Small Addition Of Cu Research Articles

Influence of a Small Addition of Cu on the Magnetization Process of Rapid Quenched Alloys in Strong Magnetic Fields

Influence of a Small Addition of Cu on the Magnetization Process of Rapid Quenched Alloys in Strong Magnetic Fields

Effect of composition, electrolyte pH, annealing temperature and electrodeposition waveform on the magnetic properties of Co-Cu nanowire alloys

Arrays of Co0.2Cux, with 0<x<0.1, nanowires (NWs) have been synthesized. CoCu NWs have been grown into the AAO templates by ac electrodeposition. The anodic aluminum oxide template (AAO) were synthesized by a two-step anodization process of pure Al foils in sulfuric acid. The effect of small addition of Cu to Co NWs by varying the concentrations of Cu+2 ions in the electrolyte, as well as the effect of annealing on the magnetic properties of NWs was investigated. Eventually, the effect of changing waveforms applied to nanowire deposition was studied. The results showed that the coercivity of cobalt NWs decreased by adding copper impurity as a non-magnetic material from 1337 Oe to 660 Oe. By annealing of the alloy NWs up to 450 °C, the coercivity increases from 1140 Oe value for pure Co NWs up to 1541 Oe for CoCu NWs due to the removal of structural stresses of the nanowire.

Investigation of structural and magnetic properties of Cu-substituted NiZn spinel ferrites

In this paper, Cu-substituted NiZn ferrites with nominal compositions of (Ni0.3Zn0.7)1−xCuxFe2O4 (0 ≤ x ≤ 0.4) were prepared by solid-state reaction method. Then, the structural, element composition, valence distribution, surface morphology and magnetic properties of the samples were investigated systematically. As the concentration of composition (x) increases, the lattice constant gradually decreases. When x = 0.1, the μ′ are much higher than of the pure sample, and the power loss lower than that of the sample without Cu, which indicating a significant improvement as substituting in an appropriately extend. Thus, the high permeability and low power loss can be obtained by the small addition of Cu in NiZn ferrites, which improve the application range of the NiZn ferrites.

Pelletized Cu-Ni/CePr5 catalysts for H2 purification via Water Gas Shift reaction

Water Gas Shift (WGS) reaction recently gained attraction as a purifying method to remove CO in H2 stream produced from bio-alcohols reforming for fuel cells applications. In previous works, we tested Cu-Ni samples supported on Pr promoted ceria as catalysts for WGS reaction. However, powder samples are not recommended for a scale-up process and ceria samples lack of cohesive forces to obtain a pellet. Then, supported catalysts can be an interesting alternative to study. In the present work, alumina spheres were impregnated in order to replicate the same chemical formulation of powder-state samples. It was studied the influence in catalytic performance of several textural and catalytic features such as: pellet size, active phase content and distribution, Cu:Ni ratio in bimetallic samples, and contact time. The Cu samples showed a moderate activity and the Ni ones a better performance, but tendency to generate CH4. For all catalysts, the decrease in the pellet size induced a higher CO conversion, indicating strong mass diffusion effects. Besides, it was observed that small addition of Cu to Ni samples significantly moderated the methanation reaction, but maintaining the activity. The change in active metal content slightly modified the activity and changed the selectivity, in agreement with the characterization techniques results (H2-TPR and OSC). In summary, the sample with Cu:Ni ratio equal to 1:2 with 1.5 wt%, presented a great performance, by removing 8 to 2 %v/v of CO with an acceptable contact time and high selectivity, being the most promissory catalyst for higher scale tests.

Improving magnetocaloric properties of Fe68–xCrxTb5B23Nb4 (x = 0, 2, 4, 6 and 8) metallic glasses having high glass-forming ability with tunable Curie temperature

The impacts of adding Cr on the Curie temperature (TC), glass-forming ability (GFA), and magnetocaloric effect were studied in Fe68−xCrxTb5B23Nb4 (x = 0, 2, 4, 6 and 8) metallic glasses prepared by suction casting. GFA depends on Cr content in the composition. For Fe68−xCrxTb5B23Nb4 bulk metallic glasses (BMGs), with critical diameters up to ~3 mm can be produced by suction casting and maximum value of GFA was found for x = 6. By exchanging Cr with Fe partially, TC could effectively be adjusted in a quite broad temperature interval from 487 K for x = 0 to 267 K for x = 8, whereas maximum magnetic entropy change decreased from 1.16 to 0.53 Jkg−1 K−1 and refrigeration capacity (RC) changed from 116 to 45.05 J/kg under a low field change of 2 T. Though TC is shifted to room temperature, maximum magnetic entropy change and RC decreased almost half of the base alloy. To enhance these properties (Fe0.62Cr0.06Tb0.05B0.23Nb0.04)100−yCuy (y = 0.75, 1), metallic glasses are prepared. By the help of small addition of Cu, magnetocaloric properties can be effectively increased without changing the TC. These findings show that the successful synthesis of the Fe-based Fe62Cr6Tb5B23Nb4 and (Fe0.62Cr0.06Tb0.05B0.23Nb0.04)100−yCuy (y = 0.75, 1) BMGs near room temperature, could be considered as promising candidates as magnetic refrigerant materials.

Formation of Transition Phases on Interface between Monocrystalline Fe and Cu Due to Mutual Solid-State Diffusion

Abstract Interdiffusion between Fe (Armco) and Cu single crystals of similar orientation (around [110]) annealed at temperatures of 873 and 973K in air for 0.5 up to 4 h is studied. Formation of three phases different in their chemical composition has been observed: 1) oxide layer on Cu border (porous), 2) a layer rich in copper, iron and oxygen, 3) a layer of iron and oxygen with only small addition of Cu. All reactions of interface formation occurred in solid state. It was noted that oxygen plays an important role in development of new phases. Strong Kirkendall effect is observed due to large difference in diffusion coefficients of copper atoms to iron, DCu→Fe=300exp(-67800/RT) and iron atoms to copper DCu→Fe=0.091exp(-46140/RT).

ВЛИЯНИЕ ДОБАВОК КОБАЛЬТА И СКАНДИЯ НА МЕХАНИЧЕСКИЕ ХАРАКТЕРИСТИКИ И КОРРОЗИОННУЮ СТОЙКОСТЬ ПРОФИЛЕЙ ИЗ СРЕДНЕПРОЧНОГО СПЛАВА СИСТЕМЫ Al–Zn–Mg С ДОБАВКОЙ МЕДИ

ВЛИЯНИЕ ДОБАВОК КОБАЛЬТА И СКАНДИЯ НА МЕХАНИЧЕСКИЕ ХАРАКТЕРИСТИКИ И КОРРОЗИОННУЮ СТОЙКОСТЬ ПРОФИЛЕЙ ИЗ СРЕДНЕПРОЧНОГО СПЛАВА СИСТЕМЫ Al–Zn–Mg С ДОБАВКОЙ МЕДИ

Regulating the passive film of NiCoCrMo alloy in hydrofluoric acid solution by small addition of Cu

The effect of 2wt.% Cu addition on the corrosion resistance of Ni–30Co–16Cr–15Mo–6Fe alloy in hydrofluoric acid was investigated by immersion testing at 100°C. Microstructural observations of the passive film of samples after immersion testing via various methods revealed that the small addition of Cu yielded a tremendous improvement in corrosion resistance, even after cold forging. In addition, the passivation of Ni–30Co–16Cr–15Mo–6Fe alloy by a Mo-oxide-dominated passive film was completely changed to passivation by a Cu-dominated one in Ni–30Co–16Cr–15Mo–6Fe–2Cu alloy during immersion in hydrofluoric acid solution because the segregation behaviour of Cu was much stronger compared to that of Mo.

Effect of Heat Treatment Conditions and Small Addition of Cu on Occurrence of Serration in Al-Si Alloys

In this study, the effect of heat treatment conditions and small addition of Cu on occurrence of serration in Al-Si alloys was investigated. Specimens were aged for various times up to 87ks at 273K or 473K after quenching from 853K, and tensile-tested at room temperature. In the binary alloy, serration was observed even after aging for 87ks at 273K, while in the case of aging at 473K, serration did not occur under aging conditions at aging time, tA≧20s. On the other hand, serration was observed even after aging for 72ks at 473K in the Cu-added alloy. In both alloys, serration was also recognized when the specimens were furnace-cooled from 853K to room temperature. Thus, for aging at 473K of the binary alloy serration was observed only when the aging period was short enough, but addition of Cu to the binary alloy prolonged the aging period where serration could be recognized. Aging rate of both alloys measured by tensile strength was almost the same. The size of precipitates in the Cu-added alloy was smaller than that in binary alloy. Moreover, the number of the precipitates at the grain boundary in the Cu-added alloy was smaller than that in the binary alloy. It is considered that serration occurs for Al-Si alloys when the specimen is heat-treated so that small precipitates may be formed. Now the details of the effect of Cu addition are not clear.

CoFeCu electroplated nanowire arrays: Role of composition and annealing on structure and magnetic properties

CoxFe100−x and CoxFe95−xCu5, with 30 &lt; x &lt; 90, arrays of nanowire, around 20 nm in diameter and about 5 μm long, have been prepared by electrodeposition filling the self‐assembled nanopores of anodic alumina templates. These samples were later thermally annealed for 2 h in the range of temperatures up to 600 °C. Crystalline anisotropy was confirmed to exhibit bcc cubic structure with [110] texture in as‐prepared state. First structural changes are observed after annealing at 450 °C when a refinement of such cubic phase is observed. Annealing at higher temperatures promotes the appearance of Co and Fe oxides. Small addition of Cu to CoFe alloys induces only limited variations in the magnetic properties for as‐prepared samples. Nevertheless, the presence of small Cu content promotes a significant magnetic hardening in comparison with the effect observed in CoFe nanowires. From the temperature dependence of magnetic properties in as‐prepared and annealed samples we conclude a complex contribution of various anisotropy energy terms coming from the annealing and from the presence of Cu.The presence of Cu in small amount induces significant changes in the magnetic properties of annealed CoFeCu nanowires.

The sintering densification, microstructure and mechanical properties of gamma Ti–48Al–2Cr–2Nb alloy with a small addition of copper

Titanium aluminide based alloys are difficult to consolidate by pressureless sintering. A systematic study has been made of the effect of small additions of copper on the sintering densification, microstructure and mechanical properties of gamma Ti–48Al–2Cr–2Nb (in at% throughout). The density of the Ti–48Al–2Cr–2Nb alloy sintered at 1375°C for 120min increased consistently from 74% theoretical density (TD) without Cu to >98%TD with an addition of up to 2at%Cu. The enabling effect of a small addition of Cu is due to the formation of a wetting liquid, supported by dilatometry, differential scanning calorimetry (DSC) and Thermal-Calc analyses. Rapid sintering shrinkage occurred around 1251°C and 1370°C corresponding to liquid formation. Transmission electron microscopy (TEM) identified the formation of a Cu- and Cr-enriched hexagonal close-packed Ti(Al, Cr, Cu, Nb) phase with a=0.520Å and c=0.803Å. Its presence increased with increasing Cu content. The compressive, tensile and flexure properties of the as-sintered Ti–48Al–2Cr–2Nb–2Cu alloy were assessed. The tensile properties are similar or superior to those of the Ti–48Al–2Cr–2Nb alloy fabricated by metal injection moulding and sintering while the compression strength is about twice that of the as-cast Ti–48Al–2Cr–2Nb.

Effects of a Small Addition of Cu or Ge on the Microstructure and Mechanical Property of an Al-Si Alloy

In this study, we investigated the effects of a small addition of Cu (0.1%) or Ge (0.1%) on the microstructure and mechanical property of Al-Si alloys. The results are as follows. The size of precipitates in the Cu-added or Ge-added alloys is smaller than that in the binary alloy. The size of the precipitates at the grain boundary in the Cu-added or Ge-added alloys is larger than the size of the precipitates in the binary alloy. However, the number of the precipitates at the grain boundary in the Cu-added and Ge-added alloys is smaller than that in the binary alloy. It was found that a small addition of Cu or Ge has the effect of raising the fatigue strength under repeated tensile loading as well as the tensile strength.

Morphology and growth kinetics of intermetallic compounds in solid-state interfacial reaction of electroless Ni-P with Sn-based lead-free solders

A comparative study of solid/solid interfacial reactions of electroless Ni-P (15 at.% P) with lead-free solders, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, and pure Sn, was carried out by performing thermal aging at 150°C up to 1000 h. For pure Sn and Sn-3.5Ag solder, three distinctive layers, Ni3Sn4, SnNiP, and Ni3P, were observed in between the solder and electroless Ni-P; while for Sn-0.7Cu and Sn-3.8Ag-0.7Cu solders, two distinctive layers, (CuNi)6Sn5 and Ni3P, were observed. The differences in morphology and growth kinetics of the intermetallic compounds (IMCs) at the interfaces between electroless Ni-P and lead-free solders were investigated, as well as the growth kinetics of the P-enriched layers underneath the interfacial IMC layers. With increasing aging time, the coarsening of interfacial Ni3Sn4 IMC grains for pure Sn and Sn-3.5Ag solder was significantly greater than that of the interfacial (CuNi)6Sn5 IMC grains for Sn-0.7Cu and Sn-3.8Ag-0.7Cu solders. Furthermore, the Ni content in interfacial (CuNi)6Sn5 phase slightly increased during aging. A small addition of Cu (0.7 wt.%) resulted in differences in the type, morphology, and growth kinetics of interfacial IMCs. By comparing the metallurgical aspects and growth kinetics of the interfacial IMCs and the underneath P-enriched layers, the role of initial Cu and Ag in lead-free solders is better understood.

Analysis of the redeposition of AuSn4 on Ni/Au contact pads when using SnPbAg, SnAg, and SnAgCu solders

Interfacial reactions between SnPbAg, SnAg, and SnAgCu solders and Ni/Au surface finish on printed wiring board and especially the redeposition of AuSn4 intermetallic compound have been investigated. The following major results were obtained. The first phase to form during soldering in the (SnPbAg)/Ni/Au and the (SnAg)/Ni/Au systems was Ni3Sn4. During the subsequent solid-state annealing, the redeposition of AuSn4 as (Au,Ni)Sn4 occurred in both systems. This was explained with the help of the concept of local equilibrium and the corresponding ternary phase diagrams. It was concluded that the stabilizing effect of Ni on the (Au,Ni)Sn4 provided the driving force for the redeposition. Contrarily, when the solder alloy contained some Cu, the first intermetallic to form was (Cu,Ni,Au)6Sn5 and no redeposition of AuSn4 was observed. Thus, a very small addition of Cu to the Sn-rich solder alloys changed the behavior of the interconnection system completely. This behavior was explained thermodynamically by using Cu-Ni-Sn and Au-Cu-Sn ternary phase diagrams. The growth kinetics of the interfacial reaction products in the three systems was observed to be somewhat different. The reasons for the observed differences are also discussed.

Effect of Cu addition on the $alpha;1+$alpha;2 miscibility gap of the Al?Zn system

The effect of the Cu addition on the ( α 1 + α 2 ) miscibility gap of the Al–Zn binary system was studied by using diffusion couple technique. The Zn concentrations in both α 1 and α 2 phases are decreased due to the small addition of Cu, and the Cu element is enriched in the α 2 phase, resulting in both α 1 /( α 1 + α 2 ) and ( α 1 + α 2 )/ α 2 phase boundaries of the miscibility gap shifting to the Al-rich corner in the Al–Zn–Cu ternary system.

Effect of Cu addition on the α1+ α2 miscibility gap of the Al–Zn system

The effect of the Cu addition on the ( α 1+ α 2) miscibility gap of the Al–Zn binary system was studied by using diffusion couple technique. The Zn concentrations in both α 1 and α 2 phases are decreased due to the small addition of Cu, and the Cu element is enriched in the α 2 phase, resulting in both α 1/( α 1+ α 2) and ( α 1+ α 2)/ α 2 phase boundaries of the miscibility gap shifting to the Al-rich corner in the Al–Zn–Cu ternary system.

微量Cu,Ge添加によるAl-1.2%Si合金の機械的性質改善(機械材料・材料加工II)

微量Cu,Ge添加によるAl-1.2%Si合金の機械的性質改善(機械材料・材料加工II)

Clustering of Cu prior to the crystallization reaction in an Fe-Zr-B-Cu amorphous alloy

While nanocrystalline structure evolves in Fe-Zr-B ternary alloys by primary crystallization, it was reported that a small addition of Cu reduced the crystallization temperature slightly and made the grain size much smaller. Similar effect of Cu was reported in Fe-Si-B-Nb-Cu alloys, but in this case, addition of Cu was essential to obtain a nanocrystalline structure. Previous atom probe works revealed that Cu atoms form clusters prior to the crystallization reaction. Similar effect is expected in the Fe-Zr-B-Cu system but this remains unconfirmed. The aim of this study was to examine the behavior of Cu in Fe-Zr-B-Cu amorphous alloy in the early stage of primary crystallization and to understand the effect of Cu on the crystallization of Fe-Zr-B based amorphous alloys.

金属間化合物の粉末冶金と諸物性 ｎ型およびｐ型β‐ＦｅＳｉ２の熱電特性に及ぼすＣｕ添加の影響

The thermoelectric properties of n-type FelyCoySi2Cux(0.02≤y≤0.06)(0≤X≤0.06) and ptype Fe0.92Mn0.08Si2-xCux(0≤X≤0.07) were investigated. Mixture of Fe, Si and Co or Mn powders with or without Cu was arc-melted in an argon atmosphere to form a button composed of α -Fe2Si5 and e-FeSi phases. The button was ground under -60mesh and Cu powder was mixed for the samples without Cu doping. Then they were ground (MA) in a conventional ball mill for 360 ks or in a high energy vibrational mill for 72 ks. β-FeSi2 phase was not formed during MA, but was obtained by hot pressing of MA powders at 1173 K for 1.8 ks under 25MPa. It was found that the small addition of Cu improves the power factor(Q2/ρ) of n-type Fe1-yCoySi2 by decreasing the electrical resistivity and increasing the thermoelectric power. On the other hand, for p-type Fe0.92Mn0.08Si2 the electrical resistivity slightly increased and thermoelectric power decreased, as the result the power factor decreased. Cu addition slightly increased the thermal conductivity for both of n-type and p-type β-FeSi2.

Magnetic properties of Pr-Fe-B alloy powders prepared by mechanical grinding

The effect of ball milling on the magnetic properties of the Pr15Fe80B5 alloy, whose as-cast structure was composed of matrix phase Pr2Fe14B and Pr-rich and α-Fe phases, has been investigated by measuring iHc, thermomagnetic curves, and x-ray diffraction (XRD) patterns. By ball milling using a planetary ball mill up to 96 h, iHc decreased with the amorphization of the matrix and Pr-rich phases. However, subsequent heat treatments gave rise to the marked increase of iHc. The alloy, after 48 h of ball milling and subsequent 600 °C annealing possessed iHc of 17.4 kOe, Br of 5.8 kG, and (BH)max of 6.5 MGOe. This alloy showed sharp diffraction peaks of Pr2Fe14B phase, while the α-Fe phase peak, which persisted through the ball milling process, almost disappeared. The high iHc of the Pr-Fe-B alloy, subjected to optimum milling and subsequent annealing, was attributed to a very fine Pr2Fe14B phase precipitation from the amorphous state and to the effective solution of the α-Fe phase into the matrix phase. Also, a small addition of Cu to the Pr15Fe80B5 alloy was found to increase the coercivity. Further, the alloy milled for 12 h and annealed at 600 °C for 1 h showed iHc of 19.7 kOe, Br of 7.0 kG, and (BH)max of 10.2 MGOe.