On possibility of BaCeO3 production when depositing YBa2Cu3O7-χ films on a cerium oxide surface

International Nuclear Information System (INIS)

Mashtakov, A.D.; Kotelyanskij, I.M.; Luzanov, V.A.; Mozhaev, P.B.; Ovsyannikov, G.A.; Bdikin, I.D.

1997-01-01

Consideration is given to experimental results of investigation into crystallographic parameters of hetero-structural (1102)Al 2 O 3 /(001)CeO 2 (001)YBa 2 Cu 3 O 7-χ films, prepared by the method of cathode sputtering at substrate temperature, equal to 600-800 deg C. It is shown that main limitation for precipitation temperature of YBa 2 Cu 3 O 7-χ film on CeO 2 surface is caused by chemical interaction of YBa 2 Cu 3 O 7-χ with CeO 2 with formation of polycrystalline BaCeO 3 layer

Effects of Ce and Zr addition on microstructure and hardness of Al-Si-Cu-Mg alloy

International Nuclear Information System (INIS)

Bevilaqua, William Lemos; Reguly, Afonso; Froehlich, Andre Ronaldo; Stadtlander, Antonio Ricardo

2016-01-01

The effects of cerium and zirconium contents (0.3%-0.16%Zr; 0.3%-0.27%Zr e 0.3%-0.36%Zr) to aluminum alloy 354.0 was investigated by microstructural analysis and hardness measurements in as-cast and heat-treated conditions. The macrostructure show an excellent grain refinement for all Ce and Zr contents used. Additionally, the Cu-Ce reaction during solidification changes significantly the age hardening process of modified alloys. (author)

Cooperative effects in CeCu2Si2

International Nuclear Information System (INIS)

Lang, M.; Modler, R.; Ahlheim, U.; Helfrich, R.; Reinders, P.H.P.; Steglich, F.; Assmus, W.; Sun, W.; Bruls, G.; Weber, D.; Luethi, B.

1991-01-01

Heavy-fermion superconductivity and other cooperative effects have been explored by thermal expansion, specific heat and ultrasound measurements on CeCu 2 Si 2 single crystals. Crystals annealed under Cu atmosphere show sharp superconducting transitions at Tc max =0.63 K. At the same temperature the ''as grown'', i.e., non-bulk-superconducting, crystals reveal a pronounced phase-transition anomaly, presumably of structural origin. This new transition is associated with an expansion of the volume upon cooling and gives rise to magnetic correlations. Our results indicate a complex interplay between lattice instability, magnetic phenomena and superconductivity in CeCu 2 Si 2 . (orig.)

Glass forming ability of the Al-Ce-Ni system; Avaliacao da capacidade de formacao vitrea do sistema Al-Ce-Ni

Energy Technology Data Exchange (ETDEWEB)

Triveno Rios, C. [Engenharia Mecanica, Universidade Federal de Mato Grosso, Rondonopolis, MT (Brazil)], e-mail: triveno@ufmt.br; Surinach, S.; Baro, M.D. [Departamento de Engenharia de Materiais - Universidade Federal de Sao Carlos, SP (Brazil); Bolfarini, C.; Botta, W.J.; Kiminami, C.S. [Departamento de Fisica da Universidade Autonoma de Barcelona, Bellaterra (Spain)

2010-07-01

In the present work, the glass forming ability (GFA) and its compositional dependence on Al-Ni-Ce system alloys were investigated in function of several thermal parameters. Rapidly quenched Al{sub 85}Ni{sub 15}-{sub X}Ce{sub X} (X=4,5,6,7,10), Al{sub 90}Ni{sub 5}Ce{sub 5}, Al{sub 89}Ni{sub 2}.{sub 4}Ce{sub 8}.{sub 6}, Al{sub 80}Ni{sub 15.6}Ce{sub 4}.{sub 4} and Al{sub 78}Ni{sub 18.5}Ce{sub 3.5} amorphous ribbons were produced by melt-spinning and the structural transformation during heating was studied using a combination of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results showed that the GFA and the thermal stability in the Al-rich corner of Al- Ni-Ce system alloys were enhanced by increasing the solute content and specifically the Ce content (author)

Coupled growth of Al-Al2Cu eutectics in Al-Cu-Ag alloys

International Nuclear Information System (INIS)

Hecht, U; Witusiewicz, V; Drevermann, A

2012-01-01

Coupled eutectic growth of Al and Al 2 Cu was investigated in univariant Al-Cu-Ag alloys during solidification with planar and cellular morphology. Experiments reveal the dynamic selection of small spacings, below the minimum undercooling spacing and show that distinct morphological features pertain to nearly isotropic or anisotropic Al-Al 2 Cu interfaces.

Constitutive Model for Hot Deformation of the Cu-Zr-Ce Alloy

Science.gov (United States)

Zhang, Yi; Sun, Huili; Volinsky, Alex A.; Wang, Bingjie; Tian, Baohong; Liu, Yong; Song, Kexing

2018-02-01

Hot compressive deformation behavior of the Cu-Zr-Ce alloy has been investigated according to the hot deformation tests in the 550-900 °C temperature range and 0.001-10 s-1 strain rate range. Based on the true stress-true strain curves, the flow stress behavior of the Cu-Zr-Ce alloy was investigated. Microstructure evolution was observed by optical microscopy. Based on the experimental results, a constitutive equation, which reflects the relationships between the stress, strain, strain rate and temperature, has been established. Material constants n, α, Q and ln A were calculated as functions of strain. The equation predicting the flow stress combined with these materials constants has been proposed. The predicted stress is consistent with experimental stress, indicating that developed constitutive equation can adequately predict the flow stress of the Cu-Zr-Ce alloy. Dynamic recrystallization critical strain was determined using the work hardening rate method. According to the dynamic material model, the processing maps for the Cu-Zr and Cu-Zr-Ce alloy were obtained at 0.4 and 0.5 strain. Based on the processing maps and microstructure observations, the optimal processing parameters for the two alloys were determined, and it was found that the addition of Ce can promote the hot workability of the Cu-Zr alloy.

Synthesis of Mixed Cu/Ce Oxide Nanoparticles by the Oil-in-Water Microemulsion Reaction Method

Science.gov (United States)

Pemartin-Biernath, Kelly; Vela-González, Andrea V.; Moreno-Trejo, Maira B.; Leyva-Porras, César; Castañeda-Reyna, Iván E.; Juárez-Ramírez, Isaías; Solans, Conxita; Sánchez-Domínguez, Margarita

2016-01-01

Cerium oxide and mixed Cu/Ce oxide nanoparticles were prepared by the oil-in-water (O/W) microemulsion reaction method in mild conditions. The Cu/Ce molar ratio was varied between 0/100 and 50/50. According to X-ray diffraction (XRD), below 30/70 Cu/Ce molar ratio, the materials presented a single phase consistent with cubic fluorite CeO2. However, above Cu/Ce molar ratio 30/70, an excess monoclinic CuO phase in coexistence with the predominant Cu/Ce mixed oxide was detected by XRD and High-Resolution Transmission Electron Microscopy (HRTEM). Raman spectroscopy showed that oxygen vacancies increased significantly as the Cu content was increased. Band gap (Eg) was investigated as a function of the Cu/Ce molar ratio, resulting in values from 2.91 eV for CeO2 to 2.32 eV for the mixed oxide with 30/70 Cu/Ce molar ratio. These results indicate that below 30/70 Cu/Ce molar ratio, Cu2+ is at least partially incorporated into the ceria lattice and very well dispersed in general. In addition, the photodegradation of Indigo Carmine dye under visible light irradiation was explored for selected samples; it was shown that these materials can remove such contaminants, either by adsorption and/or photodegradation. The results obtained will encourage investigation into the optical and photocatalytic properties of these mixed oxides, for widening their potential applications. PMID:28773602

Synthesis of Mixed Cu/Ce Oxide Nanoparticles by the Oil-in-Water Microemulsion Reaction Method

Directory of Open Access Journals (Sweden)

Kelly Pemartin-Biernath

2016-06-01

Full Text Available Cerium oxide and mixed Cu/Ce oxide nanoparticles were prepared by the oil-in-water (O/W microemulsion reaction method in mild conditions. The Cu/Ce molar ratio was varied between 0/100 and 50/50. According to X-ray diffraction (XRD, below 30/70 Cu/Ce molar ratio, the materials presented a single phase consistent with cubic fluorite CeO2. However, above Cu/Ce molar ratio 30/70, an excess monoclinic CuO phase in coexistence with the predominant Cu/Ce mixed oxide was detected by XRD and High-Resolution Transmission Electron Microscopy (HRTEM. Raman spectroscopy showed that oxygen vacancies increased significantly as the Cu content was increased. Band gap (Eg was investigated as a function of the Cu/Ce molar ratio, resulting in values from 2.91 eV for CeO2 to 2.32 eV for the mixed oxide with 30/70 Cu/Ce molar ratio. These results indicate that below 30/70 Cu/Ce molar ratio, Cu2+ is at least partially incorporated into the ceria lattice and very well dispersed in general. In addition, the photodegradation of Indigo Carmine dye under visible light irradiation was explored for selected samples; it was shown that these materials can remove such contaminants, either by adsorption and/or photodegradation. The results obtained will encourage investigation into the optical and photocatalytic properties of these mixed oxides, for widening their potential applications.

Calculation of Gibbs energy of Zr-Al-Ni, Zr-Al-Cu, Al-Ni-Cu and Zr-Al-Ni-Cu liquid alloys based on quasiregular solution model

International Nuclear Information System (INIS)

Li, H.Q.; Yang, Y.S.; Tong, W.H.; Wang, Z.Y.

2007-01-01

With the effects of electronic structure and atomic size being introduced, the mixing enthalpy as well as the Gibbs energy of the ternary Zr-Al-Cu, Ni-Al-Cu, Zr-Ni-Al and quaternary Zr-Al-Ni-Cu systems are calculated based on quasiregular solution model. The computed results agree well with the experimental data. The sequence of Gibbs energies of different systems is: G Zr-Al-Ni-Cu Zr-Al-Ni Zr-Al-Cu Cu-Al-Ni . To Zr-Al-Cu, Ni-Al-Cu and Zr-Ni-Al, the lowest Gibbs energy locates in the composition range of X Zr 0.39-0.61, X Al = 0.38-0.61; X Ni = 0.39-0.61, X Al = 0.38-0.60 and X Zr = 0.32-0.67, X Al = 0.32-0.66, respectively. And to the Zr-Ni-Al-Cu system with 66.67% Zr, the lowest Gibbs energy is obtained in the region of X Al = 0.63-0.80, X Ni = 0.14-0.24

Superconductivity in CeCu/sub 2/Si/sub 2/: dependence of Tsub(c) on alloying and stoichiometry

Energy Technology Data Exchange (ETDEWEB)

Spille, H; Rauchschwalbe, U; Steglich, F [Technische Hochschule Darmstadt (Germany, F.R.). Inst. fuer Festkoerperphysik

1938-01-01

The authors have determined the transition temperatures of the alloy systems (Ce,M)Cu/sub 2/Si/sub 2/ with M = La, Y, Sc, Ce(Cu,T)/sub 2/Si/sub 2/ with T = Ag, Au, Mn, Ru, Rh, Pd and CeCu/sub 2/(Si,Ge)/sub 2/ as well as of CeCu/sub 2/Si/sub 2/ samples with varying stoichiometry. In each case, alloying is found to depress Tsub(c), the critical concentrations necessary to destroy superconductivity ranging between < 1 at.% and 10 at.%. Off-stoichiometry samples with a Cu- or Ce-deficiency of a few at.% are not superconducting, while samples prepared with a comparable excess of Cu or Ce show sharp transitions at Tsub(c) >approx. 600 mK. It is inferred that stoichiometric CeCu/sub 2/Si/sub 2/ contains substantial concentrations of Cu- and Ce-vacancies, which hinder superconductivity. First results on CeCu/sub 2/Si/sub 2/ single crystals, which exhibit bulk superconductivity, are also reported.

/Cu-Al System

Science.gov (United States)

Kish, Orel; Froumin, Natalya; Aizenshtein, Michael; Frage, Nachum

2014-05-01

Wettability and interfacial interaction of the Ta2O5/Cu-Al system were studied. Pure Cu does not wet the Ta2O5 substrate, and improved spreading is achieved when relatively a high fraction of the active element (~40 at.% Al) was added. The Al2O3 and AlTaO4 phases were observed at the Ta2O5/Cu-Al interface. A thermodynamic evaluation allowed us to suggest that the lack of wetting bellow 40 at.% Al is due to the presence of a native oxide, which covers the drop. The conditions of the native oxide decomposition and the formation of the volatile Al2O suboxide strongly depend on the vacuum level during sessile drop experiments and the composition of the Cu-Al alloy. In our case, Al contents greater than 40% provides thermodynamic conditions for the formation of Al2O (as a result of Al reaction with Al2O3) and the drop spreading. It was suggested that the final contact angle in the Ta2O5/Cu-Al system (50°) is determined by Ta adsorption on the newly formed alumina interlayer.

Solution growth of the Gd-Cu-Al systems in the low-gadolinium concentration range

International Nuclear Information System (INIS)

Uhlirova, Klara; Sechovsky, Vladimir

2009-01-01

Solution growth of Gd-Cu-Al resulted in the formation of single crystals of GdCu 4 Al 8 with tetragonal ThMn 12 -type structure (a = 8.751 Aa, c = 5.148 Aa), Gd 2 Cu 9.4-6.7 Al 7.6-10.3 with hexagonal Th 2 Zn 17 -type structure (a = 8.83 Aa c = 1.28 Aa), and Gd(Cu, Al) 4 with orthorhombic CeNi 2+x Sb 2-x -type structure. An antiferromagnetic ordering of GdCu 4 Al 8 was found below 35 K, which is in agreement with the previously reported T N = 35 K and T N = 32 K measured on polycrystalline samples. In the temperature range 50-320 K the magnetic susceptibility χ follows the Curie-Weiss law with μ eff = 7.8 μ B /f.u. and θ p = -17 K for B parallel c, μ eff = 7.9 μ B /f.u. and θ p = - 18 K for B perpendicular to c. The a-axis is the easy magnetization direction. The Gd(Cu, Al) 4 and Gd(Cu, Al) 4 compounds order antiferromagnetically below T N = 35 K and T N = 31 K, respectively. (orig.)

Relationship between Microstructure and Properties of Cu-Cr-Ag-(Ce) Alloy Using Microscopic Investigation.

Science.gov (United States)

Chen, Huiming; Yuan, Dawei; Wu, Shanjiang; Wang, Hang; Xie, Weibin; Yang, Bin

2017-01-01

Microstructure, precipitation hardening response, and mechanical and physical properties of Cu-Cr-Ag alloy and Cu-Cr-Ag-Ce alloy have been investigated using transmission electron microscopy, scanning electron microscope, optical microscope, electrical conductivity analysis, and tensile test. The influence of element Ce on the matrix refinement, impurity removal, and precipitation in the Cu-Cr-Ag alloys has been analyzed. The experimental results show that the strength and electrical conductivity of Ce containing alloys are greater than those of Ce-free alloys after each processing step. Improvement of strength and electrical conductivity of the Cu-Cr-Ag alloy by adding Ce element is attributed to removing oxygen and sulfur from as-cast alloy.

Nanoporous Al sandwich foils using size effect of Al layer thickness during Cu/Al/Cu laminate rolling

Science.gov (United States)

Yu, Hailiang; Lu, Cheng; Tieu, A. Kiet; Li, Huijun; Godbole, Ajit; Kong, Charlie

2018-06-01

The roll bonding technique is one of the most widely used methods to produce metal laminate sheets. Such sheets offer interesting research opportunities for both scientists and engineers. In this paper, we report on an experimental investigation of the 'thickness effect' during laminate rolling for the first time. Using a four-high multifunction rolling mill, Cu/Al/Cu laminate sheets were fabricated with a range of thicknesses (16, 40, 70 and 130 μm) of the Al layer. The thickness of the Cu sheets was a constant 300 μm. After rolling, TEM images show good bonding quality between the Cu and Al layers. However, there are many nanoscale pores in the Al layer. The fraction of nanoscale pores in the Al layer increases with a reduction in the Al layer thickness. The finite element method was used to simulate the Cu/Al/Cu rolling process. The simulation results reveal the effect of the Al layer thickness on the deformation characteristics of the Cu/Al/Cu laminate. Finally, we propose that the size effect of the Al layer thickness during Cu/Al/Cu laminate rolling may offer a method to fabricate 'nanoporous' Al sandwich laminate foils. Such foils can be used in electromagnetic shielding of electrical devices and noisy shielding of building.

Study of the magnetic properties of CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2} by means of neutron scattering; Untersuchung der magnetischen Eigenschaften von CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2} mittels Neutronenstreuung

Energy Technology Data Exchange (ETDEWEB)

Faulhaber, Enrico

2008-07-01

In 1979 the first heavy-fermion superconductor CeCu{sub 2}Si{sub 2} was discovered by Steglich et al. The system is near a quantum critical point (QCP), where the magnetic order is just suppressed. The distance to the QCP can be varied with hydrostatic pressure as well as by germanium substitution on the silicon site. Next to the superconductivity in CeCu{sub 2}Si{sub 2} one finds distinct magnetic phases while increasing the germanium content. CeCu{sub 2}Si{sub 2} shows a magnetic order of a spin-density-type below T{sub N}-0.8 K, whereas the heavy fermion system CeCu{sub 2}Ge{sub 2} orders below T{sub N}=4.1 K as an antiferromagnet. The focus of this thesis is on neutron-diffraction in the system CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2}. Starting with a sample with a high germanium content of x=0.45, the magnetic structures are investigated in detail. Following a step-by-step approach, samples with reduced x are investigated subsequently to figure out the properties of pure CeCu{sub 2}Si{sub 2}, which were not accessible before. Furthermore, the complex interaction between magnetism and superconductivity is investigated in detail. Using a specially designed setup, the ac-susceptibility could be recorded simultaneously during the neutron diffraction experiments. Due to the direct correlation between antiferromagnetic signals and diamagnetic features, the microscopic coexistence of superconductivity and magnetic order can be ruled out. Instead, a phase separation on the microscopic scale is found. (orig.)

Synthesis of Cu and Ce co-doped ZnO nanoparticles: crystallographic, optical, molecular, morphological and magnetic studies

Directory of Open Access Journals (Sweden)

Rawat Mohit

2017-07-01

Full Text Available In the present research work, crystallographic, optical, molecular, morphological and magnetic properties of Zn1-xCuxO (ZnCu and Zn1-x-yCeyCuxO (ZnCeCu nanoparticles have been investigated. Polyvinyl alcohol (PVA coated ZnCu and ZnCeCu nanoparticles have been synthesized by chemical sol-gel method and thoroughly studied using various characterization techniques. X-ray diffraction pattern indicates the wurtzite structure of the synthesized ZnCu and ZnCeCu particles. Transmission electron microscopy analysis shows that the synthesized ZnCu and ZnCeCu particles are of spherical shape, having average sizes of 27 nm and 23 nm, respectively. The incorporation of Cu and Ce in the ZnO lattice has been confirmed through Fourier transform infrared spectroscopy. Room temperature photoluminescence spectra of the ZnO doped with Cu and co-doped Ce display two emission bands, predominant ultra-violet near-band edge emission at 409.9 nm (3 eV and a weak green-yellow emission at 432.65 nm (2.27 eV. Room temperature magnetic study confirms the diamagnetic behavior of ZnCu and ferromagnetic behavior of ZnCeCu.

Morphology-Dependent Properties of Cu/CeO2 Catalysts for the Water-Gas Shift Reaction

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Zhibo Ren

2017-02-01

Full Text Available CeO2 nanooctahedrons, nanorods, and nanocubes were prepared by the hydrothermal method and were then used as supports of Cu-based catalysts for the water-gas shift (WGS reaction. The chemical and physical properties of these catalysts were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, N2 adsorption/desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS, hydrogen temperature-programmed reduction (H2-TPR and in situ diffuse reflectance infra-red fourier transform spectroscopy (DRIFTS techniques. Characterization results indicate that the morphology of the CeO2 supports, originating from the selective exposure of different crystal planes, has a distinct impact on the dispersion of Cu and the catalytic properties. The nanooctahedron CeO2 catalyst (Cu-CeO2-O showed the best dispersion of Cu, the largest amount of moderate copper oxide, and the strongest Cu-support interaction. Consequently, the Cu-CeO2-O catalyst exhibited the highest CO conversion at the temperature range of 150–250 °C when compared with the nanocube and nanorod Cu-CeO2 catalysts. The optimized Cu content of the Cu-CeO2-O catalysts is 10 wt % and the CO conversion reaches 91.3% at 300 °C. A distinctive profile assigned to the evolution of different types of carbonate species was observed in the 1000–1800 cm−1 region of the in situ DRIFTS spectra and a particular type of carbonate species was identified as a potential key reaction intermediate at low temperature.

Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression

OpenAIRE

Qian, Suxin; Geng, Yunlong; Wang, Yi; Pillsbury, Thomas E.; Hada, Yoshiharu; Yamaguchi, Yuki; Fujimoto, Kenjiro; Hwang, Yunho; Radermacher, Reinhard; Cui, Jun; Yuki, Yoji; Toyotake, Koutaro; Takeuchi, Ichiro

2016-01-01

This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu68Al16Zn16 (CuAlZn) and Cu73Al15Mn12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s−1 (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔTad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hystere...

CuAlO2 and CuAl2O4 thin films obtained by stacking Cu and Al films using physical vapor deposition

Science.gov (United States)

Castillo-Hernández, G.; Mayén-Hernández, S.; Castaño-Tostado, E.; DeMoure-Flores, F.; Campos-González, E.; Martínez-Alonso, C.; Santos-Cruz, J.

2018-06-01

CuAlO2 and CuAl2O4 thin films were synthesized by the deposition of the precursor metals using the physical vapor deposition technique and subsequent annealing. Annealing was carried out for 4-6 h in open and nitrogen atmospheres respectively at temperatures of 900-1000 °C with control of heating and cooling ramps. The band gap measurements ranged from 3.3 to 4.5 eV. Electrical properties were measured using the van der Pauw technique. The preferred orientations of CuAlO2 and CuAl2O4 were found to be along the (1 1 2) and (3 1 1) planes, respectively. The phase percentages were quantified using a Rietveld refinement simulation and the energy dispersive X-ray spectroscopy indicated that the composition is very close to the stoichiometry of CuAlO2 samples and with excess of aluminum and deficiency of copper for CuAl2O4 respectively. High resolution transmission electron microscopy identified the principal planes in CuAlO2 and in CuAl2O4. Higher purities were achieved in nitrogen atmosphere with the control of the cooling ramps.

Effect of Preparation Methods on Al2O3 Supported CuO-CeO2-ZrO2 Catalysts for CO Oxidation

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Gaurav Rattan

2012-12-01

Full Text Available To examine the effect of preparation methods, four catalyst samples having same composition (CuCe5.17Zr3.83Ox/g-Al2O3 (15wt% were prepared by four different methods for CO oxidation. The catalysts were prepared by co-impregnation, citric acid sol-gel, urea nitrate combustion and urea gelation co-precipitation methods, and characterized by BET, XRD, TGA/DSC and SEM. The The air oxidation of CO was carried out in a tubular fixed bed reactor under the following operating conditions: catalyst weight - 100 mg, temperature - ambient to 250 oC, pressure - atmospheric, 2.5% CO in air, total feed rate - 60 ml/min.  It was observed that the catalytic activity greatly influenced by the preparation methods. The highest activity of the catalyst prepared by the sol gel method appeared to be associated with its largest BET surface area. All the four catalysts were active for CO oxidation and did not show deactivation of catalytic activity for 50 hours of continuous runs. The ranking order of the preparation methods of the catalyst is as follows: sol-gel > co-impregnation > urea gelation > urea nitrate combustion. Copyright © 2012 by BCREC UNDIP. All rights reservedReceived: 14th June 2012, Revised: 8th September 2012, Accepted: 19th September 2012[How to Cite: G. Rattan, R. Prasad, R.C.Katyal. (2012. Effect of Preparation Methods on Al2O3 Supported CuO-CeO2-ZrO2 Catalysts for CO Oxidation. Bulletin of Chemical Reaction Engineering & Catalysis, 7(2: 112-123. doi:10.9767/bcrec.7.2.3646.112-123] [How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.2.3646.112-123 ] | View in 

Kinetics of carbon monoxide oxidation over modified supported CuO catalysts

Energy Technology Data Exchange (ETDEWEB)

Loc, Luu Cam; Tri, Nguyen; Cuong, Hoang Tien; Thoang, Ho Si [Vietnam Academy of Science and Technology (VAST), Ho Chi Minh City (Viet Nam). Inst. of Chemical Technology; Agafonov, Yu.A.; Gaidai, N.A.; Lapidus, A.L. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Institute of Organic Chemistry

2013-11-01

The following supported on {gamma}-Al{sub 2}O{sub 3} catalysts: 10(wt.)%CuO (CuAl), 10%CuO+10%Cr{sub 2}O{sub 3} (CuCrAl) and 10%CuO+20%CeO{sub 2} (CuCeAl) were under the investigation. Physico-chemical characteristics of the catalysts were determined by the methods of BET, X-ray Diffraction (XRD), and Temperature-Programmed Reduction (TPR). A strong interaction of copper with support in CuAl resulted in the formation of low active copper aluminates. The bi-oxide CuCrAl was more active than CuAl owing to the formation of high catalytically active spinel CuCr{sub 2}O{sub 4}. The fact of very high activity of the sample CuCeAl can be explained by the presence of the catalytically active form of CuO-CeO{sub 2}-Al{sub 2}O{sub 3}. The kinetics of CO total oxidation was studied in a gradientless flow-circulating system at the temperature range between 200 C and 270 C. The values of initial partial pressures of carbon monoxide (P{sup o}{sub CO}), oxygen (P{sup o}{sub O2}), and specially added carbon dioxide (P{sup o}{sub CO{sub 2}}) were varied in ranges (hPa): 10 / 45; 33 / 100, and 0 / 30, respectively. (orig.)

Compréhension de la stabilité thermique des alliages d'aluminium Al-Cu-Mg Understanding of the thermal stability of Al-Cu-Mg aluminum alloys

Directory of Open Access Journals (Sweden)

Pouget Gaëlle

2013-11-01

Full Text Available Les alliages d'aluminium 2xxx (Al-Cu-Mg sont connus pour être performants à chaud et sont par exemple utilisés pour certaines pièces de structure des avions. L'effet de la composition en Cu et Mg sur leur stabilité thermique, ainsi que celui de la précipitation durcissante associée ont été étudiés. Des comportements différents sont observés et trois zones de composition (en poids % identifiées: 3,1–3,7Cu et 1,6–2,0Mg : durcissement par la phase S' (Al2CuMg, limite d'élasticité ∼ 465 MPa à l'état T8 et bonne stabilité thermique jusqu'à 200 ∘C. 4,8–5,4Cu et 0–0,4Mg : durcissement par la phase θ' (Al2Cu, limite d'élasticité ∼ 380 MPa à l'état T8 et bonne stabilité thermique jusqu'à 300 ∘C. 3,7–4,3Cu et 0,9–1,3Mg : durcissement par S'+ θ', limite d'élasticité ∼ 470 MPa à l'état T8 mais stabilité thermique insuffisante à 150 ∘C et au delà; ce vieillissement important est associé à une concentration en Cu en solution solide élevée, ce qui accélère la cinétique de coalescence des précipités. La première zone de composition est donc recommandée pour des applications à température intermédiaire, typiquement 150 ∘C, et la seconde pour des applications à plus haute température, entre 250 et 300 ∘C. La troisième zone est à éviter pour des applications à 150 ∘C et au-delà. 2xxx aluminum alloys (Al-Cu-Mg have a good behaviour at elevated temperature and are used for some aircraft's structural parts. In this study, the effect of Cu and Mg content on the thermal stability and strengthening precipitation has been investigated. Three different behaviours are observed depending on the alloy composition: 3.1–3.7Cu, 1.6–2.0Mg: strengthening by S' (Al2CuMg, yield strength ∼ 465 MPa in T8 temper and good thermal stability up to 200 ∘C. 4.8–5.4Cu, 0–0.4Mg: strengthening by θ' (Al2Cu, yield strength ∼ 380 MPa in T8 and good thermal stability up to

Steam reforming and oxidative steam reforming of methanol over CuO-CeO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Udani, P.P.C.; Gunawardana, P.V.D.S.; Lee, Hyun Chan; Kim, Dong Hyun [Department of Chemical Engineering, Kyungpook National University, Daegu 702-701 (Korea)

2009-09-15

Steam reforming (SRM) and oxidative steam reforming of methanol (OSRM) were carried out over a series of coprecipitated CuO-CeO{sub 2} catalysts with varying copper content in the range of 30-80 at.% Cu (= 100 x Cu/(Cu + Ce)). The effects of copper content, reaction temperature and O{sub 2} concentration on catalytic activity were investigated. The activity of CuO-CeO{sub 2} catalysts for SRM and OSRM increased with the copper content and 70 at.% CuO-CeO{sub 2} catalyst showed the highest activity in the temperature range of 160-300 C for both SRM and OSRM. After SRM or OSRM, the copper species in the catalysts observed by XRD were mainly metallic copper with small amount of CuO and Cu{sub 2}O, an indication that metallic copper is an active species in the catalysis of both SRM and OSRM. It was observed that the methanol conversion increased considerably with the addition of O{sub 2} into the feed stream, indicating that the partial oxidation of methanol (POM) is much faster than SRM. The optimum 70 at.% CuO-CeO{sub 2} catalyst showed stable activities for both SRM and OSRM reactions at 300 C. (author)

Nucleation and Growth of Cu-Al Intermetallics in Al-Modified Sn-Cu and Sn-Ag-Cu Lead-Free Solder Alloys

Science.gov (United States)

Reeve, Kathlene N.; Anderson, Iver E.; Handwerker, Carol A.

2015-03-01

Lead-free solder alloys Sn-Cu (SC) and Sn-Ag-Cu (SAC) are widely used by the microelectronics industry, but enhanced control of the microstructure is needed to improve solder performance. For such control, nucleation and stability of Cu-Al intermetallic compound (IMC) solidification catalysts were investigated by variation of the Cu (0.7-3.0 wt.%) and Al (0.0-0.4 wt.%) content of SC + Al and SAC + Al alloys, and of SAC + Al ball-grid array (BGA) solder joints. All of the Al-modified alloys produced Cu-Al IMC particles with different morphologies and phases (occasionally non-equilibrium phases). A trend of increasing Cu-Al IMC volume fraction with increasing Al content was established. Because of solidification of non-equilibrium phases in wire alloy structures, differential scanning calorimetry (DSC) experiments revealed delayed, non-equilibrium melting at high temperatures related to quenched-in Cu-Al phases; a final liquidus of 960-1200°C was recorded. During cooling from 1200°C, the DSC samples had the solidification behavior expected from thermodynamic equilibrium calculations. Solidification of the ternary alloys commenced with formation of ternary β and Cu-Al δ phases at 450-550°C; this was followed by β-Sn, and, finally, Cu6Sn5 and Cu-Al γ1. Because of the presence of the retained, high-temperature phases in the alloys, particle size and volume fraction of the room temperature Cu-Al IMC phases were observed to increase when the alloy casting temperature was reduced from 1200°C to 800°C, even though both temperatures are above the calculated liquidus temperature of the alloys. Preliminary electron backscatter diffraction results seemed to show Sn grain refinement in the SAC + Al BGA alloy.

Cu-segregation at the Q'/α-Al interface in Al-Mg-Si-Cu alloy

International Nuclear Information System (INIS)

Matsuda, Kenji; Teguri, Daisuke; Uetani, Yasuhiro; Sato, Tatsuo; Ikeno, Susumu

2002-01-01

Cu segregation was detected at the Q ' /α-Al interface in an Al-Mg-Si-Cu alloy by energy-filtered transmission electron microscopy. By contrast, in a Cu-free Al-Mg-Si alloy no segregation was observed at the interface between the matrix and Type-C precipitate

The formation of intermetallic compounds during interdiffusion of Mg–Al/Mg–Ce diffusion couples

International Nuclear Information System (INIS)

Dai, Jiahong; Jiang, Bin; Li, Xin; Yang, Qingshan; Dong, Hanwu; Xia, Xiangsheng; Pan, Fusheng

2015-01-01

Graphical abstract: Al–Ce intermetallic compounds (IMCs) formed in Mg–Al/Mg–Ce diffusion couples. During the whole diffusion process, Al was the dominant diffusing species, and it substituted for Mg atoms of the Mg–Ce substrate. Five Al–Ce IMCs of Al 4 Ce, Al 11 Ce 3 , Al 3 Ce, Al 2 Ce, and AlCe were formed via the reaction of Al and Ce. - Highlights: • Al–Ce IMCs formation in the Mg–Al/Mg–Ce diffusion couples was studied. • Formation of Al 4 Ce as the first phase was rationalized using the Gibbs free energy. • The activation energy for the growth of the diffusion reaction zones was 36.6 kJ/mol. - Abstract: The formation of Al–Ce intermetallic compounds (IMCs) during interdiffusion of Mg–Al/Mg–Ce diffusion couples prepared by solid–liquid contact method was investigated at 623 K, 648 K and 673 K for 24 h, 48 h and 72 h, respectively. During the whole diffusion process, Al was the dominant diffusing species, and it substituted for Mg of the Mg–Ce substrate. Five Al–Ce IMCs of Al 4 Ce, Al 11 Ce 3 , Al 3 Ce, Al 2 Ce and AlCe were formed via the reaction of Al and Ce. The formation of Al 4 Ce as the first kind of IMC was rationalized on the basis of an effective Gibbs free energy model. The activation energy for the growth of the total diffusion reaction layer was 36.6 kJ/mol

Mechanochemical synthesis of Cu-Al and methyl orange intercalated Cu-Al layered double hydroxides

International Nuclear Information System (INIS)

Qu, Jun; He, Xiaoman; Chen, Min; Hu, Huimin; Zhang, Qiwu; Liu, Xinzhong

2017-01-01

In this study, a mechanochemical route to synthesize a Cu-Al layered double hydroxide (LDH) and a methyl orange (MO) intercalated one (MO-LDH) was introduced, in which basic cupric carbonate (Cu_2(OH)_2CO_3) and aluminum hydroxide (Al(OH)_3) with Cu/Al molar ratio at 2/1 was first dry ground for 2 h and then agitated in water or methyl orange solution for another 4 h to obtain the LDH and MO-LDH products without any heating operation. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetry (TG), Differential scanning calorimetry (DSC) and Scanning electron microscopy (SEM). The products showed high crystallinity phase of Cu-Al and MO intercalated Cu-Al LDH with no evident impurities, proving that the craft introduced here was facile and effective. The new idea can be applied in other fields to produce organic-inorganic composites. - Highlights: • A facile mechanochemical route to synthesize Cu-Al and MO intercalated Cu-Al LDH. • The products possesses high crystalline of LDH phase with no impure phases. • The dry milling process induces the element substitution between the raw materials. • The agitation operation helps the grain growth of LDH.

Mechanochemical synthesis of Cu-Al and methyl orange intercalated Cu-Al layered double hydroxides

Energy Technology Data Exchange (ETDEWEB)

Qu, Jun, E-mail: forsjun@whut.edu.cn [School of Resources and Environmental Engineering, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070 (China); He, Xiaoman; Chen, Min; Hu, Huimin [School of Resources and Environmental Engineering, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070 (China); Zhang, Qiwu, E-mail: zhangqw@whut.edu.cn [School of Resources and Environmental Engineering, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070 (China); Liu, Xinzhong [College of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou 350118 China (China)

2017-04-15

In this study, a mechanochemical route to synthesize a Cu-Al layered double hydroxide (LDH) and a methyl orange (MO) intercalated one (MO-LDH) was introduced, in which basic cupric carbonate (Cu{sub 2}(OH){sub 2}CO{sub 3}) and aluminum hydroxide (Al(OH){sub 3}) with Cu/Al molar ratio at 2/1 was first dry ground for 2 h and then agitated in water or methyl orange solution for another 4 h to obtain the LDH and MO-LDH products without any heating operation. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetry (TG), Differential scanning calorimetry (DSC) and Scanning electron microscopy (SEM). The products showed high crystallinity phase of Cu-Al and MO intercalated Cu-Al LDH with no evident impurities, proving that the craft introduced here was facile and effective. The new idea can be applied in other fields to produce organic-inorganic composites. - Highlights: • A facile mechanochemical route to synthesize Cu-Al and MO intercalated Cu-Al LDH. • The products possesses high crystalline of LDH phase with no impure phases. • The dry milling process induces the element substitution between the raw materials. • The agitation operation helps the grain growth of LDH.

Mechanické vlastnosti slitiny AlSi9Cu3 zpracovaného technologií SLM

OpenAIRE

Koutný, Filip

2017-01-01

Tato bakalářská práce se zabývá porovnáním mechanických vlastností hliníkové slitiny AlSi9Cu3 v odlitém stavu se stavem po zpracování technologií selective laser melting (SLM). Rešeršní část práce pojednává o problematice hliníkových slitin, především o jejich rozdělení, mechanických vlastnostech, tepelné úpravě a zpracování technologií SLM. V diskuzi je řešen návrh optimálního rozsahu procesních parametrů SLM tisku a jsou porovnány mechanické vlastnosti konvenčně odlité slitiny AlSi9Cu3 se s...

Tuning Ce distribution for high performanced Nd-Ce-Fe-B sintered magnets

Energy Technology Data Exchange (ETDEWEB)

Fan, Xiaodong [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China); Guo, Shuai; Chen, Kan; Chen, Renjie; Lee, Don [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China); You, Caiyin, E-mail: caiyinyou@xaut.edu.cn [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Yan, Aru, E-mail: aruyan@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China)

2016-12-01

A dual-alloy method was applied to tune the distribution of Ce for enhancing the performance of Nd-Ce-Fe-B sintered magnets with a nominal composition of (Nd{sub 0.75}Ce{sub 0.25}){sub 30.5}Fe{sub bal}Al{sub 0.1}Cu{sub 0.1}B. In comparison to the single alloy of (Nd{sub 0.75}Ce{sub 0.25}){sub 30.5}Fe{sub bal}Al{sub 0.1}Cu{sub 0.1}B, the coercivity was enhanced from 10.3 kOe to 12.1 kOe and the remanence was increased from 13.1 kG to 13.3 kG for the magnets with a dual-alloy method. In addition, the remanence temperature coefficient α and coercivity temperature coefficient β were also slightly improved for the magnet with the dual alloys. The results of microstructure characterizations show the uniform distribution of Ce for the magnet with a single alloy, and the coexistence of the Ce-rich and Ce-lean regions for the magnet with the dual alloys. In combinations with the nucleation of reversal domains and magnetic recoil curves, the property enhancement of magnets with a dual-alloy method was well explained. - Highlights: • Improved magnetic properties were obtained in dual-alloy magnet. • This is due to the tuning of Ce distribution and the change in microstructure. • The magnetic hardening effect can be observed in dual-alloy magnet.

Heteroepitaxial growth of strained multilayer superconducting thin films of Nd1.83Ce0.17CuOx/YBa2Cu3O7-δ

International Nuclear Information System (INIS)

Gupta, A.; Gross, R.; Olsson, E.; Segmueller, A.; Koren, G.; Tsuei, C.C.

1990-01-01

Heteroepitaxial growth of strained multilayer thin films of YBa 2 Cu 3 O 7-δ /Nd 1.83 Ce 0.17 CuO x by pulsed-laser deposition is reported. The coherency strain results in biaxial compression of the tetragonal Nd 1.83 Ce 0.17 CuO x layers, whereas the biaxial tension in the YBa 2 Cu 3 O 7-δ layers removes the orthorhombic distortion and makes the unit cell isotropic in the basal plane (a=b). Depending on their oxygen content, either the YBa 2 Cu 3 O 7-δ or the Nd 1.83 Ce 0.17 CuO x layers are superconducting in these multilayers. The strain-induced structural modification has a significant influence on the superconducting transition temperature of the YBa 2 Cu 3 O 7-δ layers

Hyperfine fields and spin relaxation of Ce in GdAl2 and DyAl2

International Nuclear Information System (INIS)

Waeckelgaard, E.; Karlsson, E.; Lindgren, B.; Mayer, A.

1987-04-01

We have investigated the ferromagnetic state of the cubic intermetallic compounds GdAl 2 and DyAl 2 with the 140 Ce nuclei using DPAC. The local fields of Ce are for the lowest measured temperatures B eff (30 K) = 54(2) T for GdAl 2 and B eff (12.5 K) = 27(1) T for DyAl 2 which are considerably lower than the hyperfine field measured for a free Ce ion (183 T). By introducing a crystal field, of cubic symmetry, a lower hyperfine field is obtained which is in quantitative agreement with the local field of Ce in GdAl 2 . For DyAl 2 an additional effect, represented by a non-magnetic level below the lowest magnetic level, may explain a further reduction of the hyperfine field. Two models relating to a Kondo non-magnetic state of Ce are discussed. Spin relaxation in the paramagnetic state are also studied and compared with observations of the same systems measured with μSR. (authors)

Synthesis and characterization of Ce, Cu co-doped ZnS nanoparticles

International Nuclear Information System (INIS)

Harish, G.S.; Sreedhara Reddy, P.

2015-01-01

Ce, Cu co-doped ZnS nanoparticles were prepared at room temperature using a chemical co-precipitation method. The prepared nanoparticles were characterized by X- ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and high resolution Raman spectroscopic techniques. Transmission electron microscopy (TEM) and X-ray diffraction studies showed that the diameter of the particles was around 2–3 nm. Broadened XRD peaks revealed the formation of nanoparticles with a face centered cubic (fcc) structure. DRS studies confirmed that the band gap increased with an increase in the dopant concentration. The Raman spectra of undoped and Ce, Cu ions co-doped ZnS nanoparticles showed longitudinal optical mode and transverse optical mode. Compared with the Raman modes (276 and 351 cm −1 ) of undoped ZnS nanoparticles, the Raman modes of Ce, Cu co- doped ZnS nanoparticles were slightly shifted towards lower frequency. PL spectra of the samples showed remarkable enhancement in the intensity upon doping

Polarity driven morphology of CeO2(1 0 0) islands on Cu(1 1 1)

International Nuclear Information System (INIS)

Stetsovych, O.; Beran, J.; Dvořák, F.; Mašek, K.; Mysliveček, J.; Matolín, V.

2013-01-01

Thin ceria films supported by metal substrates represent important model systems for reactivity studies in heterogeneous catalysis. Here we report the growth study of the polar CeO 2 (1 0 0) phase as part of a mixed CeO 2 (1 1 1)–CeO 2 (1 0 0) thin film supported by Cu(1 1 1). The two ceria phases grow on different areas of the substrate, what allows a reliable growth characterization of the CeO 2 (1 0 0) islands on Cu(1 1 1). Scanning tunneling microscopy measurements reveal CeO 2 (1 0 0) to grow in the form of highly dispersed three dimensional (3D) islands on a CeO 2 (1 0 0) interfacial layer. The CeO 2 (1 0 0) islands exhibit a 2 × 2 surface reconstruction. The presence of the surface reconstruction together with the highly dispersed growth of CeO 2 (1 0 0) islands corresponds to the requirement for compensation of the surface dipole moment on the CeO 2 (1 0 0). CeO 2 (1 0 0) islands are further characterized by reflection high energy electron diffraction yielding their epitaxial relations with respect to the Cu(1 1 1) substrate. The growth of well characterized CeO 2 (1 0 0) islands supported by Cu(1 1 1) represents a starting point for developing a novel template for structure-related reactivity studies of ceria based model catalysts.

A new ribbon-ignition method for fabricating p-CuO/n-CeO{sub 2} heterojunction with enhanced photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Wang, Ning [School of Materials Science and Engineering, Southeast University, Jiangsu Key Laboratory for Advanced Metallic Materials, Nanjing 211189 (China); Pan, Ye, E-mail: panye@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Jiangsu Key Laboratory for Advanced Metallic Materials, Nanjing 211189 (China); Lu, Tao; Li, Xingzhou; Wu, Shikai [School of Materials Science and Engineering, Southeast University, Jiangsu Key Laboratory for Advanced Metallic Materials, Nanjing 211189 (China); Wu, Jili [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China)

2017-05-01

Highlights: • A novel ribbon-ignition method was carried out to fabricate p-CuO/n-CeO{sub 2} heterojunction. • Cu-Ce binary amorphous ribbons are chosen as precursors. • Ribbon-ignition method has many advantages compared to traditional solution-based methods. • The CuO/CeO{sub 2} exhibited enhanced photodegradation activity towards RhB. • The formation of p-type CuO/n-type CeO{sub 2} heterojunction can promote the separation and transfer of the photoinduced carriers, resulting in the enhanced photocatalytic activity. - Abstract: The p-type CuO/n-type CeO{sub 2} heterojunction photocatalyst was synthesized by a facile combination of ribbon-ignition and calcination methods using Cu-Ce amorphous ribbons as precursors. The synthesized sample was characterized by X-ray diffraction (XRD), fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (DRS). XRD, FTIR and XPS reveal the successful synthesis of CuO/CeO{sub 2} composite. The SEM and TEM images show that the sample consists of large amounts of well-dispersed blocky-shaped particles with the size distribution from 20 nm to 2 μm. DRS exhibits the absorption band (about 491 nm) and the band gap energy (2.59 eV) of the CuO/CeO{sub 2} composite. The photocatalytic activities of the samples were evaluated by degrading rhodamine B (RhB) dye (10 mg/L) under visible light (λ > 420 nm) irradiation. Compared with pure CuO and CeO{sub 2}, the CuO/CeO{sub 2} exhibited significantly enhanced photocatalytic degradation activity. The reaction rate constant of CuO/CeO{sub 2} is 0.18 min{sup −1}, which is much higher than those of CuO (0.12 min{sup −1}) and CeO{sub 2} (0.10 min{sup −1}).

The Y-Cu-Al system

International Nuclear Information System (INIS)

Krachan, T.; Stel'makhovych, B.; Kuz'ma, Yu.

2003-01-01

The phase diagram of the Y-Cu-Al system at 820 K has been constructed using X-ray powder diffraction. The existence of earlier known ternary aluminides has been confirmed and their homogeneity regions and atomic distributions in the structures have been determined: YCu 4.6-4.0 Al 7.4-8.0 (ThMn 12 -type R I =0.049), Y 2 Cu 12.0-10.5 Al 5.0-6.5 (Th 2 Zn 17 -type R I =0.092), YCu 1.0-1.1 Al 1.0-0.9 (Fe 2 P-type R I =0.068). It has been shown that the structure of Y(Cu,Al) 3 is characterized by an ordered distribution of the Cu and Al atoms and it should be referred as Ca 3 Cu 2 Al 7 structure type (R I =0.060) besides the PuNi 3 structure type with statistical occupancies of the smaller atoms. At the investigated temperature the compound YCu 1.0-0.25 Al 3.0-3.75 (BaAl 4 -type) was not observed. However, we found the ternary aluminide with composition Y 3 Cu 2.7-2.0 Al 8.3-9.0 and related La 3 Al 11 -type (space group Immm, a=0.4192-0.4228, b=1.2423-1.2557, c=0.9812-0.9895 nm, R I =0.069). The compounds YCu 6.8 Al 4.2 (space group Fddd, Tb(Cu 0.58 Al 0.42 ) 11 -type, a=1.42755, b=1.48587, c=0.65654 nm, R I =0.062) and YCu 6.5 Al 4.5 (space group I4 1 /amd, BaCd 11 -type, a=1.02774, c=0.65838 nm, R I =0.071) have been found and structurally refined for the first time

Effect of 10Ce-TZP/Al2O3 nanocomposite particle amount and sintering temperature on the microstructure and mechanical properties of Al/(10Ce-TZP/Al2O3) nanocomposites

International Nuclear Information System (INIS)

Soltani, N.; Pech-Canul, M.I.; Bahrami, A.

2013-01-01

Highlights: • Increasing the 10Ce-TZP/Al 2 O 3 content up to 7 wt.%, enhanced composites’ hardness. • Significant enhancement in compressive strength is obtained with 7% 10Ce-TZP/Al 2 O 3 . • Sintering at 450 °C, hardness and compressive strength are higher than at 400 °C. - Abstract: A zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al 2 O 3 nanocomposite) can be a good substitute as reinforcement in metal matrix composites. In the present study, the effect of the amount of 10Ce-TZP/Al 2 O 3 particles on the microstructure and properties of Al/(10Ce-TZP/Al 2 O 3 ) nanocomposites was investigated. For this purpose, aluminum powders with average size of 30 μm were ball-milled with 10Ce-TZP/Al 2 O 3 nanocomposite powders (synthesized by aqueous combustion) in varying amounts of 1, 3, 5, 7, and 10 wt.%. Cylindrical-shape samples were prepared by pressing the powders at 600 MPa for 60 min while heating at 400–450 °C. The specimens were then characterized by scanning and transmission electron microscopy (SEM and TEM) in addition to different physical and mechanical testing methods in order to establish the optimal processing conditions. The highest compression strength was obtained in the composite with 7 wt.% (10Ce-TZP/Al 2 O 3 ) sintered at 450 °C

Unstable magnetic moments in Ce compounds

International Nuclear Information System (INIS)

Aarts, J.

1984-01-01

The problems which are connected with the appearance or disappearance of local moments in metals are well reflected in the magnetic behaviour of Ce intermetallic compounds. This work describes experiments on two Ce compounds which are typical examples of unstable moment systems. The first of these is CeAl 2 which at low temperatures, shows coexistence of antiferromagnetic order and the Kondo effect. Measurements are presented of the magnetization and the susceptibility in different magnetic field and temperature regions. An analysis of these measurements, using a model for the crystal field effects, shows the agreement between the measurements and the calculations to be reasonably good for CeAl 2 , but this agreement becomes worse upon decreasing Ce concentration. A phenomenological description of the observations is given. The second compound reported on is CeCu 2 Si 2 , the first 'heavy-fermion' superconductor to be investigated. The superconducting state is possibly formed by the quasi-particles of a non-magnetic many body singlet state, and not simply by the (sd) conduction electrons. This being a novel phenomenon, a number of experiments were performed to test this picture and to obtain a detailed description of the behaviour of CeCu 2 Si 2 . Measurements of the Meissner volume, confirmed the superconductivity to be intrinsic. (Auth.)

Stability of Cu-Precipitates in Al-Cu Alloys

Directory of Open Access Journals (Sweden)

Torsten E. M. Staab

2018-06-01

Full Text Available We present first principle calculations on formation and binding energies for Cu and Zn as solute atoms forming small clusters up to nine atoms in Al-Cu and Al-Zn alloys. We employ a density-functional approach implemented using projector-augmented waves and plane wave expansions. We find that some structures, in which Cu atoms are closely packed on {100}-planes, turn out to be extraordinary stable. We compare the results with existing numerical or experimental data when possible. We find that Cu atoms precipitating in the form of two-dimensional platelets on {100}-planes in the fcc aluminum are more stable than three-dimensional structures consisting of the same number of Cu-atoms. The preference turns out to be opposite for Zn in Al. Both observations are in agreement with experimental observations.

Crystal growth and magnetic properties of equiatomic CeAl

Science.gov (United States)

Das, Pranab Kumar; Thamizhavel, A.

2015-03-01

Single crystal of CeAl has been grown by flux method using Ce-Al self-flux. Several needle like single crystals were obtained and the length of the needle corresponds to the [001] crystallographic direction. Powder x-ray diffraction revealed that CeAl crystallizes in orthorhombic CrB-type structure with space group Cmcm (no. 63). The magnetic properties have been investigated by means of magnetic susceptibility, isothermal magnetization, electrical transport, and heat capacity measurements. CeAl is found to order antiferromagnetically with a Neel temperature TN = 10 K. The magnetization data below the ordering temperature reveals two metamagentic transitions for fields less than 20 kOe. From the inverse magnetic susceptibility an effective moment of 2.66 μB/Ce has been estimated, which indicates that Ce is in its trivalent state. Electrical resistivity data clearly shows a sharp drop at 10 K due to the reduction of spin disorder scattering of conduction electrons thus confirming the magnetic ordering. The estimated residual resistivity ratio (RRR) is 33, thus indicating a good quality of the single crystal. The bulk nature of the magnetic ordering is also confirmed by heat capacity data. From the Schottky anomaly of the heat capacity we have estimated the crystal field level splitting energies of the (2J + 1) degenerate ground state as 25 K and 175 K respectively for the fist and second excited states.

Investigation of the 600 C isothermal section of the Fe-Al-Ce ternary system

Energy Technology Data Exchange (ETDEWEB)

Zheng, Huiyun; Yin, Fucheng [Xiangtan Univ., Hunan (China). School of Materials Science and Engineering; Xiangtan Univ., Hunan (China). Key Laboratory of Materials Design and Preparation Technology of Hunan Province; Li, Zhi [Xiangtan Univ., Hunan (China). School of Materials Science and Engineering; Xiangtan Univ., Hunan (China). Key Laboratory of Materials Design and Preparation Technology of Hunan Province; Xiangtan Univ., Hunan (China). Key Laboratory of Key Film Materials and Application for Equipment (Hunan province); Ji, Li [South China University of Technology, Guangdong (China). School of Materials Science and Engineering

2017-01-15

The isothermal section of the Fe-Al-Ce system at 600 C was determined by means of scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray powder diffraction. Twenty three-phase regions were confirmed experimentally, and two three-phase regions could be deduced in this section. Five ternary compounds, i. e., τ{sub 1}, τ{sub 2}, τ{sub 3}, τ{sub 5}, and τ{sub 6}, exist at 600 C. The Fe{sub 2}Ce phase contains 6.6 at.% Al in the Fe-Al-Ce system. The Fe solubility in α-Al, αAl{sub 11}Ce{sub 3}, αAl{sub 3}Ce, Al{sub 2}Ce, AlCe, and AlCe{sub 3} is approximately 1.7 at.%, 1.1 at.%, 1.2 at.%, 1.3 at.%, 5.8 at.%, and 0.1 at.%, respectively, and the solubility of Ce in α-Al, FeAl{sub 3}, Fe{sub 2}Al{sub 5}, FeAl{sub 2}, and FeAl is approximately 0.1 at.%, 1.2 at.%, 1.9 at.%, 0.9 at.%, and 3.7 at.%, respectively.

Electromigration in Cu(Al) and Cu(Mn) damascene lines

Science.gov (United States)

Hu, C.-K.; Ohm, J.; Gignac, L. M.; Breslin, C. M.; Mittal, S.; Bonilla, G.; Edelstein, D.; Rosenberg, R.; Choi, S.; An, J. J.; Simon, A. H.; Angyal, M. S.; Clevenger, L.; Maniscalco, J.; Nogami, T.; Penny, C.; Kim, B. Y.

2012-05-01

The effects of impurities, Mn or Al, on interface and grain boundary electromigration (EM) in Cu damascene lines were investigated. The addition of Mn or Al solute caused a reduction in diffusivity at the Cu/dielectric cap interface and the EM activation energies for both Cu-alloys were found to increase by about 0.2 eV as compared to pure Cu. Mn mitigated and Al enhanced Cu grain boundary diffusion; however, no significant mitigation in Cu grain boundary diffusion was observed in low Mn concentration samples. The activation energies for Cu grain boundary diffusion were found to be 0.74 ± 0.05 eV and 0.77 ± 0.05 eV for 1.5 μm wide polycrystalline lines with pure Cu and Cu (0.5 at. % Mn) seeds, respectively. The effective charge number in Cu grain boundaries Z*GB was estimated from drift velocity and was found to be about -0.4. A significant enhancement in EM lifetimes for Cu(Al) or low Mn concentration bamboo-polycrystalline and near-bamboo grain structures was observed but not for polycrystalline-only alloy lines. These results indicated that the existence of bamboo grains in bamboo-polycrystalline lines played a critical role in slowing down the EM-induced void growth rate. The bamboo grains act as Cu diffusion blocking boundaries for grain boundary mass flow, thus generating a mechanical stress-induced back flow counterbalancing the EM force, which is the equality known as the "Blech short length effect."

Facile synthesis of uniform hierarchical composites CuO-CeO{sub 2} for enhanced dye removal

Energy Technology Data Exchange (ETDEWEB)

Xu, Pan; Niu, Helin, E-mail: niuhelin@ahu.edu.cn; Chen, Jingshuai, E-mail: cjshuai@126.com; Song, Jiming; Mao, Changjie; Zhang, Shengyi [Anhui University, Department of Chemistry, Key Laboratory of Functional Inorganic Materials of Anhui Province (China); Gao, Yuanhao [Xuchang University, Institute of Surface Micro and Nano Materials (China); Chen, Changle [University of Science and Technology of China, CAS Key Laboratory of Soft Matter Chemistry (China)

2016-12-15

The hierarchically shaped CuO-CeO{sub 2} composites were prepared through a facile solvothermal method without using any template. The as-prepared products were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and N{sub 2} adsorption–desorption analysis. In the characterization, we found that CuO-CeO{sub 2} composites were showed uniform size and morphology which were consisted of the secondary nanoflakes interconnected with each other. Most interestingly, the composites showed efficient performance to remove methyl blue and Congo red dyes from water with maximum adsorption capacities of 2131.24 and 1072.09 mg g{sup −1}, respectively. In addition, because of their larger surface area and the unique hierarchical structures, the adsorption performance of the CuO-CeO{sub 2} composites is much better than the materials of CuO and CeO{sub 2}.

Polarity driven morphology of CeO{sub 2}(1 0 0) islands on Cu(1 1 1)

Energy Technology Data Exchange (ETDEWEB)

Stetsovych, O., E-mail: stetsovycholeksandr@gmail.com; Beran, J.; Dvořák, F.; Mašek, K.; Mysliveček, J., E-mail: Josef.Myslivecek@mff.cuni.cz; Matolín, V.

2013-11-15

Thin ceria films supported by metal substrates represent important model systems for reactivity studies in heterogeneous catalysis. Here we report the growth study of the polar CeO{sub 2}(1 0 0) phase as part of a mixed CeO{sub 2}(1 1 1)–CeO{sub 2}(1 0 0) thin film supported by Cu(1 1 1). The two ceria phases grow on different areas of the substrate, what allows a reliable growth characterization of the CeO{sub 2}(1 0 0) islands on Cu(1 1 1). Scanning tunneling microscopy measurements reveal CeO{sub 2}(1 0 0) to grow in the form of highly dispersed three dimensional (3D) islands on a CeO{sub 2}(1 0 0) interfacial layer. The CeO{sub 2}(1 0 0) islands exhibit a 2 × 2 surface reconstruction. The presence of the surface reconstruction together with the highly dispersed growth of CeO{sub 2}(1 0 0) islands corresponds to the requirement for compensation of the surface dipole moment on the CeO{sub 2}(1 0 0). CeO{sub 2}(1 0 0) islands are further characterized by reflection high energy electron diffraction yielding their epitaxial relations with respect to the Cu(1 1 1) substrate. The growth of well characterized CeO{sub 2}(1 0 0) islands supported by Cu(1 1 1) represents a starting point for developing a novel template for structure-related reactivity studies of ceria based model catalysts.

[Oxidation behavior and kinetics of representative VOCs emitted from petrochemical industry over CuCeOx composite oxides].

Science.gov (United States)

Chen, Chang-Wei; Yu, Yan-Ke; Chen, Jin-Sheng; He, Chi

2013-12-01

CuCeOx composite catalysts were synthesized via coprecipitation (COP-CuCeO,) and incipient impregnation (IMP-CuCeOx) methods, respectively. The physicochemical properties of the samples were characterized by XRD, low-temperature N2 sorption, H2-TPR and O2-TPD. The influences of reactant composition and concentration, reaction space velocity, O2 content, H2O concentration, and catalyst type on the oxidation behaviors of benzene, toluene, and n-hexane emitted from petrochemical industry were systematically investigated. In addition, the related kinetic parameters were model fitted. Compared with IMP-CuCeOx, COP-CuCeOx had well-dispersed active phase, better low-temperature reducibility, and more active surface oxygen species. The increase of reactant concentration was unfavorable for toluene oxidation, while the opposite phenomenon could be observed in n-hexane oxidation. The inlet concentration of benzene was irrelevant to its conversion under high oxidation rate. The introduction of benzene obviously inhibited the oxidation of toluene and n-hexane, while the presence of toluene had a positive effect on beuzene conversion. The presence of n-hexane could promote the oxidation of toluene, while toluene had a negative influence on e-hexane oxidation. Both low space velocity and high oxygen concentration were beneficial for the oxidation process, and the variation of oxygen content had negligible effect on n-hexane and henzene oxidation. The presence of H2O noticeably inhibited the oxidation of toluene, while significantly accelerated the oxidation procedure of henzene and n-hexane. COP-CuCeOx had superior catalytic performance for toluene and benzene oxidation, while IMP-CuCeOx showed higher n-hexane oxidation activity under dry condition. The oxidation behaviors under different conditions could be well fitted and predicted by the pseudo first-order kinetic model.

Rapid Assessment of the Ce-Co-Fe-Cu System for Permanent Magnetic Applications

Science.gov (United States)

Meng, F.; Chaudhary, R. P.; Gandha, K.; Nlebedim, I. C.; Palasyuk, A.; Simsek, E.; Kramer, M. J.; Ott, R. T.

2018-04-01

This work focuses on the rapid synthesis and characterization of quaternary Ce(CoFeCu)5 alloy libraries to assess their potential viability as permanent magnets. Arrays of bulk specimens with controlled compositions were synthesized via laser engineered net shaping (LENS) by feeding different ratios of alloy powders into a melt pool created by a laser. Based on the assessment of the magnetic properties of the LENS printed samples, arc-melted and cast ingots were prepared with varying Fe (5-20 at.%) and Co (60-45 at.%) compositions while maintaining constant Ce (16 at.%) and Cu (19 at.%) content. The evolution of the microstructure and phases with varying chemical compositions and their dependence on magnetic properties are analyzed in as-cast and heat-treated samples. In both the LENS printed and cast samples, we find the best magnetic properties correspond to a predominantly single-phase Ce(CoFeCu)5 microstructure in which high coercivity (H c > 10 kOe) can be achieved without any microstructural refinement.

Rapid Assessment of the Ce-Co-Fe-Cu System for Permanent Magnetic Applications

Science.gov (United States)

Meng, F.; Chaudhary, R. P.; Gandha, K.; Nlebedim, I. C.; Palasyuk, A.; Simsek, E.; Kramer, M. J.; Ott, R. T.

2018-06-01

This work focuses on the rapid synthesis and characterization of quaternary Ce(CoFeCu)5 alloy libraries to assess their potential viability as permanent magnets. Arrays of bulk specimens with controlled compositions were synthesized via laser engineered net shaping (LENS) by feeding different ratios of alloy powders into a melt pool created by a laser. Based on the assessment of the magnetic properties of the LENS printed samples, arc-melted and cast ingots were prepared with varying Fe (5-20 at.%) and Co (60-45 at.%) compositions while maintaining constant Ce (16 at.%) and Cu (19 at.%) content. The evolution of the microstructure and phases with varying chemical compositions and their dependence on magnetic properties are analyzed in as-cast and heat-treated samples. In both the LENS printed and cast samples, we find the best magnetic properties correspond to a predominantly single-phase Ce(CoFeCu)5 microstructure in which high coercivity ( H c > 10 kOe) can be achieved without any microstructural refinement.

Thermodynamic properties of Al-Mn, Al-Cu, and Al-Fe-Cu melts and their relations to liquid and quasicrystal structure

International Nuclear Information System (INIS)

Zaitsev, A I; Zaitseva, N E; Shimko, R Yu; Arutyunyan, N A; Dunaev, S F; Kraposhin, V S; Lam, Ha Thanh

2008-01-01

Thermodynamic properties of molten Al-Mn, Al-Cu and Al-Fe-Cu alloys in a wide temperature range of 1123-1878 K and the whole range of concentrations have been studied using the integral effusion method and Knudsen mass spectrometry. Thermodynamic functions of melts were described by the associated solution model. The possibility of icosahedral quasicrystal (i-QC) precipitation from liquid Al-Mn and Al-Cu-Fe alloys was found to be a consequence of the existence in liquid associates (clusters). A geometric model is suggested for the structure of associates in liquid

Positron annihilation studies in the Nd-Ce-Cu-O superconductor

International Nuclear Information System (INIS)

Sundar, C.S.; Bharathi, A.; Jean, Y.C.; Hor, P.H.; Meng, R.L.; Huang, Z.J.; Chu, C.W.

1990-01-01

In the superconducting Nd 1.85 Ce 0.15 CuO 3.98 , the positron lifetime is observed to decrease from 211 to 205 ps in the temperature range of 150--50 K, whereas in the nonsuperconducting Nd 1.85 Ce 0.15 CuO 4 , having a lifetime value of 231 ps, no significant temperature dependence of lifetime is observed. The difference in the lifetimes of the superconducting and nonsuperconducting samples and their temperature dependencies are understood in terms of positron interaction with the vacancies in the system. Doppler-broadened line shapes of energy spectra are found to show similar results as lifetime measurements. Theoretical calculations are used to show that the oxygen vacancies are weaker traps compared with the vacancies at the Cu and Nd sites. The observed decrease in lifetime in the superconducting sample is interpreted in terms of an increase in the fraction of positrons trapped at the oxygen vacancies as the temperature is lowered. Plausible reasons for the temperature independence of lifetime across T c in the superconducting sample are discussed

Effect of Ce addition on the mechanical and electrochemical properties of a lithium battery shell alloy

International Nuclear Information System (INIS)

Zhang, Junchao; Ding, Dongyan; Xu, Xinglong; Gao, Yongjin; Chen, Guozhen; Chen, Weigao; You, Xiaohua; Huang, Yuanwei; Tang, Jinsong

2014-01-01

Highlights: • Fabrication of Ce-free and Ce-containing Al–Cu–Mn–Fe–Mg alloy. • TEM, tensile and electrochemical characterization of the alloys. • Ce element greatly affects the precipitation of the alloy. • Ce element had great impact on the tensile strength and corrosion potential of the alloys. - Abstract: Due to severe application environment lithium battery shell of new-energy automotives requires increasing demands for using high performance aluminum alloys. In the present work, effect of Ce addition on the microstructure, tensile and electrochemical properties of an Al–Cu–Mn–Mg–Fe alloy were investigated through using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), tensile tests and electrochemical tests. The experimental results indicated that the addition of Ce element could promote the precipitation of second phases. With addition of 0.36% Ce, high melting point Al 8 Cu 4 Ce phase and many Al 20 Cu 2 Mn 3 particles could be found. In addition, the precipitation of conventionally dominant phase of Al 2 Cu could be suppressed in alloy. The Ce addition was found to result in enhanced tensile strength and improved corrosion resistance

Effect of Ce addition on the mechanical and electrochemical properties of a lithium battery shell alloy

Energy Technology Data Exchange (ETDEWEB)

Zhang, Junchao [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Ding, Dongyan, E-mail: dyding@sjtu.edu.cn [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Xu, Xinglong [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Gao, Yongjin; Chen, Guozhen; Chen, Weigao; You, Xiaohua [Huafon NLM Al Co., Ltd, Shanghai 201506 (China); Huang, Yuanwei; Tang, Jinsong [Shanghai Huafon Materials Technology Institute, Shanghai 201203 (China)

2014-12-25

Highlights: • Fabrication of Ce-free and Ce-containing Al–Cu–Mn–Fe–Mg alloy. • TEM, tensile and electrochemical characterization of the alloys. • Ce element greatly affects the precipitation of the alloy. • Ce element had great impact on the tensile strength and corrosion potential of the alloys. - Abstract: Due to severe application environment lithium battery shell of new-energy automotives requires increasing demands for using high performance aluminum alloys. In the present work, effect of Ce addition on the microstructure, tensile and electrochemical properties of an Al–Cu–Mn–Mg–Fe alloy were investigated through using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), tensile tests and electrochemical tests. The experimental results indicated that the addition of Ce element could promote the precipitation of second phases. With addition of 0.36% Ce, high melting point Al{sub 8}Cu{sub 4}Ce phase and many Al{sub 20}Cu{sub 2}Mn{sub 3} particles could be found. In addition, the precipitation of conventionally dominant phase of Al{sub 2}Cu could be suppressed in alloy. The Ce addition was found to result in enhanced tensile strength and improved corrosion resistance.

Methanol steam reforming over Cu/CeO2 catalysts: influence of zinc addition

Directory of Open Access Journals (Sweden)

Franco Tonelli

2011-01-01

Full Text Available Methanol steam reforming reaction was studied over Cu(5 wt.%/CeO2 with and without the presence of Zn. The Zn addition decreased the Cu+2 reducibility and increased the oxygen mobility of ceria. The main products were CO2 and H2 with small amount of CO. Selectivity to CO decreased with the Zn addition and it was lower at lower reaction temperatures and lower space velocities. At 230 ºC and W/F MeOH = 648 g min mol-1 selectivities to H2 and to CO2 were 100% on Zn/Cu/Ce. The catalytic results indicated that CO was mainly a secondary product formed from reverse water gas shift reaction.

Formation of AlFeSi phase in AlSi12 alloy with Ce addition

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S. Kores

2012-04-01

Full Text Available The influence of cerium addition on the solidification sequence and microstructure constituents of the Al-Si alloys with 12,6 mass % Si was examined. The solidification was analyzed by a simple thermal analysis. The microstructures were examined with conventional light and scanning electron microscopy. Ternary AlSiCe phase was formed in the Al-Si alloys with added cerium during the solidification process. AlSiCe and β-AlFeSi phases solidified together in the region that solidified the last. Cerium addition influenced on the morphology of the α-AlFeSi phase solidification.

Cu-Al alloy formation by thermal annealing of Cu/Al multilayer films deposited by cyclic metal organic chemical vapor deposition

Science.gov (United States)

Moon, Hock Key; Yoon, Jaehong; Kim, Hyungjun; Lee, Nae-Eung

2013-05-01

One of the most important issues in future Cu-based interconnects is to suppress the resistivity increase in the Cu interconnect line while decreasing the line width below 30 nm. For the purpose of mitigating the resistivity increase in the nanoscale Cu line, alloying Cu with traces of other elements is investigated. The formation of a Cu alloy layer using chemical vapor deposition or electroplating has been rarely studied because of the difficulty in forming Cu alloys with elements such as Al. In this work, Cu-Al alloy films were successfully formed after thermal annealing of Cu/Al multilayers deposited by cyclic metal-organic chemical vapor deposition (C-MOCVD). After the C-MOCVD of Cu/Al multilayers without gas phase reaction between the Cu and Al precursors in the reactor, thermal annealing was used to form Cu-Al alloy films with a small Al content fraction. The resistivity of the alloy films was dependent on the Al precursor delivery time and was lower than that of the aluminum-free Cu film. No presence of intermetallic compounds were detected in the alloy films by X-ray diffraction measurements and transmission electron spectroscopy.

Improving the Efficiency of DASC by Adding CeO2/CuO Hybrid Nanoparticles in Water

Science.gov (United States)

Midhun Mohan, V.; Sajeeb, A. M.

Solar energy is the abundantly available source of renewable energy with least impact on environment. Direct absorption solar collector (DASC) is the commonly used device to absorb heat directly from sun and make use of it for different heating applications. In the past, many experiments have been done to increase the efficiency of DASC using nanofluids. In this paper, an examination of solar collector efficiency for hybrid CeO2/CuO-water (0.1% by volume) nanofluid under various flow rates and proportions of CeO2/CuO nanoparticles is investigated. The experiments were conducted at flow rates spanning from 20cc/min to 100cc/min and with CeO2/CuO nanoparticles proportions of 1:0, 1:0.5, 1:1, 0.5:1 and 0:1. The efficiency increases from 16.5% to 51.6% when the flow rate is increased from 20cc/min to 100cc/min for hybrid CeO2/CuO (1:1)-water nanofluid. The results also showed an increase in efficiency of 13.8%, 18.1%, 24.3%, 24.9% and 26.1% with hybrid combination of CeO2/CuO at ratios 1:0, 1:0.5, 1:1, 0.5:1 and 0:1, respectively, in comparison with water at a flow rate of 100cc/min.

Evidence for unconventional d-wave superconducting state in CeCu{sub 2}Si{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Vieyra, Hugo A.; Geibel, Christoph; Steglich, Frank; Oeschler, Niels [Max-Planck-Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Parker, David [US Naval Research Laboratory, Washington, DC 20375 (United States); Jeevan, Hirale S. [I. Physik. Institut, Georg-August-Universitaet Goettingen, Goettingen 37077 (Germany)

2010-07-01

The heavy-fermion CeCu{sub 2}Si{sub 2} represents a prime system to study unconventional superconductivity in the vicinity of a magnetic instability. Within the homogeneity range of pure CeCu{sub 2}Si{sub 2} different ground states can be obtained. S-type crystals exhibit a superconducting transition at T{sub c}=0.6 K, whereas A/S-type show in addition antiferromagnetic order at T{sub N}=0.8 K. In recent years, the synthesis techniques have been optimized in order to obtain large high-quality single crystals with well defined ground state properties. This allows the systematic study of the superconducting order parameter and its variation at the border with magnetic order. In this work, we present angular dependent resistivity measurements on high-quality S- and A/S-type single-crystalline CeCu{sub 2}Si{sub 2} samples. The experimental results for the angular dependence of the upper critical field B{sub c2} as well as theoretical calculations taking into account effects like the strong Pauli paramagnetism, hint towards an unconventional d-wave symmetry of the order parameter in CeCu{sub 2}Si{sub 2}.

Synthesis of Ordered Mesoporous CuO/CeO2 Composite Frameworks as Anode Catalysts for Water Oxidation

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Vassiliki Markoulaki Ι

2015-11-01

Full Text Available Cerium-rich metal oxide materials have recently emerged as promising candidates for the photocatalytic oxygen evolution reaction (OER. In this article, we report the synthesis of ordered mesoporous CuO/CeO2 composite frameworks with different contents of copper(II oxide and demonstrate their activity for photocatalytic O2 production via UV-Vis light-driven oxidation of water. Mesoporous CuO/CeO2 materials have been successfully prepared by a nanocasting route, using mesoporous silica as a rigid template. X-ray diffraction, electron transmission microscopy and N2 porosimetry characterization of the as-prepared products reveal a mesoporous structure composed of parallel arranged nanorods, with a large surface area and a narrow pore size distribution. The molecular structure and optical properties of the composite materials were investigated with Raman and UV-Vis/NIR diffuse reflectance spectroscopy. Catalytic results indicated that incorporation of CuO clusters in the CeO2 lattice improved the photochemical properties. As a result, the CuO/CeO2 composite catalyst containing ~38 wt % CuO reaches a high O2 evolution rate of ~19.6 µmol·h−1 (or 392 µmol·h−1·g−1 with an apparent quantum efficiency of 17.6% at λ = 365 ± 10 nm. This OER activity compares favorably with that obtained from the non-porous CuO/CeO2 counterpart (~1.3 µmol·h−1 and pure mesoporous CeO2 (~1 µmol·h−1.

Ethanol Sensor of CdO/Al2O3/CeO2 Obtained from Ce-DOPED Layered Double Hydroxides with High Response and Selectivity

Science.gov (United States)

Xu, Dongmei; Guan, Meiyu; Xu, Qinghong; Guo, Ying; Wang, Yao

2013-04-01

In this paper, Ce-doped CdAl layered double hydroxide (LDH) was first synthesized and the derivative CdO/Al2O3/CeO2 composite oxide was prepared by calcining Ce-doped CdAl LDH. The structure, morphology and chemical state of the Ce doped CdAl LDH and CdO/Al2O3/CeO2 were also investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), solid state nuclear magnetic resonance (SSNMR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing properties of CdO/Al2O3/CeO2 to ethanol were further studied and compared with CdO/Al2O3 prepared from CdAl LDH, CeO2 powder as well as the calcined Ce salt. It turns out that CdO/Al2O3/CeO2 sensor shows best performance in ethanol response. Besides, CdO/Al2O3/CeO2 possesses short response/recovery time (12/72 s) as well as remarkable selectivity in ethanol sensing, which means composite oxides prepared from LDH are very promising in gas sensing application.

Luminescence properties of Y3Al5O12:Ce nanoceramics

International Nuclear Information System (INIS)

Zorenko, Yu.; Voznyak, T.; Gorbenko, V.; Zych, E.; Nizankovski, S.; Dan'ko, A.; Puzikov, V.

2011-01-01

Comparative analysis of the luminescent properties of Y 3 Al 5 O 12 :Ce (YAG:Ce) transparent optical ceramics (OS) with those of single crystal (SC) and single crystalline film (SCF) analogues has been performed under excitation by pulsed synchrotron radiation in the fundamental absorption range of YAG host. It has been shown that the properties of YAG:Ce OC are closer to the properties of the SCF counterpart, where Y Al antisite defects are completely absent, rather than to the properties of SC of this garnet with large concentration of Y Al antisite defects. At the same time, the luminescence spectra of YAG:Ce OC show weak emission bands in the 200-470 nm range related to Y Al antisite defects and charged oxygen vacancies (F + and F centers). YAG:Ce OS also possesses significantly larger contribution of slow components in the Ce 3+ luminescence decay under high-energy excitation in comparison with SC and SCF of this garnet due to the involvement of antisite defects, charged oxygen vacancies as well as boundaries of grains in the energy transfer processes from the host to the Ce 3+ ions.

Effect of rare earth Ce on the fatigue life of SnAgCu solder joints in WLCSP device using FEM and experiments

International Nuclear Information System (INIS)

Zhang, Liang; Han, Ji-guang; Guo, Yong-huan; He, Cheng-wen

2014-01-01

With the addition of 0.03 wt% rare earth Ce, in our previous works, the properties of SnAgCu solder were enhanced obviously. Based on the Garofalo–Arrhenius creep constitutive model, finite element method was used to simulate the stress–strain response during thermal cycle loading, and combined with the fatigue life prediction models, the fatigue life of SnAgCu/SnAgCuCe solder joints was calculated respectively, which can demonstrate the effect of the rare earth Ce on the fatigue life of SnAgCu solder joints. The results indicated that the maximum stress–strain can be found on the top surface of the corner solder joint, and the warpage of the PCB substrate occurred during thermal cycle loading. The trends obtained from modeling results have a good agreement with the experimental data reported in the literature for WLCSP devices. In addition, the stress–strain of SnAgCuCe solder joints is lower than that of SnAgCu solder joints. The thermal fatigue lives of solder joints calculated based on the creep model and creep strain energy density model show that the fatigue life of SnAgCuCe solder joints is higher than the SnAgCu solder joints. The fatigue life of SnAgCuCe solder joints can be enhanced significantly with the addition of Ce, is 30.2% higher than that of SnAgCu solder joints, which can be attributed to the CeSn 3 particles formed resisting the motion of dislocation; moreover, the refinement of microstructure and the IMC sizes also contribute to the enhancement of fatigue life, which elucidates that SnAgCuCe solder can be utilized in electronic industry with high reliability replacing the SnAgCu solder

Application of the Rietveld method in structural analysis of catalysts based on CuO/CeO{sub 2}; Aplicacao do metodo de Rietveld na analise estrutural de catalisadores a base de CuO/CeO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Neiva, L.S.; Ribeiro, M.A.; Bispo, A.; Simoes, A.N.; Gama, L., E-mail: lsoutoneiva@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Departamento de Engenharia de Materiais

2011-07-01

This work has as aim to synthesize catalysts composed by CuO/CeO{sub 2} by means two distinct methods of synthesis, they are: combustion synthesis and Pechini. The catalysts composed by CuO/CeO{sub 2} were synthesized with CuO in condition of dopant element. The value of the CuO concentration ranged between 0 and 0.5 mol. Has been done a structural analysis related to how the kind of synthesis method used influences over physical characteristic of the catalytic material. The obtained catalysts were characterized by X-ray diffraction with refinement by Rietveld method. According to results, the synthesized catalysts showed crystalline structures formed mostly by CeO{sub 2} phase, as expected, since this is the host matrix for the dopant element. The catalysts obtained by the Pechini method presented structures with a smaller amount of segregated phases formed by CuO, according to the results of the structural analysis. (author)

A first-principles study of the structural, mechanical and electronic properties of precipitates of Al2Cu in Al-Cu alloys.

Science.gov (United States)

Ouyang, Y F; Chen, H M; Tao, X M; Gao, F; Peng, Q; Du, Y

2018-01-03

The properties of precipitates are important in understanding the strengthening mechanism via precipitation during heat treatment and the aging process in Al-Cu based alloys, where the formation of precipitates is sensitive to temperature and pressure. Here we report a first-principles investigation of the effect of temperature and pressure on the structural stability, elastic constants and formation free energy for precipitates of Al 2 Cu, as well as their mechanical properties. Based on the formation enthalpy of Guinier-Preston (GP(I)) zones, the size of the GP(I) zone is predicted to be about 1.4 nm in diameter, which is in good agreement with experimental observations. The formation enthalpies of the precipitates are all negative, suggesting that they are all thermodynamically stable. The present calculations reveal that entropy plays an important role in stabilizing θ-Al 2 Cu compared with θ C '-Al 2 Cu. The formation free energies of θ''-Al 3 Cu, θ C '-Al 2 Cu, θ D '-Al 5 Cu 3 and θ t '-Al 11 Cu 7 increase with temperature, while those of θ'-Al 2 Cu, θ O '-Al 2 Cu and θ-Al 2 Cu decrease. The same trend is observed with the effect of pressure. The calculated elastic constants for the considered precipitation phases indicate that they are all mechanically stable and anisotropic, except θ C '-Al 2 Cu. θ D '-Al 5 Cu 3 has the highest Vicker's hardness. The electronic structures are also calculated to gain insight into the bonding characteristics. The present results can help in understanding the formation of precipitates by different treatment processes.

Low-cost and eco-friendly nebulizer spray coated CuInAlS2 counter electrode for dye-sensitized solar cells

Science.gov (United States)

Dhas, C. Ravi; Christy, A. Jennifer; Venkatesh, R.; Esther Santhoshi Monica, S.; Panda, Subhendu K.; Subramanian, B.; Ravichandran, K.; Sudhagar, P.; Raj, A. Moses Ezhil

2018-05-01

CuInAlS2 thin films for different substrate temperatures were deposited by a novel nebulizer spray technique. The polycrystalline CIAS thin film exhibited tetragonal structure with the preferential orientation of (1 1 2) plane. Nanoflakes were observed from the surface morphology of CIAS film. The peak position of core level spectra confirms the presence of CuInAlS2 from XPS analysis. The absorbance spectra and optical band gap were observed from the optical property. The activation energy, carrier concentration, hole mobility and resistivity were determined by linear four probe and Hall effect measurements. The CIAS film was used as a counter electrode (CE) in dye-sensitized solar cells (DSSCs) and is characterized by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel measurements. DSSC fabricated with the CIAS CE achieved the photo conversion efficiency of about 2.55%.

Study on effects of powder and flake chemistry and morphology on the properties of Al-Cu-Mg-X-X-X powder metallurgy advanced aluminum alloys

Science.gov (United States)

Meschter, P. J.; Lederich, R. J.; Oneal, J. E.

1986-01-01

A study was conducted: (1) to develop rapid solidification processed (RSP) dispersoid-containing Al-3Cu-2Li-1Mg-0.2Zr alloys as substitutes for titanium alloys and commercial 2XXX aluminum alloys for service to at least 150 C; and (2) to develop RSP Al-4Li-Cu-Mg-Zr alloys as substitutes for high-strength commercial 7XXX alloys in ambient-temperature applications. RSP Al-3Cu-2Li-1Mg-0.2Zr alloys have density-normalized yield stresses at 150 C up to 52% larger than that of 2124-T851 and up to 30% larger than that of Ti-6Al-4V. Strength at 150 C in these alloys is provided by thermally stable delta' (Al3Li), T1 (Al2LiCu), and S' (Al2CuMg) precipitates. Density-normalized yield stresses of RSP Al-3Cu-2Li-1Mg-0.2Zr alloys are up to 100% larger than that of 2124-T851 and equivalent to that of Al-8Fe-4Ce at 260 C. Strength in the RSP alloys at 260 C is provided by incoherent dispersoids and subboundary constituent particles such as T1 and S. The RSP alloys are attractive substitutes in less than or = 100-h exposures for 2xxx and Al-4Fe-Ce alloys up to 260 C and for titanium alloys up to 150 C. RSP Al-4Li-Cu-Mg-Zr alloys have ambient-temperature yield and ultimate tensile stresses similar to that of 7050-T7651, and are 14% less dense. RSP Al-4Li-0.5Cu-1.5Mg-0.2Zr has a 20% higher specific yield stress, 40% higher specific elastic modulus, and superior corrosion resistance compared to the properties of 7050-T7651. Strength in the Al-4Li-Cu-Mg-Zr alloy class is primarily provided by the substructure and delta' precipitates and is independent of Cu:Mg ratio. Improvements in fracture toughness and transverse-orientation properties in both alloy classes depend on improved melt practices to eliminate oxide inclusions which are incorporated into the consolidated forms.

Study On Nanohardness Of Phases Occurring In ZnAl22Cu3 And ZnAl40Cu3 Alloys

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Michalik R.

2015-06-01

Full Text Available Zn-Al alloys are mainly used due to their high tribological and damping properties. A very important issue is determination of the hardness of the phases present in the Zn-Al-Cu alloys. Unfortunately, in literature there is lack of studies on the hardness of the phases present in the alloys Zn-Al-Cu. The aim of this research was to determine the hardness of the phases present in the ZnAl22Cu3Si and ZnAl40Cu3Si alloys. The scope of the research included examination of the structure, chemical composition of selected micro-regions and hardness of phases present in the examined alloys. The research carried out has shown, that CuZn4 phase is characterized by a similar hardness as the hardness of the interdendritic areas. The phases present in the structure of ZnAl40Cu3 and ZnAl22Cu3 alloys after soaking at the temperature of 185 °C are characterized by lower hardness than the phase present in the structure of the as-cast alloys.

LiCaAlF sub 6 :Ce crystal: a new scintillator

CERN Document Server

Gektin, A V; Neicheva, S; Gavrilyuk, V; Bensalah, A; Fukuda, T; Shimamura, K

2002-01-01

Scintillation properties of LiCaAlF sub 6 :Ce crystal, well known as the effective UV laser material, is reported. Ce sup 3 sup + emission at 286-305 nm with a single exponential decay time of 35 ns provides a scintillation pulse. Radiation damage in pure and Ce-doped crystals is studied. In contrast to the majority of fluoride crystals, cerium is responsible for the ultradeep traps formation revealing thermostimulated luminescence. Overlapping of color center absorption and Ce sup 3 sup + ion emission bands limits the scintillation efficiency of LiCaAlF sub 6 :Ce at high radiation doses.

Non-Enzymatic Glucose Biosensor Based on CuO-Decorated CeO2 Nanoparticles

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Panpan Guan

2016-08-01

Full Text Available Copper oxide (CuO-decorated cerium oxide (CeO2 nanoparticles were synthesized and used to detect glucose non-enzymatically. The morphological characteristics and structure of the nanoparticles were characterized through transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The sensor responses of electrodes to glucose were investigated via an electrochemical method. The CuO/CeO2 nanocomposite exhibited a reasonably good sensitivity of 2.77 μA mM−1cm−2, an estimated detection limit of 10 μA, and a good anti-interference ability. The sensor was also fairly stable under ambient conditions.

Dosimeter properties of Ce and Eu doped LiCaAlF6

International Nuclear Information System (INIS)

Yanagida, Takayuki; Fujimoto, Yutaka; Watanabe, Kenichi; Fukuda, Kentaro

2014-01-01

Optical, scintillation properties, optical stimulated luminescence, and thermally stimulated luminescence of Ce 1, 3, and 5% doped and Eu 1, 1.5, and 2% doped LiCaAlF 6 crystals fabricated by Tokuyama Corp. were investigated. In transmittance, absorption was proportional to dopant concentrations and typical optical quantum yield of Ce and Eu-doped LiCaAlF 6 were 40 and 100%, respectively. Scintillation wavelength and decay time profiles were investigated under X-ray irradiation. Ce 3+ and Eu 2+ 5d-4f luminescence appeared around 300 nm and 370 nm with typical decay time of 40 ns and 1.5 μs, respectively. Optically stimulated luminescence of Ce-doped ones appeared under 405 nm stimulation with detectable intensity while those of Eu doped ones were quite weak. Thermally stimulated luminescence of Ce- and Eu-doped LiCaAlF 6 were enough strong and they exhibited good response function from 1 to 1000 mGy exposure. - Highlights: • Optical, scintillation, OSL, and TSL properties of Ce or Eu differently doped LiCaAlF6 were studied. • PL quantum yield of Ce and Eu doped LiCaAlF6 showed 40% and 100%, respectively. • OSL was observed in Ce-doped LiCaAlF6. • TSL was observed in both material systems and exhibited a good dose response from 1 to 1000 mGy

Synergy of CuO and CeO2 combination for mercury oxidation under low-temperature selective catalytic reduction atmosphere

KAUST Repository

Li, Hailong

2016-07-19

Synergy for low temperature Hg0 oxidation under selective catalytic reduction (SCR) atmosphere was achieved when copper oxides and cerium oxides were combined in a CuO-CeO2/TiO2 (CuCeTi) catalyst. Hg0 oxidation efficiency as high as 99.0% was observed on the CuCeTi catalyst at 200 °C, even the gas hourly space velocity was extremely high. To analyze the synergistic effect, comparisons of catalyst performance in the presence of different SCR reaction gases were systematically conducted over CuO/TiO2 (CuTi), CeO2/TiO2 (CeTi) and CuCeTi catalysts prepared by sol-gel method. The interactions between copper oxides and cerium oxides in CuCeTi catalyst yielded more surface chemisorbed oxygen, and facilitated the conversion of gas-phase O2 to surface oxygen, which are favorable for Hg0 oxidation. Copper oxides in the combination interacted with NO forming more chemisorbed oxygen for Hg0 oxidation in the absence of gas-phase O2. Cerium oxides in the combination promoted Hg0 oxidation through enhancing the transformations of NO to NO2. In the absence of NO, NH3 exhibited no inhibitive effect on Hg0 oxidation, because enough Lewis acid sites due to the combination of copper oxides and cerium oxides scavenged the competitive adsorption between NH3 and Hg0. In the presence of NO, although NH3 lowered Hg0 oxidation rate through inducing reduction of oxidized mercury, complete recovery of Hg0 oxidation activity over the CuCeTi catalyst was quickly achieved after cutting off NH3. This study revealed the synergistic effect of the combination of copper oxides and cerium oxides on Hg0 oxidation, and explored the involved mechanisms. Such knowledge would help obtaining maximum Hg0 oxidation co-benefit from SCR units in coal-fired power plants.

Facile synthesis of dendritic Cu by electroless reaction of Cu-Al alloys in multiphase solution

Energy Technology Data Exchange (ETDEWEB)

Wang, Ying; Liang, Shuhua, E-mail: liangxaut@gmail.com; Yang, Qing; Wang, Xianhui

2016-11-30

Highlights: • Nano- or micro-scale fractal dendritic copper (FDC) was synthesized by electroless immersing of Cu-Al alloys in CuCl{sub 2} + HCl. • FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl{sub 2} + HCl solution. • Nanoscale Cu{sub 2}O was found at the edge of FDC. Nanoporous copper (NPC) can also be obtained by using Cu{sub 17}Al{sub 83} alloy. • The potential difference between CuAl{sub 2} and α-Al phase and the replacement reaction in multiphase solution are key factors. - Abstract: Two-dimensional nano- or micro-scale fractal dendritic coppers (FDCs) were synthesized by electroless immersing of Cu-Al alloys in hydrochloric acid solution containing copper chloride without any assistance of template or surfactant. The FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl{sub 2} + HCl solution. Compared to Cu{sub 40}Al{sub 60} and Cu{sub 45}Al{sub 55} alloys, the FDC shows hierarchical distribution and homogeneous structures using Cu{sub 17}Al{sub 83} alloy as the starting alloy. The growth direction of the FDC is <110>, and all angles between the trunks and branches are 60°. Nanoscale Cu{sub 2}O was found at the edge of FDC. Interestingly, nanoporous copper (NPC) can also be obtained through Cu{sub 17}Al{sub 83} alloy. Studies showed that the formation of FDC depended on two key factors: the potential difference between CuAl{sub 2} intermetallic and α-Al phase of dual-phase Cu-Al alloys; a replacement reaction that usually occurs in multiphase solution. The electrochemical experiment further proved that the multi-branch dendritic structure is very beneficial to the proton transfer in the process of catalyzing methanol.

Application of the Rietveld method in structural analysis of catalysts based on CuO/CeO2

International Nuclear Information System (INIS)

Neiva, L.S.; Ribeiro, M.A.; Bispo, A.; Simoes, A.N.; Gama, L.

2011-01-01

This work has as aim to synthesize catalysts composed by CuO/CeO 2 by means two distinct methods of synthesis, they are: combustion synthesis and Pechini. The catalysts composed by CuO/CeO 2 were synthesized with CuO in condition of dopant element. The value of the CuO concentration ranged between 0 and 0.5 mol. Has been done a structural analysis related to how the kind of synthesis method used influences over physical characteristic of the catalytic material. The obtained catalysts were characterized by X-ray diffraction with refinement by Rietveld method. According to results, the synthesized catalysts showed crystalline structures formed mostly by CeO 2 phase, as expected, since this is the host matrix for the dopant element. The catalysts obtained by the Pechini method presented structures with a smaller amount of segregated phases formed by CuO, according to the results of the structural analysis. (author)

Structural analysis of CuO / CeO2-based catalytic materials intended for PROX reaction: Part I

International Nuclear Information System (INIS)

Neiva, L.S.; Simoes, A.N.; Bispo, A.; Ribeiro, M.A.; Gama, L.

2011-01-01

This work relates the synthesis process of CuO/CeO 2 catalytic materials by a combustion reaction method as well as it introduces a structural analysis of the developed material, this structural analysis had as main focus to evaluate the influence of the doping substance (CuO) when being incorporated in the hostess matrix structure that is CeO 2 . The CuO/CeO catalytic materials developed in this work are destined to preferential oxidation of CO reaction (PROX). The developed materials were characterized by XRD, SEM and textural complete analysis by the BET method. According to the results, the CuO incorporation changed crystallinity of the structure of the catalytic materials. On the other hand, the morphologic and textural characteristics did not showed significant differences regarding the presence of the doping substance (CuO) in the structure of the developed materials. The porosity of the structures of the developed catalytic materials belongs to the type macroporous. (author)

27Al, 63Cu NMR spectroscopy and electrical transport in Heusler Cu-Mn-Al alloy powders

Science.gov (United States)

Nadutov, V. M.; Perekos, A. O.; Kokorin, V. V.; Trachevskii, V. V.; Konoplyuk, S. M.; Vashchuk, D. L.

2018-02-01

The ultrafine powder of the Heusler Cu-13,1Mn-12,6Al (wt.%) alloy produced by electrical spark dispersion (ESD) in ethanol and the pellets prepared by pressing of the powders and aged in various gas environment (air, Ar, vacuum) were studied by XRD, nuclear magnetic resonance, magnetic and electric transport methods. The constituent phases were identified as b.c.c. α-Cu-Mn-Al, f.c.c. γ-Cu-Mn-Al, Cu2MnAl, and oxides. The sizes of the coherently scattering domains (CSD) and the saturation magnetizations were in the range of 4-90 nm and 0-1.5 Am2/kg, respectively. 27Al and 63Cu NMR spectra of the powders and pellets have shown hyperfine structure caused by contributions from atomic nuclei of the constituent phases. The aging of pellets in different gas environments had effect on their phase composition but no effect on dispersion of the phases. In contrast to the as-cast alloy, electrical resistance of the pellets evidenced semiconducting behavior at elevated temperatures due to the presence of metal oxides formed on the surfaces of nanoparticles.

Structural analysis of CuO / CeO{sub 2}-based catalytic materials intended for PROX reaction: Part I; Analise estrutural de materiais cataliticos a base de CuO/CeO{sub 2} destinados a reacao de PROX: parte I

Energy Technology Data Exchange (ETDEWEB)

Neiva, L.S.; Simoes, A.N.; Bispo, A.; Ribeiro, M.A.; Gama, L., E-mail: lsoutoneiva@yahoo.com.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Aademica de Engenharia de Materiais

2011-07-01

This work relates the synthesis process of CuO/CeO{sub 2} catalytic materials by a combustion reaction method as well as it introduces a structural analysis of the developed material, this structural analysis had as main focus to evaluate the influence of the doping substance (CuO) when being incorporated in the hostess matrix structure that is CeO{sub 2}. The CuO/CeO catalytic materials developed in this work are destined to preferential oxidation of CO reaction (PROX). The developed materials were characterized by XRD, SEM and textural complete analysis by the BET method. According to the results, the CuO incorporation changed crystallinity of the structure of the catalytic materials. On the other hand, the morphologic and textural characteristics did not showed significant differences regarding the presence of the doping substance (CuO) in the structure of the developed materials. The porosity of the structures of the developed catalytic materials belongs to the type macroporous. (author)

CuGaTe2-CuAlTe2 system

International Nuclear Information System (INIS)

Bodnar', I.V.

2003-01-01

The results of studies on the chemical interaction in the CuGaTe 2 -CuAlTe 2 as well as on the thermal and optical properties of the formed solid solutions are presented. It is shown, that continuous number of solid solutions are formed in the CuGaTe 2 -CuAlTe 2 system, which crystallize in the chalcopyrite structure. The diagram of state of this system is plotted. The thermal expansion of these materials is studied through the dilatometric method. The linear dependence of the thermal expansion coefficient on the composition is established. The concentration dependences of the forbidden zone width diverge from the linearity [ru

Understanding lattice defects to influence ferromagnetic order of ZnO nanoparticles by Ni, Cu, Ce ions

Energy Technology Data Exchange (ETDEWEB)

Verma, Kuldeep Chand, E-mail: dkuldeep.physics@gmail.com [Department of Physics, Panjab University, Chandigarh 160014 (India); Kotnala, R.K., E-mail: rkkotnala@gmail.com [CSIR-National Physical Laboratory, New Delhi 110012 (India)

2017-02-15

Future spintronics technologies based on diluted magnetic semiconductors (DMS) will rely heavily on a sound understanding of the microscopic origins of ferromagnetism in such materials. It remains unclear, however, whether the ferromagnetism in DMS is intrinsic - a precondition for spintronics - or due to dopant clustering. For this, we include a simultaneous doping from transition metal (Ni, Cu) and rare earth (Ce) ions in ZnO nanoparticles that increase the antiferromagnetic ordering to achieve high-T{sub c} ferromagnetism. Rietveld refinement of XRD patterns indicate that the dopant ions in ZnO had a wurtzite structure and the dopants, Ni{sup 2+}, Cu{sup 2+}, Ce{sup 3+} ions, are highly influenced the lattice constants to induce lattice defects. The Ni, Cu, Ce ions in ZnO have nanoparticles formation than nanorods was observed in pure sample. FTIR involve some organic groups to induce lattice defects and the metal-oxygen bonding of Zn, Ni, Cu, Ce and O atoms to confirm wurtzite structure. Raman analysis evaluates the crystalline quality, structural disorder and defects in ZnO lattice with doping. Photoluminescence spectra have strong near-band-edge emission and visible emission bands responsible for defects due to oxygen vacancies. The energy band gap is calculated using Tauc relation. Room temperature ferromagnetism has been described due to bound magnetic polarons formation with Ni{sup 2+}, Cu{sup 2+}, Ce{sup 3+} ions in ZnO via oxygen vacancies. The zero field and field cooling SQUID measurement confirm the strength of antiferromagnetism in ZnO. The field cooling magnetization is studied by Curie-Weiss law that include antiferromagnetic interactions up to low temperature. The XPS spectra have involve +3/+4 oxidation states of Ce ions to influence the observed ferromagnetism. - Graphical abstract: The lattice defects/vacancies attributed by Ni and Ce ions in the wurtzite ZnO structure are responsible in high T{sub c} -ferromagnetism due to long-range magnetic

Structure and photocatalytic activity studies of TiO2-supported over Ce-modified Al-MCM-41

International Nuclear Information System (INIS)

Krishna Reddy, Jakkidi; Durgakumari, Valluri; Subrahmanyam, Machiraju; Sreedhar, Bojja

2009-01-01

Ce-Al-MCM-41, TiO 2 /Al-MCM-41 and TiO 2 /Ce-Al-MCM-41 materials with varying contents of Ce (by impregnation) and TiO 2 loaded (by solid-state dispersion) on Al-MCM-41 support are prepared. The Ce modified and TiO 2 loaded composite systems are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS) techniques. The DRS and XPS of low Ce content (0.2-0.5 wt.%) modified Al-MCM-41 samples are showing more characteristic of Ce 3+ species wherein cerium in interaction with Al-MCM-41 and that of high Ce (0.8, 3.0 wt.%) content modified samples are showing the characteristic of both Ce 4+ and Ce 3+ species. A series of Ce-modified Al-MCM-41 and TiO 2 loaded composite catalysts are evaluated for photocatalytic degradation of phenol under UV irradiation. Low Ce content in Ce 3+ state on Al-MCM-41 is showing good photoactivity in comparison with high Ce content samples and pure ceria. The composite TiO 2 /Ce-Al-MCM-41 is showing enhanced degradation activity due decreased rate of electron-hole recombination on TiO 2 surface by the redox properties of cerium. The photocatalyst TiO 2 /Ce-Al-MCM-41 with an optimum of 10 wt.% TiO 2 and 0.3 wt.% Ce is showing maximum phenol degradation activity. The possible mechanism of phenol degradation on the composite photocatalyst is proposed.

Luminescent and scintillation properties of the Ce3+ doped Y3−xLuxAl5O12:Ce single crystalline films

International Nuclear Information System (INIS)

Zorenko, Yu.; Gorbenko, V.; Zorenko, T.; Popielarski, P.; Mosińska, L.; Fedorov, A.

2016-01-01

The work is related to the investigation of scintillation and luminescent properties of single crystalline films (SCF) of solid solutions of Ce 3+ doped Y 3−x Lu x Al 5 O 12 :Ce garnets with x value in the 0–3 range. We have shown a possibility of realization of high-energy shift of the Ce 3+ ion emission spectrum in these garnets up to 22 nm. We have also found that the light yield of the radioluminescence under α-particle excitation of LuAG:Ce SCF can exceed by 1.3 times the corresponding values for the YAG:Ce SCF counterpart. For investigation of the luminescent properties of Y 3−x Lu x Al 5 O 12 :Ce SCF at different x values the luminescent spectroscopy of these SCFs under excitation by synchrotron radiation in the VUV range was performed. - Highlights: • Single crystalline films of Y 3−x Lu x Al 5 O 12 garnets at x=0–3.0 were grown by LPE method onto YAG substrates. • Lattice constant of Y 3−x Lu x Al 5 O 12 :Ce film and the film/substrate misfit changed linearly with increasing of Lu content in the x=0–3.0 range. • High-energy shift of the Ce 3+ emission up to 22 nm in Y 3−x Lu x Al 5 O 12 film with increasing of Lu content in the x=0–3.0 range. • Light yield of Y 3−x Lu x Al 5 O 12 :Ce film decreases in the x=0–1.8 range and increases in the x=1.8–3.0 range. • Scintillation LY of Lu 3 Al 5 O 12 :Ce film can exceed by 1.3 times the LY for YAG:Ce film counterpart.

The high-pressure phase of CePtAl

International Nuclear Information System (INIS)

Heymann, Gunter; Heying, Birgit; Rodewald, Ute C.; Janka, Oliver; Univ. Oldenburg

2017-01-01

The intermetallic aluminum compound HP-CePtAl was synthesized by arc melting of the elements with subsequent high-pressure/high-temperature treatment at 1620 K and 10.5 GPa in a multianvil press. The compound crystallizes in the hexagonal MgZn_2-type structure (P6_3/mmc) with lattice parameters of a=552.7(1) and c=898.8(2) pm refined from powder X-ray diffraction data. With the help of single crystal investigations (wR=0.0527, 187 F"2 values, 13 variables), the proposed structure type was confirmed and the mixed Pt/Al site occupations could be refined. Magnetic susceptibility measurements showed a disappearance of the complex magnetic ordering phenomena, which are observed in NP-CePtAl.

The high-pressure phase of CePtAl

Energy Technology Data Exchange (ETDEWEB)

Heymann, Gunter [Univ. Innsbruck (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie; Heying, Birgit; Rodewald, Ute C. [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie; Univ. Oldenburg (Germany). Inst. fuer Chemie

2017-03-01

The intermetallic aluminum compound HP-CePtAl was synthesized by arc melting of the elements with subsequent high-pressure/high-temperature treatment at 1620 K and 10.5 GPa in a multianvil press. The compound crystallizes in the hexagonal MgZn{sub 2}-type structure (P6{sub 3}/mmc) with lattice parameters of a=552.7(1) and c=898.8(2) pm refined from powder X-ray diffraction data. With the help of single crystal investigations (wR=0.0527, 187 F{sup 2} values, 13 variables), the proposed structure type was confirmed and the mixed Pt/Al site occupations could be refined. Magnetic susceptibility measurements showed a disappearance of the complex magnetic ordering phenomena, which are observed in NP-CePtAl.

Hydrodeoxygenation of furfuryl alcohol over Cu/MgAl and Cu/ZnAl catalysts derived from hydrotalcite-like precursors

Directory of Open Access Journals (Sweden)

Natalia Andrea Pino

2017-01-01

Full Text Available The aqueous phase hydrodeoxygenation (HDO of furfuryl alcohol over Cu/MgAl and Cu/ZnAl catalysts with different Mg/Al and Zn/Al molar ratios, were investigated. Mg-Al and Zn-Al mixed oxides derived from hydrotalcites precursors were used as supports, which were impregnated with an aqueous solution of copper nitrate by incipient wetness impregnation. The HDO reaction was carried out in a typical batch reactor at 5 MPa of H2 and 200 °C for 4 h. Among the catalysts studied, the Cu/MgAl-0.5 catalyst exhibited the higher furfuryl alcohol conversion (86% and yield of cyclopentanol (35%, which is the reaction product with the highest hydrogen-carbon (H/C ratio. With the Cu/MgAl-3 catalyst a high cyclopentanone yield (67% was achieved. The results obtained, showed that copper supported on mixed oxides catalysts derived from hydrotalcite precursors are a promising alternative to improve the bio-oil quality.

Zr-(Cu,Ag)-Al bulk metallic glasses

International Nuclear Information System (INIS)

Jiang, Q.K.; Wang, X.D.; Nie, X.P.; Zhang, G.Q.; Ma, H.; Fecht, H.-J.; Bendnarcik, J.; Franz, H.; Liu, Y.G.; Cao, Q.P.; Jiang, J.Z.

2008-01-01

In this paper, we report the formation of a series Zr-(Cu,Ag)-Al bulk metallic glasses (BMGs) with diameters at least 20 mm and demonstrate the formation of about 25 g amorphous metallic ingots in a wide Zr-(Cu,Ag)-Al composition range using a conventional arc-melting machine. The origin of high glass-forming ability (GFA) of the Zr-(Cu,Ag)-Al alloy system has been investigated from the structural, thermodynamic and kinetic points of view. The high GFA of the Zr-(Cu,Ag)-Al system is attributed to denser local atomic packing and the smaller difference in Gibbs free energy between amorphous and crystalline phases. The thermal, mechanical and corrosion properties, as well as elastic constants for the newly developed Zr-(Cu,Ag)-Al BMGs, are also presented. These newly developed Ni-free Zr-(Cu,Ag)-Al BMGs exhibit excellent combined properties: strong GFA, high strength, high compressive plasticity, cheap and non-toxic raw materials and biocompatible property, as compared with other BMGs, leading to their potential industrial applications

First-principle Calculations of Mechanical Properties of Al2Cu, Al2CuMg and MgZn2 Intermetallics in High Strength Aluminum Alloys

Directory of Open Access Journals (Sweden)

LIAO Fei

2016-12-01

Full Text Available Structural stabilities, mechanical properties and electronic structures of Al2Cu, Al2CuMg and MgZn2 intermetallics in Al-Zn-Mg-Cu aluminum alloys were determined from the first-principle calculations by VASP based on the density functional theory. The results show that the cohesive energy (Ecoh decreases in the order MgZn2 > Al2CuMg > Al2Cu, whereas the formation enthalpy (ΔH decreases in the order MgZn2 > Al2Cu > Al2CuMg. Al2Cu can act as a strengthening phase for its ductile and high Young's modulus. The Al2CuMg phase exhibits elastic anisotropy and may act as a crack initiation point. MgZn2 has good plasticity and low melting point, which is the main strengthening phase in the Al-Zn-Mg-Cu aluminum alloys. Metallic bonding mode coexists with a fractional ionic interaction in Al2Cu, Al2CuMg and MgZn2, and that improves the structural stability. In order to improve the alloys' performance further, the generation of MgZn2 phase should be promoted by increasing Zn content while Mg and Cu contents are decreased properly.

Facile synthesis of dendritic Cu by electroless reaction of Cu-Al alloys in multiphase solution

Science.gov (United States)

Wang, Ying; Liang, Shuhua; Yang, Qing; Wang, Xianhui

2016-11-01

Two-dimensional nano- or micro-scale fractal dendritic coppers (FDCs) were synthesized by electroless immersing of Cu-Al alloys in hydrochloric acid solution containing copper chloride without any assistance of template or surfactant. The FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl2 + HCl solution. Compared to Cu40Al60 and Cu45Al55 alloys, the FDC shows hierarchical distribution and homogeneous structures using Cu17Al83 alloy as the starting alloy. The growth direction of the FDC is , and all angles between the trunks and branches are 60°. Nanoscale Cu2O was found at the edge of FDC. Interestingly, nanoporous copper (NPC) can also be obtained through Cu17Al83 alloy. Studies showed that the formation of FDC depended on two key factors: the potential difference between CuAl2 intermetallic and α-Al phase of dual-phase Cu-Al alloys; a replacement reaction that usually occurs in multiphase solution. The electrochemical experiment further proved that the multi-branch dendritic structure is very beneficial to the proton transfer in the process of catalyzing methanol.

Thermopower studies of doped CeAl sub 2 and UAl sub 2

CERN Document Server

Park, J G

1997-01-01

We have studied the thermopower of U doped CeAl sub 2 and Ce and La doped UAl sub 2. Despite different ground state properties of CeAl sub 2 and UAl sub 2 , the former being an antiferromagnetic heavy-fermion compound and the latter non-magnetic, we have found that not only thermopower data for pure CeAl sub 2 and UAl sub 2 are similar but also the thermopower results of doped samples behave similarly. Although the similarity seen in pure systems is yet to be understood, we interpret the doping effects as the results of changes in energy dependent relaxation time with doping. (author)

Phase relationships in the Al-rich region of the Al-Cu-Er system

International Nuclear Information System (INIS)

Zhang Ligang; Masset, Patrick J.; Cao Fuyong; Meng Fangui; Liu Libin; Jin Zhanpeng

2011-01-01

Research highlights: → One ternary phase τ 1 -Al 8 Cu 4 Er in Al-rich region with a composition of 59.4-60.4 at.% Al, 32.2-33.8 at.% Cu, and 6.4-7.7 at.% Er is observed in both as-cast and annealed alloys. At 673 K, the binary Al 3 Er phase dissolves about 3.51 at.% Cu. → The calculated solidification paths (based on the CALPHAD method) of as-cast alloys are in agreement with the experimental results. → It can be found that the resultant thermodynamic database can be applied to case studies of as-cast alloys, showing that the literature thermodynamic description of the Al-Cu-Er system is reliable as a working basis for computer-assisted alloy design. - Abstract: The Al-rich region of the ternary Al-Cu-Er system is investigated using the method of X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy. Phase equilibria in the Al-rich region of the Al-Cu-Er system at 673 K have been obtained, and the microstructures of as-cast alloys in the Al-rich region are also investigated. One ternary phase τ 1 -Al 8 Cu 4 Er with a composition of 59.4-60.4 at.% Al, 32.2-33.8 at.% Cu, and 6.4-7.7 at.% Er is observed in both as-cast and annealed alloys. At 673 K, the binary Al 3 Er phase dissolves about 3.51 at.% Cu. The calculated solidification paths (based on the CALPHAD method) of as-cast alloys are in agreement with the experimental results.

NMR and NQR study of the electronic and structural properties of Al-Cu-Fe and Al-Cu-Ru quasicrystals

International Nuclear Information System (INIS)

Shastri, A.; Borsa, F.; Torgeson, D.R.; Shield, J.E.; Goldman, A.I.

1994-01-01

27 Al and 63,65 Cu NMR is reported for powdered stable Al-Cu-Fe and Al-Cu-Ru icosahedral quasicrystals and crystalline approximants, and for an Al-Pd-Mn single-grain quasicrystal. 27 Al NQR spectra at 4.2 K were observed in Al-Cu-Fe and Al-Cu-Ru samples. From quadrupole-perturbed NMR spectra at different magnetic fields, and from zero-field NQR spectra, a wide distribution of local electric-field gradient (EFG) tensor components and principal-axis-system orientations was found at the Al site. A model EFG calculation based on a 1/1 Al-Cu-Fe approximant successfully explained the observed NQR spectra. The average local gradient is largely determined by the p-electron wave function at the Al site, while the width of the distribution is due to EFG lattice contribution. Comparison of 63 Cu and 27 Al NMR shows the EFG distribution at the two sites is similar, but the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more s-type wave function of the conduction electrons. Overall spread of EFG values is well reproduced by calculation based on the approximant. However, the experimental spectra indicate a much larger number of nonequivalent sites when compared with the simulated NQR spectra based on the 1/1 approximant. The short-range, local chemical order is well represented by the approximant, but differences in coordination must be included at intermediate range in the quasicrystal. Measured 27 Al Knight shift, magnetic susceptibility, and nuclear spin-lattice relaxation time as a function of temperature indicate reduced density of states at the Fermi level by a factor of 7 or 8 from the value in Al metal, consistent with the notion of a pseudogap for these quasicrystals. No differences in measured parameters were detected as a function of composition of the quasicrystalline alloys

Development of accident tolerant FeCrAl-ODS steels utilizing Ce-oxide particles dispersion

Science.gov (United States)

Shibata, Hiroki; Ukai, Shigeharu; Oono, Naoko H.; Sakamoto, Kan; Hirai, Mutsumi

2018-04-01

FeCrAl-ODS ferritic steels with Ce-oxide dispersion instead of Y-oxide were produced for the accident tolerant fuel cladding of the light water reactor. Excess oxygen (Ex.O) was added to improve the mechanical property. The tensile strength at Ex.O = 0 is around 200 MPa at 700 °C, mainly owing to dispersed Ce2O3 particles in less than 10 nm size. The formation of the fine Ce2O3 particles is dominated by a coherent interface with ferritic matrix. With increasing Ex.O, an increased of number density of coarser Ce-Al type oxide particles over 10 nm size is responsible for the improvement of the tensile strength. Change of the type of oxide particle, CeO2, Ce2O3, CeAlO3, Al2O3, in FeCrAl-ODS steel was thermodynamically analyzed as a parameter of Ex.O.

Order parameter in CeCu{sub 2}Si{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Vieyra, Hugo A.; Brando, Manuel; Oeschler, Niels; Seiro, Silvia; Geibel, Christoph; Steglich, Frank [Max-Planck-Institute for Chemical Physics of Solids, Dresden (Germany); Jeevan, Hirale S. [I. Physikalisches Institut, Georg-August-Universitaet Goettingen (Germany); Parker, David [US Naval Research Laboratory, Washington, DC (United States)

2011-07-01

Understanding the interplay between magnetism and unconventional superconductivity remains a key challenge in solid-state physics. A clear example is the archetypical heavy-fermion compound CeCu{sub 2}Si{sub 2} which exhibits superconductivity (T{sub c}=600 mK) in the vicinity of a magnetic quantum critical point. It is believed that magnetic fluctuations mediate superconductivity and its order parameter possesses d-wave symmetry, both ideas still under debate. In this work, a high-quality single crystal with a purely superconducting ground state (S type) has been chosen to investigate the low-temperature thermal- and electric-transport characteristics of the superconducting state. Non-vanishing contributions of low-energy quasiparticle excitations to the thermal transport ({kappa}{sub 0}/T>0) suggest the presence of nodal structure in CeCu{sub 2}Si{sub 2}. In turn, angle-dependent resistivity measurements of the upper critical field H{sub c2} point towards unconventional superconductivity with d-wave symmetry of the order parameter. Theoretical calculations reveal the strong influence of Pauli paramagnetic effects and a d{sub xy} symmetry of the gap function.

Magnetic and transport properties of amorphous Ce-Al alloy

Science.gov (United States)

Amakai, Yusuke; Murayama, Shigeyuki; Momono, Naoki; Takano, Hideaki; Kuwai, Tomohiko

2018-05-01

Amorphous (a-)Ce50Al50 has been prepared by DC high-rate sputter method. The structure of the obtained sample has been confirmed to have an amorphous structure because there are no Bragg peaks in the X-ray diffraction measurement and have a clear exothermic peak by the differential scanning calorimetry measurement. We have measured the resistivity ρ, magnetic susceptibility χ, specific heat Cp and thermoelectric power S for a-Ce50Al50. The temperature dependence of ρ exhibits a small temperature dependence less than 10% in the whole temperature region. χ follows a Curie-Weiss behavior in the high-temperature region of T>90 K. The effective paramagnetic moment peff, estimated from C is 2.18 μB/Ce-atom. The low-temperature Cp/T increases rapidly with decreasing temperature and tends to a saturation. S(T) exhibits negative values in a wide temperature region. A minimum of S appear at around 60 K, and S decreases linearly with decreasing temperature down to 10 K. The low-temperature S is almost 0 μV/K down to 2 K. From these results, we have pointed out that present a-Ce50Al50 would be an incoherent Kondo material.

Luminescent properties of Y3Al5−xGaxO12:Ce crystals

International Nuclear Information System (INIS)

Zorenko, Yu.; Zorenko, T.; Malinowski, P.; Sidletskiy, O.; Neicheva, S.

2014-01-01

Absorption, luminescent and scintillation properties of Ce 3+ doped Y 3 Al 5−x Ga x O 12 crystals with Ga content in the x=1–5 range were investigated in this work and compared with the properties of YAG:Ce crystals. Apart from the traditional spectral methods (absorption, cathodoluminescence and light yield measurements), the intrinsic and Ce 3+ related luminescence of Y 3 Al 5−x Ga x O 12 :Ce solid-solution were also investigated using the luminescent spectroscopy under excitation by synchrotron radiation in the 3.7–25 eV range. We show that the optical properties Y 3 Al 5−x Ga x O 12 :Ce garnets monotonically change with increasing the Ga content in the x=0–3 range due to preferable localization of Ga ions in the tetrahedral position of the garnet lattice. At the highest Ga concentration (x>3) the deviation of the optical properties of Y 3 Al 5−x Ga x O 12 :Ce garnets is observed from the respective properties of these crystals with Ga content in the x=0–3 range due to occupation by Ga ions of the octahedral position in the garnet host. - Highlights: • Different dependence of optical properties of Y 3 Al 5−x Ga x O 12 :Ce crystals on Ga content in x=0–3 and 3–5 ranges. • Elimination of the luminescence of Y Al antisite defects in Y 3 Al 5−x Ga x O 12 :Ce crystals at x>2. • Significant improvement of the scintillation properties of Y 3 Al 5−x Ga x O 12 :Ce crystals at x=2 and 3 in comparison with YAG:Ce

Effect of Cu{sup 2+}/Al{sup 3+} mole ratio on structure of Cu-Al bimetallic nanoparticles prepared by radiation induced method

Energy Technology Data Exchange (ETDEWEB)

Abedini, Alam; Larki, Farhad; Saion, Elias; Noroozi, Monir [Putra Malaysia Univ., Serdang, Selangor (Malaysia). Dept. of Physics

2013-07-15

Cu-Al bimetallic nanoparticles were synthesized by gamma irradiation technique in aqueous solutions containing metal chlorides as precursors, polyvinyl alcohol (PVA) as a capping agent, isopropanol as a radical scavenger, and distilled water as a solvent. The Cu-Al bimetallic nanoparticles were characterized by transmission electron microscopy (TEM), UV-visible absorption spectrometry, powder X-ray diffractometer (XRD), and Energy-dispersive X-ray spectroscopy (EDX). The TEM, XRD, EDX, and absorption analyses confirmed the formation of core-shell structure of Cu-Al bimetallic nanoparticles at lower Cu{sup 2+}/Al{sup 3+} mole ratio, and the formation of Cu-Al alloy nanoparticles at higher Cu{sup 2+}/Al{sup 3+} mole ratio. The TEM analysis for particle size and size distribution revealed that the average particle size of Cu-Al bimetallic nanoparticles decreased with the increase of absorbed dose. It may be explained due to the competition between nucleation and aggregation processes in the formation of metallic nanoparticles under irradiation. (orig.)

Performance of Mg-14Li-1Al-0.1Ce as anode for Mg-air battery

Energy Technology Data Exchange (ETDEWEB)

Ma, Yibin; Li, Deyu [School of Chemical Engineering and Technology, Harbin Institute of Technology, West Street No. 92, Harbin 150001 (China); Li, Ning [School of Chemical Engineering and Technology, Harbin Institute of Technology, West Street No. 92, Harbin 150001 (China); Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Zhang, Milin; Huang, Xiaomei [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)

2011-02-15

In this research, a new Mg-air battery based on Mg-14Li-1Al-0.1Ce was prepared and the battery performance was investigated by constant current discharge test. The corrosion behavior of Mg, AZ31 and Mg-Li-Al-Ce were studied by self-corrosion rate measurement and potentiodynamic polarization measurement. The characteristics of Mg-Li-Al-Ce after discharge were investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that Mg-Li-Al-Ce is more active than Mg and AZ31. The self-corrosion rate is found to be in the order: Mg-Li-Al-Ce < Mg < AZ31. It has been observed that the Mg-air battery based on Mg-Li-Al-Ce offers higher operating voltage, anodic efficiency and capacity than those with Mg and AZ31. SEM and EIS results show that the discharge product of Mg-Li-Al-Ce is loosely adhered to the alloy surface, and thus Mg-Li-Al-Ce could keep high discharge activity during discharge. (author)

Microstructural stability of heat-resistant high-pressure die-cast Mg-4Al-4Ce alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, Wei; Zhang, Jinghuai; Li, Guoqiang; Feng, Yan; Su, Minliang; Wu, Ruizhi; Zhang, Zhongwu [Harbin Engineering Univ. (China). Key Laboratory of Superlight Material and Surface Technology; Jiao, Yufeng [Jiamusi Univ. (China). College of Materials Science and Engineering

2017-05-15

The thermal stability of Al-RE (rare earth) intermetallic phases with individual RE for heat-resistant high-pressure die-casting Mg-Al-RE alloys is investigated. The results of this study show that the main strengthening phase of Mg-4Al-4Ce alloy is Al{sub 11}Ce{sub 3}, whose content is about 5 wt.% according to quantitative X-ray diffraction phase analysis. The Al{sub 11}Ce{sub 3} phase appears to have high thermal stability at 200 C and 300 C, while phase morphology change with no phase structure transition could occur for Al{sub 11}Ce{sub 3} when the temperature reaches 400 C. Furthermore, besides the kinds of rare earths and temperature, stress is also an influencing factor in the microstructural stability of Mg-4Al-4Ce alloy.

Purification of hydrogen from carbon monoxide for fuel cell application over modified mesoporous CuO-CeO2 catalysts

KAUST Repository

Li, Jing

2011-08-01

Selective oxidation of CO in H2-rich streams was carried out over a series of CuO-CeO2 catalysts doped by different transition metals (Mn, Fe, Ni, Ti, Co and Cr). The effect of the dopants on the structure and catalytic properties of CuO-CeO2 catalysts was investigated by N2 adsorption/desorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectra and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques. The results show that the addition of Mn and Fe plays a beneficial role in extending the low-temperature catalytic activity of CuO-CeO2 catalysts, whereas the introduction of Cr and Co leads to a negative effect on the catalytic activity and resistance against CO2 and H2O. The superior catalytic performance of CuO-CeO2 catalysts with Mn and Fe doping originates from the enhanced interaction between copper and ceria, owing to the formation of more Cu+ and oxygen vacancies in the solid solution framework. While the poor catalytic activity of the Co doped counterpart is mainly ascribed to the substitution of introduced cobalt ions for copper ions in ceria lattice, resulting in the segregation of copper ions from the ceria lattice and the consequent aggregation of copper species on the ceria surface. The doping of Cr into CuO-CeO2 structure remarkably weakens the interaction between copper and ceria, which decreases the reducibility of copper species and inhibits the formation of Cu+. It accounts for the lowest catalytic activity. © 2011 Elsevier B.V.

Purification of hydrogen from carbon monoxide for fuel cell application over modified mesoporous CuO-CeO2 catalysts

KAUST Repository

Li, Jing; Han, Yuxi; Zhu, Yihan; Zhou, Renxian

2011-01-01

Selective oxidation of CO in H2-rich streams was carried out over a series of CuO-CeO2 catalysts doped by different transition metals (Mn, Fe, Ni, Ti, Co and Cr). The effect of the dopants on the structure and catalytic properties of CuO-CeO2 catalysts was investigated by N2 adsorption/desorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectra and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) techniques. The results show that the addition of Mn and Fe plays a beneficial role in extending the low-temperature catalytic activity of CuO-CeO2 catalysts, whereas the introduction of Cr and Co leads to a negative effect on the catalytic activity and resistance against CO2 and H2O. The superior catalytic performance of CuO-CeO2 catalysts with Mn and Fe doping originates from the enhanced interaction between copper and ceria, owing to the formation of more Cu+ and oxygen vacancies in the solid solution framework. While the poor catalytic activity of the Co doped counterpart is mainly ascribed to the substitution of introduced cobalt ions for copper ions in ceria lattice, resulting in the segregation of copper ions from the ceria lattice and the consequent aggregation of copper species on the ceria surface. The doping of Cr into CuO-CeO2 structure remarkably weakens the interaction between copper and ceria, which decreases the reducibility of copper species and inhibits the formation of Cu+. It accounts for the lowest catalytic activity. © 2011 Elsevier B.V.

Comparison of Efficiencies and Mechanisms of Catalytic Ozonation of Recalcitrant Petroleum Refinery Wastewater by Ce, Mg, and Ce-Mg Oxides Loaded Al2O3

Directory of Open Access Journals (Sweden)

Chunmao Chen

2017-02-01

Full Text Available The use of catalytic ozonation processes (COPs for the advanced treatment of recalcitrant petroleum refinery wastewater (RPRW is rapidly expanding. In this study, magnesium (Mg, cerium (Ce, and Mg-Ce oxide-loaded alumina (Al2O3 were developed as cost efficient catalysts for ozonation treatment of RPRW, having performance metrics that meet new discharge standards. Interactions between the metal oxides and the Al2O3 support influence the catalytic properties, as well as the efficiency and mechanism. Mg-Ce/Al2O3 (Mg-Ce/Al2O3-COP reduced the chemical oxygen demand by 4.7%, 4.1%, 6.0%, and 17.5% relative to Mg/Al2O3-COP, Ce/Al2O3-COP, Al2O3-COP, and single ozonation, respectively. The loaded composite metal oxides significantly increased the hydroxyl radical-mediated oxidation. Surface hydroxyl groups (–OHs are the dominant catalytic active sites on Al2O3. These active surface –OHs along with the deposited metal oxides (Mg2+ and/or Ce4+ increased the catalytic activity. The Mg-Ce/Al2O3 catalyst can be economically produced, has high efficiency, and is stable under acidic and alkaline conditions.

Model for the orientation, magnetic field, and temperature dependence of the specific heat of CeCu6

International Nuclear Information System (INIS)

Edelstein, A.S.

1988-01-01

The results of a model calculation of the orientation, magnetic field, and temperature dependence of the specific heat C of CeCu 6 are found to be in good agreement with the single-crystal data of Amato et al. The model incorporates both the Kondo and crystal-field effects. It is suggested that the low-temperature Wilson's ratio CTchi, where chi is the susceptibility, may not change in an applied field H and that both CT and chi at low temperatures as a function of H may be proportional to the many-body density of states at the energy μH

Phase equilibria in Dy-Cu-Al system at 500 deg C

International Nuclear Information System (INIS)

Kuz'ma, Yu.B.; Milyan, V.V.

1989-01-01

Using the methods of X-ray diffraction analysis a diagram of phase equilibria in Dy-Cu-Al system at 500 deg C is plotted. Boundaries of solid solutions on the basis of DyCu 2 , DyCu and DyAl 2 compounds are determined and homogeneity regions of ternary compounds Dy 2 (Cu, Al) 7 and Dy(CuAl) 5 are ascertained. Compounds DyCuAl 3 , Dy 4 Cu 4 Al 11 and Dy 5 Cu 6 Al 9 have been detected for the first time

One-pot hydrothermal growth of raspberry-like CeO{sub 2} on CuO microsphere as copper-based catalyst for Rochow reaction

Energy Technology Data Exchange (ETDEWEB)

Jin, Zheying [School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Li, Jing [State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Shi, Laishun, E-mail: lshunsh@sdu.edu.cn [School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Ji, Yongjun, E-mail: yjji@ipe.ac.cn [State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Zhong, Ziyi [School of Chemical & Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459 (Singapore); Su, Fabing, E-mail: fbsu@ipe.ac.cn [State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China)

2015-12-30

Graphical abstract: - Highlights: • Ce–CuO composites were prepared via a one-pot and template-free hydrothermal method. • Ce–CuO consisted of raspberry-like CeO{sub 2} particles dispersed on porous CuO microspheres. • CuO microspheres were formed by self-assembly of nanorods. • Ce–CuO exhibited superior catalytic activity for dimethyldichlorosilane synthesis. - Abstract: In this work, we prepared a novel structure comprising of raspberry-like CeO{sub 2} deposited on CuO microspheres (Ce–CuO) for Rochow reaction. The synthesis was carried out via a facile one-pot hydrothermal reaction without using any template, in which, the basic copper carbonate microspheres were first formed via self-assembly of basic copper carbonate nanorods, followed with deposition of cerium hydroxide. After calcination, they were transformed into Ce–CuO but still maintained the hierarchical structure, and meanwhile, mesoporous structure was formed (for simplicity, we will only state them as metal oxide in the following context). The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM) techniques. When used as a Cu-based catalyst, Ce–CuO exhibited superior catalytic property to the single CuO, CeO{sub 2} and their physically mixture in the Rochow reaction with dimethyldichlorosilane (M2) selectivity increased from ca. 65 to 83.7%. The higher M2 selectivity of Ce–CuO is mainly due to its larger surface area and the synergistic effect between CuO and CeO{sub 2}. This work demonstrates that catalytic performance of the Cu-based can be improved by adding Ce rare-earth element and by carefully controlling their structures.

Unusual behavior of nuclear relaxation in CeCu2Si2 'possible evidence for triplet superconductivity'

International Nuclear Information System (INIS)

Kitaoka, Y.; Asayama, K.; Ueda, K.; Kohara, T.

1984-01-01

Nuclear relaxation of 63 Cu in the superconducting state of the Kondo-lattice system CeCu 2 Si 2 has been studied with the use of the 63 Cu nuclear quadrupole resonance technique under zero field and down to 65mK. The nuclear spin-lattice relaxation rate (1/T 1 ) decreases drastically just below Tsub(c)=0.67 K down to 0.5Tsub(c) without the apparent enhanced behavior and then is found to be almost temperature independent below 0.3Tsub(c). These results suggest that the superconductivity in CeCu 2 Si 2 is not in the usual BCS regime. The analysis based upon the existing triplet pairing model with an anisotropic energy gap describes well the behavior from Tsub(c) down to 0.5Tsub(c), while the temperature independence below 0.3Tsub(c) remains unexplained. (author)

Effect of Al-5Ti-0.62C-0.2Ce Master Alloy on the Microstructure and Tensile Properties of Commercial Pure Al and Hypoeutectic Al-8Si Alloy

Directory of Open Access Journals (Sweden)

Wanwu Ding

2017-06-01

Full Text Available Al-5Ti-0.62C-0.2Ce master alloy was synthesized by a method of thermal explosion reaction in pure molten aluminum and used to modify commercial pure Al and hypoeutectic Al-8Si alloy. The microstructure and tensile properties of commercial pure Al and hypoeutectic Al-8Si alloy with different additions of Al-5Ti-0.62C-0.2Ce master alloy were investigated. The results show that the Al-5Ti-0.62C-0.2Ce alloy was composed of α-Al, granular TiC, lump-like TiAl3 and block-like Ti2Al20Ce. Al-5Ti-0.62C-0.2Ce master alloy (0.3 wt %, 5 min can significantly refine macro grains of commercial pure Al into tiny equiaxed grains. The Al-5Ti-0.62C-0.2Ce master alloy (0.3 wt %, 30 min still has a good refinement effect. The tensile strength and elongation of commercial pure Al modified by the Al-5Ti-0.62C-0.2Ce master alloy (0.3 wt %, 5 min increased by roughly 19.26% and 61.83%, respectively. Al-5Ti-0.62C-0.2Ce master alloy (1.5 wt %, 10 min can significantly refine both α-Al grains and eutectic Si of hypoeutectic Al-8Si alloy. The dendritic α-Al grains were significantly refined to tiny equiaxed grains. The morphology of the eutectic Si crystals was significantly refined from coarse needle-shape or lath-shape to short rod-like or grain-like eutectic Si. The tensile strength and elongation of hypoeutectic Al-8Si alloy modified by the Al-5Ti-0.62C-0.2Ce master alloy (1.5 wt %, 10 min increased by roughly 20.53% and 50%, respectively. The change in mechanical properties corresponds to evolution of the microstructure.

Al-Si/Al2O3 in situ composite prepared by displacement reaction of CuO/Al system

Directory of Open Access Journals (Sweden)

Zhang Jing

2010-02-01

Full Text Available Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al. The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350 ℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/Al system was studied by using of differential scanning calorimetry(DSC and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu2O and Al2O3 at the melting temperature of the matrix alloy, and second, Cu2O reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750–780 ℃, the second step can also take place because of the effect of exothermic reaction of the first step.

Comment on “Synthesis of ceria (CeO_2 and CeO_2_−_x) nanoparticles via decarbonation and Ce(III) oxidation of synthetic bastnaesite (CeCO_3F)” by Montes-Hernandez et al

International Nuclear Information System (INIS)

Gysi, Alexander P.; Williams-Jones, Anthony E.

2016-01-01

Montes-Hernandez et al. [5] recently reported results of a study of the decarbonation of fine-grained synthetic bastnäsite-(Ce) precipitates involving the oxidation of Ce(III) to Ce(IV) and the formation of ceria (CeO_2 and CeO_2_-_x with oxygen vacancies) nano-particles. The purpose of their study was to show that oxidation of Ce(III) to Ce(IV) occurs spontaneously during heating of bastnäsite-(Ce) in air, a vacuum, N_2 or Ar gas. However, their interpretation of the formation of CeO_2 is not supported by the findings of Gysi and Williams-Jones [3], who showed that natural bastnäsite-(Ce) decomposes to form rare earth element (REE) oxyfluorides (REEOF). The latter was documented using differential scanning calorimetric (DSC) and thermogravimetric (TGA) experiments under a deoxygenated N_2 atmosphere. In their experiments, Gysi and Williams-Jones [3] found no evidence for the oxidation of Ce(III) to Ce(IV). This raises the question of whether the experiments of Montes-Hernandez et al. [5] in a N_2 atmosphere (and by extension in an Ar atmosphere) were compromised because of contamination by O_2 and that, as a result, they reached the erroneous conclusion that Ce(III) oxidizes spontaneously to Ce(IV) during heating of bastnäsite-(Ce) under these conditions. In order to explain the disagreement between their findings and those of Gysi and Williams-Jones [3], Montes-Hernandez et al. [5], proposed that the X-ray diffraction data of the former study were incorrectly interpreted. Here, we provide further evidence that the natural bastnäsite-(Ce) employed in the study by Gysi and Williams-Jones [3] decomposed to form REE oxyfluorides (i.e., CeOF, LaOF, PrOF and NdOF) and not CeO_2, and supply explanations for why Montes-Hernandez et al. [5] erroneously concluded that CeO_2 is produced during decomposition of this mineral under N_2 and Ar atmospheres. In so doing, we hope to provide new insights into the decomposition of bastnäsite-(Ce) that will help guide future

A Quantum Multicritical point in CeCu6-xAux

International Nuclear Information System (INIS)

Robinson, R.A.; Goossens, D.J.; Torikachvili, M.S.; Kakurai, K.

2005-01-01

Full text: CeCu 6-x Au x is a well-known heavy-fermion system in which the ground state is antiferromagnetically ordered for x > 0.1 and temperatures below 1K. Non-Fermi-liquid behaviour occurs around this critical concentration. The parent compound, CeCu 6 , exhibits a structural phase transition near 230K, where it changes from the Pnma orthorhombic room-temperature structure to the P21/c monoclinic structure. The monoclinicity increases as temperature falls, with β reaching 91.44 degrees at 10K. In the work presented here, powder neutron diffraction is used to explore the monoclinicity at 10K as a function of composition for 0.0 2 , suggests that the distortion vanishes by x = 0.14. A reanalysis of single-crystal diffraction data on the magnetically ordered side of the phase diagram indicate that long-range order disappears at the same critical concentration. At a minimum, the structural distortion and antiferromagnetism seem to be competing with each other, and this raises the intriguing possibility that lattice degrees of freedom are important in the non-Fermi-liquid regime. (authors)

Investigation of new type Cu-Hf-Al bulk glassy alloys

International Nuclear Information System (INIS)

Nagy, E; Ronto, V; Solyom, J; Roosz, A

2009-01-01

In the last years new type Cu-Hf-Al ternary alloys were developed with high glass forming ability and ductility. The addition of Al to Cu-Hf alloys results in improvements in glass formation, thermal stability and mechanical properties of these alloys. We have investigated new Cu-based bulk amorphous alloys in Cu-Hf-Al ternary system. The alloys with Cu 49 Hf 42 Al 9 , Cu 46 Hf 45 Al 9 , Cu 50 Hf 42.5 Al 7.5 and Cu 50 Hf 45 Al 5 compositions were prepared by arc melting. The samples were made by centrifugal casting and were investigated by X-ray diffraction method. Thermodynamic properties were examined by differential scanning calorimetry and the structure of the crystallising phases by scanning electron microscopy. The determination of liquidus temperatures of alloys were measured by differential thermal analysis.

Investigation of annealing treatment on the interfacial properties of explosive-welded Al/Cu/Al multilayer

International Nuclear Information System (INIS)

Honarpisheh, M.; Asemabadi, M.; Sedighi, M.

2012-01-01

Highlights: ► We studied explosive-welded Al/Cu/Al multilayer. ► We investigated heat treatment influence on the bond properties of Al/Cu/Al. ► Intermetallic compounds were studied using the SEM, OM and EDS analysis. ► Variations of hardness in the thickness were investigated using micro-hardness. ► Intermetallic phases such as AlCu 3 and Al 2 C create at the interface of Al/Cu/Al. -- Abstract: In this study, an Al/Cu/Al multilayer sheet was fabricated by explosive welding process and the effects of annealing temperature on the interfacial properties of explosively bonded Al/Cu bimetal have been investigated. For this purpose, hardness changes along the thickness of the samples have been measured, and the thickness and type of intermetallic compounds formed at the joining interface have been explored by means of optical microscopy (OM), scanning electron microscopy (SEM) and also energy dispersive spectroscopy (EDS). The obtained results indicate that, with the increase of the annealing temperature, the thickness of intermetallic compounds has increased and the amount of hardness along the thickness of the joining interface has diminished. In the annealed sample at 400 °C for 30 min, it was observed that intermetallic layers have formed at the interface of Al/Cu bimetals. These layers consist of the intermetallic compounds AlCu 3 , Al 2 Cu and AlCu, and their thickness gets to about 5 μm at some points. The examinations performed by the SEM, following the Vickers micro-hardness test, indicated the existence of a number of microcracks at the top and bottom interface of the sample annealed at 400 °C. This shows the formation of brittle intermetallic compounds at the joining interface, and also indicates the low ductility of these compounds.

Some crystal chemistry of (Ln,Ce)2CuO4-δ superconductors

International Nuclear Information System (INIS)

Goodman, P.; Keating, A.; Myhra, S.; White, T.J.

1989-01-01

Compounds of the form (Ln, Sr, Ce) 2 CuO 4-δ (Ln = rare earth element) crystallise as the Nd 2 CuO 4 structure type, K 2 NiF 4 structure type or perfectly and imperfectly ordered intergrowths of these parent structures. These structurally similar phases exhibit superconductivity in which the charge carriers are holes (in Sr-doped material) or electrons (in Ce doped material). In this study, X-ray Photoelectron Spectroscopy (XPS) and High Resolution Electron Microscopy (HREM) were used to investigate the charge balancing mechanisms operating in each superconducting regime and the structural changes accompanying compositional variation. It was found that under slightly reducing conditions charge coupled cation substitutions predominate, whilst at low pO 2 ( -5 atm) perfectly ordered oxygen superlattices form. The structural and electronic changes which accompany deoxygenation were observed in situ during XPS and HREM observations. 29 refs., 8 figs., 3 tabs

Mineralization of volatile organic compounds (VOCs) over the catalyst CuO-Co3O4-CeO2 and its applications in industrial odor control

KAUST Repository

Somekawa, Shouichi; Hagiwara, Toshiya; Fujii, Kyoko; Kojima, Masayuki; Shinoda, Tsutomu; Takanabe, Kazuhiro; Domen, Kazunari

2011-01-01

Volatile organic compounds (VOCs) present at ppm levels were decomposed over the catalyst CuO-Co3O4-CeO2 (Cu:Co:Ce = 10:45:45 in mol) in an attempt to scale up for industrial odor control. In addition to enhancing the catalytic activity, CuO-Co3O4 and CeO2 helped, respectively, to maintain the strength of the pelleted catalysts and inhibit their sintering. Using toluene as a VOC model compound, kinetic analysis of the total oxidation to carbon dioxide was conducted. The odor emitted from paint-drying processes could be eliminated effectively using CuO-Co3O4-CeO2 (Cu:Co:Ce = 10:45:45) pelleted catalysts (188 ml) in a large-scale system. © 2011 Elsevier B.V. All rights reserved.

Mineralization of volatile organic compounds (VOCs) over the catalyst CuO-Co3O4-CeO2 and its applications in industrial odor control

KAUST Repository

Somekawa, Shouichi

2011-12-01

Volatile organic compounds (VOCs) present at ppm levels were decomposed over the catalyst CuO-Co3O4-CeO2 (Cu:Co:Ce = 10:45:45 in mol) in an attempt to scale up for industrial odor control. In addition to enhancing the catalytic activity, CuO-Co3O4 and CeO2 helped, respectively, to maintain the strength of the pelleted catalysts and inhibit their sintering. Using toluene as a VOC model compound, kinetic analysis of the total oxidation to carbon dioxide was conducted. The odor emitted from paint-drying processes could be eliminated effectively using CuO-Co3O4-CeO2 (Cu:Co:Ce = 10:45:45) pelleted catalysts (188 ml) in a large-scale system. © 2011 Elsevier B.V. All rights reserved.

Microstructural characterization and compression properties of TiC0.61/Cu(Al) composite synthesized from Cu and Ti3AlC2 powders

International Nuclear Information System (INIS)

Huang, Zhenying; Bonneville, Joel; Zhai, Hongxiang; Gauthier-Brunet, Veronique

2014-01-01

Highlights: • Submicro-layered TiC 0.61 /Cu(Al) nanocomposite. • MAX phase. • High yield stress. • Deformation mechanism. - Abstract: A new submicro-layered TiC 0.61 /Cu(Al) composite has been prepared by hot-pressing a mixture of 50 vol.% Ti 3 AlC 2 and 50 vol.% Cu powders at 1150 °C and 30 MPa. It is shown that the initial reinforcement Ti 3 AlC 2 particles have, after synthesis, an unusual microstructure, which consists of submicron-thick layers of TiC 0.61 and Cu(Al) alloy. Both the width of the TiC 0.61 and Cu(Al) layers are ∼150 nm. Thus, the Ti 3 AlC 2 particles are decomposed into the TiC 0.61 phase, while the additional Al atoms provided by Ti 3 AlC 2 diffuse into the molten Cu matrix at high temperature. Compression tests were performed at constant strain rate in the temperature range 20–800 °C. The new designed TiC 0.61 /Cu(Al) composite has both a high yield stress, σ 0.2 measured at 0.2% strain offset, and a high ultimate compressive strength, σ UCS , which is attributed to strong interface bonding between TiC 0.61 and Cu(Al) phase. For instance, at 20 and 200 °C, σ 0.2 is 770 MPa and 700 MPa, while σ UCS is 1.18 GPa and 1 GPa, respectively. Plastic deformation takes place in the Cu(Al) matrix. Wavy slip lines are observed indicating that cross-slip could be the dominant deformation mechanism

Experimental and thermodynamic investigation of Al-Cu-Nd ternary system

Energy Technology Data Exchange (ETDEWEB)

Bai, W.M. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Jiang, Y. [Hunan Sushi Guangbo Testing Techniques Co. LTD, Changsha (China); Guo, Z.Y.; Zeng, L.J.; Tan, M.Y. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Meggs, C. [School of Metallurgy and Materials, The University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Zhang, L.G., E-mail: ligangzhang@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Liu, L.B., E-mail: pdc@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Jin, Z.P. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China)

2017-07-01

The phase relationships in the Al–Cu-Nd ternary system at 673 K have been investigated by X-ray powder diffraction (XRD) and scanning electron microscope (SEM) with energy disperse X-ray spectroscopy (EDS) in backscattered electron imaging (BSE) modes. The existence of six ternary Stoichiometric compounds, namely τ{sub 1}-Al{sub 8}Cu{sub 4}Nd, τ{sub 2}-Al{sub 9}Cu{sub 8}Nd{sub 2}, τ{sub 3}-Al{sub 6}Cu{sub 7}Nd, τ{sub 4}-Al{sub 2.4}Cu{sub 8.6}Nd, τ{sub 5}-Al{sub 3}CuNd, τ{sub 6}-AlCuNd, have been confirmed. A complete thermodynamic description of the Al–Cu-Nd ternary system coupled with the CALPHAD method is obtained based on experimental results and first-principles calculations. The calculated phase equilibria were in agreement with the available experimental data. - Highlights: • Phase relationships in the Al-Cu-Nd system has been systematically investigated. • 9 three-phase regions and 4 two-phase regions are confirmed. • A complete thermodynamic description of the Al-Cu-Nd system is obtained. • Results of first-principle calculation consist with thermodynamic calculation.

Mechanical properties of Al-Cu alloy-SiC composites

Science.gov (United States)

Anggara, B. S.; Handoko, E.; Soegijono, B.

2014-09-01

The synthesis of aluminum (Al) alloys, Al-Cu, from mixture 96.2 % Al and 3.8 % Cu has been prepared by melting process at a temperature of 1200°C. The adding 12.5 wt% up to 20 wt% of SiC on Al-Cu alloys samples has been investigated. The structure analyses were examined by X-Ray Diffractometer (XRD) and scanning electron microscope (SEM). Moreover, the morphology of Al-Cu alloys has been seen as structure in micrometer range. The hardness was measured by hardness Vickers method. According to the results, it can be assumed that the 15 wt% of SiC content is prefer content to get better quality of back to back hardness Vickers of Al-Cu alloys.

Mechanical properties of Al-Cu alloy-SiC composites

Energy Technology Data Exchange (ETDEWEB)

Anggara, B. S., E-mail: anggorobs1960@yahoo.com [Jurusan Fisika, FMIPA Universitas Negeri Jakarta, Indonesia 13220 and PPS Ilmu Material, Department Fisika, FMIPA, Universitas Indonesia (Indonesia); Handoko, E. [Jurusan Fisika, FMIPA Universitas Negeri Jakarta, 13220 (Indonesia); Soegijono, B. [PPS Ilmu Material, Department Fisika, FMIPA, Universitas Indonesia (Indonesia)

2014-09-25

The synthesis of aluminum (Al) alloys, Al-Cu, from mixture 96.2 % Al and 3.8 % Cu has been prepared by melting process at a temperature of 1200°C. The adding 12.5 wt% up to 20 wt% of SiC on Al-Cu alloys samples has been investigated. The structure analyses were examined by X-Ray Diffractometer (XRD) and scanning electron microscope (SEM). Moreover, the morphology of Al-Cu alloys has been seen as structure in micrometer range. The hardness was measured by hardness Vickers method. According to the results, it can be assumed that the 15 wt% of SiC content is prefer content to get better quality of back to back hardness Vickers of Al-Cu alloys.

Fragility and structure of Al-Cu alloy melts

International Nuclear Information System (INIS)

Lv Xiaoqian; Bian Xiufang; Mao Tan; Li Zhenkuan; Guo Jing; Zhao Yan

2007-01-01

The dynamic viscosity measurements are performed for Al-Cu alloy melts with different compositions using an oscillating-cup viscometer. The results show that the viscosities of Al-Cu alloy melts increase with the copper content increasing, and also have a correlation with the correlation radius of clusters, which is measured by the high-temperature X-ray diffractometer. It has also been found that the fragilities of superheated melts (M) of hypereutectic Al-Cu alloys increase with the copper content increasing. There exists a relationship between the fragility and the structure in Al-Cu alloy melts. The value of the M reflects the variation of activation energy for viscous flow

Massive spalling of Cu-Zn and Cu-Al intermetallic compounds at the interface between solders and Cu substrate during liquid state reaction

Science.gov (United States)

Kotadia, H. R.; Panneerselvam, A.; Mokhtari, O.; Green, M. A.; Mannan, S. H.

2012-04-01

The interfacial intermetallic compound (IMC) formation between Cu substrate and Sn-3.8Ag-0.7Cu-X (wt.%) solder alloys has been studied, where X consists of 0-5% Zn or 0-2% Al. The study has focused on the effect of solder volume as well as the Zn or Al concentration. With low solder volume, when the Zn and Al concentrations in the solder are also low, the initial Cu-Zn and Al-Cu IMC layers, which form at the solder/substrate interface, are not stable and spall off, displaced by a Cu6Sn5 IMC layer. As the total Zn or Al content in the system increases by increasing solder volume, stable CuZn or Al2Cu IMCs form on the substrate and are not displaced. Increasing concentration of Zn has a similar effect of stabilizing the Cu-Zn IMC layer and also of forming a stable Cu5Zn8 layer, but increasing Al concentration alone does not prevent spalling of Al2Cu. These results are explained using a combination of thermodynamic- and kinetics-based arguments.

Study on Microstructure and Mechanical Properties of Al-Li Based Alloys Processed by Extrusion.

Science.gov (United States)

Kim, Yong-Ho; Yoo, Hyo-Sang; Jung, Chang-Gi; Son, Hyeon-Taek

2018-03-01

Aluminum and its alloys, due to their low density, high specific strength and high corrosion resistance amongst various structural materials, are used in a wide range of industrial applications for different aqueous solutions. In the present study, we studied effects of Ce addition on microstructure and mechanical properties of Al-2Li-1Cu-0.8Mg-0.1Zr alloys. The melt was held at 780 °C for 20 min and poured into a mold. And as-cast Al alloys were hot-extruded into a plate that was 4 mm in thickness with a reduction ratio of 14:1. The extruded plates were held at 540 °C for 4 hr in water quenching to solution treatment them. As-extruded Al-2Li-1Cu-0.8Mg-0.1Zr-xCe (x = 0.3, 0.6, 0.9 and 1.2 wt.%) alloys are composed of Al, AlLi, AlCuLi and Al11Ce3 phases. By increasing the Ce content from 0 to 1.2 wt.%, the Al11Ce3 phase is increased, after solution treatment the AlLi and AlCuLi phases are decreased. With increasing Ce addition from 0 to 1.2 wt.%, the average grain size of the as-extruded Al alloys were decreased slightly from 100.7, 113.74, 84.3, 74.7 and 61.7 μm and ultimate tensile strength was decreased slightly from 267.59, 264.92, 237.40, 220.93 and 207.83 MPa at room temperature. After solution treatment, ultimate tensile strength was measured with 205.13, 198.12, 195.50, 198.27 and 208.01 MPa at room temperature.

Magnetic domains and frustration in metallic CePdAl

Energy Technology Data Exchange (ETDEWEB)

Lucas, Stefan; Huesges, Zita; Huang, Chien-Lung; Stockert, Oliver [Max Planck Institute CPfS, Dresden (Germany); Fritsch, Veronika; Sakai, Akito [EP 6, Electronic Correlations and Magnetism, University of Augsburg (Germany); Grube, Kai; Taubenheim, Christian; Loehneysen, Hilbert von [Karlsruhe Institute of Technology (Germany)

2016-07-01

Magnetic frustration is an exciting topic in condensed matter physics, since it can lead to new ground states of materials, e.g. a spin liquid or spin glass state. Effects of magnetic frustration have been investigated intensively for insulating materials. However, the existence of magnetic frustration in metallic systems is still under debate. CePdAl is a metallic Kondo system, where geometric magnetic frustration arises from the formation of Ce ions on a distorted Kagome lattice. Neutron scattering experiments revealed, that only two thirds of the magnetic Ce moments order antiferromagnetically below T{sub N}=2.7 K, whereas the other third remains mainly disordered. Thermodynamic as well as neutron scattering measurements are presented to verify the existence of partial magnetic frustration in CePdAl. Recently neutron diffraction experiments under magnetic fields applied along two orthogonal directions in the magnetically hard basal plane were performed. They show opposite effects on the magnetic intensity of a selected magnetic domain depending on the field direction with respect to the propagation vector. If this is only an effect of different domain population or also due to a change in magnetic frustration shall be discussed.

Enhancement of oxidation resistance in Cu and Cu(Al) thin layers

International Nuclear Information System (INIS)

Horvath, Z.E.; Peto, G.; Paszti, Z.; Zsoldos, E.; Szilagyi, E.; Battistig, G.; Lohner, T.; Molnar, G.L.; Gyulai, J.

1999-01-01

High conductivity and good resistance to electromigration makes copper a promising interconnect material in microelectronics. However, one of its disadvantages is the poor corrosion resistance. Two methods of passivation are investigated and compared: Al alloying and BF 2 + ion implantation. X-ray diffraction (XRD) and Rutherford Backscattering Spectrometry (RBS) show the oxidation inhibition of both methods, but the different ratio of CuO 2 to CuO phases suggests different mechanisms of passivation. There are no definite oxide lines in the XRD spectrum of the implanted and annealed Cu(Al) sample, so the presence of Al and the implantation together give increased protection against oxidation. The difference between the two mechanisms of oxidation inhibition is discussed briefly

The electrochemical properties of melt-spun Al-Si-Cu alloys

International Nuclear Information System (INIS)

Zhang Linping; Wang Fei; Liang Pu; Song Xianlei; Hu Qing; Sun Zhanbo; Song Xiaoping; Yang Sen; Wang Liqun

2011-01-01

Highlights: → Non-equilibrium Al 75-X Si 25 Cu X alloys exhibit high lithiation storages. → The lithiation mechanism is different from melt-spun Al-Si-Mn system. → The structural evolution is mitigated in the non-equilibrium alloys. → Volume variation is alleviated due to the co-existence of Al 2 Cu, α-Si and α-Al. - Abstract: Melt spinning was used to prepare Al 75-X Si 25 Cu X (X = 1, 4, 7, 10 mol%) alloy anode materials for lithium-ion batteries. A metastable supersaturated solid solution of Si and Cu in fcc-Al, α-Si and Al 2 Cu co-existed in the alloys. Nano-scaled α-Al grains, as the matrix, formed in the as-quenched ribbons. The Al 74 Si 25 Cu 1 and Al 71 Si 25 Cu 4 anodes exhibited initial discharge specific capacities of 1539 mAh g -1 , 1324 mAh g -1 and reversible capacities above 472 mAh g -1 , 508 mAh g -1 at the 20th cycle, respectively. The specific capacities reduced as the increase of the Cu content. AlLi intermetallic compound was detected in the lithiated alloys. It is concluded that the lithiation mechanism of the Al-Si-based alloys can be affected by the third component. The structural evolution and volume variation can be mitigated due to the formation of non-equilibrium state and the co-existence of nano-scaled α-Al, α-Si, and Al 2 Cu for the present alloys.

Room Temperature Radiolytic Synthesized Cu@CuAlO₂-Al₂O₃ Nanoparticles

Directory of Open Access Journals (Sweden)

Nayereh Soltani

2012-09-01

Full Text Available Colloidal Cu@CuAlO₂-Al₂O₃ bimetallic nanoparticles were prepared by a gamma irradiation method in an aqueous system in the presence of polyvinyl pyrrolidone (PVP and isopropanol respectively as a colloidal stabilizer and scavenger of hydrogen and hydroxyl radicals. The gamma irradiation was carried out in a ⁶⁰Co gamma source chamber with different doses up to 120 kGy. The formation of Cu@CuAlO₂-Al₂O₃ nanoparticles was observed initially by the change in color of the colloidal samples from colorless to brown. Fourier transform infrared spectroscopy (FTIR confirmed the presence of bonds between polymer chains and the metal surface at all radiation doses. Results of transmission electron microscopy (TEM, energy dispersive X-ray spectrometry (EDX, and X-ray diffraction (XRD showed that Cu@CuAlO₂-Al₂O₃ nanoparticles are in a core-shell structure. By controlling the absorbed dose and precursor concentration, nanoclusters with different particle sizes were obtained. The average particle diameter increased with increased precursor concentration and decreased with increased dose. This is due to the competition between nucleation, growth, and aggregation processes in the formation of nanoclusters during irradiation.

Effect of Ag film thickness on the optical and the electrical properties in CuAlO2/Ag/CuAlO2 multilayer films grown on glass substrates

International Nuclear Information System (INIS)

Oh, Dohyun; No, Young Soo; Kim, Su Youn; Cho, Woon Jo; Kwack, Kae Dal; Kim, Tae Whan

2011-01-01

Research highlights: The CuAlO 2 /Ag/CuAlO 2 multilayer films were grown on glass substrates using radio-frequency magnetron sputtering at room temperature. Effects of Ag film thickness on the optical and the electrical properties in CuAlO 2 /Ag/CuAlO 2 multilayer films grown on glass substrates were investigated. X-ray diffraction patterns showed that the phase of the CuAlO 2 layer was amorphous. Atomic force microscopy images showed that Ag films with a thickness of a few nanometers had island structures. The morphology Ag films with a thickness of 8 nm was uniform. The morphology of the Ag films inserted in the CuAlO 2 films significantly affected the optical transmittance and the resistivity of the CuAlO 2 films deposited on glass substrates. The maximum transmittance of the CuAlO 2 /Ag/CuAlO 2 multilayer films with a thickness of 8 nm was 89.16%. The resistivity of the CuAlO 2 /Ag/CuAlO 2 multilayer films with an Ag film thickness of 18 nm was as small as about 2.8 x 10 -5 Ω cm. The resistivity of the CuAlO 2 /Ag/CuAlO 2 multilayer films was decreased as a result of the thermal annealing treatment. These results indicate that CuAlO 2 /Ag/CuAlO 2 multilayer films grown on glass substrates hold promise for potential applications as TCO films in solar cells. - Abstract: Effects of Ag film thickness on the optical and the electrical properties in CuAlO 2 /Ag/CuAlO 2 multilayer films grown on glass substrates were investigated. Atomic force microscopy images showed that Ag films with a thickness of a few nanometers had island structures. X-ray diffraction patterns showed that the phase of the CuAlO 2 layer was amorphous. The resistivity of the 40 nm-CuAlO 2 /18 nm-Ag/40 nm-CuAlO 2 multilayer films was 2.8 x 10 -5 Ω cm, and the transmittance of the multilayer films with an Ag film thickness of 8 nm was approximately 89.16%. These results indicate that CuAlO 2 /Ag/CuAlO 2 multilayer films grown on glass substrates hold promise for potential applications as

Simultaneous removal of NO and Hg{sup 0} over Ce-Cu modified V{sub 2}O{sub 5}/TiO{sub 2} based commercial SCR catalysts

Energy Technology Data Exchange (ETDEWEB)

Chi, Guilong [School of Energy & Environmental Engineering, Hebei University of Technology, Tianjin 300401 (China); College of Environmental Science & Engineering, Nankai University, Tianjin 300350 (China); Shen, Boxiong, E-mail: shenbx@nankai.edu.cn [School of Energy & Environmental Engineering, Hebei University of Technology, Tianjin 300401 (China); Yu, Ranran [School of Energy & Environmental Engineering, Hebei University of Technology, Tianjin 300401 (China); He, Chuan; Zhang, Xiao [College of Environmental Science & Engineering, Nankai University, Tianjin 300350 (China)

2017-05-15

Highlights: • Simultaneous removal of NO and Hg{sup 0} over the novel modified commercial SCR catalysts. • 7% Ce-1% Cu/SCR catalyst exhibited excellent activity of NO conversion and Hg{sup 0} oxidation. • 7% Ce-1% Cu/SCR catalyst showed higher resistance to SO{sub 2} and H{sub 2}O than other catalysts. • The synergistic interaction between Ce and Cu in the catalyst improved the activity greatly. - Abstract: A series of novel Ce-Cu modified V{sub 2}O{sub 5}/TiO{sub 2} based commercial SCR catalysts were prepared via ultrasonic-assisted impregnation method for simultaneous removal of NO and elemental mercury (Hg{sup 0}). Nitrogen adsorption, X-ray diffraction (XRD), temperature programmed reduction of H{sub 2} (H{sub 2}-TPR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalysts. 7% Ce-1% Cu/SCR catalyst exhibited the highest NO conversion efficiency (>97%) at 200–400 °C, as well as the best Hg{sup 0} oxidation activity (>75%) at 150–350 °C among all the catalysts. The XPS and H{sub 2}-TPR results indicated that 7% Ce-1% Cu/SCR possess abundant chemisorbed oxygen and good redox ability, which was due to the strong synergy between Ce and Cu in the catalyst. The existence of the redox cycle of Ce{sup 4+} + Cu{sup 1+} ↔ Ce{sup 3+} + Cu{sup 2+} could greatly improve the catalytic activity. 7% Ce-1% Cu/SCR showed higher resistance to SO{sub 2} and H{sub 2}O than other catalysts. NO has a promoting effect on Hg{sup 0} oxidation. The Hg{sup 0} oxidation activity was inhibited by the injection of NH{sub 3}, which was due to the competitive adsorption and oxidized mercury could be reduced by ammonia at temperatures greater than 325 °C. Therefore, Hg{sup 0} oxidation could easily occurred at the outlet of SCR catalyst layer due to the consumption of NH{sub 3}.

Tunable colorimetric performance of Al{sub 2}O{sub 3}-YAG:Ce{sup 3+} eutectic crystal by Ce{sup 3+} concentration

Energy Technology Data Exchange (ETDEWEB)

Sai, Qinglin, E-mail: saiql@siom.ac.cn; Xia, Changtai, E-mail: xia_ct@siom.ac.cn

2017-06-15

Ce-doped Al{sub 2}O{sub 3}-YAG eutectics with different percentage of Ce were successfully grown by the optical floating zone technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the structure. The results show that they have typical eutectic structure of interpenetrating sapphire and garnet phases with the tens of microns lamella spacing. The photoluminescence spectra of the eutectics showed that they have wide excitation band, and samples with 1.6 mol% Ce-doped has the highest emission intensity. The eutectic-packaged LED has high luminous efficiency and its color can be modulated by changing Ce concentration. The results reveal that Ce-doped Al{sub 2}O{sub 3}-YAG eutectic is a promising phosphor for white LED applications.

Elemental separation in nanocrystalline Cu-Al alloys

Science.gov (United States)

Wang, Y. B.; Liao, X. Z.; Zhao, Y. H.; Cooley, J. C.; Horita, Z.; Zhu, Y. T.

2013-06-01

Nanocrystallization by high-energy severe plastic deformation has been reported to increase the solubility of alloy systems and even to mix immiscible elements to form non-equilibrium solid solutions. In this letter, we report an opposite phenomenon—nanocrystallization of a Cu-Al single-phase solid solution by high-pressure torsion separated Al from the Cu matrix when the grain sizes are refined to tens of nanometers. The Al phase was found to form at the grain boundaries of nanocrystalline Cu. The level of the separation increases with decreasing grain size, which suggests that the elemental separation was caused by the grain size effect.

Alleviation of process-induced cracking of the antireflection TiN coating (ARC-TiN) in Al-Cu and Al-Cu-Si films

CERN Document Server

Peng, Y C; Yang, Y R; Hsieh, W Y; Hsieh, Y F

1999-01-01

The alleviation of cracking of the TiN-ARC layer on Al-Cu and Al-Cu-Si films after the development process has been achieved. For the TiN-ARC/Al-Cu system, the stress-induced defects decreased with increasing TiN-ARC layer thickness. In contrast, for the TiN-ARC/Al-Cu-Si system, Si nodules formed during cooling, thereby inducing poor coverage with high aspect-ratio holes. As a result, the photoresist developer penetrated through the films. Chemical vapor deposition of TiN-ARC or predeposition of a Ti Interposing layer was used to eliminate the formation of Si nodules.

Aluminium-rich corner in Al-Cu-La system

International Nuclear Information System (INIS)

Yunusov, I.; Ganiev, I.N.

1990-01-01

Aluminium corner of Al-Cu-La system are investigated by means of microstructural and differential thermal analysis. Existence of LaCu 2 Al 10 and LaCu 0.5 Al 3.5 ternary compounds in the system is confirmed and it is shown, as well, both compounds are in two-phase equilibrium with aluminium solid solution and form with it and between each other eutectic type state diagrams. State diagrams for quasibinary sections are plotted

Grain boundary tunnel spectroscopy of the electron-doped cuprate superconductor La{sub 2-x}Ce{sub x}CuO{sub 4}; Korngrenzen-Tunnelspektroskopie am elektronendotierten Kupratsupraleiter La{sub 2-x}Ce{sub x}CuO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Wagenknecht, Michael

2008-07-01

The electron doped superconductor La{sub 2-x}Ce{sub x}CuO{sub 4} (LCCO) has been investigated by electric transport measurements at low temperatures T down to 5 K and high magnetic fields up to 16 T. For this purpose LCCO thin film tunnel junctions have been prepared on bicrystal substrates by molecular beam epitaxy and micro structuring. The samples were characterised by measuring the thin film resistivity and the tunnel conductance of quasi particles across the grain boundary. By these measurements an unconventional symmetry of the order parameter could be revealed for La{sub 2-x}Ce{sub x}CuO{sub 4}. Furthermore it was shown, that the tunnel conductance can be used as a probe for the upper critical field B{sub c2}(T). By using this method a value of B{sub c2}{proportional_to}24 T has been found for La{sub 2-x}Ce{sub x}CuO{sub 4}, a value roughly three times bigger than previously known. By this observation it was shown that the superconducting phase covers a larger region in the B-T-phase diagram. In addition it was concluded, that the pseudogap phase in La{sub 2-x}Ce{sub x}CuO{sub 4} is either not existent at all or covers only a small temperature region. Besides quasiparticle tunneling also the tunneling of Cooper pairs in small magnetic fields has been investigated. It was shown that the critical current across the grain boundary depends on the supplier of the bicrystal substrate. (orig.)

Local atomic structure of Zr-Cu and Zr-Cu-Al amorphous alloys investigated by EXAFS method

International Nuclear Information System (INIS)

Antonowicz, J.; Pietnoczka, A.; Zalewski, W.; Bacewicz, R.; Stoica, M.; Georgarakis, K.; Yavari, A.R.

2011-01-01

Research highlights: → Coordination number, interatomic distances and mean square atomic displacement in Zr-Cu and Zr-Cu-Al glasses. → Icosahedral symmetry in local atomic structure. → Deviation from random mixing behavior resulting from Al addition. - Abstract: We report on extended X-ray absorption fine structure (EXAFS) study of rapidly quenched Zr-Cu and Zr-Cu-Al glassy alloys. The local atomic order around Zr and Cu atoms was investigated. From the EXAFS data fitting the values of coordination number, interatomic distances and mean square atomic displacement were obtained for wide range of compositions. It was found that icosahedral symmetry rather than that of corresponding crystalline analogs dominates in the local atomic structure of Zr-Cu and Zr-Cu-Al amorphous alloys. Judging from bonding preferences we conclude that addition of Al as an alloying element results in considerable deviation from random mixing behavior observed in binary Zr-Cu alloys.

Enhancement of oxidation resistance in Cu and Cu(Al) thin layers

Energy Technology Data Exchange (ETDEWEB)

Horvath, Z.E.; Peto, G. E-mail: peto@mfa.kfki.hu; Paszti, Z.; Zsoldos, E.; Szilagyi, E.; Battistig, G.; Lohner, T.; Molnar, G.L.; Gyulai, J

1999-01-02

High conductivity and good resistance to electromigration makes copper a promising interconnect material in microelectronics. However, one of its disadvantages is the poor corrosion resistance. Two methods of passivation are investigated and compared: Al alloying and BF{sub 2}{sup +} ion implantation. X-ray diffraction (XRD) and Rutherford Backscattering Spectrometry (RBS) show the oxidation inhibition of both methods, but the different ratio of CuO{sub 2} to CuO phases suggests different mechanisms of passivation. There are no definite oxide lines in the XRD spectrum of the implanted and annealed Cu(Al) sample, so the presence of Al and the implantation together give increased protection against oxidation. The difference between the two mechanisms of oxidation inhibition is discussed briefly.

The electrochemical properties of melt-spun Al-Si-Cu alloys

Energy Technology Data Exchange (ETDEWEB)

Zhang Linping; Wang Fei; Liang Pu; Song Xianlei; Hu Qing [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Sun Zhanbo, E-mail: szb@mail.xjtu.edu.cn [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Song Xiaoping; Yang Sen; Wang Liqun [MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

2011-10-03

Highlights: {yields} Non-equilibrium Al{sub 75-X}Si{sub 25}Cu{sub X} alloys exhibit high lithiation storages. {yields} The lithiation mechanism is different from melt-spun Al-Si-Mn system. {yields} The structural evolution is mitigated in the non-equilibrium alloys. {yields} Volume variation is alleviated due to the co-existence of Al{sub 2}Cu, {alpha}-Si and {alpha}-Al. - Abstract: Melt spinning was used to prepare Al{sub 75-X}Si{sub 25}Cu{sub X} (X = 1, 4, 7, 10 mol%) alloy anode materials for lithium-ion batteries. A metastable supersaturated solid solution of Si and Cu in fcc-Al, {alpha}-Si and Al{sub 2}Cu co-existed in the alloys. Nano-scaled {alpha}-Al grains, as the matrix, formed in the as-quenched ribbons. The Al{sub 74}Si{sub 25}Cu{sub 1} and Al{sub 71}Si{sub 25}Cu{sub 4} anodes exhibited initial discharge specific capacities of 1539 mAh g{sup -1}, 1324 mAh g{sup -1} and reversible capacities above 472 mAh g{sup -1}, 508 mAh g{sup -1} at the 20th cycle, respectively. The specific capacities reduced as the increase of the Cu content. AlLi intermetallic compound was detected in the lithiated alloys. It is concluded that the lithiation mechanism of the Al-Si-based alloys can be affected by the third component. The structural evolution and volume variation can be mitigated due to the formation of non-equilibrium state and the co-existence of nano-scaled {alpha}-Al, {alpha}-Si, and Al{sub 2}Cu for the present alloys.

Electronic properties of Nd{sub 2−x}Ce{sub x}CuO{sub 4+δ}: A hard X-ray photoemission investigation

Energy Technology Data Exchange (ETDEWEB)

Guarino, A., E-mail: guarino@sa.infn.it [CNR-SPIN-Salerno, Fisciano, SA (Italy); Dipartimento di Fisica “E. R. Caianiello” Università di Salerno, Fisciano, SA (Italy); Panaccione, G. [CNR-IOM Laboratorio TASC, AREA Science Park, 34012 Basovizza, TS (Italy); Offi, F. [CNISM and Dipartimento di Scienze, Università Roma Tre, Roma (Italy); Monaco, G. [Dipartimento di Fisica, Università di Trento, Trento (Italy); Fondacaro, A. [European Synchrotron Radiation Facility, BP 220, F-38042 Grenoble (France); Torelli, P. [CNR-IOM Laboratorio TASC, AREA Science Park, 34012 Basovizza, TS (Italy); Fittipaldi, R.; Vecchione, A. [CNR-SPIN-Salerno, Fisciano, SA (Italy); Pace, S.; Nigro, A. [CNR-SPIN-Salerno, Fisciano, SA (Italy); Dipartimento di Fisica “E. R. Caianiello” Università di Salerno, Fisciano, SA (Italy)

2016-10-15

Highlights: • We grow and characterize Nd{sub 2−x}Ce{sub x}CuO{sub 4+δ} samples as thin film and single crystal. • We study the Cu 2p levels of our samples by hard X-ray photoemission spectroscopy. • We investigate bulk features of the Nd{sub 2−x}Ce{sub x}CuO{sub 4+δ} samples. • Signature of the bulk response is correlated with the crystallinity of the samples. - Abstract: Cu 2p core levels spectra measured by X-ray photoemission spectroscopy of selected as-grown Nd{sub 2−x}Ce{sub x}CuO{sub 4+δ} samples are presented and discussed. The presence of a satellite peak in the 2p core level of Nd{sub 2−x}Ce{sub x}CuO{sub 4+δ} single crystal by hard X-ray photoemission is confirmed in all non-superconducting samples, films and single crystals investigated in this work. The comparison of the spectral features of the different samples suggests that the presence and the intensity of this satellite peak is not related to the electric transport properties, but to the texture characteristics.

Phase diagrams of aluminium alloys of Al-Cu-Mg, Al-Mg-Si-Cu, and Al-Mg-Li system

International Nuclear Information System (INIS)

Ber, L.B.; Kaputkin, E.Ya.

2001-01-01

Isothermal diagrams of phase transformations (DPT) and temperature-time charts (TTC) of variation of electric conductivity and of mechanical features at tension were plotted following thermal treatment according to the pattern of direct hardening and ageing and according to the pattern of normal aging for D16 commercial alloy, Al-Cu-Mg model alloy of the same system, AD37 commercial alloys of Al-Mg-Si-Cu and 1424 one of Al-Li-Mg system. Phase transformations were studied by means of fluorescence electron microscopy, micro-X-ray spectral analysis, X-ray phase analysis of single crystals and polycrystals and differential scanning calorimetry. For every alloy comparison of TTC and DPT enables to clarity the mechanism of phase composition effect on features and to optimize conditions of hardening cooling and ageing [ru

Geometrically frustrated magnetic structures of the heavy-fermion compound CePdAl studied by powder neutron diffraction

Energy Technology Data Exchange (ETDEWEB)

Doenni, A.; Fischer, P.; Zolliker, M. [Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ehlers, G.; Maletta, H. [Hahn Meitner Institute Berlin, Glienicker Strasse 100, D-14092 Berlin (Germany); Kitazawa, H. [National Research Institute for Metals, Tsukuba, Ibaraki 305 (Japan)

1996-12-09

The heavy-fermion compound CePdAl with ZrNiAl-type crystal structure (hexagonal space group P6-bar2m) was investigated by powder neutron diffraction. The triangular coordination symmetry of magnetic Ce atoms on site 3f gives rise to geometrical frustration. CePdAl orders below T{sub N} = 2.7 K with an incommensurate antiferromagnetic propagation vector k=[1/2, 0, {tau}], {tau} approx. 0.35, and a longitudinal sine-wave (LSW) modulated spin arrangement. Magnetically ordered moments at Ce(1) and Ce(3) coexist with frustrated disordered moments at Ce(2). The experimentally determined magnetic structure is in agreement with group theoretical symmetry analysis considerations, calculated by the program MODY, which confirm that for Ce(2) an ordered magnetic moment parallel to the magnetically easy c-axis is forbidden by symmetry. Further low-temperature experiments give evidence for a second magnetic phase transition in CePdAl between 0.6 and 1.3 K. Magnetic structures of CePdAl are compared with those of the isostructural compound TbNiAl, where a non-zero ordered magnetic moment for the geometrically frustrated Tb(2) atoms is allowed by symmetry. (author)

Carbon Fiber Reinforced Carbon-Al-Cu Composite for Friction Material.

Science.gov (United States)

Cui, Lihui; Luo, Ruiying; Ma, Denghao

2018-03-31

A carbon/carbon-Al-Cu composite reinforced with carbon fiber 2.5D-polyacrylonitrile-based preforms was fabricated using the pressureless infiltration technique. The Al-Cu alloy liquids were successfully infiltrated into the C/C composites at high temperature and under vacuum. The mechanical and metallographic properties, scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) of the C/C-Al-Cu composites were analyzed. The results showed that the bending property of the C/C-Al-Cu composites was 189 MPa, whereas that of the pure carbon slide material was only 85 MPa. The compressive strength of C/C-Al-Cu was 213 MPa, whereas that of the pure carbon slide material was only 102 MPa. The resistivity of C/C-Al-Cu was only 1.94 μΩm, which was lower than that of the pure carbon slide material (29.5 μΩm). This finding can be attributed to the "network conduction" structure. Excellent wettability was observed between Al and the carbon matrix at high temperature due to the existence of Al₄C₃. The friction coefficients of the C/C, C/C-Al-Cu, and pure carbon slide composites were 0.152, 0.175, and 0.121, respectively. The wear rate of the C/C-Al-Cu composites reached a minimum value of 2.56 × 10 -7 mm³/Nm. The C/C-Al-Cu composite can be appropriately used as railway current collectors for locomotives.

Synthesis and characterization of binary (CuO)0.6(CeO2)0.4 nanoparticles via a simple heat treatment method

Science.gov (United States)

Baqer, Anwar Ali; Matori, Khamirul Amin; Al-Hada, Naif Mohammed; Shaari, Abdul Halim; Kamari, Halimah Mohamed; Saion, Elias; Chyi, Josephine Liew Ying; Abdullah, Che Azurahanim Che

2018-06-01

A binary (CuO)0.6 (CeO2)0.4 nanoparticles were prepared via thermal treatment method, using copper nitrate, cerium nitrate as precursors, PVP as capping agent and de-ionized water as a solvent. The structures, morphology, composition of the element and optical properties of these nanoparticles have been studied under different temperatures using various techniques. The XRD spectrum of the samples at 500 °C and above confirmed the existence of both monoclinic (CuO) and cubic fluorite (CeO2) structures. The findings of FESEM and TEM exhibited the average practical size and agglomeration increment with an elevation in the calcination temperature. The synthesized nanoparticles were also characterized by FTIR, which indicated the formation of binary Cu-O and Ce-O bonds. The EDX analysis was performed to indicate the chemical composition of the sample. The double energy band gaps of (CuO)0.6(CeO2)0.4 reduction with rising calcination temperature, can be referred to the enhancement of the crystallinity of the samples. PL intensity of (CuO)0.6(CeO2)0.4 nanoparticles peaks, which increased with the elevation of the calcination temperature to 800 °C was observed from the PL spectrum; this was due to the increment of the particle size that occurred.

Diffusivities and atomic mobilities in Cu-rich fcc Al-Cu-Mn alloys

Energy Technology Data Exchange (ETDEWEB)

Yin, Ming; Du, Yong; Cui, Senlin; Xu, Honghui; Liu, Shuhong [Central South Univ., Changsha (China). State Key Laboratory of Powder Metallurgy; Zhang, Lijun [Bochum Univ. (DE). Interdisciplinary Centre for Advanced Materials Simulation (ICAMS)

2012-07-15

Via solid-solid diffusion couples, electron probe microanalysis and the Whittle and Green method, interdiffusivities in fcc Al-Cu-Mn alloys at 1 123 K were measured. The reliability of the obtained diffusivities is validated by comparing the computed diffusivities with literature data plus constraints among the diffusivities. Through assessments of experimentally determined diffusion coefficients by means of a diffusion-controlled transformations simulation package, the atomic mobilities of Al, Cu, and Mn in fcc Al-Cu-Mn alloys are obtained. Comprehensive comparisons between the model-predicted and the experimental data indicate that the presently obtained atomic mobilities can reproduce most of the diffusivities, concentration profiles, and diffusion paths reasonably. (orig.)

Urea-assisted synthesis of AlPO4:Ce,Tb nanorods as a redox luminescence switch

International Nuclear Information System (INIS)

Yang, Wei; Hu, Juncheng

2013-01-01

AlPO 4 :Ce,Tb nanorods were synthesized by a facile hydrothermal method. The morphology of rod-like AlPO 4 was tuned by varying urea concentrations, AlPO 4 gradually changed from nanosheets to nanorods, and urea provided hydroxyl anion (OH − ) in the aqueous solution to prepare the dispersed nanorods under the hydrothermal conditions. The emission intensity of nanorods increased significantly compared to that of nanosheets. AlPO 4 :Ce,Tb nanorods provided a novel redox luminescence switch on the basis of the reversible switching of the Ce 3+ /Ce 4+ redox couple. The luminescence is quenched (off) when the system is in the oxidized form while it is restored (on) in the reduced form. The mechanism of the energy transfer and electronic transition between Ce 3+ and Tb 3+ in the AlPO 4 nanorods was also discussed. This switch has biocompatibility and low toxicity, and may have a potential application in biomedical diagnostics and analysis

Effects of Al addition on atomic structure of Cu-Zr metallic glass

Science.gov (United States)

Li, Feng; Zhang, Huajian; Liu, Xiongjun; Dong, Yuecheng; Yu, Chunyan; Lu, Zhaoping

2018-02-01

The atomic structures of Cu52Zr48 and Cu45Zr48Al7 metallic glasses (MGs) have been studied by molecular dynamic simulations. The results reveal that the molar volume of the Cu45Zr48Al7 MG is smaller than that of the Cu52Zr48 MG, although the size of the Al atom is larger than that of the Cu atom, implying an enhanced atomic packing density achieved by introducing Al into the ternary MG. Bond shortening in unlike atomic pairs Zr-Al and Cu-Al is observed in the Cu45Zr48Al7 MG, which is attributed to strong interactions between Al and (Zr, Cu) atoms. Meanwhile, the atomic packing efficiency is enhanced by the minor addition of Al. Compared with the Cu52Zr48 binary MG, the potential energy of the ternary MG decreases and the glass transition temperature increases. Structural analyses indicate that more Cu- and Al-centered full icosahedral clusters emerge in the Cu45Zr48Al7 MG as some Cu atoms are substituted by Al. Furthermore, the addition of Al leads to more icosahedral medium-range orders in the ternary MG. The increase of full icosahedral clusters and the enhancement of the packing density are responsible for the improved glass-forming ability of Cu45Zr48Al7.

Comment on “Synthesis of ceria (CeO{sub 2} and CeO{sub 2−x}) nanoparticles via decarbonation and Ce(III) oxidation of synthetic bastnaesite (CeCO{sub 3}F)” by Montes-Hernandez et al

Energy Technology Data Exchange (ETDEWEB)

Gysi, Alexander P., E-mail: agysi@mines.edu [Department of Geology and Geological Engineering, Colorado School of Mines, 1516 Illinois Street, Golden, CO, 80401 (United States); Williams-Jones, Anthony E. [Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, QC, Canada, H3A 2A7 (Canada)

2016-11-01

Montes-Hernandez et al. [5] recently reported results of a study of the decarbonation of fine-grained synthetic bastnäsite-(Ce) precipitates involving the oxidation of Ce(III) to Ce(IV) and the formation of ceria (CeO{sub 2} and CeO{sub 2-x} with oxygen vacancies) nano-particles. The purpose of their study was to show that oxidation of Ce(III) to Ce(IV) occurs spontaneously during heating of bastnäsite-(Ce) in air, a vacuum, N{sub 2} or Ar gas. However, their interpretation of the formation of CeO{sub 2} is not supported by the findings of Gysi and Williams-Jones [3], who showed that natural bastnäsite-(Ce) decomposes to form rare earth element (REE) oxyfluorides (REEOF). The latter was documented using differential scanning calorimetric (DSC) and thermogravimetric (TGA) experiments under a deoxygenated N{sub 2} atmosphere. In their experiments, Gysi and Williams-Jones [3] found no evidence for the oxidation of Ce(III) to Ce(IV). This raises the question of whether the experiments of Montes-Hernandez et al. [5] in a N{sub 2} atmosphere (and by extension in an Ar atmosphere) were compromised because of contamination by O{sub 2} and that, as a result, they reached the erroneous conclusion that Ce(III) oxidizes spontaneously to Ce(IV) during heating of bastnäsite-(Ce) under these conditions. In order to explain the disagreement between their findings and those of Gysi and Williams-Jones [3], Montes-Hernandez et al. [5], proposed that the X-ray diffraction data of the former study were incorrectly interpreted. Here, we provide further evidence that the natural bastnäsite-(Ce) employed in the study by Gysi and Williams-Jones [3] decomposed to form REE oxyfluorides (i.e., CeOF, LaOF, PrOF and NdOF) and not CeO{sub 2}, and supply explanations for why Montes-Hernandez et al. [5] erroneously concluded that CeO{sub 2} is produced during decomposition of this mineral under N{sub 2} and Ar atmospheres. In so doing, we hope to provide new insights into the decomposition of

Photocatalytic property and structural stability of CuAl-based layered double hydroxides

International Nuclear Information System (INIS)

Lv, Ming; Liu, Haiqiang

2015-01-01

Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) were successfully synthesized by coprecipitation. Powder X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES) and UV–Vis diffuse reflectance spectrum (UV–vis) were used to confirm the formation of as-synthesized solids with good crystal structure. The photocatalytic activity of those LDH materials for CO 2 reduction under visible light was investigated. The experimental results show that CuNiAl-LDHs with narrowest band gap and largest surface areas behave highest efficiency for methanol generation under visible light compared with CuMgAl-LDHs and CuZnAl-LDHs. The CuNiAL-LDH showed high yield for methanol production i.e. 0.210 mmol/g h, which was high efficient. In addition, the influence of the different M 2+ on the structures and stability of the CuMAl-LDHs was also investigated by analyzing the geometric parameters, electronic arrangement, charge populations, hydrogen-bonding, and binding energies by density functional theory (DFT) analysis. The theoretical calculation results show that the chemical stability of LDH materials followed the order of CuMgAl-LDHs>CuZnAl-LDHs>CuNiAl-LDHs, which is just opposite with the photocatalytic activity and band gaps of three materials. - Graphical abstract: The host–guest calculation models and XRD patterns of CuMAl-LDHs: CuMgAl-LDHs (a), CuZnAl-LDHs (b) and CuNiAl-LDHs (c). - Highlights: • Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) has been synthesized. • CuMgNi shows narrower band gap and more excellent textural properties than other LDHs. • The band gap: CuMgAl based on result from UV–vis analysis. • CuMgAl shows the highest stability and lowest photocatalytic activity, while CuNiAl just opposite

Reduction in secondary dendrite arm spacing in cast eutectic Al-Si piston alloys by cerium addition

Science.gov (United States)

Ahmad, R.; Asmael, M. B. A.; Shahizan, N. R.; Gandouz, S.

2017-01-01

The effects of Ce on the secondary dendrite arm spacing (SDAS) and mechanical behavior of Al-Si-Cu-Mg alloys were investigated. The reduction of SDAS at different Ce concentrations was evaluated in a directional solidification experiment via computer-aided cooling curve thermal analysis (CA‒CCTA). The results showed that 0.1wt%-1.0wt% Ce addition resulted in a rapid solidification time, Δ t s, and low solidification temperature, Δ T S, whereas 0.1wt% Ce resulted in a fast solidification time, Δ t a-Al, of the α-Al phase. Furthermore, Ce addition refined the SDAS, which was reduced to approximately 36%. The mechanical properties of the alloys with and without Ce were investigated using tensile and hardness tests. The quality index ( Q) and ultimate tensile strength of (UTS) Al-Si-Cu-Mg alloys significantly improved with the addition of 0.1wt% Ce. Moreover, the base alloy hardness was improved with increasing Ce concentration.

RRh2Al10 (R = Ce, Yb): New intermetallic compounds in the 1 : 2 : 10 stoichiometry series

Science.gov (United States)

Strydom, A. M.; Djoumessi, R. F.; Blinova, M.; Tursina, A.; Nesterenko, S.; Avzuragova, V.

2018-05-01

The orthorhombic, space group Cmcm YbFe2Al10 structure type series of compounds are known to form with practically the entire series of rare-earth elements R, but only with the three d - electron elements Fe, Ru, and Os. The Ce-derivatives in particular have been of much interest since the first reports of their highly unusual physical properties. Classified as Kondo insulators, CeRu2Al10 and CeOs2Al10 controversially order magnetically and with uncharacteristically high Néel temperatures of ≃ 28 K. CeFe2Al10 on the other hand shows pronounced semiconducting and Kondo features but remains paramagnetic. As part of our ongoing studies into the rich physics of this class of materials we have succeeded in synthesizing new members of the 1:2:10 stoichiometry involving the chemical element Rh for the first time. CeRh2Al10 is found to crystallize in the tetragonal system with space group I41 / amd . Yb Rh2Al10 on the other hand forms in the serial Cmcm orthorhombic structure type. We discuss important similarities between the two types. At 5.310 Å the shortest Ce-Ce distance is, likewise to the situation in CeRu2Al10 and CeOs2Al10 , also well above the Hill limit of 3.40 Å. Despite the cage-like structure and large rare-earth separation distances, this study reveals the onset of long-range magnetic ordering in CeRh2Al10 at 3.9 K. The magnetic ordering develops out of an incoherent Kondo state that dominates the electrical resistivity below about 40 K.

Low cycle fatigue behavior of die cast Mg-Al-Mn-Ce magnesium alloy

Directory of Open Access Journals (Sweden)

Wu Wei

2013-11-01

Full Text Available Fatigue failure is a main failure mode for magnesium and other alloys. It is beneficial for fatigue design and fatigue life improvement to investigate the low cycle fatigue behavior of magnesium alloys. In order to investigate the low cycle fatigue behavior of die cast Mg-Al-Mn-Ce magnesium alloy, the strain controlled fatigue experiments were performed at room temperature and fatigue fracture surfaces of specimens were observed with scanning election microscopy for the alloys under die-cast and aged states. Cyclic stress response curves, strain amplitude versus reversals to failure curve, total strain amplitude versus fatigue life curves and cyclic stress-strain curves of Mg-Al-Mn-Ce alloys were analyzed. The results show that the Mg-Al-Mn-Ce alloys under die-cast (F and aged (T5 states exhibit cyclic strain hardening under the applied total strain amplitudes, and aging treatment could greatly increase the cyclic stress amplitudes of die cast Mg-Al-Mn-Ce alloys. The relationships between the plastic strain amplitude, the elastic strain amplitude and reversals to failure of Mg-Al-Mn-Ce magnesium alloy under different treatment states could be described by Coffin-Manson and Basquin equations, respectively. Observations on the fatigue fracture surface of specimens reveal that the fatigue cracks initiate on the surface of specimens and propagate transgranularly.

Behavior of aluminum oxide, intermetallics and voids in Cu-Al wire bonds

International Nuclear Information System (INIS)

Xu, H.; Liu, C.; Silberschmidt, V.V.; Pramana, S.S.; White, T.J.; Chen, Z.; Acoff, V.L.

2011-01-01

Nanoscale interfacial evolution in Cu-Al wire bonds during isothermal annealing from 175 deg. C to 250 deg. C was investigated by high resolution transmission electron microscopy (HRTEM). The native aluminum oxide film (∼5 nm thick) of the Al pad migrates towards the Cu ball during annealing. The formation of intermetallic compounds (IMC) is controlled by Cu diffusion, where the kinetics obey a parabolic growth law until complete consumption of the Al pad. The activation energies to initiate crystallization of CuAl 2 and Cu 9 Al 4 are 60.66 kJ mol -1 and 75.61 kJ mol -1 , respectively. During IMC development, Cu 9 Al 4 emerges as a second layer and grows together with the initial CuAl 2 . When Al is completely consumed, CuAl 2 transforms to Cu 9 Al 4 , which is the terminal product. Unlike the excessive void growth in Au-Al bonds, only a few voids nucleate in Cu-Al bonds after long-term annealing at high temperatures (e.g., 250 o C for 25 h), and their diameters are usually in the range of tens of nanometers. This is due to the lower oxidation rate and volumetric shrinkage of Cu-Al IMC compared with Au-Al IMC.

Tunable Luminescence of CeAl11O18 Based Phosphors by Replacement of (AlO)+ by (SiN)+ and Co-Doping with Eu

NARCIS (Netherlands)

Yin, L.J.; Chen, G.Z; Wang, C.; Xu, X.; Hao, L.Y.; Hintzen, H.T.J.M.

2014-01-01

A series of Si-N or Eu-Li doped CeAl11O18 and CeAl12O18N phosphors are prepared by solid–state reaction. Their structure and luminescence are researched carefully. Si-N doping with the concentration less than 8% can be successfully dissolved into CeAl11O18 crystal lattice and doesn't change the

TEM characterization of Al-C-Cu-Al2O3 composites produced by mechanical milling

International Nuclear Information System (INIS)

Santos-Beltran, A.; Gallegos-Orozco, V.; Estrada-Guel, I.; Bejar-Gomez, L.; Espinosa-Magana, F.; Miki-Yoshida, M.; Martinez-Sanchez, R.

2007-01-01

Novel Al-based composites (Al-C-Cu-Al 2 O 3 ) obtained by mechanical milling (MM), were characterized by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Analyses of composites were carried out in both, the as-milled and the as-sintered conditions. C nanoparticles were found in the as-milled condition and Al 2 O 3 nanofibers were found in as-sintered products, as determined by EELS. C and Cu react with Al to crystallize in Al 3 C 4 and Al 2 Cu structures, respectively

Synthesis of ceramic catalytic system based on CuO/CeO{sub 2} for preferential oxidation reaction of CO; Sintese de sistemas cataliticos ceramicos de CuO/CeO{sub 2} destinados a reacao de oxidacao preferencial do CO

Energy Technology Data Exchange (ETDEWEB)

Neiva, L.S.; Ribeiro, M.A.; Bispo, A.; Gama, L., E-mail: lsoutoneiva@yahoo.com.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais

2010-07-01

The aim this is work is to develop catalysts based on CuO/CeO{sub 2} by means two different types of synthesis methods: combustion synthesis and Pechini. CuO/CeO{sub 2} catalysts were synthesized with 0.5 mol of CuO for both synthesis methods used. The catalysts were characterized by XRD with the Rietveld refinement, EDX and textural analysis by the BET method. The results show that both methods of synthesis led to the formation of catalysts with segregated phases formed on the structures of the obtained materials, such segregated phases were formed by the presence of catalytic active species CuO and these phases had different characteristics depending on the type of method synthesis used. Small differences were observed in the evaluation of textural characteristics of the catalysts developed in this work according to the synthesis method employed. (author)

Initial Reduction of CO2 on Pd-, Ru-, and Cu-Doped CeO2(111) Surfaces: Effects of Surface Modification on Catalytic Activity and Selectivity.

Science.gov (United States)

Guo, Chen; Wei, Shuxian; Zhou, Sainan; Zhang, Tian; Wang, Zhaojie; Ng, Siu-Pang; Lu, Xiaoqing; Wu, Chi-Man Lawrence; Guo, Wenyue

2017-08-09

Surface modification by metal doping is an effective treatment technique for improving surface properties for CO 2 reduction. Herein, the effects of doped Pd, Ru, and Cu on the adsorption, activation, and reduction selectivity of CO 2 on CeO 2 (111) were investigated by periodic density functional theory. The doped metals distorted the configuration of a perfect CeO 2 (111) by weakening the adjacent Ce-O bond strength, and Pd doping was beneficial for generating a highly active O vacancy. The analyses of adsorption energy, charge density difference, and density of states confirmed that the doped metals were conducive for enhancing CO 2 adsorption, especially for Cu/CeO 2 (111). The initial reductive dissociation CO 2 → CO* + O* on metal-doped CeO 2 (111) followed the sequence of Cu- > perfect > Pd- > Ru-doped CeO 2 (111); the reductive hydrogenation CO 2 + H → COOH* followed the sequence of Cu- > perfect > Ru- > Pd-doped CeO 2 (111), in which the most competitive route on Cu/CeO 2 (111) was exothermic by 0.52 eV with an energy barrier of 0.16 eV; the reductive hydrogenation CO 2 + H → HCOO* followed the sequence of Ru- > perfect > Pd-doped CeO 2 (111). Energy barrier decomposition analyses were performed to identify the governing factors of bond activation and scission along the initial CO 2 reduction routes. Results of this study provided deep insights into the effect of surface modification on the initial reduction mechanisms of CO 2 on metal-doped CeO 2 (111) surfaces.

Study of properties of Cu-Y and Cu-Y-Al system alloys

International Nuclear Information System (INIS)

Shparo, N.B.; Nikolaev, A.K.; Rozenberg, V.M.

1978-01-01

Investigated were the strength properties of alloys Cu(0-1.2)% Y and Cu-(10-0.5)% Al-(0-0.5)% Y after being treated under various heat conditions and tested at temperatures of 20, 400 and 600 deg C. Yttrium additions raise the temperature of recrystallization of copper and of copper-aluminium alloys. Small additions of yttrium (0.05%) increase considerably strength of Cu-Al alloys without increasing their electric resistance. Optimum properties are attained after hardening, deformation and ageing at 400 deg C

Catalisadores de Cu/CeO2 modificados com La aplicados à reação de deslocamento gás-água

OpenAIRE

Tatiana de Freitas Silva

2013-01-01

A reação de deslocamento gás-água (water gas shift reaction, WGSR) é frequentemente usada em processos industriais para aumentar a produção de hidrogênio, assim como para remover quantidades de CO das correntes produzidas pela reforma a vapor de hidrocarbonetos. Neste trabalho, foram preparados catalisadores CuO/CeO2 e CuO/CeO2-La2O3 para a aplicação na reação de deslocamento gás-água. Os suportes CeO2 e CeO2-La2O3 foram preparados por três métodos diferentes: Hidrotérmico (CeO2(H) e CeO2-La2...

Preferential oxidation of CO in excess H₂ over CuO/CeO₂ catalysts: Performance as a function of the copper coverage and exposed face present in the CeO₂ support

DEFF Research Database (Denmark)

Monte, M.; Gamarra, D.; López Cámara, A.

2014-01-01

CuO/CeO2 catalysts where the support has different nanoparticle shapes exposing different lattice planes are examined for the preferential oxidation of CO in the presence of excess H2 (CO-PROX reaction) in operando DRIFTS conditions. Even for catalysts with same surface concentration of Cu...... CuO nanocrystals is more difficult on nanocube shaped CeO2 than on other CeO2 morphologies. Also EPR spectra show that the CuO entities nucleate on the ceria nanocubes differently. The higher stabilization of the oxidized state indicated by DFT, together with the mentioned structural distortion, may...

Catalytic activity of Co-Mg-Al, Cu-Mg-Al and Cu-Co-Mg-Al mixed oxides derived from hydrotalcites in SCR of NO with ammonia

Energy Technology Data Exchange (ETDEWEB)

Chmielarz, Lucjan; Kustrowski, Piotr; Rafalska-Lasocha, Alicja [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Majda, Dorota; Dziembaj, Roman [Regional Laboratory for Physicochemical Analyses and Structural Research, Ingardena 3, 30-060 Krakow (Poland)

2002-01-10

M-Mg-Al hydrotalcites (where M=Cu{sup 2+}, Co{sup 2+} and Cu{sup 2+}+Co{sup 2+}) with M ranging from 5 to 20% (as atomic ratio) were prepared by co-precipitation method. Obtained samples were characterised by XRD and TGA techniques. The influence of transition metal content on thermal decomposition of hydrotalcites was observed. Calcination of the hydrotalcites at 600C resulted in the formation of mixed oxides with surface areas in the range 71-154m{sup 2}/g. Calcined hydrotalcites were tested as catalysts in the selective reduction of NO with ammonia (NO-SCR). The catalytic activity depends on the kind of transition metal, as well as its content. For the NO-SCR the following reactivity order was found: Cu-Mg-Al>Cu-Co-Mg-Al>Co-Mg-Al. Temperature-programmed methods (TPD, TPSR, stop flow-TPD), as well as FT-IR spectroscopy have been applied to determine interaction of NO and NH{sub 3} molecules with the catalyst surface.

Electron traps and scintillation mechanism in YAlO3:Ce and LuAlO3:Ce scintillators

International Nuclear Information System (INIS)

Wojtowicz, A.J.; Glodo, J.; Drozdowski, W.; Przegietka, K.R.

1998-01-01

In this paper we present the results of thermoluminescence, isothermal decay and scintillation light yield measurements on two isostructural scintillator materials, YAlO 3 :Ce and LuAlO 3 :Ce. In addition to the variety of deep traps identified by thermoluminescence and isothermal decays, scintillation light yield experiments demonstrate the presence in both materials of a number of relatively shallow traps. While the deep traps may reduce the scintillation light yield, they do not influence the kinetics of the process. The shallow traps, on the other hand, by interfering with the process of radiative recombination of charge carriers via Ce 3+ ions, can strongly affect not only the yield of the scintillation process but its kinetics as well. The presence of shallow traps provides a consistent explanation for a number of poorly understood relationships between the two scintillator materials, including a higher room temperature scintillation light yield and longer scintillation decay time in YAlO 3 :Ce, and a longer scintillation rise time in LuAlO 3 :Ce. Theoretical analysis indicates that elimination of these traps would make the two materials nearly identical in scintillator performance. Although the specific identity of all traps remains elusive, the performance of both scintillator materials is now, in practical terms, fully understood. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Al-matrix composite materials reinforced by Al-Cu-Fe particles

International Nuclear Information System (INIS)

Bonneville, J; Laplanche, G; Joulain, A; Gauthier-Brunet, V; Dubois, S

2010-01-01

Al-matrix material composites were produced using hot isostatic pressing technique, starting with pure Al and icosahedral (i) Al-Cu-Fe powders. Depending on the processing temperature, the final reinforcement particles are either still of the initial i-phase or transformed into the tetragonal ω-Al0 0.70 Cu 0.20 Fe 0.10 crystalline phase. Compression tests performed in the temperature range 293K - 823K on the two types of composite, i.e. Al/i and Al/ω, indicate that the flow stress of both composites is strongly temperature dependent and exhibit distinct regimes with increasing temperature. Differences exist between the two composites, in particular in yield stress values. In the low temperature regime (T ≤ 570K), the yield stress of the Al/ω composite is nearly 75% higher than that of the Al/i composite, while for T > 570K both composites exhibit similar yield stress values. The results are interpreted in terms of load transfer contribution between the matrix and the reinforcement particles and elementary dislocation mechanisms in the Al matrix.

On the response of Y 3Al 5O 12: Ce (YAG: Ce) powder scintillating screens to medical imaging X-rays

Science.gov (United States)

Kandarakis, I.; Cavouras, D.; Sianoudis, I.; Nikolopoulos, D.; Episkopakis, A.; Linardatos, D.; Margetis, D.; Nirgianaki, E.; Roussou, M.; Melissaropoulos, P.; Kalivas, N.; Kalatzis, I.; Kourkoutas, K.; Dimitropoulos, N.; Louizi, A.; Nomicos, C.; Panayiotakis, G.

2005-02-01

The aim of this study was to examine Y 3Al 5O 12:Ce (also known as YAG:Ce) powder scintillator under X-ray imaging conditions. This material shows a very fast scintillation decay time and it has never been used in X-ray medical imaging. In the present study various scintillator layers (screens) with coating thickness ranging from 13 to 166 mg/cm 2 were prepared in our laboratory by sedimentation of Y 3Al 5O 12: Ce powder. Optical emission spectra and light emission efficiency (spectrum area over X-ray exposure) of the layers were measured under X-ray excitation using X-ray tube voltages (80-120 kVp) often employed in general medical radiography and fluoroscopy. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency values were determined using emission spectrum data. In addition, parameters related to X-ray detection, energy absorption efficiency and K-fluorescence characteristic emission were calculated. A theoretical model describing radiation and light transfer through scattering media was used to fit experimental data. Intrinsic conversion efficiency (η≈0.03-0.05) and light attenuation coefficients (σ≈26.5 cm/g) were derived through this fitting. Y 3Al 5O 12:Ce showed peak emission in the wavelength range 530-550 nm. The light emission efficiency was found to be maximum for the 107 mg/cm 2 layer. Due to its "green" emission spectrum, Y 3Al 5O 12:Ce showed excellent compatibility (of the order of 0.9) with the sensitivity of many currently used photodetectors. Taking into account its very fast response Y 3Al 5O 12:Ce could be considered for application in X-ray imaging especially in various digital detectors.

On the response of Y3Al5O12: Ce (YAG: Ce) powder scintillating screens to medical imaging X-rays

International Nuclear Information System (INIS)

Kandarakis, I.; Cavouras, D.; Sianoudis, I.; Nikolopoulos, D.; Episkopakis, A.; Linardatos, D.; Margetis, D.; Nirgianaki, E.; Roussou, M.; Melissaropoulos, P.; Kalivas, N.; Kalatzis, I.; Kourkoutas, K.; Dimitropoulos, N.; Louizi, A.; Nomicos, C.; Panayiotakis, G.

2005-01-01

The aim of this study was to examine Y 3 Al 5 O 12 :Ce (also known as YAG:Ce) powder scintillator under X-ray imaging conditions. This material shows a very fast scintillation decay time and it has never been used in X-ray medical imaging. In the present study various scintillator layers (screens) with coating thickness ranging from 13 to 166mg/cm 2 were prepared in our laboratory by sedimentation of Y 3 Al 5 O 12 : Ce powder. Optical emission spectra and light emission efficiency (spectrum area over X-ray exposure) of the layers were measured under X-ray excitation using X-ray tube voltages (80-120kVp) often employed in general medical radiography and fluoroscopy. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency values were determined using emission spectrum data. In addition, parameters related to X-ray detection, energy absorption efficiency and K-fluorescence characteristic emission were calculated. A theoretical model describing radiation and light transfer through scattering media was used to fit experimental data. Intrinsic conversion efficiency (ηC ∼0.03-0.05) and light attenuation coefficients (σ∼26.5cm 2 /g) were derived through this fitting. Y 3 Al 5 O 12 :Ce showed peak emission in the wavelength range 530-550nm. The light emission efficiency was found to be maximum for the 107mg/cm 2 layer. Due to its 'green' emission spectrum, Y 3 Al 5 O 12 :Ce showed excellent compatibility (of the order of 0.9) with the sensitivity of many currently used photodetectors. Taking into account its very fast response Y 3 Al 5 O 12 :Ce could be considered for application in X-ray imaging especially in various digital detectors

Confined NaAlH4 nanoparticles inside CeO2 hollow nanotubes towards enhanced hydrogen storage.

Science.gov (United States)

Gao, Qili; Xia, Guanglin; Yu, Xuebin

2017-10-05

NaAlH 4 has been widely regarded as a potential hydrogen storage material due to its favorable thermodynamics and high energy density. The high activation energy barrier and high dehydrogenation temperature, however, significantly hinder its practical application. In this paper, CeO 2 hollow nanotubes (HNTs) prepared by a simple electrospinning technique are adopted as functional scaffolds to support NaAlH 4 nanoparticles (NPs) towards advanced hydrogen storage performance. The nanoconfined NaAlH 4 inside CeO 2 HNTs, synthesized via the infiltration of molten NaAlH 4 into the CeO 2 HNTs under high hydrogen pressure, exhibited significantly improved dehydrogenation properties compared with both bulk and ball-milled CeO 2 HNTs-catalyzed NaAlH 4 . The onset dehydrogenation temperature of the NaAlH 4 @CeO 2 composite was reduced to below 100 °C, with only one main dehydrogenation peak appearing at 130 °C, which is 120 °C and 50 °C lower than for its bulk counterpart and for the ball-milled CeO 2 HNTs-catalyzed NaAlH 4 , respectively. Moreover, ∼5.09 wt% hydrogen could be released within 30 min at 180 °C, while only 1.6 wt% hydrogen was desorbed from the ball-milled NaAlH 4 under the same conditions. This significant improvement is mainly attributed to the synergistic effects contributed by the CeO 2 HNTs, which could act as not only a structural scaffold to fabricate and confine the NaAlH 4 NPs, but also as an effective catalyst to enhance the hydrogen storage performance of NaAlH 4 .

Instability of TiC and TiAl3 compounds in Al-10Mg and Al-5Cu alloys by addition of Al-Ti-C master alloy

Institute of Scientific and Technical Information of China (English)

无

2006-01-01

The performance of Al-Ti-C master alloy in refining Al-10Mg and A1-5Cu alloys was studied by using electron probe micro-analyzer (EPMA) and X-ray diffractometer (XRD) analysis.The results indicate that there are obvious fading phenomena in both Al-10Mg and Al-5Cu alloys with the addition of Al-5Ti-0.4C refiner which contains TiC and TiAl3 compounds.Mg element has no influence on the stability of TiC and TiAl3, while TiC particles in Al-10Mg alloy react with Al to form Al4C3 particles, resulting in the refinement fading.However, TiC particles are relatively stable in Al-5Cu alloy, while TiAl3 phase reacts with Al2Cu to produce a new phase Ti(Al, Cu)2, which is responsible for the refinement fading in Al-5Cu alloy.These indicate that the refinement fading will not occur only when both the TiC particles and TiAl3 compound of Al-Ti-C refiner are stable in Al alloys.

High-pressure modifications of CaZn2, SrZn2, SrAl2, and BaAl2: Implications for Laves phase structural trends

International Nuclear Information System (INIS)

Kal, Subhadeep; Stoyanov, Emil; Belieres, Jean-Philippe; Groy, Thomas L.; Norrestam, Rolf; Haeussermann, Ulrich

2008-01-01

High-pressure forms of intermetallic compounds with the composition CaZn 2 , SrZn 2 , SrAl 2 , and BaAl 2 were synthesized from CeCu 2 -type precursors (CaZn 2 , SrZn 2 , SrAl 2 ) and Ba 21 Al 40 by multi-anvil techniques and investigated by X-ray powder diffraction (SrAl 2 and BaAl 2 ), X-ray single-crystal diffraction (CaZn 2 ), and electron microscopy (SrZn 2 ). Their structures correspond to that of Laves phases. Whereas the dialuminides crystallize in the cubic MgCu 2 (C15) structure, the dizincides adopt the hexagonal MgZn 2 (C14) structure. This trend is in agreement with the structural relationship displayed by sp bonded Laves phase systems at ambient conditions. - Graphical abstract: CeCu 2 -type polar intermetallics can be transformed to Laves phases upon simultaneous application of pressure and temperature. The observed structures are controlled by the valence electron concentration

Effects of A1 substitution by Fe in CeAl2

International Nuclear Information System (INIS)

Takeuchi, A.Y.; Cunha, S.F. da.

1989-01-01

Magnetization and electrical resistivity measurements of the CeAl 2 with Al substitution by Fe up to 10% at Fe show that the competition between the increasing Kondo effect and the antiferromagnetism persists. Change of the electronic density is followed by a decreasing Neel temperature and an increasing residual electrical reistivity. The probable appearance of ferromagnetism of the Ce moments, at intermediate temperature range, is discussed. The small decrease of the lattice parameter with Fe concentration or the magnetic behaviour do not show evidence of valence changes in the Ceion. (author) [pt

The roles of Al2Cu and of dendritic refinement on surface corrosion resistance of hypoeutectic Al-Cu alloys immersed in H2SO4

International Nuclear Information System (INIS)

Osorio, Wislei R.; Spinelli, Jose E.; Freire, Celia M.A.; Cardona, Margarita B.; Garcia, Amauri

2007-01-01

Al-Cu alloys castings can exhibit different corrosion responses at different locations due to copper content and to the resulting differences on microstructural features and on Al 2 Cu fractions. The aim of this study was to investigate the influence of Al 2 Cu intermetallic particles associated to the dendritic arm spacings on the general corrosion resistance of three different hypoeutectic Al-Cu alloys samples in sulfuric acid solution. The cast samples were produced using a non-consumable tungsten electrode furnace with a water-cooled copper hearth under argon atmosphere. The typical microstructural pattern was examined by using electronic microscopy techniques. In order to evaluate the surface corrosion behavior of such Al-Cu alloys, corrosion tests were performed in a 0.5 M sulfuric acid solution at 25 deg. C by using an electrochemical impedance spectroscopy (EIS) technique and potentiodynamic polarization curves. An equivalent circuit was also used to provide quantitative support for the discussions and understanding of the corrosion behavior. It was found that Al 2 Cu has a less noble corrosion potential than that of the Al-rich phase. Despite that, dendrite fineness has proved to be more influent on corrosion resistance than the increase on alloy copper content with the consequent increase on Al 2 Cu fraction

Crystal structure and physical properties of CePt{sub 2.4}Al{sub 0.6}

Energy Technology Data Exchange (ETDEWEB)

Provino, A., E-mail: alessia.sting@gmail.com [Department of Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova (Italy); Institute SPIN-CNR, Corso Perrone 24, 16152 Genova (Italy); Bhattacharyya, A. [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Colaba, Mumbai 400005 (India); Science and Technology Facilities Council, Rutherford Appleton Laboratory, Excitations and Polarized Neutrons Group, Harwell Oxford, Didcot OX11 0QX (United Kingdom); Negretti, L. [Department of Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova (Italy); Kulkarni, R.; Thamizhavel, A.; Dhar, S.K. [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Colaba, Mumbai 400005 (India)

2015-02-15

Highlights: • New CePt{sub 2.4}Al{sub 0.6} compound crystallizes in the hexagonal CeNi{sub 3}-type (hP24, P6{sub 3}/mmc). • This crystal structure is a nearly ordered ternary derivative of CeNi{sub 3} prototype. • CePt{sub 2.4}Al{sub 0.6} compound orders ferromagnetically at 1.6 K; Ce ions in trivalent state. • Magnetization, electrical resistivity, low-T heat capacity have been measured. • Negative magnetoresistivity below ∼15 K shows short-range FM in paramagnetic state. - Abstract: The new compound CePt{sub 2.4}Al{sub 0.6} crystallizes in the hexagonal CeNi{sub 3}-type (hP24, space group P6{sub 3}/mmc, N. 194), with lattice parameters a = 5.5203(3) Å and c = 16.886(1) Å; its crystal structure represents a nearly ordered ternary derivative of this prototype. The cerium ions in CePt{sub 2.4}Al{sub 0.6} are in the normal trivalent state and order magnetically near 1.6 K as inferred from the low temperature heat capacity. The magnetic ordering is presumably ferromagnetic as suggested by the behavior of heat capacity in applied magnetic fields. The magnetoresistivity below ∼15 K is negative and is tentatively attributed to the presence of ferromagnetic short range order in the paramagnetic state.

Low-Temperature Catalytic Performance of Ni-Cu/Al2O3 Catalysts for Gasoline Reforming to Produce Hydrogen Applied in Spark Ignition Engines

Directory of Open Access Journals (Sweden)

Le Anh Tuan

2016-03-01

Full Text Available The performance of Ni-Cu/Al2O3 catalysts for steam reforming (SR of gasoline to produce a hydrogen-rich gas mixture applied in a spark ignition (SI engine was investigated at relatively low temperature. The structural and morphological features and catalysis activity were observed by X-ray diffractometry (XRD, scanning electron microscopy (SEM, and temperature programmed reduction (TPR. The results showed that the addition of copper improved the dispersion of nickel and therefore facilitated the reduction of Ni at low temperature. The highest hydrogen selectivity of 70.6% is observed over the Ni-Cu/Al2O3 catalysts at a steam/carbon ratio of 0.9. With Cu promotion, a gasoline conversion of 42.6% can be achieved at 550 °C, while with both Mo and Ce promotion, the gasoline conversions were 31.7% and 28.3%, respectively, higher than with the conventional Ni catalyst. On the other hand, initial durability testing showed that the conversion of gasoline over Ni-Cu/Al2O3 catalysts slightly decreased after 30 h reaction time.

Thermoluminescence studies of γ-irradiated Al{sub 2}O{sub 3}:Ce{sup 3+} phosphor

Energy Technology Data Exchange (ETDEWEB)

Reddy, S. Satyanarayana [Physics R & D Center, PES Institute of Technology, BSK 3rd Stage, Bangalore 560085 (India); Nagabhushana, K.R., E-mail: bhushankr@gmail.com [Physics R & D Center, PES Institute of Technology, BSK 3rd Stage, Bangalore 560085 (India); Department of Physics, PES University, BSK 3rd Stage, Bangalore 560085 (India); Singh, Fouran [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India)

2016-07-15

Pure and Ce{sup 3+} doped Al{sub 2}O{sub 3} phosphors were synthesized by solution combustion method. The synthesized samples were characterized by X-ray diffraction (XRD) and its shows α-phase of Al{sub 2}O{sub 3}. Crystallite size was estimated by Williamson–Hall (W–H) method and found to be 49, 59 and 84 nm for pure, 0.1 mol% and 1 mol% Ce{sup 3+} doped Al{sub 2}O{sub 3} respectively. Trace elemental analysis of undoped Al{sub 2}O{sub 3} shows impurities viz. Fe, Cr, Mn, Mg, Ti, etc. Photoluminescence (PL) spectra of Al{sub 2}O{sub 3}:Ce{sup 3+} shows emission at 367 nm and excitation peak at 273 nm, which are corresponding to {sup 5}D → {sup 4}F and {sup 4}F → {sup 5}D transitions respectively. PL intensity decreases with concentration up to 0.4 mol%, beyond this mol% PL intensity increases with doping concentration up to 2 mol%. Thermoluminescence (TL) studies of γ-rayed pure and Ce{sup 3+} doped Al{sub 2}O{sub 3} have been studied. Two well resolved TL glow peaks at 457.5 K and 622 K were observed in pure Al{sub 2}O{sub 3}. Additional glow peak at 566 K was observed in Al{sub 2}O{sub 3}:Ce{sup 3+}. Maximum TL intensity was observed for Al{sub 2}O{sub 3}:Ce{sup 3+} (0.1 mol%) beyond this TL intensity decreases with increasing Ce{sup 3+} concentration. Computerized glow curve deconvolution (CGCD) method was used to resolve the multiple peaks and to calculate TL kinetic parameters. Thermoluminescence emission (TLE) spectra of pure Al{sub 2}O{sub 3} glow peaks (457.5 K and 622 K) shows sharp emission at 694 nm and two small humps at 672 nm and 709 nm. The sharp peak at 696 nm corresponds to Cr{sup 3+} impurity of {sup 2}E{sub g} → {sup 4}A{sub 2g} transition of R lines and 713 nm hump is undoubtedly belongs to Cr{sup 3+} emission of near neighbor pairs. The emission at 672 nm is characteristic of Mn{sup 4+} impurity ions of {sup 2}E → {sup 4}A{sub 2} transition. TLE of Al{sub 2}O{sub 3}:Ce{sup 3+} (0.1 mol%) shows additional broad emission at 412 nm

Methanol reformer with water vapor and oxygen in catalysts of Cu/CeO2-ZrO2 to generate H2

International Nuclear Information System (INIS)

Aguila M, M.M.

2007-01-01

The environmental pollution is one of the problems more important to solve in the present time because its affect the quality of the alive beings' life. For such a reason alternatives have been looked for to diminish the percentage of air pollution (NO x , CO x , SO x , etc.), for they have been developed it the well-known catalytic converters. Another possibility is the energy use through fuel cells in vehicles using H 2 as fuel free of CO (smaller concentration to 10 ppm). Processes exist for the production of H 2 starting from the methanol and in this work the one was used reformed of methanol with water vapor and oxygen (OSRM) as the main reaction of this work. The primordial objective of this work consists on studying the catalytic properties of the copper (Cu) supported in mixed oxides (ZrO 2 -CeO 2 ) in the reaction of having reformed of methanol with water vapor and oxygen for the production of H 2 . Zirconia is synthesized (ZrO 2 ) and mixed oxides ZrO 2 -CeO 2 (with different relationship Zr/Ce) for the sol-gel method and the one cerium oxide (CeO 2 ) by direct combustion of the cerium nitrate. The oxides were stabilized thermally at 600 C by 5h. The catalysts were prepared by classic impregnation using copper acetate, the nominal concentration was of 3% in weight. The catalysts were roasted at 350 C and later on reduced in flow from H 2 to 350 C for 1h. The characterization of the catalytic materials is carried out through different techniques as: adsorption-desorption of nitrogen to determine the surface area BET, scanning electron microscopy (SEM) to determine the final morphology of the catalysts, X-ray diffraction (XRD) to identify the crystalline phases of the catalytic materials and reduction to programmed temperature (TPR) to evidence the interaction metal-support. The catalytic properties of the catalysts were studied in the reaction CH 3 OH + H 2 O + O 2 , to determine the activity and selectivity. The surface area of the mixed oxides was

Fabrication of NdCeCuO and effects of binding agents on the growth, micro-structural and electrical properties

Energy Technology Data Exchange (ETDEWEB)

Altin, S., E-mail: serdar.altin@inonu.edu.tr [Inonu Universitesi, Fen Edebiyat Fakultesi, Fizik Bolumu, Superiletkenlik Arastirma Grubu, 44280 Malatya (Turkey); Aksan, M.A.; Turkoglu, S.; Yakinci, M.E. [Inonu Universitesi, Fen Edebiyat Fakultesi, Fizik Bolumu, Superiletkenlik Arastirma Grubu, 44280 Malatya (Turkey)

2011-12-15

NdCeCuO system is a superconducting system which is dominated by electrons different from other HTc systems. Preparation of the NdCeCuO system under optimum conditions is very important for transport properties. Large grains can be obtained in NdCeCuO by employing wet-chemical route. NdCeCuO superconducting samples were fabricated using ethyl alcohol, acetone and ethylenediaminetetraacetic acid (EDTA) as binding agents. For evaporation of binding agents, the samples were heat treated at 1050 Degree-Sign C for 24 h and then at 950 Degree-Sign C for 6-48 h under argon atmosphere to obtain the superconducting phase. The best superconducting performance was found in the sample heat treated at 1050 Degree-Sign C for 24 h and then 950 Degree-Sign C for 12 h which was fabricated by using acetone as binding agent. The T{sub c} and T{sub 0} value was found to be {approx}25 K and 23.4 K, respectively. Grain size in the samples fabricated was calculated using Scherer equation and SEM data. It was found that grain size strongly depends on the binding agents and heat treatment conditions. Some cracks and voids on the surface of the samples were observed, which influences the superconducting and electrical transport properties of the samples.

Structural studies of Nd1.85Ce0.15CuO4 + Ag superconducting ...

Indian Academy of Sciences (India)

Nd1.85Ce0.15CuO4, on its crystal structure and local structural features, using synchrotron X-ray diffraction. (SXRD) and ..... extended X-ray absorption fine structure (EXAFS). ... [1] Zhang and Chongmin 1991 Thesis, University of British.

Extraordinary superconductor with nearly trivalent cerium, CeCu2Si2

International Nuclear Information System (INIS)

Ishikawa, M.; Jaccard, D.; Jorda, J.-L.

1982-01-01

Concentrating on the ternary phase diagram, the authors have performed a complementary investigation on CeCu 2 Si 2 and confirm that the compound containing nearly trivalent cerium ions is a new type of superconductor with Tsub(c) around 0.5 K. The analyses of the upper critical field curve support the description of the compound by heavy fermion quasiparticles. Other particular features of this compound are also presented. (Auth.)

Temperature Dependent Magnetoresistance of CeCu2Si2 up to 60 T [Proposal: P14728

Energy Technology Data Exchange (ETDEWEB)

Stritzinger, Laurel Elaine Winter [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lai, Y. [Florida State Univ., Tallahassee, FL (United States); Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baumbach, R. E. [Florida State Univ., Tallahassee, FL (United States)

2017-03-23

We recently investigated the chemical substitution series CeCu2Si2-xPx, for x = 0, 0.01, and 0.14, using a contactless tunnel diode oscillator technique. These measurements revealed previously unreported Shubnikov-de Haas oscillations above 45 T with an unusual temperature dependence that could potentially be explained by a high magnetic field transition. To investigate this possible transition, magnetoresistance measurements were desired. However, initial magnetoresistance measurements on CeCu2Si2 showed poor signal-to-noise due to the small value of the sample's resistivity. To overcome this obstacle, we performed micro-structuring of a single crystal specimen to increase the sample's resistance.

CuAlTe{sub 2}: A promising bulk thermoelectric material

Energy Technology Data Exchange (ETDEWEB)

Gudelli, Vijay Kumar [Department of Physics, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502 205, Telangana (India); Kanchana, V., E-mail: kanchana@iith.ac.in [Department of Physics, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502 205, Telangana (India); Vaitheeswaran, G. [Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad 500 046, Telangana (India)

2015-11-05

Transport properties of Cu-based chalcopyrite materials are presented using the full potential linear augmented plane wave method and Boltzmann Semi-classical theory. All the studied compounds appear to be direct band gap semiconductors evaluated based on the Tran-Blaha modified Becke-Johnson potential. The heavy and light band combination found near the valence band maximum (VBM) drive these materials to possess good thermoelectric properties. Among the studied compounds, CuAlTe{sub 2} is found to be more promising, in comparison with CuGaTe{sub 2}, which is reported to be an efficient thermoelectric material with appreciable figure of merit. Another interesting fact about CuAlTe{sub 2} is the comparable thermoelectric properties possessed by both n- type and p-type carriers, which might attract good device applications and are explained in detail using the electronic structure calculations. - Highlights: • Band structure calculation of Cu(Al,Ga)Ch{sub 2} compounds with the TB-mBJ functional. • Mixed heavy-light bands near Fermi level might favour good thermoelectric properties. • Among the investigated compounds CuAlTe{sub 2} appears to be more promising. • Thermoelectric properties of CuAlTe{sub 2} are almost comparable with CuGaTe{sub 2}. • Both n,p-type thermoelectric properties of CuAlTe{sub 2} can attract device applications.

Synthesis and characterization of nanocrystalline Cu-Al coatings

International Nuclear Information System (INIS)

Lau, M.L.; He, J.; Schweinfest, R.; Ruehle, M.; Levi, C.G.; Lavernia, E.J.

2003-01-01

Commercially pure Cu and Al powders were blended in a 90:10 ratio by weight and then mechanically milled in methanol or in liquid nitrogen. The milled powders, as well as as-blended (non-milled) powder, were deposited as coatings using high velocity oxygen fuel thermal spraying. Scanning and transmission electron microscopy techniques were used to investigate the microstructure of the powders and coatings. The results showed that milling of the powders in methanol induced the conversion of most of the Al into amorphous Al 2 O 3 , precluding the desired mechanical alloying. This experimental observation was consistent with available thermodynamic data. In contrast, cryomilling exhibited no significant oxidation and induced mechanical alloying of the powders, albeit incomplete. The non-milled powder generated a coating with a bimodal grain structure consisting of fine Cu grains and coarse Al grains. Amorphous oxide regions and coarse Al grains were observed intermixed with the finer Cu matrix in the coatings sprayed using the powders milled in methanol. Coatings based on cryomilled powders consisted primarily of equiaxed Cu grains and twinned martensite regions, with occasional inclusion of elongated amorphous Al 2 O 3 regions

Catalytic oxidation of n-hexane promoted by Ce{sub 1−x}Cu{sub x}O{sub 2} catalysts prepared by one-step polymeric precursor method

Energy Technology Data Exchange (ETDEWEB)

Araújo, Vinícius D., E-mail: dantas@ursa.ifsc.usp.br [Instituto de Física, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Lima, Maurício M. de [Instituto de Ciencia de los Materiales, Universidad de Valencia, E-46071 Valencia (Spain); Fundación General, Universitat de Valencia, Valencia (Spain); Cantarero, Andrés [Instituto de Ciencia de los Materiales, Universidad de Valencia, E-46071 Valencia (Spain); Bernardi, Maria I.B. [Instituto de Física, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Bellido, Jorge D.A. [CAP-Engenharia Química, Universidade Federal de São João Del-Rei – UFSJ, São João Del-Rei, MG (Brazil); Assaf, Elisabete M. [Instituto de Química, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Balzer, Rosana; Probst, Luiz F.D. [Departamento de Química, Universidade Federal de Santa Catarina – UFSC, 88040-900 Florianópolis, SC (Brazil); Fajardo, Humberto V. [Departamento de Química, Universidade Federal de Ouro Preto – UFOP, 35400-000 Ouro Preto, MG (Brazil)

2013-11-01

Ceria-supported copper catalysts (Ce{sub 1−x}Cu{sub x}O{sub 2}, with x (mol) = 0, 0.01, 0.03, 0.05 and 0.10) were prepared in one step through the polymeric precursor method. The textural properties of the catalysts were investigated by X-ray diffraction (XRD), Rietveld refinement, N{sub 2}-physisorption (BET surface area), electron paramagnetic resonance (EPR), UV–visible diffuse reflectance and photoluminescence spectroscopies and temperature-programmed reduction (TPR). In a previous study ceria-supported copper catalysts were found to be efficient in the preferential oxidation of CO. In this study, we extended the catalytic application of Ce{sub 1−x}Cu{sub x}O{sub 2} systems to n-hexane oxidation and it was verified that the catalysts were highly efficient in the proposed reaction. The best performance (up to 95% conversion) was observed for the catalysts with low copper loads (Ce{sub 0.97}Cu{sub 0.03}O{sub 2} and Ce{sub 0.99}Cu{sub 0.01}O{sub 2}, respectively). The physicochemical characterizations revealed that these behaviors could be attributed to the copper species present in the catalysts and the interaction between CuO and CeO{sub 2}, which vary according to the copper content. - Highlights: • Synthesis of CuO/CeO2 catalysts by the one-step polymeric precursor method. • 95% n-hexane conversion on Ce0.97Cu0.03O2 catalyst. • Redox properties play a key role in the catalytic performance.

Thermal Behavior and Hydrogen Production of Methanol Autothermal Reforming Performed Using Oxygen Enrichment and Cu/ZnO/Al2O3/Cr2O3/CeO2 Catalyst

Directory of Open Access Journals (Sweden)

Donny Lesmana

2015-07-01

Full Text Available A fixed-bed reactor designed for the autothermal reforming (ATR of methanol under adiabatic conditions was constructed to experimentally determine the profile of temperature and catalyst activity generated using the Cu/ZnO/Al2O3/Cr2O3/CeO2 catalyst. The effect of oxygen enrichment in this experiment was investigated, and the experimental results showed that an increase in oxygen concentration correlated with an increase in the temperature of the catalytic bed; by contrast, this increase in oxygen concentration resulted in a reduction of the startup time of the catalyst. Moreover, the reaction temperature was determined to vary with the position within the catalytic fixed bed. © 2015 BCREC UNDIP. All rights reservedReceived: 29th August 2014; Revised: 19th March 2015; Accepted: 19th March 2015

Microstructural characterization and compression properties of TiC{sub 0.61}/Cu(Al) composite synthesized from Cu and Ti{sub 3}AlC{sub 2} powders

Energy Technology Data Exchange (ETDEWEB)

Huang, Zhenying, E-mail: zhyhuang@bjtu.edu.cn [Institute of Material Science and Engineering, School of Mechanical and Electronic Control Engineering, Beijing Jiaotong University, Beijing 100044 (China); Institut PPRIME, Département de Physique et Mécanique des Matériaux, CNRS, Université de Poitiers, ENSMA, UPR 3346, SP2MI, Téléport 2 Boulevard Marie et Pierre Curie, BP 30179, F86962 Futuroscope Chasseneuil Cedex (France); Bonneville, Joel [Institut PPRIME, Département de Physique et Mécanique des Matériaux, CNRS, Université de Poitiers, ENSMA, UPR 3346, SP2MI, Téléport 2 Boulevard Marie et Pierre Curie, BP 30179, F86962 Futuroscope Chasseneuil Cedex (France); Zhai, Hongxiang [Institute of Material Science and Engineering, School of Mechanical and Electronic Control Engineering, Beijing Jiaotong University, Beijing 100044 (China); Gauthier-Brunet, Veronique [Institut PPRIME, Département de Physique et Mécanique des Matériaux, CNRS, Université de Poitiers, ENSMA, UPR 3346, SP2MI, Téléport 2 Boulevard Marie et Pierre Curie, BP 30179, F86962 Futuroscope Chasseneuil Cedex (France); and others

2014-07-25

Highlights: • Submicro-layered TiC{sub 0.61}/Cu(Al) nanocomposite. • MAX phase. • High yield stress. • Deformation mechanism. - Abstract: A new submicro-layered TiC{sub 0.61}/Cu(Al) composite has been prepared by hot-pressing a mixture of 50 vol.% Ti{sub 3}AlC{sub 2} and 50 vol.% Cu powders at 1150 °C and 30 MPa. It is shown that the initial reinforcement Ti{sub 3}AlC{sub 2} particles have, after synthesis, an unusual microstructure, which consists of submicron-thick layers of TiC{sub 0.61} and Cu(Al) alloy. Both the width of the TiC{sub 0.61} and Cu(Al) layers are ∼150 nm. Thus, the Ti{sub 3}AlC{sub 2} particles are decomposed into the TiC{sub 0.61} phase, while the additional Al atoms provided by Ti{sub 3}AlC{sub 2} diffuse into the molten Cu matrix at high temperature. Compression tests were performed at constant strain rate in the temperature range 20–800 °C. The new designed TiC{sub 0.61}/Cu(Al) composite has both a high yield stress, σ{sub 0.2} measured at 0.2% strain offset, and a high ultimate compressive strength, σ{sub UCS}, which is attributed to strong interface bonding between TiC{sub 0.61} and Cu(Al) phase. For instance, at 20 and 200 °C, σ{sub 0.2} is 770 MPa and 700 MPa, while σ{sub UCS} is 1.18 GPa and 1 GPa, respectively. Plastic deformation takes place in the Cu(Al) matrix. Wavy slip lines are observed indicating that cross-slip could be the dominant deformation mechanism.

Catalytic behavior and synergistic effect of nanostructured mesoporous CuO-MnO{sub x}-CeO{sub 2} catalysts for chlorobenzene destruction

Energy Technology Data Exchange (ETDEWEB)

He, Chi, E-mail: chi_he@mail.xjtu.edu.cn [Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Department of Environmental Science and Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Yu, Yanke [Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Shen, Qun [Research Center for Greenhouse Gases and Environmental Engineering, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China); Chen, Jinsheng, E-mail: jschen@iue.ac.cn [Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Qiao, Nanli [Department of Environmental Nano-materials, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China)

2014-04-01

Graphical abstract: - Highlights: • Mesoporous CuO-MnO{sub x}-CeO{sub 2} oxides with enhanced reducibility and oxygen mobility. • Incorporation of Cu and Mn ions causes abundant crystal defects and oxygen vacancies. • Surface oxygen concentration and active oxygen mobility determine the catalytic efficiency. • Catalysts with conspicuous chlorobenzene low-temperature removal activity and durability. - Abstract: Mesoporous CuO-MnO{sub x}-CeO{sub 2} composite metal oxides with different copper and manganese loadings were prepared by a urea-assistant hydrothermal method, and were further adopted for the complete catalytic combustion of chlorobenzene. The effects of reaction conditions such as inlet reagent concentration and water feed concentration on chlorobenzene combustion were also studied. The structure and textural properties of the synthesized catalysts were characterized via the XRD, N{sub 2} adsorption/desorption, FE-SEM, TEM, H{sub 2}-TPR, O{sub 2}-TPD, and XPS techniques. The characterization results reveal that the presence of a small amount of Mn species can facilitate the incorporation of Cu and Mn ions into ceria lattice to form Cu-Mn-Ce-O solid solution. The synergistic effect of Cu and Mn species can reduce the redox potential of the composite catalysts, and produce large amounts of oxygen vacancies in the interface of CuO{sub x}, MnO{sub x}, and CeO{sub 2} oxides. The catalyst with Cu/Mn atomic ratio of 1/1 exhibits the best chlorobenzene elimination capability, oxidizing about 95% of the inlet chlorobenzene at 264 °C with CO{sub 2} selectivity higher than 99.5%. The concentration and mobility of the chemically adsorbed oxygen are vital for the effective removal of surface Cl species, which inhibits the dissociation of oxygen molecules and decreases the reducibility of the copper and manganese species. It can be rationally concluded that the superior catalytic performance and durability of the mesoporous CuO-MnO{sub x}-CeO{sub 2} composite

Effect of Al2Cu precipitates size and mass transport on the polarisation behaviour of age-hardened Al-Si-Cu-Mg alloys in 0.05 M NaCl

International Nuclear Information System (INIS)

Vieira, A.C.; Pinto, A.M.; Rocha, L.A.; Mischler, S.

2011-01-01

Research highlights: → Influence of the size distribution of Al-Cu phases on the electrochemical behaviour of well defined alloys under controlled mass transport conditions (RDE). → Oxygen reduction occurs only the Al 2 Cu phases. → Thinner Al-Cu grains the oxygen reduction current deviates at high rotation rates from the Levich behaviour. - Abstract: The electrochemical behaviour of age-hardened Al-Si-Cu-Mg alloys was investigated in a 0.05 M NaCl solution under controlled mass transport conditions using a rotating disk electrode. This work aimed at getting better understanding of the effect of the alloy microstructure, in particular the size distribution of Al 2 Cu phase, on the corrosion behaviour of the alloy. Three different size distributions of the Al 2 Cu phase were obtained through appropriate heat treatments. The cathodic reduction of oxygen was found to occur mainly on the Al 2 Cu phases acting as preferential cathodes. Small sized Al 2 Cu phases were found to promote at high rotation rates a transition from a 4 electron to a 2 electron dominated oxygen reduction mechanisms.

Catalytic Oxidation of Propene over Pd Catalysts Supported on CeO2, TiO2, Al2O3 and M/Al2O3 Oxides (M = Ce, Ti, Fe, Mn

Directory of Open Access Journals (Sweden)

Sonia Gil

2015-04-01

Full Text Available In the following work, the catalytic behavior of Pd catalysts prepared using different oxides as support (Al2O3, CeO2 and TiO2 in the catalytic combustion of propene, in low concentration in excess of oxygen, to mimic the conditions of catalytic decomposition of a volatile organic compound of hydrocarbon-type is reported. In addition, the influence of different promoters (Ce, Ti, Fe and Mn when added to a Pd/Al2O3 catalyst was analyzed. Catalysts were prepared by the impregnation method and were characterized by ICP-OES, N2 adsorption, temperature-programmed reduction, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Catalyst prepared using CeO2 as the support was less easily reducible, due to the stabilization effect of CeO2 over the palladium oxides. Small PdO particles and, therefore, high Pd dispersion were observed for all of the catalysts, as confirmed by XRD and TEM. The addition of Ce to the Pd/Al2O3 catalysts increased the metal-support interaction and the formation of highly-dispersed Pd species. The addition of Ce and Fe improved the catalytic behavior of the Pd/Al2O3 catalyst; however, the addition of Mn and Ti decreased the catalytic activity in the propene oxidation. Pd/TiO2 showed the highest catalytic activity, probably due to the high capacity of this catalyst to reoxidize Pd into PdO, as has been found in the temperature-programmed oxidation (TPO experiments.

Spin glass and ferromagnetic properties of Ce(Cu_1_-_xNi_x)_4Mn alloys: Multicritical points in the magnetic phase diagram

International Nuclear Information System (INIS)

Synoradzki, K.; Toliński, T.

2016-01-01

We report on the CeNi_4Mn (ferromagnet FM) - CeCu_4Mn (spin-glass SG) transformation leading to a complex magnetic phase diagram (MPD). It is verified that all the Ce(Cu_1_-_xNi_x)_4Mn alloys are isostructural and the transformation is governed only by the Cu-Ni substitution. MPD is built based on the magnetic dc/ac susceptibility measurements and reveals SG formation as well as the region of the coexistence of the FM and SG state in the middle range of the Ni concentration. The complex MPD is explained by clusters formation and a competition of interactions between various crystallographic sites of the hexagonal CaCu_5-type structure, mainly the 3g-3g and 3g-2c interactions. The predominance of the SG state is confirmed by the analysis of the frequency dependence of the ac magnetic susceptibility components and the relaxation of the remanent magnetization. Additionally, the presence of two multicritical points is observed. - Highlights: • We fully characterized the magnetic properties of Ce(Cu_1_-_xNi_x)_4Mn alloys. • We show the presence of complex magnetic behaviour due to atomic-site disorder. • Magnetic phase diagram revels mixed-phase ground state. • Two multicritical points on magnetic phase diagram occurs.

Luminescence of delafossite-type CuAlO2 fibers with Eu substitution for Al cations.

Science.gov (United States)

Liu, Yin; Gong, Yuxuan; Mellott, Nathan P; Wang, Bu; Ye, Haitao; Wu, Yiquan

2016-01-01

CuAlO 2 has been examined as a potential luminescent material by substituting Eu for Al cations in the delafossite structure. CuAlO 2 :Eu 3+ nanofibers have been prepared via electrospinning for the ease of mitigating synthesis requirements and for future optoelectronics and emerging applications. Single-phase CuAlO 2 fibers could be obtained at a temperature of 1100 °C in air. The Eu was successfully doped in the delafossite structure and two strong emission bands at ~405 and 610 nm were observed in the photoluminescence spectra. These bands are due to the intrinsic near-band-edge transition of CuAlO 2 and the f-f transition of the Eu 3+ activator, respectively. Further electrical characterization indicated that these fibers exhibit semiconducting behavior and the introduction of Eu could act as band-edge modifiers, thus changing the thermal activation energies. In light of this study, CuAlO 2 :Eu 3+ fibers with both strong photoluminescence and p-type conductivity could be produced by tailoring the rare earth doping concentrations.

Preparation and characterization of p–n heterojunction CuBi2O4/CeO2 and its photocatalytic activities under UVA light irradiation

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Abdelkader Elaziouti

2015-04-01

Full Text Available CuBi2O4/CeO2 nanocomposites were synthesized by the solid state method and were characterized by a number of techniques such as X-ray diffraction, scanning electron microscopy and UV–Vis diffuse reflectance spectroscopy. The photocatalytic activity of the samples was investigated under UVA light and assessed using Congo red (CR dye as probe reaction. The efficiency of the coupled CuBi2O4/CeO2 photocatalyst was found to be related to the amount of added CuBi2O4 and to the pH medium. The CuBi2O4/CeO2 photocatalyst exhibited the high efficiency as a result of 83.05% of degradation of CR under UVA light for 100 min of irradiation time with 30 wt% of CuBi2O4 at 25 °C and pH 7, which is about 6 times higher than that of CeO2. The photodegradation reactions satisfactorily correlated with the pseudo-first-order kinetic model. The mechanism of the enhanced photocatalytic efficiency was explained by the heterojunction model.

Electronic states of the θ' phase in Cu-Al alloys as compared to C16-CuAl2: Cu Lα emission excited directly by undulator radiation

Science.gov (United States)

Dallera, C.; de Michelis, B.; Puppin, E.; Braicovich, L.; Brookes, N. B.

1996-01-01

The electronic states of the θ' phase formed by thermal aging in the Al-Cu (0.5 at. %) alloy are compared with those in C16-CuAl2, which is the final phase separated at equilibrium. This is done by means of Cu Lα fluorescence spectroscopy. The high brilliance of undulator radiation used as an excitation source is exploited. The spectra are taken using the first harmonic of the undulator at 1.7 keV, with a full width half maximum of ~250 eV. A narrowing of around 0.5 eV of the Cu Lα spectra in the θ' phase is found. This is explained in terms of the differences in the Cu 3d-Cu 3d interaction in the two phases and of the hybridization between Cu 3d and the nearly free-electron-like electrons. The results demonstrate the future possibilities of fluorescence spectroscopy of minority species in inhomogeneous systems.

Development of Cu-Hf-Al ternary systems and tungsten wire/particle reinforced Cu48Hf43Al9 bulk metallic glass composites for strengthening

International Nuclear Information System (INIS)

Park, Joyoung; An, Jihye; Choi-Yim, Haein

2010-01-01

Stable bulk glass forming alloys can be developed over a wide range of compositions in Cu-Hf-Al ternary systems starting from the Cu 49 Hf 42 Al 9 bulk metallic glass. Ternary Cu-Hf-Al alloys can be cast directly from the melt into copper molds to form fully amorphous strips with thicknesses of 1 to 6 mm. The maximum critical diameter of the new Cu-Hf-Al ternary alloy was 6 mm. X-ray diffraction patterns were used to confirm the amorphous nature of the ternary Cu-Hf-Al alloys. To increase the toughness of these metallic glasses, we reinforced the Cu 48 Hf 43 Al 9 bulk metallic glass-forming liquid with a 50% volume fraction of tungsten particles and an 80% volume fraction of tungsten wires with diameters of 242.4 μm. Composites with a critical diameter of 7 mm and length 70 mm were synthesized. The structure of the composites was confirmed by using X-ray diffraction (XRD), and the scanning electron microscopy (SEM). The mechanical properties of the composites were studied in compression tests. The thermal stability and the crystallization processes of the Cu-Hf-Al alloys and composites were investigated by using differential scanning calorimetry (DSC). Values of the glass transition temperature (T g ), the crystallization temperature (T x ), and the supercooled liquid region (ΔT = T x - T g ) are given in this paper.

Uncovering a new quasi-2D CuO2 plane between the YBa2Cu3O7 and CeO2 buffer layer of coated conductors

Science.gov (United States)

Li, Zhi-Xin; Cao, Jin-Jin; Gou, Xiao-Fan; Wang, Tian-Ge; Xue, Feng

2018-01-01

We report a discovery of the quasi-two-dimensional (quasi-2D) CuO2 plane between the superconductor YBa2Cu3O7 (YBCO) and CeO2 buffer layer (mostly used in the fabrication) of coated conductors through the atomistic computer simulations with the molecular dynamics (MD) and first-principle calculations. For an YBCO coated conductor with multilayer structures, the buffer layers deposited onto a substrate are mainly considered to transfer a strong biaxial texture from the substrate to the YBCO layer. To deeply understand the tuning mechanism of the texture transfer, exploring the complete atomic-level picture of the structure between the YBa2Cu3O7/CeO2 interfaces is firstly required. However, the related observation data have not been available due to some big challenges of experimental techniques. With the MD simulations, having tested the accuracy of the potential functions for the YBa2Cu3O7/CeO2 interface, we constructed a total of 54 possible atom stacking models of the interface and identified its most appropriate and stable structure according to the criterion of the interface adhesion energy and the coherent characterization. To further verify the stability of the identified structure, we performed the first-principle calculations to obtain the adhesion energy and developed the general knowledge of the interface structure. Finally, a coherent interface formed with a new built quasi-2D CuO2 plane that is structurally similar to the CuO2 plane inside bulk YBCO was determined.

Improved resistive switching phenomena and mechanism using Cu-Al alloy in a new Cu:AlO{sub x}/TaO{sub x}/TiN structure

Energy Technology Data Exchange (ETDEWEB)

Roy, S. [Thin Film Nano Tech. Lab., Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kwei-Shan, Tao-Yuan 333, Taiwan (China); Maikap, S., E-mail: sidhu@mail.cgu.edu.tw [Thin Film Nano Tech. Lab., Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kwei-Shan, Tao-Yuan 333, Taiwan (China); Sreekanth, G.; Dutta, M.; Jana, D. [Thin Film Nano Tech. Lab., Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kwei-Shan, Tao-Yuan 333, Taiwan (China); Chen, Y.Y.; Yang, J.R. [Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan (China)

2015-07-15

Highlights: • Cu:AlO{sub x} alloy is used for the first time to have defective TaO{sub x} film. • A relation in between formation voltage and RESET current has been developed. • A switching mechanism based on a thinner with dense Cu filament is demonstrated. • Good uniformity with yield of >90% and long cycles using 1 ms pulse are obtained. - Abstract: Improved resistive switching phenomena such as device-to-device uniformity, lower formation voltage (2.8 V) and RESET current, >500 program/erase cycles, longer read endurance of >10{sup 6} cycles with a program/erase pulse width of 1 μs, and data retention of >225 h under a low current compliance of 300 μA have been discussed by using Cu-Al alloy in Cu:AlO{sub x}/TaO{sub x}/TiN conductive bridging resistive random access memory (CBRAM) device for the first time. The switching mechanism is based on a thinner with dense Cu filament formation/dissolution through the defects in the Cu:AlO{sub x}/TaO{sub x}/TiN structure owing to enhance memory characteristics. These characteristics have been confirmed by measuring randomly picked 100 devices having via-hole size of 0.4 × 0.4 μm{sup 2}. The Cu-Al alloy becomes Cu:AlO{sub x} buffer layer and Ta{sub 2}O{sub 5} becomes TaO{sub x} switching layer owing to Gibbs free energy dependency. All layers and elements are observed by high-resolution transmission electron microscope (HRTEM) image and energy dispersive X-ray spectroscopy (EDX). By developing a numerical equation in between RESET current and formation voltage, it is found that a higher rate of Cu migration is observed owing to both the defective switching layer and larger size, which results a lower formation voltage and RESET current of the Cu:AlO{sub x}/TaO{sub x}/TiN structure, as compared to Cu/Ta{sub 2}O{sub 5}/TiN under external positive bias on the Cu electrode. This simple Cu:AlO{sub x}/TaO{sub x}/TiN CBRAM device is useful for future nanoscale non-volatile memory application.

RBS characterization of Al2O3 films doped with Ce and Mn

International Nuclear Information System (INIS)

Martinez-Martinez, R.; Rickards, J.; Garcia-Hipolito, M.; Trejo-Luna, R.; Martinez-Sanchez, E.; Alvarez-Fregoso, O.; Ramos-Brito, F.; Falcony, C.

2005-01-01

Rutherford backscattering (RBS) with 4 He energies from 2 to 6 MeV has been used to study the properties of thin amorphous photoluminescent Al 2 O 3 :Ce,Mn films grown by spray pyrolysis on Corning 7059 glass substrates. The source solutions were AlCl 3 , CeCl 3 and MnCl 2 dissolved in deionized water. Different molar concentrations (Ce 10%; Mn 1%, 3%, 5%, 7% and 10%) were investigated under the same deposition conditions at a substrate temperature of 300 deg. C. The RBS spectra show a homogeneous depth profile of both Ce and Mn within the films, and the measured quantities are consistent with the original solution concentrations. An important amount of Cl, which plays a significant role in luminescent properties, was detected, in both the doped and undoped samples

Composition of Cu/Al system constructed by means of dynamic atomic deposition

International Nuclear Information System (INIS)

Tashlykov, I.S.; Tul'ev, V.V.

2011-01-01

Rutherford backscattering and RUMP simulation programme have been applied to investigate composition of Cu/Al system prepared using dynamic atomic deposition process when deposition of Cu thin film on Al substrate was assisted with 6 keV Ar + ions irradiation. It is estimated that thin ( ~15 nm) surface layer consists of ~50 at.% Cu, ~10 at.% Ar, ~4 at.% O and the remaining is Al. Dynamic deposition of Cu on Al substrate is accompanied with radiation enhanced diffusion of Cu, O, Ar atoms in substrate and out diffusion of Al atoms in deposited Cu coating. (authors)

NiTiCu/AlN/NiTiCu shape memory thin film heterostructures for vibration damping in MEMS

Energy Technology Data Exchange (ETDEWEB)

Kaur, Navjot; Kaur, Davinder, E-mail: dkaurfph@iitr.ernet.in

2014-03-25

Highlights: • Fabrication of NiTiCu/AlN/NiTiCu heterostructure using dc/rf magnetron sputtering. • Exhibits highest hardness (38 GPa) and elastic modulus (187 GPa). • Enhanced dissipation of mechanical energy (E{sub d} = 5.7 N J). • High damping capacity (0.052) and figure of merit (∼0.62). • Can be applied for vibration damping in MEMS. -- Abstract: Shape memory alloy (NiTiCu) thin films coupled with piezoelectric AlN layer produce an intelligent material for vibration damping. In the present study pure NiTiCu, NiTiCu/AlN and NiTiCu/AlN/NiTiCu heterostructures have been deposited on Si substrate using magnetron sputtering technique. By the use of the interfaces and shape memory effect provided by NiTiCu layers, the damping capacity can be increased along with increase in stiffness and mechanical hardness. The heterostructures were characterized in terms of structural, electrical, morphological and mechanical properties by X-ray diffraction (XRD), four probe resistivity method, atomic force microscopy, field emission scanning electron microscopy, and nanoindentation. The NiTiCu/AlN/NiTiCu heterostructure exhibit enhanced mechanical and damping properties as compared to NiTiCu/AlN and pure NiTiCu. This enhancement in hardness and damping of the heterostructure could be attributed to the shape memory effect of NiTiCu, intrinsic piezoelectricity of AlN and increased number of interfaces in heterostructure that help in dissipation of mechanical vibrations. The findings of this work provide additional impetus for the application of these heterostructures in emerging fields of nanotechnology and microelectro mechanical (MEMS) devices.

NiTiCu/AlN/NiTiCu shape memory thin film heterostructures for vibration damping in MEMS

International Nuclear Information System (INIS)

Kaur, Navjot; Kaur, Davinder

2014-01-01

Highlights: • Fabrication of NiTiCu/AlN/NiTiCu heterostructure using dc/rf magnetron sputtering. • Exhibits highest hardness (38 GPa) and elastic modulus (187 GPa). • Enhanced dissipation of mechanical energy (E d = 5.7 N J). • High damping capacity (0.052) and figure of merit (∼0.62). • Can be applied for vibration damping in MEMS. -- Abstract: Shape memory alloy (NiTiCu) thin films coupled with piezoelectric AlN layer produce an intelligent material for vibration damping. In the present study pure NiTiCu, NiTiCu/AlN and NiTiCu/AlN/NiTiCu heterostructures have been deposited on Si substrate using magnetron sputtering technique. By the use of the interfaces and shape memory effect provided by NiTiCu layers, the damping capacity can be increased along with increase in stiffness and mechanical hardness. The heterostructures were characterized in terms of structural, electrical, morphological and mechanical properties by X-ray diffraction (XRD), four probe resistivity method, atomic force microscopy, field emission scanning electron microscopy, and nanoindentation. The NiTiCu/AlN/NiTiCu heterostructure exhibit enhanced mechanical and damping properties as compared to NiTiCu/AlN and pure NiTiCu. This enhancement in hardness and damping of the heterostructure could be attributed to the shape memory effect of NiTiCu, intrinsic piezoelectricity of AlN and increased number of interfaces in heterostructure that help in dissipation of mechanical vibrations. The findings of this work provide additional impetus for the application of these heterostructures in emerging fields of nanotechnology and microelectro mechanical (MEMS) devices

Al-Cu-Li and Al-Mg-Li alloys: Phase composition, texture, and anisotropy of mechanical properties (Review)

Science.gov (United States)

Betsofen, S. Ya.; Antipov, V. V.; Knyazev, M. I.

2016-04-01

The results of studying the phase transformations, the texture formation, and the anisotropy of the mechanical properties in Al-Cu-Li and Al-Mg-Li alloys are generalized. A technique and equations are developed to calculate the amounts of the S1 (Al2MgLi), T1 (Al2CuLi), and δ' (Al3Li) phases. The fraction of the δ' phase in Al-Cu-Li alloys is shown to be significantly higher than in Al-Mg-Li alloys. Therefore, the role of the T1 phase in the hardening of Al-Cu-Li alloys is thought to be overestimated, especially in alloys with more than 1.5% Li. A new model is proposed to describe the hardening of Al-Cu-Li alloys upon aging, and the results obtained with this model agree well with the experimental data. A texture, which is analogous to that in aluminum alloys, is shown to form in sheets semiproducts made of Al-Cu-Li and Al-Mg-Li alloys. The more pronounced anisotropy of the properties of lithium-containing aluminum alloys is caused by a significant fraction of the ordered coherent δ' phase, the deformation mechanism in which differs radically from that in the solid solution.

Investigation on the Structure and Electrochemical Properties of La-Ce-Mg-Al-Ni Hydrogen Storage Alloy

Directory of Open Access Journals (Sweden)

Yuqing Qiao

2013-01-01

Full Text Available Structure and electrochemical characteristics of La0.96Ce0.04Mg0.15Al0.05Ni2.8 hydrogen storage alloy have been investigated. X-ray diffraction analyses reveal that the La0.96Ce0.04Mg0.15Al0.05Ni2.8 hydrogen storage alloy consisted of a (La, MgNi3 phase with the rhombohedral PuNi3-type structure and a LaNi5 phase with the hexagonal CaCu5-type structure. TEM shows that the alloy is multicrystal with a lattice space 0.187 nm. EDS analyse shows that the content of Mg is 3.48% (atom which coincide well with the designed composition of the electrode alloy. Electrochemical investigations show that the maximum discharge capacity of the alloy electrode is 325 mAh g−1. The alloy electrode has higher discharge capacity within the discharge current density span from 60 mA g−1 to 300 mA g−1. Electrochemical impedance spectroscopy measurements indicate that the charge transfer resistance RT on the alloy electrode surface and the calculated exchange current density I0 are 0.135 Ω and 1298 mA g−1, respectively; the better eletrochemical reaction kinetic of the alloy electrode may be responsible for the better high-rate dischargeability.

Study of the ternary alloy systems Al-Ni-Fe and Al-Cu-Ru with special regard to quasicrystalline phases

International Nuclear Information System (INIS)

Lemmerz, U.

1996-07-01

Two ternary alloy-systems, the Al-Ni-Fe system and the Al-Cu-Ru system were studied with special regard to quasicrystalline phases. Isothermal sections were established in both systems in the stoichiometric area of the quasicrystalline phase. In the Al-Ni-Fe system a new stable decagonal phase was found. Its stoichiometric range is very small around Al 71.6 Ni 23.0 Fe 5.4 . The temperature range in which it is stable lies between 847 and 930 C. The decagonal phase undergoes a eutectoid reaction to the three crystalline phases Al 3 Ni 2 , Al 3 Ni and Al 13 Fe 4 at 847 C. It melts peritectically at 930 C forming Al 13 Fe 4 , Al 3 Ni 2 and a liquid. The investigations in the Al-Cu-Ru system concentrated on the phase equilibria between the icosahedral phase and its neighbouring phases in a temperature range between 600 and 1000 C. The icosahedral phase was observed in the whole temperature range. The investigated stoichiometric area extends down to Al contents of 45%, which allows the fields of existence to be determined for the ternary phases α-AlCuRu, the icosahedral phase and Al 7 Cu 2 Ru. Binary phases were determined down to the upper (high Al content) border of AlRu. No hitherto unknown phase was observed in the investigated area. Rietveld analyses were carried out on α-AlCuRu and Al 7 Cu 2 Ru showing some discrepancies from the α-AlMnSi structure taken as a base for α-AlCuRu and confirming the Al 7 Cu 2 Fe structure for Al 7 Cu 2 Ru. (orig.)

Crystal structure of the Al2CuIr phase

International Nuclear Information System (INIS)

Meshi, L.; Ezersky, V.; Kapush, D.; Grushko, B.

2010-01-01

A new ternary Al 2 CuIr phase was revealed in the Al-Cu-Ir system. It is formed below 1063 o C from the β-phase (CsCl-type structure) extending at elevated temperatures from AlIr. The crystal structure of the Al 2 CuIr phase was determined using a combination of precession electron diffraction and X-ray powder diffraction techniques. The phase has an orthorhombic C-centered unit cell with lattice parameters a = 8.1196(7) A, b = 5.0646(2) A and c = 5.18513(3) A; its crystal symmetry can be described by the Cmme (no. 67) space group (Pearson symbol oC16). The unit cell of the new phase contains 8 Al, 4 Cu and 4 Ir atoms and exhibits a new structure type. The reliability factors characterizing the Rietveld refinement procedure are: R p = 4.45%, R wp = 6.45%, R B = 3.69% and R f = 2.41%.

Thermal expansion of CeCu5.8Ag0.2

International Nuclear Information System (INIS)

Kuechler, R.; Gegenwart, P.; Heuser, K.; Scheidt, E.-W.; Stewart, G.R.; Steglich, F.

2005-01-01

We present low-temperature thermal expansion measurements on the heavy fermion system CeCu 5.8 Ag 0.2 , which is located at an antiferromagnetic (AF) quantum critical point (QCP). At zero magnetic field, the volume expansion coefficient divided by temperature shows a logarithmic divergence upon cooling below 1K. This temperature dependence is incompatible with the predictions of the itinerant spin-density wave theory for an AF QCP. The application of magnetic fields leads to a cross-over to Landau Fermi liquid behavior as expected for a zero-field QCP

Mercury embrittlement of Cu-Al alloys under cyclic loading

Science.gov (United States)

Regan, T. M.; Stoloff, N. S.

1977-01-01

The effect of mercury on the room temperature, high cycle fatigue properties of three alloys: Cu-5.5 pct Al, Cu-7.3 pct Al, and Cu-6.3 pct Al-2.5 pct Fe has been determined. Severe embrittlement under cyclic loading in mercury is associated with rapid crack propagation in the presence of the liquid metal. A pronounced grain size effect is noted under mercury, while fatigue properties in air are insensitive to grain size. The fatigue results are discussed in relation to theories of adsorption-induced liquid metal embrittlement.

Formation of metastable cubic phase in Ce{sub 100−x}Al{sub x} (x=45, 50) alloys and their thermal and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Idzikowski, Bogdan, E-mail: idzi@ifmpan.poznan.pl [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland); Śniadecki, Zbigniew [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland); Puźniak, Roman [Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warszawa (Poland); Kaczorowski, Dariusz [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław (Poland); Centre for Advanced Materials and Smart Structures, Polish Academy of Sciences, Okólna 2, 50-422 Wrocław (Poland)

2017-01-01

Ce{sub 100−x}Al{sub x} (x=45 and 50) alloys were synthesized by rapid quenching technique in the form of ribbons composed of nanocrystalline phase of CeAl with the ClCs-type structure (Pm-3m space group) embedded in an amorphous matrix. The cubic CeAl phase is known as metastable with random distribution of Ce and Al atoms in the unit cell. The crystalline volume fraction is about 7.5% in Ce{sub 55}Al{sub 45} and 3% in Ce{sub 50}Al{sub 50}. The alloy Ce{sub 55}Al{sub 45} shows better thermal stability than Ce{sub 50}Al{sub 50}, indicated by higher effective activation energy and higher crystallization temperature. Small off-stoichiometry in Ce{sub 55}Al{sub 45} results in degrading the glass forming ability and promotes formation of the cubic CeAl phase, as confirmed by magnetic measurements. In both alloys, the Ce ions are in stable trivalent state and order magnetically near 20 K. Another magnetic phase transition close to 10 K was found for Ce{sub 50}Al{sub 50} and was attributed to the presence of the well-known stable orthorhombic CeAl phase. To the best of our knowledge, the magnetic behavior of the CeAl cubic phase is reported here for the first time. - Highlights: • Synthesis of metastable cubic CeAl phase by rapid quenching. • The Ce ions in Ce{sub 55}Al{sub 45} and Ce{sub 50}Al{sub 50} are in stable trivalent state. • Magnetic transition near 10 K connected with the orthorhombic CeAl phase. • Phase transition at about 20 K originates from the cubic CeAl phase.

Study of CuAl(100) by using He ion scattering

Energy Technology Data Exchange (ETDEWEB)

Zhu, L; Zur Muhlen, E; O` Connor, D J [Newcastle Univ., NSW (Australia). Dept. of Physics

1994-12-31

The clean CuAl (100) surface has been investigated by using He{sup +} ion scattering. The polar scans show that Al atoms randomly replace the Cu atoms but sit (0.15{+-}0.05) Angstroms higher than the Cu atoms. The outmost layer concentration of Al is about (17{+-}3)%. The aluminium concentration on the outmost layer is sensitive to the sample temperature up to 300 deg C. 7 refs., 5 figs.

Study of CuAl(100) by using He ion scattering

Energy Technology Data Exchange (ETDEWEB)

Zhu, L.; Zur Muhlen, E.; O`Connor, D.J. [Newcastle Univ., NSW (Australia). Dept. of Physics

1993-12-31

The clean CuAl (100) surface has been investigated by using He{sup +} ion scattering. The polar scans show that Al atoms randomly replace the Cu atoms but sit (0.15{+-}0.05) Angstroms higher than the Cu atoms. The outmost layer concentration of Al is about (17{+-}3)%. The aluminium concentration on the outmost layer is sensitive to the sample temperature up to 300 deg C. 7 refs., 5 figs.

Surface study and thickness control of thin Al2O3 film on Cu-9%Al(111) single crystal

International Nuclear Information System (INIS)

Yamauchi, Yasuhiro; Yoshitake, Michiko; Song Weijie

2004-01-01

We were successful in growing a uniform flat Al 2 O 3 film on the Cu-9%Al(111) surface using the improved cleaning process, low ion energy and short time sputtering. The growth of ultra-thin film of Al 2 O 3 on Cu-9%Al was investigated using Auger electron spectroscopy (AES) and a scanning electron microscope (SEM). The Al 2 O 3 film whose maximum thickness was about 4.0 nm grew uniformly on the Cu-9%Al surface. The Al and O KLL Auger peaks of Al 2 O 3 film shifted toward low kinetic energy, and the shifts were related to Schottky barrier formation and band bending at the Al 2 O 3 /Cu-9%Al interface. The thickness of Al 2 O 3 film on the Cu-9%Al surface was controlled by the oxygen exposure

Precipitation and strengthening phenomena in Al-Si-Ge and Al-Cu-Si-Ge alloys

International Nuclear Information System (INIS)

Mitlin, D.; Morris, J.W.; Dahmen, U.; Radmilovic, V.

2000-01-01

The objective of this work was to determine whether Al rich Al-Si-Ge and 2000 type Al-Cu-Si-Ge alloys have sufficient hardness to be useful for structural applications. It is shown that in Al-Si-Ge it is not possible to achieve satisfactory hardness through a conventional heat treatment. This result is explained in terms of sluggish precipitation of the diamond-cubic Si-Ge phase coupled with particle coarsening. However, Al-Cu-Si-Ge displayed a uniquely fast aging response, a high peak hardness and a good stability during prolonged aging. The high hardness of the Cu containing alloy is due to the dense and uniform distribution of fine θ' precipitates (metastable Al 2 Cu) which are heterogeneously nucleated on the Si-Ge particles. High resolution TEM demonstrated that in both alloys all the Si-Ge precipitates start out, and remain multiply twinned throughout the aging treatment. Since the twinned section of the precipitate does not maintain a low index interface with the matrix, the Si-Ge precipitates are equiaxed in morphology. Copyright (2000) AD-TECH - International Foundation for the Advancement of Technology Ltd

In situ corrosion analysis of Al-Zn-In-Mg-Ti-Ce sacrificial anode alloy

International Nuclear Information System (INIS)

Ma Jingling; Wen Jiuba; Zhai Wenxia; Li Quanan

2012-01-01

The corrosion behaviour of Al-5Zn-0.02In-1Mg-0.05Ti-0.5Ce (wt.%) alloy has been investigated by immersion test, scanning electron microscopy, energy dispersive X-ray detector, electrochemical impedance spectroscopy and electrochemical noise. The results show that there exist different corrosion types of the alloy in 3.5% NaCl solution with the immersion time. At the initial stage of immersion, pitting due to the precipitates predominates the corrosion with a typical inductive loop at low frequencies in electrochemical impedance spectroscopy. The major precipitates of the alloy are MgZn 2 and Al 2 CeZn 2 particles. The corrosion potentials of the bulk MgZn 2 and Al 2 CeZn 2 alloys are negative with respect to that of α-Al, so the MgZn 2 and Al 2 CeZn 2 precipitates can act as activation centre and cause the pitting. In the late corrosion, a relative uniform corrosion predominates the corrosion process controlled by the dissolution/precipitation of the In ions and characterized by a capacitive loop at medium-high frequencies in electrochemical impedance spectroscopy. The potential noise of the pitting shows larger amplitude fluctuation and lower frequency, but the potential noise of the uniform corrosion occurs with smaller amplitude fluctuation and higher frequency.

Ordering and structural vacancies in non-stoichiometric Cu-Al γ brasses

International Nuclear Information System (INIS)

Kisi, E.H.; Browne, J.D.

1991-01-01

γ-Brass structures are based on the cubic packing of 26-atom clusters which have, as concentric subunits, an inner and an outer tetrahedron (IT, OT), an octahedron (OH) and a cuboctahedron (CO). Cu 9 Al 4 [M r = 679.37, P43m, a = 8.7046(1) A, V = 659.5 A 3 , Z = 4, D x = 6.846 Mg m -3 , R wp = 0.051, R B = 0sun017 for 238 powder reflections] is the stoichiometric γ brass of the Cu-Al system and contains two clusters (A, B) per unit cell. Al atoms occupy a 4(e) (IT) site in cluster A and a 12(i) (CO) site in cluster B. Cu atoms occupy the remaining 4(e) (OT), 6(f) (OH) and 12(i) (CO) sites of cluster A and the two 4(e) (IT, OT) and a 6(g) (OH) site of cluster B. The structure has considerable solubility for Al and this paper contains a systematic neutron powder diffraction study of the changes in the Cu 9 Al 4 structure at 295 K (λ = 1.376 A) and 77 K(λ = 1.500 A) as Al is added. The structure was found to remain cubic for compositions Cu 8.93 Al 4.08 , Cu 8.83 , Al 4.17 , Cu 8.75 Al 4.25 and Cu 8.58 Al 4.42 . At Cu 8.30 Al 4.58 the structure was slightly distorted to an undetermined symmetry. For Cu 8.03 Al 4.68 and Cu 7.55 Al 4.80 the structure was found to be rhombohedral [M r = 636.57, R3m, a = 8.7066(1) A, α = 89.74(1) deg, V = 660.0(1) A 3 , Z = , D x = 6.406, D m = 6.41 Mg m -3 , R wp = 0.064, R B = 0.025 for 702 reflections; and M r = 609.31, R3m, a = 8.6884(1) A, α = 89.78(1) deg, V = 655.9(1) A 3 , Z = 4, D x = 6.170, D m = 6.18 Mg m -3 , R wp = 0.064, R B = 0.027 for 789 reflections, respectively]. The non-cubic structures contain sufficient structural vacancies to maintain a classical valence content of 88 electrons per unit cell. Refined structures are presented for all of the above compositions, except Cu 8.30 Al 4.58 , and the results discussed in terms of current γ-brass stability theories. (orig.)

Ca2 Al2 SiO7 :Ce3+ phosphors for mechanoluminescence dosimetry.

Science.gov (United States)

Tiwari, Geetanjali; Brahme, Nameeta; Sharma, Ravi; Bisen, D P; Sao, Sanjay Kumar; Sahu, Ishwar Prasad

2016-12-01

A series of Ce 3+ ion single-doped Ca 2 Al 2 SiO 7 phosphors was synthesized by a combustion-assisted method at an initiating temperature of 600 °C. The samples were annealed at 1100 °C for 3 h and their X-ray diffraction patterns confirmed a tetragonal structure. The phase structure, particle size, surface morphology and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. Thermoluminescence (TL) intensity increased with increase in ultraviolet (UV) light exposure time up to 15 min. With further increase in the UV irradiation time the TL intensity decreases. The increase in TL intensity indicates that trap concentration increased with UV exposure time. A broad peak at 121 °C suggested the existence of a trapping level. The peak of mechanoluminescence (ML) intensity versus time curve increased linearly with increasing impact velocity of the moving piston. Mechanoluminescence intensity increased with increase in UV irradiation time up to 15 min. Under UV-irradiation excitation, the TL and ML emission spectra of Ca 2 Al 2 SiO 7 :Ce 3+ phosphor showed the characteristic emission of Ce 3+ peaking at 400 nm (UV-violet) and originating from the Ce 3+ transitions of 5d-4f ( 2 F 5/2 and 2 F 7/2 ). The photoluminescence (PL) emission spectra for Ca 2 Al 2 SiO 7 :Ce 3+ were similar to the ML/TL emission spectra. The mechanism of ML excitation and the suitability of the Ca 2 Al 2 SiO 7 :Ce 3+ phosphor for radiation dosimetry are discussed. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Intermetallic Compound Growth and Stress Development in Al-Cu Diffusion Couple

Science.gov (United States)

Mishler, M.; Ouvarov-Bancalero, V.; Chae, Seung H.; Nguyen, Luu; Kim, Choong-Un

2018-01-01

This paper reports experimental observations evidencing that the intermetallic compound phase interfaced with Cu in the Al-Cu diffusion couple is most likely α2-Cu3Al phase, not γ-Cu9Al4 phase as previously assumed, and that its growth to a critical thickness may result in interface failure by stress-driven fracture. These conclusions are made based on an interdiffusion study of a diffusion couple made of a thick Cu plate coated with ˜ 2- μm-thick Al thin film. The interface microstructure and lattice parameter were characterized using scanning electron microscopy and x-ray diffraction analysis. Specimens aged at temperature between 623 K (350°C) and 723 K (450°C) for various hours produced consistent results supporting the main conclusions. It is found that disordered α2-Cu3Al phase grows in a similar manner to solid-state epitaxy, probably owing to its structural similarity to the Cu lattice. The increase in the interface strain that accompanies the α2-Cu3Al phase growth ultimately leads to interface fracture proceeding from crack initiation and growth along the interface. This mechanism provides the most consistent explanation for interface failures observed in other studies.

I sistemi locali del credito in regioni a diverso stadio di sviluppo

OpenAIRE

Pietro Alessandrini

1996-01-01

Il lavoro si inserisce nella problematica dell'articolazione territoriale del sistema finanziario italiano, prendendo in esame i problemi di integrazione dei sistemi locali del credito operanti in regioni decentrate e diversamente sviluppate. A fronte di un quadro operativo in forte evoluzione, i sistemi locali del credito debbono divenire terreno di interscambio secondo un approccio che abbiamo definito "possibilista" , alla ricerca d'ogni possibilita' di raccordo interattivo tra reale e fin...

Synergy of CuO and CeO2 combination for mercury oxidation under low-temperature selective catalytic reduction atmosphere

KAUST Repository

Li, Hailong; Zhu, Lei; Wu, Shaokang; Liu, Yang; Shih, Kaimin

2016-01-01

.0% was observed on the CuCeTi catalyst at 200 °C, even the gas hourly space velocity was extremely high. To analyze the synergistic effect, comparisons of catalyst performance in the presence of different SCR reaction gases were systematically conducted over Cu

Electrical resistivity of Al-Cu liquid binary alloy

Science.gov (United States)

Thakor, P. P.; Patel, J. J.; Sonvane, Y. A.; Jani, A. R.

2013-06-01

Present paper deals with the electrical resistivity (ρ) of liquid Al-Cu binary alloy. To describe electron-ion interaction we have used our parameter free model potential along with Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. To see the influence of exchange and correlation effect, Hartree, Taylor and Sarkar et al local field correlation functions are used. From present results, it is seen that good agreements between present results and experimental data have been achieved. Lastly we conclude that our model potential successfully produces the data of electrical resistivity (ρ) of liquid Al-Cu binary alloy.

Neutron diffraction on CeMnAlD{sub x} (0{<=}x{<=}2.5)

Energy Technology Data Exchange (ETDEWEB)

Spatz, P.; Gross, K.; Schlapbach, L. [Fribourg Univ. (Switzerland); Fischer, P.; Fauth, F. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-09-01

CeMnAl was found to absorb considerable amounts of hydrogen. Part of the totally stored hydrogen is absorbed at low pressures (< 10 mbar). Additional hydrogen can be absorbed and desorbed reversible in a wide pressure range (10 mbar to 10 bar) at room temperature. In order to a better understanding of this new metal-hydride system, we performed neutron diffraction on deuterated CeMnAl samples with different D-concentrations. (author) 1 fig., 2 refs.

Low-temperature carbon monoxide oxidation over zirconia-supported CuO–CeO{sub 2} catalysts: Effect of zirconia support properties

Energy Technology Data Exchange (ETDEWEB)

Moretti, Elisa, E-mail: elisa.moretti@unive.it [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, INSTM Venice Research Unit, Via Torino 155/B, 30172 Mestre Venezia (Italy); Molina, Antonia Infantes [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga (Spain); Sponchia, Gabriele; Talon, Aldo; Frattini, Romana [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, INSTM Venice Research Unit, Via Torino 155/B, 30172 Mestre Venezia (Italy); Rodriguez-Castellon, Enrique [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga (Spain); Storaro, Loretta [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, INSTM Venice Research Unit, Via Torino 155/B, 30172 Mestre Venezia (Italy)

2017-05-01

Highlights: • CuO-CeO{sub 2}/ZrO{sub 2} materials were investigated in the low temperature CO oxidation. • High surface area ZrO{sub 2} synthetized by sol-gel method. • Low ZrO{sub 2} surface area synthetized by fast precipitation. • Sol-gel samples showed, after impregnation, a severe decrease of surface area. • CuO-CeO{sub 2}/ZrO{sub 2} with precipitated ZrO{sub 2} led to a very active catalyst. - Abstract: A study was conducted to investigate the effect of the preparation route of ZrO{sub 2} in CuO–CeO{sub 2}/ZrO{sub 2} catalysts for the oxidation of carbon monoxide at low temperature (COX). Four ZrO{sub 2} supports were synthetized via either type sol-gel methodology or precipitation. The final Cu-Ce-Zr oxide catalysts were prepared by incipient wetness co-impregnation with copper and cerium solutions (with a loading of 6 wt% of CuO and 20 wt% of CeO{sub 2}). The catalyst crystalline phases, texture and active species reducibility were determined by XRD, N{sub 2} physisorption at −196 °C and H{sub 2}-TPR, respectively; meanwhile the surface composition and copper-cerium electronic states were studied by XPS. The catalytic activity was evaluated in the oxidation of CO to CO{sub 2}, in the 40–215 °C temperature range. Catalytic results evidenced that the samples prepared by a sol-gel methodology showed, after the impregnation, a severe decrease of specific surface area and pore volume attributable to a wide degree of pore blockage caused by the presence of metal oxide particles and a collapse of the structure partially burying the active sites. A simple co-impregnation of a zirconia support, obtained through facile and fast precipitation, provided instead a catalyst with very good redox properties and high dispersion of the active phases, which completely oxidizes CO in the range 115–215 °C with T{sub 50} of 65 °C. This higher observed activity was ascribed to the formation of a larger fraction of highly dispersed and easily reducible Cu

On the mechanical behavior of a cryomilled Al-Ti-Cu alloy

International Nuclear Information System (INIS)

Han, Bing Q.; Lavernia, Enrique J.; Mohamed, Farghalli A.

2003-01-01

The mechanical behavior of a cryomilled Al10Ti2Cu that was later extruded was investigated in compression. The data obtained show that the strength of the extruded alloy parallel to the extrusion axis is higher than that normal to the axis. Also, a comparison between the compression behavior of the alloy and its tensile behavior reveals that there is a small asymmetry of yield strength with respect to deformation mode. Examination of the microstructure of the cryomilled alloy by means of transmission electron microscopy (TEM) indicates the presence of two phases: approximately 90% nanostructured Al(Cu) phase containing a dispersion of Al 3 Ti and 10% coarse-grained Al(Cu) phase. TEM observations indicate that as a result of the extrusion process, the larger (softer) grains of the Al(Cu) phase experience severe deformation, resulting in the development of mechanical fibering. It is suggested that the presence of coarse-grained Al(Cu) 'islands' in the matrix of the nanostructured phase and their change during extrusion into elongated bands may be responsible for the anisotropy of the mechanical properties of the extruded cryomilled Al10Ti2Cu

Synthesis of CuAlO2 nanofibrous mats by electrospinning

International Nuclear Information System (INIS)

Zhao Shizhen; Li Miaoyu; Liu Xiaomin; Han Gaoyi

2009-01-01

Electrospinning as a versatile method for preparation of nanofibers has been used to fabricate the polyvinylalcohol nanofibers containing equal molar of aluminum nitrate and copper acetate. After pretreated at 400 deg. C, the composite fibrous mats were annealed at 1100 deg. C in air for 5 h and then the delafossite-structured p-type CuAlO 2 ceramics fibrous mats were obtained. The obtained CuAlO 2 ceramics fibrous mats were characterized by scanning electrical microscope, X-ray diffraction and diffuse reflectance spectroscopy. The direct energy gap of the prepared CuAlO 2 ceramics fibrous mats was measured to be about 3.38 eV. The CuAlO 2 behaved like semiconductors and the thermally activated energy was about 0.25 eV.

Study on fast luminescence component induced by gamma-rays in Ce doped LiCaAlF6 scintillators

International Nuclear Information System (INIS)

Watanabe, Kenichi; Kondo, Yoshiyuki; Yamazaki, Atsushi; Uritani, Akira; Iguchi, Tetsuo; Kawaguchi, Noriaki; Fukuda, Kentaro; Ishizu, Sumito; Yanagida, Takayuki; Fujimoto, Yutaka; Yoshikawa, Akira

2014-01-01

We discuss the origin of the fast luminescence component induced by fast electrons generated in gamma-ray interactions in Ce doped LiCaAlF 6 scintillators. Although the slow luminescence component induced by Ce 3+ emissions depends on the Ce concentration in the LiCaAlF 6 scintillator, the fast component is independent. The fast component is suggested to be generated in the host matrix of the LiCaAlF 6 crystal. From quantitative considerations based on Frank–Tamm equation, which shows the light yield of the Cherenkov radiation, the Cherenkov radiation was determined as the origin of the fast component. We, additionally, found that the slow rise time of main Ce 3+ emissions in the Ce:LiCaAlF 6 scintillator plays an important role to perform the pulse shape discrimination. - Highlights: • The fast luminescence in Ce:LiCaAlF 6 scintillator is generated in the host matrix. • The origin of the fast luminescence is determined as the Cherenkov radiation. • The slow rise time also plays an important role to perform PSD

The Paramagnetism of Small Amounts of Mn Dissolved in Cu-Al and Cu-Ge Alloys

Energy Technology Data Exchange (ETDEWEB)

Myers, H P; Westin, R

1963-06-15

Previous measurements of the valency of Mn in Cu-Zn alloys have been confirmed by measurements with the isoelectronic Cu-Al and Cu-Ge alloys as matrices for Mn. The valency, having the value i in pure copper, decreases slightly with increasing electron to atom ratio attaining the values 0. 9 and 0. 8 at the limiting composition in the Al and Ge alloys respectively. The apparent size of Mn in these alloys is discussed.

The Paramagnetism of Small Amounts of Mn Dissolved in Cu-Al and Cu-Ge Alloys

International Nuclear Information System (INIS)

Myers, H.P.; Westin, R.

1963-06-01

Previous measurements of the valency of Mn in Cu-Zn alloys have been confirmed by measurements with the isoelectronic Cu-Al and Cu-Ge alloys as matrices for Mn. The valency, having the value i in pure copper, decreases slightly with increasing electron to atom ratio attaining the values 0. 9 and 0. 8 at the limiting composition in the Al and Ge alloys respectively. The apparent size of Mn in these alloys is discussed

Thermal expansion of the heavy-fermion compound CeInCu2 at high pressure

International Nuclear Information System (INIS)

Kagayama, Tomoko; Oomi, Gendo; Onuki, Yoshichika; Komatsubara, Takemi

1994-01-01

The thermal expansion coefficient α of the heavy-fermion compound CeInCu 2 has been measured at high pressure up to 2 GPa in the temperature range from 6 to 300 K. It is found that the linear term in α(T) at low temperature decreases by the application of pressure. ((orig.))

The roles of Al{sub 2}Cu and of dendritic refinement on surface corrosion resistance of hypoeutectic Al-Cu alloys immersed in H{sub 2}SO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Osorio, Wislei R. [Department of Materials Engineering, State University of Campinas, UNICAMP, P.O. Box 6122, 13083-970 Campinas, SP (Brazil); Spinelli, Jose E. [Department of Materials Engineering, State University of Campinas, UNICAMP, P.O. Box 6122, 13083-970 Campinas, SP (Brazil); Freire, Celia M.A. [Department of Materials Engineering, State University of Campinas, UNICAMP, P.O. Box 6122, 13083-970 Campinas, SP (Brazil); Cardona, Margarita B. [Department of Materials Engineering, State University of Campinas, UNICAMP, P.O. Box 6122, 13083-970 Campinas, SP (Brazil); Garcia, Amauri [Department of Materials Engineering, State University of Campinas, UNICAMP, P.O. Box 6122, 13083-970 Campinas, SP (Brazil)]. E-mail: amaurig@fem.unicamp.br

2007-09-27

Al-Cu alloys castings can exhibit different corrosion responses at different locations due to copper content and to the resulting differences on microstructural features and on Al{sub 2}Cu fractions. The aim of this study was to investigate the influence of Al{sub 2}Cu intermetallic particles associated to the dendritic arm spacings on the general corrosion resistance of three different hypoeutectic Al-Cu alloys samples in sulfuric acid solution. The cast samples were produced using a non-consumable tungsten electrode furnace with a water-cooled copper hearth under argon atmosphere. The typical microstructural pattern was examined by using electronic microscopy techniques. In order to evaluate the surface corrosion behavior of such Al-Cu alloys, corrosion tests were performed in a 0.5 M sulfuric acid solution at 25 deg. C by using an electrochemical impedance spectroscopy (EIS) technique and potentiodynamic polarization curves. An equivalent circuit was also used to provide quantitative support for the discussions and understanding of the corrosion behavior. It was found that Al{sub 2}Cu has a less noble corrosion potential than that of the Al-rich phase. Despite that, dendrite fineness has proved to be more influent on corrosion resistance than the increase on alloy copper content with the consequent increase on Al{sub 2}Cu fraction.

Ultrafine Nanocrystalline CeO2@C-Containing NaAlH4 with Fast Kinetics and Good Reversibility for Hydrogen Storage.

Science.gov (United States)

Zhang, Xin; Liu, Yongfeng; Wang, Ke; Li, You; Gao, Mingxia; Pan, Hongge

2015-12-21

A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

FABRICATION OF Cu-Al-Ni SHAPE MEMORY THIN FILM BY THERMAL EVOPRATION

OpenAIRE

Özkul, İskender; Canbay, Canan Aksu; Tekataş, Ayşe

2017-01-01

Among the functional, materials shape memory alloysare important because of their unique properties. So, these materials haveattracted more attention to be used in micro/nano electronic andelectromechanic systems. In this work, thermal evaporation method has been usedto produce CuAlNi shape memory alloy thin film. The produced CuAlNi thin filmhas been characterized and the presence of the martensite phase wasinvestigated and compared with the CuAlNi alloy sample. CuAlNi shape memoryalloy thin...

Phase relationship in AL-Cu-Sc alloys at 450-500 deg C

International Nuclear Information System (INIS)

Kharakterova, M.L.

1991-01-01

Al-Cu-Sc alloys containing up to 40% Cu and up to 6% Sc at 450 deg C and 500 deg C are studied using light microscopy, X-ray-spectral microanalysis, X-ray diffraction analysis, scanning electron microscopy, measurement of microhardness and electric resistance. It is determined, that in equilibrium with aluminium solid solution under the given temperature ther are Al 3 Sc, CuAl 2 phases of the respective binary systems and W (ScCu 6.6-4 Al 5.4-8 ) ternary phase. Isothermal cross sections of Al-Cu-Sc system at 450 and 500 deg C are plotted. Microhardness of equilibrium phases is measured. Combined solubility of copper and scandium in aluminium is determined

Preparation of highly oriented Al:ZnO and Cu/Al:ZnO thin films by sol-gel method and their characterization

Energy Technology Data Exchange (ETDEWEB)

Vijayaprasath, G.; Murugan, R. [School of Physics, Alagappa University, Karaikudi 630 004, Tamil Nadu (India); Mahalingam, T. [Department of Electrical and Computer Engineering, Ajou University, Suwon 443-749 (Korea, Republic of); Hayakawa, Y. [Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8011 (Japan); Ravi, G., E-mail: gravicrc@gmail.com [School of Physics, Alagappa University, Karaikudi 630 004, Tamil Nadu (India)

2015-11-15

Highly oriented thin films of Al doped ZnO (Al:ZnO) and Cu co-doped Al:ZnO (Cu/Al:ZnO) thin films were successfully deposited by sol–gel spin coating on glass substrates. The deposited films were characterized using X-ray diffraction analysis and found to exhibit hexagonal wurtzite structure with c-axis orientation. SEM images revealed that hexagonal rod shaped morphologies were grown perpendicular to the substrate surface due to repeated deposition process. High transmittance values were observed for pure ZnO compared to Al:ZnO and Cu/Al:ZnO thin films. The band gap widening is caused by the increase of carrier concentration, which is believed to be due to Burstein-Moss effect due to Al and Cu doping. PL spectra of Cu/Al:ZnO thin films indicate that the UV emission peaks slightly shifted towards lower energy side. XPS study was carried out for Zn{sub 0.80}Al{sub 0.10}Cu{sub 0.10}O thin films to analyze the binding energy of Al, Cu, Zn and O. Magnetic measurement studies exhibited ferromagnetic behavior at room temperature, which may be due to the increase in copper concentration in the doped films. The ferromagnetic behavior can be understood from the exchange coupling between localized ‘d’ spin of Cu ion mediated by free delocalized carriers. - Highlights: • High quality of Al:ZnO and Cu co-doped Al:ZnO thin films were fabricated by sol–gel method. • The XRD analyses revealed that the deposited thin films have hexagonal wurtzite structure. • XPS was carried out for Zn{sub 0.80}Al{sub 0.10}Cu{sub 0.10}O films to analyze the binding energy of Al, Cu, Zn and O. • SEM studies were made for Al:ZnO and Cu/Al:ZnO thin films. • RTFM was observed in Cu co-doped Al:ZnO thin films.

Quality analysis of the Al-Si-Cu alloy castings

Directory of Open Access Journals (Sweden)

L.A. Dobrzański

2007-04-01

Full Text Available The developed design methodologies both the material and technological ones will make it possible to improve shortly the quality of materials from the light alloys in the technological process, and the automatic process flow correction will make the production cost reduction possible, and - first of all - to reduce the amount of the waste products. Method was developed for analysis of the casting defects images obtained with the X-ray detector analysis of the elements made from the Al-Si-Cu alloys of the AC-AlSi7Cu3Mg type as well as the method for classification of casting defects using the artificial intelligence tools, including the neural networks; the developed method was implemented as software programs for quality control. Castings were analysed in the paper of car engine blocks and heads from the Al-Si-Cu alloys of the AC-AlSi7Cu3Mg type fabricated with the “Cosworth” technological process. The computer system, in which the artificial neural networks as well as the automatic image analysis methods were used makes automatic classification possible of defects occurring in castings from the Al-Si-Cu alloys, assisting and automating in this way the decisions about rejection of castings which do not meet the defined quality requirements, and therefore ensuring simultaneously the repeatability and objectivity of assessment of the metallurgical quality of these alloys.

A σ-T diagram analysis regarding the γ' inhibition in β ↔ β' + γ' cycling in CuAlNi single crystals

International Nuclear Information System (INIS)

Gastien, R.; Corbellani, C.E.; Sade, M.; Lovey, F.C.

2006-01-01

An effect of inhibition of the γ' martensitic structure in thermal and pseudoelastic β ↔ β' + γ' cycling in CuAlNi single crystals was reported previously [Gastien R, Corbellani CE, Alvarez Villar HN, Sade M, Lovey FC. Mater Sci Eng A 2003;349:191], and an experiment to determine the new thermodynamic parameters to obtain the stress-induced γ' structure was performed [Gastien R, Corbellani CE, Sade M, Lovey FC. Acta Mater 2005;53:1685]. In this paper, a thermodynamic analysis of this effect using σ-T diagrams is proposed, in order to obtain a proper estimation of the energy involved in the inhibition process for pseudoelastic β ↔ β' + γ' cycling

Interfacial phase formation of Al-Cu bimetal by solid-liquid casting method

Directory of Open Access Journals (Sweden)

Ying Fu

2017-05-01

Full Text Available The solid-liquid method was used to prepare the continuous casting of copper cladding aluminium by liquid aluminum alloy and solid copper, and the interfacial phase formation of Al-Cu bimetal at different pouring temperatures (700, 750, 800 oC was investigated by means of metallograph, scanning electron microscopy (SEM and energy dispersive spectrometry (EDS methods. The results showed that the pouring temperature of aluminum melt had an important influence on the element diffusion of Cu from the solid Cu to Al alloy melt and the reactions between Al and Cu, as well as the morphology of the Al-Cu interface. When the pouring temperature was 800 oC, there were abundant Al-Cu intermetallic compounds (IMCs near the interface. However, a lower pouring temperature (700 oC resulted in the formation of cavities which was detrimental to the bonding and mechanical properties. Under the conditions in this study, the good metallurgical bonding of Al-Cu was achieved at a pouring temperature of 750 oC.

Formation of Al70Cu20Fe10 icosahedral quasicrystal by mechanically alloyed method

International Nuclear Information System (INIS)

Yin Shilong; Bian Qing; Qian Liying; Zhang Aimei

2007-01-01

The structural evolutions of the mechanically alloyed ternary Al 70 Cu 20 Fe 10 powders with the milling time and the annealing treatment have been studied by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and X-ray absorption fine-structure spectroscopy (XAFS) techniques. Results show that an Al 2 Cu compound forms with short-time milling, while a Cu 9 Al 4 compound forms with long-time milling. Fe can react with Al-Cu alloy by annealing treatment. Al 7 Cu 2 Fe compound with tetragonal structure or Al (Cu, Fe) solid solution with cubic structure may form at lower temperature, while a quasicrystal phase of Al 65 Cu 20 Fe 15 alloy may form at higher temperature

Nanocrystallization in Cu-Zr-Al-Sm Bulk Metallic Glasses

Science.gov (United States)

Sikan, Fatih; Yasar, Bengisu; Kalay, Ilkay

2018-04-01

The effect of rare-earth element (Sm) microalloying on the thermal stability and crystallization kinetics of melt-spun ribbons and suction-cast rods of Zr48Cu38.4Al9.6Sm4 alloy were investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), and atom probe tomography (APT). The XRD results of constant heating rate annealing indicated that amorphous Zr48Cu38.4Al9.6Sm4 melt-spun ribbons devitrifies into Cu2Sm at 673 K (400 °C). The sequence continues with the precipitation of Cu10Zr7 and then these two phases coexist. XRD and TEM studies on 1 mm diameter as suction-cast rods indicated the precipitation of 30-nm-mean size Cu2Sm crystals during solidification. TEM investigation of the isothermal crystallization sequence of melt-spun ribbons and 1-mm-diameter suction-cast rods revealed the precipitation of Cu2Sm nanocrystals at the onset of crystallization and the restriction of the growth of these nanocrystals up to 10 nm diameter with further annealing. APT analysis of 1-mm-diameter suction-cast rods showed that the limited growth of Cu2Sm nanocrystals is due to sluggish diffusion of Sm and Al-Zr pile up at the interface.

Interface phenomena in the Y2O3/(Al-Cu) system

International Nuclear Information System (INIS)

Barzilai, S.; Aizenshtein, M.; Froumin, N.; Frage, N.

2006-01-01

Wetting behavior and the interface reaction in the Y 2 O 3 /(Cu-Al) system were investigated at 1423 K. A contact angle of about 130 o was measured in the Y 2 O 3 /Cu system. Aluminum addition to copper improves wetting and the transition from non-wetting to wetting (θ ≤ 90 o ) was observed for the alloy with 50 at.% Al. The microstructure examination of the interface indicates that Al reacts with yttria, yttrium dissolves in the melt and a crater of AlYO 3 is formed at the substrate. The interface interaction in the Y 2 O 3 /(Cu-Al) system is in a good agreement with the results of a thermodynamic analysis in the Y-Al-Cu-O system. The crater depth and the macroscopic final contact angles are correlated with the Y and Al activities in the melt

Magnetic behaviour of new Ce compounds

Energy Technology Data Exchange (ETDEWEB)

Sampathkumaran, E V [Tata Inst. of Fundamental Research, Bombay (India); Mallik, R [Tata Inst. of Fundamental Research, Bombay (India)

1996-07-01

We report initial results of our investigation on the magnetic behaviour of some new Ce compounds. The compounds, CeIr{sub 2}B{sub 2}C and CeIr{sub 2}Ge{sub 2}, do not appear to exhibit bulk magnetic ordering down to 2 K. The alloys, Ce{sub 2}Pd{sub 2}In and Ce{sub 2}Cu{sub 2}In, order magnetically below 4 and 6 K, respectively, and a marginal change in the Pd(Cu)/In composition does not significantly influence the ordering temperatures. (orig.).

Ductile shape memory alloys of the Cu-Al-Mn system

International Nuclear Information System (INIS)

Kainuma, R.; Takahashi, S.; Ishida, K.

1995-01-01

Cu-Al-Mn shape memory alloys with enhanced ductility have been developed by decreasing the degree of order in the β parent phase. Cu-Al-Mn alloys with Al contents lower than 18% exhibit good ductility with elongations of about 15% and excellent cold-workability arising from a lower degree of order in the Heusler (L21) β 1 parent phase, without any loss in their shape memory behavior. In this paper the mechanical and shape memory characteristics, such as the cold-workability, the Ms temperatures, the shape memory effect and the pseudo-elasticity of such ductile Cu-Al-Mn alloys are presented. (orig.)

Solidified structure of Al-Pb-Cu alloys

International Nuclear Information System (INIS)

Ikeda, Tetsuyuki; Nishi, Seiki; Kumeuchi, Hiroyuki; Tatsuta, Yoshinori.

1986-01-01

Al-Pb-Cu alloys were cast into bars or plates in different two metal mold casting processes in order to suppress gravity segregation of Pb and to achieve homogeneous dispersion of Pb phase in the alloys. Solidified structures were analyzed by a video-pattern-analyzer. Plate castings 15 to 20 mm in thickness of Al-Pb-1 % Cu alloy containing Pb up to 5 % in which Pb phase particles up to 10 μm disperse are achieved through water cooled metal mold casting. The plates up to 5 mm in thickness containing Pb as much as 8 to 10 % cast in this process have dispersed Pb particles up to 5 μm in diameter in the surface layer. Al-8 % Pb-1 % Cu alloy bars 40 mm in diameter and 180 mm in height in which gravity segregation of Pb is prevented can be cast by movable and water sprayed metal mold casting at casting temperature 920 deg C and mold moving speed 1.0 mm/s. Pb phase particles 10 μm in mean size are dispersed in the bars. (author)

Effect of similar elements on improving glass-forming ability of La-Ce-based alloys

International Nuclear Information System (INIS)

Zhang Tao; Li Ran; Pang Shujie

2009-01-01

To date the effect of unlike component elements on glass-forming ability (GFA) of alloys have been studied extensively, and it is generally recognized that the main consisting elements of the alloys with high GFA usually have large difference in atomic size and atomic interaction (large negative heat of mixing) among them. In our recent work, a series of rare earth metal-based alloy compositions with superior GFA were found through the approach of coexistence of similar constituent elements. The quinary (La 0.5 Ce 0.5 ) 65 Al 10 (Co 0.6 Cu 0.4 ) 25 bulk metallic glass (BMG) in a rod form with a diameter up to 32 mm was synthesized by tilt-pour casting, for which the glass-forming ability is significantly higher than that for ternary Ln-Al-TM alloys (Ln = La or Ce; TM = Co or Cu) with critical diameters for glass-formation of several millimeters. We suggest that the strong frustration of crystallization by utilizing the coexistence of La-Ce and Co-Cu to complicate competing crystalline phases is helpful to construct BMG component with superior GFA. The results of our present work indicate that similar elements (elements with similar atomic size and chemical properties) have significant effect on GFA of alloys.

Comparative Study of Various Preparation Methods of CuO–CeO2 Catalysts for Oxidation of n–Hexane and iso–Octane

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Ashutosh Mishra

2013-03-01

Full Text Available The complete oxidation of n-Hexane and iso-Octane was studied individually in a fixed bed tubular flow reactor over CuO-CeO2 catalysts synthesized via four different methods namely urea-nitrate combustion method, urea gelation/co-precipitation method, citric acid sol-gel method and co-impregnation method. Laser diffraction was employed in catalysts characterization. The results obtained from the complete conversion of n-Hexane and iso-Octane revealed that the CuO-CeO2 catalysts prepared by urea-nitrate combustion method (UNC showed the best performance than the catalysts prepared by other methods used in the present investigation. CuO-CeO2 catalysts prepared by UNC method achieve total n-Hexane and iso-Octane conversion to CO2 at lower temperatures of 280 0C and 340 0C respectively due to the larger surface area of the catalysts which increases the specific rate of reaction. © 2013 BCREC UNDIP. All rights reservedReceived: 30th October 2012; Revised: 30th November 2012; Accepted: 3rd December 2012[How to Cite: A. Mishra, B.D. Tripathi, A.K. Rai, R. Prasad (2013. Comparative Study of Various Preparation Methods of CuO–CeO2 Catalysts for Oxidation of n–Hexane and iso–Octane. Bulletin of Chemical Reaction Engineering & Catalysis, 7(3: 172-178. (doi:10.9767/bcrec.7.3.4076.172-178][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.7.3.4076.172-178 ] View in  |

Neutron diffraction study of dense-Kondo compound CeNi2Al5

International Nuclear Information System (INIS)

Munoz, A.; Givord, F.; Boucherie, J.X.; Flouquet, J.; Isikawa, Y.; Mizushima, T.; Sakurai, J.; Mori, K.; Oliveira, I.S.

1993-01-01

Intermetallic CeNi 2 Al 5 is a dense-Kondo compound with a magnetic transition temperature at 2.6 K. We have carried out a neutron diffraction measurement to study a magnetic structure of CeNi 2 Al 5 using a powder sample and a single crystalline sample. It is found that the magnetic structure is an incommensurate sinusoidal one with a propagation vector k = (0.5, 0.405, 0.083) and that the amplitude of magnetic moment is 1.54 μ Β and the direction of magnetic moment is declined 8 deg. from the b-axis toward the a-axis. (authors). 3 refs., 2 figs

New investigation of phase equilibria in the system Al-Cu-Si.

Science.gov (United States)

Ponweiser, Norbert; Richter, Klaus W

2012-01-25

The phase equilibria and invariant reactions in the system Al-Cu-Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ(1) and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the β-phase of Cu-Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al-Cu and Cu-Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable.

An electron microscopy study of the effect of Ce on plasma sprayed bronze coatings

Science.gov (United States)

Wensheng, Li; Wang, S. C.; Ma, Chao; Zhiping, Wang

2012-07-01

The Cu-Al eutectoid alloy is an excellent material for mould due to its superior low friction. The conventional sand casting technique, however, is not feasible to fabricate high Al bronze because of high hardness and brittleness. Plasma arc spray has been used to produce high Al/Fe bronze coatings for mould. The inherent impurities such as H, O, N, S during the spray, however, may affect the coating's mechanical strength. One approach is to utilise the active rare earth Ce to clean up these impurities. The study is to investigate the effect of Ce on the microstructure, which has few reported in the literature.

AC susceptibility and NQR measurements on CeCu6 below 5 mK

International Nuclear Information System (INIS)

Jin, C.; Lee, D.M.; Pollack, L.; Smith, E.N.; Markert, J.T.; Maple, M.B.; Hinks, D.G.

1994-01-01

We have measured the zero field ac magnetic susceptibility of single and polycrystalline CeCu 6 samples down to 100 μK. For the single crystal sample, the susceptibility shows pronounced anisotropic behavior with respect to the crystal orientation. At ∼3 mK the susceptibility along two different crystal orientations shows a broad peak, and at 500 μK the susceptibility shows a second peak along one orientation and a plateau along the other. The susceptibility of the polycrystalline sample has a similar peak at 3 mK. NQR measurements are under way to study the Cu nuclear spin system in this compound in order to gain additional information about the nature of the peaks. (orig.)

Thermal stability and primary phase of Al-Ni(Cu)-La amorphous alloys

International Nuclear Information System (INIS)

Huang Zhenghua; Li Jinfu; Rao Qunli; Zhou Youhe

2008-01-01

Thermal stability and primary phase of Al 85+x Ni 9-x La 6 (x = 0-6) and Al 85 Ni 9-x Cu x La 6 (x = 0-9) amorphous alloys were investigated by X-ray diffraction and differential scanning calorimeter. It is revealed that replacing Ni in the Al 85 Ni 9 La 6 alloy by Cu decreases the thermal stability and makes the primary phase change from intermetallic compounds to single fcc-Al as the Cu content reaches and exceeds 4 at.%. When the Ni and La contents are fixed, replacing Al by Cu increases the thermal stability but also promotes the precipitation of single fcc-Al as the primary phase

Luminescent properties of Y{sub 3}Al{sub 5−x}Ga{sub x}O{sub 12}:Ce crystals

Energy Technology Data Exchange (ETDEWEB)

Zorenko, Yu., E-mail: zorenko@ukw.edu.pl [Institute of Physics, Kazimierz Wielki University in Bydgoszcz, Powstańców Wielkopolskich No 2, 85-090 Bydgoszcz (Poland); Zorenko, T. [Institute of Physics, Kazimierz Wielki University in Bydgoszcz, Powstańców Wielkopolskich No 2, 85-090 Bydgoszcz (Poland); Department of Electronics, Ivan Franko National University of Lviv, Gen. Tarnavskyj str. 107, 70017 Lviv (Ukraine); Malinowski, P. [Institute of Physics, Kazimierz Wielki University in Bydgoszcz, Powstańców Wielkopolskich No 2, 85-090 Bydgoszcz (Poland); Sidletskiy, O.; Neicheva, S. [Institute for Scintillation Materials, National Academy of Sciences of Ukraine, Lenina pr. 60, 61001 Kharkiv (Ukraine)

2014-12-15

Absorption, luminescent and scintillation properties of Ce{sup 3+} doped Y{sub 3}Al{sub 5−x}Ga{sub x}O{sub 12} crystals with Ga content in the x=1–5 range were investigated in this work and compared with the properties of YAG:Ce crystals. Apart from the traditional spectral methods (absorption, cathodoluminescence and light yield measurements), the intrinsic and Ce{sup 3+} related luminescence of Y{sub 3}Al{sub 5−x}Ga{sub x}O{sub 12}:Ce solid-solution were also investigated using the luminescent spectroscopy under excitation by synchrotron radiation in the 3.7–25 eV range. We show that the optical properties Y{sub 3}Al{sub 5−x}Ga{sub x}O{sub 12}:Ce garnets monotonically change with increasing the Ga content in the x=0–3 range due to preferable localization of Ga ions in the tetrahedral position of the garnet lattice. At the highest Ga concentration (x>3) the deviation of the optical properties of Y{sub 3}Al{sub 5−x}Ga{sub x}O{sub 12}:Ce garnets is observed from the respective properties of these crystals with Ga content in the x=0–3 range due to occupation by Ga ions of the octahedral position in the garnet host. - Highlights: • Different dependence of optical properties of Y{sub 3}Al{sub 5−x}Ga{sub x}O{sub 12}:Ce crystals on Ga content in x=0–3 and 3–5 ranges. • Elimination of the luminescence of Y{sub Al} antisite defects in Y{sub 3}Al{sub 5−x}Ga{sub x}O{sub 12}:Ce crystals at x>2. • Significant improvement of the scintillation properties of Y{sub 3}Al{sub 5−x}Ga{sub x}O{sub 12}:Ce crystals at x=2 and 3 in comparison with YAG:Ce.

Idraulica dei sistemi fognari dalla teoria alla pratica

CERN Document Server

Gisonni, Corrado

2012-01-01

La progettazione dei sistemi fognari e dei manufatti in essi presenti richiede un’attenta conoscenza delle leggi che regolano i fenomeni idraulici, con particolare riferimento alle correnti idriche a superficie libera. Partendo dalle nozioni fondamentali dell’Idraulica, il testo intende colmare alcune importanti lacune che ancora caratterizzano la letteratura italiana nel settore e che spesso sono alla base di errori progettuali, con ovvie conseguenze sulla sicurezza dei centri abitati (come testimoniato dai frequenti fenomeni di allagamento che sono stati registrati negli ultimi anni). Il libro è rivolto agli allievi dei corsi di studio nel settore dell’ingegneria Civile ed Ambientale. Particolare interesse è rivolto ai professionisti operanti nel settore della ingegneria idraulica e della pianificazione urbana, per i quali è forte l’esigenza di testi che contengano indicazioni di carattere sia teorico sia pratico, finalizzate alla progettazione di sistemi di drenaggio nei centri abitati.

Pitting corrosion of Al and Al-Cu alloys by ClO4- ions in neutral sulphate solutions

International Nuclear Information System (INIS)

Amin, Mohammed A.; Abd El Rehim, Sayed S.; Moussa, S.O.; Ellithy, Abdallah S.

2008-01-01

The influence of various concentrations of NaClO 4 , as a pitting corrosion agent, on the corrosion behaviour of pure Al, and two Al-Cu alloys, namely (Al + 2.5 wt% Cu) and (Al + 7 wt% Cu) alloys in 1.0 M Na 2 SO 4 solution was investigated by potentiodynamic polarization and potentiostatic techniques at 25 deg. C. Measurements were conducted under the influence of various experimental conditions, complemented by ex situ energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) examinations of the electrode surface. In free perchlorate sulphate solutions, for the three Al samples, the anodic polarization exhibits an active/passive transition. The active dissolution region involves an anodic peak (peak A) which is assigned to the formation of Al 2 O 3 passive film on the electrode surface. The passive region extends up to 1500 mV with almost constant current density (j pass ) without exhibiting a critical breakdown potential or showing any evidence of pitting attack. For the three Al samples, addition of ClO 4 - ions to the sulphate solution stimulates their active anodic dissolution and tends to induce pitting corrosion within the oxide passive region. Pitting corrosion was confirmed by SEM examination of the electrode surface. The pitting potential decreases with increasing ClO 4 - ion concentration indicating a decrease in pitting corrosion resistance. The susceptibility of the three Al samples towards pitting corrosion decreases in the order: Al > (Al + 2.5 wt% Cu) alloy > (Al + 7 wt% Cu) alloy. Potentiostatic measurements showed that the rate of pitting initiation increases with increasing ClO 4 - ion concentration and applied step anodic potential, while it decreases with increasing %Cu in the Al samples. The inhibitive effect of SO 4 2- ions was also discussed

Role of aluminium concentration on the structure behaviour of Cu-Al alloys

International Nuclear Information System (INIS)

Nassar, A.M.; Taha, A.S.; Ragab, K.A.; El-Mossalamy, S.

1988-06-01

Effect of Al(5, 10, 15 and 20)% on the structure behaviour of Cu-Al alloys was investigated by both microhardness measurements and optical microscopic investigations. Pure Cu was used for comparison. The analysis of the hardness-temperature curve shows a type of dependence which obeys an empirical exponential law, but consists of several distinguishable regions. For Cu 20% Al, one region is observed, and two regions for pure Cu, while for alloys of 5 and 10% Al concentration three regions were observed. The activation energy varies between 0.03 and 0.9 ev. for these regions, depending on the Al-concentration as well as the annealing temperature. The recrystallization temperature was found to increase with increasing Al-concentration. It was also observed that Cu-20% Al alloy is very hard and brittle owing to the formation of γ2 phase, and also to phase separation as being detected from optical microscopic investigations. (author). 22 refs, 3 figs

Study of Cu-Al-Ni-Ga as high-temperature shape memory alloys

Science.gov (United States)

Zhang, Xin; Wang, Qian; Zhao, Xu; Wang, Fang; Liu, Qingsuo

2018-03-01

The effect of Ga element on the microstructure, mechanical properties and shape memory effect of Cu-13.0Al-4.0Ni- xGa (wt%) high-temperature shape memory alloy was investigated by optical microscopy, SEM, XRD and compression test. The microstructure observation results showed that the Cu-13.0Al-4.0Ni- xGa ( x = 0.5 and 1.0) alloys displayed dual-phase morphology which consisted of 18R martensite and (Al, Ga)Cu phase, and their grain size was about several hundred microns, smaller than that of Cu-13.0Al-4.0Ni alloy. The compression test results proved that the mechanical properties of Cu-13.0Al-4.0Ni- xGa alloys were improved by addition of Ga element owing to the grain refinement and solid solution strengthening, and the compressive fracture strains were 11.5% for x = 0.5 and 14.9% for x = 1.0, respectively. When the pre-strain was 8%, the shape memory effect of 4.2 and 4.6% were obtained for Cu-13.0Al-4.0Ni-0.5 Ga and Cu-13.0Al-4.0Ni-1.0 Ga alloys after being heated to 400 °C for 1 min.

Microstructure and properties in Al-C-Cu system produced by mechanical milling

International Nuclear Information System (INIS)

Goytia-Reyes, R.; Gallegos-Orozco, V.; Flores-Zuniga, H.; Alvarado-Hernandez, F.; Huirache-Acuna, R.; Martinez-Sanchez, R.; Santos-Beltran, A.

2009-01-01

Different amounts of C and C-Cu mixtures were employed to produce Al-C and Al-C-Cu powder composites by mechanical milling. In order to determine the Cu effect, hardness tests were carried out in the as-milled samples and at different sintering temperatures. Also, X-ray analyses using Rietveld program, transmission electron microscopy and calorimetry were used for the microstructural characterization. In agreement with the results, the Cu powder acts as carrier in the incorporation of graphite into the Al matrix. Also, due to the presence of graphite particles together with Al 4 C 3 precipitation, hardness values remain stable even at elevated temperatures for these Al-based composites.

Construction and evaluation of multi-component Zn-Al based bearing alloys (Zn-Al-Si, Zn-Al-Cu)

International Nuclear Information System (INIS)

Shahmiri, M.; Shahin, K.

2001-01-01

Zn-Al based alloys, with excellent mechanical properties, are finding increasing applications in various industries, especially bearing and bushing fields. Observed dimensional instabilities, in their multicomponent systems, (e. g. Zn-Al-Si and, Zn-Al Si-Cu), is believed to be as the result of some kinds of phase transformation, due to the temperature variations, while in service. Profound understanding of the phase transformations due to the temperature variation, requires detailed evaluations of the isothermal sections of the multi-components phase diagrams of Zn-Al-Si and, Zn-Al-Si-Cu alloy systems. In the present article, the isothermal sections of the aforementioned ternary and quaternary systems in the solid state regions have been investigated and observed phase transitions have been critically evaluated

Generation and reactivity of putative support systems, Ce-Al neutral binary oxide nanoclusters: CO oxidation and C-H bond activation

Science.gov (United States)

Wang, Zhe-Chen; Yin, Shi; Bernstein, Elliot R.

2013-11-01

Both ceria (CeO2) and alumina (Al2O3) are very important catalyst support materials. Neutral binary oxide nanoclusters (NBONCs), CexAlyOz, are generated and detected in the gas phase and their reactivity with carbon monoxide (CO) and butane (C4H10) is studied. The very active species CeAlO4• can react with CO and butane via O atom transfer (OAT) and H atom transfer (HAT), respectively. Other CexAlyOz NBONCs do not show reactivities toward CO and C4H10. The structures, as well as the reactivities, of CexAlyOz NBONCs are studied theoretically employing density functional theory (DFT) calculations. The ground state CeAlO4• NBONC possesses a kite-shaped structure with an OtCeObObAlOt configuration (Ot, terminal oxygen; Ob, bridging oxygen). An unpaired electron is localized on the Ot atom of the AlOt moiety rather than the CeOt moiety: this Ot centered radical moiety plays a very important role for the reactivity of the CeAlO4• NBONC. The reactivities of Ce2O4, CeAlO4•, and Al2O4 toward CO are compared, emphasizing the importance of a spin-localized terminal oxygen for these reactions. Intramolecular charge distributions do not appear to play a role in the reactivities of these neutral clusters, but could be important for charged isoelectronic BONCs. DFT studies show that the reaction of CeAlO4• with C4H10 to form the CeAlO4H•C4H9• encounter complex is barrierless. While HAT processes have been previously characterized for cationic and anionic oxide clusters, the reported study is the first observation of a HAT process supported by a ground state neutral oxide cluster. Mechanisms for catalytic oxidation of CO over surfaces of AlxOy/MmOn or MmOn/AlxOy materials are proposed consistent with the presented experimental and theoretical results.

Effect of Pressure on the Ferromagnetic Cerium Compound CeCu9Sn4

International Nuclear Information System (INIS)

Ishii, Y.; Mori, N.; Hedo, M.; Uwatoko, Y.

2003-01-01

Electrical resistivity measurements under hydrostatic pressure up to 2.2 GPa was carried out for a ferromagnetic ternary cerium compound CeCu 9 Sn 4 . The ferromagnetic transition temperature increases with increasing pressure up to 0.8 GPa and then decreases with increasing pressure above 1 GPa. Origins of this pressure dependence may be the competition between magnetic interaction in the c-plane and along the c-direction. (author)

Dispersion of CEF levels in Nd{sub 2}CuO{sub 4} and Pr{sub 0.86}Ce{sub 0.14}CuO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Henggeler, W.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Chattopadyay, T.; Roessli, B. [Institut Max von Laue - Paul Langevin, 75 - Paris (France)

1997-09-01

We performed inelastic scattering experiments to determine the dispersion of the {Gamma}{sub 6}{sup (1)}-{Gamma}{sub 6}{sup (2)}-Nd crystal field excitation in Nd{sub 2}CuO{sub 4} and of the {Gamma}{sub 4}-{Gamma}{sub 5} Pr CEF excitation in Pr{sub 1.86}Ce{sub 0.14}CuO{sub 4}. Our results can be described within the random phase approximation model. (author) 4 figs.

Critical current density of strained multilayer thin films of Nd1.83Ce0.17CuOx/YBa2Cu3O7-δ

International Nuclear Information System (INIS)

Gross, R.; Gupta, A.; Olsson, E.; Segmueller, A.; Koren, G.

1990-01-01

The superconducting transport properties of strained multilayer thin films of YBa 2 Cu 3 O 7-δ / Nd 1.83 Ce 0.17 CuO x , grown heteroepitaxially by laser ablation deposition, are reported. For individual layer thicknesses below a critical layer thickness of about 250 A, coherency strain removes the orthorhombic distortion in the YBa 2 Cu 3 O 7-δ layers and makes them twin-free. Zero-field critical current densities as high as 1.1x10 7 A/cm 2 at 77 K have been measured for the YBa 2 Cu 3 O 7-δ layers. Flux pinning energies at zero temperature and zero magnetic field in the range of 80--140 meV have been found

Quasicrystalline and crystalline phases in Al65Cu20(Fe, Cr)15 alloys

International Nuclear Information System (INIS)

Liu, W.; Koester, U.; Mueller, F.; Rosenberg, M.

1992-01-01

Two types of icosahedral quasicrystals are observed in Al 65 Cu 20 Fe 15-x Cr x (0 ≤ x ≤ 15) alloys, the face-centred AlCuFe-type icosahedral phase with dissoluted Cr and the primitive AlCuCr-type icosahedral phase with dissoluted Fe. In the vicinity of Al 65 Cu 20 Fe 8 Cr 7 a stable decagonal phase (a=0.45 nm and c=1.23 nm) forms competitively with the icosahedral quasicrystals. All these three quasicrystalline phases can be regarded as Hume-Rothery phases stabilized by the energy band factor. The density is measured to be 4.57, 4.44, and 4.11 g/cm 3 for the icosahedral Al 65 Cu 20 Fe 15 , the decagonal Al 65 Cu 20 Fe 8 Cr 7 , and the icosahedral Al 65 Cu 20 Cr 15 alloys, respectively. Depending on the composition in the range between Al 65 Cu 20 Fe 8 Cr 7 and Al 65 Cu 20 Cr 15 , several crystalline phases are observed during the transormation of the AlCuCr-type icosahedral phase: the 1/1-3/2-type orthorhombic (o) and the 1/0-3/2-type tetragonal (t) approximants of the decagonal phase, a hexagonal (h) phase, as well as a long-range vacancy ordered τ 3 -phase derived from a CsCl-type structure with a=0.2923 nm. The structures of all the crystalline phases are closely related to those of the icosahedral (i) and decagonal (d) quasicrystals, which leads to a definite orientation relationship as follows: i5 parallel d10 parallel o[100] parallel t[100] parallel h[001] parallel τ 3 [110]. (orig.)

Wetting phenomena of Al-Cu alloys on sapphire below 800 deg. C

International Nuclear Information System (INIS)

Klinter, Andreas J.; Leon-Patino, Carlos A.; Drew, Robin A.L.

2010-01-01

Using a modified dispensed drop method, a decrease in contact angle on sapphire from pure aluminum to low-copper-containing Al alloys (7-12 wt.%) was found; with higher copper additions θ transitions to the non-wetting regime. Atomic force microscopy on long-term samples showed a significantly increased surface roughness beneath the drop. Using high-resolution transmission electron microscopy, the reaction product at the interface was identified as CuAl 2 O 4 for Al-7Cu and Al 2 O 3 for an Al-99.99 drop. X-ray photoelectron spectroscopy further confirmed the formation of CuAl 2 O 4 under CuAl 2 drops. Spinel formation is caused by reaction of the alloy with residual oxygen in the furnace that is transported along the interface as modeled by thermodynamic simulations. The formation of CuAl 2 O 4 causes the reduced σ sl and hence the improved wettability of sapphire by low-copper-containing alloys compared to pure aluminum. The main reason for the increase in θ with higher copper contents is the increasing σ lv of the alloy.

Effects of Ce Addition and Isothermal Aging on the Elevated Temperature Tensile Properties of Mechanically Alloyed Al-Ti Alloys

Energy Technology Data Exchange (ETDEWEB)

Kim, JunKi; Oh, YoungMin; Kim, YongDeog; Kim, SeonJin [Hanyang Univ., Seoul (Korea, Republic of); Kim, ByungChul [KOREA ATOMIC RESEARCH INSTITUTE, TAEJON (Korea, Republic of)

1997-05-01

The room and elevated temperature tensile strength of mechanically alloyed Al-8wt%. Ti alloy increased by substituting Ce for Ti up to 25at.%. However, further substitution of Ce for Ti decreased the tensile strength. It was considered to be due to the decrease of volume fraction of Ce contained dispersoid. In the meantime, the decrease of tensile strength due to the isothermal aging was effectively reduced by the addition of Ce at 400 deg. C but not 510 deg. C. The activation energies for the deformation of Al-80wt.%(Ti+Ce)alloys measured at the temperature between 300 deg. C{approx}510 deg. C were about 1.3{approx}1.9 times higher than that for pure Al self-diffusion(142 kJ/mole). Thus, it was considered that the elevated temperature deformation of Al-8wt.%(Ti+Ce)alloys was governed by Orowan mechanism (author). 9 refs. 6 figs.

Examination of the anisotropy of the wetting behaviour of liquid Al-Cu alloys on single crystalline oriented Al{sub 2}O{sub 3}-substrates; Untersuchung der Anisotropie im Benetzungsverhalten fluessiger Al-Cu Legierungen auf einkristallinen orientierten Al{sub 2}O{sub 3}-Substraten

Energy Technology Data Exchange (ETDEWEB)

Schmitz, Julianna

2011-02-04

The wetting behaviour of liquid Al-Cu alloys and pure metals on oriented single crystalline Al{sub 2}O{sub 3}-substrates was examined, utilising the sessile drop technique. Measurements were performed at moderate temperatures of 1100 C, where the alloys are liquid. Different Al{sub 2}O{sub 3}-surfaces were studied, which are terminated by the crystallographic planes (0001), (11 anti 20), and (1 anti 102), also called C-, A-, and R-surfaces. After deposition, pure Cu-droplets show an exponential increase of the wetting angle to a value of about 115 for all investigated Al{sub 2}O{sub 3}-surfaces. The timescale of this increase is of the order of 100 s. The effect of surface- and interfacial energies on the wetting angle is discussed considering Young's equation. The most probable reason for its time-dependence seems to be an increase of the interfacial energy due to deoxidation of the droplet. Therefore it is reasonable to regard the isotropic contact angle value as the intrinsic one of the Cu/Al{sub 2}O{sub 3} system. In contrast, the wetting angle of pure Al metal with the different Al{sub 2}O{sub 3}-substrates shows a qualitatively different behaviour. In this system, it rises from about 90 to 115 roughly for C-substrates, twice as fast as in the Cu case but to a comparable value. On the other substrates a wetting angle of about 90 establishes immediately, and no pronounced time dependence is obvious. In order to study changes in the wetting behaviour of Al-Cu-alloys, which is isotropic for Cu and anisotropic for Al-rich alloys, contact angles of Al{sub 50}Cu{sub 50}, Al{sub 30}Cu{sub 70} und Al{sub 17}Cu{sub 83} on Al{sub 2}O{sub 3} were determined. For each alloy composition the wetting angle is about 120 after 300 s. The initial values on distinct surfaces hardly differ and become non-wetting with increasing Cu-content. Hence, anisotropy decreases. To determine the work of adhesion of the solid-liquid interface, the temperature- and composition

Dispersion strengthening of precipitation hardened Al-Cu-Mg alloys prepared by rapid solidification and mechanical alloying

Science.gov (United States)

Gilman, P. S.; Sankaran, K. K.

1988-01-01

Several Al-4Cu-1Mg-1.5Fe-0.75Ce alloys have been processed from either rapidly solidified or mechanically alloyed powder using various vacuum degassing parameters and consolidation techniques. Strengthening by the fine subgrains, grains, and the dispersoids individually or in combination is more effective when the alloys contain shearable precipitates; consequently, the strength of the alloys is higher in the naturally aged rather than the artificially aged condition. The strengths of the mechanically alloyed variants are greater than those produced from prealloyed powder. Properties and microstructural features of these dispersion strengthened alloys are discussed in regards to their processing histories.

Specific heat characteristics of Ce70Ga8.5Cu18.5Ni3 metallic glass at low temperatures

Science.gov (United States)

Liu, Rentao; Zhong, Langxiang; Zhang, Bo

2018-03-01

Specific heat behaviors have been studied in Ce70Ga8.5Cu18.5Ni3 bulk metallic glass (BMG) from 2 K to 50 K. The low-temperature specific heat of the Ce-based metallic glass is a combined action of the Fermi liquids term, Debye oscillator term, and Einstein oscillator term as well as excess term. We also observed an intense boson peak around 15 K and attributed it to a harmonic localized Einstein mode influenced by the dense-packed atomic cluster structure. It is also demonstrated that Ce70Ga8.5Cu18.5Ni3 BMG belongs to the strongly correlated heavy-fermion system with a great electron specific heat coefficient and a high Wilson ratio. It exhibits a typical Fermi-Liquid feature when the temperature is above 10 K, while it exhibits a Non-Fermi-Liquid feature when the temperature is below 3.5 K.

Ordered Mesoporous NiCeAl Containing Catalysts for Hydrogenolysis of Sorbitol to Glycols

Science.gov (United States)

Zhou, Zhiwei; Zhang, Jiaqi; Qin, Juan; Li, Dong; Wu, Wenliang

2018-03-01

Cellulose-derived sorbitol is emerging as a feasible and renewable feedstock for the production of value-added chemicals. Highly active and stable catalyst is essential for sorbitol hydrogenolysis. Ordered mesoporous M- xNi yCeAl catalysts with different loadings of nickel and cerium species were successfully synthesized via one-pot evaporation-induced self-assembly strategy (EISA) and their catalytic performance were tested in the hydrogenolysis of sorbitol. The physical chemical properties for the catalysts were characterized by XRD, N2 physisorption, H2-TPR, H2 impulse chemisorption, ICP and TEM techniques. The results showed that the ordered mesopores with uniform pore sizes can be obtained and the Ni nanoparticles around 6 nm in size were homogeneously dispersed in the mesopore channels. A little amount of cerium species introduced would be beneficial to their textural properties resulting in higher Ni dispersion, metal area and smaller size of Ni nanoparticles. The M-10Ni2CeAl catalyst with Ni and Ce loading of 10.9 and 6.3 wt % shows better catalytic performance than other catalysts, and the yield of 1,2-PG and EG can reach 56.9% at 493 K and 6 MPa pressure for 8 h after repeating reactions for 12 times without obvious deterioration of physical and chemical properties. Ordered mesoporous M-NiCeAl catalysts are active and stable in sorbitol hydrogenolysis.

Role of Cu-Mg-Al mixed oxide catalysts in lignin depolymerization in supercritical ethanol

NARCIS (Netherlands)

Huang, X.; Ceylanpinar, A.; Koranyi, T.I.; Boot, M.D.; Hensen, E.J.M.

2015-01-01

We investigate the role of Cu-Mg-Al mixed oxides in depolymerization of soda lignin in supercritical ethanol. A series of mixed oxides with varying Cu content and (Cu+Mg)/Al ratio were prepared. The optimum catalyst containing 20 wt% Cu and having a (Cu+Mg)/Al ratio of 4 yielded 36 wt% monomers

Characterization of the alteration products formed at the surface of LaYSiAlO and CeYSiAlO glasses using ERDA and RBS techniques

International Nuclear Information System (INIS)

Gavarini, S.; Trocellier, P.; Matzen, G.

2004-01-01

Leaching tests have been performed on LnYSiAlO glasses (Ln = La or Ce) that are considered as potential matrices for the specific immobilization of minor actinides. Elastic recoil detection analysis (ERDA) performed on leached samples indicated a superficial hydration of LaYSiAlO glass of about 100-150 nm. This hydrated layer is (Al, Y)-enriched according to SEM-EDS analysis, suggesting the formation of hydroxide (or hydroxycarbonates) compounds including these two elements. This process leads to a very efficient passivation of the material due to the low solubility of Al and Y hydroxides (and hydroxycarbonates) species in near neutral media, even when the solution is rapidly replenished is dynamic leaching experiments. Rutherford Backscattering Spectrometry elemental mapping revealed very localized and significantly Y-enriched deposits at the surface of the sample after leaching. This could be the sign of heterogeneities already present on the pristine glass. These may be correlated with the weak solubility of yttrium (and rare earth) elements in silicate matrices (Y + Ln initial content in the glass ∼11 at.%). In the case of CeYSiAlO glass, a thin layer was formed on the solid after leaching. The simulation of the corresponding RBS spectra showed a surface (Y, Ce)-enrichment and (Al, Si)-depletion in both cases. This could be explained by the oxidation of trivalent cerium initially present in the glass structure during leaching. This might be explained by the low solubility of Ce(IV)-compounds (CeO 2 and/or Ce(OH) 4 ) in solution leading to an enrichment of this element at the glass/solution interface, to form a mixture of amorphous CeO 2 and Y(OH) 3 , as confirmed by XPS and XRD experiments

Metallic oxides supported in CeO{sub 2} and CeO{sub 2}-La{sub 2} O{sub 3} for low temperature shift reaction; Oxidos metalicos suportados em CeO{sub 2} e CeO{sub 2}-La{sub 2} O{sub 3} para reacao shift a baixa temperatura

Energy Technology Data Exchange (ETDEWEB)

Maluf, Silvia Salua; Assaf, Elisabete Moreira [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Inst. de Quimica]. E-mail: sil_maluf@iqsc.usp.br

2008-07-01

This work studied copper and zinc oxides supported in CeO{sub 2} and CeO{sub 2}/La{sub 2}O{sub 3}. The catalytic tests for low temperature shift reaction, carried out for samples, showed the Cu-Ce catalyst presents the highest value of CO conversion (50%) and after the Cu-Ce-La catalysts (30%). The other catalysts showed CO conversion in range of 15%. This behavior is related with surface area, and also with the amount of Cu in the surface of samples (author)

A novel yellow-emitting SrAlSi4N7:Ce3+ phosphor for solid state lighting: Synthesis, electronic structure and photoluminescence properties

Science.gov (United States)

Ruan, Jian; Xie, Rong-Jun; Funahashi, Shiro; Tanaka, Yoshinori; Takeda, Takashi; Suehiro, Takayuki; Hirosaki, Naoto; Li, Yuan-Qiang

2013-12-01

Ce3+-doped and Ce3+/Li+-codoped SrAlSi4N7 phosphors were synthesized by gas pressure sintering of powder mixtures of Sr3N2, AlN, α-Si3N4, CeN and Li3N. The phase purity, electronic crystal structure, photoluminescence properties of SrAlSi4N7:Ce3+(Ce3+/Li+) were investigated in this work. The band structure calculated by the DMol3 code shows that SrAlSi4N7 has a direct band gap of 3.87 eV. The single crystal analysis of Ce3+-doped SrAlSi4N7 indicates a disordered Si/Al distribution and nitrogen vacnacy defects. SrAlSi4N7 was identified as a major phase of the fired powders, and Sr5Al5Si21N35O2 and AlN as minor phases. Both Ce3+ and Ce3+/Li+ doped SrAlSi4N7 phosphors can be efficiently excited by near-UV or blue light and show a broadband yellow emission peaking around 565 nm. A highest external quantum efficiency of 38.3% under the 450 nm excitation was observed for the Ce3+/Li+-doped SrAlSi4N7 (5 mol%). A white light LED lamp with color temperature of 6300 K and color rendering index of Ra=78 was achieved by combining Sr0.97Al1.03Si3.997N\\94\\maccounttest14=t0005_18193 7:Ce3+0.03 with a commercial blue InGaN chip. It indicates that SrAlSi4N7:Ce3+ is a promising yellow emitting down-conversion phosphor for white LEDs.

Microstructural evaluation of interfacial intermetallic compounds in Cu wire bonding with Al and Au pads

International Nuclear Information System (INIS)

Kim, Hyung Giun; Kim, Sang Min; Lee, Jae Young; Choi, Mi Ri; Choe, Si Hyun; Kim, Ki Hong; Ryu, Jae Sung; Kim, Sangshik; Han, Seung Zeon; Kim, Won Yong; Lim, Sung Hwan

2014-01-01

A comparative study on the difference in interfacial behavior of thermally aged Cu wire bonding with Al and Au pads was conducted using transmission electron microscopy. During high-temperature lifetime testing of Cu wire bonding with Al and Au pads at 175 °C for up to 2000 h, different growth rates and growth characteristics were investigated in the Cu–Al intermetallic compounds (IMCs), including CuAl 2 , CuAl and Cu 9 Al 4 , and in the Cu–Au IMCs, including (Au,Cu), Cu 3 Au and (Cu,Au). Because of the lower growth rates and greater ductility of Cu–Au IMCs compared to those of Cu–Al IMCs, the Cu wire bonding with the Au pad showed relatively better thermal aging properties of bond pull strength and ball shear strength than those with the Al pad counterpart. In this study, the coherent interfaces were found to retard the growth of IMCs, and a variety of orientation relationships between wire, pad and interfacial IMCs were identified

Fatigue crack behavior on a Cu-Zn-Al SMA

Directory of Open Access Journals (Sweden)

V. Di Cocco

2014-10-01

Full Text Available In recent years, mechanical property of many SMA has improved in order to introduce these alloys in specific field of industry. Main examples of these alloys are the NiTi, Cu-Zn-Al and Cu-Al-Ni which are used in many fields of engineering such as aerospace or mechanical systems. Cu-Zn-Al alloys are characterized by good shape memory properties due to a bcc disordered structure stable at high temperature called β-phase, which is able to change by means of a reversible transition to a B2 structure after appropriate cooling, and reversible transition from B2 secondary to DO3 order, under other types of cooling. In β-Cu-Zn-Al shape memory alloys, the martensitic transformation is not in equilibrium at room temperature. It is therefore often necessary to obtain the martensitic structure, using a thermal treatment at high temperature followed by quenching. The martensitic phases can be either thermally-induced spontaneous transformation, or stressinduced, or cooling, or stressing the β- phase. Direct quenching from high temperatures to the martensite phase is the most effective because of the non-diffusive character of the transformation. The martensite inherits the atomic order from the β-phase. Precipitation of many kinds of intermetallic phases is the main problem of treatment on cu-based shape memory alloy. For instance, a precipitation of α-phase occurs in many low aluminum copper based SMA alloy and presence of α-phase implies a strong degradation of shape recovery. However, Cu-Zn-Al SMA alloys characterized by aluminum contents less than 5% cover a good cold machining and cost is lower than traditional NiTi SMA alloys. In order to improve the SMA performance, it is always necessary to identify the microstructural changing in mechanical and thermal conditions, using X-Ray analyses. In this work a Cu-Zn-Al SMA alloy obtained in laboratory has been microstructurally and metallographically characterized by means of X-Ray diffraction and Light

An introduction to bicomplex variables and functions; Introduzione ai sistemi ipercomplessi commutativi a quattro unita

Energy Technology Data Exchange (ETDEWEB)

Catoni, Francesco; Cannata, Roberto [ENEA, Centro Ricerche Casaccia, Rome (Italy). Servizio Centralizzato Informatica e Reti; Catoni, Vincenzo; Zampetti, Paolo [ENEA, Centro Ricerche Casaccia, Rome (Italy). Unita tecnico scientifica Fonti Rinnovabili e Cicli Energetici Innovativi

2005-08-15

The commutative quaternions introduced by C. Segre are similar to the Hamilton quaternions but, thanks to their commutativity, allow to introduce the functions. This property opens new ways far applications. [Italian] E noto da un teorema di Scheffers che per i sistemi ipercomplessi com-mutativi esiste il calcolo integrodifferenziale che permette di definire le loro funzioni in modo perfettamente analogo alle funzioni di variabili complesse. Questa proprieta rende questi sistemi, potenzialmente utilizzabili in nuovi campi, rispetto ai quaternioni noncommutativi di Hamilton. In questo lavoro introduciamo due di questi sistemi con le loro proprieta algebriche, le condizioni differenziali (condizioni di Cauchy-Riemann generalizzate) a cui devono soddisfare le loro funzioni e, infine, sono date le espressioni delle funzioni elementari.

Tunable emission in Ln3+ (Ce3+/Dy3+, Ce3+/Tb3+) doped KNa3Al4Si4O16 phosphor synthesized by combustion method

Science.gov (United States)

Kolte, M. M.; Pawade, V. B.; Bhattacharya, A. B.; Dhoble, S. J.

2018-05-01

Ln3+ (Ln = Ce3+/Dy3+, Ce3+/Tb3+) doped KNa3Al4Si4O16 phosphor has been synthesized by Combustion method (CS) at 550° C successfully. Ln3+ (Ln = Ce3+, Dy3+, Tb3+) ions when doped in KNa3Al4Si4O16 host lattice, it shows blue and green emission band under the near Ultraviolet (NUV) excitation wavelength. The Photoluminescence excitation (PLE) and emission spectra are observed due to f-f and d-f transition of rare earth ions. Also, an effective energy transfer (ET) study from Ce3+ → Dy3+ and Ce3+ → Tb3+ ions has been studied and confirmed on the basis of Dexter-Foster theory. Further synthesized phosphor is well characterized by XRD, SEM, TEM and decay time measurement. However, the analysis of crystallite size, lattice strain has been studied by using theoretical as well as experimental techniques. Hence, the observed tunable emission in Ln3+ doped KNa3Al4Si4O16 phosphor may be applicable for solid state lighting technology.

Effect of Surface Treatment on Shear Bond Strength between Resin Cement and Ce-TZP/Al2O3

Directory of Open Access Journals (Sweden)

Jong-Eun Kim

2016-01-01

Full Text Available Purpose. Although several studies evaluating the mechanical properties of Ce-TZP/Al2O3 have been published, to date, no study has been published investigating the bonding protocol between Ce-TZP/Al2O3 and resin cement. The aim of this study was to evaluate the shear bond strength to air-abraded Ce-TZP/Al2O3 when primers and two different cement types were used. Materials and Methods. Two types of zirconia (Y-TZP and Ce-TZP/Al2O3 specimens were further divided into four subgroups according to primer application and the cement used. Shear bond strength was measured after water storage for 3 days or 5,000 times thermocycling for artificial aging. Results. The Y-TZP block showed significantly higher shear bond strength than the Ce-TZP/Al2O3 block generally. Primer application promoted high bond strength and less effect on bond strength reduction after thermocycling, regardless of the type of cement, zirconia block, or aging time. Conclusions. Depending on the type of the primer or resin cement used after air-abrasion, different wettability of the zirconia surface can be observed. Application of primer affected the values of shear bond strength after the thermocycling procedure. In the case of using the same bonding protocol, Y-TZP could obtain significantly higher bond strength compared with Ce-TZP/Al2O3.

Wetting phenomena of Al-Cu alloys on sapphire below 800 deg. C

Energy Technology Data Exchange (ETDEWEB)

Klinter, Andreas J., E-mail: andreas.klinter@mail.mcgill.ca [Mining and Materials Engineering, McGill University, M.H. Wong Building, 3610 University Street, Montreal, QC, H3A 2B2 (Canada); Leon-Patino, Carlos A. [Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, Apdo. Postal 888, CP 58000 Morelia, Michoacan (Mexico); Drew, Robin A.L. [Faculty of Engineering and Computer Science, Concordia University, 1455 Maisonneuve Blvd, EV 2.169, Montreal, QC, H3G 1M8 (Canada)

2010-02-15

Using a modified dispensed drop method, a decrease in contact angle on sapphire from pure aluminum to low-copper-containing Al alloys (7-12 wt.%) was found; with higher copper additions {theta} transitions to the non-wetting regime. Atomic force microscopy on long-term samples showed a significantly increased surface roughness beneath the drop. Using high-resolution transmission electron microscopy, the reaction product at the interface was identified as CuAl{sub 2}O{sub 4} for Al-7Cu and Al{sub 2}O{sub 3} for an Al-99.99 drop. X-ray photoelectron spectroscopy further confirmed the formation of CuAl{sub 2}O{sub 4} under CuAl{sub 2} drops. Spinel formation is caused by reaction of the alloy with residual oxygen in the furnace that is transported along the interface as modeled by thermodynamic simulations. The formation of CuAl{sub 2}O{sub 4} causes the reduced {sigma}{sub sl} and hence the improved wettability of sapphire by low-copper-containing alloys compared to pure aluminum. The main reason for the increase in {theta} with higher copper contents is the increasing {sigma}{sub lv} of the alloy.

2003: Censimento dei sistemi di Istituto

OpenAIRE

Carlesi, Carlo

2003-01-01

La procedura di 'Censimento' si propone di raccogliere informazioni relative a tutte le 'macchine' o 'sistemi' (Personal Computer, Workstation e Server) disponibili in Istituto per una migliore ed efficace utilizzazione delle risorse ai fini della sicurezza informatica. La procedura e' rivolta agli utenti che a qualunque titolo utilizzano e/o sono responsabili di una o piu' macchine. La procedura prevede la compilazione guidata (via browse) di due moduli: il primo modulo riguarda essenzialmen...

Pulsed laser deposition of {CeO_2} and {Ce_{1-x}M_xO_2} (M = La, Zr): Application to insulating barrier in cuprate heterostructures

Science.gov (United States)

Berger, S.; Contour, J.-P.; Drouet, M.; Durand, O.; Khodan, A.; Michel, D.; Régi, F.-X.

1998-03-01

SrTiO_3 had been often tentatively used as an insulating barrier for HT superconductor/insulator heterostructures. Unfortunately, the deposition of SrTiO_3 on the YBa_2Cu_3O_7 inverse interface results in a poor epitaxial regrowth producing a high roughness dislocated titanate layer. Taking into account the good matching with YBa_2Cu_3O_7 and LaAlO_3, CeO_2 and Ce_{1-x}M_xO_2 (M = La, Zr), epitaxial layers were grown by pulsed laser deposition on LaAlO_3 substrates and introduced into YBa_2Cu_3O_7 based heterostructures as insulating barrier. After adjusting the growth parameters from RHEED oscillations, epitaxial growth is achieved, the oxide crystal axes being rotated by 45^circ from those of the substrate. The surface roughness of 250 nm thick films is very low with a rms value lower than 0.5 nm over 1;μ m^2. The YBa_2Cu_3O_7 layers of a YBa_2Cu_3O_7/CeO_2 /YBa_2Cu_3O_7 heterostructures grown using these optimized parameters show an independent resistive transition, when the thickness is larger than 25 nm, respectively at T_c_1 = 89.6;K and T_c_2 = 91.4;{K}. SrTiO3 est souvent utilisé comme barrière isolante dans des hétérostructures SIS de cuprates supraconducteurs, cependant les défauts générés lors de la croissance de ce titanate sur l'interface inverse de YBa2Cu3O7 conduisent à un matériau dont la qualité cristalline et les propriétés physiques sont médiocres. L'oxyde de cérium CeO2 est également une barrière isolante potentielle intéressante pour ces structures SIS basées sur YBa2Cu3O7 car cet oxyde cubique (a = 0,5411 nm, asqrt{2}/2 = 0,3825 nm) qui est peu désaccordé par rapport au plan ab du cuprate (Δ a/a = - 0,18 %, Δ b/a = 1,6 %) présente de plus un coefficient de dilatation thermique (10,6 × 10^{-6 circ}C^{-1}) très voisin de celui de YBa2Cu3O7 (13 × 10^{-6 circ}C^{-1}). Nous avons donc étudié l'épitaxie de CeO2 et des oxydes de type Ce{1-x}MxO2 (M = La, Zr) en ablation laser pulsée afin de définir des conditions de

Effects of Ce concentrations on ignition temperature and surface tension of Mg-9wt.%Al alloy

Directory of Open Access Journals (Sweden)

Deng Zhenghua

2013-03-01

Full Text Available Magnesium alloys are well known for their excellent properties, but the potential issues with oxidation and burning during melting and casting largely limit its industrial applications. The addition of Ce in magnesium alloys can significantly raise ignition-proof performance and change the structure of the oxide film on the surface of the molten metal as well as the surface tension values. Surface tension is an important physical parameter of the metal melts, and it plays an important role in the formation of surface oxide film. In this present work, the ignition temperature and the surface tension of Mg-9wt.%Al alloy with different Ce concentrations were studied. Surface tensions was measured using the maximum bubble pressure method (MBPM. Ignition temperature was measured using NiCr-NiSi type thermocouples and was monitored and recorded via a WXT-604 desk recording device. The results show that the ignition point of Mg-9wt.%Al alloy can be effectively elevated by adding Ce. The ignition temperature reaches its highest point of 720 ℃ when the addition of Ce is 1wt.%. The surface tension of the molten Mg-9wt.%Al alloy decreases exponentially with the increase of Ce addition at the same temperature. Similarly, the experiment also shows that the surface tension of Mg-9wt.%Al alloy decreases exponentially with the increase of temperature.

Un acercamiento al paradigma cuántico

OpenAIRE

Zapata Mesa, John Fernando

2009-01-01

En este breve escrito se hace algunos comentarios sobre la física cuántica con el objetivo de hacer un acercamiento al lector a este nuevo paradigma y de motivar una reflexión en esta línea.La física cuántica es la ciencia más desarrollada y mejor fundamentada hasta el momento junto con la teoría de la relatividad de Einstein. Toda la tecnología actual es una consecuencia directa de la física cuántica, es decir sin física cuántica no hubiese sido posible la construcción de un láser, computado...

Luminescence and Tb3+-Ce3+-Eu3+ ion energy transfer in single-crystalline films of Tb3Al5O12:Ce,Eu garnet

International Nuclear Information System (INIS)

Zorenko, Y.; Gorbenko, V.; Voznyak, T.; Batentschuk, M.; Osvet, A.; Winnacker, A.

2008-01-01

The paper is devoted to investigation of the processes of excitation energy transfer between the host cations (Tb 3+ ions) and the activators (Ce 3+ and Eu 3+ ions) in single-crystalline films of Tb 3 Al 5 O 12 :Ce,Eu (TbAG:Ce,Eu) garnet which is considered as a promising luminescent material for the conversion of LED's radiation. The cascade process of excitation energy transfer is shown to be realized in TbAG:Ce,Eu: (i) from Tb 3+ ions to Ce 3+ and Eu 3+ ions; (ii) from Ce 3+ ions to Eu 3+ ions by means of dipole-dipole interaction and through Tb 3+ ion sublattice

Formation and structure of nanocrystalline Al-Mn-Ni-Cu alloys

International Nuclear Information System (INIS)

Latuch, J.; Krasnowski, M.; Ciesielska, B.

2002-01-01

This paper reports the results of the short investigation on the effect of Cu additions upon the nanocrystallization behaviour of an Al-Mn-Ni alloy. 2 at.% Cu added to the base alloy of Al 85 Mn 10 Ni 5 alloy by substitution for Mn(mischmetal). The control of cooling rate did not cause the formation of nanocrystals of fcc-Al phase. The nanocrystalline structure fcc-Al + amorphous phase in quarternary alloy was obtained by isothermal annealing and continuous heating method, but the last technique is more effective. The volume fraction, lattice parameter, and size of Al-phase were calculated. (author)

A novel yellow-emitting SrAlSi4N7:Ce3+ phosphor for solid state lighting: Synthesis, electronic structure and photoluminescence properties

International Nuclear Information System (INIS)

Ruan, Jian; Xie, Rong-Jun; Funahashi, Shiro; Tanaka, Yoshinori; Takeda, Takashi; Suehiro, Takayuki; Hirosaki, Naoto; Li, Yuan-Qiang

2013-01-01

Ce 3+ -doped and Ce 3+ /Li + -codoped SrAlSi 4 N 7 phosphors were synthesized by gas pressure sintering of powder mixtures of Sr 3 N 2 , AlN, α-Si 3 N 4 , CeN and Li 3 N. The phase purity, electronic crystal structure, photoluminescence properties of SrAlSi 4 N 7 :Ce 3+ (Ce 3+ /Li + ) were investigated in this work. The band structure calculated by the DMol 3 code shows that SrAlSi 4 N 7 has a direct band gap of 3.87 eV. The single crystal analysis of Ce 3+ -doped SrAlSi 4 N 7 indicates a disordered Si/Al distribution and nitrogen vacnacy defects. SrAlSi 4 N 7 was identified as a major phase of the fired powders, and Sr 5 Al 5 Si 21 N 35 O 2 and AlN as minor phases. Both Ce 3+ and Ce 3+ /Li + doped SrAlSi 4 N 7 phosphors can be efficiently excited by near-UV or blue light and show a broadband yellow emission peaking around 565 nm. A highest external quantum efficiency of 38.3% under the 450 nm excitation was observed for the Ce 3+ /Li + -doped SrAlSi 4 N 7 (5 mol%). A white light LED lamp with color temperature of 6300 K and color rendering index of Ra=78 was achieved by combining Sr 0.97 Al 1.03 Si 3.997 N/94/maccounttest14=t0005 1 8193 7 :Ce 3+ 0.03 with a commercial blue InGaN chip. It indicates that SrAlSi 4 N 7 :Ce 3+ is a promising yellow emitting down-conversion phosphor for white LEDs. - Graphical abstract: One-phosphor converted white light-emitting diode (LED) was fabricated by combining a blue LED chip and a yellow-emitting SrAlSi4N7:Ce 3+ phosphor (see inset), which has the color rendering index of 78 and color temperature of 6300 K. - Highlights: • We reported a new yellow nitride phosphor suitable for solid state lighting. • We solved the crystal structure and evidenced a disordered Si/Al distribution. • We fabricated a high color rendering white LEDs by using a single SrAlSi4N7:Ce

Low Temperature Mechanical Properties of Scandium-Modified Al-Zn-Mg-Cu Alloys

National Research Council Canada - National Science Library

Senkov, O

2002-01-01

Tensile properties of three wrought alloys, (1) Al-10Zn-3Mg-1.2Cu-0.15Zr, (2) Al-10Zn-3Mg-1.2Cu-0.15Zr-0.39Mn-0.49Sc, and (3) Al-12Zn-3Mg-1.2Cu-0.15Zr-0.39Mn-0.49Sc were studied in T6 and T7 conditions at 298K and 77K...

Aging behavior of an in-situ TiB2/Al-Cu-Li-x matrix composite

International Nuclear Information System (INIS)

Shen, Yanwei; Hong, Tianran; Geng, Jiwei; Han, Gaoyang; Chen, Dong; Li, Xianfeng; Wang, Haowei

2017-01-01

Transmission electron microscopy, differential scanning calorimetry and hardness tests have been performed on an in-situ TiB 2 /Al-3.3Cu-1.0Li-0.60Mg-0.40Ag-0.14Zr-0.13Si composite to study its aging behavior at 175 °C. A cubic phase suspected to be the σ (Al 5 Cu 6 Mg 2 ) phase or its variant is precipitated at all aging stages studied, and this phase is not typically observed in the Al-Cu-Li alloys. The primary hardening (aging for 3 h) phases consist of δ′ (Al 3 Li), β′ (Al 3 Zr) and the cubic phase. After aging for 18 h, all precipitates including T 1 (Al 2 CuLi), S (Al 2 CuMg), θ′ (Al 2 Cu), δ′, β′ and the cubic phase have appeared, and the formation of T 1 and S results in a rapid increase in hardness. With prolonging of aging time, the apparent coarsening of T 1 and S results in a decline in hardness. - Highlights: •The aging behavior of an in-situ TiB 2 /Al-Cu-Li-x composite was studied. •A cubic phase suspected to be σ (Al 5 Cu 6 Mg 2 ) or its variant was precipitated. •The hardness change was dominated by the evolution of T 1 (Al 2 CuLi) and S (Al 2 CuMg).

Microstructure and tribological properties of TiCu2Al intermetallic compound coating

International Nuclear Information System (INIS)

Guo Chun; Zhou Jiansong; Zhao Jierong; Wang Linqian; Yu Youjun; Chen Jianmin; Zhou Huidi

2011-01-01

TiCu 2 Al ternary intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding. Tribological properties of the prepared TiCu 2 Al intermetallic compound coating were systematically evaluated. It was found that the friction coefficient and wear rate was closely related to the normal load and sliding speed, i.e., the friction coefficient of the prepared TiCu 2 Al intermetallic compound coating decreased with increasing normal load and sliding speed. The wear rate of the TiCu 2 Al intermetallic compound coating decreased rapidly with increasing sliding speed, while the wear rate first increased and then decreased at normal load from 5 to 15 N.

Generalized planar fault energies and twinning in Cu-Al alloys

Science.gov (United States)

Kibey, S.; Liu, J. B.; Johnson, D. D.; Sehitoglu, H.

2006-11-01

We report ab initio density functional theory calculations of generalized planar fault energies of fcc Cu -xAl (x =0, 5.0, and 8.3at.%) alloys. We investigate the effects of substitutional solute Al on the unstable intrinsic γus and twin γut stacking fault energies (SFEs). Our results reveal an increased tendency of Cu-Al to deform preferentially by twinning with increasing Al content, consistent with experiment. We attribute this mechanical behavior to appreciable lowering of the twinning barrier γut, along with the stable intrinsic and twin SFEs.

Y/Gd-free yellow Lu{sub 3}Al{sub 5}O{sub 12}:Ce{sup 3+} phosphor for white LEDs

Energy Technology Data Exchange (ETDEWEB)

Park, Kwangwon [Department of Display Science and Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Kim, Taehoon; Yu, Youngmoon [LED-Marine Convergence Technology R& BD Center, Pukyong National University, Busan 608−739 (Korea, Republic of); Seo, Kwangil [L-Stone Co. Ltd., Bucheon 421−807 (Korea, Republic of); Kim, Jongsu, E-mail: jsukim@pknu.ac.kr [Department of Display Science and Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

2016-05-15

Solid solubility limit of Ce{sup 3+} ions into Lu-based garnet, Lu{sub 3(1−x)}Ce{sub 3x}Al{sub 5}O{sub 12}, was determined as below 6.7 mol% (3x<0.2 mol) through Raman spectra and X−ray diffraction patterns. Above the solid solubility limit (3x≥0.2 mol), Lu{sub 3(1−x)}Ce{sub 3x}Al{sub 5}O{sub 12} phosphors showed the significant redshift to the yellow spectral region without Y{sup 3+} and Gd{sup 3+} ions. The redshift was explained in terms of the local compressive strain at the Ce{sup 3+} sites. The optimized sample (3x=0.4 mol) had a dominant emission wavelength of 548 nm, color coordinate of CIEx=0.421, CIEy=0.548, quantum efficiency of 80%, absorbance of 91%, lumen maintenance of 90% and high color stability at 473 K under 450 nm excitation wavelength, suggesting substitutability for the commercial yellow (Y, Gd){sub 3}(Al, Ga){sub 5}O{sub 12}:Ce{sup 3+} phosphor. The measured decay times at higher Ce{sup 3+} concentration are significantly shortened at higher temperature than that of those at lower Ce{sup 3+} concentration. The yellow Lu{sub 2.6}Ce{sub 0.4}Al{sub 5}O{sub 12} and a commercial red (Sr, Ca)AlSiN{sub 3}:Eu{sup 2+} phosphor were applied to the pc-WLED, it gave an excellent luminous efficiency (138 lm/W) with a slightly lower color rendering index (Ra=76.4) under correlated color temperature of 6500 K compared to those of the (Y, Gd){sub 3}(Al, Ga){sub 5}O{sub 12}:Ce{sup 3+}-based one (136 lm/W, Ra=78.7). Especially, the quantities of the used phosphors were significantly decreased by 20% for the yellow LuAG:Ce and by 40% for the red (Sr, Ca)AlSiN{sub 3}:Eu{sup 2+}. Thus, the Y/Gd−free pure LuAG:Ce yellow phosphors can be used as alternative to the commercial yellow YAG:Ce phosphor.

Comparing the physical properties of Pr/Gd and Pr/Ce substitutions in Ru(Gd1.5Ce0.5)Sr2Cu2O10- δ

Science.gov (United States)

Khajehnezhad, A.; Nikseresht, N.; Hadipour, H.; Akhavan, M.

2008-06-01

We have compared the electrical and magnetic properties of Ru(Gd1.5- x Pr x )Ce0.5Sr2Cu2O10- δ (Pr/Gd samples) with x = 0.0, 0.01, 0.03, 0.033, 0.035, 0.04, 0.05, 0.06, 0.1 and RuGd1.5(Ce0.5- x Pr x ) Sr2 Cu2O10- δ (Pr/Ce samples) with x = 0.0, 0.01, 0.03, 0.05, 0.08, 0.1, 0.15, 0.2 prepared by the standard solid-state reaction technique. We obtained the XRD patterns for different samples with various x. The lattice parameters versus x for different substitutions have been obtained from Rietveld analysis. To determine how the magnetic and superconducting properties of these layered cuprate systems can be affected by Pr substitution, the resistivity, and magnetoresistivity, with H ext varying from 0.0 to 15 kOe, have been measured at various temperatures. Superconducting transition temperature T c and magnetic transition T irr , have been obtained through resistivity and ac susceptibility measurements. The T c suppression due to Pr/Gd and Pr/Ce substitutions show competition between pair breaking by magnetic impurities, hole doping due to different valances of ions, difference in ionic radii, and oxygen stoichiometry. Pr/Gd substitution suppresses superconductivity more rapidly than for Pr/Ce, showing that the effect of hole doping and magnetic impurity pair breaking is stronger than the difference in ionic radii. In Pr/Gd substitution, the small difference between the ionic radii of Pr3+,4+ and Gd3+, and absorption of more oxygen due to the higher valence of Pr with respect to Gd, decreases the mean Ru-Ru distance, and as a result, the magnetic exchange interaction becomes stronger with the increase of x. However, Pr/Ce substitution has the opposite effect. The magnetic parameters such as H c , obtained through magnetization measurements versus applied magnetic field isotherm at 77 K and room temperatures, become stronger with x in Pr/Gd and weaker with x in Pr/Ce substitution.

Effect of Al and Ce oxide layers electrodeposited on OC4004 stainless steel on its corrosion characteristics in acid media

International Nuclear Information System (INIS)

Stoyanova, E.; Nikolova, D.; Stoychev, D.; Stefanov, P.; Marinova, T.

2006-01-01

The changes in the corrosion characteristics of stainless steel OC4004 in 0.1 M HNO 3 after electrodeposition of thin Al and Ce oxide films on it has been investigated. The Ce 2 O 3 -CeO 2 layers have been found to possess a pronounced stabilizing effect on the steel passive state and on its corrosion resistance, respectively, whereas the Al 2 O 3 layers do not improve considerably the corrosion behaviour of the SS/Al 2 O 3 system. A twice-lower corrosion current was observed with a ternary SS/Al 2 O 3 /Ce 2 O 3 -CeO 2 system in the passive region, while the zones of potentials, where the steel is in a stable passive state, are not changed. The obtained results permit the assumption that the cerium oxides layer acts as an effective cathode playing a determining role with respect to the improvement of the corrosion behavior of the steel. It has been concluded that when the SS/Al 2 O 3 /Ce 2 O 3 -CeO 2 system is used in media containing nitric acid, the corrosion will proceed at potentials where the passive state of steel would not be disturbed

Synthesis and effect of Ce and Mn co-doping on photoluminescence characteristics of Ca6AlP5O20:Eu novel phosphors.

Science.gov (United States)

Shinde, K N; Dhoble, S J

2013-01-01

A series of Ca6AlP5O20 doped with rare earths (Eu and Ce) and co-doped (Eu, Ce and Eu,Mn) were prepared by combustion synthesis. Under Hg-free excitation, Ca6AlP5O20:Eu exhibited Eu(2+) (486 nm) emission in the blue region of the spectrum and under near Hg excitation (245 nm), Ca6AlP5O20:Ce phosphor exhibited Ce(3+) emission (357 nm) in the UV range. Photoluminescence (PL) peak intensity increased in Ca6AlP5O20:Eu,Ce and Ca6AlP5O20:Eu, Mn phosphors due to co-activators of Ce(3+) and Mn(2+) ions. As a result, these ions played an important role in PL emission in the present matrix. Ca6AlP5O20:Eu, Ce and Ca6AlP5O20:Eu, Mn phosphors provided energy transfer mechanisms via Ce(3+) → Eu(2+) and Eu(2+) → Mn(2+), respectively. Eu ions acted as activators and Ce ions acted as sensitizers. Ce emission energy was well matched with Eu excitation energy in the case of Ca6AlP5O20:Eu, Ce and Eu ions acted as activators and Mn ions acted as sensitizers in Ca6AlP5O20:Eu, Mn. This study included synthesis of new and efficient phosphate phosphors. The impact of doping and co-doping on photoluminescence properties and energy transfer mechanisms were investigated and we propose a feasible interpretation. Copyright © 2012 John Wiley & Sons, Ltd.

Investigations on Cu-Ni and Cu-Al systems with secondary ion mass spectrometry (SIMS)

International Nuclear Information System (INIS)

Rodriguez-Murcia, H.; Beske, H.E.

1976-04-01

The ratio of the ionization coefficients of secondary atomic ions emitted from the two component systems Cu-Ni and Cu-Al was investigated as a function of the concentration of the two components. In the low concentration range the ratio of the ionization coefficients is a constant. An influence of the phase composition on the ratio of the ionization coefficients was found in the Cu-Al system. In addition, the cluster ion emission was investigated as a function of the concentration and the phase composition of the samples. The secondary atomic ion intensity was influenced by the presence of cluster ions. The importance of the cluster ions in quantitative analysis and phase determination by means of secondary ion mass spectrometry are discussed. (orig.) [de

Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al

Science.gov (United States)

Galazka, Zbigniew; Ganschow, Steffen; Fiedler, Andreas; Bertram, Rainer; Klimm, Detlef; Irmscher, Klaus; Schewski, Robert; Pietsch, Mike; Albrecht, Martin; Bickermann, Matthias

2018-03-01

We experimentally evaluated segregation of Cr, Ce and Al in bulk β-Ga2O3 single crystals grown by the Czochralski method, as well as the impact of these dopants on optical properties. The segregation of Cr and Ce and their incorporation into the β-Ga2O3 crystal structure strongly depends on O2 concentration in the growth atmosphere which has a noticeable impact on decomposition of Ga2O3 and Cr2O3, as well as on the charge state of Cr and Ce. Effective segregation coefficients for Cr are in the range of 3.1-1.5 at 7-24 vol% O2, while for Ce they are roughly below 0.01 at 1.5-34 vol% O2. The effective segregation coefficient for Al is 1.1 at 1.5-21 vol% O2. Both dopants Ce and Al have a thermodynamically stabilizing effect on β-Ga2O3 crystal growth by supressing decomposition. While Ce has no impact on the optical transmittance in the ultraviolet and visible regions, in Cr doped crystals we observe three absorption bands due to Cr3+ on octahedral Ga sites, one in the ultraviolet merging with the band edge absorption of β-Ga2O3 and two in the visible spectrum, for which we estimate the absorption cross sections. Al doping also does not induce dopant related absorption bands but clearly shifts the absorption edge as one expects for a solid-solution crystal Ga2(1-x)Al2xO3 still in the monoclinic phase. For the highest doping concentration (Ga1.9Al0.1O3) we estimate an increase of the energy gap by 0.11 eV.

Research of Mechanical Property Gradient Distribution of Al-Cu Alloy in Centrifugal Casting

Science.gov (United States)

Sun, Zhi; Sui, Yanwei; Liu, Aihui; Li, Bangsheng; Guo, Jingjie

Al-Cu alloy castings are obtained using centrifugal casting. The regularity of mechanical property gradient distribution of Al-Cu alloy castings with the same centrifugal radius at different positions is investigated. The result shows that the tensile strength, yield strength, elongation and microscope hardness exhibit the following gradient distribution characteristic — high on both sides and low on the center. The trend of mechanical property gradient distribution of Al-Cu alloy increases with the increase in the rotation speed. Moreover, the mechanical properties of casting centerline two sides have asymmetry. The reason is that the grain size of casting centerline two sides and Al2Cu phase and Cu content change correspondingly.

A metastable HCP intermetallic phase in Cu-Al bilayer films

Energy Technology Data Exchange (ETDEWEB)

Cha, Limei

2006-07-01

For the present study, three kinds of layered Cu/Al films have been fabricated. The first kind of samples were multilayered Cu/Al films deposited by sputtering on (001)Si. The individual layer thicknesses were 100 nm, 200 nm and 400 nm, while the total film thickness of 800 nm was kept constant, thus leading to multilayer systems with 8, 4 and 2 layers, respectively. The second type of samples were Cu/Al bilayer films grown on (0001) sapphire by sputtering, with individual layer thicknesses of 400 nm. The third type of samples were bilayer films (100 nm Cu and 100 nm Al) deposited on (0001)sapphire by MBE at room temperature. Applying conventional transmission electron microscopy and X-ray diffraction, different epitaxial growth behaviors were found in these films. All multilayer films from the first type were polycrystalline. The second type of films show a (111) FCC texture and possess intermetallic phases at the interfaces. HRTEM investigations displayed that along [111]FCC, the atomic structure of the interlayer has an ABAB stacking sequence, which is identical with a hexagonal close-packed (HCP) structure in [0001] direction, but not with the ABCABC stacking sequence of Cu and Al in [111]FCC. The lattice parameters of the HCP structure at the interlayer were determined from a model which gave the best agreement between the experimental and simulated images. The parameters are: a=b=0.256 nm, c=0.419 nm, ?=120 , with the space group of P6m2. Furthermore, lattice distortion analysis revealed that the lattice parameters of the HCP phase are increasing from the near-Cu-side to the near-Al-side. The chemical composition of the interlayer was investigated by energy dispersive X-ray spectroscopy (EDS). EDS linescans were performed from pure Al to pure Cu layers. In order to examine the stability of this HCP phase, in-situ heating experiments were performed in the HRTEM at {proportional_to}600 C. Ex-situ heating experiments were performed at different temperatures to

Shape memory effect and microstructures of sputter-deposited Cu-Al-Ni films

International Nuclear Information System (INIS)

Minemura, T.; Andoh, H.; Kita, Y.; Ikuta, I.

1985-01-01

The shape memory effect has been found in many alloy systems which exhibit a thermoelastic martensite transformation. Cu-Al-Ni alloys exhibit an excellent shape memory effect in single crystalline states, but they have not yet been commercially used due to their brittle fracture along the grain boundaries in polycrystalline states. This letter reports the shape memory effect and microstructures of the sputter-deposited Cu-Al-Ni films. Cu-14%Al-4%Ni alloy ingot was prepared. A target for sputter deposition was cut from the ingot. Aluminium foils (20 μm thick) were used for the substrates of sputter deposition. The microstructures and crystal structures of the films were investigated by transmission electron microscopy (TEM) and X-ray diffraction using CuKα radiation, respectively. The effect of the sputtering conditions such as substrate temperature, partial pressure of argon gas, and the sputtering power on the structures of sputter-deposited Cu-14%Al-4%Ni films were investigated by X-ray diffraction. Results are shown and discussed. Photographs demonstrate shape memory behaviour of Cu-14%Al-4%Ni films sputter-deposited on aluminium foils from (a) liquid nitrogen temperature to (d) room temperature. (author)

Atomic-partial vibrational density of states of i-AlCuFe quasicrystals

International Nuclear Information System (INIS)

Parshin, P.P.; Zemlyanov, M.; Brand, R.A.; Dianoux, A.J.; Calvayrac, Y.

2002-01-01

We present new results on the separation of the atomic-partial vibrational density of states for the ternary quasicrystal i-Al 62 Cu 25.5 Fe 12.5 . The decomposition into three atomic-partial functions, Al-, Cu- and Fe-g(E), has been performed self-consistently with the calculation of the multi-phonon contributions. The results show the surprising result that both Cu- and Fe-g(E) are strongly peaked. The low-energy regions of Al- and Cu-g(E) show strong deviations from Debye behaviour due to the presence of non-propagating low-energy vibrational states. (orig.)

Interface interaction and wetting of Sc2O3 exposed to Cu-Al and Cu-Ti melts

International Nuclear Information System (INIS)

Barzilai, S.; Nagar, H.; Froumin, N.; Frage, N.; Aizenshtein, M.

2009-01-01

Scandia is a thermodynamically stable oxide and could be used as a structural material for a crucible in order to avoid a melt contamination. In the present study wetting experiments of Cu-Al and Cu-Ti melts on Scandia substrate were preformed at 1423 K by a sessile drop method. It was established that Al and Ti additions lead to the improved wetting and that the final contact angle decreases with increasing the additives concentration. For Al containing melts, the contact angle changes gradually with time, and a relatively thick interaction layer, which consists of Al 2 O 3 , Sc 2 O 3 , and metallic channels, was formed at the Sc 2 O 3 /Cu-Al interface. For Ti containing melts, the final contact angle is achieved already during heating, and an extremely thin layer based on a Ti-Sc-O compound was detected by AES at the Sc 2 O 3 /Cu-Ti interface. The results of a thermodynamic analysis, which takes into account the formation free energy of the oxides, involved in the systems, and the thermodynamic properties of the liquid solutions are in a good agreement with the experimental observations. (orig.)

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability

OpenAIRE

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-01-01

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these allo...

Effect of the heating rate on the microstructure of in situ Al2O3 particle-reinforced Al matrix composites prepared via displacement reactions in an Al/CuO system

International Nuclear Information System (INIS)

Zhao, Ge; Shi, Zhiming; Ta, Na; Ji, Guojun; Zhang, Ruiying

2015-01-01

Highlights: • The heating rate has a significant effect on the microstructures of composites. • The microstructure is determined by the diffusion rate of O and Cu in the heating stage. • The diffusion of Cu and O atoms is influenced by the heating rate. • With increasing heating rate, the Al 2 O 3 particle distribution becomes more uniformly. • With increasing heating rate, the form of Al 2 Cu changes from network to block-like. - Abstract: In this study, an in situ Al 2 O 3 particle-reinforced Al(Cu) matrix composite was successfully synthesized using a displacement reaction between Al and CuO powders. The powders were mixed at a weight ratio of 4:1 Al to CuO, cold-pressed and holding time at 900 °C for 1 h using varying heating rates. The effects of the heating rate on the microstructures of the composites were investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD), optical microscopy (MO), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results indicate that all of the composites contain Al, Al 2 O 3 particles and Al 2 Cu phases. Although the heating rate does not significantly affect the phase compositions of the composites, it has a significant effect on their microstructures, most likely because it strongly influences the diffusion rates of the Cu and O atoms. As the heating rate is increased, the Al 2 O 3 particles become more dispersed, and they have a more uniform particle size distribution. Meanwhile, the Al 2 Cu structure transforms from the network (Al + Al 2 Cu) eutectic to the block-like Al 2 Cu phase. The ∼2 μm Al 2 O 3 particles and the block-like Al 2 Cu phase are distributed uniformly in the Al matrix when the sample is placed directly into a 900 °C furnace. This sample has a relative higher Rockwell hardness B (HRB) value of 87

Electroless Cu Plating on Anodized Al Substrate for High Power LED.

Science.gov (United States)

Rha, Sa-Kyun; Lee, Youn-Seoung

2015-03-01

Area-selective copper deposition on screen printed Ag pattern/anodized Al/Al substrate was attempted using a neutral electroless plating processes for printed circuit boards (PCBs), according to a range of variation of pH 6.5-pH 8 at 70 °C. The utilized basic electroless solution consisted of copper(II) sulfate pentahydrate, sodium phosphinate monohydrate, sodium citrate tribasic dihydrate, ammonium chloride, and nickel(II) sulfate hexahydrate. The pH of the copper plating solutions was adjusted from pH 6.5 to pH 8 using NH4OH. Using electroless plating in pH 6.5 and pH 7 baths, surface damage to the anodized Al layer hardly occurred; the structure of the plated Cu-rich films was a typical fcc-Cu, but a small Ni component was co-deposited. In electroless plating at pH 8, the surface of the anodized Al layer was damaged and the Cu film was composed of a lot of Ni and P which were co-deposited with Cu. Finally, in a pH 7 bath, we can make a selectively electroless plated Cu film on a PCB without any lithography and without surface damage to the anodized Al layer.

Evaluation of Ce3+ and alkali metal ions Co-doped LiSrAlF6 crystalline scintillators

International Nuclear Information System (INIS)

Wakahara, Shingo; Yanagida, Takayuki; Fujimoto, Yutaka; Yokota, Yuui; Pejchal, Jan; Kurosawa, Shunsuke; Suzuki, Shotaro; Kawaguchi, Noriaki; Fukuda, Kentaro; Yoshikawa, Akira

2013-01-01

High scintillation efficiency of Eu-doped LiSrAlF 6 (LiSAF) and LiCaAlF 6 (LiCAF) codoped with alkali metal ions has been reported in our recent studies. Thus in this paper, we demonstrated the scintillation properties of 1% Ce-doped LiSAF crystals with 1% alkali metal ions co-doping to increase the light yield and understand the scintillation mechanism. The crystals showed intense emission band corresponding to the 5d-4f transition of Ce 3+ , and their light yields under thermal neutron excitation were higher than that of the Ce only doped crystal. Especially, the light yield of Ce–Na co-doped crystal exceeded about two times that of Ce only doped one. -- Highlights: ► Ce-doped and alkali metal co-doped LiSAF crystals were grown by μ-PD method. ► Alkali metal co-doped crystals showed higher light yield than Ce only doped crystal. ► Decay time of alkali metal co-doped LiSAF were longer than that of Ce only doped one

Creep behaviour of a casting titanium carbide reinforced AlSi12CuNiMg piston alloy at elevated temperatures; Hochtemperaturkriechverhalten der schmelzmetallurgisch hergestellten dispersionsverstaerkten Kolbenlegierung AlSi12CuNiMg

Energy Technology Data Exchange (ETDEWEB)

Michel, S.; Scholz, A. [Zentrum fuer Konstruktionswerkstoffe, TU Darmstadt (Germany); Tonn, B. [Institut fuer Metallurgie, TU Clausthal (Germany); Zak, H.

2012-03-15

This paper deals with the creep behaviour of the titanium carbide reinforced AlSi12CuNiMg piston alloy at 350 C and its comparison to the conventional AlSi12Cu4Ni2MgTiZr piston alloy. With only 0,02 vol-% TiC reinforcement the creep strength and creep rupture strength of the AlSi12CuNiMg piston alloy are significantly improved and reach the level of the expensive AlSi12Cu4Ni2MgTiZr alloy. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Solidifying incongruently melting intermetallic phases as bulk single phases using the example of Al{sub 2}Cu and Q-phase in the Al-Mg-Cu-Si system

Energy Technology Data Exchange (ETDEWEB)

Loeffler, Andrea [Institute of Materials Science and Technology, Friedrich-Schiller-University, Jena (Germany); Groebner, Joachim; Hampl, Milan [Institute of Metallurgy, Clausthal University of Technology, Clausthal-Zellerfeld (Germany); Engelhardt, Hannes [Institute of Materials Science and Technology, Friedrich-Schiller-University, Jena (Germany); Schmid-Fetzer, Rainer [Institute of Metallurgy, Clausthal University of Technology, Clausthal-Zellerfeld (Germany); Rettenmayr, Markus, E-mail: M.Rettenmayr@uni-jena.de [Institute of Materials Science and Technology, Friedrich-Schiller-University, Jena (Germany)

2012-02-25

Highlights: Black-Right-Pointing-Pointer Samples consisting of pure Al{sub 2}Cu and 95% Q-phase respectively were prepared. Black-Right-Pointing-Pointer The Q-phase composition is Al{sub 17}Cu{sub 9}Mg{sub 44}Si{sub 30}, its solubility range is negligible. Black-Right-Pointing-Pointer The Q-phase peritectic temperature was determined by DSC measurements as 703 Degree-Sign C. Black-Right-Pointing-Pointer A new thermodynamic dataset for the Q-phase has been assessed. - Abstract: Plane front directional solidification experiments were carried out for preparing incongruently melting intermetallic phases in the quaternary alloy system Al-Cu-Mg-Si, particularly the binary Al{sub 2}Cu phase and the quaternary phase ('Q-phase'). By this method, bulk samples that consist of only a single phase are generated. Sample sections consisting of 100% single phase Al{sub 2}Cu and of 95% Q-phase, respectively, were obtained. The composition of the Q-phase was measured by Energy Dispersive X-ray Spectroscopy (EDX). The measured concentrations are close to the Al{sub 3}Cu{sub 2}Mg{sub 9}Si{sub 7} composition that has recently been predicted as most stable by ab initio calculations. A peritectic temperature of 703 Degree-Sign C for the reaction Q {yields} L + Mg{sub 2}Si + (Si) was determined by differential scanning calorimetry (DSC). An optimization of the Calphad database was performed considering the measured composition and peritectic temperature. For validating the optimized database, Scheil calculations were performed and compared with the experimentally determined sequence of solidifying phases.

Zr-Cu-Ni-Al bulk metallic glasses with superhigh glass-forming ability

International Nuclear Information System (INIS)

Sun, Y.J.; Qu, D.D.; Huang, Y.J.; Liss, K.-D.; Wei, X.S.; Xing, D.W.; Shen, J.

2009-01-01

Zr-Cu-Ni-Al quaternary amorphous alloy compositions with varying glass-forming ability are developed by an efficient method of proportional mixing of binary eutectics. The critical diameter of the glassy sample is improved from 6 mm for Zr 53 Cu 18.7 Ni 12 Al 16.3 to 14 mm for Zr 50.7 Cu 28 Ni 9 Al 12.3 by straightforwardly adjusting the eutectic unit's coefficients. The drastic improvement in GFA is attributed to balancing the chemical affinities of the Zr, Cu, Ni and Al components in the melt prior to solidification which makes the precipitation of competing crystalline phases more difficult. As the glass-forming ability increases, the concentration of Cu in the alloys exhibits a same trend. Based on synchrotron radiation high-energy X-ray diffraction analysis and Miracle's structural model, it is envisioned that the substitution of additional Cu atoms for Zr atoms in the investigated alloys stabilizes the efficient cluster packing structure of the amorphous alloys, leading to the pronounced increase in their glass-forming ability

Effects of La and Ce Addition on the Modification of Al-Si Based Alloys

Directory of Open Access Journals (Sweden)

Emad M. Elgallad

2016-01-01

Full Text Available This study focuses on the effects of the addition of rare earth metals (mainly lanthanum and cerium on the eutectic Si characteristics in Al-Si based alloys. Based on the solidification curves and microstructural examination of the corresponding alloys, it was found that addition of La or Ce increases the alloy melting temperature and the Al-Si eutectic temperature, with an Al-Si recalescence of 2-3°C, and the appearance of post-α-Al peaks attributed to precipitation of rare earth intermetallics. Addition of La or Ce to Al-(7–13% Si causes only partial modification of the eutectic Si particles. Lanthanum has a high affinity to react with Sr, which weakens the modification efficiency of the latter. Cerium, however, has a high affinity for Ti, forming a large amount of sludge. Due to the large difference in the length of the eutectic Si particles in the same sample, the normal use of standard deviation in this case is meaningless.

Impact of microstructure on the thermoelectric properties of the ternary compound Ce{sub 3}Cu{sub 3}Sb{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Witas, Piotr, E-mail: pwitas@us.edu.pl [Institute of Physics, University of Silesia, Uniwersytecka 4, Katowice 40-007 (Poland); Goraus, Jerzy; Zajdel, Paweł; Balin, Katarzyna; Koperski, Janusz [Institute of Physics, University of Silesia, Uniwersytecka 4, Katowice 40-007 (Poland); Lelątko, Józef [Institute of Materials Science, University of Silesia, 75 Pułku Piechoty 1a, Chorzów 41-500 (Poland); Ślebarski, Andrzej [Institute of Physics, University of Silesia, Uniwersytecka 4, Katowice 40-007 (Poland)

2017-01-15

We present detailed structural and thermoelectric studies of the ternary compound Ce{sub 3}Cu{sub 3}Sb{sub 4}. This material is of interest due to previously reported considerable thermopower above room temperature (∼ 100 μV/K) and low thermal conductivity (2 W/(m K)). Here, we present detailed studies concerning microstructural and thermoelectric data, their variation across the samples and possible explanations for the observed behaviour. We have used X-ray diffraction, scanning electron microscopy (SEM), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) for microstructural analysis. The thermoelectric properties were examined using a physical property measurement system (PPMS). We analyse the impact of the sample quality on the thermoelectric properties. The most unstable parameter is the material resistivity which varies between 1.5 and 15 mΩ cm at room temperature. The properties variability is mainly due to structural defects caused by stresses during material preparation and also due to formation of foreign phases CeCuSb{sub 2} and CeSb. The figure of merit ZT is also strongly dependent on the quality of the sample. The largest value ZT ≈ 0.15 at 400 K is determined for the almost stoichiometric sample with small amounts of a impurity phases. - Highlights: •The Ce{sub 3}Cu{sub 3}Sb{sub 4} has considerable thermoelectric properties and potential for further chemical and/or structural modification. •The control over foreign phases formation is challenging. •The defects arising during arc melting process highly deteriorate ZT of material.

Gd3+-ESR and magnetic susceptibility of GdCu4Al8 and GdMn4Al8

International Nuclear Information System (INIS)

Coldea, R.; Coldea, M.; Pop, I.

1994-01-01

Gd ESR of GdCu 4 Al 8 and GdMn 4 Al 8 and magnetic susceptibility of GdCu 4 Al 8 , GdMn 4 Al 8 , and YMn 4 Al 8 were measured in the temperature range of 290K--460K and 90K--1050K, respectively. The occurrence of the Mn moment in YMn 4 Al 8 and GdMn 4 Al 8 is strongly correlated with the critical value of d∼2.6 angstrom of the Mn-Mn distance below which the Mn moment is not stable. The experimental data for GdMn 4 Al 8 , compared with the data for the isostructural compounds GdCu 4 Al 8 and YMn 4 Al 8 , show that near the critical value of d, the existence of Mn moment depends not only on the value of d, but also on the local magnetic surroundings. It has been revealed that the magnetic character of Mn moment in YMn 4 Al 8 and GdMn 4 Al 8 changes from an itinerant electron type to a local-moment type with increasing temperature

In-situ investigation of the icosahedral Al-Cu-Fe phase formation in thin films

Energy Technology Data Exchange (ETDEWEB)

Haidara, F., E-mail: fanta.haidara@im2np.fr [IM2NP, UMR 6242 CNRS - Universite Aix-Marseille, Av. Escadrille Normandie-Niemen, Case 142, 13397 Marseille Cedex 20 (France); Duployer, B. [Universite Paul Sabatier CIRIMAT-LCMIE 2R1, 118, Route de Narbonne, 31062 Toulouse Cedex 09 (France); Mangelinck, D.; Record, M.-C. [IM2NP, UMR 6242 CNRS - Universite Aix-Marseille, Av. Escadrille Normandie-Niemen, Case 142, 13397 Marseille Cedex 20 (France)

2012-09-05

Highlights: Black-Right-Pointing-Pointer We investigated the phase formation of i-Al{sub 62.5}Cu{sub 25}Fe{sub 12.5} in thin films. Black-Right-Pointing-Pointer We characterized the samples by DSC and in-situ XRD and resistance measurements. Black-Right-Pointing-Pointer The resistivity value for i-Al{sub 62.5}Cu{sub 25}Fe{sub 12.5} was determined. - Abstract: This work is an investigation of the formation by reactive diffusion at high temperatures of the icosahedral phase, i-Al{sub 62.5}Cu{sub 25}Fe{sub 12.5}, in thin films. The samples were prepared by sputtering at room temperature. The elements Al, Cu and Fe were sequentially deposited onto oxidized silicon substrates. The two following stacking sequences, Al/Cu/Fe and Al/Fe/Cu, were investigated. The phase formation was studied using in situ resistivity, in situ X-ray Diffraction and Differential Scanning Calorimetry measurements. Whatever the stacking sequence, the sequences of phase formation evidenced during the heating treatment are similar. However the temperatures of formation for the first phases that are formed are different; they are higher in the case of the Al/Fe/Cu stacking sequence.

Uptake of copper and cerium by alfalfa, lettuce and cucumber exposed to nCeO2 and nCuO through the foliage or the roots: Impacts on food quality, physiological and agronomical parameters

Science.gov (United States)

Hong, Jie

, with 50, 100, 200 mg/L of nCeO2, nCuO and the respective bulk material suspensions. Photosynthetic rate (Pn), stomatal conductance (gs), and transpiration (E) of cucumber leaves were measured with a portable gas exchange system. Nutritional elements and Ce/Cu uptake were determined by ICP-OES. Quality of cucumber fruits was evaluated after harvest. Results showed that cucumber absorbed Ce and Cu through foliar applied nCeO2 and nCuO and translocate them to new leaves and fruits. Photosynthetic and transpiration rates were only affected in new leaves. None of the treatment significantly affected cucumber, yield, length, and diameter of fruits. However, both nCeO2 and nCuO significantly reduced the firmness of the fruit. Mineral element determination in fruit showed that Zn decreased by 25% with 200 mg/L of both nCeO2 and bulk CeO 2 and in fruit Mo decreased by 51% and 44% with both nCuO and bulk CuO at 200 mg/L, respectively. For the aim III, 15 day-old hydroponically grown lettuce and alfalfa were exposed to 0, 5, 10, and 20 mg/L nCu, bulk Cu, nCuO, bulk CuO, Cu(OH)2 (CuPRO 2005, Kocide 3000), and CuCl2. The concentration of Cu, macro and microelements in plants were measured by using ICP-OES. The size of the plants and the activity of catalase and ascorbate peroxidase were also determined. Results showed that all Cu NPs/compounds reduced the root length by 49% in both plant species. Under all treatments, Cu, P, and S were increased (>100%, >50%, and >20%, respectively) in alfalfa shoots; while P and Fe were decreased (>50% and >50%, respectively) in lettuce shoot. In addition, catalase activity was reduced in alfalfa (root and shoot) and ascorbate peroxidase activity was increased in roots of both plant species. Our findings show that increasing concentration of atmospheric nCeO2 can affect the nutritional value of crop plants with unknown consequences for the food chain. In addition Cu NPs/compounds could impact the growth of plants and altered the quality of crops

Antifriction coating of Cu-Fe-Al-Pb system for plain bearings

Science.gov (United States)

Kotenkov, Pavel; Kontsevoi, Yurii; Mejlakh, Anna; Pastukhov, Eduard; Shubin, Alexey; Goyda, Eduard; Sipatov, Ivan

2017-09-01

Aluminium, copper and their compounds are used in common as basis for antifriction coatings of plain bearings. Antifriction testing of plain bearings (based on Al and Cu) made by leading automotive manufacturers from Germany, Japan, USA, United Kingdom and Russia were carried out to make judicious selection of basis for development of new antifriction material. Testing was carried out using friction machine. It was defined that materials based on Cu provide better durability and robustness of plain bearings in comparison with Al based ones. The new antifriction composite coatings based on copper were developed taking into account the requirements specified for plain bearings of internal-combustion engine. Pilot samples of plain bearings with antifriction coatings of Cu-Fe-Al-Pb system were produced. The antifriction composite having Cu-5Fe-5Al5Fe2-10Pb (mass %) composition has demonstrated low friction factor and high wear-resistance. Metallographic analysis of pilot samples was carried out by means of optical and scanning electron microscopy.

Chemical and electrical characterisation of the segregation of Al from a CuAl alloy (90%:10% wt) with thermal anneal

Energy Technology Data Exchange (ETDEWEB)

Byrne, C., E-mail: conor.byrne2@mail.dcu.ie [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland); Brady, A.; Walsh, L.; McCoy, A.P.; Bogan, J. [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland); McGlynn, E. [School of Physical Sciences, National Centre for Plasma Science and Technology, Dublin City University, Dublin 9 (Ireland); Rajani, K.V. [School of Electronic Engineering, Dublin City University, Dublin 9 (Ireland); Hughes, G. [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland); School of Physical Sciences, National Centre for Plasma Science and Technology, Dublin City University, Dublin 9 (Ireland)

2016-01-29

A copper–aluminium (CuAl) alloy (90%:10% wt) has been investigated in relation to segregation of the alloying element Al, from the alloy bulk during vacuum anneal treatments. X-ray photoelectron spectroscopy (XPS) measurements were used to track the surface enrichment of Al segregating from the alloy bulk during in situ ultra-high vacuum anneals. Secondary ion mass spectroscopy (SIMS) indicates a build-up of Al at the surface of the annealed alloy relative to the bulk composition. Metal oxide semiconductor (MOS) CuAl/SiO{sub 2}/Si structures show a shift in flatband voltage upon thermal anneal consistent with the segregation of the Al to the alloy/SiO{sub 2} interface. Electrical four point probe measurements indicate that the segregation of Al from the alloy bulk following thermal annealing results in a decrease in film resistivity. X-ray diffraction data shows evidence for significant changes in crystal structure upon annealing, providing further evidence for expulsion of Al from the alloy bulk. - Highlights: • CuAl alloy (90%:Al 10% wt) deposited and vacuum annealed • XPS and SIMS data show segregation of Al from the alloy bulk. • Chemical changes seen indicate the reduction of Cu oxide and growth of Al Oxide. • Electrical measurements indicate a chemical change at the metal/SiO{sub 2} interface. • All data consistent with Cu diffusion barrier layer formed.

Atomic-partial vibrational density of states of i-AlCuFe quasicrystals

CERN Document Server

Parshin, P P; Brand, R A; Dianoux, A J; Calvayrac, Y

2002-01-01

We present new results on the separation of the atomic-partial vibrational density of states for the ternary quasicrystal i-Al sub 6 sub 2 Cu sub 2 sub 5 sub . sub 5 Fe sub 1 sub 2 sub . sub 5. The decomposition into three atomic-partial functions, Al-, Cu- and Fe-g(E), has been performed self-consistently with the calculation of the multi-phonon contributions. The results show the surprising result that both Cu- and Fe-g(E) are strongly peaked. The low-energy regions of Al- and Cu-g(E) show strong deviations from Debye behaviour due to the presence of non-propagating low-energy vibrational states. (orig.)

Synthesis by Sol-gel and characterization of catalysts Ag/Al2O3-CeO2

International Nuclear Information System (INIS)

Zayas, M.L.; Perez H, R.; Rubio, E.; Velasco, A.

2004-01-01

Aluminia, cerium and mixed oxides Al 2 O 3 -CeO 2 with different relationship Al/Ce (0.75, 0.50 and 0.25) were prepared by sol-gel and used as support for the Ag. The samples were characterized by XRD, DRIFT, TPR and adsorption of N 2 to temperature of liquid nitrogen. The surface area BET showed that the materials that contain aluminia present near values among them. XRD allowed to identify to the cerianite in the oxides that whose support contains cerium and to the α-aluminia. A mixture of phases was observed in the aluminia. Vibration bands attributed to the bond Al-O and Ce-O were observed by DRIFT in the catalytic materials. TPR showed differences in the reducibility of the Ag precursor in the indicative catalysts of a different interaction with the support. (Author)

Simultaneous increase in strength and ductility by decreasing interface energy between Zn and Al phases in cast Al-Zn-Cu alloy.

Science.gov (United States)

Han, Seung Zeon; Choi, Eun-Ae; Park, Hyun Woong; Lim, Sung Hwan; Lee, Jehyun; Ahn, Jee Hyuk; Hwang, Nong-Moon; Kim, Kwangho

2017-09-22

Cast-Al alloys that include a high amount of the second element in their matrix have comparatively high strength but low ductility because of the high volume fraction of strengthening phases or undesirable inclusions. Al-Zn alloys that have more than 30 wt% Zn have a tensile strength below 300 MPa, with elongation under 5% in the as-cast state. However, we found that after substitution of 2% Zn by Cu, the tensile strength of as-cast Al-Zn-Cu alloys was 25% higher and ductility was four times higher than for the corresponding Al-35% Zn alloy. Additionally, for the Al-43% Zn alloy with 2% Cu after 1 h solution treatment at 400 °C and water quenching, the tensile strength unexpectedly reached values close to 600 MPa. For the Al-33% Zn alloy with 2% Cu, the tensile strength was 500 MPa with 8% ductility. The unusual trends of the mechanical properties of Al-Zn alloys with Cu addition observed during processing from casting to the subsequent solution treatment were attributed to the precipitation of Zn in the Al matrix. The interface energy between the Zn particles and the Al matrix decreased when using a solution of Cu in Zn.

High-pressure x-ray diffraction of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals

DEFF Research Database (Denmark)

Jiang, Jianzhong; Saksl, Karel; Rasmussen, Helge Kildahl

2001-01-01

temperature using synchrotron radiation. The icosahedral quasicrystal structure is retained up to the highest hydrostatic pressure used (approximately 28 GPa) and is reversible after decompression. The bulk modulus at zero pressure and its pressure derivative of the icosahedral Zr-Al-Ni-Cu-Ag quasicrystal......The effect of pressure on the structural stability of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals forming from a Zr65Al7.5Ni10Cu7.5Ag10 metallic glass with a supercooled liquid region of 44 K has been investigated by in situ high-pressure angle-dispersive x-ray powder diffraction at ambient......-Al-Ni-Cu-Ag quasicrystals induced by pressure....

Cube Texture Formation of Cu-33at.%Ni Alloy Substrates and CeO₂ Buffer Layer for YBCO Coated Conductors

DEFF Research Database (Denmark)

Tian, Hui; Li, Suo Hong; Ru, Liang Ya

2014-01-01

Cube texture formation of Cu-33 at.%Ni alloy substartes and CeO2 buffer layer prepared by chemical solution deposition on the textured substrate were investigated by electron back scattered diffraction (EBSD) and XRD technics systematically. The results shown that a strong cube textured Cu-33at...

A study of a stable Al-Cu-Fe quasicrystal in solid and liquid state

International Nuclear Information System (INIS)

Chen Lifan; Chen Xishen

1992-01-01

A stable Al 65 Cu 20 Fe 15 quasicrystal with an icosahedral structure is studied in solid and liquid state. It is found that the icosahedral phase in Al 65 Cu 20 Fe 15 alloy does not grow directly from the pure liquid state, but rather forms between monoclinic Al 13 Fe 4 and residual liquid state at 865degC. The melting point of the Al 65 Cu 20 Fe 15 icosahedral quasicrystal occurs at 865degC and that of the Al 65 Cu 20 Fe 15 alloy occurs at 1008degC. Moreover, the monoclinic Al 13 Fe 4 is transformed into the icosahedral phase easily at the temperature of 845degC. The icosahedral quasicrystal in Al 65 Cu 20 Fe 15 alloy has a high thermal stability even at 950degC. Above 950degC, the icosahedral structure tends to an amorphous structure. (orig.)

Electronic structure and phase stability during martensitic transformation in Al-doped ZrCu intermetallics

International Nuclear Information System (INIS)

Qiu Feng; Shen Ping; Liu Tao; Lin Qiaoli; Jiang Qichuan

2010-01-01

Martensitic transformation, phase stability and electronic structure of Al-doped ZrCu intermetallics were investigated by experiments and first-principles calculations using the pseudopotentials plane wave method. The formation energy calculations indicate that the stability of the ZrCu phase increases with the increasing Al content. Al plays a decisive role in controlling the formation and microstructures of the martensite phases in Zr-Cu-Al alloys. The total energy difference between ZrCu (B2) austenite and ZrCu martensite plays an important role in the martensitic transformation. The phase stability is dependent on its electronic structure. The densities of states (DOS) of the intermetallics were discussed in detail.

Fabrication and mechanical behavior of bulk nanoporous Cu via chemical de-alloying of Cu–Al alloys

Energy Technology Data Exchange (ETDEWEB)

Chen, Fei, E-mail: chenfei027@gmail.com [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Chen, Xi; Zou, Lijie; Yao, Yao; Lin, Yaojun; Shen, Qiang [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Lavernia, Enrique J. [Department of Chemical Engineering and Materials Science, University of California at Irvine, Irvine, CA 92697 (United States); Zhang, Lianmeng, E-mail: lmzhang@whut.edu.cn [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

2016-04-13

We report on a study of the influence of microstructure on the mechanical behavior of bulk nanoporous Cu fabricated by chemical de-alloying of Cu{sub 50}Al{sub 50}, Cu{sub 40}Al{sub 60}, Cu{sub 33}Al{sub 67} and Cu{sub 30}Al{sub 70} (at%) alloys. The precursor Cu–Al alloys were fabricated using arc melting and bulk nanoporous Cu was obtained by subsequent de-alloying of Cu–Al alloys in 20 wt% NaOH aqueous solution at a temperature of 65 °C. We studied the microstructure of the precursor Cu–Al alloys, as well as that of the as de-alloyed bulk nanoporous Cu, using X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry. Moreover, the compressive strength of bulk nanoporous Cu was measured and the relationship between microstructure and mechanical properties was studied. Our results show that the microstructure of bulk nanoporous Cu is characterized by bi-continuous interpenetrating ligament-channels with a ligament size of 130±20 nm (for Cu{sub 50}Al{sub 50}), 170±20 nm (for Cu{sub 40}Al{sub 60}) and 160±10 nm (for Cu{sub 33}Al{sub 67}). Interestingly the microstructure of de-alloyed Cu{sub 30}Al{sub 70} is bimodal with nanopores (100's nm) and interspersed featureless regions a few microns in size. The compressive strength increased with decreasing volume fraction of porosity; as porosity increased 56.3±2% to 73.9±2%, the compressive strength decreased from 17.18±1 MPa to 2.71±0.5 MPa.

Microstructure analysis of the automotive Al-Si-Cu castings

Directory of Open Access Journals (Sweden)

M. Krupiński

2008-04-01

Full Text Available The developed design methodologies both the material and technological ones will make it possible to improve shortly the quality of materials from the light alloys in the technological process, and the automatic process flow correction will make the production cost reduction possible, and - first of all - to reduce the amount of the waste products. In the metal casting industry, an improvement of component quality depends mainly on better control over the production parameters.Castings were analysed in the paper of car engine blocks and heads from the Al-Si-Cu alloys of the AC-AlSi7Cu3Mg type fabricated with the “Cosworth” technological process. In this work the AC-AlSi7Cu3Mg alloy structure was investigated, of this alloy samples were cut of for structure analysis of the cylinder part as well of crankshaft of a fuel engine. The investigation shows a difference in the (phase structure morphology as a result of cast cooling rate.

Microstructure of AlSi17Cu5 alloy after overheating over liquidus temperature

Directory of Open Access Journals (Sweden)

J. Piątkowski

2015-01-01

Full Text Available The paper presents microstructure tests of alloy AlSi17Cu5. In order to disintegrate the primary grain of silicon the so-called time-temperature transformation TTT was applied which was based on overheating the liquid alloy way over the temperature Tliq., soaking in it for 30 minutes and casting it to a casting mould. It was found that such process causes the achievement of fine-crystalline structure and primary silicon crystals take up the form of pentahedra or frustums of pyramids. With the use of X-ray microanalysis and X-ray diffraction analysis the presence of intermetallic phases Al2Cu, Al4Cu9 which are the ingredients of eutectics α - AlCu - β and phase Al9Fe2Si which is a part of eutectic α - AlFeSi - β was confirmed.

Magnetic versus nonmagnetic ion substitution effects on Tc in the La-Sr-Cu-O and Nd-Ce-Cu-O systems

International Nuclear Information System (INIS)

Tarascon, J.M.; Wang, E.; Kivelson, S.; Bagley, B.G.; Hull, G.W.; Ramesh, R.

1990-01-01

The effects of a substitution for Cu by other 3d metals (Ni, Co, and Zn) on T c in the Nd-Ce-Cu-O system was studied and compared with effects of the same ions on T c in the La-Sr-Cu-O system. We found (1) Zn suppresses T c more slowly in the Nd than in the La systems, so the disorder produced by the nonmagnetic ions is less important in the Nd system, (2) Ni and Co depress T c more quickly in the Nd than in the La system, showing that the magnetic pair breaking is stronger in the Nd system, and (3) in the La system the magnetism of the dopant has no effect on T c . Thus, within the same chemical system (cuprates) we find that as the correlation length is increased one obtains more familiar BCS-type behavior. We suggest that much of the behavior of the various high-T c oxides may be simply a function of the correlation length

Introduzione all'analisi qualitativa dei sistemi dinamici discreti e continui

CERN Document Server

Squassina, Marco

2016-01-01

Il testo è stato concepito per la struttura degli attuali corsi di laurea in Biologia, Matematica, Matematica Applicata, Ingegneria, Scienze Naturali e Mediche. Esso si concentra sugli aspetti qualitativi delle equazioni differenziali come limitatezza o illimitatezza delle soluzioni, esistenza o non esistenza di orbite periodiche, stabilità o instabilità dei punti di equilibrio, biforcazione del sistema al variare di un parametro, robustezza del sistema in presenza di perturbazioni. L'analisi qualitativa di sistemi dinamici discreti e continui è un argomento tecnicamente accessibile anche agli studenti di primo livello e consente di collegare, combinare ed esercitare nozioni che provengono dall'algebra, dal calcolo differenziale di base e dalla geometria elementare, stimolando l'intuizione matematica. Il volume si caratterizza per due aspetti: quello induttivo e quello figurativo. L'approccio induttivo si basa su un'ampia gamma di problemi risolti e pensati per introdurre, gradualmente, sia le conoscenze ...

Atomic structure and formation of CuZrAl bulk metallic glasses and composites

International Nuclear Information System (INIS)

Kaban, I.; Jóvári, P.; Escher, B.; Tran, D.T.; Svensson, G.; Webb, M.A.; Regier, T.Z.; Kokotin, V.; Beuneu, B.; Gemming, T.; Eckert, J.

2015-01-01

Graphical abstract: Partial radial distribution functions for Cu 47.5 Zr 47.5 Al 5 metallic glass and relevant crystal structures. - Abstract: Cu 47.5 Zr 47.5 Al 5 metallic glass is studied experimentally by high-energy X-ray diffraction, neutron diffraction with isotopic substitution, electron diffraction and X-ray absorption spectroscopy. The atomic structure of the glass is modeled by reverse Monte-Carlo and molecular dynamics simulations. RMC modeling of seven experimental datasets enabled reliable separation of all partial pair distribution functions for Cu 47.5 Zr 47.5 Al 5 metallic glass. A peculiar structural feature of the ternary alloy is formation of the strong Al–Zr bonds, which are supposed to determine its high viscosity and enhanced bulk glass formation. Analysis of the local atomic order in Cu 47.5 Zr 47.5 Al 5 glass and Cu 10 Zr 7 , CuZr 2 and CuZr B2 crystalline structures elucidates their similarities and differences explaining the phase formation sequence by devitrification of the glass.

Toxicity assessment and selective leaching characteristics of Cu-Al-Ni shape memory alloys in biomaterials applications.

Science.gov (United States)

Chang, Shih-Hang; Chen, Bor-Yann; Lin, Jin-Xiang

2016-04-06

Cu-Al-Ni shape memory alloys (SMAs) possess two-way shape memory effects, superelasticity, and damping capacity. Nonetheless, Cu-Al-Ni SMAs remain promising candidates for use in biomedical applications, as they are more economical and machinable than other SMAs. Ensuring the biocompatibility of Cu-Al-Ni SMAs is crucial to their development for biomedical applications. Therefore, this study aimed to assess the toxicity of Cu-Al-Ni SMAs using a Probit dose-response model and augmented simplex design. In this study, the effects of Cu2+, Al3+ and Ni2+ metal ions on bacteria (Escherichia coli DH5α) using Probit dose-response analysis and augmented simplex design to assess the actual toxicity of the Cu-Al-Ni SMAs. Extraction and repetition of Escherichia coli DH5α solutions with high Cu2+ ion concentrations and 30-hour incubation demonstrated that Escherichia coli DH5α was able to alter its growth mechanisms in response to toxins. Metal ions leached from Cu-Al-Ni SMAs appeared in a multitude of compositions with varying degrees of toxicity, and those appearing close to a saddle region identified in the contour plot of the augmented simplex model were identified as candidates for elevated toxicity levels. When the Cu-13.5Al-4Ni SMA plate was immersed in Ringer's solution, the selective leaching rate of Ni2+ ions far exceeded that of Cu2+ and Al3+. The number of Cu2+, Al3+ and Ni2+ ions leached from Cu-Al-Ni SMAs increased with immersion time; however, at higher ratios, toxicity interactions among the metal ions had the effect of gradually reducing overall toxicity levels with regard to Escherichia coli DH5α. The quantities of Cu2+, Al3+ and Ni2+ ions leached from the Cu-13.5Al-4Ni SMA plate increased with immersion time, the toxicity interactions associated with these compositions reduced the actual toxicity to Escherichia coli DH5α.

Microstructures and Properties Evolution of Al-Cu-Mn Alloy with Addition of Vanadium

Directory of Open Access Journals (Sweden)

Fansheng Meng

2016-12-01

Full Text Available The effect of the vanadium addition on the microstructure, the precipitation behavior, and the mechanical properties of the Al-5.0Cu-0.4Mn alloy has been studied. The as-cast Al-5.0Cu-0.4Mn alloy was produced by squeeze casting and the heat treatment was carried out following the standard T6 treatment. It is shown that, with the addition of V, grain refinement of aluminum occurred. During heat treatment, the addition of V accelerates the precipitation kinetics of θ′ (Al2Cu phase along the grain boundaries, and promotes the growth rate of the θ′ in the α(Al matrix. Meanwhile, the addition of V retards the precipitation of T (Al20Cu2Mn3 phase. The tensile strength of the Al-5.0Cu-0.4Mn alloy increases with the increase of V content, which can be explained by combined effects of the solid solution strengthening and precipitate strengthening. However, excessively high V addition deteriorates the mechanical properties by forming brittle coarse intermetallic phases.

Size effect on magnetic ordering in Ce3Al11

International Nuclear Information System (INIS)

Wang, C.R.; Chen, Y.Y.; Neeleshwar, S.; Ou, M.N.; Ho, J.C.

2003-01-01

To study the size dependence of magnetic ordering, magnetic measurements have been made between 1.8 and 300 K on Ce 3 Al 11 particles having an average particle size of 1400 A. The nanoparticles were single phase as confirmed by X-ray diffraction. At low temperatures a ferromagnetic transition occurs at T C =6.2 K, which is the same as that for the bulk material. On the other hand, the antiferromagnetic transition at T N =3.2 K for the bulk material is not visible down to 1.8 K. Meanwhile, the slightly smaller Curie constant of nanoparticles as compared to that of the bulk indicates a certain degree of demagnetization of Ce ions when the particle size is sufficiently reduced

Comparison among structural characteristics of Ce{sub 1-x}Cu{sub x}O{sub 2} nanocatalysts obtained by two methods of distinct synthesis; Comparacao entre as caracteristicas estruturais dos nanocatalisadores Ce{sub 1-x}Cu{sub x}O{sub 2} obtidos por dois metodos de sintese distintos

Energy Technology Data Exchange (ETDEWEB)

Neiva, L.S.; Bispo, A.; Santos, P.T.A.; Costa, A.C.F.M.; Gama, L., E-mail: lucianna@dema.ufcg.edu.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Engenharia de Materiais; Mascarenhas, A.J.S. [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Inst. de Quimica

2009-07-01

The objective this work is to synthesize nano catalysts Ce{sub 1-x}Cu{sub x}O{sub 2} type by the synthesis methods of the combustion reaction and Pechini. The value of the concentration (x) of the element dope (Cu) varies between 0,1 and 0,5 mols. It intends evaluate that form the synthesis method influences in the physical structural characteristics of this material. nano catalysts were characterized by ray- X diffraction. The results showed nano catalysts formation with a formed structure for the most part by the phase CeO{sub 2}, as it was expected, since this is the hostess matrix of the element dope (Cu). Nano catalysts obtained by the method Pechini presents crystallinity larger deg, according with patterns of ray-X. Thus, it was concluded that synthesis employee method the kind in the methodology, as well as the value of the concentration of the element dope has influence on the final structural characteristics of the developed material. (author)

Microstructure and tribological properties of TiCu{sub 2}Al intermetallic compound coating

Energy Technology Data Exchange (ETDEWEB)

Guo Chun, E-mail: guochun@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate University of Chinese Academy of Sciences, Beijing 100039 (China); Zhou Jiansong [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhao Jierong; Wang Linqian; Yu Youjun [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate University of Chinese Academy of Sciences, Beijing 100039 (China); Chen Jianmin; Zhou Huidi [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2011-04-15

TiCu{sub 2}Al ternary intermetallic compound coating has been in situ synthesized successfully on pure Ti substrate by laser cladding. Tribological properties of the prepared TiCu{sub 2}Al intermetallic compound coating were systematically evaluated. It was found that the friction coefficient and wear rate was closely related to the normal load and sliding speed, i.e., the friction coefficient of the prepared TiCu{sub 2}Al intermetallic compound coating decreased with increasing normal load and sliding speed. The wear rate of the TiCu{sub 2}Al intermetallic compound coating decreased rapidly with increasing sliding speed, while the wear rate first increased and then decreased at normal load from 5 to 15 N.

Development of amorphous and nanocrystalline Al65Cu35-xZrx alloys by mechanical alloying

International Nuclear Information System (INIS)

Manna, I.; Chattopadhyay, P.P.; Banhart, F.; Fecht, H.J.

2004-01-01

Mechanical alloying of Al 65 Cu 35-x Zr x (x=5, 15 and 25 at.% Zr) elemental powder blends by planetary ball milling up to 50 h yields amorphous and/or nanocrystalline products. Microstructure of the milled product at different stages of milling has been characterized by X-ray diffraction, (XRD) high-resolution transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). Among the different alloys synthesized by mechanical alloying, Al 65 Cu 20 Zr 15 yields a predominantly amorphous product, while the other two alloys develop a composite microstructure comprising nanocrystalline and amorphous solid solutions in Al 65 Cu 10 Zr 25 and nano-intermetallic phase/compound in Al 65 Cu 30 Zr 5 , respectively. The genesis of solid-state amorphization in Al 65 Cu 20 Zr 15 and Al 65 Cu 10 Zr 25 is investigated

Effect of ageing time 200 °C on microstructure behaviour of Al-Zn-Cu-Mg cast alloys

Directory of Open Access Journals (Sweden)

Pratiwi Diah Kusuma

2017-01-01

Full Text Available Al-Zn-Cu-Mg is heat treatable alloy that can be used in many hightech applications, such as aerospace and military. The main objective of this study is to investigate the influence of ageing process in microstrucure behaviour of Al-9Zn-5Cu-4Mg cast alloy by performing SEM analysis and its correlation with hardness tests of as-cast Al-9Zn-5Cu-4Mg alloy and heat treated Al-9Zn-5Cu-4Mg cast alloy. The results show the deployment of precipitation spread over the dendrite and also the presence of second phases Mg3Zn3Al2 , Cu2FeAl7 , CuAl2, and CuMgAl2 in as-cast Al-9Zn-5Cu-4Mg alloy. The presence of all these second phases are affecting to the toughness of aluminium alloy and the presence of MgZn2 leads the impairment of hardness value of heat-treated Al-9Zn-5Cu-5Mg cast alloy.

Aging behavior of an in-situ TiB{sub 2}/Al-Cu-Li-x matrix composite

Energy Technology Data Exchange (ETDEWEB)

Shen, Yanwei; Hong, Tianran; Geng, Jiwei; Han, Gaoyang; Chen, Dong; Li, Xianfeng, E-mail: brucelee75cn@sjtu.edu.cn; Wang, Haowei

2017-02-15

Transmission electron microscopy, differential scanning calorimetry and hardness tests have been performed on an in-situ TiB{sub 2}/Al-3.3Cu-1.0Li-0.60Mg-0.40Ag-0.14Zr-0.13Si composite to study its aging behavior at 175 °C. A cubic phase suspected to be the σ (Al{sub 5}Cu{sub 6}Mg{sub 2}) phase or its variant is precipitated at all aging stages studied, and this phase is not typically observed in the Al-Cu-Li alloys. The primary hardening (aging for 3 h) phases consist of δ′ (Al{sub 3}Li), β′ (Al{sub 3}Zr) and the cubic phase. After aging for 18 h, all precipitates including T{sub 1} (Al{sub 2}CuLi), S (Al{sub 2}CuMg), θ′ (Al{sub 2}Cu), δ′, β′ and the cubic phase have appeared, and the formation of T{sub 1} and S results in a rapid increase in hardness. With prolonging of aging time, the apparent coarsening of T{sub 1} and S results in a decline in hardness. - Highlights: •The aging behavior of an in-situ TiB{sub 2}/Al-Cu-Li-x composite was studied. •A cubic phase suspected to be σ (Al{sub 5}Cu{sub 6}Mg{sub 2}) or its variant was precipitated. •The hardness change was dominated by the evolution of T{sub 1} (Al{sub 2}CuLi) and S (Al{sub 2}CuMg).

Effect of iron content on the structure and mechanical properties of Al25Ti25Ni25Cu25 and (AlTi)60-xNi20Cu20Fex (x=15, 20) high-entropy alloys

International Nuclear Information System (INIS)

Fazakas, É.; Zadorozhnyy, V.; Louzguine-Luzgin, D.V.

2015-01-01

Highlights: • Three new refractory alloys namely: Al 25 Ti 25 Ni 25 Cu 25 , Al 22.5 Ti 22.5 Ni 20 Cu 20 Fe 15 and Al 20 Ti 20 Ni 20 Cu 20 Fe 20 , were produced by induction-melting and casting. • This kind of alloys exhibits high resistance to annealing softening. • Most the alloys in the annealed state possess even higher Vickers microhardness than the as-cast alloys. • The Al 22.5 Ti 22.5 Ni 20 Cu 20 Fe 15 and Al 20 Ti 20 Ni 20 Cu 20 Fe 20 alloys annealed at 973 K show the highest compressive stress and ductility values. - Abstract: In this work, we investigated the microstructure and mechanical properties of Al 25 Ti 25 Ni 25 C u25 Al 22.5 Ti 22.5 Ni 20 Cu 20 Fe 15 and Al 20 Ti 20 Ni 20 Cu 20 Fe 20 high entropy alloys, produced by arc melting and casting in an inert atmosphere. The structure of these alloys was studied by X-ray diffractometry and scanning electron microscopy. The as-cast alloys were heat treated at 773, 973 and 1173 K for 1800 s to investigate the effects of aging on the plasticity, hardness and elastic properties. Compared to the conventional high-entropy alloys the Al 25 Ti 25 Ni 25 Cu 25 , Al 22.5 Ti 22.5 Ni 20 Cu 20 Fe 15 and Al 20 Ti 20 Ni 20 Cu 20 Fe 20 alloys are relatively hard and ductile. Being heat treated at 973 K the Al 22.5 Ti 22.5 Ni 20 Cu 20 Fe 15 alloy shows considerably high strength and relatively homogeneous deformation under compression. The plasticity, hardness and elastic properties of the studied alloys depend on the fraction and intrinsic properties of the constituent phases. Significant hardening effect by the annealing is found.

Structure and mechanical properties of nanostructured Al-0.3%Cu alloy

DEFF Research Database (Denmark)

Wakeel, Aneela; Huang, Tianlin; Wu, Guilin

2014-01-01

An Al-0.3%Cu alloy has been produced using extremely high purity (99.9996%) Al and OFHC Cu.The alloy was cold rolled to 98% thickness reduction, forming a stable lamellar structure that has a lamellar boundary spacing of about 200nm and a tensile strength of 225MPa. During recovery annealing at t...

Changes of microstructure and magnetic properties of Nd-Fe-B sintered magnets by doping Al-Cu

International Nuclear Information System (INIS)

Ni Junjie; Ma Tianyu; Yan Mi

2011-01-01

The microstructural and magnetic properties of Al 100-x Cu x (15at%≤x≤45 at%) doped Nd-Fe-B magnets were studied. The distribution and alloying effects of Cu or Al on the intergranular microstructure were investigated by thermodynamic analysis, differential scanning calorimetery and microscopy techniques. It was observed that when the Cu content of Al 100x Cu x exceeds to 25 at%, the (Pr, Nd)Cu and CuAl 2 phases form in these magnets. The formation of (Pr, Nd)Cu phase depends on the negative formation enthalpy of (Pr, Nd)Cu and the exclusive distribution of Cu in the intergranular regions. The eutectic reaction between (Pr, Nd)Cu phase and (Pr, Nd) occurs at 480 deg. C, which forms the liquid phase that dissolves the (Pr, Nd) 2 Fe 14 B surface irregularities and thus increases the quantities of (Pr, Nd)-rich phase at the grain boundaries. These changes benefit the grain boundary microstructure, especially the distribution of (Pr, Nd)-rich phase, which effectively improves the intrinsic coercivity i H c due to the decreases of exchange coupling between the (Pr, Nd) 2 Fe 14 B grains. - Highlights: → Cu/Al effects on Nd-Fe-B structure depend on their distribution/alloying behaviors. → Cu exclusively distributes in grain boundaries different from Al and has negative mixing heat with Nd. → (Pr,Nd)Cu phase besides CuAl 2 forms in grain boundaries with Cu content increase. → (Pr,Nd)Cu phases optimize microstructure and increase magnetic properties.

Functional Performances of CuZnAl Shape Memory Alloy Open-Cell Foams

Science.gov (United States)

Biffi, C. A.; Casati, R.; Bassani, P.; Tuissi, A.

2018-01-01

Shape memory alloys (SMAs) with cellular structure offer a unique mixture of thermo-physical-mechanical properties. These characteristics can be tuned by changing the pore size and make the shape memory metallic foams very attractive for developing new devices for structural and functional applications. In this work, CuZnAl SMA foams were produced through the liquid infiltration of space holder method. In comparison, a conventional CuZn brass alloy was foamed trough the same method. Functional performances were studied on both bulk and foamed SMA specimens. Calorimetric response shows similar martensitic transformation (MT) below 0 °C. Compressive response of CuZnAl revealed that mechanical behavior is strongly affected by sample morphology and that damping capacity of metallic foam is increased above the MT temperatures. The shape memory effect was detected in the CuZnAl foams. The conventional brass shows a compressive response similar to that of the martensitic CuZnAl, in which plastic deformation accumulation occurs up to the cellular structure densification after few thermal cycles.

L10 ordered structures in Al-Cu-(Mg alloys at the early stages of elevated temperature aging

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Fuzhong, Xia

2016-09-01

Full Text Available This study concerns the precipitation structures of Al-3Cu and Al-3Cu-1.78Mg (wt. % alloys at the early stages of elevated temperature aging. The Al-3Cu and Al-3Cu-1.78 Mg alloys were solution treated at 540 °C and 500 °C for 2 h, respectively, and then aged at 190 °C for 2 min. The precipitation structures in aged Al-3Cu-(1.78Mg alloys were characterized by Transmission Electron Microscopy (TEM and High Resolution Transmission Electron Microscopy (HTREM. 001 zone axis Selected area electron diffraction patterns indicate that L10 ordered structures are formed in the two aged alloys. HRTEM experiments reveal the partial dislocations on the interfaces of L10 ordered structures. From comparing experimental results with that in the literature, it is concluded that the L10 ordered structures in aged Al-3Cu alloy consist of Al and Cu atoms, and they are comprised by Al, Cu and Mg atoms together in the aged Al-3Cu-1.78Mg alloy. On the basis of precipitate growing thermodynamics, it is thought the L10 ordered structures act as nuclei for GP zones in Al-Cu-(Mg alloys during aging.En este trabajo se estudian las estructuras de precipitación en Al-3Cu y Al-3Cu-1,78Mg (% en peso en los estados iniciales de envejecimiento a temperatura elevada. Las aleaciones Al-3Cu y Al-3Cu-1.78 Mg fueron sometidas a un tratamiento térmico de solución de 2 h a 540 °C y 500 °C, respectivamente, y posteriormente envejecidas 2 min a 190 °C. Las estructuras de precipitación en Al-3Cu-(1.78Mg envejecido fueron caracterizadas por microscopía electrónica de transmisión (TEM y por microscopía electrónica de transmisión de alta resolución (HTREM. Los diagramas de difracción de electrones de área seleccionada indican que se forman estructuras ordenadas L10 en las dos aleaciones envejecidas. Experimentos de HRTEM revelan la presencia de dislocaciones parciales en las intercaras de las estructuras L10 ordenadas. Comparando estos resultados experimentales con la