Solution combustion synthesis of Ni-Y_2O_3 nanocomposite powder

Ni-Y2O3 nanocomposite powder with uniform distribution of fine oxide particles in the metal matrix was successfully fabricated via solution combustion process followed by hydrogen reduction. The combustion behavior was investigated by DTA-TG analysis. The influence of urea to nickel nitrate（U/Ni） ratio on the combustion behavior and morphology evolution of the combusted powder was investigated. The morphological characteristics and phase transformation of the combusted powder and the reduced powder were characterized by FESEM, TEM and XRD. The HRTEM image of Ni-Y2O3 nanocomposite powder indicated that Y2O3 particles with average particle size of about 10 nm dispersed uniformly in the nickel matrix.

Study on Preparation and Properties of La_2O_3/MC Nylon Nanocomposites

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.

Photoluminescence behavior and visible light photocatalytic activity of ZnO,ZnO/ZnS and ZnO/ZnS/α-Fe_2O_3 nanocomposites

In order to achieve effective, economic, and easily achievable photocatalyst for the degradation of dye methyl orange（MeO）, ZnO, ZnO/ZnS and ZnO/ZnS/α-Fe2O3 nanocomposites were prepared by simple chemical synthetic route in the aqueous medium. Phase, crystallinity, surface structure and surface behavior of the synthesized materials were determined by X-ray diffraction（XRD） and Brunauer-Emmett-Teller analysis（BET） techniques. XRD study established formation of good crystalline ZnO, ZnO/ZnS and ZnO/ZnS/α-Fe2O3 nanomaterials. By using intensity of constituent peaks in the XRD pattern, the compositions of nanocomposites were determined. From the BET analysis, the prepared materials show mesoporous behavior, type Ⅳ curves along with H4 hysteresis. The ZnO/ZnS/α-Fe2O3 composite shows the largest surface area among three materials. From the UV-visible spectra, the band gap energy of the materials was determined. Photoluminescence spectra（PL） were used to determine the emission behavior and surface defects in the materials. In PL spectra, the intensity of UV peak of ZnO/ZnS is lowered than that of ZnO while in case of ZnO/ZnS/α-Fe2O3, the intensity further decreased. The visible emission spectra of ZnO/ZnS increased compared with ZnO while in ZnO/ZnS/α-Fe2O3 it is further increased compared with ZnO/ZnS. The as-synthesized materials were used as photocatalysts for the degradation of dye MeO. The photo-degradation data revealed that the ZnO/ZnS/α-Fe2O3 is the best photocatalyst among three specimens for the degradation of dye MeO. The decrease of intensity of UV emission peak and the increase of intensity of visible emission cause the decrease of recombination of electrons and holes which are ultimately responsible for the highest photocatalytic activity of ZnO/ZnS/α-Fe2O3.

Absorption performance of DMSA modified Fe_3O_4@SiO_2 core/shell magnetic nanocomposite for Pb^(2+) removal

The purpose of this study is to explore the adsorption performance of meso-2,3-dimercaptosuccinic acid(DMSA)modified Fe3O4@SiO2 magnetic nanocomposite(Fe3O4@SiO2@DMSA)for Pb2+ions removal from aqueous solutions.The effects of solution pH,initial concentration of Pb2+ions,contact time,and temperature on the amount of Pb2+adsorbed were investigated.Adsorption isotherms,adsorption kinetics,and thermodynamic analysis were also studied.The results showed that the maximum adsorption capacity of the Fe3O4@SiO2@DMSA composite is 50.5 mg/g at 298 K,which is higher than that of Fe3O4 and Fe3O4@SiO2 magnetic nanoparticles.The adsorption process agreed well with Langmuir adsorption isotherm models and pseudo second-order kinetics.The thermodynamic analysis revealed that the adsorption was spontaneous,endothermic and energetically driven in nature.

Morphology and Mechanical Properties of PS/Al_2O_3 Nanocomposites Based on Selective Laser Sintering

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.

Enhanced photoresponse performance in Ga/Ga_2O_3 nanocomposite solar-blind ultraviolet photodetectors

In the present work, we explore the solar-blind ultraviolet（UV） photodetectors（PDs） with enhanced photoresponse,fabricated on Ga/Ga2O3 nanocomposite films. Through pre-burying metal Ga layers and thermally post-annealing the laminated Ga2 O3/Ga/Ga2O3 structures, Ga/Ga2O3 nanocomposite films incorporated with Ga nanospheres are obtained. For the prototype PD, it is found that the photocurrent and photoresponsivity will first increase and then decrease monotonically with the thickness of the pre-buried Ga layer increasing. Each of all PDs shows a spectrum response peak at 260 nm, demonstrating the ability to detect solar-blind UV light. Adjustable photoresponse enhancement factors are achieved by means of the surface plasmon in the nanocomposite films. The PD with a 20 nm thick Ga interlayer exhibits the best solar-blind UV photoresponse characteristics with an extremely low dark current of 8.52 p A at 10-V bias, a very high light-to-dark ratio of ～ 8 × 10~5, a large photoresponsivity of 2.85 A/W at 15-V bias, and a maximum enhancement factor of ～ 220. Our research provides a simple and practical route to high performance solar-blind UV PDs and potential applications in the field of optoelectronics.

Structural characteristics and dielectric properties of glass-ceramic nanocomposites of(Pb,Sr)Nb_2O_6-NaNbO_3-SiO_2

The structure and dielectric properties of （Pb,Sr）Nb2O6-NaNbO3-SiO2 glass-ceramics with different Pb and Sr contents were investigated. The XRD pattern of glass-ceramics without Sr substitution is different from that with Sr substitution, which indicates the existence of orthorhombic phase in the latter ones. TEM bright field observation shows nanosized microstructures, while for samples with Sr, typical eutectic microstrncture with separated crystallized bands is found in the glass matrix. Dielectric properties measurement of the samples indicates an obvious improvement of dielectric constant, dielectric loss, DC field and temperature dependence of dielectric constant when the molar ratio of Sr to Pb is 4：6.

Structures and magnetic properties of nanocomposite CoFe_2O_4-BaTiO_3 fibers by organic gel-thermal decomposition process

The nanocomposite xCoFe2O4-(1-x)BaTiO3(x=0.2,0.3,0.4,0.5,molar fraction) fibers with fine diameters and high aspect ratios(length to diameter ratios) were prepared by the organic gel-thermal decomposition process from citric acid and metal salts.The structures and morphologies of gel precursors and fibers derived from thermal decomposition of the gel precursors were characterized by Fourier transform infrared spectroscopy,X-ray diffractometry and scanning electron microscopy.The magnetic properties of the nanocomposite fibers were measured by vibrating sample magnetometer.The nanocomposite fibers consisting of ferrite(CoFe2O4) and perovskite(BaTiO3) are formed at the calcination temperature of 900 ℃ for 2 h.The average grain sizes of CoFe2O4 and BaTiO3 in the nanocomposite fibers increase from 25 to 65 nm with the calcination temperature from 900 to 1 180 ℃.The single fiber constructed from these nanograins of CoFe2O4 and BaTiO3 has a necklace-like morphology.The saturation magnetization of the nanocomposite 0.4CoFe2O4-0.6BaTiO3 fibers increases with the increase of CoFe2O4 grain size,while the coercivity reaches a maximum value when the average grain size of CoFe2O4 is around the critical single-domain size of 45 nm obtained at 1 000 ℃.The saturation magnetization and remanence of the nanocomposite xCoFe2O4-(1-x)BaTiO3(x=0.2,0.3,0.4,0.5) fibers almost exhibit a linear relationship with the molar fraction of CoFe2O4 in the nanocomposites.

The design and fabrication of Co3O4/Co3V2O8/Ni nanocomposites as high-performance anodes for Li-ion batteries

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.

Preparation and Supercapacitive Properties of Fe_2O_3/Active Carbon Nanocomposites

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.

Effect of Mg addition on mechanical and thermoelectrical properties of Al-Al_2O_3 nanocomposite

The effects of Mg addition on mechanical thermo-electrical properties of Al.Mg/5%Al2O3 nanocomposite with differentMg contents （0, 5%, 10% and 20%） produced by mechanical alloying were studied. Scanning electron microscopy analysis （SEM）,X-ray diffraction analysis （XRD） and transmission electron microscopy （TEM） were used to characterize the produced powder. Theresults show that addition of Mg forms a predominant phase （Al.Mg solid solution）. By increasing the mass fraction of Mg, thecrystallite size decreases and the lattice strain increases which results from the atomic penetration of Mg atoms into the substitutionalsites of Al lattice. The microhardness of the composite increases with the increase of the Mg content. The thermal and electricalconductivities increase linearly with the temperature increase in the inspected temperature range. Moreover, the thermalconductivity increases with the increase of Mg content.

Amorphous CoSnO_3@rGO nanocomposite as an efficient cathode catalyst for long-life Li-O_2 batteries

An amorphous CoSnO3@rGO nanocomposite fabricated using a surfactant‐assisted assembly method combined with thermal treatment served as a catalyst for non‐aqueous lithium‐oxygen(Li‐O2)batteries.In contrast to the specific surface area of the bare CoSnO3 nanoboxes(104.3 m2 g–1),the specific surface area of the CoSnO3@rGO nanocomposite increased to approximately 195.8 m2 g–1 and the electronic conductivity also improved.The increased specific surface area provided more space for the deposition of Li2O2,while the improved electronic conductivity accelerated the decomposition of Li2O2.Compared to bare CoSnO3,the overpotential reduced by approximately 20 and 60 mV at current densities of 100 and 500 mA g?1 when CoSnO3@rGO was used as the catalyst.A Li‐O2 battery using a CoSnO3@rGO nanocomposite as the cathode catalyst cycled indicated a superior cyclic stability of approximately 130 cycles at a current density of 200 mA g–1 with a limited capacity of 1000 mAh g–1,which is 25 cycles more than that of the bare amorphous CoSnO3 nanoboxes.

Formation mechanism of Al2O3/MoS2 nanocomposite coating by plasma electrolytic oxidation(PEO)

In this study,an Al2O3/MoS2 nanocomposite coating was created on an aluminum 1050 substrate using the plasma electrolytic oxidation method.The zeta potential measurements showed that small MoS2 particles have negative potential and move toward the anode electrode.The nanoparticles of MoS2 were found to have a zeta potential of-25 mV,which prevents suspension in the solution.Thus,to produce an Al2O3/MoS2 nanocomposite,one has to use the microparticles of MoS2.The X-ray diffraction analyses showed that the produced coatings containedα-Al2O3,γ-Al2O3,and MoS2,and that the size of MoS2 particles can be reduced to 30 nm.It was observed that prolonged suspension in the electrolyte results in an enhanced formation of an Al2O3/MoS2 nanocomposite.Using the results,it was hypothesized that the mechanism of the formation of the Al2O3/MoS2 nanocomposite coating on the aluminum 1050 substrate is based on electrical energy discharge.

Preparation and Characteristics of Cu-Al₂O₃Nanocomposite

Thermo-chemical technique was used to synthesize Cu-Al2O3, nanocomposite powders. The process was carried out by addition of Cu powder to aqueous solution of aluminum nitrate. Afterwards, a thermal treatment at 850℃ for 1 hr was conducted to get insitu powders of CuO and stable alumina (Al2O3, ). The CuO was reduced in hydrogen atmosphere into copper powder. The nanocomposite powders of both copper and alumina were thoroughly mixed, cold pressed into briquettes and sintered at 850℃ in hydrogen atmosphere. The x-ray diffraction and scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) were used to characterize the structure of the obtained powders. The results showed that alumina nanoparticles (20 nm) and ultra fine copper crystallite (200 nm) were obtained. SEM and EDS showed that the alumina particles were uniformly dispersed within the copper crystallite matrix. The structure also revealed formation of a third phase (CuAlO2) at copper-alumina interface. The hardness and density results showed that the gain in hardness was found to be dependent on the alumina contents rather than on the relative densities. The alumina content up to 12.5% resulted in an increase of 47.9% in hardness and slight decrease (7.6%) in relative densities. The results of compression tests showed considerable increase in compression strength (67%) as alumina content increased up to 12.5%. The compression strength showed further increase in compression strength (24%) as strain rates were increased from 10-4 s to 10s. Strain hardening and strain rate parameters “n” and “m” have shown positive values that improved the total strain and they can be used to predict formability of the nanocomposite.

Structure and Magnetic Properties of FeCo/Al_2O_3 Nanocomposites

The soft magnetic nanocomposites with equiatomic FeCo particles dispersed in Al2O3 matrix were synthesized via a sol-gel technique combined with H2 reduction method. The samples were characterized by X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The FeCo nanoparticles in all the samples have the typical bcc structure. With the decreasing of Al2O3 content, the mean grain size of FeCo in the nanocomposites and the saturation magnetization of the samples increase, while the coercivity of samples increases firstly and then decreases due to different magnetic mechanisms.

高强度块状C-Al_2O_3复合气凝胶的制备

采用溶胶-凝胶法和CO2超临界干燥工艺,并经高温热处理过程得到C-Al2O3复合气凝胶。通过N2吸附-脱附实验研究热处理对气凝胶孔结构参数的影响;利用X线衍射技术表征气凝胶在热处理过程中的相结构变化;采用扫描电子显微镜观察气凝胶的微观形貌,并对气凝胶进行强度测试。结果表明:C-Al2O3复合气凝胶具有均匀的三维网络结构,而且成块性好,热处理后C-Al2O3复合气凝胶仍然具有高的比表面积。C-Al2O3复合气凝胶的最高压缩强度可达9.07 MPa,大大提高了气凝胶材料的力学性能。

具有双孔径分布的介孔C-Al_2O_3-TiO_2纳米复合材料的合成及其红外发射率

以嵌段共聚物F127(PEO106PPO70PEO106,MW=12600)为模板剂,异丙醇铝和钛酸四丁酯为金属源,低分子量的酚醛树脂为碳源,通过溶胶-凝胶三元共组装法合成了具有双孔径分布的C-Al2O3-TiO2纳米复合材料.用X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)及N2吸附-脱附对该复合材料进行结构表征.结果显示,当铝钛原子的摩尔比为1:10时,对应的纳米复合材料具有较好的有序介孔结构,其双孔径分别为3.9和6.5nm,比表面积可达259m2·g-1,孔容0.37cm3·g-1.以三元乙丙橡胶(EPDM)为粘结剂,与介孔纳米复合材料混合制备涂层.通过调节复合材料中铝钛摩尔比和涂层厚度,红外发射率在0.450-0.617之间可调.

有序介孔C-Al_2O_3纳米复合材料的合成及其红外发射率

以嵌段共聚物F127(PEO106PPO70PEO106,MW=12600)为模板剂,异丙醇铝为铝源,低分子量的酚醛树脂为碳源,通过溶胶-凝胶三元共组装法合成了C-Al2O3纳米复合材料.用X射线衍射(XRD)、透射电子显微镜(TEM)及N2吸脱附法对该复合材料进行结构与性能表征,结果显示复合材料MC5A5具有较好的有序介孔结构,其比表面积可达175m2·g-1,孔容0.22cm3·g-1.又以三元乙丙橡胶(EPDM)为粘结剂,与介孔纳米复合材料混合制备涂层.随着复合材料中Al2O3质量分数从30%增加到70%,该涂层的红外发射率从0.575降至0.456,表明Al2O3能有效降低复合材料的红外发射率,预示该复合材料在军事装备隐身需求领域将具有较好的应用前景.

基于选择性激光烧结C-Al_2O_3复合粉体微观形貌和成型机理的研究

用正交试验设计来安排试验,对高温烧结前后样品的宏观和微观结构进行表征。结果表明,样品的结构特征与激光烧结工艺参数密切相关,并且激光烧结样品的致密度、升温和降温速率、保温时间以及烧结助剂的选择,对最终样品的致密度和力学性能的提高有着重大影响。同时分析了选择性激光烧结的机理,发现激光束与粉末的作用是一个动态瞬间的熔化-凝固的平衡过程。

Research of Trap and Electron Density Distributions in the Interface of Polyimide/Al2O3 Nanocomposite Films Based on IDC and SAXS

The distributions of traps and electron density in the interfaces between polyimide （PI） matrix and Al2O3 nanoparticles are researched using the isothermal decay current and the small-angle x-ray scattering （SAXS） tests. According to the electron density distribution for quasi two-phase mixture doped by spherical nanoparticles, the electron densities in the interfaces of PI/Al2O3 nanocomposite films are evaluated. The trap level density and carrier mobility in the interface are studied. The experimental results show that the distribution and the change rate of the electron density in the three layers of interface are different, indicating different trap distributions in the interface layers. There is a maximum trap level density in the second layer, where the maximum trap level density for the nanocomposite film doped by 25 wt% is 1.054 × 10^22 eV·m^-3 at 1.324eV, resulting in the carrier mobility reducing. In addition, both the thickness and the electron density of the nanocomposite film interface increase with the addition of the doped Al2O3 contents. Through the study on the trap level distribution in the interface, it is possible to further analyze the insulation mechanism and to improve the performance of nano-dielectric materials.