Microstructural analyses of two high noble gold-platinum alloys before and after conditioning in a cell culture medium

Microstructures of two high noble experimental Au-Pt alloys were compared before and after conditioning for biocompatibility, in order to identify phases and microelements responsible for the alloys’ corrosive behaviour. Microstructural characterization was carried-out by optical and scanning electron microscopy, in addition to energy dispersive X-ray analysis. X-ray diffraction was applied to determine the phases’ composition and their contribution in the alloys. Additionally, simultaneous thermal analysis was used to identify the temperatures of phase transformations. An overall assessment before conditioning showed that Au-Pt I is a two-phase alloy containing a dominant Au-rich α₁ phase and a minor Pt-rich α₂ phase, while the Au-Pt II alloy contains in addition three minor phases: AuZn₃, Pt₃Zn and Au_1.4Zn_0.52. The highest content of Zn (up to 6.76 wt.%) was detected in the Pt3Zn phase. After RPMI cell culture medium conditioning, the Pt3Zn and AuZn3 phases disappeared, suggesting that they are predominantly responsible for Zn loss and the lower corrosive stability of the Au-Pt II alloy.     

Electrodeposition of platinum metal and platinum-rhodium alloy on titanium substrates

A method for application of an adherent platinum (Pt) and platinum-rhodium (Pt-Rh) alloy plate to a titanium (Ti) substrate includes steps of surface pretreatment, anodization, and electrodeposition of Pt and Pt-Rh alloy from their electrolytic baths consisting of H₂Pt₂Cl₆·6H₂O (20 gL⁻¹), and HCl (300 gL⁻¹) for a Pt bath. The Pt-Rh bath consists of H₂Pt₂Cl₆·6H₂O (20 gL⁻¹), and HCl (300 gL⁻¹) and Rh₂ (SO₄)₃ (2 gL⁻¹). At the optimum conditions of electroplating, the Pt and Pt-Rh deposits were formed over the anodized Ti substrates with high adhesion, brightness, and high current efficiency (35.33% for Pt and 70.38% for the Pt-Rh alloy).     

Solderability and intermetallic compounds formation of Sn-9Zn-xAg lead-free solders wetted on Cu substrate

The eutectic Sn-9Zn alloy was doped with Ag (0 wt.%-1 wt.%) to form Sn-9Zn-xAg lead-free solder alloys. The effect of the addition of Ag on the microstructure and solderability of this alloy was investigated and intermetallic compounds (IMCs) formed at the solder/Cu interface were also examined in this study. The results show that, due to the addition of Ag, the microstructure of the solder changes. When the quantity of Ag is lower than 0.3 wt.%, the needle-like Zn-rich phase decreases gradually. However, when the quantity of Ag is 0.5 wt.%-1 wt.%, Ag-Zn intermetallic compounds appear in the solder. In particular, adding 0.3 wt.% Ag improves the wetting behavior due to the better oxidation resistance of the Sn-9Zn solder. The addition of an excessive amount of Ag will deteriorate the wetting property because the glutinosity and fluidity of Sn-9Zn-(0.5, 1)Ag solder decrease. The results also indicate that the addition of Ag to the Sn-Zn solder leads to the precipitation of ε-AgZn₃ from the liquid solder on preformed interfacial intermetallics (Cu₅Zn₈). The peripheral AgZn₃, nodular on the Cu₅Zn₈ IMCs layer, is likely to be generated by a peritectic reaction L + γ-Ag₅Zn₈ → ɛ-AgZn₃ and the following crystallization of AgZn₃.     

ICP-MS法测定高纯钯中18个痕量杂质元素

以混合酸(盐酸-硝酸)溶解高纯钯样品,建立了电感耦合等离子体质谱法(ICP-MS)测定高纯钯中18个杂质元素的方法。确定了最佳测定条件为:采用普通模式测定Pt、Rh、Ir、Ru、Au、Ag、Cu、Fe、Zn、Ni、Mn、Mg、Al、Sn和Pb,氨气反应模式测定Si、Fe和Cr(氨气流速分别为0.2、0.3和0.7 mL/min);采用内标校正提高分析的准确性,其中Mg、Al、Zn、Ni、Mn、Cu、Ag、Rh、Ru和Si以Sc为内标,Fe以Y为内标,Sn、Cr和Pb以In为内标,Ir、Au、Bi、Pt以Re为内标。测定各元素的线性相关系数(r)不小于0.9997,方法检出限为0.0061~0.85 ng/mL。对高纯钯样品中18个杂质元素进行测定,相对标准偏差(RSD)为1.38%~6.11%,加标回收率86.2%~118.8%,可满足4N~5N高纯钯产品的测定要求。     

磁兼容Au-25Pt合金的组织结构及综合性能

Au-Pt合金具有优异的MRI磁兼容性、良好的生物兼容性、高的耐蚀性等优点,在医用材料领域具有巨大的应用前景。采用X射线衍射仪、金相显微镜、维氏显微硬度仪和综合物性测量系统等,研究冷加工过程Au-25Pt合金丝材的组织结构演变及其对体积磁化率和维氏硬度的影响,为制备综合性能优异的Au-Pt合金探索有效途径。结果表明,固溶处理后的Au-25Pt合金为面心立方结构的单相固溶体,经30%～70%冷变形后,没有其它相产生。冷加工变形显著增加了Au-25Pt合金的维氏硬度,尤其在冷加工初期(<30%变形量),但对磁化率影响很小。冷变形Au-25Pt合金不仅具有接近人体组织的体积磁化率(-8.5×10-6),还有较高的维氏硬度(HV0.1=160)。     

小试金-碲保护留铅灰吹富集测定矿石中痕量贵金属

采用小铅试金富集,以5 mg碲为灰吹保护剂,通过留铅灰吹法将矿石样品中痕量贵金属(金、铂、钯、铑、铱和钌)定量富集在50 mg左右的铅合粒中。铅合粒先以(1+1)硝酸溶解,再加入盐酸进一步增强溶解能力,基体通过以氯化铅形式沉淀得以分离,采用电感耦合等离子体质谱法(ICP-MS)测定。相对标准偏差(RSD,n=6)为:Au 4.6%、Pt 8.7%、Pd 4.5%、Rh 9.2%、Ir 6.1%、Ru 5.8%。方法用于国家一级标准物质和黑色页岩样品中痕量贵金属的测定,测定值与认定值基本吻合。     

碳载金铂双金属催化剂催化活性研究

采用KBH4做还原剂、PVP做保护剂,化学法一步合成Au-Pt合金纳米粒子,应用UV-Vis、TEM、XRD等手段对其进行了表征.将所合成的合金纳米粒子负载在碳黑上,获得Au-Pt双金属碳载催化剂,应用循环伏安法(CV)检测了催化剂对甲醇的电催化氧化活性.研究表明,Au-Pt/C催化剂的催化活性明显高于Pt/C的,说明...     

Age-hardening by miscibility limit in a multi-purpose dental gold alloy containing platinum

This study examined the age-hardening by miscibility limit in a multi-purpose dental gold alloy containing platinum. The hardness increased rapidly in the initial stage of the aging process, reached the maximum value, then decreased continuously with aging time. The significant hardness increase resulted from the heterogeneous precipitation of the Pt-rich β phase from the grain boundary of the Au-rich α₁ matrix due to the miscibility limit of Au-Pt system. With increasing aging time, the fine Pt-rich β precipitates covered almost the whole matrix, and by further aging, the precipitates grew coarse. The microstructural coarsening reduced the interface between the Au-rich α₁ matrix and the Pt-rich β precipitates, which released the lattice strains between the two phases, resulting in a softening effect. In the later stage of aging process, the Au-containing Pt₃In particle-like structure was transformed into the Au-depleted particle-like structure containing relatively large amounts of Cu resulting from the overlapping miscibility limit of both Au-Pt and Ag-Cu systems, which was responsible for the slow decreasing rate in hardness in the later stage of aging.     

An investigation of the Pt-Al-Ru diagram to facilitate alloy development

The platinum-rich region of the Pt-Al-Ru system was investigated with a view to stabilizing the displacive (martensite-type) transformation in Pt₃Al. In the alloys with low ruthenium contents, ruthenium was found to be partitioned almost exclusively to the fcc Pt phase with extremely limited solubility in Pt₃Al. The low-temperature D0′_C form of Pt₃Al was found to co-exist with the Pt phase. At high Ru additions (greater than 20 at.%), a two-phase mixture of an hcp Ru solid solution and the high-temperature L1₂ form of Pt₃Al was observed. No ternary phases were observed in any of the alloys studied.     

High Temperature Corrosion of a Pt-30 wt.% Rh Alloy in a Phosphorizing Gas

High temperature corrosion of a Pt-30 wt.% Rh alloy in a phosphorizing gas was isothermally investigated at 1285 K using a gas switching technique. Diffusion of P into the alloy created an outer layer of Pt-rich liquid and blocky (Pt, Rh)₂P precipitates along with an inner layer of fcc and (Pt, Rh)₂P plates in a cellular microstructure. Concentration profiles measured by SEM-WDS and EPMA across the layers at room temperature showed that there were three fcc phases: first was a 12 at.% Rh phase in the outer layer; second was a 37 at.% Rh phase in the cellular microstructure; and third was the initial 43 at.% Rh alloy. Also, the EPMA data registered approximately 0.1 at.% P in fcc of these layers. Based on the surrounding binary phase diagrams and the experimental data obtained in this study, a partial Pt-Rh-P phase diagram was constructed. A diffusion path for the corrosion microstructure was drawn on the partial phase diagram to help develop a step by step model for how the microstructure evolved. Growth kinetics of the inner layer were used to calculate a P diffusivity of about 10^?12 m²/s in the Pt-Rh alloy at 1285 K, suggesting rapid diffusion by either an interstitial or interstitialcy mechanism.     

Enhanced corrosion resistance of Zn–Cu–Ti alloy with addition of Cu–Ti amorphous ribbons in 3.5% NaCl solution

In the present study, Zn–0.3Cu–0.3Ti alloy (sample I) was fabricated by a simple low-temperature melting method using Cu–50Ti amorphous alloy ribbons for corrosion in 3.5% NaCl solution. As a comparison, crystalline Cu–50Ti master alloy was used to prepare Zn–0.3Cu–0.3Ti alloy (sample II). Sample I comprising Zn, TiZn₃, and TiZn₁₅ phases exhibits an equiaxed microstructure with subgrain structure. Large TiZn₃ particles show cluster feature, whereas intermittent small TiZn₁₅ particles exist at grain boundaries and subgrain boundaries. In sample II, the Zn matrix with typical dendritic microstructure is observed and no large particles are found. Compared with sample II, sample I shows lower weight gain and corrosion current density and a higher slope of cathode polarization curve. The weight gain for sample I is only 0.59 mg·cm⁻², but for sample II, this value reaches 0.70 mg·cm⁻². After 8 days of corrosion, corrosion products are mainly Zn₅(OH)₈Cl·H₂O and ZnO, showing loose particle shape. As corrosion time increases from 2 days to 8 days, corrosion layer thickness increases from about 15 to 24 μm for sample 1.     

Phase equilibria in Ti–Ni–Pt ternary system

Phase equilibria in Ti–Ni–Pt ternary system have been experimentally determined through diffusion triple technique combined with alloy samples approach. Assisted with electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques, isothermal sections at 1073 and 1173 K of this system were constructed and existence of ternary phase Ti₂(Ni,Pt)₃ was confirmed. In addition, binary compounds Ti₃Pt₅ and TiPt_3– were found to be stable at 1073 and 1173 K, and remarkable ternary solubility in some binary compounds was detected, e.g., solubility of Pt in TiNi can be up to about 36% (molar fraction) at 1073 K and 40% (molar fraction) at 1173 K. Furthermore, a ternary invariant transition reaction TiNi₃+Ti₃Pt₅→Ti₂(Ni,Pt)₃+TiPt₃₊ at a temperature between 1073 and 1173 K was deduced.     

Microstructure,anticorrosion, biocompatibility and antibacterial activities of extruded Mg−Zn−Mn strengthened with Ca

To find suitable biodegradable materials for implant applications, Mg?6Zn?0.3Mn?xCa (x=0, 0.2 and 0.5, wt.%) alloys were prepared by semi-continuous casting followed by hot-extrusion technique. The microstructure and mechanical properties of Mg?6Zn?0.3Mn?xCa alloys were investigated using the optical microscope, scanning electron microscope and tensile testing. Results indicated that minor Ca addition can slightly refine grains of the extruded Mg?6Zn?0.3Mn alloy and improve its strength. When 0.2 wt.% and 0.5 wt.% Ca were added, the grain sizes of the as-extruded alloys were refined from 4.8 to 4.6 and 4.2 μm, respectively. Of the three alloys studied, the alloy with 0.5 wt.% Ca exhibits better combined mechanical properties with the ultimate tensile strength and elongation of 334 MPa and 20.3%. The corrosion behaviour, cell viability and antibacterial activities of alloys studied were also evaluated. Increasing Ca content deteriorates the corrosion resistance of alloys due to the increase of amount of effective cathodic sites caused by the formation of more Ca₂Mg₆Zn₃ phases. Cytotoxicity evaluation with L929 cells shows higher cell viability of the Mg?6Zn?0.3Mn?0.5Ca alloy compared to Mg?6Zn?0.3Mn and Mg?6Zn?0.3Mn? 0.2Ca alloys. The antibacterial activity against Staphylococcus aureus is enhanced with increasing the Ca content due to its physicochemical and biological performance in bone repairing process.     

Mechanical and thermoelectric properties of Zn4Sb3 and Zn4Sb3+Zn directly synthesized using elemental powders

Direct synthesis using elemental powders has been used to produce single-phase polycrystalline ε-Zn₄Sb₃ specimens as well as composite specimens having ε-Zn₄Sb₃ (majority phase) and Zn (minority phase). The effect of the Zn phase on the elastic, thermoelectric and mechanical properties was investigated in this alloy system. Thermoelectric properties of single-phase Zn₄Sb₃ at an ambient temperature are comparable to the published data for the sample prepared by a hot-pressing of ingot-melted alloy powders. Transport properties at room temperature were also evaluated. In addition, Young’s modulus and the bulk modulus of polycrystalline Zn₄Sb₃ were measured using a resonant-ultrasonic technique. The fracture toughness in this alloy system was determined by measuring the length of cracks that formed at the corners of pyramidal indentations used for hardness tests. It is shown that the addition of Zn increases the fracture toughness, but this is achieved at the cost of reducing the thermoelectric figure of merit.     

Selective dry oxidation of the ordered Pt-11.1 at.% V alloy surface evidenced by in situ temperature-controlled X-ray diffraction

A temperature-controlled X-ray diffraction study of the cold-rolled Pt-11.1 at.% V alloy was undertaken to gain better insight into the incomplete transformation of the metastable cubic disordered phase into the tetragonal ordered Pt₈V phase, earlier reported by Nxumalo and Lang [11]. This study has revealed a complex behaviour of the alloy when is annealed in primary vacuum. Upon heating above 450 °C, an ordering of vanadium atoms in the Pt-11.1 at.% V alloy leads to the appearance of a tetragonal Pt₈V phase. Concomitantly, vanadium atoms at the surface of the ordered alloy are slowly oxidized into V₂O₃ Corundum type phase by the low oxygen partial pressure existing in primary vacuum. This segregation of vanadium oxide onto the surface depleting the subsurface region in vanadium, an almost pure Pt cubic phase grows at the V₂O₃-ordered Pt₈V alloy interface with increasing the temperature. This investigation also shows that an external selective oxidation of the cold-rolled Pt-11.1 at.% V alloy takes place when is annealed in flowing argon atmosphere.     

Central region of the Mg-Zn phase diagram

The phase equilibria in the Mg-Zn system from 0 to 85 wt pct Zn and from 335° to 93°C have been redetermined. In this region four intermetallic phases, Mg₇Zn₃, MgZn, Mg₂Zn₃, and MgZn₂, exist. Below 325°C, the Mg₇Zn₃ phase decomposes eutectoidally to magnesium solid solution + MgZn. The MgZn phase is stable over the temperature range from 335°C to 93°C; below 325°C, it is in equilibrium with the magnesium solid solution.     

An investigation of the Pt-Al-Ru diagram to facilitate alloy development

The platinum-rich region of the Pt-Al-Ru system was investigated with a view to stabilizing the displacive (martensite-type) transformation in Pt₃Al. In the alloys with low ruthenium contents, ruthenium was found to be partitioned almost exclusively to the fcc Pt phase with extremely limited solubility in Pt₃Al. The low-temperature D0′_C form of Pt₃Al was found to co-exist with the Pt phase. At high Ru additions (greater than 20 at.%), a two-phase mixture of an hcp Ru solid solution and the high-temperature L1₂ form of Pt₃Al was observed. No ternary phases were observed in any of the alloys studied.     

Microstructure and mechanical properties of Mg-8Li-2Zn-0.5(Ce, Y) alloys

0.5 wt.% Ce and Y were added into the alloy of Mg-8Li-2Zn, respectively. The different behaviors of Ce and Y in the alloy were investigated. Results show that, Ce and Y can both refine the α phase, and the α phase was spheroidized. Two kinds of compounds exist in the alloy when the alloy contains Ce/Y. They are Zn₂Ce and Mg₆Y, respectively. Zn₂Ce mainly distributes at the grain boundary of the alloy with the shape of blocky. Mg₆Y mainly distributes in the inner place of grains with the shape of granular. The size of Zn₂Ce is much larger than that of Mg₆Y. Y and Ce are both favorable for the improvement of strength, and the effect of Y is more obvious. The addition of Ce makes the elongation of the alloy become poor, while the addition of Y can increase the elongation of the alloy.     

小试金-光谱法同时测定地质试样中的痕量铂、钯、铑、铱

报道用小试金－光谱法同时测定地质试样中痕量Pt、Pd、Rh、Ir的方法。将10－20g试样中的Pt、Pd、Rh、Ir富集在毫克量的金合粒中，然后用发射光谱法同时测定痕量Pt、Pd、Rh、Ir。     

多元光谱拟合ICP-AES法同时测定钯中22个杂质元素

试样用HCl-HNO3溶解,采用多元光谱拟合(MSF)ICP-AES法同时测定钯中Pt、Rh、Ir等22个杂质元素,对基体钯的影响、MSF功能、元素分析谱线、背景校正、仪器分析参数等进行了研究,确定了最佳实验条件。杂质元素测定范围:Ag、Mg、Cu、Cr、Ti、Mn和Co为0.0004%～0.05%;Rh、Ru、Pb、Fe、Pt、Al、Zn、Si、Bi、Ca、Sb、Sn、Au和Ni为0.0005%～0.05%;Ir为0.001%～0.05%;方法的相对标准偏差(RSD)和加标回收率分别为1.9%～8.3%和85.3%～116.7%。此方法的测定元素包含国家标准GB/T 1420-2004钯中要求测定的全部杂质元素,满足SM-Pd 99.99合格性的判定要求,同时涵盖ASTM B589-94(2005)Grade 99.95的要求。