A multi-component Zr alloy with comparable strength and Higher plasticity than Zr-based bulk metallic glasses

International Nuclear Information System (INIS)

Liang, S.X.; Yin, L.X.; Ma, M.Z.; Jing, R.; Yu, P.F.; Zhang, Y.F.; Wang, B.A.; Liu, R.P.

2013-01-01

Zirconium (Zr)-based bulk metallic glass possesses the highest potential as a structural material among metallic glasses. Although Zr-based bulk metallic glass exhibits extremely high strength, its potential application has been restricted by a number of issues, such as fragility, small size, difficult fabrication into different shapes and poisonous beryllium content, among others. In this paper, a Zr-based crystal alloy with comparable strength and higher plasticity than Zr-based bulk metallic glass is presented. The proposed Zr-based alloy has a tensile strength greater than 1600 MPa. That value is comparable to the 1500 MPa to 2000 MPa strength of Zr-based bulk metallic glasses (BMGs). The ductility in terms of elongation reached 6.2%; at the same time, the 1400 MPa tensile strength was retained. This phenomenon is not possible for Zr-based BMGs. XRD results show that the proposed ultrahigh-strength Zr-based crystal alloy has two-phase structures: an hcp-structured α phase and a bcc-structured β phase. The forged specimen exhibits a typical basket-weave microstructure, which is characterised by the interlaced plate α phase separated from the β phase matrix. Fine, short bar-shaped α phases precipitated along the original β grain boundary together with ultrafine dot-shaped α phases that presented inside the original β grain when the ageing temperature was between 500 °C and 525 °C. As the ageing temperature increased, the dot-shaped α phase grew into plate shapes, decreasing the material's strength and increasing its plasticity. The ultrafine dot-shaped and short bar-shaped α phases in the original β phase matrix are the main strengthening mechanisms of the ultrahigh-strength Zr-based crystal alloy.

Oxidation behaviour of Zr-based bulk metallic glasses

International Nuclear Information System (INIS)

Wang, Bin

2011-01-01

The Zr-based bulk metallic glasses, developed since the late 1980's, have very interesting mechanical properties, which can be considered for many applications including working under oxidizing atmosphere conditions at high temperatures. It is therefore interesting to study their oxidation resistance and to characterize the oxide scale formed on alloys surface. The fundamental objective of this thesis is to enhance the understanding of the role of various thermodynamic and chemistry parameters on the oxidation behaviour of the Zr-based bulk metallic glasses at high temperature under dry air, to determine the residual stresses in the oxide layer, in comparison with their crystalline alloys with the same chemical composition after an annealing treatment. The oxidation kinetics of these glasses and the crystalline structure of oxide scale ZrO 2 depend on the temperature and the oxidation duration: for short periods of oxidation or at a temperature below Tg, the kinetics follows a parabolic law, whereas, if the sample is oxidized at T ≥ Tg, the kinetics can be divided into two parts. The crystalline counterparts are oxidized by a parabolic rule whatever the temperature; for long oxidation duration at a temperature close to Tg, the kinetics becomes more complex because of the crystallisation of the glasses during the oxidation tests. Also the crystalline structure of the oxide layers depends on the oxidation temperature: the oxide layer consists only in tetragonal Zirconia at T ≤ Tg, while monoclinic Zirconia was formed at higher temperature. The mechanism of the formation of the oxide scale is due to both the interior diffusion of Oxygen ions and the external diffusion of Zirconium ions. However the diffusion of Zirconium ions slows gradually during the crystallisation process of the glass matrix. When the crystallisation is completed, the formation of Zirconia is controlled by only the internal diffusion of oxygen ions. The corresponding residual stresses

Viscous surface flow induced on Ti-based bulk metallic glass by heavy ion irradiation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Kun [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); Hu, Zheng [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); Science and Technology on Vehicle Transmission Laboratory, China North Vehicle Research Institute, Beijing 100072 (China); Li, Fengjiang [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); Wei, Bingchen, E-mail: weibc@imech.ac.cn [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China)

2016-12-30

Highlights: • Obvious smoothing and roughening phases on the Ti-based MG surface resulted, which correspond respectively to the normal and off-normal incidence angles. • Atomic force microscopy confirms two types of periodic ripples distributed evenly over the rough surface. • The irradiation-induced viscosity of MG is about 4×10{sup 12} Pa·s, which accords with the theoretical prediction for metallic glasses close to glass transition temperature. • Surface-confined viscous flow plays a dominant quantitative role, which is due to radiation-induced softening of the low-viscosity surface layer. - Abstract: Ti-based bulk metallic glass was irradiated by a 20 MeV Cl{sup 4+} ion beam under liquid-nitrogen cooling, which produced remarkable surface smoothing and roughening that respectively correspond to normal and off-normal incidence angles of irradiation. Atomic force microscopy confirms two types of periodic ripples distributed evenly over the rough glass surface. In terms of mechanism, irradiation-induced viscosity agrees with the theoretical prediction for metallic glasses near glass transition temperature. Here, a model is introduced, based on relaxation of confined viscous flow with a thin liquid-like layer, that explains both surface smoothing and ripple formation. This study demonstrates that bulk metallic glass has high morphological instability and low viscosity under ion irradiation, which assets can pave new paths for metallic glass applications.

Superductile bulk metallic glass

International Nuclear Information System (INIS)

Yao, K.F.; Ruan, F.; Yang, Y.Q.; Chen, N.

2006-01-01

Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<2%) at room temperature. We report a newly developed Pd-Si binary bulk metallic glass, which exhibits a uniform plastic deformation and a large plastic engineering strain of 82% and a plastic true strain of 170%, together with initial strain hardening, slight strain softening and final strain hardening characteristics. The uniform shear deformation and the ultrahigh plasticity are mainly attributed to strain hardening, which results from the nanoscale inhomogeneity due to liquid phase separation. The formed nanoscale inhomogeneity will hinder, deflect, and bifurcate the propagation of shear bands

Bulk forming of industrial micro components in conventional metals and bulk metallic glasses

DEFF Research Database (Denmark)

Arentoft, Mogens; Paldan, Nikolas Aulin; Eriksen, Rasmus Solmer

2007-01-01

For production of micro components in large numbers, forging is an interesting and challenging process. The conventional metals like silver, steel and aluminum often require multi-step processes, but high productivity and increased strength justify the investment. As an alternative, bulk metallic...

New insight on glass-forming ability and designing Cu-based bulk metallic glasses: The solidification range perspective

International Nuclear Information System (INIS)

Wu, Jili; Pan, Ye; Li, Xingzhou; Wang, Xianfei

2014-01-01

Highlights: • The equation, T rg = T g /T l , was rotationally modified to T rg = κ(T m /T l ) + C/T l . • The newly generalized equation suggests a way for describing glass-forming ability. • Several new Cu-based bulk metallic glasses were discovered by solidification range. - Abstract: In this paper, a new equation was rationally generalized from the reduced glass transition temperature. This equation indicates that solidification range can be used for describing glass-forming ability, which can be calculated with the aid of computational thermodynamic approach. Based on this scenario, several new Cu-based bulk metallic glasses in the ternary Cu–Zr–Ti alloy system were discovered. The as-cast samples were characterized by X-ray diffraction and transmission electronic microscopy. The results indicate that as-cast samples have monolithic amorphous nature. Thermal analysis validates that the smaller solidification range is closely related to the higher glass-forming ability, which is contributed to the effect of solidification time on the formation of bulk metallic glasses. This work also suggests that solidus can influence glass formation

Modeling size effects on fatigue life of a zirconium-based bulk metallic glass under bending

International Nuclear Information System (INIS)

Yuan Tao; Wang Gongyao; Feng Qingming; Liaw, Peter K.; Yokoyama, Yoshihiko; Inoue, Akihisa

2013-01-01

A size effect on the fatigue-life cycles of a Zr 50 Cu 30 Al 10 Ni 10 (at.%) bulk metallic glass has been observed in the four-point-bending fatigue experiment. Under the same bending-stress condition, large-sized samples tend to exhibit longer fatigue lives than small-sized samples. This size effect on the fatigue life cannot be satisfactorily explained by the flaw-based Weibull theories. Based on the experimental results, this study explores possible approaches to modeling the size effects on the bending-fatigue life of bulk metallic glasses, and proposes two fatigue-life models based on the Weibull distribution. The first model assumes, empirically, log-linear effects of the sample thickness on the Weibull parameters. The second model incorporates the mechanistic knowledge of the fatigue behavior of metallic glasses, and assumes that the shear-band density, instead of the flaw density, has significant influence on the bending fatigue-life cycles. Promising predictive results provide evidence of the potential validity of the models and their assumptions.

Bulk and microscale compressive behavior of a Zr-based metallic glass

International Nuclear Information System (INIS)

Lai, Y.H.; Lee, C.J.; Cheng, Y.T.; Chou, H.S.; Chen, H.M.; Du, X.H.; Chang, C.I.; Huang, J.C.; Jian, S.R.; Jang, J.S.C.; Nieh, T.G.

2008-01-01

Micropillars with diameters of 3.8, 1 and 0.7 μm were fabricated from a two-phase Zr-based metallic glass using focus ion beam (FIB), and then tested in compression at strain rates from 1 x 10 -4 to 1 x 10 -2 s -1 . The apparent yield strength of the micropillars ranges from 1992 to 2972 MPa, or 25-86% increase over that of the bulk specimens. This strength increase can be rationalized by the Weibull statistics for brittle materials

Hydrogen-induced high damping of bulk metallic glasses

International Nuclear Information System (INIS)

Hasegawa, M.

2009-01-01

There are two important topics concerned with the recent researches on the damping materials of hydrogenated metallic glasses (HMGs). One is the mechanism of the high hydrogen-induced internal friction of HMGs. The other is the materials processing of 'bulk' HMGs for engineering. This article describes the summary of our recent studies on these topics. The first one is closely related to the local structure of the metallic glasses. Therefore, our recent results on the intermediate-range local structure of the simple two Zr-based metallic glasses are described, which has been clarified by the Voronoi analysis using the experimental data of the neutron diffraction measurements. The hydrogen-induced internal friction of HMGs is also discussed on the basis of these recent results of the local structure of the metallic glasses. In terms of the second topic, the first successful preparation of heavily hydrogenated Zr-based bulk HMG rods without hydrogen-induced surface embrittlement is described. They are prepared by a powder-compact-melting and liquid-casting process using Zr-Al-Ni-Cu metallic glass and ZrH 2 powders as the starting materials. It has been found that they have high damping properties.

Formation and Applications of Bulk Glassy Alloys in Late Transition Metal Base System

International Nuclear Information System (INIS)

Inoue, Akihisa; Shen Baolong

2006-01-01

This paper reviews our recent results of the formation, fundamental properties, workability and applications of late transition metal (LTM) base bulk glassy alloys (BGAs) developed since 1995. The BGAs were obtained in Fe-(Al,Ga)-(P,C,B,Si), Fe-(Cr,Mo)-(C,B), Fe-(Zr,Hf,Nb,Ta)-B, Fe-Ln-B(Ln=lanthanide metal), Fe-B-Si-Nb and Fe-Nd-Al for Fe-based alloys, Co-(Ta,Mo)-B and Co-B-Si-Nb for Co-based alloys, Ni-Nb-(Ti,Zr)-(Co,Ni) for Ni-based alloys, and Cu-Ti-(Zr,Hf), Cu-Al-(Zr,Hf), Cu-Ti-(Zr,Hf)-(Ni,Co) and Cu-Al-(Zr,Hf)-(Ag,Pd) for Cu-based alloys. These BGAs exhibit useful properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based glassy alloys have good soft magnetic properties which cannot be obtained for amorphous and crystalline type magnetic alloys. The Fe- and Ni-based BGAs have already been used in some application fields. These LTM base BGAs are promising as new metallic engineering materials

Fatigue and corrosion of a Pd-based bulk metallic glass in various environments

Energy Technology Data Exchange (ETDEWEB)

Watanabe, L.Y. [East Los Angeles College, Monterey Park, CA 91754 (United States); Roberts, S.N. [Keck Laboratory of Materials Science, California Institute of Technology, Pasadena, CA 91125 (United States); Baca, N. [Department of Chemistry and Biochemistry, California State University Northridge, Northridge, CA 91330 (United States); Wiest, A. [Naval Surface Warfare Center, Norco, CA (United States); Garrett, S.J. [Department of Chemistry and Biochemistry, California State University Northridge, Northridge, CA 91330 (United States); Conner, R.D., E-mail: rdconner@csun.edu [Department of Manufacturing Systems Engineering and Management, California State University Northridge, 18111 Nordhoff St., Mail Code 8295, Northridge, CA 91330 (United States)

2013-10-15

Bulk metallic glasses (BMGs) possess attractive properties for biomedical applications, including high strength, hardness and corrosion resistance, and low elastic modulus. In this study, we conduct rotating beam fatigue tests on Pd{sub 43}Ni{sub 10}Cu{sub 27}P{sub 20} bulk metallic glass in air and Eagle's medium (EM) and measure the corrosive resistance of the alloy by submersion in acidic and basic electrolytes. Fatigue results are compared to those of commonly used biometals in EM. Rotating beam fatigue tests conducted in air and in Eagle's medium show no deterioration in fatigue properties in this potentially corrosive environment out to 10{sup 7} cycles. A specimen size effect is revealed when comparing fatigue results to those of a similar alloy of larger minimum dimensions. Corrosion tests show that the alloy is not affected by highly basic (NaOH) or saline (NaCl) solutions, nor in EM, and is affected by chlorinated acidic solutions (HCl) to a lesser extent than other commonly used biometals. Corrosion in HCl initiates with selective leaching of late transition metals, followed by dissolution of Pd. - Highlights: • Fatigue limit of 600 MPa with no deterioration when exposed to Eagle's medium. • Fatigue shows sample size effect. • Pd-based BMG is unaffected by saline or strong basic solutions. • Pd-based BMG is substantially more resistant to chlorinated acids than CoCrMo, 316 L Stainless, or Ti6Al4V alloys. • Corrosion shows selective leaching of late transition metals, followed by Pd and P.

Glass Formation, Chemical Properties and Surface Analysis of Cu-Based Bulk Metallic Glasses

Directory of Open Access Journals (Sweden)

Akihisa Inoue

2011-04-01

Full Text Available This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs. In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu–Hf–Ti–(Mo, Nb, Ta, Ni and Cu–Zr–Ag–Al–(Nb bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance.

Hot Embossing of Zr-Based Bulk Metallic Glass Micropart Using Stacked Silicon Dies

Directory of Open Access Journals (Sweden)

Zhijing Zhu

2015-01-01

Full Text Available We demonstrated hot embossing of Zr65Cu17.5Ni10Al7.5 bulk metallic glass micropart using stacked silicon dies. Finite element simulation was carried out, suggesting that it could reduce the stress below 400 MPa in the silicon dies and enhance the durability of the brittle silicon dies when using varying load mode (100 N for 60 s and then 400 N for 60 s compared with using constant load mode (200 N for 120 s. A micropart with good appearance was fabricated under the varying load, and no silicon die failure was observed, in agreement with the simulation. The amorphous state of the micropart was confirmed by differential scanning calorimeter and X-ray diffraction, and the nanohardness and Young’s modulus were validated close to those of the as-cast BMG rods by nanoindentation tests. The results proved that it was feasible to adopt the varying load mode to fabricate three-dimensional Zr-based bulk metallic glass microparts by hot embossing process.

Roles of Co element in Fe-based bulk metallic glasses utilizing industrial FeB alloy as raw material

Directory of Open Access Journals (Sweden)

Shouyuan Wang

2017-08-01

Full Text Available A series of Fe-based bulk metallic glasses were fabricated by a conventional copper mold casting method using a kind of Fe-B industrial raw alloy. It is found that Fe-B-Y-Nb bulk metallic glass with 3 at% of Co addition possesses the best glass forming ability, thermal stability, hardness, magnetic property and anti-corrosion property. The hardness test result indicates a synchronically trend with glass-forming ability parameters. The excellent glass-forming ability and a combination of good mechanical and functional properties suggest that the alloys in this work might be good candidates for commercial use.

Sheet-bulk metal forming – forming of functional components from sheet metals

Directory of Open Access Journals (Sweden)

Merklein Marion

2015-01-01

Full Text Available The paper gives an overview on the application of sheet-bulk metal forming operations in both scientific and industrial environment. Beginning with the need for an innovative forming technology, the definition of this new process class is introduced. The rising challenges of the application of bulk metal forming operations on sheet metals are presented and the demand on a holistic investigation of this topic is motivated. With the help of examples from established production processes, the latest state of technology and the lack on fundamental knowledge is shown. Furthermore, perspectives regarding new research topics within sheet-bulk metal forming are presented. These focus on processing strategies to improve the quality of functional components by the application of process-adapted semi-finished products as well as the local adaption of the tribological system.

Ti-based bulk metallic glass with high cold workability at room temperature

International Nuclear Information System (INIS)

Park, J.M.; Park, J.S.; Kim, J.H.; Lee, M.H.; Kim, D.H.; Kim, W.T.

2005-01-01

The cold workability of Ti-based bulk metallic glasses (BMGs) have been investigated. Ti 45 Zr 16 Be 20 Cu 10 Ni 9 BMG with a large compressive plastic strain of 4.7% shows a high cold workability, i.e. total reduction ratio of 50% by cold rolling at room temperature. The multiple shear bands formed during rolling are effective in enhancing the plasticity. The cold rolled Ti 45 Zr 16 Be 20 Cu 10 Ni 9 BMG (reduction ratio: 30%) exhibits a large plastic strain of ∝14%. (orig.)

Memory phenomenon in a lanthanum based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Zhou, Ye [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Huang, Wei Min, E-mail: mwmhuang@ntu.edu.sg [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Zhao, Yong [School of Chemistry and Chemical Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013 (China); Ding, Zhen [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Li, Yan [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Tor, Shu Beng; Liu, Erjia [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

2016-07-05

In this paper, we experimentally investigate two memory phenomena in a lanthanum based bulk metallic glass (BMG). While the temperature memory effect (TME) is not found by differential scanning calorimeter (DSC) test, shape recovery is observed in samples indented at both low and high temperatures. In terms of shape memory related characteristics, this BMG shares some features of shape memory alloys (SMAs) due to its metal nature, and some other features of shape memory polymers (SMPs) owing to its glassy–rubbery transition. The formation of protrusion in the polished sample after heating to super-cooled liquid region (SCLR) indicates that surface tension is not a necessarily positive contributor for shape recovery. Release of internal elastic stress is concluded as the major player. Although the amorphous nature of BMGs enables for storing appreciable amount of internal elastic stress upon deformation, without the presence of cross-linker as in typical SMPs, the shape recovery in BMGs is rather limited. - Highlights: • Experimental investigation of shape recovery in BMG. • Surface tension is not the major reason for shape recovery in BMG. • Release of internal stress is the major contributor for shape recovery. • Comparison of shape memory features of BMG with other shape memory materials.

Memory phenomenon in a lanthanum based bulk metallic glass

International Nuclear Information System (INIS)

Zhou, Ye; Huang, Wei Min; Zhao, Yong; Ding, Zhen; Li, Yan; Tor, Shu Beng; Liu, Erjia

2016-01-01

In this paper, we experimentally investigate two memory phenomena in a lanthanum based bulk metallic glass (BMG). While the temperature memory effect (TME) is not found by differential scanning calorimeter (DSC) test, shape recovery is observed in samples indented at both low and high temperatures. In terms of shape memory related characteristics, this BMG shares some features of shape memory alloys (SMAs) due to its metal nature, and some other features of shape memory polymers (SMPs) owing to its glassy–rubbery transition. The formation of protrusion in the polished sample after heating to super-cooled liquid region (SCLR) indicates that surface tension is not a necessarily positive contributor for shape recovery. Release of internal elastic stress is concluded as the major player. Although the amorphous nature of BMGs enables for storing appreciable amount of internal elastic stress upon deformation, without the presence of cross-linker as in typical SMPs, the shape recovery in BMGs is rather limited. - Highlights: • Experimental investigation of shape recovery in BMG. • Surface tension is not the major reason for shape recovery in BMG. • Release of internal stress is the major contributor for shape recovery. • Comparison of shape memory features of BMG with other shape memory materials.

Micromechanical modeling of tungsten-based bulk metallic glass matrix composites

Energy Technology Data Exchange (ETDEWEB)

Li Hao [Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States); Li Ke [Department of Mechanical Engineering, Texas A and M University, TAMU 3123, College Station, TX 77843 (United States)]. E-mail: keli@tamu.edu; Subhash, Ghatu [Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States); Kecskes, Laszlo J. [Weapons and Materials Research Directorate, US Army Research Laboratory, Aberdeen Proving Ground, MD 21005 (United States); Dowding, Robert J. [Weapons and Materials Research Directorate, US Army Research Laboratory, Aberdeen Proving Ground, MD 21005 (United States)

2006-08-15

Micromechanics models are developed for tungsten (W)-based bulk metallic glass (BMG) matrix composites employing the Voronoi tessellation technique and the finite element (FE) method. The simulation results indicate that the computed elastic moduli are close to those measured in the experiments. The predicted stress-strain curves agree well with their experimentally obtained counterparts in the early stage of the plastic deformation. An increase in the W volume fraction leads to a decrease in the yield stress and an increase in the Young's modulus of the composite. In addition, contours of equivalent plastic strain for increasing applied strains provide an explanation why shear bands were observed in the glassy phase, along the W/BMG interface, and in the W phase of failed W/BMG composite specimens.

A route to transparent bulk metals

KAUST Repository

Schwingenschlögl, Udo

2012-07-23

Hypothetical compounds based on a sapphire host are investigated with respect to their structural as well as electronic features. The results are obtained by electronic structure calculations within density functional theory and the generalized gradient approximation. A quarter of the Al atoms in Al 2O 3 is replaced by a 4d transition metal M ion, with d 0 to d 9 electronic configuration. We perform structure optimizations for all the compounds and analyze the electronic states. Due to the sizeable band gap of the Al 2O 3 host, we can identify promising candidates for transparent bulk metals. We explain the mechanisms leading to this combination of materials properties. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanopatterned bulk metallic glass-based biomaterials modulate macrophage polarization.

Science.gov (United States)

Shayan, Mahdis; Padmanabhan, Jagannath; Morris, Aaron H; Cheung, Bettina; Smith, Ryan; Schroers, Jan; Kyriakides, Themis R

2018-06-01

Polarization of macrophages by chemical, topographical and mechanical cues presents a robust strategy for designing immunomodulatory biomaterials. Here, we studied the ability of nanopatterned bulk metallic glasses (BMGs), a new class of metallic biomaterials, to modulate murine macrophage polarization. Cytokine/chemokine analysis of IL-4 or IFNγ/LPS-stimulated macrophages showed that the secretion of TNF-α, IL-1α, IL-12, CCL-2 and CXCL1 was significantly reduced after 24-hour culture on BMGs with 55 nm nanorod arrays (BMG-55). Additionally, under these conditions, macrophages increased phagocytic potential and exhibited decreased cell area with multiple actin protrusions. These in vitro findings suggest that nanopatterning can modulate biochemical cues such as IFNγ/LPS. In vivo evaluation of the subcutaneous host response at 2 weeks demonstrated that the ratio of Arg-1 to iNOS increased in macrophages adjacent to BMG-55 implants, suggesting modulation of polarization. In addition, macrophage fusion and fibrous capsule thickness decreased and the number and size of blood vessels increased, which is consistent with changes in macrophage responses. Our study demonstrates that nanopatterning of BMG implants is a promising technique to selectively polarize macrophages to modulate the immune response, and also presents an effective tool to study mechanisms of macrophage polarization and function. Implanted biomaterials elicit a complex series of tissue and cellular responses, termed the foreign body response (FBR), that can be influenced by the polarization state of macrophages. Surface topography can influence polarization, which is broadly characterized as either inflammatory or repair-like. The latter has been linked to improved outcomes of the FBR. However, the impact of topography on macrophage polarization is not fully understood, in part, due to a lack of high moduli biomaterials that can be reproducibly processed at the nanoscale. Here, we studied

Development of friction welding process of Zr-based bulk metallic glasses

International Nuclear Information System (INIS)

Shin, Hyung Seop; Jeong, Young Jin; Kim, Ki Hyun

2004-01-01

Bulk Metallic Glasses(BMG) with good mechanical properties have problems that engineering application fields have been limited because of limitation of the alloy size. In order to solving this problem, the friction welding of BMG has been tried using the superplastic-like deformation behavior under the supercooled liquid region. The apparatus for friction welding test was designed and constructed using pneumatic cylinder and gripper based on a conventional lathe. Friction welding have been tried to combination of same BMG alloy and crystalline alloys. The results of welding test were evaluated by X-ray diffraction, measurement of hardness and mechanical properties test. In order to obtain the optimized welding test conditions the temperature of friction interface was measured using Infrared thermal imager

Fabricating Zr-Based Bulk Metallic Glass Microcomponent by Suction Casting Using Silicon Micromold

Directory of Open Access Journals (Sweden)

Zhijing Zhu

2014-08-01

Full Text Available A suction casting process for fabricating Zr55Cu30Al10Ni5 bulk metallic glass microcomponent using silicon micromold has been studied. A complicated BMG microgear with 50 μm in module has been cast successfully. Observed by scanning electron microscopy and laser scanning confocal microscopy, we find that the cast microgear duplicates the silicon micromold including the microstructure on the surface. The amorphous state of the microgear is confirmed by transmission election microscopy. The nanoindentation hardness and elasticity modulus of the microgear reach 6.5 GPa and 94.5 GPa. The simulation and experimental results prove that the suction casting process with the silicon micromold is a promising one-step method to fabricate bulk metallic glass microcomponents with high performance for applications in microelectromechanical system.

High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

International Nuclear Information System (INIS)

Hojati-Talemi, Pejman; Gibson, Mark A.; East, Daniel; Simon, George P.

2011-01-01

We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

Energy Technology Data Exchange (ETDEWEB)

Hojati-Talemi, Pejman [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia); Mawson Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Gibson, Mark A. [Process Science and Engineering, Commonwealth Scientific and Industrial Research Organisation, Clayton, Vic 3168 (Australia); East, Daniel; Simon, George P. [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia)

2011-11-07

We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

New Ti-based Ti–Cu–Zr–Fe–Sn–Si–Ag bulk metallic glass for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Pang, Shujie; Liu, Ying; Li, Haifei; Sun, Lulu [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li, Yan [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Zhang, Tao, E-mail: zhangtao@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

2015-03-15

Highlights: • Novel Ti{sub 47}Cu{sub 38}Zr{sub 7.5}Fe{sub 2.5}Sn{sub 2}Si{sub 1}Ag{sub 2} (at.%) bulk metallic glass (BMG) with a critical diameter of 7 mm was discovered. • The present BMG is the largest Ni- and Be-free Ti-based BMG containing low content of noble metal reported to date. • The glassy alloy possesses high specific strength, low Young’s modulus, and good corrosion resistance and bio-compatibility. • Combination of high glass-forming ability and good mechano- and bio-compatibility for the Ti-based BMG demonstrates the potential for use in biomedical applications. - Abstract: A novel Ni-free Ti{sub 47}Cu{sub 38}Zr{sub 7.5}Fe{sub 2.5}Sn{sub 2}Si{sub 1}Ag{sub 2} (at.%) bulk metallic glass (BMG) with superior glass-forming ability, good mechanical properties and excellent biocompatibility was discovered. The Ti-based BMG with a diameter of 7 mm can be prepared by copper mold casting and the supercooled liquid region was 52 K. Compressive strength, specific strength, Young’s modulus and microhardness of the Ti-based BMG were about 2.08 GPa, 3.2 × 10{sup 5} N m/kg, 100 GPa and 588 Hv, respectively. Electrochemical measurements indicated that the Ti-based glassy alloy possesses higher corrosion resistance than Ti–6Al–4V alloy in a simulated body fluid environment. Attachment, spreading out and proliferation of MC3T3-E1 cells on the Ti-based BMG surface demonstrated the excellent biocompatibility. Mechanisms of the formation and properties for the Ti-based glassy alloy are also discussed. The combination of high glass-forming ability, excellent mechanical properties, high corrosion resistance and good biocompatibility demonstrates the potential of the Ni-free Ti-based BMG for use in biomedical applications.

New Ti-based Ti–Cu–Zr–Fe–Sn–Si–Ag bulk metallic glass for biomedical applications

International Nuclear Information System (INIS)

Pang, Shujie; Liu, Ying; Li, Haifei; Sun, Lulu; Li, Yan; Zhang, Tao

2015-01-01

Highlights: • Novel Ti 47 Cu 38 Zr 7.5 Fe 2.5 Sn 2 Si 1 Ag 2 (at.%) bulk metallic glass (BMG) with a critical diameter of 7 mm was discovered. • The present BMG is the largest Ni- and Be-free Ti-based BMG containing low content of noble metal reported to date. • The glassy alloy possesses high specific strength, low Young’s modulus, and good corrosion resistance and bio-compatibility. • Combination of high glass-forming ability and good mechano- and bio-compatibility for the Ti-based BMG demonstrates the potential for use in biomedical applications. - Abstract: A novel Ni-free Ti 47 Cu 38 Zr 7.5 Fe 2.5 Sn 2 Si 1 Ag 2 (at.%) bulk metallic glass (BMG) with superior glass-forming ability, good mechanical properties and excellent biocompatibility was discovered. The Ti-based BMG with a diameter of 7 mm can be prepared by copper mold casting and the supercooled liquid region was 52 K. Compressive strength, specific strength, Young’s modulus and microhardness of the Ti-based BMG were about 2.08 GPa, 3.2 × 10 5 N m/kg, 100 GPa and 588 Hv, respectively. Electrochemical measurements indicated that the Ti-based glassy alloy possesses higher corrosion resistance than Ti–6Al–4V alloy in a simulated body fluid environment. Attachment, spreading out and proliferation of MC3T3-E1 cells on the Ti-based BMG surface demonstrated the excellent biocompatibility. Mechanisms of the formation and properties for the Ti-based glassy alloy are also discussed. The combination of high glass-forming ability, excellent mechanical properties, high corrosion resistance and good biocompatibility demonstrates the potential of the Ni-free Ti-based BMG for use in biomedical applications

Cast bulk metallic glass alloys: prospects as wear materials

Energy Technology Data Exchange (ETDEWEB)

Hawk, Jeffrey A.; Dogan, Omer N.; Shiflet, Gary J. (Dept. of Materials Science and Engineering, University of Virginia, Charlottesville, VA)

2005-01-01

Bulk metallic glasses are single phase materials with unusual physical and mechanical properties. One intriguing area of possible use is as a wear material. Usually, pure metals and single phase dilute alloys do not perform well in tribological conditions. When the metal or alloy is lightweight, it is usually soft leading to galling in sliding situations. For the harder metals and alloys, their density is usually high, so there is an energy penalty when using these materials in wear situations. However, bulk metallic glasses at the same density are usually harder than corresponding metals and dilute single phase alloys, and so could offer better wear resistance. This work will discuss preliminary wear results for metallic glasses with densities in the range of 4.5 to 7.9 g/cc. The wear behavior of these materials will be compared to similar metals and alloys.

Free volume model: High-temperature deformation of a Zr-based bulk metallic glass

International Nuclear Information System (INIS)

Bletry, M.; Guyot, P.; Blandin, J.J.; Soubeyroux, J.L.

2006-01-01

The homogeneous deformation of a zirconium-based bulk metallic glass is investigated in the glass transition region. Compression tests at different temperatures and strain rates have been conducted. The mechanical behavior is analyzed in the framework of the free volume model, taking into account the dependence of the flow defect concentration on deformation. The activation volume is evaluated and allows one to gather the viscosity data (for the different strain rates and temperatures) on a unique master curve. It is also shown that, due to the relation between flow defect concentration and free volume, it is not possible to deduce the equilibrium flow defect concentration directly from mechanical measurements. However, if this parameter is arbitrarily chosen, mechanical measurements give access to the other parameters of the model, these parameters for the alloy under investigation being of the same order of magnitude as those for other metallic glasses

Bulk-surface relationship of an electronic structure for high-throughput screening of metal oxide catalysts

International Nuclear Information System (INIS)

Kweun, Joshua Minwoo; Li, Chenzhe; Zheng, Yongping; Cho, Maenghyo; Kim, Yoon Young; Cho, Kyeongjae

2016-01-01

Graphical abstract: - Highlights: • Bulk-surface relationship was predicted by the ligand field nature of metal oxides. • Antibonding and bonding d-bands occupancy clarified the bulk-surface relationship. • Different surface relaxations were explained by the bulk electronic structures. • Transition from the bulk to the surface state was simulated by oxygen adsorption. - Abstract: Designing metal-oxides consisting of earth-abundant elements has been a crucial issue to replace precious metal catalysts. To achieve efficient screening of metal-oxide catalysts via bulk descriptors rather than surface descriptors, we investigated the relationship between the electronic structure of bulk and that of the surface for lanthanum-based perovskite oxides, LaMO_3 (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu). Through density functional theory calculations, we examined the d-band occupancy of the bulk and surface transition-metal atoms (n_B_u_l_k and n_S_u_r_f) and the adsorption energy of an oxygen atom (E_a_d_s) on (001), (110), and (111) surfaces. For the (001) surface, we observed strong correlation between the n_B_u_l_k and n_S_u_r_f with an R-squared value over 94%, and the result was interpreted in terms of ligand field splitting and antibonding/bonding level splitting. Moreover, the E_a_d_s on the surfaces was highly correlated with the n_B_u_l_k with an R-squared value of more than 94%, and different surface relaxations could be explained by the bulk electronic structure (e.g., LaMnO_3 vs. LaTiO_3). These results suggest that a bulk-derived descriptor such as n_B_u_l_k can be used to screen metal-oxide catalysts.

Corrosion of Metal Inclusions In Bulk Vitrification Waste Packages

Energy Technology Data Exchange (ETDEWEB)

Bacon, Diana H.; Pierce, Eric M.; Wellman, Dawn M.; Strachan, Denis M.; Josephson, Gary B.

2006-07-31

The primary purpose of the work reported here is to analyze the potential effect of the release of technetium (Tc) from metal inclusions in bulk vitrification waste packages once they are placed in the Integrated Disposal Facility (IDF). As part of the strategy for immobilizing waste from the underground tanks at Hanford, selected wastes will be immobilized using bulk vitrification. During analyses of the glass produced in engineering-scale tests, metal inclusions were found in the glass product. This report contains the results from experiments designed to quantify the corrosion rates of metal inclusions found in the glass product from AMEC Test ES-32B and simulations designed to compare the rate of Tc release from the metal inclusions to the release of Tc from glass produced with the bulk vitrification process. In the simulations, the Tc in the metal inclusions was assumed to be released congruently during metal corrosion as soluble TcO4-. The experimental results and modeling calculations show that the metal corrosion rate will, under all conceivable conditions at the IDF, be dominated by the presence of the passivating layer and corrosion products on the metal particles. As a result, the release of Tc from the metal particles at the surfaces of fractures in the glass releases at a rate similar to the Tc present as a soluble salt. The release of the remaining Tc in the metal is controlled by the dissolution of the glass matrix. To summarize, the release of 99Tc from the BV glass within precipitated Fe is directly proportional to the diameter of the Fe particles and to the amount of precipitated Fe. However, the main contribution to the Tc release from the iron particles is over the same time period as the release of the soluble Tc salt. For the base case used in this study (0.48 mass% of 0.5 mm diameter metal particles homogeneously distributed in the BV glass), the release of 99Tc from the metal is approximately the same as the release from 0.3 mass% soluble Tc

Internal shear cracking in bulk metal forming

DEFF Research Database (Denmark)

Christiansen, Peter; Nielsen, Chris Valentin; Bay, Niels Oluf

2017-01-01

This paper presents an uncoupled ductile damage criterion for modelling the opening and propagation of internal shear cracks in bulk metal forming. The criterion is built upon the original work on the motion of a hole subjected to shear with superimposed tensile stress triaxiality and its overall...... performance is evaluated by means of side-pressing formability tests in Aluminium AA2007-T6 subjected to different levels of pre-strain. Results show that the new proposed criterionis able to combine simplicity with efficiency for predicting the onset of fracture and the crack propagation path for the entire...... cracking to internal cracks formed undert hree-dimensional states of stress that are typical of bulk metal forming....

Physical factors controlling the ductility of bulk metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Liu, Y. [Central South University, China; Liu, Chain T [ORNL; Zhang, Z. [University of Tennessee, Knoxville (UTK); Keppens, V. [University of Tennessee, Knoxville (UTK)

2008-01-01

In order to identify key physical factor controlling the deformation and fracture behavior of bulk metallic glasses (BMGs), we compiled and analyzed the elastic moduli and compressive ductility for BMGs. In addition, new modulus data were generated in the critical ranges in order to facilitate the analysis. We have found that the intrinsic ductility of BMGs can be correlated with the bulk-to-shear modulus ratio B/G according to Pugh's [Philos. Mag. 45, 823 (1954) ] rule. In some individual BMG systems, for example, Fe based, the relationship seems to be very clear. The physical meaning of this correlation is discussed in terms of atomic bonding and connectivity.

Improvement of corrosion resistance in NaOH solution and glass forming ability of as-cast Mg-based bulk metallic glasses by microalloying

Directory of Open Access Journals (Sweden)

Peng Hao

2011-02-01

Full Text Available The influences of the addition of Ag on the glass forming ability (GFA and corrosion behavior were investigated in the Mg-Ni-based alloy system by X-ray diffraction (XRD and electrochemical polarization in 0.1 mol/L NaOH solution. Results shows that the GFA of the Mg-Ni-based BMGs can be improved dramatically by the addition of an appropriate amount of Ag; and the addition element Ag can improve the corrosion resistance of Mg-Ni-based bulk metallic glass. The large difference in atomic size and large negative mixing enthalpy in alloy system can contribute to the high GFA. The addition element Ag improves the forming speed and the stability of the passive film, which is helpful to decrease the passivation current density and to improve the corrosion resistance of Mg-Ni-based bulk metallic glass.

Thermoplastic deformation of ferromagnetic CoFe-based bulk metallic glasses

Science.gov (United States)

Wu, Chenguang; Hu, Renchao; Man, Qikui; Chang, Chuntao; Wang, Xinmin

2017-12-01

The superplastic deformation behavior of the ferromagnetic Co31Fe31Nb8B30 bulk metallic glass (BMG) in the supercooled liquid region was investigated. At a given temperature, the BMG exhibits a Newtonian behavior at low strain rates but a non-Newtonian behavior at high strain rates. The high thermal stability of this glassy alloy system offers an enough processing window to thermoplastic forming (TPF), and the strong processing ability was examined by simple micro-replication experiments. It is demonstrated that the TPF formability on length scales ranging down to nanometers can be achieved in the selected experimental condition. Based on the analysis of deformation behavior, the nearly full density sample (i.e. nearly 100%), was produced from water-atomized glassy powders and consolidated by the hot-pressing technique. The sample exhibits good soft-magnetic and mechanical properties, i.e., low coercive force of 0.43 Oe, high initial permeability of 4100 and high Vickers hardness 1398. These results suggest that the hot-pressing process opens up possibilities for the commercial exploitation of BMGs in engineering applications.

Spectral descriptors for bulk metallic glasses based on the thermodynamics of competing crystalline phases

OpenAIRE

Perim, Eric; Lee, Dongwoo; Liu, Yanhui; Toher, Cormac; Gong, Pan; Li, Yanglin; Simmons, W. Neal; Levy, Ohad; Vlassak, Joost J.; Schroers, Jan; Curtarolo, Stefano

2016-01-01

Metallic glasses have attracted considerable interest in recent years due to their unique combination of superb properties and processability. Predicting bulk metallic glass formers from known parameters remains a challenge and the search for new systems is still performed by trial and error. It has been speculated that some sort of "confusion" during crystallization of the crystalline phases competing with glass formation could play a key role. Here, we propose a heuristic descriptor quantif...

Cu-Zr-Ag bulk metallic glasses based on Cu8Zr5 icosahedron

International Nuclear Information System (INIS)

Xia Junhai; Qiang Jianbing; Wang Yingmin; Wang Qing; Dong Chuang

2007-01-01

Based on the cluster line criterion, the Ag addition into the Cu 8 Zr 5 cluster composition is investigated for the search of ternary Cu-Zr-Ag bulk metallic glasses with high glass forming abilities. Two initial binary compositions Cu 0.618 Zr 0.382 and Cu 0.64 Zr 0.36 are selected. The former one corresponds to a deep eutectic point; it is also the composition of the Cu 8 Zr 5 icosahedron, which is derived from the Cu 8 Zr 3 structure. The latter one, which can be regarded as the Cu 8 Zr 5 cluster plus a glue atom Cu, is the best glass-forming composition in the Cu-Zr binary system. Two composition lines (Cu 0.618 Zr 0.382 ) 1-x Ag x and (Cu 0.64 Zr 0.36 ) 1-x Ag x are thus constructed in the Cu-Zr-Ag system by linking these two compositions with the third constitute Ag. A series of Cu-Zr-Ag bulk metallic glasses are found with 2-8 at.% Ag contents in both composition lines. The optimum composition (Cu 0.618 Zr 0.382 ) 0.92 Ag 0.08 within the searched region with the highest T g /T l = 0.633, is located along the cluster line (Cu 0.618 Zr 0.382 ) 1-x Ag x , where the deep eutectic Cu 0.618 Zr 0.382 exactly corresponds to the dense packing cluster Cu 8 Zr 5 . The alloying mechanism is discussed in the light of atomic size and electron concentration factors

Linking structure to fragility in bulk metallic glass-forming liquids

International Nuclear Information System (INIS)

Wei, Shuai; Stolpe, Moritz; Gross, Oliver; Gallino, Isabella; Hembree, William; Busch, Ralf; Evenson, Zach; Bednarcik, Jozef; Kruzic, Jamie J.

2015-01-01

Using in-situ synchrotron X-ray scattering, we show that the structural evolution of various bulk metallic glass-forming liquids can be quantitatively connected to their viscosity behavior in the supercooled liquid near T g . The structural signature of fragility is identified as the temperature dependence of local dilatation on distinct key atomic length scales. A more fragile behavior results from a more pronounced thermally induced dilatation of the structure on a length scale of about 3 to 4 atomic diameters, coupled with shallower temperature dependence of structural changes in the nearest neighbor environment. These findings shed light on the structural origin of viscous slowdown during undercooling of bulk metallic glass-forming liquids and demonstrate the promise of predicting the properties of bulk metallic glasses from the atomic scale structure

Linking structure to fragility in bulk metallic glass-forming liquids

Energy Technology Data Exchange (ETDEWEB)

Wei, Shuai, E-mail: shuai.wei@asu.edu, E-mail: m.stolpe@mx.uni-saarland.de [Department of Materials Science and Engineering, Saarland University, Campus C63, 66123 Saarbrücken (Germany); Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); Stolpe, Moritz, E-mail: shuai.wei@asu.edu, E-mail: m.stolpe@mx.uni-saarland.de; Gross, Oliver; Gallino, Isabella; Hembree, William; Busch, Ralf [Department of Materials Science and Engineering, Saarland University, Campus C63, 66123 Saarbrücken (Germany); Evenson, Zach [Department of Materials Science and Engineering, Saarland University, Campus C63, 66123 Saarbrücken (Germany); Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln (Germany); Bednarcik, Jozef [Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg (Germany); Kruzic, Jamie J. [Material Science, School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, Oregon 97331 (United States)

2015-05-04

Using in-situ synchrotron X-ray scattering, we show that the structural evolution of various bulk metallic glass-forming liquids can be quantitatively connected to their viscosity behavior in the supercooled liquid near T{sub g}. The structural signature of fragility is identified as the temperature dependence of local dilatation on distinct key atomic length scales. A more fragile behavior results from a more pronounced thermally induced dilatation of the structure on a length scale of about 3 to 4 atomic diameters, coupled with shallower temperature dependence of structural changes in the nearest neighbor environment. These findings shed light on the structural origin of viscous slowdown during undercooling of bulk metallic glass-forming liquids and demonstrate the promise of predicting the properties of bulk metallic glasses from the atomic scale structure.

The effect of nanocrystallization and free volume on the room temperature plasticity of Zr-based bulk metallic glasses

International Nuclear Information System (INIS)

Mondal, K.; Ohkubo, T.; Toyama, T.; Nagai, Y.; Hasegawa, M.; Hono, K.

2008-01-01

To understand the mechanism of the room temperature plasticity of bulk metallic glasses (BMGs), microstructure observations, density measurements and positron annihilation studies were carried out for Zr-based BMGs cast at various temperatures and post-annealed under different conditions. We found that higher casting temperatures cause partial crystallization, which enhance the plasticity as long as the volume fraction of the crystalline phase is low. However, a similar nanocrystalline microstructure produced by post-annealing often leads to a large loss of plasticity, while certain conditions enhance the plasticity. Based on density measurements and positron annihilation lifetime spectroscopy, we conclude that the relative contribution of free volume and nanocrystallization is important for acquiring plasticity in metallic glasses

Comparison of mechanical behavior between bulk and ribbon Cu-based metallic glasses

International Nuclear Information System (INIS)

Jiang, W.H.; Liu, F.X.; Wang, Y.D.; Zhang, H.F.; Choo, H.; Liaw, P.K.

2006-01-01

As-cast bulk and as-spun ribbon Cu 60 Zr 30 Ti 10 metallic glasses were characterized using differential-scanning calorimetry and instrumented nanoindentation. Two alloys show a significant difference in the amount of free volume, which is attributed to the difference in a cooling rate, while exhibiting a similar serrated plastic flow. Atomic-force-microscopy observations demonstrate the pile-ups containing shear bands around the indents in both alloys. The as-cast bulk alloy has higher hardness and elastic modulus than the as-spun ribbon alloy. The difference in the strengths of two alloys may be related to the different amount of free volume. The strength seems to be more sensitive to a cooling rate during solidification than the plastic-flow behavior in the Cu 60 Zr 30 Ti 10

Forming of bulk metallic glass microcomponents

DEFF Research Database (Denmark)

Wert, John A.; Thomsen, Christian; Jensen, Rune Debel

2009-01-01

The present article considers forward extrusion, closed-die forging and backward extrusion processes for fabrication of individual microcomponents from two bulk metallic glass (BMG) compositions: Mg60Cu30Y10 and Zr44Cu40Ag8Al8. Two types of tooling were used in the present work: relatively massive...... die sets characteristic of cold forming operations for crystalline metals and lightweight die sets adapted to the special characteristics of BMGs. In addition to demonstrating that microcomponents of several geometries can be readily fabricated from BMGs, rheological properties are combined...

Influence of air and vacuum environment on fatigue behavior of Zr-based bulk metallic glasses

International Nuclear Information System (INIS)

Wang, G.Y.; Liaw, P.K.; Yokoyama, Y.; Peter, W.H.; Yang, B.; Freels, M.; Buchanan, R.A.; Liu, C.T.; Brooks, C.R.

2007-01-01

High-cycle fatigue (HCF) experiments in air and vacuum at room temperature were conducted on zirconium (Zr)-based bulk-metallic glasses (BMGs): Zr 50 Cu 40 Al 10 , Zr 50 Cu 30 Al 10 Ni 10 , and Zr 50 Cu 37 Al 10 Pd 3 in atomic percent. The fatigue-endurance limit of Zr 50 Cu 37 Al 10 Pd 3 was found to be significantly greater than those of Zr 50 Cu 40 Al 10 and Zr 50 Cu 30 Al 10 Ni 10 , which indicates that the inclusions of Pd and the resulting nano structures improve the fatigue resistances of the Zr-based BMGs. The fatigue lives in vacuum and air were generally found to be comparable

Bulk viscosity and ultrasonic attenuation in liquid metals

International Nuclear Information System (INIS)

Awasthi, O.N.; Murthy, B.V.S.

1984-11-01

Ultrasonic attenuation in simple liquid metals has been investigated using the thermodynamic theory of relaxation processes incorporating the concept of a two state model for the liquid near the melting point. Agreement of the results with the experimental values of the ultrasonic attenuation and bulk viscosity indicates that this might be an appropriate approach to explain the excess attenuation of ultrasonic waves in liquid metals. (author)

Fe-based bulk metallic glasses used for magnetic shielding

Energy Technology Data Exchange (ETDEWEB)

Serban, Va; Codrean, C; UTu, D [Politehnica University of Timisoara, Depart for Materials Science and Welding, 1, M. Viteazu Bvd., 300222, Timisoara (Romania); ErcuTa, A, E-mail: serban@mec.upt.r [West University of Timisoara, Faculty of Physics, 4, Vasile Parvan Bdv., Timisoara 300223 (Romania)

2009-01-01

The casting in complex shapes (tubular) and the main magnetic properties of bulk metallic glasses (BMG) alloys from the ferromagnetic Fe-Cr-Ni-Ga-P-Si-C system, with a small addition of Ni (3%) were studied. Samples as rods and sockets having the thickness up to 1 mm were obtained from master alloys by melt injection by low cooling rates into a Cu mold and annealed in order to ensure adequate magnetic requirements. The structure was examined by X-ray diffraction (XRD) and the basic magnetic properties (coercivity, magnetic remanence, initial susceptibility, etc.) were determined by conventional low frequency induction method. The experimental investigations on producing of BMG ferromagnetic alloys with 3% Ni show the possibility to obtain magnetic shields of complex shape with satisfactory magnetic properties. The presence of Ni does not affect the glass forming ability, but reduce the shielding capacity.

Failure by fracture in bulk metal forming

DEFF Research Database (Denmark)

Silva, C.M.A.; Alves, Luis M.; Nielsen, Chris Valentin

2015-01-01

This paper revisits formability in bulk metal forming in the light of fundamental concepts of plasticity,ductile damage and crack opening modes. It proposes a new test to appraise the accuracy, reliability and validity of fracture loci associated with crack opening by tension and out-of-plane shear...

Flow and Fracture of Bulk Metallic Glass Alloys and their Composites

International Nuclear Information System (INIS)

Flores, K M; Suh, D; Howell, R; Asoka-Kumar, P; Dauskardt, R H

2001-01-01

The fracture and plastic deformation mechanisms of a Zr-Ti-Ni-Cu-Be bulk metallic glass and a composite utilizing a crystalline reinforcement phase are reviewed. The relationship between stress state, free volume and shear band formation are discussed. Positron annihilation techniques were used to confirm the predicted increase in free volume after plastic straining. Strain localization and failure were examined for a wide range of stress states. Finally, methods for toughening metallic glasses are considered. Significant increases in toughness are demonstrated for a composite bulk metallic glass containing a ductile second phase which stabilizes shear band formation and distributes plastic deformation

Distribution of oxides in a Zr-Cu-Ni-Al-Nb-Si bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Heinrich, Jochen; Busch, Ralf [Chair of Metallic Materials, Saarland University, PO Box 151150, 66041 Saarbruecken (Germany); Mueller, Frank; Huefner, Stefan [Chair of Experimental Physics, Saarland University, PO Box 151150, 66041 Saarbruecken (Germany)

2010-07-01

The course of oxide presence with distance from the sample surface and bonding partner was studied for the bulk metallic glass with the nominal composition Zr{sub 57.9}Cu{sub 15.4}Ni{sub 12.7}Al{sub 10.2}Nb{sub 2.8}Si{sub 1} (at%) by X-ray photoelectron spectroscopy (XPS). Investigated specimens are taken from vacuum quench-cast rods subjected to oxidation at room temperature and atmosphere. Binding energies were determined in various depths using ion beam ablation of up to 100 nanometers. XPS spectra confirm oxidation primarily of the pure zirconium and aluminum constituents, all other peaks correspond to metallic bonds. While the surface area shows a passivating zirconia layer a few nanometers thick, oxygen is bonded predominantly with aluminum inside the bulk. Since the concentration of oxygen is a crucial factor in the crystallization behavior of bulk metallic glass forming liquids on basis of oxygen affine metals, so far only high purity materials were thought to be suitable. The findings in this study, however, are promising for alloys with industrial grade elements with sufficient glass forming ability. Comparisons of the alloy with differing oxygen content support the conclusion that aluminum acts as an appropriate scavenger for both adsorbed and large amounts of intrinsic oxygen in zirconium based amorphous metals.

Tuning apparent friction coefficient by controlled patterning bulk metallic glasses surfaces

Science.gov (United States)

Li, Ning; Xu, Erjiang; Liu, Ze; Wang, Xinyun; Liu, Lin

2016-12-01

Micro-honeycomb structures with various pitches between adjacent cells were hot-embossed on Zr35Ti30Cu8.25Be26.75 bulk metallic glass surface. The effect of pitch geometry on the frictional behavior of metallic glass surface was systematically investigated. The results revealed that all textured metallic glass surfaces show a reduction in friction coefficient compared to smooth surface. More intriguingly, the friction coefficient first decreased and then increased gradually with increasing pitches. Such unique behavior can be understood fundamentally from the perspective of competing effects between contact area and local stress level with increasing pitches. This finding not only enhance the in-depth understanding of the mechanism of the significant role of surface topography on the frictional behavior of metallic glass surface, but also opens a new route towards other functional applications for bulk metallic glasses.

Analysis of atomic mobility in a Cu38Zr46Ag8Al8 bulk metallic glass

International Nuclear Information System (INIS)

Qiao, J.C.; Pelletier, J.M.

2013-01-01

Highlights: ► Atomic mobility in Cu 38 Zr 46 Ag 8 Al 8 bulk metallic glass have been investigated by DMA. ► Loss factor is directly connected to the energy lost during application of the stress. ► Structural relaxation and crystallization induces a decrease of the atomic mobility. ► The concentration of quasi-point defects links to atomic mobility in metallic glasses. - Abstract: Atomic mobility in as-cast and annealed Cu 38 Zr 46 Ag 8 Al 8 bulk metallic glass samples is analyzed by performing dynamic mechanical analysis. The loss factor is directly connected to the energy lost during application of the stress. Structural relaxation process and crystallization lead to a decrease of the atomic mobility in the bulk metallic glass. A physical model, based on the concept of quasi point defects is introduced, to describe the atomic mobility. Movements in amorphous materials are correlated. The correlation factor χ reflects the atomic mobility in bulk metallic glasses: structural relaxation and crystallization lead to a decrease of χ, implying the reduction of atomic mobility. The evolution of elastic, visco-elastic and viscoplastic components after structural relaxation and partial crystallization state during the mechanical response has been obtained. Compared with as-cast state, structural relaxation induced an increase of elastic component and a decrease of visco-elastic component in the metallic glass.

Free standing bulk metallic glass microcomponents: Tooling considerations

DEFF Research Database (Denmark)

Byrne, Cormac; Eldrup, Morten Mostgaard; Ohnuma, Masato

2010-01-01

Bulk metallic glasses have enormous potential for use in small-scale devices such as MEMS and biomedical components. Thermoplastic forging of free standing components poses challenges unlike those seen when forging crystalline materials. Central to these challenges is the simultaneous advantage/disadvantage...

Bulk-plasmon contribution to the work function of metals

International Nuclear Information System (INIS)

Gutierrez, F A; DIaz-Valdes, J; Jouin, H

2007-01-01

By consideration of the Koopmans theorem expression for the work function of a metal, we find that the total height of the surface barrier potential equals the value of the bulk-plasmon energy of pure metals. As a consequence a simple formula for the work function is obtained which shows better agreement with the experimental data than the most complete existent theories

Ignition and combustion of bulk metals under elevated, normal and reduced gravity conditions

Science.gov (United States)

Abbud-Madrid, Angel; Branch, Melvyn C.; Daily, John W.

1995-01-01

This research effort is aimed at providing further insight into this multi-variable dependent phenomena by looking at the effects of gravity on the ignition and combustion behavior of metals. Since spacecraft are subjected to higher-than-1g gravity loads during launch and reentry and to zero-gravity environments while in orbit, the study of ignition and combustion of bulk metals at different gravitational potentials is of great practical concern. From the scientific standpoint, studies conducted under microgravity conditions provide simplified boundary conditions since buoyancy is removed, and make possible the identification of fundamental ignition mechanisms. The effect of microgravity on the combustion of bulk metals has been investigated by Steinberg, et al. on a drop tower simulator. However, no detailed quantitative work has been done on ignition phenomena of bulk metals at lower or higher-than-normal gravitational fields or on the combustion characteristics of metals at elevated gravity. The primary objective of this investigation is the development of an experimental system capable of providing fundamental physical and chemical information on the ignition of bulk metals under different gravity levels. The metals used in the study, iron (Fe), titanium (Ti), zirconium (Zr), magnesium (Mg), zinc (Zn), and copper (Cu) were selected because of their importance as elements of structural metals and their simple chemical composition (pure metals instead of multi-component alloys to avoid complication in morphology and spectroscopic studies). These samples were also chosen to study the two different combustion modes experienced by metals: heterogeneous or surface oxidation, and homogeneous or gas-phase reaction. The experimental approach provides surface temperature profiles, spectroscopic measurements, surface morphology, x-ray spectrometry of metals specimens and their combustion products, and high-speed cinematography of the heating, ignition and combustion

Mechanically durable underwater superoleophobic surfaces based on hydrophilic bulk metals for oil/water separation

Science.gov (United States)

Yu, Huadong; Lian, Zhongxu; Xu, Jinkai; Wan, Yanling; Wang, Zuobin; Li, Yiquan; Yu, Zhanjiang; Weng, Zhankun

2018-04-01

Despite the success of previous methods for fabricating underwater superoleophobic surfaces, most of the surfaces based on soft materials are prone to collapse and deformation due to their mechanically fragile nature, and they fail to perform their designed functions after the surface materials are damaged in water. In this work, the nanosecond laser-induced oxide coatings on hydrophilic bulk metals are reported which overcomes the limitation and shows the robust underwater superoleophobicity to a mechanical challenge encountered by surfaces deployed in water environment. The results show that the surface materials have the advantage that the underwater superoleophobicity is still preserved after the surfaces are scratched by knife or sandpaper and even completely destroyed because of the hydrophilic property of damaged materials in water. It is important that the results provide a guide for the design of durable underwater superoleophobic surfaces, and the development of superoleophobic materials in many potential applications such as the oil-repellent and the oil/water separation. Additionally, the nanosecond laser technology is simple, cost-effective and suitable for the large-area and mass fabrication of mechanically durable underwater superoleophobic metal materials.

In situ visualization of Ni-Nb bulk metallic glasses phase transition

OpenAIRE

Oreshkin, A. I.; Mantsevich, V. N.; Savinov, S. V.; Oreshkin, S. I.; Panov, V. I.; Yavari, A. R.; Miracle, D. B.; Louzguine-Luzgin, D. V.

2013-01-01

We report the results of the Ni-based bulk metallic glass structural evolution and crystallization behavior in situ investigation. The X-ray diffraction (XRD), transmission electron microscopy (TEM), nano-beam diffraction (NBD), differential scanning calorimetry (DSC), radial distribution function (RDF) and scanning probe microscopy/spectroscopy (STM/STS) techniques were applied to analyze the structure and electronic properties of Ni63.5Nb36.5 glasses before and after crystallization. It was...

Mechanical improvement of metal reinforcement rings for a finite ring-shaped superconducting bulk

Science.gov (United States)

Huang, Chen-Guang; Zhou, You-He

2018-03-01

As a key technique, reinforcement of type-II superconducting bulks with metal rings can efficiently improve their mechanical properties to enhance the maximum trapped field. In this paper, we study the magnetostrictive and fracture behaviors of a finite superconducting ring bulk reinforced by three typical reinforcing structures composed of metal rings during the magnetizing process by means of the minimization of magnetic energy and the finite element method. After a field-dependent critical current density is adopted, the magnetostriction, pinning-induced stress, and crack tip stress intensity factor are calculated considering the demagnetization effects. The results show that the mechanical properties of the ring bulk are strongly dependent on the reinforcing structure and the material and geometrical parameters of the metal rings. Introducing the metal ring can significantly reduce the hoop stress, and the reduction effect by internal reinforcement is much improved relative to external reinforcement. By comparison, bilateral reinforcement seems to be the best candidate structure. Only when the metal rings have particular Young's modulus and radial thickness will they contribute to improve the mechanical properties the most. In addition, if an edge crack is pre-existing in the ring bulk, the presence of metal rings can effectively avoid crack propagation since it reduces the crack tip stress intensity factor by nearly one order of magnitude.

Bulk metal concentrations versus total suspended solids in rivers: Time-invariant & catchment-specific relationships.

Science.gov (United States)

Nasrabadi, Touraj; Ruegner, Hermann; Schwientek, Marc; Bennett, Jeremy; Fazel Valipour, Shahin; Grathwohl, Peter

2018-01-01

Suspended particles in rivers can act as carriers of potentially bioavailable metal species and are thus an emerging area of interest in river system monitoring. The delineation of bulk metals concentrations in river water into dissolved and particulate components is also important for risk assessment. Linear relationships between bulk metal concentrations in water (CW,tot) and total suspended solids (TSS) in water can be used to easily evaluate dissolved (CW, intercept) and particle-bound metal fluxes (CSUS, slope) in streams (CW,tot = CW + CSUS TSS). In this study, we apply this principle to catchments in Iran (Haraz) and Germany (Ammer, Goldersbach, and Steinlach) that show differences in geology, geochemistry, land use and hydrological characteristics. For each catchment, particle-bound and dissolved concentrations for a suite of metals in water were calculated based on linear regressions of total suspended solids and total metal concentrations. Results were replicable across sampling campaigns in different years and seasons (between 2013 and 2016) and could be reproduced in a laboratory sedimentation experiment. CSUS values generally showed little variability in different catchments and agree well with soil background values for some metals (e.g. lead and nickel) while other metals (e.g. copper) indicate anthropogenic influences. CW was elevated in the Haraz (Iran) catchment, indicating higher bioavailability and potential human and ecological health concerns (where higher values of CSUS/CW are considered as a risk indicator).

Trace metals in bulk precipitation and throughfall in a suburban area of Japan

Science.gov (United States)

Hou, H.; Takamatsu, T.; Koshikawa, M. K.; Hosomi, M.

Throughfall and bulk precipitation samples were collected monthly for 1.5 years over bare land and under canopies of Japanese cedar ( Cryptomeria japonica), Japanese red pine ( Pinus densiflora), Japanese cypress ( Chamaecyparis obtusa), and bamboo-leafed oak ( Quercus myrsinaefolia) in a suburban area of Japan. Samples were analyzed for dissolved Al, Mn, Fe, Cu, Zn, Ag, In, Sn, Sb and Bi by ICP-AES and ICP-MS. The metal concentrations were higher in throughfall, especially that of C. japonica, than bulk precipitation. Enrichment ratios (ERs: ratios of metal concentrations in throughfall to those in bulk precipitation) ranged from 2.5 (Zn) to 5.3 (Ag) (3.9 on average), and ERs for slightly soluble metals were generally higher than those for easily soluble metals. Concentrations of Mn, Fe, Cu, and Zn accounted for 99% of the total concentration of heavy metals in rainwater, whereas those of rare metals such as Ag, In, Sn, and Bi totaled rare metals were 0.002 and 0.010 μg l -1 for Ag, 0.001 and 0.005 μg l -1 for In, 0.062 and 0.21 μg l -1 for Sn, and 0.006 and 0.023 μg l -1 for Bi in bulk precipitation and throughfall, respectively. The metal concentrations in rainwater were negatively correlated to the volume of rainwater, indicating that washout is the main mechanism that incorporates metals into rainwater. From the enrichment factors, that is, (X/Al) rain/(X/Al) crust, metals other than Fe were shown to be more enriched in rainwater than in the Earth's crust, including those present as a result of leaching from soil dust (Mn) and from anthropogenic sources (Cu, Zn, Ag, In, Sn, Sb, and Bi).

The structural relaxation effect on the nanomechanical properties of a Ti-based bulk metallic glass

International Nuclear Information System (INIS)

Huang, Yongjiang; Zhou, Binjun; Chiu, YuLung; Fan, Hongbo; Wang, Dongjun; Sun, Jianfei; Shen, Jun

2014-01-01

Highlights: • The effect of structural relaxation on the nano-mechanical behaviors of BMGs is studied. • The indent load at first pop-in event, the hardness and Young’s modulus are enhanced after annealing. • The differences in nanomechanical properties can be attributed to their different atomic structure. - Abstract: Indentation experiments were performed on the as-cast and the annealed Ti-based bulk metallic glass samples to investigate the effect of structural relaxation on the nanomechanical behaviors of the material. The onset of pop-in event, Young’s modulus, and hardness were found to be sensitive to the structural relaxation of the testing material. The difference in nanomechanical properties between the as-cast and annealed BMG samples is interpreted in terms of free volume theory

The structural relaxation effect on the nanomechanical properties of a Ti-based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Huang, Yongjiang, E-mail: yjhuang@hit.edu.cn [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Harbin Institute of Technology, Ministry of Education, Harbin 150001 (China); Zhou, Binjun [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Chiu, YuLung, E-mail: y.chiu@bham.ac.uk [School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Fan, Hongbo [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Dongjun [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Harbin Institute of Technology, Ministry of Education, Harbin 150001 (China); Sun, Jianfei; Shen, Jun [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2014-09-01

Highlights: • The effect of structural relaxation on the nano-mechanical behaviors of BMGs is studied. • The indent load at first pop-in event, the hardness and Young’s modulus are enhanced after annealing. • The differences in nanomechanical properties can be attributed to their different atomic structure. - Abstract: Indentation experiments were performed on the as-cast and the annealed Ti-based bulk metallic glass samples to investigate the effect of structural relaxation on the nanomechanical behaviors of the material. The onset of pop-in event, Young’s modulus, and hardness were found to be sensitive to the structural relaxation of the testing material. The difference in nanomechanical properties between the as-cast and annealed BMG samples is interpreted in terms of free volume theory.

Composition design and mechanical properties of ternary Cu–Zr–Ti bulk metallic glasses

International Nuclear Information System (INIS)

Pan, Ye; Zeng, Yuqiao; Jing, Lijun; Zhang, Lu; Pi, Jinhong

2014-01-01

Highlights: • Newly designed monolithic bulk metallic glasses are of good glass-forming ability. • Cu 50 Zr 44 Ti 6 exhibits excellent plastic deformation up to ∼7.4%. • Copious and intersected shear bans are observed in the fractography of Cu 50 Zr 44 Ti 6 . • Cu 50 Zr 44 Ti 6 has the best plasticity in the ternary Cu–Zr–Ti bulk metallic glasses. - Abstract: The new compositions of ternary Cu–Zr–Ti bulk metallic glasses are predicted by integrating calculation of vacancy formation energy, mixing enthalpy and configuration entropy of the alloys based on thermodynamics of glass formers. The monolithic amorphous rods of 3 mm diameter have been successfully fabricated, and characterized by X-ray diffractometry, differential scanning calorimetry, scanning electronic microscopy, transmission electronic microscopy and compression tests. The results show that the designed alloys possess good glass forming ability and excellent mechanical properties. The mechanical properties of the samples can be effectively improved by regulating their composition. The monolithic amorphous rod of Cu 50 Zr 44 Ti 6 exhibits a high fracture strength of 1855 MPa and excellent plastic deformation up to ∼7.4%. The formation and propagation of shear bands in samples are also investigated. The enhancement of plastic deformation is mainly contributed to multiplication and intersection of shear bands

Elastic properties of superconducting bulk metallic glasses

International Nuclear Information System (INIS)

Hempel, Marius

2015-01-01

Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

Formation of centimeter Fe-based bulk metallic glasses in low vacuum environment

Energy Technology Data Exchange (ETDEWEB)

Pan Jie; Chen Qi; Li Ning [State Key Lab of Materials Processing and Mould Technology, Department of Materials Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); Liu Lin [State Key Lab of Materials Processing and Mould Technology, Department of Materials Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China)], E-mail: lliu2000@public.wh.hb.cn

2008-09-08

The formation of a Fe{sub 43.7}Co{sub 7.3}Cr{sub 14.7}Mo{sub 12.6}C{sub 15.5}B{sub 4.3}Y{sub 1.9} bulk metallic glass (BMG) was attempted in low vacuum environment and in air using commercial raw materials. The glass forming ability of the Fe-based alloys was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and differential thermal analyzer (DTA). It was found that cylindric rods with diameters ranging from 10 mm to 5 mm could be successfully fabricated by copper-mold casting in the pressures from 1.5 Pa to 10{sup 5} Pa (10{sup 5} Pa = 1 atm). All BMGs exhibit a distinct glass transition and wide supercooled liquid region. The preparation condition seems not significantly affected by the thermodynamic parameters of BMG, such as supercooled liquid region, glass transition temperature and melting process. The oxygen content of the alloys prepared in different vacuum conditions was measured by a LECO oxygen analyzer, which revealed that the oxygen content was less than 100 ppm for all BMGs prepared, even in air. The good glass forming ability and excellent oxidation resistance for the present Fe-based alloy are discussed.

An interatomic potential for studying CuZr bulk metallic glasses

DEFF Research Database (Denmark)

Paduraru, Anca; Kenoufi, Abdel; Bailey, Nicholas

2007-01-01

-scale deformation events and may furthermore involve localization through formation of shear bands. In this paper, an Effective Medium Theory (EMT) potential optimized for modeling the mechanical and thermodynamic properties of CuZr bulk metallic glass is studied. The late transition metals crystallizing in close......The mechanical properties of BMGs are remarkably different from the ones of ordinary metallic alloys due to the atomic level disorder in the glassy state. Unlike crystalline materials plastic deformation in metallic glasses cannot be caused by lattice defects but takes place through atomic...

Thermal stability and magnetocaloric properties of GdDyAlCo bulk metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Liang, L. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Hui, X. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)], E-mail: huixd01@hotmail.com; Chen, G.L. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

2008-01-25

Gd{sub 56-x}Dy{sub x}Al{sub 24}Co{sub 20} (x = 16, 20 and 22) bulk metallic glasses (BMGs) alloys with a diameter of 2, 3 and 3 mm, respectively, were prepared by using copper mold casting. These alloys exhibit higher values of the glass transition temperature, crystallization temperature, and activation energy of the glass transition and crystallization, compared with those of other known rare-earth-based BMGs. A maximum magnetic entropy changes of 15.78 J/(kg K) is obtained in Gd{sub 40}Dy{sub 16}Al{sub 24}Co{sub 20}, which is the maximal among all the bulk metallic glasses, and is much larger than those of the known crystalline magnetic refrigerant compound Gd{sub 5}Si{sub 2}Ge{sub 1.9}Fe{sub 0.1} and pure Gd metal. All the three BMG alloys have a broader temperature range of the entropy change peak, resulting in larger refrigerate capacities (RC) than those of conventional crystalline materials. The excellent magnetocaloric properties combining with high thermal stability make them an attractive candidate for magnetic refrigerants in the temperature range of 20-100 K.

Carbon nanotubes grown on bulk materials and methods for fabrication

Science.gov (United States)

Menchhofer, Paul A [Clinton, TN; Montgomery, Frederick C [Oak Ridge, TN; Baker, Frederick S [Oak Ridge, TN

2011-11-08

Disclosed are structures formed as bulk support media having carbon nanotubes formed therewith. The bulk support media may comprise fibers or particles and the fibers or particles may be formed from such materials as quartz, carbon, or activated carbon. Metal catalyst species are formed adjacent the surfaces of the bulk support material, and carbon nanotubes are grown adjacent the surfaces of the metal catalyst species. Methods employ metal salt solutions that may comprise iron salts such as iron chloride, aluminum salts such as aluminum chloride, or nickel salts such as nickel chloride. Carbon nanotubes may be separated from the carbon-based bulk support media and the metal catalyst species by using concentrated acids to oxidize the carbon-based bulk support media and the metal catalyst species.

Feasibility of using bulk metallic glass for self-expandable stent applications.

Science.gov (United States)

Praveen Kumar, Gideon; Jafary-Zadeh, Mehdi; Tavakoli, Rouhollah; Cui, Fangsen

2017-10-01

Self-expandable stents are widely used to restore blood flow in a diseased artery segment by keeping the artery open after angioplasty. Despite the prevalent use of conventional crystalline metallic alloys, for example, nitinol, to construct self-expandable stents, new biomaterials such as bulk metallic glasses (BMGs) are being actively pursued to improve stent performance. Here, we conducted a series of analyses including finite element analysis and molecular dynamics simulations to investigate the feasibility of using a prototypical Zr-based BMG for self-expandable stent applications. We model stent crimping of several designs for different percutaneous applications. Our results indicate that BMG-based stents with diamond-shaped crowns suffer from severe localization of plastic deformation and abrupt failure during crimping. As a possible solution, we further illustrate that such abrupt failure could be avoided in BMG-based stents without diamond shape crowns. This work would open a new horizon for a quest toward exploiting superior mechanical and functional properties of metallic glasses to design future stents. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1874-1882, 2017. © 2016 Wiley Periodicals, Inc.

Characterization of mechanically alloyed Ti-based bulk metallic glass composites containing carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Hsu, C.F. [Institute of Materials Engineering, National Taiwan Ocean University, No. 2, Beining Road, Keelung (China); Lin, H.M. [Department of Materials Engineering, Tatung University, No.40, Sec. 3, Jhongshan N. Rd. Jhongshan District, Taipei 104 Taiwan (China); Lee, P.Y.

2008-11-15

This study explored the feasibility of preparing CNT/Ti{sub 50}Cu{sub 28}Ni{sub 15}Sn{sub 7} bulk metallic glass (BMG) composites though powder metallurgy route. The CNT/Ti{sub 50}Cu{sub 28}Ni{sub 15}Sn{sub 7} BMG composites were obtained by consolidating the 8h mechanically alloyed composite powders by vacuum hot pressing process. A significant increase in hardness (9.34 GPa) and fracture strength (1937 MPa) was achieved for the Ti{sub 50}Cu{sub 28}Ni{sub 15}Sn{sub 7} BMG composites containing 12 vol. % CNT. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

Bulk amorphous Mg-based alloys

DEFF Research Database (Denmark)

Pryds, Nini

2004-01-01

are discussed in this paper. On the basis of these measurements phase diagrams of the different systems were constructed. Finally, it is demonstrated that when pressing the bulk amorphous alloy onto a metallic dies at temperatures within the supercooled liquid region, the alloy faithfully replicates the surface...

A New Approach for Handling of Micro Parts in Bulk Metal Forming

DEFF Research Database (Denmark)

Mahshid, Rasoul; Hansen, Hans Nørgaard; Arentoft, M.

2012-01-01

of production [1]. This can fulfill the demands for mass production and miniaturization in industries and academic communities. According to the recent studies, topics related to materials, process and simulation have been investigated intensively and well documented. Machines, forming tools and handling...... systems are critical elements to complete micro forming technology for transferring knowledge to industries and toward miniature manufacturing systems (micro factory) [2]. Since most metal forming processes are multi stage, making a new handling system with high reliability on accuracy and speed...... have been optimized or handling systems based on new concepts for gripping and releasing micro parts have been proposed. Making a handling system for micro parts made by sheet metals or foils is easier than those in bulk metal forming because parts are attached to the sheet during the forming process...

Bulk metallic glasses and high entropy alloys for reprocessing applications

International Nuclear Information System (INIS)

Kamachi Mudali, U.; Jayaraj, J.

2016-01-01

Recent breakthroughs in materials engineering have generated complex alloys that retain a glassy state in bulk form (bulk metallic glasses or BMGs) via ingot casting. High corrosion resistance is expected for BMGs (amorphous) as they are free from defects associated with the crystalline state such as grain boundaries, dislocations and stacking faults. Compared with conventional alloys containing one or two principal elements, the recently developed HEAs are usually composed of five or more elements with equimolar or near equimolar elemental fractions, which forms single solid solution phase. These HEAs exhibit excellent microstructural stability with better mechanical, wear and corrosion resistance properties as they are essentially single phase. Reprocessing of spent fuel from the fast breeder reactor involves the use of high concentration of (11.5 M) nitric acid under boiling conditions for the dissolution of the fuel. Conventional AISI type 304LSS and nitric acid grade 304L stainless steel would undergo inter-granular corrosion under these conditions and cannot be used for the fabrication of dissolver vessel. Currently titanium is used and zirconium alloys are proposed for future dissolver applications. Thus searching for newer materials with higher corrosion resistance suggests metallic glasses and HEAs for critical components of the dissolver application. Several Zr-based glassy alloys with different microstructural states and Ni-Nb based glassy alloys and TiZrHfNbTa HEA were cast and characterized for microstructure and corrosion resistance in nitric acid medium. From these studies, factors such as the corrosive environment (nitric acid, chloride and fluoride), and the presence of passivating elements in the alloy were emphasized for better corrosion resistance of BMGs and HEA. Attempts were also made to prepare coatings of Zr-and Ni-based glassy alloys on 304LSS by laser based deposition technique and their corrosion properties were evaluated. (author)

Criticality in Bulk Metallic Glass Constituent Elements

Science.gov (United States)

Mota, Rodrigo Miguel Ojeda; Graedel, T. E.; Pekarskaya, Evgenia; Schroers, Jan

2017-11-01

Bulk metallic glasses (BMGs), which readily form amorphous phases during solidification, are increasingly being used in first applications of watch components, electronic casings, and sporting goods. The compositions of BMGs typically include four to six elements. Various political and geological factors have recently led to supply disruptions for several metals, including some present in BMG compositions. In this work, we assess the "criticality" of 22 technologically interesting BMG compositions, compare the results with those for three common engineering alloy groups, and derive recommendations for BMG composition choices from a criticality perspective. The criticality of BMGs is found to be generally much higher compared with those for the established engineering alloys. Therefore, criticality concerns should also be considered in the choice between existing and developing novel BMGs.

Cavitation instability in bulk metallic glasses

Directory of Open Access Journals (Sweden)

Dai L.H.

2015-01-01

Full Text Available Recent experiments have shown that fracture surfaces of bulk metallic glasses (BMGs usually exhibit an intriguing nanoscale corrugation like fractographic feature mediated by nanoscale void formation. We attribute the onset of this nanoscale corrugation to TTZs (tension transformation zones mediated cavitation. In our recent study, the spall experiments of Zr-based BMG using a single-stage light gas gun were performed. To uncover the mechanisms of the spallation damage nucleation and evolution, the samples were designed to be subjected to dynamic tensile loadings of identical amplitude but with different durations by making use of the multi-stress pulse and the double-flyer techniques. It is clearly revealed that the macroscopic spall fracture in BMGs originates from the nucleation, growth and coalescence of micro-voids. Then, a microvoid nucleation model of BMGs based on free volume theory is proposed, which indicates that the nucleation of microvoids at the early stage of spallation in BMGs is resulted from diffusion and coalescence of free volume. Furthermore, a theoretical model of void growth in BMGs undergoing remote dynamic hydrostatic tension is developed. The critical condition of cavitation instability is obtained. It is found that dynamic void growth in BMGs can be well controlled by a dimensionless inertial number characterizing the competition between intrinsic and extrinsic time scales. To unveil the atomic-level mechanism of cavitation, a systematic molecular dynamics (MD simulation of spallation behaviour of a binary metallic glass with different impact velocities was performed. It is found that micro-void nucleation is determined TTZs while the growth is controlled by shear transformation zones (STZs at atomic scale.

Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites

Science.gov (United States)

Zhang, L.; Pauly, S.; Tang, M. Q.; Eckert, J.; Zhang, H. F.

2016-01-01

The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated. PMID:26754315

Reentrant spin glass ordering in an Fe-based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Luo, Qiang; Shen, Jun, E-mail: junshen@tongji.edu.cn [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China)

2015-02-07

We report the results of the complex susceptibility, temperature, and field dependence of DC magnetization and the nonequilibrium dynamics of a bulk metallic glass Fe{sub 40}Co{sub 8}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Er{sub 2}. Solid indication of the coexistence of reentrant spin glass (SG) and ferromagnetic orderings is determined from both DC magnetization and AC susceptibility under different DC fields. Dynamics scaling of AC susceptibility indicates critical slowing down to a reentrant SG state with a static transition temperature T{sub s} = ∼17.8 K and a dynamic exponent zv = ∼7.3. The SG nature is further corroborated from chaos and memory effects, magnetic hysteresis, and aging behavior. We discuss the results in terms of the competition among random magnetic anisotropy and exchange interactions and compare them with simulation predictions.

Synthesis and devitrification of high glass-forming ability bulk metallic glasses.

OpenAIRE

Huang, Hong.

2007-01-01

In this thesis, literature on the production, microstructures and properties of bulk metallic glasses (BMG) has been reviewed with particular reference to glass forming ability (GFA) and alloys of the Fe-Zr-B and Zr-based BMG systems. The experimental procedures used in the research are presented and the results for the amorphous Fe80Zr12B8 ribbon and the Zr57Ti5Al10Cu20Ni8, Zr57Nb5Al10Cu20Ni8, Zr53Nb2Al8Cu30Ni7 BMGs are given and discussed. Wedge-shaped ingots of the Zr-based BMGs were produ...

On the anelasticity and strain induced structural changes in a Zr-based bulk metallic glass

International Nuclear Information System (INIS)

Caron, A.; Louzguine-Luzguin, D. V.; Kawashima, A.; Inoue, A.; Fecht, H.-J.

2011-01-01

We report on the anelastic behavior of a cyclically loaded Zr 62.5 Fe 5 Cu 22.5 Al 10 bulk metallic glass well below its yield strength. The dynamic mechanical behavior of the glass is discussed on the basis of its structural and thermodynamic properties before and after tests. We show how the kinetically frozen anelastic deformation accumulates at room temperature and causes a structural relaxation and densification of the glass and further leads to its partial crystallization.

Investigation of crystallization kinetics and deformation behavior in supercooled liquid region of CuZr-based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Yang, Ke; Fan, Xinhui; Li, Bing; Li, Yanhong; Wang, Xin; Xu, Xuanxuan [Xi' an Technological Univ. (China). School of Material and Chemical Engineering

2017-08-15

In this paper, a systematic study of crystallization kinetics and deformation behavior is presented for (Cu{sub 50}Zr{sub 50}){sub 94}Al{sub 6} bulk metallic glass in the supercooled liquid region. Crystallization results showed that the activation energy for (Cu{sub 50}Zr{sub 50}){sub 94}Al{sub 6} was calculated using the Arrhenius equation in isothermal mode and the Kissinger-Akahira-Sunose method in non-isothermal mode. The activation energy was quite high compared with other bulk metallic glasses. Based on isothermal transformation kinetics described by the Johson-Mehl-Avrami model, the average Avrami exponent of about 3.05 implies a mainly diffusion controlled three-dimensional growth with an increasing nucleation rate during the crystallization. For warm deformation, the results showed that deformation behavior, composed of homogeneous and inhomogeneous deformation, is strongly dependent on strain rate and temperature. The homogeneous deformation transformed from non-Newtonian flow to Newtonian flow with a decrease in strain rate and an increase in temperature. It was found that the crystallization during high temperature deformation is induced by heating. The appropriate working temperature/strain rate combination for the alloy forming, without in-situ crystallization, was deduced by constructing an empirical deformation map. The optimum process condition for (Cu{sub 50}Zr{sub 50}){sub 94}Al{sub 6} can be expressed as T∝733 K and ∝ ε 10{sup -3} s{sup -1}.

Nanopatterned Bulk Metallic Glass Biosensors.

Science.gov (United States)

Kinser, Emily R; Padmanabhan, Jagannath; Yu, Roy; Corona, Sydney L; Li, Jinyang; Vaddiraju, Sagar; Legassey, Allen; Loye, Ayomiposi; Balestrini, Jenna; Solly, Dawson A; Schroers, Jan; Taylor, André D; Papadimitrakopoulos, Fotios; Herzog, Raimund I; Kyriakides, Themis R

2017-12-22

Nanopatterning as a surface area enhancement method has the potential to increase signal and sensitivity of biosensors. Platinum-based bulk metallic glass (Pt-BMG) is a biocompatible material with electrical properties conducive for biosensor electrode applications, which can be processed in air at comparably low temperatures to produce nonrandom topography at the nanoscale. Work presented here employs nanopatterned Pt-BMG electrodes functionalized with glucose oxidase enzyme to explore the impact of nonrandom and highly reproducible nanoscale surface area enhancement on glucose biosensor performance. Electrochemical measurements including cyclic voltammetry (CV) and amperometric voltammetry (AV) were completed to compare the performance of 200 nm Pt-BMG electrodes vs Flat Pt-BMG control electrodes. Glucose dosing response was studied in a range of 2 mM to 10 mM. Effective current density dynamic range for the 200 nm Pt-BMG was 10-12 times greater than that of the Flat BMG control. Nanopatterned electrode sensitivity was measured to be 3.28 μA/cm 2 /mM, which was also an order of magnitude greater than the flat electrode. These results suggest that nonrandom nanotopography is a scalable and customizable engineering tool which can be integrated with Pt-BMGs to produce biocompatible biosensors with enhanced signal and sensitivity.

A new method for evaluating structural stability of bulk metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Zhao, Lei; Jia, Haoling [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Xie, Shenghui; Zeng, Xierong [College of Materials Science and Engineering, Shenzhen University and Shenzhen Key Laboratory of Special Functional Materials, ShenZhen 518060 (China); Zhang, Tao [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Ma, Chaoli, E-mail: machaoli@buaa.edu.c [Key Laboratory of Aerospace Materials and Performance, Ministry of Education, School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

2010-08-15

This paper proposed a new method for evaluating the structural stability of bulk metallic glasses (BMGs) based on dilatometric measurements. During heating in the dilatometric experiments, the BMGs expanded continuously with increasing temperature. When the temperature reached the glass transition temperature (T{sub g}), viscous shrinkage occurred due to the viscosity of material becoming lower. Since the inhomogeneous nature of the metallic glasses at atomic level, the processes of rigid expansion and the viscous shrinkage co-exist in a certain temperature region. The expansion stopped completely at a temperature (named T{sub p} here) beyond T{sub g}. The values of the temperature region, {Delta}T{sub gp} = T{sub p} - T{sub g}, and the corresponding time interval ({Delta}t{sub gp}) and the activation energy (E{sub p}) corresponding to the expansion processes, are the reflection of the structural stability of BMGs. Investigating the co-existing processes kinetically and thermodynamically, we can make an insight into the structural stability of metallic glasses. Based on this idea, the thermal expansion behaviors of Mg-, Pd-, Zr-, Ti- and Fe-based BMG were studied, and their structural stability was evaluated by the parameters of {Delta}T{sub gp}, {Delta}t{sub gp} and E{sub p}.

Formation and properties of two-phase bulk metallic glasses by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Xie Guoqiang, E-mail: xiegq@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Louzguine-Luzgin, D.V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Inoue, Akihisa [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2011-06-15

Research highlights: > Two-phase bulk metallic glasses with high strength and good soft magnetic properties as well as satisfying large-size requirements were produced by spark plasma sintering. > Effects of sintering temperature on thermal stability, microstructure, mechanical and magnetic properties were investigated. > Densified samples were obtained by the spark plasma sintering at above 773 K. - Abstract: Using a mixture of the gas-atomized Ni{sub 52.5}Nb{sub 10}Zr{sub 15}Ti{sub 15}Pt{sub 7.5} and Fe{sub 73}Si{sub 7}B{sub 17}Nb{sub 3} glassy alloy powders, we produced the two-phase bulk metallic glass (BMG) with high strength and good soft magnetic properties as well as satisfying large-size requirements by the spark plasma sintering (SPS) process. Two kinds of glassy particulates were homogeneously dispersed each other. With an increase in sintering temperature, density of the produced samples increased, and densified samples were obtained by the SPS process at above 773 K. Good bonding state among the Ni- and Fe-based glassy particulates was achieved.

In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

Science.gov (United States)

Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

2004-03-23

A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

Clarification on shear transformation zone size and its correlation with plasticity for Zr-based bulk metallic glass in different structural states

Energy Technology Data Exchange (ETDEWEB)

Chen, Z.Q.; Huang, L. [State Key Laboratory for Mechanical Behavior of Material, Xi' an Jiaotong University, Xi' an 710049 (China); Huang, P., E-mail: huangping@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Material, Xi' an Jiaotong University, Xi' an 710049 (China); Xu, K.W. [State Key Laboratory for Mechanical Behavior of Material, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, F., E-mail: wangfei@mail.xjtu.edu.cn [State Key Laboratory for Strength and Vibration of Mechanical Structures Xi' an Jiaotong University, Xi' an 710049 (China); Lu, T.J. [State Key Laboratory for Strength and Vibration of Mechanical Structures Xi' an Jiaotong University, Xi' an 710049 (China); MOE Key Laboratory for Multifunctional Materials and Structures Xi' an Jiaotong University, Xi' an 710049 (China)

2016-11-20

To clarify the real size of shear transformation zone (STZ) and its correlation with the plasticity of metallic glass, STZ sizes of a Zr-based bulk metallic glass (BMG) in three different structural states (as-cast, annealed and confining annealed) were examined using both rate-change and statistical methods upon nanoindentation. STZ sizes (less than 24 atoms) obtained by the statistical method approached the real STZ size of very few atoms, and showed no correlation with BMG plasticity. In sharp contrast, STZ sizes (hundreds of atoms) obtained by the rate-change method not only were much larger than the real STZ size but also exhibited a positive correlation with BMG plasticity. These discrepancies were discussed in terms of the structural evolution of BMGs upon nanoindentation.

Indentation size effects in the nano- and micro-hardness of a Fe-based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Xu, F., E-mail: xufu@xtu.edu.cn; Ding, Y.H.; Deng, X.H.; Zhang, P.; Long, Z.L.

2014-10-01

Hardness of a Fe-based bulk metallic glass (BMG) was evaluated by both atomic force microscopy (AFM) nanoindentation (nano-hardness) and instrumented indentation with a traditional indenter setup (micro-hardness) under different maximum loads at room temperature. The nano-hardness and the micro-hardness were found to be comparable. For both of the indentation methods, indentation size effect (ISE) is detected as increase in hardness with decrease in indentation peak load. It is proposed that strain rate dependent softening, loading history and the lag between free volume creation and mechanical softening should be responsible for the ISE in this BMG. Furthermore, ISE is found to be more significant in AFM nanoindentation than in instrumented indentation. This can be explained by taking into account the effect of exerted peak load and the face angle of the indenter in a qualitative manner.

Preparation, thermal stability, and magnetic properties of Fe-Zr-Mo-W-B bulk metallic glass

International Nuclear Information System (INIS)

Liu, D.Y.; Sun, W.S.; Wang, A.M.; Zhang, H.F.; Hu, Z.Q.

2004-01-01

A bulk metallic glass (BMG) cylinder of Fe 60 Co 8 Zr 10 Mo 5 W 2 B 15 with a diameter of 1.5 mm was prepared by copper mould casting of industrial raw materials. The amorphous state and the crystallization behavior were investigated by X-ray diffraction (XRD). The thermal stability parameters, such as glass transition temperature (T g ), crystallization temperature (T x ), supercooled liquid region (ΔT x ) between T g and T x , and reduced glass transition temperature T rg (T g /T m ) were measured by differential scanning calorimetry (DSC) to be 891, 950, 59 K, and 0.62, respectively. The crystallization process took place through a single stage, and involved crystallization of the phases α-Fe, ZrFe 2 , Fe 3 B, MoB 2 , Mo 2 FeB 2 , and an unknown phase, as determined by X-ray analysis of the sample annealed for 1.5 ks at 1023 K, 50 K above the DSC peak temperature of crystallization. Moessbauer spectroscopy was studied for this alloy. The spectra exhibit a broadened and asymmetric doublet-like structure that indicated paramagnetic behavior and a fully amorphous structure. α-Fe was found in the amorphous matrix for a cylinder with a diameter of 2.5 mm. The success of synthesis of the Fe-based bulk metallic glass from industrial materials is important for the future progress in research and practical application of new bulk metallic glasses

Net Shaping of Multifunctional Bulk Metallic Glass Containers and Structures, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Demand for novel manufacturing methods for space systems brings unique properties of bulk metallic glasses (BMG) into the spotlight. In addition to superior...

Thermoplastic forming of bulk metallic glasses for precision robotics components, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Demand for novel manufacturing methods for space systems brings unique properties of bulk metallic glasses (BMG) into the spotlight. In addition to superior...

Friction welding of bulk metallic glasses to different ones

International Nuclear Information System (INIS)

Shoji, Takuo; Kawamura, Yoshihito; Ohno, Yasuhide

2004-01-01

For application of bulk metallic glasses (BMGs) as industrial materials, it is necessary to establish the metallurgical bonding technology. The BMGs exhibit high-strain-rate superplasticity in the supercooled liquid state. It has been reported that bulk metallic glasses were successfully welded together by friction, pulse-current, explosion and electron-beam methods. In this study, friction welding of the BMGs to different ones were tried for Pd 40 Ni 40 P 20 , Pd 40 Cu 30 P 20 Ni 10 , Zr 55 Cu 30 Al 10 Ni 5 and Zr 41 Be 23 Ti 14 Cu 12 Ni 10 BMGs. Successful welding was obtained in the combinations of the Pd 40 Ni 40 P 20 and Pd 40 Cu 30 P 20 Ni 10 BMGs, and the Zr 55 Cu 30 Al 10 Ni 5 and Zr 41 Be 23 Ti 14 Cu 12 Ni 10 ones. No crystallization was observed and no visible defect was recognized in the interface. The joining strength of the welded BMGs was the same as that of the parent BMG or more. BMGs seem to be successfully welded to the different ones with a difference below about 50 K in glass transition temperature

Structural study of conventional and bulk metallic glasses during annealing

International Nuclear Information System (INIS)

Pineda, E.; Hidalgo, I.; Bruna, P.; Pradell, T.; Labrador, A.; Crespo, D.

2009-01-01

Metallic glasses with conventional glass-forming ability (Al-Fe-Nd, Fe-Zr-B, Fe-B-Nb compositions) and bulk metallic glasses (Ca-Mg-Cu compositions) were studied by synchrotron X-ray diffraction during annealing throughout glass transition and crystallization temperatures. The analysis of the first diffraction peak position during the annealing process allowed us to follow the free volume change during relaxation and glass transition. The structure factor and the radial distribution function of the glasses were obtained from the X-ray measurements. The structural changes occurred during annealing are analyzed and discussed.

Effect of MoSi2 Content on Dry Sliding Tribological Properties of Zr-Based Bulk Metallic Glass Composites

Science.gov (United States)

Liu, Longfei; Yang, Jun

2017-12-01

Zr55Cu30Al10Ni5 bulk metallic glass and its composites were prepared by suction casting into a copper mold. The effect of MoSi2 content on the tribological behavior of Zr55Cu30Al10Ni5 BMG was studied by using a high-speed reciprocating friction and wear tester. The results indicate that the friction coefficient and wear resistance of the BMGs can be improved by a certain amount of crystalline phase induced by MoSi2 content from 1 to 3% and deteriorated with MoSi2 content of 4%. The wear mechanism of both the metallic glass and its composite is abrasive wear. The mechanism of crystalline phase-dependent tribological properties of the composite was discussed based on the wear track and mechanical properties in the present work. The wear behavior of Zr55Cu30Al10Ni5 BMG and its composite indicates that a good combination of the toughness and the hardness can make the composite be well wear resistant.

Nanoindentation study on the characteristic of shear transformation zone in a Pd-based bulk metallic glass during serrated flow

Science.gov (United States)

Liao, G. K.; Long, Z. L.; Zhao, M. S. Z.; Peng, L.; Chai, W.; Ping, Z. H.

2018-04-01

This paper presents the research on the evolution of shear transformation zone (STZ) in a Pd-based bulk metallic glass (BMG) during serrated flow under nanoindentation. A novel method of estimating the STZ volume through statistical analysis of the serrated flow behavior was proposed for the first time. Based on the proposed method, the STZ volume of the studied BMG at various peak loads have been systematically investigated. The results indicate that the measured STZ volumes are in good agreement with that documented in literature, and the STZ size exhibits an increasing trend during indentation. Moreover, the correlation between the serrated flow dynamics and the STZ activation has also been evaluated. It is found that the STZ activation can promote the formation of self-organized critical (SOC) state during serrated flow.

Advanced Wear Simulation for Bulk Metal Forming Processes

Directory of Open Access Journals (Sweden)

Behrens Bernd-Arno

2016-01-01

Full Text Available In the recent decades the finite element method has become an essential tool for the cost-efficient virtual process design in the metal forming sector in order to counter the constantly increasing quality standards, particularly from the automotive industry as well as intensified international competition in the forging industry. An optimized process design taking precise tool wear prediction into account is a way to increase the cost-efficiency of the bulk metal forming processes. The main objective of the work presented in this paper is a modelling algorithm, which allows predicting die wear with respect to a geometry update during the forming simulation. Changes in the contact area caused by geometry update lead to the different die wear distribution. It primarily concerns the die areas, which undergo high thermal and mechanical loads.

Compressive yielding of tungsten fiber reinforced bulk metallic glass composites

Energy Technology Data Exchange (ETDEWEB)

Clausen, B.; Lee, S.-Y.; Uestuendag, E.; Aydiner, C.C.; Conner, R.D.; Bourke, M.A.M

2003-07-15

In-situ uniaxial compression tests were conducted on four tungsten fiber reinforced bulk metallic glass matrix composites using neutron diffraction. The results were interpreted with a finite element model. Both phases were seen to approximately obey the von Mises yield criterion. The fibers were observed to yield first and then transfer load to the matrix.

Compressive yielding of tungsten fiber reinforced bulk metallic glass composites

International Nuclear Information System (INIS)

Clausen, B.; Lee, S.-Y.; Uestuendag, E.; Aydiner, C.C.; Conner, R.D.; Bourke, M.A.M.

2003-01-01

In-situ uniaxial compression tests were conducted on four tungsten fiber reinforced bulk metallic glass matrix composites using neutron diffraction. The results were interpreted with a finite element model. Both phases were seen to approximately obey the von Mises yield criterion. The fibers were observed to yield first and then transfer load to the matrix

Evaluation of Ni-free Zr–Cu–Fe–Al bulk metallic glass for biomedical implant applications

Energy Technology Data Exchange (ETDEWEB)

Sun, Ying-Sui [Institute of Oral Biology, National Yang-Ming University, Taipei, Taiwan (China); Zhang, Wei [School of Materials Science and Engineering, Dalian University of Technology, Dalian (China); Kai, Wu [Institute of Materials Engineering, National Taiwan Ocean University, Keelung, Taiwan (China); Liaw, Peter K. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN (United States); Huang, Her-Hsiung, E-mail: hhhuang@ym.edu.tw [Institute of Oral Biology, National Yang-Ming University, Taipei, Taiwan (China); Department of Dentistry, National Yang-Ming University, Taipei, Taiwan (China); Department of Dentistry, Taipei City Hospital, Taipei, Taiwan (China); Department of Stomatology, Taipei Veterans General Hospital, Taipei, Taiwan (China)

2014-02-15

Highlights: ► A Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} bulk metallic glass (BMG) with 50 GPa elastic modulus was used. ► This Ni-free Zr-based BMG had lower metal ion release rate than the commercial Ti. ► This Ni-free Zr-based BMG had better proteins adsorption than the commercial Ti. ► This Ni-free Zr-based BMG has a high potential for biomedical implant applications. -- Abstract: This study was conducted to investigate the surface characteristics, including the chemical composition, metal ion release, protein adsorption, and cell adhesion, of a Ni-free Zr-based (Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10}) bulk metallic glass (BMG) with low elastic modulus for biomedical implant applications. X-ray photoelectron spectroscopy was used to identify the surface chemical composition and the protein (albumin and fibronectin) adsorption of the specimen. The metal ions released from the specimen in simulated blood plasma and artificial saliva solutions were measured using an inductively coupled plasma-mass spectrometer. The cell adhesion, in terms of the morphology, focal adhesion complex, and skeletal arrangement, of human bone marrow mesenchymal stem cells was evaluated using scanning electron microscope observations and immunofluorescent staining. For comparison purposes, the above-mentioned tests were also carried out on the widely used biomedical metal, Ti. The results showed that the main component on the outermost surface of the amorphous Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} BMG was ZrO{sub 2} with small amounts of Cu, Al, and Fe oxides. The released metal ions from Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} BMG were well below the critical concentrations that cause negative biological effects. The Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} BMG had a greater adsorption capacity for albumin and fibronectin than that of commercial biomedical Ti. The Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} BMG surface showed an attached cell number similar

High-entropy bulk metallic glasses as promising magnetic refrigerants

International Nuclear Information System (INIS)

Huo, Juntao; Huo, Lishan; Li, Jiawei; Men, He; Wang, Xinmin; Chang, Chuntao; Wang, Jun-Qiang; Li, Run-Wei; Inoue, Akihisa

2015-01-01

In this paper, the Ho 20 Er 20 Co 20 Al 20 RE 20 (RE = Gd, Dy, and Tm) high-entropy bulk metallic glasses (HE-BMGs) with good magnetocaloric properties are fabricated successfully. The HE-BMGs exhibit a second-order magnetic phase transition. The peak of magnetic entropy change (ΔS M pk ) and refrigerant capacity (RC) reaches 15.0 J kg −1 K −1 and 627 J kg −1 at 5 T, respectively, which is larger than most rare earth based BMGs. The heterogeneous nature of glasses also contributes to the large ΔS M pk and RC. In addition, the magnetic ordering temperature, ΔS M pk and RC can be widely tuned by alloying different rare earth elements. These results suggest that the HE-BMGs are promising magnetic refrigerant at low temperatures

Electrical and magnetic properties of Fe-based bulk metallic glass with minor Co and Ni addition

Energy Technology Data Exchange (ETDEWEB)

Jung, H.Y. [IFW Dresden, Institute for Complex Materials, D–01069 Dresden (Germany); Stoica, M. [IFW Dresden, Institute for Complex Materials, D–01069 Dresden (Germany); POLITEHNICA University of Timisoara, P-ta Victoriei 2, Timisoara (Romania); Yi, S. [Department of Materials Science and Metallurgical Engineering, Kyungpook National University, 702–701 Daegu (Korea, Republic of); Kim, D.H. [Center for Non-crystalline Materials, Department of Metallurgical Engineering, Yonsei University, 120–749 Seoul (Korea, Republic of); Eckert, J. [IFW Dresden, Institute for Complex Materials, D–01069 Dresden (Germany); University of Technology Dresden, Institute of Materials Science, D–01062 Dresden (Germany)

2014-09-01

The effect of minor Co and Ni alloying on soft magnetic properties and electrical resistivity of Fe{sub 75.5}C{sub 7.0}Si{sub 3.3}B{sub 5.5}P{sub 8.7} (at%) bulk metallic glass has been investigated. Within examined compositional range (Co and Ni up to 4 at%, respectively), the saturation magnetization and electrical resistivity of the alloys continuously decrease with increasing Co or Ni content, while the Curie temperature and initial permeability increase. Comparing the effect of Co and Ni additions, the alloys with Co addition have much higher Curie temperature and saturation magnetization than the alloy with Ni addition. Also, the Co-added alloys show smaller coercivity and larger permeability than the Ni-added alloys. The present results suggest that minor addition of Co can provide better effectiveness to enhance the magnetic softness of Fe-based BMGs than minor Ni addition. - Highlights: • Soft magnetic characteristics of CI-based BMGs can be enhanced with minor Co and Ni alloying. • Minor Co addition can provide better effectiveness to enhance the magnetic softness of CI-based BMG than Ni addition. • Optimum Co addition enlarges atomic packing density and randomness of amorphous structure.

A guide for validation of FE-Simulations in bulk metal forming

International Nuclear Information System (INIS)

Tekkaya, A. Erman

2005-01-01

Numerical analysis of metal forming processes is an everyday practice in industry. Forming loads, material flow, forming defects such as underfills, laps and even cracks, stresses in dies and punches, as well as product properties like new hardness distribution, dimensional accuracies and residual stresses are predicted by numerical analysis and used for technology generation. Most of the numerical analysis is done by the finite element method made available for engineers and technicians by numerous by powerful commercial software packages. These software packages act as black-boxes and usually hide the complicated numerical procedures and even their crucial parameters from the applier. Therefore, the question arises during the industrial applications: how accurate is the simulation and how can the results can be assessed? The aim of this paper is to provide a guideline to assess the results of metal forming simulations. Although some ideas are valid for any metal forming process, bulk forming is the process concern. The paper will address firstly the possible sources of error in a finite element analysis of bulk forming processes. Then, some useful elementary knowledge will be summarized. Various levels of validation such as result and ability validation and assessment will be discussed. Finally, interpretation of results will be treated. In this content also some suggestions will be given. (author)

Laser Shock Peening on Zr-based Bulk Metallic Glass and Its Effect on Plasticity: Experiment and Modeling

Science.gov (United States)

Cao, Yunfeng; Xie, Xie; Antonaglia, James; Winiarski, Bartlomiej; Wang, Gongyao; Shin, Yung C.; Withers, Philip J.; Dahmen, Karin A.; Liaw, Peter K.

2015-05-01

The Zr-based bulk metallic glasses (BMGs) are a new family of attractive materials with good glass-forming ability and excellent mechanical properties, such as high strength and good wear resistance, which make them candidates for structural and biomedical materials. Although the mechanical behavior of BMGs has been widely investigated, their deformation mechanisms are still poorly understood. In particular, their poor ductility significantly impedes their industrial application. In the present work, we show that the ductility of Zr-based BMGs with nearly zero plasticity is improved by a laser shock peening technique. Moreover, we map the distribution of laser-induced residual stresses via the micro-slot cutting method, and then predict them using a three-dimensional finite-element method coupled with a confined plasma model. Reasonable agreement is achieved between the experimental and modeling results. The analyses of serrated flows reveal plentiful and useful information of the underlying deformation process. Our work provides an easy and effective way to extend the ductility of intrinsically-brittle BMGs, opening up wider applications of these materials.

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

Low temperature incineration of mixed wastes using bulk metal oxide catalysts

International Nuclear Information System (INIS)

Gordon, M.J.; Gaur, S.; Kelkar, S.; Baldwin, R.M.

1996-01-01

Volume reduction of low-level mixed wastes from former nuclear weapons facilities is a significant environmental problem. Processing of these materials presents unique scientific and engineering problems due to the presence of minute quantities of radionuclides which must be contained and concentrated for later safe disposal. Low-temperature catalytic incineration is one option that has been utilized at the Rocky Flats facility for this purpose. This paper presents results of research regarding evaluation of bulk metal oxides as catalysts for low-temperature incineration of carbonaceous residues which are typical by-products of fluidized bed combustion of mixed wastes under oxygen-lean conditions. A series of 14 metal oxides were screened in a thermogravimetric analyzer, using on-line mass spectrometry for speciation of reaction product gases. Catalyst evaluation criteria focused on the thermal-redox activity of the metals using both carbon black and PVC char as surrogate waste materials. Results indicated that metal oxides which were P-type semiconductor materials were suitable as catalysts for this application. Oxides of cobalt, molybdenum, vanadium, and manganese were found to be particularly stable and active catalysts under conditions specific to this process (T<650C, low oxygen partial pressures). Bench-scale evaluation of these metal oxides with respect to stability to chlorine (HCl) attack was carried out at 550C using a TG/MS system. Cobalt oxide was found to be resistant to metal loss in a HCl/He gaseous environment while metal loss from Mo, Mn, and V-based catalysts was moderate to severe. XRD and SEM/EDX analysis of spent Co catalysts indicated the formation of non-stoichiometric cobalt chlorides. Regeneration of chlorinated cobalt was found to successfully restore the low-temperature combustion activity to that of the fresh metal oxide

Correlations between elastic moduli and properties in bulk metallic glasses

International Nuclear Information System (INIS)

Wang Weihua

2006-01-01

A survey of the elastic, mechanical, fragility, and thermodynamic properties of bulk metallic glasses (BMGs) and glass-forming liquids is presented. It is found that the elastic moduli of BMGs have correlations with the glass transition temperature, melting temperature, mechanical properties, and even liquid fragility. On the other hand, the elastic constants of available BMGs show a rough correlation with a weighted average of the elastic constants for the constituent elements. Although the theoretical and physical reasons for the correlations are to be clarified, these correlations could assist in understanding the long-standing issues of glass formation and the nature of glass and simulate the work of theorists. Based on the correlation, we show that the elastic moduli can assist in selecting alloying components for controlling the elastic properties and glass-forming ability of the BMGs and thus can guide BMG design. As case study, we report the formation of the families of rare-earth-based BMGs with controllable properties

Dynamic strength behavior of a Zr-based bulk metallic glass under shock loading

International Nuclear Information System (INIS)

Yu Yu-Ying; Xi Feng; Dai Cheng-Da; Cai Ling-Cang; Tan Ye; Li Xue-Mei; Wu Qiang; Tan Hua

2015-01-01

Dynamic strength behavior of Zr 51 Ti 5 Ni 10 Cu 25 Al 9 bulk metallic glass (BMG) up to 66 GPa was investigated in a series of plate impact shock-release and shock-reload experiments. Particle velocity profiles measured at the sample/LiF window interface were used to estimate the shear stress, shear modulus, and yield stress in shocked BMG. Beyond confirming the previously reported strain-softening of shear stress during the shock loading process for BMGs, it is also shown that the softened Zr-BMG still has a high shear modulus and can support large yield stress when released or reloaded from the shocked state, and both the shear modulus and the yield stress appear as strain-hardening behaviors. The work provides a much clearer picture of the strength behavior of BMGs under shock loading, which is useful to comprehensively understand the plastic deformation mechanisms of BMGs. (paper)

Copper phthalocyanine and metal free phthalocyanine bulk heterojunction photodetector

Energy Technology Data Exchange (ETDEWEB)

Farooq, Amjad, E-mail: amjad.farooq1212@hotmail.com [Wah Engineering College, University of Wah, Wah Cantt. 47040 (Pakistan); GIK Institute of Engineering Sciences and Technology, Topi 23640, Swabi (Pakistan); Karimov, Kh.S. [GIK Institute of Engineering Sciences and Technology, Topi 23640, Swabi (Pakistan); Physical Technical Institute, Aini St. 299/1, Dushanbe 734063 (Tajikistan); Ahmed, Nisar; Ali, Taimoor [GIK Institute of Engineering Sciences and Technology, Topi 23640, Swabi (Pakistan); Khalid Alamgir, M. [National Institute of Vacuum Science and Technology, NCP complex, Islamabad 44000 (Pakistan); Usman, Muhammad [Experimental Physics Laboratories, National Centre for Physics, Quaid-i-Azam University, Islamabad 44000 (Pakistan)

2015-01-15

In this study we present the dependence of electrical properties of copper phthalocyanine (CuPc) and metal free phthalocyanine (H{sub 2}Pc) bulk heterojunction structure under different illumination levels. To fabricate the device on ITO coated glass substrate the bulk heterojunction thin film of CuPc and H{sub 2}Pc with thickness varying from 100 nm to 300 nm are deposited by thermal evaporator. Aluminum thin film was deposited by thermal evaporation as a top contact. The optical properties of the fabricated device are investigated using UV–vis spectroscopy. The current-voltage characteristics in dark and under illumination show that the device is sensitive towards visible light. The absorption spectrum describes its photo sensitivity in the range of wavelength from 200 nm to 850 nm. Simulation of current-intensity of light curve is carried out and experimental results are found in good agreement with simulated ones.

Copper phthalocyanine and metal free phthalocyanine bulk heterojunction photodetector

International Nuclear Information System (INIS)

Farooq, Amjad; Karimov, Kh.S.; Ahmed, Nisar; Ali, Taimoor; Khalid Alamgir, M.; Usman, Muhammad

2015-01-01

In this study we present the dependence of electrical properties of copper phthalocyanine (CuPc) and metal free phthalocyanine (H 2 Pc) bulk heterojunction structure under different illumination levels. To fabricate the device on ITO coated glass substrate the bulk heterojunction thin film of CuPc and H 2 Pc with thickness varying from 100 nm to 300 nm are deposited by thermal evaporator. Aluminum thin film was deposited by thermal evaporation as a top contact. The optical properties of the fabricated device are investigated using UV–vis spectroscopy. The current-voltage characteristics in dark and under illumination show that the device is sensitive towards visible light. The absorption spectrum describes its photo sensitivity in the range of wavelength from 200 nm to 850 nm. Simulation of current-intensity of light curve is carried out and experimental results are found in good agreement with simulated ones

FeNbB bulk metallic glass with high boron content

Energy Technology Data Exchange (ETDEWEB)

Stoica, M.; Das, Jayanta; Eckert, Juergen [IFW Dresden, Institute for Complex Materials, P.O. Box 270016, D-01171 Dresden (Germany); Hajlaoui, Khalil; Yavari, Alain Reza [LTPCM-CNRS, I.N.P. Grenoble, 1130 Rue de la Piscine, BP 75, F-38402 University Campus (France)

2007-07-01

Fe-based alloys able to form magnetic bulk metallic glasses (BMGs) are of the type transition metal - metalloid and often contain 5 or more elements. Usually, the metalloid content is around 20 atomic %. Very recently, the Fe{sub 66}Nb{sub 4}B{sub 30} alloy was found to be able to form BMG by copper mold casting technique, despite its high metalloid content. Several composition with boron contents around 30 at. % or even higher were calculated since 1993 as possible compositions of the remaining amorphous matrix after the first stage of nanocrystallization of Finemet-type Fe{sub 77}Si{sub 14}B{sub 9} glassy ribbons with 0.5 to 1 atomic % Cu and a few percent Nb addition. Melt-spun ribbons of all calculated compositions were found to be glassy. The composition of the ternary Fe-based BMG investigated in the present study resulted as an optimization of all possibilities. The alloy is ferromagnetic with glass transition temperature T{sub g}=845 K, crystallisation temperature T{sub x}=876 K, liquidus temperature T{sub liq}=1451 K and mechanical strength of 4 GPa. The coercivity of as-cast samples is very low, around 1.5 A/m. The present contribution aims at discussing the thermal stability, mechanical and magnetic properties of the Fe{sub 66}Nb{sub 4}B{sub 30} BMG.

STRUCTURAL INTERACTIONS OF HYDROGEN WITH BULK AMORPHOUS MICROSTRUCTURES IN METALLIC SYSTEMS UNDERSTANDING THE ROLE OF PARTIAL CRYSTALLINITY ON PERMEATION AND EMBRITTLEMENT

Energy Technology Data Exchange (ETDEWEB)

Brinkman, Kyle; Fox, Elise; Korinko, Paul; Adams, Thad

2010-05-10

The development of metallic glasses in bulk form has led to a resurgence of interest into the utilization of these materials for a variety of applications. A potentially exciting application for these bulk metallic glass (BMG) materials is their use as composite membranes to replace high cost Pd/Pd-alloy membranes for enhanced gas separation processes. One of the major drawbacks to the industrial use of Pd/Pd-alloy membranes is that during cycling above and below a critical temperature an irreversible change takes place in the palladium lattice structure which can result in significant damage to the membrane. Furthermore, the cost associated with Pd-based membranes is a potential detractor for their continued use and BMG alloys offer a potentially attractive alternative. Several BMG alloys have been shown to possess high permeation rates, comparable to those measured for pure Pd metal. In addition, high strength and toughness when either in-situ or ex-situ second phase dispersoids are present. Both of these properties, high permeation and high strength/toughness, potentially make these materials attractive for gas separation membranes that could resist hydrogen 'embrittlement'. However, a fundamental understanding of the relationship between partially crystalline 'structure'/devitrification and permeation/embrittlement in these BMG materials is required in order to determine the operating window for separation membranes and provide additional input to the material synthesis community for improved alloy design. This project aims to fill the knowledge gap regarding the impact of crystallization on the permeation properties of metallic glass materials. The objectives of this study are to (i) determine the crystallization behavior in different gas environments of Fe and Zr based commercially available bulk metallic glass and (ii) quantify the effects of partial crystallinity on the hydrogen permeation properties of these metallic glass membranes.

Analysis on the phase transition behavior of Cu base bulk metallic glass by electrical resistivity measurement

International Nuclear Information System (INIS)

Ji, Young Su; Chung, Sung Jae; Ok, Myoung-Ryul; Hong, Kyung Tae; Suh, Jin-Yoo; Byeon, Jai Won; Yoon, Jin-Kook; Lee, Kyung Hwan; Lee, Kyung Sub

2007-01-01

The crystallization behavior of Cu 43 Zr 43 Al 7 Ag 7 (numbers indicate at.%) bulk metallic glass was investigated using the isothermal electrical resistivity measurements at 450 deg. C in the supercooled liquid region. The crystallization process is a single step phase transformation. To analyze the electrical resistivity reduction, microstructure evolutions were analyzed using differential scanning calorimetry, X-ray diffraction, transmission electron microscopy and small-angle X-ray scattering. The Avrami parameter of the electrical resistivity reduction step was 1.73, indicating that the crystallization process is a diffusion-controlled growth of intermetallic compounds with decreasing nucleation rate

A Zr-based bulk metallic glass for future stent applications: Materials properties, finite element modeling, and in vitro human vascular cell response.

Science.gov (United States)

Huang, Lu; Pu, Chao; Fisher, Richard K; Mountain, Deidra J H; Gao, Yanfei; Liaw, Peter K; Zhang, Wei; He, Wei

2015-10-01

Despite the prevalent use of crystalline alloys in current vascular stent technology, new biomaterials are being actively sought after to improve stent performance. In this study, we demonstrated the potential of a Zr-Al-Fe-Cu bulk metallic glass (BMG) to serve as a candidate stent material. The mechanical properties of the Zr-based BMG, determined under both static and cyclic loadings, were characterized by high strength, which would allow for the design of thinner stent struts to improve stent biocompatibility. Finite element analysis further complemented the experimental results and revealed that a stent made of the Zr-based BMG was more compliant with the beats of a blood vessel, compared with medical 316L stainless steel. The Zr-based BMG was found to be corrosion resistant in a simulated body environment, owing to the presence of a highly stable ZrO2-rich surface passive film. Application-specific biocompatibility studies were conducted using human aortic endothelial cells and smooth muscle cells. The Zr-Al-Fe-Cu BMG was found to support stronger adhesion and faster coverage of endothelial cells and slower growth of smooth muscle cells than 316L stainless steel. These results suggest that the Zr-based BMG could promote re-endothelialization and potentially lower the risk of restenosis, which are critical to improve vascular stent implantation integration. In general, findings in this study raised the curtain for the potential application of BMGs as future candidates for stent applications. Vascular stents are medical devices typically used to restore the lumen of narrowed or clogged blood vessel. Despite the clinical success of metallic materials in stent-assisted angioplasty, post-surgery complications persist due to the mechanical failures, corrosion, and in-stent restenosis of current stents. To overcome these hurdles, strategies including new designs and surface functionalization have been exercised. In addition, the development of new materials with

Cluster-based bulk metallic glass formation in Fe-Si-B-Nb alloy systems

Energy Technology Data Exchange (ETDEWEB)

Zhu, C L; Wang, Q; Li, F W; Li, Y H; Wang, Y M; Dong, C [State Key Laboratory of Materials Modification, Dalian University of Technology (DUT), Dalian 116024 (China); Zhang, W; Inoue, A, E-mail: dong@dlut.edu.c [Institute for Materials Research (IMR), Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan)

2009-01-01

Bulk metallic glass formations have been explored in Fe-B-Si-Nb alloy system using the so-called atomic cluster line approach in combination with minor alloying guideline. The atomic cluster line refers to a straight line linking binary cluster to the third element in a ternary system. The basic ternary compositions in Fe-B-Si system are determined by the inetersection points of two cluster lines, namely Fe-B cluster to Si and Fe-Si cluster to B, and then further alloyed with 3-5 at. % Nb for enhancing glass forming abilities. BMG rods with a diameter of 3 mm are formed under the case of minor Nb alloying the basic intersecting compositions of Fe{sub 8}B{sub 3}-Si with Fe{sub 12}Si-B and Fe{sub 8}B{sub 2}-Si with Fe{sub 9}Si-B. The BMGs also exhibit high Vickers hardness (H{sub v}) of 1130-1164 and high Young's modulous (E) of 170-180 GPa

Improved Plasticity of Ti-Based Bulk Metallic Glass at Room Temperature by Electroless Thin Nickel Coating

Directory of Open Access Journals (Sweden)

Xin Wang

2017-12-01

Full Text Available By restricting the dilated deformation, surface modification can stimulate multiple shear banding and improve the plasticity of bulk metallic glasses (BMGs. Aimed at modifying the surface of BMGs by thin layers, a crystalline Ni coating with ultrafine grains was coated on the surface of a Ti-based BMG by electroless plating. With a thickness of about 10 μm, the prepared thin coating could effectively limit the fast propagation of primary shear bands and stimulate the nucleation of multiple shear bands. As a result, the compression plasticity of the coated Ti-based BMG was improved to about 3.7% from near 0% of the non-coated BMG. Except for a small amount of Ni coating was adhered to the BMG substrate after fracture, most of the coatings were peeled off from the surface. It can be attributed to the abnormal growth of some coarse grains/particles in local region of the coating, which induces a large tensile stress at the interface between the coating and the BMG substrate. It is suggested that, for electroless nickel plating, improving the adhesive bonding strength between the coating and the substrate has a better geometric restriction effect than simply increasing the thickness of the coating.

The structural properties of Zr-based bulk metallic glasses subjected to high pressure torsion at different temperatures

International Nuclear Information System (INIS)

Boltynjuk, E. V.; Ubyivovk, E. V.; Kshumanev, A. M.; Gunderov, D. V.; Lukianov, A. V.; Bednarz, A.; Valiev, R. Z.

2016-01-01

The structural properties of a Zr_6_2Cu_2_2Al_1_0Fe_5Dy_1 bulk metallic glasses were investigated. Cylindrical rods of the Zr_6_2Cu_2_2Al_1_0Fe_5Dy_1 BMG were subjected to high pressure torsion at temperatures of 20°C and 150°C. X-ray diffraction, transmission electron microscopy were used to determine peculiarities of the modified structure. Analysis of fracture surfaces, nanohardness measurements were conducted to investigate the influence of structural changes on mechanical behavior of processed samples.

NMR signature of evolution of ductile-to-brittle transition in bulk metallic glasses.

Science.gov (United States)

Yuan, C C; Xiang, J F; Xi, X K; Wang, W H

2011-12-02

The mechanical properties of monolithic metallic glasses depend on the structures at atomic or subnanometer scales, while a clear correlation between mechanical behavior and structures has not been well established in such amorphous materials. In this work, we find a clear correlation of (27)Al NMR isotropic shifts with a microalloying induced ductile-to-brittle transition at ambient temperature in bulk metallic glasses, which indicates that the (27)Al NMR isotropic shift can be regarded as a structural signature to characterize plasticity for this metallic glass system. The study provides a compelling approach for investigating and understanding the mechanical properties of metallic glasses from the point of view of electronic structure. © 2011 American Physical Society

Metastability and thermophysical properties of metallic bulk glass forming alloys

International Nuclear Information System (INIS)

Wunderlich, R.K.; Fecht, H.J.

1998-01-01

The absence of crystallization over a wide time/temperature window can be used to produce bulk metallic glass by relatively slow cooling of the melt. For a number of alloys, including several multicomponent Zr-based alloys, the relevant thermodynamic and thermomechanical properties of the metastable glassy and undercooled liquid states have been measured below and above the glass transition temperature. These measurements include specific heat, viscosity, volume, and elastic properties as a function of temperature. As a result, it becomes obvious that the maximum undercooling for these alloys is given by an isentropic condition before an enthalpic or isochoric instability is reached. Alternatively, these glasses can also be produced by mechanical alloying, thus replacing the thermal disorder by static disorder and resulting in the same thermodynamic glass state. During heating through the undercooled liquid, a nanoscale phase separation occurs for most glasses as a precursor of crystallization

The structural properties of Zr-based bulk metallic glasses subjected to high pressure torsion at different temperatures

Energy Technology Data Exchange (ETDEWEB)

Boltynjuk, E. V., E-mail: boltynjuk@gmail.com; Ubyivovk, E. V.; Kshumanev, A. M. [Saint Petersburg State University, 28 Universitetskiy pr., Saint Petersburg, 198504 (Russian Federation); Gunderov, D. V.; Lukianov, A. V. [Ufa State Aviation Technical University, K. Marks 12, Ufa, 450000 (Russian Federation); Bednarz, A. [Faculty of Mechanical Engineering and Aeronautics, Department of Aircraft and Aircraft Engines, Rzeszow University of Technology, Al. Powstancow Warszawy 8, 35-959 Rzeszow (Poland); Valiev, R. Z. [Saint Petersburg State University, 28 Universitetskiy pr., Saint Petersburg, 198504 (Russian Federation); Ufa State Aviation Technical University, K. Marks 12, Ufa, 450000 (Russian Federation)

2016-06-17

The structural properties of a Zr{sub 62}Cu{sub 22}Al{sub 10}Fe{sub 5}Dy{sub 1} bulk metallic glasses were investigated. Cylindrical rods of the Zr{sub 62}Cu{sub 22}Al{sub 10}Fe{sub 5}Dy{sub 1} BMG were subjected to high pressure torsion at temperatures of 20°C and 150°C. X-ray diffraction, transmission electron microscopy were used to determine peculiarities of the modified structure. Analysis of fracture surfaces, nanohardness measurements were conducted to investigate the influence of structural changes on mechanical behavior of processed samples.

Deformation-strengthening during rolling Cu60Zr20Ti20 bulk metallic glass

DEFF Research Database (Denmark)

Cao, Q.P.; Li, J.F.; Hu, Yuyan

2007-01-01

Mechanical strength evolutions during rolling the Cu60Zr20Ti20 bulk metallic glass (BMG) at room temperature (RT) and cryogenic temperature (CT) have been investigated by measuring the microhardness. The hardness slightly increases during the initial rolling stage as a result of the gradually...

Dry Sliding Wear Behavior of Spark Plasma Sintered Fe-Based Bulk Metallic Glass/Graphite Composites

Directory of Open Access Journals (Sweden)

Xiulin Ji

2016-09-01

Full Text Available Bulk metallic glass (BMG and BMG-graphite composites were fabricated using spark plasma sintering at the sintering temperature of 575 °C and holding time of 15 min. The sintered composites exhibited partial crystallization and the presence of distributed porosity and graphite particles. The effect of graphite reinforcement on the tribological properties of the BMG/graphite composites was investigated using dry ball-on-disc sliding wear tests. The reinforcement of graphite resulted in a reduction in both the wear rate and the coefficient of friction as compared to monolithic BMG samples. The wear surfaces of BMG/graphite composites showed regions of localized wear loss due to microcracking and fracture, as was also the case with the regions covered with graphite-rich protective film due to smearing of pulled off graphite particles.

Characteristic of improved fatigue performance for Zr-based bulk metallic glass matrix composites

International Nuclear Information System (INIS)

Qiao, J.W.; Huang, E.W.; Wang, G.Y.; Yang, H.J.; Liang, W.; Zhang, Y.; Liaw, P.K.

2013-01-01

Zr 58.5 Ti 14.3 Nb 5.2 Cu 6.1 Ni 4.9 Be 11.0 bulk metallic glass matrix composites exhibit improved four-point-bending fatigue endurance with a fatigue limit of 567 MPa, compared to that under the tension–tension fatigue, due to the high-volume-fractioned dendrites, which can effectively blunt the fatigue-induced cracks. Illuminated by high-energy synchrotron X-ray at 200 and 100 K, the corresponding diffraction peaks, such as (110), (200), and (211) shift rightward to small lattice spacings, compared to those at 298 K. However, the peak widths at 100 K and 200 K are almost identical to that of room temperature. Since an identical fatigue specimen was measured under room temperature, 200 K, and 100 K, the invariant of the peak widths reveal the fact of the irreversible microstructure developments induced by fatigue. Even if the fatigue fracture stress is distinguishingly lower than the yielding strength, the deformation of dendrites locally prevails, evidenced by the occurrence of dislocations

Formation of Ti--Zr--Cu--Ni bulk metallic glasses

International Nuclear Information System (INIS)

Lin, X.H.; Johnson, W.L.

1995-01-01

Formation of bulk metallic glass in quaternary Ti--Zr--Cu--Ni alloys by relatively slow cooling from the melt is reported. Thick strips of metallic glass were obtained by the method of metal mold casting. The glass forming ability of the quaternary alloys exceeds that of binary or ternary alloys containing the same elements due to the complexity of the system. The best glass forming alloys such as Ti 34 Zr 11 Cu 47 Ni 8 can be cast to at least 4-mm-thick amorphous strips. The critical cooling rate for glass formation is of the order of 250 K/s or less, at least two orders of magnitude lower than that of the best ternary alloys. The glass transition, crystallization, and melting behavior of the alloys were studied by differential scanning calorimetry. The amorphous alloys exhibit a significant undercooled liquid region between the glass transition and first crystallization event. The glass forming ability of these alloys, as determined by the critical cooling rate, exceeds what is expected based on the reduced glass transition temperature. It is also found that the glass forming ability for alloys of similar reduced glass transition temperature can differ by two orders of magnitude as defined by critical cooling rates. The origins of the difference in glass forming ability of the alloys are discussed. It is found that when large composition redistribution accompanies crystallization, glass formation is enhanced. The excellent glass forming ability of alloys such as Ti 34 Zr 11 Cu 47 Ni 8 is a result of simultaneously minimizing the nucleation rate of the competing crystalline phases. The ternary/quaternary Laves phase (MgZn 2 type) shows the greatest ease of nucleation and plays a key role in determining the optimum compositions for glass formation. copyright 1995 American Institute of Physics

Enhancement of plasticity of Fe-based bulk metallic glass by Ni substitution for Fe

Energy Technology Data Exchange (ETDEWEB)

Guo, S.F. [State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Li, N.; Zhang, C. [State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); Liu, L., E-mail: sfguo2005@163.co [State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, 430074 Wuhan (China)

2010-08-15

Bulk metallic glasses (BMGs) (Fe{sub 1-x}Ni{sub x}){sub 71}Mo{sub 5}P{sub 12}C{sub 10}B{sub 2} (x = 0, 0.1 and 0.2) with a diameter of 3 mm were synthesized by copper mold casting. The effect of Ni substitution for Fe on the structure, thermal and mechanical properties has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and compressive testing. It was found that the substitution of Ni for Fe enhances the glass forming ability, and improves the plasticity of Fe{sub 71}Mo{sub 5}P{sub 12}C{sub 10}B{sub 2} BMG as indicated by the increase in the plastic strain from 3.1% (x = 0) to 5.2% (x = 0.2). The improvement of the plasticity is discussed in term of the reduction of glass transition temperature and the supercooled liquid region due to the substitution of Ni for Fe.

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

Energy Technology Data Exchange (ETDEWEB)

Hegde, Ganesh, E-mail: ghegde@purdue.edu; Povolotskyi, Michael; Kubis, Tillmann; Klimeck, Gerhard, E-mail: gekco@purdue.edu [Network for Computational Nanotechnology (NCN), Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Boykin, Timothy [Department of Electrical and Computer Engineering, University of Alabama, Huntsville, Alabama (United States)

2014-03-28

Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

International Nuclear Information System (INIS)

Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Klimeck, Gerhard; Boykin, Timothy

2014-01-01

Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

Science.gov (United States)

Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard

2014-03-01

Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.

Characterization of the surface film on Zr-based bulk metallic glass using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM)

International Nuclear Information System (INIS)

Tan Ming; Liu Qiao; Zhang Nian; Hu Huiqin; Li Biao; Kang Xianjie

2011-01-01

Highlights: → In this study, we have made four interesting observations. → First, the composition of Al metal ions in the film of the as-cast metallic glass (41%) is much higher than the nominal Al composition of the alloy (9.5%). → We suggest that this should be attributed to the preferential oxidation of Al atoms. → Second, the composition of Al ions in the film of the immersed metallic glass decreases significantly, indicating that the toxic Al oxide and Al ions in the film are dissolved into the solutions during immersion. → Third, the concentration of Cl - ions has no significant effect on the compositions of metal ions in the film. → Fourth, the composition of Zr ions dominates in the film of the immersed metallic glass, indicating that the ZrO 2 oxide in the film is very hard to get corroded in the corrosive solutions. - Abstract: Using XPS, we have for the first time studied the release of metal ions in the film of the Zr-based bulk metallic glass to the corrosive solutions during immersing. The composition of Al ions in the film of the as-cast metallic glass (41%) is substantially higher than the nominal Al composition of the alloy (9.5%). We proposed that the enriched Al ions can be attributed to the preferential oxidation of Al atoms. After immersing in the NaCl- and HCl-solution, the composition of Al ions in the films decreases from 41% to 28.09% and 21.76%, respectively. This indicates that some of the Al ions in the film are dissolved into the solution during immersion. The composition changes of metal ions in the film of the immersed alloys relative to those of the as-cast metallic glass were discussed using the point defect model. SEM was also used to examine the surface morphology of the samples. No pit corrosion was observed in the SEM images of the immersed metal glass.

Ductile Damage and Fatigue Behavior of Semi-Finished Tailored Blanks for Sheet-Bulk Metal Forming Processes

Science.gov (United States)

Besserer, Hans-Bernward; Hildenbrand, Philipp; Gerstein, Gregory; Rodman, Dmytro; Nürnberger, Florian; Merklein, Marion; Maier, Hans Jürgen

2016-03-01

To produce parts from sheet metal with thickened functional elements, bulk forming operations can be employed. For this new process class, the term sheet-bulk metal forming has been established recently. Since sheet-bulk metal forming processes such as orbital forming generates triaxial stress and strain states, ductile damage is induced in the form of voids in the microstructure. Typical parts will experience cyclic loads during service, and thus, the influence of ductile damage on the fatigue life of parts manufactured by orbital forming is of interest. Both the formation and growth of voids were characterized following this forming process and then compared to the as-received condition of the ferritic deep drawing steel DC04 chosen for this study. Subsequent to the forming operation, the specimens were fatigued and the evolution of ductile damage and the rearrangement of the dislocation networks occurring during cyclic loading were determined. It was shown, that despite an increased ductile damage due to the forming process, the induced strain hardening has a positive effect on the fatigue life of the material. However, by analyzing the fatigued specimens a development of the ductile damage by an increasing number of voids and a change in the void shape were detected.

Crystallization of Pd40CU30Ni10P20 bulk metallic glass with and without pressure

DEFF Research Database (Denmark)

Yang, B.; Jiang, Jianzhong; Zhuang, Yanxin

2007-01-01

The glass-transition behavior of Pd40Cu30Ni10P20 bulk metallic glass was investigated by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD). The effect of pressure on the crystallization behavior of Pd40Cu30Ni10P20 bulk glass was studied by in situ high-pressure and high...

Liquid phase and supercooled liquid phase welding of bulk metallic glasses

International Nuclear Information System (INIS)

Kawamura, Y.

2004-01-01

Recent progress on welding in bulk metallic glasses (BMGs) has been reviewed. BMGs have been successfully welded to BMGs or crystalline metals by liquid phase welding using explosion, pulse-current and electron-beam methods, and by supercooled liquid phase welding using friction method. Successful welding of the liquid phase methods was due to the high glass-forming ability of the BMGs and the high concentration of welding energy in these methods. In contrast, the supercooled liquid phase welding was successful due to the thermally stable supercooled liquid state of the BMGs and the superplasticity and viscous flow of the supercooled liquid. The successful welding of BMGs to BMGs and crystalline materials is promising for the future development of BMGs as engineering materials

Strong work-hardening behavior induced by the solid solution strengthening of dendrites in TiZr-based bulk metallic glass matrix composites

Energy Technology Data Exchange (ETDEWEB)

Ma, D.Q. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Jiao, W.T. [College of Education, Hebei Normal University of Science and Technology, Qinhuangdao 066004 (China); Zhang, Y.F. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Hebei Vocational and Technical College of Building Materials, Qinhuangdao 066004 (China); Wang, B.A.; Li, J.; Zhang, X.Y. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Ma, M.Z., E-mail: mz550509@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Liu, R.P. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

2015-03-05

Highlights: • Hardness of dendrite of TiZr-based BMGMCs increases. • Strong work-hardening behavior is obtained after solid solution strengthening. • Lattice distortions of dendrite suffering from rapid cooling are detected. - Abstract: A series of TiZr-based bulk metallic glass matrix composites (BMGMCs) with distinguished mechanical properties are successfully fabricated by adding different volume fractions of Ta (Ti{sub 38.8}Zr{sub 28.8}Cu{sub 6.2}Be{sub 16.2}Nb{sub 10} as the basic composition, denoted as Ta{sub 0.0}–Ta{sub 8.0}). Along with the growth of precipitated phase, typical dendritic morphology is fully developed in the TiZr-based BMGMCs of Ta{sub 8.0}. Energy-dispersive spectrometry analysis of the dendrites and glass matrix indicates that the metallic elements of Nb and Ta should preferentially form solid solution into dendrites. The chaotic structure of high-temperature precipitate phase is trapped down by the rapid cooling of the copper-mould. The detected lattice distortions in the dendrites are attributed to the strong solid solution strengthening of the metallic elements of Ti, Zr, Nb, and Ta. These lattice distortions increase the resistance of the dislocation motion and pin the dislocations, thus the strength and hardness of dendrite increase. Dendrites create a strong barrier for the shear band propagation and generate multiple shear bands after solid solution strengthening, thereby providing the TiZr-based BMGMCs with greatly improved capacity to sustain plastic deformation and resistance to brittle fracture. Thus, the TiZr-based BMGMCs possess distinguished work-hardening capability. Among these TiZr-based BMGMCs, the sample Ta{sub 0.5} possesses the largest plastic strain (ε{sub p}) at 20.3% and ultimate strength (σ{sub max}) of 2613 MPa during compressive loading. In addition, the sample of Ta{sub 0.5} exhibits work-hardening up to an ultrahigh tensile strength of 1680 MPa during the tensile process, and then progressively

Mechanically driven phase separation and corresponding microhardness change in Cu60Zr20Ti20 bulk metallic glass

DEFF Research Database (Denmark)

Cao, Q.P.; Li, J.F.; Zhou, Y.H.

2005-01-01

Rolling deformation of bulk Cu60Zr20Ti20 metallic glass has been performed at cryogenic temperature. The specimens exhibit excellent ductility, and are rolled up to 97% reduction in thickness without fracture. Crystallization is suppressed during the deformation, however, phase separation is obse...... is observed in the glassy matrix when the thickness reduction exceeds 89%. Once the phase separation occurs, the microhardness of the specimen increases drastically, indicating the existence of work hardening by severe plastic deformation of the metallic glass.......Rolling deformation of bulk Cu60Zr20Ti20 metallic glass has been performed at cryogenic temperature. The specimens exhibit excellent ductility, and are rolled up to 97% reduction in thickness without fracture. Crystallization is suppressed during the deformation, however, phase separation...

Induction detection of concealed bulk banknotes

Science.gov (United States)

Fuller, Christopher; Chen, Antao

2012-06-01

The smuggling of bulk cash across borders is a serious issue that has increased in recent years. In an effort to curb the illegal transport of large numbers of paper bills, a detection scheme has been developed, based on the magnetic characteristics of bank notes. The results show that volumes of paper currency can be detected through common concealing materials such as plastics, cardboard, and fabrics making it a possible potential addition to border security methods. The detection scheme holds the potential of also reducing or eliminating false positives caused by metallic materials found in the vicinity, by observing the stark difference in received signals caused by metal and currency. The detection scheme holds the potential to detect for both the presence and number of concealed bulk notes, while maintaining the ability to reduce false positives caused by metal objects.

High pressure die casting of Fe-based metallic glass

Science.gov (United States)

Ramasamy, Parthiban; Szabo, Attila; Borzel, Stefan; Eckert, Jürgen; Stoica, Mihai; Bárdos, András

2016-01-01

Soft ferromagnetic Fe-based bulk metallic glass key-shaped specimens with a maximum and minimum width of 25.4 and 5 mm, respectively, were successfully produced using a high pressure die casting (HPDC) method, The influence of die material, alloy temperature and flow rate on the microstructure, thermal stability and soft ferromagnetic properties has been studied. The results suggest that a steel die in which the molten metal flows at low rate and high temperature can be used to produce completely glassy samples. This can be attributed to the laminar filling of the mold and to a lower heat transfer coefficient, which avoids the skin effect in the steel mold. In addition, magnetic measurements reveal that the amorphous structure of the material is maintained throughout the key-shaped samples. Although it is difficult to control the flow and cooling rate of the molten metal in the corners of the key due to different cross sections, this can be overcome by proper tool geometry. The present results confirm that HPDC is a suitable method for the casting of Fe-based bulk glassy alloys even with complex geometries for a broad range of applications. PMID:27725780

High pressure die casting of Fe-based metallic glass.

Science.gov (United States)

Ramasamy, Parthiban; Szabo, Attila; Borzel, Stefan; Eckert, Jürgen; Stoica, Mihai; Bárdos, András

2016-10-11

Soft ferromagnetic Fe-based bulk metallic glass key-shaped specimens with a maximum and minimum width of 25.4 and 5 mm, respectively, were successfully produced using a high pressure die casting (HPDC) method, The influence of die material, alloy temperature and flow rate on the microstructure, thermal stability and soft ferromagnetic properties has been studied. The results suggest that a steel die in which the molten metal flows at low rate and high temperature can be used to produce completely glassy samples. This can be attributed to the laminar filling of the mold and to a lower heat transfer coefficient, which avoids the skin effect in the steel mold. In addition, magnetic measurements reveal that the amorphous structure of the material is maintained throughout the key-shaped samples. Although it is difficult to control the flow and cooling rate of the molten metal in the corners of the key due to different cross sections, this can be overcome by proper tool geometry. The present results confirm that HPDC is a suitable method for the casting of Fe-based bulk glassy alloys even with complex geometries for a broad range of applications.

High pressure die casting of Fe-based metallic glass

Science.gov (United States)

Ramasamy, Parthiban; Szabo, Attila; Borzel, Stefan; Eckert, Jürgen; Stoica, Mihai; Bárdos, András

2016-10-01

Soft ferromagnetic Fe-based bulk metallic glass key-shaped specimens with a maximum and minimum width of 25.4 and 5 mm, respectively, were successfully produced using a high pressure die casting (HPDC) method, The influence of die material, alloy temperature and flow rate on the microstructure, thermal stability and soft ferromagnetic properties has been studied. The results suggest that a steel die in which the molten metal flows at low rate and high temperature can be used to produce completely glassy samples. This can be attributed to the laminar filling of the mold and to a lower heat transfer coefficient, which avoids the skin effect in the steel mold. In addition, magnetic measurements reveal that the amorphous structure of the material is maintained throughout the key-shaped samples. Although it is difficult to control the flow and cooling rate of the molten metal in the corners of the key due to different cross sections, this can be overcome by proper tool geometry. The present results confirm that HPDC is a suitable method for the casting of Fe-based bulk glassy alloys even with complex geometries for a broad range of applications.

Influence of friction on the residual morphology, the penetration load and the residual stress distribution of a Zr-based bulk metallic glass

Directory of Open Access Journals (Sweden)

Hu Huang

2013-04-01

Full Text Available In this paper, friction between the Cube-Corner indenter and the sample surface of a Zr-based bulk metallic glass (BMG was analyzed and discussed by the experimental method, the theoretical method and the finite element simulation. Linear residua are observed on the surface of the indenter for the first time, which gives the direct evidence that strong interaction processes exist between the indenter surface and the sample surface because of strong friction and local high contact press. A simplified model was developed to correct the penetration load with the consideration of friction. Effects of friction on the penetration load-depth curves, plastic flow, surface deformation and residual stress distribution of the sample with different friction coefficients were investigated by the finite element simulation.

The effect of liquid phase separation on the Vickers microindentation shear bands evolution in a Fe-based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Askari-Paykani, M. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, North Kargar Street, Tehran 11356-4563 (Iran, Islamic Republic of); Nili Ahmadabadi, M., E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, North Kargar Street, Tehran 11356-4563 (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Seiffodini, A. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, North Kargar Street, Tehran 11356-4563 (Iran, Islamic Republic of); Yazd University, Department of Material Science and Engineering, Yazd 84196 (Iran, Islamic Republic of)

2013-11-15

The Vickers microindentation experiments and associated plastic deformation in as-cast and annealed (Fe{sub 0.9}Ni{sub 0.1}){sub 77}Mo{sub 5}P{sub 9}C{sub 7.5}B{sub 1.5} bulk metallic glass was conducted. In addition to the bulk indentation behavior, the shear band morphology underneath the Vickers microindenter was examined by employing the bonded interface technique. Microstructural characterization revealed that a liquid phase separation occurred during melting process. Atomic force microscopy of the glassy matrix of the as-cast specimen reveals the composition inhomogeneity induced by the liquid phase separation. This effect generates shear band branching or deflection during the shear band propagation. For the bulk indentation, the trends in the hardness vs. indentation load were found related to the pressure sensitive index and the phase separation process simultaneously. The results show that the as-cast as well as the annealed specimens are deformed through semi-circular and radial shear bands. In addition, in the partially crystalized specimen, the change in the properties and microstructure of the BMG induced by the partial crystallization treatment and phase separation process resulted in tertiary shear bands formation.

Relation between calculated Lennard-Jones potential and thermal stability of Cu-based bulk metallic glasses

International Nuclear Information System (INIS)

Lin, T.; Bian, X.F.; Jiang, J.

2006-01-01

Two metallic bulk glasses, Cu 60 Zr 30 Ti 10 and Cu 47 Ti 33 Zr 11 Ni 8 Si 1 , with a diameter of 3 mm were prepared by copper mold casting method. Dilatometric measurement was carried out on the two glassy alloys to obtain information about the average nearest-neighbour distance r 0 and the effective depth of pair potential V 0 . By assuming a Lennard-Jones potential, r 0 and V 0 were calculated to be 0.28 nm and 0.16 eV for Cu 60 Zr 30 Ti 10 and 0.27 nm and 0.13 eV for Cu 47 Ti 33 Zr 11 Ni 8 Si 1 , respectively. It was found that the glassy alloy Cu 60 Zr 30 Ti 10 was more stable than Cu 47 Ti 33 Zr 11 Ni 8 Si 1 against heating from both experiment and calculation

A combined arc-melting and tilt-casting furnace for the manufacture of high-purity bulk metallic glass materials.

Science.gov (United States)

Soinila, E; Pihlajamäki, T; Bossuyt, S; Hänninen, H

2011-07-01

An arc-melting furnace which includes a tilt-casting facility was designed and built, for the purpose of producing bulk metallic glass specimens. Tilt-casting was chosen because reportedly, in combination with high-purity processing, it produces the best fatigue endurance in Zr-based bulk metallic glasses. Incorporating the alloying and casting facilities in a single piece of equipment reduces the amount of laboratory space and capital investment needed. Eliminating the sample transfer step from the production process also saves time and reduces sample contamination. This is important because the glass forming ability in many alloy systems, such as Zr-based glass-forming alloys, deteriorates rapidly with increasing oxygen content of the specimen. The challenge was to create a versatile instrument, in which high purity conditions can be maintained throughout the process, even when melting alloys with high affinity for oxygen. Therefore, the design provides a high-vacuum chamber to be filled with a low-oxygen inert atmosphere, and takes special care to keep the system hermetically sealed throughout the process. In particular, movements of the arc-melting electrode and sample manipulator arm are accommodated by deformable metal bellows, rather than sliding O-ring seals, and the whole furnace is tilted for tilt-casting. This performance of the furnace is demonstrated by alloying and casting Zr(55)Cu(30)Al(10)Ni(5) directly into rods up to ø 10 mm which are verified to be amorphous by x-ray diffraction and differential scanning calorimetry, and to exhibit locally ductile fracture at liquid nitrogen temperature.

Analysis of Pressure-Volume Relationship for Bulk Metallic Glasses

Directory of Open Access Journals (Sweden)

H. K. Rai

2008-01-01

Full Text Available Relationship between compression (V/V0 and pressure have been studied for five bulk metallic glasses (BMGs viz. Zr41Ti14Cu12.5Ni10Be22.5, Zr41Ti14Cu12.5Ni9Be22.5C1, Zr48Nb8Cu12Fe8Be24, (Zr0.59Ti0.06Cu0.22Ni0.1385.7Al14.3 and SiO2.TiO2 in the compression ranges of V/V0 =1.00 to V/V0 = 0.10. Six forms of equation of state reported in the literature have been used in the present study to calculate pressure corresponding to different values of compressions. The comparison of graph plotted between the logarithms of calculated value of pressure to logarithm of calculated value of compression (V/V0 reveals that the agreement of Brennan-Stacey equation of state (EOS and Poirier-Tarantolla equation of state are not good. It has been found that the assumptions, on which these equations are based, do not satisfy well in case of given BMGs.

Effect of shock pressure on the structure and superconducting properties of Y-Ba-Cu-O in explosively fabricated bulk metal-matrix composites

Science.gov (United States)

Murr, L. E.; Niou, C. S.; Pradhan-Advani, M.

1991-01-01

While it is now well established that copper-oxide-based power, or virtually any other ceramic superconductor powder, can be consolidated and encapsulated within a metal matrix by explosive consolidation, the erratic superconductivity following fabrication has posed a major problem for bulk applications. The nature of this behavior was found to arise from microstructural damage created in the shock wave front, and the residual degradation in superconductivity was demonstrated to be directly related to the peak shock pressure. The explosively fabricated or shock loaded YBa2Cu3Ox examples exhibit drastically altered rho (or R) - T curves. The deterioration in superconductivity is even more noticeable in the measurement of ac magnetic susceptibility and flux exclusion or shielding fraction which is also reduced in proportion to increasing peak shock pressure. The high frequency surface resistance (in the GHz range) is also correspondingly compromised in explosively fabricated, bulk metal-matrix composites based on YBa2Cu3O7. Transmission electron microscopy (including lattice imaging techniques) is being applied in an effort to elucidate the fundamental (microstructural) nature of the shock-induced degradation of superconductivity and normal state conductivity. One focus of TEM observations has assumed that oxygen displaced from b-chains rather than oxygen-vacancy disorder in the basal plane of oxygen deficient YBa2Cu3Ox may be a prime mechanism. Shock-wave displaced oxygen may also be locked into new positions or interstitial clusters or chemically bound to displaced metal (possibly copper) atoms to form precipitates, or such displacements may cause the equivalent of local lattice cell changes as a result of stoichiometric changes. While the shock-induced suppression of T(sub c) is not desirable in the explosive fabrication of bulk metal-matrix superconductors, it may be turned into an advantage if the atomic-scale distortion can be understood and controlled as local

Degradation of Zr-based bulk metallic glasses used in load-bearing implants: A tribocorrosion appraisal.

Science.gov (United States)

Zhao, Guo-Hua; Aune, Ragnhild E; Mao, Huahai; Espallargas, Nuria

2016-07-01

Owing to the amorphous structure, Bulk Metallic Glasses (BMGs) have been demonstrating attractive properties for potential biomedical applications. In the present work, the degradation mechanisms of Zr-based BMGs with nominal compositions Zr55Cu30Ni5Al10 and Zr65Cu18Ni7Al10 as potential load-bearing implant material were investigated in a tribocorrosion environment. The composition-dependent micro-mechanical and tribological properties of the two BMGs were evaluated prior to the tribocorrosion tests. The sample Zr65-BMG with a higher Zr content exhibited increased plasticity but relatively reduced wear resistance during the ball-on-disc tests. Both BMGs experienced abrasive wear after the dry wear test under the load of 2N. The cross-sectional subsurface structure of the wear track was examined by Focused Ion Beam (FIB). The electrochemical properties of the BMGs in simulated body fluid were evaluated by means of potentiodynamic polarization and X-ray Photoelectron Spectroscopy (XPS). The spontaneous passivation of Zr-based BMGs in Phosphate Buffer Saline solution was mainly attributed to the highly concentrated zirconium cation (Zr(4+)) in the passive film. The tribocorrosion performance of the BMGs was investigated using a reciprocating tribometer equipped with an electrochemical cell. The more passive nature of the Zr65-BMG had consequently a negative influence on its tribocorrosion resistance, which induced the wear-accelerated corrosion and eventually speeded-up the degradation process. It has been revealed the galvanic coupling was established between the depassivated wear track and the surrounding passive area, which is the main degradation mechanism for the passive Zr65-BMG subjected to the tribocorrosion environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Biocompatible Ni-free Zr-based bulk metallic glasses with high-Zr-content: compositional optimization for potential biomedical applications.

Science.gov (United States)

Hua, Nengbin; Huang, Lu; Chen, Wenzhe; He, Wei; Zhang, Tao

2014-11-01

The present study designs and prepares Ni-free Zr60+xTi2.5Al10Fe12.5-xCu10Ag5 (at.%, x=0, 2.5, 5) bulk metallic glasses (BMGs) by copper mold casting for potential biomedical application. The effects of Zr content on the in vitro biocompatibility of the Zr-based BMGs are evaluated by investigating mechanical properties, bio-corrosion behavior, and cellular responses. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high notch toughness. Electrochemical measurements demonstrate that the Zr-based BMGs are corrosion resistant in a phosphate buffered saline solution. The bio-corrosion resistance of BMGs is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. Regular cell responses of mouse MC3T3-E1 cells, including cell adhesion and proliferation, are observed on the Zr-Ti-Al-Fe-Cu-Ag BMGs, which reveals their general biosafety. The high-Zr-based BMGs exhibit a higher cell proliferation activity in comparison with that of pure Zr and Ti-6Al-4V alloy. The effects of Zr content on the in vitro biocompatibility can be used to guide the future design of biocompatible Zr-based BMGs. Copyright © 2014 Elsevier B.V. All rights reserved.

Formation of bulk metallic glasses in the Fe-M-Y-B (M = transition metal) system

Energy Technology Data Exchange (ETDEWEB)

Huang, X.M. [International Center for New-Structured Materials (ICNSM) and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Chang, C.T. [Institute for Material Research, Tohoku University, Sendai 980-8577 (Japan); Chang, Z.Y.; Wang, X.D.; Cao, Q.P. [International Center for New-Structured Materials (ICNSM) and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Shen, B.L.; Inoue, A. [Institute for Material Research, Tohoku University, Sendai 980-8577 (Japan); Jiang, J.Z. [International Center for New-Structured Materials (ICNSM) and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)], E-mail: jiangjz@zju.edu.cn

2008-07-28

In this work, quaternary Fe{sub 72-x}M{sub x}Y{sub 6}B{sub 22} (M = Ni, Co and Mo) bulk metallic glasses (BMGs) have been developed. It is found that a fully amorphous Fe{sub 68}Mo{sub 4}Y{sub 6}B{sub 22} cylindrical rod with 6.5 mm in diameter can be prepared by copper mold injection. These alloys have a high glass transition temperature of about 900 K with high fracture strengths up to about 3 GPa although they are still brittle. Magnetic measurements reveal that they are ferromagnetic at ambient temperature with low coercive force of about 2 A/m, saturation magnetization of about 0.7 T and effective permeability of about 7000 at 100 kHz. The newly developed Fe-based quaternary alloys exhibit excellent combination properties: superior glass forming ability (GFA), high glass transition temperature, and soft magnetic properties, which could have potential applications in electronic industries. Furthermore, the effect of Mo addition on GFA in the Fe-Y-B BMG system has been discussed compared with those of Ni and Co additions.

Formation of hydroxyapatite on Ti-coated Ti-Zr-Cu-Pd bulk metallic glass

International Nuclear Information System (INIS)

Qin, F.X.; Wang, X.M.; Wada, T.; Xie, G.Q.; Asami, K.; Inoue, A.

2009-01-01

In this research, Ti coating was conducted on Ti 40 Zr 10 Cu 36 Pd 14 bulk metallic glass (BMG) in order to increase the formation rate of hydroxyapatite layer. The formation behavior of bone-like hydroxyapatite on Ti-coated and uncoated Ti 40 Zr 10 Cu 36 Pd 14 bulk metallic glasses (BMGs) was studied. The surface morphology of Ti-coated and uncoated Ti 40 Zr 10 Cu 36 Pd 14 BMG was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The results revealed that the alkali pretreatment in 5 M NaOH solution at 60degC for 24 h had a beneficial effect on the formation of porous sodium titanate on Ti-coated Ti 40 Zr 10 Cu 36 Pd 14 BMG. A bone-like hydroxyapatite layer was able to form on the alkali-treated Ti-coated Ti 40 Zr 10 Cu 36 Pd 14 BMG after a short-time immersion in simulated body fluid (SBF). On the contrary, hydroxyapatite formation was not observed on the uncoated Ti 40 Zr 10 Cu 36 Pd 14 BMG after the same chemical treatments. (author)

Review on progressive microforming of bulk metal parts directly using sheet metals (Keynote Paper

Directory of Open Access Journals (Sweden)

Fu M.W.

2015-01-01

Full Text Available Due to the ubiquitous trend of product miniaturization, energy saving and weight reduction, micro/meso-scale parts have been widely used in many industrial clusters. Micromanufacturing processes for production of such micro/meso-scale parts are thus critically needed. Microforming, as one of these micro manufacturing processes, is a promising process and thus got many explorations and researches. Compared with the research on size effect affected deformation behaviours, less attention has been paid to the process development for mass production of micro-parts. The product quality and fabrication productivity of micro-parts depend on the involved process chain. To address the difficulty in handling and transporting of the micro-sized workpiece, development of a progressive microforming process for directly fabricating bulk micro-parts using sheet metals seems quite promising as it avoids or facilitates billet handling, transportation, positioning, and ejection in the process chain. In this paper, an intensive review on the latest development of progressive microforming technologies is presented. First of all, the paper summarizes the characteristic of progressive microforming directly using sheet metal. The size effect-affected deformation behaviour and the dimensional accuracy, deformation load, ductile fracture, and the surface finish of the microformed parts by progressive microforming using sheet metals are then presented. Finally, some research issues from the implementation of mass production perspective are also discussed.

Electrical analysis of high dielectric constant insulator and metal gate metal oxide semiconductor capacitors on flexible bulk mono-crystalline silicon

KAUST Repository

Ghoneim, Mohamed T.

2015-06-01

We report on the electrical study of high dielectric constant insulator and metal gate metal oxide semiconductor capacitors (MOSCAPs) on a flexible ultra-thin (25 μm) silicon fabric which is peeled off using a CMOS compatible process from a standard bulk mono-crystalline silicon substrate. A lifetime projection is extracted using statistical analysis of the ramping voltage (Vramp) breakdown and time dependent dielectric breakdown data. The obtained flexible MOSCAPs operational voltages satisfying the 10 years lifetime benchmark are compared to those of the control MOSCAPs, which are not peeled off from the silicon wafer. © 2014 IEEE.

Schottky diodes between Bi2S3 nanorods and metal nanoparticles in a polymer matrix as hybrid bulk-heterojunction solar cells

International Nuclear Information System (INIS)

Saha, Sudip K.; Pal, Amlan J.

2015-01-01

We report the use of metal-semiconductor Schottky junctions in a conjugated polymer matrix as solar cells. The Schottky diodes, which were formed between Bi 2 S 3 nanorods and gold nanoparticles, efficiently dissociated photogenerated excitons. The bulk-heterojunction (BHJ) devices based on such metal-semiconductor Schottky diodes in a polymer matrix therefore acted as an efficient solar cell as compared to the devices based on only the semiconductor nanorods in the polymer matrix or when gold nanoparticles were added separately to the BHJs. In the latter device, gold nanoparticles offered plasmonic enhancement due to an increased cross-section of optical absorption. We report growth and characteristics of the Schottky junctions formed through an intimate contact between Bi 2 S 3 nanorods and gold nanoparticles. We also report fabrication and characterization of BHJ solar cells based on such heterojunctions. We highlight the benefit of using metal-semiconductor Schottky diodes over only inorganic semiconductor nanorods or quantum dots in a polymer matrix in forming hybrid BHJ solar cells

Determination of bulk and interface density of states in metal oxide semiconductor thin-film transistors by using capacitance-voltage characteristics

Science.gov (United States)

Wei, Xixiong; Deng, Wanling; Fang, Jielin; Ma, Xiaoyu; Huang, Junkai

2017-10-01

A physical-based straightforward extraction technique for interface and bulk density of states in metal oxide semiconductor thin film transistors (TFTs) is proposed by using the capacitance-voltage (C-V) characteristics. The interface trap density distribution with energy has been extracted from the analysis of capacitance-voltage characteristics. Using the obtained interface state distribution, the bulk trap density has been determined. With this method, for the interface trap density, it is found that deep state density nearing the mid-gap is approximately constant and tail states density increases exponentially with energy; for the bulk trap density, it is a superposition of exponential deep states and exponential tail states. The validity of the extraction is verified by comparisons with the measured current-voltage (I-V) characteristics and the simulation results by the technology computer-aided design (TCAD) model. This extraction method uses non-numerical iteration which is simple, fast and accurate. Therefore, it is very useful for TFT device characterization.

[Recycle of contaminated scrap metal]: Task 1.3.2, Bulk solids feed system. Topical report, October 1993-- January 1996

International Nuclear Information System (INIS)

1996-07-01

A critical requirement in DOE's efforts to recycle, reuse, and dispose of materials from its decontamination and decommissioning activities is the design of a robust system to process a wide variety of bulk solid feeds. The capability to process bulk solids will increase the range of materials and broaden the application of Catalytic Extraction Processing (CEP). The term bulk solids refers to materials that are more economically fed into the top of a molten metal bath than by submerged injection through a tuyere. Molten Metal Technology, Inc. (MMT) has characterized CEP's ability to process bulk solid feed materials and has achieved significant growth in the size of bulk solid particles compatible with Catalytic Extraction Processing. Parametric experimental studies using various feed materials representative of the components of various DOE waste streams have validated design models which establish the reactor operating range as a function of feed material, mass flow rate, and particle size. MMT is investigating the use of a slurry system for bulk solid addition as it is the most efficient means for injecting soils, sludges, and similar physical forms into a catalytic processing unit. MMT is continuing to evaluate condensed phase product removal systems and alternative energy addition sources to enhance the operating efficiency of bulk solids CEP units. A condensed phase product removal system capable of on-demand product removal has been successfully demonstrated. MMT is also investigating the use of a plasma arc torch to provide supplemental heating during bulk solids processing. This comprehensive approach to bulk solids processing is expected to further improve overall process efficiency prior to the deployment of CEP for the recycle, reuse, and disposal of materials from DOE decontamination and decommissioning Activities

Investigation of fatigue strength of tool steels in sheet-bulk metal forming

Science.gov (United States)

Pilz, F.; Gröbel, D.; Merklein, M.

2018-05-01

To encounter trends regarding an efficient production of complex functional components in forming technology, the process class of sheet-bulk metal forming (SBMF) can be applied. SBMF is characterized by the application of bulk forming operations on sheet metal, often in combination with sheet forming operations [1]. The combination of these conventional process classes leads to locally varying load conditions. The resulting load conditions cause high tool loads, which lead to a reduced tool life, and an uncontrolled material flow. Several studies have shown that locally modified tool surfaces, so-called tailored surfaces, have the potential to control the material flow and thus to increase the die filling of functional elements [2]. A combination of these modified tool surfaces and high tool loads in SBMF is furthermore critical for the tool life and leads to fatigue. Tool fatigue is hardly predictable and due to a lack of data [3], a challenge in tool design. Thus, it is necessary to provide such data for tool steels used in SBMF. The aim of this study is the investigation of the influence of tailored surfaces on the fatigue strength of the powder metallurgical tool steel ASP2023 (1.3344, AISI M3:2), which is typically used in cold forging applications, with a hardness 60 HRC ± 1 HRC. To conduct this investigation, the rotating bending test is chosen. As tailored surfaces, a DLC-coating and a surface manufactured by a high-feed-milling process are chosen. As reference a polished surface which is typical for cold forging tools is used. Before the rotating bending test, the surface integrity is characterized by measuring topography and residual stresses. After testing, the determined values of the surface integrity are correlated with the reached fracture load cycle to derive functional relations. Based on the gained results the investigated tailored surfaces are evaluated regarding their feasibility to modify tool surfaces within SBMF.

Flexible thermoelectric generator using bulk legs and liquid metal interconnects for wearable electronics

International Nuclear Information System (INIS)

Suarez, Francisco; Parekh, Dishit P.; Ladd, Collin; Vashaee, Daryoosh; Dickey, Michael D.; Öztürk, Mehmet C.

2017-01-01

Highlights: •Flexible thermoelectric generator (TEG) with bulk legs. •Flexible thermoelectric generator with liquid metal interconnects. •Flexible TEG with potential to match the performance of rigid TEGs. •Flexible TEG for wearable electronics. -- Abstract: Interest in wearable electronics for continuous, long-term health and performance monitoring is rapidly increasing. The reduction in power levels consumed by sensors and electronic circuits accompanied by the advances in energy harvesting methods allows for the realization of self-powered monitoring systems that do not have to rely on batteries. For wearable electronics, thermoelectric generators (TEGs) offer the unique ability to continuously convert body heat into usable energy. For body harvesting, it is preferable to have TEGs that are thin, soft and flexible. Unfortunately, the performances of flexible modules reported to date have been far behind those of their rigid counterparts. This is largely due to lower efficiencies of the thermoelectric materials, electrical or thermal parasitic losses and limitations on leg dimensions posed by the synthesis techniques. In this work, we present an entirely new approach and explore the possibility of using standard bulk legs in a flexible package. Bulk thermoelectric legs cut from solid ingots are far superior to thermoelectric materials synthesized using other techniques. A key enabler of the proposed technology is the use of EGaIn liquid metal interconnects, which not only provide extremely low interconnect resistance but also stretchability with self-healing, both of which are essential for flexible TE modules. The results suggest that this novel approach can finally produce flexible TEGs that have the potential to challenge the rigid TEGs and provide a pathway for the realization of self-powered wearable electronics.

Fine Coining of Bulk Metal Formed Parts in Digital Environment

International Nuclear Information System (INIS)

Pepelnjak, T.; Kuzman, K.; Krusic, V.

2007-01-01

At present the production of bulk metal formed parts in the automotive industry must increasingly fulfil demands for narrow tolerance fields. The final goal of the million parts production series is oriented towards zero defect production. This is possible by achieving production tolerances which are even tighter than the prescribed ones. Different approaches are used to meet this demanding objective affected by many process parameters. Fine coining as a final forming operation is one of the processes which enables the production of good manufacturing tolerances and high process stability. The paper presents the analyses of the production of the inner race and a digital evaluation of manufacturing tolerances caused by different material parameters of the workpiece. Digital optimisation of the fine coining with FEM simulations was performed in two phases. Firstly, fine coining of the inner racer in a digital environment was comparatively analysed with the experimental work in order to verify the accuracy and reliability of digitally calculated data. Secondly, based on the geometrical data of a digitally fine coined part, tool redesign was proposed in order to tighten production tolerances and increase the process stability of the near-net-shaped cold formed part

Development of Fe-B Based Bulk Metallic Glasses: Morphology of Residual Phases in Fe50Ni16Mo6B18Zr10 Glass

Directory of Open Access Journals (Sweden)

Tiburce A. Aboki

2013-04-01

Full Text Available Iron-boron based bulk metallic glasses (BMG development has been initiated using Fe40Ni38Mo4B18 as precursor. Addition of zirconium up to 10 atomic % along with the reduction of Ni proportion improves the glass forming ability (GFA, which is optimum when Ni is suppressed in the alloy. However melting instability occurred during the materials fabrication resulting in the formation of residual crystalline phases closely related to the amorphous phase. Microstructure study shows an evolution from amorphous structure to peculiar acicular structure, particularly for Fe50Ni16Mo6B18Zr10, suggesting the amorphous structure as interconnected atomic sheets like “atomic mille feuilles” whose growth affects the alloys’ GFA.

Compressive deformation of in situ formed bulk metallic glass composites

Energy Technology Data Exchange (ETDEWEB)

Clausen, B. [Lujan Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Lee, S.Y. [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States); Ustuendag, E. [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States)]. E-mail: ustundag@iastate.edu; Kim, C.P. [Liquidmetal Technologies, Lake Forest, CA 92630 (United States); Brown, D.W. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Bourke, M.A.M. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2006-02-15

A bulk metallic glass matrix composite with dendc second phase precipitates was investigated using neutron diffraction and self-consistent modeling (SCM) to ascertain its deformation mechanisms. The compressive behavior of both the composite and the second phase (in its monolithic form) were investigated. The diffraction data were compared to the predictions of a new SCM resulting in good agreement. For the first time, this model considered both amorphous and crystalline phases and allowed the calculation of single crystal elastic constants from polycrystalline diffraction data. It was shown that the ductile second phase yielded first upon loading, and this was followed by multiple shear band formation in the matrix, a process which enhanced the ductility of the composite.

Compressive deformation of in situ formed bulk metallic glass composites

International Nuclear Information System (INIS)

Clausen, B.; Lee, S.Y.; Ustuendag, E.; Kim, C.P.; Brown, D.W.; Bourke, M.A.M.

2006-01-01

A bulk metallic glass matrix composite with dendritic second phase precipitates was investigated using neutron diffraction and self-consistent modeling (SCM) to ascertain its deformation mechanisms. The compressive behavior of both the composite and the second phase (in its monolithic form) were investigated. The diffraction data were compared to the predictions of a new SCM resulting in good agreement. For the first time, this model considered both amorphous and crystalline phases and allowed the calculation of single crystal elastic constants from polycrystalline diffraction data. It was shown that the ductile second phase yielded first upon loading, and this was followed by multiple shear band formation in the matrix, a process which enhanced the ductility of the composite

Thermal properties of superconducting bulk metallic glasses at ultralow temperatures

International Nuclear Information System (INIS)

Rothfuss, Daniel Simon

2013-01-01

This thesis describes the first investigation of thermal properties of superconducting bulk metallic glasses in the range between 6mK and 300K. Measuring the thermal conductivity provides the possibility to probe the fundamental interactions governing the heat flow in solids. At ultralow temperatures a novel contactless measuring technique was used, which is based on optical heating and paramagnetic temperature sensors that are read out by a SQUID magnetometer. Below the critical temperature T c the results can be described by resonant scattering of phonons by tunneling systems. Above T c the phonon contribution to the thermal conductivity can be described successfully within a model considering not only electrons and phonons but also localized modes as scattering centres. To expand the accessible temperature range for experiments an adiabatic nuclear demagnetization refrigerator was set up. For measuring the base temperature a novel noise thermometer was developed which enables continuous measuring of the temperature in this temperature range for the first time. Therefore the magnetic Johnson noise of a massive copper cylinder is simultaneously monitored by two SQUID magnetometers. A subsequent cross-correlation suppresses the amplifier noise by more than one order of magnitude. The thermometer was characterized between 42μK and 0.8K showing no deviation from the expected linear behaviour between the power spectral density of the thermal noise and the temperature.

Second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass

DEFF Research Database (Denmark)

Cao, Q.P.; Li, J.F.; Zhang, P.N.

2007-01-01

The second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass was investigated by differential scanning calorimetry and x-ray diffractometry. The difference of the Gibbs free energies between the amorphous phase and the crystalline products during the transformation...

Optimizing Location of Bulk Metallic Minerals Processing Based on Greenhouse Gas Avoidance

Directory of Open Access Journals (Sweden)

Benjamin C. McLellan

2011-12-01

Full Text Available The bulk minerals iron ore and bauxite cause significant greenhouse emissions in their processing to steel and aluminum respectively. The level of these emissions is highly dependent on the source of electrical and thermal energy. However, they also cause significant greenhouse gas emissions from their transportation across the globe for processing. This study examines these minerals from the perspective of greenhouse gas avoidance, examining the location of processing as an option for reducing transportation-based and process-based emissions. The analysis proposes a “radius of reduction” to define the potential for transporting ore to reduce emissions by offshore processing. Overall scenarios for localized steel production indicate potential for 85% reduction of transport emissions in the steel industry and 14% of overall industry emissions. Local high-carbon electricity grids and inefficient production mean that the benefit of reduced transportation is partially counteracted by increased processing emissions. The transportation of all global bauxite to Norway and other nations with low-emissions electricity for production of aluminum could result in an overall reduction of industry emissions of up to 44%.

Hard X-ray PhotoElectron Spectroscopy of transition metal oxides: Bulk compounds and device-ready metal-oxide interfaces

International Nuclear Information System (INIS)

Borgatti, F.; Torelli, P.; Panaccione, G.

2016-01-01

Highlights: • Hard X-ray PhotoElectron Spectroscopy (HAXPES) applied to buried interfaces of systems involving Transition Metal Oxides. • Enhanced contribution of the s states at high kinetic energies both for valence and core level spectra. • Sensitivity to chemical changes promoted by electric field across metal-oxide interfaces in resistive switching devices. - Abstract: Photoelectron spectroscopy is one of the most powerful tool to unravel the electronic structure of strongly correlated materials also thanks to the extremely large dynamic range in energy, coupled to high energy resolution that this form of spectroscopy covers. The kinetic energy range typically used for photoelectron experiments corresponds often to a strong surface sensitivity, and this turns out to be a disadvantage for the study of transition metal oxides, systems where structural and electronic reconstruction, different oxidation state, and electronic correlation may significantly vary at the surface. We report here selected Hard X-ray PhotoElectron Spectroscopy (HAXPES) results from transition metal oxides, and from buried interfaces, where we highlight some of the important features that such bulk sensitive technique brings in the analysis of electronic properties of the solids.

Hard X-ray PhotoElectron Spectroscopy of transition metal oxides: Bulk compounds and device-ready metal-oxide interfaces

Energy Technology Data Exchange (ETDEWEB)

Borgatti, F., E-mail: francesco.borgatti@cnr.it [Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), Consiglio Nazionale delle Ricerche (CNR), via P. Gobetti 101, Bologna I-40129 (Italy); Torelli, P.; Panaccione, G. [Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, Trieste I-34149 (Italy)

2016-04-15

Highlights: • Hard X-ray PhotoElectron Spectroscopy (HAXPES) applied to buried interfaces of systems involving Transition Metal Oxides. • Enhanced contribution of the s states at high kinetic energies both for valence and core level spectra. • Sensitivity to chemical changes promoted by electric field across metal-oxide interfaces in resistive switching devices. - Abstract: Photoelectron spectroscopy is one of the most powerful tool to unravel the electronic structure of strongly correlated materials also thanks to the extremely large dynamic range in energy, coupled to high energy resolution that this form of spectroscopy covers. The kinetic energy range typically used for photoelectron experiments corresponds often to a strong surface sensitivity, and this turns out to be a disadvantage for the study of transition metal oxides, systems where structural and electronic reconstruction, different oxidation state, and electronic correlation may significantly vary at the surface. We report here selected Hard X-ray PhotoElectron Spectroscopy (HAXPES) results from transition metal oxides, and from buried interfaces, where we highlight some of the important features that such bulk sensitive technique brings in the analysis of electronic properties of the solids.

Elastic properties of superconducting bulk metallic glasses; Elastische Eigenschaften von supraleitenden massiven metallischen Glaesern

Energy Technology Data Exchange (ETDEWEB)

Hempel, Marius

2015-07-01

Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

Fabrication and structure of bulk nanocrystalline Al-Si-Ni-mishmetal alloys

International Nuclear Information System (INIS)

Latuch, Jerzy; Cieslak, Grzegorz; Kulik, Tadeusz

2007-01-01

Al-based alloys of structure consisting of nanosized Al crystals, embedded in an amorphous matrix, are interesting for their excellent mechanical properties, exceeding those of the commercial crystalline Al-based alloys. Recently discovered nanocrystalline Al alloys containing silicon (Si), rare earth metal (RE) and late transition metal (Ni), combine high tensile strength and good wear resistance. The aim of this work was to manufacture bulk nanocrystalline alloys from Al-Si-Ni-mishmetal (Mm) system. Bulk nanostructured Al 91-x Si x Ni 7 Mm 2 (x = 10, 11.6, 13 at.%) alloys were produced by ball milling of nanocrystalline ribbons followed by high pressure hot isostating compaction

Hypervelocity impact on Zr51Ti5Ni10Cu25Al9 bulk metallic glass

International Nuclear Information System (INIS)

Zheng, W.; Huang, Y.J.; Pang, B.J.; Shen, J.

2011-01-01

Highlights: → Hypervelocity impact experiments were performed on a bulk metallic glass. → Morphology of the bullet hole presents three different regions. → The post-impact samples keep glassy structure. → Mechanical properties of the post-impact samples were studied by nanoindentation. → Mechanical properties of the post-impact samples were discussed by free-volume model. - Abstract: In this study, the hypervelocity impact experiments were performed on Zr 51 Ti 5 Ni 10 Cu 25 Al 9 bulk metallic glass using a two-stage light gas gun. The morphologies of the bullet holes exhibit three different regions: melting area, vein-pattern area, and radiating core feature area, suggesting that various regions experience different stress states during the hypervelocity impact. For the post-impact samples, the nano-hardness increases and plastic deformability decreases both with the increase in the distance from the bullet hole and with the decrease in the impact velocity, which is discussed by means of spherical stress wave theory and free-volume model.

The effect of Nb addition on mechanical properties, corrosion behavior, and metal-ion release of ZrAlCuNi bulk metallic glasses in artificial body fluid.

Science.gov (United States)

Qiu, C L; Liu, L; Sun, M; Zhang, S M

2005-12-15

Bulk metallic glasses (BMGs) of Zr(65 - x)Nb(x)- Cu(17.5)Ni(10)Al(7.5) with Nb = 0, 2, and 5 at % were prepared by copper mold casting. Compression tests reveal that the two BMGs containing Nb exhibited superior strength and plasticity to the base alloy. The corrosion behavior of the alloys obtained was investigated in artificial body fluid by electrochemical measurements. It was found that the addition of Nb significantly enhanced the corrosion resistance of the Zr-based BMG, as indicated by a remarkable increase in corrosion potential and pitting potential. XPS analysis revealed that the passive film formed after anodic polarization was enriched in aluminum oxide and depleted in phosphate ions for the BMGs containing Nb, which accounts for the improvement of corrosion resistance. On the other hand, metal-ion release of different BMGs were determined in PPb (ng/mL) level with inductively coupled plasma mass spectrometry (ICP-MS) after being immersed in artificial body fluid at 37 degrees C for 20 days. It was found that the addition of Nb considerably reduced the ion release of all kinds of metals of the base system. This is probably attributed to the promoting effect of Nb on a rapid formation of highly protective film.

Direct band gap electroluminescence from bulk germanium at room temperature using an asymmetric fin type metal/germanium/metal structure

Energy Technology Data Exchange (ETDEWEB)

Wang, Dong, E-mail: wang.dong.539@m.kyushu-u.ac.jp; Maekura, Takayuki; Kamezawa, Sho [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Yamamoto, Keisuke; Nakashima, Hiroshi [Art, Science and Technology Center for Cooperative Research, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan)

2015-02-16

We demonstrated direct band gap (DBG) electroluminescence (EL) at room temperature from n-type bulk germanium (Ge) using a fin type asymmetric lateral metal/Ge/metal structure with TiN/Ge and HfGe/Ge contacts, which was fabricated using a low temperature (<400 °C) process. Small electron and hole barrier heights were obtained for TiN/Ge and HfGe/Ge contacts, respectively. DBG EL spectrum peaked at 1.55 μm was clearly observed even at a small current density of 2.2 μA/μm. Superlinear increase in EL intensity was also observed with increasing current density, due to superlinear increase in population of elections in direct conduction band. The efficiency of hole injection was also clarified.

The impact of elastic and plastic strain on relaxation and crystallization of Pd–Ni–P-based bulk metallic glasses

International Nuclear Information System (INIS)

Mitrofanov, Yu.P.; Peterlechner, M.; Binkowski, I.; Zadorozhnyy, M.Yu.; Golovin, I.S.; Divinski, S.V.; Wilde, G.

2015-01-01

The effects of deformation and subsequent heat treatment on the low-temperature heat capacity, enthalpy relaxation rate and mechanical losses of two Pd–Ni–P-based bulk metallic glasses of slightly different compositions and different thermal stabilities have been investigated. It was found that the crystallization temperatures decreased significantly with imposed strain and the effect was more pronounced for the alloy with a higher thermal stability. The boson heat capacity peak increases with increasing strain in both alloys. However, after annealing treatments above room temperature, it relaxes to a lower enthalpy state as compared to that of the as-quenched state for the alloy with a lower thermal stability. The existence of two counteracting processes that might be related to different shear band structures within one homogeneously deformed sample is suggested. These results agree with the internal friction data, which indicate different regimes of mechanical damping as a function of the strain amplitude, while the critical amplitude of a transition between the regimes depends on the imposed strain. The results are interpreted within the energy landscape approach and advocate that the composition-dependent local atomic configurations affect significantly the response of the glass to an applied strain

Chemoelectronic circuits based on metal nanoparticles

Science.gov (United States)

Yan, Yong; Warren, Scott C.; Fuller, Patrick; Grzybowski, Bartosz A.

2016-07-01

To develop electronic devices with novel functionalities and applications, various non-silicon-based materials are currently being explored. Nanoparticles have unique characteristics due to their small size, which can impart functions that are distinct from those of their bulk counterparts. The use of semiconductor nanoparticles has already led to improvements in the efficiency of solar cells, the processability of transistors and the sensitivity of photodetectors, and the optical and catalytic properties of metal nanoparticles have led to similar advances in plasmonics and energy conversion. However, metals screen electric fields and this has, so far, prevented their use in the design of all-metal nanoparticle circuitry. Here, we show that simple electronic circuits can be made exclusively from metal nanoparticles functionalized with charged organic ligands. In these materials, electronic currents are controlled by the ionic gradients of mobile counterions surrounding the ‘jammed’ nanoparticles. The nanoparticle-based electronic elements of the circuitry can be interfaced with metal nanoparticles capable of sensing various environmental changes (humidity, gas, the presence of various cations), creating electronic devices in which metal nanoparticles sense, process and ultimately report chemical signals. Because the constituent nanoparticles combine electronic and chemical sensing functions, we term these systems ‘chemoelectronic’. The circuits have switching times comparable to those of polymer electronics, selectively transduce parts-per-trillion chemical changes into electrical signals, perform logic operations, consume little power (on the scale of microwatts), and are mechanically flexible. They are also ‘green’, in the sense that they comprise non-toxic nanoparticles cast at room temperature from alcohol solutions.

In Situ Formation of Carbon Nanomaterials on Bulk Metallic Materials

Directory of Open Access Journals (Sweden)

J. Y. Xu

2014-01-01

Full Text Available Carbon nanomaterials were synthesized in situ on bulk 316L stainless steel, pure cobalt, and pure nickel by hybrid surface mechanical attrition treatment (SMAT. The microstructures of the treated samples and the resulted carbon nanomaterials were investigated by SEM and TEM characterizations. Different substrates resulted in different morphologies of products. The diameter of carbon nanomaterials is related to the size of the nanograins on the surface layer of substrates. The possible growth mechanism was discussed. Effects of the main parameters of the synthesis, including the carbon source and gas reactant composition, hydrogen, and the reaction temperature, were studied. Using hybrid SMAT is proved to be an effective way to synthesize carbon nanomaterials in situ on surfaces of metallic materials.

Homogeneous viscous flow behavior of a Cu–Zr based bulk metallic glass composites

International Nuclear Information System (INIS)

Zhang, X.Y.; Yuan, Z.Z.; Feng, X.L.; Cui, L.Z.; Li, D.X.

2015-01-01

In this paper, Cu 40 Zr 44 Ag 8 Al 8 bulk metallic glass composites (BMGCs) consisting of various volume fraction of nanocrystals embedded in the amorphous matrix was synthesized by controlled annealing treatment of an as-cast BMGCs. The high temperature compression behaviors of the BMGCs were characterized in the supercooled liquid region. Results show that the flow stresses keep increasing after an initial decrease with extension of the annealing time. With annealing the values of activation volume V act is determined to be increasing from 283.6216 Ǻ 3 to 305.553 Ǻ 3 , suggesting that the jump of atoms is a cooperative process during the high-temperature deformation. Flow behavior of the BMGCs annealed for less than 8 min transform from Newtonian to non-Newtonian dependant on the stain rate and can be successively fitted by the visco-plasticity model. Fitting results indicate that deformation behaviors of these samples are governed by homogeneous flow of the amorphous matrix and indeed determined by the viscosities in the Newtonian flow stage. However, the BMGCs annealed for 8 min exhibit a non-Newtonian flow over the entire compression process and fail to be fitted by the visco-plasticity model. Micrographs of the sample reflect an impinged structure, indicating that high temperature deformation behavior of the BMGCs with high volume fractions of particles is indeed controlled by that of a backbone of particles

Effect of Ge addition on mechanical properties and fracture behavior of Cu-Zr-Al bulk metallic glass

International Nuclear Information System (INIS)

Malekan, M.; Shabestari, S.G.; Gholamipour, R.; Seyedein, S.H.

2009-01-01

Effect of the addition of a small amount of Ge on mechanical properties and fracture behavior of Cu 50 Zr 43 Al 7 (at.%) bulk metallic glass were studied. The Cu 50 Zr 43 Al 7 alloy has a surprising glass-forming ability (GFA), and the glassy rods up to 4 mm in diameter can be formed. Partial addition of Ge causes the crystalline phases precipitate in the glassy matrix of (Cu 50 Zr 43 Al 7 ) 100-x Ge x (x = 0, 1, 2) rods with a diameter of 4 mm. In uniaxial compression, Cu 50 Zr 43 Al 7 bulk metallic glass exhibit high strength of 1692 MPa and very limited plasticity of 0.05%. When Ge increases from 0 to 2 at.%, the strength decreases, but plastic strain increases about 2.5%. Fracture surface and shear bands of samples were investigated by scanning electron microscopy (SEM).

Visualizing electromagnetic fields in metals by MRI

Directory of Open Access Journals (Sweden)

Chandrika Sefcikova Chandrashekar

2017-02-01

Full Text Available Based upon Maxwell’s equations, it has long been established that oscillating electromagnetic (EM fields incident upon a metal surface, decay exponentially inside the conductor, leading to a virtual absence of EM fields at sufficient depths. Magnetic resonance imaging (MRI utilizes radiofrequency (r.f. EM fields to produce images. Here we present a visualization of a virtual EM vacuum inside a bulk metal strip by MRI, amongst several findings. At its simplest, an MRI image is an intensity map of density variations across voxels (pixels of identical size (=Δx Δy Δz. By contrast in bulk metal MRI, we uncover that despite uniform density, intensity variations arise from differing effective elemental volumes (voxels from different parts of the bulk metal. Further, we furnish chemical shift imaging (CSI results that discriminate different faces (surfaces of a metal block according to their distinct nuclear magnetic resonance (NMR chemical shifts, which holds much promise for monitoring surface chemical reactions noninvasively. Bulk metals are ubiquitous, and MRI is a premier noninvasive diagnostic tool. Combining the two, the emerging field of bulk metal MRI can be expected to grow in importance. The findings here may impact further development of bulk metal MRI and CSI.

Enhanced Mechanical Properties of MgZnCa Bulk Metallic Glass Composites with Ti-Particle Dispersion

Directory of Open Access Journals (Sweden)

Pei Chun Wong

2016-05-01

Full Text Available Rod samples of Mg60Zn35Ca5 bulk metallic glass composites (BMGCs dispersed with Ti particles have been successfully fabricated via injection casting. The glass forming ability (GFA and the mechanical properties of these Mg-based BMGCs have been systematically investigated as a function of the volume fraction (Vf of Ti particles. The results showed that the compressive ductility increased with Vf. The mechanical performance of these BMGCs, with up to 5.4% compressive failure strain and 1187 MPa fracture strength at room temperature, can be obtained for the Mg-based BMGCs with 50 vol % Ti particles, suggesting that these dispersed Ti particles can absorb the energy of the crack propagations and can induce branches of the primary shear band into multiple secondary shear bands. It follows that further propagation of the shear band is blocked, enhancing the overall plasticity.

Determination of Lubricant Bulk Modulus in Metal Forming by Means of a Simple Laboratory Test and Inverse FEM Analysis

DEFF Research Database (Denmark)

Hafis, S. M.; Christiansen, P.; Martins, P. A. F.

2016-01-01

The influence of workpiece surface topography on friction, lubrication and final surface equality in metal forming operations is well known and has been pointed out by many researchers.This is especially the case when liquid lubricants are applied in situations, where increased surface roughness ...... couples lubricant flow with plastic deformation of the metal directly. Results show that the proposed procedure allows determining an approximate bulk modulus for the lubricant.......The influence of workpiece surface topography on friction, lubrication and final surface equality in metal forming operations is well known and has been pointed out by many researchers.This is especially the case when liquid lubricants are applied in situations, where increased surface roughness...... facilitates the lubricant entrainment, pressurization and possible escape by micro-plasto-hydrodynamic lubrication. In order to model these mechanisms an important lubricant propertyd esignated as the bulk modulus is needed for characterizing the compressibility of the lubricant. The present paper describes...

Effect of Nb on glass forming ability and plasticity of (Ti-Cu)-based bulk metallic glasses

International Nuclear Information System (INIS)

Suo, Z.Y.; Qiu, K.Q.; Li, Q.F.; Ren, Y.L.; Hu, Z.Q.

2010-01-01

A Ti 33 Cu 47 Zr 9 Ni 6 Sn 2 Si 1 Nb 2 bulk metallic glass has been developed by Nb partial substitution for Zr in Ti 33 Cu 47 Zr 11 Ni 6 Sn 2 Si 1 alloy. The glass forming ability Ti 33 Cu 47 Zr 9 Ni 6 Sn 2 Si 1 Nb 2 alloy has been investigated using differential scanning calorimetry and X-ray diffractometry. Partial Nb substitutes for Zr promote the glass forming ability. Ti 33 Cu 47 Zr 9 Ni 6 Sn 2 Si 1 Nb 2 BMG with diameter of 3 mm can be fabricated by Cu-mold injection casting method. The glass forming ability of Ti 33 Cu 47 Zr 9 Ni 6 Sn 2 Si 1 Nb 2 alloy is enhanced by stabilizing the undercooled liquid against crystallization. The plastic strain up to 2.5% was obtained for Ti 33 Cu 47 Zr 9 Ni 6 Sn 2 Si 1 Nb 2 BMG compared to 0.15% for Ti 33 Cu 47 Zr 11 Ni 6 Sn 2 Si 1 BMG, which demonstrates that small amount of Nb addition can have a dramatic effect on plasticity enhancement in Ti-Cu-based BMG. The intersection and branching of the shear bands are observed. The plastic strain of the Ti 33 Cu 47 Zr 9 Ni 6 Sn 2 Si 1 Nb 2 BMG can be improved by the generation of nanocrystalline particles, which lead to multiple shear bands.

Role of electrode metallization in the performance of bulk semi-insulating InP radiation detectors

International Nuclear Information System (INIS)

Zatko, B.; Dubecky, F.; Prochazkova, O.; Necas, V.

2007-01-01

This work deals with the study of three different electrode metallizations with the aim to form a Schottky barrier contact. Electrode geometry corresponds to the requirements of digital radiography systems. As substrates bulk Liquid Encapsulated Czochralski (LEC) SI InP wafers doped with Fe and Fe+Zn are used. Results of this study show that no one of the used metallization performs as a blocking contact. However, detectors with Ti/Pt/Au metallization attained a relatively good energy resolution of 7.0 keV in full-width at half-maximum (FWHM) and the charge collection efficiency (CCE) higher than 83% for 122 keV γ-photons at 255 K. The development of SI InP radiation detectors and in particular their electrode technology is discussed in the light of observed results

Impact of the structural state on the mechanical properties in a Zr–Co–Al bulk metallic glass

International Nuclear Information System (INIS)

Qiao, J.C.; Pelletier, J.M.; Esnouf, C.; Liu, Y.; Kato, H.

2014-01-01

Highlights: • Atomic mobility in metallic glass was studied by DMA, HRTEM and nanoindentation. • Physical ageing and crystallization reduce the atomic mobility. • Plastic deformation, i.e. cold-rolling enhances the atomic mobility. • Atomic mobility in glassy materials can be described by quasi-point defects model. - Abstract: This paper reports on the use of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and nanoindentation technique to investigate atomic mobility in Zr 56 Co 28 Al 16 bulk metallic glass in the as-cast state, after thermal annealing and after cold rolling. From the DMA results together with nanoindentation data point of view, the atomic mobility is significantly modified by the thermo-mechanical history. On the one hand, atomic mobility in bulk metallic glass is reduced after physical aging or crystallization. On the other hand, the atomic mobility in metallic glass is enhanced by cold rolling. To analyze the atomic mobility in amorphous materials, a physical theory is introduced. This model invoked the concept of quasi-point defects, which correspond to the density fluctuations in the glassy materials. Correlated movements of atoms are assisted by these quasi-point defects and the correlation factor χ is connected to the concentration of these “defects” in metallic glasses: (i) physical aging and crystallization decreases the parameter χ and (ii) the concentration of defects augments via plastic deformation (i.e. cold-rolling), suggesting that the correlation factor χ reflects the atomic mobility for glassy materials in a quantitative manner. This correlation bridges the gap between the mechanical properties on macroscopic scale and atomic mobility in microstructural regions in metallic glasses

Strong, ductile, and thermally stable Cu-based metal-intermetallic nanostructured composites.

Science.gov (United States)

Dusoe, Keith J; Vijayan, Sriram; Bissell, Thomas R; Chen, Jie; Morley, Jack E; Valencia, Leopolodo; Dongare, Avinash M; Aindow, Mark; Lee, Seok-Woo

2017-01-09

Bulk metallic glasses (BMGs) and nanocrystalline metals (NMs) have been extensively investigated due to their superior strengths and elastic limits. Despite these excellent mechanical properties, low ductility at room temperature and poor microstructural stability at elevated temperatures often limit their practical applications. Thus, there is a need for a metallic material system that can overcome these performance limits of BMGs and NMs. Here, we present novel Cu-based metal-intermetallic nanostructured composites (MINCs), which exhibit high ultimate compressive strengths (over 2 GPa), high compressive failure strain (over 20%), and superior microstructural stability even at temperatures above the glass transition temperature of Cu-based BMGs. Rapid solidification produces a unique ultra-fine microstructure that contains a large volume fraction of Cu 5 Zr superlattice intermetallic compound; this contributes to the high strength and superior thermal stability. Mechanical and microstructural characterizations reveal that substantial accumulation of phase boundary sliding at metal/intermetallic interfaces accounts for the extensive ductility observed.

Atmospherically deposited trace metals from bulk mineral concentrate port operations.

Science.gov (United States)

Taylor, Mark Patrick

2015-05-15

Although metal exposures in the environment have declined over the last two decades, certain activities and locations still present a risk of harm to human health. This study examines environmental dust metal and metalloid hazards (arsenic, cadmium, lead and nickel) associated with bulk mineral transport, loading and unloading port operations in public locations and children's playgrounds in the inner city of Townsville, northern Queensland. The mean increase in lead on post-play hand wipes (965 μg/m(2)/day) across all sites was more than 10-times the mean pre-play loadings (95 μg/m(2)/day). Maximum loading values after a 10-minute play period were 3012 μg/m(2), more than seven times the goal of 400 μg/m(2) used by the Government of Western Australia (2011). Maximum daily nickel post-play hand loadings (404 μg/m(2)) were more than 26 times above the German Federal Immission Control Act 2002 annual benchmark of 15 μg/m(2)/day. Repeat sampling over the 5-day study period showed that hands and surfaces were re-contaminated daily from the deposition of metal-rich atmospheric dusts. Lead isotopic composition analysis of dust wipes ((208)Pb/(207)Pb and (206)Pb/(207)Pb) showed that surface dust lead was similar to Mount Isa type ores, which are exported through the Port of Townsville. While dust metal contaminant loadings are lower than other mining and smelting towns in Australia, they exceeded national and international benchmarks for environmental quality. The lessons from this study are clear - even where operations are considered acceptable by managing authorities, targeted assessment and monitoring can be used to evaluate whether current management practices are truly best practice. Reassessment can identify opportunities for improvement and maximum environmental and human health protection. Copyright © 2015 Elsevier B.V. All rights reserved.

Tuning glass formation and brittle behaviors by similar solvent element substitution in (Mn,Fe)-based bulk metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Xu, Tao [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li, Ran, E-mail: liran@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Xiao, Ruijuan [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Gang [State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, Jianfeng [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Zhang, Tao, E-mail: zhangtao@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

2015-02-25

A family of Mn-rich bulk metallic glasses (BMGs) was developed through the similar solvent elements (SSE) substitution of Mn for Fe in (Mn{sub x}Fe{sub 80−x})P{sub 10}B{sub 7}C{sub 3} alloys. The effect of the SSE substitution on glass formation, thermal stability, elastic constants, mechanical properties, fracture morphologies, Weibull modulus and indentation fracture toughness was discussed. A thermodynamics analysis provided by Battezzati et al. (L. Battezzati, E. Garrone, Z. Metallkd. 75 (1984) 305–310) was adopted to explain the compositional dependence of the glass-forming ability (GFA). The elastic moduli follow roughly linear correlations with the substitution concentration of Mn in (Mn{sub x}Fe{sub 80−x})P{sub 10}B{sub 7}C{sub 3} BMGs. The introduction of Mn to replace Fe significantly decreases the plasticity of the resulting BMGs and the Weibull modulus of the fracture strength. A super-brittle Mn-based BMGs of (Mn{sub 55}Fe{sub 25})P{sub 10}B{sub 7}C{sub 3} BMGs were found with the indentation fracture toughness (K{sub c}) of 1.91±0.04 MPa m{sup 1/2}, the lowest value among all kinds of BMGs so far. The atomic and electronic structure of the selected BMGs were simulated by the first principles molecular dynamics calculations based on density functional theory, which provided a possible understanding of the brittleness caused by the similar chemical element replacement of Mn for Fe.

Molecular Dynamics Simulations of Grain Boundary and Bulk Diffusion in Metals.

Science.gov (United States)

Plimpton, Steven James

Diffusion is a microscopic mass transport mechanism that underlies many important macroscopic phenomena affecting the structural, electrical, and mechanical properties of metals. This thesis presents results from atomistic simulation studies of diffusion both in bulk and in the fast diffusion paths known as grain boundaries. Using the principles of molecular dynamics single boundaries are studied and their structure and dynamic properties characterized. In particular, tilt boundary bicrystal and bulk models of fcc Al and bcc alpha-Fe are simulated. Diffusion coefficients and activation energies for atomic motion are calculated for both models and compared to experimental data. The influence of the interatomic pair potential on the diffusion is studied in detail. A universal relation between the melting temperature that a pair potential induces in a simulated bulk model and the potential energy barrier height for atomic hopping is derived and used to correlate results for a wide variety of pair potentials. Using these techniques grain boundary and bulk diffusion coefficients for any fcc material can be estimated from simple static calculations without the need to perform more time-consuming dynamic simulations. The influences of two other factors on grain boundary diffusion are also studied because of the interest of the microelectronics industry in the diffusion related reliability problem known as electromigration. The first factor, known to affect the self diffusion rate of Al, is the presence of Cu impurity atoms in Al tilt boundaries. The bicrystal model for Al is seeded randomly with Cu atoms and a simple hybrid Morse potential used to model the Al-Cu interaction. While some effect due to the Cu is noted, it is concluded that pair potentials are likely an inadequate approximation for the alloy system. The second factor studied is the effect of the boundary orientation angle on the diffusion rate. Symmetric bcc Fe boundaries are relaxed to find optimal

Efficiency Enhancement in Bulk Heterojunction Polymer Photovoltaic Cells Using ZrTiO4/Bi2O3 Metal-Oxide Nanocomposites

DEFF Research Database (Denmark)

Abdul Jabbar, Mohammed Hussain; Neppolian, B.; Shim, Hee-Sang

2010-01-01

We report the effect of metal-oxide nanocomposites on the performance of bulk heterojunction polymer solar cells. A photoactive layer composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was blended with a newly developed ZrTiO4/Bi2O3 (BITZ) metal-oxide...

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.

Improvement of the thermoplastic formability of Zr65Cu17.5Ni10Al7.5 bulk metallic glass by minor addition of Erbium

International Nuclear Information System (INIS)

Hu, Q.; Zeng, X.R.; Fu, M.W.; Chen, S.S.; Jiang, J.

2016-01-01

The softness of Zr 65 Cu 17.5 Ni 10 Al 7.5 bulk metallic glass (BMG) in the super-cooled liquid range (SCLR) is obviously improved by minor addition of 2% Er, which makes (Zr 65 Cu 17.5 Ni 10 Al 7.5 ) 98 Er 2 (Zr65Er2) to be a very formable Be-free Zr-based BMG. It is found the lower glass transition temperature of Zr65Er2 has an important contribution to the improvement of formability, which is contrary to the general understanding that the larger fragility and wider super-cooled liquid region (SCLR) are the major reasons for better thermoplastic formability. This finding is well explained by using the linear simplification of the SCLR in Angell plot. Zr65Er2 also has lower crystallization temperature and melting temperature, which is believed to be related to the formation of short-range ordering with lower transition energy rather than the composition shift to near eutectic. The above results help understand the effect of minor addition of rare-earth to the formability of Zr-based bulk metallic glasses.

Hierarchical surface patterning of Ni- and Be-free Ti- and Zr-based bulk metallic glasses by thermoplastic net-shaping

Energy Technology Data Exchange (ETDEWEB)

Sarac, Baran, E-mail: b.sarac@ifw-dresden.de [IFW Dresden, Institute for Complex Materials, Helmholtzstrasse 20, D-01069 Dresden (Germany); Erich Schmid Institute of Materials Science, Austrian Academy of Sciences (ÖAW), Jahnstrasse 12, A-8700 Leoben (Austria); Bera, Supriya [IFW Dresden, Institute for Complex Materials, Helmholtzstrasse 20, D-01069 Dresden (Germany); Balakin, Sascha [IFW Dresden, Institute for Complex Materials, Helmholtzstrasse 20, D-01069 Dresden (Germany); ETH Zurich, Department of Materials, Metal physics und Technology, Vladimir-Prelog-Weg 4, HCI J 492, 8093 Zürich (Switzerland); Stoica, Mihai [IFW Dresden, Institute for Complex Materials, Helmholtzstrasse 20, D-01069 Dresden (Germany); Politehnica University of Timisoara, P-ta Victoriei 2, RO-300006 Timisoara (Romania); Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Winterbergstrasse 28, 01277, Dresden (Germany); Calin, Mariana, E-mail: m.calin@ifw-dresden.de [IFW Dresden, Institute for Complex Materials, Helmholtzstrasse 20, D-01069 Dresden (Germany); Eckert, Jürgen [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences (ÖAW), Jahnstrasse 12, A-8700 Leoben (Austria); Department Materials Physics, Montanuniversität Leoben, Jahnstrasse 12, A-8700 Leoben (Austria)

2017-04-01

In order to establish a strong cell-material interaction, the surface topography of the implant material plays an important role. This contribution aims to analyze the formation kinetics of nickel and beryllium-free Ti- and Zr-based Bulk Metallic Glasses (BMGs) with potential biomedical applications. The surface patterning of the BMGs is achieved by thermoplastic net-shaping (TPN) into anisotropically etched cavities of silicon chips. The forming kinetics of the BMG alloys is assessed by thermal and mechanical measurements to determine the most suitable processing temperature and time, and load applied. Array of pyramidal micropatterns with a tip resolution down to 50 nm is achievable for the Zr-BMG, where the generated hierarchical features are crucial for surface functionalization, acting as topographic cues for cell attachment. The unique processability and intrinsic properties of this new class of amorphous alloys make them competitive with the conventional biomaterials. - Highlights: • Micro to nano-scale hierarchical surface patterns achieved by TPN of BMGs • Ni- and Be-free Zr-/Ti-BMGs with different GFA compared in terms of flow kinetics • Correlation between filling depths of Zr- and Ti-BMGs best described by formability • Multi-scale hierarchical patterning envisaged to facilitate BMG-cell interaction.

Short-to-Medium-Range Order and Atomic Packing in Zr48Cu36Ag8Al8 Bulk Metallic Glass

Directory of Open Access Journals (Sweden)

Yong Xu

2016-10-01

Full Text Available Due to its excellent glass-forming ability (GFA, the Zr48Cu36Al8Ag8 bulk metallic glass (BMG is of great importance in glass transition investigations and new materials development. However, due to the lack of detailed structural information, the local structure and atomic packing of this alloy is still unknown. In this work, synchrotron measurement and reverse Monte Carlo simulation are performed on the atomic configuration of a Zr-based bulk metallic glass. The local structure is characterized in terms of bond pairs and Voronoi tessellation. It is found that there are mainly two types of bond pairs in the configuration, as the body-centered cubic (bcc-type and icosahedral (ico-type bond pairs. On the other hand, the main polyhedra in the configuration are icosahedra and the bcc structure. That is, the bcc-type bond pairs, together with the ico-type bond pairs, form the bcc polyhedra, introducing the distortion in bcc clusters in short range. However, in the medium range, the atoms formed linear or planar structures, other than the tridimensional clusters. That is, the medium-range order in glass is of 1D or 2D structure, suggesting the imperfect ordered packing feature.

Bulk and edge spin transport in topological magnon insulators

Science.gov (United States)

Rückriegel, Andreas; Brataas, Arne; Duine, Rembert A.

2018-02-01

We investigate the spin transport properties of a topological magnon insulator, a magnetic insulator characterized by topologically nontrivial bulk magnon bands and protected magnon edge modes located in the bulk band gaps. Employing the Landau-Lifshitz-Gilbert phenomenology, we calculate the spin current driven through a normal metal |topological magnon insulator |normal metal heterostructure by a spin accumulation imbalance between the metals, with and without random lattice defects. We show that bulk and edge transport are characterized by different length scales. This results in a characteristic system size where the magnon transport crosses over from being bulk dominated for small systems to edge dominated for larger systems. These findings are generic and relevant for topological transport in systems of nonconserved bosons.

FeSiBP bulk metallic glasses with high magnetization and excellent magnetic softness

Energy Technology Data Exchange (ETDEWEB)

Makino, Akihiro [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan)], E-mail: amakino@imr.tohoku.ac.jp; Kubota, Takeshi; Chang, Chuntao [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Makabe, Masahiro [Makabe R and D Co., Ltd., 3-1-25 Nagatake, Sendai 983-0036 (Japan); Inoue, Akihisa [Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan)

2008-10-15

Fe-based amorphous alloy ribbons are one of the major soft magnetic materials, because of their superior magnetic properties such as the relatively high saturation magnetization (J{sub s}) of 1.5-1.6 T and good magnetic softness. However, the preparation of the ordinary amorphous magnetic alloys requires cooling rates higher than 10{sup 4} K/s due to the low glass-forming ability (GFA) and thus restricts the material outer shape. Recently, Fe-metalloid-based bulk metallic glasses (BMGs) containing glass-forming elements such as Al, Ga, Nb, Mo, Y and so forth have been developed. These alloys have high GFA, leading to the formation of BMG rod with diameters of mm-order. However, the glass-forming metal elements in BMGs result in a remarkable decrease in magnetization. Basically, J{sub s} depends on Fe content; hence, high J{sub s} requires high Fe content in the Fe-based amorphous alloys or BMGs. On the other hand, high GFA requires a large amount of glass-forming elements in the alloys, which results in lower Fe content. Therefore, in substances, the coexistence of high J{sub s} and high GFA is difficult. Since this matter should be immensely important from academia to industry in the material field, a great deal of effort has been devoted; however, it has remained unsolved for many years. In this paper, we present a novel Fe-rich FeSiBP BMG with high J{sub s} of 1.51 T comparable to the ordinary Fe-Si-B amorphous alloy now in practical use as well as with high GFA leading to a rod-shaped specimen of 2.5 mm in diameter, obtained by Cu-mold casting in air.

Enhancement of room-temperature plasticity in a bulk metallic glass by finely dispersed porosity

International Nuclear Information System (INIS)

Wada, Takeshi; Inoue, Akihisa; Greer, Alan Lindsay

2005-01-01

Melts of Pd 42.5 Cu 30 Ni 7.5 P 20 (at. %) held under pressurized hydrogen are cast into bulk metallic glass (BMG) rods with fine (20-30 μm diameter) pores uniformly dispersed. The low overall porosities ( -3 , compared to 16 MJ m -3 for the pore-free BMG. The pores force the proliferation of shear bands below the overall failure stress, a process of interest for toughening BMGs, materials for which shear localization in deformation restricts structural applications

Coulombic Fluids Bulk and Interfaces

CERN Document Server

Freyland, Werner

2011-01-01

Ionic liquids have attracted considerable interest in recent years. In this book the bulk and interfacial physico-chemical characteristics of various fluid systems dominated by Coulomb interactions are treated which includes molten salts, ionic liquids as well as metal-molten salt mixtures and expanded fluid metals. Of particular interest is the comparison of the different systems. Topics in the bulk phase concern the microscopic structure, the phase behaviour and critical phenomena, and the metal-nonmetal transition. Interfacial phenomena include wetting transitions, electrowetting, surface freezing, and the electrified ionic liquid/ electrode interface. With regard to the latter 2D and 3D electrochemical phase formation of metals and semi-conductors on the nanometer scale is described for a number of selected examples. The basic concepts and various experimental methods are introduced making the book suitable for both graduate students and researchers interested in Coulombic fluids.

Biocompatible Ni-free Zr-based bulk metallic glasses with high-Zr-content: Compositional optimization for potential biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Hua, Nengbin, E-mail: flower1982cn@126.com [Department of Materials Science and Engineering, Fujian University of Technology, 350118 Fuzhou (China); Department of Materials Science and Engineering, Fuzhou University, 350116 Fuzhou (China); Huang, Lu [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996-2100 (United States); Chen, Wenzhe [Department of Materials Science and Engineering, Fujian University of Technology, 350118 Fuzhou (China); Department of Materials Science and Engineering, Fuzhou University, 350116 Fuzhou (China); He, Wei [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996-2100 (United States); Department of Mechanical, Aerospace and Biomedical Engineering, The University of Tennessee, Knoxville, TN 37996-2200 (United States); Zhang, Tao [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, 100191 Beijing (China)

2014-11-01

The present study designs and prepares Ni-free Zr{sub 60+x}Ti{sub 2.5}Al{sub 10}Fe{sub 12.5−x}Cu{sub 10}Ag{sub 5} (at.%, x = 0, 2.5, 5) bulk metallic glasses (BMGs) by copper mold casting for potential biomedical application. The effects of Zr content on the in vitro biocompatibility of the Zr-based BMGs are evaluated by investigating mechanical properties, bio-corrosion behavior, and cellular responses. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high notch toughness. Electrochemical measurements demonstrate that the Zr-based BMGs are corrosion resistant in a phosphate buffered saline solution. The bio-corrosion resistance of BMGs is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. Regular cell responses of mouse MC3T3-E1 cells, including cell adhesion and proliferation, are observed on the Zr–Ti–Al–Fe–Cu–Ag BMGs, which reveals their general biosafety. The high-Zr-based BMGs exhibit a higher cell proliferation activity in comparison with that of pure Zr and Ti-6Al-4V alloy. The effects of Zr content on the in vitro biocompatibility can be used to guide the future design of biocompatible Zr-based BMGs. - Highlights: • Ni-free Zr{sub 60+x}Ti{sub 2.5}Al{sub 10}Fe{sub 12.5−x}Cu{sub 10}Ag{sub 5} (at.%, x = 0, 2.5, 5) BMGs were fabricated. • Plasticity and notch toughness of BMGs are enhanced by high-Zr-content. • The high-Zr-based BMGs exhibit excellent bio-corrosion resistance in PBS solution. • The biosafety of BMGs is revealed by regular cell adhesion and proliferation. • High-Zr-bearing BMGs are favorable for potential applications as biomaterials.

Microstructure Effects on Spall Strength of Titanium-based Bulk Metallic Glass Composites

Science.gov (United States)

Diaz, Rene; Hofmann, Douglas; Thadhani, Naresh; Georgia Tech Team; GT-JPL Collaboration

2017-06-01

The spall strength of Ti-based metallic glass composites is investigated as a function of varying volume fractions (0-80%) of in-situ formed crystalline dendrites. With increasing dendrite content, the topology changes such that neither the harder glass nor the softer dendrites dominate the microstructure. Plate-impact experiments were performed using the 80-mm single-stage gas gun over impact stresses up to 18 GPa. VISAR interferometry was used to obtain rear free-surface velocity profiles revealing the velocity pullback spall failure signals. The spall strengths were higher than for Ti-6Al-4V alloy, and remained high up to impact stress. The influence of microstructure on the spall strength is indicated by the constants of the power law fit with the decompression strain rate. Differences in fracture behavior reveal void nucleation as a dominant mechanism affecting the spall strength. The microstructure with neither 100% glass nor with very high crystalline content, provides the most tortuous path for fracture and therefore highest spall strength. The results allow projection of spall strength predictions for design of in-situ formed metallic glass composites. ARO Grant # W911NF-09 ``1-0403 NASA JPL Contract # 1492033 ``Prime # NNN12AA01C; NSF GRFP Grant #DGE-1148903; and NDSE & G.

Bulk Restoration for SDN-Based Transport Network

Directory of Open Access Journals (Sweden)

Yang Zhao

2016-01-01

Full Text Available We propose a bulk restoration scheme for software defined networking- (SDN- based transport network. To enhance the network survivability and improve the throughput, we allow disrupted flows to be recovered synchronously in dynamic order. In addition backup paths are scheduled globally by applying the principles of load balance. We model the bulk restoration problem using a mixed integer linear programming (MILP formulation. Then, a heuristic algorithm is devised. The proposed algorithm is verified by simulation and the results are analyzed comparing with sequential restoration schemes.

AC Calorimetry and Thermophysical Properties of Bulk Glass-Forming Metallic Liquids

Science.gov (United States)

Johnson, William L.

2000-01-01

Thermo-physical properties of two bulk metallic glass forming alloys, Ti34Zr11Cu47Ni8 (VIT 101) and Zr57Nb5Ni12.6Al10CU15.4 (VIT 106), were investigated in the stable and undercooled melt. Our investigation focused on measurements of the specific heat in the stable and undercooled liquid using the method of AC modulation calorimetry. The VIT 106 exhibited a maximum undercooling of 140 K in free radiative cooling. Specific heat measurements could be performed in stable melt down to an undercooling of 80 K. Analysis of the specific heat data indicate an anomaly near the equilibrium liquidus temperature. This anomaly is also observed in y the temperature dependencies of the external relaxation time, the specific volume, and the surface tension; it is tentatively attributed to a phase separation in the liquid state. The VIT 101 specimen exhibited a small undercooling of about 50 K. Specific heat measurements were performed in the stable and undercooled melt. These various results will be combined with ground based work such as the measurement of T-T-T curves in the electrostatic levitator and low temperature viscosity and specific heat measurements for modeling the nucleation kinetics of these alloys.

Friction and surface chemistry of some ferrous-base metallic glasses

Science.gov (United States)

Miyoshi, K.; Buckley, D. H.

1982-01-01

The friction properties of some ferrous-base metallic glasses were measured both in argon and in vacuum to a temperature of 350 C. The alloy surfaces were also analyzed with X-ray photoelectron spectroscopy to identify the compounds and elements present on the surface. The results of the investigation indicate that even when the surfaces of the amorphous alloys, or metallic glasses, are atomically clean, bulk contaminants such as boric oxide and silicon dioxide diffuse to the surfaces. Friction measurements in both argon and vacuum indicate that the alloys exhibit higher coefficients of friction in the crystalline state than they do in the amorphous state.

Facile conversion of bulk metal surface to metal oxide single-crystalline nanostructures by microwave irradiation: Formation of pure or Cr-doped hematite nanostructure arrays

International Nuclear Information System (INIS)

Cho, Seungho; Jeong, Haeyoon; Lee, Kun-Hong

2010-01-01

We report a method for converting the surfaces of bulk metal substrates (pure iron or stainless steel) to metal oxide (hematite or Cr-doped hematite) nanostructures using microwave irradiation. When microwave radiation (2.45 GHz, single-mode) was applied to a metal substrate under the flow of a gas mixture containing O 2 and Ar, metal oxide nanostructures formed and entirely covered the substrate. The nanostructures were single crystalline, and the atomic ratios of the substrate metals were preserved in the nanostructures. When a pure iron sheet was used as a substrate, hematite nanowires (1000 W microwave radiation) or nanosheets (1800 W microwave radiation) formed on the surface of the substrate. When a SUS410 sheet was used as a substrate, slightly curved rod-like nanostructures were synthesized. The oxidation states of Fe and Cr in these nanorods were Fe 3+ and Cr 3+ . Quantitative analyses revealed an average Fe/Cr atomic ratio of 9.2, nearly identical to the ratio of the metals in the SUS410 substrate.

An aniso tropic brane world cosmological model with the bulk-based approach

International Nuclear Information System (INIS)

Uluyazi, G.

2010-01-01

To investigate brane world models there are two approaches; brane-based or bulk based. In the brane-based approach, the brane is chosen to be fixed on a coordinate system, where as in the bulk-based approach it is no longer static as it moves along the extra dimension. At first attempt, it is aimed to solve five dimensional field equations in the bulk, then limitation of Weyl Curvature describing geometrical anisotropy is analyzed.

Nanoindentation studies on Cu-Ti-Zr-Ni-Si-Sn bulk metallic glasses

International Nuclear Information System (INIS)

Mukhopadhyay, N.K.; Belger, A.; Paufler, P.; Kim, D.H.

2007-01-01

In the present investigation, Cu 47 Ti 33 Ni 6 Sn 2 Si 1 (numbers indicate at.%) bulk metallic glass (BMG), fabricated by injection casting has been used for indentation experiments. Microindentation and nanoindentation tests were conducted to study the indentation responses of this material. The nanohardness and the Young's modulus were calculated following the standard procedure in literature. Around the indent, shear bands can be clearly observed under scanning electron microscopy examination. Atomic-force microscopy shows the pile of the material in a step-wise manner. The thinned sample near the indent shows the evolution of nanocrystals (∼20-30 nm) by transmission electron microscopy. During nanoindentation (in single- and multi-indent mode) experiments, the load-displacement P-h curves show displacement bursts, which are also known as pop-ins or serrations. The total displacement during indentation can be accounted for by sum total effect of the individual displacement of all the displacement-bursts observed in the P-h curve. Thus the plastic deformation of this glassy material appears to proceed in a discrete manner unlike ductile metallic alloys

Compressive behavior of wire reinforced bulk metallic glass matrix composites

Energy Technology Data Exchange (ETDEWEB)

Lee, Seung-Yub [Department of Materials Science, M/C 138-78, California Institute of Technology, Pasadena, CA 91125 (United States); Clausen, Bjorn [Lujan Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Uestuendag, Ersan [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States)]. E-mail: ustundag@iastate.edu; Choi-Yim, Haein [Department of Materials Science, M/C 138-78, California Institute of Technology, Pasadena, CA 91125 (United States); Aydiner, C. Can [Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011 (United States); Bourke, Mark A.M. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2005-06-15

Bulk metallic glasses (BMGs) possess a unique set of mechanical properties that make them attractive structural materials. However, when loaded without constraint, BMGs fracture catastrophically due to formation of macroscopic shear bands and this behavior reduces their reliability. To address this issue, BMG matrix composites have been developed. In this investigation, neutron diffraction was used during uniaxial compressive loading to measure the internal strains in the second phases of various BMG composites reinforced with Ta, Mo, or stainless steel wires. The diffraction data were then employed to develop a finite element model that deduced the in situ constitutive behavior of each phase. It was found that the reinforcements yielded first and started transferring load to the matrix, which remained elastic during the whole experiment. While the present composites exhibited enhanced ductility, largely due to their ductile reinforcements, they yielded at applied stresses lower than those found in W reinforced composites.

Non-isothermal crystallization kinetics and fragility of (Cu46Zr47Al7)97Ti3 bulk metallic glass investigated by differential scanning calorimetry

International Nuclear Information System (INIS)

Zhu, Man; Li, Junjie; Yao, Lijuan; Jian, Zengyun; Chang, Fang’e; Yang, Gencang

2013-01-01

Highlights: • Non-isothermal crystallization kinetics of (Cu 46 Zr 47 Al 7 ) 97 Ti 3 BMGs was studied. • Two-stage of crystallization process is confirmed by DSC. • The nucleation process is difficult than growth process during crystallization. • The second crystallization process is the most sensitive to heating rate. • Kinetic fragility index is evaluated suggesting it is an intermediate glass. - Abstract: In this paper, bulk metallic glasses with the composition of (Cu 46 Zr 47 Al 7 ) 97 Ti 3 were prepared by copper mold casting technique. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to investigate its structure and non-isothermal crystallization kinetics. DSC traces revealed that it undergoes two-stage crystallization. The activation energies corresponding to the characteristic temperatures have been calculated, and the results reveal that the as-cast alloys have a good thermal stability in thermodynamics. Based on Kissinger equation, the activation energies for glass transition, the first and second crystallization processes were obtained as 485 ± 16 kJ/mol, 331 ± 7 kJ/mol and 210 ± 3 kJ/mol, respectively, suggesting that the nucleation process is more difficult than the grain growth process. The fitting curves using Lasocka's empirical relation show that the influence of the heating rate for crystallization is larger than glass transition. Furthermore, the kinetic fragility for (Cu 46 Zr 47 Al 7 ) 97 Ti 3 bulk metallic glasses is evaluated. Depending on the fragility index, (Cu 46 Zr 47 Al 7 ) 97 Ti 3 bulk metallic glasses should be considered as “intermediate glasses”

Fe-based bulk amorphous alloys with iron contents as high as 82 at%

Energy Technology Data Exchange (ETDEWEB)

Li, Jin-Feng; Liu, Xue; Zhao, Shao-Fan; Ding, Hong-Yu [School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Yao, Ke-Fu, E-mail: kfyao@tsinghua.edu.cn [School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

2015-07-15

Fe-based bulk amorphous alloys (BAAs) with high Fe contents are advantageous due to their high saturation magnetization and low cost. However, preparing Fe-based BAAs with Fe contents higher than 80 at% is difficult due to their poor glass forming abilities (GFA). In this study, an Fe{sub 81}P{sub 8.5}C{sub 5.5}B{sub 2}Si{sub 3} BAA with a diameter of 1 mm and a saturation magnetization of 1.56 T was successfully prepared using the fluxing and copper mold casting methods. In addition, by introducing a small amount of elemental Mo to the alloy, an Fe{sub 82}Mo{sub 1}P{sub 6.5}C{sub 5.5}B{sub 2}Si{sub 3} BAA rod with a diameter of 1 mm, a high saturation magnetization of 1.59 T, a high yield stress of 3265 MPa, and a clear plasticity of 1.3% was prepared in the same way. The cost effectiveness and good magnetic properties of these newly-developed Fe-based BAAs with Fe contents as high as 82 at% would be advantageous and promising for industrial applications. - Highlights: • Novel Fe-based BAA with no other metallic element except 81 at% Fe was prepared. • Fe-based bulk amorphous alloy (BAA) with the highest Fe content (82%) was prepared. • Very high saturation magnetization of 1.59 T has been achieved. • A new thought for designing Fe-based BAA with high Fe content was provided.

Soft magnetic properties of bulk amorphous Co-based samples

International Nuclear Information System (INIS)

Fuezer, J.; Bednarcik, J.; Kollar, P.

2006-01-01

Ball milling of melt-spun ribbons and subsequent compaction of the resulting powders in the supercooled liquid region were used to prepare disc shaped bulk amorphous Co-based samples. The several bulk samples have been prepared by hot compaction with subsequent heat treatment (500 deg C - 575 deg C). The influence of the consolidation temperature and follow-up heat treatment on the magnetic properties of bulk samples was investigated. The final heat treatment leads to decrease of the coercivity to the value between the 7.5 to 9 A/m (Authors)

A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors.

Science.gov (United States)

Chen, Weifeng; Wu, Weijing; Zhou, Lei; Xu, Miao; Wang, Lei; Ning, Honglong; Peng, Junbiao

2018-03-11

A semi-analytical extraction method of interface and bulk density of states (DOS) is proposed by using the low-frequency capacitance-voltage characteristics and current-voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs). In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson's equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco). As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS) simultaneously.

A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors

Directory of Open Access Journals (Sweden)

Weifeng Chen

2018-03-01

Full Text Available A semi-analytical extraction method of interface and bulk density of states (DOS is proposed by using the low-frequency capacitance–voltage characteristics and current–voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs. In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson’s equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco. As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS simultaneously.

Transient regimes during high-temperature deformation of a bulk metallic glass: A free volume approach

International Nuclear Information System (INIS)

Bletry, M.; Guyot, P.; Brechet, Y.; Blandin, J.J.; Soubeyroux, J.L.

2007-01-01

The homogeneous deformation of a zirconium-based bulk metallic glass is investigated in the glass transition range. Compression and stress-relaxation tests have been conducted. The stress-strain curves are modeled in the framework of the free volume theory, including transient phenomena (overshoot and undershoot). This approach allows several physical parameters (activation volume, flow defect creation and relaxation coefficient) to be determined from a mechanical experiment. This model is able to rationalize the dependency of stress overshoot on relaxation time. It is shown that, due to the relationship between flow defect concentration and free volume model, it is impossible to determine the equilibrium flow defect concentration. However, the relative variation of flow defect is always the same, and all the model parameters depend on the equilibrium flow defect concentration. The methodology presented in this paper should, in the future, allow the consistency of the free volume model to be assessed

Development of Efficient and Stable Inverted Bulk Heterojunction (BHJ) Solar Cells Using Different Metal Oxide Interfaces

OpenAIRE

Ivan Litzov; Christoph J. Brabec

2013-01-01

Solution-processed inverted bulk heterojunction (BHJ) solar cells have gained much more attention during the last decade, because of their significantly better environmental stability compared to the normal architecture BHJ solar cells. Transparent metal oxides (MeO x ) play an important role as the dominant class for solution-processed interface materials in this development, due to their excellent optical transparency, their relatively high electrical conductivity and their tunable work fun...

Fe-based bulk metallic glasses with a larger supercooled liquid region and high ductility

Energy Technology Data Exchange (ETDEWEB)

Qiu, K.Q. [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110178 (China)], E-mail: kqqiu@yahoo.com.cn; Pang, J.; Ren, Y.L.; Zhang, H.B. [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110178 (China); Ma, C.L.; Zhang, T. [School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)

2008-12-20

Bulk metallic glasses (BMGs) with compositions of Fe{sub 61.5-x}Co{sub 3}Mo{sub 14}C{sub 15}B{sub 6}Er{sub 0.5}M{sub x} (x = 2, 3; M = Ni, Nb) were fabricated by copper mold casting using raw industrial materials. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical tester and scanning electron microscope (SEM) were employed to check the phase constituent, the thermal stability, the mechanical properties and the fracture surfaces of as-cast samples. The results indicate that the BMGs with diameters of 1.5-3 mm were fabricated for the alloys investigated. The largest supercooled liquid region (SLR) up to 76 K was found for Fe{sub 58.5}Co{sub 3}Mo{sub 14}C{sub 15}B{sub 6}Er{sub 0.5}Ni{sub 3} BMG. The BMGs with Ni addition exhibit not only high fracture strengths reaching 3770 MPa for x = 2 and 3980 MPa for x = 3 alloys, respectively, but also apparently plastic strains up to 0.67% and 0.93%, respectively. The fracture surfaces of the Fe{sub 61.5-x}Co{sub 3}Mo{sub 14}C{sub 15}B{sub 6}Er{sub 0.5}Ni{sub x} (x = 2, 3) alloys with plasticity show narrow ridges characteristic of venous patterns combining with tearing flow between the ridges. While the Nb containing alloys show not only a lower SLR below 60 K but also a lower stress below 2400 MPa, as well as almost no plastic strain before fracture.

Deformation behavior, corrosion resistance, and cytotoxicity of Ni-free Zr-based bulk metallic glasses.

Science.gov (United States)

Liu, L; Qiu, C L; Chen, Q; Chan, K C; Zhang, S M

2008-07-01

Two Ni-free bulk metallic glasses (BMGs) of Zr(60)Nb(5)Cu(22.5)Pd(5)Al(7.5) and Zr(60)Nb(5)Cu(20)Fe(5)Al(10) were successfully prepared by arc-melting and copper mold casting. The thermal stability and crystallization were studied using differential scanning calorimetry. It demonstrates that the two BMGs exhibit very good glass forming ability with a wide supercooled liquid region. A multi-step process of crystallization with a preferential formation of quasicrystals occurred in both BMGs under continuous heating. The deformation behavior of the two BMGs was investigated using quasi-static compression testing. It reveals that the BMGs exhibit not only superior strength but also an extended plasticity. Corrosion behaviors of the BMGs were investigated in phosphate buffered solution by electrochemical polarization. The result shows that the two BMGs exhibit excellent corrosion resistance characterized by low corrosion current densities and wide passive regions. X-ray photoelectron spectroscopy analysis revealed that the passive film formed after anodic polarization was highly enriched in zirconium, niobium, and aluminum oxides. This is attributed to the excellent corrosion resistance. Additionally, the potential cytotoxicity of the two Ni-free BMGs was evaluated through cell culture for 1 week followed by 3-(4,5-Dimethylthiazol-2-yl-)-2,5-diphenyltetrazolium bromide assay and SEM observation. The results indicate that the two Ni-free BMGs exhibit as good biocompatibility as Ti-6Al-4V alloy, and thus show a promising potential for biomedical applications. (c) 2007 Wiley Periodicals, Inc.

Stability and electronic structure of Zr-based ternary metallic glasses and relevant compounds

International Nuclear Information System (INIS)

Hasegawa, M.; Soda, K.; Sato, H.; Suzuki, T.; Taketomi, T.; Takeuchi, T.; Kato, H.; Mizutani, U.

2007-01-01

The electronic structure of the Zr-based metallic glasses has been investigated by theoretical and experimental approaches. One approach is band calculations of the Zr 2 Ni (Zr 66.7 Ni 33.3 ) compound to investigate the electronic structure of the Zr 66.7 Ni 33.3 metallic glass (ΔT x = 0 K) of which the local atomic structure is similar to that of the Zr 2 Ni compound. The other is photoemission spectroscopy of the Zr 50 Cu 35 Al 15 bulk metallic glass (BMG) (ΔT x = 69 K). Here ΔT x = T x - T g where T x and T g are crystallization and glass transition temperature, respectively. Both results and previous ones on the Zr 55 Cu 30 Ni 5 Al 10 BMG indicate that there is a pseudogap at the Fermi level in the electronic structure of these Zr-based metallic glasses, independent of the value of the ΔT x . This implies that the pseudogap at the Fermi level is one of the factors that stabilize the glass phase of Zr-based metallic glasses

Stability of bulk metallic glass structure

Energy Technology Data Exchange (ETDEWEB)

Jain, H.; Williams, D.B.

2003-06-18

The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub (80-x)}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

Commercial Implementation of Model-Based Manufacturing of Nanostructured Metals

Energy Technology Data Exchange (ETDEWEB)

Lowe, Terry C. [Los Alamos National Laboratory

2012-07-24

Computational modeling is an essential tool for commercial production of nanostructured metals. Strength is limited by imperfections at the high strength levels that are achievable in nanostructured metals. Processing to achieve homogeneity at the micro- and nano-scales is critical. Manufacturing of nanostructured metals is intrinsically a multi-scale problem. Manufacturing of nanostructured metal products requires computer control, monitoring and modeling. Large scale manufacturing of bulk nanostructured metals by Severe Plastic Deformation is a multi-scale problem. Computational modeling at all scales is essential. Multiple scales of modeling must be integrated to predict and control nanostructural, microstructural, macrostructural product characteristics and production processes.

Oxidation behaviour of metallic glass foams

Energy Technology Data Exchange (ETDEWEB)

Barnard, B.R. [Department of Materials Science and Engineering, 434 Dougherty Hall, University of Tennessee, Knoxville, TN 37996-2200 (United States)], E-mail: bbarnard@utk.edu; Liaw, P.K. [Department of Materials Science and Engineering, 434 Dougherty Hall, University of Tennessee, Knoxville, TN 37996-2200 (United States); Demetriou, M.D.; Johnson, W.L. [Department of Materials Science, Keck Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States)

2008-08-15

In this study, the effects of porosity on the oxidation behaviour of bulk-metallic glasses were investigated. Porous Pd- and Fe-based bulk-metallic glass (BMG) foams and Metglas ribbons were studied. Oxidizing experiments were conducted at 70 deg. C, and around 80 deg. C below glass-transition temperatures, (T{sub g}s). Scanning-electron microscopy/energy-dispersive spectroscopy (SEM/EDS) studies revealed little evidence of oxidation at 70 deg. C. Specimens exhibited greater oxidation at T{sub g} - 80 deg. C. Oxides were copper-based for Pd-based foams, Fe-, Cr-, and Mo-based for Fe-based foams, and Co-based with borosilicates likely for the Metglas. Pd-based foams demonstrated the best oxidation resistance, followed by Metglas ribbons, followed by Fe-based foams.

Investigation of the microcrack evolution in a Ti-based bulk metallic glass matrix composite

Directory of Open Access Journals (Sweden)

Yongsheng Wang

2014-04-01

Full Text Available The initiation and evolution behavior of the shear-bands and microcracks in a Ti-based metallic-glass–matrix composite (MGMC were investigated by using an in-situ tensile test under transmission electron microscopy (TEM. It was found that the plastic deformation of the Ti-based MGMC related with the generation of the plastic deformation zone in crystalline and shear deformation zone in glass phase near the crack tip. The dendrites can suppress the propagation of the shear band effectively. Before the rapid propagation of cracks, the extending of plastic deformation zone and shear deformation zone ahead of crack tip is the main pattern in the composite.

Bulk-fill resin-based composites: an in vitro assessment of their mechanical performance.

Science.gov (United States)

Ilie, N; Bucuta, S; Draenert, M

2013-01-01

The study aimed to assess the mechanical performance of seven bulk-fill RBCs (Venus Bulk Fill, Heraeus Kulzer; SureFil SDR flow, Dentsply Caulk; x-tra base and x-tra fil, VOCO; Filtek Bulk Fill, 3M ESPE; SonicFill, Kerr; Tetric EvoCeram Bulk Fill, Ivoclar Vivadent) by determining their flexural strength (σ), reliability (Weibull parameter, m), flexural modulus (Eflexural), indentation modulus (YHU), Vickers hardness (HV), and creep (Cr). The significant highest flexural strengths were measured for SonicFill, x-tra base, and x-tra fil, while x-tra base, SureFil SDR flow, and Venus Bulk Fill showed the best reliability. The differences among the materials became more evident in terms of Eflexural and YHU, with x-tra fil achieving the highest values, while Filtek Bulk Fill and Venus Bulk Fill achieved the lowest. The enlarged depth of cure in bulk-fill RBCs seems to have been realized by enhancing the materials' translucency through decreasing the filler amount and increasing the filler size. The manufacturer's recommendation to finish a bulk-fill RBC restoration by adding a capping layer made of regular RBCs is an imperative necessity, since the modulus of elasticity and hardness of certain materials (SureFil SDR flow, Venus Bulk Fill, and Filtek Bulk Fill) were considerably below the mean values measured in regular nanohybrid and microhybrid RBCs. The class of bulk-fill RBCs revealed similar flexural strength values as the class of nanohybrid and microhybrid RBCs, and significantly higher values when compared to flowable RBCs. The modulus of elasticity (Eflexural), the indentation modulus (YHU), and the Vickers hardness (HV) classify the bulk-fill RBCs as between the hybrid RBCs and the flowable RBCs; in terms of creep, bulk-fill and the flowable RBCs perform similarly, both showing a significantly lower creep resistance when compared to the nanohybrid and microhybrid RBCs.

Effect of high-order multicomponent on formation and properties of Zr-based bulk glassy alloys

Energy Technology Data Exchange (ETDEWEB)

Inoue, A., E-mail: ainouebmg@yahoo.co.jp [International Institute of Green Materials, Josai International University, Togane 283-8555 (Japan); School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Department of Physics, King Abdulaziz University, Jeddah 22254 (Saudi Arabia); Wang, Z.; Louzguine-Luzgin, D.V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Han, Y. [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Kong, F.L. [International Institute of Green Materials, Josai International University, Togane 283-8555 (Japan); Shalaan, E.; Al-Marzouki, F. [Department of Physics, King Abdulaziz University, Jeddah 22254 (Saudi Arabia)

2015-07-25

Highlights: • A multicomponent Zr{sub 55}Al{sub 10}Fe{sub 6}Co{sub 6}Ni{sub 6}Cu{sub 6}Pd{sub 6}Ag{sub 5} bulk glassy alloy was formed. • The high-order multiplication suppression of the decrease in mechanical strength. • The BGAs show good corrosion resistance and slow growth rate of primary precipitates. - Abstract: We examined the formation, thermal stability, mechanical properties and corrosion behavior of a multicomponent Zr{sub 55}Al{sub 10}Fe{sub 6}Co{sub 6}Ni{sub 6}Cu{sub 6}Pd{sub 6}Ag{sub 5} bulk glassy alloy, with the aim of clarifying the effect of high-order multiplication of the number of components on their properties. The bulk glassy alloy rods of 2 and 6 mm in diameter were formed by suction casting even at the low total content of typical glass-forming 3-d late transition metals like Co, Ni and Cu. The Vickers hardness is different in the center region and in the outer surface region. The difference seems to reflect the relaxation level of glassy structure. The Young’s modulus and the compressive fracture strength are nearly the same for the base Zr{sub 55}Al{sub 10}Ni{sub 5}Cu{sub 30} alloy in spite of the existence of immiscible atomic pairs. Moreover, the multicomponent alloy exhibits better corrosion resistance than that for the base alloy. The glassy phase changes to a supercooled liquid state at 720 K and then starts to crystallize at 754 K with a single exothermic peak, in contrast to the appearance of a wide supercooled liquid region for the base alloy. The primary crystalline phase precipitates with very short incubation time and very low growth rate, which are different from those for the base alloy. The extremely low growth rate of the crystallites is presumably due to the reduction of diffusivity of late transition metal elements resulting from multiplication. Thus, the high-order multiplication has the features of (1) the maintenance of high glass-forming ability even at the lower Co, Ni and Cu content and in the absence of

A new parameter to evaluate the glass-forming ability of bulk metallic glasses

International Nuclear Information System (INIS)

Suo, Z.Y.; Qiu, K.Q.; Li, Q.F.; You, J.H.; Ren, Y.L.; Hu, Z.Q.

2010-01-01

Research highlights: → Develop a new criterion, i.e., Q=((T g +T x )/T l ).(ΔE/ΔH). → The reliability and benefits of the new criterion have been demonstrated in a wide range of BMG alloys. → It corresponds well with the critical diameter of BMGs investigated up to now. - Abstract: Based on the consideration of the liquid phase stability, the resistance to crystallization and the glass transition enthalpy, a new criterion Q, defined as ((T g + T x )/T l ).(ΔE/ΔH), where the T g , T x , T l , ΔE and ΔH are the glass transition temperature, the onset crystallization temperature, the liquidus temperature, the crystalline enthalpy and the fusion enthalpy, respectively, has been proposed for evaluating the glass-forming ability of bulk metallic glasses. The new criterion Q exhibits better correlation with the maximum cross section thickness (D m ) for glass formation compared with γ (=T x /(T l + T g )), T rg (=T g /T l ) and ΔT x (=T x - T g ) respectively. The available data from literatures and experiments have confirmed the effectiveness of the newly developed criterion.

ZrCuAl Bulk Metallic Glass spall induced by laser shock

Science.gov (United States)

Jodar, Benjamin; Loison, Didier; Yokoyama, Yoshihiko; Lescoute, Emilien; Berthe, Laurent; Sangleboeuf, Jean-Christophe

2017-06-01

To face High Velocity Impacts, the aerospace industry is always seeking for innovative materials usable as debris shielding components. Bulk Metallic Glasses (BMG) revealed interesting mechanical properties in case of static and quasi-static loading conditions: high elasticity, high tenacity, low density and high fracture threshold... The department of Mechanics and Glass of the Institut of Physics Rennes conducted on the ELFIE facility, laser shock experiments to study the behavior of a ternary ZrCuAl BMG under high strain rate, up-to fragmentation process. On the one hand, in-situ diagnostics were used to measure ejection velocities with PDV and debris morphologies were observed by Shadowgraphy. On the other hand, spalled areas (dimensions and features) were characterized through post-mortem analysis (optical observations, profilometry and SEM). These results are compared to experimental and numerical data on the crystalline forms of the ZrCuAl basic compounds.

Improvement of the thermoplastic formability of Zr{sub 65}Cu{sub 17.5}Ni{sub 10}Al{sub 7.5} bulk metallic glass by minor addition of Erbium

Energy Technology Data Exchange (ETDEWEB)

Hu, Q. [Shenzhen Key Laboratory of Special Functional Materials, College of Materials Science and Engineering, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Zeng, X.R., E-mail: zengxier@szu.edu.cn [Shenzhen Key Laboratory of Special Functional Materials, College of Materials Science and Engineering, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); JANUS Precision Components Co., LTD., Dongguan 523000 (China); Fu, M.W., E-mail: mmmwfu@polyu.edu.hk [Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Chen, S.S. [Shenzhen Key Laboratory of Special Functional Materials, College of Materials Science and Engineering, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Jiang, J. [Institute of Applied Physics, Jiangxi Academy of Sciences, Nanchang 330029 (China)

2016-12-01

The softness of Zr{sub 65}Cu{sub 17.5}Ni{sub 10}Al{sub 7.5} bulk metallic glass (BMG) in the super-cooled liquid range (SCLR) is obviously improved by minor addition of 2% Er, which makes (Zr{sub 65}Cu{sub 17.5}Ni{sub 10}Al{sub 7.5}){sub 98}Er{sub 2} (Zr65Er2) to be a very formable Be-free Zr-based BMG. It is found the lower glass transition temperature of Zr65Er2 has an important contribution to the improvement of formability, which is contrary to the general understanding that the larger fragility and wider super-cooled liquid region (SCLR) are the major reasons for better thermoplastic formability. This finding is well explained by using the linear simplification of the SCLR in Angell plot. Zr65Er2 also has lower crystallization temperature and melting temperature, which is believed to be related to the formation of short-range ordering with lower transition energy rather than the composition shift to near eutectic. The above results help understand the effect of minor addition of rare-earth to the formability of Zr-based bulk metallic glasses.

Microstructural evolution and homogeneous viscous flow behavior of a Cu–Zr based bulk metallic glass composites

International Nuclear Information System (INIS)

Zhang, X.Y.; Yuan, Z.Z.; Li, D.X.

2014-01-01

Highlights: • Stress–strain behaviors of the BMGCs are strain rate and temperature dependent. • Micro-crystals are compressed to concave polygon in shape and align in line. • Nano-crystals nuclear and aggregate during high temperature deformation. • Deformation behavior is governed by homogeneous flow of the amorphous matrix. - Abstract: The high temperature compression behavior of Cu 40 Zr 44 Ag 8 Al 8 rods with 6 mm in diameter was investigated and compared with the literature data. Microstructure of the as-cast rods were characterized by X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscope in the composites state with microscale Al 3 Zr particles embedded in the amorphous matrix. Deformation results show that the stress–strain behaviors of the bulk metallic glass composites (BMGCs) are strain rate and temperature dependent. In addition, SEM observations reveal that the initially spherical and randomly distributed microscale particles in the amorphous matrix deform to concave polygon in shape and align perpendicular to the load direction during the compression. Meanwhile nano-crystals precipitate continuously from the matrix and aggregate during deformation. Rheological analysis show that the BMGCs exhibit a transition from Newtonian to non-Newtonian in flow behavior dependent on the stain rate. Particles in the amorphous matrix have reinforcement effect on the BMGCs, but the deformation behavior is still dominated by the homogeneous flow of the amorphous matrix phase

A transparent electrode based on a metal nanotrough network.

Science.gov (United States)

Wu, Hui; Kong, Desheng; Ruan, Zhichao; Hsu, Po-Chun; Wang, Shuang; Yu, Zongfu; Carney, Thomas J; Hu, Liangbing; Fan, Shanhui; Cui, Yi

2013-06-01

Transparent conducting electrodes are essential components for numerous flexible optoelectronic devices, including touch screens and interactive electronics. Thin films of indium tin oxide-the prototypical transparent electrode material-demonstrate excellent electronic performances, but film brittleness, low infrared transmittance and low abundance limit suitability for certain industrial applications. Alternatives to indium tin oxide have recently been reported and include conducting polymers, carbon nanotubes and graphene. However, although flexibility is greatly improved, the optoelectronic performance of these carbon-based materials is limited by low conductivity. Other examples include metal nanowire-based electrodes, which can achieve sheet resistances of less than 10Ω □(-1) at 90% transmission because of the high conductivity of the metals. To achieve these performances, however, metal nanowires must be defect-free, have conductivities close to their values in bulk, be as long as possible to minimize the number of wire-to-wire junctions, and exhibit small junction resistance. Here, we present a facile fabrication process that allows us to satisfy all these requirements and fabricate a new kind of transparent conducting electrode that exhibits both superior optoelectronic performances (sheet resistance of ~2Ω □(-1) at 90% transmission) and remarkable mechanical flexibility under both stretching and bending stresses. The electrode is composed of a free-standing metallic nanotrough network and is produced with a process involving electrospinning and metal deposition. We demonstrate the practical suitability of our transparent conducting electrode by fabricating a flexible touch-screen device and a transparent conducting tape.

Residual stresses in a bulk metallic glass-stainless steel composite

Energy Technology Data Exchange (ETDEWEB)

Aydiner, C.C. [Department of Materials and Science Engineering, Iowa State University, Ames, IA 50011 (United States); Uestuendag, E. [Department of Materials and Science Engineering, Iowa State University, Ames, IA 50011 (United States)]. E-mail: ustundag@iastate.edu; Clausen, B. [Lujan Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hanan, J.C. [Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125 (United States); Winholtz, R.A. [Department of Mechanical and Aerospace Engineering and Research Reactor Center, University of Missouri, Columbia, MO 65211 (United States); Bourke, M.A.M. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Peker, A. [Liquidmetal Technologies, Lake Forest, CA 92630 (United States)

2005-06-15

Bulk metallic glasses (BMGs) are new structural materials with impressive mechanical properties. They can now be cast into large dimensions, which can lead to significant residual stress generation due to thermal tempering. In this process, a surface compression develops balanced with tension in the interior. To evaluate this phenomenon non-destructively, a model cylindrical stainless steel (SS)-BMG composite was prepared and studied using neutron diffraction and finite element (FE) modeling. The residual strain data from the SS obtained by diffraction were used in modeling calculations to show that significant tempering could be achieved in the composite (about -200 MPa surface compression in the SS). The strong bond between the SS and BMG allowed efficient load transfer and facilitated stress generation. The final values of the residual stresses were seen to be relatively insensitive to the high temperature constitutive behavior of the SS due to the physics of the thermal tempering in BMGs. The approach presented here constitutes an effective means to study non-destructively thermal tempering in BMGs.

Residual stresses in a bulk metallic glass-stainless steel composite

International Nuclear Information System (INIS)

Aydiner, C.C.; Uestuendag, E.; Clausen, B.; Hanan, J.C.; Winholtz, R.A.; Bourke, M.A.M.; Peker, A.

2005-01-01

Bulk metallic glasses (BMGs) are new structural materials with impressive mechanical properties. They can now be cast into large dimensions, which can lead to significant residual stress generation due to thermal tempering. In this process, a surface compression develops balanced with tension in the interior. To evaluate this phenomenon non-destructively, a model cylindrical stainless steel (SS)-BMG composite was prepared and studied using neutron diffraction and finite element (FE) modeling. The residual strain data from the SS obtained by diffraction were used in modeling calculations to show that significant tempering could be achieved in the composite (about -200 MPa surface compression in the SS). The strong bond between the SS and BMG allowed efficient load transfer and facilitated stress generation. The final values of the residual stresses were seen to be relatively insensitive to the high temperature constitutive behavior of the SS due to the physics of the thermal tempering in BMGs. The approach presented here constitutes an effective means to study non-destructively thermal tempering in BMGs

CARBON-CONTAINING COMPOSITES BASED ON METALS

Directory of Open Access Journals (Sweden)

VAGANOV V. E.

2015-10-01

Full Text Available Problem statement Among the developed technologies metal-composites production,a special place takes powder metallurgy, having fundamental differences from conventionally used foundry technologies. The main advantages of this technology are: the possibility of sensitive control, the structure and phase composition of the starting components, and ultimately the possibility of obtaining of bulk material in nanostructured state with a minimum of processing steps. The potential reinforcers metals include micro and nano-sized oxides, carbides, nitrides, whiskers. The special position is occupied with carbon nanostructures (CNS: С60 fullerenes, single-layer and multi-layer nanotubes, onions (spherical "bulbs", nano-diamonds and graphite,their properties are being intensively studied in recent years. These objects have a high thermal and electrical conductivity values, superelasticity, and have a strength approximate to the theoretical value, which can provide an obtaining composite nanomaterial with a unique set of physical and mechanical properties. In creation of a metal matrix composite nanomaterials (CM, reinforced by various CNS, a special attention should be given to mechanical activation processes (MA already at the stage of preparation of the starting components affecting the structure, phase composition and properties of aluminum-matrix composites. Purpose. To investigate the influence of mechanical activation on the structure and phase composition of aluminum-matrix composites. Conclusion. The results of the study of the structure and phase composition of the initial and mechanically activated powders and bulk-modified metal-composites are shown, depending on the type and concentration of modifying varieties CNS, regimes of MA and parameters of compaction. The study is conducted of tribological properties of Al-CNS OF nanostructured materials.

Preparation and characterization of rare-earth bulks with controllable nanostructures

International Nuclear Information System (INIS)

Song Xiaoyan; Zhang Jiuxing; Li Erdong; Lu Nianduan; Yin Fuxing

2006-01-01

The preparation and characterization of pure rare-earth-metal bulks with controllable nanostructures are reported in this paper. A novel 'oxygen-free' in situ synthesis technique that combines inert-gas condensation with spark plasma sintering (SPS) technology is proposed. Taking into account the special mechanisms of SPS consolidation and the scale effects of nanoparticles, we introduced practical procedures for preparing rare-earth bulks of amorphous, mixed amorphous and nanocrystals, and nanocrystalline microstructures, respectively. Compared with the conventional polycrystalline bulk, these nanostructured bulks exhibit substantially improved physical and mechanical properties. This technique enables comprehensive studies on the microstructures and properties of a large variety of nanostructured metallic materials that are highly reactive in the air

Fracture toughness study of new Zr-based Be-bearing bulk metallic glasses

OpenAIRE

Kim, C. Paul; Suh, Jin-Yoo; Wiest, Aaron; Lind, Mary Laura; Conner, R. Dale; Johnson, William L.

2009-01-01

Three new compositional variants of the Zr–Ti–Be–LTM (late transition metal) family of metallic glasses are discussed. Thermal stability, ΔT = T_x−T_g, was increased from 82 °C for Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) (Viterloy 1) to 141 °C for Zr_(44)Ti_(11)Cu_(20)Be_(25). It is found that fracture toughness is the most distinguishing parameter characterizing the alloys in contrast to other mechanical properties. Quaternary alloys consistently had fracture toughness values exceeding 8...

Glass-Forming Ability and Early Crystallization Kinetics of Novel Cu-Zr-Al-Co Bulk Metallic Glasses

Directory of Open Access Journals (Sweden)

Xiaoliang Han

2016-09-01

Full Text Available In recent years, CuZr-based bulk metallic glass (BMG composites ductilized by a shape memory B2 CuZr phase have attracted great attention owing to their outstanding mechanical properties. However, the B2 CuZr phase for most CuZr-based glass-forming compositions is only stable at very high temperatures, leading to the uncontrollable formation of B2 crystals during quenching. In this work, by introducing Co (i.e., 4, 5, and 6 at. % and 10 at. % Al into CuZr-based alloys, the relatively good glass-forming ability (GFA of CuZr-based alloys still can be achieved. Meanwhile, the B2 phase can be successfully stabilized to lower temperatures than the final temperatures of crystallization upon heating CuZr-based BMGs. Unlike previous reported CuZr-based BMGs, the primary crystallization products upon heating are mainly B2 CuZr crystals but not CuZr2 and Cu10Zr7 crystals. Furthermore, the primary precipitates during solidification are still dominated by B2 crystals, whose percolation threshold is detected to lie between 10 ± 2 vol. % and 31 ± 2 vol. %. The crystallization kinetics underlying the precipitation of B2 crystals was also investigated. Our results show that the present glass-forming composites are promising candidates for the fabrication of ductile CuZr-based BMG composites.

Crystallization in Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass under pressure

DEFF Research Database (Denmark)

Jiang, Jianzhong; Zhou, T.J.; Rasmussen, Helge Kildahl

2000-01-01

The effect of pressure on the crystallization behavior of the bulk metallic glass-forming Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy with a wide supercooled liquid region has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction measurements using synchrotron radiation......)], reporting a decrease of the crystallization temperature under pressure in a pressure range of 0-6 GPa for the bulk glass Zr41Ti14Cu12.5Ni9Be22.5C1 alloy. Compressibility with a volume reduction of approximately 22% at room temperature does not induce crystallization in the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk...... glass alloy. This indicates that the densification effect induced by pressure in the pressure range investigated plays a minor role in the crystallization behavior of this bulk glass alloy. The different crystallization behavior of the carbon-free and the carbon-containing glassy alloys has been...

Charge based DC compact modeling of bulk FinFET transistor

Science.gov (United States)

Cerdeira, A.; Garduño, I.; Tinoco, J.; Ritzenthaler, R.; Franco, J.; Togo, M.; Chiarella, T.; Claeys, C.

2013-09-01

Multiple-gate MOSFETs became an industrial reality in the last years. Due to a pragmatic trade-off between CMOS process baselines compatibility, improved performance compared to planar bulk architecture, and cost, bulk FinFETs emerged as the technological solution to provide downscaling for the 14/22 nm technological nodes. In this work, a charge based DC compact model based on the SDDG Model is demonstrated for this new generation of FinFET transistors and describes continuously the transistor characteristics in all operating regions. Validating the model against two bulk FinFET baselines (NMOS, PMOS, various gate lengths and EOT), an excellent agreement is found for transfer and output characteristics (linear and saturation regimes), transconductance/output conductance, and gm/IDS characteristics. Temperature dependence is also taken into account and validated (T range from 25 °C up to 175 °C).

Existence conditions for bulk large-wavevector waves in metal-dielectric and graphene-dielectric multilayer hyperbolic metamaterials

DEFF Research Database (Denmark)

Zhukovsky, Sergei; Andryieuski, Andrei; Lavrinenko, Andrei

2014-01-01

We theoretically investigate general existence conditions for broadband bulk large-wavevector (high-k) propagating waves (such as volume plasmon polaritons in hyperbolic metamaterials) in arbitrary subwavelength periodic multilayers structures. Treating the elementary excitation in the unit cell...... of the structure as a generalized resonance pole of reflection coefficient and using Bloch's theorem, we derive analytical expressions for the band of large-wavevector propagating solutions. We apply our formalism to determine the high-k band existence in two important cases: the well-known metal-dielectric...

Vibration-accelerated activation of flow units in a Pd-based bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Li, Ning, E-mail: hslining@mail.hust.edu.cn [School of Materials Science and Engineering, and State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Liu, Ze [Department of Engineering Mechanics, School of Civil Engineering, Wuhan University, Wuhan 430072 (China); Wang, Xinyun [School of Materials Science and Engineering, and State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang, Meng [Institute of Advanced Wear & Corrosion Resistant and Functional Materials, Jinan University, Guangzhou 510632 (China)

2017-04-24

Controlled activation of flow units and in-situ characterization of mechanical properties in metallic glasses are facing challenges thus far. Here, vibrational loading is introduced through nanoscale dynamic mechanical analysis technique to probe vibration-accelerated atomic level flow that plays a crucial role in the mechanical behavior of metallic glasses. The intriguing finding is that high vibrational frequency induces deep indentation depth, prominent pop-in events on load–depth curves and low storage modulus, exhibiting a vibration-facilitated activation of flow units in Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} metallic glass. Theoretical analysis revealed that vibration-moderated activation time-scale accelerate the activation of flow units and responsible for the above scenario.

Effects of Cu substitution for Fe on the glass-forming ability and soft magnetic properties for Fe-based bulk metallic glasses

International Nuclear Information System (INIS)

Dou, Lintao; Liu, Haishun; Hou, Long; Xue, Lin; Yang, Weiming; Zhao, Yucheng; Chang, Chuntao

2014-01-01

The effects of Cu substitution for Fe on the glass-forming ability (GFA) and soft magnetic properties for Fe 72−x Cu x B 20 Si 4 Nb 4 (x=0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) bulk metallic glasses (BMGs) are investigated. It is found that the investigated BMGs exhibit large GFA as well as excellent soft magnetic properties, and proper substitution of Fe by Cu improves the saturation magnetization, coercive force, and effective permeability without obvious deterioration of the GFA. - Highlights: • Fully glassy rods of Fe 72−x Cu x B 20 Si 4 Nb 4 BMGs were produced above 1 mm in diameter. • Investigated BMGs exhibit large glass-forming ability and excellent soft magnetic properties. • Proper Cu substitution improves magnetic properties without obvious deterioration of glass-forming ability

Crystallization kinetics and magnetic properties of Fe{sub 66}Nb{sub 4}B{sub 30} bulk metallic glass

Energy Technology Data Exchange (ETDEWEB)

Stoica, M., E-mail: m.stoica@ifw-dresden.d [IFW Dresden, Institute for Complex Materials, P.O. Box 270116, D-01171 Dresden (Germany); Kumar, S. [IFW Dresden, Institute for Complex Materials, P.O. Box 270116, D-01171 Dresden (Germany); Roth, S. [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany); Ram, S. [Materials Science Centre, Indian Institute of Technology, Kharagpur 721302 (India); Eckert, J. [IFW Dresden, Institute for Complex Materials, P.O. Box 270116, D-01171 Dresden (Germany); Vaughan, G. [European Synchrotron Radiation Facilities ESRF, 38402 Grenoble (France); Yavari, A.R. [LTPCM-CNRS, Institut National Politechnique de Grenoble, 1130 Rue de la Piscine, BP 75, Saint Martin d' Heres Campus 38402 (France)

2009-08-26

Fe-based bulk metallic glasses (BMGs) have a high application potential because of their unique soft magnetic properties, mechanical behaviour and high corrosion resistance. Also, they can be obtained directly in the final shape suitable for use as magnetic sensors, magnetic valves, magnetic clutches etc. in different devices. Fe-based alloys able to form magnetic BMGs are of the type transition metal-metalloid and often contain 5 or more elements. Usually, the metalloid content is around 20 at.%. Recently, a new Fe-based BMG containing only 3 elements and a very high boron content was synthesized. The preparation of this BMG was done by employing the copper mold casting method and using the fluxing technique. This new BMG is ferromagnetic, with a Curie temperature around 550 K and a saturation magnetization of 105 Am{sup 2}/kg. Differential scanning calorimetry (DSC) investigations revealed a reduced glass transition temperature of 0.55 and an extension of the supercooled liquid region of about 31 K, values which indicate a relatively good thermal stability. Despite of numerous studies about Fe-based BMGs, there is still a lack of data about the crystallization kinetics. Also, the intermediate metastable phases, which form upon crystallization from the amorphous state, as well as the mechanism of their formation, are not fully understood. The present work discusses the kinetics of the phase formation using the Kissinger analysis and Johnson-Mehl-Avrami plots, correlated with the results obtained upon X-ray diffraction (XRD) of samples with different metastable structures. Additionally, the magnetic behaviour of different phase(s) is presented.

Using thermoforming capacity of metallic glasses to produce multimaterials

International Nuclear Information System (INIS)

Ragani, J.; Volland, A.; Valque, S.; Liu, Y.; Gravier, S.; Blandin, J.J.; Suery, M.

2010-01-01

In addition to casting, thermoforming is a particularly interesting way to produce components in bulk metallic glasses since large strains can be achieved when the BMGs are deformed in their supercooled liquid region. The experimental window (temperature, time) in which high temperature forming can be carried out is directly related to the crystallization resistance of the glass. Such forming windows have been identified for zirconium based bulk metallic glasses thanks to thermal analysis and compression tests in the supercooled liquid region. Based on this identification, the thermoforming capacity of the studied glasses was used to produce multimaterials associating metallic glasses with conventional metallic alloys. Two processes have been preferentially investigated (co-extrusion and co-pressing) and the interface quality of the elaborated multi materials was studied.

Unified bulk-boundary correspondence for band insulators

Science.gov (United States)

Rhim, Jun-Won; Bardarson, Jens H.; Slager, Robert-Jan

2018-03-01

The bulk-boundary correspondence, a topic of intensive research interest over the past decades, is one of the quintessential ideas in the physics of topological quantum matter. Nevertheless, it has not been proven in all generality and has in certain scenarios even been shown to fail, depending on the boundary profiles of the terminated system. Here, we introduce bulk numbers that capture the exact number of in-gap modes, without any such subtleties in one spatial dimension. Similarly, based on these 1D bulk numbers, we define a new 2D winding number, which we call the pole winding number, that specifies the number of robust metallic surface bands in the gap as well as their topological character. The underlying general methodology relies on a simple continuous extrapolation from the bulk to the boundary, while tracking the evolution of Green's function's poles in the vicinity of the bulk band edges. As a main result we find that all the obtained numbers can be applied to the known insulating phases in a unified manner regardless of the specific symmetries. Additionally, from a computational point of view, these numbers can be effectively evaluated without any gauge fixing problems. In particular, we directly apply our bulk-boundary correspondence construction to various systems, including 1D examples without a traditional bulk-boundary correspondence, and predict the existence of boundary modes on various experimentally studied graphene edges, such as open boundaries and grain boundaries. Finally, we sketch the 3D generalization of the pole winding number by in the context of topological insulators.

Plastic deformation behavior of Fe–Co–B–Si–Nb–Cr bulk metallic glasses under nanoindentation

Energy Technology Data Exchange (ETDEWEB)

Kim, J.T.; Hong, S.H.; Lee, C.H. [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Park, J.M., E-mail: jinman_park@hotmail.com [Materials Research Center, Samsung Advanced Institute of Technology (SAIT), San 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-712 (Korea, Republic of); Kim, T.W.; Lee, W.H. [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Yim, H.I. [Department of Physics, Sookmyung Women’s University, Hyochangwongil 52, Yongsan-ku, Seoul 140-742 (Korea, Republic of); Kim, K.B., E-mail: kbkim@sejong.ac.kr [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

2014-02-25

Highlights: • Additional Cr modulation of atomic structure of Fe-Co-B-Si-Nb BMGs. • An amount of free volume characterized by a combination of nanoindentation and AFM. • Free volume determined by height measurement of AFM after nanoindentation. -- Abstract: In this work, we investigate the effect of Cr addition on thermal properties and indentation behavior of Fe{sub 52}Co{sub 20−x}B{sub 20}Si{sub 4}Nb{sub 4}Cr{sub x} alloys with x = 0, 1, 3 and 5 at.%, respectively. Among all studied alloys, the Fe{sub 52}Co{sub 17}B{sub 20}Si{sub 4}Nb{sub 4}Cr{sub 3} bulk metallic glass (BMG) exhibits the highest thermal stability with large supercooled liquid region of 40 K and the pronounced plastic deformation features which is serrated flow (pop-in event) and significant pile-up of materials around indents. This demonstrates that the appropriate addition of Cr in Fe-based BMG can induce the internal atomic structure modulation and promote the mechanical softening, which are discussed in terms of free volume concept.

Plastic deformation behavior of Fe–Co–B–Si–Nb–Cr bulk metallic glasses under nanoindentation

International Nuclear Information System (INIS)

Kim, J.T.; Hong, S.H.; Lee, C.H.; Park, J.M.; Kim, T.W.; Lee, W.H.; Yim, H.I.; Kim, K.B.

2014-01-01

Highlights: • Additional Cr modulation of atomic structure of Fe-Co-B-Si-Nb BMGs. • An amount of free volume characterized by a combination of nanoindentation and AFM. • Free volume determined by height measurement of AFM after nanoindentation. -- Abstract: In this work, we investigate the effect of Cr addition on thermal properties and indentation behavior of Fe 52 Co 20−x B 20 Si 4 Nb 4 Cr x alloys with x = 0, 1, 3 and 5 at.%, respectively. Among all studied alloys, the Fe 52 Co 17 B 20 Si 4 Nb 4 Cr 3 bulk metallic glass (BMG) exhibits the highest thermal stability with large supercooled liquid region of 40 K and the pronounced plastic deformation features which is serrated flow (pop-in event) and significant pile-up of materials around indents. This demonstrates that the appropriate addition of Cr in Fe-based BMG can induce the internal atomic structure modulation and promote the mechanical softening, which are discussed in terms of free volume concept

Structure and soft magnetic properties of the bulk samples prepared by compaction of the mixtures of Co-based and Fe-based powders

International Nuclear Information System (INIS)

Fuezer, J.; Bednarcik, J.; Kollar, P.; Roth, S.

2007-01-01

Ball milling of CoFeZrB ribbons and subsequent compaction of the resulting powders were used to prepare bulk amorphous samples. Further, two sets of powder samples were prepared by cryomilling of FeCuNbMoSiB alloy in amorphous and nanocrystalline state. Amorphous and nanocrystalline FeCuNbMoSiB powders were blended with CoFeZrB powder at different concentrations. Such powder mixtures were consolidated and several bulk nanocomposites have been synthesized. An addition of nanocrystalline or amorphous FeCuNbMoSiB powder to amorphous CoFeZrB powder caused a decrease of the magnetostriction of the resultant bulk samples, while the coercivity shows an opposite behavior. Our results show that the powder consolidation by hot pressing is an alternative method for the preparation of bulk metallic glasses, which are difficult to prepare by casting methods

Facile creation of bio-inspired superhydrophobic Ce-based metallic glass surfaces

Science.gov (United States)

Liu, Kesong; Li, Zhou; Wang, Weihua; Jiang, Lei

2011-12-01

A bio-inspired synthesis strategy was conducted to fabricate superhydrophobic Ce-based bulk metallic glass (BMG) surfaces with self-cleaning properties. Micro-nanoscale hierarchical structures were first constructed on BMG surfaces and then modified with the low surface energy coating. Surface structures, surface chemical compositions, and wettability were characterized by combining scanning electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, and contact angle measurements. Research indicated that both surface multiscale structures and the low surface free energy coating result in the final formation of superhydrophobicity.

Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials

DEFF Research Database (Denmark)

Moorthy, A; Hogg, C H; Dowling, A H

2012-01-01

To assess the cuspal deflection and cervical microleakage of standardised Class II cavities incrementally filled with a dimethacrylate RBC or bulk-fill flowable RBC bases.......To assess the cuspal deflection and cervical microleakage of standardised Class II cavities incrementally filled with a dimethacrylate RBC or bulk-fill flowable RBC bases....

Radiation-hardened bulk CMOS technology

International Nuclear Information System (INIS)

Dawes, W.R. Jr.; Habing, D.H.

1979-01-01

The evolutionary development of a radiation-hardened bulk CMOS technology is reviewed. The metal gate hardened CMOS status is summarized, including both radiation and reliability data. The development of a radiation-hardened bulk silicon gate process which was successfully implemented to a commercial microprocessor family and applied to a new, radiation-hardened, LSI standard cell family is also discussed. The cell family is reviewed and preliminary characterization data is presented. Finally, a brief comparison of the various radiation-hardened technologies with regard to performance, reliability, and availability is made

Dynamic behaviors of a Zr-based bulk metallic glass under ramp wave and shock wave loading

Directory of Open Access Journals (Sweden)

Binqiang Luo

2015-06-01

Full Text Available Dynamic behaviors of Zr51Ti5Ni10Cu25Al9 bulk metallic glass were investigated using electric gun and magnetically driven isentropic compression device which provide shock and ramp wave loading respectively. Double-wave structure was observed under shock compression while three-wave structure was observed under ramp compression in 0 ∼ 18GPa. The HEL of Zr51Ti5Ni10Cu25Al9 is 8.97 ± 0.61GPa and IEL is 8.8 ± 0.3GPa, respectively. Strength of Zr51Ti5Ni10Cu25Al9 estimated from HEL is 5.0 ± 0.3GPa while the strength estimated from IEL is 3.6 ± 0.1GPa. Shock wave velocity versus particle velocity curve of Zr51Ti5Ni10Cu25Al9 under shock compression appears to be bilinear and a kink appears at about 18GPa. The Lagrangian sound speed versus particle velocity curve of Zr51Ti5Ni10Cu25Al9 under ramp wave compression exhibits two discontinuances and are divided to three regions: elastic, plastic-I and plastic-II. The first jump-down occurs at elastic-plastic transition and the second appears at about 17GPa. In elastic and plastic-I regions, Lagrangian sound speed increases linearly with particle velocity, respectively. Characteristic response of sound speed in plastic-I region disagree with shock result in the same pressure region(7GPa ∼ 18GPa, but is consistent with shock result at higher pressure(18-110GPa.

Composites of amorphous and nanocrystalline Zr–Cu–Al–Nb bulk materials synthesized by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Drescher, P., E-mail: philipp.drescher@uni-rostock.de [Fluidic Technology and Microfluidics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany); Witte, K. [Physics of New Materials, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Yang, B. [Polymer Physics, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Steuer, R.; Kessler, O. [Chair of Materials Science, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany); Burkel, E. [Physics of New Materials, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Schick, C. [Polymer Physics, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Seitz, H. [Fluidic Technology and Microfluidics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany)

2016-05-15

The fabrication of Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} bulk metallic glass composite samples by spark plasma sintering (SPS) process has been successfully realized. The unique characteristics of bulk metallic glasses could lead to the possibility of future applications as new structural and functional materials. The densification of an amorphous Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} powder was realized in a systematic study changing the sintering temperature in the SPS process leading to stable composites characteristic of amorphous and nanocrystalline structures. X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) analysis, transmission electron microscopy (TEM) as well as hardness tests were applied to determine the structural and mechanical properties of the sintered materials. A stable amorphous bulk metallic glass based on Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} with a low fraction of crystallites could be fabricated applying a nominal sintering temperature of 400 °C. Higher sintering temperatures lead to composites with high fractions of nanocrystalline material with porosities below 0.5%.

Induction detection of concealed bulk banknotes

International Nuclear Information System (INIS)

Fuller, Christopher; Chen, Antao

2011-01-01

Bulk cash smuggling is a serious issue that has grown in volume in recent years. By building on the magnetic characteristics of paper currency, induction sensing is found to be capable of quickly detecting large masses of banknotes. The results show that this method is effective in detecting bulk cash through concealing materials such as plastics, cardboards, fabrics and aluminum foil. The significant difference in the observed phase between the received signals caused by conducting materials and ferrite compounds, found in banknotes, provides a good indication that this process can overcome the interference by metal objects in a real sensing application. This identification strategy has the potential to not only detect the presence of banknotes, but also the number, while still eliminating false positives caused by metal objects

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.

Positron annihilation studies on bulk metallic glass and high intensity positron beam developments

International Nuclear Information System (INIS)

Asoka-Kumar, P.; Stoeffl, W.

2003-01-01

Positron annihilation spectroscopy is an ideal probe to examine atomic scale open-volume regions in materials. Below, we summarize the recent results on studies of open-volume regions of a multicomponent Zr-Ti-Ni-Cu-Be bulk metallic glass. Our studies establish two types of open-volume regions, one group that is too shallow to trap positrons at room temperature and becomes effective only at low temperatures and the other group that localizes positrons at room temperature and is large enough to accommodate hydrogen. The second half of the paper will concentrate on the high intensity positron program at Lawrence Livermore National Laboratory. A new positron production target is under development and we are constructing two experimental end stations to accommodate a pulsed positron microprobe and an experiment on positron diffraction and holography. Important design considerations of these experiments will be described. (author)

Effect of pre-existing shear bands on the tensile mechanical properties of a bulk metallic glass

International Nuclear Information System (INIS)

Cao, Q.P.; Liu, J.W.; Yang, K.J.; Xu, F.; Yao, Z.Q.; Minkow, A.; Fecht, H.J.; Ivanisenko, J.; Chen, L.Y.; Wang, X.D.; Qu, S.X.; Jiang, J.Z.

2010-01-01

Bulk Zr 64.13 Cu 15.75 Ni 10.12 Al 10 metallic glass has been rolled at room temperature in two different directions, and the dependences of microstructure and tensile mechanical property on the degree of deformation and rolling directions have been investigated. No deformation-induced crystallization occurs except for shear bands. Shear band formation in conjugated directions is achieved in the specimen rolled in two directions, while rolling in one direction induces shear band formation only in a single direction. Pre-existing properly spaced soft inhomogeneities can stabilize shear bands and lead to tensile plastic strain, and the efficient intersection of shear bands in conjugated directions results in work-hardening behavior, which is further confirmed by in situ tensile scanning electron microscopic observation. Based on the experimental results obtained in two different specimen geometries and finite element analysis, it is deduced that a normal-stress-modified maximum shear stress criterion rather than a shear plane criterion can describe the conditions for the formation of shear bands in uniaxial tension.

Electrochemical Characteristics of Layered Transition Metal Oxide Cathode Materials for Lithium Ion Batteries: Surface, Bulk Behavior, and Thermal Properties.

Science.gov (United States)

Tian, Chixia; Lin, Feng; Doeff, Marca M

2018-01-16

Layered lithium transition metal oxides, in particular, NMCs (LiNi x Co y Mn z O 2 ) represent a family of prominent lithium ion battery cathode materials with the potential to increase energy densities and lifetime, reduce costs, and improve safety for electric vehicles and grid storage. Our work has focused on various strategies to improve performance and to understand the limitations to these strategies, which include altering compositions, utilizing cation substitutions, and charging to higher than usual potentials in cells. Understanding the effects of these strategies on surface and bulk behavior and correlating structure-performance relationships advance our understanding of NMC materials. This also provides information relevant to the efficacy of various approaches toward ensuring reliable operation of these materials in batteries intended for demanding traction and grid storage applications. In this Account, we start by comparing NMCs to the isostructural LiCoO 2 cathode, which is widely used in consumer batteries. Effects of changing the metal content (Ni, Mn, Co) upon structure and performance of NMCs are briefly discussed. Our early work on the effects of partial substitution of Al, Fe, and Ti for Co on the electrochemical and bulk structural properties is then covered. The original aim of this work was to reduce the Co content (and thus the raw materials cost) and to determine the effect of the substitutions on the electrochemical and bulk structural properties. More recently, we have turned to the application of synchrotron and advanced microscopy techniques to understand both bulk and surface characteristics of the NMCs. Via nanoscale-to-macroscale spectroscopy and atomically resolved imaging techniques, we were able to determine that the surfaces of NMC undergo heterogeneous reconstruction from a layered structure to rock salt under a variety of conditions. Interestingly, formation of rock salt also occurs under abuse conditions. The surface

Bulk Material Based Thermoelectric Energy Harvesting for Wireless Sensor Applications

International Nuclear Information System (INIS)

Wang, W S; Magnin, W; Wang, N; Hayes, M; O'Flynn, B; O'Mathuna, C

2011-01-01

The trend towards smart building and modern manufacturing demands ubiquitous sensing in the foreseeable future. Self-powered Wireless sensor networks (WSNs) are essential for such applications. This paper describes bulk material based thermoelectric generator (TEG) design and implementation for WSN. A 20cm 2 Bi 0.5 Sb 1.5 Te 3 based TEG was created with optimized configuration and generates 2.7mW in typical condition. A novel load matching method is used to maximize the power output. The implemented power management module delivers 651μW to WSN in 50 deg. C. With average power consumption of Tyndall WSN measured at 72μW, feasibility of utilizing bulk material TEG to power WSN is demonstrated.

Surface chemistry, microstructure and friction properties of some ferrous-base metallic glasses at temperatures to 750 C

Science.gov (United States)

Miyoshi, K.; Buckley, D. H.

1982-01-01

X-ray photoelectron spectroscopy analysis, transmission electron microscopy, diffraction studies, and sliding friction experiments were conducted with ferrous-base metallic glasses in sliding contact with aluminum oxide at temperatures from room to 750 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on the friction properties, surface chemistry, and microstructure of metallic glasses. The relative concentrations of the various constituents at the surface of the sputtered specimens were very different from the normal bulk compositions. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and silicon oxide at 350 C and boron nitride above 500 C. The coefficient of friction increased with increasing temperature to 350 C. Above 500 C the coefficient of friction decreased rapidly. The segregation of contaminants may be responsible for the friction behavior.

Solvent properties of hydrazine in the preparation of metal chalcogenide bulk materials and films.

Science.gov (United States)

Yuan, Min; Mitzi, David B

2009-08-21

A combination of unique solvent properties of hydrazine enables the direct dissolution of a range of metal chalcogenides at ambient temperature, rendering this an extraordinarily simple and soft synthetic approach to prepare new metal chalcogenide-based materials. The extended metal chalcogenide parent framework is broken up during this process, and the resulting metal chalcogenide building units are re-organized into network structures (from 0D to 3D) based upon their interactions with the hydrazine/hydrazinium moieties. This Perspective will review recent crystal and materials chemistry developments within this family of compounds and will briefly discuss the utility of this approach in metal chalcogenide thin-film deposition.

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

International Nuclear Information System (INIS)

Pineau, André; Amine Benzerga, A.; Pardoen, Thomas

2016-01-01

Pushing the internal or external dimensions of metallic alloys down to the nanometer scale gives rise to strong materials, though most often at the expense of a low ductility and a low resistance to cracking, with negative impact on the transfer to engineering applications. These characteristics are observed, with some exceptions, in bulk ultra-fine grained and nanocrystalline metals, nano-twinned metals, thin metallic coatings on substrates and freestanding thin metallic films and nanowires. This overview encompasses all these systems to reveal commonalities in the origins of the lack of ductility and fracture resistance, in factors governing fatigue resistance, and in ways to improve properties. After surveying the various processing methods and key deformation mechanisms, we systematically address the current state of the art in terms of plastic localization, damage, static and fatigue cracking, for three classes of systems: (1) bulk ultra-fine grained and nanocrystalline metals, (2) thin metallic films on substrates, and (3) 1D and 2D freestanding micro and nanoscale systems. In doing so, we aim to favour cross-fertilization between progress made in the fields of mechanics of thin films, nanomechanics, fundamental researches in bulk nanocrystalline metals and metallurgy to impart enhanced resistance to fracture and fatigue in high-strength nanostructured systems. This involves exploiting intrinsic mechanisms, e.g. to enhance hardening and rate-sensitivity so as to delay necking, or improve grain-boundary cohesion to resist intergranular cracks or voids. Extrinsic methods can also be utilized such as by hybridizing the metal with another material to delocalize the deformation - as practiced in stretchable electronics. Fatigue crack initiation is in principle improved by a fine structure, but at the expense of larger fatigue crack growth rates. Extrinsic toughening through hybridization allows arresting or bridging cracks. The content and discussions are based on

Metals in bulk deposition and surface waters at two upland locations in northern England

Energy Technology Data Exchange (ETDEWEB)

Lawlor, A.J.; Tipping, E

2003-02-01

Surface water concentrations of potentially-toxic metals depend upon atmospheric deposition and catchment biogeochemical processes. - Concentrations of aluminium and minor metals (Mn, Ni, Cu, Zn, Sr, Cd, Ba, Pb) were measured in precipitation and surface water at two upland locations (Upper Duddon Valley, UDV; Great Dun Fell, GDF) in northern England for 1 year commencing April 1998. At both locations, the loads in bulk precipitation were at the lower ends of ranges reported for other rural and remote sites, for the period 1985-1995. The deposited metals were mostly in the dissolved form, and their concentrations tended to be greatest when rainfall volumes were low. The concentrations of Cu, Zn and Pb in deposition were correlated (r{sup 2}{>=}0.40) with concentrations of non-marine sulphate. Three streams, ranging in mean pH from 5.07 to 7.07, and with mean concentrations of dissolved organic carbon (DOC) <1 mg l{sup -1}, were monitored at UDV, and two pools (mean pH 4.89 and 6.83, mean DOC 22 and 15 mg l{sup -1}) at GDF. Aluminium and the minor metals were mainly in the dissolved form, and in the following ranges (means of 49-51 samples, {mu}g l{sup -1}): Al 36-530, Mn 4.4-36, Ni 0.26-2.8, Cu 0.25-1.7, Zn 2.1-30, Cd 0.03-0.16, Ba 1.9-140, Pb 0.10-4.5. Concentrations were generally higher at GDF. Differences in metal concentrations between the two locations and between waters at each location, and temporal variations in individual waters, can be explained qualitatively in terms of sorption to solid-phase soil organic matter and mineral surfaces, complexation and transport by DOC, and chemical weathering. The UDV catchments are sinks for Pb and sources of Al, Mn, Sr, Cd and Ba. The GDF catchments are sources of Al, Mn, Ni, Zn, Sr, Cd and Ba. Other metals measured at the two locations are approximately in balance. Comparison of metal:silicon ratios in the surface waters with values for silicate rocks indicates enrichment of Ni and Cu, and substantial enrichment of

Mechanical behavior of Fe{sub 75}Mo{sub 5}P{sub 10}C{sub 7.5}B{sub 2.5} bulk-metallic glass under torsional loading

Energy Technology Data Exchange (ETDEWEB)

Zhang Xinjian [School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Tianjin 300072 (China); Huang Lu [Department of Materials Science and Engineering, University of Tennessee, TN 37996 (United States); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Chen Xu, E-mail: xchen@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Road, Tianjin 300072 (China); Liaw, Peter K. [Department of Materials Science and Engineering, University of Tennessee, TN 37996 (United States); An Ke [Neutron Scattering Sciences Division, Oak Ridge National Laboratory, TN 37831 (United States); Zhang Tao [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Wang Gongyao [Department of Materials Science and Engineering, University of Tennessee, TN 37996 (United States)

2010-11-15

Research highlights: {yields} Fe{sub 75}Mo{sub 5}P{sub 10}C{sub 7.5}B{sub 2.5} bulk-metallic glass exhibits a brittle characteristic under torsional loading. {yields} The BMG occurs in a tensile mode failure under torsional loading. {yields} A slight cyclic-hardening behavior was observed in the initial loading cycles during torsional-fatigue tests. {yields} The torsional fatigue-fracture surface consists of three main regions. - Abstract: Pure- and cyclic-torsional studies were conducted on a Fe{sub 75}Mo{sub 5}P{sub 10}C{sub 7.5}B{sub 2.5} (atomic percent, at.%) bulk-metallic glass at room temperature for an understanding of its damage and fracture mechanisms. Under pure-torsional loading, the metallic glass exhibited very little plastic strain before fracture. The fracture initiated along the maximum tensile-stress plane, which is about 45{sup o} to the axial direction. The shear-fracture strength ({approx}510 MPa) is much lower than the compressive-fracture strength ({approx}3280 MPa), which suggests that different deformation mechanisms be present under various loading modes. Instead of an apparent vein-type structure, the fracture morphologies revealed a crack-initiation site, a mirror region, a mist region, and a hackle region. Under cyclic-torsional loading, fatigue cracks initiated from casting defects, and propagate generally along the maximum tensile-stress plane. A slight cyclic-hardening behavior was observed in initial loading steps. The fatigue-fracture surface consists of three main regions: the fatigue crack-initiation, crack-propagation, and final-fast-fracture areas. The striations resulting from the blunting and re-sharpening of the fatigue crack tip were observed in the crack-propagation region. Based on these results, the damage and fracture mechanisms of the metallic glass induced by torsional loadings are elucidated.

Unusual glass-forming ability induced by changes in the local atomic structure in Ti-based bulk metallic glass

International Nuclear Information System (INIS)

Kim, Y C; Chang, H J; Kim, D H; Kim, W T; Cha, P R

2007-01-01

The effect of partial replacement of Cu by Be in Ti 50 Cu 32 Ni 15 Sn 3 alloy on the thermal properties, structure, and forming ability of an amorphous phase were investigated by differential scanning calorimetry (DSC), x-ray diffraction (XRD), extended x-ray absorption fine structure (EXAFS), and high-resolution transmission electron microscopy (HRTEM). Ti 50 Cu 25 Ni 15 Sn 3 Be 7 alloy shows enhanced glass-forming ability, enabling one to fabricate a fully amorphous bulk metallic glass sample 2 mm in diameter by injection casting. With the replacement, the supercooled liquid region ΔT x (= T x -T g , where T x is the crystallization temperature and T g is the glass transition temperature) decreased from 73 to 45 K and the reduced glass transition temperature T rg (= T g /T 1 , where T 1 is the liquidus temperature) increased from 0.53 to 0.57. The amorphous Ti 50 Cu 25 Ni 15 Sn 3 Be 7 phase showed a formation of short-range-ordered clusters 1-2 nm in size, which is attributed to the strong interaction between Ti and Be. The results show that ΔT x can be used as a thermal parameter reflecting the glass-forming ability of the alloy only when the phase formed during crystallization is the same as the phase competing with the glass transition during solidification

Unified computational model of transport in metal-insulating oxide-metal systems

Science.gov (United States)

Tierney, B. D.; Hjalmarson, H. P.; Jacobs-Gedrim, R. B.; Agarwal, Sapan; James, C. D.; Marinella, M. J.

2018-04-01

A unified physics-based model of electron transport in metal-insulator-metal (MIM) systems is presented. In this model, transport through metal-oxide interfaces occurs by electron tunneling between the metal electrodes and oxide defect states. Transport in the oxide bulk is dominated by hopping, modeled as a series of tunneling events that alter the electron occupancy of defect states. Electron transport in the oxide conduction band is treated by the drift-diffusion formalism and defect chemistry reactions link all the various transport mechanisms. It is shown that the current-limiting effect of the interface band offsets is a function of the defect vacancy concentration. These results provide insight into the underlying physical mechanisms of leakage currents in oxide-based capacitors and steady-state electron transport in resistive random access memory (ReRAM) MIM devices. Finally, an explanation of ReRAM bipolar switching behavior based on these results is proposed.

Flame spray synthesis under a non-oxidizing atmosphere: Preparation of metallic bismuth nanoparticles and nanocrystalline bulk bismuth metal

Energy Technology Data Exchange (ETDEWEB)

Grass, Robert N.; Stark, Wendelin J. [Institute for Chemical and Bioengineering, ETH Zuerich (Switzerland)], E-mail: wendelin.stark@chem.ethz.ch

2006-10-15

Metallic bismuth nanoparticles of over 98% purity were prepared by a modified flame spray synthesis method in an inert atmosphere by oxygen-deficient combustion of a bismuth-carboxylate based precursor. The samples were characterized by X-ray diffraction, thermal analysis and scanning electron microscopy confirming the formation of pure, crystalline metallic bismuth nanoparticles. Compression of the as-prepared powder resulted in highly dense, nanocrystalline pills with strong electrical conductivity and bright metallic gloss.

Crack initiation and fracture features of Fe–Co–B–Si–Nb bulk metallic glass during compression

Directory of Open Access Journals (Sweden)

S. Lesz

2016-01-01

Full Text Available The aim of the paper was investigation crack initiation and fracture features developed during compression of Fe-based bulk metallic glass (BMG. These Fe-based BMG has received great attention as a new class of structural material due to an excellent properties (e.g. high strength and high elasticity and low costs. However, the poor ductility and brittle fracture exhibited in BMGs limit their structural application. At room temperature, BMGs fails catastrophically without appreciable plastic deformation under tension and only very limited plastic deformation is observed under compression or bending. Hence a well understanding of the crack initiation and fracture morphology of Fe-based BMGs after compression is of much importance for designing high performance BMGs. The raw materials used in this experiment for the production of BMGs were pure Fe, Co, Nb metals and nonmetallic elements: Si, B. The Fe–Co–B–Si–Nb alloy was cast as rods with three different diameters. The structure of the investigated BMGs rod is amorphous. The measurement of mechanical properties (Young modulus - E, compressive stress - σc, elastic strain - ε, unitary elastic strain energy – Uu were made in compression test. Compression test indicates the rods of Fe-based alloy to exhibit high mechanical strength. The development of crack initiation and fracture morphology after compression of Fe-based BMG were examined with scanning electron microscope (SEM. Fracture morphology of rods has been different on the cross section. Two characteristic features of the compressive fracture morphologies of BMGs were observed. One is the smooth region. Another typical feature of the compressive fracture morphology of BMGs is the vein pattern. The veins on the compressive fracture surface have an obvious direction as result of initial displace of sample along shear bands. This direction follows the direction of the displacement of a material. The formation of veins on the

Theoretical prediction of Grüneisen parameter for SiO_2.TiO_2 bulk metallic glasses

International Nuclear Information System (INIS)

Singh, Chandra K.; Pandey, Brijesh K.; Pandey, Anjani K.

2016-01-01

The Grüneisen parameter (γ) is very important to decide the limitations for the prediction of thermoelastic properties of bulk metallic glasses. It can be defined in terms of microscopic and macroscopic parameters of the material in which former is based on vibrational frequencies of atoms in the material while later is closely related to its thermodynamic properties. Different formulation and equation of states are used by the pioneer researchers of this field to predict the true sense of Gruneisen parameter for BMG but for SiO_2.TiO_2 very few and insufficient information is available till now. In the present work we have tested the validity of two different isothermal EOS viz. Poirrior-Tarantola EOS and Usual-Tait EOS to predict the true value of Gruneisen parameter for SiO_2.TiO_2 as a function of compression. Using different thermodynamic limitations related to the material constraints and analyzing obtained result it is concluded that the Poirrior-Tarantola EOS gives better numeric values of Grüneisen parameter (γ) for SiO_2.TiO_2 BMG.

Friction and wear of some ferrous-base metallic glasses

Science.gov (United States)

Miyoshi, K.; Buckley, D. H.

1984-01-01

Sliding friction experiments, X-ray photoelectron spectroscopy (XPS) analysis, and electron microscopy and diffraction studies were conducted with ferrous base metallic glasses (amorphous alloys) in contact with aluminium oxide at temperatures to 750 C in a vacuum. Sliding friction experiments were also conducted in argon and air atmospheres. The results of the investigation indicate that the coefficient of friction increases with increasing temperature to 350 C in vacuum. The increase in friction is due to an increase in adhesion resulting from surface segregation of boric oxide and/or silicon oxide to the surface of the foil. Above 500 C the coefficient of friction decreased rapidly. The decrease correlates with the segregation of boron nitride to the surface. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and/or silicon oxide at 350 C and boron nitride above 500 C. The segregation of contaminants is responsible for the friction behavior. The amorphous alloys have superior wear resistance to crystalline 304 stainless steel. The relative concentrations of the various constituents at the surfaces of the amorphous alloys are very different from the nominal bulk compositions.

Glass transition, crystallization kinetics and pressure effect on crystallization of ZrNbCuNiBe bulk metallic glass

DEFF Research Database (Denmark)

Xing, P.F.; Zhuang, Yanxin; Wang, W.H.

2002-01-01

The glass transition behavior and crystallization kinetics of Zr48Nb8Cu14Ni12Be18 bulk metallic glass have been investigated by differential scanning calorimetry and x-ray powder diffraction (XRD). The activation energies of both glass transition and crystallization events have been obtained using...... the Kissinger method. Results indicate that this glass crystallizes by a three-stage reaction: (1) phase separation and primary crystallization of glass, (2) formation of intermetallic compounds, and (3) decomposition of intermetallic compounds and crystallization of residual amorphous phase. The pressure...

The Effect of Thermal Cycling Treatments on the Thermal Stability and Mechanical Properties of a Ti-Based Bulk Metallic Glass Composite

Directory of Open Access Journals (Sweden)

Fan Bu

2016-11-01

Full Text Available The effect of thermal cycling treatments on the thermal stability and mechanical properties of a Ti48Zr20Nb12Cu5Be15 bulk metallic glass composite (BMGC has been investigated. Results show that moderate thermal cycles in a temperature range of −196 °C (cryogenic temperature, CT to 25 °C (room temperature, RT or annealing time at CT has not induced obvious changes of thermal stability and then it decreases slightly over critical thermal parameters. In addition, the dendritic second phases with a bcc structure are homogeneously embedded in the amorphous matrix; no visible changes are detected, which shows structural stability. Excellent mechanical properties as high as 1599 MPa yield strength and 34% plastic strain are obtained, and the yield strength and elastic modulus also increase gradually. The effect on the stability is analyzed quantitatively by crystallization kinetics and plastic-flow models, and indicates that the reduction of structural relaxation enthalpy, which is related to the degradation of spatial heterogeneity, reduces thermal stability but does not imperatively deteriorate the plasticity.

Stability of Bulk Metallic Glass Structure. Final Report

Energy Technology Data Exchange (ETDEWEB)

Jain, H.; Williams, D. B.

2003-06-01

The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub 80-x}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

Structure and property evaluation of a vacuum plasma sprayed nanostructured tungsten-hafnium carbide bulk composite

NARCIS (Netherlands)

Rea, K. E.; Viswanathan, V.; Kruize, A.; De Hosson, J. Th. M.; O'Dell, S.; McKechnie, T.; Rajagopalan, S.; Vaidyanathan, R.; Seal, S.; O’Dell, S.

2008-01-01

Vacuum plasma spray (VPS) forming of tungsten-based metal matrix nanocomposites (MMCs) has shown to be a cost effective and time saving method for the formation of bulk monolithic nanostructured then no-mechanical components. Spray drying of powder feedstock appears to have a significant effect on

Brazing of Cu with Pd-based metallic glass filler

Energy Technology Data Exchange (ETDEWEB)

Terajima, Takeshi [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)], E-mail: terajima@jwri.osaka-u.ac.jp; Nakata, Kazuhiro [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Matsumoto, Yuji [Materials and Structures Laboratory, Tokyo Institute of Technology (Japan); Zhang, Wei; Kimura, Hisamichi; Inoue, Akihisa [Institute for Materials Research, Tohoku University (Japan)

2008-02-25

Metallic glass has several unique properties, including high mechanical strength, small solidification shrinkage, small elastic modulus and supercooling state, all of which are well suited as a residual stress buffer for metal and ceramic joining. In the present preliminary study, we demonstrated brazing of Cu rods with Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} metallic glass filler. The brazing was carried out at 873 K for 1 min in a vacuum atmosphere (1 x 10{sup -3} Pa), and then the specimens were quenched at the rate of 30 K/s by blowing He. The metallic glass brazing of Cu using Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} filler was successful, with the exception that several voids remained in the filler. According to micro-focused X-ray diffraction, no diffraction patterns were observed at both the center of the Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} filler and the Cu/Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} interface. The result showed that the Cu specimens were joined with Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} filler in the glassy state. The tensile fracture strength of the brazed specimens ranged from 20 to 250 MPa. The crack extension from the voids in the Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} filler may have caused the results to be uneven and very low compared to the strength of Pd-based bulk metallic glass.

Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

International Nuclear Information System (INIS)

Lee, Kee Ahn; Kim, Yong Chan; Kim, Jung Han; Lee, Chong Soo; Namkung, Jung; Kim, Moon Chul

2007-01-01

The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys

Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

Energy Technology Data Exchange (ETDEWEB)

Lee, Kee Ahn [School of Advanced Materials Engineering, Andong National University, Andong 760-749 (Korea, Republic of)]. E-mail: keeahn@andong.ac.kr; Kim, Yong Chan [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of); Kim, Jung Han [Center for Advanced Aerospace materials, POSTECH, Pohang 790-784 (Korea, Republic of); Lee, Chong Soo [Center for Advanced Aerospace materials, POSTECH, Pohang 790-784 (Korea, Republic of); Namkung, Jung [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of); Kim, Moon Chul [New Metals Research Team, RIST, Pohang 790-330 (Korea, Republic of)

2007-03-25

The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys.

Ni-free Zr-Cu-Al-Nb-Pd bulk metallic glasses with different Zr/Cu ratios for biomedical applications.

Science.gov (United States)

Huang, Lu; Yokoyama, Yoshihiko; Wu, Wei; Liaw, Peter K; Pang, Shujie; Inoue, Akihisa; Zhang, Tao; He, Wei

2012-08-01

Zr-based bulk metallic glasses (BMGs) possess attractive properties for prospective biomedical applications. The present study designs Ni-free Zr-Cu-Al-Nb-Pd BMGs and investigates their in vitro biocompatibility by studying mechanical properties, bio-corrosion resistance, and cellular responses. The Ti-6Al-4V alloy is used as a reference material. It is found that the Zr-based BMGs exhibit good mechanical properties, including high strengths above 1600 MPa, high hardness over 4700 MPa, and low elastic moduli of 85-90 GPa. The Zr-based BMGs are corrosion resistant in a simulated body environment, as revealed by wide passive regions, low passive current densities, and high pitting overpotentials. The formation of ZrO(2)-rich surface passive films of the Zr-based BMGs contributes to their high corrosion resistance, whereas their pitting corrosion in the phosphate buffered saline solution can be attributed to the sensitivity of the ZrO(2) films to the chloride ion. The general biosafety of the Zr-based BMGs is revealed by normal cell adhesions and cell morphologies. Moreover, the Zr/Cu content ratio in the alloy composition affects the biocompatibility of the Zr-based BMGs, by increasing their corrosion resistance and surface wettability with the increase of the Zr/Cu ratio. Effects of Zr/Cu ratios can be used to guide the future design of biocompatible Zr-based BMGs. Copyright © 2012 Wiley Periodicals, Inc.

Calculated Bulk Properties of the Actinide Metals

DEFF Research Database (Denmark)

Skriver, Hans Lomholt; Andersen, O. K.; Johansson, B.

1978-01-01

Self-consistent relativistic calculations of the electronic properties for seven actinides (Ac-Am) have been performed using the linear muffin-tin orbitals method within the atomic-sphere approximation. Exchange and correlation were included in the local spin-density scheme. The theory explains...... the variation of the atomic volume and the bulk modulus through the 5f series in terms of an increasing 5f binding up to plutonium followed by a sudden localisation (through complete spin polarisation) in americium...

Charge transport in metal oxide nanocrystal-based materials

Science.gov (United States)

Runnerstrom, Evan Lars

structure. Charge transport can obviously be taken to mean the conduction of electrons, but it also refers to the motion of ions, such as lithium ions and protons. In many cases, the transport of ions is married to the motion of electrons as well, either through an external electrical circuit, or within the same material in the case of mixed ionic electronic conductors. The collective motion of electrons over short length scales, that is, within single nanocrystals, is also a subject of study as it pertains to plasmonic nanocrystals. Finally, charge transport can also be coupled to or result from the formation of defects in metal oxides. All of these modes of charge transport in metal oxides gain further complexity when considered in nanocrystalline systems, where the introduction of numerous surfaces can change the character of charge transport relative to bulk systems, providing opportunities to exploit new physical phenomena. Part I of this dissertation explores the combination of electronic and ionic transport in electrochromic devices based on nanocrystals. Colloidal chemistry and solution processing are used to fabricate nanocomposites based on electrochromic tin-doped indium oxide (ITO) nanocrystals. The nanocomposites, which are completely synthesized using solution processing, consist of ITO nanocrystals and lithium bis(trifluoromethylsulfonyl)amide (LiTFSI) salt dispersed in a lithium ion-conducting polymer matrix of either poly(ethylene oxide) (PEO) or poly(methyl methacrylate) (PMMA). ITO nanocrystals are prepared by colloidal synthetic methods and the nanocrystal surface chemistry is modified to achieve favorable nanocrystal-polymer interactions. Homogeneous solutions containing polymer, ITO nanocrystals, and lithium salt are thus prepared and deposited by spin casting. Characterization by DC electronic measurements, microscopy, and x-ray scattering techniques show that the ITO nanocrystals form a complete, connected electrode within a polymer electrolyte

Enhanced thermoelectric properties of metal film on bismuth telluride-based materials

International Nuclear Information System (INIS)

Chao, Wen Hsuan; Chen, Yi Ray; Tseng, Shih Chun; Yang, Ping Hsing; Wu, Ren Jye; Hwang, Jenn Yeu

2014-01-01

Diffusion barriers have a significant influence on the reliability and life time of thermoelectric modules. Although nickel is commonly used as a diffusion barrier in commercial thermoelectric modules, several studies have verified that Ni migrates to bismuth telluride-based material during high temperature cycles and causes a loss in efficacy. In this paper, the influence of metal layers coated to p-type and n-type Bi 2 Te 3 on the interface characterization and thermoelectric property is studied using a RF magnetron sputtering. The findings from this study demonstrate the structural and thermoelectric properties of p-type and n-type Bi 2 Te 3 coated with different metal layers. The crystalline phase and compositional change of the interface between the Bi 2 Te 3 materials and the metal layers were determined using an X-ray diffractometer and scanning electron microscopy with energy dispersive spectroscopy. Formation of NiTe was observed in the sample of Ni/p-type Bi 2 Te 3 based films post-annealed in an N 2 atmosphere at 200 °C. In contrast, no Co x Te y was formed in the sample of Co/p-type Bi 2 Te 3 based films post-annealed at 200 °C. For as-deposited Ni/p-type and n-type Bi 2 Te 3 based legs, the Ni slightly diffused into the Bi 2 Te 3 based legs. A similar phenomenon also occurred in the as-deposited Co/p-type and n-type Bi 2 Te 3 based legs. The Seebeck coefficients of the Co contacts on the Bi 2 Te 3 based material displayed better behavior than those of the Ni contacts on the Bi 2 Te 3 based legs. Thus Co could be a suitable diffusion barrier for bulk Bi 2 Te 3 based material. The observed effects on the thermoelectric and structural properties of metal/Bi 2 Te 3 based material are crucial for understanding the interface between the diffusion barrier and thermoelectric materials. - Highlights: • Interface characterization of metal coated to p-type and n-type Bi 2 Te 3 is studied. • We examined the phase transformation of metal/Bi 2 Te 3 based films

Bulk metallic glass for low noise fluxgate, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The team of Prime Photonics, Virginia Tech, and Utron Kinetics propose to demonstrate a method for fabrication of a bulk, amorphous, cobalt-rich material that...

Permanent magnet with MgB{sub 2} bulk superconductor

Energy Technology Data Exchange (ETDEWEB)

Yamamoto, Akiyasu, E-mail: yamamoto@appchem.t.u-tokyo.ac.jp [The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Ishihara, Atsushi; Tomita, Masaru [Railway Technical Research Institute, 2-8-38 Hikari, Kokubunji, Tokyo 185-8540 (Japan); Kishio, Kohji [The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

2014-07-21

Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB{sub 2}) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB{sub 2} permanent bulk magnet was determined. Because MgB{sub 2} is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB{sub 2} bulks promising for the next generation of Tesla-class permanent-magnet applications.

Nitrogen Detection in Bulk Samples Using a D-D Reaction-Based Portable Neutron Generator

Directory of Open Access Journals (Sweden)

A. A. Naqvi

2013-01-01

Full Text Available Nitrogen concentration was measured via 2.52 MeV nitrogen gamma ray from melamine, caffeine, urea, and disperse orange bulk samples using a newly designed D-D portable neutron generator-based prompt gamma ray setup. Inspite of low flux of thermal neutrons produced by D-D reaction-based portable neutron generator and interference of 2.52 MeV gamma rays from nitrogen in bulk samples with 2.50 MeV gamma ray from bismuth in BGO detector material, an excellent agreement between the experimental and calculated yields of nitrogen gamma rays indicates satisfactory performance of the setup for detection of nitrogen in bulk samples.

On the use of atomistic simulations to aid bulk metallic glasses structural elucidation with solid-state NMR.

Science.gov (United States)

Ferreira, Ary R; Rino, José P

2017-08-24

Solid-state nuclear magnetic resonance (ssNMR) experimental 27 Al metallic shifts reported in the literature for bulk metallic glasses (BMGs) were revisited in the light of state-of-the-art atomistic simulations. In a consistent way, the Gauge-Including Projector Augmented-Wave (GIPAW) method was applied in conjunction with classical molecular dynamics (CMD). A series of Zr-Cu-Al alloys with low Al concentrations were selected as case study systems, for which realistic CMD derived structural models were used for a short- and medium-range order mining. That initial procedure allowed the detection of trends describing changes on the microstructure of the material upon Al alloying, which in turn were used to guide GIPAW calculations with a set of abstract systems in the context of ssNMR. With essential precision and accuracy, the ab initio simulations also yielded valuable trends from the electronic structure point of view, which enabled an overview of the bonding nature of Al-centered clusters as well as its influence on the experimental ssNMR outcomes. The approach described in this work might promote the use of ssNMR spectroscopy in research on glassy metals. Moreover, the results presented demonstrate the possibility to expand the applications of this technique, with deeper insight into nuclear interactions and less speculative assignments.

Bulk metallic glass matrix composite for good biocompatibility

International Nuclear Information System (INIS)

Hadjoub, F; Metiri, W; Doghmane, A; Hadjoub, Z

2012-01-01

Reinforcement volume fraction effects on acoustical parameters of Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 matrix composites reinforced by Mg, Ag and Cd metals have been studied via a simulation program based on acoustic microscopy technique. Moreover, acoustical parameters of human bone were compared to those of BMGs in both monolithic and reinforced case. It was found that elastic behavior of BMGs matrix composites in high reinforcement volume fraction is similar of that of human bone. This behavior leads to high biocompatibility and good transfer of stress between composite material and human system.

Enhanced glass forming ability and refrigerant capacity of a Gd55Ni22Mn3Al20 bulk metallic glass

International Nuclear Information System (INIS)

Xia, L.; Chan, K.C.; Tang, M.B.

2011-01-01

Highlights: → A new Gd 55 Ni 22 Mn 3 Al 20 bulk metallic glass (BMG) was synthesized by minor Mn addition. → The BMG has enhanced glass forming ability and excellent refrigerant capacity (RC). → The RC of the BMG reaches a high value of 825 J kg -1 under a field of 3979 kA/m. → Its excellent RC is related to its large effective magnetic moment. - Abstract: In this work, a small amount of Mn was added to a Gd 55 Ni 25 Al 20 glass forming alloy, as a replacement for Ni, and a Gd 55 Ni 22 Mn 3 Al 20 bulk metallic glass (BMG) was obtained by suction casting. Its glass forming ability (GFA) was characterized by X-ray diffraction and differential scanning calorimetry, and its magnetic properties were measured using a magnetic property measurement system. It is found that the minor Mn addition can significantly improve both the GFA and the magnetocaloric effect (MCE) of the alloy. The refrigerant capacity (RC) of the BMG can reach a high value of 825 J kg -1 under a field of 3979 kA/m, which is about 29% larger than that of a Gd 55 Ni 25 Al 20 BMG. The effect of the minor Mn addition on the GFA and MCE of the BMG was investigated in the study.

Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials.

Science.gov (United States)

Moorthy, A; Hogg, C H; Dowling, A H; Grufferty, B F; Benetti, A R; Fleming, G J P

2012-06-01

To assess the cuspal deflection and cervical microleakage of standardised Class II cavities incrementally filled with a dimethacrylate RBC or bulk-fill flowable RBC bases. Twenty-four sound upper premolar teeth with Class II cavities were allocated to three groups (n=8). Restoration of the teeth involved the placement of an RBC (GrandioSO) in eight oblique increments (Group A) or Groups B and C were restored to within 2 mm of the palatal cusp in a single increment with bulk-fill flowable RBC bases (SDR and x-tra base) before the two occlusal cavity increments were placed with GrandioSO. Buccal and palatal cusp deflections were recorded postirradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage. The mean total cuspal deflection for the oblique incremental restoration technique was 11.26 (2.56) μm (Group A) and 4.63 (1.19) μm (Group B) and 4.73 (0.99) μm (Group C) for the bulk-fill flowable RBC bases. A significant increase in the mean total cuspal deflection for the incrementally filled GrandioSO compared with the SDR (P=0.007) and x-tra base (P=0.005) restored teeth was evident. No significant difference in the cervical microleakage scores was recorded between groups AC (P>0.05). The bulk-fill flowable RBC bases significantly reduced cuspal deflection compared with a conventional RBC restored in an oblique incremental filling technique with no associated change in cervical microleakage recorded. Copyright © 2012 Elsevier Ltd. All rights reserved.

Glass forming ability and mechanical properties of Zr50Cu42Al8 bulk metallic glass

International Nuclear Information System (INIS)

Xia, L; Chan, K C; Wang, G; Liu, L

2008-01-01

In this work, we report that Zr 50 Cu 42 Al 8 bulk metallic glass (BMG) exhibits excellent glass forming ability and mechanical properties. Zr 50 Cu 42 Al 8 glassy rods with a diameter of 3 mm were prepared using conventional copper mould suction casting. The glassy rod exhibits a modulus of about 115 GPa and a fracture strength of about 2 GPa, and, as compared with other large-scale BMGs, it has excellent room-temperature plasticity of up to 20% under compression. The fracture mechanism of the rod was investigated by microstructural investigations, and it was found that the large plasticity of the as-cast rod is closely related to the in situ formation of nano-crystalline particles embedded in the amorphous matrix.

Insights into metals in individual fine particles from municipal solid waste using synchrotron radiation-based micro-analytical techniques.

Science.gov (United States)

Zhu, Yumin; Zhang, Hua; Shao, Liming; He, Pinjing

2015-01-01

Excessive inter-contamination with heavy metals hampers the application of biological treatment products derived from mixed or mechanically-sorted municipal solid waste (MSW). In this study, we investigated fine particles of heavy metal content, using bulk detection techniques. A total of 17 individual fine particles were evaluated using synchrotron radiation-based micro-X-ray fluorescence and micro-X-ray diffraction. We also discussed the association, speciation and source apportionment of heavy metals. Metals were found to exist in a diffuse distribution with heterogeneous intensities and intense hot-spots of metals revealed the potential sources of fine particles from size-reduced waste fractions (such as scraps of organic wastes or ceramics) or from the importation of other particles. The diverse sources of heavy metal pollutants within the fine particles suggested that separate collection and treatment of the biodegradable waste fraction (such as food waste) is a preferable means of facilitating the beneficial utilization of the stabilized products. Copyright © 2014. Published by Elsevier B.V.

Theoretical calculations of positron lifetimes for metal oxides

International Nuclear Information System (INIS)

Mizuno, Masataka; Araki, Hideki; Shirai, Yasuharu

2004-01-01

Our recent positron lifetime measurements for metal oxides suggest that positron lifetimes of bulk state in metal oxides are shorter than previously reported values. We have performed theoretical calculations of positron lifetimes for bulk and vacancy states in MgO and ZnO using first-principles electronic structure calculations and discuss the validity of positron lifetime calculations for insulators. By comparing the calculated positron lifetimes to the experimental values, it wa found that the semiconductor model well reproduces the experimental positron lifetime. The longer positron lifetime previously reported can be considered to arise from not only the bulk but also from the vacancy induced by impurities. In the case of cation vacancy, the calculated positron lifetime based on semiconductor model is shorter than the experimental value, which suggests that the inward relaxation occurs around the cation vacancy trapping the positron. (author)

Purcell effect for finite-length metal-coated and metal nanowires

DEFF Research Database (Denmark)

Filonenko, Konstantin V.; Willatzen, Morten; Bordo, Vladimir G.

2014-01-01

We investigate the modification (enhancement and suppression) of the spontaneous emission rate of a dipole emitter in two configurations: inside a finite-length semiconductor nanowire surrounded by bulk metal and in the vicinity of a finite metal nanowire. Our analysis is based on a first......-principle approach, which is reduced to a seminumeric one in the limit of large nanowire aspect ratios. The numerical calculations are carried out for an emitter in a GaAs nanowire embedded in Ag or Au and for that nearby an Ag or Au nanowire in vacuum or dielectric. We consider in detail the Purcell and β factors...

Polycrystalline silicon ring resonator photodiodes in a bulk complementary metal-oxide-semiconductor process.

Science.gov (United States)

Mehta, Karan K; Orcutt, Jason S; Shainline, Jeffrey M; Tehar-Zahav, Ofer; Sternberg, Zvi; Meade, Roy; Popović, Miloš A; Ram, Rajeev J

2014-02-15

We present measurements on resonant photodetectors utilizing sub-bandgap absorption in polycrystalline silicon ring resonators, in which light is localized in the intrinsic region of a p+/p/i/n/n+ diode. The devices, operating both at λ=1280 and λ=1550  nm and fabricated in a complementary metal-oxide-semiconductor (CMOS) dynamic random-access memory emulation process, exhibit detection quantum efficiencies around 20% and few-gigahertz response bandwidths. We observe this performance at low reverse biases in the range of a few volts and in devices with dark currents below 50 pA at 10 V. These results demonstrate that such photodetector behavior, previously reported by Preston et al. [Opt. Lett. 36, 52 (2011)], is achievable in bulk CMOS processes, with significant improvements with respect to the previous work in quantum efficiency, dark current, linearity, bandwidth, and operating bias due to additional midlevel doping implants and different material deposition. The present work thus offers a robust realization of a fully CMOS-fabricated all-silicon photodetector functional across a wide wavelength range.

Bulk-Fill Resin Composites

DEFF Research Database (Denmark)

Benetti, Ana Raquel; Havndrup-Pedersen, Cæcilie; Honoré, Daniel

2015-01-01

the restorative procedure. The aim of this study, therefore, was to compare the depth of cure, polymerization contraction, and gap formation in bulk-fill resin composites with those of a conventional resin composite. To achieve this, the depth of cure was assessed in accordance with the International Organization...... for Standardization 4049 standard, and the polymerization contraction was determined using the bonded-disc method. The gap formation was measured at the dentin margin of Class II cavities. Five bulk-fill resin composites were investigated: two high-viscosity (Tetric EvoCeram Bulk Fill, SonicFill) and three low......-viscosity (x-tra base, Venus Bulk Fill, SDR) materials. Compared with the conventional resin composite, the high-viscosity bulk-fill materials exhibited only a small increase (but significant for Tetric EvoCeram Bulk Fill) in depth of cure and polymerization contraction, whereas the low-viscosity bulk...

Cuspal Flexure and Extent of Cure of a Bulk-fill Flowable Base Composite.

Science.gov (United States)

Francis, A V; Braxton, A D; Ahmad, W; Tantbirojn, D; Simon, J F; Versluis, A

2015-01-01

To investigate a bulk-fill flowable base composite (Surefil SDR Flow) in terms of cuspal flexure and cure when used in incremental or bulk techniques. Mesio-occluso-distal cavities (4 mm deep, 4 mm wide) were prepared in 24 extracted molars. The slot-shaped cavities were etched, bonded, and restored in 1) two 2-mm increments Esthet-X HD (control), 2) two 2-mm increments Surefil SDR Flow, or 3) 4-mm bulk Surefil SDR Flow (N=8). The teeth were digitized after preparation (baseline) and restoration and were precisely aligned to calculate cuspal flexure. Restored teeth were placed in fuchsin dye for 16 hours to determine occlusal bond integrity from dye penetration. Extent of cure was assessed by hardness at 0.5-mm increments through the restoration depth. Results were analyzed with analysis of variance and Student-Newman-Keuls post hoc tests (α=0.05). Surefil SDR Flow, either incrementally or bulk filled, demonstrated significantly less cuspal flexure than Esthet-X HD. Dye penetration was less than 3% of cavity wall height and was not statistically different among groups. The hardness of Surefil SDR Flow did not change throughout the depth for both incrementally and bulk filled restorations; the hardness of Esthet-X HD was statistically significantly lower at the bottom of each increment than at the top. Filling in bulk or increments made no significant difference in marginal bond quality or cuspal flexure for the bulk-fill composite. However, the bulk-fill composite caused less cuspal flexure than the incrementally placed conventional composite. The bulk-fill composite cured all the way through (4 mm), whereas the conventional composite had lower cure at the bottom of each increment.

350 keV accelerator based PGNAA setup to detect nitrogen in bulk samples

Energy Technology Data Exchange (ETDEWEB)

Naqvi, A.A., E-mail: aanaqvi@kfupm.edu.sa [Department of Physics and King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Al-Matouq, Faris A.; Khiari, F.Z.; Gondal, M.A.; Rehman, Khateeb-ur [Department of Physics and King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Isab, A.A. [Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Raashid, M.; Dastageer, M.A. [Department of Physics and King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia)

2013-11-21

Nitrogen concentration was measured in explosive and narcotics proxy material, e.g. anthranilic acid, caffeine, melamine, and urea samples, bulk samples through thermal neutron capture reaction using 350 keV accelerator based prompt gamma ray neutron activation (PGNAA) setup. Intensity of 2.52, 3.53–3.68, 4.51, 5.27–5.30 and 10.38 MeV prompt gamma rays of nitrogen from the bulk samples was measured using a cylindrical 100 mm×100 mm (diameter×height ) BGO detector. Inspite of interference of nitrogen gamma rays from bulk samples with capture prompt gamma rays from BGO detector material, an excellent agreement between the experimental and calculated yields of nitrogen gamma rays has been obtained. This is an indication of the excellent performance of the PGNAA setup for detection of nitrogen in bulk samples.

350 keV accelerator based PGNAA setup to detect nitrogen in bulk samples

International Nuclear Information System (INIS)

Naqvi, A.A.; Al-Matouq, Faris A.; Khiari, F.Z.; Gondal, M.A.; Rehman, Khateeb-ur; Isab, A.A.; Raashid, M.; Dastageer, M.A.

2013-01-01

Nitrogen concentration was measured in explosive and narcotics proxy material, e.g. anthranilic acid, caffeine, melamine, and urea samples, bulk samples through thermal neutron capture reaction using 350 keV accelerator based prompt gamma ray neutron activation (PGNAA) setup. Intensity of 2.52, 3.53–3.68, 4.51, 5.27–5.30 and 10.38 MeV prompt gamma rays of nitrogen from the bulk samples was measured using a cylindrical 100 mm×100 mm (diameter×height ) BGO detector. Inspite of interference of nitrogen gamma rays from bulk samples with capture prompt gamma rays from BGO detector material, an excellent agreement between the experimental and calculated yields of nitrogen gamma rays has been obtained. This is an indication of the excellent performance of the PGNAA setup for detection of nitrogen in bulk samples

350 keV accelerator based PGNAA setup to detect nitrogen in bulk samples

Science.gov (United States)

Naqvi, A. A.; Al-Matouq, Faris A.; Khiari, F. Z.; Gondal, M. A.; Rehman, Khateeb-ur; Isab, A. A.; Raashid, M.; Dastageer, M. A.

2013-11-01

Nitrogen concentration was measured in explosive and narcotics proxy material, e.g. anthranilic acid, caffeine, melamine, and urea samples, bulk samples through thermal neutron capture reaction using 350 keV accelerator based prompt gamma ray neutron activation (PGNAA) setup. Intensity of 2.52, 3.53-3.68, 4.51, 5.27-5.30 and 10.38 MeV prompt gamma rays of nitrogen from the bulk samples was measured using a cylindrical 100 mm×100 mm (diameter×height ) BGO detector. Inspite of interference of nitrogen gamma rays from bulk samples with capture prompt gamma rays from BGO detector material, an excellent agreement between the experimental and calculated yields of nitrogen gamma rays has been obtained. This is an indication of the excellent performance of the PGNAA setup for detection of nitrogen in bulk samples.

Structure and property evaluation of a vacuum plasma sprayed nanostructured tungsten-hafnium carbide bulk composite

International Nuclear Information System (INIS)

Rea, K.E.; Viswanathan, V.; Kruize, A.; Hosson, J.Th.M. de; O'Dell, S.; McKechnie, T.; Rajagopalan, S.; Vaidyanathan, R.; Seal, S.

2008-01-01

Vacuum plasma spray (VPS) forming of tungsten-based metal matrix nanocomposites (MMCs) has shown to be a cost effective and time saving method for the formation of bulk monolithic nanostructured thermo-mechanical components. Spray drying of powder feedstock appears to have a significant effect on the improved mechanical properties of the bulk nanocomposite. The reported elastic modulus of the nanocomposite nearly doubles due to the presence of HfC nano particulates in the W matrix. High resolution transmission electron microscopy (HRTEM) revealed the retention of nanostructures at the select process conditions and is correlated with the enhanced mechanical properties of the nanocomposite

Effect of composition and technique of production, on the mechanical behaviour of based-zirconium metallic glasses

International Nuclear Information System (INIS)

Nowak, Sophie

2009-01-01

The metallic glasses are relatively new materials (50 years), produced by quenching a molten alloy. The amorphous structure of these materials gives them unique properties: very high strength (fracture stress is about 1.7 GPa for Zr based alloys), an elastic deformation reaching 2%, but little or no ductility. The compositions, which could produce both amorphous and bulk samples, are limited. The work, detailed in this manuscript, shows the possibility of sintering using SPS (Spark Plasma Sintering) amorphous powders obtained by atomization (Φaverage = 70 microns). The result is a fully densified and near fully amorphous sample. The optimization of this technique, with the composition Zr 57 Cu 20 Al 10 Ni 8 Ti 5 , gave samples for which mechanical behaviour is close to the bulk metallic glass behaviour. However, partial crystallization of the material occurs, localized at the contact points of particles, but could be reduced by deepening the sintering model outlined in this manuscript. In view of these results, new compositions are designed, and the production of ribbons was conducted. The characterization by nano-indentation estimates reliably the mechanical properties of these alloys. Finally, a new method, evaluating the activation volume, which is the elementary volume initiating plastic deformation, is presented. This technique is a statistical analysis of pseudo-creep tests performed by nano-indentation, at room temperature. In conclusion, this work opens new perspectives to develop bulk samples in broad range of compositions. (author)

Source apportionment of atmospheric bulk deposition in the Belgrade urban area using Positive Matrix factorization

Science.gov (United States)

Tasić, M.; Mijić, Z.; Rajšić, S.; Stojić, A.; Radenković, M.; Joksić, J.

2009-04-01

The primary objective of the present study was to assess anthropogenic impacts of heavy metals to the environment by determination of total atmospheric deposition of heavy metals. Atmospheric depositions (wet + dry) were collected monthly, from June 2002 to December 2006, at three urban locations in Belgrade, using bulk deposition samplers. Concentrations of Fe, Al, Pb, Zn, Cu, Ni, Mn, Cr, V, As and Cd were analyzed using atomic absorption spectrometry. Based upon these results, the study attempted to examine elemental associations in atmospheric deposition and to elucidate the potential sources of heavy metal contaminants in the region by the use of multivariate receptor model Positive Matrix Factorization (PMF).

Source apportionment of atmospheric bulk deposition in the Belgrade urban area using Positive Matrix factorization

International Nuclear Information System (INIS)

Tasic, M; Mijic, Z; Rajsic, S; Stojic, A; Radenkovic, M; Joksic, J

2009-01-01

The primary objective of the present study was to assess anthropogenic impacts of heavy metals to the environment by determination of total atmospheric deposition of heavy metals. Atmospheric depositions (wet + dry) were collected monthly, from June 2002 to December 2006, at three urban locations in Belgrade, using bulk deposition samplers. Concentrations of Fe, Al, Pb, Zn, Cu, Ni, Mn, Cr, V, As and Cd were analyzed using atomic absorption spectrometry. Based upon these results, the study attempted to examine elemental associations in atmospheric deposition and to elucidate the potential sources of heavy metal contaminants in the region by the use of multivariate receptor model Positive Matrix Factorization (PMF).

Second amorphous-to-crystalline phase transformation in Cu(60)Ti(20)Zr(20) bulk metallic glass.

Science.gov (United States)

Cao, Q P; Li, J F; Zhang, P N; Horsewell, A; Jiang, J Z; Zhou, Y H

2007-06-20

The second amorphous-to-crystalline phase transformation in Cu(60)Ti(20)Zr(20) bulk metallic glass was investigated by differential scanning calorimetry and x-ray diffractometry. The difference of the Gibbs free energies between the amorphous phase and the crystalline products during the transformation is estimated to be about 2.46 kJ mol(-1) at 753 K, much smaller than the 61 kJ mol(-1) obtained assuming that it is a polymorphic transformation. It was revealed that the phase transformation occurs through a eutectic crystallization of Cu(51)Zr(14) and Cu(2)TiZr, having an effective activation energy of the order of 400 kJ mol(-1). The average Avrami exponent n is about 2.0, indicating that the crystallization is diffusion controlled.

Alloying effect on the room temperature creep characteristics of a Ti-Zr-Be bulk metallic glass

Science.gov (United States)

Gong, Pan; Wang, Sibo; Li, Fangwei; Wang, Xinyun

2018-02-01

The effect of alloying elements (e.g. Fe, Al, and Ni) on the room temperature creep behavior of a lightweight Ti41Zr25Be34 bulk metallic glass (BMG) was investigated via nanoindentation tests. The generalized Kelvin model was adopted to describe the creep curves. The strain rate sensitivity m has been derived as a measure of the creep resistance. The compliance spectrum and retardation spectrum were also derived. The results show that the creep resistance of Ti41Zr25Be34 alloy can be obviously improved with the addition of alloying elements, and the most effective element is found to be Al. The mechanism for enhancing the creep resistance was discussed in terms of the scale variation of the shear transformation zone induced by alloying.

Transport properties of metal-metal and metal-insulator heterostructures

Energy Technology Data Exchange (ETDEWEB)

Fadlallah Elabd, Mohamed Mostafa

2010-06-09

In this study we present results of electronic structure and transport calculations for metallic and metal-insulator interfaces, based on density functional theory and the non-equilibrium Green's function method. Starting from the electronic structure of bulk Al, Cu, Ag, and Au interfaces, we study the effects of different kinds of interface roughness on the transmission coefficient (T(E)) and the I-V characteristic. In particular, we compare prototypical interface distortions, including vacancies, metallic impurities, non-metallic impurities, interlayer, and interface alloy. We find that vacancy sites have a huge effect on transmission coefficient. The transmission coefficient of non-metallic impurity systems has the same behaviour as the transmission coefficient of vacancy system, since these systems do not contribute to the electronic states at the Fermi energy. We have also studied the transport properties of Au-MgO-Au tunnel junctions. In particular, we have investigated the influence of the thickness of the MgO interlayer, the interface termination, the interface spacing, and O vacancies. Additional interface states appear in the O-terminated configuration due to the formation of Au-O bonds. An increasing interface spacing suppresses the Au-O bonding. Enhancement of T(E) depends on the position and density of the vacancies (the number of vacancies per unit cell). (orig.)

Atmospheric heavy metal deposition in the Copenhagen area

Energy Technology Data Exchange (ETDEWEB)

Andersen, A; Hovmand, M F; Johnsen, I

1978-10-01

Transport of heavy metals from the atmosphere to the soil and vegetation takes place by dust fall, bulk precipitation, and gas/aerosol adsorption processes. Atmospheric dry and wet deposition of the heavy metals lead, zinc, nickel, vanadium, iron, and copper over the Copenhagen area was measured by sampling in plastic funnels from 17 stations throughout the area for 12 months. Epigeic bryophytes, epiphytic lichen, and topsoil samples were analyzed. A linear correlation between bulk precipitation and heavy metal concentration in lichens and bryophytes was found. An exponential correlation between bulk precipitation and heavy metal concentration in soil was noted. Regional variation of the heavy metal levels in the Copenhagen area was described, and three sub-areas with high metal burdens were distinguished. (10 diagrams, 8 graphs, 13 references, 2 tables)

Amorphous Metallic Alloys: Pathways for Enhanced Wear and Corrosion Resistance

Science.gov (United States)

Aditya, Ayyagari; Felix Wu, H.; Arora, Harpreet; Mukherjee, Sundeep

2017-11-01

Amorphous metallic alloys are widely used in bulk form and as coatings for their desirable corrosion and wear behavior. Nevertheless, the effects of heat treatment and thermal cycling on these surface properties are not well understood. In this study, the corrosion and wear behavior of two Zr-based bulk metallic glasses were evaluated in as-cast and thermally relaxed states. Significant improvement in wear rate, friction coefficient, and corrosion penetration rate was seen for both alloys after thermal relaxation. A fully amorphous structure was retained with thermal relaxation below the glass transition. There was an increase in surface hardness and elastic modulus for both alloys after relaxation. The improvement in surface properties was explained based on annihilation of free volume.

Fiber‐free coupling between bulk laser beams and on‐chip polymer‐based multimode waveguides

DEFF Research Database (Denmark)

Jensen, Thomas Glasdam; Nielsen, Lars Bue; Kutter, Jörg Peter

2011-01-01

light from a bulk beam to on‐chip waveguides and back into a bulk beam again. Using this setup, as much as 20% of the light coming from the source can be retrieved after passing through the on‐chip waveguides. The proposed setup is based on a pin‐aided alignment system that makes it possible to change...

Glass formation and crystallization in Zr based alloys

International Nuclear Information System (INIS)

Dey, G. K.

2011-01-01

Metallic glasses have come in to prominence in recent times because their nanocrystalline atomic arrangement imparts many useful and unusual properties to these metallic solids. Though these have been produced for the last four decades, the necessity of rapid solidification at cooling rates of 10 5 K/sec or higher for their production, have restricted their geometry to thin ribbons and prevented their application to many areas despite their excellent properties. It has been shown in recent investigations that, many Zr base multicomponent alloys can be obtained in glassy state by cooling at much lower rate typically 10 2 to 10 3 K/sec. This has enabled production of these alloys in the glassy stat in bulk. By now, bulk metallic glasses have been produced in Mg, Ln, Zr, Fe, Pd-Cu, Pd-Fe, Ti and Ni- based alloys. Production of these glasses in bulk has opened avenue for their application in many areas where their excellent mechanical properties an corrosion resistance can be exploited. The transformation of the amorphous phase in these alloys to one or more crystalline phases, is an interesting phase transformation and can lead to formation of crystals in a variety of morphologies and a wide range of crystal sizes, including nanometer size crystals or nanocrystals. The bulk amorphous alloys exhibit higher fracture stress, combined with higher hardness and lower young's modulus than those of any crystalline alloy. The Zr- and Ti-based bulk amorphous alloy exhibit high bending and flexural strength values which are typically 2.0 to 2.5 time higher than those for crystalline counterparts. The composites of bulk metallic glass containing crystalline phases have been found to have special properties. This has been demonstrated in the case of composites of bulk metallic glass and tungsten wires wit the glass forming the matrix. Such a composite has a very high impact strength and is especially suitable for application as an armour penetrator in various types of shells used

Computational analysis of the atomic size effect in bulk metallic glasses and their liquid precursors

International Nuclear Information System (INIS)

Kokotin, V.; Hermann, H.

2008-01-01

The atomic size effect and its consequences for the ability of multicomponent liquid alloys to form bulk metallic glasses are analyzed in terms of the generalized Bernal's model for liquids, following the hypothesis that maximum density in the liquid state improves the glass-forming ability. The maximum density that can be achieved in the liquid state is studied in the 2(N-1) dimensional parameter space of N-component systems. Computer simulations reveal that the size ratio of largest to smallest atoms are most relevant for achieving the maximum packing for N = 3-5, whereas the number of components plays a minor role. At small size ratio, the maximum packing density can be achieved by different atomic size distributions, whereas for medium size ratios the maximum density is always correlated to a concave size distribution. The relationship of the results to Miracle's efficient cluster packing model is also discussed

Molten Salt-Based Growth of Bulk GaN and InN for Substrates

Energy Technology Data Exchange (ETDEWEB)

Waldrip, Karen Elizabeth [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Power Sources Technology Dept.; Tsao, Jeffrey Yeenien [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Energy Sciences Dept.; Kerley, Thomas M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Materials Sciences Dept.

2006-09-01

An atmospheric pressure approach to growth of bulk group III-nitrides is outlined. Native III-nitride substrates for optoelectronic and high power, high frequency electronics are desirable to enhance performance and reliability of these devices; currently, these materials are available in research quantities only for GaN, and are unavailable in the case of InN. The thermodynamics and kinetics of the reactions associated with traditional crystal growth techniques place these activities on the extreme edges of experimental physics. The technique described herein relies on the production of the nitride precursor (N^3-) by chemical and/or electrochemical methods in a molten halide salt. This nitride ion is then reacted with group III metals in such a manner as to form the bulk nitride material. The work performed during the period of funding (July 2004-September 2005) focused on the initial measurement of the solubility of GaN in molten LiCl as a function of temperature, the construction of electrochemical cells, the modification of a commercial glove box (required for handling very hygroscopic LiCl), and on securing intellectual property for the technique.

Influence of minor alloying additions on the glass-forming ability of Mg-Ni-La bulk metallic glasses

International Nuclear Information System (INIS)

Gonzalez, S.; Figueroa, I.A.; Todd, I.

2009-01-01

Bulk metallic glasses of Mg 60 Ni 23.6 Y x La (16.4-x) and Mg 65 Ni 20 Y x LaMM (15-x) with 0 ≤ x ≤ 1 at.% have been produced by injection casting. For the La-containing alloy a maximum amorphous diameter of 4 mm for x = 0.5 and 0.75 was obtained. The LaMM-containing alloy showed a maximum amorphous diameter of 2 mm for x = 0 and 0.25 but decreased to 1 mm with further Y additions. The glass-forming ability of the Mg 60 Ni 23.6 La 16.4 alloy decreased when La is partially substituted by small amounts of small atoms (Si or B) or by large atoms (Y and Si).

Stability of medium range order in Al-based metallic glass compacted by severe plastic deformation

Energy Technology Data Exchange (ETDEWEB)

Kovács, Zs.; Henits, P. [Department of Materials Physics, Eötvös University, P.O.B. 32, H-1518 Budapest (Hungary); Varga, L.K. [Research Institute for Solid state Physics and Optics, Hungarian Academy of Sciences, P.O.B. 49, H-1525 Budapest (Hungary); Schafler, E. [Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, A-1090 Vienna (Austria); Révész, Á., E-mail: reveszadam@ludens.elte.hu [Department of Materials Physics, Eötvös University, P.O.B. 32, H-1518 Budapest (Hungary)

2013-06-05

Highlights: ► High pressure torsion has been applied to produce low-porosity bulk Al-based amorphous specimens. ► The compacted disks possess higher hardness than the original glass. ► Mechanical and thermal impacts have only minor effects on the glassy structure. ► Medium range order is an inherent feature of the amorphous state. -- Abstract: High pressure torsion has successfully been applied to produce low-porosity, bulk specimens from Al-based metallic glass ribbons (Al{sub 85}Y{sub 8}Ni{sub 5}Co{sub 2}, Al{sub 85}Ce{sub 8}Ni{sub 5}Co{sub 2} and Al{sub 85}Gd{sub 8}Ni{sub 5}Co{sub 2}). The compacted disks possess higher hardness than the original glass and have substantial glass fraction with nanocrystalline precipitations. Mechanical and thermal impacts have only minor effects on the glassy structure as demonstrated by the stability of the X-ray diffraction halo positions. Unchanged halos reveal that medium range order is a key characteristic of the amorphous state.

Precious-metal-base advanced materials

International Nuclear Information System (INIS)

Nowicki, T.; Carbonnaux, C.

1993-01-01

Precious metals constitute also the base of several advanced materials used in the industry in hundreds of metric tons. Platinum alloys have been used as structural materials for equipments in the glass industry. The essential reason for this is the excellent resistance of platinum alloys to oxidation and electrolytical corrosion in molten glasses at temperatures as high as 1200-1500 C. The major drawback is a weak creep resistance. The unique way for significant improvement of platinum base materials creep resistance is a strengthening by an oxide dispersion (ODS). In the case of CLAL's patented ''Plativer'' materials, 0.05 wt% of Y 2 O 3 is incorporated within the alloy matrix by the flame spraying process. Further improvement of platinum base materials is related, in the authors opinion, to the development of precious metals base intermetallics. Another interesting applications of precious metals are silver base electrical contacts. They are in fact silver matrix composites containing varying amounts of well-dispersed particles of constituents such as CdO, SnO 2 , Ni, WC or C. In the case of such materials, particular properties are required and tested : resistance to arc erosion, resistance to welding and contact resistance. Many other technically fascinating precious metals base materials exist: brazing alloys for assembling metals, superconductors and ceramics; dental materials including magnetic biocompatible alloys; silver composites for superconductor wire jackets. The observation of current evolution indicates very clearly that precious metals cannot be replaced by common metals because of their unique characteristics due to their atomic level properties

Preparation and properties of Fe{sub 80−x}Ni{sub x}P{sub 14}B{sub 6} bulk metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Zhang, Ling; Ma, XiuHua [School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046 (China); Li, Qiang, E-mail: qli@xju.edu.cn [School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046 (China); Zhang, Jijun [School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046 (China); Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Dong, Yaqiang; Chang, Chuntao [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China)

2014-09-01

Highlights: • Fe{sub 80−x}Ni{sub x}P{sub 14}B{sub 6} (x = 20–50 at.%) BMGs were prepared by fluxing and J-quenching techniques. • The highest GFA is reached at x = 40 and the corresponding critical diameter is up to 2.5 mm. • The present FeNi-based BMGs exhibit very large ε{sub p} and the ε{sub p} of Fe{sub 30}Ni{sub 50}P{sub 14}B{sub 6} BMG is 11.7%. • The present FeNi-based BMGs have much higher corrosion resistance than stainless steel. - Abstract: Bulk Fe{sub 80−x}Ni{sub x}P{sub 14}B{sub 6} (x = 20, 30, 40, 50 at.%) glassy alloy rods with the diameters of 1.0–2.5 mm were synthesized by combining fluxing technique and J-quenching technique. The glassy alloy rods were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). It is found that the range of supercooled liquid region (ΔT{sub x}) is 27–32 K. The saturation magnetization of Fe{sub 80−x}Ni{sub x}P{sub 14}B{sub 6} (x = 20, 30, 40, 50 at.%) bulk glassy alloys gradually decreases from 1.13 T to 0.58 T with increasing Ni content from x = 20 to x = 50. More importantly, the present quaternary FeNiPB bulk metallic glasses (BMGs) shows a significant plastic strain, in particular, the plastic strain of Fe{sub 30}Ni{sub 50}P{sub 14}B{sub 6} BMG reaches as high as 11.7%. The corrosion resistance of the present FeNiPB BMGs was studied by weight-loss method, potentiodynamic polarization curves and scanning electron microscopy (SEM). It is shown that the corrosion resistance of the present FeNiPB BMGs in 0.5 M NaCl and 1 M HCl solution increases with Ni content, and further the present FeNiPB BMGs exhibit larger E{sub corr} values and lower I{sub corr} values, i.e. higher corrosion resistances, than that of stainless steel.

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. II. Application—Effect of quantum confinement and homogeneous strain on Cu conductance

Science.gov (United States)

Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Charles, James; Klimeck, Gerhard

2014-03-01

The Semi-Empirical tight binding model developed in Part I Hegde et al. [J. Appl. Phys. 115, 123703 (2014)] is applied to metal transport problems of current relevance in Part II. A systematic study of the effect of quantum confinement, transport orientation, and homogeneous strain on electronic transport properties of Cu is carried out. It is found that quantum confinement from bulk to nanowire boundary conditions leads to significant anisotropy in conductance of Cu along different transport orientations. Compressive homogeneous strain is found to reduce resistivity by increasing the density of conducting modes in Cu. The [110] transport orientation in Cu nanowires is found to be the most favorable for mitigating conductivity degradation since it shows least reduction in conductance with confinement and responds most favorably to compressive strain.

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. II. Application—Effect of quantum confinement and homogeneous strain on Cu conductance

International Nuclear Information System (INIS)

Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Charles, James; Klimeck, Gerhard

2014-01-01

The Semi-Empirical tight binding model developed in Part I Hegde et al. [J. Appl. Phys. 115, 123703 (2014)] is applied to metal transport problems of current relevance in Part II. A systematic study of the effect of quantum confinement, transport orientation, and homogeneous strain on electronic transport properties of Cu is carried out. It is found that quantum confinement from bulk to nanowire boundary conditions leads to significant anisotropy in conductance of Cu along different transport orientations. Compressive homogeneous strain is found to reduce resistivity by increasing the density of conducting modes in Cu. The [110] transport orientation in Cu nanowires is found to be the most favorable for mitigating conductivity degradation since it shows least reduction in conductance with confinement and responds most favorably to compressive strain

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. II. Application—Effect of quantum confinement and homogeneous strain on Cu conductance

Energy Technology Data Exchange (ETDEWEB)

Hegde, Ganesh, E-mail: ghegde@purdue.edu; Povolotskyi, Michael; Kubis, Tillmann; Charles, James; Klimeck, Gerhard, E-mail: gekco@purdue.edu [Network for Computational Nanotechnology (NCN), Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2014-03-28

The Semi-Empirical tight binding model developed in Part I Hegde et al. [J. Appl. Phys. 115, 123703 (2014)] is applied to metal transport problems of current relevance in Part II. A systematic study of the effect of quantum confinement, transport orientation, and homogeneous strain on electronic transport properties of Cu is carried out. It is found that quantum confinement from bulk to nanowire boundary conditions leads to significant anisotropy in conductance of Cu along different transport orientations. Compressive homogeneous strain is found to reduce resistivity by increasing the density of conducting modes in Cu. The [110] transport orientation in Cu nanowires is found to be the most favorable for mitigating conductivity degradation since it shows least reduction in conductance with confinement and responds most favorably to compressive strain.

Development of Efficient and Stable Inverted Bulk Heterojunction (BHJ) Solar Cells Using Different Metal Oxide Interfaces.

Science.gov (United States)

Litzov, Ivan; Brabec, Christoph J

2013-12-10

Solution-processed inverted bulk heterojunction (BHJ) solar cells have gained much more attention during the last decade, because of their significantly better environmental stability compared to the normal architecture BHJ solar cells. Transparent metal oxides (MeO x ) play an important role as the dominant class for solution-processed interface materials in this development, due to their excellent optical transparency, their relatively high electrical conductivity and their tunable work function. This article reviews the advantages and disadvantages of the most common synthesis methods used for the wet chemical preparation of the most relevant n -type- and p -type-like MeO x interface materials consisting of binary compounds A x B y . Their performance for applications as electron transport/extraction layers (ETL/EEL) and as hole transport/extraction layers (HTL/HEL) in inverted BHJ solar cells will be reviewed and discussed.

Development of Efficient and Stable Inverted Bulk Heterojunction (BHJ Solar Cells Using Different Metal Oxide Interfaces

Directory of Open Access Journals (Sweden)

Ivan Litzov

2013-12-01

Full Text Available Solution-processed inverted bulk heterojunction (BHJ solar cells have gained much more attention during the last decade, because of their significantly better environmental stability compared to the normal architecture BHJ solar cells. Transparent metal oxides (MeOx play an important role as the dominant class for solution-processed interface materials in this development, due to their excellent optical transparency, their relatively high electrical conductivity and their tunable work function. This article reviews the advantages and disadvantages of the most common synthesis methods used for the wet chemical preparation of the most relevant n-type- and p-type-like MeOx interface materials consisting of binary compounds AxBy. Their performance for applications as electron transport/extraction layers (ETL/EEL and as hole transport/extraction layers (HTL/HEL in inverted BHJ solar cells will be reviewed and discussed.

Development of Efficient and Stable Inverted Bulk Heterojunction (BHJ) Solar Cells Using Different Metal Oxide Interfaces

Science.gov (United States)

Litzov, Ivan; Brabec, Christoph J.

2013-01-01

Solution-processed inverted bulk heterojunction (BHJ) solar cells have gained much more attention during the last decade, because of their significantly better environmental stability compared to the normal architecture BHJ solar cells. Transparent metal oxides (MeOx) play an important role as the dominant class for solution-processed interface materials in this development, due to their excellent optical transparency, their relatively high electrical conductivity and their tunable work function. This article reviews the advantages and disadvantages of the most common synthesis methods used for the wet chemical preparation of the most relevant n-type- and p-type-like MeOx interface materials consisting of binary compounds AxBy. Their performance for applications as electron transport/extraction layers (ETL/EEL) and as hole transport/extraction layers (HTL/HEL) in inverted BHJ solar cells will be reviewed and discussed. PMID:28788423

The Effects of a High Magnetic Field on the Annealing of [(Fe0.5Co0.50.75B0.2Si0.05]96Nb4 Bulk Metallic Glass

Directory of Open Access Journals (Sweden)

Peng Jia

2016-11-01

Full Text Available In contrast with amorphous alloys, nanocrystalline soft magnetic materials show improved thermal stability and higher soft magnetic properties. The nanocrystalline soft magnetic composites are usually fabricated by partially crystallizing from parent amorphous alloys. This paper reports our experimental observation on the sequence of crystallization in metallic glass under a high magnetic field (HMF. An application of a HMF to bulk metallic glass (BMG of [(Fe0.5Co0.50.75B0.2Si0.05]96Nb4 prioritizes the precipitation of α-(Fe,Co phase separated from the subsequent precipitation of borides, (Fe,Co23B6, upon isothermal annealing at a glass transition temperature. Furthermore, it was observed that, through the annealing treatment under a HMF, a soft magnetic nanocomposite, in which only α-(Fe,Co phase uniformly distributes in amorphous matrix, was achieved for boron-bearing BMG. The promotion of the α-Fe or (Fe,Co phase and the prevention of the boride phases during the isothermal annealing process help to produce high-quality soft magnetic nanocomposite materials. The mechanism by which a HMF influences the crystallization sequence was interpreted via certain changes in Gibbs free energies for two ferromagnetic phases. This finding evidences that the annealing treatment under a HMF is suitable for enhancing the soft magnetic properties of high B content (Fe,Co-based bulk amorphous and nanocrystalline materials.

Molecular dynamics simulations of zinc oxide solubility: From bulk down to nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Escorihuela, Laura; Fernández, Alberto; Rallo, Robert; Martorell, Benjamí

2018-02-01

The solubility of metal oxides is one of the key descriptors for the evaluation of their potential toxic effects, both in the bulk form and in nanoparticulated aggregates. Current work presents a new methodology for the in silico assessment of the solubility of metal oxides, which is demonstrated using a well-studied system, ZnO. The calculation of the solubility is based on statistical thermodynamics tools combined with Density Functional Tight Binding theory for the evaluation of the free energy exchange during the dissolution process. Models of small ZnO clusters are used for describing the final dissolved material, since the complete ionic dissolution of ZnO is hindered by the formation of O2- anions in solution, which are highly unstable. Results show very good agreement between the computed solubility values and experimental data for ZnO bulk, up to 0.5 mg·L-1 and equivalents of 50 g·L-1 for the free Zn2+ cation in solution. However, the reference model for solid nanoparticles formed by free space nanoparticles can only give a limited quantitative solubility evaluation for ZnO nanoparticles.

Magnetic levitation and its application for education devices based on YBCO bulk superconductors

International Nuclear Information System (INIS)

Yang, W.M.; Chao, X.X.; Guo, F.X.; Li, J.W.; Chen, S.L.

2013-01-01

Highlights: • A small superconducting maglev propeller system has been designed and constructed based on YBCO bulk superconductors. • Several small maglev vehicle models have been designed and constructed based on YBCO bulk superconductors. • The models can be used as experimental or demonstration devices for the magnetic levitation applications. -- Abstract: A small superconducting maglev propeller system, a small spacecraft model suspending and moving around a terrestrial globe, several small maglev vehicle models and a magnetic circuit converter have been designed and constructed. The track was paved by NdFeB magnets, the arrangement of the magnets made us easy to get a uniform distribution of magnetic field along the length direction of the track and a high magnetic field gradient in the lateral direction. When the YBCO bulks mounted inside the vehicle models or spacecraft model was field cooled to LN 2 temperature at a certain distance away from the track, they could be automatically floating over and moving along the track without any obvious friction. The models can be used as experimental or demonstration devices for the magnetic levitation applications

Magnetic levitation and its application for education devices based on YBCO bulk superconductors

Energy Technology Data Exchange (ETDEWEB)

Yang, W.M., E-mail: yangwm@snnu.edu.cn; Chao, X.X.; Guo, F.X.; Li, J.W.; Chen, S.L.

2013-10-15

Highlights: • A small superconducting maglev propeller system has been designed and constructed based on YBCO bulk superconductors. • Several small maglev vehicle models have been designed and constructed based on YBCO bulk superconductors. • The models can be used as experimental or demonstration devices for the magnetic levitation applications. -- Abstract: A small superconducting maglev propeller system, a small spacecraft model suspending and moving around a terrestrial globe, several small maglev vehicle models and a magnetic circuit converter have been designed and constructed. The track was paved by NdFeB magnets, the arrangement of the magnets made us easy to get a uniform distribution of magnetic field along the length direction of the track and a high magnetic field gradient in the lateral direction. When the YBCO bulks mounted inside the vehicle models or spacecraft model was field cooled to LN{sub 2} temperature at a certain distance away from the track, they could be automatically floating over and moving along the track without any obvious friction. The models can be used as experimental or demonstration devices for the magnetic levitation applications.

Ductile Bulk Aluminum-Based Alloy with Good Glass-Forming Ability and High Strength

International Nuclear Information System (INIS)

Long-Chao, Zhuo; Shu-Jie, Pang; Hui, Wang; Tao, Zhang

2009-01-01

Based on a new approach for designing glassy alloy compositions, bulk Al-based alloys with good glass-forming ability (GFA) are synthesized. The cast Al 86 Si 0.5 Ni 4.06 Co 2.94 Y 6 Sc 0.5 rod with a diameter of 1 mm shows almost fully amorphous structure besides about 5% fcc-Al nucleated in the center of the rod. The bulk alloy with high Al concentration exhibits an ultrahigh yield strength of 1.18 GPa and maximum strength of 1.27 GPa as well as an obvious plastic strain of about 2.4% during compressive deformation. This light Al-based alloy with good GFA and mechanical properties is promising as a new high specific strength material with good deformability. (condensed matter: structure, mechanical and thermal properties)

Effect of rolling deformation on the microstructure of bulk Cu60Zr20Ti20 metallic glass and its crystallization

DEFF Research Database (Denmark)

Cao, Q.P.; Li, J.F.; Zhou, Y.H.

2006-01-01

Bulk Cu60Zr20Ti20 metallic glass has been rolled at room temperature (RT) and cryogenic temperature (CIF) up to 97% in thickness reduction, and the dependences of microstructure on the strain and temperature have been investigated. It is revealed that as the deformation proceeds below a critical...... thickness reduction, which is 87% at RT and 89% at CT, only the shear band density and the free-volume content increase, whereas the thermal stability of the deformed glass remains unchanged. Deformation above the critical thickness reduction results in phase separation plus nanocrystallization at RT...

Amorphous Metals and Composites as Mirrors and Mirror Assemblies

Science.gov (United States)

Hofmann, Douglas C. (Inventor); Davis, Gregory L. (Inventor); Agnes, Gregory S. (Inventor); Shapiro, Andrew A. (Inventor)

2016-01-01

A mirror or mirror assembly fabricated by molding, pressing, assembling, or depositing one or more bulk metal glass (BMG), bulk metal glass composite (BMGMC), or amorphous metal (AM) parts and where the optical surface and backing of the mirror can be fabricated without machining or polishing by utilizing the unique molding capabilities of this class of materials.

Investigation on Explosive Welding of Zr53Cu35Al12 Bulk Metallic Glass with Crystalline Copper

Science.gov (United States)

Feng, Jianrui; Chen, Pengwan; Zhou, Qiang

2018-05-01

A Zr53Cu35Al12 bulk metallic glass (BMG) was welded to a crystalline Cu using explosive welding technique. The morphology and the composition of the composite were characterized using optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy and transmission electron microscopy. The investigation indicated that the BMG and Cu were tightly joined together without visible defects, and a thin diffusion layer appeared at the interface. The captured jet at the end of the welding region mostly comes from the Cu side. Amorphous and partially crystallized structures have been observed within the diffusion layer, but the BMG in close proximity to the interface still retains its amorphous state. Nanoindentation tests reveal that the interface exhibits an increment in hardness compared with the matrix on both sides.

Effect of annealing on the magnetic properties of Nd70Fe20Al10 bulk metallic glasses

International Nuclear Information System (INIS)

Olivetti, Elena; Baricco, Marcello; Ferrara, Enzo; Tiberto, Paola; Martino, Luca

2005-01-01

In this work, the influence of thermal treatments on the hysteresis behaviour of Nd 70 Fe 20 Al 10 bulk metallic glasses is studied. Two samples obtained applying different quenching rates have been characterized: (a) master alloy ingots, prepared through arc melting, and (b) cone-shaped ingots obtained by copper mould casting. DSC measurements have been performed on both alloys. Selected samples have been submitted to subsequent annealing. Hard magnetic properties have been observed at room temperature either in the as-cast master alloy or in the cone-shaped ingots. High values of coercivity are still observed after treatment at temperatures close to the crystallisation temperature (up to 500 deg. C). The different magnetic behaviour of the samples is discussed in terms of differences in the residual amorphous phase composition

Screening of catalytic oxygen reduction reaction activity of metal-doped graphene by density functional theory

International Nuclear Information System (INIS)

Chen, Xin; Chen, Shuangjing; Wang, Jinyu

2016-01-01

Highlights: • The screened M-G structures are very thermodynamically stable, and the stability is even higher than that of the corresponding bulk metal surfaces. • The binding energies of ORR intermediates suggest that they are not linear dependence, which are different form the cases found on some metal-based catalysts. • The Au-, Co-, and Ag-G structures could be used as the ORR catalysts. - Abstract: Graphene doping is a promising direction for developing effective oxygen reduction reaction (ORR) catalysts. In this paper, we computationally investigated the ORR performance of 10 kinds of metal-doped graphene (M-G) catalysts, namely, Al-, Si-, Mn-, Fe-, Co-, Ni-, Pd-, Ag-, Pt-, and Au-G. The results shown that the binding energies of the metal atoms incorporated into the graphene vacancy are higher than their bulk cohesive energies, indicating the formed M-G catalysts are even more stable than the corresponding bulk metal surfaces, and thus avoid the metals dissolution in the reaction environment. We demonstrated that the linear relation among the binding energies of the ORR intermediates that found on metal-based materials does not hold for the M-G catalysts, therefore a single binding energy of intermediate alone is not sufficient to evaluate the ORR activity of an arbitrary catalyst. By analysis of the detailed ORR processes, we predicted that the Au-, Co-, and Ag-G materials can be used as the ORR catalysts.

Thermodynamic data-base for metal fluorides

Energy Technology Data Exchange (ETDEWEB)

Yoo, Jae Hyung; Lee, Byung Gik; Kang, Young Ho and others

2001-05-01

This study is aimed at collecting useful data of thermodynamic properties of various metal fluorides. Many thermodynamic data for metal fluorides are needed for the effective development, but no report of data-base was published. Accordingly, the objective of this report is to rearrange systematically the existing thermodynamic data based on metal fluorides and is to use it as basic data for the development of pyrochemical process. The physicochemical properties of various metal fluorides and metals were collected from literature and such existing data base as HSC code, TAPP code, FACT code, JANAF table, NEA data-base, CRC handbook. As major contents of the thermodynamic data-base, the physicochemical properties such as formation energy, viscosity, density, vapor pressure, etc. were collected. Especially, some phase diagrams of eutectic molten fluorides are plotted and thermodynamic data of liquid metals are also compiled. In the future, the technical report is to be used as basic data for the development of the pyrochemical process which is being carried out as a long-term nuclear R and D project.

Thermodynamic data-base for metal fluorides

International Nuclear Information System (INIS)

Yoo, Jae Hyung; Lee, Byung Gik; Kang, Young Ho and others

2001-05-01

This study is aimed at collecting useful data of thermodynamic properties of various metal fluorides. Many thermodynamic data for metal fluorides are needed for the effective development, but no report of data-base was published. Accordingly, the objective of this report is to rearrange systematically the existing thermodynamic data based on metal fluorides and is to use it as basic data for the development of pyrochemical process. The physicochemical properties of various metal fluorides and metals were collected from literature and such existing data base as HSC code, TAPP code, FACT code, JANAF table, NEA data-base, CRC handbook. As major contents of the thermodynamic data-base, the physicochemical properties such as formation energy, viscosity, density, vapor pressure, etc. were collected. Especially, some phase diagrams of eutectic molten fluorides are plotted and thermodynamic data of liquid metals are also compiled. In the future, the technical report is to be used as basic data for the development of the pyrochemical process which is being carried out as a long-term nuclear R and D project

Comprehensive recovery of gold and base-metal sulfide minerals from a low-grade refractory ore

Science.gov (United States)

Li, Wen-juan; Liu, Shuang; Song, Yong-sheng; Wen, Jian-kang; Zhou, Gui-ying; Chen, Yong

2016-12-01

The comprehensive recovery of small amounts of valuable minerals such as gold and base-metal sulfide minerals from a low-grade refractory ore was investigated. The following treatment strategy was applied to a sample of this ore: gold flotation-gold concentrate leaching-lead and zinc flotation from the gold concentrate leaching residue. Closed-circuit trials of gold flotation yielded a gold concentrate that assayed at 40.23 g·t-1 Au with a recovery of 86.25%. The gold concentrate leaching rate was 98.76%. Two variants of lead-zinc flotation from the residue—preferential flotation of lead and zinc and bulk flotation of lead and zinc—were tested using the middling processing method. Foam from the reflotation was returned to the lead rougher flotation or lead-zinc bulk flotation, whereas middlings from reflotation were discarded. Sulfur concentrate was a byproduct. The combined strategy of flotation, leaching, and flotation is recommended for the treatment of this kind of ore.

Cohesion and device reliability in organic bulk heterojunction photovoltaic cells

KAUST Repository

Brand, Vitali

2012-04-01

The fracture resistance of P3HT:PC 60BM-based photovoltaic devices are characterized using quantitative adhesion and cohesion metrologies that allow identification of the weakest layer or interface in the device structure. We demonstrate that the phase separated bulk heterojunction layer is the weakest layer and report quantitative cohesion values which ranged from ∼1 to 20 J m -2. The effects of layer thickness, composition, and annealing treatments on layer cohesion are investigated. Using depth profiling and X-ray photoelectron spectroscopy on the resulting fracture surfaces, we examine the gradient of molecular components through the thickness of the bulk heterojunction layer. Finally, using atomic force microscopy we show how the topography of the failure path is related to buckling of the metal electrode and how it develops with annealing. The research provides new insights on how the molecular design, structure and composition affect the cohesive properties of organic photovoltaics. © 2011 Elsevier B.V. All rights reserved.

The influence of Zr substitution for Nb on the corrosion behaviors of the Ni-Nb-Zr bulk metallic glasses

Science.gov (United States)

Li, DengKe; Zhu, ZhengWang; Zhang, HaiFeng; Wang, AiMin; Hu, ZhuangQi

2012-12-01

The influence of Zr content on corrosion behaviors of the Ni61.5Nb38.5- x Zr x ( x=1, 3, 5, 7, 9 at.%) bulk metallic glasses (BMGs) in 1 M HCl aqueous solution was investigated by potentiodynamic polarization measurements and X-ray photo-electron spectroscopy (XPS). It was found that these BMG alloys possess superior corrosion resistance, that is, with large passive region of about 1.5 V and low passive current density (as low as 0.05 Am-2 for Ni61.5Nb31.5Zr7). XPS analysis indicates that the high corrosion resistance is attributed to the formation of Nb- and Zr-enriched surface films formed in the aggressive acid solution. The Zr substitution for Nb effectively reduces the Ni content, particularly the metallic state Ni content in the surface films, which depresses the electrical conduction of the surface films and reduces the passive current density, thus leading to the enhancement of the corrosion resistance of these Ni-Nb-Zr BMGs. These alloys may potentially be useful for engineering applications.

In situ Raman spectroscopy studies of bulk and surface metal

NARCIS (Netherlands)

Weckhuysen, B.M.; Wachs, I.E.; Jehng, J.M.; Deo, G.; Guliants, V.V.; Benziger, J.B.

1996-01-01

Bulk V-P-O and model supported vanadia catalysts were investigated with in situ Raman spectroscopy during n-butane oxidation to maleic anhydride in order to determine the fundamental molecular structure-reactivity/selectivity insights that can be obtained from such experiments. The in situ Raman

Metal chemistry of the transactinides

International Nuclear Information System (INIS)

Eichler, B.

2000-12-01

The elements with atomic numbers between 104 and 116 are expected to behave as metals. Their interaction with metal surfaces is of uppermost importance both to design experimental separation procedures as well as for their chemical characterization. This interaction is quantified by the net adsorption enthalpy. The determination of the net adsorption enthalpy requires the calculation of the solution enthalpy of transactinides in the bulk-phases of the solid adsorbent metals. These solution enthalpies have been calculated with the Miedema-model. For that purpose the necessary parameters of the transactinides: the metal radius, the molar volume, the electronic density at the Wigner-Seitz-Cell boundary and the electronegativity (Miedema Scale) have been obtained on the basis of empirical correlations starting from the entropies of solid transactinides. These entropies were estimated by extrapolations as a function of atomic masses along the groups of the periodic table. The results of the calculations show a strong dependence on the cohesion energy of the solid adsorbent metals as well as on the solution enthalpies of transactinides in the bulk-phase of these metals. The enthalpies of segregation of transactinides from the metallic bulk-phases as the 'driving forces' of the surface enrichment process were calculated. The calculated data allow the selection of the best suitable materials for the gas phase transport as well as of the adsorbent metal for chromatographic separations, for sampling and for electrochemical deposition in experiments with the transactinides. (author)

Decrease in electrical resistivity on depletion of islands of mobility during aging of a bulk metal glass

Science.gov (United States)

Aji, Daisman P. B.; Johari, G. P.

2018-04-01

The effect of structural relaxation on electrical resistivity, ρglass, of strain-free Zr46.75Ti8.25Cu7.5Ni10Be27.5 bulk metallic glass was studied during isothermal aging at several temperatures, Tas. Since cooling of a liquid metal increases its resistivity ρliq, one expects ρglass to increase on aging toward ρliq at T = Ta. Instead, ρglass decreased non-exponentially with the aging time. The activation energy of aging kinetics is 189 kJ mol-1, which is higher than the activation energy of the Johari-Goldstein (JG) relaxation. After considering the sample's contraction, phase separation, and crystallization as possible causes of the decrease in ρglass, we attribute the decrease to depletion of islands of atomic mobility, soft spots, or static heterogeneity. Vibrations of the atoms in these local (loosely packed) regions and in the region's interfacial area contribute to electron scattering. As these deplete on aging, the contribution decreases and ρglass decreases, with a concomitant decrease in macroscopic volume, enthalpy, and entropy (V, H, and S). Local regions of faster mobility also decrease on cooling as V, H, and S of a liquid decrease, but structure fluctuations dominate electron scattering of a liquid metal and ρliq increases effectively according to the Ziman-Nagel theory for a homogenously disordered structure. Whether depletion of such local regions initiates the structural relaxation of a glass, or vice versa, may be resolved by finding a glass that physically ages but shows no JG relaxation.

Mechanical and dynamical behaviors of ZrSi and ZrSi{sub 2} bulk metallic glasses: A molecular dynamics study

Energy Technology Data Exchange (ETDEWEB)

Ju, Shin-Pon, E-mail: jushin-pon@mail.nsysu.edu.tw [Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-sen University, Kaohsiung 804, Taiwan (China); Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Wu, Tsang-Yu; Liu, Shih-Hao [Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-sen University, Kaohsiung 804, Taiwan (China)

2015-03-14

The mechanical and dynamical properties of ZrSi and ZrSi{sub 2} bulk metallic glasses (BMGs) have been investigated by molecular dynamics simulation. The Honeycutt-Anderson (HA) index analysis indicates that the major indexes in ZrSi and ZrSi{sub 2} bulk metallic glasses are 1551, 1541, and 1431, which refers to the liquid structure. For uniaxial tension, the results show that the ZrSi and ZrSi{sub 2} BMGs are more ductile than their crystal counterparts. The evolution of the distribution of atomic local shear strain clearly shows the initialization of shear transformation zones (STZs), the extension of STZs, and the formation of shear bands along a direction 45° from the tensile direction when the tensile strain gradually increases. The self-diffusion coefficients of ZrSi and ZrSi{sub 2} BMGs at temperatures near their melting points were calculated by the Einstein equation according to the slopes of the MSD profiles at the long-time limit. Because the HA fraction summation of icosahedral-like structures of ZrSi BMG is higher than that of ZrSi{sub 2} BMG, and these local structures are more dense, the self-diffusion coefficients of the total, Zr, and Si atoms of ZrSi{sub 2} BMG are larger than those of ZrSi BMG. This can be attributed to the cage effect, where a denser local structure has a higher possibility of atoms jumping back to form a backflow and then suppress atomic diffusivity. For ZrSi{sub 2} BMG, the self-diffusion coefficient of Si increases with temperature more significantly than does that of Zr, because more open packing rhombohedra structures are formed by the Si-Si pair.

Bulk substrate porosity verification by applying Monte Carlo modeling and Castaing's formula using energy-dispersive x-rays

Science.gov (United States)

Yung, Lai Chin; Fei, Cheong Choke; Mandeep, Jit Singh; Amin, Nowshad; Lai, Khin Wee

2015-11-01

The leadframe fabrication process normally involves additional thin-metal layer plating on the bulk copper substrate surface for wire bonding purposes. Silver, tin, and copper flakes are commonly adopted as plating materials. It is critical to assess the density of the plated metal layer, and in particular to look for porosity or voids underneath the layer, which may reduce the reliability during high-temperature stress. A fast, reliable inspection technique is needed to assess the porosity or void weakness. To this end, the characteristics of x-rays generated from bulk samples were examined using an energy-dispersive x-ray (EDX) detector to examine the porosity percentage. Monte Carlo modeling was integrated with Castaing's formula to verify the integrity of the experimental data. Samples with different porosity percentages were considered to test the correlation between the intensity of the collected x-ray signal and the material density. To further verify the integrity of the model, conventional cross-sectional samples were also taken to observe the porosity percentage using Image J software measurement. A breakthrough in bulk substrate assessment was achieved by applying EDX for the first time to nonelemental analysis. The experimental data showed that the EDX features were not only useful for elemental analysis, but also applicable to thin-film metal layer thickness measurement and bulk material density determination. A detailed experiment was conducted using EDX to assess the plating metal layer and bulk material porosity.

Inert anode containing base metal and noble metal useful for the electrolytic production of aluminum

Science.gov (United States)

Ray, Siba P.; Liu, Xinghua

2000-01-01

An inert anode for production of metals such as aluminum is disclosed. The inert anode comprises a base metal selected from Cu and Ag, and at least one noble metal selected from Ag, Pd, Pt, Au, Rh, Ru, Ir and Os. The inert anode may optionally be formed of sintered particles having interior portions containing more base metal than noble metal and exterior portions containing more noble metal than base metal. In a preferred embodiment, the base metal comprises Cu, and the noble metal comprises Ag, Pd or a combination thereof.

Materials processing and machine applications of bulk HTS

Science.gov (United States)

Miki, M.; Felder, B.; Tsuzuki, K.; Xu, Y.; Deng, Z.; Izumi, M.; Hayakawa, H.; Morita, M.; Teshima, H.

2010-12-01

We report a refrigeration system for rotating machines associated with the enhancement of the trapped magnetic flux of bulk high-temperature superconductor (HTS) field poles. A novel cryogenic system was designed and fabricated. It is composed of a low-loss rotary joint connecting the rotor and a closed-cycle thermosiphon under a GM cryocooler using a refrigerant. Condensed neon gas was adopted as a suitable cryogen for the operation of HTS rotating machines with field poles composed of RE-Ba-Cu-O family materials, where RE is a rare-earth metal. Regarding the materials processing of the bulks HTS, thanks to the addition of magnetic particles to GdBa2Cu3O7 - d (Gd123) bulk superconductors an increase of more than 20% in the trapped magnetic flux density was achieved at liquid nitrogen temperature. Field-pole Gd123 bulks up to 46 mm in diameter were synthesized with the addition of Fe-B alloy magnetic particles and assembled into the synchronous machine rotor to be tested. Successful cooling of the magnetized rotor field poles down to 35 K and low-output-power rotating operation was achieved up to 720 rpm in the test machine with eight field-pole bulks. The present results show a substantial basis for making a prototype system of rotating machinery of applied HTS bulks.

Materials processing and machine applications of bulk HTS

Energy Technology Data Exchange (ETDEWEB)

Miki, M; Felder, B; Tsuzuki, K; Xu, Y; Deng, Z; Izumi, M [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan); Hayakawa, H [Kitano Seiki Co. Ltd, 7-17-3, Chuo, Ohta-ku, Tokyo 143-0024 (Japan); Morita, M; Teshima, H, E-mail: d082025@kaiyodai.ac.j [Nippon Steel Co. Ltd, 20-1, Shintomi, Huttsu-shi, Chiba 293-8511 (Japan)

2010-12-15

We report a refrigeration system for rotating machines associated with the enhancement of the trapped magnetic flux of bulk high-temperature superconductor (HTS) field poles. A novel cryogenic system was designed and fabricated. It is composed of a low-loss rotary joint connecting the rotor and a closed-cycle thermosiphon under a GM cryocooler using a refrigerant. Condensed neon gas was adopted as a suitable cryogen for the operation of HTS rotating machines with field poles composed of RE-Ba-Cu-O family materials, where RE is a rare-earth metal. Regarding the materials processing of the bulks HTS, thanks to the addition of magnetic particles to GdBa{sub 2}Cu{sub 3}O{sub 7-d} (Gd123) bulk superconductors an increase of more than 20% in the trapped magnetic flux density was achieved at liquid nitrogen temperature. Field-pole Gd123 bulks up to 46 mm in diameter were synthesized with the addition of Fe-B alloy magnetic particles and assembled into the synchronous machine rotor to be tested. Successful cooling of the magnetized rotor field poles down to 35 K and low-output-power rotating operation was achieved up to 720 rpm in the test machine with eight field-pole bulks. The present results show a substantial basis for making a prototype system of rotating machinery of applied HTS bulks.

Metallic Nanostructures Based on DNA Nanoshapes

Directory of Open Access Journals (Sweden)

Boxuan Shen

2016-08-01

Full Text Available Metallic nanostructures have inspired extensive research over several decades, particularly within the field of nanoelectronics and increasingly in plasmonics. Due to the limitations of conventional lithography methods, the development of bottom-up fabricated metallic nanostructures has become more and more in demand. The remarkable development of DNA-based nanostructures has provided many successful methods and realizations for these needs, such as chemical DNA metallization via seeding or ionization, as well as DNA-guided lithography and casting of metallic nanoparticles by DNA molds. These methods offer high resolution, versatility and throughput and could enable the fabrication of arbitrarily-shaped structures with a 10-nm feature size, thus bringing novel applications into view. In this review, we cover the evolution of DNA-based metallic nanostructures, starting from the metallized double-stranded DNA for electronics and progress to sophisticated plasmonic structures based on DNA origami objects.

Plastic Deformation of Metal Surfaces

DEFF Research Database (Denmark)

Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

2013-01-01

of metal components. An optimization of processes and material parameters must be based on a quantification of stress and strain gradients at the surface and in near surface layer where the structural scale can reach few tens of nanometers. For such fine structures it is suggested to quantify structural...... parameters by TEM and EBSD and apply strength-structural relationships established for the bulk metal deformed to high strains. This technique has been applied to steel deformed by high energy shot peening and a calculated stress gradient at or near the surface has been successfully validated by hardness...

A geological interpretation of heavy metal concentrations in soils and sediments in the southern Netherlands

NARCIS (Netherlands)

Huisman, D.J.; Vermeulen, F.J.H.; Baker, J.; Veldkamp, A.; Kroonenberg, S.B.; Klaver, G.Th.

1997-01-01

The natural variation in heavy metal contents of subsurface sediments in the southern Netherlands is described, based on a series of 820 bulk geochemical analyses. The detrital heavy metal contents of these sediments show linear correlations with Al as a result of their joint occurrence in

Perspectives on environmental protection of refractory metals

International Nuclear Information System (INIS)

Perking, R.A.

1992-01-01

Alloys of refractory metals which combine high strength to weight ratios with useful low-temperature toughness and ductility have been designed to meet the requirements for the next generation of high-temperature aerospace structural materials with one exception: long term resistance to oxidation. It is considered unlikely that refractory metal alloys can be modified to possess useful resistance to oxidation as bulk materials or that coating can be designed to provide high reliability fail-safe protection for the structural alloys developed to date. Recent developments indicate that bulk alloys of W and Mo can be designed to possess short term resistance to oxidation, providing a base material which can be coated to extend useful life with fail-safe protection in the event of random coating failures. Current research on silicide coatings indicates that significant improvements in coating reliability and performance also are feasible. The technical basis for these conclusions is presented in this paper and the direction of future work that could lead to environmentally stable refractory metal alloy/coating systems is discussed

Hydrogen storage alloys for nickel/metal hydride battery

Energy Technology Data Exchange (ETDEWEB)

Kuriyama, Nobuhiro; Sakai, Tetsuo; Myamura, Hiroshi; Tanaka, Hideaki; Ishikawa, Hiroshi; Uehara, Itsuki [Osaka National Research Inst. (Japan)

1996-06-01

Efforts to improve performance of metal hydride electrodes such as substitution of alloy components, heat treatment, and surface treatment intended to change surface and bulk structure of hydrogen storage alloys, mainly LaNi{sub 5} based alloys, are reviewed. The importance of control of morphology is emphasized. (author)

Base Metal Co-Fired Multilayer Piezoelectrics

Directory of Open Access Journals (Sweden)

Lisheng Gao

2016-03-01

Full Text Available Piezoelectrics have been widely used in different kinds of applications, from the automobile industry to consumer electronics. The novel multilayer piezoelectrics, which are inspired by multilayer ceramic capacitors, not only minimize the size of the functional parts, but also maximize energy efficiency. Development of multilayer piezoelectric devices is at a significant crossroads on the way to achieving low costs, high efficiency, and excellent reliability. Concerning the costs of manufacturing multilayer piezoelectrics, the trend is to replace the costly noble metal internal electrodes with base metal materials. This paper discusses the materials development of metal co-firing and the progress of integrating current base metal chemistries. There are some significant considerations in metal co-firing multilayer piezoelectrics: retaining stoichiometry with volatile Pb and alkaline elements in ceramics, the selection of appropriate sintering agents to lower the sintering temperature with minimum impact on piezoelectric performance, and designing effective binder formulation for low pO2 burnout to prevent oxidation of Ni and Cu base metal.

Ultra-stiff metallic glasses through bond energy density design.

Science.gov (United States)

Schnabel, Volker; Köhler, Mathias; Music, Denis; Bednarcik, Jozef; Clegg, William J; Raabe, Dierk; Schneider, Jochen M

2017-07-05

The elastic properties of crystalline metals scale with their valence electron density. Similar observations have been made for metallic glasses. However, for metallic glasses where covalent bonding predominates, such as metalloid metallic glasses, this relationship appears to break down. At present, the reasons for this are not understood. Using high energy x-ray diffraction analysis of melt spun and thin film metallic glasses combined with density functional theory based molecular dynamics simulations, we show that the physical origin of the ultrahigh stiffness in both metalloid and non-metalloid metallic glasses is best understood in terms of the bond energy density. Using the bond energy density as novel materials design criterion for ultra-stiff metallic glasses, we are able to predict a Co 33.0 Ta 3.5 B 63.5 short range ordered material by density functional theory based molecular dynamics simulations with a high bond energy density of 0.94 eV Å -3 and a bulk modulus of 263 GPa, which is 17% greater than the stiffest Co-B based metallic glasses reported in literature.

Magnetic properties and microstructural homogeneity in NdFeAl bulk metallic glasses

International Nuclear Information System (INIS)

Ortega-Zempoalteca, R.; Valenzuela, R.; Betancourt, I.

2011-01-01

Bulk metallic glasses of nominal composition Nd 60 Fe 30 Al 10 were prepared by copper mold casting in the form of rods of 3 mm in diameter and 50 mm in length. Preparation conditions were varied to assess the effects of the injection distance and the injection pressure of the melt. In order to determine their microstructure, disk-shaped samples were obtained from different cut zones along the axis rod. A non-homogeneous phase distribution was observed, which resulted from the heat transfer regime during the cooling of the melt in the copper mold. As expected, the nature, distribution and volumetric fraction of the various phases produced play an important role on the resulting magnetic properties. Among the main observed phases are Fe-rich rod-like crystals, Nd-rich dendritic crystals and a ''like-amorphous'' matrix. The hard magnetic properties of these materials can be associated with this matrix. In these cooling regimes, the coercive field increases as the cooling rate of the amorphous matrix increases. Hysteresis loops showed a high degree of coupling between phases with different magnetic order. Both the coercive field and the magnetization showed a significant variation along the rod axis; a maximum appeared as a function of the axis length. In order to gather more information about the coupling between the observed phases, δM (or Henkel) plots were obtained, showing an exchange character for interactions (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

THE IMPACT OF PARTIAL CRYSTALLIZATION ON THE PERMEATION PROPERTIES BULK AMORPHOUS GLASS HYDROGEN SEPARATION MEMBRANES

Energy Technology Data Exchange (ETDEWEB)

Brinkman, K; Paul Korinko, P; Thad Adams, T; Elise Fox, E; Arthur Jurgensen, A

2008-11-25

It is recognized that hydrogen separation membranes are a key component of the emerging hydrogen economy. A potentially exciting material for membrane separations are bulk metallic glass materials due to their low cost, high elastic toughness and resistance to hydrogen 'embrittlement' as compared to crystalline Pd-based membrane systems. However, at elevated temperatures and extended operation times structural changes including partial crystallinity may appear in these amorphous metallic systems. A systematic evaluation of the impact of partial crystallinity/devitrification on the diffusion and solubility behavior in multi-component Metallic Glass materials would provide great insight into the potential of these materials for hydrogen applications. This study will report on the development of time and temperature crystallization mapping and their use for interpretation of 'in-situ' hydrogen permeation at elevated temperatures.

Approach and issues toward development of risk-based release standards for radioactive scrap metal recycle and reuse

International Nuclear Information System (INIS)

Chen, S.Y.; Nieves, L.A.; Nabelssi, B.K.; LePoire, D.J.

1994-01-01

The decontamination and decommissioning of nuclear facilities is expected to generate large amounts of slightly radioactive scrap metal (RSM). It is likely that some of these materials will be suitable for recycling and reuse. The amount of scrap steel from DOE facilities, for instance, is estimated to be more than one million tons (Hertzler 1993). However, under current practice and without the establishment of acceptable recycling standards, the RSM would be disposed of primarily as radioactive low-level waste (LLW). In the United States, no specific standards have been developed for the unrestricted release of bulk contaminated materials. Although standards for unrestricted release of radioactive surface contamination (NRC 1974) have existed for about 20 years, the release of materials is not commonly practiced because of the lack of risk-based justifications. Recent guidance from international bodies (IAEA 1988) has established a basis for deriving risk-based release limits for radioactive materials. It is important, therefore, to evaluate the feasibility of recycling and associated issues necessary for the establishment of risk-based release limits for the radioactive metals

Mining the bulk positron lifetime

International Nuclear Information System (INIS)

Aourag, H.; Guittom, A.

2009-01-01

We introduce a new approach to investigate the bulk positron lifetimes of new systems based on data-mining techniques. Through data mining of bulk positron lifetimes, we demonstrate the ability to predict the positron lifetimes of new semiconductors on the basis of available semiconductor data already studied. Informatics techniques have been applied to bulk positron lifetimes for different tetrahedrally bounded semiconductors in order to discover computational design rules. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Simulation and analysis of microwave heating while joining bulk ...

African Journals Online (AJOL)

ATHARVA

Processing of bulk metallic materials using microwave energy is challenging. ... The distributed power and heat source were computed in a stationary, .... the heat transfer equation is used in order to get the temperature distributions and other system properties. ... equation (2) to obtain the distribution of the E and H fields.

Superhard MgB sub 2 bulk material prepared by high-pressure sintering

CERN Document Server

Ma, H A; Chen, L X; Zhu, P W; Ren, G Z; Guo, W L; Fu, X Q; Zou Guang Tian; Ren, Z A; Che, G C; Zhao, Z X

2002-01-01

Superhard MgB sub 2 bulk material with a golden metallic shine was synthesized by high-pressure sintering for 8 h at 5.5 GPa and different temperatures. Appropriate pressure and temperature conditions for synthesizing polycrystalline MgB sub 2 with high hardness were investigated. The samples were characterized by means of atomic force microscopy and x-ray diffraction. The Vickers hardness, bulk density, and electrical resistivity were measured at room temperature.

Metallization for Yb14MnSb11-Based Thermoelectric Materials

Science.gov (United States)

Firdosy, Samad; Li, Billy Chun-Yip; Ravi, Vilupanur; Sakamoto, Jeffrey; Caillat, Thierry; Ewell, Richard C.; Brandon, Erik J.

2011-01-01

Thermoelectric materials provide a means for converting heat into electrical power using a fully solid-state device. Power-generating devices (which include individual couples as well as multicouple modules) require the use of ntype and p-type thermoelectric materials, typically comprising highly doped narrow band-gap semiconductors which are connected to a heat collector and electrodes. To achieve greater device efficiency and greater specific power will require using new thermoelectric materials, in more complex combinations. One such material is the p-type compound semiconductor Yb14MnSb11 (YMS), which has been demonstrated to have one of the highest ZT values at 1,000 C, the desired operational temperature of many space-based radioisotope thermoelectric generators (RTGs). Despite the favorable attributes of the bulk YMS material, it must ultimately be incorporated into a power-generating device using a suitable joining technology. Typically, processes such as diffusion bonding and/or brazing are used to join thermoelectric materials to the heat collector and electrodes, with the goal of providing a stable, ohmic contact with high thermal conductivity at the required operating temperature. Since YMS is an inorganic compound featuring chemical bonds with a mixture of covalent and ionic character, simple metallurgical diffusion bonding is difficult to implement. Furthermore, the Sb within YMS readily reacts with most metals to form antimonide compounds with a wide range of stoichiometries. Although choosing metals that react to form high-melting-point antimonides could be employed to form a stable reaction bond, it is difficult to limit the reactivity of Sb in YMS such that the electrode is not completely consumed at an operating temperature of 1,000 C. Previous attempts to form suitable metallization layers resulted in poor bonding, complete consumption of the metallization layer or fracture within the YMS thermoelement (or leg).

Evaluation of surface energy state distribution and bulk defect concentration in DSSC photoanodes based on Sn, Fe, and Cu doped TiO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Ako, Rajour Tanyi [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Ekanayake, Piyaisiri, E-mail: piyasiri.ekanayake@ubd.edu.bn [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Young, David James [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research -A*STAR, 3 Research Link, 117602 (Singapore); Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, Queensland, 4558 (Australia); Hobley, Jonathan [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Chellappan, Vijila [Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research - A*STAR, 3 Research Link, 117602 (Singapore); Tan, Ai Ling [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam); Gorelik, Sergey; Subramanian, Gomathy Sandhya [Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research - A*STAR, 3 Research Link, 117602 (Singapore); Lim, Chee Ming [Faculty of Science, Universiti Brunei Darussalam, Jalan Tungku Link, BE1410, Negara (Brunei Darussalam)

2015-10-01

Graphical abstract: - Highlights: • The structural, optical and optoelectronic properties of 1 mol.% Fe, Sn and Cu doped TiO{sub 2} have been compared. • Transient lifetimes for pure TiO{sub 2} and Sn doped TiO{sub 2} were considerably shorter than Fe and Cu doped TiO{sub 2}. • A good correlation between the bulk defects and transient decay for the doped TiO{sub 2} powders was observed. • Photon to current conversion efficiency of DSSC based on the metal doped TiO{sub 2} were in order Sn-TiO{sub 2} > Cu-TiO{sub 2} > Pure >> Fe-TiO{sub 2}. • DSSC based on Fe doped photoanodes is limited by a high concentration of surface free holes observed at 433 nm. - Abstract: Electron transfer dynamics in the oxide layers of the working electrodes in both dye-sensitized solar cells and photocatalysts greatly influences their performance. A proper understanding of the distribution of surface and bulk energy states on/in these oxide layers can provide insights into the associated electron transfer processes. Metal ions like Iron (Fe), Copper (Cu) and Tin (Sn) doped onto TiO{sub 2} have shown enhanced photoactivity in these processes. In this work, the structural, optical and transient properties of Fe, Cu and Sn doped TiO{sub 2} nanocrystalline powders have been investigated and compared using EDX, Raman spectroscopy, X-ray Photoelectron spectroscopy (XPS), and Transient Absorption spectroscopy (TAS). Surface free energy states distributions were probed using Electrochemical Impedance spectroscopy (EIS) on Dye Sensitized Solar Cells (DSSC) based on the doped TiO{sub 2} photoanodes. Raman and XPS Ti2p{sub 3/2} peak shifts and broadening showed that the concentration of defects were in the order: Cu doped TiO{sub 2} > Fe doped TiO{sub 2} > Sn doped TiO{sub 2} > pure TiO{sub 2}. Nanosecond laser flash photolysis of Fe and Cu doped TiO{sub 2} indicated slower transient decay kinetics than that of Sn doped TiO{sub 2} or pure TiO{sub 2}. A broad absorption peak and fast

Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

Energy Technology Data Exchange (ETDEWEB)

Taette, Tanel; Hussainov, Medhat; Paalo, Madis; Part, Marko; Talviste, Rasmus; Kiisk, Valter; Maendar, Hugo; Pohako, Kaija; Reivelt, Kaido; Lohmus, Ants [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Pehk, Tonis [National Institute of Chemical and Biological Physics, Akadeemia tee 23, Tallinn 12618 (Estonia); Natali, Marco [ICIS-CNR, Corso Stati Uniti 4, Padova 35127 (Italy); Gurauskis, Jonas [Instituto de Ciencia de Materiales de Aragon C.S.I.C., University of Zaragoza Fac. De Ciencias, c/Pedro Cerbuna 12, Zaragoza 50009 (Spain); Maeeorg, Uno, E-mail: tanelt@fi.tartu.ee [Institute of Chemistry, University of Tartu, Ravila 14a, Tartu 50411 (Estonia)

2011-06-15

The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO{sub 2}, TiO{sub 2}, ZrO{sub 2}, HfO{sub 2} and CeO{sub 2}) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol-gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.

Speciation in Metal Toxicity and Metal-Based Therapeutics

Directory of Open Access Journals (Sweden)

Douglas M. Templeton

2015-04-01

Full Text Available Metallic elements, ions and compounds produce varying degrees of toxicity in organisms with which they come into contact. Metal speciation is critical to understanding these adverse effects; the adjectives “heavy” and “toxic” are not helpful in describing the biological properties of individual elements, but detailed chemical structures are. As a broad generalization, the metallic form of an element is inert, and the ionic salts are the species that show more significant bioavailability. Yet the salts and other chelates of a metal ion can give rise to quite different toxicities, as exemplified by a range of carcinogenic potential for various nickel species. Another important distinction comes when a metallic element is organified, increasing its lipophilicity and hence its ability to penetrate the blood brain barrier, as is seen, for example, with organic mercury and tin species. Some metallic elements, such as gold and platinum, are themselves useful therapeutic agents in some forms, while other species of the same element can be toxic, thus focusing attention on species interconversions in evaluating metal-based drugs. The therapeutic use of metal-chelating agents introduces new species of the target metal in vivo, and this can affect not only its desired detoxification, but also introduce a potential for further mechanisms of toxicity. Examples of therapeutic iron chelator species are discussed in this context, as well as the more recent aspects of development of chelation therapy for uranium exposure.

Effects of bulk and surface conductivity on the performance of CdZnTe pixel detectors

DEFF Research Database (Denmark)

Bolotnikov, A.E.; Chen, C.M.H.; Cook, W.R.

2002-01-01

, the existence of a thin (10-100 A) oxide layer on the surface of CZT, formed during the fabrication process, affects both bulk and surface leakage currents. We demonstrate that the measured I-V dependencies of bulk current can be explained by considering the CZT detector as a metal-semiconductor-metal system......-collection efficiency in detectors with multicontact geometry; some fraction of the electric field lines that originated on the cathode intersects the surface areas between the pixel contacts where the charge produced by an ionizing particle gets trapped. To overcome this effect, we place a grid of thin electrodes...

Thermo-physical characterization of the Fe_6_7Mo_6Ni_3_._5Cr_3_._5P_1_2C_5_._5B_2_._5 bulk metallic glass forming alloy

International Nuclear Information System (INIS)

Bochtler, Benedikt; Gross, Oliver; Gallino, Isabella; Busch, Ralf

2016-01-01

The iron-phosphorus based bulk metallic glass forming alloy Fe_6_7Mo_6Ni_3_._5Cr_3_._5P_1_2C_5_._5B_2_._5 is characterized with respect to its thermophysical properties, crystallization and relaxation behavior, as well as its viscosity. The alloy provides a high critical casting thickness of 13 mm, thus allowing for the casting of amorphous parts with a considerable size. Calorimetric measurements reveal the characteristic transformation temperatures, transformation enthalpies, and the specific heat capacity. The analyses show that no stable supercooled liquid region exists upon heating. The specific heat capacity data are used to calculate the enthalpy, entropy, and Gibbs free energy differences between the crystalline and the supercooled liquid state. The crystallization behavior of amorphous samples upon heating is analyzed by differential scanning calorimetry and X-ray diffraction, and a time-temperature-transformation diagram is constructed. Dilatometry is used to determine the thermal expansion behavior. The equilibrium viscosity below the glass transition as well as volume relaxation behavior are measured by three-point beam bending and dilatometry, respectively, to assess the kinetic fragility. With a kinetic fragility parameter of D* = 21.3, the alloy displays a rather strong liquid behavior. Viscosity above the melting point is determined using electromagnetic levitation in microgravity on a reduced gravity aircraft in cooperation with the German Aerospace Center (DLR). These high-temperature viscosity data are compared with the low-temperature three-point beam bending measurements. The alloy displays a strong liquid behavior at low temperatures and a fragile behavior at high temperatures. These results are analogous to the ones observed in several Zr-based bulk metallic glass forming liquids, indicating a strong to fragile liquid-liquid transition in the undercooled liquid, which is obscured by crystallization.

5 MJ flywheel based on bulk HTS magnetic suspension

Science.gov (United States)

Poltavets, V.; Kovalev, K.; Ilyasov, R.; Glazunov, A.; Maevsky, V.; Verzbitsky, L.; Akhmadyshev, V.; Shikov, A.

2014-05-01

Nowadays the flywheel energy storage systems (FES) are developed intensively as uninterruptible power supply (UPS) devices for on-land and transport (especially airborne) applications worldwide. This work is devoted to the FES with magnetic suspension on the base of bulk HTS YBCO elements and permanent magnets. The developed FES is intended to be used as UPS in Russian atomic industry in case of an emergency. For the successful design of the FES the following questions should be solved: design of the motor/generator, design of the rotor (flywheel), design of the bearing system, design of the control system and system of power load matching, design of the cooling system. The developed small-scale FES with the stored energy 0.5 MJ was used to solve these basic questions. The elaborated FES consists of the synchronous electric machine with permanent magnets, the solid flywheel with axial magnetic suspension on the base of YBCO bulks and permanent magnets, the system of control and power load matching, and the system of liquid nitrogen cooling. The results of theoretical modeling of different schematics of magnetic suspension and experimental investigations of the constructed FES are presented. The design of the future full-scale FES with the stored energy ~5 MJ and output power up to 100 kW is described. The test results of the flywheel rotor and HTS magnetic suspension of 5 MJ FES are presented. This work is done under support of Rosatom within the frames of Russian Project "Superconducting Industry"

Insights into metals in individual fine particles from municipal solid waste using synchrotron radiation-based micro-analytical techniques

Institute of Scientific and Technical Information of China (English)

Yumin Zhu; Hua Zhang; Liming Shao; Pinjing He

2015-01-01

Excessive inter-contamination with heavy metals hampers the application of biological treatment products derived from mixed or mechanically-sorted municipal solid waste (MSW).In this study,we investigated fine particles of ＜2 mm,which are small fractions in MSW but constitute a significant component of the total heavy metal content,using bulk detection techniques.A total of 17 individual fine particles were evaluated using synchrotron radiation-based micro-X-ray fluorescence and micro-X-ray diffraction.We also discussed the association,speciation and source apportionment of heavy metals.Metals were found to exist in a diffuse distribution with heterogeneous intensities and intense hot-spots of ＜10 μm within the fine particles.Zn-Cu,Pb-Fe and Fe-Mn-Cr had significant correlations in terms of spatial distribution.The overlapped enrichment,spatial association,and the mineral phases of metals revealed the potential sources of fine particles from size-reduced waste fractions (such as scraps of organic wastes or ceramics) or from the importation of other particles.The diverse sources of heavy metal pollutants within the fine particles suggested that separate collection and treatment of the biodegradable waste fraction (such as food waste) is a preferable means of facilitating the beneficial utilization of the stabilized products.

Effect of alloying on elastic properties of ZrN based transition metal nitride alloys

KAUST Repository

Kanoun, Mohammed; Goumri-Said, Souraya

2014-01-01

We report the effect of composition and metal sublattice substitutional element on the structural, elastic and electronic properties of ternary transition metal nitrides Zr1-xMxN with M=Al, Ti, Hf, V, Nb, W and Mo. The analysis of the elastic constants, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio provides insights regarding the mechanical behavior of Zr1-xMxN. We predict that ternary alloys are more ductile compared to their parent binary compounds. The revealed trend in the mechanical behavior might help for experimentalists on the ability of tuning the mechanical properties during the alloying process by varying the concentration of the transition metal. © 2014 Elsevier B.V.

Effect of alloying on elastic properties of ZrN based transition metal nitride alloys

KAUST Repository

Kanoun, Mohammed

2014-09-01

We report the effect of composition and metal sublattice substitutional element on the structural, elastic and electronic properties of ternary transition metal nitrides Zr1-xMxN with M=Al, Ti, Hf, V, Nb, W and Mo. The analysis of the elastic constants, bulk modulus, shear modulus, Young\\'s modulus, and Poisson\\'s ratio provides insights regarding the mechanical behavior of Zr1-xMxN. We predict that ternary alloys are more ductile compared to their parent binary compounds. The revealed trend in the mechanical behavior might help for experimentalists on the ability of tuning the mechanical properties during the alloying process by varying the concentration of the transition metal. © 2014 Elsevier B.V.

Watching the growth of bulk grains during recrystallization of deformed metals

DEFF Research Database (Denmark)

Schmidt, Søren; Fæster Nielsen, Søren; Gundlach, C.

2004-01-01

, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical...

Impact of intracellular metallothionein on metal biouptake and partitioning dynamics at bacterial interfaces.

Science.gov (United States)

Présent, Romain M; Rotureau, Elise; Billard, Patrick; Pagnout, Christophe; Sohm, Bénédicte; Flayac, Justine; Gley, Renaud; Pinheiro, José P; Duval, Jérôme F L

2017-11-08

Genetically engineered microorganisms are alternatives to physicochemical methods for remediation of metal-contaminated aquifers due to their remarkable bioaccumulation capacities. The design of such biosystems would benefit from the elaboration of a sound quantitative connection between performance in terms of metal removal from aqueous solution and dynamics of the multiscale processes leading to metal biouptake. In this work, this elaboration is reported for Escherichia coli cells modified to overexpress intracellular metallothionein (MTc), a strong proteinaceous metal chelator. Depletion kinetics of Cd(ii) from bulk solution following biouptake and intracellular accumulation is addressed as a function of cell volume fraction using electroanalytical probes and ligand exchange-based analyses. It is shown that metal biouptake in the absence and presence of MTc is successfully interpreted on the basis of a formalism recently developed for metal partitioning dynamics at biointerfaces with integration of intracellular metal speciation. The analysis demonstrates how fast sequestration of metals by intracellular MTc bypasses metal excretion (efflux) and enhances the rate of metal depletion to an extent such that complete removal is achieved at sufficiently large cell volume fractions. The magnitude of the stability constant of nanoparticulate metal-MTc complexes, as derived from refined analysis of macroscopic bulk metal depletion data, is further confirmed by independent electrochemical measurement of metal binding by purified MTc extracts.

Bulk disk resonator based ultrasensitive mass sensor

DEFF Research Database (Denmark)

Cagliani, Alberto; Davis, Zachary James

2009-01-01

range. The sensor has been characterized in terms of sensitivity both for distributed mass detection, performing six consecutive depositions of e-beam evaporated Au, and localized mass detection, depositing approximately 7.5 pg of Pt/Ga/C three times consecutively with a Focused Ion Beam system......In the framework of developing an innovative label-free sensor for multiarrayed biodetection applications, we present a novel bulk resonator based mass sensor. The sensor is a polysilicon disk which shows a Q-factor of 6400 in air at 68.8 MHz, resulting in mass resolutions down in the femtogram....... The sensor has an extremely high distributed mass to frequency shift sensitivity of 60104 Hzcm2/¿g and shows a localized mass to frequency sensitivity up to 4405 Hz/pg with a localized mass resolution down to 15 fg. The device has been fabricated with a new microfabrication process that uses only two...

Study of low dimensional SiGe island on Si for potential visible Metal-Semiconductor-Metal photodetector

Science.gov (United States)

Rahim, Alhan Farhanah Abd; Zainal Badri, Nur'Amirah; Radzali, Rosfariza; Mahmood, Ainorkhilah

2017-11-01

In this paper, an investigation of design and simulation of silicon germanium (SiGe) islands on silicon (Si) was presented for potential visible metal semiconductor metal (MSM) photodetector. The characterization of the performances in term of the structural, optical and electrical properties of the structures was analyzed from the simulation results. The project involves simulation using SILVACO Technology Computer Aided Design (TCAD) tools. The different structures of the silicon germanium (SiGe) island on silicon substrate were created, which were large SiGe, small SiGe, combination SiGe and bulk Ge. All the structures were tested for potential Metal Semiconductor Metal (MSM) photodetector. The extracted data such as current versus voltage characteristic, current gain and spectral response were obtained using ATLAS SILVACO tools. The performance of SiGe island structures and bulk Ge on Si substrate as (MSM) photodetector was evaluated by photo and dark current-voltage (I-V) characteristics. It was found that SiGe islands exhibited higher energy band gap compared to bulk Ge. The SiGe islands current-voltage characteristics showed improved current gain compared to bulk Ge. Specifically the enhancement of the islands gain was contributed by the enhanced photo currents and lower dark currents. The spectral responses of the SiGe islands showed peak response at 590 nm (yellow) which is at the visible wavelength. This shows the feasibility of the SiGe islands to be utilized for visible photodetections.

Study of low dimensional SiGe island on Si for potential visible Metal-Semiconductor-Metal photodetector

Directory of Open Access Journals (Sweden)

Abd Rahim Alhan Farhanah

2017-01-01

Full Text Available In this paper, an investigation of design and simulation of silicon germanium (SiGe islands on silicon (Si was presented for potential visible metal semiconductor metal (MSM photodetector. The characterization of the performances in term of the structural, optical and electrical properties of the structures was analyzed from the simulation results. The project involves simulation using SILVACO Technology Computer Aided Design (TCAD tools. The different structures of the silicon germanium (SiGe island on silicon substrate were created, which were large SiGe, small SiGe, combination SiGe and bulk Ge. All the structures were tested for potential Metal Semiconductor Metal (MSM photodetector. The extracted data such as current versus voltage characteristic, current gain and spectral response were obtained using ATLAS SILVACO tools. The performance of SiGe island structures and bulk Ge on Si substrate as (MSM photodetector was evaluated by photo and dark current-voltage (I-V characteristics. It was found that SiGe islands exhibited higher energy band gap compared to bulk Ge. The SiGe islands current-voltage characteristics showed improved current gain compared to bulk Ge. Specifically the enhancement of the islands gain was contributed by the enhanced photo currents and lower dark currents. The spectral responses of the SiGe islands showed peak response at 590 nm (yellow which is at the visible wavelength. This shows the feasibility of the SiGe islands to be utilized for visible photodetections.

Projections for the Production of Bulk Volume Bio-Based Polymers in Europe and Environmental Implications

NARCIS (Netherlands)

Patel, M.K.; Crank, M.

2007-01-01

In this paper we provide an overview of the most important emerging groups of bio-based polymers for bulk volume applications and we discuss market projections for these types of bio-based polymers in the EU, thereby distinguishing between three scenarios. Bio-based polymers are projected to reach a

Surface/structure functionalization of copper-based catalysts by metal-support and/or metal-metal interactions

Science.gov (United States)

Konsolakis, Michalis; Ioakeimidis, Zisis

2014-11-01

Cu-based catalysts have recently attracted great attention both in catalysis and electro-catalysis fields due to their excellent catalytic performance and low cost. Given that their performance is determined, to a great extent, by Cu sites local environment, considerable efforts have been devoted on the strategic modifications of the electronic and structural properties of Cu sites. In this regard, the feasibility of tuning the local structure of Cu entities by means of metal-support or metal-metal interactions is investigated. More specifically, the physicochemical properties of Cu entities are modified by employing: (i) different oxides (CeO2, La2O3, Sm2O3), or (ii) ceria-based mixed oxides (Ce1-xSmxOδ) as supporting carriers, and (iii) a second metal (Cobalt) adjacent to Cu (bimetallic Cu-Co/CeO2). A characterization study, involving BET, XRD, TPR, and XPS, reveal that significant modifications on structural, redox and electronic properties of Cu sites can be induced by adopting either different oxide carriers or bimetallic complexes. Fundamental insights into the tuning of Cu local environment by metal-support or metal-metal interactions are provided, paving the way for real-life industrial applications.

Design of multi materials combining crystalline and amorphous metallic alloys

International Nuclear Information System (INIS)

Volland, A.; Ragani, J.; Liu, Y.; Gravier, S.; Suéry, M.; Blandin, J.J.

2012-01-01

Highlights: ► Elaboration of multi materials associating metallic glasses and conventional crystalline alloys by co-deformation performed at temperatures close to the glass transition temperature of the metallic glasses. ► Elaboration of filamentary metal matrix composites with a core in metallic glass by co extrusion. ► Sandwich structures produced by co-pressing. ► Detection of atomic diffusion from the glass to the crystalline alloys during the processes. ► Good interfaces between the metallic glasses and the crystalline alloys, as confirmed by mechanical characterisation. - Abstract: Multi materials, associating zirconium based bulk metallic glasses and crystalline metallic alloys like magnesium alloys or copper are elaborated by co-deformation processing performed in the supercooled liquid regions (SLR) of the bulk metallic glasses. Two processes are investigated: co-extrusion and co-pressing. In the first case, filamentary composites with various designs can be produced whereas in the second case sandwich structures are obtained. The experimental window (temperature, time) in which processing can be carried out is directly related to the crystallisation resistance of the glass which requires getting information about the crystallisation conditions in the selected metallic glasses. Thermoforming windows are identified for the studied BMGs by thermal analysis and compression tests in their SLR. The mechanical properties of the produced multi materials are investigated thanks to specifically developed mechanical devices and the interfaces between the amorphous and the crystalline alloys are characterised.

Interaction of hydrogen and oxygen with bulk defects and surfaces of metals

International Nuclear Information System (INIS)

Besenbacher, F.

1994-05-01

The thesis deals with the interaction of hydrogen with defects in metals and the interaction of hydrogen and oxygen with metal surfaces studied by ion-beam techniques and scanning tunneling microscopy (STM), respectively. The first part of the thesis discusses the interaction of hydrogen with simple defects in transition metals. The trap-binding enthalpies and the lattice location of hydrogen trapped to vacancies have been determined, and an extremely simple and versatile picture of the hydrogen-metal interaction has evolved, in which the trap strength is mainly determined by the local electron density. Any dilution of the lattice will lead to a trap, vacancies and voids being the strongest trap. It is found that hydrogen trapped to vacancies in fcc metals is quantum-mechanically delocalized, and the excitation energies for the hydrogen in the vacancy potential are a few MeV only. The interaction of hydrogen with metal surfaces is studied by the transmission channeling (TC) technique. It is found that hydrogen chemisorbs in the highest-coordinated sites on the surfaces, and that there is a direct relationship between the hydrogen-metal bond length and the coordination number for the hydrogen. In the final part of the thesis the dynamics of the chemisorption process for oxygen and hydrogen on metal surfaces is studied by STM, a fascinating and powerful technique for exploring the atomic-scale realm of surfaces. It is found that there is a strong coupling between the chemisorption process and the distortion of the metal surface. The adsorbates induce a surface reconstruction, i.e. metal-metal bond breaks and metal-adsorbate bounds form. Whereas hydrogen interacts weakly with the metals and induces reconstructions where only nnn metals bonds are broken, oxygen interacts strongly with the metal, and the driving force for the O-induced reconstructions appears to be the formation of low-coordinated metal-O rows, formed by breaking of nn metal bonds. Finally it is shown

Study of oxidation behaviour of Zr-based bulk amorphous alloy Zr 65 ...

Indian Academy of Sciences (India)

The oxidation behaviour of Zr-based bulk amorphous alloy Zr65Cu17.5Ni10Al7.5 has been studied in air environment at various temperatures in the temperature range 591–684 K using a thermogravimetric analyser (TGA). The oxidation kinetics of the alloy in the amorphous phase obeys the parabolic rate law for oxidation ...

A high energy microscope for local strain measurements within bulk materials

DEFF Research Database (Denmark)

Lienert, U.; Poulsen, H.F.; Martins, R.V.

2000-01-01

A novel diffraction technique for local, three dimensional strain scanning within bulk materials is presented. The technique utilizes high energy, micro-focussed synchrotron radiation which can penetrate several millimeters into typical metals. The spatial resolution can be as narrow as 1 mum...... in one dimension and in three dimensions about 5x10x100 mum(3) Bulk properties are probed non-destructively and in-situ measurements during thermo-mechanical processing are feasible. A dedicated experimental station has been constructed at the ID11 beamline of the European Synchrotron Radiation Facility...

Glass formation ability, structure and magnetocaloric effect of a heavy rare-earth bulk metallic glassy Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} alloy

Energy Technology Data Exchange (ETDEWEB)

Jo, C.-L. [Shanghai University, School of Materials Science and Engineering, Yanchang Road 149, Zhabei District, 200072 Shanghai (China)], E-mail: jochollong@163.com; Xia Lei; Ding Ding; Dong Yuanda; Gracien, Ekoko [Shanghai University, School of Materials Science and Engineering, Yanchang Road 149, Zhabei District, 200072 Shanghai (China)

2008-06-30

The glass formation ability, the structure and the magnetocaloric effect of the bulk metallic glassy Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} alloy were investigated. Bulk metallic glassy (BMGs) alloys were prepared by a copper-mold casting method. The glass forming ability and their structure were studied by using X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The XRD analysis revealed that the as-cast cylinder of Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} alloy showed fully amorphous structure in 2 mm diameter. The DSC revealed that the bulk cylinder of the Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} alloy showed a distinct glass transition temperature and a relatively wide supercooled liquid region before crystallization. SQUID investigated the magnetic properties and the entropy changes. The Curie temperature of Gd{sub 55}Co{sub 20}Fe{sub 5}Al{sub 20} BMGs alloy was about 130 K, but the maximum magnetic entropy changes(-{delta}S{sub M}) showed at about 125 K, a little lower than the Curie temperature 130 K. The reason could probably be due to the presence of a little amount of nanocrystalline particles between amorphous phases. The BMG alloy has the characteristic of second-order transition (SOT) on Arrott plots. The results showed that the amorphous sample had a relatively improved magnetocaloric effect, indicating that the amorphous alloy could be considered as a candidate for magnetic refrigeration applications in the temperature interval range of 100-200 K.

Porous 3D graphene-based bulk materials with exceptional high surface area and excellent conductivity for supercapacitors

Science.gov (United States)

Zhang, Long; Zhang, Fan; Yang, Xi; Long, Guankui; Wu, Yingpeng; Zhang, Tengfei; Leng, Kai; Huang, Yi; Ma, Yanfeng; Yu, Ao; Chen, Yongsheng

2013-01-01

Until now, few sp2 carbon materials simultaneously exhibit superior performance for specific surface area (SSA) and electrical conductivity at bulk state. Thus, it is extremely important to make such materials at bulk scale with those two outstanding properties combined together. Here, we present a simple and green but very efficient approach using two standard and simple industry steps to make such three-dimensional graphene-based porous materials at the bulk scale, with ultrahigh SSA (3523 m2/g) and excellent bulk conductivity. We conclude that these materials consist of mainly defected/wrinkled single layer graphene sheets in the dimensional size of a few nanometers, with at least some covalent bond between each other. The outstanding properties of these materials are demonstrated by their superior supercapacitor performance in ionic liquid with specific capacitance and energy density of 231 F/g and 98 Wh/kg, respectively, so far the best reported capacitance performance for all bulk carbon materials. PMID:23474952

Survival of Direct Posterior Composites With and Without a Bulk Fill Base.

Science.gov (United States)

McGuirk, C; Hussain, F; Millar, B J

2017-09-01

Direct composite restorations are increasingly popular and a flowable bulk-fill base material (SDR, Dentsply) claims to minimise stress through a more flexible polymerisation process. This retrospective audit of restorations placed in general practice compares SDR based restorations with conventional composite restorations. Restorations were all placed by one operator using a similar clinical technique and were audited as Group G, placed with a conventional layering composite (G-aenial, GC) and Group S which had a bulk-fill base of SDR (Dentsply) and then were covered with G-aenial (GC). Data regarding survival, post-operative sensitivity and mode of failure were recorded and analysed. In total 54 Group S restorations and 71 Group G restorations were followed for a minimum of 24 months. Group S had a 92.6% survival and Group G 93%. Group S was more prone to failure by tooth fracture (p=0.033). In both groups failure was more likely in larger cavities, in both those with an increased number of surfaces (p⟨0.001) and cuspal coverage (p=0.004). There appears to be similar survival of the two techniques in the short-term although there were significantly more tooth fractures in teeth restored with SDR. Copyright© 2017 Dennis Barber Ltd.

Definitive difference among [DS-D2O], [DS-H2O] and [Bulk-D2O] cells in the deuterization and deuterium-reaction

International Nuclear Information System (INIS)

Arata, Yoshiaki; Zhang, Yue Chang

2000-01-01

We observed a new phenomena that the enormous amount of deuterium/hydrogen can be absorbed quickly as a 'solute-atom' into fine metal powders embedded inside a double-structure (DS) cathode in the electrolyses of D 2 O and H 2 O-electrolytes, respectively, but such highly deuterated powders can be produced only using DS-cathode immersed in D 2 O-electrolyte; [DS-D 2 O], and never generated in H 2 O-electrolyte even using the DS-cathode; [DS-H 2 O]. On the other hand, [Bulk-D 2 O] with bulk-cathode made by the bulk Pd metal never produces highly deuterated metal as mentioned above even though using D 2 O-electrolyte. In short, the deuterium-concentration generating in [Bulk-D 2 O] is found to be much lower than that in [DS-D 2 O]. As a result, because of reason mentioned above, in marked contrast to the case with the [DS-D 2 O], neither excess heat nor 4 He production are observed with both [DS-H 2 O] and [Bulk-D 2 O]. (author)

Solution processed organic bulk heterojunction tandem solar cells

Energy Technology Data Exchange (ETDEWEB)

Albrecht, Steve; Neher, Dieter [Soft Matter Physics, University of Potsdam, D-14476 Potsdam (Germany)

2011-07-01

One of the critical issues regarding the preparation of organic tandem solar cells from solution is the central recombination contact. This contact should be highly transparent and conductive to provide high recombination currents. Moreover it should protect the 1st subcell from the solution processing of the 2nd subcell. Here, we present a systematic study of various recombination contacts in organic bulk heterojunction tandem solar cells made from blends of different polymers with PCBM. We compare solution processed recombination contacts fabricated from metal-oxides (TiO{sub 2} and ZnO) and PEDOT:PSS with evaporated recombination contacts made from thin metal layers and molybdenum-oxide. The solar cell characteristics as well as the morphology of the contacts measured by AFM and SEM are illustrated. To compare the electrical properties of the varying contacts we show measurements on single carrier devices for different contact-structures. Alongside we present the results of optical modeling of the subcells and the complete tandem device and relate these results to experimental absorption and reflection spectra of the same structures. Based on these studies, layer thicknesses were adjusted for optimum current matching and device performance.

Mesoporous Transition Metal Oxides for Supercapacitors.

Science.gov (United States)

Wang, Yan; Guo, Jin; Wang, Tingfeng; Shao, Junfeng; Wang, Dong; Yang, Ying-Wei

2015-10-14

Recently, transition metal oxides, such as ruthenium oxide (RuO₂), manganese dioxide (MnO₂), nickel oxides (NiO) and cobalt oxide (Co₃O₄), have been widely investigated as electrode materials for pseudo-capacitors. In particular, these metal oxides with mesoporous structures have become very hot nanomaterials in the field of supercapacitors owing to their large specific surface areas and suitable pore size distributions. The high specific capacities of these mesoporous metal oxides are resulted from the effective contacts between electrode materials and electrolytes as well as fast transportation of ions and electrons in the bulk of electrode and at the interface of electrode and electrolyte. During the past decade, many achievements on mesoporous transition metal oxides have been made. In this mini-review, we select several typical nanomaterials, such as RuO₂, MnO₂, NiO, Co₃O₄ and nickel cobaltite (NiCo₂O₄), and briefly summarize the recent research progress of these mesoporous transition metal oxides-based electrodes in the field of supercapacitors.

Facile Formation of High-quality InGaN/GaN Quantum-disks-in-Nanowires on Bulk-Metal Substrates for High-power Light-emitters

KAUST Repository

Zhao, Chao; Ng, Tien Khee; Wei, Nini; Prabaswara, Aditya; Alias, Mohd Sharizal; Janjua, Bilal; Shen, Chao; Ooi, Boon S.

2016-01-01

High-quality nitride materials grown on scalable and low-cost metallic substrates are considerably attractive for high-power light emitters. We demonstrate here, for the first time, the high-power red (705 nm) InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) self-assembled directly on metal-substrate. The LEDs exhibited a low turn-on voltage of ~2 V without efficiency droop up to injection current of 500 mA (1.6 kA/cm2) at ~5 V. This is achieved through the direct growth and optimization of high-quality nanowires on titanium (Ti) coated bulk polycrystalline-molybdenum (Mo) substrates. We performed extensive studies on the growth mechanisms, obtained high-crystal-quality nanowires, and confirmed the epitaxial relationship between the cubic titanium nitride (TiN) transition layer and the hexagonal nanowires. The growth of nanowires on all-metal stack of TiN/Ti/Mo enables simultaneous implementation of n-metal contact, reflector and heat-sink, which greatly simplifies the fabrication process of high-power light emitters. Our work ushers in a practical platform for high-power nanowires light emitters, providing versatile solutions for multiple cross-disciplinary applications that are greatly enhanced by leveraging on the chemical stability of nitride materials, large specific surface of nanowires, chemical lift-off ready layer structures, and reusable Mo substrates.

Facile Formation of High-quality InGaN/GaN Quantum-disks-in-Nanowires on Bulk-Metal Substrates for High-power Light-emitters

KAUST Repository

Zhao, Chao

2016-01-08

High-quality nitride materials grown on scalable and low-cost metallic substrates are considerably attractive for high-power light emitters. We demonstrate here, for the first time, the high-power red (705 nm) InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) self-assembled directly on metal-substrate. The LEDs exhibited a low turn-on voltage of ~2 V without efficiency droop up to injection current of 500 mA (1.6 kA/cm2) at ~5 V. This is achieved through the direct growth and optimization of high-quality nanowires on titanium (Ti) coated bulk polycrystalline-molybdenum (Mo) substrates. We performed extensive studies on the growth mechanisms, obtained high-crystal-quality nanowires, and confirmed the epitaxial relationship between the cubic titanium nitride (TiN) transition layer and the hexagonal nanowires. The growth of nanowires on all-metal stack of TiN/Ti/Mo enables simultaneous implementation of n-metal contact, reflector and heat-sink, which greatly simplifies the fabrication process of high-power light emitters. Our work ushers in a practical platform for high-power nanowires light emitters, providing versatile solutions for multiple cross-disciplinary applications that are greatly enhanced by leveraging on the chemical stability of nitride materials, large specific surface of nanowires, chemical lift-off ready layer structures, and reusable Mo substrates.

Laser-Based Additive Manufacturing of Zirconium

Directory of Open Access Journals (Sweden)

Himanshu Sahasrabudhe

2018-03-01

Full Text Available Additive manufacturing of zirconium is attempted using commercial Laser Engineered Net Shaping (LENSTM technique. A LENSTM-based approach towards processing coatings and bulk parts of zirconium, a reactive metal, aims to minimize the inconvenience of traditional metallurgical practices of handling and processing zirconium-based parts that are particularly suited to small volumes and one-of-a-kind parts. This is a single-step manufacturing approach for obtaining near net shape fabrication of components. In the current research, Zr metal powder was processed in the form of coating on Ti6Al4V alloy substrate. Scanning electron microscopy (SEM and energy dispersive spectroscopy (EDS as well as phase analysis via X-ray diffraction (XRD were studied on these coatings. In addition to coatings, bulk parts were also fabricated using LENS™ from Zr metal powders, and measured part accuracy.

Metal chemistry of the transactinides; Metallchemie der Transaktinoide

Energy Technology Data Exchange (ETDEWEB)

Eichler, B

2000-12-01

The elements with atomic numbers between 104 and 116 are expected to behave as metals. Their interaction with metal surfaces is of uppermost importance both to design experimental separation procedures as well as for their chemical characterization. This interaction is quantified by the net adsorption enthalpy. The determination of the net adsorption enthalpy requires the calculation of the solution enthalpy of transactinides in the bulk-phases of the solid adsorbent metals. These solution enthalpies have been calculated with the Miedema-model. For that purpose the necessary parameters of the transactinides: the metal radius, the molar volume, the electronic density at the Wigner-Seitz-Cell boundary and the electronegativity (Miedema Scale) have been obtained on the basis of empirical correlations starting from the entropies of solid transactinides. These entropies were estimated by extrapolations as a function of atomic masses along the groups of the periodic table. The results of the calculations show a strong dependence on the cohesion energy of the solid adsorbent metals as well as on the solution enthalpies of transactinides in the bulk-phase of these metals. The enthalpies of segregation of transactinides from the metallic bulk-phases as the 'driving forces' of the surface enrichment process were calculated. The calculated data allow the selection of the best suitable materials for the gas phase transport as well as of the adsorbent metal for chromatographic separations, for sampling and for electrochemical deposition in experiments with the transactinides. (author)

Caltech Center for Structural and Amorphous Metals

Science.gov (United States)

2005-05-10

Flores, D. Suh, R. Howell, P. Asoka -Kumar, P.A. Sterne, and R. H. Dauskardt, "Flow and Fracture of Bulk Metallic Glass Alloys and Their Composites...Behavior of Zr-Ti-Cu-Ni-Be Bulk Metallic Glass Alloys," Materials Transactions, JIM, 42 [4], 638-641, 2001. K. M. Flores, D. Suh, P. Asoka -Kumar, P.A...Materials Research, 17[5], 1153-1161, 2002. D. Suh, P. Asoka -Kumar and R. H. Dauskardt, "The Effects of Hydrogen on Viscoelastic Relaxation in Zr-Ti-Ni-Cu

Color stability of bulk-fill and incremental-fill resin-based composites polished with aluminum-oxide impregnated disks

Directory of Open Access Journals (Sweden)

Uzay Koc-Vural

2017-05-01

Full Text Available Objectives This study aimed to evaluate the color stability of bulk-fill and nanohybrid resin-based composites polished with 3 different, multistep, aluminum-oxide impregnated finishing and polishing disks. Materials and Methods Disk-shaped specimens (8 mm in diameter and 4 mm in thickness were light-cured between two glass slabs using one nanohybid bulk-fill (Tetric EvoCeram, Ivoclar Vivadent, one micro-hybrid bulk-fill (Quixfil, Dentsply, and two nanohybrid incremental-fill (Filtek Ultimate, 3M ESPE; Herculite XRV Ultra, Kerr resin-based composites, and aged by thermocycling (between 5 - 55℃, 3,000 cycles. Then, they were divided into subgroups according to the polishing procedure as SwissFlex (Coltène/Whaledent, Optidisc (Kerr, and Praxis TDV (TDV Dental (n = 12 per subgroup. One surface of each specimen was left unpolished. All specimens were immersed in coffee solution at 37℃. The color differences (ΔE were measured after 1 and 7 days of storage using a colorimeter based on CIE Lab system. The data were analyzed by univariate ANOVA, Mann-Whitney U test, and Friedmann tests (α = 0.05. Results Univariate ANOVA detected significant interactions between polishing procedure and composite resin and polishing procedure and storage time (p 0.05. Polishing reduced the discoloration resistance of Tetric EvoCeram/SwissFlex, Tetric EvoCeram/Praxis TDV, Quixfil-SwissFlex, and all Herculite XRV Ultra groups after 7 days storage (p < 0.05. Conclusions Discoloration resistance of bulk-fill resin-based composites can be significantly affected by the polishing procedures.

Sediment accretion and carbon storage in constructed wetlands receiving water treated with metal-based coagulants

Science.gov (United States)

Stumpner, Elizabeth; Kraus, Tamara; Liang, Yan; Bachand, Sandra M.; Horwath, William R.; Bachand, Philip A.M.

2018-01-01

In many regions of the world, subsidence of organic rich soils threatens levee stability and freshwater supply, and continued oxidative loss of organic matter contributes to greenhouse gas production. To counter subsidence in the Sacramento-San Joaquin Delta of northern California, we examined the feasibility of using constructed wetlands receiving drainage water treated with metal-based coagulants to accrete mineral material along with wetland biomass, while also sequestering carbon in wetland sediment. Nine field-scale wetlands were constructed which received local drainage water that was either untreated (control), or treated with polyaluminum chloride (PAC) or iron sulfate (FeSO4) coagulants. After 23 months of flooding and coagulant treatment, sediment samples were collected near the inlet, middle, and outlet of each wetland to determine vertical accretion rates, bulk density, sediment composition, and carbon sequestration rates. Wetlands treated with PAC had the highest and most spatially consistent vertical accretion rates (~6 cm year-1), while the FeSO4 wetlands had similarly high accretion rates near the inlet but rates similar to the untreated wetland (~1.5 cm year-1) at the middle and outlet sites. The composition of the newly accreted sediment in the PAC and FeSO4 treatments was high in the added metal (aluminum and iron, respectively), but the percent metal by weight was similar to native soils of California. As has been observed in other constructed wetlands, the newly accreted sediment material had lower bulk densities than the native soil material (0.04-0.10 g cm-3 versus 0.2-0.3 g cm-3), suggesting these materials will consolidate over time. Finally, this technology accelerated carbon burial, with rates in PAC treated wetland (0.63 kg C m-2 yr-1) over 2-fold greater than the untreated control (0.28 kg C m-2 yr-1). This study demonstrates the feasibility of using constructed wetlands treated with coagulants to reverse subsidence by accreting the

Interlayer excitons in a bulk van der Waals semiconductor.

Science.gov (United States)

Arora, Ashish; Drüppel, Matthias; Schmidt, Robert; Deilmann, Thorsten; Schneider, Robert; Molas, Maciej R; Marauhn, Philipp; Michaelis de Vasconcellos, Steffen; Potemski, Marek; Rohlfing, Michael; Bratschitsch, Rudolf

2017-09-21

Bound electron-hole pairs called excitons govern the electronic and optical response of many organic and inorganic semiconductors. Excitons with spatially displaced wave functions of electrons and holes (interlayer excitons) are important for Bose-Einstein condensation, superfluidity, dissipationless current flow, and the light-induced exciton spin Hall effect. Here we report on the discovery of interlayer excitons in a bulk van der Waals semiconductor. They form due to strong localization and spin-valley coupling of charge carriers. By combining high-field magneto-reflectance experiments and ab initio calculations for 2H-MoTe 2 , we explain their salient features: the positive sign of the g-factor and the large diamagnetic shift. Our investigations solve the long-standing puzzle of positive g-factors in transition metal dichalcogenides, and pave the way for studying collective phenomena in these materials at elevated temperatures.Excitons, quasi-particles of bound electron-hole pairs, are at the core of the optoelectronic properties of layered transition metal dichalcogenides. Here, the authors unveil the presence of interlayer excitons in bulk van der Waals semiconductors, arising from strong localization and spin-valley coupling of charge carriers.

Physics of amorphous metals

CERN Document Server

Kovalenko, Nikolai P; Krey, Uwe

2008-01-01

The discovery of bulk metallic glasses has led to a large increase in the industrial importance of amorphous metals, and this is expected to continue. This book is the first to describe the theoretical physics of amorphous metals, including the important theoretical development of the last 20 years.The renowned authors stress the universal aspects in their description of the phonon or magnon low-energy excitations in the amorphous metals, e.g. concerning the remarkable consequences of the properties of these excitations for the thermodynamics at low and intermediate temperatures. Tunneling

Bulk-Like Electrical Properties Induced by Contact-Limited Charge Transport in Organic Diodes: Revised Space Charge Limited Current

KAUST Repository

Xu, Guangwei

2018-02-22

Charge transport governs the operation and performance of organic diodes. Illuminating the charge-transfer/transport processes across the interfaces and the bulk organic semiconductors is at the focus of intensive investigations. Traditionally, the charge transport properties of organic diodes are usually characterized by probing the current–voltage (I–V) curves of the devices. However, to unveil the landscape of the underlying potential/charge distribution, which essentially determines the I–V characteristics, still represents a major challenge. Here, the electrical potential distribution in planar organic diodes is investigated by using the scanning Kelvin probe force microscopy technique, a method that can clearly separate the contact and bulk regimes of charge transport. Interestingly, by applying to devices based on novel, high mobility organic materials, the space-charge-limited-current-like I–V curves, which are previously believed to be a result of the bulk transport, are surprisingly but unambiguously demonstrated to be caused by contact-limited conduction. A model accounting is developed for the transport properties of both the two metal/organic interfaces and the bulk. The results indicate that pure interface-dominated transport can indeed give rise to I–V curves similar to those caused by bulk transport. These findings provide a new insight into the charge injection and transport processes in organic diodes.

Influence of compositions on thermal stability and thermodynamic parameter in Ca-Mg-Cu bulk metallic glasses

Science.gov (United States)

Deshmukh, A. A.; Khond, A. A.; Palikundwar, U. A.

2018-05-01

In the present manuscript, influence of compositions on thermal stability (ΔTx) and thermodynamic parameter PHSS of Ca-Mg-Cu bulk metallic glasses (BMGs) is evaluated. The statistical approach of regression analysis is adopted to investigate the compositional variation with ΔTx and PHSS. It is found that calcium (Ca) and copper (Cu) content has goodlinear relationship with ΔTx and PHSS. It is observed that with increase in Ca content, ΔTx and PHSS decreases. On the other hand, increase in Cu content, both ΔTx and PHSS increases. Correlation fit of magnesium (Mg) content with both ΔTx and PHSS is very poor. A graph is also plotted to understand the relationship between ΔTx and PHSS. Result of the relationship between ΔTx and PHSS reveals that the alloy composition having more negative value of PHSS will have more stability. Therefore, compositions with more negative value of PHSS will lead to ease of BMGs formation in Ca-Mg-Cu alloy system and hence more stable it will be. It is expected that these results will be supportive in identifying the compositions having these elements for making BMGs.

Purity Evaluation of Bulk Single Wall Carbon Nanotube Materials

International Nuclear Information System (INIS)

Dettlaff-Weglikowska, U.; Hornbostel, B.; Cech, J.; Roth, S.; Wang, J.; Liang, J.

2005-01-01

We report on our experience using a preliminary protocol for quality control of bulk single wall carbon nanotube (SWNT) materials produced by the electric arc-discharge and laser ablation method. The first step in the characterization of the bulk material is mechanical homogenization. Quantitative evaluation of purity has been performed using a previously reported procedure based on solution phase near-infrared spectroscopy. Our results confirm that this method is reliable in determining the nanotube content in the arc-discharge sample containing carbonaceous impurities (amorphous carbon and graphitic particles). However, the application of this method to laser ablation samples gives a relative purity value over 100 %. The possible reason for that might be different extinction coefficient meaning different oscillator strength of the laser ablation tubes. At the present time, a 100 % pure reference sample of laser ablation SWNT is not available, so we chose to adopt the sample showing the highest purity as a new reference sample for a quantitative purity evaluation of laser ablation materials. The graphitic part of the carbonaceous impurities has been estimated using X-ray diffraction of 1:1 mixture of nanotube material and C60 as an internal reference. To evaluate the metallic impurities in the as prepared and homogenized carbon nanotube soot inductive coupled plasma (ICP) has been used

Disulphide linkage: To get cleaved or not? Bulk and nano copper based SERS of cystine

Science.gov (United States)

P. J., Arathi; Seemesh, Bhaskar; Rajendra Kumar Reddy, G.; Suresh Kumar, P.; Ramanathan, V.

2018-05-01

Different nano-structures of noble metals have been the conventional substrates for carrying out Surface Enhanced Raman Spectroscopy (SERS). In this paper we examine electrodeposited copper (Cu) nano-structures on pencil graphite as novel substrate to carry out SERS measurements by considering L-cystine (Cys-Cys) (dimer of the amino acid cysteine) as the probe. The formation of monolayer of the probe molecule on the substrates was confirmed using cyclic voltammetric measurements. Mode of adsorption of Cys-Cys was observed to be different on bulk Cu (taken in the wire form) and nano-structured Cu on pencil graphite. Whereas in the former the disulphide bond of Cys-Cys remained intact, it got cleaved when Cys-Cys was adsorbed on electrodeposited copper indicating the activated nature of the nano-structure compared to bulk copper. Csbnd S stretching mode of vibration underwent blue shift in Cys-Cys adsorbed on Cu on pencil graphite vis-à-vis Cys-Cys adsorbed on Cu wire. Further evidence on the cleavage of the Csbnd S bond on an activated substrate was obtained by considering a bimetallic substrate comprising of silver on copper which was electrodeposited on pencil graphite. Our studies have demonstrated that nano-copper surface is an excellent substrate for SERS giving 200 μM as lower detection limit for Cys-Cys.

The effect of dose enhancement near metal interfaces on synthetic diamond based X-ray dosimeters

Science.gov (United States)

Alamoudi, D.; Lohstroh, A.; Albarakaty, H.

2017-11-01

This study investigates the effects of dose enhancement on the photocurrent performance at metallic interfaces in synthetic diamond detectors based X-ray dosimeters as a function of bias voltages. Monte Carlo (MC) simulations with the BEAMnrc code were carried out to simulate the dose enhancement factor (DEF) and compared against the equivalent photocurrent ratio from experimental investigations. The MC simulation results show that the sensitive region for the absorbed dose distribution covers a few micrometers distances from the interface. Experimentally, two single crystals (SC) and one polycrystalline (PC) synthetic diamond samples were fabricated into detectors with carbon based electrodes by boron and carbon ion implantation. Subsequently; the samples were each mounted inside a tissue equivalent encapsulation to minimize unintended fluence perturbation. Dose enhancement was generated by placing copper, lead or gold near the active volume of the detectors using 50 kVp and 100 kVp X-rays relevant for medical dosimetry. The results show enhancement in the detectors' photocurrent performance when different metals are butted up to the diamond bulk as expected. The variation in the photocurrent measurement depends on the type of diamond samples, their electrodes' fabrication and the applied bias voltages indicating that the dose enhancement near the detector may modify their electronic performance.

Magneto-thermo-gravimetric technique to investigate the structural and magnetic properties of Fe-B-Nb-Y Bulk Metallic Glass

Energy Technology Data Exchange (ETDEWEB)

Lee, Sangmin; Makino, Akihiro; Inoue, Akihisa [Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Masood, Ansar; Tamaki, Takahiko; Valter, Strom; Rao, K V, E-mail: smlee@imr.tohoku.ac.j [Royal Institute of Technology (KTH), SE-100 44 Stockhom (Sweden)

2009-01-01

Magneto-thermo-gravimetric (MTG) technique is highly informative about the changes in the magnetic state, as well as structural changes in a system, which cannot be often noticed in calorimetric measurements. We demonstrate the versatility of this technique in determining the magnetic transition temperature, and the subsequent crystallization process in a (Fe{sub 0.72}B{sub 0.24}Nb{sub 0.04}){sub 95.5}Y{sub 4.5} Bulk Metallic Glass (BMG). MTG and DSC analyses were carried out at the heating rate of 0.67 K/s from RT {approx}1170 K. As a result of the repeated MTG measurements, a magnetic 2nd amorphous phase was observed in the BMG sample, which could be the first measurement for the Magnetic Short Range Ordering (MSRO). Consequently, the MTG measurement is proved as the most convenient method for determining the various structural and magnetic transitions in a glassy material.

Electronic structure of Pd42.5Ni7.5Cu30P20, an excellent bulk metallic glass former: Comparison to the Pd40Ni40P20 reference glass

International Nuclear Information System (INIS)

Hosokawa, S.; Sato, H.; Happo, N.; Mimura, K.; Tezuka, Y.; Ichitsubo, T.; Matsubara, E.; Nishiyama, N.

2007-01-01

In-house photoemission and inverse-photoemission spectra (PES and IPES) were measured on Pd 42.5 Ni 7.5 Cu 30 P 20 and Pd 40 Ni 40 P 20 bulk metallic glasses in order to clarify the origin of excellent glass-forming ability from the viewpoint of electronic structure. Minima are observed for both the metallic glasses at a slightly higher energy than the Fermi level. Incident photon-energy dependent PES spectra were obtained using synchrotron radiation and the Pd 4d partial density of states (DOS) was estimated from the PES data. Soft X-ray emission spectra were also measured near the Ni and Cu 2p 3/2 absorption edges to evaluate, respectively, the Ni and Cu 3d partial DOS in the valence band. The Pd 4d and the Ni and Cu 3d partials in the conduction band were obtained from X-ray absorption spectra around the Pd 3p 3/2 and Ni and Cu 2p 3/2 absorption edges, respectively. It was found that the Pd 4d partial DOS near the Fermi energy largely decreases and becomes localized by replacing the Ni atoms with the Cu atoms, which may be closely related to the excellent glass-forming ability of the Pd 42.5 Ni 7.5 Cu 30 P 20 bulk metallic glass due to a selective formation of Pd-P covalent bonds

Development and Testing of Tailored Tool Surfaces for Sheet Metal Forming

DEFF Research Database (Denmark)

Sulaiman, Mohd Hafis Bin

MPa. The above mentioned simple experimental procedure for determining lubricant bulk modulus gives a first rough estimate, and it is supplemented by a more advanced laboratory test based on a newly designed equipment. The lubricant compressibility experiment with a direct pressure measurement inside...... to achieve this purpose. A simple laboratory test consisting of upsetting a specially designed metal cylinder with a lubricant reservoir together with elasto-plastic, numerical modelling of the metal cylinder is carried out in order to determine the bulk modulus at low pressure regimes of approximately 100...... for the manufacturing. The SRT tools were manufactured with longitudinal, shallow pocket geometries oriented perpendicular to the sliding direction. The pockets have small angles to the workpiece surface and varying distance. The experiments show an optimum distance between the pockets to exist that creates a table...

Metal hydride-based thermal energy storage systems

Science.gov (United States)

Vajo, John J.; Fang, Zhigang

2017-10-03

The invention provides a thermal energy storage system comprising a metal-containing first material with a thermal energy storage density of about 1300 kJ/kg to about 2200 kJ/kg based on hydrogenation; a metal-containing second material with a thermal energy storage density of about 200 kJ/kg to about 1000 kJ/kg based on hydrogenation; and a hydrogen conduit for reversibly transporting hydrogen between the first material and the second material. At a temperature of 20.degree. C. and in 1 hour, at least 90% of the metal is converted to the hydride. At a temperature of 0.degree. C. and in 1 hour, at least 90% of the metal hydride is converted to the metal and hydrogen. The disclosed metal hydride materials have a combination of thermodynamic energy storage densities and kinetic power capabilities that previously have not been demonstrated. This performance enables practical use of thermal energy storage systems for electric vehicle heating and cooling.

Liquid-Metal-Based Super-Stretchable and Structure-Designable Triboelectric Nanogenerator for Wearable Electronics.

Science.gov (United States)

Yang, Yanqin; Sun, Na; Wen, Zhen; Cheng, Ping; Zheng, Hechuang; Shao, Huiyun; Xia, Yujian; Chen, Chen; Lan, Huiwen; Xie, Xinkai; Zhou, Changjie; Zhong, Jun; Sun, Xuhui; Lee, Shuit-Tong

2018-02-27

The rapid advancement of intelligent wearable electronics imposes the emergent requirement for power sources that are deformable, compliant, and stretchable. Power sources with these characteristics are difficult and challenging to achieve. The use of liquid metals as electrodes may provide a viable strategy to produce such power sources. In this work, we propose a liquid-metal-based triboelectric nanogenerator (LM-TENG) by employing Galinstan as the electrode and silicone rubber as the triboelectric and encapsulation layer. The small Young's modulus of the liquid metal ensures the electrode remains continuously conductive under deformations, stretching to a strain as large as ∼300%. The surface oxide layer of Galinstan effectively prevents the liquid Galinstan electrode from further oxidization and permeation into silicone rubber, yielding outstanding device stability. Operating in the single-electrode mode at 3 Hz, the LM-TENG with an area of 6 × 3 cm 2 produces an open-circuit voltage of 354.5 V, transferred short-circuit charge of 123.2 nC, short-circuit current of 15.6 μA, and average power density of 8.43 mW/m 2 , which represent outstanding performance values for TENGs. Further, the LM-TENG maintains stable performance under various deformations, such as stretching, folding, and twisting. LM-TENGs in different forms, such as bulk-shaped, bracelet-like, and textile-like, are all able to harvest mechanical energy from human walking, arm shaking, or hand patting to sustainably drive wearable electronic devices.

Synthesis and mechanical properties of Fe–Nb–B thin-film metallic glasses

International Nuclear Information System (INIS)

Yao, J.H.; Hostert, C.; Music, D.; Frisk, A.; Björck, M.; Schneider, J.M.

2012-01-01

Fe–Nb–B thin-film metallic glasses (TFMGs) were synthesized via a combinatorial sputtering approach to probe the property–composition correlation. The boron content was found to dominate the mechanical properties of the TFMGs. The ∼10% smaller strength of Fe–Nb–B TFMGs compared to existing bulk metallic glass with similar composition may be attributed to the absence of a network-like structure based on (Fe,M) 23 B 6 phase due to the extreme quenching conditions employed.

Ferromagnetic bulk glassy alloys

International Nuclear Information System (INIS)

Inoue, Akihisa; Makino, Akihiro; Mizushima, Takao

2000-01-01

This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material

Long-term field metal extraction by Pelargonium: phytoextraction efficiency in relation to plant maturity.

Science.gov (United States)

Shahid, Muhammad; Arshad, Muhammad; Kaemmerer, Michel; Pinelli, Eric; Probst, Anne; Baque, David; Pradere, Philippe; Dumat, Camille

2012-01-01

The long length of periods required for effective soil remediation via phytoextraction constitutes a weak point that reduces its industrial use. However, these calculated periods are mainly based on short-term and/or hydroponic controlled experiments. Moreover, only a few studies concern more than one metal, although soils are scarcely polluted by only one element. In this scientific context, the phytoextraction of metals and metalloids (Pb, Cd, Zn, Cu, and As) by Pelargonium was measured after a long-term field experiment. Both bulk and rhizosphere soils were analyzed in order to determine the mechanisms involved in soil-root transfer. First, a strong increase in lead phytoextraction was observed with plant maturity, significantly reducing the length of the period required for remediation. Rhizosphere Pb, Zn, Cu, Cd, and As accumulation was observed (compared to bulk soil), indicating metal mobilization by the plant, perhaps in relation to root activity. Moreover, metal phytoextraction and translocation were found to be a function of the metals' nature. These results, taken altogether, suggest that Pelargonium could be used as a multi-metal hyperaccumulator under multi-metal soil contamination conditions, and they also provide an interesting insight for improving field phytoextraction remediation in terms of the length of time required, promoting this biological technique.

Local microstructure and flow stress in deformed metals

DEFF Research Database (Denmark)

Zhang, Xiaodan; Hansen, Niels; Nielsen, Chris Valentin

2017-01-01

The microstructure and flow stress of metals are related through many well-known strength-structure relationships based on structural parameters, where grain size and dislocation density are examples. In heterogeneous structures, the local stress and strain are important as they will affect...... the bulk properties. A microstructural method is presented which allows the local stress in a deformed metal to be estimated based on microstructural parameters determined by an EBSD analysis. These parameters are the average spacing of deformation introduced boundaries and the fraction of high angle...... boundaries. The method is demonstrated for two heterogeneous structures: (i) a gradient (sub)surface structure in steel deformed by shot peening; (ii) a heterogeneous structure introduced by friction between a tool and a workpiece of aluminum. Flow stress data are calculated based on the microstructural...

Atomistic materials modeling of complex systems: Carbynes, carbon nanotube devices and bulk metallic glasses

Science.gov (United States)

Luo, Weiqi

The key to understanding and predicting the behavior of materials is the knowledge of their structures. Many properties of materials samples are not solely determined by their average chemical compositions which one may easily control. Instead, they are profoundly influenced by structural features of different characteristic length scales. Starting in the last century, metallurgical engineering has mostly been microstructure engineering. With the further evolution of materials science, structural features of smaller length scales down to the atomic structure, have become of interest for the purpose of properties engineering and functionalizing materials and are, therefore, subjected to study. As computer modeling is becoming more powerful due to the dramatic increase of computational resources and software over the recent decades, there is an increasing demand for atomistic simulations with the goal of better understanding materials behavior on the atomic scale. Density functional theory (DFT) is a quantum mechanics based approach to calculate electron distribution, total energy and interatomic forces with high accuracy. From these, atomic structures and thermal effects can be predicted. However, DFT is mostly applied to relatively simple systems because it is computationally very demanding. In this thesis, the current limits of DFT applications are explored by studying relatively complex systems, namely, carbynes, carbon nanotube (CNT) devices and bulk metallic glasses (BMGs). Special care is taken to overcome the limitations set by small system sizes and time scales that often prohibit DFT from being applied to realistic systems under realistic external conditions. In the first study, we examine the possible existence of a third solid phase of carbon with linear bonding called carbyne, which has been suggested in the literature and whose formation has been suggested to be detrimental to high-temperature carbon materials. We have suggested potential structures for

On the thermodynamic efficiency of a nickel-based multiferroic thermomagnetic generator: From bulk to atomic scale

Energy Technology Data Exchange (ETDEWEB)

Sandoval, Samuel M., E-mail: samuel.m.sandoval@gmail.com; Sepulveda, Abdon E., E-mail: abdon.sepulveda@gmail.com; Keller, Scott M., E-mail: smkeller@ucla.edu [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095 (United States)

2015-04-28

A model is developed to correlate the effects of size on the thermodynamic efficiency for a nickel-based multiferroic thermomagnetic generator device. Three existing models are combined in order to estimate this correlation, they are (1) thermodynamic efficiency relations, (2) a model of ferromagnetic transition behavior, and (3) the bond-order length strength correlation. At the smallest size considered, a monolayer of nickel atoms shows a reduction in Curie temperature from its bulk value of T{sub c,Bulk}=630 K to T{sub c,ML}=240 K. This difference is analytically shown to affect the thermodynamic efficiency values when compared to bulk. Various nickel nanofilms are considered as a working body, such that the combined model predicts relative efficiency values that are comparable to the bulk scale, but operating closer to room-temperature when compared to bulk form. This result is unexpected since the absolute efficiency is shown to increase as a function of decreasing size, this discrepancy is explained as a consequence of Curie point suppression. The combined model is also applied to a hypothetical composite made of separated layers of nickel with distinct thicknesses. This composite material is predicted to spread the ferromagnetic transition across a much larger temperature range as compared to bulk nickel, such that this material may be better suited for different applications; for example, as a sensor or thermal switch. Moreover, this combined model is also shown to give a lower-bound estimate for thermodynamic efficiency, since the actual performance depends on material characterizations that have yet to be determined.

Metal-mediated DNA base pairing: alternatives to hydrogen-bonded Watson-Crick base pairs.

Science.gov (United States)

Takezawa, Yusuke; Shionoya, Mitsuhiko

2012-12-18

With its capacity to store and transfer the genetic information within a sequence of monomers, DNA forms its central role in chemical evolution through replication and amplification. This elegant behavior is largely based on highly specific molecular recognition between nucleobases through the specific hydrogen bonds in the Watson-Crick base pairing system. While the native base pairs have been amazingly sophisticated through the long history of evolution, synthetic chemists have devoted considerable efforts to create alternative base pairing systems in recent decades. Most of these new systems were designed based on the shape complementarity of the pairs or the rearrangement of hydrogen-bonding patterns. We wondered whether metal coordination could serve as an alternative driving force for DNA base pairing and why hydrogen bonding was selected on Earth in the course of molecular evolution. Therefore, we envisioned an alternative design strategy: we replaced hydrogen bonding with another important scheme in biological systems, metal-coordination bonding. In this Account, we provide an overview of the chemistry of metal-mediated base pairing including basic concepts, molecular design, characteristic structures and properties, and possible applications of DNA-based molecular systems. We describe several examples of artificial metal-mediated base pairs, such as Cu(2+)-mediated hydroxypyridone base pair, H-Cu(2+)-H (where H denotes a hydroxypyridone-bearing nucleoside), developed by us and other researchers. To design the metallo-base pairs we carefully chose appropriate combinations of ligand-bearing nucleosides and metal ions. As expected from their stronger bonding through metal coordination, DNA duplexes possessing metallo-base pairs exhibited higher thermal stability than natural hydrogen-bonded DNAs. Furthermore, we could also use metal-mediated base pairs to construct or induce other high-order structures. These features could lead to metal-responsive functional

Vacancies and a generalised melting curve of metals

International Nuclear Information System (INIS)

Gorecki, T.

1979-01-01

The vacancy mechanism of the melting process is used as a starting point for deriving an expression for the pressure dependence of the melting temperature of metals. The results obtained for the initial slope of the melting curve are compared with experimental data for 45 metals and in most cases the agreement is very good. The nonlinearity of the melting curve and the appearance of a maximum on the melting curve at a pressure approximately equal to the bulk modules is also predicted, with qualitative agreement with experimental data. A relation between bonding energy, atomic volume, and bulk modulus of metals is established. On the basis of this relation and the proposed vacancy mechanism, a generalised equation for the pressure dependence of the melting temperature of metals is derived. (author)

Effect of Yttrium Addition on Glass-Forming Ability and Magnetic Properties of Fe–Co–B–Si–Nb Bulk Metallic Glass

Directory of Open Access Journals (Sweden)

Teruo Bitoh

2015-06-01

Full Text Available The glass-forming ability (GFA and the magnetic properties of the [(Fe0.5Co0.50.75B0.20Si0.05]96Nb4−xYx bulk metallic glasses (BMGs have been studied. The partial replacement of Nb by Y improves the thermal stability of the glass against crystallization. The saturation mass magnetization (σs exhibits a maximum around 2 at. % Y, and the value of σs of the alloy with 2 at. % Y is 6.5% larger than that of the Y-free alloy. The coercivity shows a tendency to decrease with increasing Y content. These results indicate that the partial replacement of Nb by Y in the Fe–Co–B–Si–Nb BMGs is useful to simultaneous achievement of high GFA, high σs, and good soft magnetic properties.

Studies of bulk heterojunction solar cells

Science.gov (United States)

Cossel, Raquel; McIntyre, Max; Tzolov, Marian

We are studying bulk heterojunction solar cells that were fabricated using a mixture of PCPDTBT and PCBM­C60. The impedance data of the cells in dark responded like a simple RC circuit. The value of the dielectric constant derived from these results is consistent with the values reported in the literature for these materials. We are showing that the parallel resistance in the equivalent circuit of linear lump elements can be interpreted using the DC current­voltage measurements. The impedance spectra under light illumination indicated the existence of additional polarization. This extra feature can be described by a model that includes a series RC circuit in parallel with the equivalent circuit for a device in dark. The physical interpretation of the additional polarization is based on photo­generated charges getting trapped in wells, which have a characteristic relaxation time corresponding to the observed break frequency in the impedance spectra. We have studied the influence of the anode and cathode interface on this phenomena, either by using different interface materials, or by depositing the metal electrode while the substate is heated.

Mesoporous Transition Metal Oxides for Supercapacitors

Science.gov (United States)

Wang, Yan; Guo, Jin; Wang, Tingfeng; Shao, Junfeng; Wang, Dong; Yang, Ying-Wei

2015-01-01

Recently, transition metal oxides, such as ruthenium oxide (RuO2), manganese dioxide (MnO2), nickel oxides (NiO) and cobalt oxide (Co3O4), have been widely investigated as electrode materials for pseudo-capacitors. In particular, these metal oxides with mesoporous structures have become very hot nanomaterials in the field of supercapacitors owing to their large specific surface areas and suitable pore size distributions. The high specific capacities of these mesoporous metal oxides are resulted from the effective contacts between electrode materials and electrolytes as well as fast transportation of ions and electrons in the bulk of electrode and at the interface of electrode and electrolyte. During the past decade, many achievements on mesoporous transition metal oxides have been made. In this mini-review, we select several typical nanomaterials, such as RuO2, MnO2, NiO, Co3O4 and nickel cobaltite (NiCo2O4), and briefly summarize the recent research progress of these mesoporous transition metal oxides-based electrodes in the field of supercapacitors. PMID:28347088

Mesoporous Transition Metal Oxides for Supercapacitors

Directory of Open Access Journals (Sweden)

Yan Wang

2015-10-01

Full Text Available Recently, transition metal oxides, such as ruthenium oxide (RuO2, manganese dioxide (MnO2, nickel oxides (NiO and cobalt oxide (Co3O4, have been widely investigated as electrode materials for pseudo-capacitors. In particular, these metal oxides with mesoporous structures have become very hot nanomaterials in the field of supercapacitors owing to their large specific surface areas and suitable pore size distributions. The high specific capacities of these mesoporous metal oxides are resulted from the effective contacts between electrode materials and electrolytes as well as fast transportation of ions and electrons in the bulk of electrode and at the interface of electrode and electrolyte. During the past decade, many achievements on mesoporous transition metal oxides have been made. In this mini-review, we select several typical nanomaterials, such as RuO2, MnO2, NiO, Co3O4 and nickel cobaltite (NiCo2O4, and briefly summarize the recent research progress of these mesoporous transition metal oxides-based electrodes in the field of supercapacitors.

Merging Metallic Catalysts and Sonication: A Periodic Table Overview

Directory of Open Access Journals (Sweden)

Claudia E. Domini

2017-04-01

Full Text Available This account summarizes and discusses recent examples in which the combination of ultrasonic waves and metal-based reagents, including metal nanoparticles, has proven to be a useful choice in synthetic planning. Not only does sonication often enhance the activity of the metal catalyst/reagent, but it also greatly enhances the synthetic transformation that can be conducted under milder conditions relative to conventional protocols. For the sake of clarity, we have adopted a structure according to the periodic-table elements or families, distinguishing between bulk metal reagents and nanoparticles, as well as the supported variations, thus illustrating the characteristics of the method under consideration in target synthesis. The coverage focuses essentially on the last decade, although the discussion also strikes a comparative balance between the more recent advancements and past literature.

Glass forming ability and magnetic properties of Co(40.2−x)Fe(20.1+x)Ni6.7B22.7Si5.3Nb5 (x=0–10) bulk metallic glasses produced by suction casting

International Nuclear Information System (INIS)

Sarlar, Kagan; Kucuk, Ilker

2015-01-01

The effect of Fe concentration on the glass forming ability (GFA) and magnetic properties in Co (40.2−x) Fe (20.1+x) Ni 6.7 B 22.7 Si 5.3 Nb 5 (x=0–10) bulk metallic glasses were investigated. By suction casting method, the bulk metallic glasses with diameters up to 2 mm were produced. We try to find out which Fe concentration makes an influence on Co based system's magnetic properties and glass forming ability. The curves of thermal analysis, obtained using differential scanning calorimetry (DSC), show that the Co (40.2−x) Fe (20.1+x) Ni 6.7 B 22.7 Si 5.3 Nb 5 (x=0–10) have a supercooled liquid region (∆T x ) of about 44 K. The saturation magnetizations (J s ) for as-cast BMG alloys were in the range of 0.62 T−0.81 T. - Highlights: • The effect of Fe concentration on the glass forming ability. • The substitution of an appropriate amount of Fe can enhance the GFA. • The substitution of Fe for Co also improves soft magnetic properties of the BMGs. • The high of J s 0.62−0.81 T with a low H c of 2−289 A/m of the alloys

Homogeneous nucleation limit on the bulk formation of metallic glasses

International Nuclear Information System (INIS)

Drehman, A.J.

1983-01-01

Glassy Pd 82 Si 18 spheres, of up to 1 mm diameter, were formed in a drop tube filled with He gas. The largest spheres were successfully cooled to a glass using a cooling rate of less than 800 K/sec. Even at this low cooling rate, crystallization (complete or partial) was the result of heterogeneous nucleation at a high temperature, relative to the temperature at which copious homogeneous nucleation would commence. Bulk underscoring experiments demonstrated that this alloy could be cooled to 385 K below its eutectic melting temperature (1083 K) without the occurrence of crystallization. If heterogeneous nucleation can be avoided, it is estimated that a cooling rate of at most 100 K/sec would be required to form this alloy in the glassy state. Ingots of glassy Pd 40 Ni 40 P 20 were formed from the liquid by cooling at a rate of only 1 K/sec. It was found that glassy samples of this alloy could be heated well above the glass transition temperature without the occurrence of rapid divitrification. This is a result due, in part of the low density of pre-existing nuclei, but, more importantly, due to the low homogeneous nucleation rate and the slow crystal growth kinetics. Based on the observed devitrification kinetics, the steady-state homogeneous nucleation rate is approximately 1 nuclei/cm 3 sec at 590 K (the temperature at which the homogeneous nucleation rate is estimated to be a maximum). Two iron-nickel based glass-forming alloys (Fe 40 Ni 40 P 14 B 6 and Fe 40 Ni 40 B 20 , were not successfully formed into glassy spheres, however, microstructural examination indicates that crystallization was not the result of copious homogeneous nucleation. In contrast, glass forming iron based alloys (Fe 80 B 20 and Fe/sub 79.3/B/sub 16.4/Si/sub 4.0/C/sub 0.3/) exhibit copious homogeneous nucleation when cooled at approximately the same rate

Novel 14-nm Scallop-Shaped FinFETs (S-FinFETs) on Bulk-Si Substrate

OpenAIRE

Xu, Weijia; Yin, Huaxiang; Ma, Xiaolong; Hong, Peizhen; Xu, Miao; Meng, Lingkuan

2015-01-01

In this study, novel p-type scallop-shaped fin field-effect transistors (S-FinFETs) are fabricated using an all-last high-k/metal gate (HKMG) process on bulk-silicon (Si) substrates for the first time. In combination with the structure advantage of conventional Si nanowires, the proposed S-FinFETs provide better electrostatic integrity in the channels than normal bulk-Si FinFETs or tri-gate devices with rectangular or trapezoidal fins. It is due to formation of quasi-surrounding gate electrod...

Non-destructive identification of unknown minor phases in polycrystalline bulk alloys using three-dimensional X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Yang, Yiming, E-mail: yangyiming1988@outlook.com [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xu, Liang [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Yudan; Du, Guohao [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Yang, Sam [Commonwealth Scientific and Industrial Research Organization, Melbourne, VIC 3168 (Australia); Xiao, Tiqiao, E-mail: tqxiao@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

2017-02-15

Minor phases make considerable contributions to the mechanical and physical properties of metals and alloys. Unfortunately, it is difficult to identify unknown minor phases in a bulk polycrystalline material using conventional metallographic methods. Here, a non-destructive method based on three-dimensional X-ray diffraction (3DXRD) is developed to solve this problem. Simulation results demonstrate that this method is simultaneously able to identify minor phase grains and reveal their positions, orientations and sizes within bulk alloys. According to systematic simulations, the 3DXRD method is practicable for an extensive sample set, including polycrystalline alloys with hexagonal, orthorhombic and cubic minor phases. Experiments were also conducted to confirm the simulation results. The results for a bulk sample of aluminum alloy AA6061 show that the crystal grains of an unexpected γ-Fe (austenite) phase can be identified, three-dimensionally and nondestructively. Therefore, we conclude that the 3DXRD method is a powerful tool for the identification of unknown minor phases in bulk alloys belonging to a variety of crystal systems. This method also has the potential to be used for in situ observations of the effects of minor phases on the crystallographic behaviors of alloys. - Highlights: •A method based on 3DXRD is developed for identification of unknown minor phase. •Grain position, orientation and size, is simultaneously acquired. •A systematic simulation demonstrated the applicability of the proposed method. •Experimental results on a AA6061 sample confirmed the practicability of the method.

Slurry erosion induced surface nanocrystallization of bulk metallic glass

Science.gov (United States)

Ji, Xiulin; Wu, Jili; Pi, Jinghong; Cheng, Jiangbo; Shan, Yiping; Zhang, Yingtao

2018-05-01

Microstructure evolution and phase transformation of metallic glasses (MGs) could occur under heating condition or mechanical deformation. The cross-section of as-cast Zr55Cu30Ni5Al10 MG rod was impacted by the solid particles when subjected to erosion in slurry flow. The surface microstructure was observed by XRD before and after slurry erosion. And the stress-driven de-vitrification increases with the increase of erosion time. A microstructure evolution layer with 1-2 μm thickness was formed on the topmost eroded surface. And a short range atomic ordering prevails in the microstructure evolution layer with crystalline size around 2-3 nm embedded in the amorphous matrix. The XPS analysis reveals that most of the metal elements in the MG surface, except for Cu, were oxidized. And a composite layer with ZrO2 and Al2O3 phases were formed in the topmost surface after slurry erosion. The cooling rate during solidification of MG has a strong influence on the slurry erosion induced nanocrystallization. And a lower cooling rate favors the surface nanocrystallization because of lower activation energy and thermo-stability. Finally, the slurry erosion induced surface nanocrystallization and microstructure evolution result in surface hardening and strengthening. Moreover, the microstructure evolution mechanisms were discussed and it is related to the cooling rate of solidification and the impact-induced temperature rise, as well as the combined effects of the impact-induced plastic flow, inter-diffusion and oxidation of the metal elements.

Two-extremum electrostatic potential of metal-lattice plasma and the work function of an electron

Directory of Open Access Journals (Sweden)

Surma S.A.

2015-06-01

Full Text Available Metal-lattice plasma is treated as a neutral two-component two-phase system of 2D surface and 3D bulk. Free electron density and bulk chemical potential are used as intensive parameters of the system with the phase boundary position determined in the crystalline lattice. A semiempirical expression for the electron screened electrostatic potential is constructed using the lattice-plasma polarization concept. It comprises an image term and three repulsion/attraction terms of second and fourth orders. The novel curve has two extremes and agrees with certain theoretical forms of potential. A practical formula for the electron work function of metals and a simplified schema of electronic structure at the metal/vacuum interface are proposed. This yields 10.44 eV for the Fermi energy of free electron gas; -5.817 eV for the Fermi energy level; 4.509 eV for the average work function of bcc tungsten. Selected data are also given for fcc Cu and hcp Re. For harmonic frequencies ~ 10E16 per s of the self-excited metal-lattice plasma, energy gaps of 14.54 and 8.02 eV are found, which correspond to the bulk and surface plasmons, respectively. Further extension of this thermodynamics and metal-lattice theory based approach may contribute to a better understanding of theoretical models which are employed in chemical physics, catalysis and materials science of nanostructures.

Trap state passivation improved hot-carrier instability by zirconium-doping in hafnium oxide in a nanoscale n-metal-oxide semiconductor-field effect transistors with high-k/metal gate

International Nuclear Information System (INIS)

Liu, Hsi-Wen; Tsai, Jyun-Yu; Liu, Kuan-Ju; Lu, Ying-Hsin; Chang, Ting-Chang; Chen, Ching-En; Tseng, Tseung-Yuen; Lin, Chien-Yu; Cheng, Osbert; Huang, Cheng-Tung; Ye, Yi-Han

2016-01-01

This work investigates the effect on hot carrier degradation (HCD) of doping zirconium into the hafnium oxide high-k layer in the nanoscale high-k/metal gate n-channel metal-oxide-semiconductor field-effect-transistors. Previous n-metal-oxide semiconductor-field effect transistor studies demonstrated that zirconium-doped hafnium oxide reduces charge trapping and improves positive bias temperature instability. In this work, a clear reduction in HCD is observed with zirconium-doped hafnium oxide because channel hot electron (CHE) trapping in pre-existing high-k bulk defects is the main degradation mechanism. However, this reduced HCD became ineffective at ultra-low temperature, since CHE traps in the deeper bulk defects at ultra-low temperature, while zirconium-doping only passivates shallow bulk defects.

Interface control: A modified rooting technique for enhancing field emission from multiwall carbon nanotube based bulk emitters

Energy Technology Data Exchange (ETDEWEB)

Lahiri, Indranil [Nanomaterials and Device Lab, Department of Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174 (United States); Choi, Wonbong, E-mail: choiw@fiu.edu [Nanomaterials and Device Lab, Department of Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174 (United States)

2011-08-15

The unique properties of carbon nanotubes (CNTs) have raised hopes that these materials might find wide application as cold cathodes in various electron sources. The excellent field emission properties shown by CNT-based field emitters has further stimulated this expectation. However, efficient performance of a practical field emitter, which comprises a large number of randomly or regularly oriented CNTs, is restricted primarily due to poor junctions formed between CNTs and substrates. This study is aimed at enhancing the junction performance by way of a modified 'rooting' technique-interface control. In this process, the interface between CNTs and substrate has been tailored with different metals in an attempt to improve the CNT-substrate junction performance. Multiwall carbon nanotubes (MWCNTs) were synthesized on different interface-controlled substrates, i.e. Cu, Al, W, Si and low-temperature co-fired ceramic. All the samples produced mat-type, randomly oriented MWCNT structures. Among the four different substrates studied, MWCNT-based field emitters on Cu substrate demonstrated the best field emission response, in terms of low turn-on field, high emission current, good field enhancement factor and excellent stability in long-term operation. Emitter structures and their field emission behavior were correlated and it was shown that interface control, as an advanced 'rooting' process, plays an important role in determining the emission response from a bulk field emitter.

Interface control: A modified rooting technique for enhancing field emission from multiwall carbon nanotube based bulk emitters

International Nuclear Information System (INIS)

Lahiri, Indranil; Choi, Wonbong

2011-01-01

The unique properties of carbon nanotubes (CNTs) have raised hopes that these materials might find wide application as cold cathodes in various electron sources. The excellent field emission properties shown by CNT-based field emitters has further stimulated this expectation. However, efficient performance of a practical field emitter, which comprises a large number of randomly or regularly oriented CNTs, is restricted primarily due to poor junctions formed between CNTs and substrates. This study is aimed at enhancing the junction performance by way of a modified 'rooting' technique-interface control. In this process, the interface between CNTs and substrate has been tailored with different metals in an attempt to improve the CNT-substrate junction performance. Multiwall carbon nanotubes (MWCNTs) were synthesized on different interface-controlled substrates, i.e. Cu, Al, W, Si and low-temperature co-fired ceramic. All the samples produced mat-type, randomly oriented MWCNT structures. Among the four different substrates studied, MWCNT-based field emitters on Cu substrate demonstrated the best field emission response, in terms of low turn-on field, high emission current, good field enhancement factor and excellent stability in long-term operation. Emitter structures and their field emission behavior were correlated and it was shown that interface control, as an advanced 'rooting' process, plays an important role in determining the emission response from a bulk field emitter.

Mechanical properties of Zr41.2Ti13.8Ni10Cu12.5Be22.5 bulk metallic glass with different geometric confinements