硅钼黄和硅钼蓝测定三元复合驱采出水中硅的比较

三元复合驱采出水中硅含量的测定分别采用硅钼黄分光光度法和硅钼蓝分光光度法,并对两种测试方法进行了比较。实验结果表明,当样品的硅离子浓度较低时,采用硅钼蓝法的精密度要高于硅钼黄法。当硅离子浓度较高时,硅钼黄法精密度高于硅钼蓝法。因此,建议在测试三元复合驱采出水硅含量时,可根据样品的硅含量选取适当的分析方法。     

硅肥中有效硅含量的分析测试研究

采用草酸－硫酸亚铁硅钼蓝分光光度法,测定硅肥中有效硅含量,克服了其它方法的不足,试验满意,便于推广应用。     

硅钼兰比色法测定锅炉水中二氧化硅的优化

通过探讨分光光度法测定水中常量二氧化硅的方法,在盐酸浓度为0.12 mol/L的酸度条件下,水样中活性硅与钼酸铵生成为硅钼黄,酒石酸掩蔽磷酸根等干扰物质,用抗坏血酸还原生成硅钼蓝,生成硅钼蓝络合物的颜色深度与水样中硅浓度成正比,符合郞伯比尔定律。本方法适用于SiO_2含量较高的水样中SiO_2的测定,如原水、循环冷却水和炉水等。此方法操作简单,准确度高,具有推广价值。     

硅钼蓝分光光度法测定磷矿石中的二氧化硅

对硅钼蓝分光光度法测定磷矿石中的二氧化硅进行了研究。研究了硅钼黄的显色条件及干扰因素,在本方法试验控制Ｈ２ＳＯ４浓度范围内硅与钼酸钠生成硅钼黄,经ＦｅＳＯ４还原成硅钼蓝,ＳｉＯ２含量在０～６００μｇ／１００ｍｌ范围内服从比耳定律。操作简便,重现性好,结果准确,测定磷矿石中的二氧化硅含量,结果满意。     

硅钼蓝分光光度法测定水中硫

在酸性介质中,硫离子可以定量地将硅钼黄还原为硅钼蓝,通过测定硅钼蓝的吸光度,可间接测定硫离子的含量,从而建立了硅钼蓝分光光度法测定水中硫的新方法。论文详细探讨了硅钼蓝分光光度法测定硫离子的各种影响因素。结果表明,显色体系的最大吸收波长为730nm,硫离子质量浓度在0.4000~8.000μg/mL范围内服从比尔定律,线性相关系数γ=0.9996。方法用于测定河水、山泉水、井水、温泉水中硫离子的含量,标准加入回收率分别为97.5%~105.0%、97.1%~101.0%、95.8%~96.7%、101.4%~102.1%。     

硅钼蓝光度法快速测定SAPO-34分子筛中硅含量

建立一种以分光光度法测定SAPO-34分子筛中硅含量的分析方法。以硅和钼酸铵在盐酸介质中形成硅钼黄杂多酸,再以抗坏血酸将硅钼黄还原成硅钼蓝后,对硅含量进行测定。结果表明,体系中硅钼蓝的最大吸收波长为806 nm,绘制的标准曲线在0.100 0~6.000 mg/L内服从朗伯-比尔定律,所得相关系数为R2=0.999 5。该分析方法用于SAPO-34分子筛中硅含量的测定,精密度及稳定性良好,操作简单、快速。     

分光光度法测定煤沥青中硅含量

研究了分光光度法测定煤沥青中硅含量,试样经灰化后与碳酸钠高温熔融生成可溶性硅酸盐,与钼酸铵反应生成硅钼黄,在强酸性条件下用硫酸亚铁铵还原为硅钼蓝,在波长810nm下有最大吸收,用标准曲线法定量。进行了显色反应条件试验以及精密度试验、回收率试验、对照试验,方法的加标回收率为91%～105%,相对标准偏差(RSD)小于7%。     

还原硅钼酸盐分光光度法测定偏钒酸铵中硅的含量

介绍了还原硅钼酸盐分光光度法测定偏钒酸铵中的硅含量 ,讨论了吸收波长、还原剂、酸度及掩蔽剂加入量等因素对测定结果的影响。结果表明 ,还原硅钼酸盐分光光度法测定偏钒酸铵中的硅含量 ,数据准确     

硅钼蓝法测定粘土矿浸出渣中可溶性硅的不确定度评定

采用硅钼蓝分光光度法测定粘土矿微生物浸出渣中可溶性硅的含量,建立了测量数学模型,运用统计学原理对检测过程中产生不确定度的各分量影响因素进行了分析,同时对一个粘土矿微生物浸出渣中可溶性硅含量测定结果的不确定度进行了评定。     

钽铁、铌铁精矿中硅量的测定

钽铁、铌铁精矿中硅含量的测量分为5%以下使用硅钼蓝分光光度法;5%~20%使用重量法和硅钼蓝分光光度法相结合的方法。本实验分别从条件试验、干扰试验、回收试验、精密度试验、方法对比试验等方面对试验结果进行考察。试验结果表明,该法精密度和准确度均好,适用于钽铁、铌铁精矿中0.50%~20.00%硅的测定。     

Silicon Carbide Monofilament-Reinforced Silicon Nitride or Silicon Carbide Matrix Composites

SiC-monofilament-reinforced SiC or Si₃N₄ matrix composites were fabricated by hot-pressing, and their mechanical properties and effects of filaments and filament coating layers were studied. Relationships between frictional stress of filament/matrix interface and fracture toughness of SiC monofilament/Si₃N₄ matrix composites were also investigated. As a result, it was confirmed experimentally that in the case of composites fractured with filament pullout, the fracture toughness increased as the frictional stress increased. On the other hand, when frictional stress was too large (>about 80 MPa) for the filament to be pulled out, fracture toughnesses of the composites were almost the same and not so much improved over that of Si₃N₄ monolithic ceramics. The filament coating layers were found to have a significant effect on the frictional stress of the SiC monofilament/Si₃N₄ matrix interface and consequently the fracture toughness of the composites. Also the crack propagation behavior in the SiC monofilament/Si₃N₄ matrix composites was observed during flexural loading and cyclic loading tests by an in situ observation apparatus consisting of an SEM and a bending machine. The filament effect which obstructed crack propagation was clearly observed. Fatigue crack growth was not detected after 300 cyclic load applications.     

Silicon Carbide/Silicon and Silicon Carbide/Silicon Carbide Composites Produced by Chemical Vapor Infiltration

Composites of SiC/Si and SiC/SiC were prepared from single yarns of SiC. The use of carbon coatings on SiC yarn prevented the degradation normally observed when chemically vapor deposited Si is applied to SiC yarn. The strength, however, was not retained when the composite was heated at elevated temperatures in air. In contrast, the strength of a SiC/C/SiC composite was not reduced after this composite was heated at elevated temperatures, even when the fiber ends were exposed.     

以二氧化硅为硅源制备纯硅的方法

介绍了纯硅材料的类型及其主要用途,叙述了国内外以二氧化硅为硅源,热还原法(包括金属、非金属和耦合热还原法)、熔盐电解法(包括氟化物、氯化物和耦合熔盐电解法)等制备纯硅的方法,评叙了各种方法的优缺点。指出氯化钙熔盐电解法工艺简单、产品纯度高、能耗小、成本低、经济效益好、环境友好、市场潜力与前景较好。     

Silicon Carbide Platelet/Silicon Carbide Composites

α-silicon carbide platelet/β-silicon carbide composites have been produced in which the individual platelets were coated with an aluminum oxide layer. Hot-pressed composites showed a fracture toughness as high as 7.2 MPa·m^1/2. The experiments indicated that the significant increase in fracture toughness is mainly the result of crack deflection and accompanying platelet pullout. The coating on the platelets also served to prevent the platelets from acting as nucleation sites for the α- to β-phase transformation, so that the advantageous microstructure remains preserved during high-temperature processing.     

氮化钒铁中硅含量的硅钼蓝分光光度法研究

采用硅钼蓝分光光度法测定氮化钒铁中的硅含量,研究了氮化钒铁溶样方法,通过溶样效果,选择确定溶样酸。结果表明,该方法准确度高、重复性好,操作简便,可广泛运用于氮化钒铁中硅的检测。     

Silicon/Silicon Carbide Composites Fabricated by Infiltration of a Silicon Melt into Charcoal

Dense Si/SiC composites were fabricated via a conventional reaction-bonding process, using oak charcoal that exhibited a honeycomb structure. The silicon melt was infiltrated into the porous oak charcoal (density of ~0.6 g/cm³) while the sample was heated to 1700°C under vacuum (10^-3 torr (~0.133 Pa)), which resulted in in situ silicon-fiber/SiC composites. The reaction product had an average density of 2.8 g/cm³ and showed three-point flexural strengths of 330 MPa at room temperature and 280 MPa at 1300°C. Good oxidation resistance also was observed at temperatures up to 1300°C in flowing air. This process provided excellent shape-making capability, because the charcoal that was used as a preform was readily machinable.     

Nonaqueous Processing of Silicon for Reaction-Bonded Silicon Nitride

Ethanolic silicon suspensions, with and without a polyethoxylated amine of low molecular weight, were studied by rheological, adsorption, electrophoretic, and sedimentation methods. Pellets were pressure-cast and nitrided to form reaction-bonded silicon nitride. Density and binding strength in the green state relate well to rheological behavior and other collodial aspects of the suspensions used, particularly the additive's role and distribution. Density and degree of nitridation in the final state are not importantly affected by the additive's use. Its greatest benefit is to modify the binding strength in the green state. The mode by which this small molecule affects the processing of silicon consists of adsorption, combined with an increased electrostatic interparticle repulsion which increases the suspension viscosity and that of undried pellets. Although the improved binding strength is accompanied by decreased green and nitrided densities, high degrees of conversion to silicon nitride are still achieved.     

Oxidation of Chemically-Vapor-Deposited Silicon Nitride and Slnglem-Crystal Silicon

Oxidation of {111} single-crystal silicon and dense, chemically-vapor-deposited silicon nitride was done in clean silica tubes at temperatures of 1000° to woo°C. The oxidation rates of silicon nitride under various atmospheres (dry O₂, wet O₂, wet inert gas, and steam) were several orders of magnitude slower than those of silicon under the identical conditions. The activation energy for the oxidation of silicon nitride decreased from 330 to 259 kJ/mol in going from dry O₂ to steam while that for Si decreased from 120 to 94 kJ/mol. The parabolic rate constant for Si increased linearly as the water vapor pressure increased. However, the parabolic rate constant for silicon nitride showed nonlinear dependency on the water vapor pressure in the presence of oxygen. The oxidation kinetics of silicon nitride is explained by the formation of nitrogen compounds (NO and NH₃) at the reaction interface and the counterpermeation of these reaction products.     

Silicon Carbide Powder Synthesis from Silicon Monoxide and Methane

SiC was synthesized via the gas-phase reaction between SiO and CH₄ at 1500° and 1560°C in a tubular flow reactor. SiO vapor was generated from equimolar powder mixtures of Si and SiO₂ in the reactor while CH₄ was externally supplied. Products of different morphologies were collected at different longitudinal locations: whiskers, crystal aggregates, scale, and powder. The total yield of SiC, based on the amount of SiO generated, reached as high as 99%, of which 25–46% by mass was fine powder with sizes ranging from 60 to 300 nm.     

ICP—AES法测定高硅钢中的硅

研究了用ICP-AES法快速测定高硅钢中的硅,确定了最佳测定条件.在此条件下测定,获得满意结果.实验结果表明,该方法简便、快速、灵敏,检出限为0.000 9 μg/mL;RSD＜0.5 %;回收率为99 %～101 %,结果令人满意.