金红石瓷无模成形技术中引发剂液滴运动的Runge-Kutta解析

分析了金红石瓷无模成形技术中,PVA-TiO2浆料胶凝前引发剂Na2B4O7·10H2O水溶液液滴的运动,建立了金属管阵列中竖直向下运动液滴的运动微分方程.在MATLAB 6.5中用四阶Runge-Kutta法求解液滴运动的常微分方程.建立了沿浆料层方向及沿浆料层法向液滴运动速度与时间及浆料层倾斜角的数学模型.研究结果表明:液滴运动速度随着时间呈二阶非线性增加,其中二次项可以定量分析空气阻力与时间的变化关系;漏斗形金属管阵列中,所有竖直向下的液滴沿平行于PVA-TiO2浆料层方向的速度分量,随着浆料层倾斜角的增加而增加,但延法向的速度分量减小;两个方向的速度随着运动时间增加均增加,同时增加空气的阻力.     

TiO_2-V_2O_5-K_2O系湿敏陶瓷材料的改性研究

研究了添加正硅酸酯[Si(OC_2H_s)_4]对TiO_2-V-2O_5-K_2O(Na_2O)湿敏陶瓷材料性能的影响.结果表明:材料是以金红石型TiO_2为主相,粒界生成含K~+(Na~+)离子的硅玻璃相.其中添加聚合度为3.0或2.5的Si(OC_2H_5)_4,经900℃烧结2h的材料具有较完善的微结构、较高的湿度灵敏度和稳定性.     

Preparation of chemical vapor sensing materials from composites of esterified poly(vinyl alcohol) and carbon black

Poly(vinyl alcohol) was modified by esterification to prepare poly(vinyl alcohol) copolymers. The degree of esterification on poly(vinyl alcohol) was elucidated by FTIR, ¹H NMR, and elemental analysis. The obtained products were poly(vinyl benzoate)-co-poly(vinyl alcohol) (B-PVA) and poly(vinyl p-toluoate)-co-poly(vinyl alcohol) (P-PVA). The chemical vapor sensors were fabricated by the mixtures of polymer and carbon black in dimethyl sulfoxide and their subsequent preparation as thin films onto the interdigited electrodes by the application of the spin-coating technique. The chemical vapor sensing properties of the sensors were examined with various solvents, such as hexane, toluene, methanol, ethanol, isopropanol, tetrahydrofuran, ethyl acetate, acetonitrile, dimethyl sulfoxide, and water. The experimental results indicated that modifying the chemical structure of PVA results in the decreased polarity of the obtained products. The composites of modified PVA consequently responded well to low polarity solvents, such as THF or ethyl acetate.     

Functionalized poly (vinyl alcohol) polymer as chemodosimeter material for the colorimetric sensing of cyanide in pure water

New poly (vinyl alcohol) (PVA) derivative containing pendant chemoselective functionality is prepared for the cyanide detection in pure water. Particularly, incorporation of the chemodosimeter 4 on PVA is performed by direct coupling of the hydroxyl group of the dye 4 and PVA hydroxyl groups via ethereal linkage using di-bromoalkane as a cross-linking agent. The chemosensory capacity of the polymeric material for the colorimetric sensing of cyanide in water is based on the reactivity of this anion toward the chemodosimeter, and its water solubility is given by PVA moiety. The chemodosimeter is developed on the basis of the trifluoroacetyl group as electrophile receptor of the cyanide anions. The final water soluble functionalized polymer presents a sensible selectivity toward cyanide anions in pure water.     

Fluorescence quenching of benzo[k]fluoranthene in poly(vinyl alcohol) film: a possible optical sensor for nitro aromatic compounds

Benzo[k]fluoranthene (BkF) is a condensed multi-ring compounds with high fluorescence quantum yield and Stokes’ shift. Nitro aromatic compounds (NACs) are known to be good electron acceptors and quenchers. The fluorescence quenching of benzo[k]fluoranthene in poly(vinyl alcohol) film by different NACs, e.g. nitrobenzene, m-dinitrobenzene, o-nitrotoluene, m-nitrotoluene, p-nitrobromobenzene, o-nitroaniline, p-nitrophenol, etc. has been studied. The BkF film shows a strong quenching in the NACs concentration range from 1×10⁻⁴ to 1×10⁻³ M. The Stern–Volmer plots for NACs are found to be non-linear, but regular in this concentration range, which can be used for estimation of these compounds. The typical response time of the sensing film is found to be 2–10 s. The sensor film also shows minimal interference from different organic molecules and has good reversibility and reproducibility. The sensor gives a sensitivity of 1×10⁻⁵ M for p-nitrophenol.     

碳黑/聚乙烯醇电纺复合纤维的制备与气敏特性研究

通过碳黑(CB)/聚乙烯醇(PVA)混合溶液的电纺,制备了掺纳米CB的PVA复合纤维,用扫描电镜(SEM)观察了它的形貌。CB/PVA复合纳米纤维的形貌取决于混合物中CB的含量。随CB含量的增加,CB颗粒在纤维中的分布逐渐变得均匀;最佳CB/PVA的质量比为3∶10;继续增加CB含量,CB颗粒聚合成团析出,杂乱分布于PVA纤维中。乙醇蒸气测试表明:质量比为3∶10的CB/PVA纤维具有灵敏度高、响应恢复快等特点。     

聚邻苯二胺在传感器中的应用

根据最新研究文献,系统论述了聚邻苯二胺在生物传感器、湿度传感器、重金属离子传感器等领域的应用.指出聚邻苯二胺具有很好的酶固定性能、离子选择透过性能和耐腐性能等,在分析探测领域显示出广阔的应用前景.     

用聚合亚甲蓝修饰的酶电极进行青霉素残留的测定研究

将青霉素酶与亚甲蓝用循环伏安法共聚合到玻碳电极上,制成青霉素酶电极,通过交流阻抗谱对酶电极表征.研究了聚合亚甲蓝在不同pH值下,酸催化还原反应的活化能随pH值的变化.在一定电位范围内,青霉素微小浓度变化与亚甲蓝循环伏安还原峰电流成正比,据此可间接测定牛奶中残留青霉素含量,分别利用计时电流法和循环伏安法在磷酸缓冲溶液和牛奶中测量,计时电流法的线性范围分别为1.40×10-4～2.81×10-3mmol/L和5.61×10-4～2.81×10-3mmol/L,循环伏安法的线性范围分别为2.81×10-4～2.81×10-3mmol/L和1.12×10-3～2.81×10-3mmol/L.     

聚L-半胱氨酸修饰电极的制备及测定抗坏血酸

研究了聚L-半胱氨酸修饰玻碳电极的制备及其抗坏血酸在该修饰电极上的电化学特性,建立了线性扫描溶出伏安法测定抗坏血酸的电化学分析新方法.在pH4.0的磷酸盐缓冲溶液中,用该电极测定抗坏血酸的线性范围为:2.0 ×10-6～4.0×10-3mol/L,检出限(信噪比=3)为1.0×10-7mol/L.对1.0×10-4mol/L抗坏血酸平行测定10次,相对标准偏差为1.3%.该电极具有良好的重现性和稳定性,已用于药剂中抗坏血酸的测定,结果令人满意.     

Assembly of Cu nanoparticles in a polyacrylamide grafted poly(vinyl alcohol) copolymer matrix and vapor-induced response

A vapor-sensitive electroconductive film was designed and assembled by inserting Cu²⁺ particles into a polyacrylamide grafted poly(vinyl alcohol) (PAM-g-PVA) in virtue of a complexation between Cu²⁺ and PVA even PAM, as well as the establishment of inter- and intramolecular attractions between polymer matrices, which were in turn reduced into Cu nanoparticles by sodium hypophosphite as a reducing agent. The PAM-g-PVA graft copolymer was prepared via a simple free radical polymerization reaction initiated by a redox reaction. The resistance responsiveness of the film samples to various organic vapor surroundings was investigated. The responsive magnitude, response time and recovery properties depend on the molecular weight of the graft polymer or the PAM chain length and initial resistances of the film samples or Cu particle contents upon exposed to ether and petroleum ether vapor, etc. The structure and morphologies of the PAM-g-PVA/Cu were characterized by a Fourier transform infrared spectroscope and a transmission electron microscope. The response mechanism of the PAM-g-PVA/Cu films to solvent vapors was accounted for by a swelling theory and an interaction between solvent vapor molecules and nanocomposites as well as the type and strength of interaction that each solvent vapor exhibits on the material.     

Improvements in the long-term stability of a LiCl dew-point sensor using cross-linked porous poly(vinyl alcohol) film

A novel sensing film for a LiCl dew-point sensor was prepared by incorporating LiCl into the cross-linked porous PVA film. Their impedance characteristics and long-term stability was examined. The porous PVA film cross-linked with formaldehyde exhibited superior stability for more than 50 days, even when the film was stored in 50% RH atmosphere where dewdrops appear on the surface of the film. FTIR analysis, dielectric measurements, and SEM observation suggested that this superior stability may be attributed to the unique layered morphology of the coating, which is composed of a cross-linked PVA exterior layer and a primarily porous PVA interior layer that holds LiCl inside.     

苯乙烯-马来酸酐交替共聚物钠盐/聚苯乙烯磺酸钠复合物的湿敏特性

以苯乙烯-马来酸酐交替共聚物钠盐(NaSMA)与聚苯乙烯磺酸钠(NaPSS)复合物为湿敏材料,在叉指金电极上浸涂成膜制备了电阻型湿度传感器,考察了NaSMA和NaPSS浓度对复合湿度传感器响应特性的影响.研究表明,加入NaPSS可降低传感器在低湿下电阻,同时提高传感器的高湿灵敏度.在最佳条件下,当环境湿度从33%RH增...