化学法制备ZA复合粉体的研究

采用溶胶-凝胶法和共沉淀法两种化学方法制备了氧化铝-氧化锆复合粉体,并对其进行表征:采用激光粒度分析仪测定粉体粒径及粒度分布,X射线衍射仪(XRD)进行矿物相组成分析,扫描电子显微镜(SEM)观察微观下氧化铝与氧化锆的分布情况.结果表明:溶胶-凝胶法制备的粉体相对于共沉淀法制备的粉体粒度较细,四方相氧化锆含量高,而且氧化铝和氧化锆分散较均匀.     

羰基镍粉焙烧制备高纯度微米氧化亚镍粉体的研究

以羰基镍粉为原料,采用焙烧法制备了氧化亚镍,并将其球磨后得到微米粉体。采用热重-差示扫描量热仪（TG-DSC）研究了羰基镍粉在空气气氛中加热时的氧化行为,利用激光粒度分析仪、等离子体光谱仪、X射线衍射仪（XRD）和扫描电镜（SEM）等分析了样品结构、成分和形貌。结果表明：空气和氧气两种气氛对产物纯度影响不明显。在两种载气条件下,通过优化焙烧温度和焙烧时间（焙烧温度为700 ℃、焙烧时间为2 h、载气流量为1.5 L/min）,羰基镍粉可直接焙烧制备得到纯度为100%、结晶度高的面心立方体氧化亚镍,球磨后得到粒度为4~19 μm的类球形微米氧化亚镍粉末。制备过程具有工艺简单、环境友好的特点。     

Dual role of activated carbon as fuel and template for solution combustion synthesis of porous zinc oxide powders

In this work, nanosized zinc oxide (ZnO) powders were fabricated by urea–nitrate solution combustion synthesis using activated carbon as a structure-directing template and secondary fuel at different fuel–oxidant ratios. The as-synthesized powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption–desorption measurements, UV–Vis diffuse reflectance spectroscopy, and photoluminescence. The effect of fuel amount on photocatalytic activity of ZnO powders was evaluated by the degradation of an azo dye Orange G. It was observed that combustion synthesis with activated carbon as a secondary fuel had a profound effect on reducing crystallite size and enhancement of specific surface area. The crystallite size of the as-synthesized powders varied from 46 to 26 nm. The ZnO powder prepared at a fuel–oxidant ratio of 1.8 possessed the small crystallite size and high specific surface area of 69 m²/g. It correspondingly resulted in the highest dye removal percentage of 99% with a rate constant of 0.027 min⁻¹. The improvement in dye degradation can be due to the synergistic interaction and interplay of enhanced surface area and catalytic ability of the photocatalyst. This study provides a simple single-step synthesis methodology to produce metal oxide nanopowders with tunable surface properties for high potential applications in catalysis, optoelectronics, and gas sensors.     

PVC/竹粉复合材料制备

在固相反应器中对竹粉进行机械活化乙酰化改性,将改性竹粉与聚氯乙烯(PVC)混合均匀,热压成型制备PVC/竹粉复合材料.考察催化剂浓硫酸用量、乙酸酐用量、机械活化时间和温度对复合材料力学性能的影响,并对改性前后的竹粉及其复合材料断面进行表征.结果表明,当乙酸酐与改性竹粉的物质的量之比为3.5︰1、机械活化温度为80℃、机...     

Effect of chromium addition on the structural,morphological and magnetic properties of nano-crystalline cobalt ferrite system

Nano-crystalline chromium doped cobalt ferrite powders have been synthesized by PEG assisted hydrothermal route. The structural, morphological and magnetic properties of the products were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and vibrating sample magnetometer (VSM). X-ray analysis showed that the samples were cubic spinel. SEM images reveal that the samples' surfaces exhibit well-defined crystalline nanoparticles of spherical shapes with small agglomeration. The addition of Cr³⁺ ions caused a decrease in the average crystallite size, magnetization and the coercive field of the sample. The observed decreases in saturation magnetization and coercivity are explained on the bases of exchange interactions.     

Preparation of cobalt oxalate powders with the presence of a pulsed electromagnetic field

The size and morphology of cobalt oxalate powders are the keys to metal cobalt powder production. Spheroidic and fine cobalt oxalate powders were prepared by conventional precipitation when a pulsed electromagnetic field (PEMF) was introduced. The phase structures of the produces were characterized by means of X-ray powder diffraction (XRD). Scanning electron microscopy (SEM) images were used to observe the morphologies of the cobalt oxalate powders. Thermal analyses were performed using TG–DSC thermogravimetric analyzer. Meanwhile, a possible mechanism was proposed based on the interaction between pulsed electromagnetic field and cobalt oxalate cluster.     

氢氧化镍粉末的化学镀Co-Zn合金表面改性研究

采用化学沉积技术对由水溶液络合沉淀法合成的氢氧化镍粉末进行了表面包覆Co—Zn改性处理,利用扫描电子显微镜分析、比表面积测量、X一射线光电子能谱及原子吸收光谱等对处理前后氢氧化镍粉末的表面形貌、微晶结构、比表面积、元素化学态及镀层组成等进行了表征和研究。结果表明,Co—Zn合金镀层可以均匀包覆在氢氧化镍颗粒表面,氢氧化镍经化学镀处理后其表面微观组织形貌发生了明显变化。化学镀表面改性使氢氧化镍粉末的比表面积有所降低,镀层中的Co、Zn元素均以氧化态形式存在。     

Synthesis and characterization of submicron silicon carbide powders with silicon and phenolic resin

A novel three-step process is used to fabricate submicron silicon carbide powders in this paper. The commercially available silicon powders and phenolic resin are used as raw materials. In the first step, precursor powders are produced by coating each silicon powder with phenolic resin shell. Then, precursor powders are converted into carbonized powders by decomposing the phenolic resin shell. The submicron silicon carbide powders are formed in the reaction of silicon with carbon during the third step of thermal treatment. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and thermogravimetric (TG) analyses are employed to characterize the microstructure, phase composition and free carbon content. It is found that the sintered powders consist of β-SiC with less than 0.2 wt.% of free carbon. The particle size of the obtained silicon carbide powders varies from 0.1 to 0.4 μm and the mean particle size is 0.2 μm. The silicon carbide formation mechanism of this method is based on the liquid-solid reaction between liquid silicon and carbon derived from phenolic resin. The heat generated during the reaction leads to great thermal stress in silicon carbide shell, which plays an important role in its fragmenting into submicron powders.     

共沉淀法制备ZnO基纳米复合粉体及高压ZnO压敏电阻的电性能

以金属离子盐为原料,氨水、乙醇胺为沉淀剂,十二烷基苯磺酸钠、聚乙二醇2000为表面改性剂,采用共沉淀法制备ZnO基纳米复合粉体。以共沉淀法最佳工艺所得粉体制备高压ZnO压敏电阻。采用热重–差示扫描量热分析、X射线衍射、扫描电子显微镜、激光粒径分析对ZnO基复合前驱体及ZnO基纳米复合粉体进行表征,探讨了沉淀剂种类、溶液pH值、Zn2＋起始浓度和表面改性剂对粉体粒度的影响。结果表明：以氨水为沉淀剂、溶液体系pH值为6.0、Zn2＋浓度为1.0mol/L、聚乙二醇2000为表面改性剂时可制备出粒径分布窄、平均粒径为89nm的ZnO基复合粉体。用该粉体制备的高压ZnO压敏电阻的平均电位梯度为543V/mm,非线性系数为29.3,漏电流为49μA。通过共沉淀工艺,可制备出电性能优良的高压ZnO压敏电阻。     

CFD modeling of primary breakup during metal powder atomization

Powder metals are the basis of powder metallurgy with a large variety of applications, including sintering and thermal spray coatings. The Gas atomization process has been widely employed as an effective method to produce fine spherical metal powders. New applications and emerging surface technologies demand high quality powders with a very narrow particle size distribution. A computational fluid dynamics (CFD) approach is developed to examine complex fluids during atomization from different nozzle designs, using the volume of fluid (VOF) method and the Reynolds Stress Model (RSM). The modeling results show that the swirling gas atomizer is not beneficial to the atomization process while the inner-jet atomizer can improve the powder generation processing.     

Influence of mechanical activation on sphene based ceramic material synthesis

Sphene (CaTiSiO₅), a calcium titanosilicate ceramic has been prepared from a powder mixture of CaCO₃, TiO₂ and SiO₂ using vibro-milling for homogenization and activation of precursors. The mechanochemical process initially yielded amorphous powders, which on further calcination, crystallized to yield sphene ceramic. The evolution of the phase composition with thermal treatment was investigated by X-ray powder diffraction (XRPD). Powder morphology and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction, respectively. Rietveld refinement was employed to get the structural information of the synthesized powder. Densification and microstructure evolution was determined by means of density and scanning electron microscopy (SEM). The most favorable conditions for mechanical activation and synthesis of sphene based ceramic material are reported.     

新型活化环氧富锌涂层的耐腐蚀性研究

富锌涂料在防腐蚀领域具有广泛应用,然而其长效防护性能却受到锌粉活性影响。本文以冷涂锌涂层、传统环氧富锌涂层作为对照,研究了新型具有电化学活性的环氧富锌涂层在盐雾加速腐蚀试验后的耐腐蚀性。宏观形貌分析表明:盐雾加速腐蚀1 800 h后,活化环氧富锌涂层表面并未出现锈点;采用扫描电子显微镜、维体式显微镜观察试验后涂层的表面形貌和涂层结构,发现活化环氧富锌涂层微观表面更加平滑,锌粉并未出现大面积的氧化,涂层内部大小锌粉颗粒均匀排列;通过电化学方法研究涂层的耐蚀机理与防护性,发现活化富锌涂层具有更持久的低防护电位。以上研究结果表明,较冷涂锌及传统环氧富锌涂层而言,新型活化环氧富锌涂层具有优异的长期防护性能,是值得关注和研究的一种新型技术。     

Fat encapsulation in spray-dried food powders

The surface composition of spray-dried sodium caseinate/lactose emulsions having different oil phases were estimated using electron spectroscopy for chemical analysis (ESCA), and the particle structure was studied using scanning electron microscopy (SEM) both before and after storage under humid conditions. After spray-drying, powders in which the oil phases consisting of fats with intermediate melting points, such as hardened coconut oil and butter fat, had the highest surface coverage of fat, approximately 34%. The powder with soybean oil as the oil phase had a surface coverage of fat of approximately 15%. The high-melting hardened rapeseed oil was almost completely encapsulated after spray-drying. After storage in a humid atmosphere, fat was released onto all the powder surfaces (surface fat after storage, between 50–65%) except for those with hardened rapeseed oil in which the fat remained encapsulated. These observations are consistent with the powder structure observed by SEM. The surface composition estimated by ESCA for spray-dried sodium caseinate/lactose-containing emulsions with different amounts of soybean oil and a constant lactose/sodium caseinate ratio showed an almost completely encapsulated oil-phase after drying. Storage of these powders in a humid atmosphere leads to a release of fat onto the powder surface even if the soybean oil content is low (1% of the dry weight). Powders made from soybean oil emulsions with sodium caseinate alone exhibit a much lower degree of encapsulation than in the system where lactose is present.     

Auger Electron Spectroscopy of Aluminum Nitride Powder Surfaces

The chemical states of powder surfaces depend on the manufacturing processes of the powders. The surface chemistry of three different commercial AIN powders, which are processed by carbothermal nitridation of Al₂O₃, chemical vapor deposition (CVD), and direct nitridation of aluminum, were evaluated by using Auger electron spectroscopy (AES). In order to obtain reference AES spectra of aluminum compounds, α-, γ-, θ-Al₂O₃, γ-AIOOH, γ-AION, and sintered AIN were also examined. Line shapes of aluminum LVV ; Al( LVV ), nitrogen KLL ; N( KLL ) and oxygen KLL ; O( KLL ) are discussed for the AIN powders and all the other aluminum compounds. The differential Auger electron spectra, i.e., E dn /AE were obtained directly, where n is the number of Auger electrons, and E is the kinetic energy of the electron. Their integrated spectra, i.e., n ( E ) are also employed for analysis. The results confirm the conclusions of our previous temperature-programmed desorption work. The AES line shape analysis implies the presence of an oxide-like θ -Al₂O₃ containing AION phase on the carbothermal nitride AIN powder surfaces. The surfaces of CVD and direct-nitrided AIN powders are covered by an oxide–like γ-Al₂O₃ with an oxygen diffusion layer and does not have AION phase.     

In Vitro Biological Evaluations of Zn Doped CaSiO<Subscript>3</Subscript> Synthesized by Sol–Gel Combustion Technique

Wollastonite (CaSiO₃) is one of the calcium silicate based material and is widely applied in hard tissue engineering applications. Combustion based sol–gel method was adopted to prepare the phase pure CaSiO₃ with inclusion of Zn ions (1, 3 and 5 wt%) using glycine as a reducing agent. The synthesized pure and Zn doped CaSiO₃ powders were characterized by attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), dynamic light scattering (DLS), scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), transmission electron microscopy (TEM) analyses to confirm their functional groups, phase composition, thermal stability, particle size, surface morphology and topography, respectively. In vitro biological examinations were carried out to evaluate the biological behaviour of pure and Zn doped CaSiO₃ powders. The antibacterial activity was tested for 1–5 wt% of Zn doped CaSiO₃ powders against E. coli and S. aureus by colony forming unit (CFU) which proved that with increase of Zn concentration, the microbial restriction was found to be enhanced for both pathogens than control and pure CaSiO₃. In vitro apatite layer formation was observed on the surface of Zn doped CaSiO₃ powders with existence of ball like crystals for 14 days. In vitro cytocompatible study revealed that 5 wt% of Zn doped CaSiO₃ powder exhibited good cellular interaction of MG-63 cells at concentrations of 200–1000 µg/ml for 24 h. Thus, these biological studies reveal that the developed Zn doped CaSiO₃ powders could be applied for better clinical applications.     

Bioorthogonal surface modified α-TCP-based bone filler for enhancement of apatite formation and bioactivity

The aim of the present study was to investigate the effect of click chemistry reactants on morphology and physico-chemical properties of alpha tricalcium phosphate (α-TCP)-based powders. The powders were synthesized by solid-state reaction. The powders were modified with azide and cycloalkyne to form triazole as a consequence of reactions of these molecules. The presence of the band related to the triazole ring and the click molecules in powder structure was confirmed by Fourier transform infrared (FTIR) and Liquid chromatography- mass spectroscopy (LC-MS) analyses. Based on scanning electron microscopy (SEM) observations, the modified powder exhibited a different microstructure and morphology of apatite precipitates after one day and 7 days of soaking in distilled water and SBF solution, respectively, with respect to unmodified powder. According to the acellular in vitro test, X-ray diffraction (XRD) patterns represented triple characteristic peaks of hydroxyapatite (HA) in modified powder compared with control. Besides, the tendency of conversion of α-TCP to HA is more enhanced for modified powder as well. The SEM analysis depicted the plate-like and needle-like morphology of HA on the surface of modified and control powders, respectively. Since plate-like morphology of HA enhances bone generation and is found in trabecular bone, therefore, a future design can be considered for triazole-modified α-TCP-based fillers as good candidates for bone substitute application.     

Preparation and antibacterial properties of titanium-doped ZnO from different zinc salts

To research the relationship of micro-structures and antibacterial properties of the titanium-doped ZnO powders and probe their antibacterial mechanism, titanium-doped ZnO powders with different shapes and sizes were prepared from different zinc salts by alcohothermal method. The ZnO powders were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED), and the antibacterial activities of titanium-doped ZnO powders on Escherichia coli and Staphylococcus aureus were evaluated. Furthermore, the tested strains were characterized by SEM, and the electrical conductance variation trend of the bacterial suspension was characterized. The results indicate that the morphologies of the powders are different due to preparation from different zinc salts. The XRD results manifest that the samples synthesized from zinc acetate, zinc nitrate, and zinc chloride are zincite ZnO, and the sample synthesized from zinc sulfate is the mixture of ZnO, ZnTiO₃, and ZnSO₄ · 3Zn (OH)₂ crystal. UV-vis spectra show that the absorption edges of the titanium-doped ZnO powders are red shifted to more than 400 nm which are prepared from zinc acetate, zinc nitrate, and zinc chloride. The antibacterial activity of titanium-doped ZnO powders synthesized from zinc chloride is optimal, and its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) are lower than 0.25 g L⁻¹. Likewise, when the bacteria are treated by ZnO powders synthesized from zinc chloride, the bacterial cells are damaged most seriously, and the electrical conductance increment of bacterial suspension is slightly high. It can be inferred that the antibacterial properties of the titanium-doped ZnO powders are relevant to the microstructure, particle size, and the crystal. The powders can damage the cell walls; thus, the electrolyte is leaked from cells.     

纳米TiO2复合粉体的制备及吸收光谱研究

对纳米锐钛矿型TiO2进行了稀土元素铈的负载，同时加入电气石粉体，制备出掺杂硝酸铈、电气石的纳米锐钛矿型TiO2复合粉体，借助X射线衍射、扫描电子娃微镜对复合粉体进行了表征，并用紫外分光光度计对它的吸收光谱进行分析。结果发现，复合粉体形成了以电气石为核心的TiO2微粒簇，其中TiO2微粒具有阶梯层状结构和表面纳米凸起；样品的吸光度随电气石的添加量而有很大区别，适当添加量的电气石能使TiO2的吸光能力增强、光谱响应范围拓宽。     

Improving hydrogen storage/release properties of magnesium with nano-sized metal catalysts as measured by tapered element oscillating microbalance

An effective catalyst doping method was developed for directly depositing nano-particles of various metal catalysts (palladium, platinum and ruthenium) on the outer surface of magnesium powders through a wet chemistry process. The catalyst-doped magnesium was characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). Catalysts of nano-meter size were uniformly deposited on the outer surface of the magnesium particles. The hydrogen storage and hydrogen release properties of magnesium and catalysts-doped magnesium were measured in situ by the tapered element oscillating microbalance (TEOM), and also by the volumetric method. Both the hydrogen absorption and hydrogen release kinetics of magnesium were significantly improved by doping the nano-particle catalysts. Among the three metals-doped and examined, palladium showed the best catalytic effect. Upon doping 0.5 mol% nano-particle palladium, the hydrogen absorption and hydrogen release rates of magnesium increased 1 and 14 times, respectively, as revealed by the dynamic measurement of storage/release by TEOM, which indicated a strong catalytic effect.     

Cosmetic properties of TiO2/mica-BN composite powder prepared by spray drying

In the present study, the spray drying process was used to prepare spherical composite powders from TiO₂/mica and h-BN powders. The starting and the as-prepared powders were examined by X-ray diffraction, scanning electron microscopy, particle size analyzer, spectrophotometer, and oil absorption analysis. Particle size distribution, crystalline phases, whiteness, and oil absorption ability were analyzed in order to determine powder morphology. These powders were then mixed into linseed oil to prepare an emulsion for sunscreen protection application. The resultant emulsions were examined using UV–visible–near infra-red (NIR) spectroscopy, sun protection factor tester, and thermal conductivity tester. The experimental results show that spherical composite powder prepared by spray drying not only possess good oil and NIR absorption ability, but also thermal conductivity. The emulsion prepared by spray dried powder exhibits superior sunscreen protection performance compared to its starting counterparts.