Nanotubes, such as boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs), exhibit excellent mechanical properties. In this work, high-quality BNNTs were synthesized by ball milling and annealing. Subsequently, w...Nanotubes, such as boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs), exhibit excellent mechanical properties. In this work, high-quality BNNTs were synthesized by ball milling and annealing. Subsequently, well-dispersed 3vol%BNNTs/Cu and 3vol%CNTs/Cu composites were successfully prepared using ball milling, spark plasma sintering, and followed by hot-rolling. Moreover, the mechanical properties and strengthening mechanisms of BNNTs/Cu and CNTs/Cu composites were compared and discussed in details. At 293 K,both BNNTs/Cu and CNTs/Cu composites exhibited similar ultimate tensile strength (UTS) of~404 MPa, which is approximately 170%higher than pure Cu. However, at 873 K, the UTS and yield strength of BNNTs/Cu are 27%and 29%higher than those of CNTs/Cu, respectively.This difference can be attributed to the stronger inter-walls shear resistance, higher thermomechanical stability of BNNTs, and stronger bonding at the BNNTs/Cu interface as compared to the CNTs/Cu interface. These findings provide valuable insights into the potential of BNNTs as an excellent reinforcement for metal matrix composites, particularly at high temperature.展开更多
The adsorption of Fe(CO)4 on various types of boron nitride nanotubes (BNNTs) areinvestigated by employing density functional theory. Our results indicate that Fe(CO)4 prefers to adsorb on the top of nitrogen at...The adsorption of Fe(CO)4 on various types of boron nitride nanotubes (BNNTs) areinvestigated by employing density functional theory. Our results indicate that Fe(CO)4 prefers to adsorb on the top of nitrogen atom via Fe atom, and the electronic property analysis indicates that the adsorption of Fe(CO)4 can reduce the band-gap of BNNTs.展开更多
Understanding the chemistry of BNNT is a crucial step toward their ultimate practical use. A comparative study of Reactions A (ASWCNT (5,5) and CCl2) and B (ASWBNNT (5,5) and CCl2) have been performed by using...Understanding the chemistry of BNNT is a crucial step toward their ultimate practical use. A comparative study of Reactions A (ASWCNT (5,5) and CCl2) and B (ASWBNNT (5,5) and CCl2) have been performed by using ONIOM (B3LYP/6-31G*: AM1) method in Gaussian03 program package. The results show that (1) the two reactions are both exothermic; (2) the mechanism of Reaction B is a two-step mechanism; (3) the difference in energy barriers suggests that the reaction of CCl2 with BNNT is easier than with CNT; (4) in reaction B, CCl2 prefers to attack the boron atom of BNNT first.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 work focuses on the preferable orientation analysis of the hybrid system where the C60 molecules are encap- sulated inside the boron nitride nanotubes by using the two-molecule model. The low-energy state can be ...This work focuses on the preferable orientation analysis of the hybrid system where the C60 molecules are encap- sulated inside the boron nitride nanotubes by using the two-molecule model. The low-energy state can be acquired in the contour map, which provides the visual information of the systematical van der Waals interaction potential for the C60 molecules adopting different orientations. Our results show that the C60 molecules exhibit the pre- ferred pentagon and hexagon orientations with the tube's diameter smaller and larger than 13.55A, respectively. The preferred two-bond orientation obtained in the single-molecule model is absent in this study, indicating that the intermolecular interaction of adjacent C60 molecules plays an important role in the orientational behaviors of this peapod structure.展开更多
Armchair (n, n) single walled boron nitride nanotubes with n = 2-17 are studied by the density functional theory at the B3LYP/3-21G(d) level combined with the periodic boundary conditions for simulating the ultra ...Armchair (n, n) single walled boron nitride nanotubes with n = 2-17 are studied by the density functional theory at the B3LYP/3-21G(d) level combined with the periodic boundary conditions for simulating the ultra long model. The results show that the structure parameters and the formation energies bear a strong relationship to n. The fitted analytical equations are developed with correlation coefficients larger than 0.999. The energy gaps of (2, 2) and (3, 3) tubes are indirect gaps, and the larger tubes (n = 4-17) have direct energy gaps. Results show that the armchair boron nitride nanotubes (n = 2-17) are insulators with wide energy gaps of between 5.93 eV and 6.23 eV.展开更多
We report on a first-principles study of a novel band modulation in zigzag double-walled boron nitride nan- otubes (DBNNTs) by applying radial strain and coupled ex- ternal electric field. We show that the band alig...We report on a first-principles study of a novel band modulation in zigzag double-walled boron nitride nan- otubes (DBNNTs) by applying radial strain and coupled ex- ternal electric field. We show that the band alignment be- tween the inner and outer walls of the DBNNTs can be tuned from type I to type II with increasing radial strain, accompa- nied with a direct to indirect band gap transition and a sub- stantial gap reduction. The band gap can be further signifi- cantly reduced by applying a transverse electric field. The coupling of electric field with the radial strain makes the field-induced gap reduction being anisotropic and more re- markable than that in undeformed DBNNTs. In particular, the gap variation induced by electric field perpendicular to the radial strain is the most remarkable among all the modu-lations. These tunable properties by electromechanical cou- pling in DBNNTs will greatly enrich their versatile applica- tions in future nanoelectronics.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
Boron nitride nanotubes(BNNTs)show exceptional physical properties including high mechanical strength and thermal conductivity;however,their applications have been restricted due to limited dispersibility in processin...Boron nitride nanotubes(BNNTs)show exceptional physical properties including high mechanical strength and thermal conductivity;however,their applications have been restricted due to limited dispersibility in processing solvents.Here,a novel BNNT dispersion method with exceptional dispersibility in a wide range of solvents has been demonstrated by surtace polarity modulation through short-molecule pyridine attachment.Nitrogen atoms in pyridine are selectively bonded to electron-deficient boron atoms of the BNNT surface through Lewis acid-base reaction,which changes the surface polarity of BNNTs from neutral to negative.Re-dispersing pyridine-attached BNNTs(Py-BNNTs)create a thick and stable electronic double layer(EDL),resulting in uniform dispersion of BNNTs in solvents with an exceptional solubility parameter range of 18.5-48 MPa^1/2.The uniform dispersion of BNNTs is maintained even after the mixing with diverse polymers.Finally,composites incorporating uniformly-distributed BNNTs have been realized,and extraordinary property enhancements have been observed.The thermal conductivity of 20 wt.%Py-BNNT/epoxy composite has been significantly improved by 69.6%and the tensile strength of 2 wt.%Py-BNNT/PVA has been dramatically improved by 75.3%.Our work demonstrates a simple and facile route to dispersing BNNTs in diverse solvents,consequently leading to selective utlization of BNNT dispersed solvents in various application fields.展开更多
High-purity and high-yield boron nitride nanotubes with large aspect ratio were prepared by a facile two-step process,including the synthesis of boron/nickel containing precursors by precipitation reactions and subseq...High-purity and high-yield boron nitride nanotubes with large aspect ratio were prepared by a facile two-step process,including the synthesis of boron/nickel containing precursors by precipitation reactions and subsequent thermally catalytic chemical vapor deposition reactions.The influence of catalyst content and annealing temperature on the phase composition and microstructure of the products were investigated.The results show that it is difficult to exert the catalytic effect of nickel-based catalyst at low temperatures(<1400℃).At appropriate temperatures(1400-1500℃),highly crystalline boron nitride nanotubes with a length of more than 50 mm and a diameter of 50 nm are formed.The content of catalyst in the precursor mainly affects the morphology of the boron nitride product.If the content is too low,it is easy to form boron nitride particles;while high catalyst content can easily lead to catalyst aggregation and form a submicron one-dimensional boron nitride with unregular structure.Based on microstructural evolutions,phase changes,and thermodynamic analysis,the vapor-liquid-solid(V-L-S)growth mechanism of the tip growth mode dominates the formation of boron nitride nanotubes has also been verified.展开更多
The electronic structure of the heterojunction is the foundation of the study on its working mechanism. Models of the heterojunctions formed by an (8, 0) boron nitride nanotube and an (8, 0) carbon nanotube with C...The electronic structure of the heterojunction is the foundation of the study on its working mechanism. Models of the heterojunctions formed by an (8, 0) boron nitride nanotube and an (8, 0) carbon nanotube with C-B or C-N interface have been established. The structures of the above heterojunctions were optimized with first-principle calculations based on density functional theory. The rearrangements of the heterojunctions concentrate mainly on their interfaces. The highest occupied molecular orbital and the lowest unoccupied molecular orbital of the heterojunctions distribute in the carbon nanotube section. As the band offsets of the above heterojunctions are achieved with the average bond energy method, the band structure is plotted.展开更多
We have investigated the behavior of two nanotube systems,carbon and boron nitride,under controlled applied voltages in a high-resolution transmission electron microscope(TEM)equipped with a scanning tunneling microsc...We have investigated the behavior of two nanotube systems,carbon and boron nitride,under controlled applied voltages in a high-resolution transmission electron microscope(TEM)equipped with a scanning tunneling microscope(STM)unit.Individual nanotubes(or thin bundles)were positioned between a piezo-movable gold electrode and a biased(up to±140 V)STM tip inside the pole-piece of the microscope.The structures studied include double-and multi-walled carbon nanotubes(the latter having diverse morphologies due to the various synthetic procedures utilized),few-layered boron nitride nanotube bundles and multi-walled boron nitride nanotubes(with or without functionalized surfaces).The electrical breakdown,physical failure,and electrostatic interactions are documented for each system.展开更多
基金financially supported by the National Natural Science Foundation of China (No.52171144)。
文摘Nanotubes, such as boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs), exhibit excellent mechanical properties. In this work, high-quality BNNTs were synthesized by ball milling and annealing. Subsequently, well-dispersed 3vol%BNNTs/Cu and 3vol%CNTs/Cu composites were successfully prepared using ball milling, spark plasma sintering, and followed by hot-rolling. Moreover, the mechanical properties and strengthening mechanisms of BNNTs/Cu and CNTs/Cu composites were compared and discussed in details. At 293 K,both BNNTs/Cu and CNTs/Cu composites exhibited similar ultimate tensile strength (UTS) of~404 MPa, which is approximately 170%higher than pure Cu. However, at 873 K, the UTS and yield strength of BNNTs/Cu are 27%and 29%higher than those of CNTs/Cu, respectively.This difference can be attributed to the stronger inter-walls shear resistance, higher thermomechanical stability of BNNTs, and stronger bonding at the BNNTs/Cu interface as compared to the CNTs/Cu interface. These findings provide valuable insights into the potential of BNNTs as an excellent reinforcement for metal matrix composites, particularly at high temperature.
基金the Key Project of Fujian Province (2005HZ01-2-6)
文摘The adsorption of Fe(CO)4 on various types of boron nitride nanotubes (BNNTs) areinvestigated by employing density functional theory. Our results indicate that Fe(CO)4 prefers to adsorb on the top of nitrogen atom via Fe atom, and the electronic property analysis indicates that the adsorption of Fe(CO)4 can reduce the band-gap of BNNTs.
基金supported by the National Natural Science Foundation of China (No 20303010, 20273034 and 20673063)NKStar HPC Program The authors appreciate the assistance provided by Professor Zun-Sheng Cai
文摘Understanding the chemistry of BNNT is a crucial step toward their ultimate practical use. A comparative study of Reactions A (ASWCNT (5,5) and CCl2) and B (ASWBNNT (5,5) and CCl2) have been performed by using ONIOM (B3LYP/6-31G*: AM1) method in Gaussian03 program package. The results show that (1) the two reactions are both exothermic; (2) the mechanism of Reaction B is a two-step mechanism; (3) the difference in energy barriers suggests that the reaction of CCl2 with BNNT is easier than with CNT; (4) in reaction B, CCl2 prefers to attack the boron atom of BNNT first.
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 Basic Research Program of China under Grant No 2011CB808200the National Natural Science Foundation of China under Grant Nos 11504150,11304020 and 51320105007the Cheung Kong Scholars Programme of China
文摘This work focuses on the preferable orientation analysis of the hybrid system where the C60 molecules are encap- sulated inside the boron nitride nanotubes by using the two-molecule model. The low-energy state can be acquired in the contour map, which provides the visual information of the systematical van der Waals interaction potential for the C60 molecules adopting different orientations. Our results show that the C60 molecules exhibit the pre- ferred pentagon and hexagon orientations with the tube's diameter smaller and larger than 13.55A, respectively. The preferred two-bond orientation obtained in the single-molecule model is absent in this study, indicating that the intermolecular interaction of adjacent C60 molecules plays an important role in the orientational behaviors of this peapod structure.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50572089)the Basic Research Foundation of Northwestern Polytechnical University (Grant No. JC201269)
文摘Armchair (n, n) single walled boron nitride nanotubes with n = 2-17 are studied by the density functional theory at the B3LYP/3-21G(d) level combined with the periodic boundary conditions for simulating the ultra long model. The results show that the structure parameters and the formation energies bear a strong relationship to n. The fitted analytical equations are developed with correlation coefficients larger than 0.999. The energy gaps of (2, 2) and (3, 3) tubes are indirect gaps, and the larger tubes (n = 4-17) have direct energy gaps. Results show that the armchair boron nitride nanotubes (n = 2-17) are insulators with wide energy gaps of between 5.93 eV and 6.23 eV.
基金supported by the 973 Program(2012CB933403 and 2013CB932604)the National Natural Science Foundation of China(11172124 and 91023026)+5 种基金Jiangsu Province Natural Science Foundation(BK2011722)MOE doctoral discipline Foundation(20113218120033)China and Jiangsu Province Postdoctoral Science Foundation(2012T50494,20110490132 and 1002015B)the Fundamental Research Funds for the Central Universities(NS2012067)supported by the National Science Foundation(CMMI and NIRT)the U.S.Army Research Office MURI(W911NF-11-1-0362)
文摘We report on a first-principles study of a novel band modulation in zigzag double-walled boron nitride nan- otubes (DBNNTs) by applying radial strain and coupled ex- ternal electric field. We show that the band alignment be- tween the inner and outer walls of the DBNNTs can be tuned from type I to type II with increasing radial strain, accompa- nied with a direct to indirect band gap transition and a sub- stantial gap reduction. The band gap can be further signifi- cantly reduced by applying a transverse electric field. The coupling of electric field with the radial strain makes the field-induced gap reduction being anisotropic and more re- markable than that in undeformed DBNNTs. In particular, the gap variation induced by electric field perpendicular to the radial strain is the most remarkable among all the modu-lations. These tunable properties by electromechanical cou- pling in DBNNTs will greatly enrich their versatile applica- tions in future nanoelectronics.
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.
基金This study was supported financially by the Fundamental Research Program(PNK6050 and PNK6550)of the Korea Institute of Materials Science(KIMS).
文摘Boron nitride nanotubes(BNNTs)show exceptional physical properties including high mechanical strength and thermal conductivity;however,their applications have been restricted due to limited dispersibility in processing solvents.Here,a novel BNNT dispersion method with exceptional dispersibility in a wide range of solvents has been demonstrated by surtace polarity modulation through short-molecule pyridine attachment.Nitrogen atoms in pyridine are selectively bonded to electron-deficient boron atoms of the BNNT surface through Lewis acid-base reaction,which changes the surface polarity of BNNTs from neutral to negative.Re-dispersing pyridine-attached BNNTs(Py-BNNTs)create a thick and stable electronic double layer(EDL),resulting in uniform dispersion of BNNTs in solvents with an exceptional solubility parameter range of 18.5-48 MPa^1/2.The uniform dispersion of BNNTs is maintained even after the mixing with diverse polymers.Finally,composites incorporating uniformly-distributed BNNTs have been realized,and extraordinary property enhancements have been observed.The thermal conductivity of 20 wt.%Py-BNNT/epoxy composite has been significantly improved by 69.6%and the tensile strength of 2 wt.%Py-BNNT/PVA has been dramatically improved by 75.3%.Our work demonstrates a simple and facile route to dispersing BNNTs in diverse solvents,consequently leading to selective utlization of BNNT dispersed solvents in various application fields.
基金supported by the National Natural Science Foundation of China,China(52002293)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology,China(2021QNRC001,YESS20210230)+3 种基金the Open Project of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing of Wuhan University of Technology,China(21-KF-25)the Innovative Project of Key Laboratory of Green Chemical Engineering Process of Ministry of Education(GCX202106)Science Research Fund(K202029)College Students Innovation and Entrepreneurship Training Program(S202110490021)of Wuhan Institute of Technology,China.
文摘High-purity and high-yield boron nitride nanotubes with large aspect ratio were prepared by a facile two-step process,including the synthesis of boron/nickel containing precursors by precipitation reactions and subsequent thermally catalytic chemical vapor deposition reactions.The influence of catalyst content and annealing temperature on the phase composition and microstructure of the products were investigated.The results show that it is difficult to exert the catalytic effect of nickel-based catalyst at low temperatures(<1400℃).At appropriate temperatures(1400-1500℃),highly crystalline boron nitride nanotubes with a length of more than 50 mm and a diameter of 50 nm are formed.The content of catalyst in the precursor mainly affects the morphology of the boron nitride product.If the content is too low,it is easy to form boron nitride particles;while high catalyst content can easily lead to catalyst aggregation and form a submicron one-dimensional boron nitride with unregular structure.Based on microstructural evolutions,phase changes,and thermodynamic analysis,the vapor-liquid-solid(V-L-S)growth mechanism of the tip growth mode dominates the formation of boron nitride nanotubes has also been verified.
基金supported by the Pre-Research Foundation from the National Ministries and Commissions(No.51308040203).
文摘The electronic structure of the heterojunction is the foundation of the study on its working mechanism. Models of the heterojunctions formed by an (8, 0) boron nitride nanotube and an (8, 0) carbon nanotube with C-B or C-N interface have been established. The structures of the above heterojunctions were optimized with first-principle calculations based on density functional theory. The rearrangements of the heterojunctions concentrate mainly on their interfaces. The highest occupied molecular orbital and the lowest unoccupied molecular orbital of the heterojunctions distribute in the carbon nanotube section. As the band offsets of the above heterojunctions are achieved with the average bond energy method, the band structure is plotted.
基金by the Nanoscale Materials Center Project,and,in part,by the World Premier International Center for Materials Nanoarchitectonics(MANA)Project,both tenable at the National Institute for Materials Science(NIMS).
文摘We have investigated the behavior of two nanotube systems,carbon and boron nitride,under controlled applied voltages in a high-resolution transmission electron microscope(TEM)equipped with a scanning tunneling microscope(STM)unit.Individual nanotubes(or thin bundles)were positioned between a piezo-movable gold electrode and a biased(up to±140 V)STM tip inside the pole-piece of the microscope.The structures studied include double-and multi-walled carbon nanotubes(the latter having diverse morphologies due to the various synthetic procedures utilized),few-layered boron nitride nanotube bundles and multi-walled boron nitride nanotubes(with or without functionalized surfaces).The electrical breakdown,physical failure,and electrostatic interactions are documented for each system.