Synthesis of Y_2O_3 Nano-Powder from Yttrium Oxalate under Ambient Temperature

High purity Y_2O_3 nano-powders was synthesized directly from solution ofindustrial YCl_3 by method of oxalate precipitation through super-micro-reactors made by complexnon-ionic surfactant. The purity and diameter of Y_2O_3 particles were controlled by such processingparameters as concentration of YCl_3 and oxalic acid and complex non-ionic surfactant etc. TEMphotomicrographs show that Y_2O_3 particles are spherical in shape, with an average diameter of lessthan 30 nm. Test results certify that the purity and particle diameter as well as the dispersion ofY_2O_3 nano-powder depend on the concentrations of YCl_3, oxalic acid and complex non-ionicsurfactant. The optimum ranges of the concentrations for YCl_3 and complex non-ionic surfactant whenthe diameter of Y_2O_3 particles is smaller than 100 nm are 0.43 ～1.4 mol ? L^(-1) and0.031～0.112 mol·L^(-1) respectively, while the mass fraction range of oxalic acid is 10% ～18% .The purity of Y_2O_3 nano-powder tested by ICP-AES analysis is 99.99% .

Progress on grain growth dynamics in sintering of nano-powders

Nanostructured materials, characterized by an ultrafine grain size, have stimulated much research interest by virtue of their unusual mechanical, electrical, optical, and magnetic properties. In this paper, the sintering process of nano-powders were reviewed, to which sintering of the traditional materials compared. The microstructural development, i.e., grain growth and densification during sintering as well as the mechanism of crystal surface diffusion and boundary migration were analyzed, and the dynamic models on sintering process were summarized by the relationship of grain growth and pores size, interface diffusion, densification rate, and sintering temperature. Finally, the research tendency of this major on the basis of above models was discussed.

ITO nano-powders prepared by microwave-assisted co-precipitation in aqueous phase

By using microwave-assisted co-precipitation in aqueous phase, adding surface activation agent PEG-6000 into the mixture of InCl3 solution and SnCl4 solution, and dropping the ammonia solution with the density (volume ratio) of 1-0 to 1-4, ITO precursor was prepared at different reaction system temperatures of 35 ℃-85 ℃, then ITO nano-powder was obtained after it was calcinated at 800 ℃ for 1 h. The morphology of ITO nano-powder was characterized by SEM and its electrical conductivity was determined by conductivity meter. The effects of different temperatures and ammonia concentration in microwave-assisted reaction system on its morphology and electric conductivity were discussed. The experimental results indicate that with the dilution of the ammonia solution or the rise of reacting system temperature, the morphology of ITO particles is transformed from spherical to rod-like one with the decline of its electric conductivity. And the electric conductivity of ITO nano-powders with spherical morphology is higher than that of ITO nano-powders with rod-like morphology.

Effects of Yb ^(3+)-Doping on Phase Transformation and Photocatalytic Activities of TiO_2 Nano-Powders

Yb 3+-doped TiO_2 composite nano-particles were prepared by the acid-catalyzed sol-gel method using Ti(OC_4H_9)_4 and Yb(NO_3)_3 as precursors. The effects of the amount of Yb 3+ doping and calcination temperature on the phase transformation, crystallite size, surface texture of the nanopowders were investigated by XRD and BET specific surface area. Their photocatalytic activities were evaluated using the photocatalytic degradation of methylene blue in aqueous solution as a probe reaction. At the interface, titanium ions substitute for ytterbium ions in the lattice of Yb_2O_3 to form Ti-O-Yb bonds, which cause distortion and inhibit the anatase to rutile phase transformation in TiO_2. The results indicate that Yb 3+-doping can enhance the photocatalytic activity of TiO_2 nano-powders as compared with pure TiO_2. 0.125%(mass fraction) Yb 3+ doped TiO_2 nano-powders calcined at 600 ℃ for 2 h show the highest photocatalytic activity. The increase in photoactivity is due to the effects of the factors such as crystal phase, crystallite size, surface chemical property, surface density of OH groups, and surface texture properties of the TiO_2 nano-powders.

Influence of current injection ways on efficiency and size of powders in preparation of nano-powders with electrical explosion

Wire electrical explosion may result in the existence of micro-sized large particles in powders while current injection ways may influence the size and content of micro-sized large particles. Therefore, two kinds of electrical explosion devices with different electrodes by gas discharge were designed in this paper. The pole-board electrodes and the cone electrodes were used respectively for studying copper wire electrical explosion process. The current and voltage data were measured with the Rogowski coil and high voltage probe. The results show that the pulverizing process of electrical explosion is more efficient when the wire electrode current density injected into the cone electrodes is approximately twice as much as the pole-board electrodes. The content of micro-sized large particles is the least among the products of the electrical explosion, when the total deposition energy of the wire prior to vaporization stage is 2. 5 times larger than that of the theoretical value of the completed vaporization.

Molybdenum Carbide Nano-Powder for Production of Mo-99 Radionuclides

At present, there are two ways to produce 99Mo in a reactor: 1) fission process—from U fission product by reaction 235U (n, f) 99Mo and 2) activation process—by radiation capture reaction 98Mo (n, γ) 99Mo. This paper presents the results of experiments performed with molybdenum carbide nano-powder to produce 99Mo. These results show the implementation of the above idea in practice.

Preparation of tetragonal CaO-ZrO_2 nano-powder by chemical coprecipitation method

With zirconium oxychloride, nitrate of lime and ammonia as raw materials, nano powder of CaO ZrO 2 was prepared by chemical coprecipitation method. By use of azeotropic distillation processing, chemical coprecipitation precursor was obtained. Phase transformation of the precursor was observed at the temperature of 593.81 ℃ and 1 234.56 ℃ respectively with DTA analyses. Phase structure was analyzed through XRD and Raman spectra. The average particle size of tetragonal zirconium oxide powder was 9.8 and 43.7 nm after calcination at 600 and 1 100 ℃ respectively which was tested by TEM and BET analyses. Furthermore, the influences of the doping of nitrate of lime and the average particle size of zirconium oxide on the stability of tetragonal zirconium oxide were also discussed.

Fabrication,microstructures,and optical properties of Yb:Lu_(2)O_(3) laser ceramics from co-precipitated nano-powders

The Yb:Lu_(2)O_(3)precursor made up of spherical particles was synthesized through the co-precipitation method in the water/ethanol solvent.The 5 at% Yb:Lu_(2)O_(3)powder is in the cubic phase after calcination at 1100℃ for 4 h.The powder also consists of spherical nanoparticles with the average particle and grain sizes of 96 and 49 nm,respectively.The average grain size of the pre-sintered ceramic sample is 526 nm and that of the sample by hot isostatic pressing grows to 612 nm.The 1.0 mm-thick sample has an in-line transmittance of 81.6%(theoretical value of 82.2%)at 1100 nm.The largest absorption cross-section at 976 nm is 0.96×1^(0-20)cm^(2) with the emission cross-section at 1033 nm of 0.92×10^(-20)cm^(2) and the gain cross sections are calculated with the smallest population inversion parameter β of 0.059.The highest slope efficiency of 68.7% with the optical efficiency of 65.1% is obtained at 1033.3 nm in quasi-continuous wave(QCW)pumping.In the case of continuous wave(CW)pumping,the highest slope efficiency is 61.0% with the optical efficiency of 54.1%.The obtained laser performance indicates that Yb:Lu_(2)O_(3)ceramics have excellent resistance to thermal load stresses,which shows great potential in high-power solid-state laser applications.

Preparation of CeB_6 nano-powders by self-propagating high-temperature synthesis(SHS)

CeB6 powders were prepared by high-temperature self-propagating synthesis （SHS） in which CeO2, B203 and Mg were taken as reactants. The adiabatic temperature and dynamics of SHS reactions were investigated. The SHS reaction products and leached products were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indicated that the adiabatic temperature of Mg-B2Oa-CeO2 reaction system was rather higher than 1800 K to make the reaction propagate by itself, and the apparent activation energy （Ea） and reaction order （n） of exothermic peak on Mg-BzO3-CeO2 differential scanning calorimetry （DSC） curve were 23.03 kJ/mol and 1.31, respectively. The apparent activation energy was lower, so the reaction occurred easily. The SHS products consisted of MgO, CeB6 and little MgaB2O6. The leached products consisted of single CeB6 phase and its purity was higher than 99.0%, and the average particle sizes of CeB6 were smaller than 150 nm.

PREPARATION OF PMNT NANO-POWDERS

Sol-gel-derived nano-powders of lead magnesium niobate and lead titanate solid solutions （PMN-PT or PMNT） were prepared from lead acetate trihydrate （Pb（CH3COO）2·3H2O）, magnesium acetate trihydrate （Mg（CH3COO）2·3H2O）, niobium ethoxide （Nb（OC2H5）5） and titanium isopropoxide （Ti（OCH（CH3）2）4）. The key steps in the preparation process were discussed, The crystalline phases in the powders were investigated using X-ray diffraction （XRD） analysis and the size of grains was observed by field-emission scanning electron microscopy （SEM）. These powders, with good dispersion characteristics and narrow grain size distribution （ranging from 50 nm to 200 nm）, may be used to prepare PMNT thick films and ceramics.

Evaluation of Layered Inorganic Nano-powder Modified Bitumen

Thermal oxidative and aging as an inevitable process in the practical application of road asphalt has great effect on the properties of asphalt. In this paper,the influences of short-term thermal oxidative ageing and ultraviolet radiation(UV) aging on the dynamic viscosity,penetration,softening point and rheological properties of two kinds of layered inorganic nano-powder including organo-modified montmorillonite (OMMT) and nanometer brucite (Mg(OH)2) modified asphalts were studied respectively. The rheological properties of these binders have been determined using a dynamic shear rheometer (DSR) through temperatures sweep tests.The rheological and physical analysis showed the two major influences of ageing on the properties for two kinds of layered inorganic nano-powder modified bitumens. On one hand,ageing decreased the viscous behaviors of modified binders,on the other hand,ageing improved the elastic behaviors of modified binders. The performances of binders after aging depended on the combined effect between the modifier and the bitumen. Both the two modifiers resisted the aging of bitumens and the effect of OMMT was better.

Synthesis and Characterization of Neodymium and Ytterbium-doped Yttrium Aluminum Garnet Nano-powder

Nd/Yb-co-doped YAG transparent ceramic nano-powder was prepared by a sol-gel combustion method.The structure,morphology and properties were characterized by thermogravimetric-differential thermal analysis,X-ray diffraction,transmission electron microscopy,infrared spectroscopy,absorption analysis and fluorescence spectroscopy,respectively.The results show that the mass loss of the powder calcinated at 900 ℃ for 3 h is 49.56%.A well-crystallized Nd/Yb:YAG nano-powder with the superior sintering performance and high purity is obtained,and the morphology of the particles with the average diameter in the range of 60-100 runs appears regular.The nano-powder exhibits an intense absorption at 808 nm,corresponding to the 4I/9/2-4F7/2 transition of Nd^(^(3+) ions,which is suitable to absorb the wavelength of 808 nm from a laser diode source.The emission peak at 1046 nm of the Nd/Yb:YAG powder is more intense than that of Nd^(^(3+):YAG powder.It is indicated that the energy absorbed by Yb^(^(3+) ions from the laser diode source can be transmitted to Nd^(^(3+) ions based on the cross relaxation process of[(4F3/2)Nd,(2F7/2)Yb]-[(479/2)Nd,(2F5/2)Yb].

微纳化封装芳香载体的制备及缓释性能研究

芳香纺织品是备受关注的功能纺织品。芳香气味具有舒缓压力、调节情绪、改善睡眠等功效。但是芳香物质存在易挥发的问题,提高香味的长效释放和耐水洗性一直是芳香纺织品制备有待解决的问题。文中以硅烷偶联剂对纳米二氧化硅进行表面结构调控处理,构建有机-无机复合材料,探索芳香物质微纳化封装;将微纳化封装的芳香载体材料通过原位固定法负载到织物上,并对织物的芳香释放性能和耐久效果进行评价。结果表明,由微纳化封装的有机-无机复合芳香载体制备的芳香纤维结构体具有适宜的香气和长效释放的效果,由此形成的织物加香技术,可广泛应用于纺织品芳香整理,在芳香功能纺织品的制备应用中拥有巨大潜力。

纳米粉体TiO_(2)对靛蓝染色织物光褪色的影响

采用钛酸四正丁酯(TBOT)作为TiO_(2)的前驱体,通过水热反应合成单晶粒TiO_(2)粉体,制备了颗粒状的锐钛型纳米粉体TiO_(2)。结果表明:紫外光照条件下,纳米粉体二氧化钛可以使靛蓝织物表观深度发生大幅度下降,粉体TiO_(2)浓度为10%时,K/S值下降率达到51.81%;促进剂的参与有助于靛蓝织物的褪色效果;涂抹粉体TiO_(2)后的染色布样,在紫外线照射后,颜色值ΔL^(*)偏亮白,同时随着粉体TiO_(2)浓度的增大,ΔL*增大,颜色亮度增大,Δa^(*)初始为负值,颜色偏绿,随着粉体TiO_(2)浓度的增大,样品颜色绿光减少,红光增加;当粉体TiO_(2)浓度为10%,随着光照时间的增加,Δa^(*)值偏向正值,染色布样色光向偏红光偏移,紫外光照射6~8 h时Δa^(*)变化幅度较大,10 h之后,趋于缓慢。

融合石膏组分和微纳米结构“双基因”调控的铁尾矿粉无熟料固结体力学性能

为了探究超细铁尾矿粉颗粒表面非晶态SiO_(2)和Al_(2)O_(3)在石灰-石膏体系中的水化固化机理及调控因素,本工作考察了石膏掺量和铁尾矿粉中微纳米级颗粒含量之间的匹配对固结体强度的影响,利用XRD、TG-DSC、SEM和化学滴定法测试分析了固结体试样中水化产物的种类、形貌及含量的变化,研究了这些变化对固结体强度的影响及作用机理。结果表明,超细铁尾矿粉中小于1.096μm的微纳米颗粒含量显著影响着铁尾矿粉在碱溶液中Si和Al元素的溶出行为,固结体强度随着这些微纳米颗粒含量的增加而提高。固结体中的主要水化产物是铝掺杂的水化硅酸钙(C-(A)-S-H)和钙矾石(AFt)。石膏掺量与铁尾矿粉中微纳米颗粒含量的最佳匹配值对固结体的强度具有显著影响,并且微纳米颗粒含量越高,对应的石膏最佳掺量越大。石膏组分保证了AFt的生成和稳定,同时也加速了铁尾矿粉颗粒表面非晶态成分的水化。本工作探明了固结材料中最佳石膏掺量与微纳米铁尾矿粉颗粒含量的关联关系及其机理,证实了微纳米级颗粒是无熟料固结体结构中的基本活性单元,石膏的掺入对微纳米颗粒的水化起到调控作用,水化后的微纳米颗粒演变为固结体的基本结构单元,这种组分和结构的“双基因”调控机制影响着固结体的力学性能。

碳化硅纳米介质电火花线切割加工研究

采用SiC纳米混粉工作液对Cr12MoV模具钢进行高速走丝线切割加工试验,重点分析了脉冲宽度、脉冲间隔、峰值电流和混粉浓度对切割加工的影响。试验表明,在脉冲宽度45μs,脉冲间隔6倍,峰值电流25A,混粉浓度0.3g/L的加工条件下,采用混粉工作液较采用常规工作液加工的切割速度提高21.16%,表面粗糙度降低15.05%。研究认为,纳米微粒的介入,极间绝缘性降低,放电间隙增大,改善了极间放电条件,提高了工件加工稳定性和切割速度;同时,纳米微粒促使极间火花放电通道增多、放电点分散,提高了工件表面加工质量。

TiO_(2)原位包覆提升球形纳米铝粉活性

纳米铝(Al)粉是一种高能金属纳米粉末,但过高的表面能带来的易氧化问题显著降低其活性,限制其应用。针对该问题,本文通过液相法在去除球形纳米Al粉表面氧化层的同时原位生长TiO_(2)包覆层,通过工艺优化,获得了活性Al含量最高的Al@TiO_(2)复合粉体,包覆层厚度约为2 nm,且粉末中没有过量的TiO_(2)存在,包覆处理后的复合粉体中活性Al含量达到87.3%。

微波加热对纳米铁粉的磁性和微波吸收性能的影响

将纳米铁粉置于家用微波炉微波加热10 min后,一些样品的纳米铁粉没有出现明显的氧化,而另一些样品发生了部分氧化,且同时出现了两种氧化物Fe_(2)O_(3)和Fe_(3)O_(4).对3种样品的形貌、磁性和微波吸收性能进行对比实验.实验结果表明:相对于Fe和MS-Fe@FexOy,微波退火使MS-Fe吸收电磁波、减少电磁波污染的性能增强更显著,MS-Fe具有更高的反射性能、更薄的涂层和更宽的吸波带宽.

新微乳液体系下超细ZrO_(2)纳米粉体的可控合成及形成机理探究

ZrO_(2)纳米粉体由于其优异的性能被广泛应用于热障涂层、功能陶瓷、燃料电池、催化剂载体等多个领域。本文开发了一种新的微乳液体系(油酸/2-氨基-2-甲基-1-丙醇(AMP)/正辛醇/煤油/水溶液),经过热脱乳处理和煅烧成功制备出了超细ZrO_(2)纳米粉体。XRD、Raman和SAED分析证实,粉体在550~750℃范围内焙烧,物相结构保持为四方相ZrO_(2),说明该超细纳米粉体具有良好的稳定性。HRTEM结果表明,晶面间距为0.291 nm左右,与四方相ZrO_(2)的(101)面相对应。通过控制不同条件,如溶液用量、正辛醇用量、表面活性剂油酸用量,实现了ZrO_(2)纳米粉体尺寸在10~20 nm的区间内可以精确调控,基于微结构的演变并讨论了上述参数对形成机理的影响。

非水溶液体系中晶种法制备球形银纳米颗粒

以丙三醇作溶剂,硝酸银为原料,聚乙烯吡咯烷酮(PVP)为分散剂,硼氢化钠为还原剂制备了银纳米晶种;以此银纳米粒子作为初级晶种,以丙三醇作溶剂和还原剂,通过升温提高丙三醇的还原性制备银纳米颗粒。研究分散剂种类、生长液银浓度、晶种加入量对银粉的影响,采用X射线粉末衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)对制备产物的结构、物相、形貌进行表征。结果表明,通过改变条件可以制备出分散性良好、粒径均匀的70nm左右的球形银粉。