共沉淀法合成磷酸盐陶瓷Ca1-xBaxZr4P6O24粉体的研究

用共沉淀法合成了磷酸锆钡钙[Ca1-xBaxZr4(PO4)6,0≤x≤1]陶瓷粉体的先驱体,研究了消除团聚并聚得结晶良好,配比准确的单相Ca1-xBaxZr4(PO4)6粉体的方法。结果表明：在共沉淀反应过程中控制pH=9,并采用低分子有机溶剂分散处理共沉淀物,可有效防止反应过程及凝固分离过程中团聚体的形成,使制备的粉体具有较窄的粒度分布,平均粒径2μm左右;采取反加料顺序并保持沉淀剂过量,可避免分别沉淀。将先驱体在900℃下煅烧2h后,经XRD分析发现为单相的Ca1-xBaxZr4(PO4)6粉体。     

共沉淀法合成磷酸盐陶瓷Ca_(1-x)Ba_xZr_4P_6O_(24)粉体的研究

用共沉淀法合成了磷酸锆钡钙 [Ca1 -xBaxZr4(PO4) 6 ,0≤x≤ 1]陶瓷粉体的先驱体 ,研究了消除团聚并获得结晶良好、配比准确的单相Ca1 -xBaxZr4(PO4) 6 粉体的方法 .结果表明 :在共沉淀反应过程中控制pH =9,并采用低分子有机溶剂分散处理共沉淀物 ,可有效防止反应过程及液固分离过程中团聚体的形成 ,使制备的粉体具有较窄的粒度分布 ,平均粒径 2 μm左右 ;采取反加料顺序并保持沉淀剂过量 ,可避免分别沉淀 .将先驱体在 90 0℃下煅烧 2h后 ,经XRD分析发现为单相的Ca1 -xBaxZr4(PO4) 6 粉体     

薄水铝石粒度对煅烧形成α-Al2O3粉体的影响

研究了薄水铝石粒度对其煅烧形成α-Al2O3粉体的影响.先用水热法制备出均匀分散的纳米、亚微米及几个微米的薄水铝石前驱体,用x射线衍射仪和电子显微镜分析了薄水铝石在不同温度煅烧所得产物的相结构及形貌.结果表明,粒度30～100 nm的薄水铝石在1200℃煅烧1 h转变为α-Al2O3,为蠕虫状的烧结颗粒;粒度0.4～0.6 μm的薄水铝石在1 250℃煅烧1 h可转变为α-Al2O3,颗粒尺寸变化不大,仍在0.4～0.6 μm范围内;粒度1 μm左右的薄水铝石在1350℃下煅烧2 h尚不能完全转变为α相,并已出现明显烧结.因此,以水热法制备的亚微米级薄水铝石晶体作为前驱体,经直接煅烧可以制备出分散性较好的亚微米级α-Al2O3粉体.     

有机物对低温超强碱法制备纳米四方多晶氧化锆粉体性能的影响

利用低温超强碱法制备出了纳米四方多晶氧化锆粉体。为改善该粉体分散性较差、氧化钠含量较高的缺点 ,用有机物对粉体进行了表面改性处理 ,采用X射线荧光光谱、X射线衍射、透射电镜等对粉体性能进行了分析。结果表明 ,采用无水乙醇和柠檬酸铵对粉体进行改性处理 ,使得粉体粒度均匀、分布变窄 ,形态近球形 ,其中柠檬酸铵的处理效果尤为显著 ,使粉体平均粒径从 0 .6 9μm减小到 0 .5 4μm ;进一步的高分辨像分析结果表明 ,粉体颗粒多由 2～ 3个大小为 2 0～ 30nm的单晶组成 ,较大的团聚体较少 ,因此有机物对粉体的表面改性处理有利于获得分散性好、粒度均匀的高质量纳米氧化锆粉体。     

金属基覆铜板高导热半固化膜的制备及其成膜性研究

以环氧树脂(EP)为连续相,线性PF(酚醛树脂)为固化剂,向EP中添加不同类型、粒度和比例的粉体颗粒;在高速分散机作用下将粉体颗粒分散均匀,制得高导热半固化膜材料。研究结果表明:以α-氧化铝为基础填料、硅烷偶联剂为成膜剂以及控制半固化时的升温速率,并且当m(1~5μm氧化铝)∶m(1~5μm氮化铝)∶m(1~5μm氮化硼)=3∶4∶1时,可制得综合性能良好的金属基覆铜板用高导热成膜物质。     

顺序共沉淀法制备Nd:YAG陶瓷

以NH4Al(SO4)2·12H2O、Y2O3、Nd2O3为原料,NH4 HCO3为沉淀剂,采用顺序共沉淀法制备Nd:YAG粉体.并研究了碳酸氢铵浓度对粉体性能的影响,研究结果表明:较佳的碳酸氢铵浓度为1.0 mol/L.制得的粉体颗粒尺寸小,粒度分布窄,分散性好,具有良好的烧结活性,在1800℃真空烧结15 h制备了Nd:YAG透明陶瓷,其近红外波段的透过率为78％.断面和表面形貌显示陶瓷晶粒尺寸均匀,晶界清晰,结晶性好,瓷体致密,平均晶粒尺寸约为15 μm.     

凝胶预碳化处理对Ca0.4Sr0.6Bi4Ti4O15纳米晶粉体的影响

用凝胶预碳化处理工艺的溶胶-凝胶法制备了晶粒粒径小且分散性能较好的钙锶铋钛(Ca0.4Sr0.6Bi4Ti4O15)纳米晶粉体.借助差热-热重分析仪、X射线衍射仪和扫描电镜等分别确定凝胶的预碳化处理温度,研究了预碳化处理工艺对粉体的物相结构、粉体的微观形貌以及分散性能的影响,并分析讨论了预碳化机理.结果表明:在300℃对前驱体凝胶进行预碳化处理增强了粉体的分散性,降低粉体的粒度,提高粉体的均匀性.凝胶预碳化处理工艺并未对粉体的物相结构造成影响.经过预碳化处理制备的粉体的颗粒尺寸集中在100nm左右;未经预碳化处理的粉体的颗粒尺寸为100nm～1 μm.凝胶预碳化处理后,高吸附活性的有机碳包覆在前驱体的表面是有效减少粉体团聚的原因.     

SO2-4离子在微波均相合成YAG纳米粉体过程中的作用

采用Al(NO3)3·9H2O,NH4Al(SO4)2·12H2O以及Y(NO3)3为母盐,尿素为沉淀剂,利用微波均相沉淀法制备YAG纳米粉体.分析比较了SO2-4离子在粉体制备过程中的作用,对添加不同量SO2-4离子所制备的粉体的可烧结性进行了比较.利用IR、XRD、TEM分析了前驱体的化学组成、物相变化以及形貌;利用激光粒度分析仪对粉体的粒度分布进行了表征;利用SEM对烧结体的显微结构进行了观测.结果表明:SO2-4离子的含量影响前驱体的分散程度、组成及形貌,进而对YAG粉体的可烧结性有显著的影响,添加8%硫酸根的粉体具有良好的可烧结性,经1550℃常压烧结致密化程度达到98%以上.     

共沉淀法制备NZP族低膨胀陶瓷前驱体BZP的工艺探索与研究

本实验用共沉淀法合成磷酸盐陶瓷粉体。合成过程中分析了加料顺序的影响,考察了反应物浓度、反应溶液的pH值、溶液反应时间、煅烧温度等因素对合成率的影响。实验结果表明：共沉淀反应过程中PH=9,采取反加料顺序,并保持沉淀剂（NH4）2HPO4过量,对共沉淀物用乙醇进行分散处理后在950℃煅烧2h,经过XRD分析发现可得到合成率极高、结晶良好的单相BaZr4（PO4）（6BZP）粉体。     

直接共沉淀法制备CaZr4(PO4)6粉体

以硝酸钙、氯氧化锆、磷酸二氢铵为原料，用直接共沉淀法制备了CaZr4（PO4）6（简称CZP）粉末。控制反应过程中溶液的pH．并用低分子有机溶剂分散处理共沉淀物，防止反应过程及固液分离过程中团聚体的形成。用TG—DTA、XRD、SEM、激光粒度分析仪对CZP粉末进行了表征。CZP粉末的结晶状况和颗粒大小及团聚情况取决于热处理温度的高低，粉体中添加3％（质量分数）氧化锌作为助烧剂及3％（质量分数）二氧化硅作为晶粒抑制剂，在1150℃下烧结2h制成CZP陶瓷。结果表明：经860℃热处理之后的粉体制成的CZP陶瓷具有较好的综合性能，弯曲强度为74．96MPa，相对密度为96．6％。     

超临界快速膨胀法制备植物甾醇超细微粒

通过药物颗粒的微细化,降低其粒度,增大比表面积,进而提高药物颗粒的溶解度,可以有效地改善难溶药物的生物利用度。该文采用超临界流体快速膨胀法(RESS)微细化植物甾醇颗粒。利用SEM分析了沉淀颗粒的形貌及粒径大小。分析了过程参数与所制备颗粒粒度的关系。研究发现,当喷嘴内径Dn从60μm减小到40μm,植物甾醇颗粒粒径由10～20μm减小为5μm;预膨胀压力p0从15MPa增加到25MPa时,颗粒粒径由10～15μm降至5μm;预膨胀温度T0由318K升高到333K时,颗粒粒径由5～10μm减小为1μm,粒径分布也趋于均匀。喷嘴温度Tn对粒径无显著影响。该法制备得到1～20μm无定形植物甾醇微细颗粒,且具有更高的溶解速率,比原料植物甾醇早3h达到饱和溶解度。     

玻璃粉粒度对复合胶凝材料性能的影响

用激光粒度分析仪测定不同细度的玻璃粉粒度分布,以灰色关联方法( GIA)和扫描电子显微镜( SEM)研究了玻璃粉粒度对复合胶凝材料性能的影响。研究结果表明,玻璃粉中10μm以下的颗粒关联性均为正,说明这些颗粒对复合胶凝材料强度发展有积极贡献,其中以5~10μm的关联度为最大;而?45μm的颗粒呈负关联,其火山灰活性没有得到充分发挥;玻璃粉经适当物理磨细(35 min)后,能更有效地分散到复合胶凝材料的孔隙中,使复合胶凝材料的结构更加密实,从而提高了复合胶凝材料的抗压强度。     

激光粒度分析仪在微细粒级荧光粉粒度测量中的应用

采用激光粒度分析仪对某种微细粒级荧光粉运用不同的样品循环运动速度和加载超声波进行粒度组成与分布的测量。通过正态曲线叠加比较获得:该微细粒级荧光粉颗粒平均直径为4.128μm,中值为3.145μm,标准差为3.930μm,变异系数为95.10%,众数为4.048μm,并测得不同粒径颗粒所占的质量分数。结果表明,该方法是粉末粒度及粒度分布测量的准确方法。     

Electrostatic effects on inertial particle transport in bifurcated tubes

Most aerosols found naturally in the ambient environment or those dispersed from artificial devices such as dry powder inhalers, are electrically charged. It is known that a strong electrostatic charge on aerosols can result in transport behavior dramatically different from that of uncharged aerosols, even in the absence of an external electric field. In the present work, we study pneumatic transport of corona‐charged particles in bifurcated tubes. This is accomplished by tracking the motion of discrete particles numerically under the influence of drag, gravitational, and electrostatic forces. The model aerosol is fly ash powder, whose size and charge distributions have been determined experimentally. The electrical mobility of the charged particle cloud is modeled through coulombic interactions between discrete point charges. For the case of polydispersed particles electrically charged across a distribution, the deposition efficiency was found to be greater than what is indicated by the mean charge and size. In particular, use of negatively charged fly ash powder of mean size of 2 μm and mean charge of ?1.5 C/kg led to significant increase in deposition efficiency (～29%) compared with uncharged fly ash powder of the same size distribution (～8%). Analysis of particle residence times suggests significant interaction between electrical and drag forces. These findings could have implications for pneumatic powder conveying or pulmonary drug delivery applications. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

氢氧化钠沉淀沽制备Bi2O3粉末的研究

对氢氧化钠沉淀法制备Bi2O3粉末进行了详细的研究,大量探索实验发现,反应温度、终点pH值和搅拌速度对Bi2O3的纯度有较大的影响。研究表明,最佳工艺条件控制为反应温度70－90℃,pH值12左右,搅拌速度约300r/min时,制得的Bi2O3为β型、针状、粒度为1－10μm的高纯度粉末。该粉末用于对粒度和纯度有一定要求的无机颜料、阻燃剂、抑烟剂、高折光玻璃和核工程玻璃等领域。     

煤矸石对泡沫混凝土孔结构的影响

本文将粉磨之后的煤矸石替代部分水泥掺入到混凝土中,通过物理发泡工艺制备煤矸石泡沫混凝土。采用FiJi-imageJ图像分析技术等对泡沫混凝土的孔径分布、平均孔径、气孔直径等进行表征,分析了煤矸石改善泡沫混凝土成孔的原因以及煤矸石粉磨粒径对泡沫混凝土抗压强度的影响。结果表明:当掺入粒径为45 μm的煤矸石粉时,泡沫混凝土的强度随着掺量的增加逐步下降,而掺入粒径为15 μm的煤矸石粉时,强度则随掺量的增加呈先上升后下降的趋势;在调节孔结构方面,粒径为45 μm的煤矸石粉优于粒径为15 μm的煤矸石粉,并在50%(质量分数)掺量下达到最优效果。     

Modal Characteristics of Elemental and Organic Carbon in an Urban Location in Guangzhou,China

Carbonaceous matter is a major constituent in urban aerosols, especially in those collected in China. The size distributions of elemental carbon (EC) and organic carbon (OC) in the range of 0.01–18 μm were measured in an urban location in Guangzhou, China in July 2006. The EC size distribution in the accumulation-mode size was characterized by three significant modes with mass median aerodynamic diameters (MMAD) of ～0.15 μm, ～0.40 μm, and ～0.90 μm, with the second one being the most prominent and accounting for approximately half of the total EC mass. The coexistence of the first two accumulation modes in Guangzhou's urban atmosphere could be explained to be a result of emissions from vehicles operating at different loadings. The dominance of the EC accumulation mode at ～0.40 μm has not often been reported in studies conducted in developed countries, but this observation is consistent with EC size distributions measured in a roadway tunnel in this region. This information is important when modeling the role of EC in modulating the radiative balance and investigating the health effects of EC. The third accumulation mode was postulated to be a result of in-cloud processing after emission. OC had the same size modes as EC but different mass distributions among the modes. The carbonaceous materials in the nucleation mode were dominated by OC. Among particles in the accumulation size range, the OC/EC ratio was higher in the third accumulation mode (MMAD: 0.90 μm) than in the first two accumulation modes, suggesting that in-cloud processing was an important pathway for accumulating OC mass during atmospheric processing of EC particles.     

Particle size analysis of dioctyl phthalate aerosols using the stöber aerosol spectrometer

Particle size distributions of nearly monodisperse dioctyl phthalate aerosols (dia. between 0–5 and 1–4 μm) have been determined using the Stöber aerosol spectrometer. The particle size distributions can be approximated very well by bimodal distribution functions. From a statistical analysis it turned out that the accuracy of the approximation is limited in case of small particles (dia. ～ 0·5 μm). This is due to evaporation of the particles during the analysis.The mean of the particle size distribution determined with the Stöber aerosol spectrometer was in fair agreement with the particle diameter determined with the higher order Tyndall spectrometer.     

采用高压静电雾化法制备W/O乳化液的实验研究

采用静电雾化方法进行了W/O玉米油乳化液制备的实验研究,在雾化流量2.8~15 mL/min、电极施加电压5.2~11 kV的条件下,用Winner99颗粒图像测试仪测试了所制乳化液的离散相滴径,分析了施加电压及雾化流量对平均滴径及滴径分布的影响. 结果表明,静电雾化法可制备离散相滴径比搅拌法更均匀的乳化液,离散液滴平均滴径约为28 mm且绝大多数液滴直径为20~40 mm,其稳定性明显优于搅拌法所制乳化液. 乳化液离散相滴径与施加电压及雾化流量密切相关,电压增大、雾化电流增大,乳化液离散相滴径急剧减小,滴径分布变窄. 流量增大,单位时间内液滴携带及输运的电量增大,故雾化电流增大;但液滴荷积比随流量增大而减小,故滴径变大,滴径分布变宽. 高电压、低流量有助于获得稳定性更好的乳化液.     

Effects of particle size and color on photocuring performance of Si3N4 ceramic slurry by stereolithography

Due to high absorbance of UV light and low solid loading, the stereolithography-based additive manufacturing of gray-colored and dense Si₃N₄ ceramic is of significant difficulty and challenge. The effects of geometric properties of ceramic powders on the curing performance were investigated by studying the absorption difference of the Si₃N₄ ceramic particles with different colors and particle sizes and ultraviolet light. The results show that the transmission of ultraviolet light and curing performance of the darker Si₃N₄ ceramic slurry are much poor. Under the same particle size, the Si₃N₄ ceramic slurry using lighter particles presents the smaller scattering coefficient. The scattering coefficient (～202) of the gray powder with ～0.8 μm average particle size is the smallest. Under the same color, the larger the particle size, the smaller the scattering coefficient. The smallest scattering coefficient of the white powder with ～2.0 μm average particle size is ～110.