氧化法对玉米黄浆的脱色工艺研究

玉米黄浆是玉米淀粉生产中产生的主要下脚料,其中大约含有60％的蛋白质。为了合。理利用这些蛋白质,对玉米黄浆的脱色工艺进行了研究,并初步探讨了其在蛋白质复合纤维上的应用。首先,筛选出脱色效果较好的H2O2做为氧化性脱色剂;其次,探讨H2O2脱色工艺中反应浓度、时间、温度及pH值对脱色效果的影响,并由正交试验得出脱色处理最佳工艺为：H2O2浓度为70g／L,pH值为8,反应温度为70℃,反应时间为60min。由红外谱图可以看出脱色前后浆液中蛋白质基本无明显变化.脱色后浆液纺制的蛋白质复合纤维白度明显提高,断裂强度和断裂伸长率均略低于原浆液纺制的纤维。     

电石炉自焙电极事故分析及处理措施

根据自焙电极的特点,掌握电极糊烧结质量特性及在焙烧过程中的性质变化,分析了电极软断和硬断事故的产生原理及其处理措施。     

吸附伏安法测定抗坏血酸实验条件的确定

采用吸附伏安法,在纳米介孔二氧化硅修饰碳糊电极上测定抗坏血酸,讨论了支持电解质溶液、pH值、富集电位、富集时间以及扫描速率对检测峰电流的影响,确定出当支持电解质为PBS缓冲溶液,pH值为5．5,开路富集时间为120s,扫描速率为50mV／s时,可获得最大检测峰电流。     

高温下矿渣复合胶凝材料早期的水化性能

通过对矿渣复合胶凝材料早期水化程度和水化产物种类的测定,以及对硬化浆体显微形貌和孔结构的观察,研究了高温养护对矿渣复合胶凝材料早期水化性能和硬化浆体结构的影响.结果表明:高温养护能明显缩短矿渣胶凝材料水化诱导期,激发矿渣活性,加快早期水化反应速率,但对水化产物种类的影响很小;高温养护使矿渣复合胶凝材料早期硬化浆体结构更致密,孔结构明显改善,孔隙率降低,粗孔比例减少.     

乙二醇介质中铜微粉表面化学镀银的研究

在新生成的铜微粉表面化学镀银,用扫描电镜、X射线衍射仪、动态光散射粒径测试仪和热重仪对粉体进行表征和性能测试,分析了粉体导电性、抗氧化性及粒径大小和分布的影响因素。结果表明:在乙二醇介质中采用液相还原法,通过葡萄糖预还原,用甲醛进行二次还原,控制银与铜物质的量之比为2∶1,可得到抗氧化性、导电性良好的银包铜微粉。     

The fabrication of front electrodes of Si solar cell by dispensing printing

The dispensing printing was applied to fabricate the front electrodes of silicon solar cell. In this method, a micro channel nozzle and normal Ag paste were employed. The aspect ratio and line width of electrodes could be controlled by the process variables such as the inner diameter of nozzle, dispensing speed, discharge pressure, and the gap between wafer and nozzle. For the nozzle with the inner diameter of 50 μm, the line width and aspect ratio of electrode were under 90 μm and more than ∼0.2, respectively. When comparing the efficiency of solar cell prepared by conventional screen printing and the dispensing printing, the latter exhibited 19.1%, which is 0.8% absolute higher than the former even with the same Ag paste. This is because the electrode by dispensing printing has uniform aspect ratio and narrow line width over the length of electrode.     

Processing of electron microprobe data from the analysis of altered cementitious materials

The purpose of this paper is to present a method for processing electron microprobe data coming from the analysis of degraded cementitious materials. The application domain is that of cement matrices exposed to attack by aggressive media inducing the leaching of one or more chemical elements from the cement paste — typically attacked by neutral or acid aqueous environments. As raw data obtained from electron probe microanalysis (EPMA) come in the form of relative quantities of elements, the aim of the processing is to obtain the absolute variation of the specimen's chemical composition in the degraded zone and consequently to allow a better understanding of the degradation mechanisms by the aggressive environment under consideration. This method was designed for degraded specimens in which the porosity was not filled with resin before the EPMA. The method uses the titanium content of the cement matrix as a control, this element being stable during attack by neutral or acidic media. The method is described in detail using the example of the attack of cement pastes by a mix of several organic acids (notably acetic acid) at pH 4. The use of EPMA for sound and altered cement pastes is also validated. The application domain of the correction method is discussed.     

Porosity and specific surface area of Roman cement pastes

Mercury porosimetry, water vapour and nitrogen adsorption were used to follow the hydration of Roman cements — belite cements calcined at low temperature. Generally, unimodal distribution of pore sizes was observed, with the threshold pore width decreasing considerably with increasing curing time. An open porous structure with the threshold pore diameter between 0.2 and 0.8 μm and the specific surface area not exceeding 20 m²/g was produced at early ages when quick growth of the C–A–H phases is observed. The surface area reached up to 120 m²/g and the threshold pore width shifted to around 0.02 μm when the subsequent formation of C–S–H gel filled the larger pores. Both mercury porosimetry and water vapour adsorption were found to be capable of following the progress of hydration of the Roman cements with high reliability at least for a comparative evaluation of historic Roman cement mortars and repair materials used in restoration projects.     

Modelling and simulations of the chemo-mechanical behaviour of leached cement-based materials: Leaching process and induced loss of stiffness

The present paper aims at modelling the decalcification process in cement-based materials and its impact on the material stiffness, which represents a serious matter in terms of long-term durability. The resistance of cementitious materials to this chemical alteration is strongly conditioned by their mineral composition and porosity. For this purpose, a multi-scale homogenization approach (Stora et al., Trans. Por. Med. 73, 3, 2008) is implemented in the numerical platform ALLIANCES (P. Montarnal, C. Mügler, J. Colin, M. Descotes, A. Dimier, E. Jacquot, Presentation and use of a reactive transport code in porous media, Phys. Chem. Earth 32, 2007) to estimate from these data the elastic and diffusive properties of cement-based materials. The association of this homogenization model and of the integration platform, which can couple different numerical codes, then allows for evaluating the evolution of the mineral composition and of the diffusive and mechanical properties of a concrete material during chemical deterioration processes. Simulations of pure water leaching of hydrated cement pastes are performed and the consequences of this decalcification on the material's residual elastic behaviour are estimated. The numerical results are confronted with available experimental data and analyzed. The simulations of the non-linear mechanical behaviour of leached cementitious materials taking into account interactions between damage and leaching is not reported here for conciseness but can be found in another document (Stora, Modelling and simulations of the chemo-mechanical behaviour of leached cement-based materials. PhD Dissertation, univ. of Paris-Est 2008).