凝胶-溶胶法制备单分散菱柱形草酸镍的研究

以Ni(OH)2凝胶为前驱体.采用凝胶-溶胶法制备了单分散菱柱形二水草酸镍.采用SEM,XRD 等方法及Imagetool图像分析软件,对所制备的NiC2O4·2H2O粉末形貌及形成机理等进行了研究,结果表明,控制适当条件,可使NiC2O4·2H2O颗粒在低过饱和度下均匀生长,其形成机理为溶解-再结晶;随温度升高,粉末...     

燃料电池硅钨酸掺杂有机硅质子交换膜

为了寻找质优价廉且易于制备的新型聚合物来取代现用价高难制备的全氟磺酸聚合物作为质子交换膜燃料电池(PEMFC)的质子交换膜(PEM),达到大幅度降低PEMFC成本的目的,以具有环氧乙烷结构的有机硅烷为原料,采用低温溶胶-凝胶法再配之以掺杂无机杂多酸硅钨酸的方法来制备新型有机-无机复合型质子交换膜,并采用红外光谱(FI-IR)、X射线衍射(XRD)、阻抗分析等实验方法对膜的结构和电性能进行了较深入地研究。研究结果表明,所制备的硅钨酸掺杂的有机硅聚合物分子中存在聚氧乙烯(PEO)结构,掺杂的硅钨酸(STA)通过分子间的化学键作用镶嵌在聚合物的内部;所制备的含有30%STA的硅钨酸掺杂有机硅聚合物质子交换膜在100℃的质子传导率为2.0×10-2S/cm,与市售Nafion115膜的性能基本相当。     

羧基化碳纳米管增强的杂化超分子水凝胶及其物理性能

通过物理交联方法制备了含羧基化碳纳米管(CNTs-COOH)的杂化超分子水凝胶,采用透射电子显微镜(TEM)观察样品的微观形貌,探究了碳纳米管的引入对凝胶的溶胀性、凝胶-溶胶转变温度和力学性能的影响。结果显示,与初始纯凝胶相比,质量分数2.5%的碳纳米管的引入不但没有改变凝胶的初始形貌和微观结构,反而提高了其凝胶-溶胶转变温度,且凝胶的力学性能也明显得到增强。进一步研究表明,制备的杂化水凝胶依然具有超分子水凝胶的基本特性,特别是剪切变稀、温度响应性和自恢复特性。     

Effects of Salts on the Thermal Reversibility of Starch and Hsian-tsao (Mesona procumbens Hemsl) Leaf Gum Mixed System

ABSTRACT: Two-cycle rapid-visco analysis was performed on the admixture of 1% hsian-tsao leaf gum and 2% wheat starch as a function of salt types and concentrations. The salt concentrations (C_s) studied were 5 to 75 mM for sodium and potassium chloride, and 3.4 to 8.5 mM for calcium and magnesium chloride. The gelling temperature, gelling rate and gel viscosity of the mixed system increased with increasing C_s. In addition, the melting temperature increased, but melting rate and percentage of viscosity loss decreased with increasing C_s. These results indicated the presence of appropriate amount of salts could facilitate and reinforce the formation of junction zones, and provided a more pronounced thermal resistance.     

Low-fat akawi cheese made from bovine-camel milk blends: Rheological properties and microstructural characteristics

Camel milk (CM) can be used as an ingredient to produce various dairy products but it forms weak rennet-induced and acid-induced gels compared with bovine milk (BM). Therefore, in this study, we aimed to investigate the effect of blending bovine milk with camel milk on the physicochemical, rheological (amplitude sweep and frequency sweep), and microstructural properties of low-fat akawi (LFA) cheese. The cheeses were made of BM only or BM blended with 15% (CM15%) or 30% (CM30%) camel milk and stored at 4°C for 28 d. The viscoelastic properties as a function of temperature were assessed. The LFA cheeses made from blended milks had higher moisture, total Ca, and soluble Ca contents, and had higher pH 4.6–water-soluble nitrogen compared with those made from BM. Analysis by scanning electron microscopy demonstrated that the microstructures formed in BM cheese were rough with granular surfaces, whereas those in blended milk cheeses had smooth surfaces. Hardness was lower for LFA cheeses made from blended milk than for those made from BM only. The LFA cheeses demonstrated viscoelastic behavior in a linear viscoelastic range from 0.1 to 1.0% strain. The storage modulus (G′) was lower in LFA cheese made from BM over a range of frequencies. Adding CM reduced the resistance of LFA cheeses to flow as temperature increased. Blended cheeses exhibited lower complex viscosity values than BM cheeses during temperature increases. Thus, the addition of camel milk improved the rheological properties of LFA cheese.