An Experimental Investigation for Agglomeration of Aerosols in Alternating Electric Fields

Electrostatic precipitators have a relatively low efficiency for the collection of submicron particles. One way to increase their efficiency is to enforce the agglomeration and thereby form larger particles. In this work, a study has been initiated for enhancing the agglomeration between oppositely charged particles by using an alternating electric field to increase the relative motion between such particles. A simple first order computer model was developed for establishing the magnitude of agglomeration and for characterizing the interdependence of different parameters of importance. A laboratory experimental unit was established for studying various practical configurations for agglomeration in alternating electric field, using finely dispersed limestone powder. For the measurements of particle size distributions, a Berner Low Pressure Impactor was used. The preliminary results have shown a 50% reduction in the mass concentration of submicron particles, for oppositely charged particles in an alternating electric field. On the other hand, no agglomeration was measured by the use of a quadrupole field.     

交流电铝阳极氧化的研究

在恒电流条件下研究Ｖ－ｔ曲线，电流波形及膜的表面形貌，低电流密度下，初期Ｖ－ｔ曲线不出现峰值，相应的电流波形不发生畸变，阳极氧化和化学氧化都优先发生在基体的缺陷附近。     

Demagnetization Treatment of Remanent Composite Microspheres Studied by Alternating Current Susceptibility Measurements

The magnetic remanence of silica microspheres with a low concentration of embedded cobalt ferrite nanoparticles is studied after demagnetization and remagnetization treatments. When the microspheres are dispersed in a liquid, alternating current (AC) magnetic susceptibility spectra reveal a constant characteristic frequency, corresponding to the rotational diffusion of the microparticles; this depends only on particle size and liquid viscosity, making the particles suitable as a rheological probe and indicating that interactions between the microspheres are weak. On the macroscopic scale, a sample with the dry microparticles is magnetically remanent after treatment in a saturating field, and after a demagnetization treatment, the remanence goes down to zero. The AC susceptibility of a liquid dispersion, however, characterizes the remanence on the scale of the individual microparticles, which does not become zero after demagnetization. The reason is that an individual microparticle contains only a relatively small number of magnetic units, so that even if they can be reoriented magnetically at random, the average vector sum of the nanoparticle dipoles is not negligible on the scale of the microparticle. In contrast, on the macroscopic scale, the demagnetization procedure randomizes the orientations of a macroscopic number of magnetic units, resulting in a remanent magnetization that is negligible compared to the saturation magnetization of the entire sample.     

粉煤灰水泥硬化浆体微结构的交流阻抗研究

采用交流阻抗方法对掺有粉煤灰的水泥硬化浆体的微结构及对不同龄期粉煤灰水泥硬化浆体的交流阻抗参数和硬化水泥浆体微结构的关系、抗压强度进行了研究,并与纯硅酸盐水泥体系进行了比较。结果表明,与纯硅酸盐水泥相比,粉煤灰水泥水化后期的水化程度较高,浆体总孔隙率较低。     

Alternating Current Electrophoretic Deposition of Antibacterial Bioactive Glass-Chitosan Composite Coatings

Alternating current (AC) electrophoretic deposition (EPD) was used to produce multifunctional composite coatings combining bioactive glass (BG) particles and chitosan. BG particles of two different sizes were used, i.e., 2 μm and 20–80 nm in average diameter. The parameter optimization and characterization of the coatings was conducted by visual inspection and by adhesion strength tests. The optimized coatings were investigated in terms of their hydroxyapatite (HA) forming ability in simulated body fluid (SBF) for up to 21 days. Fourier transform infrared (FTIR) spectroscopy results showed the successful HA formation on the coatings after 21 days. The first investigations were conducted on planar stainless steel sheets. In addition, scaffolds made from a TiAl4V6 alloy were considered to show the feasibility of coating of three dimensional structures by EPD. Because both BG and chitosan are antibacterial materials, the antibacterial properties of the as-produced coatings were investigated using E. coli bacteria cells. It was shown that the BG particle size has a strong influence on the antibacterial properties of the coatings.     

单扫描极谱法快速测定蛋白质的研究

在pH 4.7的HAc-NaAc缓冲溶液中,邻二氮菲与蛋白质相互作用,使邻二氮菲在-0.99 V(vs.SCE)处的还原峰电流下降,电流降低值与所加的蛋白质(人血清白蛋白、牛血清白蛋白、溶菌酶)的量在一定范围内呈线性关系,线性范围分别为2.0~22 mg/L,2.0~20 mg/L和4.0~26 mg/L;检测限分别为1.0 mg/L,1.0 mg/L,2.0mg/L。运用该方法测定了人血清中白蛋白的含量,结果满意。     

极谱法测定金矿石中的砷

在氢氧化钠-硼砂的底液体系中对金矿石进行极谱测定,在峰电位-0.35 V,砷的质量浓度在2～400μg/mL之间时砷的浓度与峰电流成线性关系。选用含有甘露醇的氢氧化钠硼砂的底液测定砷,精度好,准确度高,检出限为0.002μg/mL。     

甲基橙极谱法测定痕量甲醛

稀硫酸介质中,痕量甲醛的存在对溴酸钾氧化甲基橙的反应有很强的催化作用。而甲基橙及其氧化产物均能在滴汞电极上产生灵敏的极谱吸附波。本文以极谱法测定催化反应过程中甲基橙浓度的变化,建立了催化动力学极谱法测定痕量甲醛的方法。     

工业纯铝交流电阳极氧化膜着色实验研究

以工业纯铝L2为实验材料,采用硫酸交流阳极氧化-着色工艺在铝表面制备黑色膜层,重点分析着色溶液pH、温度及乙酸钴质量浓度对黑色膜层的影响,通过分析型扫描电镜测试,结果表明,电解液成分为200 g/LH2SO4、1 g/LAl2O3,U为12V,θ为(20±1)℃,t为60min的交流电阳极氧化条件下,着色液成分为30~40 g/LCo(CH3COO)2,1 g/LNiF2.2H2O,θ为50~60℃,pH为4.5~6.0,t为30min的工艺条件下可以获得与工业纯铝L2基体良好结合力,耐蚀、耐热及吸光性较好的黑色膜层。     

极谱法测定放射性废水中的铕

<正> 关于极谱测定铕的方法,曾研究过在LiCl、LiI 支持电解质中的测定和在0～60%的甲酰胺、0.1～0.2MNaClO_4底液中铕的极谱行为,讨论过在0.3～2MKCl 底液中铕的电极反应,但上述工作均未用于样品的分析;曾在30%的CaCl_2底液中,于pH4.5～5间极谱测定铕,但较大量的Pb、Cd 干扰铕的测定;曾在含10%EDTA 的15%NaCl 底液中,于pH9时,用方波极谱测定希土氧化物中的铕。至于放射性废水中铕的     

示波极谱法测定人发中的铅

采用了HNO3 HClO4消化样品,盐酸溶解后在酒石酸 碘化钾 抗坏血酸体系中,铅(Ⅱ)于-0.54V得到一灵敏的一阶导数吸附催化波。铅在0.025～3μg/mL范围内,峰高与铅(Ⅱ)质量浓度之间呈良好的线性关系,检出下限为0.025μg/mL。加入标准平均回收率为91.3%～105%。此方法具有灵敏、准确、快速等特点,适用于人发和食品中微量铅的测定。     

废水及空气中微量苯胺的极谱法分析

用极谱方法分析环境中的苯胺污染物的含量,苯胺重氮化反应产物再与亚硫酸钠、甲醛的反应物有一灵敏的二阶导数极谱波,峰电位-0.71V(vs、SCE)。研究了影响因素,优化了分析条件。线性范围在8.0×10-7～5.0×10-4mol/L,可用于废水与空气中微量苯胺的测定。     

粉煤灰的细度和交流阻抗谱的关系

通过对同一电厂同一时段的不同细度的低钙粉煤灰在干燥和含水混合浆体状态下的交流阻抗谱的测定,研究了粉煤灰细度与交流阻抗谱的关系。结果表明,粉煤灰的活性虽然可由多种因素决定,但交流阻抗谱可以较全面地对它进行表征,其中细度是影响粉煤灰活性的主要因素之一。     

Polarography of conjugated unsaturated lipids

Conjugated fat-soluble vitamins, methylenic interrupted and conjugated fatty acids were polarographically investigated in both basic and neutral solvents. The half-wave potentials of all-trans-retinol, 13-cis-retinol, all-trans-retinyl acetate, all-trans-retinal, and Vitamin D₂ and D₃ were related to the number of double bonds in conjugation and their geometrical configuration. A minimum of three double bonds in conjugation and their geometrical configuration. A minimum of three double bonds in conjugation was required before reduction took place at the cathode, and as the number of conjugated bonds increased in the lipid compounds, the initial reduction wave took place at a lower half-wave potential. Investigation of conjugated double bonds in triglycerides and in alkali-isomerized linolenic and arachidonic acids gave reduction waves the half-wave potentials of which were related to the number of double bonds in conjugation. In both basic and neutral solvents there was a minimum of three double bonds in conjugation necessary to obtain a reduction wave at the dropping mercury electrode. Ultraviolet absorption curves of the prolonged reduction of polyunsaturated conjugated fatty acids indicate a step-wise reduction of each end of the polyunsaturated conjugated double bonds. In neutral solvent the log of the conjugated double bonds versus the half-wave potential (versus mercury pool anode) gave a linear equation, E₁=2.98−1.6 log C. A proposed mechanism for the step-wise reduction of conjugated lipids is presented and discussed. Presented in part at AOCS Meeting, Chicago, October 1964.     

An Investigation of Current Reversal Mode for Gas Sensing With a Solid Electroyte

Current reversal mode (CRM) is a dynamic measuring technique, which has the potential to determine accurately the equilibrium emf of a solid electrolyte sensor, while providing additional information regarding sensor resistance. This can be exploited as a diagnostic tool. A fundamental study, using an oxygen sensor with yttria-stabilized zirconia as the solid electrolyte, has been performed to identify the CRM parameters of frequency and bias voltage for making accurate measurements. A mathematical model has been developed for the application of CRM in terms of an equivalent electrical circuit. The predictions of the model agree well with the experimental data.     

交流示波极谱滴定法测定磷

在ｐＨ５．５六次甲基四胺－盐酸缓冲溶液中,用硝酸铅滴定磷酸根,生成磷酸氯化铅复盐沉淀,根据过量的铅离子在交流示波极谱图上切口出现指示滴定终点。方法准确性好,酸度范围宽,操作简便,已用于磷肥中可溶性磷的测定。     

Polarography of 5-nitro-orotic acid

Polarography of 5-nitro-orotic acid in aqueous medium has been carried out in the pH range 1–10, using different buffer systems. There are two well-defined steps up to pH 9·0; the first step is purely diffusion-controlled (6 e) reduction at all pH values, and the second step (4 e) is purely diffusion-controlled in the acidic range and shows adsorption characteristics in the alkaline. Above pH 9, the compound is reduced in three steps: the first is purely diffusion-controlled (4 e); the second (4 e) and third (2 e) steps have adsorption character. At pH> 11, the reduction involves three steps, but the wave heights are not reproducible. The number of electrons involved in the diffusion-controlled steps was determined by comparing the wave heights with that of the first step of nitrobenzene reduction under identical conditions, which was confirmed by finding the diffusion coefficient D with the help of the McBain-Dowson cell. Kinetic parameters (n_a and −log k°) have been computed for the diffusion-controlled steps, using Koutecky's method. The probable reduction mechanism is discussed.     

催化波极谱法测定化探样品中钨量及钼量

试样经碱熔分解,水提取,铁、锰、钴、镍元素呈氢氧化物沉淀与钨、钼分离。在0.34 moL/L硫酸-2 g/L苯羟乙酸-24 g/L氯酸钠-0.08g/L辛克宁体系中,钨和钼均能产生灵敏的极谱催化波,峰电位约为-0.70 V和-0.07 V(对饱和甘汞电极)。方法检出限为W 0.29μg/g、Mo 0.26μg/g,精密度(RSD,n=12)为W 1.21%~10.1%、Mo 2.7%~12.4%,准确度(RE,n=12)为W-3.7%~2.33%、Mo-4.79%~3.17%。适用于化探样品中钨钼元素的连续测定。     

Direct and High Frequency Alternating Current Conduction Mechanisms in Solution Cast Polyaniline Films

Frequency dependent (ac) and independent (dc) conductivity measurements have been carried out on polyaniline (PANI) films deposited by solution casting technique. Under low electric field (1 × 10³ V/cm) condition, the dc conductivity measured in the temperature range of 173–303 K obeys the three-dimensional variable range hopping (3D VRH) formalism. The Mott parameters such as localization length (α^?1 ≈ 7 Å), density of states [N(E _F ) = 1.04 × 10¹⁹ states/eV cm³], hopping range (R _hop = 60 Å) and hopping energy (W _hop = 0.38 eV) are computed. The ac conductivity measured in the frequency range 10 kHz–5 MHz and in the temperature range 150–380 K follow a power-law dependence σ _ac ～ ω ^s, typical for charge transport by hopping or tunnelling processes. Therefore, the experimental results are analyzed with reference to various theoretical models based on quantum-mechanical tunnelling and classical hopping over barriers. The observed minimum in the temperature dependence of the frequency exponent s strongly suggests that tunnelling of large polarons is the dominant transport process. The polaron radius (r _p ≈ 25 Å) and barrier height for infinite site separation (W _HO ≈ 0.22 eV) are evaluated. The density of states [N(E _F)] and tunnelling distances (R _ω ) are estimated and discussed in terms of frequency and temperature.     

催化极谱法连续测定化探样品中的钨、钼

通过试验及理论分析,讨论了催化极谱法测定化探样品中的W、Mo的影响因素.综合主要影响因素,选择了最佳实验条件.W、Mo的方法检出限分别为0.4 μg/g,0.6 μg/g.W、Mo的浓度均在0～0.036 μg/mL,0.036～0.36 μg/mL与电流强度呈线性关系.用国家一级标样GBW07123进行精密度实验,W、Mo的RSD(n=12)均为15.5%.加标回收试验结果,W、Mo的回收率分别为95.0%～108%,92.0%～105%.经化探样品国家一级标准物质验证,测定结果与标准值相符.