悬浮液进样-火焰原子吸收光谱法测定茶叶中的微量铬

将茶叶悬浮于琼脂胶体中制成悬浮液 ,直接喷入空气 -乙炔火焰 ,用火焰原子吸收光谱法测定茶叶中的微量铬 ,方法简便、快速、灵敏度和精密度高、测定结果与用灰化法处理样品一致 ,检验表明 ,两种样品前处理方法之间无显著性差异。相对标准偏差为 3.4 %～ 6 .1% ,加标回收率为 95 .7%～ 10 3.8 %。     

烧结法制备微晶玻璃过程中晶化和致密化两种典型的关系

以钢渣和粉煤灰为主要原料,采用烧结工艺,制得以透辉石为主晶相的微晶玻璃;通过热分析、X射线衍射、收缩率、扫描电镜等分析方法,阐述了烧结过程中晶化和致密化的关系;详细说明了由于在微晶玻璃热处理过程中二者发生的先后顺序不同,而使微晶玻璃结构和性质不同。     

聚丙烯／轻质碳酸钙／三单体固相接枝物复合体系结构与性能的研究

将聚丙烯与马来酸酐、甲基丙烯酸甲酯、丙烯酸丁酯三种单体的固相接枝物应用于聚丙烯侥质碳酸钙复合体系，研究接枝物对复合体系力学性能、微观形态和耐热性等的影响。结果表明，在PP中加入CaCO3进行填充改性，在一定用量的三单体固相接枝物作用下，PP的力学性能及耐热性得到明显的提高。     

ABA triblock copolymers from poly(p‐dioxanone) and poly(ethylene glycol)

Poly(p‐dioxanone)–poly(ethylene glycol)–poly(p‐dioxanone) ABA triblock copolymers (PEDO) were synthesized by ring‐opening polymerization from p‐dioxanone using poly(ethylene glycol) (PEG) with different molecular weights as macroinitiators in N₂ atmosphere. The copolymer was characterized by ¹H NMR spectroscope. The thermal behavior, crystallization, and thermal stability of these copolymers were investigated by differential scanning calorimetry and thermogravimetric measurements. The water absorption of these copolymers was also measured. The results indicated that the content and length of PEG chain have a greater effect on the properties of copolymers. This kind of biodegradable copolymer will find a potential application in biomedical materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1092–1097, 2006     

Effect of high polymerization temperature on the microstructure of isotactic polypropylene prepared using heterogeneous ticl4/mgcl2 catalysts

The effects of alkylaluminum and polymerization temperature on propylene polymerization without an external donor in the use of a TiCl₄–MgCl₂–diether(BMMF) catalyst were investigated. The results indicated that with increasing polymerization temperature the concentrations of [mmmm] of heptane‐insoluble poly(propylene) (PP) fraction increased. Crystallization analysis fractionation (CRYSTAF) results showed the fractions of different crystallization temperatures were changed according to various polymerization temperatures. The activity with Et₃Al as cocatalyst at 100°C was much lower than that at 70°C. However, the activity with i‐Bu₃Al at 100°C was as high as that at 70°C. The fraction of high‐crystallization temperature of PPs obtained with i‐Bu₃Al increased with increasing polymerization temperature, which was opposite to that with Et₃Al, thus implying that the copolymerization of propylene with the monomer arising from Et₃Al led to the lower crystallization ability of PPs obtained with Et₃Al. The terminal groups of PP suggested that the chain‐transfer reaction by β‐H abstraction was the main chain‐transfer reaction at 120°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3980–3986, 2003     

Fe doping effect on EuTiO3: The magnetic properties and giant magnetocaloric effect

The magnetic properties and magnetocaloric effect for EuTi_1-xFe_xO₃ (x = 0.05, 0.1) compounds are investigated. When a part of Ti⁴⁺ions were substituted by Fe ions, the AFM ordering can be significantly changed to be FM. The EuTi_1-xFe_xO₃ (x = 0.05, 0.1) compounds exhibit a PM to FM transition with decreasing temperature and the Curie temperature is 6 K. Under the field changes of 1 T, and RC are valued to be 10.1 J/kg K and 50.2 J/kg for EuTi_0.95Fe_0.05O₃; 9.6 J/kg K and 47.7 J/kg for EuTi_0.9Fe_0.1O₃, without magnetic and thermal hysteresis. RC is almost twice as much as EuTiO₃ (27 J/kg) as substitution of Fe³⁺ ions for Ti⁴⁺ions, which may be attributed to the magnetic transition (AFM to FM). Therefore, the giant and large RC suggest the EuTi_1-xFe_xO₃ compounds are good materials for magnetic refrigerant.     

Synthesis and characterization of polystyrene initiated using polymeric peroxide

Polymer peroxides were synthesized by copolymerizing tert‐butyl‐3‐isopropenylcumylperoxide (D‐120) with styrene (St). Exothermic peak at 192.7°C in DSC thermogram indicated that peroxy bonds in D‐120 remained intact during the copolymerizing process. The polymeric peroxide was used to initiate polymerization of St. GPC results showed that polystyrene (PS) initiated by the polymeric peroxides was composed of both linear and branched molecules. In addition, the rheology test showed that PS samples initiated by polymeric peroxide contained branched structure and had lower shear viscosities. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 197–202, 2006     

十六烷基三甲基溴化铵对化学镀Co-Ni-P的影响

通过正交试验得到化学镀Co-Ni-P的优化基础配方(g.L-1)和施镀条件:CoSO4.7H2O为16、NiSO4.6H2O为9、NaH2PO2.H2O为30、Na3C6H5O7.2H2O为60、(NH4)2SO4为70,于pH=10、80℃施镀1 h;研究了阳离子表面活性剂十六烷基三甲基溴化铵对Co-Ni-P镀层成分以及镀层与基体结合力的影响。实验结果表明,在优化的基础配方中加入30 mg.L-1的十六烷基三甲基溴化铵,镀液稳定性好,沉积速率加快,镀层表面光亮,镀层与基体的结合力增强,镀层中钴含量增加,镍、磷含量降低,镀层的性能得到了很大的改善。     

橡胶行业9项标准2月1日开始实施

最近,国家质量监督检验检疫总局发布2006年第11号(总第98号)国家标准批准公告,其中涉及橡胶行业的9项标准均自2007年2月1日开始实施。     

滴状冷凝强化含不凝气的蒸气冷凝传热机制

为了深入考察滴状冷凝强化混合蒸气冷凝传热传质过程的作用机制，在竖直表面上设计了完全滴状（DWC）、没有液滴向下脱落运动的条形分割滴膜共存（DFC）和膜状（FWC）3种冷凝形态的实验表面。对纯蒸气及含不凝气蒸气的冷凝传热过程进行了分析和实验研究，结果表明纯蒸气滴状冷凝与滴膜共存冷凝传热特性相近；而对含不凝气的冷凝，滴膜共存表面与膜状冷凝表面的传热特性相近；不凝气摩尔分数分别为0.9%、4.8%时，滴状冷凝较其他两种形态下的冷凝传热系数提高了30%～80%。其主要原因是由于混合蒸气冷凝传热阻力主要由气相边界层控制，滴膜共存冷凝并没有使气相的扩散传质过程得到强化，而完全滴状冷凝与设计的滴膜共存冷凝的区别在于后者仅存在小液滴的合并运动而没有大液滴向下脱落和对表面冲刷过程。根据二者实验结果的分析，认为滴状冷凝的大液滴脱落运动是影响气相传质的主要因素，大液滴脱落过程对气相边界层的扰动和剪切作用强化了气液界面传热传质特性。