bluuebunny/crossref_metadata_2025 huggingface dataset:
Gelcasting of Fused Quartz Crucible with Large Scale
Authors: Sun Cheng Gong , Niu Jin Ye , Li Hai Jian , Lian Qiang , Yu Hai Jie , Zhang Fei Fei
Published: June 2012

Fused Quartz crucible with large scale was formed by gelcasting processing in this paper. Effects of dispersant, pH values and particle grading on solids content of slurries were discussed to increase the volume density of the green compacts and decrease the shrinkage and deformation during sintering. Effects of acrylamide content and the ratio of acrylamide to coupling agent on bending strength of the green compacts were investigated. Effects of the amount of initiator and curing temperature on the gelcasting processing were studied as well. The green compacts with solids content of 80% was obtained when the addition ratio of dispersant to Quartz powders was 0.3wt %, the ratio of Quartz powders in D50 of 1.9μm and 7.6μm was adjusted to 3:7, the addition ratio of acrylamide to Quartz powders was 1.0wt % and the ratio of acrylamide to coupling agent was 16:1. The bending strength of the sinterred produts was found to be 76.0MPa with volume density of 1.94 g/cm2. Fused Quartz crucible prepared under conditions mentioned above was 800mm in length, 800mm in width and 400mm in height.
Preparation and Mechanism of Interconnected Mesoporous Carbon Monoliths from Phenolic Resin/Ethylene Glycol Mixtures
Authors: Zhang Gang , Xiao Ze Wen , Qiao Guan Jun
Published: June 2012

The preparation of interconnected mesoporous carbon monoliths (MCMs) derived from phenolic resin/ethylene glycol mixtures based on polymerization-induced phase separation have been investigated for fabrication of complex-shape SiC ceramics. The effect of the ethylene glycol content, curing catalyst and the curing temperature on the pore structure and pore distribution of carbon monoliths has also been studied, with emphasis on controlling the apparent porosity and pore size distribution. Fractal dimensions (DF) was proposed to evaluate the morphologies of carbon monoliths by using the box counting method. The results show that interconnected mesoporous carbon monoliths with narrow pore size distribution were obtained by changing the curing temperature and the content of ethylene glycol, curing catalyst in the resin mixtures and its mechanism was discussed in this paper. In this paper, interconnected mesoporous structure was attributed to the mechanism of spinodal decomposition (SD), which was discussed in detail. Carbon monoliths inherit their porosity from cured resins where it was formed as a result of phase separation of resin-rich and glycol- rich phases.
The Effects of Different Slurry on the Joining Characteristics of SiC Green Body
Authors: Huo Yan Li , Liu Hai Lin , Wang Chun Peng , Tang Jie , Chen Yu Feng , Wu Ming Hui
Published: June 2012

Experiments were carried out to join reaction-bonded silicon carbide (RBSC) ceramic in green body. SiC green bodies were fabricated by gel-casting method. The slurries for joint were prepared by different grain size of SiC. The results indicate the solid loading and the grain size of SiC influence the strength of welding. There is no clear welding interface between the two substrates in an appropriate solid volume loading and grain size. The average bending strength of welding after sintering can reach 300MPa. SEM was used to observe the cross-section morphology and microstructure of binding sites. The test result shows that its microstructure is similar to the RB-SiC ceramic. The mechanical properties of binding sites were tested. The result shows a desirable mechanical property.
Microstructure and Mechanical Performances of C/C Composite and TC4 Alloy Brazed Joints
Authors: Li Jia Ke , Liu Xin , Zhou Jian Er
Published: June 2012

C/C composite and TC4 alloy were successfully brazed using 70Ag28Cu2Ti (wt. %) as filler metal at brazing temperature 820 º°C~920 °C for soaking time 5 min ~30 min. The effects of brazing parameters on the microstructures and phase composition and the fracture modes of the brazed joints were investigated by SEM and XRD. The mechanical performances of the brazed joints were measured by a universal mechanical testing machine. The results show that the maximum shear strength of the brazed joint is 28 MPa at brazing temperature 860°C and soaking time 10min. Fracture surface analysis of the brazed joints indicates that the position of the fracture surface is related to the orientation of carbon fiber. The brazed joints are fractured in the C/C composite when the carbon fiber is parallel to the joined surface, and the brazed joints are fractured at the C/C composite / 70Ag28Cu2Ti interface when the carbon fiber is vertical to the joined surface.
Debinding Behaviors and Mechanism of Injection Molded ZrO2 Ceramics Using Kerosene as Solvents
Authors: Liu Wei , Xie Zhi Peng , Zhang Li Li , Yang Xian Feng
Published: June 2012

In this study, low-cost kerosene with low toxicity was used as organic solvent to research the solvent debinding behavior of ceramic compact produced by injection molding. The Influences of time, temperature and solid loading on the debinding rate were investigated, the mechanism of which was also discussed. The results show that: The debinding rate increased with increasing temperature and decreased with extended time; Diffusion is the controlling factor at the initial stage and temperature was the main factor influencing the reaction rate; Dissolution is the controlling factor and concentration difference was the main factor at the later stage; The higher the solid loading of green body, the slower the debinding rate and the lower the final proportion of binder removal.
Bond Strength of Different Adhesive Luting Materials to Zirconia Ceramics
Authors: Liu Qi , Shao Long Quan , Hu Chen , Yi Yuan Fu , Deng Bin , Wen Ning
Published: June 2012

To investigate the bond strength of different adhesive luting materials bond to zirconia ceramics. 40 (30mm×5mm×5mm) Cercon Smart Ceramics samples were divided into groups: (1) glass-ionomer bonded (control group), (2) Clearfil™ Repair bonded, (3) Panavia F bonded, (4) Variolink N bonded. Tensile bond strength and shear bond strength were evaluated after 24h storage at 37°C in distilled water. Each group had 10 samples for different test. Data were evaluated using ANOVA analysis (α=0.05). The experiment groups are statistically significant differences with control group (P<0.05). The shear bond strength of the Glass ionomer FX Ι, the Clearfil™ Repair, Panavia F and Variolink N groups were 14.23±4.48 MPa, 21.95±1.32 MPa, 31.16±1.50 MPa and 43.54±1.97 MPa, separately. Comparisons among groups were significant differences (P<0.001). Variolink N bonded ceramics achieved highest tensile and shear bond strength. Different adhesive materials significantly influence the bond strength of zirconia ceramics.
Fabrication and Optical Properties of Sm2Zr2O7-NiCr2O4
Authors: Li Tao , Liu L. , Xu Q. , Zhu S.Z.
Published: June 2012

Sm2Zr2O7 is one of the promising candidate materials for the next generation thermal barrier coatings because of its excellent thermal properties. But at high temperature the thermal conductivity of rare-earth zirconate increases because of radiation conduction. NiCr2O4, which can absorb the infrared photons intensely, was introduced to reduce the radiation conduction of rare-earth zirconate. NiCr2O4 powder was prepared by coprecipitation. The bulks of Sm2Zr2O7— NiCr2O4 with different content of NiCr2O4 were prepared by using non-pressure sintering. The phase and microstructure of the samples were characterized by XRD and SEM. The optical absorption was also investigated. The absorptivity of the composite, which was generally higher than that of pure Sm2Zr2O7 prepared by coprecipitation and non-pressure sintering, was enhanced with the content of NiCr2O4 increasing. The enhancement of absorptivity will reduce the radiation conduction of rare-earth zirconate potentially.
Modeling the Cracking Process of the YSZ Thermal Barrier Coating under the Thermal Shocking Loads
Authors: Liu Jin Tao , Shen Wei , Fan Qun Bo , Cai H.N.
Published: June 2012

For low thermal conductivity and high corrosion resistance, yttria stabilized zirconia (YSZ), as a top coat (TC), is widely used in thermal barrier coatings (TBCs), and the micro-structure of the TC has significant effects on it thermal shock resistance. Combining digital image processing technique with finite element mesh generation methods, finite element (EF) models based on actual microstructures of plasma sprayed YSZ thermal barrier coatings are built in this paper, so as to simulate the coating’s dynamic failure process when suffering thermal shocking loads. The cracking process is revealed by calculating both the stress and strain evolutions within the coating. Based on the proposed method, the effects of porosity and distribution are further studied. The simulation results agree well with the experimental observation, indicating that the cracks are mainly caused by pore connectivity, which promotes the growth of cracks. This work is expected to be helpful to establish the quantitative relationship between the TBCs porosity and the coating’s service performance.
A Simple Laminated Alumina Based Composite with High Work of Fracture
Authors: Li Wei Xin , Lu Ying , Rao Ping Gen , Huang Xiu Lin
Published: June 2012

A kind of laminated composite named Al2O3/Nylon/Al with high work of fracture was prepared by a simple process using epoxy resin adhesives as binder in a leaky mold at a pressure of 5 MPa. Light microscopy and scanning electron microscopy were employed to observe the microstructures and crack propagation of the laminated composites. The flexural strength and fracture toughness were measured through three-point bending test, and the work of fracture of the laminated composite was calculated from load-displacement curves of three-point bending test. The experimental results show the composite have low Young's modulus and flexural strength, however, the work of fracture of the laminated composite appears to be high of 2850 J/m2, and the fracture toughness reaches about 11 MPa•m1/2. Analysis of microstructure and crack propagation reveals that the failure of the laminated composite exhibit distinctive characteristic.
CASTEP Calculation of Surface Energy of α-Al2O3
Authors: Liang Yan Yuan , Chen Da Ming , Tong Jiang Feng
Published: June 2012

First principles calculations were run on bulk and the （110）（001）（012）（113） surfaces of α-Al2O3 in order to examine the growth habit of α-Al2O3 crystals.The Materials Studio package was used, specifically the program CASTEP, utilizing Perdew Burke Ernzerh of exchange-correlation pseudo-potentials. The calculation results shows that the ranking of the face energy on different crystal face are E(001)‹ E(113) ‹ E(012) ‹E(110) which is in good agreement with experiment phenomenon observed that the ranking of the growth rates of different crystal faces are V(001) ‹ V(113) ‹ V(012) ‹ V(110).
Hydrothermal Corrosion of Alumina Ceramics under Static and Quasi-Dynamic Conditions
Authors: Galusková D. , Hnatko Miroslav , Galusek D. , Šajgalík Pavol
Published: June 2012

Corrosion resistance of solid state (SSS) and liquid phase sintered (LPS) alumina under hydrothermal conditions (subcritical water and sodium chloride solution at temperatures up to 290 °C, and pressures up to 7 MPa) was evaluated. The influence of sintering additives as well as the conditions of the test (temperature, corrosion medium) on dissolution of ceramics was studied. For evaluation of the corrosion mechanisms special attention was paid to determination of the eluate chemistry combined with the chemical and phase analysis of corroded surfaces. Corrosion of LPS alumina in both media was controlled by dissolution of calcium aluminosilicate grain boundary glass. Corrosion rates of SSS ceramics were several times lower and were largely controlled by dissolution of highly resistant alumina matrix. Corrosion of the ceramics was moderately faster in sodium chloride solution. The data are supplemented by calculations of phase equilibria in the corrosion solutions.
Influence of the Two Metal Dopant Improves the Specific Surface Area of Alumina in Catalyst Support
Authors: Zhang Wei Jun , Hu Jin , He Xiao Kun , Shen Li , Yan Lei , Luo Hong
Published: June 2012

The study of this paper is La and Ba(La⁄Ba=1:1) doped modifying alumina. And we focus on the need for influence on content(La+Ba) and calcination temperature on the S.A of modified alumina. Factors considered were the S.A, it’s attenuation and phase in calcined etc. Screening out the sample of better comprehensive performance. At the same time the less content(La+Ba) can reduce the manufacturing cost of the catalyst.
Effects of Solvents on Synthesis and Dispersion of Zircon Powder via Non-Hydrolytic Sol-Gel Route
Authors: Jiang Wei Hui , Cheng Si , Zhu Qing Xia , Liu Jian Min
Published: June 2012

Zircon nano–powder has been synthesized via the non-hydrolytic sol–gel route, using industral zirconium tetrachloride (ZrCl4) and tetraethoxysilane (TEOS) as precursors, lithium fluoride (LiF) as mineralizer, PEG1000 as dispersant. The effects of solvents on the synthesis and dispersion of zircon nano-powder were investigated by means of XRD and TEM. The results indicate that the aprotic solvent N, N-dimethyl formamide (DMF) is not conducive to the nucleophilic substitution reaction, which directly affect the zircon synthesis, and the particles are easy to agglomerate due to the large surface tension; the powder with size of 30nm and good dispersion can be obtained using dichloromethane (CH2Cl2) as solvent; different anhydrous alcohols as solvents influence zircon synthesis, the order of the synthesis ratio is listed as EtOH›propanol (PrOH)› isopropanol (PriOH). Powder particles are larger than 50nm with wide distribution and serious agglomeration when taking PrOH and PriOH as solvents. Nano-zircon with good dispersion and synthesis ratio up to 94.5% can be obtained via using ethanol as solvent.
A Novel Way to Synthesis Magnesium Aluminate Spinel Powders by Polymer Gel Reaction
Authors: Tong Jiang Feng , Chen Da Ming
Published: June 2012

In this paper, a fine pure Magnesium aluminate spinel powder was synesised by Gel solid reaction,using Al(NO3)36H2O and Mg(NO3)26H2O as raw materials under given condition. The precursor was formed by polymer gelling.The phase changed according to heating temperatures from 700°C to 900°C.The single phase of Magnesium aluminate spinel was obtained by calcining the precursor at temperatures higher than 900°C. The phase changing process and relationship among calcination parameters, phase composition and image of particle are studied to determine the optimal conditions for the synthesis of fine Magnesium aluminate spinel powder. The powder obtained was characterized by XRD,TEM etc. The results of analysis showed that the ultrafine powder is of spinel phase, high purity, good dispersion.This process for preparing fine Magnesium aluminate spinel powder was very simple and inexpensive.The results of analysis showed that the ultrafine powder was of mullite phase, high purity, good dispersion, and the particle were homogeneous.
Properties of Boehmite AlO(OH) Nanoparticles as the Coatings and Fillers
Authors: Nagai Naofumi , Ihara Kazuhiro , Itoi Ayaka , Kodaira Tetsuya , Hakuta Yukiya , Takashima Hiroshi , Bando Kyoko K. , Itou Naotsugu , Mizukami Fujio
Published: June 2012

Boehmite nanoparticles with different shapes and lengths were used in the preparation of the boehmite films and coatings, and as the fillers for an organic polymer. Then, it was investigated how the shapes and lengths of the particles reflected the characteristics of the films, coatings and fillers. The films were prepared by casting an aqueous sol of the nanoparticles on a Teflon-lined plate, drying and peeling. The coatings were fabricated on porous alumina tubes or graphite sheets by dipping the substrates into a sol of the nanoparticles. The boehmite-polyvinyl alcohol (PVA) composite films, in which the nanoparticles are fillers, were prepared by casting a mixture of a boehmite nanoparticle sol and PVA. The films, coatings and composites were characterized by TEM, TG-DTA, gas permeability, pore size distribution and thermal expansion measurements. In the films, fibrous particles with aspect ratios over 50 aggregated in parallel to each other to form slit-like micropores, on the other hand, plate- and rod-like particles with aspect ratios below 10 randomly aggregated to form meso pores. Corresponding to this, for the coatings on porous alumina tubes and graphite sheets, the fibrous particles gave much low gas permeability and high thermostability, respectively, compared with the plate-like and rod-like particles. For the boehmite-PVA composite films, the fibrous particles gave lower thermal expansion than the plate-like and rod-like particles.
Hollow Multiphase Ceramic Microspheres of Al+Cr2O3+SiO2 System Prepared by Self-Reaction Quenching Technology
Authors: Cai Xu Dong , Wang Jian Jiang , Xu Bao Cai , Lou Hong Fei , Huo Xing Jian
Published: June 2012

This paper aims to study preparation and mechanism of hollow ceramic microspheres. With Al+Cr2O3+SiO2+sucrose+epoxy resin as reactive system, Al2O3-based hollow ceramic microspheres are synthesized and reaction mechanism of hollow ceramic microspheres is established. Results show that the quenching products consist of hollow spherical or irregularly spherical particles and irregularly powders. Spherical or irregularly spherical particles are hollow structure and constitutive of Al2O3-SiC diphase and a few Cr3Si、Cr7C3. The preparation of hollow ceramic microspheres includes igniting by heating, forming ceramic thawy droplets and fast cooling. The great deal of air produced by burning epoxy resin and sucrose is the key reason why hollow ceramic microspheres are formed.
Microstructure and Properties of Laser Cladding Cu-TiB2 Composite Coating on Copper
Authors: Guo Xiao Qin , Chen Jing Bo , Zhang Xin Fang , Wang Yong Kai , Zhang Rui
Published: June 2012

Cu-TiB2 composite coatings were in-situ synthesized on the copper substrate by using a Nd: YAG laser. The microstructure of the coating and the bonding interface between the laser cladding layer and the substrate were studied by X-ray and SEM. The microhardness and the wear resisting property were tested. The results show that the TiB2 particles were well-proportioned and spherical existing in the coating layer, the bonding interface between the layer and substrate was metallurgical bonding. The microhardness reaches HV450 and the wear resistance is about 10 times as much as that of Cu substate.
Ion Irradiation Effects on Ho2+xTi2-xO7-x</>/2 (x=0, 0.4 and 0.67)
Authors: Li Yu Hong , Wang Yong Qiang , Wen Juan , James Valdez A. , Sickafus Kurt E.
Published: June 2012

We recently synthesized different composition polycrystalline Ho2+xTi2-xO7-x/2 (x=0, 0.4 and 0.67), which is derivative fluorite compounds known as and pyrochlore phases in Ho3O2-TiO2 phase diagram by using conventional solid state synthesis methods. The samples were irradiated with 400 keV Ne2+ ions at cryogenic temperature (~77 K), using the Danfysik ion accelerator at the Ion Beam Materials Laboratory (IBML) of Los Alamos National Laboratory (LANL). The irradiation fluences in the experiments ranged from 5×1014-5×1015ions/cm2. An order-to-disorder (O-D) transformation was observed for α, β and pyrochlore phases, as determined using grazing incidence X-ray diffraction (GIXRD) at an incident angle of 0.25°. The O-D transformation threshold fluence for α phase was found to be noticeably lower than those for β phase and pyrochlore, and the O-D transformation threshold fluence for β phase was the highest. The O-D transformation threshold fluence was found to be coherent with the phase transformation temperature in the Ho3O2-TiO2temperature-composition (T-C) phase diagram.
Fabrication of Graphene/Zirconia Nanocomposite by Mixing Graphite Oxide and Zirconia Nanopowders and Pressureless Sintering
Authors: Yin Zheng E , Zhang He , Kang Yan Ru , Feng Jian Min , Li Ya Li
Published: June 2012

Graphene has unique two-dimensional nanostructure with high specific surface areas, superior mechanical properties which has promising applications for the development of high performance nanocomposite materials. Most of previous work on graphene nanocomposites addresses on polymer matrix. In the present work, we have fabricated zirconia and graphene nanocomposites (ZrO2/GNS) by simple mechanical mixing and pressureless sintering process. Microstructural observations of the composite show the homogeneous and random distributions of graphene nanosheet in the zirconia matrix. Scanning electronic microscopy observes partially pulled out graphene nanosheets with well combined interface with the matrix in fractural surface, showing promising reinforcement effects.
Study on Properties of Slurry for Making Zirconia Fiber
Authors: Sun Hao Ran , Chen Yu Feng , Shi Xing , Zhang Shi Chao , Wu Wei
Published: June 2012

Zirconia fibers have recently become a research hotspot for their superior physical and chemical properties. In this paper, zirconia slurry was prepared by inorganic salt solution added with zirconia powders, the effect of content of PVA, PEG and zirconia powder solid content of the slurry on properties of slurry was studied. Research shows that: the content of PEG as a dispersing agent was 5wt.%, The dispersibility of zirconia powder and stability of slurry got the best, but slurry viscosity was correspondingly higher. Solid content of zirconia powder had an important impact on the rheological properties of slurry, when zirconia solid content was less than 30%, the slurry showed as a pseudoplastic fluid, whereas the zirconia solid content of slurry became 40% and 50% it exhibited plastic fluid characteristics. Solid content of slurry was 50wt.%, the stability of slurry got the best.
Preparation and Assessment of C/C-ZrB2-SiC Ultra-High Temperature Ceramics
Authors: Fan Jie , Zhou Chang Ling , Wang Chong Hai , Wang Yan Yan , Liu Rui Xiang
Published: June 2012

With the background of thermal protection applications of anti-oxidation carbon fiber reinforced composites, carbon fiber reinforced ultra-high temperatureceramics with homogeneous disperse complex matrix of C-ZrB2-SiC (C/C-ZrB2-SiC) was prepared. Carbon fiber performs were deposited with pyrolytic carbon by chemical vapor infiltration method. Subsequently, the composite precursors were prepared by completely mutually dissolving of ZrB2 polymeric precursor and polycarbosilane dimethylbenzene solution. Then the nano-dispersed ZrB2-SiC composite ceramic was introduced into the C/C preforms by polymer impregnant and pyrolysis process. The C/C-ZrB2-SiC composite shows excellent ablation behavior with the ablating rate of 8*10-4mm/s. The microstructural and compositional characterizations of the C/C-ZrB2-SiC composites indicates that ZrB2 nanoparticle is distributed homogeneously in the continuous SiC phase, which is beneficial to enhance ultra-high temperature ablation resistance of the composites.
Electrical and Mechanical Properties of ZrB2-Based Composite Ceramic
Authors: Wang Yan Yan , Liu Kai , Zhou Chang Ling , Wang Chong Hai , Liu Rui Xiang , Luan Yi Na
Published: June 2012

The ZrB2-SiC composite ceramic was prepared using Al2O3 and Y2O3 as additives through pressureless sintering under 1800°C. The electrical and mechanical properties were studied with the different mass ratio of ZrB2 and SiC. The microstructure and phase transformation of the ZrB2-SiC composites ceramic were characterized by scanning electron microscopy. Results show that the densities of the samples are decreased with the decrease of the mass ratio of ZrB2 and SiC while the resistivities are increased. When the mass ratio of ZrB2 and SiC is 4 the resistivity reaches 14μΩ•mm while the density is 4.85g/cm3. When the mass ratio of ZrB2 and SiC is13:7, the flexural strength reaches the max value and toughness reaches the minimum value. The flexural strength reaches 233Mpa and the toughness reaches 4.51 Mpa• m 1/2. The changes of the properties of the ceramic were analyzed through the microstructure and the conduction mechanism was studied.
Effect of Carbon Fibers’ Surface Modification on the In Situ Growth of Carbon Nanotubes
Authors: Hu Jian Bao , Dong Shao Ming , Zhang Xiang Yu , Hu Zhi Hui , Lu Bo , Yang Jin Shan , Li Qing Gang , Wu Bin
Published: June 2012

Surface modification of carbon fibers(CF) by physicochemical methods directs an attractive approach for improvement of metal uptake from solutions. We investigated pretreatment of carbon fibers by HNO3 with different time on absorption of catalysts, which is related to the coverage of carbon nanotubes (CNTs) grown on Carbon fibers. The effects of surface modifications on the properties of carbon fibers were studied by X-Ray photoelectron spectroscopy. The modifications bring about variation in the chemical properties. The modification increased a large number of surface functional groups such as hydroxyl and carbonyl. The HNO3 modification increases the catalysts absorption. The coverage of CNTs on CF increases with pretreatment time, which was studied by SEM.
Low Temperature Molten Salt Synthesis of Nano Crystalline MgAl2O4
Authors: Safaei Naeini Yousef , Golestani-Fard Farhad
Published: June 2012

MgAl2O4 (MA) spinel nano powder was synthesized using a molten salt technique, by heating stochiometric composition of MgO and AlOOH. NaCl salt was used as reactor media for MA spinel formation. Reactants and molten salt mixtures were fired in an alumina crucible for 3 h at temperature ranges from 850 oC to 1000 oC. The synthesis temperature was decreased from 1300 oC required by the conventional solid–solid reaction process to 850 oC for molten salt approach. The synthesized powders were characterized by X-ray diffraction pattern (XRD), scaning electron microscopy (SEM) and Brunauer-Emmett-Teller technique (BET). XRD revealed complete formation of MA without remaining of any secondary phase for synthesized powder fired at 850 oC for 3 h. Moreover, electron microscopy illustrated that the MA morphology and size was the same as the nano boehmite morphology which confirmed the existence of a ‘template process’ mechanism during the molten salt synthesis. In addition, high surface area for nano MA powders was achieved in this method.
Effect of Aging pH Value on the Properties of Porous SiC Ceramics Produced through Coat-Mix Process
Authors: Yang Hui , Zhao Hong Sheng , Liu Zhong Guo , Li Zi Qiang , Zhang Kai Hong
Published: June 2012

The core-shell structure precursor powder was synthesized through coat-mix process, and a small amount of Al2O3, SiO2and Y2O3composite additives were added. Porous silicon carbide ceramics were produced after molding, carbonization and sintering, and the crystalline phase, weight loss, porosity, bending strength, and thermal expansion coefficient were measured. The effect of aging pH value of coat-mix process on the characterization of porous SiC ceramics had been analyzed. The results indicate that the crosslink degree and curing rate of the phenolic resin is adjusted by changing the aging pH value, and the coating effect in the coat-mix process is improved. Thereby, the flexural strength, thermal expansion coefficient, porosity and pore distribution of the porous SiC ceramics could be adjusted according to the application requirements. When the pH value ranges from 3 to 5 or higher than 7, the phenolic resin shows a lower crosslink degree and char yield, while the ceramics show a higher porosity and a lower thermal expansion coefficient; and the flexural strength decreases as the aging environmental pH value increases.
Preparation and Properties of SiC Nanocrystallite Reinforced Amorphous Si–B–C–N Ceramics
Authors: Huang Xia , Li Ya Jing , Li Song , Tang Xiao Xia , Zhang Yue
Published: June 2012

Amorphous Si–B–C–N ceramics synthesized by polymer thermolysis possess excellent chemical, thermal and mechanical stability at high temperature. Many attentions have been devoted to study the crystallization and stability of Si–B–C–N ceramics. The SiC nanocrystallite reinforced amorphous Si–B–C–N ceramics have been fabricated by pyrolysis of single-source precursors at high temperature. The heat-treatment at high temperature commonly impaired the thermal stability of the composites. Crack and pore limit the development of the composites. New processing routes that overcome those problems are desirable. Here we reported the thermolysis of binary-source precursors mixed by polycarbosilane and boron-modified polyvinylsilazanen to fabricate Si–B–C–N composites with relative densities up to 96%. Green bodies were obtained by compaction of precursors using warm pressing at different temperature. The obtained composites were characterized by Scanning Electron Microscope and X-ray Diffraction.
Silicon Carbide Composites Deposited in Silicon Carbide Whiskers by CVI Process
Authors: Meng Fan Tao , Du Shan Yi , Zhang Yu Min
Published: June 2012

Chemical vapor deposition (CVD) is an effective method of preparing silicon carbide whiskers or films and chemical vapor infiltration (CVI) can be successfully used as the preparation of SiC composites. In this paper, silicon carbides whiskers were firstly deposited on substrates of RB-SiC by CVD process and then silicon carbide composites were prepared by chemical vapor infiltration in the SiC whiskers in an upright chemical vapor deposition furnace of Φ150mm×450mm with methyltrichloride silicane (MTS) as precursor gas, H2 as carrier gas and Ar as dilute gas. The morphologies of the SiC whiskers grown on RB-SiC substrate and SiC composites infiltrated in SiC whiskers were determined by scanning electron microscope (SEM), and the crystalline phase of the final deposits were confirmed with X-ray diffractometry (XRD) As a result, the curly defects of whiskers decrease with the addition of dilute gas. And by chemical vapor infiltration in SiC whiskers the, SiC composites were successfully prepared. Finally the deposits were determined as β-SiC.
Pressureless Sintering of Silicon Nitride Porous Ceramics with High Porosity and Bimodal Pore Structure
Authors: Chen Fei , Shen Qiang , Zhang Lian Meng
Published: June 2012

In this paper, silicon nitride porous ceramics with high porosity and bimodal pore structure were prepared using pressureless sintering at 900~1100°C. In these porous ceramics, zirconium phosphate (ZrP2O7) was used as a binder and starch and naphthalene powders were used as pore forming agents. The obtained results showed that the porosity could be controlled in the range of 34 % to 70 % by changing the content of pore forming agents. The pores were formed by the continuous reaction of ZrP2O7 at ~250 °C and burnout of starch at ~550 °C (when starch was used as a pore forming agent), or sublimation of naphthalene at 80°C (when naphthalene was used as a pore forming agent). The bimodal pore structure was produced with pore size of less than 0.5m and ~10 m when using starch as a pore forming agent and the pore size of less than 0.5m and ~30μm when using naphthalene as a pore forming agent.
Preparation and Properties of Polyalcohol Phase Change Material for Insulation
Authors: Wu Wei , Chen Yu Feng , Shi Xing , Zhang Shi Chao , Sun Hao Ran
Published: June 2012

In this paper, the composite phase change materials for insulation were prepared by melt-soaking method. Trimethylolethane (PG) was chosen to be the phase change material (PCM) and two kinds of porous materials as the supporting matrices separately. The effects of both matrices to PG were analyzed by X-ray diffraction (XRD), and the heat insulation properties of composites were evaluated by Plat heat insulation test device. At last, microstructures of composites were observed by scanning electron microscope (SEM) and their effects to composites were discussed.
The Pyrolysis Processing of Polycarbosilane Studied by TG, XRF, IR, XRD, and XPS
Authors: Jiao Jian , Qiu Hai Peng , Li Xiu Qian , Luo Jing Hua , Wang Yu
Published: June 2012

Polycarbosilane (PCS) is one of precursor systems applied in industry for the Polymer Infiltration Pyrolysis (PIP) processing of C or SiC fiber reinforced SiC matrix composites (Cf/SiC or SiCf/SiC CMC) materials. In this work, a series of PCS-derived SiC specimens treated at 300, 550, 800, and 1100 °C was studied by XRF, IR, XRD and XPS methods. The results show that a slight amount of PCS molecules with low softening point evaporates below 300 °C; the cross-link between PCS chains takes place to form a 3D -Si-C-Si- network via the reaction between -Si-CH3, -Si-CH2-Si- and -Si-H groups in the temperature range of 300-550 °C; an amorphous phase of SiC was observed when PCS was heated up to 800 °C, which indicates the completion of transformation from organic to inorganic; above 800 °C, β-SiC domain grows. Furthermore, a surface structure evolution of PCS-derived SiC specimens with temperature is proposed after the analyzing the XPS spectra.
Microstructure and Properties of Ferrite/Organic Nanocomposite Prepared with Microemulsion Method
Authors: Zheng Xu , Yu Shu Hui , Sun Rong , Yang Wen Hu , Du Ru Xu
Published: June 2012

A magnetite composite composed of the organic compounds and Fe3O4nanoparticles was prepared with microemulsion method. The Tween 80 and ammonia were used as surfactant and reducing agent, respectively, in synthesizing the Fe3O4nanoparticles. The experimental results showed that the composite possessed good stability while the volume ratio of Tween 80 to butanol was 0.4 and the molar ratio of NH4OH to Fe3+was 14.6. The saturation magnetization of the composite depends on the molar ratio of NH4OH to Fe3+. The mechanism of this stable Fe3O4paste was realized by the Fe3O4nanocomposite film using TEM. The microstructures of the film show that the magnetic nanoparticles in the composite are surrounded by Tween 80, which separates the magnetic nanoparticles and leads to good stability.
Drilling Simulation of High Manganese Steel Processing Based on the J-C Constitutive Relation
Authors: Yang Liang , Xu Li , Shi Zhi Hui , Teng Tao
Published: June 2012

The finite element physical model of the high-manganese steel drilling has been established on Johnson-Cook (J-C) constitutive equation derived using experimental methods. Through simulation, the variation of drilling force and heat is given and stress and temperature nephograms in cutting zone is obtained. A comparative study of the experimental data and simulation values is carried out using drilling force measurement system self-designed and developed, which proves the accuracy and reliability of simulation results and the model.
Using the Flat-End Mill in the Strip Width Machining
Authors: Zhao Can , Guan Yun Fei , Guo Yan Yan
Published: June 2012

Surface machining has become a difficult problem in aviation manufacturing, we always using ball-end mills, it is easy to determine the tool position in five-axis machining, but because of the large program, low material remove rate, the processing cycle long, and the surface accuracy is also poor. The paper suggests using the flat-end mill to strip width machining. Using this way, the CNC program is shorter, surface quality is better, the most import is reducing the machining time obviously. Now this method only used in the simple surface, so it requires further research.
Experiment Study of Tool Wear and Surface Integrity in High Speed Milling of a New Damage-Tolerant Titanium Alloy
Authors: Shi Qi , Yang Yin Fei , He Ning , Li Liang , Zhao Wei
Published: June 2012

TC4-DT is a new damage-tolerant titanium alloy. In the paper, a series of experiments on tool wear and surface integrity in high speed milling of the alloy were carried out. The tool lives of different tool materials were studied and the wear mechanism of cutting tools was also investigated. Then surface integrity, including surface roughness, microhardness and metallurgical structure was studied and analyzed in high speed milling at different tool wear status. Results showed that K10 is the most suitable cutting tool after considering a combination of factors. And good surface integrity could be obtained in high speed milling of TC4-DT under all cutting situations. In addition, even with acutely worn stages, there has been no so-called serious hardening layer (or white layer) according to the study of microhardness and metallurgical structure beneath the machined surface.
Influence of Material Flow Stress on Surface Roughness in High-Speed Machining
Authors: Wang Su Yu , Yang Wen Jie , Wang Wen Chao
Published: June 2012

A mechanical model of surface roughness is established based on the Kragelskii-Drujanov theory of friction and wear and Hertz elastic contact theory. Effect of material flow stress on remnant height of the machined surface was investigated. Test showed that the machined surface morphology provides the phenomena of the side flow in the vertical direction of ploughing in high-speed machining. The remnant height values on the machined surface of the high-speed machining are obtained by DEFORM-3D simulation. Based on the results it can be concluded that the surface roughness values of the workpiece increase with material flow stress.
Experimental Study on Orthogonal Cutting of Ti6Al4V with Surface Micro-Groove Textured Cutting Tool
Authors: Qi Bao Yun , Li Liang
Published: June 2012

Currently biomimetic tribology study shows that high performance surface texture can achieve good friction, anti-adhesion and improve the wear resistance, which brings a new research direction for tool antifriction technology. The orthogonal cutting tests of surface micro-groove cutting tool in machining titanium alloy were presented. Different types of micro-grooves were made using laser in the rake face of uncoated tungsten carbide cutting inserts. Dry with no lubricant and minimal quantity lubricant (MQL) were used as lubrication conditions. Cutting force and cutting temperature were measured and compared. It was found that under MQL condition the surface micro-grooves could effectively improve the friction status between the tool and chip, thereby reducing cutting force and cutting temperature, and also reduce cutting temperature under no lubricant condition. The micro-grooves paralleling with cutting edge had the best effect in three types of micro-grooves.
Measurement Method of HSK Tool Holder’s Unbalance in HSM
Authors: Yu Jun Jian , Wang Shu Lin , Chen Jian , Wang Gui Cheng
Published: June 2012

The hazards of HSK toolholders caused by unbalance vibration are described The vibration information can be more accurately extracted by choosing the appropriate method of measuring unbalance and using FFT transform to reconstruct wavelet signal. Finally, the HSK tool holders unbalance measurement software module diagram are shown. This way can be a good basis for scientific research and the development of the HSK integrated measurement system.
Numerical Analysis of Face Milling Ti6Al4V with Different Tool Materials
Authors: Liu Zhan Qiang , Lin Qi
Published: June 2012

Ti6Al4V is one kind of difficult-to-machine aeronautical materials, which is generally machined by coated cemented carbide tools. A three-dimensional face milling model is developed in this paper with finite element analysis software AdvantEdge to analyze influences of tool materials on tool temperatures, cutting forces and tool stresses. The simulation results have shown that PCBN tools are the most appropriate for machining titanium alloy when it is machined with heavier cutting parameters. Cemented carbide-K tools and PCD tools are suitable for finish machining titanium alloy. The PCD tools are superior to cemented carbides-K under the same machining conditions. Nature diamond cutting tools are incompatibility to machine titanium alloy due to their higher costs and carbonization at high temperature. In the view of cutting forces and distributions of tool stresses, nature diamond tools are optimal and the cemented carbides-K are the poorest in machinability rate at the same cutting conditions, while super-hard tools gets longer tool life.
Experimental Study on Spray Cutting Ni-Based Superalloy
Authors: Wang Yu , Zhai Yuan Sheng , Yan Fu Gang , Liu Xian Li
Published: June 2012

In this paper, the effect of cutting parameters on cutting force, cutting temperature and surface roughness on cutting force, cutting temperature and surface roughness are experimentally studied in spray cutting GH4169 Ni-base superalloy used carbide cutting tools. The results showed that reasonable choice of cutting parameters can effective reduction of cutting force and cutting temperature, and improve the machining surface roughness. Thus realizing clean production mode.
Experimental Research on Damaged Layer of High Strength Alloys in Precision Cutting
Authors: Zhai Yuan Sheng , Wang Yu
Published: June 2012

In this paper, the effects of cutting parameters and tool geometry parameters on the damaged layer were investigated with precision cutting of high strength alloy experiments. The mechanical and thermal effects on microstructure of sub-surfaces in precision turning high strength alloy are studied with a scanning electron microscope (SEM) analysis. A thin disturbed or plastically deformed layer is distinguished by the presence of grains that are elongated and rotated in the direction of cutting. No significant heat affected layer and phase transformation is found below the machined surface in all the tests. It also implies that mechanical deformation plays a larger role during precision turning.
Effect of Holding Time on Microstructure and Properties of VC/Fe Composite
Authors: Zhang Guo Jun , Sun Zhi Ping , Zou Li Yan
Published: June 2012

The microstructure and mechanical properties of samples were examined, and the relationship of structure and mechanical properties for VC/Fe composite sintered at different holding time were studied. Holding time can influence the mechanical properties, with the holding time rising, when the holding time is 80 min, the hardness is Max, it’s 10.71 GPa, the enhancing range is 37.66%; The relative density changes slower from 60 to 100 min; when the holding time is 60 minutes, fracture toughness and bending strength of material is 16.17 MPa•m 1/2 and 1070 MPa, it’s better than before.
Tool Wear Characters in Micro-Milling of Fully Sintered ZrO2 Ceramics by Diamond Coated End Mills
Authors: Bian Rong , Ferraris Eleonora , Qian Jun , Reynaerts Dominiek , Li Liang , He Ning
Published: June 2012

This work presents an experimental investigation on micro-milling of fully sintered Zirconia (ZrO2) by diamond coated tools. The experiments were conducted on a Kern MMP 2522 micro-milling centre and WC micro end mills, diamond coated by chemical vapour deposition (CVD) and of stiff geometry were employed as cutting tools. The effects of cutting parameters and milling time on tool wear were investigated. The results revealed that the tool wear characters included diamond coating delamination and wear of substrate WC. Both cutting forces and machined surface quality were affected by tool wear with the progress of milling.
Analyses of Size Effect on Surface Roughness in Micro Turning Process
Authors: Zhao Meng , He Ning , Li Liang , Liu Zhan Qiang , Wu Wen Feng , Zheng Kai Bo
Published: June 2012

The downscaling of the cutting process into micro dimensions poses some new problems compared to machining in macro dimensions, which is called size effect. In this paper, a mathematical model of ideal turning surface roughness and a turning surface roughness experiment was done, trying to find out whether the theory roughness equals to the real roughness by the influence of size effect.
Experimental Study on Drilling Force during Mandible Drilling Process
Authors: Wei Ying Ying , Zheng Xiao Hu , Yu De Dong , Dong Da Peng , Chen Ming
Published: June 2012

Drilling procedure is widely used in orthopedic surgery to insert the steel nail to stabilize the bone. However, successful execution of bone drilling requires a high level of dexterity and experience, because the drilling resistance is large and sometimes vibrates violently to even break the slender drill. This paper introduces the study of drill force in different cutting parameters and different bone density. The density of cortical bone is higher than that of cancellous bone, so the drilling force decreases suddenly from the peak and then maintains a stable value. Drilling forces are more related with feed speeds and bone density. Drilling force increases as feed speed increases and bone density increases. Accurate drilling process can be obtained to provide effective surgery training and rehearsal.
Research on the Cutting Fluid Effect on Cutting Force and Surface Roughness in Rotor Milling
Authors: Wang Jian Lu , Wu Liang Liang , Zhang Jun , Zhao Wan Hua , Jiang Yi Fei , Shui Yan
Published: June 2012

A series of milling experiments with and without cutting fluid, arranged by uniform design method, were carried out on rotor material. The influence of cutting fluid on cutting force and surface roughness was explored and compared for the two kinds of conditions. The associated model was established between cutting force & surface roughness and cutting parameters according to the linear multivariable regression method. The results show that the cutting force deceases with the increase of the cutting speed or with the decrease of the feed per tooth and the cutting depth. Cutting fluid has little effect on cutting force, and for surface roughness, the influence of cutting fluid is uncertain.
Formation and Control of the Cutting Vibration in High-Speed Machining
Authors: Chen Jian , Song Zhi Peng , Wang Gui Cheng , Shen Chun Gen
Published: June 2012

Based on the System Engineering theory, the main factors that lead to the vibration in high-speed cutting were presented, which were the structure of the high-speed machine tool, the component of the tool system, the characters of the workpiece material, the choosing of the cutting parameters and the machining environment conditions. The forming mechanism of the vibration in high-speed machining was discussed, according to the characters of controlling each part of the high-speed machining system. The main controlling strategy and improving paths of the active vibration control in high-speed machining were brought forward.
Time Molding in Rough Milling of Circular Cavity
Authors: Ren Xiao Ping , Liu Zhan Qiang , Wan Yi
Published: June 2012

Numerical controlled milling is widely used in the manufacturing industry because of its high productivity and workpiece surface quality. The aim of this work is to establish a methodology to evaluate the rough machining time and to predict optimal values of cutting speed to minimise machining time of circular cavity, during high speed milling. The circular cavity is divided into volumes distributed according to the real radial depth. The obtained results show that the proposed method is consistent with the actual situation.
Recent Applications of Landau-Ginzburg Theory to Ferroelectric Superlattices: A Review
Authors: Chew Khian Hooi
Published: June 2012

This article briefly reviews recent developments of Landau-Ginzburg theory to ferroelectric phase transitions in superlattices. An overview of the contributions of Landau-type theory to study ferroelectric superlattices is given. Recent findings from first-principles calculations and experiments on intermixing, local polarization coupling and polar discontinuity at interfaces that are not address in these contributions are highlighted. This is followed by a review of recent developments of Landau-Ginzburg theory that addresses these emergent phenomena at interfaces, which is the focus of this review article. The Landau-Ginzburg approach to ferroelectric superlattices with spatial distribution of polarization is outlined. It describes the formation of intermixed layer with properties different from those of both layers. These intermixed layers are mutually coupled through the local polarization at interfaces. Polarization continuity or continuity at interfaces is determined by the nature of the intermixed layer formed at the interface region. Recent results obtained in investigating superlattices comprised primarily of ferroelectric and paraelectric materials are discussed. The results include modulated polarizations, phase transitions, dielectric susceptibilities and switching behaviors.