Fine particle physics and technology; some results

The new techniques of fine particle synthesis are shown to lead to better ceramic materials such as yttrium iron garnet (YIG) and ferroelectric lead zirconate titanate (PZT). The densities are greater than 99% of the theoretical density and the grain size can be easily controlled from 2 microns upwards. For YIG this means higher values of the nonlinear spin-wave excitation thresholdh _c. For PZT the result is higher values of the tensor componentd ₃₃ and poling voltage. It is also shown that the fine particle systems and the fine-grain microstructure lead to interesting physics results. For PZT the lowering of the peak dielectric constant, the increasing transition temperatures and the decreasing values ofd ₃₃ with decreasing grain size can be understood in terms of the changing low-frequency cut-off of the soft lattice vibration mode. Another interesting result is that for 2000 Å size particles of α-Fe₂O₃ the anisotropy constant is found to be 1·38 × 10² ergs/cm³ from Mössbauer measurements.     

莫来石/SiO2复合涂层的制备及微观组织研究

以天然红柱石为原料,采用高温煅烧使其发生莫来石化转变,然后经喷雾造粒、热处理,得到热喷涂用球形莫来石/SiO2复合粉末.采用大气等离子喷涂工艺在1Cr18Ni9Ti不锈钢上喷涂莫来石/SiO2粉末制得涂层,对涂层的微观组织、硬度和相成分进行了分析.研究结果表明:天然红柱石粉末莫来石化后,其相组成主要为莫来石和游离态SiO2喷雾造粒粉末在1 000℃热处理后,松装密度得到改善;涂层具有良好的微观形貌,表面显微硬度较高,主要由莫来石、石英和非晶玻璃相构成.     

喷雾干燥荔枝固体饮料制备工艺及配方研究

研究了喷雾干燥荔枝固体饮料的工艺配方,实验以荔枝汁为原料,麦芽糊精、蔗糖、羧甲基纤维素钠(CMC)、β-环状糊精为辅料,利用均质与喷雾干燥相结合的工艺制成荔枝固体饮料。试验得到荔枝固体饮料的最佳配方为:荔枝汁65%、麦芽糊精27.55%、β-环状糊精2.30%、CMC 0.15%、蔗糖含量为5%。     

纳豆菌微生态制剂加工中两种干燥方法的比较

本文比较了加工纳豆菌微生态制剂过程中真空冷冻干燥和喷雾干燥两种工艺对制剂活菌数、纳豆激酶活力及纳豆菌存活率的影响,结果表明:两种干燥方法下制剂最高活菌数分别可达1.21×109CFU/g和0.96×109CFU/g,最高存活率分别为84.71%和67.49%,最高酶活力分别为11516.58IU/g和7203.96IU/g。     

Supercritical fluid extraction of encapsulated oil products

Standard methods of oil analysis, for example, Soxhlet extraction and supercritical fluid extraction (SFE), were ineffective for recovering oil from encapsulated food products. Efforts were made to enhance SFE of the oil for these products. Samples were hydrated and heated, which helped to break down the encapsulating structure. In addition, extra diatomaceous earth was needed to absorb and disperse the added water. Optimal extraction conditions were established, and quantitative extraction of oil was achieved for various laboratory-prepared and commercially encapsulated food products.     

喷雾干燥-流化床脱硝法制备Bi系超导前驱体粉末

介绍了一种制备2212相Bi系超导前驱体粉末的新方法.首先,将组成为Bi:Pb:Sr:Ca:Cu=1.84:0.34:1.91:2.03:3.06的五种金属硝酸盐混合溶液通过喷雾干燥得到混合硝酸盐粉末蓝粉,喷雾干燥的溶液浓度按Bi3 浓度表示为0.34 mol·L-1,干燥器进出口空气温度分别为563和413K.然后蓝粉在流化床中700℃下进行脱硝得到褐粉,脱硝过程为扩散控制.最后褐粉经800℃焙烧48 h后得到Bi系2212相超导前驱体粉末黑粉.研究确定了各阶段粉末形成的最佳工艺条件,通过粒度分析仪、SEM和XRD等测试手段表征了粉体的形貌和晶型特征,观察了粉末由非晶型到2212相的变化过程.结果表明,新方法所制得的黑粉具有明显的2212超导相片层状结构和特征晶型,符合Bi超导材料对前驱体粉末的要求.     

Red ginseng extract capsule fabricated using W/O/W emulsion techniques

The objective of the present study was to investigate the physicochemical characteristics and storage stability of water-in-oil-in-water (W/O/W) emulsions and spray-dried red ginseng extract capsules (RGEC) prepared using different secondary coating materials such as maltodextrin (MD), whey protein concentrate (WPC), or arabic gum (AG). The particle sizes of W/O/W emulsions and spray-dried RGEC coated with MD were considerably lower than those of W/O/W emulsions and spray-dried RGEC coated with WPC or AG. The zeta-potential value (?36 mV) of spray-dried RGEC coated with MD was significantly higher than that of spray-dried RGEC coated with WPC or AG (p < 0.05), indicating that spray-dried RGEC coated with MD were much more stable than spray-dried RGEC coated with WPC and AG. In the storage stability study, it was found that the refrigerator temperature (4°C) was preferred for storing spray-dried samples for a long time. Based on these results, it was confirmed that MD could be the most efficient coating material for W/O/W emulsions and nano-sized spray-dried RGEC.     

速溶茶的研制

将绿茶粉粉碎并经过正交试验确定影响茶叶固形物浸提的主要影响因素，再通过离心分离、真空浓缩、喷雾干燥等工艺，研究出保持了茶叶风味特色、饮用方便的速溶茶。经研究确定水浸提茶叶固形物主要影响因素：浸提温度为60℃，浸提时间为15min，浸提水量为18mL/g茶叶，浸提率达29％。浸提时结合超声波处理，固形物浸提率达到31％。     

猕猴桃籽油的微胶囊化研究

以超临界CO2萃取猕猴桃籽油并对其进行微胶囊化研究。结果表明:猕猴桃籽油微胶囊配方中对产品包埋率的影响大小顺序为,芯材与壁材配比>壁材配比(阿拉伯胶/麦芽糊精)>料液浓度;正交试验所得微胶囊最佳配比为,阿拉伯胶和麦芽糊精质量比为2∶1,芯材与壁材质量比为1∶3,料液质量分数为25%;所得微胶囊产品的包埋率为70%,微胶囊化处理后氧化稳定性显著增强。经最佳配比和工艺制成的猕猴桃籽油微胶囊产品的外形颗粒较圆整,大小分布均匀,表面光滑。