The electrochemical CO_(2) reduction(ECR)into value-added products presents an appealing approach to mitigate CO_(2) emission caused by excess consumption of fossil fuels.To obtain high catalytic activity and selectiv...The electrochemical CO_(2) reduction(ECR)into value-added products presents an appealing approach to mitigate CO_(2) emission caused by excess consumption of fossil fuels.To obtain high catalytic activity and selectivity toward target product in ECR,designing and developing a stable and efficient electrocatalyst is of significant importance.To date,metal nanomaterials have been widely applied as electrocatalysts for ECR due to their unique physicochemical properties.The structural modulation of metal nanomaterials is an attractive strategy to improve the catalytic performance.In this review,the recent progress of structural modulation,including size,facet,grain boundary,composition,interface,ligand modification,and crystal phase,is systematically summarized from both theoretical and experimental aspects.Finally,the opportunities and perspectives of structural modulation of metal nanomaterials for ECR are proposed.展开更多
The existing recycling and regeneration technologies have problems,such as poor regeneration effect and low added value of products for lithium(Li)-ion battery cathode materials with a low state of health.In this work...The existing recycling and regeneration technologies have problems,such as poor regeneration effect and low added value of products for lithium(Li)-ion battery cathode materials with a low state of health.In this work,a targeted Li replenishment repair technology is proposed to improve the discharge-specific capacity and cycling stability of the repaired LiCoO_(2) cathode materials.Compared with the spent cathode material with>50%Li deficiency,the Li/Co molar ratio of the regenerated LiCoO_(2) cathode is>0.9,which completely removes the Co_(3)O_(4) impurity phase formed by the decomposition of LixCoO_(2) in the failed cathode material after repair.The repaired LiCoO_(2) cathode mater-ials exhibit better cycling stability,lower electrochemical impedance,and faster Li^(+)diffusion than the commercial materials at both 1 and 10 C.Meanwhile,Li_(1.05)CoO_(2) cathodes have higher Li replenishment efficiency and cycling stability.The energy consumption and greenhouse gas emissions of LiCoO_(2) cathodes produced by this repair method are significantly reduced compared to those using pyrometallurgical and hydro-metallurgical recycling processes.展开更多
A series of hydrogenated silicon thin films were prepared by the radio frequency plasma enhanced chemical vapor deposition method (RF-PECVD) with various si-lane concentrations. The influence of silane concentration o...A series of hydrogenated silicon thin films were prepared by the radio frequency plasma enhanced chemical vapor deposition method (RF-PECVD) with various si-lane concentrations. The influence of silane concentration on structural and elec-trical characteristics of these films was investigated to study the phase transition region from amorphous to microcrystalline phase. At the same time,optical emis-sion spectra (OES) from the plasma during the deposition process were monitored to get information about the plasma properties,Raman spectra were measured to study the structural characteristics of the deposited films. The combinatorial analysis of OES and Raman spectra results demonstrated that the OES can be used as a fast method to diagnose phase transition from amorphous to microcrystalline silicon. At last the physical mechanism,why both OES and Raman can be used to diagnose the phase transition,was analyzed theoretically.展开更多
Energetic structural materials(ESMs)integrated a high energy density and rapid energy release with the ability to serve as structural materials.Here,a novel triple-phase TiZrHfTa_(0.7)W_(0.3)high-entropy alloy(HEA)was...Energetic structural materials(ESMs)integrated a high energy density and rapid energy release with the ability to serve as structural materials.Here,a novel triple-phase TiZrHfTa_(0.7)W_(0.3)high-entropy alloy(HEA)was fabricated and investigated as a potential ESM.A hierarchical microstructure was obtained with a main metastable body-centered-cubic(BCC)matrix with distributed Ta-W-rich BCC precipitates of various sizes and interwoven hexagonal close-packed(HCP)lamellar nano-plates.The compressive me-chanical properties were tested across a range of strain rates and demonstrated a brittle-to-ductile tran-sition as the strain rate increased while maintaining a high ultimate strength of approximately 2.5 GPa.This was due to the phase transformation from metastable matrix BCC to HCP structures.In addition,during the dynamic deformation,metal combustion originating from the failure surface was observed.Furthermore,the composition of the fragments was studied,and the results indicated that the addition of tungsten promoted combustion.Finally,the potential application of this HEA was evaluated by high-velocity penetration tests,and the results were compared to other typical structural materials for pene-trators and bullets.A comparison was conducted by assessing the geometries of the penetration channel employing two dimensionless parameters normalized by the projectile size,representing longitudinal and lateral damage,respectively.The normalized depth of the TiZrHfTa_(0.7)W_(0.3)HEA projectile was comparable to those of the other investigated materials,but the normalized diameter was the largest,showing an excellent ability to deliver lateral damage.展开更多
The title compound, tetramethylammonium nickel nitrite [（CH3）4N][Ni（NO2）3], has a hexagonal perovskite-type structure with formula ABX3. It undergoes two reversible phase transitions occurring at about 409.1 and 4...The title compound, tetramethylammonium nickel nitrite [（CH3）4N][Ni（NO2）3], has a hexagonal perovskite-type structure with formula ABX3. It undergoes two reversible phase transitions occurring at about 409.1 and 428.4 K, associated with dielectric transitions. DSC measurement and dielectric measurement confirm the transition. The variable-temperature X-ray structural determinations and the powder X-ray diffraction （PXRD） experiments reveal that this compound has the same space group P3ml （No. 164） at 293 K, 413 K and 438 K. The phase transitions are caused by the rotation of the [（CH3）4N]＋ cation.展开更多
In the realm of molecular phase transition research,particularly for applications in sensors,data storage and switching technologies,the role of organic-inorganic hybrid perovskite materials has been increasingly reco...In the realm of molecular phase transition research,particularly for applications in sensors,data storage and switching technologies,the role of organic-inorganic hybrid perovskite materials has been increasingly recognized for their significant potential.Nevertheless,hybrid post-perovskites,as a critical subclass of perovskites,have not been thoroughly studied and mainly limit in the instances based on polyatomic bridging agents like dicyanamide(dca^(-))and non-cyclic organic cations.Herein,a polar cyclic quaternary ammonium cation,N,N-dimethylpyrrolidinium(DMP^(+)),was used to assemble a new hybrid post-perovskite,(DMP)[Mn(dca)_(3)](1),which undergoes a phase transition from orthorhombic Bmmb to monoclinic P2_(1)/n space group at 249 K.By employing multiple techniques such as differential scanning calorimetry,variable-temperature single-crystal X-ray analysis,dielectric measurements,and Hirshfeld surface analysis,we disclosed the role of polar cyclic quaternary ammonium DMP^(+)in elevating the phase-transition temperature by 48 K,generating significant dielectric switching effect and facilitating interlayer sliding of inorganic framework.展开更多
基金financially supported by the National Key R&D Program(N os.2017 YF A0204503 and 2016YFB0401100)the National Natural Science Foundation of China(Nos.91833306,21875158,51633006 and 51703159)。
文摘The electrochemical CO_(2) reduction(ECR)into value-added products presents an appealing approach to mitigate CO_(2) emission caused by excess consumption of fossil fuels.To obtain high catalytic activity and selectivity toward target product in ECR,designing and developing a stable and efficient electrocatalyst is of significant importance.To date,metal nanomaterials have been widely applied as electrocatalysts for ECR due to their unique physicochemical properties.The structural modulation of metal nanomaterials is an attractive strategy to improve the catalytic performance.In this review,the recent progress of structural modulation,including size,facet,grain boundary,composition,interface,ligand modification,and crystal phase,is systematically summarized from both theoretical and experimental aspects.Finally,the opportunities and perspectives of structural modulation of metal nanomaterials for ECR are proposed.
基金supported by the National Natural Science Foundation of China (Nos. 51972030 and 51772030)the S&T Major Project of Inner Mongolia Autonomous Region in China (No. 2020ZD0018)+1 种基金the Beijing Outstanding Young Scientists Program (No. BJJWZYJH01201910007023)the Guangdong Key Laboratory of Battery Safety (No. 2019B121203008)
文摘The existing recycling and regeneration technologies have problems,such as poor regeneration effect and low added value of products for lithium(Li)-ion battery cathode materials with a low state of health.In this work,a targeted Li replenishment repair technology is proposed to improve the discharge-specific capacity and cycling stability of the repaired LiCoO_(2) cathode materials.Compared with the spent cathode material with>50%Li deficiency,the Li/Co molar ratio of the regenerated LiCoO_(2) cathode is>0.9,which completely removes the Co_(3)O_(4) impurity phase formed by the decomposition of LixCoO_(2) in the failed cathode material after repair.The repaired LiCoO_(2) cathode mater-ials exhibit better cycling stability,lower electrochemical impedance,and faster Li^(+)diffusion than the commercial materials at both 1 and 10 C.Meanwhile,Li_(1.05)CoO_(2) cathodes have higher Li replenishment efficiency and cycling stability.The energy consumption and greenhouse gas emissions of LiCoO_(2) cathodes produced by this repair method are significantly reduced compared to those using pyrometallurgical and hydro-metallurgical recycling processes.
基金Supported by the National Basic Research Program of China (Grant Nos. 2006CB202602 and 2006CB202603)
文摘A series of hydrogenated silicon thin films were prepared by the radio frequency plasma enhanced chemical vapor deposition method (RF-PECVD) with various si-lane concentrations. The influence of silane concentration on structural and elec-trical characteristics of these films was investigated to study the phase transition region from amorphous to microcrystalline phase. At the same time,optical emis-sion spectra (OES) from the plasma during the deposition process were monitored to get information about the plasma properties,Raman spectra were measured to study the structural characteristics of the deposited films. The combinatorial analysis of OES and Raman spectra results demonstrated that the OES can be used as a fast method to diagnose phase transition from amorphous to microcrystalline silicon. At last the physical mechanism,why both OES and Raman can be used to diagnose the phase transition,was analyzed theoretically.
基金supported by the National Natu-ral Science Foundation of China(Nos.51401028,51271193 and 11790292)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040303)the Innovation Pro-gram(No.237099000000170004).
文摘Energetic structural materials(ESMs)integrated a high energy density and rapid energy release with the ability to serve as structural materials.Here,a novel triple-phase TiZrHfTa_(0.7)W_(0.3)high-entropy alloy(HEA)was fabricated and investigated as a potential ESM.A hierarchical microstructure was obtained with a main metastable body-centered-cubic(BCC)matrix with distributed Ta-W-rich BCC precipitates of various sizes and interwoven hexagonal close-packed(HCP)lamellar nano-plates.The compressive me-chanical properties were tested across a range of strain rates and demonstrated a brittle-to-ductile tran-sition as the strain rate increased while maintaining a high ultimate strength of approximately 2.5 GPa.This was due to the phase transformation from metastable matrix BCC to HCP structures.In addition,during the dynamic deformation,metal combustion originating from the failure surface was observed.Furthermore,the composition of the fragments was studied,and the results indicated that the addition of tungsten promoted combustion.Finally,the potential application of this HEA was evaluated by high-velocity penetration tests,and the results were compared to other typical structural materials for pene-trators and bullets.A comparison was conducted by assessing the geometries of the penetration channel employing two dimensionless parameters normalized by the projectile size,representing longitudinal and lateral damage,respectively.The normalized depth of the TiZrHfTa_(0.7)W_(0.3)HEA projectile was comparable to those of the other investigated materials,but the normalized diameter was the largest,showing an excellent ability to deliver lateral damage.
基金supported by the Project 973(No. 2014CB848800)National Natural Science Foundation of China (Nos.91022003 and 21301029)+1 种基金Jiangsu Province NSF(No. BK20130600)Program for NCET and Ph.D.Programs Foundation of Ministry of Education of China(No.20130092120013)
文摘The title compound, tetramethylammonium nickel nitrite [（CH3）4N][Ni（NO2）3], has a hexagonal perovskite-type structure with formula ABX3. It undergoes two reversible phase transitions occurring at about 409.1 and 428.4 K, associated with dielectric transitions. DSC measurement and dielectric measurement confirm the transition. The variable-temperature X-ray structural determinations and the powder X-ray diffraction （PXRD） experiments reveal that this compound has the same space group P3ml （No. 164） at 293 K, 413 K and 438 K. The phase transitions are caused by the rotation of the [（CH3）4N]＋ cation.
基金supported by the National Natural Science Foundation of China(22071273 and 21821003)Fundamental Research Funds for the Central Universities,Sun Yat Sen University(23lgzy001).
文摘In the realm of molecular phase transition research,particularly for applications in sensors,data storage and switching technologies,the role of organic-inorganic hybrid perovskite materials has been increasingly recognized for their significant potential.Nevertheless,hybrid post-perovskites,as a critical subclass of perovskites,have not been thoroughly studied and mainly limit in the instances based on polyatomic bridging agents like dicyanamide(dca^(-))and non-cyclic organic cations.Herein,a polar cyclic quaternary ammonium cation,N,N-dimethylpyrrolidinium(DMP^(+)),was used to assemble a new hybrid post-perovskite,(DMP)[Mn(dca)_(3)](1),which undergoes a phase transition from orthorhombic Bmmb to monoclinic P2_(1)/n space group at 249 K.By employing multiple techniques such as differential scanning calorimetry,variable-temperature single-crystal X-ray analysis,dielectric measurements,and Hirshfeld surface analysis,we disclosed the role of polar cyclic quaternary ammonium DMP^(+)in elevating the phase-transition temperature by 48 K,generating significant dielectric switching effect and facilitating interlayer sliding of inorganic framework.
