Mullite nanowhiskers with Al-rich structure were prepared by molten salt synthesis at 1000°C for 3 h in air using silica, amorphous silica, and ultrafine silica as the silica sources. The phase and morphology of ...Mullite nanowhiskers with Al-rich structure were prepared by molten salt synthesis at 1000°C for 3 h in air using silica, amorphous silica, and ultrafine silica as the silica sources. The phase and morphology of the synthesized products were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy. A thermogravimetric and differential thermal analysis was carried out to determine the reaction mechanism. The results reveal that the silica sources play an important role in determining the morphology of the obtained mullite nanowhiskers. Clusters and disordered arrangements are obtained using common silica and amorphous silica, respectively, whereas the use of ultrafine silica leads to highly ordered mullite nanowhiskers that are 80-120 nm in diameter and 20-30 μm in length. Considering the growth mechanisms, mullite nanowhiskers in the forms of clusters and highly ordered arrangements can be attributed to heterogeneous nucleation, whereas disordered mullite nanowhiskers are obtained by homogenous nucleation.展开更多
This paper reports that the lead zirconate titanate (PZT) piezoelectric composites incorporating zinc oxide nanowhiskers (ZnOw) were prepared by the conventional solid state processing. The whisker-dispersed PZT c...This paper reports that the lead zirconate titanate (PZT) piezoelectric composites incorporating zinc oxide nanowhiskers (ZnOw) were prepared by the conventional solid state processing. The whisker-dispersed PZT composites (PZT/ZnOw) presented a significant enhancement in the mechanical properties such as Young's modulus, tensile strength and compressive strength. Especially, the compressive strength increased from 153 MPa for the PZT to 228 MPa for the PZT/ZnOw composites. The reinforcement mechanism in strength of the composites was discussed. The me- chanical quality factors of the PZT/ZnOw composites increased considerably, while the piezoelectric constants and electromechanical coupling coefficient decreased slightly. The composites with good electrical and excellent mechanical properties are promising for further applications.展开更多
Dispersed cuprite (Cu2O) nanowhiskers were synthesized in a water/butanol/cyclohexane/cetyl trimethyl ammonium bromide (CTAB) water-in-oil microemulsion system at 25℃. The nanowhiskers with a diameter of about 8 ...Dispersed cuprite (Cu2O) nanowhiskers were synthesized in a water/butanol/cyclohexane/cetyl trimethyl ammonium bromide (CTAB) water-in-oil microemulsion system at 25℃. The nanowhiskers with a diameter of about 8 am exhibit a well-crystallized one-dimensional (1D) structure over several hundreds nanometers in length and mainly grow along the 〈111〉 direction. However, without CTAB, only cubic and hexagonal bulks are obtained. Without emulsifier, short and thick nanowhiskers can be prepared but they are apt to agglomerate. The possible growth mechanism of Cu2O nanowhiskers is speculated. The surfactant and the microemulsion system are related to the 1D shape formation and the even dispersion of Cu2O nanomaterials, respectively.展开更多
Structural control and element doping are two popular strategies to produce semiconductors with surface enhanced Raman spectroscopy(SERS)properties.For TiO2 based SERS substrates,maintaining a good crystallinity is cr...Structural control and element doping are two popular strategies to produce semiconductors with surface enhanced Raman spectroscopy(SERS)properties.For TiO2 based SERS substrates,maintaining a good crystallinity is critical to achieve excellent Raman scattering.At elevated temperatures(N600°C),the phase transition from anatase to rutile TiO2 could result in a poor SERS performance.In this work,we report the successful synthesis of TiO2 nanowhiskers with excellent SERS properties.The enhancement factor,an index of SERS performance,is 4.96×106 for methylene blue molecule detecting,with a detection sensitivity around 10-7 mol·L-1.Characterizations,such as XRD,Raman,TEM,UV–vis and Zeta potential measurement,have been performed to decrypt structural and chemical characteristics of the newly synthesized TiO2 nanowhiskers.The photo absorption onset of MB adsorbed TiO2 nanowhiskers was similar to that of bare TiO2 nanowhiskers.In addition,no new band was observed from the UV–vis of MB modified TiO2 nanowhiskers.Both results suggest that the high enhancement factor cannot be explained by the charge-transfer mechanism.With the support of ab initio density functional theory calculations,we reveal that interfacial potassium is critical to maintain thermal stability of the anatase phase up to 900°C.In addition,the deposition of potassium results in a negatively charged TiO2 nanowhisker surface,which favors specific adsorption of methylene blue molecules and significantly improves SERS performance via the electrostatic adsorption effect.展开更多
A novel method for controlled synthesis of crystalline molybdenum dioxides nanowhiskers (whisker-MoO2) by using moderate reductive and precursor ion under hydrothermal conditions is reported. The result shows that t...A novel method for controlled synthesis of crystalline molybdenum dioxides nanowhiskers (whisker-MoO2) by using moderate reductive and precursor ion under hydrothermal conditions is reported. The result shows that the as-obtained samples have a monoclinic structure, and the whisker-MoO2 is composed of nanowires with diameters of ca. 20 nm. Formation of whisker-MoO2 was through a typical precursor-reduction process, in which cetyltrimethylammonium bromide (CTAB) served as a cationic surfactant and acetone as a reductant. The electrochemical behavior of whisker-MoO2 was studied.展开更多
ZnO nanopowders were prepared by oxidizing Zn vapor in the atmosphere of mixture gas of At and O2 at low pressure. Tetrapod nanowhiskers synthesized at a pressure of 1.6 kPa show pure ZnO feet and Zn phase in the core...ZnO nanopowders were prepared by oxidizing Zn vapor in the atmosphere of mixture gas of At and O2 at low pressure. Tetrapod nanowhiskers synthesized at a pressure of 1.6 kPa show pure ZnO feet and Zn phase in the core of the nanopowder. The ellipsoid ZnO nanoparticles were produced at the pressure of 10 kPa. The photodegradation rate of aniline and chemical oxygen demand removal demonstrate that the photocatalytic efficiency of Zn/ZnO nanowhiskers with UV irradiation is higher than that ofZnO nanoparticles. The tetrapod morphology and Zn phase inside nanowhiskers play key a role in photodegradation process.展开更多
With recent developments in nanoscience and nanotechnology, carbon-based nanomaterials, such as carbon nanotubes or Fullerene nanowhiskers (FNWs), are attracting a great deal of interest. However, nanomaterials have n...With recent developments in nanoscience and nanotechnology, carbon-based nanomaterials, such as carbon nanotubes or Fullerene nanowhiskers (FNWs), are attracting a great deal of interest. However, nanomaterials have novel properties that may cause safety problems in biological systems. Although the toxic effects of multiwall carbon nanotubes (MWCNTs) in vitro and in vivo have been well described, the effect of FNWs on cells remains unclear. In the present study, we analyzed the gene expression and cytotoxicity of FNWs-treated cells. The results of cell viabil-ity and gene expression analysis indicate that FNWs has a relatively smaller ability to induce cellular gene expression as compared with MWCNTs or titania nanoparticles. Our results suggest that FNWs have weak cytotoxic effects as compared to the effects of MWCNTs and tita-nia nanoparticles.展开更多
Inspired by the transport behavior of water and ions through the aligned channels in trees,we demonstrate a facile,scalable approach for constructing biomorphic cellular Si_(3)N_(4) ceramic frameworks with well-aligne...Inspired by the transport behavior of water and ions through the aligned channels in trees,we demonstrate a facile,scalable approach for constructing biomorphic cellular Si_(3)N_(4) ceramic frameworks with well-aligned nanowhisker arrays on the surface of directionally aligned microchannel alignments.Through a facile Y(NO_(3))_(3) solution infiltration into wood-derived carbon preforms and subsequent heat treatment,we can faultlessly duplicate the anisotropic wood architectures into free-standing bulk porous Si_(3)N_(4) ceramics.Firstly,α-Si3N4 microchannels were synthesized on the surface of CB-templates via carbothermal reduction nitridation(CRN).And then,homogeneous distributed Y–Si–O–N liquid phase on the walls of microchannel facilitated the anisotropicβ-Si3N4 grain growth to form nanowhisker arrays.The dense aligned microchannels with low-tortuosity enable excellent load carrying capacity and thermal conduction through the entire materials.As a result,the porous Si_(3)N_(4) ceramics exhibited an outstanding thermal conductivity(TC,k_(R)≈6.26 W·m^(−1)·K^(−1)),a superior flexural strength(σ_(L)≈29.4 MPa),and a relative high anisotropic ratio of TC(k_(R)/k_(L)=4.1).The orientation dependence of the microstructure–property relations may offer a promising perspective for the fabrication of multifunctional ceramics.展开更多
Due to their excellent dielectric properties and the rapid response to microwave irradiation,silicon carbide nanowhiskers(SiCNWs)were employed as microwave susceptor in this study to absorb microwave and locally melt ...Due to their excellent dielectric properties and the rapid response to microwave irradiation,silicon carbide nanowhiskers(SiCNWs)were employed as microwave susceptor in this study to absorb microwave and locally melt the surrounding polypropylene(PP)substrates for the joining of PP substrates.Complete welded joint is formed after the melted PP was cooled and resolidified.Other than microwave susceptor,SiCNWs also acted as the nanofillers in strengthening the welded joint through the formation of SiCNWs reinforced PP nanocomposite at the interface of PP substrates.Besides,the effect of microwave power on the microwave welding of PP substrates using SiCNWs as susceptor was studied and reported.It was found that the tensile strength and modulus of elasticity of the welded joint improved as microwave power increased.However,it deteriorates the flexibility of the welded joint as high stiffness SiCNWs were incorporated deeper into the PP matrix which restricted the PP chain mobility.Aside from microwave power,clamping pressure is also critical in determining the mechanical properties of a welded joint.When compared to unclamped welded joint,the tensile strength,modulus of elasticity and flexibility of welded joint subjected to clamping pressure improved drastically.Moreover,the tensile strength of welded joint increased when the clamping pressure was increased from P1 to P3,but decreased when the clamping pressure was further increased to P4 due to the occurrence of flashing at welded joint.The formation mechanism of SiCNWs reinforced PP welded joint was also proposed in this study.Compared to conventional welding,this welding process is easy,straightforward and is able to produce welded joint with outstanding mechanical properties via precise controlling of the processing parameters.Thus,microwave welding is thought to offer an option for the joining of thermoplastics and other applications.展开更多
Synthesis of AlN by NH4Cl-assisted direct nitridation of secondary Al resources was studied. Aluminum alloy scrap contained Mg and Zn element was used. Milled Al scrap (-1 mm) was mixed with NH4Cl and heated at 1000...Synthesis of AlN by NH4Cl-assisted direct nitridation of secondary Al resources was studied. Aluminum alloy scrap contained Mg and Zn element was used. Milled Al scrap (-1 mm) was mixed with NH4Cl and heated at 1000℃ for 1 h in presence of 1 L/min N2 flow gas. The nitrided product was evaluated by X-ray diffraction semi-quantitative analysis and scanning electron microscopy (SEM). Aluminium nitride of 90.5% concentration was obtained with a hexagonal crystalline form. AlN is mostly formed in nano-whisker morphology (50~150 nm) which is homogenously distributed.展开更多
基金the New Century Excellent Talents in Universities (No. NECT-12-0779)the Fundamental Research Funds for the Central Universities (No. FRF-SD-13-006A)the Program for Changjiang Scholars and Innovative Research Team in Universities (No. IRT1207) for financial support
文摘Mullite nanowhiskers with Al-rich structure were prepared by molten salt synthesis at 1000°C for 3 h in air using silica, amorphous silica, and ultrafine silica as the silica sources. The phase and morphology of the synthesized products were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy. A thermogravimetric and differential thermal analysis was carried out to determine the reaction mechanism. The results reveal that the silica sources play an important role in determining the morphology of the obtained mullite nanowhiskers. Clusters and disordered arrangements are obtained using common silica and amorphous silica, respectively, whereas the use of ultrafine silica leads to highly ordered mullite nanowhiskers that are 80-120 nm in diameter and 20-30 μm in length. Considering the growth mechanisms, mullite nanowhiskers in the forms of clusters and highly ordered arrangements can be attributed to heterogeneous nucleation, whereas disordered mullite nanowhiskers are obtained by homogenous nucleation.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 50572010, 50742007 and 10672020)the National Defense Foundation of China (Grant No 401050301)the Scientific Project of 863 of China (Grant No 2007AA03Z103)
文摘This paper reports that the lead zirconate titanate (PZT) piezoelectric composites incorporating zinc oxide nanowhiskers (ZnOw) were prepared by the conventional solid state processing. The whisker-dispersed PZT composites (PZT/ZnOw) presented a significant enhancement in the mechanical properties such as Young's modulus, tensile strength and compressive strength. Especially, the compressive strength increased from 153 MPa for the PZT to 228 MPa for the PZT/ZnOw composites. The reinforcement mechanism in strength of the composites was discussed. The me- chanical quality factors of the PZT/ZnOw composites increased considerably, while the piezoelectric constants and electromechanical coupling coefficient decreased slightly. The composites with good electrical and excellent mechanical properties are promising for further applications.
基金This work was financially supported by the National Natural Science Foundation of China (No. 20207002).
文摘Dispersed cuprite (Cu2O) nanowhiskers were synthesized in a water/butanol/cyclohexane/cetyl trimethyl ammonium bromide (CTAB) water-in-oil microemulsion system at 25℃. The nanowhiskers with a diameter of about 8 am exhibit a well-crystallized one-dimensional (1D) structure over several hundreds nanometers in length and mainly grow along the 〈111〉 direction. However, without CTAB, only cubic and hexagonal bulks are obtained. Without emulsifier, short and thick nanowhiskers can be prepared but they are apt to agglomerate. The possible growth mechanism of Cu2O nanowhiskers is speculated. The surfactant and the microemulsion system are related to the 1D shape formation and the even dispersion of Cu2O nanomaterials, respectively.
基金supported by National Natural Science Foundation of China(21878143,21476106,and 21838004)Joint Research Fund for Overseas Chinese Scholars and Scholars in Hong Kong and Macao Young Scholars(21729601)+3 种基金the fund of State Key Laboratory of MaterialsOriented Chemical Engineering(ZK201702,KL16-01)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the U.S.National Science Foundation(NSF)for support through Grant No.CHE-1710102the High-Performance Computing Center of Nanjing Tech University for supporting the computational resources。
文摘Structural control and element doping are two popular strategies to produce semiconductors with surface enhanced Raman spectroscopy(SERS)properties.For TiO2 based SERS substrates,maintaining a good crystallinity is critical to achieve excellent Raman scattering.At elevated temperatures(N600°C),the phase transition from anatase to rutile TiO2 could result in a poor SERS performance.In this work,we report the successful synthesis of TiO2 nanowhiskers with excellent SERS properties.The enhancement factor,an index of SERS performance,is 4.96×106 for methylene blue molecule detecting,with a detection sensitivity around 10-7 mol·L-1.Characterizations,such as XRD,Raman,TEM,UV–vis and Zeta potential measurement,have been performed to decrypt structural and chemical characteristics of the newly synthesized TiO2 nanowhiskers.The photo absorption onset of MB adsorbed TiO2 nanowhiskers was similar to that of bare TiO2 nanowhiskers.In addition,no new band was observed from the UV–vis of MB modified TiO2 nanowhiskers.Both results suggest that the high enhancement factor cannot be explained by the charge-transfer mechanism.With the support of ab initio density functional theory calculations,we reveal that interfacial potassium is critical to maintain thermal stability of the anatase phase up to 900°C.In addition,the deposition of potassium results in a negatively charged TiO2 nanowhisker surface,which favors specific adsorption of methylene blue molecules and significantly improves SERS performance via the electrostatic adsorption effect.
基金This work was financially supported by the National Natural Science Foundation of China (No.20271001).
文摘A novel method for controlled synthesis of crystalline molybdenum dioxides nanowhiskers (whisker-MoO2) by using moderate reductive and precursor ion under hydrothermal conditions is reported. The result shows that the as-obtained samples have a monoclinic structure, and the whisker-MoO2 is composed of nanowires with diameters of ca. 20 nm. Formation of whisker-MoO2 was through a typical precursor-reduction process, in which cetyltrimethylammonium bromide (CTAB) served as a cationic surfactant and acetone as a reductant. The electrochemical behavior of whisker-MoO2 was studied.
基金the National Natural Science Foundation of China(No:30571536)Junye Nano Materials Company Limited(Shenzhen,China)
文摘ZnO nanopowders were prepared by oxidizing Zn vapor in the atmosphere of mixture gas of At and O2 at low pressure. Tetrapod nanowhiskers synthesized at a pressure of 1.6 kPa show pure ZnO feet and Zn phase in the core of the nanopowder. The ellipsoid ZnO nanoparticles were produced at the pressure of 10 kPa. The photodegradation rate of aniline and chemical oxygen demand removal demonstrate that the photocatalytic efficiency of Zn/ZnO nanowhiskers with UV irradiation is higher than that ofZnO nanoparticles. The tetrapod morphology and Zn phase inside nanowhiskers play key a role in photodegradation process.
文摘With recent developments in nanoscience and nanotechnology, carbon-based nanomaterials, such as carbon nanotubes or Fullerene nanowhiskers (FNWs), are attracting a great deal of interest. However, nanomaterials have novel properties that may cause safety problems in biological systems. Although the toxic effects of multiwall carbon nanotubes (MWCNTs) in vitro and in vivo have been well described, the effect of FNWs on cells remains unclear. In the present study, we analyzed the gene expression and cytotoxicity of FNWs-treated cells. The results of cell viabil-ity and gene expression analysis indicate that FNWs has a relatively smaller ability to induce cellular gene expression as compared with MWCNTs or titania nanoparticles. Our results suggest that FNWs have weak cytotoxic effects as compared to the effects of MWCNTs and tita-nia nanoparticles.
文摘Inspired by the transport behavior of water and ions through the aligned channels in trees,we demonstrate a facile,scalable approach for constructing biomorphic cellular Si_(3)N_(4) ceramic frameworks with well-aligned nanowhisker arrays on the surface of directionally aligned microchannel alignments.Through a facile Y(NO_(3))_(3) solution infiltration into wood-derived carbon preforms and subsequent heat treatment,we can faultlessly duplicate the anisotropic wood architectures into free-standing bulk porous Si_(3)N_(4) ceramics.Firstly,α-Si3N4 microchannels were synthesized on the surface of CB-templates via carbothermal reduction nitridation(CRN).And then,homogeneous distributed Y–Si–O–N liquid phase on the walls of microchannel facilitated the anisotropicβ-Si3N4 grain growth to form nanowhisker arrays.The dense aligned microchannels with low-tortuosity enable excellent load carrying capacity and thermal conduction through the entire materials.As a result,the porous Si_(3)N_(4) ceramics exhibited an outstanding thermal conductivity(TC,k_(R)≈6.26 W·m^(−1)·K^(−1)),a superior flexural strength(σ_(L)≈29.4 MPa),and a relative high anisotropic ratio of TC(k_(R)/k_(L)=4.1).The orientation dependence of the microstructure–property relations may offer a promising perspective for the fabrication of multifunctional ceramics.
基金financially supported by the Department of Education,Ministry of Education Malaysia(MOE)through Fundamental Research Grant Scheme(FRGS/1/2019/TK05/UNIMAP/02/7)[FRGS 9003-00729]。
文摘Due to their excellent dielectric properties and the rapid response to microwave irradiation,silicon carbide nanowhiskers(SiCNWs)were employed as microwave susceptor in this study to absorb microwave and locally melt the surrounding polypropylene(PP)substrates for the joining of PP substrates.Complete welded joint is formed after the melted PP was cooled and resolidified.Other than microwave susceptor,SiCNWs also acted as the nanofillers in strengthening the welded joint through the formation of SiCNWs reinforced PP nanocomposite at the interface of PP substrates.Besides,the effect of microwave power on the microwave welding of PP substrates using SiCNWs as susceptor was studied and reported.It was found that the tensile strength and modulus of elasticity of the welded joint improved as microwave power increased.However,it deteriorates the flexibility of the welded joint as high stiffness SiCNWs were incorporated deeper into the PP matrix which restricted the PP chain mobility.Aside from microwave power,clamping pressure is also critical in determining the mechanical properties of a welded joint.When compared to unclamped welded joint,the tensile strength,modulus of elasticity and flexibility of welded joint subjected to clamping pressure improved drastically.Moreover,the tensile strength of welded joint increased when the clamping pressure was increased from P1 to P3,but decreased when the clamping pressure was further increased to P4 due to the occurrence of flashing at welded joint.The formation mechanism of SiCNWs reinforced PP welded joint was also proposed in this study.Compared to conventional welding,this welding process is easy,straightforward and is able to produce welded joint with outstanding mechanical properties via precise controlling of the processing parameters.Thus,microwave welding is thought to offer an option for the joining of thermoplastics and other applications.
文摘Synthesis of AlN by NH4Cl-assisted direct nitridation of secondary Al resources was studied. Aluminum alloy scrap contained Mg and Zn element was used. Milled Al scrap (-1 mm) was mixed with NH4Cl and heated at 1000℃ for 1 h in presence of 1 L/min N2 flow gas. The nitrided product was evaluated by X-ray diffraction semi-quantitative analysis and scanning electron microscopy (SEM). Aluminium nitride of 90.5% concentration was obtained with a hexagonal crystalline form. AlN is mostly formed in nano-whisker morphology (50~150 nm) which is homogenously distributed.