纳米SiC颗粒对Al_2O_3-ZrO_2复合材料断裂模式的影响

本文观察了Al2O3-ZrO2和纳米SiC复合的Al2O3-ZrO2陶瓷材料的断口形貌。在Al2O3-ZrO2样品中表现为典型的沿晶断裂。复合纳米SiC颗粒后,出现相当一部分的穿晶断裂形貌。并且讨论了残余热应力对断裂模式的影响。

聚乳酸纳米颗粒对大鼠凝血系统影响的初步研究

目的:研究聚乳酸纳米颗粒对凝血系统功能的影响。方法:20只实验大鼠随机分为4组,尾静脉注射不同剂量的聚乳酸纳米颗粒悬浮液、表面活性剂、生理盐水,检测反映凝血系统功能的主要指标APTT、PT、TT、Fbg。结果:实验组与对照组的APTT、PT、TT、Fbg的差异均无显著性意义(P>0.05)。结论:聚乳酸纳米颗粒及其表面包被的吐温80对大鼠内、外源凝血系统均无影响,从而为其作生物大分子载体的可行性提供了实验依据。

高能超声法制备SiCp／AZ91D纳米复合材料

采用高能超声法制备纳米SiC颗粒增强AZ91D镁基纳米复合材料。高能超声能够使纳米级陶瓷颗粒在镁合金熔体中有效分散,所制备的复合材料抗拉强度和屈服强度等力学性能比基体有所提高。其中所用SiC颗粒粒径在40nm左右,在0.5%的添加量下复合材料可以获得较好的性能,铸态条件下抗拉强度超过200MPa。

纳米复合镀层的研究现状

综述了纳米颗粒在复合镀层中对提高镀层的硬度、耐磨性、耐蚀性、耐高温性能、减摩性能的作用 。

板料拉深成形润滑模式研究

对板料拉深成形中的两种常用润滑模式进行了研究 ,并按膜厚尺寸对这两种润滑模式进行分类。在分析其润滑机理的基础上提出一种复合润滑模式 ,这种润滑模式使液体润滑剂和微米级粉体两种润滑介质的优势互相补充。实验证明 ,具有很好的润滑效果。另外 。

新型AgI/Ag/BiOBr光催化剂的构建及其增强的可见光催化活性

通过在光催化的过程中光还原二元AgI/BiOBr复合物原位合成一种新型的三元AgI/Ag/BiOBr复合物.在可见光条件下(λ>420 nm),AgI/Ag/BiOBr光催化剂对偶氮染料甲基橙(MO)和无色苯酚的降解呈现出优异的降解效率分别高达94.8%和86.2%.光催化活性的增强主要归因于金属Ag在Z型AgI/Ag/BiOBr光催化剂充当电子迁移桥,不仅降低界面电子迁移阻力,而且加速光生载流子的分离和迁移.本研究不仅证明Ag作为电荷传输桥的应用,而且为设计和制备高效、稳定的光催化剂提供一条新的途径.

Effects of Au-Ce strong interactions on catalytic activity of Au/CeO_2/3DOM Al_2O_3 catalyst for soot combustion under loose contact conditions

Au/3DOM（three-dimensionally ordered macroporous） Al2O3 and Au/CeO2/3DOM Al2O3 were prepared using a reduction-deposition method and characterized using scanning electron microscopy,N2 adsorption-desorption,X-ray diffraction,transmission electron microscopy,ultraviolet-visible spectroscopy,temperature-programmed hydrogen reduction,and X-ray photoelectron spectroscopy.Au nanoparticles of similar sizes were well dispersed and supported on the inner walls of uniform macropores.The norminal Au loading is 2%.Al-Ce-O solid solution in CeO2/3DOM Al2O3 catalysts can be formed due to the incorporation of Al^3＋ ions into the ceria lattice,which causes the creation of extrinsic oxygen vacancies.The extrinsic oxygen vacancies improved the oxygen-transport properties.The strong metal-support interactions between Au and CeO2 increased the amount of active oxygen on the Au nanoparticle surfaces,and this promoted soot oxidation.The activities of the Au-based catalysts were higher than those of the supports（Al2O3 or CeO2/3DOM Al2O3） at low temperature.Au/CeO2/3DOM Al2O3 had the highest catalytic activity for soot combustion,with T（10）,T（50）,and T（90） values of 273,364,and 412℃,respectively.

Effect of TiC nanoparticle on friction and wear properties of TiC/AA2219 nanocomposites and its strengthening mechanism

TiC nanoparticles reinforced 2219 aluminum matrix composites were successfully prepared by ultrasonic casting, followed by forging and T6 heat treatment. The friction and wear properties of the disc-to-column were studied under four separate normal values of 5, 10, 20 and 30 N. The increasing hardness value of the nanocomposite may be attributed to the large amount of TiC(i.e., 1.3 wt.% and 1.7 wt.%) introduced to the composites. The friction coefficient of the nanocomposite decreased with the increase of TiC nanoparticles(0-1.7 wt.%) under the same load. But the wear resistance of the TiC/AA2219 nanocomposite increased by 30%-90% as compared to the 2219 matrix alloy. And it decreased with the increasing load. The composite with 0.9 wt.% TiC produced the best results in terms of friction and wear because of its relatively higher hardness and perfect ability to retain a transfer layer of a comparatively larger thickness. On the wear surface, some Al2O3particles were found which aided in the development of protective shear regions and improved the wear resistance. The wear mechanism for the TiC/AA2219 nanocomposite was a combination of adhesive and oxidative wear, with the composites containing hard TiC nanoparticles being mainly abrasive.

Si_3N_4/Ni nanocomposite formed by electroplating: Effect of average size of nanoparticulates

Properties of Si3N4/Ni electroplated nanocomposite such as corrosion current density after long time immersion,roughness of obtained layer and distribution of nanometric particulates were studied.Other effective factors for fabrication of nanocomposite coatings were fixed for better studying the effect of the average size of nanoparticulates.The effects of the different average size of nanometric particulates(ASNP)from submicron scale(less than 1μm)to nanometric scale(less than 10 nm)were studied.The nanostructures of surfaces were examined by scanning electron microscopy(SEM),transmission electron microscopy(TEM)and atomic force microscopy(AFM).Corrosion rates of the coatings were determined using the Tafel polarization test.It is seen that decreasing the ASNP will lead to lower corrosion current densities;however,in some cases,pitting phenomena are observed.The roughness illustrates a minimum level while the distribution of nanometric particulates is more uniform by decreasing the ASNP.The effects of pulsed current on electrodeposition(frequency,duty cycle)and concentration of nanoparticulates in electrodeposition bath on trend of obtained curves have been discussed.Response surface methodology was applied for optimizing the effective operating conditions of coatings.The levels studied were frequency range between 1 000 and 9 000 Hz,duty cycle between 10%and 90%and concentration of nanoparticulates of 10-90 g/L.

Microstructure and properties of alumina-silicon carbide nanocomposites fabricated by pressureless sintering and post hot-isostatic pressing

A1203/5%SIC nanocomposites were fabricated by pressureless sintering using MgO as a sintering aid and then post hot-isostatic pressed （HIP）, which can subsequently break through the disadvantage of hot-pressing process. The MgO additive was able to promote the densification of the composites, but could not induce the grain growth of A1203 matrix due to the grain growth inhibition by nano-sized SiC particles. After HIP treatment, A12OJSiC nanocomposites achieved full densification and homogeneous distribution of nano-sized SiC particles. Moreover, the fracture morphology of HIP treated specimens was identical with that of the hot-pressed A1203/SiC nanocomposites showing complete transgranular fracture. Consequently, high fracture strength of 1 GPa was achieved for the A1203/5%SIC nanocomposites by pressureless sintering and post HIP process.

Improvement of high-temperature strength of 6061 Al matrix composite reinforced by dual-phased nano-AlN and submicron-Al_(2)O_(3)particles

Nano-AlN and submicron-Al_(2)O_(3) particles were simultaneously utilized in a 6061 Al matrix composite to improve the high-temperature strength.According to the SEM and TEM characterization,nano-AlN and submicron-Al_(2)O_(3) particles are uniformly distributed in the Al matrix.Brinell hardness results indicate that different from the traditional 6061 Al matrix alloy,the aging kinetics of the composite is obviously accelerated by the reinforcement particles.The T6-treated composite exhibits excellent tensile properties at both room temperature and elevated temperature.Especially at 350℃,the T6-treated composite not only has a high yield strength of 121 MPa and ultimate tensile strength of 128 MPa,but also exhibits a large elongation of 11.6%.Different strengthening mechanisms of nano-AlN and submicron-Al_(2)O_(3) particles were also discussed in detail.

Mn nanoparticles enhanced dehydrogenation and hydrogenation kinetics of MgH_(2) for hydrogen storage

Mn nanoparticles(nano-Mn)were successfully synthesized and doped into MgH_(2) to improve its de/hydrogenation properties.Compared with MgH_(2),the onset desorption temperature of 10 wt.%nano-Mn modified MgH_(2) was decreased to 175℃ and 6.7,6.5 and 6.1 wt.%hydrogen could be released within 5,10 and 25 min at 300,275 and 250℃,respectively.Besides,the composite started to take up hydrogen at room temperature and absorbed 2.0 wt.%hydrogen within 30 min at low temperature of 50℃.The hydrogenation activation energy of MgH_(2) was reduced from(72.5±2.7)to(18.8±0.2)kJ/mol after doping with 10 wt.%nano-Mn.In addition,the MgH_(2)+10 wt.%nano-Mn composite exhibited superior cyclic property,maintaining 92%initial capacity after 20 cycles.

Simulation Study of Electron Beam Induced Surface Plasmon Excitation at Nanoparticles

Phenomenon of localized surface plasmon excitation at nanostructured materials has attracted much attention in recent decades for their wide applications in single molecule detection,surface-enhanced Raman spectroscopy and nano-plasmonics.In addition to the excitation by external light field,an electron beam can also induce the local surface plasmon excitation.Nowadays,electron energy loss spectroscopy(EELS)technique has been increasingly employed in experiment to investigate the surface excitation characteristics of metallic nanoparticles.However,a present theoretical analysis tool for electromagnetic analysis based on the discrete dipole approximation(DDA)method can only treat the case of excitation by light field.In this work we extend the DDA method for the calculation of EELS spectrum for arbitary nanostructured materials.We have simulated EELS spectra for different incident locations of an electron beam on a single silver nanoparticle,the simulated results agree with an experimental measurement very well.The present method then provides a computation tool for study of the local surface plasmon excitation of metallic nanoparticles induced by an electron beam.

Thermal reliabilities of Sn−0.5Ag−0.7Cu−0.1Al_(2)O_(3)/Cu solder joint

The effects of trace addition of Al_(2)O_(3) nanoparticles(NPs)on thermal reliabilities of Sn−0.5Ag−0.7Cu/Cu solder joints were investigated.Experimental results showed that trace addition of Al_(2)O_(3) NPs could increase the isotheraml aging(IA)and thermal cyclic(TC)lifetimes of Sn−0.5Ag−0.7Cu/Cu joint from 662 to 787 h,and from 1597 to 1824 cycles,respectively.Also,trace addition of Al_(2)O_(3) NPs could slow down the shear force reduction of solder joint during thermal services,which was attributed to the pinning effect of Al_(2)O_(3) NPs on hindering the growth of grains and interfacial intermetallic compounds(IMCs).Theoretically,the growth coefficients of interfacial IMCs in IA process were calculated to be decreased from 1.61×10^(−10 )to 0.79×10^(−10) cm^(2)/h in IA process,and from 0.92×10^(−10) to 0.53×10^(−10) cm^(2)/h in TC process.This indicated that trace addition of Al_(2)O_(3) NPs can improve both IA and TC reliabilities of Sn−0.5Ag−0.7Cu/Cu joint,and a little more obvious in IA reliability.

Preparation and characterization of polyvinylchloride membrane embedded with Cu nanoparticles for electrochemical oxidation in direct methanol fuel cell

Copper nanoparticles were prepared by the chemical reduction method.These copper particles were embedded into the polyvinylchloride(PVC)matrix as support and used as an electrode(PVC/Cu)for the oxidation of methanol fuel for improving the current response.The PVC/Cu electrodes were characterized by thermal gravimetric analysis(TGA)for thermal stability of the electrode,X-ray diffraction(XRD)for identification of copper nanoparticles in the electrode,Fourier transform infrared spectroscopy(FTIR)to identify the interaction between PVC and Cu and scan electron microscopy(SEM)with EDAX for the morphology of the electrode.The electrocatalytic activity of the electrode was characterized by the cyclic voltammetry,linear sweep voltammetry,and chronoamperometry techniques.An increase in the electrode activity was observed with the increase of copper quantity from 0.18 g(PVC/Cu-0.18 g)to 0.24 g(PVC/Cu-0.24 g)and the maximum was found at 0.24 g of copper in the electrode.Also,it was observed that the electrode achieved the maximum catalytic current in 0.5 mol/L CH3OH+1 mol/L Na OH solution.FTIR identified that water molecules,C—H group,copper nanoparticle and its oxide were available in the electrode.SEM images with EDAX showed that copper particles were properly embedded in the polyvinylchloride matrix.

Facile synthesis of porous LiNiVO_4 powder as high-voltage cathode material for lithium-ion batteries

Porous LiNiVO4 powder was synthesized via solution combustion synthesis method using lithium nitrate, nickel nitrate,ammonium metavanadate and citric acid as raw materials. Thermogravimetry (TG) and differential scanning calorimetry (DSC),X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM) were used toevaluate the structures and morphologies of samples. The results show that the calcination temperature has significant effect on thecrystallinity and morphologies. Pure LiNiVO4 flaky nanoparticles with a mean particle size around 20 nm can be readily prepared bycalcining the precursor in air at 500 °C for 2 h. As a cathode material for lithium-ion batteries, the porous LiNiVO4 powder exhibits agood structural reversibility.

Spectroscopic Investigated Interaction between Silver Nanocomposites Based of Poly-N-Vinylpyrrolidone and Doxorubicin for Drug Delivering

It is investigated to synthesis of Ag nanoparticles by presence the synthetic polymer poly-N-vinylpyrrolidone. It was determined with X-ray analyses that the size ofnanoparticles changed between 18-42 nm. Then, the authors studied sorption process of doxorubicine by silver nanocomposites and investigated chemical interaction between antibiotic and poly-N-vinyplyrrolidone with UV-VIS （ultraviolet visible） and FT-IR （Fourier transform infrared） spectroscopy. It is shown that formation of the nanoparticles doxorubicin complex mainly occurs in the 190-208 nm wavelengths on polymers 〉C=O functional groups. Also, the four main absorbing peaks of doxorubicin--234, 253, 288 and 495 nm undergo chemists shift （A2 = 12-15 nm）. When increases to pH = 7-8, the size of Ag-doxorubicin particles decreases. It is determined that the 410 nm absorption peak of Ag nanoparticles undergo 409-418 nm interval and the 3,500, 1,600, 1,645 and 1,190 sm^-1 absorption lines of PVPr （polymer poly-N-vinylpyrrolidone） slightly altered.

Change in Aggregate Shape of Heat Treated Carbon Nanoparticles

To better understand the fusion mechanism of heated carbon black, heat treatment is conducted for carbon black produced by benzene pyrolysis. The effects of （a） heating time, （b） heating temperature and （c） heating rate on the aggregate shape and mean primary particle diameter of the carbon black are investigated using TEM （transmission electron microscopy）. The mean primary particle diameter does not change significantly when carbon black is heat treated. For short heating times and low heating temperatures, the aggregate shapes become simple when compared with those of non-heated carbon black, and shapes become complex with an increase in the heating time. Also, for low heating rates, the aggregate shapes become significantly simple when compared with those of non-heated carbon black. The results of this study suggest that sintering between primary particles is promoted under relatively low heating temperatures, and Ostwald ripening among aggregates is promoted under relatively high heating temperatures.

Green synthesis of nickel nanoparticles using Ocimum sanctum and their application in dye and pollutant adsorption

Nickel nanoparticles as an eco-friendly adsorbent was biosynthesized using Ocimum sanctum leaf extract. The physiochemical properties of green synthesized nickel nanoparticles(Ni Gs) were characterized by UV–Vis spectroscopy(UV–Vis), Fourier Transform Infrared Spectroscopy(FTIR), X-ray diffraction(XRD), Scanning Electron Microscope(SEM) and Transmission Electron Microscope(TEM). Ni Gs were used as adsorbent for the removal of dyes such as crystal violet(CV), eosin Y(EY), orange II(OR) and anionic pollutant nitrate(NO3-), sulfate(SO42-) from aqueous solution. Adsorption capacity of Ni Gs was examined in batch modes at different p H, contact time, Ni G dosage, initial dye and pollutant concentration. The adsorption process was p H dependent and the adsorption capacity increased with increase in contact time and with that of Ni G dosage, whereas the adsorption capacity decreased at higher concentrations of dyes and pollutants. Maximum percentage removal of dyes and pollutants were observed at 40, 20,30, 10 and 10 mg·L-1initial concentration of CV, EY, OR, NO3-and SO42-respectively. The maximum adsorption capacities in Langmuir isotherm were found to be 0.454, 0.615, 0.273, 0.795 and 0.645 mg·g-1at p H 8, 3, 3, 7and 7 for CV, EY, OR, NO3-and SO42-respectively. The higher coef ficients of correlation in Langmuir isotherm suggested monolayer adsorption. The mean energies(E), 2.23, 3.53, 2.50, 5.00 and 3.16 k J·mol-1for CV, EY, OR, NO3-and SO42-respectively, calculated from the Dubinin–Radushkevich isotherm showed physical adsorption of adsorbate onto Ni Gs. Adsorption kinetics data was better fitted to pseudo-second-order kinetics with R2 N 0.870 for all dyes and pollutants. Ni Gs were found to be an effective adsorbent for the removal of dyes and pollutants from aqueous solution and can be applied to treat textile and tannery ef fluents.

Effect of Fe_2O_3/SiO_2 ratio on maghemite-silica particulate nanocomposites

Abstract： Maghemite-silica particulate nanocomposites were prepared by modified 2-step sol-gel process. Superparamagnetic maghemite nanoparticles were successfully produced using Massart＇s procedure. Nanocomposites consisting of synthesized maghemite nanoparticles and silica were produced by dispersing the as-synthesized maghemite nanoparticles into the silica particulate form. The system was then heated at 140 ℃for 3 d. A variety of mass ratios of Fe2O3/SiO2 was investigated. Moreover, no surfactant or other unnecessary precursor was involved. The nanocomposites were characterized using XRD, BET and AGM. The XRD diffraction patterns show the reflection corresponding to maghemite nanoparticles and a visible wide band at 20 from 20° to 35° which are the characteristics of the amorphous phase of the silica gel. The patterns also exhibit the presence of only maghemite and SiO2 amorphous phase, which indicates that there is no chemical reaction between the silica particulate gel and maghemite nanoparticles to form other compounds. The calculated crystallite size for encapsulated maghemite nanoparticles is smaller than the as-synthesized maghemite nanoparticles indicating the dissolution of the nanoparticles. Very high surface area is attained for the produced nanocomposites （360-390 m^2/g）. This enhances the sensitivity and the reactivity of the nanocomposites. The shapes of the magnetization curves for nanocomposites are very similar to the as-synthesized maghemite nanoparticles. Superparamagnetic behaviour is exhibited by all samples, indicating that the size of the maghemite nanoparticles is always within the nanometre range. The increase in iron content gives rise to a small particle growth.