氢化物发生-原子荧光光谱法测定生物血中硒

应用氢化物发生-原子荧光法对生物血液中硒含量进行测定。探索了分析测定条件,方法简便、快速。测定硒的线性范围为0~40μg.L-1。线性相关系数0.9999。应用于样品测定,测定结果的相对偏差小于1.1%。加标回收率为97.1%~101.6%。     

火焰原子吸收法测定复(混)合肥料中的钾

实验确定了最佳测定工作条件,利用火焰原子吸收分光光度法测定复(混)合肥料中的氧化钾含量,测定的含量范围较大,可达200mg/L,干扰易消除,操作步骤少、简便,条件易控制,分析速度快,加标回收率达95%-106.8%,RSD为1.3%.经大量试验证明,采用此法测定,方便快速,结果令人满意.     

氢化物发生-原子荧光法测定亚硝酸钠中砷含量

应用氢化物发生-原子荧光法对亚硝酸钠中砷含量进行测定。分析了分析测定条件。方法简便、快速。测定砷的线性范围为0~40μg.L-1,相关0.9999。应用于样品测定,测定结果的相对偏差小于1.20%。加标回收率为98.8%~103.5%。     

ICP-AES法测定粉煤灰全组分化学元素的研究

采用偏硼酸锂熔样 ,电感耦合等离子体原子发射光谱 (ICPˉAES)法对粉煤灰实现一次熔样 ,全组分同时分析。对影响光谱测量的各种因素进行了较详细的研究 ,确定了最佳测定条件。该法的检出限为 0 .0 0 9～ 0 .83 1μg·ml-1,回收率为 91.5 4%～ 10 4.45 % ,RSD <3 .2 2 %。方法准确、快速、简便 ,用于粉煤灰中全组分测定 ,结果满意。     

微波消解-氢化物原子荧光法测定保健食品中的汞

本文采用微波消解 -氢化物原子荧光法测定了保健食品中的汞。研究了微波消解样品的最佳条件 ,探讨了硼氢化钾以及盐酸的浓度对测定结果的影响。实验结果表明 ,本法具有快速、简便、重现性好、准确度高、无污染等优点。方法的检出限为 :0 .30ng·mL-1,相对标准偏差为 3.1%～ 6 .7% ,回收率为91.0 %～ 10 3.1%。     

石灰石全组分化学元素同时测定的研究

采用偏硼酸锂熔样,电感耦合等离子体原子发射光谱(ICP-AES)法对石灰石实现了一次熔样,全组分同时分析.对影响其光谱测量的各种因素进行了研究,确定了实验的最佳测定条件.结果表明,方法的检出限为0.005～0.221μg·mL-1 ,回收率为87.00%～110.00%,RSD小于3.25%.该法准确、快速、简便,应用于石灰石中全组分的测定,结果满意.     

火焰原子吸收光谱法测定复(混)合肥料中的钾

确定了利用火焰原子吸收分光光度法测定复(混)合肥料中的氧化钾含量的最佳工作条件,测定的含量范围较大,可达200 mg/L,干扰易消除,操作步骤少、简便,条件易控制,分析速度快,使用仪器设备少,消耗试剂量小,工作时间大大缩短,劳动强度大大降低,加标回收率达95 %～106.8 %,RSD(11)为1.3 %,结果稳定可靠.经大量试验证明,采用此法测定,方便快速,结果令人满意.     

以8-羟基喹啉为偶联剂测定水中NO2--N

报道了以8-羟基喹啉为偶联剂测定水中微量NO-2-N的方法.在拟定的实验条件下,NO-2-N浓度在0.01～1.60mg·L-1范围内与吸光度呈良好的线性关系,用于环境水中NO-2-N的测定,回收率在97%～103%之间,且简便、快速.     

TAM胶粘剂中铅镉汞铬砷有害元素的同时测定

研究了HF +HCl消解样品 ,试液用ICP -AES法同时测定TAM胶粘剂中铅、镉、汞、铬、砷的新方法。在选定的最佳条件下测铅、镉、汞、铬、砷的检出限分别为 0 .0 0 15、0 .0 0 0 8、0 .0 0 11、0 .0 0 17、0 .0 0 0 9μg·L- 1 ,回收率为 93 .5 %～ 10 8.3 % ,RSD为 0 .62 %～ 5 .65 %。该法准确、快速、简便 ,应用于TAM胶粘剂的测定 ,结果满意     

ICP-AES法同时测定水中二十种金属元素

采用ICP-AES法直接同时测定水中二十种金属元素,优化了仪器条件,测定了方法检出限,回收率为90%￣110%,相对标准偏差<5%,方法准确、可靠、快速。     

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。     

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/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.     

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.