Synthesis and Conductivity of Nano Crystalline Ceria

Nanoparticles of cerium oxide were synthesized by the co-precipitation method. Synthesis conditions were optimized for phase purity, particularly the effect of pH (=14,13,11) of solutions during reaction, was studied. The phase analysis and structural properties of the prepared particles were determined by X-ray diffraction analysis. The average crystallite size decreased with the increase in pH of solution. The temperature-dependent DC conductivity was measured in the temperature range 300 °C to 700 °C and was found to be increasing with the increase in measurement temperature. AC conductivity and dielectric constants were measured in the frequency range of 1 kHz to 3 MHz and also at different temperatures.     

热分解法制备Ni_(0.5)Zn_(0.5)Fe_2O_4纳米颗粒

采用热分解法制备Ni_(0.5)Zn_(0.5)Fe_2O_4纳米颗粒,研究表面活性剂用量、回流温度和回流时间对产物尺寸、形貌以及分散性的影响。通过X射线衍射仪(XRD)、透射电子显微镜(TEM)和振动样品磁强计(VSM)对样品的结构、形貌与磁性能进行了表征。结果表明:增加表面活性剂的用量,产物的粒径减小,分散性明显提高,而提高回流温度和延长回流时间则会使产物粒径增加,但粒径分布也会变宽。在三辛基氧化膦(TOPO)用量为0.6mmol,260℃回流1h条件下制备产物的饱和磁化强度为49.38A·m2/kg,矫顽力为7143.20A/m,剩余磁化强度为5.76A·m2/kg,表现为亚铁磁性。     

微波辅助燃烧法制备镁铝尖晶石纳米粉体的研究

Stoichiometric MgAl2O4 spinel nanoparticles were synthesized by microwave assisted combustion reaction from aluminium nitrate nanohydrate(Al(NO3)3.9H2O) and Sol-Gel prepared magnesium hydroxide(Mg(OH)2) in the presence of urea((NH2)2CO) as a fuel,in about 20 min of irradiation.X-ray diffraction(XRD) studies reveal that mi-crowave assisted combustion synthesis route yields single-phase spinel nanoparticles with larger crystalline size(around 75 nm) than other conventional heating methods.Scanning electronic microscope(SEM) images show nanoparticles with spherical shape and homogenous morphology.The surface area measurements(SBET) show crystals with 2.11 m2/g and 0.0033 mL/g pore volume.     

电弧等离子体法制备纳米Ce-NiO的气敏特性

用Ｈ２＋Ａｒ电弧等离子体法制备纳米Ｃｅ－ＮｉＯ并研究其气敏特性。实验结果表明：与通常用作氧敏传感器的Ｐ型ＮｉＯ半导体材料相比，Ｈ２＋Ａｒ电弧等离子体法制备的纳米Ｃｅ－ＮｉＯ气敏材料表现出一定的ｎ型导电性，对乙炔具有很好的选择性和较高的灵敏度；其气敏特性与纳米Ｃｅ－ＮｉＯ晶粒的显微结构有关。     

碳包裹纳米铁、镍及铁镍合金粒子的制备及其吸波性能

以聚丙烯酸阳离子交换树脂(PAA)为碳源,与铁、镍二价离子交换后形成含金属的前驱体(M/PAA),经500℃热解制备碳包裹纳米铁、镍及其合金粒子.采用TG研究了前驱体PAA和M/PAA的热解特性;采用XRD、HRTEM等对热解产物的形貌和结构进行了分析表征,并采用弓形法测试了热解产物对电磁波的吸收性能.结果表明,M/PAA的热稳定性强于PAA;500℃热解M/PAA可获得粒径为10～35nm的碳包裹纳米铁、镍及其合金粒子.以碳包裹纳米铁、镍和铁镍合金粒子为吸收剂(质量分数为50%),石蜡为粘结剂,涂层厚为2mm时,碳包裹纳米铁粒子的吸波性能最好,在11.7GHz频率时吸收峰值Rmin为-10dB,频宽△dB可达6.0GHz.     

Comparative Study of Nano Crystalline Ceria Synthesized by Different Wet-Chemical Methods

Cerium oxide (CeO₂) nanoparticles were synthesized by using sol–gel methods and the Composite Mediated Hydrothermal Method (CMHM). Sol–gel synthesis was done for 0.6 M molarity of the precursor solution of cerium nitrate hexa hydrated [Ce(NO₃)₃?6H₂O] and the hydrothermal synthesis was done at 180 °C for 45 min. X-Ray diffraction (XRD) was used to measure the structural properties of the prepared ceria. Scherrer’s formula was used to calculate the crystallite sizes of average and most intense peak. Temperature dependent (200 °C to 700 °C) dc conductivity was measured and found to be increasing with the increase in measuring temperature. The frequency dependent (20 Hz to 3 MHz) ac conductivity and dielectric properties were measured at different temperatures. The comparison of electric and dielectric properties was studied. Both synthesis techniques were further analyzed by the Raman spectrum at 514 nm excitation laser line for the different bands of cerium oxide and oxygen vacancies.     

Synthesis of Superparamagnetic Nanoparticle Ni0.50Zn0.50Fe2O4 Using Wet Chemical Method

The nanoparticles of Ni_0.50Zn_0.50Fe₂O₄ were prepared using cotton base wet chemical method. The X-ray diffraction (XRD) spectrum shows single phase cubic spinel structure, and crystallize size calculated using the Debye–Scherrer formula for 311 planes was found to be 41 nm ± 5 %. The nano range sizes of particle were confirmed using transmission electron microscope (TEM) and atomic force microscopy (AFM) images. The porosity value of the sample is promising towards sensor applications. Infrared spectroscopic results reveal two main absorption bands, indicating sample is having single phase spinel structure with two sublattices. The high DC resistivity of the sample is attributed to nano range particle sizes. The superparamagnetic (SPM) nature was confirmed from a variation of magnetic moment with applied magnetic field using VSM. The Mössbauer spectrum recorded at room temperature shows two major sextets corresponding to A- and B-site Fe ions. The relaxed sextet is associated with the atoms near the surface of the nanoparticles experiencing disordered spins. The central doublet in Mössbauer spectra of the sample indicates SPM particles. The isomer shift results show that all the Fe ions are in high state.     

脱附油气回送冷凝系统进行再回收的研究

从理论上对汽油油气的冷凝回收进行了讨论,对冷凝＋吸附组合工艺中的脱附油气的回送冷凝系统再回收进行了分析研究,以证明其可行性。     

具有优异力敏特性的纳米Fe50Ni50粉体/丁基橡胶复合材料薄膜

为开发力敏性能更为优异的复合材料薄膜,首先,通过液相还原法制备了粒径约为100 nm的纳米Fe50Ni50粉体,并通过液态混合分散工艺将纳米粉体与丁基橡胶(IIR)混合分散;然后,通过机械混炼及压制得到了粉体分布均匀、含量为65wt%的纳米Fe50Ni50粉体/IIR复合材料薄膜;最后,研究了在连续加载/卸载速度为0.10 mm/min、测试频率为1 kHz的条件下,纳米Fe50Ni50粉体/IIR复合材料薄膜的力敏特性。结果表明:液态混合分散工艺可使Fe50Ni50粉体在复合材料薄膜中达到纳米级均匀分散效果;当压应力为0.20~0.90 MPa时,薄膜越厚,其标准偏差越大,力敏稳定性越差;随压应力增大,厚度为185μm的薄膜在加载阶段的阻抗近似线性下降,力敏灵敏度稳定在40~60范围内,标准偏差约为1~2。所得结论表明在压应力为0.20~0.90 MPa时,制备的薄膜具有优异的力敏特性。      

三乙醇胺-水溶液介质水热合成纳米四方相氧化锆粉体

以氨水为沉淀剂,将其缓慢滴加至氧氯化锆和硝酸钇混合溶液制备氧化锆前驱体;以有机溶剂三乙醇胺为矿化剂,水热晶化制备纳米四方相氧化锆。着重研究了水热温度、时间、矿化剂浓度对粉体结晶性能、分散性、粒径、形貌的影响,通过XRD、TEM对粉体进行表征。结果表明,通过选择适当的条件,可制得分散性良好、粒径分布窄的四方相纳米氧化锆;有机矿化剂的加入和水热温度的升高有助于提高粉体的结晶度和分散性能。     

气体辅助注射成型高密度聚乙烯的结晶形态

通过扫描电镜(SEM)观察了气体辅助注射成型(GAIM)和常规注射成型(CIM)高密度聚乙烯(HDPE)的结晶形态,发现CIM试样为区分不明显的皮芯结构,而GAIM试样形成了包括球晶、串晶和取向片晶的多层结构.且GAIM试样球晶尺寸显著小于CIM制品.在结晶形态分析的基础上,初步探讨了气体辅助注射成型制品结晶形态的形成机理.     

Strong Subsonic Condensation of Polyatomic Gas

The effect of temperature on correlations in the Knudsen layer under conditions of strong subsonic condensation of a polyatomic gas is investigated. The method of moments is used to demonstrate that the dependence of pressure outside of the Knudsen layer on the flow temperature at a fixed value of the Mach number has a maximum. The limiting dependences of pressure on the Mach number are obtained for low and high values of flow temperature.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 4, 2005, pp. 601–605.Original Russian Text Copyright © 2005 by A. V. Butkovskii.     

Ordering and recovery processes in the Ni/Fe system near Ni3Fe

The ordering and recovery processes in 72/28 and 80/20 at.% Ni/Fe alloys have been investigated. A parameter related to the thermal scattering contribution of the electrical resistivity was used to follow the establishment of atomic order. It was found that the initial condition of the alloys — quenched or cold-worked — has little influence on the ordering kinetics at high temperatures. However, it greatly influences the recovery behaviour, as indicated by the residual resistivity measurements. Strain-ageing effects reported earlier are interpreted in the light of the present findings. Results are also discussed on the basis of existing theories for atomic ordering.     

纳米级FePt/Fe多层膜中微结构的优化与耦合效应

本文用磁控溅射法制备了一系列不同厚度Fe层的FePt/Fe多层膜,经过热处理后成功地制备出具有fct结构的FePt有序相和exchange-spring型永磁体.研究了不同热处理条件下多种膜层厚度与FePt/Fe多层膜结构、磁性及其内在关系,并探讨了FePt/Fe多层膜铁中的磁耦合失效问题.观察了不同热处理条件和层厚的FePt/Fe多层膜的结构变化过程,包括结构相变、有序度和晶粒度.研究了其磁性能随结构变化的规律,发现了耦合失效的模式.     

超声化学法合成纳米羟基磷灰石粉体的研究

以Ca(NO3)2和(NH4)2HPO4为原料,应用超声化学法制备得到了尺寸约20nm×120nm、分散性良好的针状羟基磷灰石(HAp)纳米粉体.对比研究了超声化学法与传统的化学沉淀法对HAp粉体的结晶性能、Ca/P摩尔比和产率的影响.研究表明,与传统的化学沉淀法相比,超声化学法可以在较短的时间内显著地提高纳米HAp的合成效率、结晶度、Ca/P摩尔比和产率.     

Synthesis and thermo-optical stability of o-methyl red-intercalated Ni–Fe layered double hydroxide material

In the present letter, an anionic azo dye, o-methyl red (2-(4-(dimethyl-amino) phenylazo) benzoic acid, MR), was incorporated successfully into the interlayer domain of Ni–Fe layered double hydroxide (LDH) by coprecipitation route. X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR) and simultaneous thermogravimetric and differential thermal analysis (TG-DTA) revealed the presence of supramolecular host–guest interaction between the host matrix and interlayer anionic dye guest with an expanded interlayer distance. The UV–visible diffuse reflectance (UV–VIS/DR) spectra showed that the dye-intercalated LDH had higher photostability than the pristine dye. Moreover, there was no significant change for the interlayer MR anions in the UV–VIS/DR spectra of the dye-intercalated sample after heating up to 200 °C, indicating that the thermostability of dye is markedly enhanced by the intercalation into the gallery domain of NiFe-LDH.     

纳米α-MnO2的制备及其性能研究

用溶胶－凝胶法制备纳米级α－ＭｎＯ２;并对实验条件进行了 ,对所得的样品进行了ＸＲＤ,ＩＣＰ、ＴＥＭ、等一系列测试,并与国际一号样相比较,虽然纳米级α－ＭｎＯ２的单独放电性能并不好,但是当纳米级α－ＭｎＯ２以一定比例与Ｉ．Ｃ．Ｎｏ．１号样混合时,在浅度和深度放电区内的放电容量都比Ｉ．Ｃ．Ｎｏ．１高。     

（Fe,Ni）_4N包覆（Fe,Ni）纳米复合粒子的微波吸收特性

以直流电弧等离子体法制备（Fe,Ni）的纳米粒子为前驱体,分别在350℃、400℃和450℃的氨气气氛中,通过热氨解反应合成（Fe,Ni）_4N包覆（Fe,Ni）纳米复合粒子。应用XRD,TEM,VSM,微波矢量网络分析仪对纳米粒子相成分、形貌、磁性和电磁参数进行了分析。结果表明,形成了（Fe,Ni）_4N包覆（Fe,...     

氮杂碳包Fe、Co、Ni材料的合成及介电特性

采用交流电弧法,在氮气氛下合成了氮杂碳包金属Fe、Co、Ni纳米晶.采用热重分析(TG)法测量了合成材料中Fe、Co、Ni等金属的含量.借助于透射电子显微镜(TEM)、粉末衍射法(XRD)、X光电子能谱法(XPS)等分析手段进行了合成材料的形貌观察和结构表征.采用反射-传输网络参数法在HP8510B矢量网络分析仪上进行了材料复介电常数测量.结果表明氮杂碳包金属Fe、Co、Ni纳米晶在8.2～12.4GHz频率范围内具有复介电特性,其损耗角正切tgδε=ε"/ε′平均值分别达到0.9,0.31和0.30,显示出氮杂碳包金属Fe、Co、Ni纳米晶对微波具有较好的介电损耗特性.