Production and characterization of partially purified thermostable α-galactosidases from Streptomyces griseoloalbus for food industrial applications

Solid-state fermentation was carried out for the production of extracellular α-galactosidase by Streptomyces griseoloalbus. Soybean flour was the best solid substrate for α-galactosidase production. In flask-level optimization, the highest enzyme yield of 111 ± 0.2 U/gds was obtained under optimal conditions. The partially purified α-galactosidase preparation showed highest activity at pH 5.0 and 65 °C. The enzyme was completely stable at pH 5.0 to 7.0 and at 50 and 55 °C for 5 h. The t_1/2 of the enzyme at 65 °C was 3.5 h. The information obtained from the present investigation is advantageous for food industrial applications of S. griseoloalbus α-galactosidases.     

中高分子量聚乙二醇的热分析研究

本文利用热分析仪通过ＤＳＣ对所合成的中高分子量聚乙二醇（ＰＥＧ）进行了熔融过程的热力学参数（Ｔｍ、△Ｈｍ）测定，得出了其随分子量变化的规律，并利用其在氧化裂解过程中的热失重曲线（ＴＧ）进行动力学参数（Ｅ、ｎ、Ａ）测定和热稳定性的研究。     

固相法氯化聚乙烯脱HCl热稳定性研究

本文采用固相氯化法制备了各种氯含量的氯化聚乙烯（ＣＰＥ）并用氯化氢吸收法系统考察了氯化条件、氯含量对固相法ＣＰＥ热稳定性的影响。结果表明氯化温度对ＣＰＥ的热稳定性有较大影响，高温氯化可以提高ＣＰＥ的热稳定性。在一定范围内随氯含量增加，ＣＰＥ热稳定性也相应增大。对ＣＰＥ脱除ＨＣｌ前后红外光谱及凝胶含量变化的研究表明ＣＰＥ热分解过程伴有交联结构形成。     

Thermostability,oxidation, and high-temperature tribological properties of nano-multilayered AlCrSiN/VN coatings

In this study, monolithic AlCrSiN, VN, and nano-multilayered AlCrSiN/VN coatings were deposited using a hybrid deposition system combining arc ion plating and pulsed direct current magnetron sputtering. The microstructure, thermostability, mechanical, oxidation and tribological properties of the coatings were comparably investigated. The multilayered AlCrSiN/VN coating exhibited a face-centered cubic (fcc) structure with (200) preferred orientation and showed the highest hardness (30.7 ± 0.5 GPa) among these three coatings due to the multilayer interface enhancement mechanism and higher compressive stress. The AlCrSiN sublayers effectively prevented the V element from rapid outward diffusion to the surface of AlCrSiN/VN coating at elevated temperatures, which improved the oxidation resistance of the coating. Decomposition of V (Cr)–N bonds occurred at annealing temperatures from 800 °C to 1000 °C and V₂N phase appeared at 1100 °C. The AlCrSiN/VN coating showed excellent tribological performance at high temperatures by combining the merits of VN layers for low friction coefficient and AlCrSiN layers for superior oxidation resistance. Compared to VN and AlCrSiN coatings, AlCrSiN/VN coating showed the lowest wear rate of 2.6×10^-15 m³/N·m at 600 °C and lowest friction coefficient of 0.26 at 800 °C with a relativity low wear rate of 39.4×10^-15 m³/N·m.     

MC尼龙6/纳米TiO2原位复合材料性能研究

通过阴离子原位聚合法制备了MC尼龙6／纳米TiO2复合材料,采用透射电子显微镜观察了纳米TiO2在复合材料中的分散形态,并研究了纳米TiO2含量对复合材料的热稳定性和力学性能的影响。结果表明：在纳米TiO2质量分数低于2％时,纳米TiO2能较均匀地分散在复合材料中,对复合材料同时具有增强和增韧的作用;纳米TiO2的加入提高了复合材料热稳定性,使MC尼龙6的起始降解温度提高2～3℃,最大失重速率温度大幅度提高,并随纳米TiO2用量的增加而升高。     

石油树脂/聚氨酯防水材料热性能研究

以聚氨酯预聚体为基料,以石油树脂为改性剂,制备了石油树脂／聚氨酯防水材料;分析了石油树脂／聚氨酯防水材料的热降解过程,研究了石油树脂／聚氨酯防水材料的热降解动力学。根据求得的热降解活化能讨论了石油树脂含量对防水材料热稳定性的影响。结果表明,石油树脂／聚氨酯防水材料的热降解分为两个阶段,起始平衡降解温度是231．04℃,热降解机理符合Freeman—Carroll假设,防水材料的热稳定性随着石油树脂用量的增大而有所降低。     

Synthesis of polyguanamines from 2-N,N-dibutylamino-4,6-dichloro-1,3,5-triazine with aromatic diamines

Solution polycondensation of 2-N,N-dibutylamino-4,6-dichloro-1,3,5-triazine (BDCT) with various aromatic diamines, including 4,4′-oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), o-tolidine (oTD), 4,4′-(9-fluorenylidene)dianiline (BAFL), and 2,4-diamino-6-(N,N-dibutylamino)-1,3,5-triazine (DABT), was investigated. High molecular weight (>10,000) polyguanamines (PGs) were obtained via the polymerization of BDCT with ODA, pPDA, oTD, and BAFL at 150–180 °C in N-methylpyrrolidone (NMP) for 6 h. The polymerizability with BDCT was determined on the basis of the molecular weights of the polymers and the chemical shifts of the NMR data as follows: ODA > oTD > BAFL > pPDA > mPDA ? DABT. PGs were obtained from the reaction of BDCT with ODA and mPDA in only 55–77% yield, which may be attributed to the formation of cyclic oligomers. All of the polymers showed high thermostability (5% weight-loss temperature in N₂ greater than 444 °C), and the polymers generated from reaction of BDCT with ODA, mPDA, and BAFL exhibited good solubility in tetrahydrofuran and polar aprotic solvents such as NMP.     

Atomic structure and enhanced thermostability of a new structure MgYZn4 formed by ordered substitution of Y for Mg in MgZn2 in a Mg-Zn-Y alloy

A new phase MgYZn₄ in Mg-Zn-Y alloy was studied using aberration-corrected scanning-transmission electron microscopy and first-principles calculations. Nanometer-sized MgYZn₄ precipitates were formed through ordered substitutions of Y with 50% Mg atoms in MgZn₂. MgYZn₄ has an orthorhombic structure with a space group of Pmnn, and lattice parameters a =5.2965 Å, b =9.4886 Å, and c =8.5966 Å. Importantly, both size and structure of MgYZn₄ are stable at 625 K for 5 h, showing higher thermostability than MgZn₂, which should be important for applications at elevated temperatures. The enhanced thermostability of MgYZn₄ is attributed to the lower formation energy and bonding enhancement due to Y substitution.     

Synthesis of mesoporous alumina TUD-1 with high thermostability

Mesoporous alumina, TUD-1, was prepared via a sol-gel process by using tetraethylene glycol (TEG) as template. The effect of TEG and solvents on the pore structure of the final products was studied. A mechanism using non-surfactant template was proposed. It was found that TUD-1 has amorphous framework, high surface area, large pore volume and narrow pore size distribution together with high thermal stability upon prolonged heat treatment at high temperatures, which is essential for applications in adsorption and catalysis.