TiO_2/SiO_2复合薄膜的晶型和晶粒尺寸研究

通过溶胶 -凝胶工艺在普通钠钙玻璃表面制备了均匀透明的TiO2 /SiO2 复合薄膜 .由紫外可见光谱发现 :在TiO2 薄膜中添加SiO2后 ,薄膜中TiO2 晶粒尺寸变小 ,TiO2 /SiO2 复合薄膜的吸收边缘波长发生了明显的“蓝移” .进一步用X射线衍射 (XRD)和透射电镜 (TEM )表征了TiO2 /SiO2 复合粉末和TiO2 粉末的晶型和晶粒尺寸 ,结果发现 :在TiO2 凝胶粉末中添加少量SiO2 (如摩尔分数为 5 % )后 ,TiO2 的晶粒生长受到明显抑制 ,晶粒尺寸明显变小 ,为 6～ 7nm ;当TiO2 凝胶粉末中添加的SiO2 量较高时 ,随热处理温度升高 ,TiO2 的晶型转变和晶粒生长受到更大抑制 ,晶型转变和晶粒生长更缓慢     

TiO2/SiO2复合薄膜的晶型和晶粒尺寸研究

通过溶胶－凝胶工艺在普通钠钙玻璃表面制备了均匀透明的TiO2/SiO2复合薄膜，由紫外可见光谱发现：在TiO2薄膜中添加SiO2后，薄膜中TiO2晶粒尺寸变小，TiO2/SiO2复合薄膜的吸收边缘波长发生了明显的“蓝移”。进一步用X射线衍射（XRD）和透射电镜（TEM）表征了TiO2/SiO2复合粉末和TiO2粉末的晶型和晶粒尺寸，结果发现，在TiO2凝胶粉末中添加少量SiO2（如摩尔分数为5％）后，TiO2和晶粒生长受到明显抑制，晶粒尺寸明显变小，为6－7nm；当TiO2凝胶粉末中添加的SiO2量较高时，随热处理温度升高，TiO2的晶型转变和晶粒生长受到更大抑制，晶型转变的晶粒生长更缓慢。     

β晶型聚丙烯的研究进展

对近年来在β晶型聚丙烯(PP)形态结构，影响β晶型含量的因素，β晶型成核剂，β晶型转变及β晶型PP性能等方面的研究工作进行了综述。添加成核剂可得到高含量的β晶型。与α晶型相比，β晶型PP的球晶尺寸大幅度减小，晶粒细化，具有良好的抗冲击性能和较高的热变形温度。     

无模板两步法合成亚微米A型沸石

不添加有机模板剂,采用较廉价的硅酸钠和铝酸钠分别作为硅源和铝源,经由两步法合成粒度分布均匀且晶型较好的亚微米A型沸石。研究了经不同陈化时间后硅铝凝胶结构发生的变化及经过晶化后产物的粒径变化。结果表明:陈化时间为0~85h时,主要表现为诱导成核,在这段时期硅铝凝胶中对A型沸石成核过程有重要影响的四元环、双四元环数量显著增加,而陈化时间为85~139h主要表现为晶核的生长;随着陈化时间的延长硅铝凝胶中SiO2/Al2O3逐渐减小,且尺寸也逐渐变小;在0~85h区间,合成最终产物的平均粒径随着陈化时间延长而减小,在85h时最小,可达500nm左右;继续延长陈化时间至139h将导致小颗粒A型沸石发生团聚,且形貌也变的不规整。     

以水玻璃和硫酸铝为原料合成T型沸石的研究

以工业水玻璃和硫酸铝为原料,于K2O-Na2O-SiO2-Al2O3-H2O体系中水热合成制得不同晶粒度的T型沸石.晶化温度在85～135℃可得到晶相纯的T型沸石;搅拌晶化能有效减小T型沸石的晶粒度,但搅拌速度在200～800 r/min内对晶粒大小的影响不明显;凝胶n(SiO2)/n(Al2O3)在16～32可合成出结晶度高、晶相纯的T型沸石,但大于32时晶化产物中出现钙十字沸石杂晶;凝胶n(SiO2)/n(Al2O3)改变对T型沸石产物硅铝比基本无影响.水玻璃合成体系晶化诱导期短.产物中n(K+)/n(Na+)比值远大于起始凝胶中两者的比值,这可能是由于钾离子在T型沸石晶化中起主要的结构导向作用.     

低硅铝比纳米团聚体ZSM-5的合成工艺研究

纳米团聚体ZSM-5因具有较高的活性及水热稳定性而被广泛用于催化剂的制备。以水玻璃为硅源、硫酸铝为铝源、正丁胺为模板剂,合成低硅铝比纳米团聚体ZSM-5分子筛。考察了钠硅比、陈化时间、晶种添加量等因素对合成分子筛形貌和晶粒尺寸的影响。采用X射线衍射（XRD）、扫描电镜（SEM）、氮气物理吸附、透射电镜（TEM）和X射线荧光光谱仪（XRF）等手段对样品进行了物性分析。结果表明：钠硅比（氧化钠与二氧化硅物质的量比）大于0.11可以合成出结晶度较好的ZSM-5分子筛,当钠硅比大于0.13时ZSM-5晶粒增大;延长陈化时间有助于降低分子筛的晶粒尺寸,提高晶粒尺寸的均一度,陈化12 h时晶体的平均尺寸约为160 nm;晶种添加量为3%~4%（按总二氧化硅质量计算）时,对样品晶粒尺寸及均匀度的影响较小。     

不同晶型纳米二氧化钛的水热合成

水热法合成了不同晶型、形貌和大小的纳米二氧化钛。利用X射线衍射(XRD)和透射电镜(TEM)对所得的样品进行了表征。研究了pH值、水热反应温度和水热反应时间对纳米二氧化钛晶型、形貌和晶粒尺寸的影响。结果表明,前驱体pH值是决定产品晶型、晶粒尺寸和形貌的主要因素。随着水热反应温度的升高,纳米二氧化钛的晶粒尺寸逐渐变大,但pH=3.0时所形成的锐钛矿型纳米二氧化钛的晶粒尺寸却几乎不变;随着水热反应时间的延长,金红石型纳米二氧化钛晶粒的生长速度最快,而锐钛矿型的纳米二氧化钛的晶粒生长速度则最慢。     

小晶粒NaY型分子筛的合成与表征

采用添加晶种和表面活性剂,通过水热晶化的方法合成了小晶粒NaY型分子筛,考察了铝源、硅源、表面活性剂、水等用量对NaY型分子筛合成的影响。采用XRD、N2吸附-脱附、SEM、XRF等手段对合成的分子筛进行了表征。结果表明:在合成体系中各组成的摩尔比n(Na2O):n(Al2O3):n(SiO2):n(H2O)=2.5:0.3:6.7:192.4的条件下,制备出的NaY型分子筛与常规NaY型分子筛的XRD谱图基本一致,且比表面积高达858m2/g;SEM结果显示,NaY型分子筛呈小晶粒聚集态,粒径在100~300nm。     

从粉煤灰中提取铝源制取ZSM-5及其动态水热晶化过程的研究

以粉煤灰分级处理获得的Al(OH)3作为铝源,在动态水热不同晶化时间下合成ZSM-5分子筛,并将固液两相分离,对固相ZSM-5分子筛进行XRD、SEM、PSD、XRF表征分析,对液相进行FT-IR表征分析.结果表明,ZSM-5分子筛晶化过程呈"S"型生长曲线规律,包括诱导期,成核期,快速生长期和晶化后期;随晶化时间延长,ZSM-5特征峰增强,产物结晶度提高,达到5 h后保持不变;晶粒尺寸由90～450μm逐渐向100 nm～1μm转变;Si/Al比呈现先升后降最后趋于稳定的趋势.在晶化过程中液相OH-含量不断增加;液相硅氧、铝氧化合物组成不断发生变化.推测ZSM-5晶化机制:固相在液相中不断溶解和沉积,固相发生化学重组并由大尺寸凝胶向小晶粒ZSM-5转变.     

镁碱沸石结晶度及晶体形貌的影响因素

以硅溶胶为硅源,偏铝酸钠为铝源,乙二胺为模板剂制备镁碱沸石.考察了晶化温度、晶化时间、碱度、陈化时间和晶种加入量对镁碱沸石结晶度和晶体形貌的影响.用X射线衍射仪(XRD)、扫描电子显微镜(SEM)等对所合成的样品进行了表征.结果表明:在碱度为0.12~0.15、晶化温度为160 ℃、晶化时间为60 h的条件下能够合成出晶化良好的样品;随着晶化温度的升高样品结晶度先升高后降低,其晶体尺寸逐渐增加;随着晶化时间的延长样品的结晶度和晶体尺寸先增加后趋于稳定;适当温度的陈化可以减小晶体尺寸,而添加晶种则可以显著改变晶体的形貌和尺寸.     

Dry gel conversion synthesis of shape controlled MFI type zeolite materials

Acid treated silica fibers, coming either from asbestos cord waste or calcium aluminosilicate glass, were engaged as reactants to product MFI type zeolite fibers applying a dry gel conversion (DGC) type synthesis. The impact of amorphous silica fiber shape and synthesis conditions on morphology of the final product was investigated. Enhanced zeolite nucleation and restricted crystal growth are necessary to maintain the initial fiber morphology. Whereas a DGC type crystallization in hydroxide media results in the formation of zeolite fibers, the use of fluoride ions leads to the formation of large individual zeolite particles. Synthesis conditions have to be adapted to form zeolite particles with an average size smaller than the silica fiber diameter to allow a good conservation of the fiber morphology. Final zeolite fibers have textural properties comparable to a standard zeolite product and are promising for adsorption applications.     

惰性粒子对流化结晶过程动力学特性的影响

通过惰性粒子对氯化钾流化结晶过程成核速率、晶体生长速率及晶型影响的实验研究，揭示了外加惰性粒子对流化床结晶动力学特性的影响机理和规律,并回归建立了相关数学模型。实验结果表明，惰性粒子主要通过与晶体的碰撞产生大量二次晶核，进而对晶体生长速率产生负面影响，并改变了晶型。其主要影响因素为惰性粒子的密度和尺寸。     

磷酸二氢铵结晶影响因素研究

采用间歇结晶法研究了pH值、降温速度、搅拌速度对磷酸二氢铵(MAP)结晶过程的影响。实验结果表明,MAP的溶解度随pH值变化明显,当pH值为3.2时溶解度最小。在pH值为3.2时,结晶速度、晶体析出温度、单晶长径比和平均粒径均为最大,且随着pH值增大,均显著减小;降温速率对于晶形及长径比没有影响,随着降温速度增大,晶体平均粒径减小,介稳区宽度增大,MAP的成核级数约为1.1;搅拌速度加快,结晶诱导时间显著缩短,介稳区宽度变窄。     

在线分析乙醇及超声波对硫酸钾晶核粒度的影响

目前,国内外生产的硫酸钾产品普遍存在粒度小、形貌差等问题。先用在线粒度仪分析无水乙醇加入量、搅拌转速、超声波功率等条件对硫酸钾起晶晶核的影响,然后研究硫酸钾晶核在浓缩的含硫酸钾洗脱液中生长的产品晶形的特点,为企业利用糖蜜酒精废液中的钾离子生产大颗粒硫酸钾提供理论支持。实验结果表明：在低温浴槽温度为30 ℃、搅拌转速为250 r/min、超声波功率为50 W、无水乙醇与饱和硫酸钾溶液质量比为1∶1条件下起晶,制得的硫酸钾晶核尺寸均匀、表面完整,颗粒平均弦长为14.5 μm。将制备的硫酸钾晶核投入到浓缩的从糖蜜酒精废液中分离出来的含硫酸钾的洗脱液中生长,可以得到粒度较大、晶形完整的硫酸钾产品,硫酸钾产品中粒度大于385 μm的晶体质量占结晶体质量的81.2%左右,钾离子结晶回收率约为85.8%。     

Hydrothermal synthesis of gallosilicate (MFI) zeolite: Factors influencing crystallization kinetics and crystal size/growth

The kinetics of the hydrothermal synthesis of gallosilicate (MFI) zeolite (under autogeneous pressure at 180°C) from a gel containing a source of silica (Na-trisilicate or fumed silica), gallium nitrate, templating agent (TPA-Br or TPA-OH), deionized water and sulfuric acid have been thoroughly investigated in order to understand the influence of various synthesis parameters (viz. gel composition, source of silica, template, method of gel preparation and pH of gel) on the crystallization kinetics and crystal size/growth of the zeolite. The zeolite samples were characterized for their crystallinity by XRD and crystal size and morphology by SEM. The crystallization rate and crystal size of the zeolite were found to be strongly influenced by the above synthesis parameters. © 1998 SCI     

Interfacial sol–gel processing for preparation of porous titania particles using a piezoelectric inkjet nozzle

The aim of the present work is to apply the liquid–liquid interfacial crystallization using a piezoelectric inkjet nozzle to the sol–gel processing. The instillation process was compared with the batch process to elucidate the effectiveness of the inkjet technique on the liquid–liquid interfacial sol–gel processing. The effect of frequency and water concentration in titanium tetraisopoxide (TTIP) solution on titania particle properties was investigated for sol–gel processing with a piezoelectric inkjet nozzle. Titania particles produced by each process were calcined at 500 °C. The crystal structure, morphology, pore size distribution and specific surface area of titania particles were evaluated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen physisorption measurement. The photocatalytic activity of titania particles was evaluated by the photodegradation of methylene blue solution under UVC light irradiation.     

超声波对铅膏湿法转化产物结晶形貌的影响

通过柠檬酸湿法工艺处理废旧铅酸蓄电池铅膏,浸出转化得到的前体柠檬酸铅结晶产物粒度较小,不易过滤。通过超声波的方式对柠檬酸铅的结晶过程加以控制,对处理前后的样品进行XRD、TG-DTA和SEM表征,对比超声波处理前后的柠檬酸铅晶体形貌变化。结果表明,经过超声波处理后,柠檬酸铅晶体由薄片状转变为长径比约为8∶1的柱状,柱状晶体长20～50 μm,超声波处理前柠檬酸铅晶体的粒度均小于5 μm。因此,超声波处理能够有效调控柠檬酸铅晶体的结晶形貌,改善柠檬酸铅前体的过滤性能,提高铅膏湿法转化的效率。     

Interfacial enhancement by shish-calabash crystal structure in polypropylene/inorganic whisker composites

The polymer matrix structure and the interface are strongly influenced by filler in semi-crystalline polymer composites because the fillers have the potential to nucleate the polymer crystallization. The structure of the nucleated crystalline polymer on filler is of particular interest and is a key to the interfacial enhancement. In this work, whiskers, with a large length/diameter ratio and with a diameter (0.2-2 μm) much larger than that of carbon nanotubes but much smaller than that of common fibers, were used to nucleate crystal morphology in polypropylene (PP)/whisker composites. The crystal morphology, interfacial adhesion and tensile properties of the composites were carefully investigated. A kind of peculiar shish-calabash crystallization morphology, with whisker serves as shish and PP spherulites serves as calabash, was observed for the first time in the thin film via PLM and in the injection molded bars by SEM. The formation mechanism of this shish-calabash structure was attributed to be that only a few nuclei could be induced on the whisker surface, which develop into large PP spherulites without hindrance, and finally stringed by the whisker, forming the shish-calabash structure. As a result, a significant improvement of interfacial interaction and tensile properties has been achieved.     

FOX-7晶体的制备和热性质

为了解FOX-7晶体形状和尺寸对其热性质的影响,通过冷却结晶和阻溶剂结晶的方法从DMF/H2O、NMP/H2O体系中获得FOX-7晶体.SEM结果表明,得到的晶体基本为延长的四面或六面棱柱和斜方菱晶两种类型,不同溶剂体系中得到晶体的尺寸不同和包含的颗粒数量也不同,超声处理得到的晶体具有单一形状,只是其表面较粗糙.DSC测试结果表明,不同结晶方式和不同溶剂体系中获得的FOX-7晶体的热性质有一定的差别.由此得出,不同的结晶方式和溶剂体系可以获得不同形状、尺寸和热性质的FOX-7晶体,而超声处理可以很好地控制晶体的形状.     

Computer modeling of isothermal crystallization in short fiber reinforced composites

Computer modeling and simulation for the isothermal crystallization of short fiber reinforced composites with athermal nucleation is presented. The “pixel coloring” technique which is capable of capturing the morphology evolution and calculating the crystallization kinetics is implemented. A parametric study is used to explore the influences of fibers on the crystallization in the reinforced system. The results indicate that the fibers depress the crystallization rate when compared to that of neat polymers or accelerate the crystallization rate by providing nucleation sites. The constraining effect is mainly dependent on fiber content while the enhancing effect is mainly determined by fiber surface and fiber nucleation density. Fiber orientation has almost no effect on the crystallization kinetics but changes the ultimate morphology. Fiber length and fiber diameter have different influences on crystallization kinetics and mean size of spherulites. Results show that fiber diameter affects the crystallization much more than that of fiber length.