Corrosion and adherence properties of cement clinker on porous periclase-spinel refractory aggregates with varying spinel content

The corrosion and adherence properties of cement clinker on porous periclase-spinel refractory aggregates with varying spinel content were examined using a static crucible test and a sandwich test, respectively. The reaction characteristics of porous periclase-spinel aggregates and cement clinker and the effects of spinel content on the adherence property were investigated through scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and FactSage^® thermo-chemical software. It was observed that the spinel content and pore characteristics strongly affected the corrosion results and thus affected the adherence ability of cement clinker on porous periclase-spinel aggregates. With an increase in the spinel content, the amount of glass phase formed from the reaction of the refractory and cement clinker increases because the rate of the spinel dissolution into the cement clinker is higher than that of periclase. The glass phase acts as a bridge between the cement clinker and the aggregate to enhance the adherence property, which depends on the amount, area distribution and viscosity of the glass phase and its penetration in aggregates. When the spinel content is 15–40 wt%, the refractory aggregate not only has a high cement clinker resistance but also a high adherence property. Once the spinel content exceeds 50 wt%, the skeletal structure of the aggregate will be destroyed, which will lead to a substantial decline in the cement clinker resistance.     

Coagulation dynamics of fractal flocs induced by enmeshment and electrostatic patch mechanisms

The size and structure of flocs during floc formation were monitored for various coagulation mechanisms. Two distinctive mechanisms, namely, enmeshment and electrostatic patch, govern the dynamics of kaolin particles coagulation by polyaluminum chloride (PACl). They were investigated by small angle static light scattering (SASLS) and solid-state ²⁷Al NMR. In addition, a novel wet SEM (WSEM) was used in-situ to image the morphology of the aggregate in aqueous solution. Synthetic suspended particles were coagulated by two PACl products, a commercial product (PACl) and one laboratory product (PACl-E). The PACl-E contained more than 60% Al₁₃ while the PACl contained only 7% Al₁₃, with large percentage of colloidal Al. For coagulation by PACl at neutral pH and high dosage where the strong repulsion between particles occurs, the enmeshment ruled by reaction-limited aggregation (RLA) results in larger sweep flocs as well as higher fractal dimensional structure. For coagulation by PACl-E at alkaline pH and low dosage, the flocs were coagulated predominately by electrostatic patch with Al₁₃ aggregates. At such condition, it is likely that diffusion-limited aggregation (DLA) predominately rule PACl-E coagulation. The fractal dimension (D_s) values of PACl and PACl-E flocs formed at enmeshment and electrostatic patch increased with dosage, respectively. When breakage of flocs occurs, the breakage rate of PACl-E flocs is slower than that of sweep flocs. By WSEM imaging, the adsorption of spherical Al precipitates onto the particles was observed to form sweep flocs with a rough and ragged contour, while the PACl-E flocs were formed with a smooth and glossy structure.     

含沙高浊水架桥絮体的质量分形

处理含沙量在20-30kg／m^3以上的高浊水时须采用高分子絮凝剂，然而对架桥絮体的构造特征却知之甚少，为此采用沉降及图像分析技术，探讨了含沙高浊水架桥絮体的分形结构特征。结果表明，稳态絮体具有多孔、开放的分形结构，渗透率较大。这种分形构造对絮体的混凝及沉降性能影响显著，质量分维值不同则沉速差异较大。     

混凝土配合比设计中粗细骨料用量确定方法的比较

本文探讨了混凝土配合比设计中粗细骨料用量确定方法，对我国现行规范方法与ACI方法进行了比较，建议借鉴ACI的方法来确定混凝土配合比设计中粗细骨料用量。     

外加电场气相法制备纳米无机氧化物

气相燃烧法纳米无机氧化物粉体特征一方面取决于前驱体的水解反应速度和粒子的成核生长动力学, 另一方面受到燃烧反应器内物料的流动混合、热质传递等多种过程因素的影响。电场控制气相燃烧法制备纳米 无机氧化物是在原有的基础上外加电场,使火焰的轴向高度降低、径向宽度增大,形成厚度相对均匀的火焰层, 火焰温度梯度也随之增大,抑制粒子表面的生长和粒子之间的烧结,获得“粒径分布较窄的粒子和结构相似的 聚集体”。     

京尼平交联制备枯草杆菌碱性蛋白酶聚集体

本研究利用新型交联剂京尼平制备了枯草杆菌碱性蛋白酶交联聚集体(BAP-CLEAs)。以酶活回收率为指标,确定了BAP-CLEAs制备的最佳条件为:交联剂质量浓度0.50%,交联温度35℃,交联时间12 h,此时BAP-CLEAs的酶活回收率为55.04%。采用扫描电镜及红外光谱对BAP-CLEAs进行表征,结果证明枯草杆菌碱性蛋白酶在京尼平的作用下成功交联。与游离酶相比,BAP-CLEAs的最适p H值向碱性方向偏移,由9.4变为10.3,在较宽的p H范围和温度范围内保持较高的酶活。另外,在2%浓度的酪蛋白底物中重复使用5次后,BAP-CLEAs还能保持86.42%的酶活性。以上催化特性的结果表明,枯草杆菌碱性蛋白酶在京尼平的作用下可成功交联形成酶聚集体,且该交联酶聚集体具有比游离酶更优越的p H稳定性、温度稳定性和重复使用稳定性,有良好的工业应用前景。     

酸性热致大豆分离蛋白聚集体制备高冻融稳定性类蛋黄酱乳液

本文对酸性（pH 3.0）热致大豆分离蛋白聚集体（AHSPI）的平均粒径（Dh）、表面电位（ζ）、表面疏水性（H0）与溶解度进行了表征与测定,并用酸性（pH 3.0）天然大豆分离蛋白（ANSPI）、中性（pH 7.0）热致大豆分离蛋白聚集体（HSPI）作为对比分析,同时选用了AHSPI代替蛋黄制备高冻融稳定性的类蛋黄酱乳液,探讨了不同蛋白浓度对类蛋黄酱乳液的外观质地、微观结构、流变性质、DSC特性的影响。结果表明：AHSPI的平均粒径（204.67 nm）及H0（79418）均大于ANSPI与HSPI（pH 7.0）,但ζ电位绝对值（35.93 mV）小于ANSPI与HSPI（pH 7.0）,溶解度（89.47%）较HSPI（pH 7.0）更好。用AHSPI制备的类蛋黄酱乳液经过3次冻融循环保持稳定的最低浓度可达0.3 wt%,冻融前后乳液结构保持不变,只是乳液粒径的略微增大,流变性质表明类蛋黄酱乳液具有以弹性为主的凝胶网络结构,随着蛋白浓度的增大,油滴粒径逐渐减小,粘弹特性增强。DSC热分析表明：随着蛋白浓度的增加,类蛋黄酱乳液的结晶凝固点降低（-18→-28 ℃）,而蛋黄酱即使具有低于冷冻温度（-20 ℃）的结晶凝固点（-27.89 ℃）,仍发生了冻融破乳现象,类蛋黄酱乳液较好的界面稳定性赋予了其较好的冻融稳定性,为开发一类天然低胆固醇高冻融稳定性的酱类乳液提供了研究基础。     

Natural Aggregates at Makkah Governate, Western Saudi Arabia

 Natural coarse and fine aggregates which accumulated along six selected wadis in the region of Makkah were assessed both qualitatively and quantitatively. The six wadis were Numan, Al-Yamanyah, Al-Shamyah, Hwarah, Alaf and Faydah. More than 440 aggregate samples were collected and their physical, mechanical and chemical properties determined. Petrographic studies on the gravel samples were undertaken to characterise the aggregate types. The results were compared with ASTM and British Standard specifications. The aggregates were generally within the acceptable limits for use in concrete although there were the relatively high values of chloride, sulphate and total dissolved salts in the fine aggregates in Wadis Alaf, Hwarah and Faydah. Nine fine aggregate samples representing upstream, midstream and downstream deposits from these saline wadis were washed in distilled waters after which the aggregates were within the acceptable limits for structural concrete. There were indications of material which could cause alkali-silica in the coarse aggregate at Wadi Faydah. The study proved reserves of 12.5 million m³ of coarse aggregate and 23 million m³ of fine aggregate. Received: 27 May 1998 · Accepted: 18 February 1999     

Paper sizing agents from micelle‐like aggregates of polystyrene‐based cationic copolymers

A series of polystyrene‐based cationic copolymers (PSCC) were synthesized by copolymerization of styrene and the cationic comonomer vinylbenzyl trimethylammonium chloride. These copolymers can be used as internal paper sizing agents in a broad pH range. The effect of the charge density on the PSCC colloid properties was investigated. It was found that at room temperature the PSCC could change from water insoluble to colloidally dispersible and finally to fully water soluble as the charge density was increased. Based on the understanding of their colloid behavior, PSCCs were applied as internal sizing agents for paper. The results showed that the hydrophobicity of handsheets could be significantly improved by PSCCs and the sizing performance was a function of copolymer addition, charge density, particle size, drying temperature, and pH conditions. The present study indicated some potential advantages of PSCC copolymers as internal sizes. PSCC can be self‐retained on the fiber surface, no hydrolysis occurs during the storage and application, and no sizing reversion occurs. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2067–2073, 2000     

秸秆还田对植烟土壤有机质及团聚体特征的影响

通过2010—2012年的秸秆还田定位试验,利用干、湿筛法研究了不同用量小麦以及玉米秸秆还田后对植烟土壤有机质和团聚体特征的影响。结果表明,随着秸秆还田量的增加,土壤有机质含量、团聚体平均重量直径（MWD）及几何平均直径（GMD）有所增加,但不同秸秆还田对土壤有机质及团聚体特征的效果不同。干筛法测得土壤团聚体的分形维数随两种秸秆还田量增加而减少,湿筛法测得高量玉米秸秆还田（7500 kg/hm²）较低量秸秆还田（1500 kg/hm²）处理的团聚体分形维数显著降低,同时分形维数随着小麦秸秆还田量的增加而降低。等量玉米秸秆较小麦秸秆在提高土壤有机质含量及团聚体特征方面效果较好。土壤有机质与干筛测得MWD及GMD呈极显著正相关,与干筛测得分形维数呈极显著负相关,与湿筛测得GMD及>0.25 mm团聚体含量呈显著性的正相关。总之,通过秸秆还田可增加土壤有机质含量,影响团聚体分布并提高团聚体稳定性。