Preparation of micro-sized and uniform spherical Ag powders by novel wet-chemical method

A novel wet-chemical method was presented for the preparation of the micro-sized and uniform spherical Ag powders on a mass-production scale.The well-defined particles were synthesized by mixing the iron(II) sulfate heptahydrate solution with silver nitrate solution directly by high-speed stirring at room temperature.It is found that a large number of micro-sized and uniform spherical particles with rough surfaces are obtained.The mass ratio of iron(II) sulfate heptahydrate to silver nitrate greatly affects the shape of particles,and when it is relatively low,spherical particles cannot be obtained.The reaction temperature has a great impact on the particle size.As the reaction temperature increases from 8 to 15°C,the mean diameter of particles decreases from 3.5 to 1.6 μm.The additive n-methyl-2-pyrrolidone improves the surface smoothness and compactness of the particles while the particle size is kept unchanged.Scanning electron microscopy,X-ray diffractometry and energy dispersive X-ray analysis were used to characterize the particle products.

Preparation of ultrafine silver powders with controllable size and morphology

The ultrafine silver powders were prepared by liquid reduction method using Arabic gum as dispersant.The effects of different dispersants,pH values,and temperature on the morphology and particle size of silver powders were investigated.It is found that Arabic gum can better adsorb on silver particles via chemical adsorption,and it shows the best dispersive effect among all the selected dispersants.The particle size of silver powders can be finely tuned from 0.34 to 4.09μm by adjusting pH values,while the morphology of silver powders can be tuned by changing the temperature.The silver powders with high tap density higher than 4.0 g/cm3 were successfully prepared in a wide temperature range of 21.8-70°C.Especially,the tap density is higher than 5.0 g/cm3 when the temperature is optimized to be 50°C.The facile process and high silver concentration of this method make it a promising way to prepare high quality silver powders for electronic paste.

Fabrication and Characterization of Nano Silver Powder Prepared by Spray Pyrolysis

Silver powder was fabricated by spray pyrolysis, using 2%-20% AgNO3 solution, 336-500 mL/h flux of AgNO3 solution, 0.28-0.32 MPa flux of carrier gas and in the 620-820 ℃ temperature range. The effects of furnace set temperature, concentration of AgNO3 aqueous solution, flux of AgNO3 aqueous solution as well as carrier gas on the morphology and particle size distribution of silver powder, were investigated. The experimental results showed that with the high concentration of AgNO3 aqueous solution, the average grain size of silver decreased with the increasing of furnace set temperature. But the gain size distribution was not homogenous, the discontinuous grain growth occurred. With the low concentration of AgNO3 aqueous solution, the higher furnace set temperature made the nano sliver grains sintered together to grow. Nano silver powder about 100 nm was fabricated by spray pyrolysis, using 2wt% AgNO3 solutions, 336 mL/h flux of AgNO3 aqueous solution, 0.32 MPa flux of carrier gas at 720 ℃ furnace set temperature.

PREPARATION OF SILVER POWDER FOR CONDUCTIVE PASTE

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Effect of Water Chestnut Powder on Gel Properties of Silver Carp Surimi

[Objectives]The effects of water chestnut powder on the gel properties and quality of silver carp surimi were investigated.[Methods]The surimi gel was prepared by adding 0%,1%,2%,3%,4%and 5%of water chestnut powder to the surimi of silver carp.The gel properties,water-holding capacity,cooking loss,whiteness value,puncture and texture profile analysis(TPA)indexes of surimi products were determined to assess the effects of adding different amounts of water chestnut powder on surimi gel.[Results]The results showed that the gel strength,breaking force and depression distance of surimi products increased first and then decreased with the increase of the addition of water chestnut powder.Compared with the control group,the hardness and chewiness of surimi gel in TPA could be significantly improved by adding water chestnut powder.When the addition of water chestnut powder was 2%,the maximum water-holding capacity was 83.68%;the cooking loss rate was the lowest;and the whiteness value was the highest.Adding 2%of water chestnut powder could significantly improve the gel properties of silver carp surimi and obtain a good gel product.[Conclusions]This study provides a scientific basis for the effective utilization of water chestnut resources and the development of new fish surimi products.

Preparation of titanium dioxide/silver sulfate powder and its antibacterial activity

Antibacterial powders of titanium dioxide/silver sulfate were produced by heat-treatment of the metatitanic acid, as precursor, into which the silver nitrate was added. The influences of heating temperature on the structure and composition of the product were investigated through XRD and SEM. The results show that the powder is spherical in the phase of TiO2-Ag2SO4. The granularity of the particles increases from 10.7nm to 28.7nm with the temperature of heat-treatment increasing from 300℃ to 800℃. The antibacterial activity of the powder was judged in the way of the minimum inhibitory contents （MiCs）. When the content of silver sulfate is less than 2%, the photocatalysis of titanium dioxide and silver ions cooperate to kill bacteria. And the MiCs decrease and keep around 1.0×10 -41.5×10 -4 constantly with the increase of silver content. Furthermore, the MiCs decrease with the increase of temperature of heat-treatment when the temperature is lower than 500℃. But when the temperature is beyond 600℃ the MiCs increase quickly, which shows the inferior antibacterial performance.

Silver removal from molten lead through zinc powder injection

A silver removal process was carried out on a Pb-Ag alloy through zinc powder injection of three different sizes （3.55, 44.4 and 734.8μm） with a top submerged lance using nitrogen as carrying gas. The higher silver removal was obtained for the zinc powder size of 44.4μm, while the lowest silver removal efficiency was attained for the smaller particle size. The AgZn phase was detected in the slag for the 44.4 and 734.8μm particle sizes by XRD, which was in agreement with SEM-EDS analysis. Experimental behavior was explained according to the melting and residence time of the injected particles.

Study on Properties of Silver Powder for Maki-e

Maki-e is a traditional Japanese decorative technique that uses the natural lacquer Urushi and metal powders. In 2014, there exist only two companies that manufacture silver powder for the purpose of Maki-e, and this study focuses on comparing the powders manufactured by them. Gloss and color of each silver powder were measured after Maki-e decoration was finished, and EDS (energy-dispersive X-ray spectroscopy) was used to determine the differences in their chemical composition. In addition, to verify the effect of polishing, residual gloss after sulfuration and polishing was measured. The study revealed that the shapes of the silver powders (Maru-fun, No. 1) manufactured by the two companies are different and it affects the occupancy rate of Urushi and powder, which in turn affects their gloss and color. Wakou silver has a very strong resistance to sulfuration;however, owing to its Pd content, its chroma is much lower than that of other powders. It was shown that sulfuration on powder surface can be removed by polishing irrespective of the shape and chemical composition ratio of the particles.

Effects of Supplemental Amount of Tuanfeng Lotus Seed Powder on Quality of Silver Carp Surimi Products

[Objectives]This study was conducted to improve the gel properties of freshwater surimi and its products. [Methods] Tuanfeng lotus seed powder was added to frozen silver carp, and the relationship between the addiamount of Tuanfeng lotus seed powder(1%, 2%, 3%, 4% and 5%) and the quality of surimi products was studied, so as to improve the quality of surimi products. [Results] The water holding capacity(86.71%±0.36%), hardness(3 566.64±51.15) g, chewiness(2 697.16±15.81) g and gel strength(692.54±23.19) of surimi products increased to the maximums when the addition amount of lotus seed powder was 3%. Meanwhile, the cooking loss rate was reduced to the minimum(13.00%±0.17%), and the sensory quality was the best, although the whiteness of surimi products decreased slightly with the increase of Tuanfeng lotus seed powder. Therefore, the quality of silver carp surimi products could be improved obviously when the dosage of Tuanfeng lotus seed powder was 3%. [Conclusions] This study provides more new ideas for improving the quality of silver carp surimi products, and simultaneously makes the development of lotus seed food more diversified.

枸杞粉对白鲢鱼糜凝胶品质的影响

该研究以冷冻白鲢鱼糜为实验原料,向其中添加枸杞粉(wolfberry powder,WP),分析不同添加量[0.25%、0.5%、0.75%、1%、1.5%(质量分数)]的WP对白鲢鱼糜凝胶持水性、蒸煮损失率、白度值、水分分布、凝胶特性、微观结构、感官评价及气味特征的影响。结果表明,随着WP含量的增加,鱼糜凝胶的持水性、硬度、咀嚼性和凝胶强度都表现出先增大后减小的趋势,当WP的添加量为0.5%时达到最大,分别为78.55%、(2716.77±75.76)g、(2185.15±32.46)g和1087 g·cm;而蒸煮损失率则表现出先减小后增大的趋势,在0.5%的添加量时,蒸煮损失率最小,为7.49%。在鱼糜中加入WP后,可以减少鱼糜凝胶中自由水的比例,增加不易流动水的比例,使鱼糜凝胶保留更多水分,且当WP在最适添加量0.5%时,鱼糜凝胶中只检测到结合水和不易流动水,未检测到自由水。适量WP的添加会增强鱼糜凝胶的网络结构,使其变得更加致密均匀。WP的添加会减小鱼糜凝胶的白度值和色泽评分,但在最适添加量0.5%时,其颜色总体可接受。此外,感官评价和电子鼻分析结果表明,当WP在最适添加量0.5%时,可以显著改善鱼糜凝胶的风味品质。研究结果可为生产高品质的鱼糜产品提供理论依据。

银粉对硅异质结太阳电池用低温银浆的影响综述

银浆是硅异质结太阳电池的重要材料,更低的体积电阻率和接触电阻、良好的附着力、优良的细线印刷性能及组件栅线抗腐蚀老化是其不断改进的方向。作为导电相,银粉的性能和含量对银浆有着至关重要的影响。该文基于低温固化银浆导电机理以及SHJ电池对银浆性能的追求,综述了银粉的振实密度、形貌、粒径、表面处理剂及其与有机物的适配。进一步探讨了纳米银粉和银包铜粉在SHJ太阳电池用低温银浆中的应用。

非水溶液体系中晶种法制备球形银纳米颗粒

以丙三醇作溶剂,硝酸银为原料,聚乙烯吡咯烷酮(PVP)为分散剂,硼氢化钠为还原剂制备了银纳米晶种;以此银纳米粒子作为初级晶种,以丙三醇作溶剂和还原剂,通过升温提高丙三醇的还原性制备银纳米颗粒。研究分散剂种类、生长液银浓度、晶种加入量对银粉的影响,采用X射线粉末衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)对制备产物的结构、物相、形貌进行表征。结果表明,通过改变条件可以制备出分散性良好、粒径均匀的70nm左右的球形银粉。

高功率半导体用纳米银焊膏的研究现状

第3代半导体作为核心部件,使得更紧凑、高频率、高功率的电子器件在射频和微波电子、能源转换与储存、雷达和通信等领域展现出广泛的应用潜力。然而,高性能电子器件对其封装材料的导电性、导热性以及连接处的机械性能提出了更为严格的要求。纳米银焊膏因其卓越的低温烧结性能和在高温环境下的出色表现引起了广泛关注。然而,国内银粉和银焊膏产品的质量相对较低,且研发过程缺乏理论指导,必须依赖进口材料。基于高功率半导体用纳米银焊膏,综述了通过液相化学还原法合成纳米银粉的研究进展,以及纳米银焊膏的烧结机理、影响其性能的因素和控制方法,有望为国内纳米银焊膏的研发和生产提供有益的指导和支持。

臭氧+MVR+脱氨+MBR工艺对银粉加工废水的处理

银粉加工废水具有高盐、高COD_(Cr)和高氨氮等特点,对环境污染大,且处理难度大。针对某单位的银粉加工废水,采用臭氧催化氧化+MVR蒸发+氨氮吹脱+MBR生化组合工艺对其原有工艺进行改造。结果显示,废水出水水质COD为17 mg/L、氨氮为0.72 mg/L、TDS为601 mg/L、总氮为6.55 mg/L、pH为6~9,出水达到《四川省岷江、沱江流域水污染物排放标准》DB 51/2311-2016水质标准。采用臭氧催化氧化替代芬顿氧化,直接运行费用为71.12元/m~3,比芬顿单元降低157.88元/m~3,危险废物减少791.29 kg/d。该方法具有显著的环境效益和经济效益。

超声波法制备银合金粉末的研究

光谱分析用标准样品在标准样品的发展中逐渐占主导地位,贵金属标准样品因成分偏析等因素使其标准样品难以制备。粉末冶金技术可制备出成分均匀、晶粒细小的合金,优质粉末的制备可为标准样品的制备提供原料基础。本文借助超声波清洗机对银合金进行振动,探究能否制得银合金粉末,并通过测试分析结果探究该方法能否达到细化晶粒的效果。实验分别从形态、粒径与晶粒、化学成分三个方面来进行对比说明,通过使用偏光显微镜、扫描电镜及能谱仪对银合金及银合金粉末进行观察测试,X射线荧光光谱仪对化学成分结果进行验证。使用超声波振动银合金制备银合金粉末,作为一种新型的制备银合金粉末的方法,超声功率达到600 W时,可以制备出平均粒径为9.54μm的粉末,其中超过70%的银合金粉末小于10μm。银合金的平均晶粒尺寸为22.5μm,说明超声波振动银合金具备细化晶粒的条件,结合形态和成分测试观察结果,说明通过制备粉末的方式既可以细化晶粒,也可以改善组织均匀性。

一种无溶剂型电子封装用导电胶的研制

为了解决导电胶黏剂因综合性能不足而导致大规模应用的受限,本文以酚醛环氧、多官能环氧为导电胶树脂基体,选用了4,4′-二氨基二苯砜(DDS)作为固化剂,片状银粉作为导电填料,通过调节银粉和固化剂的用量,制备了有良好流变性、导电性、力学性能的导电胶。通过分析测试,得到导电胶的黏度为32 800 mPa·s,触变指数为4.0,体积电阻率为4.34×10^(-4)Ω·cm,剪切强度为17 MPa,热导率为3.96 W/(m·K),Cl^(-)、Na^(+)和K^(+)分别仅为6.79×10^(-5)、6.31×10^(-5)和<10^(-5)。该导电胶综合性能优异,可应用于电子元器件及其他导电导热功能性材料的粘接。

化学还原法制备银粉及其在导电胶中的应用

研究化学还原法制备银粉过程中Ag~+浓度、还原液滴加方式、分散体系对银粉形貌的影响机理,获得一款适合用于导电胶制备的银粉。采用硝酸银为银源,分别以明胶、阿拉伯树胶以及聚乙烯吡咯烷酮(简称PVP)和明胶混合体系作为分散剂,研究不同分散体系对银粉形貌及粒径等性能。结果表明银粉粒径随着溶液中Ag~+浓度升高呈现变大趋势;不同分散体系制备的银粉形貌差别较大,而粒径差别不大。以明胶为分散剂制备的银粉为规则的球状,以阿拉伯树胶为分散剂制备的银粉为规则的片簇状,以PVP和明胶混合体系作为分散剂制备的银粉形貌为球状与片状的混合。还原液加入方式对银粉粒径也有较大影响,以一次加入方式制备的银粉粒径分布范围较大。此外,银粉粒径随反应温度升高呈现逐渐变大的趋势。通过对比发现最适合用于导电胶制备的银粉为用以阿拉伯明胶单分散体系制备的球状银粉。化学还原法制备银粉过程中,溶液中Ag^(+)浓度、还原液滴加方式以及分散体系均对银粉形貌和粒径有不同程度的影响,用不同形貌的银粉制备导电胶时的体积电阻率有差别。

硫酸-硫酸亚铁体系制备高分散球形银粉

以AgNO_(3)作为银源,FeSO_(4)作为还原剂,H_(2)SO_(4)作为稳定剂,通过一步还原法制备球形银粉。研究了还原剂用量、稳定剂用量及操作方式对银粉形貌的影响。结果表明,对2.5gAgNO_(3),当FeSO_(4)用量在11g,0.1mol/LH_(2)SO_(4)用量在0.1g时,向AgNO_(3)-H_(2)SO_(4)溶液中快速加入FeSO_(4)溶液,制备所得银粉形貌均一,粒径分布范围窄,形貌为形状规则球形银粉,分散性好。对反应体系中的吸附反应机理进行分析,发现SO4^(2-)及Fe^(2+)浓度对银颗粒形貌有明显的影响。

响应面法优化板栗鱼肠的加工工艺

以信阳本地产南湾鲢鱼和板栗粉为主要原料,并添加大豆分离蛋白、卡拉胶等辅料制成鱼肠。以鱼肠的色泽、持水性、凝胶强度、TPA、感官评分为指标,研究了鱼糜/板栗粉质量比、大豆分离蛋白、卡拉胶、食盐、料酒的添加量对鱼肠品质的影响。得到鱼肠最佳制作配方:鱼糜/板栗粉质量比12∶1、大豆分离蛋白、卡拉胶、料酒、食盐质量分数为6%、0.8%、4%,2%。所得鱼肠平均白度78.2%、感官评分95.6、持水率87.7%、凝胶强度3761.2 g·mm。所得鱼肠肉质细腻嫩滑,具有光泽,肉味浓郁伴有板栗清香。本研究为新型鱼肠产品的研发提供一定的理论依据和参考,有利于丰富市售鱼糜制品种类。

化学镀温度对镀银镍粉的微观结构及其性能的影响

为探究在镀银镍粉制备过程中温度对其性能的影响,以硝酸银为银源,Ni颗粒为基材,采用置换-还原化学复合镀法制备镀银镍粉。以粉体为填料,不饱和聚酯树脂为基体,制备导电涂层,并对其导电性和电磁屏蔽性进行测试分析。利用扫描电子显微镜、能谱仪、X射线衍射仪、松装密度测试仪、振实密度测试仪、直流低电阻测试仪等对镀银镍粉微观形貌和宏观特征进行表征与测试分析。结果表明:当化学镀温度为40℃,所制镀银镍粉的Ag层包覆完整、均匀、致密,银的质量分数可达75.01%,粉体的压实电阻可低至293.15 mΩ。粉体松装密度为5.417 g·cm^(-3),振实密度为5.778 g·cm^(-3)。所制导电涂层的电阻率为4.30 mΩ·cm,电磁屏蔽效能为45.27 dB,具有良好的电磁屏蔽性能。