Nanocomposite films consisting of carboxymethyl cellulose,polyethylene oxide(CMC/PEO),and anatase titanium diox-ide(TO)were produced by the use of sol-gel and solution casting techniques.TiO2 nanocrystals were effecti...Nanocomposite films consisting of carboxymethyl cellulose,polyethylene oxide(CMC/PEO),and anatase titanium diox-ide(TO)were produced by the use of sol-gel and solution casting techniques.TiO2 nanocrystals were effectively incorporated into CMC/PEO polymers,as shown by X-ray diffraction(XRD)and attenuated total reflectance fourier transform infrared(ATR-FTIR)analysis.The roughness growth is at high levels of TO nanocrystals(TO NCs),which means increasing active sites and defects in CMC/PEO.In differential scanning calorimetry(DSC)thermograms,the change in glass transition temperature(Tg)val-ues verifies that the polymer blend interacts with TO NCs.The increment proportions of TO NCs have a notable impact on the dielectric performances of the nanocomposites,as observed.The electrical properties of the CMC/PEO/TO nanocomposite undergo significant changes.The nanocomposite films exhibit a red alteration in the absorption edge as the concentration of TO NCs increases in the polymer blend.The decline in the energy gap is readily apparent as the weight percentage of TO NCs increases.The photoluminescence(PL)emission spectra indicate that the sites of the luminescence peak maximums show slight variation;peaks get wider,while their intensities decrease dramatically as the concentration of TO increases.These nanocomposite materials show potential for multifunctional applications including optoelectronics,antireflection coatings,pho-tocatalysis,light emitting diodes,and solid polymer electrolytes.展开更多
The properties of the combustion and deflagration to detonation transition(DDT)of Al/Fe_(2)O_(3)/RDX hybrid nanocomposites,a type of potentially novel lead-free primary explosives,were tested in weakly confined condit...The properties of the combustion and deflagration to detonation transition(DDT)of Al/Fe_(2)O_(3)/RDX hybrid nanocomposites,a type of potentially novel lead-free primary explosives,were tested in weakly confined conditions,and the interaction of Al/Fe_(2)O_(3)nanothermite and RDX in the DDT process was studied in detail.Results show that the amount of the Al/Fe_(2)O_(3)nanothermite has a great effect on the DDT properties of Al/Fe_(2)O_(3)/RDX nanocomposites.The addition of Al/Fe_(2)O_(3)nanothermite to RDX apparently improves the firing properties of RDX.A small amount of Al/Fe_(2)O_(3)nanothermite greatly increases the initial combustion velocity of Al/Fe_(2)O_(3)/RDX nanocomposites,accelerating their DDT process.When the contents of Al/Fe_(2)O_(3)nanothermite are less than 20 wt%,the DDT mechanisms of Al/Fe_(2)O_(3)/RDX nanocomposites follow the distinct abrupt mode,and are consistent with that of RDX,though their DDT processes are different.The RDX added into the Al/Fe_(2)O_(3)nanothermite increases the latter's peak combustion velocity and makes it generate the DDT when the RDX content is at least 10 wt%.RDX plays a key role in the shock compressive combustion,the formation and the properties of the DDT in the flame propagation of nanocomposites.Compared with RDX,the fast DDT of Al/Fe_(2)O_(3)/RDX nanocomposites could be obtained by adjusting the chemical constituents of nanocomposites.展开更多
A series of La2O3/MC nylon nanocomposites were prepared via in situ polymerization. The effects of content of nano-La2O3 on the mechanical properties of nanocomposites were studied. Dispersion of nano-La2O3 in MC nylo...A series of La2O3/MC nylon nanocomposites were prepared via in situ polymerization. The effects of content of nano-La2O3 on the mechanical properties of nanocomposites were studied. Dispersion of nano-La2O3 in MC nylon matrix was observed with SEM. The crystal structure of nanocomposites was characterized by means of XRD. SEM analysis shows that La2O3 nanoparticles are uniformly dispersed in MC nylon matrix and little clustering exists when the content of nano- La2O3 is lower than 1%, however, when the content of nano-La2O3 is more than 1%, it begins to cluster. XRD analysis indicats that nano-La2O3 does not change the crystal structure of MC nylon. Mechanical properties tests show that the tensile strength, elongation at break, impact strength, flexural strength, and flexural modulus of nanocomposites first increase then decrease as the content of nano-La2O3 is increased. When the content of nano-La2O3 is 0.5%, the tensile strength and elongation at break of nanocomposites reach maximum, which are 17.9% and 52.1% higher respectively than those of MC nylon. When the content of nano-La2O3 is 1.0%, the impact strength, flexural strength and flexural modulus of nanocomposites reach maximum, which are 36.6 %, 12.7 % and 16.3 % higher respectively than those of MC nylon.展开更多
Surface-functionalized nitrogen/carbon co-doped polymorphic TiO_(2) phase junction nanoparticles uniformly distributed in porous carbon matrix were synthesized by a simple one-step pyrolysis of titanium based metal-or...Surface-functionalized nitrogen/carbon co-doped polymorphic TiO_(2) phase junction nanoparticles uniformly distributed in porous carbon matrix were synthesized by a simple one-step pyrolysis of titanium based metal-organic framework(MOF),NH_(2)-MIL^(-1)25(Ti) at 700℃ under water vapour atmosphere.Introducing water vapour during the pyrolysis of NH_(2)-MIL^(-1)25(Ti) not only functionalizes the derived porous carbon matrix with carboxyl groups but also forms additional oxygen-rich N like interstitial/intraband states lying above the valence band of TiO2 along with the self-doped carbo n,which further narrows the energy band gaps of polymorphic TiO2 nanoparticles that enhance photocatalytic charge transfer efficiency.Without co-catalyst,sample N-C-TiO2/CArW demonstrates H_(2) evolution activity of 426 μmol gcat-1h^(-1),which remarkably outperforms commercial TiO_(2)(P-25) and N-C-TiO_(2)/CAr with a 5-fold and 3-fold H_(2) generation,respectively.This study clearly shows that water vapour atmosphere during the pyrolysis increases the hydrophilicity of the Ti-MOF derived composites by functionalizing porous carbon matrix with carboxylic groups,as well as enhancing the electrical conductivity and charge transfer efficiency due to the formation of additional localized oxygen-rich N like interstitial/intraband states.This work also demonstrates that by optimizing the anatase-rutile phase composition of the TiO2 polymorphs,tuning the energy band gaps by N/C co-doping and functionalizing the porous carbon matrix in the N-C-TiO2/C nanocomposites,the photocatalytic H_(2) generation activity can be further enhanced.展开更多
Two-dimensional(2D)nanomaterials have demonstrated great potential in the field of flexible gas sensing due to their inherent high specific surface areas,unique electronic properties and flexibility property.However,n...Two-dimensional(2D)nanomaterials have demonstrated great potential in the field of flexible gas sensing due to their inherent high specific surface areas,unique electronic properties and flexibility property.However,numerous challenges including sensitivity,selectivity,response time,recovery time,and stability have to be addressed before their practical application in gas detection field.Development of graphene-like 2D/2D nanocomposites as an efficient strategy to achieve high-performance 2D gas sensor has been reported recently.This review aims to discuss the latest advancements in the 2D/2D nanocomposites for gas sensors.We first elaborate the gas-sensing mechanisms and the collective benefits of 2D/2D hybridization as sensor materials.Then,we systematically present the current gas-sensing applications based on different categories of 2D/2D nanocomposites.Finally,we conclude the future prospect of 2D/2D nanocomposites in gas sensing applications.展开更多
Selective laser sintering (SLS) is a new process to prepare the polystyrene (PS)/Al2O3 nanocomposites. In this paper, with different laser power and other processing parameters unchanged, the morphology, density a...Selective laser sintering (SLS) is a new process to prepare the polystyrene (PS)/Al2O3 nanocomposites. In this paper, with different laser power and other processing parameters unchanged, the morphology, density and mechanical properties of the sintered specimens were investigated. It was found that nano-sized inorganic particles are uniformly located in the PS matrix and the maximum density of the sintered specimens with pure PS powder reaches 1.07 g/cm^3, higher than 1.04 g/cm^3 that of the sintered specimens with mixture powder. Due to strengthening and toughness of the nano-sized Al2O3 inorganic particles, the maximum notched impact strength and tensile strength of the sintered part mixed with nano-sized inorganic particles are improved greatly from 7.5 to 12.1 kJ/m^2 and from 6.5 to 31.2 MPa, respectively, under the same sintering condition.展开更多
A resistive humidity sensor was prepared based on sodium polystyrenesulfonate (NaPSS)/TiO2 nanocomposites, and its electrical response to humidity was examined. The sensor exhibits better linearity, smaller hysteresis...A resistive humidity sensor was prepared based on sodium polystyrenesulfonate (NaPSS)/TiO2 nanocomposites, and its electrical response to humidity was examined. The sensor exhibits better linearity, smaller hysteresis (< 4% RH) and quicker response (absorption: less than 2 s; desorption: less than 20 s) in comparison with sensor composed of NaPSS. The effect of concentration of NaPSS and TiO2 on humidity response of sensors was discussed.展开更多
The objective in this study is to investigate the adsorption-degradation of the methylene blue(MB)dye using a fabricated heterojunction Ag@TiO_(2)nanocomposite.The batch factors used in photo catalytic reactions were ...The objective in this study is to investigate the adsorption-degradation of the methylene blue(MB)dye using a fabricated heterojunction Ag@TiO_(2)nanocomposite.The batch factors used in photo catalytic reactions were pH,UV-irradiation time,temperature,catalytic dosage,and concentration of MB.The results showed that 0.2×10^(3) g·ml^(-1))of the catalytic dose caused the Ag@TiO_(2)adsorption to degrade by 96.67%with darks and UV exposure.Using the Langmuir-Hinshelwood model to determine the kinetic,the Ag@TiO_(2)displays a greater kinetic rate than TiO_(2)and silver nanoparticle(AgNPs).The photocatalytic degradation of MB,which is an endothermic reaction involving all catalysts,is shown by the thermodynamic parameter to have the positive value of enthalpy(ΔH°).The enthalpies observed were Ag@TiO_(2)(126.80 kJ·mol^(-1))<AgNPs(354.47 kJ·mol^(-1))<TiO_(2)(430.04 kJ·mol^(-1)).Ascorbic acid(·OH scavenger),2-propanol(·O_(2)scavenger),and ammonium oxalate(AO)(hole h+scavenger)were employed to conduct the scavenger effects.The Ag@TiO_(2)demonstrated a reduction in MB degradation when combined with 2-propanol,and this clearly demonstrated that,in contrast to hydroxyl radicals(·OH)and holeh scavengers,superoxide radical anion(O_(2)scavenger)plays a significant role in MB degradation.Utilizing density functional theory(DFT)to elucidate the mechanism and B3LYP/6-311+G(d,p)level optimization,the degradation-adsorption process was explained.When the N-N,C-N or C-C bonds were severed,the Fukui faction was demonstrated for nucleophilic,electrophilic,and radical attack.展开更多
Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical p...Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical particle solidification velocity for swamp and thus offers better dispersal.In the present investigation,the friction stir processing(FSP)is utilized to produce AZ31/Al_(2)O_(3)nanocomposites at various tool rotation speeds(i.e.,900,1200,and 1500 rpm)with an optimized 1.5%volume alumina(Al_(2)O_(3))reinforcement ratio.The mechanical and corrosion behavior of AZ31/Al_(2)O_(3)-developed nanocomposites was investigated and compared with that of the AZ31 base alloy.The AZ31 alloy experienced a comprehensive dynamic recrystallization during FSP,causing substantial grain refinement.Grain-size strengthening is the primary factor contributed to the enhancement in the strength of the fabricated nanocomposite.Tensile strength and yield strength values were lower than those for the base metal matrix,although an upward trend in both values has been observed with an increase in tool rotation speed.An 19.72%increase in hardness along with superior corrosion resistance was achieved compared to the base alloy at a tool rotational speed of 1500 rpm.The corrosion currents(Jcorr)of all samples dropped with increase in the rotational speed,in contrast to the corrosion potentials(Ecorr),which increased.The values of Jcorr of AZ31/Al_(2)O_(3)were 42.3%,56.8%,and 65.5%lower than those of AZ31 alloy at the chosen rotating speeds of 900,1200,and 1500 rpm,respectively.The corrosion behavior of friction stir processed nanocomposites have been addressed in this manuscript which has not been given sufficient attention in the existing literature.Further,this work offers an effective choice for the quality assurance of the FSP process of AZ31/Al_(2)O_(3)nanocomposites.The obtained results are relevant to the development of lightweight automobile and aerospace structures and components.展开更多
Fe2O3/active carbon(Fe2O3/AC) nanocomposites were readily fabricated by pyrolyzing Fe3+ impregnated active carbon in a nitrogen atmosphere. The as-prepared composites were studied by X-ray powder diffraction(XRD)...Fe2O3/active carbon(Fe2O3/AC) nanocomposites were readily fabricated by pyrolyzing Fe3+ impregnated active carbon in a nitrogen atmosphere. The as-prepared composites were studied by X-ray powder diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM). The capacitive property of the composites was investigated by cyclic voltammetry(CV) and galvanostatic charge-discharge test. Physical characterizations show that the γ-Fe2O3 fine grains dispersed in the AC well, with a mean size of 21.24 nm. Electrochemical tests in 6 mol/L KOH solutions indicate that the as-prepared nanocomposites exhibited improved capacitive properties. The specific capacitance(SC) of Fe2O3/AC nanocomposites was up to 188.4 F/g that was derived from both electrochemical double-layer capacitance and pseudo-capacitance, which was 78% larger than that of pristine AC. A symmetric capacitor with Fe2O3/AC nanocomposites as electrode showed an excellent cycling stability. The SC was only reduced by a factor of 9.2% after 2000 cycles at a current density of 1 A/g.展开更多
Poly (N, N, N-trimethyl-(2-pyrrol-1-yl) ethyl ammonium iodide)/V2O5 (PTPAI/V2O5) nanocomposites were synthesized by sol-gel method. This method involved formation of vanadium pentoxide xerogel in the presence of polyp...Poly (N, N, N-trimethyl-(2-pyrrol-1-yl) ethyl ammonium iodide)/V2O5 (PTPAI/V2O5) nanocomposites were synthesized by sol-gel method. This method involved formation of vanadium pentoxide xerogel in the presence of polypyrrole derivatives solution. X-ray diffraction (XRD) indicated that the polypyrrole derivative particles encapsulated in the fibrous V2O5 network and the layered distance significantly increased from 1. 077 39 to 1. 354 56 nm. The interaction between polypyrrole and V2O5 in the ‘nanocomposites’ was characterized by IR spectroscopy. The Scanning Electron Microscope (SEM) micrographs reveal the structural contrasts between the hybrid materials and the pristine vanadium oxide xerogel. Key words polypyrrole/V2O5 - nanocomposites - XRD - SEM CLC number O 633. 5 Foundation item: Supported by the Natural Science Foundation of Hubei Province (2003ABA030)Biography: Shi Chuang (1978-), male, Master candidate, research direction: synthesis chemistry.展开更多
The CoO/CoVO/Ni nanocomposites were rationally designed and prepared by a two-step hydrothermal synthesis and subsequent annealing treatment. The one-dimensional(1D) CoOnanowire arrays directly grew on Ni foam, wher...The CoO/CoVO/Ni nanocomposites were rationally designed and prepared by a two-step hydrothermal synthesis and subsequent annealing treatment. The one-dimensional(1D) CoOnanowire arrays directly grew on Ni foam, whereas the 1D CoVOnanowires adhered to parts of CoOnanowires.Most of the hybrid nanowires were inlayed with each other, forming a 3D hybrid nanowires network.As a result, the discharge capacity of CoO/CoVO/Ni nanocomposites could reach 1201.8 mAh/g after100 cycles at 100 mA/g. After 600 cycles at 1 A/g, the discharge capacity was maintained at 828.1 mAh/g.Moreover, even though the charge/discharge rates were increased to 10 A/g, it rendered reversible capacity of 491.2 mAh/g. The superior electrochemical properties of nanocomposites were probably ascribed to their unique 3D architecture and the synergistic effects of two active materials. Therefore, such CoO/CoVO/Ni nanocomposites could potentially be used as anode materials for high-performance Li-ion batteries.展开更多
An improved sol-gel method was used to prepare Eu3+ ions doped SiO-Y2O3 nanocomposites. Systematic study on the effect of post-annealling treatment on photoluminescence (PL) properties of the samples under various eur...An improved sol-gel method was used to prepare Eu3+ ions doped SiO-Y2O3 nanocomposites. Systematic study on the effect of post-annealling treatment on photoluminescence (PL) properties of the samples under various europium ions doping concentrations were carried out. XRD patterns indicate that the samples show an amorphous matrix structure, and the SEM patterns show that the samples present a multi-hole loosen structure, and a rod structure after high-temperature annealling treatment (800 ℃) for 3 h. Raman spectra demonstrate that Y3+ and Eu3+ ions were incorporated into the composites successfully through the sol-gel and post-anneal process. Under the excitation of 387 nm (7F0→5G2) violet light (but not 394 nm (7F0→5L6)), the strongest emission spectrum, the red light, was observed at around 616 nm (5D0→7F2) when the samples were re-treated by annealing at high temperature after 3 months laying aside. Without annealing treatment, the optimized doping mole ratio of Eu ions is about 9%, which is much higher than that doped in SiOglass with the concentration of 3.5%, and it then becomes 5% when the samples are treated by high temperature annealing. In addition, the excitation of 532 nm (7F0→5D1) light can also arouse a comparatively strong emission.展开更多
Rechargeable lithium–oxygen batteries have been considered as a promising energy storage technology because of their ultra-high theoretical energy densities which are comparable to gasoline. In order to improve the e...Rechargeable lithium–oxygen batteries have been considered as a promising energy storage technology because of their ultra-high theoretical energy densities which are comparable to gasoline. In order to improve the electrochemical properties of lithium–oxygen batteries(LOBs), especially the cycling performance, a high-efficiency cathode catalyst is the most important component.Hence, we aim to demonstrate that CuCr_2O_4@rGO(CCO@rGO) nanocomposites, which are synthesized using a facile hydrothermal method and followed by a series of calcination processes, are an effective cathode catalyst. The obtained CCO@rGO nanocomposites which served as the cathode catalyst of the LOBs exhibited an outstanding cycling performance for over 100 cycles with a fixed capacity of 1000 mAh g^(-1) at a current density of 200 mA g^(-1). The enhanced properties were attributed to the synergistic effect between the high catalytic efficiency of the spinel-structured CCO nanoparticles, the high specific surface area, and high conductivity of the rGO.展开更多
Phase evolution and magnetic properties of (Nd_o.95La_0.05)9.5-11Febal.M_2B10.5. where M=Cr, Ti, Nb, V, Mo, Zr, Hf, Ta, Mn or W, melt spun ribbons have been investigated. Almost all the alloy ribbons. except for(Nd_0....Phase evolution and magnetic properties of (Nd_o.95La_0.05)9.5-11Febal.M_2B10.5. where M=Cr, Ti, Nb, V, Mo, Zr, Hf, Ta, Mn or W, melt spun ribbons have been investigated. Almost all the alloy ribbons. except for(Nd_0.95La_0.05)_9.5Fe_78M_2B_10.5(M=Mo and Mn),consist merely two magnetic phases, namely α-Fe and R_2Fe_14B, which display a better combination of _iH_c and magnetic energy product. Remanence (Br) and coercivity (i_H_c) values in the range of 8.0 to 9.1 kG and 9.5 to 18.9 kOe. respectively, can be achieved. Among compositions studied, the Ti and W-substitutions were found to be most effective in increasing the Br and i_H_c, respectively. For a fixed refractory metal substitution, namely, M=C_r, Ti or Nb, an increase in the total rare earth concentration resulted in nanocomposites of small grain sizes and a high volume fraction of the R_2Fe_14B phase, leading to an increase in the magnetic properties.展开更多
High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)and ferromagnetic cobalt ferrite(CoFe_(2)O_(4))(0.00 wt%to 0.2 wt%)are prepared by a solution casting method acc...High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)and ferromagnetic cobalt ferrite(CoFe_(2)O_(4))(0.00 wt%to 0.2 wt%)are prepared by a solution casting method accompanied by uniaxial stretching and high electric field poling.The decisive effect of the poling electric field on the power generating capability was confirmed by the experiments.For pure PVDF-HFP films,when the maximum electric field Emax is 120 MV/m,the calibrated open circuit voltage reaches 2.93 V,which is much higher than those poled at lower electric fields(70 MV/m:1.41 V;90 MV/m:2.11 V).Furthermore,the addition of CoFe_(2)O_(4)also influences the piezoelectricity dramatically.In the samples containing 0.15 wt%CoFe_(2)O_(4),the calibrated open circuit voltage increases to the maximum value of 3.57 V.Meanwhile,the relative fraction of theβ-phase and the crystallinity degree are 99%and 48%,respectively.The effects of CoFe_(2)O_(4)nanoparticles on initial crystallization,uniaxial stretching and high electric field poling are investigated by XRD,FTIR and DSC.展开更多
Zinc oxide/low-density polyethylene (LDPE) nanocomposites were prepared for intrauterine devices. The change of Zn^2+ release rates of nanocomposites ( doped with various mass fractions of zinc oxide nanoparticles...Zinc oxide/low-density polyethylene (LDPE) nanocomposites were prepared for intrauterine devices. The change of Zn^2+ release rates of nanocomposites ( doped with various mass fractions of zinc oxide nanoparticles between 5wt% and 65 wt% ) for 264 days in a simulated uterine solution were investigated. The resuits show that initial burst phases are followed by near zero-order release phases. SEM technique was employed to observe the surface morphology of the 45wt% ZnO/ LDPE composite. Elements and phases on the surface of the nanocomposite after incubation were also analyzed by EDX and XRD respectively. The experimental results show that incrustation formation does not occur after incubation.展开更多
ZrO2/Graphene nanocomposites are fabricated from graphene oxide by one-step, green, facile and low-cost SCCO2 method. The as-prepared nanocomposites are characterized by means of X-ray photoelectron, transmission elec...ZrO2/Graphene nanocomposites are fabricated from graphene oxide by one-step, green, facile and low-cost SCCO2 method. The as-prepared nanocomposites are characterized by means of X-ray photoelectron, transmission electron microscopy and catalytic chemiluminescence measurement. The ZrO2 nanoparticles with size of several nanometers are uniformly coated on the graphene surface. The chemiluminescence characteristic to ethanol of the as-prepared nanocomposite paper is also investigated. The nanocomposite paper obtained displays high catalytic chemiluminescence sensitivity and highly selectivity to the ethanol gas. This study provides a facile, green and low-cost route to prepare nanoscopic gas sensing devices with application in safe protection, food fermentation, medical process and traffic safe.展开更多
文摘Nanocomposite films consisting of carboxymethyl cellulose,polyethylene oxide(CMC/PEO),and anatase titanium diox-ide(TO)were produced by the use of sol-gel and solution casting techniques.TiO2 nanocrystals were effectively incorporated into CMC/PEO polymers,as shown by X-ray diffraction(XRD)and attenuated total reflectance fourier transform infrared(ATR-FTIR)analysis.The roughness growth is at high levels of TO nanocrystals(TO NCs),which means increasing active sites and defects in CMC/PEO.In differential scanning calorimetry(DSC)thermograms,the change in glass transition temperature(Tg)val-ues verifies that the polymer blend interacts with TO NCs.The increment proportions of TO NCs have a notable impact on the dielectric performances of the nanocomposites,as observed.The electrical properties of the CMC/PEO/TO nanocomposite undergo significant changes.The nanocomposite films exhibit a red alteration in the absorption edge as the concentration of TO NCs increases in the polymer blend.The decline in the energy gap is readily apparent as the weight percentage of TO NCs increases.The photoluminescence(PL)emission spectra indicate that the sites of the luminescence peak maximums show slight variation;peaks get wider,while their intensities decrease dramatically as the concentration of TO increases.These nanocomposite materials show potential for multifunctional applications including optoelectronics,antireflection coatings,pho-tocatalysis,light emitting diodes,and solid polymer electrolytes.
基金supported by National Nature Science Foundation of China(No.22075230)the financial support of the doctoral research foundation(No.19ZX7102)from Southwest University of Science and Technology。
文摘The properties of the combustion and deflagration to detonation transition(DDT)of Al/Fe_(2)O_(3)/RDX hybrid nanocomposites,a type of potentially novel lead-free primary explosives,were tested in weakly confined conditions,and the interaction of Al/Fe_(2)O_(3)nanothermite and RDX in the DDT process was studied in detail.Results show that the amount of the Al/Fe_(2)O_(3)nanothermite has a great effect on the DDT properties of Al/Fe_(2)O_(3)/RDX nanocomposites.The addition of Al/Fe_(2)O_(3)nanothermite to RDX apparently improves the firing properties of RDX.A small amount of Al/Fe_(2)O_(3)nanothermite greatly increases the initial combustion velocity of Al/Fe_(2)O_(3)/RDX nanocomposites,accelerating their DDT process.When the contents of Al/Fe_(2)O_(3)nanothermite are less than 20 wt%,the DDT mechanisms of Al/Fe_(2)O_(3)/RDX nanocomposites follow the distinct abrupt mode,and are consistent with that of RDX,though their DDT processes are different.The RDX added into the Al/Fe_(2)O_(3)nanothermite increases the latter's peak combustion velocity and makes it generate the DDT when the RDX content is at least 10 wt%.RDX plays a key role in the shock compressive combustion,the formation and the properties of the DDT in the flame propagation of nanocomposites.Compared with RDX,the fast DDT of Al/Fe_(2)O_(3)/RDX nanocomposites could be obtained by adjusting the chemical constituents of nanocomposites.
文摘A series of La2O3/MC nylon nanocomposites were prepared via in situ polymerization. The effects of content of nano-La2O3 on the mechanical properties of nanocomposites were studied. Dispersion of nano-La2O3 in MC nylon matrix was observed with SEM. The crystal structure of nanocomposites was characterized by means of XRD. SEM analysis shows that La2O3 nanoparticles are uniformly dispersed in MC nylon matrix and little clustering exists when the content of nano- La2O3 is lower than 1%, however, when the content of nano-La2O3 is more than 1%, it begins to cluster. XRD analysis indicats that nano-La2O3 does not change the crystal structure of MC nylon. Mechanical properties tests show that the tensile strength, elongation at break, impact strength, flexural strength, and flexural modulus of nanocomposites first increase then decrease as the content of nano-La2O3 is increased. When the content of nano-La2O3 is 0.5%, the tensile strength and elongation at break of nanocomposites reach maximum, which are 17.9% and 52.1% higher respectively than those of MC nylon. When the content of nano-La2O3 is 1.0%, the impact strength, flexural strength and flexural modulus of nanocomposites reach maximum, which are 36.6 %, 12.7 % and 16.3 % higher respectively than those of MC nylon.
基金EPSRC CDT in Metamaterials at University of Exeter and Leverhulme Trust(RPG-2018-320) for financial support。
文摘Surface-functionalized nitrogen/carbon co-doped polymorphic TiO_(2) phase junction nanoparticles uniformly distributed in porous carbon matrix were synthesized by a simple one-step pyrolysis of titanium based metal-organic framework(MOF),NH_(2)-MIL^(-1)25(Ti) at 700℃ under water vapour atmosphere.Introducing water vapour during the pyrolysis of NH_(2)-MIL^(-1)25(Ti) not only functionalizes the derived porous carbon matrix with carboxyl groups but also forms additional oxygen-rich N like interstitial/intraband states lying above the valence band of TiO2 along with the self-doped carbo n,which further narrows the energy band gaps of polymorphic TiO2 nanoparticles that enhance photocatalytic charge transfer efficiency.Without co-catalyst,sample N-C-TiO2/CArW demonstrates H_(2) evolution activity of 426 μmol gcat-1h^(-1),which remarkably outperforms commercial TiO_(2)(P-25) and N-C-TiO_(2)/CAr with a 5-fold and 3-fold H_(2) generation,respectively.This study clearly shows that water vapour atmosphere during the pyrolysis increases the hydrophilicity of the Ti-MOF derived composites by functionalizing porous carbon matrix with carboxylic groups,as well as enhancing the electrical conductivity and charge transfer efficiency due to the formation of additional localized oxygen-rich N like interstitial/intraband states.This work also demonstrates that by optimizing the anatase-rutile phase composition of the TiO2 polymorphs,tuning the energy band gaps by N/C co-doping and functionalizing the porous carbon matrix in the N-C-TiO2/C nanocomposites,the photocatalytic H_(2) generation activity can be further enhanced.
基金supported by Zhejiang Provincial Natural Science Foundation of China (No. LY18F010009)Ningbo Natural Science Foundation (No. 2018A610002)
文摘Two-dimensional(2D)nanomaterials have demonstrated great potential in the field of flexible gas sensing due to their inherent high specific surface areas,unique electronic properties and flexibility property.However,numerous challenges including sensitivity,selectivity,response time,recovery time,and stability have to be addressed before their practical application in gas detection field.Development of graphene-like 2D/2D nanocomposites as an efficient strategy to achieve high-performance 2D gas sensor has been reported recently.This review aims to discuss the latest advancements in the 2D/2D nanocomposites for gas sensors.We first elaborate the gas-sensing mechanisms and the collective benefits of 2D/2D hybridization as sensor materials.Then,we systematically present the current gas-sensing applications based on different categories of 2D/2D nanocomposites.Finally,we conclude the future prospect of 2D/2D nanocomposites in gas sensing applications.
文摘Selective laser sintering (SLS) is a new process to prepare the polystyrene (PS)/Al2O3 nanocomposites. In this paper, with different laser power and other processing parameters unchanged, the morphology, density and mechanical properties of the sintered specimens were investigated. It was found that nano-sized inorganic particles are uniformly located in the PS matrix and the maximum density of the sintered specimens with pure PS powder reaches 1.07 g/cm^3, higher than 1.04 g/cm^3 that of the sintered specimens with mixture powder. Due to strengthening and toughness of the nano-sized Al2O3 inorganic particles, the maximum notched impact strength and tensile strength of the sintered part mixed with nano-sized inorganic particles are improved greatly from 7.5 to 12.1 kJ/m^2 and from 6.5 to 31.2 MPa, respectively, under the same sintering condition.
基金This work was supported by the National and Zhejiang Provincial Natural Science Foundation of China (No. 59773012).
文摘A resistive humidity sensor was prepared based on sodium polystyrenesulfonate (NaPSS)/TiO2 nanocomposites, and its electrical response to humidity was examined. The sensor exhibits better linearity, smaller hysteresis (< 4% RH) and quicker response (absorption: less than 2 s; desorption: less than 20 s) in comparison with sensor composed of NaPSS. The effect of concentration of NaPSS and TiO2 on humidity response of sensors was discussed.
基金University of Burdwan was for instrumental and financial support from DST-FIST(SR/FST/ESI-141/2015,dt:30.09.2019)Govt.of India and WBDST-BOOST(39/WBBDC/1p-2/2013,dt:25.03.2015),Govt.of West Bengal.
文摘The objective in this study is to investigate the adsorption-degradation of the methylene blue(MB)dye using a fabricated heterojunction Ag@TiO_(2)nanocomposite.The batch factors used in photo catalytic reactions were pH,UV-irradiation time,temperature,catalytic dosage,and concentration of MB.The results showed that 0.2×10^(3) g·ml^(-1))of the catalytic dose caused the Ag@TiO_(2)adsorption to degrade by 96.67%with darks and UV exposure.Using the Langmuir-Hinshelwood model to determine the kinetic,the Ag@TiO_(2)displays a greater kinetic rate than TiO_(2)and silver nanoparticle(AgNPs).The photocatalytic degradation of MB,which is an endothermic reaction involving all catalysts,is shown by the thermodynamic parameter to have the positive value of enthalpy(ΔH°).The enthalpies observed were Ag@TiO_(2)(126.80 kJ·mol^(-1))<AgNPs(354.47 kJ·mol^(-1))<TiO_(2)(430.04 kJ·mol^(-1)).Ascorbic acid(·OH scavenger),2-propanol(·O_(2)scavenger),and ammonium oxalate(AO)(hole h+scavenger)were employed to conduct the scavenger effects.The Ag@TiO_(2)demonstrated a reduction in MB degradation when combined with 2-propanol,and this clearly demonstrated that,in contrast to hydroxyl radicals(·OH)and holeh scavengers,superoxide radical anion(O_(2)scavenger)plays a significant role in MB degradation.Utilizing density functional theory(DFT)to elucidate the mechanism and B3LYP/6-311+G(d,p)level optimization,the degradation-adsorption process was explained.When the N-N,C-N or C-C bonds were severed,the Fukui faction was demonstrated for nucleophilic,electrophilic,and radical attack.
文摘Nano-sized reinforcements improved the mechanical characteristics efficiently by promoting more implicit particle hardening mechanisms compared to micron-sized reinforcements.Nano-sized particles lessen the critical particle solidification velocity for swamp and thus offers better dispersal.In the present investigation,the friction stir processing(FSP)is utilized to produce AZ31/Al_(2)O_(3)nanocomposites at various tool rotation speeds(i.e.,900,1200,and 1500 rpm)with an optimized 1.5%volume alumina(Al_(2)O_(3))reinforcement ratio.The mechanical and corrosion behavior of AZ31/Al_(2)O_(3)-developed nanocomposites was investigated and compared with that of the AZ31 base alloy.The AZ31 alloy experienced a comprehensive dynamic recrystallization during FSP,causing substantial grain refinement.Grain-size strengthening is the primary factor contributed to the enhancement in the strength of the fabricated nanocomposite.Tensile strength and yield strength values were lower than those for the base metal matrix,although an upward trend in both values has been observed with an increase in tool rotation speed.An 19.72%increase in hardness along with superior corrosion resistance was achieved compared to the base alloy at a tool rotational speed of 1500 rpm.The corrosion currents(Jcorr)of all samples dropped with increase in the rotational speed,in contrast to the corrosion potentials(Ecorr),which increased.The values of Jcorr of AZ31/Al_(2)O_(3)were 42.3%,56.8%,and 65.5%lower than those of AZ31 alloy at the chosen rotating speeds of 900,1200,and 1500 rpm,respectively.The corrosion behavior of friction stir processed nanocomposites have been addressed in this manuscript which has not been given sufficient attention in the existing literature.Further,this work offers an effective choice for the quality assurance of the FSP process of AZ31/Al_(2)O_(3)nanocomposites.The obtained results are relevant to the development of lightweight automobile and aerospace structures and components.
基金Supported by the National Natural Science Foundation of China(No.21271138)the Natural Science Foundation of Tianjin City, China(No.10JCZDJC21500)
文摘Fe2O3/active carbon(Fe2O3/AC) nanocomposites were readily fabricated by pyrolyzing Fe3+ impregnated active carbon in a nitrogen atmosphere. The as-prepared composites were studied by X-ray powder diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM). The capacitive property of the composites was investigated by cyclic voltammetry(CV) and galvanostatic charge-discharge test. Physical characterizations show that the γ-Fe2O3 fine grains dispersed in the AC well, with a mean size of 21.24 nm. Electrochemical tests in 6 mol/L KOH solutions indicate that the as-prepared nanocomposites exhibited improved capacitive properties. The specific capacitance(SC) of Fe2O3/AC nanocomposites was up to 188.4 F/g that was derived from both electrochemical double-layer capacitance and pseudo-capacitance, which was 78% larger than that of pristine AC. A symmetric capacitor with Fe2O3/AC nanocomposites as electrode showed an excellent cycling stability. The SC was only reduced by a factor of 9.2% after 2000 cycles at a current density of 1 A/g.
文摘Poly (N, N, N-trimethyl-(2-pyrrol-1-yl) ethyl ammonium iodide)/V2O5 (PTPAI/V2O5) nanocomposites were synthesized by sol-gel method. This method involved formation of vanadium pentoxide xerogel in the presence of polypyrrole derivatives solution. X-ray diffraction (XRD) indicated that the polypyrrole derivative particles encapsulated in the fibrous V2O5 network and the layered distance significantly increased from 1. 077 39 to 1. 354 56 nm. The interaction between polypyrrole and V2O5 in the ‘nanocomposites’ was characterized by IR spectroscopy. The Scanning Electron Microscope (SEM) micrographs reveal the structural contrasts between the hybrid materials and the pristine vanadium oxide xerogel. Key words polypyrrole/V2O5 - nanocomposites - XRD - SEM CLC number O 633. 5 Foundation item: Supported by the Natural Science Foundation of Hubei Province (2003ABA030)Biography: Shi Chuang (1978-), male, Master candidate, research direction: synthesis chemistry.
基金supported by the National Natural Science Foundation of China(no.51362018)the Foundation for Innovation Groups of Basic Research in Gansu Province(no.1606RJIA322)
文摘The CoO/CoVO/Ni nanocomposites were rationally designed and prepared by a two-step hydrothermal synthesis and subsequent annealing treatment. The one-dimensional(1D) CoOnanowire arrays directly grew on Ni foam, whereas the 1D CoVOnanowires adhered to parts of CoOnanowires.Most of the hybrid nanowires were inlayed with each other, forming a 3D hybrid nanowires network.As a result, the discharge capacity of CoO/CoVO/Ni nanocomposites could reach 1201.8 mAh/g after100 cycles at 100 mA/g. After 600 cycles at 1 A/g, the discharge capacity was maintained at 828.1 mAh/g.Moreover, even though the charge/discharge rates were increased to 10 A/g, it rendered reversible capacity of 491.2 mAh/g. The superior electrochemical properties of nanocomposites were probably ascribed to their unique 3D architecture and the synergistic effects of two active materials. Therefore, such CoO/CoVO/Ni nanocomposites could potentially be used as anode materials for high-performance Li-ion batteries.
基金NSFC (50272063)The Sci-Tec Project of Jiangmen City Nanocomposites (2006-10 &No .2007-11)
文摘An improved sol-gel method was used to prepare Eu3+ ions doped SiO-Y2O3 nanocomposites. Systematic study on the effect of post-annealling treatment on photoluminescence (PL) properties of the samples under various europium ions doping concentrations were carried out. XRD patterns indicate that the samples show an amorphous matrix structure, and the SEM patterns show that the samples present a multi-hole loosen structure, and a rod structure after high-temperature annealling treatment (800 ℃) for 3 h. Raman spectra demonstrate that Y3+ and Eu3+ ions were incorporated into the composites successfully through the sol-gel and post-anneal process. Under the excitation of 387 nm (7F0→5G2) violet light (but not 394 nm (7F0→5L6)), the strongest emission spectrum, the red light, was observed at around 616 nm (5D0→7F2) when the samples were re-treated by annealing at high temperature after 3 months laying aside. Without annealing treatment, the optimized doping mole ratio of Eu ions is about 9%, which is much higher than that doped in SiOglass with the concentration of 3.5%, and it then becomes 5% when the samples are treated by high temperature annealing. In addition, the excitation of 532 nm (7F0→5D1) light can also arouse a comparatively strong emission.
基金jointly supported by National Science Foundation of China (Grant Numbers: 11572271 and 51302236)the Principal Fund of Xiamen University (Hosted by Guanghui Yue, 2018)
文摘Rechargeable lithium–oxygen batteries have been considered as a promising energy storage technology because of their ultra-high theoretical energy densities which are comparable to gasoline. In order to improve the electrochemical properties of lithium–oxygen batteries(LOBs), especially the cycling performance, a high-efficiency cathode catalyst is the most important component.Hence, we aim to demonstrate that CuCr_2O_4@rGO(CCO@rGO) nanocomposites, which are synthesized using a facile hydrothermal method and followed by a series of calcination processes, are an effective cathode catalyst. The obtained CCO@rGO nanocomposites which served as the cathode catalyst of the LOBs exhibited an outstanding cycling performance for over 100 cycles with a fixed capacity of 1000 mAh g^(-1) at a current density of 200 mA g^(-1). The enhanced properties were attributed to the synergistic effect between the high catalytic efficiency of the spinel-structured CCO nanoparticles, the high specific surface area, and high conductivity of the rGO.
基金National Science Council, Taiwan! under grant !No. NSC-87-2112-M194-005.
文摘Phase evolution and magnetic properties of (Nd_o.95La_0.05)9.5-11Febal.M_2B10.5. where M=Cr, Ti, Nb, V, Mo, Zr, Hf, Ta, Mn or W, melt spun ribbons have been investigated. Almost all the alloy ribbons. except for(Nd_0.95La_0.05)_9.5Fe_78M_2B_10.5(M=Mo and Mn),consist merely two magnetic phases, namely α-Fe and R_2Fe_14B, which display a better combination of _iH_c and magnetic energy product. Remanence (Br) and coercivity (i_H_c) values in the range of 8.0 to 9.1 kG and 9.5 to 18.9 kOe. respectively, can be achieved. Among compositions studied, the Ti and W-substitutions were found to be most effective in increasing the Br and i_H_c, respectively. For a fixed refractory metal substitution, namely, M=C_r, Ti or Nb, an increase in the total rare earth concentration resulted in nanocomposites of small grain sizes and a high volume fraction of the R_2Fe_14B phase, leading to an increase in the magnetic properties.
基金supported by National Natural Science Foundation of China(No.51703015)Fundamental Research Funds for the Central Universities(No.2020CDJQY-A008).
文摘High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)and ferromagnetic cobalt ferrite(CoFe_(2)O_(4))(0.00 wt%to 0.2 wt%)are prepared by a solution casting method accompanied by uniaxial stretching and high electric field poling.The decisive effect of the poling electric field on the power generating capability was confirmed by the experiments.For pure PVDF-HFP films,when the maximum electric field Emax is 120 MV/m,the calibrated open circuit voltage reaches 2.93 V,which is much higher than those poled at lower electric fields(70 MV/m:1.41 V;90 MV/m:2.11 V).Furthermore,the addition of CoFe_(2)O_(4)also influences the piezoelectricity dramatically.In the samples containing 0.15 wt%CoFe_(2)O_(4),the calibrated open circuit voltage increases to the maximum value of 3.57 V.Meanwhile,the relative fraction of theβ-phase and the crystallinity degree are 99%and 48%,respectively.The effects of CoFe_(2)O_(4)nanoparticles on initial crystallization,uniaxial stretching and high electric field poling are investigated by XRD,FTIR and DSC.
文摘Zinc oxide/low-density polyethylene (LDPE) nanocomposites were prepared for intrauterine devices. The change of Zn^2+ release rates of nanocomposites ( doped with various mass fractions of zinc oxide nanoparticles between 5wt% and 65 wt% ) for 264 days in a simulated uterine solution were investigated. The resuits show that initial burst phases are followed by near zero-order release phases. SEM technique was employed to observe the surface morphology of the 45wt% ZnO/ LDPE composite. Elements and phases on the surface of the nanocomposite after incubation were also analyzed by EDX and XRD respectively. The experimental results show that incrustation formation does not occur after incubation.
文摘ZrO2/Graphene nanocomposites are fabricated from graphene oxide by one-step, green, facile and low-cost SCCO2 method. The as-prepared nanocomposites are characterized by means of X-ray photoelectron, transmission electron microscopy and catalytic chemiluminescence measurement. The ZrO2 nanoparticles with size of several nanometers are uniformly coated on the graphene surface. The chemiluminescence characteristic to ethanol of the as-prepared nanocomposite paper is also investigated. The nanocomposite paper obtained displays high catalytic chemiluminescence sensitivity and highly selectivity to the ethanol gas. This study provides a facile, green and low-cost route to prepare nanoscopic gas sensing devices with application in safe protection, food fermentation, medical process and traffic safe.