水溶性丙烯酸涂料的合成

制备了透明性高、光泽度好、附着力强、冲击强度高、成本低、污染小的水溶性丙烯酸涂料。讨论了共聚单体的含量、中和胺的种类和用量对乳液黏度、水溶性、稳定性等的影响。     

Synthesis and surface characterization of poly(methyl methacrylate)‐block‐polydimethylsiloxane copolymers from macroazoinitiator

Poly(methyl methyacrylate)‐block‐polydimethylsiloxane (PMMA‐b‐PDMS) copolymers with various compositions were synthesized with PDMS‐containing macroazoinitiator (MAI), which was first prepared by a facile one‐step method in our lab. Results from the characterizations of X‐ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM) showed that the copolymer films took on a gradient of composition and more PDMS segments enriched at the film surfaces, which then resulted in the low surface free energy and little microphase separation at the film surfaces. By contrast, transmission electron microscopy (TEM) analysis demonstrated that distinct microphase separation occurred in bulk. Slight crosslinking of the block copolymers led to much steady morphology and more distinct microphase separation, in particularly for copolymers with low content of PDMS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

增韧聚丙烯三元共混体阻燃性能的研究

研究了多种阻燃剂，包括Ｓｂ２Ｏ３、Ａｌ（ＯＨ）３、ＣＰＣ、ＤＢＤＰＯ对聚丙烯／高密度聚乙烯／乙丙橡胶（ＰＰ／ＨＤＰＥ／ＥＰＲ）三元共混体—增韧聚丙烯—阻燃性能的影响；阻燃剂间的协同作用；并探讨了阻燃机理。结果表明：１、ＡＬ（ＯＨ）３的重量含量超过４０％时，阻燃效果显著；２、三种阻燃剂（Ｓｂ２Ｏ３、ＤＢＤＰＯ、ＣＰＥ）并用，阻燃效果明显提高，含卤化合物（ＤＢＤＰＯ与ＣＰＥ）是Ｓｂ２Ｏ３重量的四倍时，阻燃性能最佳；３、Ｓｂ２Ｏ３与ＤＢＤＰＯ并用时，当Ｂｒ／Ｓｂ的摩尔比为３∶１时阻燃效果最好     

多孔催化剂效率因子的多组分扩散模型(Ⅴ) 表面中毒并伴有平衡死区圆柱状催化剂效率因子的有限元求解

针对表面中毒并伴有平衡死区二维圆柱状催化剂的反应-扩散偏微分方程组的特殊性,引入有限元方法求解该类问题,建立了求解步骤。实际计算所得效率因子与实验值对照表明,本法结果准确,过程简单,容易推广应用于各种相类似的体系。     

The atactic polystyrene molecular weight effect on the thermal properties and crystal structure of syndiotactic polystyrene/atactic polystyrene blends

This work examined how the molecular weight of atactic polystyrene (aPS) affects the thermal properties and crystal structure of syndiotactic polystyrene (sPS)/aPS blends using differential scanning calorimetry, polarized light microscopy and wide angle X-ray diffraction (WAXD) technique. For comparative purposes, the structure and properties of the parent sPS was also investigated. The experimental results indicated that these blends showed single glass transition temperatures (T_gs), implying the miscibility of these blends in the amorphous state regardless of the aPS molecular weight. The non-isothermal and isothermal melt crystallization of sPS were hindered with the incorporation of aPSs. Moreover, aPS with a lower molecular weight caused a further decrease in the crystallization rate of sPS. Complex melting behavior was observed for parent sPS and its blends as well. The melting temperatures of these blends were lower than those of the parent sPS, and they decreased as the molecular weight of aPS decreased. Compared with the results of the WAXD study, the observed complex melting behavior resulted from the mixed polymorphs (i.e. the α and β forms) along with the melting-recrystallization-remelting of the β form crystals during the heating scans. The degree of melting-recrystallization-remelting phenomenon for each specimen was dependent primarily on how fast the sPS crystals were formed instead of the incorporation of aPSs. Furthermore, the existence of aPS in the blends, especially the lower molecular weight aPS, apparently reduced the possibility of forming the less stable α form in the sPS crystals.     

A－6型甲胺催化剂的工业应用

Ａ－６型甲醇胺化制甲胺催化剂．液空速１１．７ｈ（－１）条件下考察５００ｈ，甲醇转化率９７．５２ｍｏｌ％，活性稳定，产物分布几乎不随时间变化．该催化剂已工业运转１５０天，转化率９８～９９ｍｏｌ％．Ｎ／Ｃ＝１．９５条件下产物粗肢中一、二、三甲胺分别为（ｗｔ％）：２９．２４、４０．７６和３０．００．     

Surface Modification of Titania Nanoparticles Using Ultrathin Ceramic Films

Surface modification of titania nanoparticles was achieved by coating them with ultrathin alumina films using atomic layer deposition. The coating process was performed in a fluidized bed reactor at low pressure and under mechanical vibration. Films were deposited using self-limiting, sequential surface reactions of trimethylaluminum and water. The composition of alumina-coated particles was verified using infrared spectroscopy. The deposited films had an average growth rate of 0.2 nm/coating cycle and were highly uniform and conformal as demonstrated by transmission electron microscopy and X-ray spectroscopy. Deposited alumina films were amorphous as verified through X-ray diffraction and high-resolution electron microscopy. The coating process did not promote particle sintering as validated via particle size and surface area analysis.     

ELECTROKINETIC EFFECTS: CARBONIC ANHYDRASE AND CO2 ELECTRODE DYNAMICS

It is well known that the dynamic response rate of the Severinghaus-type CO₂ electrode is improved significantly in some cases by addition of the enzyme carbonic anhydrase to the electrode assembly. Hysteresis in the response rate also is reduced. Experimental data and modelling results indicate that catalysis of the CO₂ hydration reaction in the bulk of the bicarbonate layer (the Nernst film) is not responsible for the improved response behavior, Evidence is presented to show that catalysis in the electrostatic double layer region at the glass electrode surface is a possible explanation. This proposed phenomenon may have widespread implications for the optimal design of analytical devices, commercial processes involving electrochemical phenomena, and may also provide insight into electrobiologi-cal processes.     

Effect of structural and electrochemical properties of different Cr-doped contents of Li[Ni1/3Mn1/3Co1/3]O2

Layered Li[Ni_(1−x)/3Mn_(1−x)/3Co_(1−x)/3Cr_x]O₂ materials with x = 0, 0.01, 0.02, 0.03, 0.05 are prepared by a solid-state pyrolysis method. The oxide compounds were calcined with various Cr-doped contents, which result in greater difference in morphological (shape, particle size and specific surface area) and the electrochemical (first charge profile, reversible capacity and rate capability) differences. The Li[Ni_(1−x)/3Mn_(1−x)/3Co_(1−x)/3Cr_x]O₂ powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry, and SEM. XRD experiment revealed that the Li[Ni_(1−x)/3Mn_(1−x)/3Co_(1−x)/3Cr_x]O₂ (x = 0, 0.01, 0.02, 0.03, 0.05) were crystallized to well layered -NaFeO₂ structure. The first specific discharge capacity and coulombic efficiency of the electrode of Cr-doped materials were higher than that of pristine material. When x = 0.02, the sample showed the highest first discharge capacity of 241.9 mAh g⁻¹ at a current density of 30 mA g⁻¹ in the voltage range 2.3–4.6 V, and the Cr-doped samples exhibited higher discharge capacity and better cycleability under medium and high current densities at room temperature.     

Low temperature solid-state synthesis routine and mechanism for Li3V2(PO4)3 using LiF as lithium precursor

Monoclinic lithium vanadium phosphate, Li₃V₂(PO₄)₃, has been successfully synthesized using LiF as lithium source. The one-step reaction with stoichiometric composition and relative lower sintering temperature (700 °C) has been used in our experimental processes. The solid-state reaction mechanism using LiF as lithium precursor has been studied by X-ray diffraction and Fourier transform infrared spectra. The Rietveld refinement results show that in our product sintered at 700 °C no impurity phases of VPO₄, Li₅V(PO₄)₂F₂, or LiVPO₄F can be detected. The solid-state reaction using Li₂CO₃ as Li-precursor has also been carried out for comparison. X-ray diffraction patterns indicate that impurities as Li₃PO₄ can be found in the product using Li₂CO₃ as Li-precursor unless the sintering temperatures are higher than 850 °C. An abrupt particle growth (about 2 μm) has also been observed by scanning electron microscope for the samples sintered at higher temperatures, which can result in a poor cycle performance. The product obtained using LiF as Li-precursor with the uniform flake-like particles and smaller particle size (about 300 nm) exhibits the better performance. At the 50th cycle, the reversible specific capacities for Li₃V₂(PO₄)₃ measured between 3 and 4.8 V at 1C rate are found to approach 147.1 mAh/g (93.8% of initial capacity). The specific capacity of 123.6 mAh/g can even be hold between 3 and 4.8 V at 5C rate.