Ce3(PO4)4在酸性溶液加热条件下化学形态转化及机理研究

磷酸高铈(Ce3(PO4)4)是一种难溶于水的化合物,本文测定磷酸高铈在常温pH=0.4的Ksp值为1~8×10-34,但在测定过程中发现Ce3(PO4)4的溶解度受温度变化的影响较大,尤其在50℃以上时,Ce3(PO4)4饱和溶液体系中的Ce4 、PO43-和pH值均变化异常。根据测得的Ce4 、PO43-浓度以及pH值,推断出50℃以上时Ce3(PO4)4转化为Ce(HPO4)2,并建立了相应的转化机理,测定出Ce(HPO4)2的Ksp为3~7×10-13。     

Rheology and gelation of cellulose/ammonia/ammonium thiocyanate solutions

Liquid crystalline solutions of cellulose in an ammonia/ammonium thiocyanate solvent will form thermoreversible gels at temperatures below 30°C. These gels are of interest both for processing the cellulose/ammonia/ammonium thiocyanate system and because they have an unusual structure, containing neither crystalline nor covalently bonded crosslinks. Although these gels contain neither crystalline nor covalently bonded crosslinks, the dynamic rheological behavior of the system at the gel point was found to be the same as for gels with covalent or crystalline crosslinks with a loss tangent, tan δ, independent of frequency. The kinetics of the gelation process was monitored via dynamic elastic modulus, G′. All samples revealed an exponential increase in G′ with time during gelation, very different from that observed in covalently bonded or crystalline crosslinked systems. Measurements of the loss tangent enabled precise determination of the gelation time for these systems as a function of cellulose concentration and temperature. We found the gel time to be inversely related to cellulose concentration and directly related to temperature. The strong dependence of gel time on these parameters offers a windows of spinnability that can be tailored for processing high modulus cellulose fibers. © 1996 John Wiley & Sons, Inc.     

Photopolymerization studies of alkyl and aryl ester derivatives of ethyl α-hydroxymethylacrylate

Several new benzoate ester derivatives of ethyl α-hydroxymethylacrylate were synthesized using phase transfer catalysis and found to display unexpectedly rapid photopolymerization; i.e., from 2 to 8 times faster than MMA. New derivatives described here include the 4-fluoro-, 4-trifluoromethyl-, 4-methyl-, 2-hydroxy-, 4-nitro-, 4-methoxy-, 4-cyano-, and 3,4,5-trimethoxybenzoate esters along with the parent benzoate ester. Relative reactivities of these monomers in photopolymerizations were compared with those of the nonaromatic formate, acetate, hexanoate, and stearate derivatives. Reactivities of the nonaromatic ester derivatives increased with the length of the side chain while for the more reactive aromatic esters, rates increased in the order 4-methyl-, 4-fluoro- and benzoate < 4-trifluoromethyl- and 2-hydroxy- < 4-cyano- < 4-methoxy- < 3,4,5-trimethoxybenzoate. T_gs of the benzoate polymers ranged from 125°C for the 4-fluoro to 163°C for the 4-cyanobenzoate while those of the alkyl ester derivatives ranged from 15 to 78°C. Number average molecular weights of photoinitiated polymers (ca 10,000–20,000) were lower than those found for bulk and solution polymers (20,000—708,000) consistent with higher radical concentrations from photoinitiation. These materials greatly expand the number of candidates available for rapid photocure in thin film and coating applications, especially because their physical properties are those of linear rather than highly crosslinked structures formed from multifunctional systems. © 1996 John Wiley & Sons, Inc.     

改性壳聚糖质子交换膜在隔膜电解制备FeO42-中的应用

由壳聚糖,经2%H2SO4交联处理、1%H2SO4掺杂制备壳聚糖质子交换膜.膜特性(如溶胀率、交换容量、渗透性、电解隔膜等)测试表明,该壳聚糖膜可适用于隔膜电解制备高铁酸盐.与Nafion膜相比,具有工艺简便,价格便宜等优点.     

电解质对锂离子电池正极材料界面特性的影响

研究L iPF6、L iC lO4和L iBF43种电解质对L iCoO2材料界面特性的影响.结果表明:化成后的L iCoO2表面存在固态电解质膜(SEI膜);在不同成分的电解液中,L iCoO2表面SEI膜的形成电位、形貌特征以及材料的可逆容量、平均放电电压和电化学反应阻抗不同.     

二次概周期系数微分方程的概周期解

利用指数二分性,Schauder不动点定理和Grownwall不等式证明了一类概周期系数微分方程的概周期解、有界解的存在唯一性及概周期解的全局吸引性.     

正整数的一类三分拆的应用

利用正整数n的一类特殊的3分拆n=n1+n2+n3,n1>n2>n3≥1,且n2+n3>n1的Ferrers图将不定方程4x1+3x2+2x3=n(n≥9)的正整数解与这种分拆联系起来,从而得到了该不定方程的正整数解数公式;同时也给出了正整数n的一类4分拆的计数公式.此外,还给出了周长为n的整边三角形的计数公式的一个简单证明.     

Boussinesq方程行波解的存在性

利用平面动力系统方法的分支理论,研究了Boussinesq方程,通过对Boussinesq方程进行行波变换,得到了相应行波系统的首次积分和平衡点,给出了不同参数条件下的相图,证实了Boussinesq方程存在孤立波解和周期波解。     

序线性空间中向量优化问题的K-T型定理

本文在广义凸性条件下,研究实线性空间中一类向量优化问题的最优性条件,我们引入F ritz-John鞍点,、“K-T鞍点”讨论它们与有效解、弱有效解之间的关系.     

具有Holling Ⅲ类功能反应捕食者食脉冲系统正周期解的存在性

利用重合度理论中的连续性定理研究一类具有Holling Ⅲ类功能反应捕食者食脉冲系统正周期解的存在性, 建立了存在正周期解的充分条件, 推广 并改进了已有的相关结果.