Explanation of the thermal formation of dioxins from thermodynamic viewpoint

The thermal formation of dioxins is typical of recent environmental issues relating to metallurgy. To analyze the behavior of these toxic species, computer assisted thermodynamic assessments were extensively carried out. In the homogeneous gas phase equilibria of the C−O−H−Cl system, the formation of dioxins is usually observed below 300–350°C, but is observed at higher temperature under the condition of oxygen deficiency. It has become clear that the presence of enough oxygen and hydrogen, as well as a decrease in chlorine content, would be desirable to prevent dioxin formation. From a strict thermodynamic standpoint, dioxins are meta-stable products observed under the retardation of the carbon deposition reaction which must be very slow at low temperature. The effects of some inhibitors or accelerators on the formation of dioxins are also discussed. This article based on a presentation made in the symposium “2000 Spring Meeting of the Korean Institute of Metals and Materials”, held at Sunchon National University, Sunchon, Korea, April 21–22 under the auspices of The Korean Institute of Metals and Materials.     

Optical and electrical transport properties of polyaniline–silver nanocomposite

Polyaniline–silver nanocomposite has been synthesized successfully by the chemical oxidative polymerization of aniline with ammonium peroxydisulphate as an initiator in presence of negatively charged silver nanoparticles. Silver nanoparticles are prepared by standard citrate reduction method. TEM, SEM, XRD, FTIR, TGA, DSC, optical absorption and photoluminescence studies are done for the morphological, structural, thermal and optical characterization of the polyaniline nanocomposite. From the TEM and SEM image, it is observed that nanoparticles are well dispersed in the polyaniline matrix. XRD pattern shows that polyaniline is amorphous, but peaks present in XRD pattern in polymer nanocomposites are for silver nanoparticles. TGA and DSC results show that polyaniline silver nanocomposite is more crystalline and more thermally stable. A surface plasmon absorption band is obtained from the optical absorption at 380 nm, which indicates that silver nanoparticles are present in the polyaniline matrix. The optical band gap of nanocomposite decreases with increasing content of silver nanoparticles. An enhancement in photoluminescence has been observed in polyaniline–silver nanocomposite than that in pure polyaniline. The electrical conductivity of polyaniline–silver nanocomposite increases with increase in silver nanoparticle content than that of pure polyaniline. This is a simple way by which optical and electrical properties of polyaniline may be enhanced by doping with suitable nanoparticles.     

NaOH和NiSO4添加剂浓度对短碳纤维化学镀银结构和导电率的影响

目的制备镀层均匀、结合力好的短碳纤维镀银层。方法以葡萄糖为还原剂,在短碳纤维表面进行化学镀银,研究了NaOH浓度、NiSO_4添加剂浓度对短碳纤维化学镀银层结构和性能的影响。采用X射线衍射仪、扫描电子显微镜对镀银碳纤维的结构、形貌和成分进行分析,测试了镀银后纤维的密度、导电率。采用冷热循环法评估镀层与碳纤维的结合强度。结果增大NaOH浓度可提高银氨络合物离子浓度,加快了反应速率。合适的NaOH浓度有助于获得高质量的镀银层,低浓度和高浓度NaOH条件下均会产生漏镀和镀层不均匀现象,导致镀银碳纤维性能的降低。NiSO_4添加剂加入到溶液中后,Ni~(2+)将优先吸附在碳纤维表面,这不仅增大了碳纤维表面银单质的形核率,同时也降低了反应速率。合适的NiSO_4浓度有助于改善银镀层的质量,低浓度和高浓度NiSO_4条件下得到的镀层性能均不足。结论 NaOH质量浓度为7g/L时获得的镀银层分布均匀,结晶度良好,密度较大,导电率也较好。NiSO_4浓度为5×10~(-5) mol/L时能获得光滑、均匀、平整的镀层,密度最大,导电率最优。     

中温快烧银浆表面亮度的影响因素

银层不亮是中低温烧结银浆经常出现的问题。研究了乙基纤维素、玻璃、添加剂及银粉对烧结银层发红的影响。结果表明,乙基纤维素的灰分和玻璃中的重金属氧化物是导致烧结银层发红的重要原因。优化配方使用混合银粉,加入复合添加剂和氧化剂,选用合适的玻璃粉,所得银浆料快速烧结,银层表面白色光亮、致密,其粘度、印刷性能、方阻、附着力等各项指标符合要求。     

The method of conventional calorimetric probes — A short review and application for the characterization of nanocluster sources

A short overview on the method of applying (passive) calorimetric probes is given. Calorimetric probes have been used for the characterization of a large variety of process plasmas ranging from arc discharges, different types of magnetrons, rf-discharges for plasma polymerisation and etching purposes, ion beam sources and atmospheric pressure discharges. The aim of this work is to show the versatility of the calorimetric method for the characterization of metal cluster sources. In a second part we show the current status of the calorimetric method and first measurements for the characterization of such a plasma source which is used for deposition of silver nanoclusters which will be embedded into a polymer matrix to form nanostructured materials with special optical and electrical properties.     

微波辅助法制备纳米银胶及其在拉曼表面增强方面的应用

采用一步微波辅助法制备了纳米银胶,并利用紫外-可见吸收光谱,透射电子显微镜(TEM)和原子力显微镜(AFM)等检测手段对纳米银胶相应的性质和结构进行了表征。利用罗丹明6G(R6G)为探针分子,考察了不同反应时间制备的纳米银胶对拉曼散射(SERS)的表面增强效果。结果表明,纳米银胶可以提高拉曼散射的信号强度,比较和分析了增强后的拉曼光谱。同时,我们对纳米银胶增强拉曼散射信号的机理进行了详细的研究。     

Mechanism of silver-influenced bacterial leaching of chalcopyrite, pyrite and a copper ore

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Effects of silver powder particle size on the microstructure and properties of Ag-Yb<Subscript>2</Subscript>O<Subscript>3</Subscript> electrical contact materials prepared by spark plasma sintering

Ag-Yb₂O₃ electrical contact materials were fabricated by spark plasma sintering (SPS). The effects of silver powder particle size on the microstructure and properties of the samples were investigated. The surface morphologies of the sintered samples were examined by optical microscope (OM), and the fracture morphologies were observed by scanning electron microscopy (SEM). The physical and mechanical properties such as density, electrical resistivity, microhardness, and tensile strength were also tested. The results show that the silver powder particle size has evident effects on the sintered materials. Comparing with coarse silver powder (5 μm), homogeneous and fine microstructure was obtained by fine silver powder (≤0.5 μm). At the same time, the electrical conductivity, microhardness, and tensile strength of the sintered samples with fine silver powder were higher than those of the samples with coarse silver powder. However, silver powder particle size has little influence on the relative densities, which of all samples (both by fine and coarse silver powders) is more than 95%. The fracture characteristics are ductile.     

INFLUENCES OF DENSITY AND DIMENSION OF CARBON NANOTUBES ON THEIR FIELD EMISSION

The influences of density and dimension of carbon nanotubes on their electron emission from arrays are studied. The tip electric field of nanotubes, electric field enhancement factor, and optimum nanotube density are expressed by analytic equations. The theoretical analyses show that the field enhancement factor is sensitive to nanotube density, and can be sharply improved at a specific and optimum density. Some experiments have demonstrated these. Owning to electrostatic screening effect, the length of carbon nanotubes has little effect on their emission. A uniformly-distributed carbon nanotube array model is set up, and applied to analysis of carbon nanotube arrays. The results obtained here are in good agreement with the experimental data.     

Stabilization of a surface plasmon resonance (SPR) optical fibre sensor with an ultra-thin organic film: application to the detection of chloro-fluoro-carbon (CFC)

Surface plasmon resonance (SPR) is a powerful technique for direct sensitive (bio) chemical detection. This phenomenon can be used to measure the refractive index of either bulk chemical samples or chemically sensing thin layers. In this work, a SPR fibre optic sensor has been developed. A 50 nm thick silver film is deposited by thermal evaporation onto the silica core of the optical fibre. To protect silver from oxidation, the evaporated silver film was covered with self-assembled monolayers (SAMs) of long-chain alkanethiols (1-octadecanethiol). To characterize these SAMs, silver films evaporated onto macroscopic glass surfaces as test samples and several techniques such as contact angle measurements (sessile drop method), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used. In the subsequent step, a chemically sensing thin layer (polyfluorosiloxane) was deposited onto the thiol surface. In such a configuration the SPR fibre optic sensor was able to detect a few percent of chloro-fluoro-carbon (CFC) vapours.     

The effects of dye dopants on the conductivity and optical absorption properties of polypyrrole

Ten anionic compounds, including four acidic dyes, were used to dope polypyrrole powder. The effects of the dopants on density, optical absorption and conductivity of the polypyrroles were studied. The presence of the dopant in the conducting polymer matrix was verified by ATR-FTIR spectroscopy. Density function theory (DFT) simulation was used to understand the effect of the dopants on the solid structure, optical absorption and energy band structures. Anthraquinone-2-sulfonic acid-doped polypyrrole yielded the highest conductivity. The dye-doped polypyrrole showed an enhancement in its UV–vis optical absorption.     

SPCC钢碱性无氰直接预镀铜工艺研究

目的提高LED支架的性价比,减少SPCC钢表面镀银预镀铜工艺的镀液污染,简化现有的预镀镍-镀铜施镀工艺,提高预镀层质量。方法采用HEDP碱性无氰直接预镀铜方法来简化工艺,用单因素实验法,系统研究了电流密度、镀液pH、电镀温度、HEDP/Cu~(2+)摩尔比、电镀时间等参数,对镀层镀速、孔隙率及镀层表面质量的影响,并表征镀层的微观组织及镀层结合力。结果在阴极电流密度为1.41 A/dm~2,pH值为9.5,温度为50℃,HEDP/Cu~(2+)摩尔比为3.75:1(Cu~(2+)为10 g/L),时间为11 min的条件下,可获得镀速约为1.7 mg/(cm~2·min)的预镀铜层,且镀层与基体的结合力良好,无孔隙,呈良好的光亮/半光亮状的细晶镀层。结论与钢铁表面氰化镀铜及镀银前预镀铜工艺相比,推荐的HEDP直接预镀铜工艺的镀层质量好,可满足直接镀铜和镀银前预镀铜工艺要求,可有效减少镀液污染和简化施镀工艺,对SPCC钢的镀铜工艺改善具有较好的推广价值。     

SnO2表面改性对Ag/SnO2复合粉末烧结组织及性能的影响

采用沉积法和蒸发法分别对SnO2粉末进行WO3、Bi2O3 CuO表面改性处理,并用化学镀方法制备Ag/SnO2复合粉末.通过粉末冶金的方法对Ag/SnO2复合粉末进行烧结实验,并通过光学显微镜、扫描电镜观察烧结体的金相组织及复合粉末的形貌,对SnO2表面改性方法及添加剂种类对Ag/SnO2烧结性能和组织的影响进行了研究.结果表明:沉积法改性使烧结体组织中的SnO2分布更均匀,且能明显提高烧结体Ag/SnO2的致密度.Bi2O3 -CuO改性可消除SnO2的网络状分布,而WO3改性则显著改善电弧侵蚀后的表面组织.     

银纪念币的腐蚀变色研究

银纪念币在大气环境中表面发生变色，失去原有的金属光泽。采用OM，SEM，EMPA，XPS，XRD等现代物理测试技术对变色的银纪念币进行分析。结果表明，银纪念币的变色部位呈均匀的浅褐色，并随机分布着深褐色的斑点。变色银纪念币表面沿着划痕密集分布着蚀孔。表面分析显示，除Ag外，还有S和O元素。XPS，XRD分析发现，变色银纪念币表面存在Ag2S，Ag2SO3和Ag2O。实验室加速变色试验毒明，在含S气体环境中，Ag被氧化生成A82S，导致银纪念币表面变色,从而验证银纪念币的变色是由电化学腐蚀引起的，S和O元素参与了腐蚀历程。     

三种荧光分光光度法测定肿瘤组织中阿霉素含量的研究

目的: 通过比较测定肿瘤组织中阿霉素(ADR)含量的3 种荧光分光光度法, 建立简便、快捷的测定肿瘤组织中阿霉素含量的荧光分光光法。方法: 分别采用正丁醇法、硝酸银法、酸性异丙醇法测定水溶液及肿瘤组织匀浆中ADR 的含量, 比较荧光光谱曲线、回收率和灵敏度。结果: 硝酸银法测定瘤组织匀浆中的ADR 含量, 背景荧光值低, 线性范围0.2～0.8 mg·L^-1, 最低检出量0.15 mg·L^-1, 回收率超过97 %以上。酸性异丙醇法与正丁醇法测定瘤组织中的ADR 含量, 背景荧光值高, 回收率分别<40 %和50 %。结论: 硝酸银法适合肿瘤组织中的ADR 的含量测定, 该方法准确、灵敏、可靠。     

压力与温度敏感涂料用高分子粘结剂的研究进展

压力敏感涂料(PSP)以及温度敏感涂料(TSP)是通过光学手段研究物体表面压力和温度的功能涂层。简述了气体在聚合物中的渗透机理,发光分子氧猝灭以及热猝灭机理,综述了国内外PSP、TSP中常用的高分子粘结剂,并对PSP、TSP所用高分子粘结剂的未来发展方向进行了展望。这两种涂层均由高分子粘结剂和发光分子探针组成,PSP通过发光探针与氧分子作用产生的光物理行为变化来反映压力大小,TSP是通过发光探针随模型表面温度变化导致光物理行为变化来反映温度高低。目前,已发展的PSP用高分子粘结剂主要为氧透过率较高的含硅聚合物及丙烯酸酯类聚合物;已发展的TSP用高分子粘结剂主要为氧透过率较低的聚苯乙烯、聚丙烯腈、聚氨酯等。高分子粘结剂的主链结构、侧基种类与极性、分子间堆砌密度以及与发光分子相互作用,对涂层光物理性能、力学性能以及与基材结合力产生影响。因此,研究PSP与TSP中的高分子粘结剂对于未来两种技术的优化以及一定特殊要求下的应用有较为重要的意义。     

三角形纳米银片合成及其性能表征

在适量的二异辛基磺化琥珀酸钠和柠檬酸钠表面修饰剂存在下,采用硼氢化钠还原硝酸银,在一定的水浴条件下合成出高产率的形貌规则的三角形纳米银片.透射电子显微镜、高分辨透射电子显微镜、原子力显微镜和X射线衍射仪表征表明,银纳米片是具有整齐的原子排列的良好单晶体.紫外-可见一近红外分光光度计表征表明,纳米银三角形片的面内偶极共振峰可达约1230 nm的近红外波段.这种特殊的光谱学特征使得三角形纳米银片在光热触发释放药物、红外吸收及光纤等领域具有重要的用途.研究结果表明,只有在一定的二异辛基磺化琥珀酸钠浓度、反应时间及pH值条件下才能够获得高产率、形貌规则的三角形纳米银片.根据对三角形纳米银片生长过程的显微镜结构表征提出了以三角形框形成为框架的纳米三角形融合生长机制.     

片状银粉的特性及其电性能

系统讨论了片状银粉特性与由它制成的银浆电性能之关系。银浆电性能与片状银粉凇 装密度、比表面积、片状大小不均匀分布及片状厚薄有关。     

Enhancement of the photoluminescence of porous silicon by sputter deposition of semitransparent metal films

Optoelectronic devices based on porous silicon (PS) undergo substantial degradation in luminescence with aging due to atmospheric oxidation. The passivation of PS has been reported with a transparent conducting material or a semi-transparent metal. In this paper, we report enhancement of the photoluminescence (PL) of PS by the passivation of PS with ultrathin metal films such as silver (Ag), aluminum (Al), and gold (Au). It has been found that Ag and Au are respectively most and least effective in enhancing the PL of PS among those three different metals. The highest PL enhancing effect of Ag is mostly attributed to the high electrical conductivity of Ag, whereas the lowest PL enhancing effect of Au is due to the lowest optical transmittance of Au. The details of the PL enhancing effect of metal passivation are discussed with the aid of FTIR analysis results.     

银的二次资源综合回收

因优良的电学、光学和磁学性质,银在工业上的用量越来越大,从银的二次资源物料中回收银具有十分重要的意义。文章重点介绍了银的二次资源和银的回收工艺现状,通过各生产装备和技术,详细阐述了银二次资源综合回收的产业化应用情况。