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11.
A novel method for preparation of nano-crystalline gadolinium aluminate (GdAlO3) powder, based on combustion synthesis, is reported. It was observed that aluminium nitrate and gadolinium nitrate exhibit different combustion characteristics with respect to urea, glycine and β-alanine. While urea was proven to be a suitable fuel for direct formation of crystalline α-Al2O3 from its nitrate, glycine and β-alanine are suitable fuels for gadolinium nitrate for preparation of its oxide after combustion reaction. Based on the observed chemical characteristics of gadolinium and aluminium nitrates with respect to above mentioned fuels for the combustion reaction, the fuel mixture composition could be predicted that could lead to phase pure perovskite GdAlO3 directly after the combustion reaction without any subsequent calcination step. The use of single fuel, on the other hand, leads to formation of amorphous precursor powders that call for subsequent calcination for the formation of crystalline GdAlO3. The powders produced directly after combustion reactions using fuel mixtures were found to be highly sinterable. The sintering of the powders at 1550 °C for 4 h resulted in GdAlO3 with sintered density of more than 95%. T.D. 相似文献
12.
Subramanian Palaniappan Yu-Tsern Chang Chung-Ming Liu Paramasivam Manisankar 《Materials Chemistry and Physics》2011
A facile and sustainable mechanochemical route for the synthesis of undoped polydiphenylamine (PDPA) and inorganic acid doped nanostructures are reported. Field emission scanning electron microscopic (FESEM) images highlighted the formation of distinctly different nanostructures for each of the inorganic acid doped PDPA. Elemental analysis carried out for the polymers revealed the presence of more repeating units in their backbone. The X-ray diffraction (XRD) results of the as-prepared PDPA nanostructures indicated the high degree of crystallinity ever reported for PDPA. Spectroscopic profile of the polymers showed that the prepared PDPA is in a doped conducting form. Electrochemical studies performed for the polymeric particles ascertained the redox behaviour and the good electrochemical activity of obtained PDPA samples. The probable mechanistic aspect behind the formation of PDPA nanostructures through this simple and efficient route is discussed. 相似文献
13.
The effect of increasing vanadium carbide (VC) content on the corrosion behaviour of tungsten carbide - 10 wt% cobalt hardmetals was investigated in 1 M hydrochloric (HCl), and sulphuric (H2SO4) acids solutions. Increasing VC content makes the open circuit potential (OCP) in the test solutions more negative than the base alloy. Specimens exhibited pseudo passivation in all the test solutions. Increasing VC led to decreasing corrosion current density. However, the corrosion current densities during chronoamperometric tests were lower for 0 wt% VC. XRD and Raman spectroscopy showed that hydrated WO3 formed in the surface films of all specimens in hydrochloric acid (HCl), while hydrated vanadyl sulphate also formed for higher VC content specimens in sulphuric acid (H2SO4). 相似文献
14.
15.
F. X. Xiu Z. Yang D. T. Zhao J. L. Liu K. A. Alim A. A. Balandin M. E. Itkis R. C. Haddon 《Journal of Electronic Materials》2006,35(4):691-694
Low-temperature (LT) buffer-layer techniques were employed to improve the crystalline quality of ZnO films grown by molecular-beam
epitaxy (MBE). Photoluminescence (PL) spectra show that CdO, as a hetero-buffer layer with a rock-salt structure, does not
improve the quality of ZnO film grown on top. However, by using ZnO as a homo-buffer layer, the crystalline quality can be
greatly enhanced, as indicated by PL, atomic force microscopy (AFM), x-ray diffraction (XRD), and Raman scattering. Moreover,
the buffer layer grown at 450°C is found to be the best template to further improve the quality of top ZnO film. The mechanisms
behind this result are the strong interactions between point defects and threading dislocations in the ZnO buffer layer. 相似文献
16.
采用脉冲激光沉积(PLD)技术在Si(111)衬底上生长了Eu3+、Li+共掺杂的ZnO薄膜。分别对样品进行了X射线衍射(XRD)谱测试和光致发光(PL)谱分析,重点研究了退火处理对样品结构和发射光谱的影响。XRD谱测试表明,样品具有很好的C轴择优取向。PL谱研究表明,当用325nm光激发样品时,样品的发射光谱仅由ZnO基质的紫外发射和蓝光发射组成,并没有发现稀土Eu3+的特征发光峰;样品的蓝光发射源于电子从Zn填隙形成的浅施主能级到Zn空位形成的浅受主能级跃迁;和真空中退火的样品相比,O2中制备的样品的蓝光发射减弱,紫外发光增强。用395nm的光激发时,退火前样品分别在594nm和613nm处存在两个明显的Eu3+特征发光峰,退火后的样品仅发现Eu3+位于594nm的特征发光峰,这表明,退火处理不利于稀土离子的特征发射,但O2中退火的样品ZnO基质红绿波段发射光谱明显增强。 相似文献
17.
在高纯半绝缘4H-SiC偏8°衬底上同质外延生长了高质量的外延层,利用X射线双晶衍射、原子力显微镜(AFM)、汞探针C-V以及霍尔效应等测试方法,对样品的结晶质量、表面粗糙度、掺杂浓度以及电子迁移率进行了分析测试,证实外延层的结晶质量相对于衬底有着很大的改善。在同质外延7.5μm的外延层后,其半高宽从衬底的30.55arcsec减小到27.85arcsec;外延层表面10μm×10μm的粗糙度(RMS)为0.271nm;室温下,样品的掺杂浓度为1×1015cm-3时,霍尔迁移率高达987cm2/(V.s);浓度为1.5×1016cm-3时,霍尔迁移率为821cm2/(V.s)。77K时,霍耳迁移率分别为1.82×104cm2/(V.s)和1.29×104cm2/(V.s)。掺杂浓度的汞探针C-V测试结果与霍尔效应的实验数据一致。 相似文献
18.
P. Rozenak 《Journal of Electronic Materials》1997,26(7):868-872
Silicon strained epitaxial films were grown on Si (001) substrates by low energy ion beam assisted molecular beam epitaxy.
Films grown in the range of 450– 550°C with concurrent Ar+ ion bombardment (100 eV) were characterized using x-ray diffraction and transmission electron microscopy and found to be
disloca-tion free and ununiformly strained. During aging, the strained layers stay stable until 500°C. Relaxation of most
of the strain occurred at temperatures of 500-650°C. At higher aging temperatures, the strained layers relaxed by the formation
of dense dislocation structures. 相似文献
19.
对离子交换法和一步沉积法引进铈离子的系列Y分子筛进行了铈离子定位研究。建立了铈离子在Y分子筛中定位的简便有效的基础表征体系:利用Ce3d XPS谱获得Ce4+/Ce3+摩尔比,通过Ce3d谱及XPS定量结果分析铈离子在分子筛笼内外的存在情况;利用XRD和Py IR确定铈离子在笼内的定位。研究了不同方法引进不同含量铈离子的定位规律。结果表明,离子交换法较沉积法利于铈离子迁移进分子筛笼内,从而进一步迁移进β笼;Ce2O3质量分数为4%、8%、12%和14%时,离子交换法引进的铈离子基本能迁移进β笼。一步沉积法引进的Ce2O3质量分数为4%时,易进入β笼;更多的铈离子则易留在分子筛笼外,可用于防止重金属中毒。 相似文献
20.
Commercial mixed-phase aluminum oxide was used as a heterogeneous catalyst support, providing slightly basic properties which are well-suited for the condensation of bio-ethanol to C4 hydrocarbons, such as 1-butanol. Different metals (Cu, Ni and Co), at various metal loadings were deposited on the support. Consequently, the catalytic reactions were carried out in a continuous laboratory-scale fixed bed reactor operated at 240 °C and 70 bar. The catalysts were characterized by means of XRD, TEM, FT-IR, XPS and ICP-OES. Different metals were found to give entirely different product distributions. With the best catalysts, the selectivities towards 1-butanol close to 70% were reached, while the ethanol conversion typically varied between 10 and 30% – strongly depending on the metal applied. It was observed that low loading of copper and high loading of nickel were responsible for the formation of 1-butanol, whereas cobalt and high loading of copper resulted in the production of ethyl acetate. The reaction was found to be extremely sensitive to catalyst preparation conditions and procedures such as metal loading, calcination/reduction temperature and, thereby, to the formation of corresponding crystallite structure. 相似文献