By employing the nonlinear von Karman shell theory and the theory of piezoelect ricity including thermal effec ts,the constitutive relations of the BNNT-reinforced piezoelec trie shell are built.Recurring to the'X...By employing the nonlinear von Karman shell theory and the theory of piezoelect ricity including thermal effec ts,the constitutive relations of the BNNT-reinforced piezoelec trie shell are built.Recurring to the'XY‘rec tangle model,the material consta nts are reckoned.Then,the nonlinear governing equations of the st rue ture are derived t hrough the Reissner variational principle and solved by the fourth-order Runge-Kutta method.In numerical calculations,the effects of temperature,voltage,volume fraction,etc.,on the bifurcation and chaos of piezoelectric shell reinforced with BNNTs are discussed in detail.展开更多
By means of density functional theory calculations, an orthogonal boron-carbon-nitrogen compound called （3,0）- BC2N is predicted, which can be obtained by transversely compressing （3,03 carbon nanotubes （CNTs） an...By means of density functional theory calculations, an orthogonal boron-carbon-nitrogen compound called （3,0）- BC2N is predicted, which can be obtained by transversely compressing （3,03 carbon nanotubes （CNTs） and boron nitride nanotubes （BNNTs）. Its structural stability, elastic properties, mechanical properties and electronic structure are systematically investigated. The results show that （3,0）-BU2N is a superhard material with a direct bandgap. However, its similar structures, （3,0）-C and （3,0）-BN are indirect semiconductors. Strikingly, （3,0）-C is harder than diamond. We also simulate the x-ray diffraction of （3,0）-BC2N to support future experimental investigations. In addition, our study shows that the transition from （3,03 CNTS and BNNTs to （3,0）-BC2N is irreversible.展开更多
Under combined electro-thermo-mechanical loadings, the nonlinear bending of piezoelectric cylindrical shell reinforced with boron nitride nanotubes (BNNTs) is investigated in this paper. By employing nonlinear strains...Under combined electro-thermo-mechanical loadings, the nonlinear bending of piezoelectric cylindrical shell reinforced with boron nitride nanotubes (BNNTs) is investigated in this paper. By employing nonlinear strains based on Donnell shell theory and utilizing piezoelectric theory including thermal effects, the constitutive relations of the piezoelectric shell reinforced with BNNTs are established. Then the governing equations of the structure are derived through variational principle and resolved by applying the finite difference method. In numerical examples, the effects of geometric nonlinear, voltage, temperature, as well as volume fraction on the deflection and bending moment of axisymmetrical piezoelectric cylindrical shell reinforced with BNNTs are discussed in detail.展开更多
A thin BN interphase is applied on BNNTs surface to tailor the interfacial bonding between BNNTs and SiC matrix in hierarchical SiCf/SiC composites. The thickness of BN interphase ranging from 10 to 70 nm can be optim...A thin BN interphase is applied on BNNTs surface to tailor the interfacial bonding between BNNTs and SiC matrix in hierarchical SiCf/SiC composites. The thickness of BN interphase ranging from 10 to 70 nm can be optimized by chemical vapor deposition after BNNTs are in situ grown on SiC fiber surface. Without BN interphase, the fracture toughness of hierarchical Si Cf/Si C composites can be impaired by 13.6% due to strong interfacial bonding. As long as BN interphase with 30–45 nm thickness is applied, the interfacial bonding can be optimized and fracture toughness of hierarchical composites can be improved by 27.3%. It implies that tailoring BNNTs/matrix interface by depositing a layer of BN interphase is in favor of activating energy dissipation mechanisms at nanoscale induced by BNNTs.展开更多
Boron nitride nanotubes(BNNTs)were treated as brittle materials and could be used to enhance the composite mechanical properties.Many approaches were used to verify the theoretical prediction experimentally,but how to...Boron nitride nanotubes(BNNTs)were treated as brittle materials and could be used to enhance the composite mechanical properties.Many approaches were used to verify the theoretical prediction experimentally,but how to in situ real-time characterize nanomechanical properties of BNNTs was still interested to the researchers.An in situ transmission electron microscopy(TEM)equipped with a force transducer holder had been used to study the structure evolution behavior of BNNTs with axial compression.Real-time video and the force transducer had been used synchronously to record the whole force loading process where the mechanical deformation of BNNT began,buckled and ended with fracture.An in dividual ultrathin BNNT was employed to con duct the loading test.The results showed that the elastic deformation happened on the BNNT.Young's modulus?1.05-1.37 Tpa and elasticity coefficient?198.7-255.9 N/m of BNNT were calculated by Euler formula and Hooker's law,respectively.展开更多
Boron nitride nanotube（BNNT） films were synthesized by combining ball milling and thermal chemical vapor deposition（CVD） using nano-Fe3O4 as a catalyst. The as-produced BNNTs have a bamboo-like structure and have ...Boron nitride nanotube（BNNT） films were synthesized by combining ball milling and thermal chemical vapor deposition（CVD） using nano-Fe3O4 as a catalyst. The as-produced BNNTs have a bamboo-like structure and have a diameter in the range of 50~200 nm with an average length of more than 40 mm.Moreover, BNNT nanojunction structures were synthesized. The structure and morphology of the BNNTs were characterized by XRD, SEM, TEM and HRTEM. The possible growth mechanism of BNNTs and BNNT nanojunction structures were proposed. Though the BNNT films were observed, out of our expectation,BNNTs with thin tube wall and small average diameter have not been achieved, and this could be mainly ascribed to the aggregation of the nanoparticle catalyst, resulting in greater catalyst particles during the process of BNNT growth. This result will provide a promising approach to obtain the desired shape of BNNTs and produce branched junctions of BNNTs.展开更多
The first principles calculations based on density functional theory（DFT） were performed for investigating the interaction of amino acids with（5, 5） armchair and（8, 0） zigzag boron nitride nanotubes（BNNTs）. Fi...The first principles calculations based on density functional theory（DFT） were performed for investigating the interaction of amino acids with（5, 5） armchair and（8, 0） zigzag boron nitride nanotubes（BNNTs）. Findings showed that the adsorption and solvation energies were negative for（5, 5）/（8,0） BNNTs-amino acid complexes, implying the thermodynamic favorability and spontaneous interactions of amino acids with BNNTs sidewall. Based on calculated results, the BNNTs are expected to be a potential efficient adsorbent as well as a suitable drug delivery vehicle for the adsorption of amino acids within biological systems.展开更多
This study reports an efficient method for growing high-quality boron nitride nanotubes(BNNTs)via chemical vapor deposition of low-melting-point precursors—magnesium diboride(MgB_(2)),magnesium nitride(Mg_(3)N_(2)),a...This study reports an efficient method for growing high-quality boron nitride nanotubes(BNNTs)via chemical vapor deposition of low-melting-point precursors—magnesium diboride(MgB_(2)),magnesium nitride(Mg_(3)N_(2)),and diboron trioxide(B_(2)O)at a growth temperature of 1000–1300℃.The strong oxygen-capturing ability of Mg_(3)N_(2)inhibits the formation of high-melting-point Mg_(3)B_(2)O_(6),which helps MgB_(2)to maintain an efficient and stable catalytic capacity,thereby enhancing its growth efficiency and utilization of the boron source.Moreover,polydimethylsiloxane(PDMS)composites formed from these BNNTs demonstrated much greater thermal conductivities than pure PDMS.Thus,this novel strategy for preparing BNNTs is efficient,and they have great potential for application as thermal interface materials.展开更多
基金the supports from National Natural Science Foundation of China(Project No.51822803).
文摘By employing the nonlinear von Karman shell theory and the theory of piezoelect ricity including thermal effec ts,the constitutive relations of the BNNT-reinforced piezoelec trie shell are built.Recurring to the'XY‘rec tangle model,the material consta nts are reckoned.Then,the nonlinear governing equations of the st rue ture are derived t hrough the Reissner variational principle and solved by the fourth-order Runge-Kutta method.In numerical calculations,the effects of temperature,voltage,volume fraction,etc.,on the bifurcation and chaos of piezoelectric shell reinforced with BNNTs are discussed in detail.
基金Supported by the National Natural Science Foundation of China under Grant No 11464028the Science Foundation of Department of Education of Jiangxi Province under Grant No GJJ150025
文摘By means of density functional theory calculations, an orthogonal boron-carbon-nitrogen compound called （3,0）- BC2N is predicted, which can be obtained by transversely compressing （3,03 carbon nanotubes （CNTs） and boron nitride nanotubes （BNNTs）. Its structural stability, elastic properties, mechanical properties and electronic structure are systematically investigated. The results show that （3,0）-BU2N is a superhard material with a direct bandgap. However, its similar structures, （3,0）-C and （3,0）-BN are indirect semiconductors. Strikingly, （3,0）-C is harder than diamond. We also simulate the x-ray diffraction of （3,0）-BC2N to support future experimental investigations. In addition, our study shows that the transition from （3,03 CNTS and BNNTs to （3,0）-BC2N is irreversible.
文摘Under combined electro-thermo-mechanical loadings, the nonlinear bending of piezoelectric cylindrical shell reinforced with boron nitride nanotubes (BNNTs) is investigated in this paper. By employing nonlinear strains based on Donnell shell theory and utilizing piezoelectric theory including thermal effects, the constitutive relations of the piezoelectric shell reinforced with BNNTs are established. Then the governing equations of the structure are derived through variational principle and resolved by applying the finite difference method. In numerical examples, the effects of geometric nonlinear, voltage, temperature, as well as volume fraction on the deflection and bending moment of axisymmetrical piezoelectric cylindrical shell reinforced with BNNTs are discussed in detail.
基金supported by National Natural Science Foundation of China (Grant Nos. 51772310 and 51502323)the National Key Research and Development Program of China (Grant No. 2017YFB0703200)+2 种基金the research grant from Science and Technology Commission of Shanghai Municipality (Grant No. 16DZ2260600)Science Foundation for Youth Scholar of State Key Laboratory of High Performance Ceramics (Grant No. SKL201601)Chinese Academy of Science (Grant No. QYZDY-SSW-JSC031).
文摘A thin BN interphase is applied on BNNTs surface to tailor the interfacial bonding between BNNTs and SiC matrix in hierarchical SiCf/SiC composites. The thickness of BN interphase ranging from 10 to 70 nm can be optimized by chemical vapor deposition after BNNTs are in situ grown on SiC fiber surface. Without BN interphase, the fracture toughness of hierarchical Si Cf/Si C composites can be impaired by 13.6% due to strong interfacial bonding. As long as BN interphase with 30–45 nm thickness is applied, the interfacial bonding can be optimized and fracture toughness of hierarchical composites can be improved by 27.3%. It implies that tailoring BNNTs/matrix interface by depositing a layer of BN interphase is in favor of activating energy dissipation mechanisms at nanoscale induced by BNNTs.
基金supported by the National Natural Science Foundation of China(Nos. 51573201, 21773205, 51501209 and 201675165)Key R&D Program of Yunnan Province(No. 2018BA068)+7 种基金NSFC-Zhejiang Joint Fund for the Integration of Industrialization and Informatization(No. U1709205)National Key R&D Program of China(No. 2017YFB0406000)the Project of the Chinese Academy of Sciences(Nos. YZ201640 and KFZD-SW409)Public Welfare Project of Zhejiang Province (No. 2016C31026)Science and Technology Major Project of Ningbo (Nos.2016B10038 and 2016S1002)International S&T Cooperation Program of Ningbo(No. 2017D10016)the 3315 Program of Ningbo for financial supportthe financial support by the Science and Technology Major Project of Ningbo (No. 2015S1001)
文摘Boron nitride nanotubes(BNNTs)were treated as brittle materials and could be used to enhance the composite mechanical properties.Many approaches were used to verify the theoretical prediction experimentally,but how to in situ real-time characterize nanomechanical properties of BNNTs was still interested to the researchers.An in situ transmission electron microscopy(TEM)equipped with a force transducer holder had been used to study the structure evolution behavior of BNNTs with axial compression.Real-time video and the force transducer had been used synchronously to record the whole force loading process where the mechanical deformation of BNNT began,buckled and ended with fracture.An in dividual ultrathin BNNT was employed to con duct the loading test.The results showed that the elastic deformation happened on the BNNT.Young's modulus?1.05-1.37 Tpa and elasticity coefficient?198.7-255.9 N/m of BNNT were calculated by Euler formula and Hooker's law,respectively.
基金supported by the National Natural Science Funds of China (No. 61404036)the National Basic Research Program of China (No. 2012CB934104)the Fundamental Research Funds for the Central Universities (Nos. HIT.NSRIF. 2015039, 01508536)
文摘Boron nitride nanotube（BNNT） films were synthesized by combining ball milling and thermal chemical vapor deposition（CVD） using nano-Fe3O4 as a catalyst. The as-produced BNNTs have a bamboo-like structure and have a diameter in the range of 50~200 nm with an average length of more than 40 mm.Moreover, BNNT nanojunction structures were synthesized. The structure and morphology of the BNNTs were characterized by XRD, SEM, TEM and HRTEM. The possible growth mechanism of BNNTs and BNNT nanojunction structures were proposed. Though the BNNT films were observed, out of our expectation,BNNTs with thin tube wall and small average diameter have not been achieved, and this could be mainly ascribed to the aggregation of the nanoparticle catalyst, resulting in greater catalyst particles during the process of BNNT growth. This result will provide a promising approach to obtain the desired shape of BNNTs and produce branched junctions of BNNTs.
文摘The first principles calculations based on density functional theory（DFT） were performed for investigating the interaction of amino acids with（5, 5） armchair and（8, 0） zigzag boron nitride nanotubes（BNNTs）. Findings showed that the adsorption and solvation energies were negative for（5, 5）/（8,0） BNNTs-amino acid complexes, implying the thermodynamic favorability and spontaneous interactions of amino acids with BNNTs sidewall. Based on calculated results, the BNNTs are expected to be a potential efficient adsorbent as well as a suitable drug delivery vehicle for the adsorption of amino acids within biological systems.
基金supported by the National Natural Science Foundation of China(No.51972162).
文摘This study reports an efficient method for growing high-quality boron nitride nanotubes(BNNTs)via chemical vapor deposition of low-melting-point precursors—magnesium diboride(MgB_(2)),magnesium nitride(Mg_(3)N_(2)),and diboron trioxide(B_(2)O)at a growth temperature of 1000–1300℃.The strong oxygen-capturing ability of Mg_(3)N_(2)inhibits the formation of high-melting-point Mg_(3)B_(2)O_(6),which helps MgB_(2)to maintain an efficient and stable catalytic capacity,thereby enhancing its growth efficiency and utilization of the boron source.Moreover,polydimethylsiloxane(PDMS)composites formed from these BNNTs demonstrated much greater thermal conductivities than pure PDMS.Thus,this novel strategy for preparing BNNTs is efficient,and they have great potential for application as thermal interface materials.
