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Nonlinear Electrical Characteristics of Antimony and Copper Doped Tin Oxide Based Varistor Ceramics 被引量:1
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作者 王春明 王矜奉 苏文斌 《Chinese Physics Letters》 SCIE CAS CSCD 2006年第3期728-731,共4页
The novel CuO-doped dense tin oxide varistor ceramics are investigated. The densification of tin oxide varistor ceramics could be greatly improved by doping copper oxide additives. The introduction of antimony additiv... The novel CuO-doped dense tin oxide varistor ceramics are investigated. The densification of tin oxide varistor ceramics could be greatly improved by doping copper oxide additives. The introduction of antimony additives into a SnO2. CuO ceramic system would make it possess excellent nonlinearity. The sample doped with 0.05 mol% Sb2 03 possesses the highest nonlinearity coefficient (α = 17.9) and the lowest leakage current density ( JL = 52μA cm^-2) among all the samples. A modified defect barrier model is introduced to explain the formation of the grainboundary barrier. The nonlinear behaviour of (Cu, Sb)-doped SnO2 varistor system could be explained by the barrier model. 展开更多
关键词 grain-boundaries SYSTEM BEHAVIOR OXYGEN SIZE
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Enhancement of room-temperature magnetoresistance in La_(0.5)Sm_(0.2)Sr_(0.3)MnO_3/(Ag_2O)_(x/2) 被引量:10
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作者 PENG Zhensheng WANG Guiying +2 位作者 TANG Yonggang LIU Peng NIU Xiaofei 《Rare Metals》 SCIE EI CAS CSCD 2010年第1期45-49,共5页
La0.5Sm0.2Sr0.3MnO3/(Ag2O)x/2 (x = 0.00, 0.04, 0.08, 0.25, 0.30) samples were prepared by the solid-state reaction method, and their transport behaviors, transport mechanism, and magnetoresistance effect were stud... La0.5Sm0.2Sr0.3MnO3/(Ag2O)x/2 (x = 0.00, 0.04, 0.08, 0.25, 0.30) samples were prepared by the solid-state reaction method, and their transport behaviors, transport mechanism, and magnetoresistance effect were studied through the measurement and fitting of p-T curves. The results show that the element Ag takes part in reaction when the doping amount is small. Ag is mainly distributed at the grain boundary of the host material and is in metallic state when the doping amount is relatively large; then the system becomes a two-phase composite. A small amount of Ag doping can apparently increase grain-boundary magnetoresistance induced by the spin-dependent scattering. The resistivity of the sample doped with 30 mol% Ag is one order of magnitude smaller than that of low-doped samples, and its magnetoresistance in the magnetic field of 0.5 T and at 300 K is strengthened apparently reaching 9.4%, which is connected not only with the improvement of the grain-boundary structure of the host material but also with the decrease of material resistivity. 展开更多
关键词 low-field magnetoresistance room-temperature magnetoresistance grain-boundary magnetoresistance two-phase composite perovskite manganite
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Correlations among stress corrosion cracking,grain-boundary microchemistry,and Zn content in high Zn-containing Al-Zn-Mg-Cu alloys 被引量:11
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作者 Ding-ling YUAN Song-yi CHEN +4 位作者 Kang-hua CHEN Lan-ping HUANG Jiang-yu CHANG Liang ZHOU Yun-feng DING 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2021年第8期2220-2231,共12页
The correlations among the corrosion behaviour,grain-boundary microchemistry,and Zn content in Al-Zn-Mg-Cu alloys were studied using stress corrosion cracking(SCC)and intergranular corrosion(IGC)tests,combined with sc... The correlations among the corrosion behaviour,grain-boundary microchemistry,and Zn content in Al-Zn-Mg-Cu alloys were studied using stress corrosion cracking(SCC)and intergranular corrosion(IGC)tests,combined with scanning electron microscopy(SEM)and high-angle angular dark field scanning transmission electron microscopy(HAADF-STEM)microstructural examinations.The results showed that the tensile strength enhancement of high Zn-containing Al-Zn-Mg-Cu alloys was mainly attributed to the high density nano-scale matrix precipitates.The SCC plateau velocity for the alloy with 11.0 wt.%Zn was about an order of magnitude greater than that of the alloy with 7.9 wt.%Zn,which was mainly associated with Zn enrichment in grain boundary precipitates and wide precipitates-free zones.The SCC mechanisms of different Zn-containing alloys were discussed based on fracture features,grain-boundary microchemistry,and electrochemical properties. 展开更多
关键词 Al-Zn-Mg-Cu alloy stress corrosion cracking Zn content grain-boundary microchemistry
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SIMULATION OF THE CHANGE OF SINTERING NECK BETWEEN TWO GRAINS IN TWO DIMENSIONS 被引量:3
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作者 Y.Y.Zhu S.H.Liang +2 位作者 Z.J.Zhan P.Xiao Z.K.Fan 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2006年第6期397-404,共8页
A modified two-sphere model of sintering neck has been proposed, wherein three diffusion mechanisms including surface diffusion, grain-boundary diffusion and coupled surface and grain-boundary diffusion are assumed. S... A modified two-sphere model of sintering neck has been proposed, wherein three diffusion mechanisms including surface diffusion, grain-boundary diffusion and coupled surface and grain-boundary diffusion are assumed. Sintering neck is appropriately simulated using the modified model. The dynamic change of sintering neck is presented using the simulation. The variational shape of sintering neck in surface diffusion mechanism is continuous, whereas in grain-boundary diffusion mechanism, besides the variational shape of sintering neck being continuous, the center distance between the particles is also assumed to contract. However, the variational shape of sintering neck in coupling diffusion mechanism is integrated using the two diffusion mechanisms mentioned above. 展开更多
关键词 sintering simulation neck growth surface diffusion grain-boundary diffusion
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The Role of Nd Solid-Solution and Grain-Boundary Segregation in Binary NiAl Intermetallic Compound 被引量:1
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作者 WeiliREN JiantingGUO +1 位作者 GusongLI JiyangZHOU 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2004年第2期163-166,共4页
The role of Nd solid-solution and grain-boundary segregation in binary NiAl alloy was studied based on microhardness and compressive macrostrain. X-ray and Auger spectra studies indicate that Nd not only is soluble in... The role of Nd solid-solution and grain-boundary segregation in binary NiAl alloy was studied based on microhardness and compressive macrostrain. X-ray and Auger spectra studies indicate that Nd not only is soluble in grain interiors, but also segregates to the grain boundaries. Nd solid-solution induces an increase of the microhardness from 269 to 290 HV in grain interiors and segregation results in an enhancement of hardness from 252 to 342 HV on grain boundaries. Thus, the cohesion of grain boundaries is enhanced by Nd segregation, which make the alloy doped with 0.05 wt pct Nd exhibit more compressive microstrain, i.e. the higher the compressive ductility at room temperature, the better the final surface condition at elevated temperature. Finally, a discussion was made on the reason that Nd strengthens the grain boundaries in NiAl intermetallic alloy. 展开更多
关键词 ND NiAl alloys SOLID-SOLUTION Grain-boundary segregation Mechanical properties
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A novel technology of high-voltage pulse discharge for comminution of galena ore 被引量:1
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作者 Yong-hong QIN Peng GAO +2 位作者 Shuai YUAN Ning-yu ZHANG Li-ren HAN 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2021年第8期2479-2492,共14页
An innovative technology of high-voltage pulse discharge(HVPD)was proposed to investigate the comminution characteristics of galena ore.The optimal experiment parameters were determined as follows:spark gap spacing of... An innovative technology of high-voltage pulse discharge(HVPD)was proposed to investigate the comminution characteristics of galena ore.The optimal experiment parameters were determined as follows:spark gap spacing of 25 mm,pulse number of 120,and voltage of 25 k V.The mass fraction with size<0.074 mm in ground products was improved by the HVPD.Meanwhile,the relative grindability declined with the increase of the grinding time,which indicated that the superiority of HVPD was weakened.The ground products of HVPD were distributed more homogeneously than those of mechanical crushing.The liberation of breakage products was improved by 24.57%via the HVPD.Moreover,the Brunauer–Emmett–Teller(BET)specific surface area,pore volume,and average pore size were increased via the HVPD.Scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS)analyses suggested that obvious grain-boundary breakage and several stomatal traces were observed in the HVPD products. 展开更多
关键词 galena ore high-voltage pulse discharge LIBERATION MICROSTRUCTURE grain-boundary breakage
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Reconsideration of Anelastic Relaxation Peaks in Pure Aluminium 被引量:1
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作者 商丽燕 水嘉鹏 +1 位作者 蔡彬 崔平 《Chinese Physics Letters》 SCIE CAS CSCD 2005年第9期2338-2341,共4页
The temperature dependence of internal friction ( T- tan φ curves) in pure aluminium (Al) is measured at sixteen different frequencies. Based on T- tan φ curves, the frequency dependence of internal friction (f... The temperature dependence of internal friction ( T- tan φ curves) in pure aluminium (Al) is measured at sixteen different frequencies. Based on T- tan φ curves, the frequency dependence of internal friction (f -tan φ curves) is also obtained by the interpolation method. An internal friction peak is observed in both the T - tan φ curves and the f - tan φ curves. The activation energy of the peak in the f - tan φ curves is found to be 2.08 ± 0.02 eV and compared to the value of 1.60 ± 0.04 eV in the T - tan φ curves. It is suggested that the change of relaxation strength with temperature should be considered when one calculates the activation energy of the peak in T- tan φ curves. 展开更多
关键词 INTERNAL-FRICTION PEAKS GRAIN-BOUNDARY RELAXATION METALS AL
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Effect of graphene grain boundaries on MoS2/graphene heterostructures
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作者 Yue Zhang Xiangzhe Zhang +7 位作者 Chuyun Deng Qi Ge Junjie Huang Jie Lu Gaoxiang Lin Zekai Weng Xueao Zhang Weiwei Cai 《Chinese Physics B》 SCIE EI CAS CSCD 2020年第6期44-48,共5页
The grain boundaries of graphene are disordered topological defects,which would strongly affect the physical and chemical properties of graphene.In this paper,the spectral characteristics and photoresponse of MoS2/gra... The grain boundaries of graphene are disordered topological defects,which would strongly affect the physical and chemical properties of graphene.In this paper,the spectral characteristics and photoresponse of MoS2/graphene heterostructures are studied.It is found that the blueshift of the G and 2D peaks of graphene in Raman spectrum is due to doping.The lattice mismatch at the graphene boundaries results in a blueshift of MoS2 features in the photoluminescence spectra,comparing to the MoS2 grown on SiO2.In addition,the photocurrent signal in MoS2/hexagonal single-crystal graphene heterostructures is successfully captured without bias,but not in MoS2/polycrystalline graphene heterostructures.The electron scattering at graphene grain boundaries affects the optical response of MoS2/graphene heterostructures.The photoresponse of the device is attributed to the optical absorption and response of MoS2 and the high carrier mobility of graphene.These findings offer a new approach to develop optoelectronic devices based on two-dimensional material heterostructures. 展开更多
关键词 PHOTORESPONSE HETEROSTRUCTURES GRAIN-BOUNDARY
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Realization of Superplastic State of Polycrystals under Grain-boundary Diffusion
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作者 Yu.R.Kolobov and I.V.Ratochka(Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences,634055, Tomsk, Russia) 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 1995年第1期38-40,共3页
Creep behaviour of Mo and Fe polycrystals has been studied for a wide range of Strain rates in the presence of grain-boundary diffusion flux of Ni. The role of the impurity grain-boundary diffusion and grain-boundary ... Creep behaviour of Mo and Fe polycrystals has been studied for a wide range of Strain rates in the presence of grain-boundary diffusion flux of Ni. The role of the impurity grain-boundary diffusion and grain-boundary migratin in the realization of the superplastic strain of metals under these conditions is examined 展开更多
关键词 Realization of Superplastic State of Polycrystals under Grain-boundary Diffusion
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Advances in grain-boundary diffusion for high-performance permanent magnets
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作者 Prajna Paramita Mohapatra Guomeng Li +1 位作者 Perumal Alagarsamy Xiandong Xu 《Materials Futures》 2024年第4期41-70,共30页
High-performance permanent magnets play an indispensable role in manufacturing highly efficient motors and generators,ultimately contributing to the sustainability of our planet.Achieving high coercivity(µ0Hc)in ... High-performance permanent magnets play an indispensable role in manufacturing highly efficient motors and generators,ultimately contributing to the sustainability of our planet.Achieving high coercivity(µ0Hc)in hard magnetic materials at or above room temperature without relying on heavy rare-earth elements remains a challenge.Effective strategies for augmentingµ0Hc utilizing low-cost materials involve inter-granular addition and the grain-boundary diffusion(GBD)processes.This review provides a comprehensive overview of selected techniques for developing grain-boundary(GB)modification through a specific focus on the reduction of using heavy rare earth(HRE)elements and utilizing cost-effective non-rare earth and light rare earth(LRE)sources for GBD.To date,the successful application of HRE based metals and compounds,and LRE based alloys as diffusion sources has significantly contributed toµ0Hc enhancement.Drawing upon global advancements and findings from various research groups,this comprehensive review offers a critical analysis of the fundamentals and progress in GBD processes(GBDPs).Considering the different types of permanent magnets,the GBDPs,based on the diverse diffusion sources and diffusion processes,are thoroughly compared and summarized.This encapsulates the current state of knowledge in the field,providing valuable insights into the ongoing developments in GB modification to improve permanent magnet performance. 展开更多
关键词 rare earth metal grain-boundary diffusion processes NdFeB magnets COERCIVITY
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Creating and destroying vacancies in solids and nonequilibrium grain boundary segregation 被引量:14
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作者 徐庭栋 《Science China(Technological Sciences)》 SCIE EI CAS 2003年第4期373-380,共8页
How the vacancies in excess of equilibrium concentration are created and destroyed in solids is crucial for understanding many of their physical characteristics and processes. Grain boundaries are known as sources and... How the vacancies in excess of equilibrium concentration are created and destroyed in solids is crucial for understanding many of their physical characteristics and processes. Grain boundaries are known as sources and sinks for bulk vacancies, but what exchange will occur between the grain boundary and the bulk under a stress is still obscure. In the present paper, we show that grain boundaries will work as sources to emit vacancies when a compressive stress is exerted on them and as sinks to absorb vacancies when a tensile stress is exerted. This is the sixth method of introducing and annihilating vacancies in solids in addition to the five methods mentioned in literature. At the same time, this, physical process will produce solute none quilibrium grain-boundary segregation/dilution. A set of kinetic equations is established to describe such a physical process. Additionally an attempt has been made to simulate Misra’s experimental data with the kinetic equations to justify the physical process. 展开更多
关键词 vacancy grain-boundary stress segregation dynamics.
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Theoretical progress in non-equilibrium grain-boundary segregation (Ⅰ): Thermally induced non-equilibrium grain-boundary segregation and intergranular embrittlement 被引量:3
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作者 XU TingDong1, WANG Kai1 & SONG ShenHua2 1 Central Iron and Steel Research Institute, Superalloy Department, Beijing 100081, China 2 Department of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China 《Science China(Technological Sciences)》 SCIE EI CAS 2009年第4期893-905,共13页
The research progress of non-equilibrium grain-boundary segregation theories in the last 20 years is reviewed. Based on studies by the present authors, the critical time of non-equilibrium segregation and its impact o... The research progress of non-equilibrium grain-boundary segregation theories in the last 20 years is reviewed. Based on studies by the present authors, the critical time of non-equilibrium segregation and its impact on the development of non-equilibrium segregation theories are described. Quasi- thermo- dynamics and kinetics for thermal non-equilibrium grain boundary segregation are detailed along with a non-equilibrium grain boundary cosegregation model. The experimental validation of the theories and their application to the reversible temper embrittlement of steels and the intermediate temperature brittleness in metals and alloys are also addressed. 展开更多
关键词 GRAIN-BOUNDARY SEGREGATION EMBRITTLEMENT
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Supermodulus effect by grain-boundary wetting in nanostructured multilayers 被引量:1
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作者 Jing Wang Lu Han +5 位作者 Xiaohu Li Dongguang Liu Laima Luo Yuan Huang Yongchang Liu Zumin Wang 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2021年第6期202-209,共8页
The effect of thermal treatments on mechanical properties was systematically investigated in Ni/Mo multilayers with a constant modulation period(160 nm)prepared by magnetron sputtering deposition.A supermodulus effect... The effect of thermal treatments on mechanical properties was systematically investigated in Ni/Mo multilayers with a constant modulation period(160 nm)prepared by magnetron sputtering deposition.A supermodulus effect was found in the annealed multilayers as compared to the as-deposited state.A large tensile stress development was observed in the multilayers.The evolution of grain-boundary(GB)wetting was observed at the interfaces of the multilayers,which results in an enhanced modulus based on the mechanism of GB-wetting-induced interfacial stress/strain.The GB wetting phenomenon was further supported by a thermodynamic calculation.The results not only bring clear evidence of the important role of interfacial structures in governing the elastic behavior of metallic multilayers,but also allow designing the multilayers with special properties through atomic diffusion and wetting at the interfaces based on the thermodynamic calculation. 展开更多
关键词 MULTILAYER Elastic modulus Grain-boundary wetting STRESS Thermodynamic calculation
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Enhanced mechanical performance of grain boundary precipitation-hardened high-entropy alloys via a phase transformation at grain boundaries 被引量:1
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作者 Y.L.Qi L.Zhao +10 位作者 X.Sun H.X.Zong X.D.Ding F.Jiang H.L.Zhang Y.K.Wu L.He F.Liu S.B.Jin G.Sha J.Sun 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2021年第27期271-284,共14页
Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external loading.Herein,we r... Grain-boundary(GB)precipitation has a significant adverse effect on plasticity of alloys,which easily leads to catastrophic intergranular failure in safety-critical applications under high external loading.Herein,we report a novel strategy that uses the local stress concentration induced by GB precipitates as a driving force to trigger phase transformation of preset non-equiatomic high-entropy solid-solution phase at GBs.This in situ deformation-induced phase transformation at GBs introduces a well-known effect:transformation-induced plasticity(TRIP),which enables an exceptional elongation to fracture(above 38%)at a high strength(above 1.5 GPa)in a GB precipitation-hardened high-entropy alloy(HEA).The present strategy in terms of"local stress concentration-induced phase transformations at GBs"may provide a fundamental approach by taking advantage of(rather than avoiding)the GB precipitation to gain a superior combination of high strength and high ductility in HEAs. 展开更多
关键词 Non-equiatomic Grain-boundary precipitation High-entropy alloys DUCTILITY Transformation-induced plasticity
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Voltage Dependence of Resistivity in Semiconducting Ceramics
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作者 郑振华 缪容之 陈羽 《Chinese Science Bulletin》 SCIE EI CAS 1994年第7期548-552,共5页
Voltage dependence of resistivity(VDR)is a widely existing phenomenon insemiconducting ceramics, but there is no quantitative study on this phenomenon. Inthis note, the quantitative results of voltage dependence of re... Voltage dependence of resistivity(VDR)is a widely existing phenomenon insemiconducting ceramics, but there is no quantitative study on this phenomenon. Inthis note, the quantitative results of voltage dependence of resistivity insemiconducting ceramics are obtained from the grain boundary barrier model, andthe methods to decrease the voltage dependence of resistivity in sendconductingceramics are proposed. 展开更多
关键词 SEMICONDUCTING CERAMICS RESISTIVITY voltage DEPENDENCE GRAIN-BOUNDARY barrier.
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Piezoresistive effect in p-type polycrystalline diamond films
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作者 方亮 王万录 +2 位作者 廖克俊 丁培道 王健 《Science China Mathematics》 SCIE 1999年第7期769-777,共9页
The piezoresistive effect of boron-doped polycrystalline diamond films was analyzed and discussed by the famous M-S polycrystalline model. It is found that the valence bands splitting-off and the grain-boundary scatte... The piezoresistive effect of boron-doped polycrystalline diamond films was analyzed and discussed by the famous M-S polycrystalline model. It is found that the valence bands splitting-off and the grain-boundary scattering are the main factors responsible for the piezoresistive effect in the p-type polycrystalline diamond films. The gauge-factor calculation formula including the effect of both background scattering and grain-boundary scattering were obtained, and the calculation results are in accordance with the experimental results. 展开更多
关键词 diamond films PIEZORESISTIVE effect GRAIN-BOUNDARY scattering VALENCE BANDS split-off.
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Structural and mechanical properties of nano-crystal TiN coatings
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作者 ZHANG Chenhui PAN Guoshun LUO Jianbin LI Wenzhi CHEN Darong 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2004年第z1期1-7,共7页
The structural and mechanical properties of TiN coatings prepared by ion beam assisted deposition (IBAD) were studied. The coatings have a polycrystal structure with grain size of ~10 nm or less. The hardness of the ... The structural and mechanical properties of TiN coatings prepared by ion beam assisted deposition (IBAD) were studied. The coatings have a polycrystal structure with grain size of ~10 nm or less. The hardness of the coatings increases with increasing grain size of TiN crystallites. The coating with grain size of 10.3 nm even has a superhardness of 44.7GPa. The relationship between the hardness and the grain size in the nano-crystalline coatings was discussed on the basis of grain-boundary triple junctions. 展开更多
关键词 TiN nano-crystal microstructure hardness GRAIN-BOUNDARY TRIPLE junctions.
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High-strain-rate superplasticity in oxide ceramics:a trial of microstructural design based on creep-cavitation mechanisms
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作者 Keijiro HIRAGA Byung-Nam KIM +3 位作者 Koji MORITA Hidehiro YOSHIDA Yoshio SAKKA Masaaki TABUCHI 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2011年第3期195-204,共10页
From existing knowledge about high-temperature cavitation mechanisms, necessary conditions were discussed for the suppression of cavitation failure during superplastic deformation in ceramic materials. The discussion,... From existing knowledge about high-temperature cavitation mechanisms, necessary conditions were discussed for the suppression of cavitation failure during superplastic deformation in ceramic materials. The discussion, where special attention was placed on the relaxation of stress concentrations during grain-boundary sliding and cavity nucleation and growth, leaded to a conclusion that cavitation failure could be retarded by the simultaneous controlling of the initial grain size, the number of residual defects, diffusivity, dynamic grain growth and the homogeneity of microstructure. On the basis of this conclusion, high-strain-rate superplasticity (defined as superplasticity at a strain rate higher than 0.01 s^-1) could be intentionally attained in some oxide ceramic materials. This was shown in tetragonal zirconia and composites consisting of zirconia, a-alumina and a spinel phase. 展开更多
关键词 Grain-boundary sliding ACCOMMODATION Stress concentration Diffusional relaxation Cavity nucleation Cavity growth Dynamic grain growth
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