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Young Tae Moon Hong Kyu Park Do Kyung Kim Chong Hee Kim In-Sig Seog 《Journal of the American Ceramic Society》1995,78(10):2690-2694
A novel method is demonstrated which yields a spherical ZrO2 powder of narrow size distribution through heating of a zirconyl chloride solution with an alcohol–water mixture as the solvent. The kind and composition of the solvent mixture greatly influenced the behavior of the precipitation and the morphology of the resulting particles. When 1-propanol or 2-propanol was employed as the alcohol of the solvent mixture, the resulting particles had a spherical shape and a narrow size distribution. The particle size and the particle agglomeration level could be controlled by the amount of hydroxypropyl cellulose (HPC) in the solution. As-prepared amorphous powder was crystallized to a mixture of metastable tetragonal phase and monoclinic phase at about 460°C. The metastable tetragonal phase was converted to the monoclinic phase as the calcination temperature was increased. After calcination, the spherical shape of the zirconia powder was retained, while its particle size was decreased slightly. 相似文献
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In this study, the solventing‐out recrystallization method was applied to prepare insensitive and spherical high bulk density nitroguanidine (NQ). Experiments were performed at various operating conditions by using N‐methyl‐pyrrolidone (NMP) and acetone as solvent and antisolvent, respectively. The effects of different operating parameters such as NQ/NMP ratio, amount of acetone used, crystallization temperature, stirring speed and stirring time were investigated. The particle size and morphology of the prepared NQ crystals were observed by scanning electron microscopy (SEM), the bulk density was measured by the Archimedes’ method and the impact sensitivity was determined by fall hammer method. The experimental results showed that the solventing‐out recrystallization method could be used to prepare spherical high bulk density NQ with a narrow particle size distribution and the particle size could be controlled by changing the operating conditions. The bulk density of these spherical NQ particles was found to be in the range of 0.94–0.97 g cm−3, which is higher than that of needle‐shaped NQ particles, and they became less sensitive towards impact. 相似文献
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采用手工搅拌、机械搅拌以及超声波作用对纳米SiO2进行分散处理,通过纳米粒度Zeta电位仪测定纳米SiO2胶体粒径及粒径分布,研究了纳米SiO2的分散性及其对水泥胶砂强度和毛细吸水的影响.研究结果表明,比较三种分散效果,超声波作用最好,机械搅拌次之,手工搅拌最差;增加超声波作用时间,纳米SiO2胶体平均粒径降低,分散性提高,超声波作用超过10 min,纳米SiO2胶体小颗粒增多,但粒径分布曲线整体向大颗粒方向偏移,分散性提高不明显;水泥胶砂强度和毛细吸水性与纳米SiO2的分散性有关,随纳米SiO2分散性的提高,水泥胶砂强度增大,毛细吸水系数降低,胶砂试件的密实度提高. 相似文献
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采用反溶剂重结晶法进行了青蒿素超细粉体的制备研究。以乙醇为溶剂,水为反溶剂,系统考察了药用辅料类型、反溶剂溶剂体积比、药物溶液浓度和混合强度对产品颗粒形貌和大小的影响。结果表明,辅料羟丙甲纤维素(HPMC)与聚乙烯吡咯烷酮 (PVP)联用可有效控制颗粒形貌,反溶剂溶剂体积比为20,青蒿素乙醇溶液浓度为20 mg·ml-1,搅拌转速为8000 r·min-1时,浆料中可得到平均短径0.84 μm、长径3 μm的针状颗粒,此浆料经喷雾干燥可得到粒径为2~3 μm的类球形粉体颗粒。进一步采用红外光谱、X射线衍射、差热分析、比表面积测试对原料药及产品的特性进行了表征,结果显示,青蒿素经反溶剂重结晶过程与辅料HPMC间产生一定的氢键作用,超细粉体产品的结晶度及熔点降低,比表面积增至原料药的26.4倍。体外溶出测试结果表明,青蒿素超细粉体的溶出速率远优于原料药,超细药物粉体15 min即可溶出88.3%,而同期原料药的溶出度仅为2.1%。 相似文献
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以球形SiO2颗粒为研究对象搭建高温测试实验台,用光学粒子计数器(OPC)测定了25?800℃下的颗粒数及其累计分布,并进行扫描电镜(SEM)和X射线衍射(XRD)分析,研究了高温对颗粒物在线检测结果的影响。结果表明,随加热温度升高,SiO2颗粒的粒径先变小后增大再变小,但颗粒物形状未发生变化;XRD衍射峰强度整体变弱,2θ?25.5o处的衍射峰宽化并移动,晶胞体积先增大后变小。根据SiO2晶胞体积与晶体介电常数的关系可排除加热使颗粒物粒径变化,温度升高导致SiO2颗粒晶体内部结构变化、晶体折射率变化,使测量结果存在2?3个粒径通道的误差,影响测量精度。 相似文献
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Yujun Xiang Weijian Xu Encai Ou Qing Su Lijuan Chen Yonggong Zhan Xinnian Xia Yuanqing Xiong Yuzi Xiong 《Iranian Polymer Journal》2013,22(10):749-756
Lignosulfonate is one of the main byproducts of paper industry. The development and research activities on this important substance have drawn widespread interest in the world. Sodium lignosulfonate was modified by heating in acidic environment and then transferred the modified sodium lignosulfonate into sodium hydroxide solution for further stirring. An insoluble fraction was separated and washed thoroughly with de-ionized water to neutral. Finally, the modified sodium lignosulfonate hydrogel particles were obtained. The obtained hydrogel particles were ultrasonically dispersed in water to form a modified sodium lignosulfonate micro-hydrogel with mean sizes of 300–400 nm. This indicated that the modified sodium lignosulfonate hydrogel particles were generated by the agglomeration of modified sodium lignosulfonate micro-hydrogel. The hydrogel particles were characterized by physical and spectral methods involving infrared radiation, thermogravimetric analysis, dynamic light scattering, and scanning electron microscope. The xerogels formed by drying modification of sodium lignosulfonate hydrogel particles showed a high water-adsorption of 31.2 g/g. In addition, the effect of reaction parameters on water swelling capacity and xerogel yield were also investigated, which include heating temperature, base treatment temperature, and concentration of sodium hydroxide solution. The research results indicated that the yield of modified sodium lignosulfonate hydrogel increases with higher heating temperature and decreases with higher alkali treatment temperature and concentration of sodium hydroxide solution. The water swelling capacity of the modified sodium lignosulfonate hydrogel increased slightly with higher heating temperature, but remained unaffected by the alkali treatment temperature and concentration of sodium hydroxide. 相似文献
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ZrO2/PMMA nanocomposite particles are synthesized through an in-situ free radical emulsion polymerization based on the silane coupling agent (Z-6030) modified ZrO2 nanoparticles, and the morphology, size and its distribution of nanocomposite particles are investigated. Scanning electron microscopy (SEM) images demonstrate that the methyl methacrylate (MMA) feeding rate has a significant effect on the particle size and morphology. When the MMA feeding rate decreases from 0.42ml·min-1 to 0.08ml·min-1 , large particles (about 200-550nm) will not form, and the size distribution become narrow (36-54nm). The average nanocomposite particles size increases from 34nm to 55nm, as the MMA/ZrO2 nanoparticles mass ratio increased from 4:1 to 16:1. Regular spherical ZrO2/PMMA nanocomposite particles are synthesized when the emulsifier OP-10 concentration is 2mg·ml-1. The nanocomposite particles could be mixed with VAc-VeoVa10 polymer matrix just by magnetic stirring to prepare the ZrO2 /PMMA/VAc-VeoVa10 hybrid coatings. SEM and atomic force microscopy (AFM) photos reveal that the distribution of the ZrO2 /PMMA nanocomposite particles in the VAc-VeoVa10 polymer matrix is homogenous and stable. Here, the grafted-PMMA polymer on ZrO2 nanoparticles plays as a bridge which effectively connects the ZrO2 nanoparticles and the VAc-VeoVa10 polymer matrix with improved comparability. In consequence, the hybrid coating with good dispersion stability is obtained. 相似文献
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Aerosolization of polystyrene solutions followed by drying in a tubular furnace produced submicron-sized polystyrene particles. Characterization using x-ray diffraction, scanning electron microscopy (SEM), and infrared spectroscopy (FT-IR) revealed that the particles were amorphous, spherical, and free of residual solvent. The average particle size and size distribution varied with furnace temperature, the initial polystyrene solution concentration, and solvent type. The particles' BET-based specific surface area depended upon these parameters as well as the carrier gas flow rate. Analysis of the competing rates of convection, solvent evaporation, droplet collisions, and polymer diffusion help to rationalize the results. The dependence of the solvent evaporation rate on temperature controls the particle diameter, but droplet coalescence cannot be ignored. Long residence times and high furnace temperatures softened the particles; after filtration, polymer diffusion between solid particles produced visual evidence of partial coalescence. © 1995 John Wiley & Sons, Inc. 相似文献
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Mahdi Norouzi Malihe Tahernejad Seyed Ghorban Hosseini Saeed Tavangar 《化学工程与技术》2020,43(11):2215-2223
The sphericity and size of ammonium perchlorate (AP) particles significantly influence the properties of composite propellants. As the AP particles become more spherical, the accumulation coefficient increases, the viscosity during casting decreases, and the particle loading and burning rate increase. Hence, the production of micronized AP particles with an average size between 1 and 20 μm is important to increase the loading percentage of AP in the composite propellant. Here, the Taguchi experimental design was used to optimize the solvent-antisolvent crystallization (SAC) process for the preparation of micronized AP particles with higher sphericity. SAC parameters such as the type of antisolvent, the solvent-to-antisolvent ratio, the antisolvent temperature, the stirring speed, and the retention time were investigated at four levels. The type of antisolvent and the solvent-to-antisolvent ratio were found to mainly contribute to improving the sphericity and size of the AP particles, respectively. 相似文献
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With a view to promoting dispersion of lycopene in water, the precipitation of an inclusion complex of lycopene and β-cyclodextrin was investigated using the solution-enhanced dispersion by supercritical fluids (SEDS) process. The inclusion complex, which was prepared in N,N-dimethylformamide (DMF), was dissolved in the same solvent and then micronized by SEDS, using carbon dioxide (CO2) as a supercritical antisolvent. The effects of the initial concentrations of lycopene and β-cyclodextrin, the CO2 flow rate, the solution flow rate, and the pressure and temperature at which the process was conducted were examined. The morphologies of the resulting particles were observed by scanning electron microscopy (SEM) and field emission-scanning electron microscopy (FE-SEM). Small spherical particles were obtained at all operating conditions. At high pressure, high temperature, high CO2 flow rate and low solution flow rate, particles with an average particle size of about 40 nm were obtained. 相似文献
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The temperature, supersaturation, seeding procedure, stirring speed and other parameters were varied in crystallization experiments of calcium carbonate performed in aqueous solutions to control size, particle size distribution and morphology of the particles. Particle size information was obtained by focused beam reflectance measurements and the Coulter Counter Multisizer. Crystals of CaCO3 could be crystallized as spherical polycrystalline particles of the vaterite polymorph, needle‐like crystals of aragonite and both cube‐like and novel plate‐like crystals of calcite. Filtration experiments for calcium carbonate, performed at a constant pressure difference of 2 bar, show that spherical particles with a larger size show better filterability and that spheres with a wider size distribution, as a result of high supersaturation and nucleation, give higher average cake resistance values. Comparing different particle morphologies, plate‐like crystals and needle‐like crystals show worse filterability than spherical particles and cube‐like particles. © 2011 American Institute of Chemical Engineers AIChE J, 2012 相似文献
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Monodispersed spherical β-SiC powder was synthesized by heating spherical gel powder derived from the hydrolysis of a mixture of phenyltriethoxysilane and tetraethyl orthosilicate. The solution was prepared in a beaker and hydrolyzed by NH4 OH without stirring. The monodispersed spherical gel powder of submicrometer size was obtained when the added amount of NH4 OH was greater than 16 moles per mole of silane plus alkoxide, and it became monodispersed spherical β-SiC powder by heat-treating at 1500°C for 4 h in an Ar atmosphere. The SiC content of the powder was 92.6 wt%. 相似文献
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The exploration of a method to tailor a biodegradable polymer into microparticles/nanoparticles with a desirable morphology and size may result in their enhanced performance as biomedical devices for drug delivery and simplify the preparation process. A modified electrohydrodynamic liquid atomization (EHDA) process is reported here for the preparation of poly(lactic‐co‐glycolic acid) (PLGA) microparticles. To understand systematically the EHDA method for the preparation of PLGA microparticles, PLGAs of four different molecular weights were electrosprayed under different conditions involving changes in the applied potential, liquid flow rate, polymer concentration, and solvent. The results show that the right concentration range of PLGA is key for electrospraying the spherical particles. A solution with a low‐molecular‐weight PLGA has a wider concentration range for electrospraying into spherical particles than a solution with a high‐molecular‐weight PLGA. At the concentration at which spherical particles are formed, the diameter of the as‐sprayed particles is not affected substantially by the applied potential and PLGA molecular weight, but it increases monotonically with the liquid flow rate and PLGA concentration. Experimentation further demonstrated that low electric conductivity, a low dielectric constant, and a high vapor pressure of chloroform are favorable for controlling the EHDA process to obtain quasi‐monodisperse particles. The addition of the solvent N,N‐dimethylformamide with opposite solvent properties extremely disturbs the stability of the EHDA process and, at the same time, produces smaller and polydisperse particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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Monir Noroozi Shahidan Radiman Azmi Zakaria Sepideh Soltaninejad 《Nanoscale research letters》2014,9(1):645
Silver nanoparticles were successfully prepared in two different solvents using a microwave heating technique, with various irradiation times. The silver nanoparticles were dispersed in polar liquids (distilled water and ethylene glycol) without any other reducing agent, in the presence of the stabilizer polyvinylpyrrolidone (PVP). The optical properties, thermal properties, and morphology of the synthesized silver particles were characterized using ultraviolet-visible spectroscopy, photopyroelectric technique, and transmission electron microscopy. It was found that for the both solvents, the effect of microwave irradiation was mainly on the particles distribution, rather than the size, which enabled to make stable and homogeneous silver nanofluids. The individual spherical nanostructure of self-assembled nanoparticles has been formed during microwave irradiation. Ethylene glycol solution, due to its special properties, such as high dielectric loss, high molecular weight, and high boiling point, can serve as a good solvent for microwave heating and is found to be a more suitable medium than the distilled water. A photopyroelectric technique was carried out to measure thermal diffusivity of the samples. The precision and accuracy of this technique was established by comparing the measured thermal diffusivity of the distilled water and ethylene glycol with values reported in the literature. The thermal diffusivity ratio of the silver nanofluids increased up to 1.15 and 1.25 for distilled water and ethylene glycol, respectively. 相似文献
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以甲基丙烯酸甲酯、丙烯酸丁酯、α-甲基丙烯酸和苯乙烯为单体,以过硫酸钠为引发剂,温度控制在78℃,搅拌速度为800 r/min,采用半连续加料法,经乳液聚合分别制得了种子、核及具有核壳结构的聚合物粒子。用动态光散射(DLS)、原子力显微镜(AFM)、扫描电镜(SEM)测得其平均粒径分别为72.1、400及500 nm。核壳粒子用w(NaOH)=10%的水溶液进行溶胀,得到的粒子经透射电子显微镜(TEM)显示为中空结构,在SEM下观察,其平均粒径在900 nm左右。用微电泳仪测得,该中空粒子在四氯乙烯分散介质中电泳淌度为0.004 98 s2.mA.kg,Zeta电位为0.032 2 mV,在水分散相中,Zeta电位为-43.880 mV。 相似文献