火焰原子吸收分光光度法测定锌精矿中的锌

采用原子吸收分光光度法对测定锌精矿中的锌含量进行了研究。通过实验,证明该方法干扰少,操作简便,结果准确可靠,适用于高含量锌分析。     

Graft polymerization of vinyl acetate onto silica

The free‐radical graft polymerization of vinyl acetate onto nonporous silica particles was studied experimentally. The grafting procedure consisted of surface activation with vinyltrimethoxysilane, followed by free‐radical graft polymerization of vinyl acetate in ethyl acetate with 2,2′‐azobis(2,4‐dimethylpentanenitrile) initiator. Initial monomer concentration was varied from 10 to 40% by volume and the reaction was spanned from 50 to 70°C. The resulting grafted polymer, which was stable over a wide range of pH levels, consisted of polymer chains that are terminally and covalently bonded to the silica substrate. The experimental polymerization rate order, with respect to monomer concentration, ranged from 1.61 to 2.00, consistent with the kinetic order for the high polymerization regime. The corresponding rate order for polymer grafting varied from 1.24 to 1.43. The polymer graft yield increased with both initial monomer concentration and reaction temperature, and the polymer‐grafted surface became more hydrophobic with increasing polymer graft yield. The present study suggests that a denser grafted polymer phase of shorter chains was created upon increasing temperature. On the other hand, both polymer chain length and polymer graft density increased with initial monomer concentration. Atomic force microscopy–determined topology of the polymer‐grafted surface revealed a distribution of surface clusters and surface elevations consistent with the expected broad molecular‐weight distribution for free‐radical polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 300–310, 2003     

CMOS图像传感器中分段电容DAC非理想因素研究

CMOS图像传感器信号处理中通常采用分段电容DAC产生斜坡参考电压。研究了分段电容DAC精确的电容失配及寄生与其转换精度的关系式。基于对分段电容DAC工作原理的研究,导出了电容失配及寄生模型;针对其分数桥接电容失配、各二进制电容间的失配及寄生电容问题进行了理论分析;对分段电容DAC进行非理想因素仿真,设计了一个采用分段电容DAC的10位单斜ADC并对其进行测试,仿真和测试结果均验证了理论分析的正确性。上述理论分析结果可作为分段电容DAC的设计指导。     

钽平台-石墨炉原子吸收法测定高背景废水样品中的Cd、Pb

运用钽平台石墨管测定基体成分复杂的废水样品中的Cd、Pb元素,基本消除了基体残留影响和记忆效应,降低了背景吸收,提高了灵敏度。样品经超声波仪粉碎后直接进样,用校正曲线法测定,简化了操作步骤,减少了测定时间,延长了石墨管使用寿命。其测定值与石墨平台标准加入法测定值结果一致。样品回收率:Cd为96.9%～104%,Pb为98.2%～106%,Cd的相对标准偏差(RSD)为3.04%～4.24%,Pb的RSD为2.93%～6.53%。     

基于原子任务构建职业教育“微”教学资源

在我国数字化教学资源建设领域,建设微型教学资源受到了广泛的关注。建设职业教育微型教学资源时,因工作过程知识类别多、情境多样、注重实践等特点,使资源建设存在一定的难度。分析工作任务的关联逻辑,借助工作流技术对工作流程建模,划分最小粒度的原子任务,并通过分析原子任务工作过程知识的要素组织逻辑,设计资源的框架结构,为职业教育＂微＂资源建设提供了更具操作性的方法。     

Initial Deposition of Colloidal Particles on a Rough Nanofiltration Membrane

The initial rate of colloid deposition onto semi‐permeable membranes is largely controlled by the coupled influence of permeation drag and particle‐membrane colloidal interactions. Recent studies show that the particle‐membrane interactions are subject to immense local variations due to the inherent morphological heterogeneity (roughness) of reverse osmosis (RO) and nanofiltration (NF) membranes. This experimental investigation reports the effect of membrane roughness on the initial deposition of polystyrene latex particles on a rough NF membrane during cross flow membrane filtration under different operating pressures and solution chemistries. Atomic force microscopy was used to characterize the roughness of the membrane and observe the structure of particle deposits. At the initial stages of fouling, the AFM images show that more particles preferentially accumulate near the “peaks” than in the “valleys” of the rough NF membrane surface.     

悬浮液进样-火焰原子吸收光谱法测定茶叶中的微量铬

将茶叶悬浮于琼脂胶体中制成悬浮液 ,直接喷入空气 -乙炔火焰 ,用火焰原子吸收光谱法测定茶叶中的微量铬 ,方法简便、快速、灵敏度和精密度高、测定结果与用灰化法处理样品一致 ,检验表明 ,两种样品前处理方法之间无显著性差异。相对标准偏差为 3.4 %～ 6 .1% ,加标回收率为 95 .7%～ 10 3.8 %。     

Films formed from polystyrene latex/clay composites: A fluorescence study

This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (t₃) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (I_s) and fluorescence intensity (I_p) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, I_tr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum film formation temperature, T_q, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films.     

填充玻璃纤维滤膜基钛酸锶钡的手控注射式富集器对水中锌的富集性能

以多孔玻璃纤维滤膜基钛酸锶钡（BBST）为吸附材料,制备了手控注射式富集器;考察了该富集器对水中Zn2＋的吸附富集性能.结果表明：当介质的pH值为3-7时,多孔玻璃纤维滤膜基钛酸锶钡对水中的Zn2＋具有很强吸附能力,其静态吸附容量为24.30 mg/g;制备的富集器可实现对Zn2＋的动态吸附,被吸附的Zn2＋可用2.0%的EDTA溶液动态洗脱回收,其浓集因子可达500.提出了手控注射式钛酸锶钡富集器富集,火焰原子吸收光谱法测定水中痕量Zn2＋的新方法.方法检出限为0.09μg/L.应用于一次蒸馏水和纯净水中痕量Zn2＋的富集,用火焰原子吸收法测定,回收率为93.0%-102.0%.     

流动注射在线预富集测定环境样品中痕量铅

流动注射在线无过滤沉淀-溶解系统被应用于火焰原子吸收测定环境水样中痕量铅。通过样品溶液和氨溶液的混合已经可以达到痕量铅的在线析出。结果沉淀物无需过滤就被收集在编结反应器的内壁上。引入1mol/L的HNO3溶液来溶解沉淀物并将分析物输送至火焰原子吸收光谱仪(FAAS)进行在线分析。样品载入流速为3.5mol?L-1/m in,富集时间40 s,增强因子37,检测频率60/h。检测限(3σ)为7.5μg/L。50μg/L水平时,精密度(RSD,n=11)为2.9%。采用该方法测定用简单水溶液标准校准后的国家标准材料(GBW 08607,河道水),所得铅浓度0.96±0.04g/g。结果与标准值(1.00±0.02g/g)非常接近。该方法也可以成功应用于多种水样中痕量铅的测定。