<sub>2</sub>N simultaneously formed within thediffussional nitrided layers in an H13 steel nitrided at 580℃.It was.found that the nitrideswere precipitated by continuous clustering and subsequent ordering of both interstitial（N）andsubstitutional（Cr,V,Mo）solutes on {001} habit plane,and that the observed morphologyand crystallography of the nitrides were in good agreement with the predictions from theinvariant line stain model proposed for precipitation transformations.
文摘Ultrafine particles of Al_(2)O_(3),MoO_(3),TiO_(2)and SiO_(2)were prepared by irradiate high power laser beams on material surface in O_(2)atmosphere as well as TiN in N_(2) atmosphere.X-ray diffractometer analysis identified that all oxides and nitrides powder obtained are crystalline except SiO_(2) particles which have amorphous struc-ture.
基金financially supported by the Hong Kong Scholars Program (XJ2018009)the City University of Hong Kong Strategic Research Grant (SRG) (7005505)+3 种基金the Shenzhen – Hong Kong Innovative Collaborative Research and Development Program (SGLH20181109110802117 and CityU 9240014)the National Natural Science Foundation of China(U2004210, 21875080, 51572100 and 52003129)the Innovative Research Group Project of the Natural Science Foundation of Hubei Province (2019CFA020)the Shandong Provincial Natural Science Foundation (ZR2019BB006)。
文摘Large-scale deployment of Internet of Things (IoT),a revolutionary innovation for a better world,is hampered by the limitation of energy self-sufficiency.Constructing transition metal nitride (TMN)-based micro-supercapacitors is a possible solution by taking advantage of the high conductivity,large specific capacitance,and large tap density of the materials.However,the pseudocapacitive storage mechanism of TMNs is still unclear consequently impeding the design of microdevices.Herein,the functions and mechanism of TMNs with different metal oxynitride (TMNO_(x)) concentrations in pseudocapacitive electrodes are investigated systematically by in situ Raman scattering,ex situ X-ray photoelectron spectroscopy,as well as ion isolation and substitution cyclic voltammetry.It is found that the specific capacitances of TMNs depend on the TMNO_(x) concentrations and the N–M–O site is responsible for the large pseudocapacitance via the Faradic reaction between TMNO_(x) and OH^(-).Our study elucidates the mechanism pertaining to pseudocapacitive charge storage of TMNs and provides insights into the design and optimization of TMNO_(x) as well as other electrode materials for pseudocapacitors.
基金financially supported by the National Natural Science Foundation of China(22002140)Zhejiang Provincial Natural Science Foundation of China(LR21B030001 and LR22b030003)+1 种基金Young Elite Scientist Sponsorship Program by CAST(No.2019QNRC001)Use of the Advanced Photon Source(beamlines 17-BM,for in-situ XRD characterization)was supported by the U.S.DOE under contract no.DE-AC02-06CH11357。
文摘Three transition metal-like facet centered cubic structured transition metal nitrides,γ-Mo_(2)N,β-W_(2)N andδ-NbN,are synthesized and applied in the reaction of CO_(2)hydrogenation to CO.Among the three nitride catalysts,theγ-Mo_(2)N exhibits superior activity to target product CO,which is 4.6 and 76 times higher than the other two counterparts ofβ-W_(2)N andδ-NbN at 600℃,respectively.Additionally,γ-Mo_(2)N exhibits excellent stability on both cyclic heating-cooling and high space velocity steady state operation.The deactivation degree of cyclic heating-cooling evaluation after 5 cycles and long-term stability performance at 773 and 873 K in 50 h are all less than 10%.In-situ XRD and kinetic studies suggest that theγ-Mo_(2)N itself is able to activate both of the reactants CO_(2)and H_(2).Below 400℃,the reaction mainly occurs at the surface ofγ-Mo_(2)N catalyst.CO_(2)and H_(2)competitively adsorbe on the surface of catalyst and CO_(2)is the relatively stronger surface adsorbate.At a higher temperature,the interstitial vacancies of theγ-Mo_(2)N can be reversibly filled with the oxygen from CO_(2)dissociation.Both of the surface and bulk phase sites ofγ-Mo_(2)N participate in the high temperature CO_(2)hydrogenation pathway.
文摘The samples of microdiamond as an inclusion of Os Ir alloy, coesite, stishovite, high pressure form of Tio2, high pressure nitrides associated with SiC along with boron carbide, have been reported in the past from the placer deposits of Luobasa ophiolite of Yarlung Zangbo region of Tibet. For the formation of these ultra high findings, pressure in the range of 4 to 9 Gpa and temperature in the range of 700° C - 1300° C is required. Thus these minerals can either be incorporated into the chromitite in the deep upper mantle or they have an impact origin. In absence of impact crater, Prof. Fang and others have favored the mantle origin but for the formation of nitrides in the deep mantle, the source of N is not clear. However, the event of comet impact provides better explanation for the formation process. It also simplifies the explanation of coexistence of most of these minerals in a single crystal with the shallow origin and the perfect preservation of the coesite as consequence of rapid cooling after the shock metamorphism.
基金supported by the Natural Science Foundation of Hebei Province(Grant No.E2022209039)Key Research Project of North China University of Science and Technology(Grant No.ZD-YG-202301)Tangshan Talent Funding Project(Grant No.A202202007).
文摘A series of carbon nitride(CN)materials represented by graphitic carbon nitride(g-C3N4)have been widely used in bioimaging,biosensing,and other fields in recent years due to their nontoxicity,low cost,and high luminescent quantum efficiency.What is more attractive is that the luminescent properties such as wavelength and intensity can be regulated by controlling the structure at the molecular level.Hence,it is time to summarize the related research on CN structural evolution and make a prospect on future developments.In this review,we first summarize the research history and multiple structural evolution of CN.Then,the progress of improving the luminescence performance of CN through structural evolution was discussed.Significantly,the relationship between CN structure evolution and energy conversion in the forms of photoluminescence,chemiluminescence,and electrochemiluminescence was reviewed.Finally,key challenges and opportunities such as nanoscale dispersion strategy,luminous efficiency improving methods,standardization evaluation,and macroscopic preparation of CN are highlighted.
基金supported by the National Natural Science Foundation of China(Nos.22174014 and 22074015).
文摘Artificial photocatalysis offers a promising strategy to sustainably produce hydrogen peroxide(H_(2)O_(2))that is one of the most valuable multifunctional chemicals.Among various photocatalysts,polymeric carbon nitride(pCN)has drawn continuous attention in non-sacrificial H_(2)O_(2)production.However,the poor activ-ity of half reactions,ie.,the oxygen reduction reaction(ORR)and water oxidation reaction(WOR),greatly restricts the efficiency of photocatalytic H_(2)O_(2) production.In this highlight,we discuss the significant ad-vances in molecular engineering of carbon nitrides for H_(2)O_(2) photosynthesis and the importance of the deep understanding of the photocatalysis process for rational design and reaction pathways of organic conjugated polymers to address the growing H_(2)O_(2)demand.Furthermore,we summarize the emerging applications of photocatalytic H_(2)O_(2)productions beyond energy and environment.
基金We thank Professor Francis J.DiSalvo(Cornell)for valuable discussions and use of his laboratory facility.The work is supported by the National Science Foundation(NSF)under Grant No.CHE-1805400This work used the Cornell Center for Materials Research Shared Facilities which were supported through the NSF Materials Research Science and Engineering Center program(DMR-1120296).
文摘The development of non-precious,acid-stable,oxygen reduction reaction(ORR)electrocatalysts can significantly aid the commercialization of proton exchange membrane fuel cells(PEMFCs).We report a survey of the ORR electrocatalysis on 3d metal substituted(M=Mn,Fe,Co)molybdenum and tungsten nitrides in acidic environments.We find that molybdate catalysts are more active than tungstates,with the specific activity depending on the chemistry of the substituted 3d metal.In both families,more electronegative 3d metals led to higher ORR activity(i.e.,Co>Fe>Mn).We attribute this result to the ability of the more electro negative 3d metal to withdraw electro ns from the Mo-or W-based active sites,effectively oxidizing the metal centers of the catalysts.Based on our observation,future nitride ORR electrocatalysts can be further optimized by oxidizing the Mo sites further by,for example,addi ng eve n more electro negative dopa nt metals or in corporati ng anion vaca ncies.
基金supported by the National Key R&D Program of China(Grant No.2016YFB0400101)the National Science Fund for Distinguished Young Scholars(Grant No.61725403)+4 种基金the National Natural Science Foundation of China(Grant Nos.61574142,61874118)the Key Program of the International Partnership Program of Chinese Academy of Sciences(Grant No.181722KYSB20160015)the Jilin Provincial Science&Technology Department(Grant No.20180201026 GX)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA22020602)the Youth Innovation Promotion Association of CAS
文摘Inorganic semiconductor plays a key role for today’s technological progress [1–4]. Comparing with other organic semiconductors [5,6] and two-dimensional(2D) metal sulfides [7–10], Ⅲ-nitrides as direct bandgap semiconductors have achieved enormous success in commercial applications.
基金supported by the Natural Science Foundation of Jiangsu Province (No. BK20191430)Six Talent Peaks Project in Jiangsu Province (No. XNY-009)+2 种基金High-tech Research Key Laboratory of Zhenjiang (No. SS2018002)Jiangsu Province Key Laboratory of Intelligent Building Energy Efficiency (No. BEE201904)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘With the increasing demand for energy, various emerging energy storage/conversion technologies have gradually penetrated human life, providing numerous conveniences. The practical application efficiency is often affected by the slow kinetics of hydrogen or oxygen electrocatalytic reactions(hydrogen evolution and oxidation reactions, oxygen evolution and reduction reactions) among the emerging devices. Therefore, the researchers devote to finding cost-effective electrocatalysts. Non-noble metal catalysts have low cost and good catalytic activity, but poor stability, agglomeration, dissolution, and other problems will occur after a long cycle, such as transition metal oxides and carbides. Transition metal nitrides(TMNs) stand out among all kinds of non-noble metal catalysts because of the intrinsic platinum-like electrocatalytic activities, relatively high conductivity, and wide range of tunability. In this review, the applications of TMNs in electrocatalytic fields are summarized based on the number of metals contained in TMNs. The practical application potentials of TMNs in fuel cell, water splitting, zinc-air battery and other electrochemical energy storage/conversion devices are also listed. Finally, the design strategies and viewpoints of TMNs-based electrocatalyst are summarized. The potential challenges of TMNs-based electrocatalyst in the development of electrocatalytic energy devices in the future are prospected.
基金supported by the National Natural Science Foundation of China(51902045,51904059)Fundamental Research Funds for the Central Universities(N2002005,N2125004,N2225038,N2225044)+2 种基金Applied Basic Research Program of Liaoning(2022JH2/101300200)Young Elite Scientist Sponsorship Program by CAST(YESS)2019-2021QNRCNational Research Foundation of Korea(NRF)grant funded by the Korean government(Ministry of Science,ICT&Future Planning)(NRF-2020R1F1A1075601 and NRF-2021R1A4A2001658).
文摘Graphitic carbon nitride(g-C_(3)N_(4))is emerging as a promising visible-light photocatalyst while the low crystallinity with sluggish charge separation/migration dynamics significantly restricts its practical applications.Currently,synthesizing highly crystalline g-C_(3)N_(4) with sufficient surface activities still remains challenging.Herein,different from using alkali molten salts which is commonly reported,we propose an approach for synthesis of highly crystalline g-C_(3)N_(4) with FeCl3/KCl rock/molten mixed salts.The rock salt can serve as the structure-directing template while molten salt provides the required liquid medium for re-condensation.Intriguingly,the synthesized photocatalyst showed further enhanced crystallinity and improved surface area along with high p/p*excitation compared with crystalline C_(3)N_(4) prepared from conventional molten-salt methods.These catalytically advantageous features lead to its superior photocatalytic and piezocatalytic activities with a high reactivity for overall water splitting that is not commonly reported for C_(3)N_(4).This work provides an effective strategy for structural optimization of organic semiconductor based materials and may inspire new ideas for the design of advanced photocatalysts.
基金Funded by the State Grid Henan Electric Power Company Technology Project(No.521790200018)the 2021 Key Scientific Research Projects of Higher Education Institutions in Henan Province(No.21A430047)the Excellent Team Project of Scientific and Technological Innovation in Henan Province(HNST [2017] No.9)。
文摘In order to explore the thermal conductivity of polypropylene(PP)/hexagonal boron nitride(BN) composites,PP composites filled with different proportions of BN were prepared through extrution compounding,injection moulding and compression moulding.The composites were filled with BN particles of 5 and 20 μm respectively,and their mass fractions in composites were considered.Percentage of BN was varied from 0 to 25wt% in steps of 5wt%.The effects of BN filler on mechanical properties of the composites were evaluated.The thermal behaviors were studied using DSC and TGA,and the thermal conductivity was also investigated by Laser Flash Device and the Model of 3D Heat Conduction respectively.The experimental results show that impact strength of PP/BN can be enhanced with the addition of BN,but that composites exhibit lower breaking elongation & tensile strength when compared to unfilled ones.It is found that mass fraction of BN influenced the final thermal stability and degree of crystallization of PP matrix,the degree of crystallization of PP with 15wt% of 20 μm BN can be improved by 25% than neat PP.Meanwhile,crystallization temperatures of PP composites are elevated by about 10 ℃.The thermal conductivity results demonstrate that the maximum value of the thermal conductivity is achieved from PP/BN with 20wt% of 20 μm BN,higher than that of pure PP by 95.65%,close to the simulation one.
基金Project supported by the National Key R&D Program of China (Grant No. 2019YFA0708202)the National Natural Science Foundation of China (Grant Nos. 11974023, 52021006, 61974139, 12074369, and 12104017)+1 种基金the “2011 Program” from the Peking–Tsinghua–IOP Collaborative Innovation Center of Quantum Matterthe Youth Supporting Program of Institute of Semiconductors
文摘To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In_(0.15)Ga_(0.85)N five-period multiquantum wells.The lattice-composition-energy relationship was established with the help of energy-dispersive x-ray spectroscopy,and the bandgaps of In_(0.15)Ga_(0.85)N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence spectra.The luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were revealed.Our study establishing the direct relationship between the atomic structure of In_(x)Ga_(1-x)N multiquantum wells and photoelectric properties provides useful information for nitride applications.
基金This work was supported by the National Key Research and Development Project(Nos.2019YFA0705403,2022YFA1205300)the National Natural Science Foundation of China(No.T2293693)+3 种基金the Guangdong Innovative and Entrepreneurial Research Team Program(No.2017ZT07C341)the Guangdong Basic and Applied Basic Research Foundation(No.2020B0301030002)the Shenzhen Basic Research Project(Nos.WDZC20200824091903001,JSGG20220831105402004)Zhiyuan Xiong thanks the financial support from South China University of Technology.
文摘Hexagonal boron nitride nanosheets(BNNSs)exhibit remarkable thermal and dielectric properties.However,their self-assembly and alignment in macroscopic forms remain challenging due to the chemical inertness of boron nitride,thereby limiting their performance in applications such as thermal management.In this study,we present a coaxial wet spinning approach for the fabrication of BNNSs/polymer composite fibers with high nanosheet orientation.The composite fibers were prepared using a superacid-based solvent system and showed a layered structure comprising an aramid core and an aramid/BNNSs sheath.Notably,the coaxial fibers exhibited significantly higher BNNSs alignment compared to uniaxial aramid/BNNSs fibers,primarily due to the additional compressive forces exerted at the core-sheath interface during the hot drawing process.With a BNNSs loading of 60 wt%,the resulting coaxial fibers showed exceptional properties,including an ultrahigh Herman orientation parameter of 0.81,thermal conductivity of 17.2 W m^(-1)K^(-1),and tensile strength of 192.5 MPa.These results surpassed those of uniaxial fibers and previously reported BNNSs composite fibers,making them highly suitable for applications such as wearable thermal management textiles.Our findings present a promising strategy for fabricating high-performance composite fibers based on BNNSs.
基金supported by the National Natural Science Foundation of China(21875118,22111530112)the support from the Smart Sensing Interdisciplinary Science Center,Nankai University。
文摘Photocatalysis driven by abundant yet intermittent solar energy has considerable potential in renewable energy generation and environmental remediation.The outstanding electronic structure and physicochemical properties of graphitic carbon nitride(g-C_(3)N_(4)),together with unique metal-free characteristic,make them ideal candidates for advanced photocatalysts construction.This review summarizes the up-to-date advances on g-C_(3)N_(4)based photocatalysts from ingenious-design strategies and diversified photocatalytic applications.Notably,the advantages,fabrication methods and limitations of each design strategy are systemically analyzed.In order to deeply comprehend the inner connection of theory–structure–performance upon g-C_(3)N_(4)based photocatalysts,structure/composition designs,corresponding photocatalytic activities and reaction mechanisms are jointly discussed,associated with introducing their photocatalytic applications toward water splitting,carbon dioxide/nitrogen reduction and pollutants degradation,etc.Finally,the current challenges and future perspectives for g-C_(3)N_(4)based materials for photocatalysis are briefly proposed.These design strategies and limitations are also instructive for constructing g-C_(3)N_(4) based materials in other energy and environment-related applications.
基金The authors are grateful for the support and funding from the Foundation of National Natural Science Foundation of China(52373089 and 51973173)Startup Foundation of Chongqing Normal University(23XLB011),Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202300561)Fundamental Research Funds for the Central Universities。
文摘With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent.In this work,“high-temperature solid-phase&diazonium salt decomposition”method is carried out to prepare benzidine-functionalized boron nitride(m-BN).Subsequently,m-BN/poly(pphenylene benzobisoxazole)nanofiber(PNF)nanocomposite paper with nacremimetic layered structures is prepared via sol–gel film transformation approach.The obtained m-BN/PNF nanocomposite paper with 50 wt%m-BN presents excellent thermal conductivity,incredible electrical insulation,outstanding mechanical properties and thermal stability,due to the construction of extensive hydrogen bonds andπ–πinteractions between m-BN and PNF,and stable nacre-mimetic layered structures.Itsλ∥andλ_(⊥)are 9.68 and 0.84 W m^(-1)K^(-1),and the volume resistivity and breakdown strength are as high as 2.3×10^(15)Ωcm and 324.2 kV mm^(-1),respectively.Besides,it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640°C,showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.
