bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy-Flow Methodology for Thermodynamic Analysis of Manufacturing Processes: A Case Study of Welding Processes
Authors: Zambrana D. , Aranda A. , Ferreira G. , Barrio F.
Published: May 2012

Manufacturing processes involve the input of high quality energy and/or dissipation of low quality energy to manipulate a material; similarly the input of high quality material usually leads to the generation of low quality materials. A useful output involves the operation of conventional processes including a wide variety of functions such as lubrication, air compression, cooling, heating, pumping, etc., which have, on the one hand, high energy and material consumption and, on the other hand, losses due to an inherent departure from reversible processes.
This paper presents an energy-flow methodology to determine the ratio between the additional energy required per useful energy unit for the manufacturing processes. As an application of the method proposed in this work, an assembly and welding production line is shown as a case study. This process is a common technique used in the manufacturing industry and its energy consumption depends on several parameters e.g. heat and electrical input. As a result of this study, the energy consumption of the production line has been reduced by approximately 30% from the 645.94 Wh of total energy consumption, where the consumption of real useful energy is 4% of this total.
Effect of Structure on the Electrochemical Oxidation Rate of Copper and Nickel Sulfides
Authors: Nechvoglod O.V. , Selivanov Evgeny N. , Mamyachenkov S.V.
Published: May 2012

Synthesized samples were crystallized at 10 - 1000 K/sec (νcooling) to study the effect of sulfides structure on the electrochemical oxidation rates. The methods of X-ray, optical and electronic microscopy are used to analyze the phase composition, and the methods of voltamperometry and chronoamperometry are used to study the laws of electrochemical oxidation. Slow cooling of the samples with sulfide phase (Cu1,96S, Ni3S2) leads to crystallization of the metal (Ni, Cu). High cooling rate leads to crystallization of non-equilibrium phases, increasing of proportion of the sulfide phase and decreasing of metallic component up to complete disappearance. It is shown that electrochemical oxidation of copper and nickel sulfides proceeds stepwise: Me2S Me2-XS Me1+XS MeS Me2+ + S. Experiments have revealed the rates of electrochemical oxidation of granular sulfides that exceed the rates established for the slowly cooled samples. The rates of the electrochemical oxidation of Ni3S2 at potential of 1500 mV are 8.810-8 g/sec·mm2 (at vcooling = 10 К/sec) and 1.310-7 g/sec·mm2 (at νcooling = 1000 К/sec). The rates of the electrochemical oxidation of Cu2S at potential of 1000 mV are 2.810-8 g/sec·mm2 (at νcooling = 10 К/sec) and 4.310-8 g/sec·mm2 (at νcooling = 1000 К/sec).
It is found that the forming of a passivation layer effects the rate of the electrochemical oxidation of copper sulfide and nickel sulfide. Non-equilibrium phase composition and refinement provide greater reactivity of sulfides in the conditions of anodic polarization. The oxidation and passivation of metallic phase along with sulfide phases proceed from the surface of Me2S Me alloys. As for the samples crystallized at 1000 K/sec only anodic oxidation of sulfides occurs due to a lack of metallic phase. The compositions of passivation films and potentials providing the extraction of sulfur in the elemental state from the sulfides crystallized at high rates were determined.
Assessment of Heat Affected Zone of Submerged Arc Welding Process through Digital Image Processing
Authors: Ghosh Aniruddha , Chattopadhyaya Somnath , Singh N.K.
Published: May 2012

Submerged arc welding (SAW) is a high quality, high deposition rate welding process commonly used to join plates of higher thickness in load bearing components. This process of arc welding provides a purer and cleaner high volume weldment that has relatively a higher material deposition rate compared to the traditional welding methods. A common issue in the application of SAW process raises a concern about the uncertainties involved with the heat affected zone (HAZ) in and around the weldment. The most intriguing issue is about HAZ softening that imparts some uncertainties in the welded quality. It increases the probability of fatigue failures at the weakest zones caused by the heating and cooling cycle of the weld zone. An attempt has been made in this paper to assess the heat affected zone of submerged arc welding of structural steel plates through the analysis of the grain structure by means of digital image processing techniques.
Dispersion in Metal Foam: A Pore Scale Numerical Study
Authors: Hugo Jean Michel , Topin Frédéric
Published: May 2012

We determine thermal dispersion in metal foams using a pore scale numerical approach. Samples are contained in a channel crossed by a steady fully established fluid flow. The size of the foam sample is chosen according to a Representative Elementary Volume (REV).Two configurations are tested with several foam structures, pore size and pore shape. In the first configuration, heat and mass fluxes are in the same direction, in the second one, fluxes are perpendicular such as in heat exchanger. Results obtained on apparent fluid phase conductivity are discussed along with pressure drop data and compared to available literature data.
Back Diffusion during Zone Melting of Metallurgical Silicon
Authors: Mei Paulo Roberto , Moreira S.P. , Côrtes A.D.S. , Silva D.S. , Marques F.C.
Published: May 2012

As the silicon melting point is very high (1414 °C), the temperature in the solid fraction, near the interface solid/liquid during solidification is also high and this can provoke a solute redistribution in the solidified portion. This phenomena is called back diffusion. So, it is important to estimate the potential of back diffusion during the solidification processes. This calculation is complex and there is commercial software, such as DICTRA, to do this in binary alloys. For zone melting, a simple method to predict the extension of the back diffusion is not available. In this study, it was developed a simple method to evaluate the back diffusion during zone melting, which does not require computational calculation.
Heat Transfer Enhancement Using Cu-Water Nanofluid in an Enclosure with Moving Cold Sidewalls
Authors: Sheikhzadeh Ghanbar Ali , Tavakoli M. , Alizadeh H.
Published: May 2012

Mixed convection of Cu-water nanofluid in a lid-driven square cavity with a heat source embedded in the bottom wall is studied numerically. The governing equations together with the respective boundary conditions are solved numerically using the finite volume method and the SIMPLER algorithm. The computations are performed for various Richardson numbers (), heat source length () and volume fraction of the nanoparticles (). It is observed from the results that the average Nusselt number is increased by increasing the Richardson number and the volume fraction of the nanoparticles. Moreover, the maximum temperature at the heat source surface decreases by increasing the Richardson number and the volume fraction of the nanoparticles.
Phase Field Simulation of the Collapse of the Rafted Structure in Ni-Based Superalloys
Authors: Tanimoto Toshiya , Tsukada Yuhki , Murata Yoshinori , Koyama Toshiyuki
Published: May 2012

Microstructural evolution in single crystal Ni-based superalloys is investigated by the phase field simulation. During creep, the morphology of the γ phase changed from the cuboidal shape to the rafted one, and the rafted structure was collapsed in the late stage of creep. The simulation on the microstructural evolution is based on thermodynamic information, diffusion equation, elastic anisotropy and a homogeneous lattice misfit. It is found that caused by external stress result in the morphological change of the γ phase to the rafted structure, and this rafted structure is collapsed by inhomogeneous lattice misfit. These morphological changes can be explained by the change in stable morphology of the γ phase.
Metal-Ceramic Composite Foams and their Fire Resistance
Authors: Grabian Janusz
Published: May 2012

The development of aviation and outer space technologies necessitated working out new materials, resistant to increased temperatures, and satisfying specific requirements concerning high strength and low density. These requirements are met by metal composite materials produced by proper joining of the matrix (aluminium or magnesium alloys) and reinforcement components, mostly ceramic fibres, particles or whiskers. Such composite materials combine properties that traditional materials cannot yield. This contribution presents the method of composite foam production (SiC reinforcement, aluminium alloy matrix) by the mechanical method and testing of non-combustibility of these materials in accordance to the international FTP Code and the testing procedure PB-KTZ-01 (equivalent of ISO 1182).
Numerical Simulation of Rising Damp Phenomenon
Authors: Guimarães A.S. , Delgado João M.P.Q. , de Freitas V.P.
Published: May 2012

The treatment of rising damp in historical buildings walls is very complex. Moisture transfer in walls of old buildings, which are in direct contact with the ground, leads to a migration of soluble salts responsible for many building pathologies.
The present work describes an extensive numerical analyse of rising damp phenomenon, using the software WUFI-2D, developed by Fraunhofer Institute for Building Physics. The results show that the numerical simulation describes very well the rising damp front for different boundary conditions and materials. The influence of the wall thickness, boundary conditions, composition of walls and material properties, such as, porosity and water absorption coefficient were analysed in detail.
Determination of Creep Parameters of Ti-6Al-4V with Bimodal and Equiaxed Microstructure
Authors: Briguente L.A.N.S. , Couto Antônio Augusto , Guimarães Nara Miranda , Reis Danieli A.P. , de Moura Neto Carlos , Barboza M.J.R.
Published: May 2012

Ti-6Al-4V is the most used of titanium alloy and presents some important properties as metallurgical stability, high specific strength, corrosion and creep resistance [. The aim of this study is to evaluate the creep behavior of Ti-6Al-4V alloy with equiaxed and bimodal microstructures and determine the creep parameters of Ti-6Al-4V in these conditions. It was used a Ti-6Al-4V alloy forged and annealed at 190°C for 6 hours and cooled in air. The material in this condition shows an equiaxed microstructure. For bimodal microstructure, the material was heat-treated at 950°C for 60 minutes and cooled in water until room temperature. After this the material was heat-treated at 600°C for 24 hours and cooled in air until room temperature. Creep tests were performed at 600°C in stress conditions of 125, 250 and 319 MPa at constant load. The alloy with Bimodal microstructure shows higher creep resistance with a longer life time in creep.
The Analysis of Heat Transfer and Thermal Stresses in Thermal Barrier Coatings under Exploitation
Authors: Sadowski Tomasz , Golewski Przemysław
Published: May 2012

Effectiveness of internal combustion turbines in aero-engines is limited by comparatively low temperature of exhaust gas at the entry to turbine of the engine. A thermal efficiency and other capacities of turbine strongly depend on the ratio of the highest to the lowest temperature of a working medium. Continuous endeavour to increase the thermal resistance of engine elements requires, apart from laboratory investigations, also numerical studies in 3D of different aero-engine parts.
In the present work, the effectiveness of the protection of turbine blades by thermal barrier coating and internal cooling under thermal shock cooling was analysed numerically using the ABAQUS code. The phenomenon of heating the blade from temperature of combustion gases was studied. This investigation was preceded by the CFD analysis in the ANSYS Fluent program which allows for calculation of the temperature of combustion gases. The analysis was conducted for different levels of the shock temperature, different thickness of applied TBC, produced from different kinds of materials.
Numerical Simulation of Diffusive Processes in Heated Cylinder Using the Finite Volume and Finite Difference Methods
Authors: de Campos M.D. , Romão E.C. , Mendes de Moura L.F.
Published: May 2012

A comparative investigation of a series of numerical tests in the solution of heat transfer problems in the heated cylinder using radiation is presented. The numerical application, in steady state and cylindrical coordinates is studied through of Finite Volume and Finite Difference Methods. The numerical temperature profiles were compared with the analytical solution.
Measurement of the Transverse Diffusion Coefficient of Charge in Liquid Xenon
Authors: Chen W. T. , Carduner H. , Cussonneau J. P. , Donnard J. , Duval S. , Mohamad-Hadi A. F. , Lamblin J. , Lemaire O. , Le Ray P. , Morteau E. , Oger T. , Scotto-Lavina L. , Stutzmann J. S. , Thers D.
Published: May 2012

Liquid xenon (LXe) is a very attractive material as a detection medium for ionization detectors due to its high density, high atomic number, and low energy required to produce electron-ion pairs. Therefore it has been used in several applications, like γ detection or direct detection of dark matter. Now Subatech is working on the R & D of LXe Compton telescope for 3γ medical imaging, which can make precise tridimensional localization of a (β+, γ) radioisotope emitter. The diffusion of charge carriers will directly affect the spatial resolution of LXe ionization signal. We will report how we measure the transverse diffusion coefficient for different electric field (0.5 ~ 1.2 kV/cm) by observing the spray of charge carriers on drift length varying until 12 cm. With very-low-noise front-end electronics and complete Monte-Carlo simulation of the experiment, the values ​​of transverse diffusion coefficient are measured precisely.
Effect of Manganese on Titanium Thin Films Adhesion Deposited on Steel Substrates
Authors: Gheriani R. , Mechiakh Raouf
Published: May 2012

The mainly property of thin solid films technologies is their adhesion to the substrates. Because of its good wear resistance and its low coefficient of friction against steel, TiC is an attractive coating material for wear applications such as bearing components. The adhesion of TiC coatings, however suffers from insufficient reproducibility, which is probably due to uncontrolled process parameters. In our work pure titanium thin films of approximately 0.6 µm in thickness were prepared on 100C6 stainless steel substrates by cathodic sputtering. The samples were subjected to secondary vacuum annealing at a temperature between 400 and 1000°C for 30 min. The reaction between substrates and thin films was characterized using an x-ray diffractometer (XRD). Surface morphology and elements diffusion evaluations were carried out by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The interaction substrates-thin films is accompanied by nucleation and growth of titanium carbide as a function of annealing temperature. By the SEM and EDS results, it appears clearly that the diffusion of manganese to the external layers leads to the destruction of adhesion especially at high temperatures.
Thermal Expansion of Alloys from the Al-Fe System
Authors: Śmiglewicz Anna , Jabłońska Magdalena
Published: May 2012

In this work, the results of a dilatometric study of alloys on the base of the Al-Fe system were presented. Thermal expansion investigations of the alloys of the Al-Fe system with concentration of Al equal to - 38, 48, 58 at.% were also presented. The alloys were obtained by classical casting technique. The thermal expansion studies of the alloys were carried out by dilatometric analysis method using a Setsys thermal analyzer made by Setaram. A linear thermal expansion coefficient α was calculated using standard methods. A temperature dependence of the α coefficient was noted. The results are an important supplement of knowledge on the alloys of the Al-Fe system.
Influence of Thermal Treatment on the Heat Transfer of 10GN2MFA Steel
Authors: Seidl David , Koštial Pavel , Jonšta Petr , Jančíková Zora , Ružiak Ivan
Published: May 2012

Three samples of 10GN2MFA steel were thermally treated at quenching temperatures equal to 900°C, 1000°C and 1100°C, and temperature of the tempering was 670°C. Thermo-physical properties of the steel were modelled by lumped capacity model. The sample was mechanically stressed under yield strength and then the cooling curve of stressed material on air was measured. The heat transfer through grips was taken into account. Thermo-physical properties were obtained by parametric fitting of time-temperature data obtained from cooling curve. Both thermal diffusivity and thermal conductivity increase with the quenching temperature. Specific heat capacity of steel samples after thermal treatment does not change significantly. All the measured thermo-physical parameters were in good agreement with the table values for low carbon Ni steels.
Flow Controllability of Hydrogen Diffusion Driven by Local Stress Field for Steel under Cyclic Loading Condition
Authors: Ohmi Toshihito , Yokobori Jr. A.Toshimitsu , Takei Kenichi
Published: May 2012

The hydrogen diffuses and accumulates at the stress concentration area like a crack tip and it causes hydrogen embrittlement. To clarify the mechanism of hydrogen embrittlement, it is important to obtain the hydrogen concentration behavior. However, experimental detection is not feasible due to the high diffusivity of hydrogen and numerical analyses have been preceded. In this paper, by using a finite element and finite difference coupled method at which the diffusion analysis is performed by FDM coupled with the stress analysis by FEM, the analyses of hydrogen diffusion were conducted under cyclic loading conditions.
Effect of Synthesis Duration on the Physicochemical Properties of Siliceous Mesoporous Molecular Sieve (Si-MMS)
Authors: Ramli Anita , Ahmed Sohail , Yusup Suzana
Published: May 2012

Pure silica mesoporous molecular sieve (MMS) solid has been synthesized at 100°C by hydrothermal process. The effect of synthesis duration from 2 to 10 days has been investigated on the physicochemical properties of mesoporous molecular sieve. Samples were characterized by low angle XRD, N2 adsorption-desorption and HRTEM analysis. XRD patterns of the as-synthesized samples showed four well-defined diffraction peaks corresponding to 100, 110, 200 and 210 planes. These peaks are the fingerprint characteristics of MCM-41 mesoporous material. The high intensity diffraction peaks were observed in 8-days sample that define the high ordering of the pores and long range order. N2 adsorption-desorption results showed that all samples possessed a type IV isotherm having hysteresis loop of type H1 which is an identification of mesoporous material. Calcined samples exhibited high surface area i.e., 984-1036 m2 g-1, pore volume i.e., 1.00-1.13 cm3 g-1 and average pore diameter i.e., 3.04-3.30 nm. A hexagonal pore structure was found in the synthesized materials by HRTEM analysis, which confirms that the synthesized materials are MCM-41. HRTEM analysis showed the effect of synthesis duration on the materials and found that 8-days sample exhibited highly ordered hexagonal pore structure like honeycomb structure. All the samples were calcined at 550°C to remove the template and to study the changes in the mesoporous framework. The results showed that the mesoporous structure remained intact after calcination at 550°C, indicating that the mesoporous materials exhibit high thermal stability.
Exploitation of Artificial Intelligence Methods for Prediction of Atmospheric Corrosion
Authors: Seidl David , Jančíková Zora , Koštial Pavel , Ružiak Ivan , Kopal Ivan , Kreislova Katerina
Published: May 2012

The contribution deals with the use of artificial neural networks for prediction of corrosion loss of structural carbon steel. Nowadays there is certain chance to predict a corrosion loss of materials by artificial intelligence methods, especially by neural networks. A model of neural network for prediction of corrosion loss of structural carbon steel based on the input environmental parameters affecting the corrosion of metals in the atmospheric environment (temperature, relative humidity, air pollution by sulphur dioxide and the exposition time) was created. The model enables to predict corrosion loss of steel with a sufficiently small error.
The Effect of Shading Devices in Rising Damp Phenomenon of Historical Buildings
Authors: Delgado João M.P.Q. , Guimarães A.S. , de Freitas V.P.
Published: May 2012

Rising damp is the upward movement of ground water through a permeable masonry wall. The water rises through the pores in the masonry via a process called capillarity. Capillarity is a process whereby water molecules are electrochemically attracted to mineral surfaces, enabling water to move vertically through pores of a certain size despite the counteractive force of gravity. The great majority of the papers presented in literature only analyse the external shading effect on building energy conservation; and this work intends to present a preliminary analyse of the effect of shadows in rising damp phenomenon. We present an exhaustive numerical analyse of the shading effect on historical buildings. The shading effect due vertical nearby obstacles, as trees, or horizontal obstacles is causing mould and or rising damp phenomenon in historical buildings, as a result of moisture increasing. The results show the importance of obstacles (shading effect), as trees, nearby the old constructions in the rising damp, namely in the height of steady-state capillary rise and in the drying process.
Quantum Dots Based Optical Sensors
Authors: Lobnik Aleksandra , Korent Urek Špela , Turel Matejka
Published: May 2012

Luminescent sensors are chemical systems that can deliver information on the presence of selected analytes through the variations in their luminescence emission. With the advent of luminescent nanoparticles several new applications in the field of chemical sensing were explored. Among them, quantum dots (QD) represent inorganic semiconductor nanocrystals that are advantageous over conventional organic dyes from many different points of view. In this short review, the optical detection of various analytes using QD-based probes/sensors is presented and significant sensors characteristics are discussed. The biosensing approaches are not included in this article.
The Influence of Carbon Fillers on Thermal Transport in Polyurethane
Authors: Koštial Pavel , Jančíková Zora , Stýskala Vítězslav , Kubliha Marián , Madaj Rudolf , Ružiak Ivan , Dedičová Jana , Hrehuš Rudolf , Jonšta Petr
Published: May 2012

The paper is devoted to the study of thermal, as well as mechanical properties of polyurethane samples (PU) filled by carbon black (CB), graphite (G) and MWCNT(CNT). Thermal conductivity k(W.m-1.K-1), specific heat capacity cp(J.kg-1.K-1) and thermal diffusivity a(mm2.s-1) were measured by the impulse method. An increase of all the above mentioned thermal parameters after addition of fillers under investigation was observed. The dc electrical conductivity drastically increases from PUPU+CBPU+GPU+CNT.
Diffusion of Oxygen and Nitrogen in the Ti-15Mo Alloy Used for Biomedical Applications
Authors: Martins José Roberto Severino , Nogueira Renata Abdallah , de Araújo Raul Oliveira , Grandini Carlos Roberto
Published: May 2012

The Ti-15Mo alloy is a promising material for use as a biomaterial because of its excellent corrosion resistance and its good combination of mechanical properties, such as fatigue, hardness, and wears resistance. This alloy has a body-centered predominantly cubic crystalline structure and the addition of interstitial atoms, such as oxygen and nitrogen, strongly alters its mechanical properties. Mechanical spectroscopy is a powerful tool to study the interaction of interstitial elements with the matrix metal or substitutional solutes, providing information such as the distribution and the concentration of interstitial elements. The objective of this paper is to study of the effects of heavy interstitial elements, such as oxygen and nitrogen, on the anelastic properties of the Ti-15Mo alloy by using mechanical spectroscopy measurements. In this study, the diffusion coefficients, pre-exponential factors, and activation energies were calculated for the oxygen in the Ti-15Mo alloy.
Study of the Anelastic Behavior of PZT and PLZT Ferroelectric Ceramics
Authors: Florêncio Odila , Silva Paulo Sergio , Eiras José Antônio , Garcia Ducinei , Botero Eriton Rodrigo
Published: May 2012

The anelastic behavior of the ferroelectric ceramics (Pb)(Zr/Ti)O3 (PZT) and (Pb/La)(Zr/Ti)O3 (PLZT), with Zr/Ti = 65/35, La = 5 at.% and 8 at.%, was investigated in the region of the ferroelectric phase transitions. Anelastic spectroscopy experiments were performed in an acoustic elastometer system, operating in a kilohertz bandwidth, at temperatures rising from 300 K to 770 K, at a heating rate of 1 K/min, under pressure of 10-5mbar. Anelastic measurements on PZT showed only one anomaly, associated with the occurrence of a ferroelectric-paraelectric phase transition, while the PLZT data showed two anomalies, which were associated with the following transitions: the ferroelectric-paraelectric phase transition and a ferro-ferroelectric phase transition between distinct rhombohedral ferroelectric phases. The behavior of the relative variation of the elastic moduli with temperature, near the phase transitions, which describes the change in the type of coupling between strain and the order parameter in ferroelectric-paraelectric phase transition, with the increase of lanthanum amount and, linear coupling in the strain and order parameter type to PZT ceramic and linear coupling in the strain but quadratic in order parameter type for PLZT ceramics.
Numerical Simulation of 2D Flow through a Packed Bed of Square Cylinders
Authors: Ferreira de Sousa P.J.S.A. , Malico Isabel , Fernandes Gérson
Published: May 2012

This paper is centred on a compact finite differences method for the calculation of two-dimensional viscous flows through complex geometries. The immersed boundaries are set through body forces that allow for the imposition of boundary conditions that coincide with the computational grid. Two different flow configurations are simulated. First, the flow past a cylinder with square cross-section inside a plane channel is calculated. The computed average drag coefficient and Strouhal number are compared to data available in the literature. The agreement between the results is good. The second flow configuration analyzed is the flow through a porous matrix composed of equal size staggered square cylinders. Flow visualization results are shown. The work presented in this paper illustrates the potential of the immersed boundary method in general and of this implementation in particular to simulate the flow through porous matrices.
Novel Arrangement of Rough Tubes for Heat Flux Improvement
Authors: Farahbod Farshad , Farahmand Sara , Farahbod Farzaneh
Published: May 2012

The objective of the research is to represent a novel arrangement of conical three dimensional rough tubes (FS3D) for heat transfer coefficient enhancement. Experiments were performed with 316 stainless steel tubes of FS3D roughness and hot crude oil was circulated in constant heat flux condition in the related set up. The pressure drop is measured in this set up and compared with the pressure drop in a smooth tube with the same operating conditions. The heat transfer coefficient is one of essential parameters for design of heat transfer equipments and in this experimental work this is investigated for an Iranian crude oil in the FS3D rough tube. The heat transfer coefficient in FS3D rough tubes is higher than in other commercial enhanced tubes. FS3D rough tubes improve the performance of heat transfer equipments and also optimize the size of the mentioned devices. Consequently this type, the FS3D rough tube, is advantageous in energy and cost saving.
Fabrication of 4H-SiC/Nanocrystalline Diamond PN Junctions
Authors: Amano Ryo , Goto Masaki , Kato Yoshimine , Teii Kungen
Published: May 2012

Nitrogen-incorporated, n-type nanocrystalline diamond (NCD) films are deposited on p-type Si(001) and 4H-SiC(0001) substrates by moderate-pressure, microwave plasma-enhanced chemical vapor deposition using a mixture of 1%CH4-30%N2-69%Ar. X-ray diffraction and visible Raman spectroscopy reveal that the structure of the NCD films is identical independent of the substrate materials, such that diamond nanoparticles with apparent crystal sizes of 5-8 nm are embedded in amorphous sp2 carbon matrix. For p-Si/n-NCD heterojunctions in a diode configuration, the rectifying behavior in current-voltage curves depends upon the substrate temperature for film deposition, and the rectification ratio reaches a maximum of about 300 when the film is deposited at 830 °C. For p-4H-SiC/n-NCD heterojunctions, the rectification ratio increases greatly to about 10000 when the film is deposited at 830 °C due exclusively to suppression of the reverse leakage current.
Reliable Operation of 1200-V SiC Vertical Junction-Field-Effect-Transistor Subjected to 16,000-Pulse Hard Switching Stressing
Authors: Lawson Kevin , Alvarez G. , Bayne S. B. , Veliadis Victor , Ha H.C. , Urciuoli Damian , Scozzie C.
Published: May 2012

A necessity for the successful commercialization of SiC power devices is their long term reliability under the switching conditions encountered in application. Normally-ON 1200 V SiC JFETs were stressed in hard-switching conditions to determine their fault handling capabilities. The hard-switching included single shot tests ranging from drain voltages of 100 V to 500 V and repetition rate tests at 1 Hz, 5 Hz, 10 Hz, and 100 Hz with peak currents exceeding 100 A (8 times the rated current at 250 W/cm22). The JFET conduction and blocking-voltage characteristics are unchanged after 4,000 pulsed and numerous single shot hard switching events proving the devices are reliable for handling high surge-current faults.
Characterization of SiC JFET in Novel Packaging for 1 MHz Operation
Authors: Okamura Katsuya , Ise Keiichi , Wake Masayoshi , Osawa Yutaka , Takaki Koichi , Takayama Ken
Published: May 2012

A high power discrete SiC-JFET package for accelerator applications has been developed and tested. Successful operation with a dc voltage of 1 kV, a drain current of 27 A, and a repetition rate of 1 MHz was confirmed. Thermal analysis was carefully attempted. The heat dissipation capacity of 235 W with a water-cooled heat sink and the thermal resistance from its junction to outer-surface of 0.56 K/W were demonstrated. These results exhibit the SiC-JFET is a promising device for a switching power supply in future digital accelerators.
Design of an Integrated SiC JFET Power Switch and Flyback Diode
Authors: Radhakrishnan Rahul , Zhao Jian Hui
Published: May 2012

In this paper, we describe the design of a high voltage SiC VJFET monolithically integrated with a JBS diode. The integrated device that was demonstrated up to 834 V in forward blocking doesn’t add any steps to the VJFET fabrication process. While the diode and VJFET share the same surface field termination mechanism, they are partially isolated using implanted field rings. We describe TCAD based optimization of the dimensions of these field rings and outline the design of the JBS diode using a fully analytical 2-D model.
High Performance SiC IEMOSFET/SBD Module
Authors: Harada Shinsuke , Hoshi Yasuyuki , Harada Yuichi , Tsuji Takashi , Kinoshita Akimasa , Okamoto Mitsuo , Makifuchi Youichi , Kawada Yasuyuki , Imamura Kouji , Gotoh Masahide , Tawara Takeshi , Nakamata Shinichi , Sakai T. , Imai Fumikazu , Ohse Naoyuki , Ryo Mina , Tanaka Atsushi , Tezuka Kazuo , Tsuyuki Tatsurou , Shimizu Saburou , Iwamuro Noriyuki , Sakai Yoshiyuki , Kimura Hiroshi , Fukuda Kenji , Okumura Hajime
Published: May 2012

SiC power module with low loss and high reliability was developed by utilizing IEMOSFET and SBD. The IEMOSFET is the SiC MOSFET with high channel mobility in which the channel region is the p-type carbon-face epitaxial layer with low acceptor concentration. Elemental technologies for the high channel mobility and the high reliability of the gate oxide have been developed to realize the excellent characteristics by the IEMOSFET. The SBD was designed so as to minimize the forward voltage drops and the reverse leakage current. For the fabrication of these SiC power devices, the mass production technology such as gate oxidation, ion implantation and following activation annealing have been also developed.
High-Temperature Performance of 1200 V, 200 A 4H-SiC Power DMOSFETs
Authors: Cheng Lin , Ryu Sei Hyung , Agarwal Anant K. , O'Loughlin Michael  J. , Burk Albert A. , Richmond Jim , Lelis Aivars J. , Scozzie Charles , Palmour John W.
Published: May 2012

We have investigated the thermal behavior of our recently developed 1200 V, 200 A 4H-SiC power DMOSFETs operating from 20°C up to 300°C. Compared to the first generation SiC DMOSFET that was commercially released early this year, this 4H-SiC power DMOSFET shows a ~ 50% reduction in the total specific on-resistance at room temperature. Temperature dependence of the key parameters of this MOSFET, such as on-resistance, threshold voltage, and the MOS channel mobility, are reported in this paper. The MOSFET showed normally-off characteristics throughout the entire experimental temperature range. Different temperature dependence of the total on-resistance in different temperature regimes has been observed.
SiC MOSFET Reliability Update
Authors: Das Mrinal K. , Haney Sarah K. , Richmond Jim , Olmedo Anthony , Zhang Q. Jon , Ring Zoltan
Published: May 2012

Significant advancement has been made in the gate oxide reliability of SiC MOS devices to enable the commercial release of Cree’s Z-FET™ product. This paper discusses the key reliability results from Time-Dependent-Dielectric-Breakdown (TDDB) and High Temperature Gate Bias (HTGB) measurements that indicate that the SiC MOSFETs can demonstrate excellent lifetime and stable operation in the field.
Large Area 1200 V SiC BJTs with β>100 and ρON<3 mΩcm2
Authors: Domeij Martin , Konstantinov Andrei , Lindgren Anders , Zaring Carina , Gumaelius Krister , Reimark Mats
Published: May 2012

Large (4.3 mm2) area SiC BJTs were demonstrated with a current gain of 117 and a specific on-resistance of 2.8 mΩcm2. The open-base and open-emitter breakdown voltages are stable and with margin sufficient for 1200 V blocking. Fast and tail-current free switching behaviour was shown with rise- and fall-times in the range of 10-30 ns and the SiC BJTs were shown to be rugged in short-circuit and unclamped inductive switching.
1200 V-Class 4H-SiC “Super” Junction Transistors with Current Gains of 88 and Ultra-Fast Switching Capability
Authors: Singh Ranbir , Jeliazkov Stoyan , Lieser Eric
Published: May 2012

1200 V-Class Super-High Current Gain Transistors or SJTs developed by GeneSiC are distinguished by low leakage currents of 2. Two-stage cascaded SJTs display a record high current gain of 3475. Results from detailed on-state, blocking, switching and reliability characterization of 1200 V-class 4 mm2 and 16 mm2 SiC SJTs are presented in this paper.
Investigation of Current Gain Degradation in 4H-SiC Power BJTs
Authors: Buono Benedetto , Ghandi Reza , Domeij Martin , Malm B. Gunnar , Zetterling Carl Mikael , Östling Mikael
Published: May 2012

The current gain degradation of 4H-SiC BJTs with no significant drift of the on-resistance is investigated. Electrical stress on devices with different emitter widths suggests that the device design can influence the degradation behavior. Analysis of the base current extrapolated from the Gummel plot indicates that the reduction of the carrier lifetime in the base region could be the cause for the degradation of the gain. However, analysis of the base current of the base-emitter diode shows that the degradation of the passivation layer could also influence the reduction of the current gain.
Development of 15 kV 4H-SiC IGBTs
Authors: Ryu Sei Hyung , Cheng Lin , Dhar Sarit , Capell Craig , Jonas Charlotte , Clayton Jack , Donofrio Matt , O'Loughlin Michael  J. , Burk Albert A. , Agarwal Anant K. , Palmour John W.
Published: May 2012

We present our latest developments in ultra high voltage 4H-SiC IGBTs. A 6.7 mm x 6.7 mm 4H-SiC N-IGBT with an active area of 0.16 cm2 showed a blocking voltage of 12.5 kV, and demonstrated a room temperature differential specific on-resistance of 5.3 mΩ-cm2 with a gate bias of 20 V. A 4H-SiC P-IGBT exhibited a record high blocking voltage of 15 kV, while showing a differential specific on-resistance of 24 mΩ-cm2. A comparison between P- and N- IGBTs in 4H-SiC is provided in this paper.
Ultra high performance of 12kV Clustered Insulated Gate Bipolar Transistor (CIGBT) in 4H-SiC
Authors: Menon Kalyani G. , Ngwendson Luther King , Nakajima Akira , Sankara Narayanan Ekkanath Madathil , Bruce Graham P.
Published: May 2012

The performance of a 12kV planar Clustered Insulated Gate Bipolar Transistor (CIGBT) is compared to an equivalent IGBT in 4H-SiC through extensive 2D numerical simulations. The CIGBT shows 40% reduction in Eoff-Vce(sat) trade off losses with a short circuit endurance time of more than 10µs.
Integrated SiC Anode Switched Thyristor Modules for Smart-Grid Applications
Authors: Sundaresan Siddarth G. , Lieser Eric , Singh Ranbir
Published: May 2012

Silicon Carbide Anode Switched Thyristors (ASTs) overcome major limitations of conventional Si and SiC IGBT and GTO Thyristor solutions by providing robust, latch-up free turn-off at high currents, current saturation in the output characteristics, and a wide safe operating area (SOA) through series current controlled device turn-off. In this work, detailed static and switching characteristics of 6.5 kV-class SiC ASTs are reported, which include a low on-state voltage drop of 4 V at 100 A/cm2, slight positive temperature co-efficient of Von, current saturation at > 100 A Cathode currents and fast turn-on and turn-off times of 500 ns while switching 1300 V and 20 A.
Fabrication and Characterization of 4H-SiC 6kV Gate Turn-Off Thyristor
Authors: Lin Lei , Zhao Jian Hui
Published: May 2012

In this paper, we report a 0.1cm2 4H-SiC gate-turn-off (GTO) thyristor with 6 kV blocking voltage fabricated on a structure with a 60µm blocking layer. A relatively large area, high voltage 4H-SiC GTO that exhibits encouraging characteristic at the on- and off-states, and a low leakage current with 63% devices blocking 3kV or higher. Initial pulse testing result shows that the fabricated GTOs are capable of both high current density and high turn-off speed.
Comparison of 4H Silicon Carbide Epitaxial Growths at Various Growth Pressures Using Dicholorosilane and Silane Gases
Authors: Rana Tawhid , Song Hai Zheng , Chandrashekhar M.V.S. , Sudarshan Tangali S.
Published: May 2012

SiC epitaxial films grown in an inverted chimney CVD reactor using silane-propane-hydrogen and dichlorosilane (DCS)-propane-hydrogen systems are compared for growth rates and doping concentrations at various growth pressures. Parasitic depositions in the gas injector tube using these precursor gases are also compared for precursor depletion. Virtual Reactor, a commercial software, is employed to predict growth rates and compare them to experimental results for the same growth conditions using DCS and silane gases.
High-Yield 4H-SiC Thyristors for Wafer-Scale Interconnection
Authors: Nechay Bettina , Snook Megan , Hearne Harold , McNutt Ty , Veliadis Victor , Woodruff Sharon , Howell R.S. , Giorgi David , White Joseph , Davis Stuart
Published: May 2012

Modern power conditioning systems require large active area devices which can support high currents. Though the breakdown and thermal properties of SiC make it an excellent choice for power switching applications, active area size is currently limited due to material and processing defects. One alternative is to parallel discrete diced die to achieve large active areas. However, this increases cost and complexity through dicing, soldering, and forming multiple wire bonds. Furthermore, paralleling discrete devices increases package volume/weight and reduces power density. To overcome these issues and achieve devices of high current switching capabilities, thyristors were designed and fabricated for the purpose of wafer-scale interconnection - which avoids the need of dicing and bonding and can achieve significant current density improvement over the paralleled diced device approach. Discrete thyristors fabricated for interconnection exhibited excellent yields and good uniformity of both blocking and on-state characteristics, showing great promise for large-scale interconnection.
Pulse Characterization of Optically Triggered SiC Thyristors
Authors: Dheilly Nicolas , Pâques Gontran , Scharnholz Sigo , Planson Dominique
Published: May 2012

This paper deals with the pulse capabilities of 4H-SiC optically triggered thyristors. The device structure and the fabrication process are presented. The results of pulse characterizations are shown. Two types of current pulses were used, a short (pulse width of 10 µs) and a long (pulse width of 650 µs). Peak current densities of 17 kA.cm-2 and 4 kA.cm-2 were attained with short and long pulses respectively. The failures and degradation caused by these experiments are also shown in this paper.
Characterization of Large Area 4H-SiC and 6H-SiC Capacitive Devices at 600 °C
Authors: Ghosh Ruby N. , Loloee Reza
Published: May 2012

SiC based capacitive devices have the potential to operate in high temperature, chemically corrosive environments provided that the electrical integrity of the gate oxide and metallization can be maintained in these environments. We report on the performance of large area, up to 8 x 10-3 cm2, field-effect capacitive sensors fabricated on both the 4H and 6H polytypes at 600°C. Large area capacitors improve the signal/noise (S/N) ratio which is proportional to the slope of the capacitance-voltage characteristic. At 600 °C we obtain a S/N ~ 20. The device response is independent of polytype, either 4H or 6H-SiC. These results demonstrate the reliability of our field-effect structure, operating as a simple potentiometer at high temperature.
Development of High Temperature SiC Based Hydrogen/Hydrocarbon Sensors with Bond Pads for Packaging
Authors: Xu Jennifer C. , Hunter Gary W. , Chen Liang Yu , Biaggi-Labiosa Azlin M. , Ward Benjamin J. , Lukco Dorothy , Gonzalez III Jose M. , Lampard Peter S. , Artale Michael A. , Hampton Christopher L.
Published: May 2012

This paper describes efforts towards the transition of existing high temperature hydrogen and hydrocarbon Schottky diode sensor elements to packaged sensor structures that can be integrated into a testing system. Sensor modifications and the technical challenges involved are discussed. Testing of the sensors at 500°C or above is also presented along with plans for future development.
Laser-Doped SiC as Wireless Remote Gas Sensor Based on Semiconductor Optics
Authors: Lim Geunsik , Manzur Tariq , Kar Aravinda
Published: May 2012

An uncooled SiC-based electro-optic device is developed for gas sensing applications. P-type dopants Ga, Sc, P and Al are incorporated into an n-type crystalline 6H-SiC substrate by a laser doping technique for sensing CO2, CO, NO2 and NO gases, respectively. Each dopant creates an acceptor energy level within the bandgap of the substrate so that the energy gap between this acceptor level and the valence band matches the quantum of energy emitted by the gas of interest. The photons of the gas excite electrons from the valence band to the acceptor level, which alters the electron density in these two states. Consequently, the refractive index of the substrate changes, which, in turn, modifies the reflectivity of the substrate. This change in reflectivity represents the optical signal of the sensor, which is probed remotely with a laser such as a helium-neon laser. Although the midwave infrared (3-5 mm) band is studied in this paper, the approach is applicable to other spectral bands.
Silicon Carbide Ultraviolet Photodetector Modeling, Design and Experiments
Authors: Akturk Akin , Dandin Marc , Vert Alexey V. , Soloviev Stanislav I. , Sandvik P. , Potbhare Siddharth , Goldsman Neil , Abshire Pamela
Published: May 2012

We report measurements and modeling of silicon carbide (SiC) based ultraviolet photodetectors for the detection of light in the mid-to-short ultraviolet range where SiC’s absorption coefficients are high and the corresponding penetration depths are low. These large absorption coefficients result in increased susceptibility of photo-generated electron and holes to surface recombination and therefore give rise to lower quantum efficiencies. To increase responsivity and extend the detection capability of these photodetectors to short ultraviolet wavelengths (or UVC), we measure an existing silicon carbide avalanche photodiode (APD) designed and fabricated for 280 nm operation by General Electric Global Research Center, and then develop models and techniques to increase their operation range to lower UV wavelengths. The measurements aid the development and calibration of a silicon carbide modeling and design suite that is currently being used to assist the design of a new silicon carbide APD for UVC detection. Here the design considerations require low operating voltages, low noise, low dark count rate and high responsivity. We plan to satisfy design criteria by engineering thickness and doping of stacked layers as well as by designing an APD surface that gives rise to minimal recombination of electrons and holes generated by the incident light.
Characterization of Poly-SiC Pressure Sensors for High Temperature and High Pressure Applications
Authors: Jin Sheng , Rajgopal Srihari , Mehregany Mehran
Published: May 2012

We report two improvements of our all-silicon carbide (SiC) micromachined capacitive diaphragm-based pressure sensors: Ti/TaSi2/Pt contact metallization to enhance temperature cycling durability and a 0.5 μm-thin sensing gap to further improve sensor sensitivity. Three sensors with 0.5 μm and 1.5 μm sensing gaps were packaged individually in high temperature ceramic packages and characterized to designed (static) pressures of 2.1 MPa (300 psi), 3.4 MPa (500psi) and 6.9 MPa (1000 psi) up to 550°C. For the 3.4 MPa range sensor (0.5 μm gap, 70 μm diaphragm radius), a sensitivity of 0.06 fF/Pa and a nonlinearity of 2.0% was obtained at 550°C in contact mode operation. In comparison, the 2.1 MPa range sensor (1.5 μm gap, 95 μm diaphragm radius) demonstrated a sensitivity of 0.07 fF/Pa and a nonlinearity of 4.6% at 550°C in contact mode operation. The 6.9 MPa range sensor (1.5 μm gap, 70 μm diaphragm radius) demonstrated a sensitivity of 0.03 fF/Pa and a nonlinearity of 4.0% at 500°C, also in contact mode.