bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Oxygen Partial Pressure on Properties of ZnO Films Deposited on Freestanding Diamond Films
Authors: Tang Ke , Wang Lin Jun , Huang Jian , Ren Bing , Zhou Jie , Le Jun , Xia Yi Ben
Published: March 2013

Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of freestanding diamond (FSD) films by the direct current (DC) magnetron sputtering method in an oxygen (O2) + argon (Ar) gas mixture. The effect of oxygen partial pressure on properties of ZnO films was investigated by X-ray diffraction (XRD). The results showed that when flux ratio of argon to oxygen was 1, the ZnO films had a better crystalline quality.
Preparation of the Ceramic Hollow Balls of Aluminium Titanate-Based by Rolling-Ball Method
Authors: Liu Xiu , Li Jia Ke , Gu Xing Yong
Published: March 2013

Aluminium titanate - based hollow balls were prepared by using aluminum titanate, mullite and magnesia aluminate spinel as starting materials followed by the rolling-ball method. The effect of different pore-making agents (namely the amylum, flour, millet and urea) on the forming properties and the apparent qualities of the precursors of the hollow balls were investigated. The results show that the precursors of the hollow balls own both good forming properties and apparent qualities when using the amylum as pore-making agent; an appropriate heat treatment was carried out on the above precursors, and the obtained hollow balls have particle size of 5 mm, aperture diameter of 3 mm and wall thickness of 1 mm; the average compressive strength of the hollow balls reaches 15.0 N. Since this method is very simple and effective for preparation of the hollow balls, it may provide a new approach for preparation of high performance heat insulation-porous materials.
Mechanical Properties of Dental Porcelain Discs by Different Producing Methods
Authors: Wang Hai Ttao , Liu Yi Hong , Wang Yong , Chen Hui Juan , Qiu Yan , Bao Yi Wang
Published: March 2013

The conventional method of producing porcelain standard disc specimens is based on the dental lab method for bilayer ceramic crowns, in order to reflect the clinical using condition. However heavy task is facing to the researchers, which is producing a large amount of the specimens efficiently. The press molding method is used to produce dental porcelain disc specimens in this study. Then, the basic mechanical properties of two groups of porcelain specimens were tested respectively, comparing with handmade and press molding method. The density was measured by Archimedes' method, the flexural strength was tested by biaxial bending test, and the hardness was checked by microhardness tester. The micro features of the specimens before and after bending test were observed under optical microscope and SEM. The results showed that there was no significant difference in the flexural strength, microhardness and density of porcelain discs made by two methods. Air pores were found in all specimens with size between 5-50 micrometers. The size and distribution of pores in the specimens by press molding method are more homogeneous than handmade method. Producing dental porcelain discs for laboratory testing specimens by press molding method was much easy than handmade method. Furthermore, the mechanical properties and microstructures of the specimens made by handmade method and press molding method were almost same.
Effects of Calcium Hexaluminate Addition on the Mechanical Properties of Zirconia-Toughened-Alumina
Authors: Hu Mei Ling , Fang Ming Hao , Chen Shu Sen , Yang Tao , Huang Zhao Hui , Liu Yan Gai
Published: March 2013

The effects of calcium hexaluminate addition on the microstructure and mechanical properties of zirconia-toughened-alumina ceramic were investigated. Zirconia-toughened-alumina (ZTA) composite ceramics which have different additions of calcium hexaluminate were successfully fabricated by pressureless sintering at 1600°C for 3h. The result shows that the bending strength and abrasive wearing improved with the increasing of CaAl12O19addition while the fracture toughness declined.
Effect of Coupled Conditions of Thermal Cycle and Dump Environment on Microstructure of 5mol% Yttria Stabilized Zirconia
Authors: Xia Jin Feng , Liu Ge Ming , Peng Niu Sheng , Feng Tao , Xu Hai Fang , Huang De Xin , Jiang Dan Yu
Published: March 2013

In some applications such as automotive oxygen sensor, 5mol% Y2O3stabilized zirconia (5YSZ) is generally used because it has both excellent ionic conductivity and mechanical properties. the automotive oxygen sensor would experience a cyclic change from high temperature (engine running) environment to the lowtemperature damp environment (in the tail pipe when vehicle stops). The microstructures change with coupled conditions of thermal cycle and dump environment in the 5mol%Y2O3–ZrO2 (5YSZ) system was examined by XRD，Raman spectroscopy and scanning electron microscopy (SEM) in this paper.
The Effect of Liner Thickness on the Color of Y-TZP Based All-Ceramic Restorations
Authors: Liu Ruo Yu , Zhang Yao Kun , Zhou Shan Yu , Hu Chen , Jing Dong Dong , Fan Hua , Shao Long Quan
Published: March 2013

To evaluate the effect of various liner thickness on the color of Y-TZP based all-ceramic restorations. Forty disc specimens (10 mm diameter, 0.5 mm thick) were fabricated from IPS e.max ZirCAD core material. The specimens were randomly divided into four groups (n=10) according to layering with different ZL1 IPS e.max ZirLiner thicknesses as: 0.1 mm, 0.2 mm, 0.3 mm and one group had received no treatment as the control group. And 0.6 mm veneering porcelain was fired on the IPS e.max ZirCAD core material by traditional layering technique. Using a spectrophotometer to measure Color parameters L, a and b of the specimens after veneered. ΔE were calculated to compare color difference among the four groups. Intergroup differences of ΔE in different thicknesses were statistically significant at P<0.05. The ΔE between groups with different thickness were 2.03±0.07, 2.88±0.07, 3.54±0.07, 0.86±0.06, 1.47±0.06 and 0.67±0.06 respectively.Usually researchers apply ΔE=1.5 as the threshold for distinguishing two different colors by the human eye. Color difference ΔE between different groups with and without liner application was more than 1.5, which was in the perceptible range, but ΔE of liner application with the thickness of 0.1 mm, 0.2 mm and 0.3 mm were undistinguishable by human eye (ΔE<1.5). Thus liner application of the all ceramic system could significantly affected the final color of the all ceramic restorations and it ameliorated esthetics of Y-TZP all-ceramic restorations to good purpose. However, Changes in the thickness (0.1 mm-0.3 mm) of liner application have no significant effect on the final shade of Y-TZP based all-ceramic restorations.
Thermal Fatigue of Ceramics: Theory, Life Predication and Characterization Methods
Authors: Guo Dai Dong , Hou Xian Qin , Liu Shi Quan
Published: March 2013

Thermal fatigue is a common problem when ceramics are used at high temperature. Typically, the mechanic properties of ceramics decrease after either long service times at high temperatures or cycles of temperature changes. The thermal fatigue process, the factors influencing the thermal fatigue and the prediction of the thermal fatigue life of ceramics are concerned topics. The thermal fatigue of ceramics is mainly explained by the critical stress fracture and thermal shock damage theories. The thermal fatigue tests include the traditional strength method, the quench-indentation method and the non-destructive detection such as the acoustic emission technique. Based on the thermal fatigue theories, the thermal fatigue life can be predicted using built models. The establishment of the standards for the testing of ceramic thermal fatigue will enhance the comparability of experimental data and further promote the development of analysis theory of thermal fatigue, benefiting the design of engineering ceramics.
Measuring Isostatic Pressing Strength of Hollow Glass Microspheres’ by Mercury-Injection Apparatus
Authors: Wang Yun , Peng Shou
Published: March 2013

In this passage, we introduce the theory and the method of measuring isostatic pressing strength of hollow glass microspheres’ by Mercury-injection Apparatus. We show in detail that how to measure isostatic pressing strength of hollow glass microspheres’ We also get some results in this way by comparing with the results of 3M’s，and the error is less than 2.85% .We analysize the reason of the error. This way is simple and accurate. Its repeatability is very good and it’s suitable to measure isostatic pressing strength of all kinds of hollow glass microspheres’. The requirements of production and scientific research could be satisfied.
Development of the Coaxiality Calibration System Based on the American Standard ASTME1012
Authors: Xu Jian , Chen Ke Xing
Published: March 2013

This paper describes the composition of the Coaxiality Calibration System based on the American Standard ASTME1012. The design of the test bar with different cross-section shape, the paste method of the strain gauge and formation of bridge are illustrated in the paper. The paper also introduces the signal amplifier, data collection system and measurement software in detail. The measurement precision of the coaxiality calibration device is up to grade 0.5.The device has successfully conducted coaxiality measurement and verification in fatigue testing machine, universal testing machine and material testing machine and achieved good test effect.
The Difference of Jadeite-Jade Lavender under Three Light Sources
Authors: Zhao Jia Hui , Chen Da Peng , Guo Ying , Wang Shuang
Published: March 2013

Compare the different appearance of jadeite-jade with three standard light sources, daylight D65,incandescent light A and fluorescent light F2(CWF),whose colors are purple to bluish violet with low chroma and low lightness in. The analysis of color index in the CIE 1976L* a* b uniform color space shows that the hue of lavender is influence by the light of standard light sources, followed by chroma, simultaneously value is seldom influenced obviously. And the color saturation of purple jade samples with CWF is usually higher, showing more vivid purple. However, D65 is benefit to the lightness of the purple jade, in which the average of color differences is known as the largest while the variance is the smallest. As D65 can be used to distinguish the purple color of jade samples most greatly, it is intended to be the best light source for appreciation of jadeite-jade. In consideration of the better quality of the purple color displayed with the CWF, it can be used during business transaction process.
Synthesis and Properties of Composite Stabilized ZrO2
Authors: Cui Jing Hui , Feng Tao , Xia Jin Feng , Jiang Dan Yu , Liu Ge Ming , Peng Niu Sheng , Li Qiang
Published: March 2013

Through Mechanical grounding method, CaZrO3 – 8YSZ(8% in mol yttria stabilized zirconia) electrolyte samples with different amounts of CaZrO3 at 10wt%, 20wt%, 30wt% were sintered at different temperatures in Muffle furnace. The decomposition temperature of CaZrO3 is 825°C-900°C under one atmosphere. At high temperature, CaZrO3 decomposes into CaO and ZrO2. So Y2O3-CaO-ZrO2 complex is composed. The effects of the sintering temperature and the contents of the CaZrO3 on the conductivity, porosity, flexure strength, hardness were investigated. XRD and SEM were used to analyse the compositions and microcosmic morphology.
Influence of Surface Morphology of Textured Substrate against Poly-Si Thin Film Solar Cells Performance
Authors: Muhida Riza , Toyama Toshihiko , Okamoto Hiroaki
Published: March 2013

Since poly-Si is an indirect band gap material and has low optical absorption coefficient in the visible-infrared region, the light trapping in thin film poly-Si layer by using textured substrate is one of the important technical issue for achievement of high short current. Surface texture of a transparent conductive oxide (TCO) layer on a glass substrate as well as SnO2 with a large grain are usually utilized for the light-trapping technique, i.e., path lengths of the incident light in the poly-Si layer are effectively enhanced by the light-scattering at the textured surface. In this paper, a systematic investigation has been carried out concerning the relationship between poly-Si thin film solar cells performance and surface morphology of substrate texture as a function of root mean square roughness of substrate surface, in order to find the optimum textured substrate and realize the light trapping in the poly-Si solar cells. Furthermore, the influence of textured substrate on optical reflectance, poly-Si microstructure and photovoltaic performance are also discussed.
Performance of TiO2 Aggregates-Based Dye Solar Cells
Authors: Mohamed Norani Muti , Zaine Siti Nur Azella
Published: March 2013

TiO2 aggregates-based dye solar cells (DSCs) have gained an increasing interest due to their better light harvesting efficiency as a result of enhanced light scattering effect from the submicron spherical aggregates that can generate more electrons and the high internal surface area for dye chemisorption provided by nanocrystallites which made up the aggregates. Optimized TiO2 aggregates (0.45 µm) composing of nanocrystallites (10-40 nm) with desired physicochemical properties for enhanced overall light conversion efficiency of DSC were synthesized by varying the calcination temperature and water content in the hydrolysis of titanium alkoxide in ethanol. TiO2 aggregates obtained were characterized using FESEM, XRD and UV-Vis spectroscopy. The assembled DSCs were then evaluated using solar simulator under AM 1.5 (100 mW/cm2) simulated sunlight. Nanocrystallites were found to have an increasing size of 12 nm to 36 nm with increasing calcination temperature of 400C to 600C. Sample of aggregates calcined at 500C recorded the highest efficiency (4.456%) as the 20-nm nanocrystallites produced is considered to be the optimum size for dye absorption. With higher water content in the hydrolysis process, the aggregates lose their spherical shapes resulting in lower absorption intensity indicating the occurrence of low light scattering in the TiO2 film. Highest conversion efficiency was observed for DSC that used well-defined spherical TiO2 aggregates composing of 20-nm nanocrystallites which were synthesized using ethanol with low water content (0.9 vol%) followed by calcination at 500C. Thus, optimized TiO2 nanocrystallites which form spherical aggregate is critical in order to improve light harvesting efficiency of DSCs.
Beta-Carotene Dye of Daucus carota as Sensitizer on Dye-Sensitized Solar Cell
Authors: Suryana Risa , Khoiruddin Khoiruddin , Supriyanto Agus
Published: March 2013

Beta-carotene dye which is extracted from daucus carota material was used as sensitizer to fabricate dye-sensitized solar cell (DSSC). DSSCs were arranged in a sandwich structure consisting of fluorine-doped tin oxide (FTO) as a transparent conducting oxide (TCO), titanium dioxide (TiO2) layer, beta-carotene dye, iodide/tri-iodide redox electrolyte, and carbon layer as a counter electrode. Beta-carotene dye has an absorbance in wavelength zones from 415 to 508 nm. Meanwhile, it has the largest photoconductivity of 28.3×10-4 and 8.2×10-4 (Ω.m)-1 in dark and bright conditions, respectively. Moreover, the photoelectrochemical performance of the DSSC based on beta-carotene dye showed that the maximum voltage of 23.9×10-2 V and the maximum current of 3.3×10-5 A. However, the photo-to-electric conversion efficiency of this DSSC was very low i.e. 12.5×10-4 %.
Resonance Frequency Change in Microcantilever-Based Sensor due to Humidity Variation
Authors: Nuryadi Ratno , Djajadi Arko , Adiel Reyhan , Aprilia Lia , Aisah Nuning
Published: March 2013

Microcantilever-based sensors have attracted interest in the last decade because of their small size, rapid detection and high sensitivity. This sensor can be applied in the many fields, i.e. physics, chemistry, biology, biochemistry, medical, and environment. In this paper, we describe microcantilever-based sensor for environmental monitoring, especially for a humidity detection. This sensor was operated in dynamic mode where a change in mass or spring constant of the microcantilever provides the resonance frequency change. Here, a change of humidity is detected by the resonance frequency and the amplitude changes. It is found that the increase in the humidity causes the decreasing the resonance frequency but increasing the amplitude. This result opens up the possibility of the humidity detection using microcantilever-based sensor.
Role of Multiwall Carbon Nanotubes (MWCNT) on Electrical Conductivity of Polymer Composite as Alternative Materials for Bipolar Plate Fuel Cell
Authors: Zulfia Anne , Sutopo Sutopo , Indriyana Bangkit , Albar M.E. , Rohman S.
Published: March 2013

Polypropylene can be improved an electrical conductivity by addition of carbon and multiwall carbon nanotube (MWCNT) as well as combination with copper (Cu) powder. Multiwall carbon nanotube used from 0.1 wt%, 0.5 wt% to 1 wt% while the addition of Cu powder into PP/C was various from 0.1 wt%, 0.2wt% to 0.5wt% respectively. This research focuses on material design of composite based on polymer and carbon to improve an electrical conductivity according to electrical conductivity requirement for bipolar plate. Bipolar plate is one of the components in PEMFC constituted a crucial component that collects and transfers electron from the anode to the cathode, therefore it should possess high electrical conductivity. The main discussion in this research is to analyze the role of multiwall carbon nano tube (MWCNT) and copper on electrical conductivity of polymer composites produced. Functional groups analysis using Fourier Transform Infrared Spectroscopy (FTIR) was also carried out to investigate whether carbon has been mixed perfectly within polypropylene. It is found that the effect of adding a small amount of MWCNT and Cu have improved their electrical conductivity of composites up to 15.62 S/cm.
Thermal Conductivity Enhancement of Brine Containing Charcoal Particles
Authors: Alaa' Siti , Khairurrijal Khairurrijal , Abdullah Mikrajuddin
Published: March 2013

Experiments to measure the thermal conductivity of brine containing coconut shell charcoal particles have been performed at different volumetric concentrations and temperatures. SEM was used to observe the morphology of particles. The thermal conductivity increased with increasing the temperature. In addition, the thermal conductivity of brine containing coconut shell charcoal particles was higher than that of brine containing activated carbon particles
Application of Electrocatalytic Technique to Degrade the Color of Tea Wastewater
Authors: Shen Shan Yi , Chang Jih Hsing , Hsieh Yung Hsu
Published: March 2013

The color elimination of real tea wastewater by the electrocatalytic system was investigated. The electrocatalytic system composed IrO2 electrode as the anode and DSA electrode as the cathode under the current density of 40 mA cm-2. Various concentrations of NaCl and wastewater volumes were tested to understand their effects. For the effect of NaCl addition, the color removal efficiency increased 25% under the condition of NaCl addition. The relatively proper operation was 0.25 M NaCl and 1.0 liter wastewater, which caused the color removal efficiency up to 85%. Based on this color removal efficiency, the tea wastewater of 1.0 L consumed the electricity of 0.03KWh.
Neutron Diffraction Study of a Non-Stoichiometric Ni-Mn-Ga MSM Alloy
Authors: Ari-Gur Pnina , Ovidiu Garlea V. , Coke Ashley , Ge Yan Ling , Aaltio Ilkka , Hannula Simo Pekka , Cao Hui Bo , Madiligama Amila S.B. , Koledov Victor
Published: March 2013

Abstract. The structure and chemical order of a Heusler alloy of non-stoichiometric composition Ni-Mn-Ga were studied using constant-wavelength (1.538 Å) neutron diffraction at 363K and the diffraction pattern was refined using the FullProf software. At this temperature the structure is austenite (cubic) with Fm space group and lattice constant of a = 5.83913(4) [Å]. The chemical order is of critical importance in these alloys, as Mn becomes antiferromagnetic when the atoms are closer than the radius of the 3d shell. In the studied alloy the refinement of the site occupancy showed that the 4b (Ga site) contained as much as 22% Mn; that significantly alters the distances between the Mn atoms in the crystal and, as a result, also the exchange energy between some of the Mn atoms. Based on the refinement, the composition was determined to be Ni1.91Mn1.29Ga0.8
Twinning in Ti-48%Ni-2%Fe Single Crystals under Rolling
Authors: Isaenkova Margarita , Perlovich Yuriy , Fesenko Vladimir , Dementyeva Tatyana
Published: March 2013

Under rolling of Ti-48%Ni-2%Fe single crystals in the phase B2 at 350oC the twinning is the main mechanism of plastic deformation by many initial orientations of these single crystals, as texture data show clearly. Splitting of initial maxima in the stereographic projection of single crystal into several new ones is an evident manifestation of twinning. But this mode of reorientation is observed only at initial stages of rolling, when deformation degrees do not exceed ~10-15%. A geometrical analysis of pole figures for rolled single crystals showed, that at the used rolling temperature the preferable twinning planes there were {114} and {118}.
Dynamical Behavior of Martensite-Austenite Transitions: Simulations and Experiments
Authors: Laguna María Fabiana , Aguilar Ireth García , Larochette Pierre Arneodo , Pelegrina Jorge Luis
Published: March 2013

The dynamical behavior of the reverse martensitic transformation has been numerically simulated with an atomistic model and compared with experiments in Cu-Zn-Al alloys. Starting from different configurations of the martensitic variants (varying mainly their mean size), the transformation to austenite was studied as a function of the heating speed. Both, experimental and numerical results show that at low velocities there is no dependence of the transition temperatures, whereas at higher speeds they gradually increase. Simulations allow us to have an insight of the underlying processes during the transition to austenite. They also show that a heating speed independent transition can only be obtained when a microstructure of very small variants is present.
Simulation of Vibration Isolation by Shape Memory Alloy Springs Using a Microstructural Model of Shape Memory Alloy
Authors: Volkov Aleksandr E. , Evard Margarita E. , Vikulenkov Andrey V. , Uspenskiy Evgeniy S.
Published: March 2013

A vibroisolation of a payload connected to a vibrating housing by two helical shape memory alloy (SMA) elements is considered. A microstructural theory is used for the simulation of the mechanical behavior of the SMA. The simulations have shown that the resonant frequency and the mitigation of the external vibrations depend on the shape memory alloy state. The maximum reduction of the acceleration amplitude for harmonic excitation is reached when the SMA is in the martensitic pseudoplastic state or in the two-phase state. Variation of temperature allows changing the resonance frequency and thus escaping from resonance. The acceleration of the payload at impact is the smallest when the SMA elements are in the pseudoelastic state.
Characterization and Comparative Study of Pseudo-Elastic Cu-Zn-Al Foams Synthesized by Two Different Methods
Authors: Weiss Brenda A. , Larochette Pierre Arneodo , Bertolino Graciela , Castrodeza Enrique M. , Baruj Alberto , Troiani Horacio E.
Published: March 2013

Low cost Cu-Zn-Al foams present, in specific composition ranges, good pseudoelastic properties associated with interesting damping capacities, which establish these materials as attractive from the point of view of structural applications. These foams are manufactured by infiltration of small SiO2 spheres into the molten alloys. After alloy solidification the SiO2 spheres are removed by immersing the material in a solution of aqueous hydrofluoric acid. In this work, we have investigated the effect of two different foam preparation techniques: inductive and resistive melting. The paper details both the physico-chemical and mechanical characterization of the foams synthesized with the two different methods. The purpose of this study is to determine the quality of each synthesis method in order to identify the best alternative.
About the Mechanism of Deformation at Martensite Transformation in the Fe-31 wt%Ni Alloy
Authors: Gundyrev Vyacheslav , Zel'dovich Vitaly
Published: March 2013

The criterion of an estimation of a reality of the mechanism of deformation of a lattice at martensite transformation is proposed. The most real mechanism of deformation of a lattice in FeNi alloy with the twinned martensite is determined. The Kurdjumov-Sachs shear on a plane (111) fcc in a direction [11-2] fcc is the basic component of deformation of a lattice in the given mechanism.
Structural and Hardness Gradients in the Heat Affected Zone of Welded Low Carbon Martensitic Steels
Authors: Dunne Druce P. , Pang W.
Published: March 2013

Welding of low carbon martensitic steels with yield strengths above 690 MPa requires careful attention to the welding procedure to avoid hydrogen assisted cold cracking (HACC) and to minimise degradation of the mechanical properties of the weldment. Investigations of the microstructural and hardness gradients in the heat affected zone (HAZ) of these types of steels revealed that the peak hardness does not occur in the grain coarsened heat affected zone (GCHAZ) adjacent to the fusion boundary, as normally observed for ferritic steels, but is displaced towards the grain refined region (GRHAZ). This phenomenon, referred to as the displaced hardness peak (DHP) effect, is considered to arise when the hardenability of the steel is sufficiently high to produce the same microstructure in the both the GC and GR heat affected zones, but the enhanced structural refinement of the GRHAZ increases the hardness and strength above that of the GCHAZ. Implications relative to the susceptibility of the weldments to HACC are discussed.
Study of Nickel Segregation at the TiNi-Titanium Oxide Interface
Authors: Kulkova Svetlana E. , Bakulin Alexander V. , Hu Q. M. , Yang Rui
Published: March 2013

Ab-intio investigations of atomic and molecular oxygen on TiNi(110) surface are performed by using the projector augmented wave method with generalized gradient approximation for the exchange-correlation functional. Our results confirm the formation of a Ni-rich interface TiO2(100)/TiNi(110), for which the formation energies (Hf) of point defects at the interfacial layers were estimated. It is shown that Hf of swap Ti-Ni defect has a lower energy than that for the Ni antisites at the interfacial layers. The formation energies of point defects in bulk TiNi, monoclinic TiO, and rutile TiO2 are also calculated. Our results demonstrate that Hf of Ni-antisites in TiO is twice less than that in TiO2. The formation of small Ni clusters is also discussed.
Thermomechanical Fatigue Behavior of NiTi Wires
Authors: Isalgué Antonio , Fernández Javier , Cinca Nuria , Cano Irene García , Grau Ramón , Auguet Carlota , Torra Vicenç
Published: March 2013

Applications of the functional, smart materials SMA need a careful evaluation of the working conditions and fatigue life. Structural fatigue failure in NiTi usually comes from a surface defect inducing crack growth, and this means that fatigue has to be studied for concrete applications, with the correct samples, as the state of the material presents size effects. Testing machine experiments on Ni-rich pseudoelastic wires indicate that the main parameter controlling the fatigue life in the traction-traction experiments is the effective stress on the NiTi wire. Long wire life (in the million cycle regime) can be achieved under limited stresses (under 170 MPa) in traction-traction tests. Also, experiments have been done on thermal actuation of NiTi wire under traction at constant load. Long actuator life (larger than 400000 cycles) can be achieved at low stresses (around 100 MPa), coherently with the results from the mechanical cycling.
Shape Memory Effect in NiTiCo Strip Produced by Twin Roll Casting Technique
Authors: Goryczka Tomasz , Ochin Patrick , Lelątko Józef
Published: March 2013

The ternary Ni47Ti50Co3 alloy was produced using twin roll technique and traditional casting. The bulk alloy was hot rolled and thermally treated. Both alloys showed presence of the reversible martensitic transformation, in which the parent phase transformed to the B19’monoclinic martensite via the R-phase. However, they significantly differed in grains orientation. Thermally treated alloy showed weak fibre texture (35% of total amount), whereas the strip revealed fibre and {100} sheet texture components. In the strip more than 70% of total amount of grains were preferentially oriented. Presence of the texture affected the shape memory effect. In the strip, the two-way shape memory effect was induced after 30 training cycles. In thermally treated bulk, 52% of shape recovery was reached after 100 training cycles.
TiNiCu Martensitic Transformation Characterization at Low Stress Levels through Thermomechanical Cycling
Authors: Fabregat-Sanjuan Albert , Ferrando Francesc , Urbina Cristina , de la Flor Silvia
Published: March 2013

This investigation has studied the characterization of the thermomechanical behaviour of a TiNiCu shape memory alloy with different heat treatments. This characterization has been done by analyzing martensitic transformation at constant stress tests. The martensitic transformation was analyzed by measuring electrical resistance and strain. The results showed that orientation is reached at different stress levels during each heat treatment; low stress thermomechanical cycling does not affect transformation temperatures and thermomechanical cycling at upper stress levels produces different changes of behaviour depending on the stress level and/or heat treatment.
3D Energy Analysis of Magnetic-Field Induced Martensite Reorientation in Magnetic Shape Memory Alloys
Authors: He Yong Jun , Chen Xue , Moumni Ziad
Published: March 2013

This paper explains the magnetic-field induced martensite reorientation in Ferromagnetic Shape Memory Alloys (FSMA) through a simple energy analysis from which the role of the martensite’s magnetic anisotropy is emphasized. In particularly, with a three-dimensional (3D) energy analysis, we study the switching between the three tetragonal martensite variants driven by a rotating magnetic field (with a constant magnitude) and a non-rotating magnetic field (with a fixed direction but varying magnitudes). Finally, a simple planar phase diagram is proposed to describe the martensite reorientation in general 3D loadings.
Microstructures of Fe-Pd Alloy Ribbons Subjected to Rapidly Solidified Melt Spinning
Authors: Kishi Yoichi , Kubota Takeshi , Yajima Zenjiro , Okazaki Teiko , Furuya Yasubumi , Wuttig Manfred
Published: March 2013

Microstructures of the Fe-29.6at%Pd alloy ribbons were observed with an X-ray diffractometer and a transmission electron microscope. The X-ray diffraction profiles at room temperature showed that the ribbon consists of FCT martensitic phase and FCC parent phase. Moreover, the ribbon exhibits a strongly 200-oriented texture analyzing with pole figure measurements. TEM bright field images for the cross section of the ribbon showed high-density striation in the FCT martensite variants. Twin-related two sets of reflections were observed in the SAED patterns taken of the FCT martensite variants. FCT was nearly parallel to the thickness direction according to the analysis of the SAED patterns. This result corresponds to the pole figure measurements.
Magnetocaloric and other Properties of Cold Rolled Gd Ribbons
Authors: Taskaev Sergey , Buchelnikov Vasiliy D. , Pellenen Anatoliy , Bataev Dmitry , Skokov Konstantin , Khovaylo Vladimir , Aliev Akhmed
Published: March 2013

In this work we investigate magnetocaloric effect and heat capacity of Gd cold rolled ribbons. Such materials are easy to produce, they are flexible and convenient for using in magnetic cooling devices. It is shown that the magnetocaloric effect is strongly dependent on thickness of the ribbons. Severely rolled ribbons demonstrate rather a small magnetocaloric effect. However, a special heat treatment procedure makes it possible to enhance the effect up to the value observed in polycrystalline Gd.
Experimental Study of Magnetocaloric Effect in Ni-Fe-Mn-Ga and Ni-Co-Mn-Ga Heusler Alloys
Authors: Fayzullin Rafael , Buchelnikov Vasiliy D. , Taskaev Sergey , Drobosyuk Mikhail , Khovaylo Vladimir V.
Published: March 2013

In this work we experimentally studied the MCE in the Heusler alloys Ni2.19-xFexMn0.81Ga (x = 0.01, 0.02, 0.03, 0.04) and Ni2.16-xCoxMn0.84Ga (x = 0.03, 0.06, 0.09). Magnetocaloric effect was measured by the direct method using the installation from the company AMT&C. The temperature dependencies of ∆Tad for the magnetic field change ∆H = 2 T were measured. The phase transition temperatures were determined from temperature dependencies of low field magnetization measured by original setup using Hall effect. Studies have shown that replacement of the Ni atoms with the iron atoms slightly reduces the temperature magnetostructural transition for x = 0.01,0.02, and starting with x = 0.03, magnetic and structural transitions occur separately and a further increase in iron concentration leads to the Curie temperature increase, while the temperature martensitic transformation decreases. When replacing the Ni atoms with the Co atoms of the martensitic transformation temperature and Curie temperature increase.
Martensitic Transformation in Ni-Al-Pt High Temperature Shape Memory Alloys
Authors: Monastyrsky Gennady E. , Ochin Patrick , Odnosum Valery V. , Pasko Alexander Yu. , Kolomytsev Victor I. , Koval Yuri
Published: March 2013

In alloys Ni–39(41)Al–xPt (x = 5,10,15,20 at.%) the alloying by Pt strongly increases the Ms point. There is no direct proportionality between the Pt content and the Ms point increasing. No traces of Ni3Al were found in the alloys. The precipitation of Ni5Al3 was observed in Ni–39Al–15Pt alloy after cycling through the temperature range between the room temperature and 800°C. The effect of Pt alloying on the martensitic transformation and high temperature martensitic transformation stability is governed by the competition between the martensitic transformation and formation of the Ni5Al3 phase upon the cooling. Pt addition, instead of Ni, can resolve the problem of decomposition processes because the alloy composition is shifted out of the Ni3Al domain on the phase diagram and it reduces the influence of the Ni5Al3 phase on the degradation of martensitic transformation.
Reactive Stresses and Burst Character of Shape Memory Deformation in Single Crystals Cu-Al-Ni and Ni-Fe-Ga Single Crystals
Authors: Nikolaev Vladimir I. , Malygin Gennady A. , Pulnev Serguey A. , Yakushev Pavel N. , Egorov Victor M.
Published: March 2013

Abstract. The paper is a presentation of two new phenomena which have been recently revealed and investigated by authors in well-known shape memory alloys such as Cu-Al-Ni and Ni-Fe-Ga. The first is a strong decrease of the martensitic transfornation heat evolved (absorbed) in single crystals of Cu-13.5 wt. % Al - 4.0 wt. % Ni alloy in the course of their in-situ calorimetric study under constrained shape memory deformation conditions. The second is a burst character of emerg-ing shape memory strain in the course of heating single crystals of Ni49Fe27Ga18CoSubscript text6 ferromagnetic alloy. The crystals were preliminary compressed along [110] crystallographic axis for the purpose of giving them a shape memory deformation. As a result of burst martensitic transition, the monocrystalline samples standing on a hard base and loaded additional weight of 400 g threw up this weight on 66 mm height .
Crack Growth by the Isothermal Martensitic Phase Transformation in Tetragonal Zirconia Polycrystals
Authors: Hwang Kyu Hong , Lee Jong Kook
Published: March 2013

In this study, we investigated the crack nucleation and growth and propagation on the surface of Y-TZP during isothermal phase transformation by low temperature ageing. Crack initiation and growth on the surface of Y-TZP specimen was dependent on the sintered microstructure, i.e, sintered density, grain size, pore structure, residual stress etc.. In the case of Y-TZP with 2mol % yttria content, phase transformation of tetragonal to monoclinic began on the surface and induced a crack nucleation of specimen at the initial stage of low temperature ageing. Most of cracks in 2Y-TZP by low temperature ageing were firstly formed on the surface of specimens (free surface, weak bonding grains, etc.) where the change of strain free energy for a tetragonal to monoclinic transformation was small, and surface cracks grew into the bulk interior through the grain boundaries.
Mechanical Behavior Study of NiTi Endodontic Files Taking into Account Anatomic Shape of Root Canals
Authors: Legrand Vincent , Moyne Sylvain , Pino Laurent , Chirani Shabnam Arbab , Calloch Sylvain , Arbab Chirani Reza , Chevalier Valerie
Published: March 2013

Superelastic NiTi SMA is the base of endodontic files. The flexibility of these instruments permits the preparation of root canals. Unfortunately the intracanal file separation can occur. To have a good idea of the mechanical behavior of these instruments, we propose in this study the finite elements simulations taking into account the real shape of root canals. This has been possible by using a well adapted model describing all the particularities of superelastic SMA and by using representative limit conditions.
Electric Resistivity as Phase Volume Fractions Indicator in Metastable Alloys
Authors: Saint Sulpice Luc , Lakrit Mohamed , Chirani Shabnam Arbab , Calloch Sylvain
Published: March 2013

The microstructure of metastable alloys varies with the thermomechanical history of the material. During a thermomechanical loading, different phases can be present in the material simultaneously. They can be at the origin of macroscopic stress and strain. Consequently, it is important to determine the proportion of each phase to understand the transformation kinetic. However, the techniques usually used to carry out these measurements such as magnetic properties measurements, neutron or X-ray diffraction, are heavy and require a lot of resources. This study, thanks to experimental tests based on electric resistance measurements, permits to determine the volume fraction of the different states present in the material. The study has been realized on a 301 stainless steel in order to take into account the effects of elasticity, transformation and plasticity. Then the volume fraction of the different phases of the material has been determined during transformation with the plasticity presence.
Prediction of Transformation Behavior of R-Phase SMA Actuators by the Application of Fuzzy Logic
Authors: Lygin Konstantin , Labenda Patrick , Sadek Tim
Published: March 2013

The rhombohedral R-phase is an intermediate phase during the transformation from cubic austenite (B2) to monoclinic martensite (B19’). Compared to the martensitic transformation (B2 → B19’), the R-phase transformation (B2 → R) in NiTi based shape memory alloys (SMA) has a lot of advantages. The main advantages of the R-phase transformation are the very small temperature hysteresis (2-5K) and the high durability (> 100.000 cycles). The main disadvantage of actuators based on R-phase transformation is the small SMA effect (approx. 0,8%). Due to the small temperature hysteresis, the R-phase actuators are usable for temperature sensitive applications in heating technology or in air conditioning. The R-phase transformation doesn’t appear in each SMA alloy and needs a special thermo-mechanical treatment to be induced. Fuzzy logic is an approach to computing, based on degrees of truth, rather than the usual true or false (1 or 0) Boolean logic. It includes 0 and 1 as extreme cases of truth but also the various states of truth. The objective of this paper is to show the applicability of the approach of fuzzy logic in the field of SMA. To gain basic knowledge about influences, different binary NiTi alloys were investigated. The parameters annealing temperature, annealing time and Ni-concentration were varied and their influence on the transformation behavior of the R-phase was noted and added to the fuzzy logic knowledge base.
Superficial Modifying by Materials with SME in Engineering Appendices
Authors: Blednova Zhesfina , Rusinov Peter Olegovich , Stepanenko Maya A.
Published: March 2013

Some technical applications of superficial modifying by materials with SME in mechanical engineering and aspects of practical realisation are considered. Economic feasibility of use of superficial modifying in thermomechanical operated connections of "shaft-plug" type and in bolted connection working in the conditions of vibrations is proved. The necessary thickness of blankets providing reliability of connections are defined. On the basis of the analysis of the stress-strain state of carving connection it is shown, that a material with SME carries out some functions: prevents self-unscrewing, stabilizes force of an inhaling, protects from corrosion, influences friction factor.
Full Simulation Study of UV Photodetectors Based on Pn Junctions in Silicon Carbide
Authors: Ottaviani Laurent , Vervisch Wilfried , Biondo Stephane , Palais Olivier
Published: March 2013

This paper deals with optical and electrical simulations of 4H-SiC UV-Photodetectors based on pn junctions. The simulations are performed under the UV light, with wavelengths varying between 200 nm and 300 nm. Under reverse bias, the simulation results point out the influence of surface patterns on the current density. The studied structures of the patterns consist in a semicircle with or without a flat surface. The patterned surfaces are parametrized according to the semicircle radius R and the flat surface length L. We show that the optical absorption strongly depends on these parameters, giving a maximum value whatever the wavelength with R = 100 nm and L = 0 nm (no flat surface). However, to optimise the carrier harvest, it is important for the space charge region to be situated in a zone where the optical generation is high. This study shows that the photodetector current density increases within three orders of magnitude (from 9x10-14 A.cm-2 to 3x10-10 A.cm-2), by using the specific surface pattern given above.
Power Module Package Structure Capable of Surviving Greater ΔTj Thermal Cycles
Authors: Tanimoto Satoshi , Tanisawa Hidekazu , Watanabe Kinuyo , Matsui Kohei , Sato Shinji
Published: March 2013

A new SiC power module package structure is proposed that is capable of withstanding greater ΔTj cycle stress. Its most notable feature is the use of a SiN substrate having Cu/Invar/Cu foils (C/I/C thickness ratio of 1/8/1) brazed on both sides as conductor plates. The CIC foils show a very low coefficient of thermal expansion (CTE) of 5.1 ppm/°C and therefore can significantly reduce package degradation resulting from the larger CTE mismatch of the conductor to SiC and SiN. A thermal cycle test (TCT) was conducted between -40°C and 250°C (ΔTj = 290°C). It was found that the SiC/Au-Ge/CIC-SiN die attachment maintained joint strength of 78 MPa even after 3000 cycles.
Effect of a Gas Pressure on the Growth Rate of AlN Layer
Authors: Mokhov E.N. , Wolfson A.A. , Kazarova Olga P.
Published: March 2013

The dependence of the layer growth rate on a gas (argon, nitrogen) pressure inside the reactor has been examined in order to analyze the conditions of growth of AlN thick layers and bulk crystals by the sublimation sandwich-method. It is shown that the layer growth rate steadily increases as the pressure in the reactor decreases in a wide pressure interval 1–0.02 bar. This suggests that a key role in the layer growth kinetics is played by the source-to-substrate transfer of the components (Al, N), rather than the adsorption - desorption processes on the source and substrate surface. In addition the growth rate in argon atmosphere is much higher than in nitrogen one for the high pressures and is practically the same for the lowest (0.05 – 0.02 bar).
A Compact Switching Power Supply Utilizing SiC-JFET for an Induction Synchrotron
Authors: Okamura Katsuya , Mizushima Toshiya , Takaki Koichi , Takayama Ken
Published: March 2013

Utilizing a high power discrete SiC-JFET developed by KEK, a switching power supply (SPS) that had a circuit topology of H-bridge was designed and constructed to drive the induction acceleration system for the KEK digital accelerator. The SPS was operated with a 38 Ω dummy resistance load and bipolar outputs of 800V and 21A were successfully demonstrated at 1 MHz. Also, the combination test with an actual accelerator cell is being conducted.
Modeling of the Impact of Parameter Spread on the Switching Performance of Parallel-Connected SiC VJFETs
Authors: Lim Jang Kwon , Peftitsis Dimosthenis , Rabkowski Jacek , Bakowski Mietek , Nee Hans Peter
Published: March 2013

Operation of parallel-connected 4H-SiC VJFETs from SemiSouth was measured and modeled using numerical simulations. The unbalanced current waveforms in parallel-connected VJFETs were related to spread in the critical parameters of the device structure and to the influence of the parasitic inductances in the measurement circuit. The physical device structure was reconstructed based on SEM analysis, electrical characterization, and device simulations. The two hypothetical critical design parameters that were studied with respect to spread were the p-gate doping profile (Case 1) and the emitter doping (Case 2). Variation in both parameters could be related to variation in the emitter breakdown voltage, the on-state characteristics, and the threshold voltage of the experimental devices. The switching performance of the parallel-connected JFETs was measured using a single gate driver in a double pulse test and compared with simulations. In both investigated cases a very good agreement between measurements and simulations was obtained. The modeling of the transient performance relies on good reproduction of transfer characteristics and circuit parasitics.
SiC Single Crystal Growth on Dual Seed with Different Surface Properties
Authors: Lee Sang Il , Jung Jung Young , Park Mi Seon , Lee Hee Tae , Lee Doe Hyung , Lee Won Jae , Hong Soon Ku , Yeo Im Gyu , Kim Heung Rak , Chun Myong Chuel
Published: March 2013

SiC crystal ingots were grown on 6H-SiC dual-seed crystal with different surface properties by a PVT (Physical Vapor Transport) technique. And then SiC crystal wafers sliced from the SiC ingots were systematically investigated in order to find out the dependence of surface properties for seed on the polytype formation. While n-type SiC crystals exhibiting the 4H polytype were grown on seed crystal having high root-mean-square (rms) value, 6H-SiC crystals were grown on seed having lower rms value. However, 6H polytype was maintained on on-axis and off-axis seeds during the entire growth period. The crystal quality of 6H-SiC single crystals grown on on-axis seed were revealed to be slightly better than that of 6H-SiC crystal grown on off-axis seed.
Compact Modeling of the Punch-Through Effect in SiC-IGBT for 6.6kV Switching Operation with Improved Performance
Authors: Miyake Masataka , Ueno Fumiya , Navarro Dondee , Miura-Mattausch Mitiko
Published: March 2013

We developed a compact model of SiC-IGBT for circuit simulation of power conversion systems under 6.6kV / 100A/cm2 bias operation at a few hundred Hz switching frequency. The model includes punch-through effects occurring at the base/buffer surface of the base region. The model allows accurate prediction of switching waveforms and energy loss improvement caused by the punch-through effect (PT-effect).