Reactive Laser Ablation Synthesis of Nanosize Aluminum Nitride

An aluminum (Al) target was laser ablated in a nitrogen (N₂) atmosphere, producing aluminum nitride (AlN) powder. These powders were calcined at 900°C for 2 h. Powders were produced at various nitrogen pressures, and the calcined powders were tested for unreacted aluminum content, using differential thermal analysis (DTA). The AlN powder, produced at a laser fluence of 12 J/cm² and a nitrogen pressure of 10.0 kPa (75 torr), showed no evidence of unreacted aluminum by DTA and was phase-pure AlN by X-ray diffraction (XRD). The surface area of this powder is 82 m²/g, corresponding to a particle size of ∼11 nm, which is in good agreement with TEM observations.     

片状氧化铝粉体的熔盐法合成

片状氧化铝由于其独特的片状结构,在珠光颜料、化妆品、填料及抛光粉等领域得到了广泛的应用.本文采用熔盐法制备了片状氧化铝粉体,考察了熔盐种类和熔盐用量对粉体形貌的影响.以硫酸铝为铝源,复合硫酸盐(Na2SO4+K2SO4)为熔盐,辅以外加添加剂,合成出了厚度为200～400 nm,平均径厚比约为50的形貌较好的片状氧化铝.     

脉冲激光溅射合成八-(甲基硅倍半氧烷)

以脉冲浙江溅射作用于聚甲基硅氧烷,经真空升华,直接得到了一种产物的单晶。经Ｘ－射线晶体衍射测定确定其为具有（ＣＨ３ＳｉＯ１．５）８组成的硅氧烷。该种产物具有多环立体空间构型。结果表明,在脉冲激光的作用下,反应物的链状结构发生解离,并在等离子体条件下进行结构重组,生成了具有立体空间构型的产物。     

液相化学合成法制备高纯Al2O3超细粉体

综述了目前制备高纯Al2O3超细粉体的三大类方法,对其中应用和研究最多的液相化学合成法的各种方法作了较详细的介绍,分析了各种方法的优缺点。简述了高纯Al2O3超细粉体的特性及应用。     

Laser Ablation Synthesis and Optical Characterization of Silicon Carbide Nanowires

Silicon carbide (SiC) nanowires were synthesized at 900°C by the laser ablation technique. The growth morphology, microstructure, and defects in SiC nanowires were characterized by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The Raman scattering study indicated that the Raman peaks corresponding to the TO and LO phonon modes of the SiC nanowires had larger red shifts compared to those of bulk SiC material. The red shift, broadening peak, and the asymmetry of the Raman peak could be explained by the size confinement effect in the radial and growth directions. The growth mechanism of SiC nano-wires was discussed based on the vapor–liquid–solid reaction.     

Synthesis of Nanosized Aluminum Nitride Powders by Pulsed Laser Ablation

The influence of the target material, fluence, laser wavelength, and nitrogen pressure on the synthesis of AlN nanosized powders via reactive laser ablation has been investigated. Using infrared laser radiation and fluences of ≥11 J/cm², pure AlN nanosized powders were produced at nitrogen pressures of ≥1.3 kPa via ablation of an AlN target and ≥13.3 kPa via ablation of an aluminum target. With ultraviolet laser radiation, AlN powders could be synthesized at a lower fluence (9 J/cm² at a pressure of 8 kPa). The mean powder size was 7.5−15 nm.     

Compaction of Aggregated Alumina Powder

The behavior of aggregated powders during compaction was studied using powders differing only in their aggregate size distribution. The relations between aggregate size distribution, compaction pressure, and green density were determined. The crushing of aggregates during compaction was followed by determining the changes in the aggregate size distribution. The presence of aggregates retards the compaction at all stages in the compaction process.     

Reactive Hot-Pressing of Clays and Alumina

The temperature, pressure, and time dependence of bulk density and the compressive strength of clay and boehmite compacts subjected to reactive hot-pressing were determined. The strength and the bulk density are linearly related to the extent of the dehydroxylation reaction which occurs during reactive hot-pressing. In decomposition reactions the reactivity (for interparticle bond formation) and mobility (for densification) may result from the broken bonds and resultant unsatisfied valence links produced by the reaction. On the basis of this postulation, the following empirical relation, correlating the functional relation between strength or density and temperature and pressure was obtained: Application of this equation to the data obtained experimentally produced energy values, for both densification and interparticle bonding, which are much less than that of the activation energy or the enthalpy of the reaction involved. The different energy values for interparticle bonding and densification are believed to indicate different controlling modes for these processes.     

激光材料专用YAG粉体制备技术研究进展

本文对国内外目前激光材料专用的YAG粉体制备技术现状做了系统概述。重点介绍了目前YAG粉体制备的几种方法;固相反应法,气相化学法.沉淀法,溶剂热法,溶胶-凝胶法等:并对各种方法的优缺点做了对比:指出以钇铝醇盐为原料,以溶胶-凝胶法为基础制备YAG粉体是最具产业潜力的方法.     

Nanosize Powder of Zirconia. Explosive Method of Production and Properties

A powder of zirconia with a typical particle size of 5–6 nm is synthesized by an explosive method. It is shown that the stabilization of the hightemperature cubic modification under standard conditions is due to the small particle size. The sequence of phase transformations is studied. The phasetransition temperatures are found to be twice those for the standard powders. It is suggested that release of a considerable amount of heat during transition of the amorphous phase to the crystalline state plays a determining role in the stabilization of the size of the primary gel particles in the explosive synthesis.     

Influence of Reactive Alumina and Calcined Alumina on properties of Free Flowing Castables

Reactive alumina is a well-established group of raw materials for refractory castables to improve their rheological behavior.In this article the influence of bi...     

利用海南高岭土制备氧化铝条件的研究

采用海南高岭土为原料制备纳米氧化铝成本低,可以提高海南高岭土的产品附加值,对海南经济发展具有重要意义。本研究采用正交试验方法,研究了盐酸质量浓度、酸浸温度及干凝胶煅烧温度对纳米氧化铝的提取率和结晶度的影响。结果表明干凝胶煅烧温度对氧化铝的提取率和结晶度影响最显著。为了提高氧化铝的提取率和结晶度,优化配比方案为:酸浸温度95℃左右,盐酸质量浓度为333mg/L,煅烧温度为950℃。     

Preparation of Fine Alumina Powder in Alcohol

The preparation of fine alumina powder from alcoholic solutions of the metal alkoxide is described. The water for the hydrolysis reaction is generated in situ as a result of dehydration of the solvent at elevated temperature in an autoclave. The amount of water generated can be controlled according to the time temperature schedule employed. Control over the amount of water formed provides a means of controlling certain physical properties of the products, e. g., crystal structure and surface area.     

Solidification Microstructures of Laser-Melted Alumina Powder Compacts

Dense, thin sheets of α-alumina formed after solidification of powder compact surfaces which were melted using CO₂ laser radiation. The microstructures and surface topographies varied with the depth of melt. Most significant was a zone of columnar grains oriented in the [661] direction which yielded smooth surfaces for intermediate depths.     

球形氧化铝粉体制备的研究进展

球形氧化铝粉体是氧化铝产品中不可缺少的一部分,因其特殊的物理化学性质而备受关注。与不规则氧化铝粉体相比,球形氧化铝粉体的形貌和尺寸能极大地提高其产品的使用性能。目前,已有大量文献探讨了制备球形氧化铝粉体的方法,但缺少文献系统性地比较不同含铝原料适用的制备方法和优缺点。本文从不同的含铝原料出发,对已有文献进行总结分析,发现不同的含铝原料决定了不同的制备方法,从而决定了工业化的难易程度,其中无规则氧化铝是球形氧化铝粉体工业化并实现量产的最佳原料。     

Green Synthesis of Gold Nanoparticles in Pomegranate Seed Oil Stabilized Using Laser Ablation

In this paper, gold nanoparticles were synthesized in pomegranate seed oil using a laser ablation. The nano fluids were characterized using UV–Vis spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The nanoparticles were formed inside the pomegranate seed oil in spherical form, and the particle size ranged from 12 to 4 nm, and the gold nanoparticles were capped with COO^? of carboxylic acid groups of fatty acid in pomegranate seed oil.     

微波水热辅助沉淀法制备氧化铝/碳化硅复合粉体

用微波水热辅助沉淀法制得氧化铝前驱体/碳化硅复合粉体,用XRD、SEM、TG-DSC对粉体进行了表征.研究表明:经过微波水热后,氧化铝的前驱体转变为AlO(OH),随着微波水热时间延长,AlO(OH)的结晶程度越来越高.pH值为7时,煅烧后的Al2 O3/SiC复合粉体的包覆效果最佳.     

Microstructure Evolution of Alumina/Alumina Joint Bonded by Boron Oxide–Alumina Nonmetal Powder Interlayer

Alumina was successfully joined to itself in air environment by B₂O₃ + Al₂O₃ powder mixture as the interlayer to synthesize aluminum borate whiskers in the joint. The microstructure evolution was analyzed by means of scanning electron microscope (SEM) and X‐ray diffraction (XRD). The possible mechanism of microstructure evolution was also discussed. The effects of parameters such as heating cycles and temperature on the microstructure as well as the 3‐point flexural strength of the joint were investigated. It was found that heating the specimen for several heating cycles instead of holding at a constant temperature for a long time can eliminate the voids among the whiskers to achieve a dense microstructure, and the phenomenon that higher temperatures can accelerate the reaction was also observed. The highest strength of the joint reaches 90.29MPa with the heating temperature of 800°C after four heating cycles.     

氧化铝陶瓷激光泵浦腔的研制

采用纯度较高的白粘土、锻烧高岭土及工业氧化铝为主要原料成功地研制了氧化铝陶瓷激光泵浦腔体.采用KZJ-30型电动抗折仪、DSDB-1型数显白度计、日立340型分光光度计及XRD,SEM等现代测试技术测定了样品的理化性能和微观结构.结果表明:制备的样品的反射率高达99%以上,抗折强度达50～100MPa.     

浅谈硅微粉在氧化铝泡沫陶瓷中的作用

本文简单阐述了硅微粉的分类、应用和性质,分析了硅微粉在氧化铝泡沫陶瓷中的作用及高温反应的结合机理,同时研究了硅微粉对氧化铝泡沫陶瓷浆料性能和制品性能的影响。经试验分析,适量的硅微粉可促进氧化铝泡沫陶瓷的烧结,提高制品的强度,而对氧化铝浆料无不良影响。