干燥技术在制备纳米粉体中的应用

由于纳米粒子的表面效应,用湿法制备出的纳米粉体的前躯体在干燥过程中极易形成团聚,已经不能采用传统的干燥方法。根据粉体干燥的理论,阐述了纳米粉体干燥过程的团聚机理,综述了微波干燥法、超临界干燥法、冷冻干燥法、共沸蒸馏法、喷雾干燥法等在制备纳米粉体中的应用,并指出了各种方法的优缺点。     

微波干燥技术在纳米材料制备中的研究进展

湿化学法是制备纳米材料的一种重要方法,但采用湿化学法制备的纳米粉体均存在干燥的过程,干燥方法的选择将对材料最终性能将产生明显的影响。微波干燥技术是最近发展而来的一种新型干燥技术,作者对几种微波干燥的模型以及微波干燥制备纳米粉体的进展作了说明。     

纳米粉体干燥方法的研究进展

由于纳米粒子的表面效应，用湿法制备出的纳米粉体的前驱——胶体的干燥已不能采用传统的干燥方法。根据胶体干燥的理论，阐述了纳米粉体干燥过程的团聚机理，并综述了纳米粉体在超临界干燥、共沸蒸馏、真空冷冻干燥、微波干燥等干燥领域的研究进展。     

微波干燥技术在纳米材料制备中的研究进展

湿化学法是制备纳米材料的一种重要方法，但采用湿化学法制备的纳米粉体均存在干燥的过程，干燥方法的选择将对材料最终性能将产生明显的影响。微波干燥技术是最近发展而来的一种新型干燥技术，作者对几种微波干燥的模型以及微波干燥制备纳米粉体的进展作了说明。     

超临界流体干燥技术在纳米粉体制备中的应用

由于纳米粒子的表面效应，用传统的干燥方法干燥纳米粉体时极可能产生团聚结构。超临界流体干燥技术是制备具有高比表面积、孔体积、较低密度和低热导率的块状气凝胶和纳米粉体的重要途径之一。介绍了超临界流体的性质、超临界流体干燥技术的研究进展、超临界流体干燥的工艺与设备及过程的影响因素，阐述了超临界流体干燥技术在纳米材料制备中的应用，并指出了超临界流体干燥过程的控制技术及注意点，为进一步加强超临界流体干燥技术的理论研究和拓展超临界流体干燥技术的应用领域奠定了基础。     

溶胶-凝胶法制备纳米粉体的研究进展

介绍了用溶胶-凝胶法制备纳米粉体的工艺方法,并讨论了它的影响因素。从制备纳米粉体时防团聚的干燥技术和化学改性法等方面介绍了溶胶-凝胶法制备纳米粉体的研究进展。     

吸水树脂-冷冻复合干燥法制备纳米碳酸钙粉体

湿法工艺制备的纳米材料悬浮液在后处理过程中常发生团聚现象,严重影响纳米粉体材料的性能。本文提出了一种吸水树脂脱水与冷冻干燥相耦合的复合干燥方法,以纳米碳酸钙浆料的干燥过程为研究对象,考察了复合干燥方法对制备的纳米粉体材料性能的影响。研究结果表明,采用该复合干燥方法,可以制得无团聚、分散性能好的粉体产品,且在吸水树脂处理阶段,浆料的脱水率最大可达到78%左右,可以大幅降低后续冷冻干燥过程的能耗。本文同时研究了吸水树脂干燥时间、外部压力、吸水树脂用量和吸水袋面积等因素对干燥过程脱水率的影响规律。     

纳米氯化银光催化降解亚甲基蓝性能的研究

气液沉淀法制备了氯化银胶体和纳米粉体,并研究了其在紫外光下对亚甲基蓝的催化降解性能。结果表明:氯化银纳米粉体对亚甲基蓝溶液的催化降解效率明显高于胶体氯化银。通过动力学分析,胶体氯化银的光催化过程符合拟一级反应动力学,而氯化银纳米粉体的光催化过程符合双曲线动力学模型。在多次降解实验中,氯化银纳米粉体重复催化效果较好,具有较高的稳定性。     

超细二氧化锆干燥方式探讨

介绍了几种常用的制备纳米粉体的干燥方法。研究了水热反应制备二氧化锆粉体过程中，直接干燥法、共沸蒸镏和超临界干燥3种常用的干燥方法对最终产品粒子大小和微观形态的影响。通过比较，直接干燥法制备的纳米粒子粒径大于100nm，而采用共沸蒸馏和超临界干燥制得的粉体分散性好，可制备出粒径小于10nm的粉体。因此，共沸蒸馏和超临界干燥法是良好的干燥方法。     

纳米颗粒干燥方法的研究进展

由于纳米粒子的表面效应，用湿法制备出的纳米粉体的前驱-胶体的干燥已不能采用传统的干燥方法。本文根据胶体干燥的一般理论，综述了纳米颗粒干燥方法的研究进展。     

Preparation of Silver Nanopowder by Freeze-Drying Procedure

A freeze-drying procedure is developed for manufacturing silver nanopowder with regular shape and uniform diameter. The procedure includes four steps: preparing the precursor solution, freezing the solution, drying the congelation, and calcining the drying product. The starting substances are silver nitrate and caustic soda and the precursor is diammine silver solution. Three freezing styles including direct freezing, vacuum evaporation freezing, and spray freezing are adopted to freeze the precursor solution. In the drying stage, two heating styles for the frozen solution are compared. X-ray diffraction (XRD) and energy disperse spectroscopy (EDS) spectrograms show that the products of freeze drying are pure amorphous silver nanopowder without hard agglomerations. Silver cubic nanocrystals are subsequently obtained by calcination. The chemical fundamentals and the drying curves of freeze drying are given. The processes of preparing silver nanopowder are described in detail. The effect of freezing and heating on characteristics of the powder are discussed. The mechanism of grain forming and growing up is analyzed according to the observation results. The characteristics of powder freeze drying and its feasibility for volume production are presented.     

Preparation of polysaccharide solutions for electron microscope investigations of supermolecular morphologic formations of the solid component

A new preparation process, which preserves the original morphological state of polysaccharides in solution during removal of the solvent and so makes possible direct electron microscope investigations, has been developed. The process consists of lyophylization of the sample (in very low concentration of water solution) by freeze-drying, modified for the purpose of electron-microscopic examination. Water-soluble mixture of the polysaccharides of hemicelluloses isolated from the wood tissues of beech and the water solution of the mannan from Saccharomyces cerevisieae treated by means of the new preparation process (preparation with freeze-drying) and, for comparison, these same samples treated without the application of freeze-drying (by means of drying at laboratory temperature and atmospheric pressure, standard preparation process) are introduced as instance from many polysaccharides electron microscopic examined after this preparation process. This method allows one to make direct electron microscope investigations of the water-soluble polysaccharides in no way stained or otherwise shadowed with good resolutions of details in the supermolecular range.     

液相水解法制备纳米二氧化钛粉体及工艺研究

以四氯化钛和正辛醇为原料,通过液相水解法制备纳米二氧化钛粉体。重点讨论了原料配比、碳酸铵饱和溶液温度、焙烧温度等因素对制备工艺的影响。通过XRD、SEM对纳米粉体的形貌、晶型、粒径进行了表征对比,并结合二氧化钛粉体制备的产率,确定了最佳工艺参数:四氯化钛∶正辛醇=1∶4(质量比),碳酸铵饱和溶液温度为50℃,真空干燥温度为110℃,焙烧温度350℃,焙烧时间3 h。并制备出粒径约为12 nm、比表面积为229.77 m2/g的纳米二氧化钛粉体。     

辅酶A的冻干工艺及其性状结构

引言辅酶A(coenzyme A,CoA)是生物体内乙酰化酶的辅酶,也是人体内最重要的酶之一,参与三羧酸循环,起着传递乙酰基的作用,对糖、蛋白质和脂类的代谢起重要作用[1-2]。大量的研究证明辅酶A能促进脂类的正常代谢,抑制过氧化脂质的形成,阻止血小板的凝集,防止胆固醇在血管壁的     

吸湿多孔介质冷冻干燥传质传热模型

本研究在作者提出的吸附—解吸平衡关系的基础上,建立了一个全新的考虑吸湿效应的多孔介质冷冻干燥数学模型。模型用有限差分法进行求解,并带有一个移动边界,以模拟介电材料辅助的微波冷冻干燥过程。介电材料选用碳化硅（SiC）,原料液为脱脂奶。模拟结果表明：介电材料能够有效强化微波冷冻干燥过程。在典型操作条件下,介电材料辅助的微波冷冻干燥所用的时间比普通微波冷冻干燥减少33.1%。当料液中固体含量较低或者固体产品的损耗因子较小时,介电材料对微波加热的效果不明显。基于冰饱和度、温度和水蒸气浓度的分布,本文分析了干燥过程中的传质传热机理,并对干燥速率控制因素进行了讨论。     

大鲵糖肽溶液共晶点及冷冻浓缩过程研究

在制备大鲵糖肽干粉过程中,其溶液浓度较低,导致其冷冻干燥速度较慢。为了提高大鲵糖肽冷冻干燥速度,需要研究它的共晶点、冻融过程以及冷冻浓缩过程。采用电阻法测定了共晶点。结果表明：大鲵糖肽溶液共晶点为-3.6℃,缓慢融化时溶液中大鲵糖肽浓度逐渐降低,搅拌速度对大鲵糖肽溶液冷冻浓缩效果影响较小。     

Heat and mass transfer model of dielectric-material-assisted microwave freeze-drying of skim milk with hygroscopic effect

A new porous media mathematical model for freeze-drying was developed based on the adsorption-desorption relationship proposed in this paper. A finite difference solution was obtained from a moving boundary problem for the dielectric-material-assisted microwave freeze-drying process. Silicon carbide (SiC) was selected as the dielectric material; and frozen skim milk was used as the aqueous solution to be dried. Simulation results showed that the dielectric material can significantly enhance the microwave freeze-drying process. The drying time was 33.1% shorter than that of ordinary microwave freeze-drying under typical operating conditions. When the solid content of the solution to be freeze-dried was very low, or the solid product had a very small loss factor, microwave heating was less effective without the assistance of dielectric material. The mechanisms of heat and mass transfer during drying were analyzed based on profiles of ice saturation, temperature and vapor concentration. Drying rate-controlling factors were discussed. A comparison was made between the model predictions and the reported experimental data.     

Synthesis and characterization of bioactive forsterite nanopowder

Forsterite ceramic is a new bioceramic with good biocompatibility. However, the degradation rate of forsterite ceramic is extremely low, and the apatite-formation ability is also poor. On the other hand, nanostructured bioceramics are expected to have better bioactivity than coarser crystals. The aim of this work was preparation, characterization and bioactivity evaluation of forsterite nanopowder. Forsterite nanopowder was synthesized by the sol–gel process. Bioactivity evaluation was preformed by immersing the forsterite powder in the simulated body fluid (SBF) and apatite formation on the surface of the immersed forsterite nanopowders was investigated. Results showed the particle size of pure forsterite was 25–45 nm. During immersion in SBF, the dissolution rate of the forsterite nanopowder was higher than conventional forsterite powders and apatite was formed after soaking for 14 days. Our study indicated that forsterite nanopowder unlike micron-sized forsterite possessed apatite-formation ability and might be used for preparation of new biomaterials.     

Effect of surfactants on synthesis of TiO2 nano-particles by homogeneous precipitation method

TiO₂ nanopowder was synthesized by a homogeneous precipitation process, with industrial titani-ferous solution and urea as primary materials. The effects of different surfactants on the surface tension of the titani-ferous solution was investigated. The influence of surfactant amount on the particle size and morphology was also examined. The results show that the surfactants have their optimum additive amount, with which the nano-scale particles with smaller size and better shape can be prepared. Moreover, it is indicated that the combined use of various surfactants is more effective for the preparation of nano-scale TiO₂ particles, compared to the use of sole one surfactant.     

酒石酸吉他霉素冻干法研究

虚用冻干法制备酒石酸吉他霉素,比用喷干法制备的成品收率高,成本低,流动性好,溶解速度快,残留溶媒低,其理化指标符合标准规定因此,通过测定成品酒石酸吉他霉素效价、色级等理化指标,对成盐工艺、冻干曲线进行优化选择。