bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis on the Performance of High Insulation Materials for Current Bending XLPE Cable
Authors: Yu Xin , Gao Peng Fei , Gao Nai Kui , Huang Zhen , Jin Hai Yun
Published: June 2018

Cross-linked polyethylene (XLPE) as insulation material has been widely used in the manufacturing of medium and high voltage cables for its excellent physical, chemical, mechanical and electrical properties. However, as cable insulation, the XLPE will degradate under service conditions, such as thermal oxidative degradation, mechanical treatment, operating environment etc. In this paper, the closed cable loop had been heated for 7 days by induced current of 1000A, and several diagnostic measurements had been adopted to characterize the performance of XLPE. Firstly FTIR has been conducted on different bending degree cable samples in order to reveal the effect of mechanical treatment on the content changes which occur in XLPE insulation layers. DSC analysis showed the effect of cooling process on the shoulder melting peak temperatures. In the last part, microstructure of the insulation of high current bending XLPE cable was studied. The results showed that the properties of the bending cable after heating by the high current changed a lot and the degree of bending also has an effect on the performance of the cable.
Analysis of Physical and Chemical Properties of XLPE Insulation for Long Term Running Cable
Authors: Zhang Tao , Nie Shi Chao , Pan Ze Hua , Li Zhi Wei , Gao Nai Kui , Yu Xin
Published: June 2018

High temperature caused by copper core would have a certain impact on the performance of XLPE insulation during the long running process of the cable. In this paper, the XLPE/PVC cable running for 17years was investigated by using thermal analysis, microstructure analysis, mechanical property analysis and dielectric properties analysis. The influences of long-term operation for the physical and chemical properties of cable insulation are analyzed by the performance of the insulation material. DSC results indicated that position of shoulder peak would characterize the thermal history of material and express the crystal size distribution of XLPE indirectly. Mechanical property test results showed that effect of long term high temperature would decrease the elongation at break and breaking strength of XLPE. SEM results showed that the effect of long term high temperature increased the average size of crystal and the distribution of the crystal became concentrated, meanwhile it verified the relevant conclusion of DSC.
Surface Functionalization of Zirconia Nanocrystals with Silane Coupling Agent and its Dispersion Behavior in O-Phenylphenoxyethyl Acrylate
Authors: Lee Hee Seon , Park Jeong Min , Hwang Kyu Hong , Lim Hyung Mi
Published: June 2018

Highly crystalline and dispersible zirconia, synthesized by solvothermal reaction of zirconium (IV) isopropoxide isopropanol complex in benzyl alcohol, were functionalized with silane coupling agent and dispersed with o-phenylphenoxyethyl acrylate (OPPEA). Silane coupling agents such as 3-aminopropyltriethoxysilane (APTES) of amino functional silane, decyltrimethoxysilane (DTMS) of alkyl functional silane and 3-(trimethoxysilyl) propyl methacrylate (MPS) of acrylate functional silane have been used to modify nanoparticle surfaces and obtain dispersion of nanoparticles within OPPEA. The surface modified zirconia was compared according to silane coupling agent, FT-IR and TGA demonstrated that APTES, DMTS and MPS are chemically attached to the surface of the zirconia. The MPS-zirconia is dispersed as about 5 nm sized, whereas the APTES-zirconia, DTMS-zirconia are agglomerated. The MPS-zirconia/tetrahydrofuran (THF) sol at 15wt% loading shows high transmittance of 68 % at 550 cm-1 and the 50wt% surface modified-zirconia/OPPEA sol show refractive index of 1.657.
Effect of the Addition of ZrO2 Having Different Crystal Structures on the Mechanical Properties of Al2O3
Authors: Lim Hyung Yu , Kim Bo Lang , Chae Ji Hoon , Kang Jong Bong , Cho Bum Rae
Published: June 2018

Alumina has been widely used as a structural ceramic because of high hardness and chemical stability. However, due to the unique characteristics of low fracture toughness of ceramic materials, it has seen limited use as a dynamic structural material. Recently, zirconia toughened alumina (ZTA) has been receiving spotlight, which has various toughness mechanisms caused by the volume change associated in the phase transformation process of ZrO2 particles dispersed in Al2O3 to increase the toughness of Al2O3. In this study, 8 mol% Y-ZrO2 and 12 mol% Y-ZrO2 with different crystal structures was dispersed in Al2O3 individually as a stabilizer and the mechanical properties of the ZTA were observed by differing the composition of the stabilizer. Experimental results show that the ZTA specimens with 12 mol% Y-ZrO2 which contains a large amount of stable cubic crystal phases had relatively higher micro hardness values. Whereas, fracture toughness of ZTA specimens with 8 mol% Y-ZrO2 which contains many unstable tetragonal crystal phases, was measured to have higher values than ZTA specimens with 12 mol% Y-ZrO2, which was opposite to that of micro hardness.
Dispersion of TiO2 Nanoparticles in Aqueous Solution
Authors: Liu Wen Xiu , Sun Peng , Zhang Jun , Cao Wen Bin
Published: June 2018

Stable TiO2aqueous dispersion with an averaged secondary particle size of about 10 nm was achieved by using commercially available dispersant Di-7N. The stability of the dispersion was measured by Zeta-potential test. And the results showed that the optimal mass fraction of Di-7N was 12 wt%. The adsorption mechanism examined by FTIR analysis indicates that the carboxylate groups in Di-7N is absorbed on the surface of nano-TiO2particles and the adsorbed structure is proposed to be bidentate chelating.
An Assessment of Characteristics of Densified High-Performance Concrete Incorporating High Volume Fly Ash
Authors: Huynh Trong Phuoc , Hwang Chao Lung
Published: June 2018

The present study evaluates the mechanical-microstructural characteristics of the densified high-performance concrete (HPC) incorporating high volume fly ash (FA). The densified mixture design algorithm (DMDA) technology was applied to design the concrete proportions. The effects of various FA contents on both fresh and hardened concrete were investigated. A scanning electron microscope (SEM) was used to observe the microstructure of the concrete samples. The effectiveness of using DMDA in mix deign was also discussed in this study. As the experimental results, the FA content was found to affect the concrete properties significantly. The maximum compressive strength value of 65.1 MPa was obtained at the concrete samples containing 40% FA. Additionally, the 40% FA samples exhibited a denser microstructure as compared to the others. Generally, all of the tested concrete samples exhibited good performance in terms of workability, strength development, water absorption, and porosity. The results of this study further show the effectiveness of using DMDA technology in proportioning of the concrete mixture.
Effectiveness of Polypropylene Fiber Reinforced Concrete in Enhancement of Long-Term Durability of Hydraulic Structures
Authors: Zia Asad , Ali Majid
Published: June 2018

The long-term durability of concrete hydraulic structures can be improved by controlling their rate of water absorption and linear shrinkage. Incorporation of fibers in concrete composites has the potential to improve these properties of concrete. Artificial fibers are commonly used in concrete due to its durable nature for long serviceable life. So, the overall aim of this research program is to study the effectiveness of artificial fibers for improvement of long-term durability of concrete hydraulic structures. To start with, polypropylene fibers are considered. The polypropylene fibers (PPF) have the unique properties of chemically inertness and low cost raw materials. The pilot study presents the experimental evaluation of water absorption and linear shrinkage of polypropylene fiber reinforced concrete (PPFRC) in comparison to that of plain concrete (PC). The mix design proportion of 1:3:1.5:0.7 (cement:sand:aggregates:water) is used in preparation of PC and PPFRC. For PPFRC, the fiber length of 50 mm and content of 5% by mass of cement are added. All tests are performed as per ASTM standard. Discussions on the considered properties of PC and PPFRC are made. As per expected outcomes PPFRC showed less water absorption and less linear shrinkage as compared to that of PC. Because of this possible attribute, the PPFRC can be used in hydraulic structures.
Analysis of Selected Rheological Properties and Ageing Processes of Bitumens Used in Waterproofing Products
Authors: Babiak Michał , Ratajczak Maria , Kosno Jacek
Published: June 2018

Commonly used waterproofing membranes consist, in over 80%, of bituminous blend. That is why thorough knowledge of factors having impact on the destruction of waterproofing products is of utmost importance. In many cases it is caused by rheological changes, especially ageing processes occurring in bitumen. The purpose of the research is to develop modern solutions that will slow down the processes which occur and thus will extend the life of waterproofing materials. The paper discusses factors affecting the intensity of bitumen ageing and describes physicochemical changes caused by ageing. It also presents test results of bitumen modified with imidazoline which can be used as inhibitors of ageing processes.
Simulation and Experiment on Extrusion Molding of Five-Lumen Medical Catheter
Authors: Wan Yue , Fu Zhi Hong , Zhang Jin Xia , Zang Gong Zheng , Zhang Lei
Published: June 2018

We choose the optimal cross-sectional shape of the polymer five-lumen catheter products as the goal, and the simulation and experiment of extrusion process parameters were carried out. Firstly, the effect of gas injection pressure and extrusion rate on the extrusion expansion ratio, and the influence of gas injection pressure, extrusion rate and traction speed on the cross-section size, was studied by using Polyflow software; The effects of gas injection pressure, extrusion rate and traction velocity on the five-lumen catheter were studied, the experimental results are compared with the numerical simulation results. The optimal combination of the parameters of the extruded five-lumen catheter is obtained by orthogonal experiment, I.e., the head temperature T = 210 °C, injection pressure P = 4515Pa, the extrusion rate v = 4.5mm / s, pulling speed vp = 33.83mm / s; The corresponding relative error is: Primary lumen relative error Y1 = 3.46%, secondary lumen relative error Y2 = 3.33%, the minimum relative error lumen Y3 = 1%, the outer contour relative error Y0 = 0.61%.
Behaviour of Coir-Glass/Epoxy Double Lap Bolted Joint under Tensile Loading
Authors: Khalid Asad A.
Published: June 2018

Experimental work on tensile behaviour and failure mechanism of composite double lap bolted joint has been carried out. Chopped strand mat (CSM) coir, glass and coir-glass/epoxy composite plates were fabricated by hand lay-up method. The bolted joint specimens were of 155 mm length and 48 mm width. Steel bolts of 4 mm and 8 mm diameters were used. Effect of material type, number of layers and width to diameter ration (w/d) on tensile load, bearing strength and failure behaviour were examined. Results show that, the maximum load obtained from the glass/epoxy, coir/epoxy and coir-glass/epoxy specimens increased with the increase in the number of layers and (w/d) ratio. Maximum load obtained from the six layers glass/epoxy with w/d ratio of 12 is found higher respectively 15.2% and 50.14% than that obtained from hybrid coir-glass and coir/epoxy composite specimens. The percentages of difference were 14.2% and 42.97% for the specimens with w/d ratio of 6. It has been found that the maximum strength of the six layers glass/ epoxy specimens was found higher in the range between 17.5% to 18.46 % and 51.67% to 57.74 % than the hybrid coir-glass and coir/epoxy specimens respectively. Net tension failure and cleavage failure modes were observed for the two and four layers coir/ epoxy specimens with w/d ratios of 6 and 12. Bearing failure mode was observed for the six layers coir, glass and hybrid coir-glass/epoxy specimens.
Effect of TiO2 Incorporation on Separation Performance of Pure PES and PES/PVAc Blend Membranes
Authors: Abdullah Mohd Afzan , Mukhtar Hilmi , Fong Yeong Yin , Shaharun Maizatul Shima , Mannan Hafiz Abdul
Published: June 2018

In this research work, polyethersulfone (PES) and polyethersulfone/polyvinyl acetate (PES/PVAc) blend were incorporated with 10 wt.% of TiO2 nanoparticles to form mixed matrix membranes (MMM). FESEM and TGA were utilized respectively to scrutinize the morphology and thermal stability of the developed membranes. Permeation tests of ideal CO2 and CH4 gases were also conducted to assess the separation performance of resultant membranes. The PES/PVAc/TiO2 polymer blend MMM was found to be the most thermally resistant and has the highest CO2 permeability and CO2/CH4 selectivity as compared to the other membranes.
3D Liquid Bioprinting of the PCL/β-TCP Scaffolds
Authors: Aydogdu Mehmet Onur , Ekren Nazmi , Kilic Osman , Oktar Faik Nüzhet , Gunduz Oguzhan
Published: June 2018

In this present work, an original 3D bioprinting method has been developed by modifying an exceptional 3D printer. Using a composite material, bioprinting was carried out to create the ideal scaffold material to contribute regeneration of the certain amount of tissue types in humans. After bypassing the extruder and heating system of the 3D printer, instead of using solid filaments, polymer-ceramic composite was dissolved using an organic agent and bioprinting was conducted. During the bioprinting, dissolving agent was evaporated quickly and solidification process was completed. Despite of the traditional 3D printing, which benefits from the glass transition temperature of the materials, regardless of the temperature, rapid prototyping technology has been merged with controlled flow rate of the composite solution and evaporation of the solvents were adjusted meticulously for proper solidification and layer by layer bioprinting of the scaffolds.
Structure and Mechanical Properties of Retrograded Rice Starch and Cow Bone Powder Composite Sponge
Authors: Punyanitya Sittiporn , Koonawoot Rungsarit , Ruksanti Anucha , Thiensem Sakdiphon , Raksujarit Anirut
Published: June 2018

To study the effect of addition purified cow bone (CB) powder (20, 30, 40 and 50 wt%) in slurry suspension of retrograded rice starch (RRS). The composite sponges were used as in bone repair. The RRS-CB composite sponges were prepared from the mixture of RRS, CB and additive into distill water. The prepared samples were characterized including SEM, XRD, physical and mechanical properties. The results of optimized condition have shown the samples of 40 wt% CB that had the swelling rate as 102± 0.01%, area of expansion was 20 ± 0.03 % for 72 hours and the compressive strength was 64.35±0.05KPa. In addition, it was found that this content resulted in sufficient soft porous material, foldable by hand and self recovered body.
Optimization of 150 mm 4H SiC Substrate Crystal Quality
Authors: Manning Ian , Chung Gil Yong , Sanchez Edward , Yang Yu , Guo Jian Qiu , Goue Ouloide , Raghothamachar Balaji , Dudley Michael
Published: June 2018

Continuous optimization of bulk 4H SiC PVT crystal growth processes has yielded an improvement in 150 mm wafer shape, as well as a marked reduction in stacking fault density. Mean wafer bow and warp decreased by 26% and 14%, respectively, while stacking faults were nearly eliminated from wafers produced using the refined process. These quality enhancements corresponded to an adjustment to key thermal parameters predicted to control intrinsic crystal stresses, and a reduction in crystal dome curvature.
Performance and Reliability Impacts of Extended Epitaxial Defects on 4H-SiC Power Devices
Authors: van Brunt Edward , Burk Albert , Lichtenwalner Daniel J. , Leonard Robert , Sabri Shadi , Gajewski Donald A. , Mackenzie Andrew , Hull Brett , Allen Scott , Palmour John W.
Published: June 2018

This work explores the effects of extended epitaxial defects on 4H-SiC power devices. Advanced defect mapping techniques were used on large quantities of power device wafers, and data was aggregated to correlate device electrical characteristics to defect content. 1200 V class Junction Barrier Schottky (JBS) diodes and MOSFETs were examined in this manner; higher voltage 3.3 kV class devices were examined as well. 3C inclusions and triangular defects, as well as heavily decorated substrate scratches, were found to be device killing defects. Other defects were found to have negligible impacts on device yield, even in the case of extremely high threading dislocation content. Defect impacts on device reliability was explored on MOS-gate structures, as well as long-term device blocking tests on both MOSFETs and JBS diodes. Devices that passed on-wafer electrical parametric tests were found to operate reliably in these tests, regardless of defect content.
Comparison of Conduction Mechanisms in Heavily Al-Doped 4H-SiC and Heavily Al- and N-Codoped 4H-SiC
Authors: Matsuura Hideharu , Takeshita Akinobu , Imamura Tatsuya , Takano Kota , Okuda Kazuya , Hidaka Atsuki , Ji Shi Yang , Eto Kazuma , Kojima Kazutoshi , Kato Tomohisa , Yoshida Sadafumi , Okumura Hajime
Published: June 2018

The conduction mechanism in heavily Al-doped or heavily Al-and N-codoped p-type 4H-SiC epilayers was investigated. In both the singly-doped and codoped samples with an Al concentration (CAl) between 4x1019 and 2x1020 cm-3, band and nearest-neighbor hopping (NNH) conductions appeared in high and low temperature ranges, respectively. The codoping of N donors makes the NNH conduction dominant at temperatures higher than in the singly-doped samples. In both the singly-doped and codoped samples with CAl between 1x1019 and 4x1019 cm-3, an unexpected conduction appeared between the regions of the band and NNH conductions.
Dislocation Analysis of p Type and Insulating HPHT Diamond Seed Crystals
Authors: Shikata Shinichi , Kamei Eiichi , Yamaguchi Koji , Tsuchida Yuki , Takahashi Hiroyuki
Published: June 2018

The dislocation of a p+ high-temperature, high-pressure (HPHT) seed crystal is analyzed by X-ray topography using a SR light source, and compared with that of an insulating HPHT seed crystal. The dislocation density of the typical insulating HPHT substrate is around 250 cm-2. Over several years, significant progress has been achieved in reducing the dislocation density of the typical insulating HPHT substrate from the order of 104–105 cm-2 to 102 cm-2. The p+ HPHT seed crystal has unique properties, especially in terms of the number of stacking faults (SFs), and very clear growth sector boundaries with dislocation densities of up to 3000 cm-2. As most research activities have been focused on the “insulating substrate” in HPHT growth technology for a long time, several challenges need to be overcome with respect to the growth of a p+ HPHT crystal.
Comparison of the Effects of Electron and Proton Irradiation on 4H-SiC and Si Device Structures
Authors: Lebedev Alexander A. , Davydovskaya Klavdia S. , Strel'chuk Anatoly M. , Yakimenko Andrey N. , Kozlovski Vitalii V.
Published: June 2018

The change in the current-voltage characteristics and in Nd-Na values in the base of 4H-SiC Schottky diodes and JBS diodes under irradiation with 0.9 MeV electrons and 15 MeV protons has been studied. The carrier removal rate for the diodes irradiated with electrons was 0.07-0.15 cm-1, and that in the case of protons, 50-70 cm-1. It was shown that the devices under study retain rectifying current-voltage characteristics up to electron doses of ~1017 cm-2. It was found that the radiation resistance of the SiC-based devices significantly exceeds that of silicon p-i-n-diodes with similar breakdown voltages. The simultaneous effect of high temperature and proton irradiation on the characteristics of 4H-SiC pn structures was examined.
Oxidation-Process Dependence of Single Photon Sources Embedded in 4H-SiC MOSFETs
Authors: Abe Yuta , Umeda Takahide , Okamoto Mitsuo , Onoda Shinobu , Haruyama Moriyoshi , Kada Wataru , Hanaizumi Osamu , Kosugi Ryoji , Harada Shinsuke , Ohshima Takeshi
Published: June 2018

We investigated single photon sources (SPSs) in 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) by means of confocal microscope techniques. We found SPSs only in 4H-SiC/SiO2 interface regions of wet-oxide C-face MOSFETs. The other regions of MOSFETs such as source, drain and well did not exhibit SPSs. The luminescent intensity of the SPSs at room temperature was at least twice larger than that of the most famous SPSs, the nitrogen-vacancy center, in diamond. We examined four types of C-face and Si-face 4H-SiC MOSFETs with different oxidation processes, and found that the formation of the SPSs strongly depended on the preparation of SiC/SiO2 interfaces.
Oxide Traps Probed by Transient Capacitance Measurements on Lateral SiO2/4H-SiC MOSFETs
Authors: Fiorenza Patrick , Iucolano Ferdinando , Saggio Mario , Roccaforte Fabrizio
Published: June 2018

In this paper, near interface traps (NITs) in lateral 4H-SiC MOSFETs were investigated employing temperature dependent transient gate capacitance measurements (C-t). The C-t measurements as a function of temperature indicated that the effective NITs discharge time is temperature independent and electrons from NITs are emitted toward the semiconductor via-tunnelling and/or trap-to-trap tunnelling. The NITs discharge time was modelled taking into account also the interface state density in a distributed circuit and it allowed to locate traps within a distance of about 1.3nm from the SiO2/4H-SiC interface.
About the Electrical Activation of 1×1020 cm-3 Ion Implanted Al in 4H-SiC at Annealing Temperatures in the Range 1500 - 1950°C
Authors: Nipoti Roberta , Carnera Alberto , Alfieri Giovanni , Kranz Lukas
Published: June 2018

The electrical activation of 1×1020 cm-3 implanted Al in 4H-SiC has been studied in the temperature range 1500 - 1950 °C by the analysis of the sheet resistance of the Al implanted layers, as measured at room temperature. The minimum annealing time for reaching stationary electrical at fixed annealing temperature has been found. The samples with stationary electrical activation have been used to estimate the thermal activation energy for the electrical activation of the implanted Al.
Local Lifetime Control in 4H-SiC by Proton Irradiation
Authors: Hazdra Pavel , Popelka Stanislav , Schöner Adolf
Published: June 2018

The effect of local lifetime control by proton irradiation on the OCVD response of a 10 kV SiC PiN diode was investigated. Carrier lifetime was reduced locally by irradiation with 800 keV protons at fluences up to 1x1011 cm-2. Radiation defects were characterized by DLTS and C-V profiling; excess carrier dynamics were measured by the OCVD and analyzed using the calibrated device simulator ATLAS from Silvaco, Inc. Results show that proton implantation followed by low temperature annealing can be used for controllable local lifetime reduction in SiC devices. The dominant recombination centre is the Z1/2 defect, whose distribution can be set by irradiation energy and fluence. The local lifetime reduction, which improves diode recovery, can be monitored by OCVD response and simulated using the SRH model accounting for the Z1/2 defect.
Effect of High Temperature Forming Gas Annealing on Electrical Properties of 4H-SiC Lateral MOSFETs with Lanthanum Silicate and ALD SiO2 Gate Dielectric
Authors: Kang Min Seok , Lawless Kevin , Lee Bong Mook , Misra Veena
Published: June 2018

We investigated the impact of an initial lanthanum oxide (La2O3) thickness and forming gas annealing (FGA) conditions on the MOSFET performance. The FGA has been shown to dramatically improve the threshold voltage (VT) stability of 4H-SiC MOSFETs. The FGA process leads to low VT shift and high field effect mobility due to reduction of the interface states density as well as traps by passivating the dangling bonds and active traps in the Lanthanum Silicate dielectrics. By optimizing the La2O3 interfacial layer thickness and FGA condition, SiC MOSFETs with high threshold voltage and high mobility while maintaining minimal VT shift are realized.
Effect of Post Oxide Annealing on the Electrical and Interface 4H-SiC/Al2O3 MOS Capacitors
Authors: Idris Muhammad I. , Wright Nick G. , Horsfall Alton B.
Published: June 2018

This paper reports on the effect of forming gas annealing on the C-V characteristics and stability of Al2O3/SiC MOS capacitors deposited by atomic layer deposition, (ALD). C-V and I-V measurements were performed to assess the quality of the Al2O3 layer and the Al2O3/SiC interface. In comparison to as-deposited sample, the post oxide annealing (POA) in forming gas at high temperatures has improved the stability of C-V characteristic and the properties at the interface of Al2O3/SiC capacitors. However, the oxide capacitance and oxide breakdown electric field degrade with increased annealing temperature. The results provide indications to improve the performance of Al2O3/SiCcapacitors 4H-SiC devices by optimizing the annealing temperature.
PRESiCETM: Process Engineered for Manufacturing SiC Electronic Devices
Authors: Baliga B. Jayant , Sung Woong Je , Han Ki Jeong , Harmon J. , Tucker A. , Syed S.
Published: June 2018

PowerAmerica sponsored the development by NCSU of a process for manufacturing power MOSFETs and JBS Rectifiers in 2015. This process, named PRESiCETM, was successful in making 1.2 kV rated state-of-the-art 4H-SiC power devices (MOSFETs, BiDFETs, and JBS Rectifiers) in the X-Fab foundry. In addition, we were successful in monolithically integrating a JBS fly-back rectifier into the power MOSFET structure to create the power JBSFET which allows saving significant (~ 40 %) chip area and reducing package count in half. In the second year (2016), NCSU has qualified the process for manufacturing these power devices at X-Fab.
4H-SiC 1200 V Junction Barrier Schottky Diodes with High Avalanche Ruggedness
Authors: Gendron-Hansen Amaury , Sdrulla Dumitru , Odekirk Bruce , Kashyap Avinash S. , Starr Linda
Published: June 2018

A state-of-the art family of 1200 V junction barrier Schottky (JBS) diodes was developed. These devices are highly competitive in switching applications thanks to low specific series resistance (1.8 mΩ.cm2 at current rating) and low capacitive charge (1420 nC.cm-2 at 800 V). A uniform avalanche distribution over the active area combined with an optimized high-voltage termination provides industry-leading UIS capabilities. Stringent reliability tests were performed to meet the qualification requirements for the industrial market.
4H-SiC Trench MOSFET with Ultra-Low On-Resistance by Using Miniaturization Technology
Authors: Ichimura Aiko , Ebihara Yasuhiro , Mitani Shuhei , Noborio Masato , Takeuchi Yuichi , Mizuno Shoji , Yamamoto Toshimasa , Tsuruta Kazuhiro
Published: June 2018

The authors have developed 4H-SiC trench MOSFETs with orthogonal Deep-P structures (ODSs) to improve the trade-off between the on-resistance and the gate oxide field. The conditions of photolithography to realize a miniaturized Deep-P pattern have been optimized. The fabricated MOSFETs with ODS have demonstrated a low on-resistance of 2 mΩcm2 and a high breakdown voltage of 1.8 kV.
Growth of 150 mm 4H-SiC Epitaxial Layer by a Hot-Wall Reactor
Authors: Sun Yong Qiang , Feng Gan , Kang Jun Yong , Qian Wei Ning , Li Yi Yang , Li Kai Xi , Zhao Jian Hui
Published: June 2018

In this work we report the latest epitaxial growth of 150 mm 4H-SiC on 4° off-axis substrates by a commercial hot-wall reactor. A statistical analysis of more than 300 runs with an epi thickness range of 6μm~15μm shows that the average uniformities of the thickness and the doping concentration are 1.34% (sigma/mean) and 3.90% (sigma/mean), respectively, and the average 2 mm x 2 mm projected device yield is 97.79%. The growths of ~60 μm-thick 150 mm 4H-SiC epitaxial layers have also been carried out. The repeatability of this system for thick epitaxial layer growth has been verified, showing a run-to-run uniformity similar to that of the thin wafers. These results of 150 mm 4H-SiC epitaxial growths indicate that this comercial hot-wall reactor has the potential for mass production of large diameter 4H-SiC epitaxial wafers.
Planar to Trench: Short Circuit Capability Analysis of 1.2 kV SiC MOSFETs
Authors: Kakarla Bhagyalakshmi , Ziemann Thomas , Nida Selamnesh , Doenni Elias , Grossner Ulrike
Published: June 2018

This paper presents an insight into the short circuit (SC) capability of Rohm’s discrete 1.2 kV, 80 mΩ state-of-the-art silicon carbide (SiC) double trench metal-oxide-semiconductor field effect transistor (MOSFET). SC measurements are performed to compare the behavior of Wolfspeed’s similarly rated 1.2 kV, 80 mΩ planar MOSFET with the Rohm trench devices. Short circuit withstand time (SCWT) of both designs under nominal operating conditions at room temperature is measured by performing destructive SC tests.
Recent Developments Accelerating SiC Adoption
Authors: Bhalla Anup
Published: June 2018

The benefits of SiC devices for use in power electronics has been long understood, and over 25 years of sustained development in materials and devices has brought adoption to a tipping point [1,15]. It takes the confluence of many separate developments to build the necessary momentum for accelerated adoption, and we will examine these factors.
Prolonged 500°C Operation of 100+ Transistor Silicon Carbide Integrated Circuits
Authors: Spry David J. , Neudeck Philip G. , Lukco Dorothy , Chen Liang Yu , Krasowski Michael J. , Prokop Norman F. , Chang Carl W. , Beheim Glenn M.
Published: June 2018

This report describes more than 5000 hours of successful 500 °C operation of semiconductor integrated circuits (ICs) with more than 100 transistors. Multiple packaged chips with two different 4H-SiC junction field effect transistor (JFET) technology demonstrator circuits have surpassed thousands of hours of oven-testing at 500 °C. After 100 hours of 500 °C burn-in, the circuits (except for 2 failures) exhibit less than 10% change in output characteristics for the remainder of 500 °C testing. We also describe the observation of important differences in IC materials durability when subjected to the first nine constituents of Venus-surface atmosphere at 9.4 MPa and 460 °C in comparison to what is observed for Earth-atmosphere oven testing at 500 °C.
Extended Method of Volume Change Measurements during Solidification of Lamellar Graphite Iron
Authors: Svidró Péter , Diószegi Attila , Jönsson Pär G.
Published: June 2018

Lamellar graphite iron (LGI) is an important technical alloy used to produce cast components for the automotive and the marine industry. The performance of the component is defined by the solidification sequence. Therefore, a lot of research work has been done in the field of solidification. The present work introduces a new measurement approach that combines advanced dilatation measurements with thermal analysis to investigate the solidification of LGI. The method involves a thermally balanced spherical sample. The temperature values are measured in the geometrical center and on the surface of the sample. The released heat of solidification is calculated by using the Fourier Thermal Analysis (FTA) method. The displacement values are measured on the surface of the sample. The volume change is calculated from the displacement data. The dilatation results clearly shows the advantage of the multidirectional measurement.
Transformation Kinetics and Mechanical Properties of Copper-Alloyed and Copper-Nickel Alloyed ADI
Authors: Górny Marcin , Tyrała Edward , Sikora Gabriela
Published: June 2018

In this study the effect of copper and nickel in shaping the structure and properties of ADI (Austempered Ductile Iron) was investigated. The austenitization and austempering transformations were studied in order to follow the changes exhibited in transformation kinetics. The dilatometric results indicated that the addition of Cu and the addition of both Cu and Ni resulted in reducing relative expansion during austenitization, due to a larger pearlite fraction in the microstructure. In the initial stage of the austempering process, the addition of Cu, and to a greater extent, additions of both Cu and Ni led to a reduction in the transformation rate, shifting the maximum transformation rate values toward longer times. X-ray diffraction, dilatometric, metallographic and magnetic examinations allowed us to determine the phases fraction in the structure of ADI with the presence of Cu and Ni. From SEM-EDS analysis, it follows that in the copper alloyed ADI, highly dispersed particles are formed containing Mg and Cu, whose size does not exceed <1 µm. The exhibited mechanical properties were determined as a function of Cu and Ni additions and also variable austempering period of time. It was found that the addition of Cu resulted in increased tensile strength and hardness but simultaneously decreased the impact strength of ADI. The outcome of this work indicates that in order to obtain a satisfactory combination of static and dynamic mechanical properties of ADI, an optimal combination - aside from proper heat treatment - Cu and Ni should be selected.
Impact of Molybdenum on Heat-Treatment and Microstructure of ADI
Authors: Gogolin Julius Alexander , Tonn Babette
Published: June 2018

Austempered Ductile Iron (ADI) is characterized by high tensile strength with acceptable ductility. Steel, as a large competitor to ADI, also meets the tensile and yield strength. Nevertheless, the main advantages of ADI compared to steel are the lower density (7.2 g/cm3 to 7.85 7.87 g/cm3) for weight reduction and lower manufacturing costs because of less energy consumption during the production. One of the main problems of producing ADI is the quenching process during heat treatment of thick-walled castings. The inner part of a massive casting – in contrast to the outer part – cools down more slowly, resulting in a heterogeneous microstructure with parts of pearlite and ferrite embedded in austenite before reaching the isothermal transformation temperature. Molybdenum is, besides nickel, copper and manganese, one of the possible alloying elements that postpone the transition point of ferrite and/or pearlite. To investigate the influence of molybdenum in thick-walled castings experiments with different molybdenum contents were performed. In dependence on the molybdenum content, different austenisation and ausferritisation temperatures and times are examined in order to investigate the transformation points, fraction and morphology of different phases. The mechanism of molybdenum in ADI has been investigated by means of dilatometer tests, microstructure analysis and mechanical tests.
Correlation between Microstructure and Mechanical Properties of Austempered Ductile Irons
Authors: Alves Vinicius Cardilo Campos , Baracho Luciano Lobo de Almeida , dos Santos Césio Túlio Alves , Lopes Luiz Carlos Rolim , Silva Éder dos Reis , Freitas da Silva Fabiane Roberta , da Fonseca Gláucio Soares , Leal Ricardo Henriques , Fonseca Maria da Penha Cindra
Published: June 2018

Austempered ductile cast irons (ADI) have received great attention in last years because their combined properties of good ductility, high strength and fracture toughness, good fatigue strength, good wear properties and low production cost. Such combination of properties can be reached because of their microstructures consist of a mixture acicular ferrite (bainite), residual austenite with a high carbon content and nodular graphite. In this work, the effect of austempering heat treatment on the microstructure of a commercial alloy to produce three different grades of ADI, with different strength level, is analyzed. Microstructure characterization has been performed using techniques of optical microscopy, scanning electron microscopy and x-ray diffraction. Mechanical properties were evaluated from tensile and impact tests at room temperature. In addition, the residual stress due to heat treatment was evaluated. The results of this study show that there is a strong relationship between austempering temperatures and mechanical properties. The highest tensile and yield strength obtained were 1599 and 1427 MPa, respectively, for the sample austempered at 280°C. The sample austempered at 320°C presented the highest Charpy absorption energy (99,90 J) and highest volume fraction of austenite (27%).
Influence of Cooling Rate on Nature and Morphology of Intercellular Precipitates in Si-Mo Ductile Irons
Authors: Youssef Mervat , Nofal Adel , Hussein Abdelhamid
Published: June 2018

This work is designed to better understand the influence of cooling rate on the nature and morphology of intercellular precipitates in Silicon-Molybdenum ferritic ductile iron (SiMo). Plates of 3, 6, 9 mm thickness were cast in greensand and investment casting molds to give a wide spectrum of cooling rates. It was found that at higher cooling rates, the intercellular regions have a lamellar structure typical of pearlite. With decreasing cooling rates, the precipitate contains complex (Fe-Mo-Si) carbides of fine spheroidal or rod-like structure surrounding the eutectic carbides.Intensive Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) and Optical Microscopy (OM) investigations showed that the eutectic carbides are mainly (Fe, Mo, Si) C containing up to 48% Mo, whereas the fine precipitates contain lower Mo-contents. Both carbide types did not show to have a strict stoichometric composition. The solidification and solid-state transformation path was determined using both phase diagram calculated from Thermo-Calc software as well as Differential Scanning Calorimetry (DSC).
Influence of Local Microstructure on Stresses, Durability and Fracture Mechanics of Cast Iron Components
Authors: Thomser Corinna , Olofsson Jakob , Gurevitch Vitalii
Published: June 2018

Cast iron components show a large variety of different microstructures in dependence on chemical composition, inoculation and cooling conditions. In conventional static and dynamic calculations as well as in fracture mechanics assessment of cast iron components, the influence of local microstructure on the overall behavior of the component is not considered. Usually one material dataset is applied for the whole material. The paper describes recent developments in the field of the prediction of local microstructure and its correlation to local stress-strain, fatigue durability as well as fracture toughness. The benefit of combining casting process simulation with lifetime predictions and fracture mechanics assessment is shown for selected examples. By integrating casting process simulation, microstructure modelling, local material characterization and load analysis, a simulation based approach for predicting the behavior and performance of cast iron components already during the design stage is enabled. Thus, the local assessment helps designers to assess risks and strive for light weight designs before the casting is made.
Strength Prediction of Lamellar Graphite Iron: From Griffith’s to Hall-Petch Modified Equation
Authors: Fourlakidis Vasilios , Diaconu Lucian Vasile , Diószegi Attila
Published: June 2018

Traditionally, ultimate tensile strength (UTS) is used as the main property for the characterization of lamellar graphite iron (LGI) alloys under static loads. The main models found in the literature for predicting UTS of pearlitic lamellar graphite iron are based on either regression analysis on experimental data or on modified Griffith or Hall-Petch equation.In pearlitic lamellar graphite iron the primary austenite dendritic network, transformed to pearlite, reinforces the bulk material while the distance between those pearlite grains, defines the maximum continuous defect size in the bulk material. Recently the novel parameter of the Diameter of Interdendritic Space has been used to express the flow length in a modified Griffith equation for the prediction of the UTS in LGI. Nevertheless this model neglects the strengthening effect of the pearlite lamellar spacing within the perlite grains. A model based on modified Hall-Petch equation was developed in this work. The model considers the effect of both microstructure parameters and covers a broad spectrum of microstructure sizes typical for complex shape castings with various wall thicknesses.
Mechanism of Damage of Ferritic Ductile Iron, Influence of Matrix Heterogeneity
Authors: Fernandino Diego O. , Boeri Roberto Enrique , Massone Juan M.
Published: June 2018

Ferritic ductile cast iron (FDI) microstructure is composed by graphite nodules embedded in a ferritic matrix. It is usual to assume that the ferritic matrix is homogeneous. However, the experimental analysis shows impurities and in some cases a high degree of heterogeneity. It is necessary to investigate the influence of these heterogeneities on the mechanical properties of FDI.This work focusses on the characterization of the elastoplastic properties of different zones of the ferritic matrix of FDI and the identification of the sequence and extent of the damage mechanisms at the micro-scale under uniaxial tensile loading.The methodologies for the characterization of the material micro constituents and micro-segregated zones involve nano-indentation and atomic force microscopy techniques in combination with computational modelling. The analysis is performed by applying inverse analysis algorithms proposed in the literature. The microsegregated zones are identified by using color etching. The assessment of the micro-scale damage mechanisms was performed by in-situ optical microscopy observation of tensile tests of very small specimens.The results led to the quantification of the differences in mechanical properties along the metallic matrix as a result of the existing heterogeneities and allow for a better understanding of the ductile iron damage mechanism.
Evaluation of Microstructure Quality in Ductile Irons Based on Tensile Behaviour Analysis
Authors: Donnini Riccardo , Zanardi Franco , Vettore Federico , Angella Giuliano
Published: June 2018

Dislocation-density-related equations were proved to be promising tools to correlate tensile plastic behaviour and microstructure in ductile irons (DIs), revealing distinct relationships between equation parameters and microstructure features in austempered ductile irons (ADI) and isothermed ductile irons (IDI). These equations resulted to be successful also in the characterization of the austempering process through the plastic behaviour analysis of tensile tests of an ADI 1050 that was quenched at different times during austempering. The equation parameters could indeed be correlated to the time window for the best ausferrite, and could predict the precipitation of the deleterious ε' carbides for long austempering times. In the present work the results of the tensile plastic behaviour analysis of different DIs through dislocation-density-related equations are reported. The aim of the analysis was to test the capability of these equations to assess the microstructure quality of DIs and support their industrial production.
High-Temperature Oxidation of a High Silicon SiMo Spheroidal Cast Iron in Air with In Situ Change in H2O Content
Authors: Ebel André , Brou Serge Yapi , Malard Benoît , Lacaze Jacques , Monceau Daniel , Vaissière Loïc
Published: June 2018

Exhaust manifolds for diesel engines are made of high-Si ferritic nodular cast irons. It is experimentally well established that their oxidation kinetics are highly sensitive to the presence of water vapor, though the mechanism for such an effect is still controversial. In the present work, isothermal oxidation tests were performed on a SiMo nodular cast iron at 700°C and 800°C in dry and humid air for 25 and 50 hours. Other samples were oxidized for 50 h with in-situ change in H2O content after 25 h, switching from dry air to humid air or the other way round. Samples were then analyzed using XRD, SEM-EDS and Raman spectroscopy. Thermogravimetric records clearly showed the effect of temperature and environment on oxidation and decarburization. The kinetics of these phenomena depends on silica formation at the metal-oxide interface. At both temperatures, water vapor was seen to promote internal oxidation of Si instead of its external oxidation. This leads to higher oxidation kinetics at 700°C and higher decarburization kinetics at 800°C.
Oxidation Resistant Cast Iron for High Temperature Application
Authors: Scheidhauer Nico , Dommaschk Claudia , Wolf Gotthard
Published: June 2018

This paper focusses on the development of materials for exhaust gas components. The present work will focus on a ferritic SiMo-cast iron to create an economic alternative to the austenitic D5S. Aluminum and silicon are essential for this material development because they increase the transformation temperature. They also improve the durability of the protective oxide layer. Additionally, aluminum improves the high temperature mechanical properties by precipitation of a kappa-phase. The ferritic SiMoAl cast iron shows very good oxidation resistance and also mechanical properties.
Prediction of Shrinkage Defects in Iron Castings Using a Microporosity Model
Authors: Kim Sung Bin , Yim Young Hoon , Yoon Joong Mook , Ştefănescu Doru Michael
Published: June 2018

A numerical model for prediction of shrinkage defects in iron castings has been developed. The model is based on gas pores evolution during solidification. It describes the evolution of gas concentration using mass conservation, and the change in melt pressure due to solidification contraction using Darcy’s equation, with mixture continuity assumption in the liquid and the mushy zone. Gas pores nucleation has been calculated using the partial pressure of gas obtained from Sievert’s law. The growth of porosity has been estimated using an equation based upon the total melt pressure on the pore, concentration and temperature of the gas. The porosity model was calibrated against literature data for microporosity, and then applied to the prediction of shrinkage defects in a ductile iron casting. Comparison between the model predictions and experimental measurements indicated that the porosity model can be applied not only to the prediction of micro-shrinkage but also to that of macro-shrinkage. Existing shrinkage prediction models based upon thermal models, such as Niyama criterion and the modulus of retained melt in mushy regions cannot predict correctly both micro- and macro-shrinkage.
Three-Dimensional Modeling of Green Sand and Squeeze Molding Simulation
Authors: Ito Yuuka , Maeda Yasuhiro
Published: June 2018

The green sand mold with good mold properties are useful to obtain the sound cast iron castings. For example, the green sand mold with high density and uniform for compacting characteristics would be required. Molding simulation is indispensable to make a good sand mold. In recent years, the package software was released from software vendors of foundry CAE, and the demand for molding simulation is increasing. Fundamental algorithms of the green sand particulate model and the three-dimensional Discrete Element Method (DEM) were proposed. They take into consideration of the particle size distribution and the cohesion of green sand particles.In this study, the squeeze molding simulation is carried out and we execute the re-development of this method under the current computer environment. They are tried to simulate the dynamic behavior during molding and to predict the mold properties after squeeze molding. The characteristics of green sand with cohesion are reflected in the particle model called Hard-Core/Soft-Shell. The compacting behavior of squeeze molding is traced numerically, and the visualization by a three-dimensional model and comparison of dynamics molding are carried out. From the simulation with several kinds of particle distribution, it becomes clear the relationship between the void fraction and the squeeze pressure during molding. The effect of particle size distribution on sand compacting behavior is also clarified. Furthermore, the three-dimensional display of green sand with particle size distribution is very effective in the post-processing.