The government of India has set up distributed network in India for sharing the knowledge among the higher learning Institutions in the year 2009 under Next Generation Services (NGN) and slowly-slowly it is expanding ...The government of India has set up distributed network in India for sharing the knowledge among the higher learning Institutions in the year 2009 under Next Generation Services (NGN) and slowly-slowly it is expanding as the distributed computing network becomes very popular now days due to low cost involvement. This network is called as a National Knowledge Network (NKN) whose main purpose is to connect all the Indian universities, research institutions, research labs, digital libraries, countrywide classroom, etc. under one platform. In the present work, sharing of different kinds of facilities under NKN is demonstrated for the static step topology designed by the authors. The different kinds of facilities are connected through step topology and a well known modeling technique i.e. Unified Modeling Language (UML) is used for demonstrating the UML class diagram for sharing of all these facilities through step topology. Some experimental results are also demonstrated for the topology.展开更多
用熔盐法合成铌酸钾钠(Na_(0.52)K_(0.48)NbO_3,N_(52)K_(48)N)陶瓷粉体,用传统固相烧结工艺制备N_(52)K_(48)N陶瓷。研究了熔盐含量和烧结温度对N_(52)K_(48)N陶瓷粉体及其所制备陶瓷的相结构、微观形貌及电学性能的影响。结果发现,熔...用熔盐法合成铌酸钾钠(Na_(0.52)K_(0.48)NbO_3,N_(52)K_(48)N)陶瓷粉体,用传统固相烧结工艺制备N_(52)K_(48)N陶瓷。研究了熔盐含量和烧结温度对N_(52)K_(48)N陶瓷粉体及其所制备陶瓷的相结构、微观形貌及电学性能的影响。结果发现,熔盐法在750℃就合成了单一钙钛矿结构的N_(52)K_(48)N陶瓷粉体;随熔盐含量增加,N_(52)K_(48)N陶瓷粉体粒径增大,粉体团聚现象明显减弱。当熔盐与反应物质量之比为1∶5,烧结温度T=1050℃时,所制备的N_(52)K_(48)N陶瓷具有优异的电学性能:压电常数d33=137 p C/N,机电耦合系数kp=32.6%,居里温度Tc=410℃,表明熔盐法是一种很有前途的铌酸钾钠陶瓷制备方法。展开更多
Lead-free piezoelectric NaxK1-xNbO3（x = 0.3-0.8）（NKN） ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special ...Lead-free piezoelectric NaxK1-xNbO3（x = 0.3-0.8）（NKN） ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na content.The grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary（MPB） in NaxK1-xNbO3 ceramics.Such MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N, planar-mode electromechanical coupling coefficient kP of 28.6%, and dielectric constant εr of 703, respectively for the Na0.7K0.3NbO3 ceramic.Cubic temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C, respectively.展开更多
Crystalline(Na_(1-x)K_(x))NbO_(3)(NKN)thin films were deposited on Sr_(2)Nb_(3)O_(10)/TiN/Si(S-TS)substrates at 370°C.Sr_(2)Nb_(3)O_(10)(SNO)nanosheets served as a template for the formation of crystalline NKN fi...Crystalline(Na_(1-x)K_(x))NbO_(3)(NKN)thin films were deposited on Sr_(2)Nb_(3)O_(10)/TiN/Si(S-TS)substrates at 370°C.Sr_(2)Nb_(3)O_(10)(SNO)nanosheets served as a template for the formation of crystalline NKN films at low temperatures.When the NKN film was deposited on one SNO monolayer,the NKN memristor exhibited normal bipolar switching characteristics,which could be attributed to the formation and destruction of oxygen vacancy filaments.Moreover,the NKN memristor with one SNO monolayer exhibited artificial synaptic properties.However,the NKN memristor deposited on two SNO monolayers exhibited self-rectifying bipolar switching properties,with the two SNO monolayers acting as tunneling barriers in the memristor.The conduction mechanism of the NKN memristor with two SNO monolayers in the highresistance state is attributed to Schottky emission,direct tunneling,and Fowler–Nordheim(FN)tunneling.The current conduction in this memristor in the low-resistance state was governed by direct tunneling and FN tunneling.Additionally,the NKN memristor with two SNO monolayers exhibited large ON/OFF and rectification ratios and artificial synaptic properties.Therefore,an NKN memristor with two SNO monolayers can be used for fabricating artificial synaptic devices with a cross-point array structure.展开更多
Lead-free alkali niobates Na_(0.5)K_(0.5)NbO_(3)(NKN)ceramics,with significantly enhanced ferroelectric remanent polarization(Pr),were prepared using Spark Plasma Sintering(SPS).Three types of boundaries were observed...Lead-free alkali niobates Na_(0.5)K_(0.5)NbO_(3)(NKN)ceramics,with significantly enhanced ferroelectric remanent polarization(Pr),were prepared using Spark Plasma Sintering(SPS).Three types of boundaries were observed in the ceramics,being grain boundaries between faceted grains,domain boundaries that separate ferroelectric domains inside individual grains,and nanoscale sub-grain boundaries that reveal the nano-scale mosaicity of individual grains.Part of the sub-grain boundaries were from initial powder particles.The other sub-grain boundaries were built by ordered coalescence of nano-crystals during rapid SPS process.It was worthwhile to emphasize that the ordered coalescence of nano-crystals in bulk ceramics during sintering takes place and completes within minutes.These sub-grain features would disappear at higher temperature by long time sintering.Rapid Spark Plasma Sintering allowed us to capture this transient microstructure.The significantly enhanced ferroelectric Pr of NKN was attributed to nanoscale sub-boundaries,which stimulated the dynamics of ferroelectric domain formation and switching.展开更多
文摘The government of India has set up distributed network in India for sharing the knowledge among the higher learning Institutions in the year 2009 under Next Generation Services (NGN) and slowly-slowly it is expanding as the distributed computing network becomes very popular now days due to low cost involvement. This network is called as a National Knowledge Network (NKN) whose main purpose is to connect all the Indian universities, research institutions, research labs, digital libraries, countrywide classroom, etc. under one platform. In the present work, sharing of different kinds of facilities under NKN is demonstrated for the static step topology designed by the authors. The different kinds of facilities are connected through step topology and a well known modeling technique i.e. Unified Modeling Language (UML) is used for demonstrating the UML class diagram for sharing of all these facilities through step topology. Some experimental results are also demonstrated for the topology.
文摘用熔盐法合成铌酸钾钠(Na_(0.52)K_(0.48)NbO_3,N_(52)K_(48)N)陶瓷粉体,用传统固相烧结工艺制备N_(52)K_(48)N陶瓷。研究了熔盐含量和烧结温度对N_(52)K_(48)N陶瓷粉体及其所制备陶瓷的相结构、微观形貌及电学性能的影响。结果发现,熔盐法在750℃就合成了单一钙钛矿结构的N_(52)K_(48)N陶瓷粉体;随熔盐含量增加,N_(52)K_(48)N陶瓷粉体粒径增大,粉体团聚现象明显减弱。当熔盐与反应物质量之比为1∶5,烧结温度T=1050℃时,所制备的N_(52)K_(48)N陶瓷具有优异的电学性能:压电常数d33=137 p C/N,机电耦合系数kp=32.6%,居里温度Tc=410℃,表明熔盐法是一种很有前途的铌酸钾钠陶瓷制备方法。
基金supported by the National Natural Science Foundation of China (No. 50842028)the National Basic Research Priorities Program of China (No. 2007CB613301)
文摘Lead-free piezoelectric NaxK1-xNbO3（x = 0.3-0.8）（NKN） ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na content.The grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary（MPB） in NaxK1-xNbO3 ceramics.Such MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N, planar-mode electromechanical coupling coefficient kP of 28.6%, and dielectric constant εr of 703, respectively for the Na0.7K0.3NbO3 ceramic.Cubic temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C, respectively.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2020R1A2B5B01002063)the KU-KIST Graduate School Program of the Korea University。
文摘Crystalline(Na_(1-x)K_(x))NbO_(3)(NKN)thin films were deposited on Sr_(2)Nb_(3)O_(10)/TiN/Si(S-TS)substrates at 370°C.Sr_(2)Nb_(3)O_(10)(SNO)nanosheets served as a template for the formation of crystalline NKN films at low temperatures.When the NKN film was deposited on one SNO monolayer,the NKN memristor exhibited normal bipolar switching characteristics,which could be attributed to the formation and destruction of oxygen vacancy filaments.Moreover,the NKN memristor with one SNO monolayer exhibited artificial synaptic properties.However,the NKN memristor deposited on two SNO monolayers exhibited self-rectifying bipolar switching properties,with the two SNO monolayers acting as tunneling barriers in the memristor.The conduction mechanism of the NKN memristor with two SNO monolayers in the highresistance state is attributed to Schottky emission,direct tunneling,and Fowler–Nordheim(FN)tunneling.The current conduction in this memristor in the low-resistance state was governed by direct tunneling and FN tunneling.Additionally,the NKN memristor with two SNO monolayers exhibited large ON/OFF and rectification ratios and artificial synaptic properties.Therefore,an NKN memristor with two SNO monolayers can be used for fabricating artificial synaptic devices with a cross-point array structure.
基金This work was supported by grants of the Swedish Research Council(to Z.S.and L.B.)the Royal Society(to Z.S.and H.Y.)+1 种基金the National Natural Science Foundation of China(to C.N.and Z.S.)L.B.acknowledges support from the Knut and Alice Wallenberg Foundation and the Swedish Foundation for Strategic Research.SEM and TEM studies were performed at the Electron Microscopy Centre at Arrhenius Laboratory,Stockholm University,which is supported by the Knut and Alice Wallenberg Foundation.
文摘Lead-free alkali niobates Na_(0.5)K_(0.5)NbO_(3)(NKN)ceramics,with significantly enhanced ferroelectric remanent polarization(Pr),were prepared using Spark Plasma Sintering(SPS).Three types of boundaries were observed in the ceramics,being grain boundaries between faceted grains,domain boundaries that separate ferroelectric domains inside individual grains,and nanoscale sub-grain boundaries that reveal the nano-scale mosaicity of individual grains.Part of the sub-grain boundaries were from initial powder particles.The other sub-grain boundaries were built by ordered coalescence of nano-crystals during rapid SPS process.It was worthwhile to emphasize that the ordered coalescence of nano-crystals in bulk ceramics during sintering takes place and completes within minutes.These sub-grain features would disappear at higher temperature by long time sintering.Rapid Spark Plasma Sintering allowed us to capture this transient microstructure.The significantly enhanced ferroelectric Pr of NKN was attributed to nanoscale sub-boundaries,which stimulated the dynamics of ferroelectric domain formation and switching.
