LY12铝合金早期性能退化下超声非线性系数测量和金相观察

针对材料早期力学性能退化问题,通过试验研究了疲劳加载下LY12铝合金试件的超声非线性系数和微观结构特征变化.结果表明,早期性能退化情况下,超声非线性系数和微观形态随着疲劳程度发生变化.超声非线性测量和微结构观察相结合的方法对于材料早期力学性能退化的疲劳寿命评估具有潜在的应用前景.     

添加剂对橡胶籽油生物柴油氧化稳定性的改进

测定了橡胶籽油的物化性能及组成. 加入6种抗氧化剂,采用Rancimat法研究了其添加量及复配、温度、0#柴油添加量、金属铜、铁等对橡胶籽油生物柴油氧化稳定性能的影响. 结果表明,橡胶籽油所制生物柴油不饱和脂肪酸含量达82.1%,诱导期为0.81 h,达不到国家标准(6 h). 6种抗氧化剂在添加量为4000′10-6(w)时对橡胶籽油生物柴油的氧化稳定性能均有提升,其中TBHQ效果最好,使其氧化稳定性诱导期达13.09 h,6种抗氧化剂的抗氧化效果为TBHQ>BHT>D-TBHQ>OG>PG>BHA. PG与其他抗氧化剂复配后效果较好,而TBHQ与其他抗氧化剂复配后效果降低. 温度和0#轻柴油添加量对橡胶籽油生物柴油的氧化稳定性能影响很大,随温度升高,诱导期明显缩短,而随0#柴油添加量增大,诱导期增加,添加量较大时诱导期增幅很大. 铁、铜对其氧化稳定性能也有一定影响.     

Chemical synthesis of phytosterol esters of polyunsaturated fatty acids with ideal oxidative stability

In this study, direct esterification of phytosterols with polyunsaturated fatty acid (PUFA) catalyzed by sodium bisulfate to produce sterol esters of PUFA was performed without organic solvent. Considering on both degree of esterification (DE) and oxidative stability, response surface methodology (RSM) was employed for modeling the phytosterol esters of PUFA production to obtain a food grade process. The optimal and mild reaction conditions were obtained as follows: mass ratio of PUFA:phytosterols = 4:1; amount of catalyst: 3% of the raw materials weight; reaction temperature 130°C; reaction time 8 h. Under these conditions, the degree of esterification was up to 96%, GC, TLC, NMR and GC‐MS results showed that purity of purified sterol ester was above 99%, and β‐sitosterol linolenate account for about 88%. Sterol ester of PUFA possessed low peroxide value (PV) (0.96 meq/kg) and conjugated diene (CD) value (2.15 mmol/kg), and high oxidative induction period (OIP) (10.4 h). Addition amount of sterol ester of PUFA into soybean oil, rapeseed oil, and flaxseed oil below 1, 1, and 3%, respectively, could increase OIP of the vegetable oil. The primrose phytosterol esters of PUFA possessed very low melting point, crystallization temperature, and greater solubility in oils. All the characteristics favored the wide application of sterol ester of PUFA produced by the food grade process in different formulations of functional foods.     

过氧化氢诱导HepG2细胞产生氧化应激细胞模型的建立

不同浓度过氧化氢作用人肝癌细胞(HepG2)4h后,用单细胞凝胶电泳技术测定DNA损伤状况,分光光度法测定丙二醛(MDA)含量、超氧化物歧化酶(SOD)及谷胱甘肽过氧化物酶(GSH-Px)活性,研究过氧化氢的最佳作用浓度,构建体外氧化应激细胞模型。结果表明,过氧化氢的最佳作用浓度为100μmol/L,作用细胞的时间选择4h,可以成功构建以过氧化氢为氧化应激诱导剂的HepG2细胞体外氧化应激模型。     

核壳结构Fe3O4纳米催化剂催化降解酸性废水的研究

利用静电自组装法,将羧甲基纤维素(CMC)组装到Fe3O4上得到Fe3O4@CMC,再通过自由基聚合反应将丙烯酸(AA)和丙烯酰胺(AM)接枝交联到Fe3O4@CMC上,制备出F e3O4@CMC-g-p(AA-co-AM)(Fe3O4@hydrogel)微球。利用TEM、XRD、FTIR、TGA、XPS、BET等技术对Fe3O4hydrogel微球进行了表征,并将其作为催化剂应用于类芬顿高级氧化反应中催化降解酸性红73。结果表明:Fe3O4@hydrogel仍为反尖晶石型结构,共聚物CMC-g-p(AA-c o-AM)成功包覆在Fe3O4表面,且含量为17.7%,复合微球平均粒径在10n m左右,饱和磁化强度为44.8 emu/g,BET表面积为73.5m2/g,平均孔直径为8.3nm,为介孔结构。Fe3O4@hydrogel微球对酸性染料废水有良好的催化降解性能,通过调节芬顿反应体系中初始pH值、催化剂用量以及H2O2浓度,得到反应最适条件为pH3.5、H2O210mmol/l、催化剂用量200mg/l。在此条件下3h内能达到对酸性红7399.83%以上的降解。     

沙棘粉对大鼠肝脏脂质代谢及氧化应激的影响

本文研究了沙棘粉对高脂膳食大鼠肝脏脂质代谢及氧化应激的影响。将50只成年雄性Wistar大鼠按体重随机分为对照组、高脂模型组、沙棘低剂量、中剂量和高剂量组5个组。对照组给予基础饲料,其余各组给予高脂饲料饲养,同时每日分别用0.5 mg/g bw、2.5 mg/g bw和5 mg/g bw的沙棘粉匀浆液灌胃大鼠。4 W后处死动物,采集肝脏,分别测定肝脏脂质含量、脂代谢相关酶活性和氧化应激水平。结果表明,与高脂模型组比较,一定剂量的沙棘粉可降低肝脏总胆固醇(TC)和甘油三脂(TG)水平,提高高密度脂蛋白(HDL-C)水平;使肝脏组织肝脂酶(HL)和脂蛋白脂酶(LPL)活性增强;还原型谷胱甘肽(GSH)含量和总超氧化物歧化酶(T-SOD)活力提高,丙二醛(MDA)含量下降。说明沙棘粉可降低高脂膳食大鼠肝脏脂质水平,提高肝脏脂代谢酶活性,增强抗氧化能力,减缓肝细胞的脂质过氧化。     

Ion bombardment induced surface electrical degradation monitoring by means of luminescence in aluminas

Oxide ceramics for use as electrical insulators in future fusion devices, will be exposed to ionization and displacement damage (neutrons, gammas, ion bombardment). Enhanced oxygen loss due to ion bombardment increases surface electrical conductivity, and at the same time the surface emits light due to ion beam induced luminescence (IBIL). Results for 3 types of α-alumina and sapphire measuring electrical surface conductivity and IBIL as a function of dose at different temperatures between 20 and 200 °C, show a clear correlation between luminescence and surface electrical degradation. This indicates the potential to remotely monitor insulating material degradation not only in ITER and beyond, but also in the more immediate in-reactor experiments required for materials testing. Partial reduction of degradation by heating in air suggests the possibility for in situ recovery of the insulating properties.     

Modelling of polyurethane foam thermal degradation within annular region subject to fire conditions

Abstract

Nuclear materials are placed in shielded, stainless steel packaging for storage or transport. These drum type packages often employ a layer of foam, honeycomb, wood or cement that is sandwiched between thin metal shells to provide impact and thermal protection during hypothetical accidents, as those prescribed in the Code of Federal Regulations (10 CFR 71·73). The present work discusses the modelling of the thermal degradation of polyurethane (PU) foam within an annular region during an 800°C fire. Measurements and analysis by Hobbs and Lemmon [M. L. Hobbs and G. H. Lemmon: ‘Polyurethane foam response to fire in practical geometries’, Polym. Degrad. Stab., 2004, 84, 183–197.] indicate that at elevated temperatures, PU foam exhibits a two-stage, endothermic degradation. The first stage produces a degraded solid and a combustible gas; the second stage reaction consumes the degraded solid and produces another combustible gas. As a result, during a prolonged fire, a gas filled void develops beside the outer metal shell and grows inward toward the inner shell and the containment vessel. As a result of the radial symmetry in the drum geometry, a one-dimensional finite difference model is constructed for the annular foam region. Heat flux is applied to the inner surface to model the decay heat of the containment vessel contents. Thermal radiation and convection boundary conditions with a specified environmental temperature are applied to the outer surface. The material and reaction rate properties determined by Hobbs and Lemmon are applied to the foam. The annular region temperature and composition are determined as functions of radius and time after the environmental conditions are changed from room temperature to those of an 800°C fire. The effects of surface to surface radiation between the package’s outer skin and the undegraded foam and the reaction rate reduction due to material damage during the reaction are evaluated for fires lasting 20 h. The peak package liner temperature caused by a 30 min fire is predicted to be 129°C, well below the short term limit for containment vessel seal (377°C).     

Anode Performance of Electron Irradiated Mesocarbon Microbeads for Secondary Lithium Batteries

Mesocarbon microbeads (MCMBs) heat-treated at 1,273 and 3,073 K were irradiated with an electron beam current density ~1.34μA/cm² of 0.5–1.5 MeV for 0–600 s, and the irradiated MCMBs were examined as anode materials for secondary lithium-ion batteries. Charge capacity of both materials irradiated for short time within 100 s became larger than that before irradiation. Improvement of discharge capacity of MCMB annealed at 3,073 K was achieved by irradiation with 0.5 and 1.5 MeV electrons for 600 s. Good performance of cyclical discharge of MCMB annealed at 3,073 K was also attained by the irradiation with 0.5–1.5 MeV electrons for 600 s.     

力化学降解和化学降解结合制备PVC加工助剂

采用力化学降解和化学降解相结合的方法,研制了一种低相对分子质量的聚氯乙烯树脂(LMPVC).讨论了影响LMPVC性能的工艺条件和LMPVC对PVC加工性能的影响.实验表明,这种LMPVC具有较低的塑化温度和较高的熔体流动性,且与高相对分子质量的PVC树脂有良好的相容性.LMPVC对PVC树脂有良好的塑化作用,并且能提高PVC树脂的力学性能,因此LMPVC是一种理想的PVC加工助剂.