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。     

熔断器用银带变色初步分析

纯银熔体材料极易变色,采用扫描电镜(SEM)、X射线光电子能谱(XPS)和X射线衍射(XRD)等手段对银带变色状况和变色的机理进行了初步分析。结果表明,大气条件下退火会在银带表面形成一层白雾,其主要为Ag_2O;晶界处生成的一些不连续的黑色点状相,其主要成分为Ag、C和O;银带在大气条件长时间放置时,其表面将失去金属光泽,变成灰色,局部地区有黑斑散布,且斑点的分布离散,无明显的生长特点;银带加工过程中极易在其表面残留的C、Cu、Fe、Na、Mg等元素并非引起银币变色的主要因素;银带易与空气中的硫化氢、二氧化硫等发生反应,对银带产生腐蚀,致使银带变色,其腐蚀产物主要有Ag_2S、Ag_2SO_3、Ag_2O。     

银币变色机理研究进展

银币的锈斑、变色问题是世界性难题,至今没有清晰的成因解释。本文综述了银币变色状况和变色的机理研究进展。重点评述了腐蚀介质对银变色的影响,包括氧、硫化氢、单质硫和二氧化硫的影响;简要介绍了环境湿度、温度、光照等环境因素对银变色的影响;对银币的大气腐蚀产物进行了分析,并展望了研究的发展方向。     

925Ag75Cu和925Ag40Cu35Zn合金在人造汗液和H2S气氛中的腐蚀与变色行为

采用静态腐蚀、XRD、SEM、EDS和XPS,研究了250℃时效4h和70%冷变形+200℃时效4h两种硬化状态下的925Ag75Cu与925Ag40Cu35Zn合金在37℃人造汗液和室温H2S气氛中的腐蚀与变色行为。结果表明,这两种925银合金在37℃人造汗液中的腐蚀变色是由Cl-和OH-离子引起的,但925Ag40Cu35Zn合金的变色过程明显比925Ag75Cu合金缓慢,腐蚀过程中产生的白色AgCl和灰黑色Ag2O难以在其表面沉积而形成灰黑色腐蚀膜。这两种925银合金在室温H2S气氛中的腐蚀变色是由S2-引起的,但925Ag40Cu35Zn合金的腐蚀变色过程明显比925Ag75Cu合金缓慢,这是由于腐蚀过程中白色ZnS最先形成,从而延缓了灰黑色Ag2S和黑色Cu2S的形成。     

Chemical tracers in archaeological and natural gold: Aliseda Tartessos treasure and new discovered nuggets (SW Spain)

The gold outcrops employed by the ancient kingdom of Tartessos, settled in the SW of the Iberian Peninsula from ca. 10th to the 6th century BC, for the Aliseda treasure manufacture, has been discovered. This paper reports on the finding of collected gold nuggets, more than 80 units up to 218 g, in an ancient mining area located in Casas de Pedro (Extremadura, SW of Spain). The comparative physical-chemical analyses between these gold nuggets picked at present and the archaeological gold collected in 1920, have been performed by microscopy, X-ray diffraction (XRD), thermoluminescence (TL), X-ray photoelectron spectrometry (XPS) and electron microprobe analyses (EMPA). Pieces of Aliseda treasure and the picked gold nuggets show a highly homogeneous chemical composition of trace elements namely: As 0.01%, S 0.02%, Bi 0.35%, Fe 0.016%, Ag 0.8%, Sb 0.05% and Te 0.04%. The small difference between both gold samples is only of 0.2% extra copper in Aliseda due to an anthropogenic addition of a silver-copper mixture during a second firing of the jewel to weld ornamental spheres.     

浸渍法制备Ag_2O-TiO_2纳米纤维及其光催化活性

采用浸渍法制备直径约20nm,长度达到微米级,且形态分布均匀的Ag2O-TiO2纳米纤维。以TEM、XRD、DRS及XPS手段对样品晶型结构、微观形貌以及化学组成进行表征,探讨掺杂对TiO2纤维结构和性质的影响。结果表明:未掺杂纤维表面平滑,浸渍法制备的Ag2O-TiO2纤维表面有明显的球状颗粒存在,颗粒直径为2～5nm,分布均匀,且其XRD谱出现Ag2O的衍射峰。与未掺杂样品相比,掺杂纤维的DRS谱线发生蓝移,光催化降解亚甲基蓝实验表明Ag2O-TiO2纤维光催化活性较高。     

PDA@Ag纳米复合材料的制备及抑菌性能研究

以多巴胺为原料,在碱性条件下通过自聚合制备聚多巴胺(PDA)亚微球,将银离子(Ag+)原位还原为银(Ag),负载在亚微球表面合成核壳型纳米PDA@Ag复合材料。采用透射电镜(TEM)、X射线衍射(XRD)、紫外-可见漫反射光谱(UV-Vis DRS)、X射线光电子能谱(XPS)和热重分析(TGA)对其进行表征,结果表明合成了核壳型PDA@Ag复合材料,吸附在亚微球表面的纳米银尺寸约为25nm。以金黄色葡萄球菌(S. aureus)和大肠杆菌(E. coli)为模式菌,用纳米银作参比,比较其抑菌活性。结果表明,PDA@Ag比纳米银具有更优异的抑菌性能,且对细胞壁中含有少量的磷脂双分子层的大肠杆菌更为敏感。     

石墨烯/银纳米复合材料的制备及抗菌性能研究

采用改进的Hummers法制备氧化石墨(GO),加入一定量的聚乙烯亚胺和硝酸银(PEI-Ag+)配位复合物,通过自组装法组装,利用硼氢化钠的还原性,制备石墨烯/银纳米复合材料。用紫外可见吸收光谱(UV-Vis)、红外吸收光谱(FT-IR)、X射线衍射(XRD)、循环伏安法(CV)、扫描电镜(SEM)、拉曼光谱(Raman)等手段对所制备的石墨烯/银纳米复合材料进行表征。以金黄色葡萄球菌和大肠杆菌为模型对纳米复合材料的抗菌性能进行研究。结果表明:银纳米粒子负载在石墨烯表面形成石墨烯/银纳米复合物材料,石墨烯/银纳米复合材料对金黄色葡萄球菌和大肠杆菌生长具有较好的抑制作用,且抗菌性能稳定。当石墨烯/银纳米复合材料浓度为4和15 mg/m L时,分别对金黄色葡萄球菌和大肠杆菌的抑菌效果好。     

Synthesis and Characterization of Ag/Graphene Nano- composite

采用氧化还原法制备不同银含量的银/石墨烯纳米复合材料 (银质量分数分别为0%, 30%, 46%, 56%, 63%)。并通过X射线衍射(XRD)、光电子能谱仪(XPS)、高倍透射电子显微镜(HRTEM)和拉曼光谱(Raman)分析银含量对银/石墨烯纳米复合材料形态和显微结构的影响。结果表明,氧化石墨和银离子被成功地还原成银/石墨烯纳米复合材料,所得石墨烯由3~4单层碳原子层堆砌缠绕而成,同时银纳米颗粒沉积在石墨烯的表面。银纳米颗粒的介入有效地阻碍了石墨烯的团聚,增大了石墨烯的比表面积。银纳米颗粒的尺寸与银含量相关,当银含量较低时,银纳米颗粒在石墨烯表面具有很好的分散性且粒度基本分布在25~50 nm之间,而当银含量超过46%时将会导致银纳米颗粒的团聚。另外, 银纳米颗粒增强了石墨烯的拉曼效应。     

Structure and antibacterial activity of new layered perovskite compounds

New layered perovskite compounds, AgxNa（2-x）La2Ti3O10（x=0.2, 0.3 and 0.5） were synthesized by an ion-exchange reaction of Na2La2Ti3O10 with AgNO3 solution and characterized by energy dispersive X-ray analysis（EDX）, X-ray diffractometly（XRD）, scanning electron microscopy（SEM） and X-ray photoelectron spectroscopy（XPS）. The ion-exchange processes were optimized, and the antibacterial activity, light permanency and water-resistance were evaluated. Surprisedly, no significant changes in crystal structure of Na2La2Ti3O10 are found by the exchange of silver ions. The Ago.3Na1.7La2Ti3O10 particles conglomerate obviously with irregular shape and size. Ago.3Na1.7La2Ti3O10, possessing the minimum inhibitory concentrations（MICs） against Escherichia coli （E. coli）, Staphylococcus aureus （S. aureus） of 180 mg/L and 240 mg/L, has high antibacterial activity, good light permanency and water-resistance. The ionic state silver in AgxNa（2-x）La2Ti3O10 is the antibacterial active component.     

银金修饰TiO2纳米管阵列光阳极的制备及其光伏性质

采用阳极氧化法,以金属钛箔为原料制备了TiO2纳米管阵结构染料敏化纳米晶太阳能电池(DSSC)光阳极,并用电沉积、光沉积和真空蒸发法对其表面分别进行金属Ag和Au修饰。对金属修饰前后的光阳极用扫描电子显微镜(SEM)和X射线衍射分析仪(XRD)表征发现:阳极氧化法制备的TiO2纳米管阵列结构规整有序;经过化学沉积后,其表面均覆盖有一层致密的金属粒子薄膜。测量光电流密度-电压(J-V)曲线和电化学阻抗谱(EIS)发现:相比纯TiO2纳米管阵列,经过Ag修饰后的TiO2阵列其短路电流密度和开路电压最大可以分别提高到前者的4.9和1.7倍,并且其电化学阻抗出现显著降低。研究表明:金属Ag修饰改善了TiO2纳米管之间的连通性,提高了TiO2光阳极中电子的传输效率,并通过等离子共振激发出光电子,同时与TiO2相互作用,使其在可见光区域也能够促进电子-空穴对的分离。     

多孔钛表面聚多巴胺层修饰及其载银研究

通过多巴胺自聚合在碱热处理多孔钛表面构建了聚多巴胺(PDA)膜层,利用聚多巴胺自身的还原性,成功将纳米银颗粒载入聚多巴胺修饰多孔钛表面,并探讨了沉积时间对纳米银颗粒负载量的影响。利用傅里叶变换红外光谱仪(FTIR)、场发射扫描电镜(FE-SEM)、能谱仪(EDS)、接触角测定仪和X射线光电子能谱(XPS)对聚多巴胺修饰及其载银多孔钛表面进行表征。研究结果表明,多巴胺能够在多孔钛表面自聚合形成聚多巴胺层,保留了钛表面的多孔结构;纳米银颗粒均匀沉积在PDA修饰的多孔钛表面,随着沉积时间的增加,多孔钛表面纳米银颗粒的负载量增加。     

水溶液中银表面自组装膜工艺

采用银在水溶液表面形成C18SH自组装膜(SAMs)的工艺,在银表面得到致密、平整,表现出明显疏水性的SAMs。EMPA和XPS测试表明,表面活性剂分别作为C18SH的分散剂,自组装过程中起到传输作用,本身不参与成膜,但影响SAMs的厚度和倾斜角。银试样表面的Ag2O在成膜过程中被硫醇中的H-S键还原为Ag,同时有Ag-S-C18H37键的形态形成。     

Electrochemical and surface studies on the passivity of a dental Pd-based casting alloy in alkaline sulphide solution

The corrosion and tarnish behavior of a dental casting Pd-25Ag-18Cu-12Au alloy in 0.1% Na₂S solution at 37 °C was investigated using potentiodynamic polarization and spectrocolorimetric techniques. The surface film was characterized by X-ray photoelectron spectroscopy (XPS).This alloy exhibited markedly higher resistance to corrosion and tarnish than did the Ag-20Pd-18Cu-12Au alloy in current clinical use. XPS spectra indicated the presence of a thin sulphide film composed of PdS. It was found that the PdS film is very protective and is responsible for the passivity of the Pd-25Ag-18Cu-12Au alloy in 0.1% Na₂S solution.     

Novel plating solution for electroless deposition of gold film onto glass surface

In this paper, a simple and environmentally friendly electroless plating solution of chloroauric acid (HAuCl₄) and hydrogen peroxide (H₂O₂) for depositing gold film onto (3-aminopropyl)-trimethoxysilane (APTMS) -coated glass surface has been developed. APTMS as an adhesive reagent was used to attach the gold nanoparticles (AuNPs) onto the glass substrate. These AuNPs could be regarded as the preferential nucleation or catalytic sites for gold electroless reduction, which accelerated the reduction of Au³⁺ on the glass surface and effectively prevented the formation of gold metal in the bulk solution. During the gold plating process, H₂O₂ as the reducing agent was thermodynamically capable of reducing Au³⁺ ions from the HAuCl₄ precursor to gold atoms, which deposited onto the glass surface and finally formed the continuous gold film. The resulting gold film was characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscope (AFM), respectively.     

SO_2气体环境中金属钽丝表面变化探讨

在SO2气体环境中对金属钽丝表面变化进行了研究。用SEM和XPS分析研究了试样表面发生的变化,发现在长时间SO2气体环境中,钽丝表面并没有发生明显的腐蚀现象。并讨论了钽丝表面硫元素的变化机理及其对钽的影响。     

载银TiO2纳米管阵列的光催化和抗菌性能研究

利用阳极氧化法在钛金属基体表面制备高度有序的TiO2纳米管阵列薄膜(TNA),将其浸泡在AgNO3溶液中,通过紫外光照射,得到Ag纳米颗粒负载在TNA表面的复合结构(Ag-TNA)。采用SEM、EDS、XRD、XPS、UV-Vis光谱等手段对Ag-TNA复合结构进行分析,研究了Ag-TNA复合纳米结构的光催化性能、光电化学性能及抗菌性能。结果表明,相对于TNA,Ag-TNA复合结构表现出更为优良的光电化学活性,同时又具有优良的广谱抗菌性能。     

Electroless Ni-Co-P Coating of Cenospheres Using Ag(NH_3)_2~+ Activator

FLY ASH CENOSPHERES are primarily a by-productin power generation plants.Research is in progress toeffectively use this by-product to produce new usableand profitable materials as they pose major disposaland environmental problems.Fly ash cenospheres areunique,property stable,non-toxic,non-metallic hollowmicro-particles.Due to the unique hollow structure andphysical mechanics properties,Cu^Ag and other metalsare often coated on cenospheres to produce lightweightmetal matrix composites,w…     

Corrosion resistance of Zambian silver coin from the “African Wildlife” series

The surface of Zambian silver coin from the “African Wildlife” series is studied by local X-ray fluorescent analysis, mass-spectrometry, and electrode potential measurements. High purity of the coin metal is pointed out. Faint yellow tarnish at some spots on the surface is caused by local contamination during the coin production or storage. Original Russian Text ? I.G. Erusalimchik, M.N. Filippov, I.V. Murav’eva, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 324–325.     

Antibacterial activity of silver surface modified polyethylene terephthalate by filtered cathodic vacuum arc method

Silver (Ag) modified polyethylene terephthalate (PET) surface by filtered cathodic vacuum arc (FCVA) technique is performed. The structure and component of the modified surface are characterized by X-ray photoelectron spectroscopy (XPS) and the cross-section is observed by scanning electron microscope (SEM). The results show that a 4-5 μm silver layer is formed on the PET surface. The results of the colony forming units (CFU) plate counting in vitro indicate that the adhesion of Staphylococcus epidermidis (SE) to PET is suppressed by silver coating. The adhesion efficiency of SE on the modified surface is only about 25% of the untreated PET surface. The interfacial free energy of adhesion (ΔF_Adh) of SE onto the silver coating deposited on PET is + 8.6 mJ/m², and this means that bacterial adhesion is energetically unfavorable. The releasing rate of silver ions from the PET modified by silver FCVA is 0.12 μg/mL during 2 h. The release of antibacterial silver ion may be another reason of less SE adhered to the PET surface modified by Ag FCVA. The release of lactate dehydrogenase (LDH) was used to evaluate the immediate toxicity of the PET modified by silver FCVA method. It is showed that this modified surface has low toxicity.