bluuebunny/crossref_metadata_2025 huggingface dataset:
Surfactant-Assisted Synthesis of Birnessite-Type MnO2 Nanoflowers
Authors: Hao Xin Li , Zhao Jing Zhe , Song Yue Hong , Huang Zhi Fang
Published: June 2018

Flower-like birnessite-type MnO2 (Bir-MnO2) was synthesized through decomposition of KMnO4 under acid condition at 90 °C in open system. The addition of surfactant was a key factor for synthesis of Bir-MnO2 at low temperature and ambient pressure. Crystal nucleus obtained via reaction between surfactant and KMnO4 can catalyze decomposition of KMnO4, which led to the higher velocity of reaction. Reducibility of surfactant additional had an impact on yield and size of sample obtained. As-prepared sample with highest yield and smallest size was synthesized by using SOA as surfactant. Long reaction time and high reaction temperature were propitious to the growth of sample. The as-prepared samples were used to degrade rhodamine B (RhB), and the efficiency was different as the size of nanoflowers changed.
Effects of Environment on the Wear Behavior of P/M Ti-47Al-2Cr-0.2Mo
Authors: Qiu Jing Wen , Pan Di , Liu Yong , Baker Ian , Zhang Wei Dong
Published: June 2018

The wear behavior of powder metallurgical Ti-47Al-2Cr-0.2Mo alloy prepared by pre-alloyed powders was investigated using pin-on-disk wear tests in different environments, viz, argon, 4% hydrogen in nitrogen, air and oxygen. The disk material was sinter-hot isostatically pressed, yttria-stabilized zirconia. Lower wear rates were found for the TiAl pins in oxygen-free environments, indicating that oxygen play a key role in the wear rate. In contrast, the presence of molecular hydrogen and moisture have nearly no effect. A combination of X-ray diffraction and energy dispersive X-ray spectroscopy indicated that the abrasive particles present mainly consisted of the zirconia. In addition, zirconia particles were embedded in the worn tips of the TiAl pins and mixed into the tribolayers. The high stress and high contact temperature at the wear surface made the zirconia disk undergo a phase transformation during the dry sliding wear, accompanied by grain pullout, surface uplifting and microcracking. The hard tribolayer with embedded zirconia particles provides some protection against further wear of the TiAl pin. The highly localized, repetitive shear stress during the wear tests may bring about amorphous TiAl in the wear debris. The main wear mechanisms were abrasive wear of two-body and three-body, some delamination and plastic deformation.
From Powder to Solid: The Material Evolution of Ti-6Al-4V during Laser Metal Deposition
Authors: Surrey Philipp , Möller Mauritz , Emmelmann Claus , Heilemann Markus , Weber Julian
Published: June 2018

The additive manufacturing of titanium parts by laser metal deposition (LMD) offers a promising alternative to conventional machining of aviation parts. The technology enables the production of near net shape parts with higher deposition rates than powder bed-based processes. Ti-6Al-4V powder is fed directly into a high-power laser beam in order to form a deposition track on the underlying material. For three dimensional parts several tracks are stacked on top of each other. In this paper the material evolution from powder to a solid wall during LMD is investigated. Powder properties as well as the microstructure in deposited structures are thoroughly described and analyzed. The gained knowledge provides a deeper process comprehension and is an important step towards high-quality additive manufacturing of Ti-6Al-4V. At first, the influence of powder particle size on the LMD process is quantified by creating two powder fractions with different sieving procedures. The used material is recycled Ti-6Al-4V powder from a powder bed-based AM process with particle sizes up to 150 µm. The powder is characterized according to current standards; apparent density, tap density and the flowability are determined as well as the particle size distribution. Additionally, the particle morphology is analyzed using electron beam microscopy. In order to link the powder properties to the LMD process and to identify impact factors to the feeding behavior the mass flow of both powder fractions is measured. Secondly, walls are manufactured with the characterized powder and the resulting microstructure is analyzed. Because of the layer-wise deposition and the resultant periodic heat input each layer experiences several thermal cycles. As a result various solid phase transformations occur during the deposition of consecutive tracks. In addition the thermal boundary conditions change with increasing wall height and a heterogeneous microstructure is observed. It consists of non-equilibrium phases (martensitic or massive α) and α+β lamellae. Based on an existing numerical model the thermal history of each layer is estimated and an explanation is presented for the complex sequence of solid phase transformations in each area of the structure.
Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Samples Fabricated by Selective Laser Melting
Authors: Gao Jing Bo , Zhao Xiao Li , Yue Ju Kun , Qi Meng Chao , Zhang De Liang
Published: June 2018

Ti-6Al-4V (wt%) alloy samples with dog-bone and box shapes respectively were fabricated by selective laser melting (SLM). The microstructures and mechanical properties of the 3D printed Ti-6Al-4V samples with and without heat treatment were characterized and tested. The microstructures of the as-fabricated dog-bone shaped samples were mainly composed of acicular α’ phase. After annealing at 700°C, the acicular α’ phase changed into an α/β lamellar structure. After solution treatment at 955°C, water quenching and aging at 550°C, the microstructure was mainly composed of primary α phase and α/β lamellar structure. The optimum heat treatment is annealing, and the mechanical properties of the annealed sample are as follows: yield strength: 1015 MPa, ultimate tensile strength (UTS): 1083 MPa and elongation to fracture: 7.9%. The microstructures of the box-shaped samples after annealing mainly consist of α phase and α/β lamellar structure. When stretched along the direction parallel to the crystal growth direction, the yield strength and UTS of the sample are 1054 and 1090 MPa，and its elongation to fracture is 6.3%. When stretched along the direction perpendicular to the crystal growth direction, the yield strength and UTS of the sample are 1019 and 1068 MPa respectively, and its elongation to fracture is 8.7%.
Powder Injection Molding of Ti-6Al-4V Alloy for Defect-Free High Performance Titanium Parts with Low Carbon/Oxygen Contents
Authors: Lin Dong Guo , Park Jae Man , Kang Tae Gon , Chung Seong Taek , Kwon Young Sam , Park Seong Jin
Published: June 2018

In this work, powder injection molding (PIM) of Ti-6Al-4V alloy powder has been studied. Defect-free high performance Ti-6Al-4V parts with low carbon/oxygen contents have been successfully prepared by PIM. A pre-alloyed Ti-6Al-4V alloy powder and wax-polymer binder system have been mixed together to prepare the feedstock. In mixing stage, the solid loading percentage and mixing conditions have been optimized. Rheological and thermal debinding behaviors of prepared feedstock have been characterized and numerically expressed based on rheometry and thermal gravity experimental results. In addition, the injection molding process of Ti-6Al-4V parts has been numerically analyzed to optimize the injection molding conditions. Consequently, the defect-free Ti-6Al-4V parts with low carbon and oxygen contents have been successfully fabricated by PIM, which exhibits excellent physical and mechanical properties.
Comparative Rheology Techniques for Assessment of MIM Titanium Metal Powder Feedstocks
Authors: Ewart Paul D. , Verbeek Casparus J. , Ahn Seok Young
Published: June 2018

In this work standard industrial processing equipment, the torque mixer and twin screw extruder, are used to measure the melt flow of several titanium metal powder feedstocks. The study was to determine whether test data from specialised rheology equipment might be reproduced with standard processing equipment used by the MIM industry.Considering the wide range of flow defects possible with MIM there is a valid assumption that flow behaviour measurement will be better represented by a number of processes, especially those most representative of the injection moulding process.In this study process data was collected and analysed based on mixing torque, screw work, specific mechanical energy and viscosity. Viscosity was further calculated relative to (L/D) ratio and strain rates during extrusion. Subsequently the data was compared with viscosity values from a capillary rheometer both without, and with, account for end effects and slip.The results showed that all the techniques provide similar ranking for the feedstocks with regard to melt flow during processing. The results also showed an inversion of the ranking where the shear rate increased from (1000 to 5000) s-1 as a result of shear sensitivity. The agreement of results from the different techniques clearly show that conventional processing equipment may provide valid feedstock assessment. The results if not definitive will provide good comparative measure where upper and lower bounds can be determined.
Study of a Binder System for Ti-MIM: A Potential Low Temperature Backbone Polymer
Authors: Zhang Hong Zhou , Hayat Muhammad Dilawer , Qu Xuan Hui , Jadhav Pratik Prakash , Wang Xin Gang , Cao Peng
Published: June 2018

Impurity control remains to be a challenge to titanium metal injection moulding (Ti-MIM). Much attention has been paid to polyethylene glycol (PEG) based binder systems due to the eco-friendly and water-soluble feature of PEG. In this study, a new easy-to-debind PEG/polypropylene carbonate (PPC)-based binder system (76% PEG+17% PPC+3% polymethyl methacrylate (PMMA)+2% stearic acid (SA)+2% polyvinyl acetate (PVAc)) was developed. The rheological properties of the feedstocks prepared with the binder system in different proportions were assessed. Debinding behaviours of the moulded samples and impurity contents of oxygen (O), carbon (C), and nitrogen (N) of the thermal debound specimens were investigated as well.
Advances in Ti-Based Systems as High Temperature Shape Memory Alloys
Authors: Chauke Hasani , Mashamaite Mordecai , Modiba Rosinah , Ngoepe Phuti
Published: June 2018

In this study, we investigate the effect of ternary addition on the structural, mechanical properties and temperature dependence of Ti-based as potential shape memory alloys using molecular dynamics approach. We found that binary Ti-Pt alloys exhibit shape memory properties and display possible martensitic transformation from B2 to B19 phases. Partial addition with Zr, Co, Pd, Ir showed preferential ternary high temperature shape memory alloys formation of 6.25 at. % X composition (Ti-Pt-X). We found that the equilibrium lattice constants are in better agreement with the available experimental values. The heats of formation and elastic properties reveal possible composition and phases at temperature above 900 K with good shape memory properties. Their structures were confirmed using the X-ray diffraction patterns at different temperatures.
Preparation of TiO2 Coating on Pure Ti with Sodium Borate Glass as Catalyst
Authors: Lu Zhi , Wang Guang Xin , Wang Ya Ming , Yan Yan Fu
Published: June 2018

TiO2 coating was prepared by a novel approach on pure titanium substrates. In this study, we presented a new method to induce the crystal growth of rutile on pure Ti which covered with uniform Na2O·2B2O3 glass powders, and through heating to control the grow process of TiO2 crystal. The results showed that during the heating process, the crystal of rutile grew on the interface between the glass coating and the Ti substrates. To keep the growth of TiO2 crystal controllably, the presence of Na2O·2B2O3 glass powder was essential. Meanwhile, TiO2 crystal grew fast with a higher heating temperature. The mechanism about the growth of TiO2 coating was also investigated in this work.
Microstructure Characterization of In Situ Ti-TiB Metal Matrix Composites Prepared by Powder Metallurgy Process
Authors: Singh Harshpreet , Hayat Muhammad Dilawer , Das Raj , Wang Xin Gang , Cao Peng
Published: June 2018

Metal matrix composites (MMCs) are the new generation materials that combine both the metallic properties (ductility and toughness) and ceramic characteristics (high strength and modulus), leading to higher strength in shear and compression, at higher service temperatures. Titanium matrix composites possess light weight, high strength and good corrosion resistance and are used as structural materials in automobiles and aerospace industries. In the present study, in situ Ti-TiB composites were fabricated by reinforcing (2, 5, 10 and 20 wt. %) TiB2 powder (mean size <10 microns) into titanium powder (mean particle size ~26.58 μm) and subsequently consolidated by vacuum sintering at 1300 °C for 3 h. X-ray diffraction, scanning electron microscopy (SEM) and density measurements were carried out to characterize the prepared composites. The results showed that all compositions led to high density composites, and the hardness of the composites increased with an increase in the amount of reinforcement. The mechanism of vacuum sintering is yet to be understood in the consolidation of composites and the detailed evolution of microstructure needs to be analysed.
Optimization of Milling Parameters for Titanium Alloys Based on Support Vector Machine (Machine Learning) and Ant Colony Optimization Algorithm
Authors: Zhang Xiao Xia , Wang Zhi Chao , Chen Hong Yang
Published: June 2018

In this paper, the titanium alloy milling process is analysized by finite element method, and the processing quality of this materials will be affected by the milling force. A milling force prediction model was established based on support vector machine (SVM) and ant colony optimization (ACO) for titanium alloy milling process cutting parameters. The main feature of this model design methodology is to hybridize the solution construction mechanism of ant colony optimization (ACO) with support vector machine (SVM) regression based on HYPERLINK "https://cn.mathworks.com/discovery/supervised-learning.html" supervised learning algorithm. The results show that this methodology is very efficient, and thus can be used in the machining process parameters optimum and other material processing fields.
Preparation of Ti-5553 Alloy by Different Extrusion Processes from Elemental Powder Mixtures
Authors: Yang Fei , Gabbitas Brian , Raynova Stiliana , Singh Ajit Pal , Bolzoni Leandro
Published: June 2018

Ti-5553 (Ti-5Al-5V-5Mo-3Cr, wt. %) alloy is a recently developed near β titanium alloy and it has a very good hardenability, good ductility and high strength. In this study, we discussed the feasibility of preparing Ti-5553 alloy by different processes from powder mixtures of hydride-dehydride titanium powder, elemental powders and master alloy powders, including (1) direct extrusion of powder compact in argon, (2) extrusion of the vacuum-sintered billet in air and (3) extrusion of the hot-pressed billet in air. XRD, OM and SEM were used to determine the phase constitutions and microstructures of the prepared Ti-5553 alloys, and mechanical test was performed to examine their mechanical properties. The results showed the microstructures and phase constitutions of Ti-5553 alloys were significantly affected by different processes, which resulted in the relevant mechanical properties. The effect of the selected heat treatment on the microstructures and properties of Ti-5553 alloy were investigated as well.
Effect of Microwave Sintering Parameters on the Physical and Mechanical Properties of Pure Ti and Blended Elemental Ti Alloys
Authors: Raynova Stiliana , Imam M. Ashraf , Taylor Hunter , Yang Fei , Bolzoni Leandro
Published: June 2018

Microwave sintering (MWS) was used to consolidate hydride de-hydride Ti powder and blended elemental Ti6Al4V, Ti5Fe and Ti5Al5Mo5V3Cr (Ti5553) powder mixtures. The amount of powders used to prepare the powder compacts was scaled up to 500g.The effect of the MWS conditions on the relative density, porosity distribution, microstructure and tensile properties were studied. Furthermore, uniformity in distribution of the alloying elements was checked. For most of the materials considered, a combinations of sintering temperature of 1200oC and 1300oC and holding time of 5 to 30 min resulted in significantly improved density. Nevertheless sintering temperature of at least 1300oC was required for pore coalescence and high tensile properties.
Processing, Microstructures and Properties of a Ti-6Al-4V Extrusion Produced by an Industrial Scale Setup
Authors: Singh Ajit Pal , Yang Fei , Torrens Rob , Gabbitas Brian , Robinson Barry , Bolzoni Leandro
Published: June 2018

In this paper, a Ti-6Al-4V rectangular bar was successfully produced from a 5kg blended powder mixture using an industrial scale extrusion facility. The elemental hydride-dehydride (HDH) titanium and 60Al-40V master alloy mixture was warm pressed and vacuum sintered prior to β extrusion in air. The as-processed material was characterised for compositional homogeneity, oxygen pickup, microstructure, tensile properties and fracture behavior. Variation in microstructure and properties along the length of the extruded bar were also studied. It was found that oxygen pickup mainly occurred during vacuum sintering of the green billet and consequently the as-extruded material had an oxygen content of 0.55 wt.%. The processed material had a typical lamellar morphology with some evidence of micro-cracks at high magnification. A significant deviation in prior β grain and α colony sizes was observed along the length of the bar, due to variations in extrusion temperature and cooling rate. Both grains and colonies became finer as the location changed from the tip of the extruded bar to the back end. The as-processed material had ultimate tensile strength in the range of 1068-1268 MPa and elongation to fracture of 1.2-4.5%, mainly due to the high oxygen content and non-optimised microstructure. Fractographic analysis was consistent with the variation in mechanical performances obtained.
Influence of Alloying Elements in Fatigue Properties of α/β Titanium Alloys
Authors: Hidalgo Alexandra Amherd , Limberg Wolfgang , Ebel Thomas , Frykholm Robert , Carreño-Morelli Efrain , Pyczak Florian
Published: June 2018

One strategy to make PM titanium components competitive in terms of mechanical properties is the addition of suitable alloying elements. PM offers the possibility to adapt the alloy composition in order to achieve the required properties. In this study, different alloying elements were introduced into α/β titanium alloys and fatigue behaviour was evaluated. Four-point bending fatigue tests with a stress ratio of 0.2 were performed on specimens manufactured by metal injection moulding (MIM) and shot peening. Results showed an enhanced sintering activity of Ti-6Al-7Nb by adding small amounts of iron. The impact on fatigue properties was evaluated. The increase of oxygen in Ti-6Al-7Nb from 0.15 wt.% to 0.45 wt.% caused a decrease in elongation from 16% to 6%. However the fatigue strength at 107 cycles is just slightly reduced from 450 to 350 MPa. The addition of 0.5 wt.% yttrium powder to gas atomized Ti‑6Al‑4V powder led to a noticeable refinement of the microstructure of the sintered parts, due to the formation of Y2O3 particles, which hinder grain growth. In spite of a slightly higher residual porosity, the microstructural refinement increased the fatigue strength at 107 cycles from 450 to 470 MPa. At 106 cycles, the fatigue strength increased even from 705 to 765 MPa. The addition of yttrium did not result in a higher oxygen pick up, which indicates a scavenging of oxygen from the titanium matrix by formation of Y2O3 during sintering. Contrary to the fatigue strength results, the scavenging effect led to a decrease in tensile strength of about 70 MPa. The microstructure of fatigue-tested specimens was characterized by using optical and scanning electron microscopy.
Mathematical Modeling of Thermal Association in a Porous Medium with a Capillary Effect in Anisotropic Composite Materials
Authors: Kuznetsova Ekaterina , Rabinskiy Lev
Published: June 2018

Authors developed a mathematical model of heat and mass transfer in multidimensional bodies made of composite materials, taking into account porosity and capillarity. Continuity equations for pyrolysis gases were taken for the research: the pressure ratio at the outer boundary of the body. Based on the nonstationary heat conduction problem, under conditions of high-intensity heat transfer at the boundaries of bodies, taking into account the laws of decomposition and non-linear filtration of pyrolysis gases through a porous residue, the time distribution of the movable boundary of phase transformations and the distribution of the temperature field along the variable coordinate at different instants of time are obtained. It was found that, although the thermal load at the outer boundaries is symmetric with respect to the symmetry axis, there is an obvious asymmetry in the temperature field and the movable boundary of the phase transformations.
Formation of Engineering Thinking in Multilevel Architectural Education
Authors: Perkova Margarita , Kolesnikova Lyudmila , Korotun Elena
Published: June 2018

The issues of the development of engineering thinking in the training of architects, starting with pre-university training at school, are considered; the optimal list of disciplines and their content within the school process are determined. The methods of training specialists, their adaptation to the conditions of professional work in the learning process are considered. The method of competitive real design as an elective part of "Architectural Design" of students of the Belgorod Architectural School is discussed, which will improve the training of architects in higher education and develop engineering thinking.
Mathematical Modelling of the Calculation of the Stiffness Characteristics of Composite Materials
Authors: Kucheryuk Viktor I. , Umanskaya Olga L. , Krivchun Natalya A.
Published: June 2018

This article provides an overview of the analysis of the selection of the reduced (equivalent) characteristics of the material. The selection and definition of the elastic characteristics of composite materials depend on many factors: the geometry of the design element of the structure, the stress-strain state and the mathematical model of this state, the calculation methods, and the necessary accuracy of the solution. Technical methods for calculating elements such as rods, plates, and shells are analytically related to the formulation of resolving equations. One of the most common approaches to implementing practical tasks is the method of bringing an inhomogeneous material to a homogeneous isotropic or orthotropic material. In this paper, the most common options for choosing the mechanical characteristics of a composite material are considered. A restriction is introduced - work in the elastic region and the compatibility of deformations of the matrix with reinforcement. These limitations are in good agreement with the reliability of the construction. The article gives a qualitative analysis of formulas depending on the task. A choice of design for a dispersion-hardened material is proposed for a uniform reinforcement distribution for bent elements. The above analysis of formulas for determining the efficiency of physical and mathematical characteristics of composite rods, plates, and shells, allows for the calculation of more complex problems.
Evaluation of the Thermal Processes and Simulation Methods for Additive Manufacturing Based on the Geometry Voxel Representation
Authors: Ripetskiy Andrey , Zelenov Sergey , Kuznetsova Ekaterina , Rabinskiy Lev
Published: June 2018

Currently, the technological and hardware base additive production technologies are actively developing. The emergence of new developments in the field of materials science and their possibilities for the creation of products using layer-by-layer method promotes the development of innovative solutions that increase the efficiency of complex technical parts and improves their quality. This paper describes simulation methods based on the Model Voxel Representation part discretization allowing evaluating thermal processes during 3D printing process. The simulation model was extended taking into consideration the following criteria: heat conduction coefficient as a constant; temperature in the center of the elementary volume equals to the temperature at the volume border; temperature of the powder surrounding the item taken as a constant. It was determined that the convergence is affected by numerous factors: temperature in the machine chamber, material properties, heat exchange and the processes running into the chamber of the certain machines.
Oxidation Resistance and Bending Strength at High Temperatures of Ni/(ZrO2+Al2O3) Hybrid Materials
Authors: Pham Hai Vu , Nanko Makoto , Nakao Wataru
Published: June 2018

Oxidation resistance and bending strength at high temperatures of 5 vol% Ni/(10 vol% ZrO2+Al2O3) were investigated in this paper. Oxidation tests were conducted at temperature ranging from 1100 to 1300oC for 1 to 24 h in air. The oxidation resistance of the composites was studied via observation of oxidized-zone development from a cross-section view after oxidation. Three-point bending tests were conducted at temperatures ranging from room temperature to 1200oC in order to estimate its performance at high temperatures. Bending strength of the composites achieved 1200 MPa at room temperature and 460 MPa at 1200oC. Dispersion of ZrO2in Ni/Al2O3composites enhanced both their room and high temperature bending strength. Nevertheless, ZrO2slightly degraded the oxidation resistance of the composites. The oxidation rate of Ni/(ZrO2+Al2O3) was one order of magnitude higher than that of Ni/Al2O3.
Torsion Strength Measurement of Engineering Ceramics
Authors: Feng Fen Jie , Yasuda Kouichi
Published: June 2018

This paper discusses the relationship between torsion strength and bending strength of Al2O3 and Si3N4 ceramics. Measurement of the torsion strength was carried out by a simplified torsion test method proposed by Yasuda and Tsutsumi. In this experiment, the average torsion strength was approximately 2/3 of its average bending strength for both ceramics. By estimating the characteristic strength σ0 in Weibull distribution from the strength data, σ0 in torsion is almost the same as that in bending, which agrees to the basic discussion in mechanics of materials. The characteristic strength σ0 is one of the normalized strength by eliminating the effects of specimen shape, dimensions and also its stress distribution, and therefore the apparent difference between torsion and bending strengths can be explained by the difference in effective surface area (Conversely, the measured torsion strength data by the simplified method must be reasonable). It reveals that biaxial fracture in tension/compression during torsion test is equivalent to uniaxial tensile fracture by this experiment.
Mechanical Properties of MgO-Doped Transparent Crystalline Alumina Fabricated by Two-Step Pressureless Sintering
Authors: Wang Xu Dong , Zhang Ya Ming , Wang Zi Jing , Zhi Qiang , Gao Chang Le , Wang Bo , Yang Jian Feng
Published: June 2018

Transparent polycrystalline alumina with high bending strength has been fabricated using two-step pressureless sintering. The microstructure and mechanical property has been investigated by varying the MgO doping concentration and sintering parameters. The results showed that the grain size markedly decreased with the increasing content of MgO addition. Although the density of alumina could be increased by the higher temperature for the first sintering step, the larger grain would depress the bending strength. Hence, the optimum bending strength was achieved with 0.5 wt% MgO with the two-step sintering of 1450°C for 20 min and 1400°C for 20 h. The Vickers hardness of the transparent PCA increased doping content, and the variation tendency was well accelerated with the relative density, indicated that the porosity plays a more important on hardness than the grain size.
Effect of Dealloying Process on Microstructure and Electrochemical Properties of Ni Foam
Authors: Hou Guang Ya , Li Ji Yu , Wu Lian Kui , Tang Yi Ping , Cao Hua Zhen , Zheng Guo Qu
Published: June 2018

Ni foam with 3D porous structure has attracted attention in the field of catalysis. Expanding the specific surface area of Ni foam is an important method to enhance its chemical properties. In this study, the Cu-Ni/Ni foam were obtained by electroless plating copper on Ni foam and then heat treatment for homogenizing at 750°C. The dealloying of the Cu-Ni/Ni foam was carried out by electrochemical etching for obtaining the Ni foam with hierarchical pore structure. The microstructure, phase and electrochemical performance were characterized by SEM, XRD and electrochemical testing. The results showed that the optimized temperature of electroless plating Cu on Ni foam is 60oC. Ni-Cu alloy can be obtained by counter diffusion above 750°C. With prolonging time of etching, the content of Cu component decreased and the size of pores on the sturts of the Cu-Ni/Ni foam changed from nano to micro scale. The electrochemical properties of the alloywere significantly higher than that of the pure nickel foam.
Upconversion Luminescence of ZnO-TiO2: Ho3+/Yb3+ Phosphor Powder
Authors: Kobwittaya Krisana , Oishi Yushi , Torikai Toshio , Yada Mitsunori , Watari Takanori
Published: June 2018

Ho3+/Yb3+ co-doped ZnO-TiO2 composite system were synthesized by powder-solution mixing method and their upconversion (UC) luminescence characteristics were investigated under the 980 nm laser excitation. The effect of various ZnO/TiO2 mixing ratios, and Ho3+ and Yb3+ concentrations were also studied. The XRD patterns showed that the product fired at 1300 °C consisted of Zn2TiO4, TiO2, RE2Ti2O7, and RE2TiO5 (RE = Ho3+ and/or Yb3+) phases. The green emission centered at 538 nm wavelength was detected as the strongest emission intensity which it was in accordance with the 5F4,5S2 → 5I8 transition of Ho3+ ion. The emission intensity of the product changed by varying ZnO/TiO2 mixing ratios, and Ho3+ and Yb3+ concentrations. Brightest UC emission was observed in the sample of 1ZnO:1TiO2 (in mole) doped with 0.03 mol% Ho3+, 9 mol% Yb3+ fired at 1300 °C for 1 h. Besides, the dependence of the UC emission intensity on the excitation power indicated that the two-photon process was responsible for this UC system.
High Emissivity of Ca2+/Fe3+-Doped LaAlO3 Based Ceramic Materials
Authors: Liu Jun , He Gang , Li Jiang Tao
Published: June 2018

High emissive Ca2+/Fe3+-doped LaAlO3 based ceramic materials were prepared by flame spraying and controlled crystallization method. The phase composition, microstructure, infrared optical properties of Ca2+/Fe3+-doped LaAlO3 based ceramic powders were investigated. The physical mechanism for the significantly enhanced infrared emissivity of LaAlO3 by doping with Ca2+ and Fe3+ was analysized. This high emissive Ca2+/Fe3+-doped LaAlO3 based ceramic materials shows promising applications in high temperature thermal process field to enhance the radiative heat transfer and improve its thermal efficiency.
Effects of Characteristic of Green Body on the Microstructure and Properties of Reaction Bonded Silicon Carbide
Authors: Xu Shao Chun , Wang Zi Jing , Zhang Ya Ming , Zhi Qiang , Matsushita Jun-Ichi , Yang Jian Feng
Published: June 2018

In this paper, reaction bonded silicon carbide (RBSC) was prepared by silicon infiltration with silicon carbide and carbon black as raw materials. The effects of the mixing methods with different binders on density of green body were compared. The influences of phenolic resin content, forming pressure, sintering temperature of samples on the performance of green body, mechanical microstructure and properties of RBSC were studied. The result shows that the density of green body by wet-mixing with alcohol-soluble binder (phenolic resin) was much better than semi-dry-mixing with usual water-soluble binders (polyvinyl alcohol and carboxy methyl cellulose sodium). The bending strength of green body prepared with phenolic resin at the content of 12 wt.% reached to the maximum value. The density of RBSC increased generally with phenolic resin content increasing at temperature range from 1550 to 1650 °C. The bending strength of RBSC increased firstly and then decreased with phenolic resin content increasing at a sintering temperature of 1600 °C. The optimum condition for fabricating RBSC was sintering at 1600 °C with 12 wt.% phenolic resin, the density, porosity and bending strength of the obtained RBSC was 3.06 g·cm-3, 0.05% and 370±54 MPa, respectively.
Ecological Hydrophobizing Admixture in Special Purpose Concretes
Authors: Babiak Michał , Ratajczak Maria , Kulczewski Piotr , Kosno Jacek
Published: June 2018

Nowadays, on the construction market, there are offered agents for concrete hydrophobization. In most cases, these are preparations that are applied on surfaces of already existing elements. The main disadvantage of such agents are strictly specified conditions, under which they can be applied. It is not recommended to apply the preparations for the elements under water level, exposed to contact with water under pressure, and with visible cracks and scratches [1, 2]. The article presents the results of tests of an innovative agent for concrete hydrophobization that has not disadvantages of the currently applied materials – application of the developed solution takes place at the stage of creating concrete mix. The preparation may be classified as an admixture for concretes.
Effect of Modern Air Entraining Admixtures on Physical Properties of Construction Mortars
Authors: Babiak Michał , Ratajczak Maria , Kulczewski Piotr , Kosno Jacek
Published: June 2018

The basic feature characterising the concrete’s quality and its usefulness for a structure is compressive strength. However, other features, such as frost resistance, absorbability, tightness, abrasiveness, decide on the durability of concrete in the structure as well. The paper presents the results of tests conducted on an ecological air entraining agent applied as a concrete mix admixture. The air entrainment of a concrete mix is aimed at entraining additional air pores with appropriate shape, size, and distribution into the concrete structure. The air entrainment is one of the main technological processes aimed at improving the concrete’s resistance to destructive effect of frost [1,2,3,4].
2D Geometrical Parameters Optimization Design Method of CMC/Metal Dovetail Joint
Authors: Yang Tian Yuan , Shi Duo Qi , Cheng Zhen
Published: June 2018

This paper establishes a 2D geometrical parameter optimization design method of CMC/metal dovetail joint by using ABAQUS and ISIGHT. Firstly, use the ABAQUS script to finish the 2D geometric parametric modeling and the whole process of the finite element analysis of the simplified dovetail joint in the Python language. Then use ISIGHT software to optimize the 2D geometrical parameters. Finally, compare the optimization results of different optimization methods and get the optimal design parameters. This method is really efficient for the preliminary 2D design of the CMC/metal dovetail.
Comparative Damage Analysis of Impact Induced Traditional and Graded Filament Wound Glass Fiber/Epoxy Composite Pipes
Authors: Ahankari Sandeep S. , Suryawanshi Atul , Warerkar Udayraj
Published: June 2018

Epoxy-glass fiber composite pipes were fabricated with filament winding machine. Full automation and precise control over the processing parameters are the major advantages of this manufacturing technique. Stacking sequence is one of the important processing parameters on which the properties of filament wound components depend to a large extent. This paper comes up with a comparative damage analysis of traditional composite pipes (TCPs) of stacking sequence [±55]6, and functionally graded composite pipes (FGCP) of stacking sequence [70-55-40-40-55-70]. The stacking sequence in FGCP was chosen such that the average stacking angle is retained the same as of TCPs, i.e. [±55]. An impact analysis of these pipes was carried out. Impact energy of 45 J was applied on both pipes and damage was quantified using back-lighting technique. It was observed that the damage occurred in FGCPs was 30% lesser compared to TCPs.
Production and Characterization of Whey Protein Concentrate (WPC) Based Nano-Fibers
Authors: Oktar Faik Nüzhet , Su Sena , Ozbek Burak , Yücel Sevil , Kazan Dilek , Gunduz Oguzhan
Published: June 2018

In this study, whey protein concentrate (WPC) and poly (ε-caprolactone) (PCL) composite nanofibers were prepared by electrospinning in the diameter of 50-350nm. Characterization tests of the polymer solutions such as density, viscosity, conductivity was studied. Fourier-transformed infrared spectroscopy (IR) results confirmed that the processed fibers were composed of both PCL and WPC constituents. Morphology of nanofibers composite was observed using scanning electron microscopy (SEM). Moreover the PCL/WPC nanofibers with high WPC content exhibited the maximum tensile strength (about 1.40 MPa).
Effect of Arenga Pinnata “Ijuk” Fiber as Nucleating Agent on Crystallization Kinetics of Impact Polypropylene Copolymer
Authors: Chalid Mochamad , Yuanita Evana , Ramahdita Ghiska , Fatriansyah Jaka Fajar
Published: June 2018

Impact Polypropylene Copolymer (IPC) is one of the PP type which is widely used. IPC was made with addition of ethylene in PP which decreases PP crystallinity. Many efforts have been made to improve the properties of PP crystallinity by addition of nucleating agents. In this study, we use Arenga Pinnata “Ijuk” fiber as PP nucleating agent. In order to determine the effect of “Ijuk” fiber as nucleating agents in kinetics aspect, we used DSC measurement based on Avrami equation. The results showed that the addition of ijuk decreases crystallizationhalf timeand dimension of crystal growth which indicate the effects of “Ijuk” fiber as a nucleating agent.
Conducting Properties of Polyaniline Emeraldine Salt on Paper in the Low-Frequency Region
Authors: Perez Phoebe Nicole G. , Sino Paul Albert L. , Herrera Marvin U. , Tapia Alvin Karlo Garcia
Published: June 2018

Polyaniline emeraldine salt (PAni-ES) was successfully deposited on paper through layer-by-layer technique. In this method, a paper was alternately dipped in aniline monomer and an oxidizing agent for different dipping cycles. This process produced green PAni-ES on paper. The morphology of the samples showed polymeric networks with pores, fiber-like structures and aggregates. There is a transition from frequency-independent to frequency-dependent conductivities of the samples. The conductivity increased with increasing number of dipping cycles. The frequency-dependent conductivities follow the power-law behavior reflecting conducting network and hopping mechanisms. Lastly, the conductivities with frequency followed a scaling behavior reflecting a common physical mechanism in PAni-ES on paper.
Microstructural and Mechanical Properties of Nano-Yttria-Oxide Doped Hydroxyapatite Composites
Authors: Gunduz Oguzhan , Yetmez Mehmet , Ekren Nazmi , Kilic Osman , Ben Nissan Besim , Oktar Faik Nüzhet
Published: June 2018

Nowadays hydroxyapatite (HA) bioceramics are very important because increasing traffic accidents and ageing of the population. They can be produced from synthetic or natural sources with different production methods. The biggest negative issue of HA is being very brittle and unstable under pressure. Various materials are added for restoring these weaknesses, but there is not so much studies adding nano-ingredients for restoring the mechanical properties of HA. In this study, 5-10% nano-yittria-oxide is added to bovine derived HA (BHA) and to commercial synthetic (CSHA) as a control group. Physical and mechanical properties are examined. Results show that adding of nano-ingredients are really helping to mechanical properties of HA.
Electrical Properties of Clinoptilolite/Aluminium Oxide/Bovine Hydroxyapatite Composites
Authors: Kalkandelen Cevriye , Moukbil Yunis , Oktar Faik Nüzhet , Ekren Nazmi , Kilic Osman , Gunduz Oguzhan
Published: June 2018

In current study the electrical properties of clinoptilolite/aluminium oxide/bovine hydroxyapatite composites (Cp/Al2O3/BHA) were analysed. Different concentrations of Cp and Al2O3 (5 and 15 wt% for both Cp and Al2O3) were added to BHA (70 and 90 wt% BHA) and studied after being sintered at 1000, 1100, 1200, and 1300°C for 4 hours under ambient conditions. The dielectric constant (ɛ'), theoretical dielectric constant (ɛ"), dielectric loss factor (tanδ), capacity and conductivity properties were measured on the frequency of 0.1Hz to 10MHz. As the experiment indicates the electrical capacity, loss factor and dielectric values of BHA, CSHA and Al2O3 are high at lower frequencies. While the composite materials, especially the 5wt% Cp and Al2O3 exhibits high stability, smaller amount of change and better conductive properties than pure substances.
Triangular Defects Reduction and Uniformity Improvement of 4H-SiC Epitaxial Growth in a Planetary Reactor
Authors: Lu Wei Li , Li Jia , Fang Yu Long , Yin Jia Yun , Feng Zhi Hong
Published: June 2018

High quality SiC Epilayers are essential for the development of high performance power devices. Killer defects such as triangular defects could cause leakage current paths within the high voltage SiC devices. This paper reports on the recent advances in 4H-SiC epitaxial growth toward high-throughput production in a commercial planetary reactor. The triangular defects are suppressed by the optimized pre-etching process, and the physics behind was investigated. The doping and thickness uniformities of the intra-wafer and wafer-to-wafer have also been improved.
CVD Filling of Narrow Deep 4H-SiC Trenches in a Quasi-Selective Epitaxial Growth Mode
Authors: Ji Shi Yang , Kosugi Ryoji , Kojima Kazutoshi , Mochizuki Kazuhiro , Kawada Yasuyuki , Adachi Kohei , Saito Shingo , Nagata Akiyo , Matsukawa Yasuko , Yonezawa Yoshiyuki , Yoshida Sadafumi , Okumura Hajime
Published: June 2018

By mapping the source and HCl flow rates dependent growth rates, the evolving trend of a quasi-selective epitaxial growth (quasi-SEG) that growing very thin epilayer on mesa top and ensuring an extremely low risk of voids defect generation was firstly figured out on a 5-μm 4H-SiC trench. Then, basing on the acquired knowledge, a 25-μm 4H-SiC trench with an aspect ratio up to ~10 was completely filled in the quasi-SEG mode.
Hot Filament CVD Growth of 4H-SiC Epitaxial Layers
Authors: Van Zeghbroeck Bart J. , Robinson Hannah , Brow Ryan R.
Published: June 2018

Hot filament CVD (HFCVD) growth of undoped 4H-SiC epitaxial layers on 100 mm n-type 4o-off 4H-SiC substrates is presented as an alternate growth method for the first time. High quality crystalline material with a low density of polytype inclusions has been demonstrated and characterized with optical micrographs, SEM imaging, micro-Raman measurements, and high resolution XRD. Typical growth rates are ~3 μm/hour. Double rocking omega scans revealed diffraction peaks with a FWHM of 23 arcsec.
Silicon (001) Heteroepitaxy on 3C-SiC(001)/Si(001) Seed
Authors: Yeghoyan Taguhi , Alassaad Kassem , McMitchell Sean R.C. , Gutierrez Marina , Soulière Véronique , Araujo Daniel , Ferro Gabriel
Published: June 2018

We report for the first time the successful heteroepitaxial growth of Si(100) oriented layer on top of a 3C-SiC(001) seed. By using a post-growth modification of the 3C-SiC surface (pulse insertion of precursors during cooling), it led to a change in Si nucleation, favoring squared (100) islands instead of elongated (110) ones. Without this surface modification step, the Si layers grown on 3C-SiC were always polycrystalline with a mixture of (110) and (100) orientations. Using such Si(100) layer grown on top of 3C-SiC(100), a (100) oriented 3C-SiC single crystalline layer was successfully grown on top, fabricating thus for the first time a fully (100) oriented multilayer heterostructure made of Si(substrate)/SiC/Si/SiC.
Defects and Polytype Instabilities
Authors: Pezoldt Joerg , Kalnin Andrei Alexandrovich
Published: June 2018

A model based on the generation and recombination of defect was developed to describe the stability of stacking faults and basal plane dislocation loops in crystals with layered polytype structures. The stability of the defects configuration was analysed for stacking faults surrounded by Shockley and Frank partial dislocation as well as Shockley dislocation dipoles with long range elastic fields. This approach allows the qualitative prediction of defect subsystems in polytype structure in external fields.
Extension, Closure and Conversion of In-Grown Stacking Faults in 4H-SiC Epilayers
Authors: Li Zhe , Ju Tao , Zhang Bao Shun , Zhang Xuan , Zhang Li Guo , Zhang Ze Hong
Published: June 2018

In-grown stacking faults (IGSFs) generated in 4H-SiC epilayers were characterized. Melted KOH etching, room-temperature cathodoluminescence, low-temperature photoluminescence and cross-section transmission electron microscopy was conducted to investigate the propagation of the IGSFs in the down-stream region of a 3C inclusion. It was found that the SFs could extend, close and convert during the epitaxial growth. The origin of these IGSFs were attributed to the interference introduced by the 3C inclusion to the step-flow growth, and the propagating behaviors of these IGSFs were discussed.
Immobilization Phenomenon of Partials Surrounding Double Shockley Stacking Faults in Heavily Nitrogen Doped 4H-SiC Crystal with Thermal Anneal
Authors: Sugiyama Naohiro , Suo Hiromasa , Eto Kazuma , Tokuda Yuichiro , Kamata Isaho , Hoshino Norihiro , Kato Tomohisa , Tsuchida Hidekazu , Okumura Hajime
Published: June 2018

The expansion behavior of double Shockley stacking faults (DSFs) was investigated in heavily nitrogen doped 4H-SiC crystals at high temperatures up to 1350°C. An immobilization phenomenon of partials surrounding DSFs was discovered by a thermal annealing at temperatures over 1275°C. The electric properties of SiC crystal were maintained after the partial dislocations were immobilized with a high temperature annealing. The mobile partial dislocations extended straight, but the immobile ones bent toward the glide direction. This immobilization phenomenon is significant and useful for achieving low-resistance SiC substrates without DSFs.
Influence of Triangular Defects on the Electrical Characteristics of 4H-SiC Devices
Authors: Schoeck Johannes , Schlichting Holger , Kallinger Birgit , Erlbacher Tobias , Rommel Mathias
Published: June 2018

Using a combination of photoluminescence and electrical characterization, defects in the epitaxial layer of unipolar 4H-SiC power devices were matched to device characteristics and statistically analyzed. In-grown triangles had no significant effect on diode and VDMOS blocking or conduction mode, while surface triangles lead to high leakage currents even below 1 V reverse bias.
Origin Analysis and Elimination of Obtuse Triangular Defects in 4° Off 4H-SiC Epitaxy
Authors: Mao Kai Li , Wang Ying Min , Li Bin , Zhao Gao Yang
Published: June 2018

The obtuse triangular defects would result in higher leakage currents and the preferential gate oxide breakdown of SiC devices. The formation and structural features of obtuse triangular defects on the 4° off 4H-SiC epilayers were investigated by confocal microscope and photoluminescence image. Two structrures of obtuse triangular defects were found. By optimizing the growth process, obtuse triangular defect free epitaxial layers were abtained on SiC substrate with serveral stacking fault. The number of triangular SFs defects was less than 0.5/cm2.