Ag15Cu85二元合金高温氧化行为对去合金机制的影响

近年来,纳米多孔材料成为光催化、储能等领域的研究热点.本工作将高温氧化和去合金工艺相结合,研究高温氧化对Ag15 Cu85二元合金前驱体制备纳米多孔银的影响.在650～750℃温度下,氧化1～5 min,Ag15 Cu85二元合金表面产生纳米级二维微孔、颗粒析出物及岛状平台.随着氧化时间的延长,合金表面呈现出相似的微观氧化形貌.铸态合金薄带在60℃、5％HNO3(质量分数)中去合金0.5 h时,合金表面活性组元溶解;去合金进行1.5 h时,获得三维双连续的纳米多孔银结构.氧化态前驱体在腐蚀溶液浓度相同、去合金温度更低(45℃)的情况下,去合金15 min就能得到均匀的韧带和孔隙尺寸更大的纳米多孔银,仅为铸态合金薄带去合金持续时间的1/6.这说明氧化行为对去合金过程产生了较大影响,高温氧化改变了去合金反应的中间过程,去合金反应的参与者由单一α?Cu(Ag)固溶体转变为α?Cu(Ag)固溶体和Cu的氧化产物.氧化产物参与去合金反应,极大地促进了去合金反应进程,提高了活性组元溶解效率.     

Cu-Au-Ag三元去合金化制备纳米多孔金材料

采用磁控溅射镀铜金银多层膜,经过长时间高温热处理合金化制备前驱体三元合金,以不同的酸溶液自由腐蚀去合金化去除合金中的铜元素和银元素,成功制备出纳米多孔金薄膜。采用扫描电镜和X射线能谱仪对去合金腐蚀前后样品的形貌和成分进行了分析。结果表明,400℃,36h热处理后铜金银多层膜完全合金化,获得了Au_3Ag_(28.5)Cu_(68.5)合金材料;FeCl_3+HCl溶液自由腐蚀去除铜可获得连续均匀的纳米尺寸孔隙结构,获得了几乎不含铜的样品;采用渐进浓度的硝酸自由腐蚀去合金化后去除银后获得了孔隙率约84%的纳米多孔金薄膜,其微观结构为连续的三维多孔结构,其系带尺寸10~35nm,并且20~25nm的系带分布达77%。     

纳米多孔Pd-Cu/Pd-Ag催化剂的制备及其电催化性能EI北大核心CSCD

针对直接甲醇燃料电池(direct methanol fuel cell,DMFE)对高效阳极催化剂的需求,设计研发Ca-Mg-Pd-M(M=Cu,Ag)非晶合金前躯体体系,并采用去合金化制备系带-孔道双连续结构的纳米多孔Pd-Cu/Pd-Ag合金。通过设计前驱体合金比例可调节多孔结构的元素比例和尺寸,Pd元素可与Cu,Ag元素形成连续固溶体,在去合金化过程中可以降低Cu,Ag元素的扩散,进而细化纳米多孔的系带尺寸(由100 nm减小到10 nm)。相较于纳米多孔Pd,纳米多孔Pd-Cu/Pd-Ag合金表现出更优异的甲醇催化活性(催化电流强度:45 mA/mg)和抗毒化能力(J f/J b值为1.56),还具有低成本的优点,在直接甲醇燃料电池阳极催化剂方面有着良好的应用前景。     

纳米多孔铜的去合金法制备及性能研究

通过电弧炉和管式炉烧结制备不同原子比的铜锰合金前驱体,室温下在0.1 mol/L盐酸溶液中对制备出的前驱体合金进行自腐蚀制备纳米多孔铜.采用SEM、EDS、Autosorb -1等分析了样品的表观形貌、元素含量和微观孔结构.结果表明:采用去合金法得到结构均匀的三维连通纳米多孔铜片体材料,管式炉制备的Cu∶Mn原子比为3∶7的样品获得相对分布更为均匀、孔结构更为明显的多孔铜.     

纳米晶Cu-Al合金去合金化制备纳米多孔铜及其力学性能研究

采用高能球磨结合放电等离子烧结技术(SPS)制备了纳米晶Cu-Al合金,进而通过去合金化法获得纳米多孔铜块体材料。研究了合金成分对纳米晶Cu-Al前驱体物相演变、去合金化处理获得的纳米多孔铜微观结构和力学性能的影响。结果表明,当合金中铜含量较低时,纳米晶Cu-Al前驱体由α-Al固溶体和Al_2Cu两相组成;随着铜含量的增加,前驱体中α-Al固溶体相逐渐减少,Al_2Cu相逐渐增加;当铜含量增加到32%时,纳米晶Cu-Al前驱体中仅有Al_2Cu单相。此外,随着铜含量的增加,纳米晶Cu-Al前驱体去合金化处理后,其纳米多孔铜微观结构由微米/纳米双级复合孔逐渐转变为孔径均匀的三维连通纳米孔,并且纳米多孔铜块材的压缩强度逐渐增大。     

腐蚀添加剂对Cu-Mn合金制备孔径可控纳米多孔铜的影响

以铜锰单相固溶体为前躯体合金,利用去合金化法,在盐酸腐蚀液中添加适量不同的络合剂、金属盐可制备出成分纯净、孔形貌可控的三维连通纳米多孔铜(NPC)。采用X射线衍射仪(XRD)、扫描电镜能谱(SEM-EDS)、图像分析软件(Image-Pro Plus)对样品的物相、组分、微观形貌和平均孔径尺寸进行表征。结果表明：腐蚀添加剂的种类和浓度对孔结构形成过程和孔形貌具有重要影响。与未添加络合剂相比,添加硫脲、柠檬酸等络合剂后,腐蚀后的样品的孔径和韧带尺寸都发生不同程度的细化,络合常数越大,铜原子表面扩散系数越小,细化效果越明显;添加硫脲后能显著细化多孔结构,NPC平均韧带尺寸可在18～90 nm之间调控,且其浓度越高,孔径、韧带尺寸越小;添加适量金属盐Fe₂(SO₄)₃、CuSO₄、ZnSO₄后腐蚀液中出现副反应,反应速率大幅度提高,孔结构发生粗化,出现韧带尺寸分布呈纳米级和微米级共存的多孔结构,当CuSO₄添加浓度超过20 mmol/L时,多孔样品断裂截面失去初...     

微量Cu掺杂对TA10合金组织、力学性能与腐蚀行为的影响

研究了掺杂(0.5%~2.5%) Cu元素对TA10合金的微观组织、力学性能及腐蚀性能的影响,采用扫描电子显微镜(SEM)、金相显微镜(OM)研究合金的微观组织,并用XRD进行物相分析;采用电化学腐蚀、静态浸泡腐蚀试验研究合金的腐蚀性能。选出最佳合金成分,并通过原子力显微镜(AFM)对其做进一步分析。结果表明,随着Cu元素含量的增加,TA10合金基体组织被不断细化,添加2.5% Cu时,该合金的硬度值达到最大。Cu含量在1.0%~2.0%之间,合金的耐腐蚀性能较好。含Cu为0.5%的合金耐腐蚀性能优异。     

Fe-Cu合金相分离过程

采用喷铸和单辊旋淬快速冷却法制备Fe_(80)Cu_(20),Fe_(60)Cu_(40),Fe_(50)Cu_(50)3种成分Fe-Cu合金,利用SEM,XRD,DSC对其凝固微观组织、相结构及相变热力学过程进行观察和分析。结果表明:3种成分的Fe-Cu合金均发生了不同程度的相分离,且Cu含量越高,DSC降温曲线上出现的液-液相分离温度越高,结晶组织中相分离现象越明显;Fe_(80)Cu_(20)合金随着过冷度的增加,富Fe相枝晶晶粒尺寸变小的同时富Cu相的体积分数也不断减少,而Fe相、Cu相的晶格常数均随过冷度的增加而增大,过冷度的增加提高了分离相的固溶度;在Fe_(60)Cu_(40)及Fe_(50)Cu_(50)合金中富Cu区出现二次相分离的富Fe小球,且富Fe小液滴不断聚集以降低界面能。揭示了Fe-Cu相分离型合金的快速凝固过程。     

孔隙可调控多孔铜粉的气相去合金制备及性能研究

多孔铜粉具有独特的孔隙结构和大比表面积,是适合于催化生长和化学负载的基元功能材料。但受限于粉末尺寸小、活性高,目前鲜有关于多孔铜粉制备工艺的研究。以球磨后的铜锌合金粉末为前驱体,采用气相去合金的方法成功制备了多孔铜粉。应用SEM、EDS、XRD、TEM等表征手段研究了去合金温度、时间、原始合金成分和球磨变形对粉末性能的影响。实验结果表明,孔隙结构变化是Zn原子去合金驱动力,Cu原子表面扩散和Cu原子体扩散三者互相竞争的结果。表面孔隙粗化过程受Cu原子表面扩散主导,而Cu原子体扩散会引起孔隙结构的收缩。球磨引入的位错通过提供快速扩散通道的方式降低了孔隙粗化过程的扩散激活能,加快了去合金过程的进行。制备的多孔粉末最大表面孔隙率为17%,平均孔隙尺寸为0.6～1.1μm。通过调整工艺参数,可以调控多孔铜粉的表面孔隙。     

脱合金化法制备纳米多孔铂合金的研究进展

纳米多孔金属由纳米尺度的孔隙和金属韧带组成，具有三维双连通的网络状结构，兼具纳米材料和金属材料的双重特性，在催化、传感和药物输送等领域具有广阔的应用前景。脱合金化法操作简单，工艺流程短，成本相对较低，是制备纳米多孔金属的常用方法。目前，利用脱合金化法制备的纳米多孔Pt合金因其对甲醇氧化和氧还原反应具有优异的催化活性而备受关注，有望在燃料电池等相关领域实现应用。近年，研究学者不断丰富纳米多孔Pt合金的合金体系，通过优化合金成分和脱合金化工艺对其结构和性能进行调控，发展出多种形态的纳米多孔Pt合金，系统调查了前驱体的结构和成分、脱合金工艺参数对纳米多孔Pt合金的组织结构、形貌和性能的影响，并对纳米多孔形成和优异性能的机理进行了广泛的研究。利用脱合金化法制备的纳米多孔Pt合金具有多种形态，如低维的纳米颗粒、纳米花、纳米线和薄膜以及三维的纳米多孔带材等。低维的纳米多孔Pt合金因其更大的比表面积和纳米尺寸效应而具有更为突出的催化活性，而三维的纳米多孔带材具有均匀的纳米多孔结构，且克服了低维合金易团聚的问题。通过调整前驱体合金的化学成分和组织结构，改变脱合金化工艺参数，以及对纳米多孔合金进行退火处...     

Effect of ribbon-wheel contact on the microstructure of melt-spun Al-Cu eutectic alloy ribbons

The microstructure of melt-spun Al-17.3 at% Cu eutectic alloy ribbons with different thicknesses have been revealed by means of electron microscopy and X-ray techniques. Thick ribbons (>20μm) consist of finely-dispersed α-Al and Al₂Cu equilibrium phases showing lamellar or irregular morphology. In thin ribbons a considerable fraction of supersaturated α-Al solid solution and the metastable Al₄Cu₉ phase have been detected. The experimental facts on the identity of the phases, their morphology and particle size for given processing conditions are discussed within the framework of a heat flow model including the solidification process as well as post-solidification transformations. The microstructural features are considered to be determined by local and time variations of the ribbon-wheel contact.     

Influence of silver additions on electrical, mechanical and structures properties of rapidly solidified Sn–0.7%Cu alloy from melt

The eutectic alloy Sn_99.3-xCu_0.7Ag_x has been examined as one of the lead free solder alloys. Melting point, electrical resistivity, internal friction, elastic moduli, microhardness and the microstructure of the Sn_99.3Cu_0.7, Sn_95.8Cu_0.7Ag_3.5 and Sn_95.3Cu_0.7Ag₄ rapidly solidified lead free solder alloys have been investigated. The examined physical properties are improved by increasing silver contents in the studied lead free solder alloys. These improved properties indicate that these alloys are adequate for low temperature soldering applications.     

Structural, mechanical, hardness indentation measurements of Sn65−x Ag25Sb10Cu x solder alloys rapidly solidified from melt at cooling rate 1.1×105 K s−1

Structural, mechanical properties, and hardness indentation measurements of Sn_65–x Ag₂₅Sb₁₀Cu _x (x=0, 0.5, 1.0, 1.5, 2.0, and 2.5 wt %) solder alloys have been studied and analyzed. The alloy exhibits mechanical properties superior to those in both the Sn–Ag₂₅ binary and Sn–Ag₂₅Sb₁₀ ternary solder alloys. The addition of small amounts of Cu is found to refine the effective grain size, while retaining the uniform distribution of Ag₃Sn, SnSb, and Cu₁₀Sn₃ precipitates in the solidification microstructure, thus significantly improving the ductility and strength.     

Effects of rare earth La on microstructure and properties of Ag–21Cu–25Sn alloy ribbon prepared by melt spinning

Ag–21Cu–25Sn alloy ribbon as a promising intermediate temperature alloy solder (400–600 °C) was prepared by melt spinning technique in this paper. Rare earth La was added into Ag–21Cu–25Sn alloy to refine the microstructures and improve the wettabilities of as-prepared alloy solders. The phase constitutions, microstructures, melting temperatures and wettabilities of selected specimens were respectively tested. The results showed that the dominant phase constitutions of Ag–21Cu–25Sn–xLa alloy ribbons were Ag₃Sn and Cu₃Sn. The grain size of Ag–21Cu–25Sn–xLa alloy decreased with the addition of La increasing. La addition reduced the melting temperatures of Ag–21Cu–25Sn–xLa alloy ribbons, and effectively improved the wettabilities of the alloy ribbons. When the addition of La was 0.5 wt%, the wettability of as-prepared alloy solder achieved the optimal value of 158 cm² g⁻¹ under brazing temperature 600 °C and dwell time 15 min. In addition, raising brazing temperature and prolonging dwell time could improve the wettability of Ag–21Cu–25Sn–xLa alloy ribbon.     

Reactive wetting of Sn–2.5Ag–0.5Cu solder on copper and silver coated copper substrates

In the present work, wetting characteristics and morphology of intermetallic compounds (IMCs) formed between Sn–2.5Ag–0.5Cu lead-free solder on copper (Cu) and silver (Ag) coated copper substrates were compared. It was found that, Ag coated Cu substrate improved the wettability of solder alloy. The average values of contact angles of solder alloy solidified on Ag coated Cu substrate were reduced to about 50 % as compared to contact angles obtained on Cu substrates. Flow restrictivity for spreading of solder on Ag coated Cu was found to be lower as compared to Cu substrate. The spreading of solder alloy on Ag coated Cu exhibited halo zone. Coarse needle shaped Cu₆Sn₅ IMCs were observed at the solder/Cu substrate interface whereas at the solder/Ag coated Cu interface Cu₆Sn₅ IMCs showed scallop morphology. The formation of Cu₃Sn IMC was observed for the spreading of solder alloy on both substrates. The solder/Ag coated Cu substrate interface exhibited more particulates of Ag₃Sn precipitates as compared to solder/Cu substrate interface. The improved wettability of solder alloy on Ag coated Cu substrate is due to the formation of scallop IMCs at the interface.     

Creep behavior of near-peritectic Sn-5Sb solders containing small amount of Ag and Cu

Sn-5%Sb is one of the materials considered for replacing Pb-bearing alloys in electronic packaging. In the present study, the effects of minor additives of Ag and Cu on the as-cast microstructure and creep properties of the Sn-5Sb solder alloy are investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscope (EDS) and tensile tests. Results show that addition of Ag and Cu resulted not only in the formation of new Ag₃Sn and Cu₆Sn₅ intermetallic compounds (IMCs), but also in the refinement of the grain size of Sn-5Sb solder. Accordingly, the creep properties of the Ag or Cu-containing solder alloys are notably improved. Attention has been paid to the role of IMCs on creep behavior. The lead-free Sn-5Sb-0.7Cu solder shows superior creep performance over the other two solders in terms of much higher creep resistance and vastly elongated creep fracture lifetime. An analysis of the creep behavior at elevated temperatures suggested that the presence of hard Cu₆Sn₅ and fine SbSn IMCs in the Sn-5Sb-0.7Cu alloy increases the resistance to dislocation movement, which improves the creep properties.     

Effect of silver addition on formation of secondary phases in squeeze cast Al–Cu–Mg alloys

Abstract

The effect of silver addition on the formation of secondary phases in squeeze cast Al–4.0Cu–1.5Mg and Al–4.0Cu–1.5Mg–0.7Ag (all wt-%) alloys has been investigated using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffractometry, and transmission electron microscopy. The as cast microstructure of both alloys consists of primary dendritic α-Al and various types of secondary solidification phase, e.g. Al₂Cu, Al₂CuMg, Al(Cu,Ag)Mg, and icosahedral (I) and decagonal (D) quasicrystalline phases. However, the solidification path in the interdendritic region during squeeze casting is different for each alloy, i.e. L→ternary α-Al–Al₂Cu–Al₂CuMg eutectic in Al–4.0Cu–1.5Mg and L→L′+Al₂Cu→α-Al–Al₂Cu–Al(Cu_0.75Ag_0.25)Mg eutectic in Al–4.0Cu–1.5Mg–0.7Ag. This indicates that silver acts as an alloying element stabilising the formation of Al(Cu,Ag)Mg Laves phase. The remaining copper and iron rich liquid in the interdendritic region at the final stage of solidification solidifies into a mixed structure of α-Al, Al₂Cu, and AlCuFe I (or D) phases. The composition of the I and D phases, measured by energy dispersive X-ray spectroscopy, is in the range Al–(27～28)Cu–(9～10)Fe and Al–(26～27)Cu–(7～9)Fe (all at.-%) respectively.     

Microstructure of laser-induced combustion synthesis of Cu<Subscript>59.6</Subscript>Zr<Subscript>36.9</Subscript>Al<Subscript>3.5</Subscript> alloy

Cu_59.6Zr_36.9Al_3.5 alloy are prepared by laser-induced combustion synthesis technology. The microstructure and phases formed of the product is studied by XRD and TEM. The product consists of mixtures of amorphous and crystalline phases, mainly(α-Zr, Zr₂Cu, Zr₁₀Cu₇ and Cu₈Zr₃. The amorphous and nanocrystalline phases content over 50% in volume estimated from the broad peak in the XRD spectrum. TEM and HRTEM results show that the microstructure is characterized by inhomogeneously distributed amorphous, nano Zr₂Cu, relatively gross (∼100 nm) Zr₂Cu, and large grain Cu₁₀Zr₇.     

Effects of rare earth additions on structures and properties of rapidly solidified copper alloys

Abstract

Copper based Cu–RE alloys (where RE represents lanthanum, neodymium, or samarium) with alloying content up to 16 wt-% were prepared by chill block melt spinning into ribbons of thickness between 40 and 100 μm. The melt spun ribbons were heat treated isochronally for 2 h at 300, 400, 500, 600, 700, and 800°C, respectively. The melt spun and heat treated ribbons were tested for microhardness and resistivity and were characterised by optical and transmission electron microscopy (TEM) and X-ray diffractometry (XRD). Microstructures were of the typical zone B type for Cu–1RE and Cu–3RE ribbons and of the zone B/zone A type for Cu–5RE, Cu–8RE, and Cu–12RE ribbons. Only microstructures of the zone A type were found in Cu–15La ribbons. The metastable extended solid solubilities of the rare earth elements were evaluated by measurements of the lattice parameters of the supersaturated solid solutions and significant extension from the equilibrium solid solubility was found for all three alloys. The secondary phase was identified by TEM and XRD as Cu₆RE for all ribbons except Cu–15La ribbons in which metastable Cu₅La and Cu₁₃La phases were also found. Observations using TEM and XRD also showed a reduction in the α-Cu grain size of the as spun ribbons with increasing alloying content, producing nanosized α-Cu grains on the chill side of the ribbons. Heat treatment of the ribbons at 400°C for 2 h produced no significant coarsening of α-Cu grains as the size of these grains was still in the nanometer region. Both α-Cu and Cu₆RE grains coarsened as a result of heat treatment for 2 h at temperatures of 600°C and above for all the alloys.     

Fabrication of porous Ag by dealloying of Ag–Zn alloys in H2SO4 solution

In the present work, the fabrication of porous silver through the dealloying of Ag_24.3Zn_75.7, Ag_33.4Zn_66.6, and Ag_57.6Zn_42.4 alloys in dilute H₂SO₄ solution is reported. Different length scales and distribution could be achieved through varying the alloy’s composition and concentration of H₂SO₄ solution. Multi-porosity distribution of Ag_33.4Zn_66.6 alloy also indicates the possibility to tailor the microfilter’s structure by using common microstructure controlling method in materials science.