Synthesis and characterizations of new morphological ZnO and Ce-doped ZnO powders by sol–gel process

ZnO micro-tori and cerium-doped hexangulars ZnO have been prepared by the sol–gel method under methanol hypercritical conditions of temperature and pressure. X-ray diffraction (XRD) measurement has revealed the high crystalline quality and the nanometric size of the samples. Scanning electron microscopy (SEM) has shown that the ZnO powder has a torus-like shape while that of ZnO:Ce has a hexangular-like shape, either standing free or inserted into the cores of ZnO tori. Transmission electron microscopy (TEM) has revealed that the ZnO particles have sizes between 25 and 30 nm while Ce-doped ZnO grains have diameters ranging from 75 nm to 100 nm. It is demonstrated from photoluminescence (PL) spectra at room temperature that the introduction of cerium in ZnO reduces the emission intensity lines, particularly the ZnO red and green ones.     

Estimation of the superhigh-frequency magnetic permeability of alsifer from the measured permeability of composites

The magnetic permeability of alsifer was restored from the frequency dependences of the dielectric and magnetic permeabilities of powder alsifer (AlSiFe alloy)–wax matrix composites. The permeabilities were measured using the coaxial line technique within a frequency range of 0.05–20 GHz. The effect of the concentration, shape, and size of powder particles on the microwave magnetic properties of composites was considered. A good agreement between the measurement results and the Maxwell–Garnett formula generalized with consideration for the particle shape, the percolation threshold, and the skin-effect was obtained. The found sizes of particles agreed with electron microscopy and granulometry data. Both the frequency and the ferromagnetic resonance line figure of merit (FOM) for lamellar particles proved to be higher than for spherical ones. Alsifer powders were shown to be promising fillers for radioabsorbing materials.     

射频感应等离子体制备球形氧化铝的工艺研究

采用射频(RF)感应等离子体对颗粒形状不规则的氧化铝粉作球化处理,当氧化铝以极短暂时间快速穿越射频等离子体炬时,颗粒因受热而熔化成液滴,快速冷却,形成球形固态颗粒。应用单因素法讨论射频等离子体制备球形氧化铝的工艺参数,研究了制备过程中相关的中气流量、抽风负压、送粉速度和分散方式等主要工艺参数对球形氧化铝粉的影响。用电子扫描显微镜(SEM)观测评估球化效果,测定松装密度和振实密度。     

Comparative study of morphology and surface composition of Al–Cr–Fe alloy powders produced by water and gas atomisation technologies

The morphology and surface composition of Al–Cr–Fe alloy powders of 0–63 and 63–100 μm size fractions, produced by gas and water atomisation, have been studied by scanning electron microscopy and Auger electron spectroscopy. While gas atomised particles are of spherical shape, water atomised powders are usually irregular in shape with a complex branched relief. The morphology and composition of surface oxides have been estimated. The surface oxide film is composed of aluminium oxides/hydroxides and contains no Fe and Cr atoms. Two to five water molecules are associated with one Al₂O₃ molecule on the surface of powders. The surface oxide film has a non-uniform thickness, with thick oxide islands separated by thinner oxide film. The parameters of the surface film morphology, such as the island coverage, the oxygen content and the thin film thickness, depend on the atomisation technology used and powder size fraction. Heavily and weakly oxidised powder groups present in all powder fractions are distinguished by Auger spectra analysis. Relationships between heavily and weakly oxidised powder groups are discussed as a function of atomisation technology and size fraction.     

The effects of powder properties on in-flight particle velocity and deposition process during low pressure cold spray process

In cold spray process, impacting velocity and critical velocity of particles dominate the deposition process and coating properties for given materials. The impacting velocity and critical velocity of particles depend on the powder properties and cold spray conditions. In the present study, the in-flight particle velocity of copper powder in low pressure cold spraying was measured using an imaging technique. The effects of particle size and particle morphology on in-flight particle velocity and deposition efficiency were investigated. The critical velocity of copper powder was estimated by combining the in-flight particle velocity and deposition efficiency. The effect of annealing of feedstock powder on deposition and critical velocity was also investigated. The results showed that the irregular shape particle presents higher in-flight velocity than the spherical shape particle under the same condition. For irregular shape particles, the in-flight velocity decreased from 390 to 282 m/s as the particle size increases from 20 to 60 μm. Critical velocities of about 425 m/s and more than 550 m/s were estimated for the feedstock copper powder with spherical and irregular shape morphology, respectively. For the irregular shape particles, the critical velocity decreased from more than 550 to 460 m/s after preheating at 390 °C for 1 h. It was also found that the larger size powder presents a lower critical velocity in this study.     

基于超椭圆拟合的水下小目标分类*

水下小目标分类技术在海底探测、水下考古等方面应用广泛,在实际的水下声图像中,小目标投影产生的阴影区域通常在形状和尺寸方面显著于目标本身产生的亮区,故阴影分析算法对于目标的检测、识别和分类均有重要的研究意义。本文采用超椭圆曲线拟合算法拟合目标阴影区域,通过控制超椭圆函数的几个参数变化,实现不同的超椭圆曲线拟合不同的目标阴影形状,并将控制超椭圆曲线尺寸、形状和位置的参数作为特征向量输入到分类器,通过对比多个分类器得出分类结果,证明了以拟合参数为特征的分类方法有效。     

Optical properties of silver colloidal centers in KCl crystals

The Ag colloidal centers in additively colored KCl: Ag crystals have been studied by optical and electron microscope methods. The transmission electron microscope studies reveal that the colloidal particles are spherical in shape and have a size distribution which can be described by the skewed zeroth order logarithmic distribution (ZOLD) function. The band shape of the experimental absorption spectra of colloidal particles agrees well with that calculated on the basis of Mie theory, if the optical constants are suitably modified and if the particle size distribution is taken into account. If the particle size is so small that the size distribution cannot be measured by electron microscope the optical absorption bands can be used to determine the size distribution parameters provided the distribution is well described by ZOLD, which in turn is used to calculate theoretical extinction bands.     

Synthesis and Structural Characterization of a New Phase of GaAsO 4

A new polymorph of GaAsO 4 has been synthesised at high pressure and temperature (60 kbar and 1273 K). Samples were characterised by powder X-ray diffraction, scanning electron microscopy and EDAX spectroscopy. This material shows an hexagonal symmetry with cell parameters, a =8.1931(4) Å and c =4.3744(2) Å; particles are of hexagonal shape with a narrow size distribution around 2-3 w m and composition close to the Ga:As atomic ratio=1:1. This new high pressure phase of GaAsO 4 represents a new transition path for the ABO 4 compounds.     

A Method of Separation of Polydisperse Particles in the Plasma of Radio‐Frequency Discharge

A method of separation of polydisperse dust particles in the plasma of radio‐frequency (RF) capacitive discharge is considered. Investigations of plasma equipotential field enabled us to determine conditions for separation of polydisperse dust particles. The simplicity of the technology made it possible to obtain small dispersed particles of different materials. Samples of small dispersed microparticles of silica and alumina were obtained. The size and chemical composition of samples were examined using a Quanta 3D 200i scanning electron microscope (SEM, FEI, USA). The average size of separated silica nanoparticles was 600 nm, that of silica and alumina microparticles was 5 μm. Two separation methods were developed: the first one used a special trap and shape of the bottom electrode of RF discharge (for separation of microparticles) and the second used an electrical trap (for separation of nanoparticles). The graphs of particle size distribution were constructed using graphical and mathematical calculations. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

炸药爆轰法制备纳米石墨粉及其在高压合成金刚石中的应用

介绍了一种制备纳米石墨粉的新方法——负氧平衡炸药爆轰法. 对合成的黑粉产物进行x射线衍射分析，确认其为石墨结构，平均晶粒度为2.58 nm. 透射电子显微分析的结果表明，炸药爆轰法制备的黑粉为六方结构的纳米石墨粉，颗粒呈球形或椭球形. 用小角x射线散射法测定纳米石墨粉的粒度分布在1—50 nm，有92.6wt%的粉末粒度小于16 nm. 平均粒径为8.9 nm. 纳米石墨粉的比表面积约为500—650 m²/g. 在六面顶压机中用纳米石墨粉在Fe粉触媒的作用下进行金刚石的高压合成实验 关键词： 纳米石墨粉 爆轰 金刚石 合成     

Particle size,size distribution and morphological evaluation of glass fiber reinforced plastic (GRP) industrial by-product

The waste management of glass fiber reinforced polymer (GRP) materials, in particular those made with thermosetting resins, is a critical issue for the composites industry because these materials cannot be reprocessed. Therefore, most thermosetting GRP waste is presently sent to landfill, in spite of the significant environmental impact caused by their disposal in this way. The limited GRP waste recycling worldwide is mostly due to its intrinsic thermosetting properties, lack of characterization data and unavailability of viable recycling and recovery routes. One of the possibility for re-using GRP industrial by-product is in form of powder as a partial aggregate replacement or filler addition in cement based composites for applications in sustainable construction materials and technologies. However, the feasibility of this kind of reutilization strongly depends on the morphology and particle size distribution of a powder made up of polymer granules and glass fibers. In the present study, the use of image analysis method, based on scanning electron microscopy (SEM) and ImageJ processing program, is proposed in order to evaluate the morphology of the particles and measure the particle size and size distribution of fine GRP waste powder. The obtained results show a great potential of such a method in order to be considered as a standardized method of measurement and analysis in order to characterize the grain size and size distribution of GRP particles before exploiting any compatibility issue for its recycling management.     

Analysis of precipitates in ultrafine-grained metallic materials

In the present work, new possibilities of the X-ray diffraction for investigations of the phase composition, size, shape and volume fraction of particles in ultrafine-grained ferritic/martensitic steel and the Cu-Cr-Zr alloy have been demonstrated. For the first time, the method of X-ray diffraction in the transmission mode was used to identify particles with a volume fraction of less than one percent in the ultrafine-grained materials studied. The small-angle X-ray scattering method was used to estimate the size and shape of dispersed particles. Specific features of the ultrafine-grained structure determined by the X-ray diffraction and transmission electron microscopy studies were used for estimation of dispersion hardening in the samples obtained by equal-channel angular pressing in comparison with the samples subjected to standard treatment.     

球形ZnO的微波辅助合成及光谱研究

以Zn(NO₃)₂为原料,CO(NH₂)2为沉淀剂,加入表面活性剂甲基丙烯酸甲酯,经微波加热制备获得颗粒尺度为亚微米级的ZnO.采用X射线衍射(XRD)、扫描电镜(SEM)研究了制备条件对样品结构、形貌的作用;PL方法讨论了其荧光发光光谱.发现采用微波加热法获得的ZnO呈球形,尺度在100nm左右,相比较,传统高温加热获得的样品呈c轴优先取向的短棒状.讨论认为,由于微波辅助方法能够使前驱物温度梯度变化小,表面Zn²⁺,O²⁺析出均匀,因此有助于获得球形的粉末粒子.     

Structural properties of diamond fine particles and clusters prepared by detonation and decomposition of TNT

The thermal parameter B for three different particle sizes of diamond samples (bulk powder 1–4 μm, fine particle 144–195 Å and cluster 55–61 Å) was determined by the grazing incidence X-ray diffraction method. The values of B were found to be in the range 0.50–0.70 Å² for particles in the size range 195–55 Å and 0.27 Å² for 1–4 μm. All of them are larger than that of diamond bulk. A clear size dependence of B, increasing with decreasing particle size, was found. By analysing X-ray diffraction data at several temperatures the magnitude of B was found to be due to B_S (static part) instead of B_T (dynamic part). The average B_S values obtained were 0.04 Å², 0.19 Å² and 0.27 Å² for bulk powder, fine particle and cluster samples respectively. Ultrahigh resolution transmission electron microscope (TEM) observation confirmed the presence of strain, distortion, roughness and dislocation lines in many particles. TEM images of particles indicate that the clusters were not spherical in shape; they were mostly cubiform and some were truncated prism-like polyhedral. The present study reveals that the B_S component is responsible for the large B value in diamond fine particles and clusters. No clear surface local atomic distortion was found in the particles.     

Production of new haemostatic materials by deposition of dispersed proteins onto porous matrices using supercritical carbon dioxide

The main features of microparticle formation from protein substances (trypsin, lysozyme) using supercritical fluids (SAA method) are studied. Optical and scanning electron microscopies are employed to examine the morphology of the particles. The size distribution of the particles is studied using a cascade impactor. A method of deposition of particles onto Collachit-G haemostatic material is developed.     

Magnetic and Gas Sensing Property of Nanosized NiFe2O4 Powders Synthesized by Pulsed Wire Discharge

Nickel ferrite (NiFe₂O₄) powders were synthesized by pulsed wire discharge method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses show that only nickel ferrite spinel and no other phase was observed in the powders. Mean size of the obtained particles strongly depended on the oxygen pressure: the higher oxygen pressure corresponds to larger powder size, as determined by Brunauer–Emmet–Teller (BET). The room temperature saturation magnetization of the synthesized powders was 42–46 emu/g depending on the powder size. These powders also showed high chlorine sensitivity at about 280–360°C, and a good linear sensitivity with chlorine concentration.     

Relationships Between Particle Properties and Bulk Behaviour for some industrial powders

A series of industrial powders, most of them organic, were characterized in terms of volumetric mean size, size distribution, density, particle shape, water rentention characteristics (under a series of controlled ambient relative humidities) and loosely packed and densely packed voidages (giving the compressibility). The behaviour of the powders in powder handling apparatus (a precision powder filler) was also determined. The minimum and maximum bulk densities of the powders were related to the properties of the individual particles by means of a semi-empirical equation. The filling capacity of the powder handling apparatus was found to be related to the maximum bulk density of the powder while the filling accuracy turned out to be related to the compressibility of the powder. Knowing these interrelations made it possible to predict the powder behaviour in the handling apparatus directly on basis of the particle properties.     

Synthesis and characterization of zinc oxide nanoparticles: application to textiles as UV-absorbers

We report the synthesis and characterization of nanosized zinc oxide particles and their application on cotton and wool fabrics for UV shielding. The nanoparticles were produced in different conditions of temperature (90 or 150 °C) and reacting medium (water or 1,2-ethanediol). A high temperature was necessary to obtain small monodispersed particles. Fourier transformed infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray powder diffractometry (XRD) were used to characterize the nanoparticles composition, their shape, size and crystallinity. The specific surface area of the dry powders was also determined. ZnO nanoparticles were then applied to cotton and wool samples to impart sunscreen activity to the treated textiles. The effectiveness of the treatment was assessed through UV–Vis spectrophotometry and the calculation of the ultraviolet protection factor (UPF). Physical tests (tensile strength and elongation) were performed on the fabrics before and after the treatment with ZnO nanoparticles.     

Synthesis of wide band gap nanocrystalline NiO powder via a sonochemical method

A sonochemistry-based synthesis method was used to produce nanocrystalline nickel oxide powder with ∼20 nm average crystallite diameter from Ni(OH)₂ precursor. Ultrasound waves were applied to the primary solution to intensify the Ni(OH)₂ precipitation. Dried precipitates were calcined at 320 °C to form nanocrystalline NiO particles. The morphology of the produced powder was characterized by transmission electron microscopy. Using sonochemical waves resulted in lowering of the size of the nickel oxide crystallites. FT-IR spectroscopy and X-ray diffraction revealed high purity well-crystallized structure of the synthesized powder. Photoluminescence spectroscopy confirmed production of a wide band-gap structure.     

Synthesis and optical properties of tetragonal KTa0.6Nb0.4O3 nanoparticles

Tetragonal phase KTa_0.6Nb_0.4O₃ (KTN) nanoparticles have been prepared by hydrothermal method. The obtained particles were characterized by X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and UV-vis absorption spectrum techniques. A systematic change in crystal structure from cubic to tetragonal is observed with the increase of reaction temperature and KOH concentration. Room temperature UV-vis absorption spectrums of KTN particles show that the band gap changes from 3.24 to 3.34 eV with grain size diminished, which reveals the existence of blue-shift phenomenon of absorption bands.