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.

Formation Mechanism of Impure Phases and Crystallinity Investigation of YAG Powders Synthesized via the Co-precipitation Method

We investigated the impure phase problem and summarized its two formation mechanisms of YAG powders synthesized via the co-precipitation method.The ions loss problem caused by high concentration reaction solution in the titration process was emphatically studied,and the corresponding thermodynamic explanation was carried out.In addition,influence of powder crystallinity and its new qualitative and quantitative standards were studied.One reason of impure phase is the local nonuniform mixture of Y and Al elements in precursor,which easily causes intermediate phases during calcination and difficulty of high pure powders at low temperatures.The other reason is the precipitation dissolution during titration and then the Y^(3+)/Al^(3+) loss,caused by high concentration of reaction solution.The powder crystallinity can be promoted by increasing calcination temperature or holding time of precursor.Besides the routine XRD method,the TEM-EDX method should be also introduced to directly determine the quality of crystallinity.

Optimize two-phase distribution of lithium-rich materials to stabilize structure and suppress voltage attenuation

Lithium-rich materials possess the ultra-high specific capacity,but the redox of oxygen is not completely reversible,resulting in voltage attenuation and structural instability.A stepwise co-precipitation method is used for the first time in this paper to achieve the control of the two-phase distribution through controlling the distribution of transition metal elements and realize the modification of particle surface structure without the aid of heterologous ions.The results of characterization tests show that the content of LiMO_(2) phase inside the particles and the content of Li_(2)MnO_(3) phase on the surface of the particles are successfully increased,and the surface induced formation of Li_(4)Mn_(5)O_(12) spinel phase or some disorderly ternary.The electrochemical performance of the modified sample is as follows:LR(pristine)shows specific discharge capacity of 72.7 mA·h·g^(−1)after 500 cycles at 1 C,while GR(modified sample)shows specific discharge capacity of 137.5 mA·h·g^(−1) at 1 C,and the discharge mid-voltage of GR still remains above 3 V when cycling to 220 cycles at 1 C(mid-voltage of LR remains above 3 V when cycling to 160 cycles at 1 C).Therefore,deliberately regulating the local state of the two phases is a successful way to reinforced the material structure and inhibition the voltage attenuation.

石蜡基相变材料导热性和液相渗漏研究进展

石蜡具有相变潜热高,相变温度范围宽,无过冷现象,低廉稳定性好,无毒无腐蚀的优点,但存在着导热性差,固液相变时存在渗漏等缺点。目前石蜡已经是最为广泛的一类材料,具有很好的应用前景。论述了解决石蜡基相变材料两大缺点的方向,并展望了石蜡基相变材料的发展趋势。

大衬底面积GaAs红外发光二极管

报道了影响用于红外控制技术和红外遥控技术的光源——GaAs 红外发光二极管性能参数的二个重要因素:(1)液相外延生长;(2)欧姆接触。此外,还报道了该器件的主要电光参数,给出了 P-I、V-I 特性曲线以及发射光谱曲线。

改进沉淀法合成β-磷酸三钙

以Ca(NO3)2和Ca(NO3)2·4H2O为原料,加入分散剂聚苯乙烯,采用液相沉淀法制备β-磷酸三钙前体,经过800℃高温煅烧制得结晶度较高的β-磷酸三钙粉体,采用XRD、TEM、FTIR等手段对粉体进行测试分析。结果表明,液相沉淀法制备的β-磷酸三钙为纳米级,经800℃煅烧2h后,可获得晶粒细小、结晶状态良好、分散性好的β-TCP粉体。

Preparation of Nano-MnFe2O4 and Its Catalytic Performance of Thermal Decomposition of Ammonium Perchlorate

Nano-MnFe2O4 particles were synthesized by co-precipitation phase inversion method and low-temperature combustion method respectively, using MnCl2, FeCl3, Mn（NO3）2, Fe（NO3）3, NaOH and C6H8O7. X-ray diffraction （XRD）, transmission electron microscope （TEM）, Fourier transform infrared spectroscopy （FT-IR）, thermogravim-etry-differential thermal analysis （TG-DTA） and differential scanning calorimetry （DSC） were used to characterize the structure, morphology, thermal stability of MnFe2O4 and its catalytic performance to ammonium perchlorate. Results showed that single-phased and uniform spinel MnFe2O4 was obtained. The average particle size was about 30 and 20 nm. The infrared absorption peaks appeared at about 420 and 574 cm-1, and the particles were stable below 524 ℃. Using the two prepared catalysts, the higher thermal decomposition temperature of ammonium perchlorate was decreased by 77.3 and 84.9 ℃ respectively, while the apparent decomposition heat was increased by 482.5 and 574.3 J？g？1. The catalytic mechanism could be explained by the favorable electron transfer space provided by outer d orbit of transition metal ions and the high specific surface absorption effect of MnFe2O4 particles.

Morphological Change and Its Mechanism of Eutectic Silicon for Strontium-Modified Alloy A357

The Y 2O 3-CeO 2-ZrO 2 powders were prepared using a co-precipitation process and the corresponding coatings were prepared by plasma spraying. The results show that an optimal composition exists in Y 2O 3-doped CeO 2-ZrO 2, but not in CeO 2-doped Y 2O 3-ZrO 2. The powders mainly contain tetragonal phase and a trace amount of monoclinic phase. The homogeneity in composition, large agglomerate size, ideal particle size distribution and high flowability were obtained. The as-sprayed coatings are composed of non-transformable tetragonal phase, tz′structure, and resistant to transformation under thermal or mechanical stresses.

Ultra-fine W-Y_(2)O_(3)composite powders prepared by an improved chemical co-precipitation method and its interface structure after spark plasma sintering

Y_(2)O_(3)-doped tungsten(W-Y_(2)O_(3))composite powders prepared by a traditional chemical co-precipitation method possess obvious bimodal distribution in size,which would deteriorate their sintering properties.The bimodal distribution can be effectively eliminated by an improved chemical co-precipitation method,in which the cationic surfactant cetyltrimethyl-ammonium bromide(CTAB)was innovatively employed.The reduced powders with excellent uniformity have an average grain size of only~31.5 nm.It is noteworthy that Y_(2)O_(3)particles would fuse and grow with the growth of W grains during subsequent spark plasma sintering(SPS)process,which was rarely reported in relevant literature before.On top of that,phase interfaces of sintered W-Y_(2)O_(3)alloys were systematically analyzed.Compared to the intracrystalline oxygen content,the oxygen content at W/Y_(2)O_(3)phase boundaries is relatively higher.It can be found that the(110)crystal planes of W form coherent,semi-coherent,and non-coherent interfaces with different crystal planes of Y_(2)O_(3).The weak interfacial bonding strength between W and Y_(2)O_(3)phases results from relatively more oxygen impurities as well as more semi-coherent/non-coherent interfaces at phase boundaries compared with the inner W grains.

Fabrication and Growing Kinetics of Highly Dispersed Gadolinium Zirconate Nanoparticles

Highly dispersed gadolinium zirconate(GZ)nanoparticles with fluorite structure were successfully synthesized by co-precipitation method,and their phase composition and microstructure,formation mechanism,and grain growth kinetics were investigated.The results suggest that the nanoparticles were obtained through hydroxide dehydration and solid phase reaction.High dispersion was accomplished by ethanol solvent to reduce the hydrogen bond and sodium dodecyl benzene sulfonate(SDBS)surfactant to increase the electrostatic repulsion between the nanoparticles.The grain growth activation energy of GZ powders calcined at lower temperature(<1200°C)is 86.5 kJ/mol(Ql),and the grain growth activation energy of GZ powders calcined at higher temperature(>1200°C)is 148.4 kJ/mol(Qh).The current study shows that the optimal process to synthesize dispersed GZ nanoparticles includes ethanol solvent,3 wt.%SDBS surfactant,and 1100°C as calcining temperature.

Effect of stabilizing treatment on microstructure and stress rupture properties of phosphorus microalloyed Inconel 706 alloy

The microstructure and stress rupture properties of Inconel 706 alloy microalloyed with phosphorus are examined under stabilizing and unstabilizing heat treatment conditions.It was found that applying the stabilizing treatment resulted in a 98% increment in the stress rupture life and a 215% increment in the elongation tested at 650℃/690 MPa for the alloy compared to that under the unstabilizing heat treatment condition.The stabilizing treatment led to the precipitation of rod-shaped and needle-shaped n phases at the grain boundaries.Morphologies of γ'-γ" co-precipitates in the grain interior were noncompact form and compact form for the alloy under unstabilizing and stabilizing heat treatment conditions,respectively.Based on the microstructure characterizations,the improvement of stress rupture properties by the stabilizing treatment was attributed to the precipitation of n phases at the grain boundaries,which can hinder cracks initiation and propagation and relieve the stress concentration.