Dynamic Mechanical,DSC, and Electrical Investigations on Nano Al2O3 Filled PVA:NH4SCN:DMSO Polymer Composite Dried Gel Electrolytes

This paper reports the dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and ionic conductivity studies on nanosized Al₂O₃(aluminium oxide) filled PVA:NH₄SCN:DMSO polymer composite dried gel electrolytes prepared by the wet chemistry route. Better mechanical stability and thermal behavior are noticed in the composite system. Multiple relaxation peaks seen in tangent loss measurements (in DMA studies) have been suitably correlated. Enhancement in ionic conductivity has been noticed with an optimum value of 4.02 × 10^?3 Scm^?1 for 4 wt% nano Al₂O₃ filled composite electrolytes. Temperature dependence of ionic conductivity shows a combination of Arrhenius and VTF (Vogel-Tamman-Fulcher) behavior.     

Wavelength conversion using rare earth doped oxides in polyolefin based nanocomposite films

Nanocomposites are a new class of polymeric materials which include organic or inorganic nano‐phase materials. These nanocomposite films can show interesting properties which have many applications for wavelength conversion and energy saving. In this paper, we present polyolefin based nanocomposite films prepared using wavelength‐converting red ‘phosphors’ such as Y₂O₃: Eu³⁺ and LiAl₅O₈:Fe³⁺ and blue ‘phosphor’ CaMgSi₂O₆: Eu²⁺. The durability of the polymer chain is unaffected by incorporation of inorganic nanoparticles as there is no direct interaction between them. The addition of surfactant in the nanocomposite film helps to improve the dispersion ability of the nanoparticles and increase the flexibility of the polymer film. Wavelength‐converting ‘nanophosphors’ incorporated in a polymer matrix help to increase the tensile strength of the film. The films show excellent wavelength conversion ability of UV light into the visible and near IR range. These nanocomposite films have great application in energy saving devices. Copyright © 2012 Society of Chemical Industry     

On the experimental and numerical investigation of clay/epoxy nanocomposites

Due to increasing use of clay/epoxy nanocomposites in industry, investigation of mechanical properties of clay nanocomposites has become of great interest. While the stiffening mechanism of clay nanocomposites is well documented, there is still not a clear understanding about how addition of clays affect the fracture behavior of clay/epoxy nanocomposites. The main aim of this paper is to measure and explain the effect of clays on ductility reduction of these nanocomposites. First, epoxy and clay/epoxy nanocomposites with different clay weight ratio were built. Then, the damage parameters of epoxy and clay/epoxy nanocomposites were measured by variation of the elasticity modulus. Based on loading–unloading experiments, the Lemaitre damage parameters for epoxy and clay/epoxy nanocomposites were extracted. Crack initiation and propagation in dog-bone sample were simulated for epoxy and clay/epoxy nanocomposites using the eXtended Finite Element Method (XFEM). The comparison between experimental and numerical results shows that the proposed method can predict the crack initiation location and propagation path in clay/epoxy nanocomposites.     

电沉积方式对Ni-CeO_2纳米复合镀层摩擦磨损性能的影响

采用直流电沉积、脉冲电沉积和超声辅助脉冲电沉积制备Ni-CeO2纳米复合镀层,研究电沉积方式对纳米复合镀层表面形貌、显微硬度和摩擦磨损性能的影响,并用扫描电子显微镜分析其磨损机理。结果表明:电沉积方式对Ni-CeO2纳米复合镀层的晶粒尺寸和性能有较大影响;当超声波引入脉冲电沉积过程时,超声波的强力搅拌作用和超声空化效应能促进CeO2纳米颗粒在镀层中均匀分布,进一步减小镀层的晶粒尺寸,明显提高镀层的显微硬度,从而改善镀层的摩擦磨损性能;Ni-CeO2纳米复合镀层的摩擦磨损性能均优于纯Ni镀层的;而超声辅助脉冲电沉积制备的Ni-CeO2纳米复合镀层的晶粒更加细小、显微硬度最高,其摩擦因数最低,耐磨损性能最佳。     

真空热处理对快淬纳米复合NdFeB电磁特性的影响

采用真空快淬技术制备低Nd含量的NdFeB纳米复合磁性材料,通过差示扫描量热法(DSC)、X射线衍射(XRD)、振动样品磁强计(VSM)和微波矢量网络分析仪等手段研究了真空热处理前后样品微观结构和电磁特性的变化。DSC结果显示在510℃和630℃处出现两个放热峰,在稍微高于这两个温度分别热处理后,相对于快淬态样品,材料的磁导率(μ')和磁损耗(μ″)降低,并且磁损耗出现多重频散特性,同时复介电常数减小,特别在2 GHz处ε″分别为-103.7(540℃)和ε″为-245.3(650℃)。根据传输线理论模拟计算涂层的反射损耗,发现快淬态样品在3.7 GHz下厚度为1.5 mm时最小反射损耗为-5.3 dB;而热处理后的样品在12 GHz处获得最小反射损耗,分别为-3.3 dB(540℃)和-2.1 dB(650℃)。     

The synergistic ability of Al2O3 nanoparticles to enhance mechanical response of hybrid alloy AZ31/AZ91

AZ31/AZ91 hybrid alloy nanocomposite containing Al₂O₃ nanoparticle reinforcement was fabricated using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size to the monolithic hybrid alloy, reasonable Al₂O₃ nanoparticle distribution, non-dominant (0 0 0 2) texture in the longitudinal direction, and 25% higher hardness than the monolithic hybrid alloy. Compared to the monolithic hybrid alloy (in tension), the nanocomposite synergistically exhibited higher 0.2%TYS, UTS, failure strain and work of fracture (WOF) (+12%, +7%, +99% and +108%, respectively). Compared to the monolithic hybrid alloy (in compression), the nanocomposite exhibited higher 0.2%CYS and UCS, and lower failure strain and WOF (+5%, +3%, −7% and −7%, respectively). The beneficial effects of Al₂O₃ nanoparticle addition on the enhancement of tensile and compressive properties of AZ31/AZ91 hybrid alloy are investigated in this paper.     

Microstructural and mechanical evaluation of Al-TiB2 nanostructured composite fabricated by mechanical alloying

Production of bulk Al-TiB₂ nanocomposite from mechanically alloyed powder was studied. Al-20 wt.% TiB₂ metal matrix nanocomposite powder was obtained by mechanical alloying (MA) of pure Ti, B and Al powder mixture. A double step process was used to prevent the formation of undesirable phases like Al₃Ti intermetallic compound, which has been described in our previous papers. The resultant powder was consolidated by spark plasma sintering (SPS) followed up by hot extrusion. The structural characteristics of powder particles and sintered samples were studied by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hardness measurements were conducted on the cross section of powder particles and sintered sample and the tensile behavior of extruded samples was evaluated. The results showed that the prepared Al-20 wt.% TiB₂ nanocomposite has good thermal stability against grain growth and particle coarsening. Extruded Al-20 wt.% TiB₂ showed a hardness value of 180 VHN and yield and tensile strength of 480 and 540 MPa, respectively, which are much higher than those reported for similar composites made by other processes.     

层状硅酸盐纳米复合材料的阻燃研究及现状分析

聚合物/层状硅酸盐(PLS)纳米复合材料是国内外阻燃材料领域中近年来研究的热点。它满足了新型阻燃材料发展的要求,在提高阻燃性能的同时能够很少降低或者不降低材料原有的其他性能,有时甚至可以提高部分聚合物基体的机械性能、气体阻隔性能、环保性能等。本文综述了聚合物/层状硅酸盐纳米复合材料的研究近况;简要介绍了该纳米复合材料的特点及阻燃性能的测试;讨论了其燃烧性能和阻燃机理;重点研究了以聚酰胺(PA)等聚合物为基质、以层状硅酸盐为无机阻燃添加剂的纳米复合材料的阻燃性能。通过与常规阻燃剂进行比较,发现聚合物/层状硅酸盐纳米复合材料在阻燃性能、机械性能、加工性能和环保等方面均优于常规阻燃剂;最后本文还指出了该材料在阻燃研究中目前尚存在的问题,并对其开发应用前景进行了展望。     

TiO2/MQ硅树脂反应型杂化材料的制备及其性能研究

以钛酸丁酯、MQ硅树脂为原料,利用溶胶-凝胶法制备了TiO2/MQ硅树脂无机-有机杂化材料.采用傅里叶变换红外光谱(FT - IR)、紫外-可见光谱、热重分析仪(TGA)、X-射线衍射仪(XRD)、扫描电镜(SEM)表征杂化材料的结构与性能.结果表明:杂化材料中存在Ti-O-Si共价键合;杂化材料对可见光吸收极低,对紫...     

Facile synthesis, magnetic and microwave absorption properties of Fe3O4/polypyrrole core/shell nanocomposite

Fe₃O₄/polypyrrole (PPy) core/shell nanocomposite, with Fe₃O₄ nanoparticle as core and PPy as shell, could be facilely synthesized via in situ chemical oxidative polymerization of pyrrole monomers on the surface of Fe₃O₄ nanoparticles. The results indicate that core/shell nanocomposite consists of Fe₃O₄ core with the mean diameter of 100 nm and adjacent PPy shell with a thickness of about 70 nm. The as-prepared Fe₃O₄/PPy core/shell nanocomposite exhibits a saturated magnetization of 20.1 emu/g and coercivity value of 368.3 Oe, respectively. The electromagnetic characteristics of Fe₃O₄/PPy core/shell nanocomposite were also investigated with a vector network analyzer in the 2-18 GHz range. The absorbing peak position moves to lower frequency with increasing the thicknesses of samples. The value of the minimum reflection loss is −22.4 dB at 12.9 GHz for Fe₃O₄/PPy core/shell nanocomposite with a thickness of 2.3 mm, and a broad peak with a bandwidth lower than −10 dB is about 5 GHz. Such strong absorption is attributed to better electromagnetic matching due to the existence of PPy and the special core/shell structure.