Effect of Rare Earth on Microstructure and Properties of Pure Copper

Metallograph and scanning electron microscope studies of the distributionand function of rare earthmetals in copper show that RE can reduce the oxygen content,fine the grain Ceils of copper,and enhancethe mechanical and electrical properties.Excess RE in copper will lead to the formation of some RE com-pounds like Fe-Cu-RE and RECu_6.     

Magnetic,Dielectric and Complex Impedance Properties of xBa_(0.95)Sr_(0.05)TiO_3–(1-x)BiFe_(0.9)Gd_(0.1)O_3Multiferroic Ceramics

xBa_(0.95)Sr_(0.05)TiO_3–(1-x)BiFe_(0.9)Gd_(0.1)O_3[x BST–(1-x)BFGO](x = 0.00, 0.10, 0.20 and 0.25) multiferroic ceramics were prepared by the standard solid-state reaction technique. Structural characterization was performed by X-ray diffraction. All the samples showed rhombohedral distorted perovskite structure. Surface morphology of the ceramics was studied by the field emission scanning electron microscope(FESEM). From the FESEM observation, the grain size was observed to be decreased with increasing BST content. Enhanced magnetic properties were observed in BFGO with the increase in BST content because of large lattice distortion. The complex initial permeability increased with the increasing of BST content. The study of dielectric properties showed that the dielectric constant increased, whereas dielectric loss decreased with increasing of BST content due to the reduction of oxygen vacancies. An analysis of the electric impedance and modulus with frequency was performed at different temperatures. Non-Debye-type relaxation processes occur in the compound which was confirmed from the nature of the Cole–Cole plot. The DC conductivity was found to increase with the rise in temperature which indicates the semiconducting behavior of the compound with characteristics of the negative temperature coefficient of resistance. The activation energy, responsible for the relaxation determined from the modulus spectra(0.246 eV), was found to be almost same as the value obtained from the impedance study(0.240 eV), indicating that charge carriers overcome the same energy barrier during relaxation. The frequency response of imaginary parts of electric impedance and modulus suggested that the relaxation in xB ST–(1-x)BFGO ceramics follows the same mechanism at various temperatures.     

Effect of Heat Treatments on Microstructures and Tensile Properties of Cu–3 wt%Ag–0.5 wt%Zr Alloy

The microstructures and tensile properties of Cu–3 wt%Ag–0.5 wt%Zr alloy sheets under different aging treatments are investigated in this research. As one kind of precipitate, Ag nanoparticles with coherent orientation relationship with matrix precipitate. However, after the peak-age point, most of Ag nanoparticles grow into short rod shape with the interface translating to semi-coherent, which leads to the lower strength of over-aging sample. The yield strength is estimated by considering solid solute, grain boundary and precipitation strengthening mechanisms. The result shows that the Ag precipitates provide the main strengthening role. Then a constitutive equation representing the evolution of dislocation density with plastic strain is built by considering work-hardening behavior coming from shearable and non-shearable precipitates which is mainly the particles containing Zr. The flow stress contributed by shearable particle hardening is higher than that of non-shearable one. Due to the coarsening of grain boundary precipitates and low rate of damage accumulation of these non-shearable particles, the micro-cracks nucleate easily at grain boundary which leads to intergranular fracture.     

Effect of N Doping on Microstructure,Mechanical and Tribological Properties of V-Al-C CoatingsEI北大核心CSCD

The crises of resource shortage have prompted ocean exploitation to spring up all over the world. Some crucial frictional components of marine equipment have to be directly faced with the conjoint action of wear and corrosion. Transition metal nitrides or carbides hard coatings have been widely used to improve tribological performance in various applications. However, the poor toughness, wear and corrosion resistance of coatings cannot meet the harsher marine environment, which needs to obtain multi-functional hard coatings providing complex properties. The nanocomposite structure coatings containing nanocrystalline phase embedded in an amorphous matrix allow tailoring their properties to desired value by designing chemical composition and nanostructure. In this work, V-Al-C and V-Al-C-N coatings were deposited on silicon and high speed steel (HSS) substrates by magnetron sputtering. The crystal microstructure, chemical composition, surface morphology, cross-sectional structure, mechanical property and friction behavior of the coatings under different contact conditions (air, distilled water and artificial seawater) were studied by XRD, XPS, SEM, nano-indentation and ball-on-disc tribometer. The results showed that the V-Al-C coating displayed columnar structure with coarse grain. When the nitrogen was incorporated, the coating structure evolved into nanocomposite structure composed of nanocrystallite and amorphous carbon. The hardness increased from (14 +/- 0.48) GPa to (24.5 +/- 0.8) GPa, and the toughness was significantly improved (H/E>0.1). In air condition, the friction coefficient decreased from 0.70 to 0.42, owing to the synergy interaction between V2O5 and amorphous carbon during sliding. The friction coefficients of the both coatings in distilled water and artificial seawater were lower than those in air owing to the boundary lubrication forming lubricative film by absorbed water. The friction coefficient in seawater was lower than those in distilled water, resulting from the formation of Mg(OH)(2) and CaCO3 during sliding. However, the wear rates of the both coatings in artificial seawater were larger than that in distilled water, which demonstrated a synergism between corrosion and wear in artificial water. The V-Al-C coating was all worn out under different contact conditions owing to severe abrasive wear, while the V-Al-C-N coating showed better wear resistance, with a wear rate of 3.0x10(-16) m(3)/(N center dot m) in air and 1.4x10(-15) m(3)/(N center dot m) in artificial water, respectively.     

Fabrication,Pore Structures and Mechanical Properties of (TiB_2–Al_2O_3)/NiAl Porous Composites

Open-celled porous(Ti B_2–Al_2O_3)/Ni Al composites were successfully fabricated by using spherical carbamide as space holders via self-propagating high-temperature synthesis(SHS).Effects of 10Al–3B_2O_3–3Ti O_2contents(0–20 wt%)on the pore structures and the quasi-static compressive behaviors of the resultant materials were investigated.The porous(Ti B_2–Al_2O_3)/Ni Al composites exhibit composite pore structure consisting of homogeneously distributed and interconnected millimeter pores and micropores.The millimeter pores virtually inherit the shape and size of carbamide particles,while the pore size of micropores increases with increasing the 10Al–3B_2O_3–3Ti O_2content.Depending on the volume fraction of the carbamide,the porosity of the porous materials can be easily controlled in a range of 55%–85%.When the porosity is about 72%,the compressive strengths of porous Ni Al and porous(Ti B_2–Al_2O_3)/Ni Al composite with 15% 10Al–3B_2O_3–3Ti O_2in green compact are 19 and 32 MPa,and the corresponding strains are 2.9%and 5.7%,respectively.Furthermore,the quasi-static compressive behavior of porous(Ti B_2–Al_2O_3)/Ni Al composites can be estimated by Gibson–Ashby model.     

A Study on Effect of Reactive and Rare Earth Element Additions on the Oxidation Behavior of Mo–Si–B System

Mo–9Si–8B–1Ti, Mo–9Si–8B–1.8Ti, Mo–9Si–8B–0.2La and Mo–9Si–8B–0.4La₂O₃ (at.%) alloys were prepared using mechanical alloying followed by hot isostatic pressing and field assisted sintering. XRD, SEM and EBSD analysis confirmed the formation of Mo solid solution, A15 and T2 phases in the alloys. Isothermal oxidation behavior of the specimens was studied in the temperature range from 750 to 1,300 °C for up to 100 h. Both the Ti and La containing alloys showed superior oxidation behavior compared to unalloyed Mo–Si–B at 900 °C at the initial periods of oxidation. Ti-added alloys suffered higher rate of weight loss at higher temperatures (1,000–1,300 °C) due to the formation of non-protective low viscosity SiO₂-TiO₂-B₂O₃ scale. La-alloyed Mo–Si–B showed superior oxidation resistance at intermediate temperatures (900 °C) as well as at higher temperatures. Enrichment of La at the oxide/alloy interface was found to be the reason for improved oxidation behavior of La-alloyed Mo–Si–B. Amongst the four materials studied, the La₂O₃ containing alloy showed the best oxidation resistance at 900 °C.     

Effect of Solution Treatment on Microstructure and Corrosion Properties of Mg–4Gd–1Y–1Zn–0.5Ca–1Zr Alloy

The as-cast multi-element Mg–4Gd–1Y–1Zn–0.5Ca–1Zr alloy with low rare earth additions was prepared, and the solution treatment was applied at different temperatures. The microstructural evolution of the alloy was characterized by optical microscopy and scanning electron microscopy, and corrosion properties of the alloy in 3.5% NaCl solution were evaluated by immersion and electrochemical tests. The results indicate that the as-cast alloy is composed of the a-Mg matrix,lamellar long-period stacking-ordered(LPSO) structure and eutectic phase. The LPSO structure exists with more volume fraction in the alloy solution-treated at 440 °C, but disappears with the increase in the solution temperature. For all the solution-treated alloys, the precipitated phases are detected. The corrosion rates of the alloys decrease first and then increase slightly with the increase in the solution temperature, and the corrosion resistance of the solution-treated alloys is more than four times as good as that of the as-cast alloy. In addition, the alloy solution-treated at 480 °C for 6 h shows the best corrosion property.     

Effect of ball milling and electrolyte on properties of high-voltage LiNi_(0.5)Mn_(1.5)O_4 spinel

1 INTRODUCTIONRecently ,several research groups have repor-ted transition-metal-substituted spinel materials(Li MxMn2 -xO4, M: Cr , Co , Fe , Ni , Cu) withhigh-voltage plateaus above 4 .5 V[1 5]. Amongthese materials ,Li Ni0 .5Mn1 .5O4is the most prom-ising and attractive one because of its good cyclicproperty and relatively high capacity with a plateauat around 4 .7 V[3 ,6].Now, a variety of methods were used forpreparation of Li Ni0 .5Mn1 .5O4,such as solid-statereaction[4 ,7 ,8]…     

Multiferroic Consequence of Porous (BiFeO_3)_x–(BiCrO_3)_(1-x) Composite Thin Films by Novel Sol–Gel Method

In this work, we have presented a spin-coating method to produce thin films started with pure BiCrO_3(BCO) and ended up with BiFeO_3(BFO) by increasing x values in the(BiFeO_3)_x–(BiCrO_3)_(1-x)composites. All the produced thin films have been crystallized at the annealing temperatures of 400 °C for 0.5 h. The XRD and EDAX spectrums give insight that the two crystal phases related to BCO and BFO stayed together within the thin film matrices. SEM analysis showed that the prepared composite had macroporous morphology with interconnected pores and its width(size) decreased with increasing x values. The strong correlations are observed among the microstructure, dielectric, ferroelectric, ferromagnetic properties and Fe concentration. Among all composites, the composition of 0.75 shows an attractive magnetization, polarization, switching and improved dielectric behaviors at room temperature. Significant increase in the multiferroic characteristics of 0.75 composition is due to arise of lower leakage current by causing reduction in oxygen vacancy density, and enhancement of super-exchange magnetic interaction between Fe~(3+) and Cr~(3+) at BFO/BCO interface layers. Our result shows that the thin layer on Pt(111)/Ti/SiO_2/Si substrate possesses simultaneously improved ferroelectric and ferromagnetic properties which make an inaccessible potential application for nonvolatile ferroelectric memories.     

Preparation of Ultrafine Li_(4 x) Al_xSi_(1-x)O_4 by Sol-Gel Method and Its Ionic Conductivity

1 ＩｎｔｒｏｄｕｃｔｉｏｎＬｉｔｈｉｕｍｉｏｎｃｏｎｄｕｃｔｏｒｓａｒｅｐｒｏｍｉｓｉｎｇｍａｔｅｒｉａｌｓｆｏｒｄｅｖｅｌｏｐｉｎｇｈｉｇｈ ｅｎｅｒｇｙｄｅｎｓｉｔｙｂａｔｔｅｒｉｅｓ[1 ].Ｔｈｅｐｒｏｐｅｒｔｉｅｓｏｆｈｉｇｈｉｏｎｉｃｃｏｎｄｕｃｔｉｖｉｔｙ ,ｈｉｇｈｄｅｃｏｍｐｏｓｉｔｉｏｎｐｏｔｅｎｔｉａｌａｎｄｌｅｓｓｒｅａｃｔｉｖｉｔｙｗｉｔｈｗａｔｅｒａｎｄｃａｒｂｏｎｄｉｏｘｉｄｅｗｉｌｌｂｅｒｅｑｕｉｒｅｄｗｈｅｎｔｈｅｙａｒｅａｐ ｐｌｉｅｄｔｏｓｏｌｉｄｅｌｅｃｔｒｏｌｙ…     

锰掺杂对（Na0.5Bi0.5）TiO3-BaTiO3-（K0.5Bi0.5）TiO3陶瓷介电和压电性能的影响

采用传统陶瓷工艺制备了锰掺杂0.8(Na0.5Bi0.5)TiO3-0.1BaTiO3-0.1(K0.5Bi0.5)TiO3(BNT-B-BKT)无铅压电陶瓷材料,研究了材料的介电、压电和铁电性能.发现锰掺杂大幅降低了0.8(Na0.5Bi0.5)TiO3-0.1BaTiO3-0.1(K0.5Bi0.5)TiO3陶瓷的电导率和矫顽场,最佳掺杂量为0.1%(质量分数),该配方的最佳烧结温度为1150℃.这一温度下烧结所得样品在130℃时的电导率仅为1.36×10-1Ω-1cm-1,约为掺杂前的1/40,矫顽场Ec仅为2.78 kV/mm,剩余极化强度Pr为38μC/cm2,压电系数d33达到143 pC/N.     

稀土组成对贮氢合金La0．8（1-x）Ce0．8x（PrNd）0．2B5性能的影响

系统研究了A侧稀土元素中Ce含量对AB5犁贮氢合金La0．8（1-x)Ce0．8x(PrNd)0．2B5的结构、热力学性能、电化学性能和动力学性能的影响。结果表明：Ce含量对合金的结构基本上没有明显的影响，合金的晶胞参数a、c及晶胞体积与Ce的含量的变化呈线性关系；随着Ce含量增加，合金的吸放氢平台压力升高，滞后效应减小，吸氢量减小，合金氢化物的热力学稳定性变差：Ce含量的变化对合金的电化学活化速度影响很小，但Ce含量的增加可以明显提高合金的放电中值电位，改善合金的高倍率、高功率放电性能和动力学性能。     

掺杂稀土元素对Ag(Nb1-xTax)O3介电性能的影响

研究了添加稀土元素Gd2O3,Dy2O3对本系统介电性能的影响规律.实验表明,适量添加稀土元素能有效减少材料内部的缺陷和空位,并抑制B位Nb5 离子的松弛极化,明显改善材料的介电损耗(tgδ<1×10-3).另外Gd3 ,Dy3 取代部分Ag ,减小A位离子的平均半径,导致材料介电常数增大和减小的两种机制同时存在.当添加量适当时可以使材料的介电常数ε达到550以上.     

Fe73.5Cu1Nb3-xTixSi13.5B9 (x=0, 1, 2, 3)合金粉的结构与磁性

将Fe73.5Cu1Nb3-xTixSi13.5B9(x=0,1,2,3)合金快淬带进行高能球磨制成粉末样品,在550℃真空退火1h,研究了磁粉的相结构及磁性。结果表明,随球磨时间延长,不添加Ti的Fe73.5Cu1Nb3Si13.5B9合金中析出晶化相的晶格常数增大。添加Ti的Fe73.5Cu1Nb3-xTixSi13.5B9(x=0,1,2,3)合金在球磨60h后再退火,可以得到单一α-Fe(Si)软磁相,且随Ti含量增大,析出晶化相的晶格常数减小,饱和磁化强度增大、矫顽力降低。     

Effect of addition of Ba(W0.5Cu0.5)O3 in Pb(Mg1/3Nb2/3)O3-Pb(Zn1/3Nb2/3)O3-Pb(Zr0.52Ti0.48)O3 ceramics on the sintering temperature, electrical properties and phase transition

In this work, we report on the Pb(Mg_1/3Nb_2/3)O₃-Pb(Zn_1/3Nb_2/3)O₃-Pb(Zr_0.52Ti_0.48)O₃ (PMN-PZN-PZT) ceramics with Ba(W_0.5Cu_0.5)O₃ as the sintering aid that was manufactured in order to develop the low-temperature sintering materials for piezoelectric device applications. The phase transition, microstructure, dielectric, piezoelectric properties, and the temperature stability of the ceramics were investigated. The results showed that the addition of Ba(W_0.5Cu_0.5)O₃ significantly improved the sintering temperature of PMN-PZN-PZT ceramics and could lower the sintering temperature from 1005 to 920 °C. Besides, the obtained Ba(W_0.5Cu_0.5)O₃-doped ceramics sintered at 920 °C have optimized electrical properties, which are listed as follows: (K_p = 0.63, Q_m = 1415 and d₃₃ = 351 pC/N), and high depolarization temperature above 320 °C. These results indicated that this material was a promising candidate for high-power multilayer piezoelectric device applications.     

稀土掺杂Nd2O3对YSZ/(Ni,Al)复合涂层组织与性能的影响

目的提高YSZ/(Al,Ni)复合涂层与基体的结合强度和抗高温氧化性。方法采用电泳沉积方法在Inconel600高温合金表面沉积YSZ/(Al,Ni)复合涂层和掺杂稀土Nd_2O_3-YSZ/(Al,Ni)(N-YSZ/(Al,Ni))复合涂层,然后进行真空烧结,最后对制备好的热障复合涂层进行划痕实验和等温循环氧化实验。通过对样品进行等温循环氧化实验,获取不同氧化时间段的复合涂层样品,并通过采用SEM和XRD分别对复合涂层形貌和微观结构进行分析。结果在1100℃等温氧化过程中,未掺杂稀土元素复合涂层的氧化增重速率为0.0057 mg/cm~2,而掺杂钕元素的复合涂层的氧化增重速率为0.0046 mg/cm~2,比未掺杂稀土YSZ/(Al,Ni)复合涂层低。N-YSZ/(Al,Ni)热障复合涂层在等温氧化过程中颗粒较小,裂纹少,表面更加致密,并且发生自愈合现象。真空烧结后的YSZ/(Al,Ni)复合涂层和N-YSZ/(Al,Ni)复合涂层与基体的结合强度大约为4.0 N,在经过氧化100 h后,掺杂稀土的N-YSZ/(Al,Ni)复合涂层的结合强度为3.26 N,未掺杂稀土钕元素YSZ/(Al,Ni)复合涂层与基体的结合强度为2.6 N。N-YSZ/(Al,Ni)热障复合涂层中存在Nd_2Zr_2O_7相和稳定的NiAl_2O_4相,Nd_2Zr_2O_7相具有良好的稳定性以及耐高温氧化性。结论掺杂稀土氧化钕N-YSZ/(Al,Ni)复合涂层,在1100℃、空气氛围下等温氧化过程中发生自愈合现象。随着氧化时间的增加,掺杂稀土元素钕的N-YSZ/(Al,Ni)复合涂层表面的颗粒趋于均匀化,裂纹明显变少,使得涂层更加致密和平整。掺杂了稀土钕元素的N-YSZ/(Al,Ni)复合涂层与基体之间具有更高的结合强度。在1100℃、空气氛围下等温氧化100 h时,掺杂了稀土钕元素的N-YSZ/(Al,Ni)复合涂层与基体的结合强度明显大于YSZ/(Al,Ni)复合涂层,提高了N-YSZ/(Al,Ni)复合涂层的抗剥落性和服役寿命。在1100℃、空气氛围下等温氧化过程中,掺杂稀土元素钕的N-YSZ/(Al,Ni)复合涂层的抗高温氧化性能比未掺杂稀土元素的YSZ/(Al,Ni)复合涂层的抗高温氧化性能显著提高。     

Ce/Zr比对PdO/Ce_xZr_(1-x)O_2催化剂三效催化性能的影响

采用溶胶-凝胶法制备一系列CexZr1-xO2(x=0～1)复合氧化物,并以该复合氧化物为载体制备负载贵金属的PdO/CexZr1-xO2(x=0～1)催化剂,选择NO-CO反应和CO以及CH4氧化反应为模型反应对催化剂的三效催化性能进行评价,并通过XRD、H2-TPR等手段对载体和催化剂进行初步表征。结果表明:Ce/Zr比对CexZr1-xO2载体及负载PdO催化剂三效催化性能均存在重要影响,不同Ce/Zr比的CexZr1-xO2复合氧化物载体具有不同的晶相结构及还原性能,由其负载的PdO催化剂的三效催化性能也各不相同。同时,催化剂的NO还原活性与CO氧化活性与α还原峰存在一定的对应关系。     

C含量对电弧离子镀TiAlC_xN_(1-x)(x=0,0.18,0.41,0.49,0.69)薄膜性能的影响

在GCr15轴承钢基体上,利用多弧离子镀技术低温(175℃)沉积TiAl CN涂层。利用SEM、EPMA、XRD、附着力测试仪、纳米压痕仪和UMT-2高温摩擦磨损测试仪研究薄膜性质。结果表明,涂层表面光滑平整、均匀致密且无明显孔洞。涂层表面存在一定数量的液滴颗粒,薄膜厚度约为2μm。在涂层中,发现了晶体结构为fcc-Ti N结构,薄膜的晶粒大小为10~30 nm;随着薄膜中C元素的加入,XRD谱中(Ti0.5,Al0.5)N峰出现了宽化;在Ti Al N中引入C,附着力下降,随着涂层中C含量的增加,薄膜中的Al和Ti比例未发生明显变化,附着力略微增加,但硬度和弹性模量先增加后减小,摩擦系数一直减小。     

Effects of lanthanum doping on the preferred orientation, phase structure and electrical properties of sol-gel derived Pb1-3x/2Lax (Zr0.6Ti0.4)O3 thin films

Pb_1-3x/2La_x (Zr_0.6Ti_0.4)O₃ thin films (0 ≤ x ≤ 0.08) were prepared on the Pt (1 1 1)/Ti/SiO₂/Si (1 0 0) substrates by a sol-gel method. The morphology, preferred orientation, phase structure, dielectric and ferroelectric properties of the films have been investigated. Our results show that lanthanum doping is favorable to enhance crystalline and obtain (1 0 0)-preferred orientation of the films. Meanwhile, it is suggested that the films undergo a structure change from “rhombohedral” phase to monoclinic phase as the lanthanum-doped content is increased to x ≈ 0.05. Results of dielectric properties and ferroelectric properties indicate that lanthanum doping contributes to improve film dielectric constant and dielectric loss while it brings about a striking decrease in remnant polarization value. Possible explanations for the variations of electrical properties have been discussed in terms of preferred orientation, phase structure and large lattice distortion.