Longitudinal Magnetoresistance Effect at Low Temperature in Silver Telluride Thin Films

Large longitudinal magnetoresistance(LMR)was observed in nonmagnetic silver telluride Sims.The magnitude of the LMR is not simply dependent on T and H,for example,multi-peaks of p at low held and low temperature appear in the Ag-Te Sim.Because both of-△ρ/ρand a transition from-△ρ/ρto+△ρ/ρexist in Ag-Te Sims,the magnetoresistance(MR)behavior of the Ag-Te Sim does not like the bulk Ag-Te,but likes the doped semiconductors.About-27%of LMR was observed at low Seld in the Ag-Te Sims,while it could be negligible in the doped semiconductors.The MR behavior in Ag-Te Sims is discussed by means of a formation of impurity bands in the films.

Mutagenic breeding of silver-resistant Acidithiobacillus ferrooxidans and exploration of resistant mechanism

The silver-resistant Acidithiobacillus ferrooxidans were isolated from 22 acid mine drainage (AMD) samples collected from Dexing Copper Mine and Chengmen Mountain Mine, Jiangxi Province, China. Isolate DX16 is obtained from the sample taken from Dexing Copper Mine and still carries out ferrous ion oxidation when incubated in 9K medium containing silver nitrate (240 mg/L). While isolate H1, a less resistant strain taken from Yin Mountain Mine, has a tolerate level of only 60 mg/L. Based on 16S ribosomal DNA sequencing, both bacterial 16SrDNA sequences are 100% similar to Acidithiobacillus ferrooxidans ATCC 23270. Through ultraviolet irradiation induced mutations, isolate mDX16 that is obtained from DX16 carries out ferrous ion oxidation when incubated in 9K medium containing higher concentration of silver nitrate (250 mg/L). When silver-resistant gene (SilC) analysis is carried out on the two isolates, it is seen that this gene was absent in both.

Temperature Dependent Surface Resistivity Measures of Commercial, Multiwall Carbon Nanotubes (MWCNT), and Silver Nano-Particle Doped Polyvinyl Alcohol (PVA) Films

Pure and doped Polyvinylidene difluoride (PVDF) films, for the detection of infrared radiation, have been well documented using the mechanism of pyroelectricity. Alternatively, the electrical properties of films made from Polyvinyl Alcohol (PVA) have received considerable attention in recent years. The investigation of surface resistivities of both such films, to this point, has received far less consideration in comparison to pyroelectric effects. In this research, we report temperature dependent surface resistivity measurements of commercial, and of multiwall carbon nanotubes (MWCNT), or Ag-nanoparticle doped PVA films. Without any variation in the temperature range from 22°C to 40°C with controlled humidity, we found that the surface resistivity decreases initially, reaches a minimum, but rises steadily as the temperature continues to increase. This research was conducted with the combined instrumentation of the Keithley Model 6517 Electrometer and Keithley Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films. With the objective to quantify the suitability of PVDF and PVA films as IR detector materials, when using the surface resistivity phenomenon, instead of or in addition to the pyroelectricity, surface resistivity measurements are reported when considering bolometry. We found that the surface resistivity measurements on PVA films were readily implemented.

Effects of pre-deformation on microstructure and properties of Al–Cu–Mg–Ag heat-resistant alloy

The effects of the pre-deformation on the microstructure, mechanical properties and corrosion resistance of Al–Cu–Mg–Ag alloys were investigated by means of hardness tests, tensile tests, intergranullar corrosion (IGC) tests and transmission electron microscopy (TEM), respectively. The results show that with the increase of deformation amount, the aging hardening rate increases while the strength of the alloy decreases and then increases. The sample with a pre-deformation of 6% possesses the highest tensile strength due to the refinedly and homogeneously distributed precipitations. The pre-deformation aging accelerates the heterogeneous nucleation of Ω and θ′ phases at dislocations, and also refines the precipitations both in the grains and along the grain boundaries. The precipitation of Ω phase is restrained while that of θ′ phase is accelerated in pre-deformed Al–Cu–Mg–Ag alloy compared with the sample without pre-deformation. In addition, the width of the precipitate free zone decreases with increasing the pre-deformation amount, leading to a narrower IGC passageway. This results in an enhanced IGC resistance of Al–Cu–Mg–Ag alloy treated by pre-deformation aging. © 2017, Central South University Press and Springer-Verlag GmbH Germany.

Effect of Introducing Conductive Organic Carrier on Properties of Low-Temperature Conductive Silver Paste

The poly(epoxy-N-methylaniline)conductive organic carrier was used as the bonding phase of the low-temperature conductive silver paste.Then,this was mixed with different proportions of silver powder to prepare the low-temperature conductive silver paste.Afterwards,the effect of the conductive organic carrier on the properties of the low-temperature conductive silver paste was determined by IR,DMA and SEM.The results revealed that the prepared conductive paste has good conductivity,film-forming performance,printing performance,low-temperature curing performance,and anti-aging performance.When the mass percentage of the bonding phase/conductive phase was 40/60,the lowest volume resistivity of the conductive silver paste was 4.9×10^(−6)Ω⋅cm,and the conductivity was the best.

Silver nanoparticle technology in orthopaedic infections

The irrational and prolonged use of antibiotics in orthopaedic infections poses a major threat to the development of antimicrobial resistance.To combat antimi-crobial resistance,researchers have implemented various novel and innovative modalities to curb infections.Nanotechnology involves doping ions/metals onto the scaffolds to reach the target site to eradicate the infective foci.In this conno-tation,we reviewed silver nanoparticle technology in terms of mechanism of action,clinical applications,toxicity,and regulatory guidelines to treat ortho-paedic infections.

Silver Film Growth on Glass Ceramic by Radio Frequency Magnetron Sputtering

Thin silver films are deposited by radio frequency magnetron sputtering on glass ceramic at room temperature.Variations of sputtering power,bios voltage and power density are carried out for each deposition,then parts of as-deposited samples are subjected to annealing at 600 ℃ within a vacuum chamber.Structural properties are studied by X-ray diffraction(XRD),scanning electron microscope(SEM)and laser scanning confocal microscope(LSCM).It is shown that structural properties have a strong dependency on sputtering power and annealing temperature.Electrical contact resistance measured by a four point probe instrument is directly affected by the thickness of films.It is also found that the film conductivity,especially in thinner films,is improved by the increasing grain size.Finally,the film adhesion is observed by scratch tests.And the adhesive ability deposited by radio frequency magnetron sputtering shows a better performance than that produced by traditional methods.

Solid/Liquid Interface of Ag/Sn/Ag Trilayers by In Situ Resistivity Measurement

The in situ four-point probe resistivity measurement was used as a main method to study the solid/liquid interfacial characteristics in Ag/Sn/Ag trilayers at temperatures ranging from 150 to 305℃.It is found from the variation of resistivity that three processes take place on annealing:the dissolution of silver atoms,the diffusion of silver atoms,and the formation of Ag3Sn in liquid tin layer.The first one plays the leading role in the variation of resistivity during annealing process.The apparent diffusivity of silver in liquid tin at 305℃ is determined to be 7.3×10^(-17)cm^(2)/s.

Mycosynthesis,characterization and antibacterial properties of AgNPs against multidrug resistant(MDR)bacterial pathogens of female infertility cases

Recently,biosynthesis of silver nanoparticles using bacteria,fungus and plants has emerged as a simple and viable alternative to more complex physical and chemical synthetic procedures.The present investigation explains rapid and extracellular synthesis of silver nanoparticles using fungus Fusarium oxysporum NGD and characterization of the synthesized silver nanoparticles using UV-Vis spectroscopy,scanning electron microscopy,energy dispersive spectroscopy and X-ray diffraction analysis.The size range of the synthesized silver nanoparticles was around 16.3e70 nm.The FTIR studies showed major peaks of proteins involved in the synthesis of silver nanoparticles.Further,antibacterial effect of the silver nanoparticles against multidrug resistant pathogens Enterobacter sp.ANT 02[HM803168],Pseudomonas aeruginosa ANT 04[HM803170],Klebsiella pneumoniae ANT 03[HM803169]and Escherichia coli ANT 01[HM803167]was tested using turbidometric assay at 10,20,30,40 mg AgNPs/ml alone and in combination with ampicillin using agar well diffusion assay.All the resistant bacteria were found to be susceptible to the antibiotic in the presence of the silver nanoparticles.

无氰镀银层水性硅溶胶封闭工艺及镀层结构与耐蚀性

[目的]镀银层往往存在孔隙,使其耐蚀性无法满足苛刻的海洋环境应用要求,因此有必要对其进行封闭处理。[方法]采用水性硅溶胶对5,5-二甲基乙内酰脲(DMH)体系无氰镀银层进行封闭,通过正交试验优化封闭处理的工艺条件。借助扫描电镜(SEM)、X射线光电子能谱仪(XPS)及电化学阻抗谱(EIS)测试分析了封闭后Ag镀层的微观结构、化学组成及耐蚀性。考察了1Cr18Ni9Ti不锈钢和GH2132合金表面Ag镀层经硅溶胶封闭后的耐酸性盐雾性能。[结果]较佳的封闭液组成和工艺条件为:丙烯酸树脂100 g/L,中性硅溶胶26 g/L,表面活性剂1 g/L,室温,时间60 s。在该条件下封闭后,Ag镀层表面疏水性和耐蚀性提高;Ag镀层的微观表面形貌未发生改变,封闭剂仅渗入镀层孔隙,而未在表面形成连续的膜。1Cr18Ni9Ti不锈钢和GH2132高温合金经“无氰镀银+水性硅溶胶封闭”处理后可以通过192 h的酸性盐雾试验。[结论]采用水性硅溶胶封闭处理可显著提高无氰镀银层的耐蚀性,对航空零部件的发展具有重要意义。

银狐源沙门菌的分离鉴定、致病性及耐药性检测

为了解秦皇岛地区不同养殖场中银狐源沙门菌致病性、耐药情况及耐药基因的携带情况,本研究2019—2021年采集秦皇岛地区不同养殖场中患腹泻病银狐的肛拭子、粪便等病料组织194份,采用RT-PCR、PCR方法对采集的样品检测其犬瘟热病毒、轮状病毒及犬细小病毒;采用细菌常规分离鉴定、PCR方法进行沙门菌鉴定,采用人工感染小白鼠试验、K-B药敏纸片法和PCR法分别检测沙门菌的致病性、耐药性及耐药基因型。结果显示,犬瘟热病毒、冠状病毒及犬细小病毒检测为阴性;从194份病料组织中分离得到101株沙门菌,其中78株沙门菌分离菌株对小白鼠具有致病,死亡率为40%~100%;78株致病性沙门菌对氨苄西林、阿莫西林、土霉素等9种药物耐药率在50%以上,对其他药物耐药率为5.1%~32.1%,以耐12、11、10种药物为主;耐药基因Sul1、Sul2、Sul3、aac(3)-Ⅰv、aac(6')-Ⅰb、TetA、TetM、TetR检出率在48.7%以上,其他耐药基因检出率为7.7%~21.8%,除了多粘菌素类药物,耐药表型与耐药基因之间存在相关性。本研究对该地区银狐源沙门菌病防控提供参考依据。

基于有限元分析的高性能耐高温导电胶的制备及性能研究

针对目前导电胶基体在耐温性方面的瓶颈,选取耐高温、吸湿率低、热稳定性良好的氰酸酯作为基体,以银作为导电填料,通过COMSOL有限元仿真软件中APP开发器功能导入随机分布的导电颗粒代码,建立模型仿真,探究此新型导电胶中导电颗粒形状和大小对导电性的影响。研究结果表明,相比于银球导电胶,银片导电胶模拟的导电性能更好,当银的质量分数达到90%时,银片导电胶的电阻率比银颗粒导电胶低3个数量级。结合仿真结果,加入片状银粉,双马来酰亚胺作为增韧剂,二月桂酸二丁基锡作为固化剂,制备出银片导电胶,其电阻率随着银片含量增加而下降,在银片质量分数为50%~60%时迅速下降至43.9 mΩ·cm,之后变化平缓,胶粘的剪切强度在15 MPa以上,可以承受300℃的高温。

ZHL-02置换镀和电镀银层的耐蚀性能研究

镀银方法可分为置换镀和电镀,为了比较这2种方法制得的镀层的耐蚀性能和电偶腐蚀行为,利用扫描电子显微镜、XRD、电化学工作站、Tafel曲线和电偶腐蚀方法研究了以5, 5-二甲基酰胺为主配位剂的无氰镀银工艺中ZHL-02置换镀和ZHL-02电镀镀层的耐蚀性能和电偶腐蚀行为。结果表明:置换镀层结晶好,覆盖更完整,在同等厚度条件下,抗电偶腐蚀性能略优于电镀层。随着置换镀银时间的延长,镀层的自腐蚀速率逐渐下降。但其耗时长,且难以获得1μm以上的厚度,一定程度上限制了其应用。相较于置换镀,电镀的速率快得多,电镀5 min就可获得> 2.4μm的银镀层。随着电镀时间的延长,银层中会出现较大的颗粒,形成细小气孔等缺陷结构,电镀银时间为1、2、5 min时,对应的自腐蚀速率分别为7.15×10^(-3)、5.30×10^(-3)、4.27×10^(-3) mm/a。电镀时间从1 min延长到2 min,再延长到5 min时,镀层的平均电偶腐蚀速率出现了先下降后增大的现象。

氧化石墨烯强化银镀层的耐蚀性和耐磨性研究

为满足电连接器在服役过程中对导电银镀层的耐蚀性和耐磨性的需求,本文基于5,5-二甲基乙内酰脲作为主络合剂的无氰镀银溶液,通过添加氧化石墨烯纳米片,采用直流电沉积在铜基材表面制备了银-氧化石墨烯复合镀层。采用光学显微镜、扫描电子显微镜、能谱仪、X射线衍射仪对镀层表面形貌、成分和晶体结构进行了表征,并通过电化学实验和摩擦磨损试验对复合镀层的耐蚀性和耐磨性进行了测试。结果表明,氧化石墨烯的掺入改变了银的晶体生长方向,并细化了组织,提高了银镀层的硬度、耐蚀性与耐磨性。

镀银铜材料在大电流条件下的载流微动磨损特性

利用化学电镀方法在T2紫铜管表面镀银制备镀银铜试样,采用自主研制的切向微动磨损试验设备在圆柱/圆柱的正交点接触模式下进行室温载流切向微动磨损试验,探究了镀银铜试样在5 A电流以及不同法向载荷(5,10,15 N)和位移幅值(30,50,70,100μm)下的载流微动磨损行为及其磨损机制。结果表明:随着位移幅值的增加,镀银铜试样的载流微动磨损程度加剧,随着循环次数的增加,不同位移幅值下的摩擦因数整体呈先减小后增大最后趋于稳定的趋势,而接触电阻呈相反趋势,不同位移幅值下稳定阶段的摩擦因数相差不大;随着载荷的增加,载流微动磨损程度先变大后变小,当载荷为10 N时,磨损程度最大,此时有效接触面积较大,接触电阻较低;随着载荷的增加,稳定阶段的摩擦因数增大。镀银铜试样在磨损初期的磨损机制主要黏着磨损和氧化磨损,在磨损后期主要为磨粒磨损、氧化磨损和剥层,且随着循环次数的增加,氧化磨损程度加剧。

纳米银浆低温烧结工艺及可靠性分析

对纳米银浆烧结前后的微观组织形貌进行分析,研究了不同烧结温度、烧结时间和升温速率对纳米银浆烧结样件剪切强度的影响,并对比分析了Au80Sn20和纳米银浆两种不同连接材料对GaN芯片散热性能的影响。结果表明:GaN芯片通过纳米银浆烧结到管壳后,银层与金层之间存在一个明显的互扩散层,实现了芯片和壳体之间优异互连。在烧结温度200℃、时间90 min、升温速率5℃/min的烧结条件下,样件剪切强度可达47.2 MPa。纳米银浆与Au80Sn20装配的芯片温度分布基本一致,但纳米银浆散热性能优于Au80Sn20。在经历温度冲击、扫频振动、温度循环及射频老炼试验后,纳米银浆烧结的芯片热阻波动不明显,剪切力性能略微提升。

轮毂用水性烤漆的制备及性能

[目的]为提升车轮毂的耐腐蚀性能,制备出一款水性烤漆。[方法]以水性丙烯酸乳液搭配氨基树脂为成膜物质,探讨了水性丙烯酸乳液与氨基树脂的种类及用量,水性铝银浆的种类及用量,以及烘烤温度对涂层综合性能及外观的影响。[结果]以丙烯酸乳液3711与氨基树脂CYMEL 303按8∶1的质量比交联后得到的涂层性能较好,铅笔硬度3H,附着力0级,耐冲击性(1kg)95cm,耐中性盐雾时间336h。[结论]所制涂料漆膜具有良好的外观及综合性能,在搭配环氧底漆和罩光清漆的情况下可用于车轮毂表面装饰与防护。

复方黄柏液联合磺胺嘧啶银乳膏对烧伤合并多重耐药菌创面感染患者创面愈合及炎性因子的影响

目的探讨复方黄柏液联合磺胺嘧啶银乳膏对烧伤合并多重耐药菌(MDROS)创面感染患者创面愈合及炎性因子的影响。方法选取2019年7月—2022年1月本院收治的86例烧伤合并MDROS创面感染患者,采用数字奇偶法分为对照组(给予磺胺嘧啶银乳膏治疗)和观察组(给予复方黄柏液联合磺胺嘧啶银乳膏治疗),每组各43例。比较2组患者创面中医症状评分、创面面积、创面愈合率、炎性因子[降钙素原(PCT)、C反应蛋白(CRP)]水平、创面分泌物细菌培养结果和不良反应。结果治疗后观察组主症、次症评分及总分均低于对照组(P<0.05),观察组总有效率高于对照组(P<0.05);治疗后观察组创面面积低于对照组(P<0.05),观察组创面愈合率高于对照组(P<0.05);治疗后观察组PCT和CRP水平均低于对照组(均P<0.05);治疗后观察组革兰阳性菌、革兰阴性菌感染病例数低于对照组(P<0.05);2组不良反应发生率相近(P>0.05)。结论烧伤合并MDROS创面感染患者采用复方黄柏液、磺胺嘧啶银乳膏联合治疗有利于促进创面愈合,降低炎性因子水平,控制创面细菌感染,缓解临床症状,提高临床疗效,且安全可靠。

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。

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。