Interfacial reaction in SiC_f/Ti-6Al-4V composite by using transmission electron microscopy

International Nuclear Information System (INIS)

Huang, Bin; Li, Maohua; Chen, Yanxia; Luo, Xian; Yang, Yanqing

2015-01-01

The interfacial reactions of continuous SiC fiber reinforced Ti-6Al-4V matrix composite (SiC_f/Ti-6Al-4V composite) and continuous SiC fiber coated by C reinforced Ti-6Al-4V matrix composite (SiC_f/C/Ti-6Al-4V composite) were investigated by using micro-beam electron diffraction (MBED) and energy disperse spectroscopy (EDS) on transmission electron microscopy (TEM). The sequence of the interfacial reactions in the as-processed and exposed at 900°C for 50h SiC_f/Ti-6Al-4V composites can be described as SiC||TiC||Ti_5Si_3 + TiC||Ti-6Al-4V and SiC||TiC||Ti_5Si_3||TiC||Ti_5Si_3||TiC||Ti_5Si_3||Ti-6Al-4V, respectively. Additionally, both in as-processed and exposed composites, Ti_3SiC_2 and Ti_3Si are absent at the interfaces. For the SiC_f/C/Ti-6Al-4V composite exposed at 900 °C for 50 h, the sequence of the interfacial reaction can be described as SiC||C||TiC_F||TiC_C||Ti-6Al-4V before C coating is completely consumed by interfacial reaction. When interfacial reaction consumes C coating completely, the sequence of the interfacial reaction can be described as SiC||TiC||Ti_5Si_3||TiC||Ti-6Al-4V. Furthermore, in SiC_f/C/Ti-6Al-4V composite, C coating can absolutely prevent Si diffusion from SiC fiber to matrix. Basing on these results, the model of formation process of the interfacial reaction products in the composites was proposed. - Highlights: • We obtained the sequence of the interfacial reactions in the as-processed and exposed at 900 °C for 50 h SiC_f/Ti-6Al-4 V composites as well as in the SiC_f/C/Ti-6Al-4 V composite exposed at 900 °C for 50 h. • We verified that both in as-processed and exposed SiC_f/Ti-6Al-4 V composites, Ti_3SiC_2 and Ti_3Si are absent at the interfaces. • Carbon coating can absolutely prevent silicon diffusion from SiC fiber to matrix. • Basing on these results, the model of formation process of the interfacial reaction products in the composites was proposed.

Dynamic study of the thermal stability of impure Ti 3SiC 2 in argon and air by neutron diffraction

Science.gov (United States)

Oo, Z.; Low, I. M.; O'Connor, B. H.

2006-11-01

The dynamic thermal stability and topotactic phase transition of impure Ti 3SiC 2 in air and argon have been investigated by neutron diffraction (ND). In the presence of a low oxygen partial pressure as in argon, Ti 3SiC 2 underwent a surface dissociation and TiC and/or Ti 5Si 3C were detected at 1200 °C. In contrast, oxide layers of rutile (TiO 2), TiO and cristobalite (SiO 2) were detected at ∼1000, 1250 and 1300 °C respectively when exposed to an oxygen-rich environment. Near-surface depth profiling of Ti 3SiC 2 oxidized in air at 1200 °C by secondary ion mass spectroscopy (SIMS) has revealed a distinct gradation in phase composition at the interface of homogeneous rutile and heterogeneous cristobalite-rutile layers.

Dynamic study of the thermal stability of impure Ti3SiC2 in argon and air by neutron diffraction

International Nuclear Information System (INIS)

Oo, Z.; Low, I.M; O'Connor, B.H.

2006-01-01

The dynamic thermal stability and topotactic phase transition of impure Ti 3 SiC 2 in air and argon have been investigated by neutron diffraction (ND). In the presence of a low oxygen partial pressure as in argon, Ti 3 SiC 2 underwent a surface dissociation and TiC and/or Ti 5 Si 3 C were detected at 1200 deg. C. In contrast, oxide layers of rutile (TiO 2 ), TiO and cristobalite (SiO 2 ) were detected at ∼1000, 1250 and 1300 deg. C respectively when exposed to an oxygen-rich environment. Near-surface depth profiling of Ti 3 SiC 2 oxidized in air at 1200 deg. C by secondary ion mass spectroscopy (SIMS) has revealed a distinct gradation in phase composition at the interface of homogeneous rutile and heterogeneous cristobalite-rutile layers

Synergetic Effect of Graphene and MWCNTs on Microstructure and Mechanical Properties of Cu/Ti3SiC2/C Nanocomposites

Science.gov (United States)

Jiang, Xiaosong; Song, Tingfeng; Shao, Zhenyi; Liu, Wanxia; Zhu, Degui; Zhu, Minhao

2017-11-01

Multi-walled carbon nanotubes (MWCNTs) and graphenes have been taken for novel reinforcements due to their unique structure and performance. However, MWCNTs or graphenes reinforced copper matrix composites could not catch up with ideal value due to reinforcement dispersion in metal matrix, wettability to metal matrix, and composite material interface. Taking advantage of the superior properties of one-dimensional MWCNTs and two-dimensional graphenes, complementary performance and structure are constructed to create a high contact area between MWCNTs and graphenes to the Cu matrix. Mechanical alloying, hot pressing, and hot isostatic pressing techniques are used to fabricate Cu matrix self-lubricating nanocomposites. Effects of MWCNTs and graphenes on mechanical properties and microstructures of Cu/Ti3SiC2/C nanocomposites are studied. The fracture and strengthening mechanisms of Cu/Ti3SiC2/C nanocomposites are explored on the basis of structure and composition of Cu/Ti3SiC2/C nanocomposites with formation and function of interface.

Pore Formation Process of Porous Ti3SiC2 Fabricated by Reactive Sintering

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Huibin Zhang

2017-02-01

Full Text Available Porous Ti3SiC2 was fabricated with high purity, 99.4 vol %, through reactive sintering of titanium hydride (TiH2, silicon (Si and graphite (C elemental powders. The reaction procedures and the pore structure evolution during the sintering process were systematically studied by X-ray diffraction (XRD and scanning electron microscope (SEM. Our results show that the formation of Ti3SiC2 from TiH2/Si/C powders experienced the following steps: firstly, TiH2 decomposed into Ti; secondly, TiC and Ti5Si3 intermediate phases were generated; finally, Ti3SiC2 was produced through the reaction of TiC, Ti5Si3 and Si. The pores formed in the synthesis procedure of porous Ti3SiC2 ceramics are derived from the following aspects: interstitial pores left during the pressing procedure; pores formed because of the TiH2 decomposition; pores formed through the reactions between Ti and Si and Ti and C powders; and the pores produced accompanying the final phase synthesized during the high temperature sintering process.

Wear Resistance of TiC Reinforced Cast Steel Matrix Composite

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Sobula S.

2017-03-01

Full Text Available Wear resistance of TiC-cast steel metal matrix composite has been investigated. Composites were obtained with SHSB method known as SHS synthesis during casting. It has been shown the differences in wear between composite and base cast steel. The Miller slurry machine test were used to determine wear loss of the specimens. The slurry was composed of SiC and water. The worn surface of specimens after test, were studied by SEM. Experimental observation has shown that surface of composite zone is not homogenous and consist the matrix lakes. Microscopic observations revealed the long grooves with SiC particles indented in the base alloy area, and spalling pits in the composite area. Due to the presence of TiC carbides on composite layer, specimens with TiC reinforced cast steel exhibited higher abrasion resistance. The wear of TiC reinforced cast steel mechanism was initially by wearing of soft matrix and in second stage by polishing and spalling of TiC. Summary weight loss after 16hr test was 0,14÷0,23 g for composite specimens and 0,90 g for base steel.

Correlated silicon and titanium isotopic compositions of presolar SiC grains from the Murchison CM2 chondrite

Science.gov (United States)

Gyngard, Frank; Amari, Sachiko; Zinner, Ernst; Marhas, Kuljeet Kaur

2018-01-01

We report correlated Si, and Ti isotopic compositions and elemental concentrations of 238 presolar SiC grains from the Murchison CM2 meteorite. Combined with measurements of the C and N isotopic compositions of these 238 grains, 220 were determined to be of type mainstream, 10 type AB, 4 type Y and 4 type Z. SiC grains of diameter ≳2.5 μm, to ensure enough material to attempt Ti measurements, were randomly chosen without any other prejudice. The Ti isotopic compositions of the majority of the grains are characterized by enrichments in 46Ti, 47Ti, 49Ti, and 50Ti relative to 48Ti, and show linear isotopic correlations indicative of galactic chemical evolution and neutron capture of the grains parent stars. The variability in the observed Ti signal as a function of depth in most of the grains indicates the presence of distinct subgrains, likely TiC that have been previously observed in TEM studies. Vandium-51 concentrations correlate with those of Ti, indicating V substitutes for Ti in the TiC matrix in many of the grains. No isotopic anomalies in 52Cr/53Cr ratios were observed, and Cr concentrations did not correlate with those of either Ti or V.

[Application of Raman spectroscopy to investigation of CVD-SIC fiber].

Science.gov (United States)

Liu, Bin; Yang, Yan-Qing; Luo, Xian; Huang, Bin

2011-11-01

The CVD-SiC fiber was studied by using laser Raman spectra. It was found that the sharp TO peak exists in the first SiC deposit layer, indicating the larger SiC grains. But the second SiC deposit layer is with small grains. Raman peak of carbon and silicon was detected respectively in the first and second layer. Compared with that of the single SiC fiber, the TO peaks move to the high wave number for the SiC fiber in SiC(f)/Ti-6Al-4V composite. It indicates that the compressive thermal residual stress is present in the SiC fiber during the fabrication of the composite because of the mismatched coefficient of thermal expansion between Ti-6Al-4V matrix and SiC fiber. The average thermal residual stress of the SiC fiber in SiC(f)/Ti-6Al-4V composite was calculated to be 318 MPa and the residual stress in first deposit layer is 436 MPa which is much higher than that in the second layer.

Compared production behavior of borax and unborax premixed SiC reinforcement Al7Si-Mg-TiB alloys composites with semi-solid stir casting method

Science.gov (United States)

Haryono, M. B.; Sulardjaka, Nugroho, Sri

2016-04-01

The present study was aimed to investigate the effect of borax additive on physical and mechanical properties of Al7Si-Mg-TiB with the reinforcement of silicon carbide. In this case, the different weight percentage from the reinforcement of SiC (10, 15, and 20% wt), and the borax additive (ratio 1:4) were homogenously added into the matrix by employing the semi-solid stir casting method at the temperature of 590°C. Al7Si-Mg-TiB melted in an electric resistance furnace at 800°C for 25 minutes and the holding time of 5 minutes; SiC was stirred with borax inside the chamber and heated at the temperature of 250°C for 25 minutes. Then, it melted by lowing the temperature into 590°C. The SiC-borax mixture was added into the electric resistance furnace, and automatically stirred by the stirrer at a constant speed (500 rpm for 3 minutes) in the composite A17Si-Mg-TiB. It melted when heated at 750°C for 17minutes,then, casting was performed on the prepared mould. The characterizations of Al7Si-Mg-TiB-SiC/borax were porosity, hardness, and microstructure on the Al7Si-Mg-TiB-SiC/ borax. The porosity of AMC tended to increase along with the increaseof the wt% SiC (1.4%-3.6%); however, borax additive underwent a decrease in porosity (0.14%-1.3%). Further, hardness tended to improve along with the increase of wt% SiC. The unboraxmixture had 79,6 HRB up to 94 HRB. Whereas, the borax additive mixture had 105,8 HRB up to 121 HRB.

Electronic Structure and Chemical Bond of Ti3SiC2 and Adding Al Element

Institute of Scientific and Technical Information of China (English)

MIN Xinmin; LU Ning; MEI Bingchu

2006-01-01

The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation (DFT-DVM) method. When Al element is added into Ti3SiC2, there is a less difference of ionic bond, which does not play a leading role to influent the properties. After adding Al, the covalent bond of Al and the near Ti becomes somewhat weaker, but the covalent bond of Al and the Si in the same layer is obviously stronger than that of Si and Si before adding. Therefore, in preparation of Ti3SiC2, adding a proper quantity of Al can promote the formation of Ti3SiC2. The density of state shows that there is a mixed conductor character in both of Ti3SiC2 and adding Al element. Ti3SiC2 is with more tendencies to form a semiconductor. The total density of state near Fermi lever after adding Al is larger than that before adding, so the electric conductivity may increase after adding Al.

Si/C composite lithium-ion battery anodes synthesized using silicon nanoparticles from porous silicon

International Nuclear Information System (INIS)

Park, Jung-Bae; Lee, Kwan-Hee; Jeon, Young-Jun; Lim, Sung-Hwan; Lee, Sung-Man

2014-01-01

The synthesis of Si nanoparticles by ultrasonication processing of porous Si powder and a novel method for preparing a high-capacity Si/C composite using this technique is reported. The porous Si powder is prepared by selectively etching the silicide phase of a Ti 24 Si 76 alloy consisting of Si and silicide phases. The particle size of the nanocrystalline Si is determined by the crystallite size of the Si and silicide phases in the alloy powder. Ultrasonication of the porous Si obtained from the mechanically alloyed Ti 24 Si 76 alloy generates nanocrystalline Si particles of size about 5 nm. Growth of the Si and silicide phases in the alloy is induced by annealing of the mechanically alloyed sample, with a consequent increase in the size of the Si particles obtained after ultrasonication. Application of the ultrasonication process to the fabrication of Si/C composite anode materials generates nanometer-scale Si particles in situ that are distributed in the matrix. Analysis of the phases obtained and evaluation of the distribution of the nanometer-scale Si particles in the composites via XRD/TEM measurements show that the nanometer-scale Si particles are effectively synthesized and uniformly distributed in the carbon matrix, leading to enhanced electrochemical performance of the Si/C composites

Interface and interaction of graphene layers on SiC(0001[combining macron]) covered with TiC(111) intercalation.

Science.gov (United States)

Wang, Lu; Wang, Qiang; Huang, Jianmei; Li, Wei-Qi; Chen, Guang-Hui; Yang, Yanhui

2017-10-11

It is important to understand the interface and interaction between the graphene layer, titanium carbide [TiC(111)] interlayer, and silicon carbide [SiC(0001[combining macron])] substrates in epitaxial growth of graphene on silicon carbide (SiC) substrates. In this study, the fully relaxed interfaces which consist of up to three layers of TiC(111) coatings on the SiC(0001[combining macron]) as well as the graphene layers interactions with these TiC(111)/SiC(0001[combining macron]) were systematically studied using the density functional theory-D2 (DFT-D2) method. The results showed that the two layers of TiC(111) coating with the C/C-terminated interfaces were thermodynamically more favorable than one or three layers of TiC(111) on the SiC(0001[combining macron]). Furthermore, the bonding of the Ti-hollow-site stacked interfaces would be a stronger link than that of the Ti-Fcc-site stacked interfaces. However, the formation of the C/Ti/C and Ti/C interfaces implied that the first upper carbon layer can be formed on TiC(111)/SiC(0001[combining macron]) using the decomposition of the weaker Ti-C and C-Si interfacial bonds. When growing graphene layers on these TiC(111)/SiC(0001[combining macron]) substrates, the results showed that the interaction energy depended not only on the thickness of the TiC(111) interlayer, but also on the number of graphene layers. Bilayer graphene on the two layer thick TiC(111)/SiC(0001[combining macron]) was thermodynamically more favorable than a monolayer or trilayer graphene on these TiC(111)/SiC(0001[combining macron]) substrates. The adsorption energies of the bottom graphene layers with the TiC(111)/SiC(0001[combining macron]) substrates increased with the decrease of the interface vertical distance. The interaction energies between the bottom, second and third layers of graphene on the TiC(111)/SiC(0001[combining macron]) were significantly higher than that of the freestanding graphene layers. All of these findings provided

Matrix densification of SiC composites by sintering process

International Nuclear Information System (INIS)

Kim, Young-Wook; Jang, Doo-Hee; Eom, Jung-Hye; Chun, Yong-Seong

2007-02-01

The objectives of this research are to develop a process for dense SiC fiber-SiC composites with a porosity of 5% or less and to develop high-strength SiC fiber-SiC composites with a strength of 500 MPa or higher. To meet the above objectives, the following research topics were investigated ; new process development for the densification of SiC fiber-SiC composites, effect of processing parameters on densification of SiC fiber-SiC composites, effect of additive composition on matrix microstructure, effects of additive composition and content on densification of SiC fiber-SiC composites, mechanical properties of SiC fiber-SiC composites, effect of fiber coating on densification and strength of SiC fiber-SiC composites, development of new additive composition. There has been a great deal of progress in the development of technologies for the processing and densification of SiC fiber-SiC composites and in better understanding of additive-densification-mechanical property relations as results of this project. Based on the progress, dense SiC fiber-SiC composites (≥97%) and high strength SiC fiber-SiC composites (≥600 MPa) have been developed. Development of 2D SiC fiber-SiC composites with a relative density of ≥97% and a strength of ≥600 MPa can be counted as a notable achievement

TiC growth in C fiber/Ti alloy composites during liquid infiltration

Science.gov (United States)

Warrier, S. G.; Lin, R. Y.

1993-01-01

A cylindrical model is developed for predicting the reaction zone thickness of carbon fiber-reinforced Ti-matrix composites, and good agreement is obtained between its predicted values and experimental results. The reaction-rate constant for TiC formation is estimated to be 1.5 x 10 exp -9 sq cm/sec. The model is extended to evaluate the relationship between C-coating thicknesses on SiC fibers and processing times.

Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

Energy Technology Data Exchange (ETDEWEB)

Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

2015-05-16

MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including x-ray diffraction, electron backscatter diffraction, energy dispersive x-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

Internal strain evolution during heating of Ti-6Al-4V/SCS-6 composite

International Nuclear Information System (INIS)

Choo, H.; Rangaswamy, P.; Bourke, M.A.M.

1999-01-01

The characteristics of the residual stresses and their effects on the properties in continuous SiC fiber reinforced Ti-6Al-4V matrix composites (TMCs) have been extensively studied. However, to date, few experimental studies (e.g. Ti-14Al-21Nb/SCS-6) have characterized the thermal residual strain in TMCs at elevated temperatures. Therefore, the authors investigated the evolution of the thermal residual strain during heating of Ti-6Al-4V/35vol% SiC composite. In this study the authors used in situ high temperature neutron diffraction to measure strains: (1) in the matrix (α and β phases) and in the fiber, (2) for several lattice reflections in each phase and (3) from both axial and the transverse directions. One distinguishing feature is the wide temperature range (from room temperature up to 1,170K) over which the study was performed. Although the proposed application temperature is typically less than 800K, TMCs are subject to higher temperatures during fabrication and may experience high temperature excursions while in service. Therefore, the authors extended the study to the high temperature regime where the matrix starts to undergo a phase transformation between αminus and βminusTi. Measurements from this regime (800approximately1,170K) provide insights on; (1) the inelastic relaxation of the residual strains through matrix yielding and creep, (2) the effect of the phase transformation on the residual strains and (3) the effect of the presence of SiC on the matrix phase evolution

Effects of metallic Ti particles on the aging behavior and the influenced mechanical properties of squeeze-cast (SiCp+Ti)/7075Al hybrid composites

International Nuclear Information System (INIS)

Liu, Yixiong; Chen, Weiping; Yang, Chao; Zhu, Dezhi; Li, Yuanyuan

2015-01-01

The effects of metallic Ti particles on the aging behavior of squeeze-cast (SiC p +Ti)/7075Al hybrid composites and the mechanical properties of the aging treated composites were investigated. Results shown that the precipitation hardening of the hybrid composites during aging processes was delayed due to the segregation of solute Mg atoms in the vicinity of the Ti particles even though the activation energy of the η′ precipitates in the hybrid composites was reduced when compared with the Ti particle-free composites. The segregation of the solute Mg atoms was facilitated as a result of the high diffusivity paths formed by the generated dislocations in the matrix induced by the thermal misfit between the SiC particle and the matrix. The smaller activation energy for the hybrid composite may attribute to a significant reduction in the nucleation rate of the dislocation nucleated η′ precipitates compared with the Ti particle-free composite. After aging treated under the optimum aging conditions, the tensile strength of both composites was improved because of the precipitation hardening of the matrix alloy. In contrast with the reduced ductility of the traditional Ti particle-free composites after aging treatment, the ductility of the Ti particle-containing composites was improved as a result of the strengthened interfaces between the Ti particles and the matrix alloy

Characterization of SiC based composite materials by the infiltration of ultra-fine SiC particles

International Nuclear Information System (INIS)

Lee, J.K.; Lee, S.P.; Byun, J.H.

2010-01-01

The fabrication route of SiC materials by the complex compound of ultra-fine SiC particles and oxide additive materials has been investigated. Especially, the effect of additive composition ratio on the characterization of SiC materials has been examined. The characterization of C/SiC composites reinforced with plain woven carbon fabrics was also investigated. The fiber preform for C/SiC composites was prepared by the infiltration of complex mixture into the carbon fabric structure. SiC based composite materials were fabricated by a pressure assisted liquid phase sintering process. SiC materials possessed a good density higher than about 3.0 Mg/m 3 , accompanying the creation of secondary phase by the chemical reaction of additive materials. C/SiC composites also represented a dense morphology in the intra-fiber bundle region, even if this material had a sintered density lower than that of monolithic SiC materials. The flexural strength of SiC materials was greatly affected by the composition ratio of additive materials.

Enhanced tribological behavior of anodic films containing SiC and PTFE nanoparticles on Ti6Al4V alloy

International Nuclear Information System (INIS)

Li, Songmei; Zhu, Mengqi; Liu, Jianhua; Yu, Mei; Wu, Liang; Zhang, Jindan; Liang, Hongxing

2014-01-01

Highlights: • An environmental friendly sodium tartrate (C 4 O 6 H 4 Na 2 ) electrolyte is used. • SiC and PTFE nanoparticles reduce friction coefficient of composite films. • SiC and PTFE nanoparticles demonstrate a favorable synergistic effect on improving tribological properties of composite films. • Lubricating mechanisms of SiC and PTFE nanoparticles are discussed. - Abstract: Anodic films containing SiC and polytetrafluoroethylene (PTFE) nanoparticles were successfully fabricated on Ti6Al4V alloy by using anodic oxidation method in an environmental friendly electrolyte. The morphology, structure and composition of the films were studied with the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results showed that the film contained a layered structure and have a surface full of petaloid bulges, which was totally different from the common anodic oxide film of the porous kind. The tribological properties of the films were investigated with dry friction tests in terms of the friction coefficient, wear rate and the morphology of worn surfaces. The results indicated that the SiC/PTFE composite film exhibited much better anti-wear and anti-friction performances than that of the SiC composite film, the PTFE composite film and the ordinary film without nanoparticles. The SiC/PTFE composite film has friction coefficient of 0.1 and wear rate of 20.133 mg/m, which was decreased respectively by 80% and 44.5% compared with that of the ordinary film. The lubricating mechanisms of the composite film containing SiC and PTFE nanoparticles were discussed. PTFE nanoparticles could lead to the formation of lubricating layer while SiC nanoparticles inside the lubricating layer turned sliding friction to rolling friction

A comparative study of the mechanical and thermal properties of defective ZrC, TiC and SiC.

Science.gov (United States)

Jiang, M; Zheng, J W; Xiao, H Y; Liu, Z J; Zu, X T

2017-08-24

ZrC and TiC have been proposed to be alternatives to SiC as fuel-cladding and structural materials in nuclear reactors due to their strong radiation tolerance and high thermal conductivity at high temperatures. To unravel how the presence of defects affects the thermo-physical properties under irradiation, first-principles calculations based on density function theory were carried out to investigate the mechanical and thermal properties of defective ZrC, TiC and SiC. As compared with the defective SiC, the ZrC and TiC always exhibit larger bulk modulus, smaller changes in the Young's and shear moduli, as well as better ductility. The total thermal conductivity of ZrC and TiC are much larger than that of SiC, implying that under radiation environment the ZrC and TiC will exhibit superior heat conduction ability than the SiC. One disadvantage for ZrC and TiC is that their Debye temperatures are generally lower than that of SiC. These results suggest that further improving the Debye temperature of ZrC and TiC will be more beneficial for their applications as fuel-cladding and structural materials in nuclear reactors.

Thermal stability of Ti3SiC2 thin films

International Nuclear Information System (INIS)

Emmerlich, Jens; Music, Denis; Eklund, Per; Wilhelmsson, Ola; Jansson, Ulf; Schneider, Jochen M.; Hoegberg, Hans; Hultman, Lars

2007-01-01

The thermal stability of Ti 3 SiC 2 (0 0 0 1) thin films is studied by in situ X-ray diffraction analysis during vacuum furnace annealing in combination with X-ray photoelectron spectroscopy, transmission electron microscopy and scanning transmission electron microscopy with energy dispersive X-ray analysis. The films are found to be stable during annealing at temperatures up to ∼1000 deg. C for 25 h. Annealing at 1100-1200 deg. C results in the rapid decomposition of Ti 3 SiC 2 by Si out-diffusion along the basal planes via domain boundaries to the free surface with subsequent evaporation. As a consequence, the material shrinks by the relaxation of the Ti 3 C 2 slabs and, it is proposed, by an in-diffusion of O into the empty Si-mirror planes. The phase transformation process is followed by the detwinning of the as-relaxed Ti 3 C 2 slabs into (1 1 1)-oriented TiC 0.67 layers, which begin recrystallizing at 1300 deg. C. Ab initio calculations are provided supporting the presented decomposition mechanisms

Multilayer oxidation resistant coating for SiC coated carbon/carbon composites at high temperature

International Nuclear Information System (INIS)

Li Hejun; Jiao Gengsheng; Li Kezhi; Wang Chuang

2008-01-01

To prevent carbon/carbon (C/C) composites from oxidation, a multilayer coating based on molybdenum disilicide and titanium disilicide was formed using a two-step pack cementation technique in argon atmosphere. XRD and SEM analysis showed that the internal coating was a bond SiC layer that acts as a buffer layer, and that the external multilayer coating formed in the two-step pack cementation was composed of two MoSi 2 -TiSi 2 -SiC layers. This coating, which is characterized by excellent thermal shock resistance, could effectively protect the composites from exposure to an oxidizing atmosphere at 1773 K for 79 h. The oxidation of the coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating

Microstructure and wear property of the Ti5Si3/TiC reinforced Co-based coatings fabricated by laser cladding on Ti-6Al-4V

Science.gov (United States)

Weng, Fei; Yu, Huijun; Liu, Jianli; Chen, Chuanzhong; Dai, Jingjie; Zhao, Zhihuan

2017-07-01

Ti5Si3/TiC reinforced Co-based composite coatings were fabricated on Ti-6Al-4V titanium alloy by laser cladding with Co42 and SiC mixture. Microstructure and wear property of the cladding coatings with different content of SiC were investigated. During the cladding process, the original SiC dissolved and reacted with Ti forming Ti5Si3 and TiC. The complex in situ formed phases were found beneficial to the improvement of the coating property. Results indicated that the microhardness of the composite coatings was enhanced to over 3 times the substrate. The wear resistance of the coatings also showed distinct improvement (18.4-57.4 times). More SiC gave rise to better wear resistance within certain limits. However, too much SiC (20 wt%) was not good for the further improvement of the wear property.

A comparative study of low energy radiation responses of SiC, TiC and ZrC

International Nuclear Information System (INIS)

Jiang, M.; Xiao, H.Y.; Zhang, H.B.; Peng, S.M.; Xu, C.H.; Liu, Z.J.; Zu, X.T.

2016-01-01

In this study, an ab initio molecular dynamics method is employed to compare the responses of SiC, TiC and ZrC to low energy irradiation. It reveals that C displacements are dominant in the cascade events of the three carbides. The associated defects in SiC are mainly Frenkel pairs and antisite defects, whereas damage end states in TiC and ZrC generally consist of Frenkel pairs and very few antisite defects are created. It is proposed that the susceptibility to antisite formation in SiC contributes to its crystalline-to-amorphous transformation under irradiation that is observed experimentally. The stronger radiation tolerance of TiC and ZrC than SiC can be originated from their different electronic structures, i.e., the and bonds are a mixture of covalent, metallic, and ionic character, whereas the bond is mainly covalent. The presented results provide underlying mechanisms for defect generation in SiC, TiC and ZrC, and advance the fundamental understanding of the radiation resistances of carbide materials.

Selected mechanical properties of aluminum composite materials reinforced with SiC particles

Directory of Open Access Journals (Sweden)

A. Kurzawa

2008-07-01

Full Text Available This work presents the results of research concerning influence of ceramic particles’ content of silicon carbide on selected mechanical properties of type AW-AlCu4Mg2Mn - SiC composite materials. Composites produced of SiC particles with pressure infiltration method of porous preform and subject to hot plastic forming in the form of open die forging were investigated. The experimental samples contained from 5% up to 45% of reinforcing SiC particles of 8÷10μm diameter. Studies of strength properties demonstrated that the best results, in case of tensile strength as well as offset yield strength, might be obtained while applying reinforcement in the amount of 20-25% vol. of SiC. Application of higher than 25% vol. contents of reinforcing particles leads to gradual strength loss. The investigated composites were characterized by very high functional properties, such as hardness and abrasive wear resistance, whose values increase strongly with the increase of reinforcement amount. The presented results of the experiments shall allow for a more precise component selection of composite materials at the stage of planning and design of their properties.

Development of the fabrication process of SiC composite by polycarbosilane

International Nuclear Information System (INIS)

Park, Ji Yeon; Kim, Weon Ju; Kim, Jung Il; Ryu, Woo Seog

2004-11-01

This technical report reviewed the fabrication process of fiber reinforced ceramic composites, characteristics of the PIP process, and applications of SiC f /SiC composite to develop a silicon carbide composite by PIP method. Additionally, characteristics and thermal behaviors of a PCS+SiC powder slurry and infiltration behaviors of slurry into the SiC fabric was evaluated. The stacking behaviors of SiC fabrics infiltrated a PCS+SiC powder slurry was also investigated. Using this stacked preforms, SiC f /SiC composites were fabricated by the electron beam curing and pyrolysis process and the thermal oxidation curing and pyrolysis process, respectively. And the characteristics of both composites were compared

Properties of stabilized MgB2 composite wire with Ti barrier

International Nuclear Information System (INIS)

Kovac, P; Husek, I; Melisek, T; Holubek, T

2007-01-01

Stabilized four-filament in situ MgB 2 /Ti/Cu/Monel composite wire was produced by the rectangular wire-in-tube (RWIT) technique. 10 wt% of nanosize SiC was added into the Mg-B powder mixture, which was packed into the Ti/Cu and Monel tubes, respectively. The assembled composite was two-axially rolled into wire and/or tape form and sintered at temperatures of 650-850 deg. C/0.5 h. Stabilized MgB 2 wire with Ti barrier is studied in terms of field-dependent transport critical current density, effects of filament size reduction and thermal stability

Surface Properties of the IN SITU Formed Ceramics Reinforced Composite Coatings on TI-3AL-2V Alloys

Science.gov (United States)

Liu, Peng; Guo, Wei; Hu, Dakui; Luo, Hui; Zhang, Yuanbin

2012-04-01

The synthesis of hard composite coating on titanium alloy by laser cladding of Al/Fe/Ni+C/Si3N4 pre-placed powders has been investigated in detail. SEM result indicated that a composite coating with metallurgical joint to the substrate was formed. XRD result indicated that the composite coating mainly consisted of γ-(Fe, Ni), FeAl, Ti3Al, TiC, TiNi, TiC0.3N0.7, Ti2N, SiC, Ti5Si3 and TiNi. Compared with Ti-3Al-2V substrate, an improvement of the micro-hardness and the wear resistance was observed for this composite coating.

Ceramic matrix micro-composites prepared by P-Rcvd within the (Ti-Si-B-C) system

International Nuclear Information System (INIS)

Jacques, Sylvain

2014-01-01

Nano-scale carbide multilayered inter-phases were deposited within the (Ti-Si-B-C) system by pressure-Pulsed Reactive Chemical Vapor Deposition (P-RCVD) on single filament Hi-Nicalon fibers and embedded in a SiC matrix sheath. The Reactive method, in which the titanium-containing layer growth involves the consumption of the pre-deposited Si-B-C sublayer, allowed TiC- and TiB 2 -based films to be obtained with a porous multilayer microstructure as a result of the Kirkendall effect. A first difficulty relied on the protection of the fiber surface which was very sensitive to chemical attack by P-RCVD. This difficulty could be circumvented through a first deposited SiC sub-layer thick enough to protect the surface of the fiber. But, because the porosity volume fraction was still not high enough, the role of mechanical fuse of these pyrocarbon-free inter-phases could not be evidenced from the micro-composite tensile curves, which remained fully linear up to the failure. Finally, the P-RCVD method was applied to the matrix processing itself. Micro-composites, this time with a pyrocarbon interphase but also with new matrix materials such as Ti 3 SiC 2 , were prepared and characterized. (author)

Residual stresses and mechanical properties of Si3N4/SiC multilayered composites with different SiC layers

International Nuclear Information System (INIS)

Liua, S.; Lia, Y.; Chena, P.; Lia, W.; Gaoa, S.; Zhang, B.; Yeb, F.

2017-01-01

The effect of residual stresses on the strength, toughness and work of fracture of Si3N4/SiC multilayered composites with different SiC layers has been investigated. It may be an effective way to design and optimize the mechanical properties of Si3N4/SiC multilayered composites by controlling the properties of SiC layers. Si3N4/SiC multilayered composites with different SiC layers were fabricated by aqueous tape casting and pressureless sintering. Residual stresses were calculated by using ANSYS simulation, the maximum values of tensile and compressive stresses were 553.2MPa and −552.1MPa, respectively. Step-like fracture was observed from the fracture surfaces. Fraction of delamination layers increased with the residual stress, which can improve the reliability of the materials. Tensile residual stress was benefit to improving toughness and work of fracture, but the strength of the composites decreased. [es

SURFACE PROPERTIES OF THE IN SITU FORMED CERAMICS REINFORCED COMPOSITE COATINGS ON TI-3AL-2V ALLOYS

OpenAIRE

PENG LIU; WEI GUO; DAKUI HU; HUI LUO; YUANBIN ZHANG

2012-01-01

The synthesis of hard composite coating on titanium alloy by laser cladding of Al/Fe/Ni+C/Si3N4 pre-placed powders has been investigated in detail. SEM result indicated that a composite coating with metallurgical joint to the substrate was formed. XRD result indicated that the composite coating mainly consisted of γ-(Fe, Ni), FeAl, Ti3Al, TiC, TiNi, TiC0.3N0.7, Ti2N, SiC, Ti5Si3 and TiNi. Compared with Ti-3Al-2V substrate, an improvement of the micro-hardness and the wear resistance was obser...

Fabrication of Multi-Layerd SiC Composite Tube for LWR Applications

Energy Technology Data Exchange (ETDEWEB)

Kim, Daejong; Jung, Choonghwan; Kim, Weonju; Park, Jiyeon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Jongmin [Chungnam National Univ., Daejeon (Korea, Republic of)

2013-05-15

In this study, the chemical vapor deposition (CVD) and chemical vapor infiltration (CVI) methods were employed for the fabrication of the composite tubes. SiC ceramics and SiC-based composites have recently been studied for LWR fuel cladding applications because of good mechanical/physical properties, neutron irradiation resistance and excellent compatibility with coolant under severe accident. A multi-layered SiC composite tube as the nuclear fuel cladding is composed of the monolith SiC inner layer, SiC/SiC composite intermediate layer, and monolith SiC outer layer. Since all constituents should be highly pure, stoichiometric to achieve the good properties, it has been considered that the chemical process is a well-suited technique for the fabrication of the SiC phases.

Designing the fiber volume ratio in SiC fiber-reinforced SiC ceramic composites under Hertzian stress

International Nuclear Information System (INIS)

Lee, Kee Sung; Jang, Kyung Soon; Park, Jae Hong; Kim, Tae Woo; Han, In Sub; Woo, Sang Kuk

2011-01-01

Highlights: → Optimum fiber volume ratios in the SiC/SiC composite layers were designed under Hertzian stress. → FEM analysis and spherical indentation experiments were undertaken. → Boron nitride-pyrocarbon double coatings on the SiC fiber were effective. → Fiber volume ratio should be designed against flexural stress. -- Abstract: Finite element method (FEM) analysis and experimental studies are undertaken on the design of the fiber volume ratio in silicon carbide (SiC) fiber-reinforced SiC composites under indentation contact stresses. Boron nitride (BN)/Pyrocarbon (PyC) are selected as the coating materials for the SiC fiber. Various SiC matrix/coating/fiber/coating/matrix structures are modeled by introducing a woven fiber layer in the SiC matrix. Especially, this study attempts to find the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics under Hertzian stress. The analysis is performed by changing the fiber type, fiber volume ratio, coating material, number of coating layers, and stacking sequence of the coating layers. The variation in the stress for composites in relation to the fiber volume ratio in the contact axial or radial direction is also analyzed. The same structures are fabricated experimentally by a hot process, and the mechanical behaviors regarding the load-displacement are evaluated using the Hertzian indentation method. Various SiC matrix/coating/fiber/coating/matrix structures are fabricated, and mechanical characterization is performed by changing the coating layer, according to the introduction (or omission) of the coating layer, and the number of woven fiber mats. The results show that the damage mode changes from Hertzian stress to flexural stress as the fiber volume ratio increases in composites because of the decreased matrix volume fraction, which intensifies the radial crack damage. The result significantly indicates that the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics should be designed for

Reaction Synthesis of TiC Particle by Pressureless Sintering%无压烧结反应合成片状TiC晶粒

Institute of Scientific and Technical Information of China (English)

李新

2013-01-01

TiC particle was synthesized by heat treatment using 3TiC/Si/0.2Al powders. The phase composition and microstructure of the material was characterized by XRD and SEM. The composition of the sample was determined by EDS. The results show that the main phase of the product is Ti3SiC2 at 1100-1200 ℃. In addition, some amounts of TiC and SiC are also synthesized. At 1300℃ , Ti3SiC2 begins to decompose. When the temperature reaches 1350℃ , Ti3SiC2 totally decomposes into TiC. The product is mainly composed of TiC and small amounts of SiC. The length side of TiC hexagonal particle is 5 μm.%采用3TiC/Si/0.2A1粉体为原料,通过无压烧结反应合成了片状TiC晶粒.采用XRD、SEM和EDS对试样的物相组成、微观形貌和微区成分进行分析.结果表明,在1100～1200℃、保温2h,原料反应合成了主相Ti3SiC2,同时含有少量TiC、SiC相；当温度为1300℃时,Ti3SiC2开始明显分解；当温度升至1350℃时,试样中Ti3SiC2完全分解,产物主要由TiC相和少量SiC组成；六方TiC晶粒边长5μm.

Influence of microstructure on hydrothermal corrosion of chemically vapor processed SiC composite tubes

Science.gov (United States)

Kim, Daejong; Lee, Ho Jung; Jang, Changheui; Lee, Hyeon-Geun; Park, Ji Yeon; Kim, Weon-Ju

2017-08-01

Multi-layered SiC composites consisting of monolithic SiC and a SiCf/SiC composite are one of the accident tolerant fuel cladding concepts in pressurized light water reactors. To evaluate the integrity of the SiC fuel cladding under normal operating conditions of a pressurized light water reactor, the hydrothermal corrosion behavior of multi-layered SiC composite tubes was investigated in the simulated primary water environment of a pressurized water reactor without neutron fluence. The results showed that SiC phases with good crystallinity such as Tyranno SA3 SiC fiber and monolithic SiC deposited at 1200 °C had good corrosion resistance. However, the SiC phase deposited at 1000 °C had less crystallinity and severely dissolved in water, particularly the amorphous SiC phase formed along grain boundaries. Dissolved hydrogen did not play a significant role in improving the hydrothermal corrosion resistance of the CVI-processed SiC phases containing amorphous SiC, resulting in a significant weight loss and reduction of hoop strength of the multi-layered SiC composite tubes after corrosion.

Stress Wave attenuation in SiC3D/Al Composite

International Nuclear Information System (INIS)

Yuan Chunyuan; Wang Yangwei; Li Guoju; Zhang Xu; Gao Jubin

2013-01-01

SiC 3D /Al composite is a kind of special composite with interpenetrating network microstructure. The attenuation properties of stress wave propagation along the SiC 3D /Al composite are studied by a Split Hopkinson Pressure Bar system and FEM simulations, and the attenuation mechanism is discussed in this paper. Results show that the attenuation rate of the stress wave in the composite is up to 1.73MPa·mm −1 . The reduction of the amplitude of waves is caused by that plenty of interfaces between SiC and Al within the composite acting with stress waves. When the incident plane wave reaches the SiC 3D /Al interface, reflection wave and transmission wave propagates in different directions along the irregular interface between SiC phase and aluminium phase due to the impedance mismatch of them, which leads to the divergence of stress wave. At the same time, some stress micro-focuses occurs in the aluminium phase for the complex wave superimposition, and some plastic deformation may take place within such micro-regions, which results in the consumption of stress wave energy. In conclusion, the stress wave attenuation is derived from divergence and consumption of stress wave.

Determining the fracture resistance of advanced SiC fiber reinforced SiC matrix composites

International Nuclear Information System (INIS)

Nozawa, T.; Katoh, Y.; Kishimoto, H.

2007-01-01

Full text of publication follows: One of the perceived advantages for highly-crystalline and stoichiometric silicon carbide (SiC) and SiC composites, e.g., advanced SiC fiber reinforced chemically-vapor-infiltrated (CVI) SiC matrix composites, is the retention of fast fracture properties after neutron irradiation at high-temperatures (∼1000 deg. C) to intermediate-doses (∼15 dpa). Accordingly, it has been clarified that the maximum allowable stress (or strain) limit seems unaffected in certain irradiation conditions. Meanwhile, understanding the mechanism of crack propagation from flaws, as potential weakest link to cause composite failure, is somehow lacking, despite that determining the strength criterion based on the fracture mechanics will eventually become important considering the nature of composites' fracture. This study aims to evaluate crack propagation behaviors of advanced SiC/SiC and to provide fundamentals on fracture resistance of the composites to define the strength limit for the practical component design. For those purposes, the effects of irreversible energies related to interfacial de-bonding, fiber bridging, and microcrack forming on the fracture resistance were evaluated. Two-dimensional SiC/SiC composites were fabricated by CVI or nano-infiltration and transient-eutectic-phase (NITE ) methods. Hi-Nicalon TM Type-S or Tyranno TM -SA fibers were used as reinforcements. In-plane mode-I fracture resistance was evaluated by the single edge notched bend technique. The key finding is the continuous Load increase with the crack growth for any types of advanced composites, while many studies specified the gradual load decrease for the conventional composites once the crack initiates. This high quasi-ductility appeared due primarily to high friction (>100 MPa) at the fiber/matrix interface using rough SiC fibers. The preliminary analysis based on the linear elastic fracture mechanics, which does not consider the effects of irreversible energy

Electrolytic Production of Ti5Si3/TiC Composites by Solid Oxide Membrane Technology

Science.gov (United States)

Zheng, Kai; Zou, Xingli; Xie, Xueliang; Lu, Changyuan; Chen, Chaoyi; Xu, Qian; Lu, Xionggang

2018-02-01

This paper investigated the electrolytic production of Ti5Si3/TiC composites from TiO2/SiO2/C in molten CaCl2. The solid-oxide oxygen-ion-conducting membrane tube filled with carbon-saturated liquid tin was served as the anode, and the pressed spherical TiO2/SiO2/C pellet was used as the cathode. The electrochemical reduction process was carried out at 1273 K and 3.8 V. The characteristics of the obtained cathode products and the reaction mechanism of the electroreduction process were studied by a series of time-dependent electroreduction experiments. It was found that the electroreduction process generally proceeds through the following steps: TiO2/SiO2/C → Ti2O3, CaTiO3, Ca2SiO4, SiC → Ti5Si3, TiC. The morphology observation and the elemental distribution analysis indicate that the reaction routes for Ti5Si3 and TiC products are independent during the electroreduction process.

The effect of SiC particle size on the properties of Cu–SiC composites

International Nuclear Information System (INIS)

Celebi Efe, G.; Zeytin, S.; Bindal, C.

2012-01-01

Graphical abstract: The relative densities of Cu–SiC composites sintered at 700 °C for 2 h are ranged from 97.3% to 91.8% for SiC with 1 μm particle size and 97.5% to 95.2% for SiC with 5 μm particle size, microhardness of composites ranged from 143 to 167 HV for SiC having 1 μm particle size and 156–182 HVN for SiC having 5 μm particle size and the electrical conductivity of composites changed between 85.9% IACS and 55.7% IACS for SiC with 1 μm particle size, 87.9% IACS and 65.2%IACS for SiC with 5 μm particle size. It was found that electrical conductivity of composites containing SiC with 5 μm particle size is better than that of Cu–SiC composites containing SiC with particle size of 1 μm. Highlights: ► In this research, the effect of SiC particle size on some properties of Cu–SiC composites were investigated. ► The mechanical properties were improved. ► The electrical properties were obtained at desirable level. -- Abstract: SiC particulate-reinforced copper composites were prepared by powder metallurgy (PM) method and conventional atmospheric sintering. Scanning electron microscope (SEM), X-ray diffraction (XRD) techniques were used to characterize the sintered composites. The effect of SiC content and particle size on the relative density, hardness and electrical conductivity of composites were investigated. The relative densities of Cu–SiC composites sintered at 700 °C for 2 h are ranged from 97.3% to 91.8% for SiC with 1 μm particle size and from 97.5% to 95.2% for SiC with 5 μm particle size. Microhardness of composites ranged from 143 to 167 HV for SiC having 1 μm particle size and from 156 to 182 HV for SiC having 5 μm particle size. The electrical conductivity of composites changed between 85.9% IACS and 55.7% IACS for SiC with 1 μm particle size, between 87.9% IACS and 65.2% IACS for SiC with 5 μm particle size.

Low dose irradiation performance of SiC interphase SiC/SiC composites

International Nuclear Information System (INIS)

Snead, L.L.; Lowden, R.A.; Strizak, J.; More, K.L.; Eatherly, W.S.; Bailey, J.; Williams, A.M.; Osborne, M.C.; Shinavski, R.J.

1998-01-01

Reduced oxygen Hi-Nicalon fiber reinforced composite SiC materials were densified with a chemically vapor infiltrated (CVI) silicon carbide (SiC) matrix and interphases of either 'porous' SiC or multilayer SiC and irradiated to a neutron fluence of 1.1 x 10 25 n m -2 (E>0.1 MeV) in the temperature range of 260 to 1060 C. The unirradiated properties of these composites are superior to previously studied ceramic grade Nicalon fiber reinforced/carbon interphase materials. Negligible reduction in the macroscopic matrix microcracking stress was observed after irradiation for the multilayer SiC interphase material and a slight reduction in matrix microcracking stress was observed for the composite with porous SiC interphase. The reduction in strength for the porous SiC interfacial material is greatest for the highest irradiation temperature. The ultimate fracture stress (in four point bending) following irradiation for the multilayer SiC and porous SiC interphase materials was reduced by 15% and 30%, respectively, which is an improvement over the 40% reduction suffered by irradiated ceramic grade Nicalon fiber materials fabricated in a similar fashion, though with a carbon interphase. The degradation of the mechanical properties of these composites is analyzed by comparison with the irradiation behavior of bare Hi-Nicalon fiber and Morton chemically vapor deposited (CVD) SiC. It is concluded that the degradation of these composites, as with the previous generation ceramic grade Nicalon fiber materials, is dominated by interfacial effects, though the overall degradation of fiber and hence composite is reduced for the newer low-oxygen fiber. (orig.)

Deposition of titanium coating on SiC fiber by chemical vapor deposition with Ti-I{sub 2} system

Energy Technology Data Exchange (ETDEWEB)

Luo, Xian, E-mail: luo_shenfan@hotmail.com; Wu, Shuai; Yang, Yan-qing; Jin, Na; Liu, Shuai; Huang, Bin

2017-06-01

Highlights: • The transformation paths of (Ti + I{sub 2}) powder to Ti coating is: Ti + I{sub 2} → (TiI{sub 2}, TiI{sub 3}) → Ti. • Uniform coating was obtained on SiC fiber, but it contained Si and C elements. • Deposition rate of the coating increased with the increase of temperature. • Deposition thickness increased with time and achieved the maximum at 90 min. - Abstract: Titanium coating was prepared on SiC fiber using titanium-iodine (Ti-I{sub 2}) mixture by hot-wall chemical vapor deposition. Thermodynamic analysis and experimental observation were carried out in this work. The thermodynamic analysis of the reactions in the Ti-I{sub 2} system indicates that Ti and I{sub 2} raw powder materials transform to titanium coating as follows: Ti + I{sub 2} → (TiI{sub 2}, TiI{sub 3}), and (TiI{sub 2}, TiI{sub 3}) → Ti. In theory, the conversions of TiI{sub 3} and TiI{sub 2} reach the maximum when Ti:I{sub 2} is 1:1.5, while in actual experiment that reached the maximum when Ti:I{sub 2} was 1:2, as there existed the waste of I{sub 2} due to sublimation. Typical deposited coating is relatively flat and uniform. However, as SiC is prone to react with Ti at high temperatures, the obtained coating contained some Si and C elements except for Ti. So the coating was not a pure Ti coating but contained some carbides and silicides. Deposition rate of the coating increased with the increase of temperature. The deposited thickness increased with the increase of heat preservation time, and achieved the maximum thickness at 90 min.

Effect of SiC particles on microarc oxidation process of magnesium matrix composites

International Nuclear Information System (INIS)

Wang, Y.Q.; Wang, X.J.; Gong, W.X.; Wu, K.; Wang, F.H.

2013-01-01

SiC particles are an important reinforced phase in metal matrix composites. Their effect on the microarc oxidation (MAO, also named plasma electrolytic oxidation-PEO) process of SiC p /AZ91 Mg matrix composites (MMCs) was studied and the mechanism was revealed. The corrosion resistance of MAO coating was also investigated. Voltage–time curves during MAO were recorded to study the barrier film status on the composites. Scanning electron microscopy was used to characterize the existing state of SiC particles in MAO. Energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy were used to analyze the chemical composition of the coating. Corrosion resistance of the bare and coated composites was evaluated by potentiodynamic polarization curves in 3.5% NaCl solution. Results showed that the integrality and electrical insulation properties of the barrier film on the composites were destroyed by the SiC particles. Consequently, the sparking discharge at the early stage of MAO was inhibited, and the growth efficiency of the MAO coating decreased with the increase in the volume fraction of SiC particles. SiC particles did not exist stably during MAO; they were oxidized or partially oxidized into SiO 2 before the overall sparking discharge. The transformation from semi-conductive SiC to insulating SiO 2 by oxidation restrained the current leakage at the original SiC positions and then promoted sparking discharge and coating growth. The corrosion current density of SiC p /AZ91 MMCs was reduced by two orders of magnitude after MAO treatment. However, the corrosion resistances of the coated composites were lower than that of the coated alloy.

Spherical nanostructured Si/C composite prepared by spray drying technique for lithium ion batteries anode

Energy Technology Data Exchange (ETDEWEB)

Chen Libao [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Xie Xiaohua [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Wang Baofeng [Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang Ke [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Xie Jingying [Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China) and Graduate School of Chinese Academy of Sciences, Beijing 100049 (China)]. E-mail: jyxie@mail.sim.ac.cn

2006-07-15

Spherical nanostructured Si/C composite was prepared by spray drying technique, followed by heat treatment, in which nanosized silicon and fine graphite particles were homogeneously embedded in carbon matrix pyrolyzed by phenol formaldehyde resin. Cyclic voltammetry tests showed two pairs of redox peaks corresponding to lithiation and delithiation of Si/C composite. The Si/C composite exhibited a reversible capacity of 635 mAh g{sup -1} and good cycle performance used in lithium ion batteries. To improve cycle performance of this Si/C composite further, the carbon-coated Si/C composite was synthesized by the second spray drying and heat treatment processing. The cycle performance of carbon-coated Si/C composite was improved significantly, which was attributed to the formation of stable SEI passivation layers on the outer surface of carbon shell which protected the bared silicon from exposing to electrolyte directly.

Spherical nanostructured Si/C composite prepared by spray drying technique for lithium ion batteries anode

International Nuclear Information System (INIS)

Chen Libao; Xie Xiaohua; Wang Baofeng; Wang Ke; Xie Jingying

2006-01-01

Spherical nanostructured Si/C composite was prepared by spray drying technique, followed by heat treatment, in which nanosized silicon and fine graphite particles were homogeneously embedded in carbon matrix pyrolyzed by phenol formaldehyde resin. Cyclic voltammetry tests showed two pairs of redox peaks corresponding to lithiation and delithiation of Si/C composite. The Si/C composite exhibited a reversible capacity of 635 mAh g -1 and good cycle performance used in lithium ion batteries. To improve cycle performance of this Si/C composite further, the carbon-coated Si/C composite was synthesized by the second spray drying and heat treatment processing. The cycle performance of carbon-coated Si/C composite was improved significantly, which was attributed to the formation of stable SEI passivation layers on the outer surface of carbon shell which protected the bared silicon from exposing to electrolyte directly

Laser alloying of Al with mixed Ni, Ti and SiC powders

CSIR Research Space (South Africa)

Mabhali, Luyolo AB

2010-11-01

Full Text Available Laser alloying of aluminium AA1200 was performed with a 4.4kW Rofin Sinar Nd:YAG laser to improve the surface hardness. Alloying was carried out by depositing Ni, Ti and SiC powders of different weight ratios on the aluminium substrate. The aim...

Synthesis of micro-sized interconnected Si-C composites

Science.gov (United States)

Wang, Donghai; Yi, Ran; Dai, Fang

2016-02-23

Embodiments provide a method of producing micro-sized Si--C composites or doped Si--C and Si alloy-C with interconnected nanoscle Si and C building blocks through converting commercially available SiO.sub.x (0

Microwave joining of SiC ceramics and composites

Energy Technology Data Exchange (ETDEWEB)

Ahmad, I.; Silberglitt, R.; Tian, Y.L. [FM Technologies, Inc., Fairfax, VA (United States); Katz, J.D. [Los Alamos National Lab., NM (United States)

1997-04-01

Potential applications of SiC include components for advanced turbine engines, tube assemblies for radiant burners and petrochemical processing and heat exchangers for high efficiency electric power generation systems. Reliable methods for joining SiC are required in order to cost-effectively fabricate components for these applications from commercially available shapes and sizes. This manuscript reports the results of microwave joining experiments performed using two different types of SiC materials. The first were on reaction bonded SiC, and produced joints with fracture toughness equal to or greater than that of the base material over an extended range of joining temperatures. The second were on continuous fiber-reinforced SiC/SiC composite materials, which were successfully joined with a commercial active brazing alloy, as well as by using a polymer precursor.

Conversion of wood flour/SiO2/phenolic composite to porous SiC ceramic containing SiC whiskers

Directory of Open Access Journals (Sweden)

Li Zhong

2013-01-01

Full Text Available A novel wood flour/SiO2/phenolic composite was chosen to be converted into porous SiC ceramic containing SiC whiskers via carbothermal reduction. At 1550°C the composite is converted into porous SiC ceramic with pore diameters of 10~40μm, and consisting of β-SiC located at the position of former wood cell walls. β-SiC wire-like whiskers of less than 50 nm in diameter and several tens to over 100 μm in length form within the pores. The surface of the resulting ceramic is coated with β-SiC necklace-like whiskers with diameters of 1~2μm.

Features of film growth during plasma anodizing of Al 2024/SiC metal matrix composite

Energy Technology Data Exchange (ETDEWEB)

Xue Wenbin [Key Laboratory for Radiation Beam Technology and Materials Modification, Institute of Low Energy Nuclear Physics, Beijing Normal University, Beijing 100875 (China)]. E-mail: xuewb@bnu.edu.cn

2006-07-15

Plasma anodizing is a novel promising process to fabricate corrosion-resistant protective films on metal matrix composites. The corrosion-resistant films were prepared by plasma anodizing on SiC reinforced aluminum matrix composite. The morphology and microstructure of films were analyzed by scanning electron microscopy. Specifically, the morphology of residual SiC reinforcement particles in the film was observed. It is found that the most SiC reinforcement particles have been molten to become silicon oxide, but a few tiny SiC particles still remain in the film close to the composite/film interface. This interface is irregular due to the hindering effect of SiC particles on the film growth. Morphology and distribution of residual SiC particles in film provide direct evidence to identify the local melt occurs in the interior of plasma anodizing film even near the composite/film interface. A model of film growth by plasma anodizing on metal matrix composites was proposed.

Features of film growth during plasma anodizing of Al 2024/SiC metal matrix composite

International Nuclear Information System (INIS)

Xue Wenbin

2006-01-01

Plasma anodizing is a novel promising process to fabricate corrosion-resistant protective films on metal matrix composites. The corrosion-resistant films were prepared by plasma anodizing on SiC reinforced aluminum matrix composite. The morphology and microstructure of films were analyzed by scanning electron microscopy. Specifically, the morphology of residual SiC reinforcement particles in the film was observed. It is found that the most SiC reinforcement particles have been molten to become silicon oxide, but a few tiny SiC particles still remain in the film close to the composite/film interface. This interface is irregular due to the hindering effect of SiC particles on the film growth. Morphology and distribution of residual SiC particles in film provide direct evidence to identify the local melt occurs in the interior of plasma anodizing film even near the composite/film interface. A model of film growth by plasma anodizing on metal matrix composites was proposed

Interfacial reactions in Ti-6Al-4V with laser-embedded SiC particles and the origin of intergranular corrosion susceptibility of an Al-Mg alloy

NARCIS (Netherlands)

Kooi, BJ; De Hosson, JTM; Carter, CB; Hall, EL; Nutt,; Briant, CL

2000-01-01

In the first part of the paper the microstructure of Ti-6Al-4V with laser embedded SiC particle is explained. The interfacial reaction between Ti and SiC is responsible for the largely improved wear resistance of the Ti alloy. In the second part the phase responsible for the intergranular corrosion

Zirconia toughened SiC whisker reinforced alumina composites small business innovation research

Science.gov (United States)

Loutfy, R. O.; Stuffle, K. L.; Withers, J. C.; Lee, C. T.

1987-01-01

The objective of this phase 1 project was to develop a ceramic composite with superior fracture toughness and high strength, based on combining two toughness inducing materials: zirconia for transformation toughening and SiC whiskers for reinforcement, in a controlled microstructure alumina matrix. The controlled matrix microstructure is obtained by controlling the nucleation frequency of the alumina gel with seeds (submicron alpha-alumina). The results demonstrate the technical feasibility of producing superior binary composites (Al2O3-ZrO2) and tertiary composites (Al2O3-ZrO2-SiC). Thirty-two composites were prepared, consolidated, and fracture toughness tested. Statistical analysis of the results showed that: (1) the SiC type is the key statistically significant factor for increased toughness; (2) sol-gel processing with a-alumina seed had a statistically significant effect on increasing toughness of the binary and tertiary composites compared to the corresponding mixed powder processing; and (3) ZrO2 content within the range investigated had a minor effect. Binary composites with an average critical fracture toughness of 6.6MPam sup 1/2, were obtained. Tertiary composites with critical fracture toughness in the range of 9.3 to 10.1 MPam sup 1/2 were obtained. Results indicate that these composites are superior to zirconia toughened alumina and SiC whisker reinforced alumina ceramic composites produced by conventional techniques with similar composition from published data.

Influence of extrusion parameters on sic distribution and properties of AA6061/SiC composites produced by kobo method

Energy Technology Data Exchange (ETDEWEB)

WoĨniak, Jarosáaw; Kostecki, Marek; Broniszewski, Kamil; Olszyna, Andrzej [Faculty of Material Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Bochniak, Wáodzimierz [Faculty of Non-Ferrous Metals, AGH University of Science and Technology, Cracow (Poland)

2013-07-01

The influence of extrusion parameters on reinforcements distribution and properties of AA6061+x% vol. SiC p (x=0; 2.5; 5; 7.5; 10) composites was discussed in this paper The averages size of AA6061 and SiC particles were 10.6 μ m and 0.42 μ m, respectively. The composites were consolidated via powder metallurgy processing (without the sintering) and extruded by KoBo method. The microstructure was examined on each steps of production. High values of density for all produced composites were achieved. Additionally, hardness and Young’s modulus were investigated. The best reinforcement distribution and mechanical properties were obtained for composites extruded with the highest extrusion ratio. Key words: aluminum alloy, extrusion, aged hardening, metal matrix composites, microstructure.

Residual Stress Measurement of SiC tile/Al7075 Hybrid Composites by Neutron Diffraction

Energy Technology Data Exchange (ETDEWEB)

Park, Jong Bok; Lee, Jun Ho; Hong, Soon Hyung; Ryu, Ho Jin [KAIST, Daejeon (Korea, Republic of); Lee, Sang Bok; Lee, Sang Kwan [Korea Institute of Materials Science, Changwon (Korea, Republic of); Muslihd, M. Rifai [Center for Advanced Materials Science and Technology, Tangerang (India)

2016-05-15

In this research, SiC which has low density, high compressive strength, and high elastic modulus was used to fabricate the armor plate. In addition, Al which has low density and high toughness was used for a metal matrix of the composites. If two materials are combined, the composite can be effective materials for light weight armor applications. However, the existence of a large difference in coefficients of thermal expansion (CTE) between SiC and Al matrix, SiC/Al composites can have residual stresses while cooled in the fabrication process. Previous research reported that residual stresses in the composites or microstructures have an effect on the fatigue life and their mechanical properties. Some researchers reported about the residual stresses in the SiCp/Al metal matrix composites by numerical simulation systems, X-ray diffraction, and destructive methods. In order to analyze the residual stress of SiC/Al composites, the neutron diffraction as the non-destructive method was performed in this research. The 50 vol.% SiC{sub p}/Al7075 composites and SiC tile inserted 50 vol.% SiC{sub p}/Al7075 hybrid composites were measured to analyze the residual stress of Al (111) and SiC (111). Both samples had the tensile residual stresses in the Al (111) and the compressive residual stresses in the SiC (111) due to the difference in CTE.

In situ NiTi/Nb(Ti) composite

International Nuclear Information System (INIS)

Jiang, Daqiang; Cui, Lishan; Jiang, Jiang; Zheng, Yanjun

2013-01-01

Graphical abstract: - Highlights: • In situ NiTi/Nb(Ti) composites were fabricated. • The transformation temperature was affected by the mixing Ti:Ni atomic ratios. • The NiTi component became micron-scale lamella after forging and rolling. • The composite exhibited high strength and high damping capacity. - Abstract: This paper reports on the creation of a series of in situ NiTi/Nb(Ti) composites with controllable transformation temperatures based on the pseudo-binary hypereutectic transformation of NiTi–Nb system. The composite constituent morphology was controlled by forging and rolling. It is found that the thickness of the NiTi lamella in the composite reached micron level after the hot-forging and cold-rolling. The NiTi/Nb(Ti) composite exhibited high damping capacity as well as high yield strength

Corrosion and wear behavior of functionally graded Al2024/SiC composites produced by hot pressing and consolidation

Energy Technology Data Exchange (ETDEWEB)

Erdemir, Fatih; Canakci, Aykut, E-mail: aykut@ktu.edu.tr; Varol, Temel; Ozkaya, Serdar

2015-09-25

Highlights: • Functionally graded Al2024/SiC composites were produced by hot pressing. • Effect of the number of graded layers was investigated on the corrosion behavior. • Functionally graded composites has the most corrosion resistant than composites. • Wear mechanisms of Al2024/SiC composites were explained. - Abstract: Functionally graded Al2024/SiC composites (FGMs) with varying percentage of SiC (30–60%) were produced by hot pressing and consolidation method. The effects of SiC content and number of layers of Al2024/SiC FGMs on the corrosion and wear behaviors were investigated. The microstructures of these composites were characterized by a scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5% NaCl solution. Corrosion experiments shows that corrosion rate (1109 mpy) of two layered FGMs which containing 50 wt.% SiC were much higher than Al2024 matrix (2569 mpy) and Al2024/50 wt.% SiC composite (2201 mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disk wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40 wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role.

Effect of Copper Coated SiC Reinforcements on Microstructure, Mechanical Properties and Wear of Aluminium Composites

Science.gov (United States)

Kori, P. S.; Vanarotti, Mohan; Angadi, B. M.; Nagathan, V. V.; Auradi, V.; Sakri, M. I.

2017-08-01

Experimental investigations are carried out to study the influence of copper coated Silicon carbide (SiC) reinforcements in Aluminum (Al) based Al-SiC composites. Wear behavior and mechanical Properties like, ultimate tensile strength (UTS) and hardness are studied in the present work. Experimental results clearly revealed that, an addition of SiC particles (5, 10 and 15 Wt %) has lead in the improvement of hardness and ultimate tensile strength. Al-SiC composites containing the Copper coated SiC reinforcements showed better improvement in mechanical properties compared to uncoated ones. Characterization of Al-SiC composites are carried out using optical photomicrography and SEM analysis. Wear tests are carried out to study the effects of composition and normal pressure using Pin-On Disc wear testing machine. Results suggested that, wear rate decreases with increasing SiC composition, further an improvement in wear resistance is observed with copper coated SiC reinforcements in the Al-SiC metal matrix composites (MMC’s).

New High-Performance SiC Fiber Developed for Ceramic Composites

Science.gov (United States)

DiCarlo, James A.; Yun, Hee Mann

2002-01-01

Sylramic-iBN fiber is a new type of small-diameter (10-mm) SiC fiber that was developed at the NASA Glenn Research Center and was recently given an R&D 100 Award for 2001. It is produced by subjecting commercially available Sylramic (Dow Corning, Midland, MI) SiC fibers, fabrics, or preforms to a specially designed high-temperature treatment in a controlled nitrogen environment for a specific time. It can be used in a variety of applications, but it currently has the greatest advantage as a reinforcement for SiC/SiC ceramic composites that are targeted for long-term structural applications at temperatures higher than the capability of metallic superalloys. The commercial Sylramic SiC fiber, which is the precursor for the Sylramic-iBN fiber, is produced by Dow Corning, Midland, Michigan. It is derived from polymers at low temperatures and then pyrolyzed and sintered at high temperatures using boron-containing sintering aids (ref. 1). The sintering process results in very strong fibers (>3 GPa) that are dense, oxygen-free, and nearly stoichiometric. They also display an optimum grain size that is beneficial for high tensile strength, good creep resistance, and good thermal conductivity (ref. 2). The NASA-developed treatment allows the excess boron in the bulk to diffuse to the fiber surface where it reacts with nitrogen to form an in situ boron nitride (BN) coating on the fiber surface (thus the product name of Sylramic-iBN fiber). The removal of boron from the fiber bulk allows the retention of high tensile strength while significantly improving creep resistance and electrical conductivity, and probably thermal conductivity since the grains are slightly larger and the grain boundaries cleaner (ref. 2). Also, as shown in the graph, these improvements allow the fiber to display the best rupture strength at high temperatures in air for any available SiC fiber. In addition, for CMC applications under oxidizing conditions, the formation of an in situ BN surface layer

FABRICATION AND MATERIAL ISSUES FOR THE APPLICATION OF SiC COMPOSITES TO LWR FUEL CLADDING

Directory of Open Access Journals (Sweden)

WEON-JU KIM

2013-08-01

Full Text Available The fabrication methods and requirements of the fiber, interphase, and matrix of nuclear grade SiCf/SiC composites are briefly reviewed. A CVI-processed SiCf/SiC composite with a PyC or (PyC-SiCn interphase utilizing Hi-Nicalon Type S or Tyranno SA3 fiber is currently the best combination in terms of the irradiation performance. We also describe important material issues for the application of SiC composites to LWR fuel cladding. The kinetics of the SiC corrosion under LWR conditions needs to be clarified to confirm the possibility of a burn-up extension and the cost-benefit effect of the SiC composite cladding. In addition, the development of end-plug joining technology and fission products retention capability of the ceramic composite tube would be key challenges for the successful application of SiC composite cladding.

Oxidation of BN-coated SiC fibers in ceramic matrix composites

International Nuclear Information System (INIS)

Sheldon, B.W.; Sun, E.Y.

1996-01-01

Thermodynamic calculations were performed to analyze the simultaneous oxidation of BN and SiC. The results show that, with limited amounts of oxygen present, the formation of SiO 2 should occur prior to the formation of B 2 O 3 . This agrees with experimental observations of oxidation in glass-ceramic matrix composites with BN-coated SiC fibers, where a solid SiO 2 reaction product containing little or no boron has been observed. The thermodynamic calculations suggest that this will occur when the amount of oxygen available is restricted. One possible explanation for this behavior is that SiO 2 formation near the external surfaces of the composite closes off cracks or pores, such that vapor phase O 2 diffusion into the composite occurs only for a limited time. This indicates that BN-coated SiC fibers will not always oxidize to form significant amounts of a low-melting, borosilicate glass

Investigation into solubility and diffusion in SiC-NbC, SiC-TiC, SiC-ZrC systems

International Nuclear Information System (INIS)

Safaraliev, G.K.; Tairov, Yu.M.; Tsvetkov, V.F.; Shabanov, Sh.Sh.

1991-01-01

An investigation is carried out which demonstrates solid-phase interaction between SiC and NbC, TiC and ZrC monocrystals. The monocrystals are subjected to hot pressing in SiC powder with dispersity of 5x10 -6 m. The pressing temperature is 2270-2570 K and pressure is varied in the range of 20-40 MPa. Element composition and the distribution profile in a thin layer near the boundary of SiC-NbC, SiC-TiC and SiC-ZrC are investigated by the Anger spectroscopy method. The obtained results permit to make the conclusion in the possibility of solid solution formation in investigated systems

Tribological Behavior of Si3N4/Ti3SiC2 Contacts Lubricated by Lithium-Based Ionic Liquids

Directory of Open Access Journals (Sweden)

Haizhong Wang

2014-01-01

Full Text Available The tribological performance of Si3N4 ball sliding against Ti3SiC2 disc lubricated by lithium-based ionic liquids (ILs was investigated using an Optimol SRV-IV oscillating reciprocating friction and wear tester at room temperature (RT and elevated temperature (100°C. Glycerol and the conventional imidazolium-based IL 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonylimide (L-F106 were used as references under the same experimental conditions. The results show that the lithium-based ILs had higher thermal stabilities than glycerol and lower costs associated with IL preparation than L-F106. The tribotest results show that the lithium-based ILs were effective in reducing the friction and wear of Si3N4/Ti3SiC2 contacts. [Li(urea]TFSI even produced better tribological properties than glycerol and L-F106 both at RT and 100°C. The SEM/EDS and XPS results reveal that the excellent tribological endurance of Si3N4/Ti3SiC2 contacts lubricated by lithium-based ILs was mainly attributed to the formation of surface protective films composed of various tribochemical products.

Effect of SiC whisker addition on the microstructures and mechanical properties of Ti(C, N)-based cermets

International Nuclear Information System (INIS)

Wu, Peng; Zheng, Yong; Zhao, Yongle; Yu, Haizhou

2011-01-01

Ti(C, N)-based cermets with addition of SiC whisker (SiC w ) were prepared by vacuum sintering. The microstructures of the prepared cermets were investigated by using X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Mechanical properties such as transverse rupture strength (TRS), fracture toughness (K IC ) and hardness (HRA) were also measured. It was found that the grain size of the cermets was affected by the SiC whisker addition. The cermets with 1.0 wt.% SiC whisker addition exhibited the smallest grain size. The porosities of the cermets increased with increasing SiC whisker additions. The addition of the SiC whisker had no influence on the phase constituents of the cermets. Compared with the cermets with no whisker addition, the highest TRS and fracture toughness for cermets with 1.0 wt.% SiC whisker addition increased by about 24% and 29%, respectively. The strengthening mechanisms were attributed to finer grain size, homogeneous microstructure and moderate thickness of rim phase. The toughening mechanisms were characterized by crack deflection, whisker bridging and whisker pulling-out.

Effect of Si3N4 Addition on Oxidation Resistance of ZrB2-SiC Composites

Directory of Open Access Journals (Sweden)

Manab Mallik

2017-06-01

Full Text Available The oxidation behavior of ZrB2-20 vol % SiC and ZrB2-20 vol % SiC-5 vol % Si3N4 composites prepared by hot-pressing and subjected to isothermal exposure at 1200 or 1300 °C for durations of 24 or 100 h in air, as well as cyclic exposure at 1300 °C for 24 h, have been investigated. The oxidation resistance of the ZrB2-20 vol % SiC composite has been found to improve by around 20%–25% with addition of 5 vol % Si3N4 during isothermal or cyclic exposures at 1200 or 1300 °C. This improvement in oxidation resistance has been attributed to the formation of higher amounts of SiO2 and Si2N2O, as well as a greater amount of continuity in the oxide scale, because these phases assist in closing the pores and lower the severity of cracking by exhibiting self-healing type behavior. For both the composites, the mass changes are found to be higher during cyclic exposure at 1300 °C by about 2 times compared to that under isothermal conditions.

High-temperature mechanical and material design for SiC composites

International Nuclear Information System (INIS)

Ghoniem, N.M.

1992-01-01

Silicon Carbide (SiC) fiber reinforced composites (FRC's) are strong potential candidate structural and high heat flux materials for fusion reactors. During this past decade, they have been vigorously developed for use in aerospace and transportation applications. Recent fusion reactor systems studies, such as ARIES, have concluded that further development of SiC composites will result in significant safety, operational, and waste disposal advantages for fusion systems. A concise discussion of the main material and design issues related to the use of SiC FRC's as structural materials in future fusion systems is given in this paper. The status of material processing of SiC/SiC composites is first reviewed. The advantages and shortcomings of the leading processing technology, known as Chemical Vapor Infiltration are particularly highlighted. A brief outline of the design-relevant physical, mechanical, and radiation data base is then presented. SiC/SiC FRC's possess the advantage of increased apparent toughness under mechanical loading conditions. This increased toughness, however, is associated with the nucleation and propagation of small crack patterns in the structure. Design approaches and failure criteria under these conditions are discussed

synthesis and characterization of al/sic composite made by stir casting method

International Nuclear Information System (INIS)

Ghauri, K.M.; Ahmad, A.; Ahmad, R.; Din, K.M.; Chaudhry, J.A.

2013-01-01

Ceramics contain a distinctive property of completely absence of slip planes and have least probability of deforming by the application of force. Among these ceramics, the silicon carbide occupies a competent place to be used as a reinforcing agent for aluminum or its alloys. It has the density close to aluminum and is best for making composite having good strength and good heat conductivity. Stir casting has been used to synthesize Al/SiC MMCs by reinforcing silicon carbide particles into aluminum matrix. The reason for using stir casting is to develop technology for the development of MMCs at affordable cost. The selection of SiC as reinforcement and Al as matrix is because of their easy availability. The practical data acquired, analyzed and optimized will be interpreted in the light of information available in the literature and be shared with the relevant industries. The present work was mainly carried out to characterize the SiC/Al composite which was produced by reinforcing the various proportions of SiC (5, 10, 15, 25 and 30%) in aluminum matrix using stir casting technique. Mechanical properties of test specimens made from stir-casted Aluminum-Silicon Carbide composites have been studied using metallographic and mechanical testing techniques. It was observed that as the volume fraction of SiC in the composite is gradually increased, the hardness and toughness increase. However, beyond a level of 25-30 percent SiC, the results are not very consistent, and depend largely on the uniformity of distribution of SiC in the aluminum matrix. (author)

Residual stresses and mechanical properties of Si3N4/SiC multilayered composites with different SiC layers; Las tensiones residuales y las propiedades mecánicas de compuestos multicapa de Si3N4/SiC con diferentes capas de SiC

Energy Technology Data Exchange (ETDEWEB)

Liua, S.; Lia, Y.; Chena, P.; Lia, W.; Gaoa, S.; Zhang, B.; Yeb, F.

2017-11-01

The effect of residual stresses on the strength, toughness and work of fracture of Si3N4/SiC multilayered composites with different SiC layers has been investigated. It may be an effective way to design and optimize the mechanical properties of Si3N4/SiC multilayered composites by controlling the properties of SiC layers. Si3N4/SiC multilayered composites with different SiC layers were fabricated by aqueous tape casting and pressureless sintering. Residual stresses were calculated by using ANSYS simulation, the maximum values of tensile and compressive stresses were 553.2MPa and −552.1MPa, respectively. Step-like fracture was observed from the fracture surfaces. Fraction of delamination layers increased with the residual stress, which can improve the reliability of the materials. Tensile residual stress was benefit to improving toughness and work of fracture, but the strength of the composites decreased. [Spanish] Se ha investigado el efecto de las tensiones residuales en la resistencia, dureza y trabajo de fractura de los compuestos multicapa de Si3N4/SiC con diferentes capas de SiC. Puede ser una manera eficaz de diseñar y optimizar las propiedades mecánicas de los compuestos multicapa de Si3N4/SiC mediante el control de las propiedades de las capas de SiC. Los compuestos multicapa de Si3N4/SiC con diferentes capas de SiC se fabricaron por medio de colado en cinta en medio acuoso y sinterización sin presión. Las tensiones residuales se calcularon mediante el uso de la simulación ANSYS, los valores máximos de las fuerzas de tracción y compresión fueron 553,2 MPa y −552,1 MPa, respectivamente. Se observó una fractura escalonada a partir de las superficies de fractura. La fracción de capas de deslaminación aumenta con la tensión residual, lo que puede mejorar la fiabilidad de los materiales. La fuerza de tracción residual era beneficiosa para la mejora de la dureza y el trabajo de fractura, pero la resistencia de los compuestos disminuyó.

Surface passivation of nano-textured fluorescent SiC by atomic layer deposited TiO2

DEFF Research Database (Denmark)

Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas

2016-01-01

Nano-textured surfaces have played a key role in optoelectronic materials to enhance the light extraction efficiency. In this work, morphology and optical properties of nano-textured SiC covered with atomic layer deposited (ALD) TiO2 were investigated. In order to obtain a high quality surface fo...

Fabrication and characterization of SiC and ZrC composite coating on TRISO coated particle

Energy Technology Data Exchange (ETDEWEB)

Lee, H. G.; Lee, S. H.; Kim, D. J.; Park, J. Y.; Kim, W. J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

SiC coating is widely suggested as structural materials for nuclear application due to its excellent high irradiation resistance properties and high temperature mechanical properties. SiC coating on TRistructural-ISOtropic (TRISO) coated fuel particles plays an important role as a protective layer from radioactive fission gas and a mechanical structural layer. TRISO coating layer was deposited on a spherical particle by a FBCVD method. The ZrO{sub 2} spherical particles were used as a simulant kernel. TRISO coating layers consisting of a porous buffer layer, an inner PyC layer were sequentially deposited before depositing SiC or ZrC coating layer. In order investigate the phase of each composite coating layer, Raman analysis was conducted. SiC, ZrC coating and SiC/ZrC composite coating on spherical particle were successfully deposited via FBCVD method by adjusting source gas flow rate. In the SiC and ZrC composite coating, SiC phase and ZrC phase were observed by XRD and SEM analysis. In the condition of 100 sccm of ZrCl{sub 4}, 25 sccm of CH{sub 4}, and 30 sccm of MTS, only two phases of SiC and ZrC were observed and two phases are located with clean grain boundary.

Rare-earth element doped Si3N4/SiC micro/nano-composites-RT and HT mechanical properties

Czech Academy of Sciences Publication Activity Database

Lojanová, Š.; Tatarko, P.; Chlup, Zdeněk; Hnatko, M.; Dusza, J.; Lenčéš, Z.; Šajgalík, P.

2010-01-01

Roč. 30, č. 9 (2010), s. 1931-1944 ISSN 0955-2219 Institutional research plan: CEZ:AV0Z20410507 Keywords : Si3N4 * SiC * Nano-composites * Fracture toughness * Hardness * Strength * Creep Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.574, year: 2010

Preparation and characterization of the electrodeposited Cr-Al{sub 2}O{sub 3}/SiC composite coating

Energy Technology Data Exchange (ETDEWEB)

Gao Jifeng, E-mail: readlot@tom.com [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Suo Jinping, E-mail: jpsuo@yahoo.com.cn [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

2011-09-01

To increase the SiC content in Cr-based coatings, Cr-Al{sub 2}O{sub 3}/SiC composite coatings were plated in Cr(VI) baths which contained Al{sub 2}O{sub 3}-coated SiC powders. The Al{sub 2}O{sub 3}-coated SiC composite particles were synthesized by calcining the precursor prepared by heterogeneous deposition method. The transmission electron microscopy analysis of the particles showed that the nano-SiC particle was packaged by alumina. The zeta potential of the particles collected from the bath was up to +23 mV, a favorable condition for the co-deposition of the particles and chromium. Pulse current was used during the electrodeposition. Scanning Electron Microscopy (SEM) indicated that the coating was compact and combined well with the substrate. Energy dispersive X-ray analysis of Cr-Al{sub 2}O{sub 3}/SiC coatings demonstrated that the concentration of SiC in the coating reached about 2.5 wt.%. The corrosion behavior of the composite coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The data obtained suggested that the Al{sub 2}O{sub 3}/SiC particles significantly enhanced the corrosion resistance of the composite coating in 0.05 M HCl solution.

Electronic-structure origin of the anisotropic thermopower of nanolaminated Ti3SiC2 determined by polarized x-ray spectroscopy and Seebeck measurements

DEFF Research Database (Denmark)

Magnuson, Martin; Mattesini, Maurizio; Van Nong, Ngo

2012-01-01

Nanolaminated materials exhibit characteristic magnetic, mechanical, and thermoelectric properties, with large contemporary scientific and technological interest. Here we report on the anisotropic Seebeck coefficient in nanolaminated Ti3SiC2 single-crystal thin films and trace the origin to aniso......Nanolaminated materials exhibit characteristic magnetic, mechanical, and thermoelectric properties, with large contemporary scientific and technological interest. Here we report on the anisotropic Seebeck coefficient in nanolaminated Ti3SiC2 single-crystal thin films and trace the origin...... value of 4–6 μV/K. Employing a combination of polarized angle-dependent x-ray spectroscopy and density functional theory we directly show electronic structure anisotropy in inherently nanolaminated Ti3SiC2 single-crystal thin films as a model system. The density of Ti 3d and C 2p states at the Fermi...... level in the basal ab plane is about 40% higher than along the c axis. The Seebeck coefficient is related to electron and hole-like bands close to the Fermi level, but in contrast to ground state density functional theory modeling, the electronic structure is also influenced by phonons that need...

Thermodynamic modelling of phase equilibrium in system Ti-B-Si-C, synthesis and phases composition of borides and carbides layers on titanic alloyVT-1 at electron beam treatment in vacuum

Science.gov (United States)

Smirnyagina, N. N.; Khaltanova, V. M.; Lapina, A. E.; Dasheev, D. E.

2017-01-01

Composite layers on the basis of carbides and borides the titan and silicon on titanic alloy VT-1 are generated at diffused saturation in vacuum. Formation in a composite of MAX phase Ti3SiC2 is shown. Thermodynamic research of phase equilibrium in systems Ti-Si-C and Ti-B-C in the conditions of high vacuum is executed. The thermodynamics, formation mechanisms of superfirm layers borides and carbides of the titan and silicon are investigated.

Anodization Mechanism on SiC Nanoparticle Reinforced Al Matrix Composites Produced by Power Metallurgy.

Science.gov (United States)

Ferreira, Sonia C; Conde, Ana; Arenas, María A; Rocha, Luis A; Velhinho, Alexandre

2014-12-19

Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiC np ) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiC np on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiC np . The current peaks and the steady-state current density recorded at each voltage step increases with the SiC np volume fraction due to the oxidation of the SiC np . The formation mechanism of the anodic film on Al/SiC np composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiC np in the anodic film.

Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

Science.gov (United States)

Halbig, Michael Charles; Singh, Mrityunjay

2015-01-01

Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

Fiber/matrix interfaces for SiC/SiC composites: Multilayer SiC coatings

Energy Technology Data Exchange (ETDEWEB)

Halverson, H.; Curtin, W.A. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States)

1996-08-01

Tensile tests have been performed on composites of CVI SiC matrix reinforced with 2-d Nicalon fiber cloth, with either pyrolitic carbon or multilayer CVD SiC coatings [Hypertherm High-Temperature Composites Inc., Huntington Beach, CA.] on the fibers. To investigate the role played by the different interfaces, several types of measurements are made on each sample: (i) unload-reload hysteresis loops, and (ii) acoustic emission. The pyrolitic carbon and multilayer SiC coated materials are remarkably similar in overall mechanical responses. These results demonstrate that low-modulus, or compliant, interface coatings are not necessary for good composite performance, and that complex, hierarchical coating structures may possibly yield enhanced high-temperature performance. Analysis of the unload/reload hysteresis loops also indicates that the usual {open_quotes}proportional limit{close_quotes} stress is actually slightly below the stress at which the 0{degrees} load-bearing fibers/matrix interfaces slide and are exposed to atmosphere.

Moissanite (SiC) with metal-silicide and silicon inclusions from tuff of Israel: Raman spectroscopy and electron microscope studies

Science.gov (United States)

Dobrzhinetskaya, Larissa; Mukhin, Pavel; Wang, Qin; Wirth, Richard; O'Bannon, Earl; Zhao, Wenxia; Eppelbaum, Lev; Sokhonchuk, Tatiana

2018-06-01

Here, we present studies of natural SiC that occurs in situ in tuff related to the Miocene alkaline basalt formation deposited in northern part of Israel. Raman spectroscopy, SEM and FIB-assisted TEM studies revealed that SiC is primarily hexagonal polytypes 4H-SiC and 6H-SiC, and that the 4H-SiC polytype is the predominant phase. Both SiC polytypes contain crystalline inclusions of silicon (Sio) and inclusions of metal-silicide with varying compositions (e.g. Si58V25Ti12Cr3Fe2, Si41Fe24Ti20Ni7V5Zr3, and Si43Fe40Ni17). The silicides crystal structure parameters match Si2TiV5 (Pm-3m space group, cubic), FeSi2Ti (Pbam space group, orthorhombic), and FeSi2 (Cmca space group, orthorhombic) respectively. We hypothesize that SiC was formed in a local ultra-reduced environment at respectively shallow depths (60-100 km), through a reaction of SiO2 with highly reducing fluids (H2O-CH4-H2-C2H6) arisen from the mantle "hot spot" and passing through alkaline basalt magma reservoir. SiO2 interacting with the fluids may originate from the walls of the crustal rocks surrounding this magmatic reservoir. This process led to the formation of SiC and accompanied by the reducing of metal-oxides to native metals, alloys, and silicides. The latter were trapped by SiC during its growth. Hence, interplate "hot spot" alkali basalt volcanism can now be included as a geological environment where SiC, silicon, and silicides can be found.

Impact damage, hardness and tribology characterization of epoxy resin based composites reinforced with basalt fibers in combination with TiO_2, BaSO_4 and SiC

International Nuclear Information System (INIS)

Babu, T. Narendiranath; Mangalaraja, R.V.; Saravanan, S.; Prabha, D. Rama

2016-01-01

Impact damage, hardness characterization, frictional and wear behavior of epoxy resin based composites reinforced with basalt fibers in combination with TiO_2, BaSO_4 and SiC were investigated using an impact testing machine, a hardness testing machine and a pin on disc machine. The basalt contained different fillers and short fibers whose presence varied in steps of weight percentage from 23 % to 50 %. It was fabricated using the conventional hand-layup technique followed by the light compression moulding technique. The frictional behavior of the composite specimen was determined by testing on a pin on disc test machine under different operating conditions. The present investigation focused on the determination of the friction coefficient of epoxy resin based composites reinforced with basalt fibers in combination with the fillers. The effects of basalt short fibers content and load were examined under dry conditions. The results showed that the friction coefficient decreased with the filler contents increase. The hardness and the impact damage of epoxy resin reinforced with basalt fiber was examined and it was found that its reinforcement with basalt fiber along with fillers such as titanium oxide, silicon carbide, barium sulphate and graphite made it more advantageous than other specimens. Keywords: basalt fiber, impact behavior, hardness, wear resistance.

Interlaminar shear strength of SiC matrix composites reinforced by continuous fibers at 900 °C in air

International Nuclear Information System (INIS)

Zhang, Chengyu; Gou, Jianjie; Qiao, Shengru; Wang, Xuanwei; Zhang, Jun

2014-01-01

Highlights: • The application of SiC fiber could improve ILSS of the SiC matrix composites. • The orientation of the warp fibers plays a critical role in determining ILSS of 2.5D-C/SiC. • The failure mechanisms of 2D composites involve matrix cracking, and interfacial debonding. - Abstract: To reveal the shear properties of SiC matrix composites, interlaminar shear strength (ILSS) of three kinds of silicon carbide matrix composites was investigated by compression of the double notched shear specimen (DNS) at 900 °C in air. The investigated composites included a woven plain carbon fiber reinforced silicon carbide composite (2D-C/SiC), a two-and-a-half-dimensional carbon fiber-reinforced silicon carbide composite (2.5D-C/SiC) and a woven plain silicon carbon fiber reinforced silicon carbide composite (2D-SiC/SiC). A scanning electron microscope was employed to observe the microstructure and fracture morphologies. It can be found that the fiber type and reinforcement architecture have significant impacts on the ILSS of the SiC matrix composites. Great anisotropy of ILSS can be found for 2.5D-C/SiC because of the different fracture resistance of the warp fibers. Larger ILSS can be obtained when the specimens was loaded along the weft direction. In addition, the SiC fibers could enhance the ILSS, compared with carbon fibers. The improvement is attributed to the higher oxidation resistance of SiC fibers and the similar thermal expansion coefficients between the matrix and the fibers

Characterizing the Soldering Alloy Type In–Ag–Ti and the Study of Direct Soldering of SiC Ceramics and Copper

Directory of Open Access Journals (Sweden)

Roman Koleňák

2018-04-01

Full Text Available The aim of the research was to characterize the soldering alloy In–Ag–Ti type, and to study the direct soldering of SiC ceramics and copper. The In10Ag4Ti solder has a broad melting interval, which mainly depends on its silver content. The liquid point of the solder is 256.5 °C. The solder microstructure is composed of a matrix with solid solution (In, in which the phases of titanium (Ti3In4 and silver (AgIn2 are mainly segregated. The tensile strength of the solder is approximately 13 MPa. The strength of the solder increased with the addition of Ag and Ti. The solder bonds with SiC ceramics, owing to the interaction between active In metal and silicon infiltrated in the ceramics. XRD analysis has proven the interaction of titanium with ceramic material during the formation of the new minority phases of titanium silicide—SiTi and titanium carbide—C5Ti8. In and Ag also affect bond formation with the copper substrate. Two new phases were also observed in the bond interphase—(CuAg6In5 and (AgCuIn2. The average shear strength of a combined joint of SiC–Cu, fabricated with In10Ag4Ti solder, was 14.5 MPa. The In–Ag–Ti solder type studied possesses excellent solderability with several metallic and ceramic materials.

Influence of SiC coating thickness on mechanical properties of SiCf/SiC composite

Science.gov (United States)

Yu, Haijiao; Zhou, Xingui; Zhang, Wei; Peng, Huaxin; Zhang, Changrui

2013-11-01

Silicon carbide (SiC) coatings with varying thickness (ranging from 0.14 μm to 2.67 μm) were deposited onto the surfaces of Type KD-I SiC fibres with native carbonaceous surface using chemical vapour deposition (CVD) process. Then, two dimensional SiC fibre reinforced SiC matrix (2D SiCf/SiC) composites were fabricated using polymer infiltration and pyrolysis (PIP) process. Influences of the fibre coating thickness on mechanical properties of SiC fibre and SiCf/SiC composite were investigated using single-filament test and three-point bending test. The results indicated that flexural strength of the composites initially increased with the increasing CVD SiC coating thickness and reached a peak value of 363 MPa at the coating thickness of 0.34 μm. Further increase in the coating thickness led to a rapid decrease in the flexural strength of the composites. The bending modulus of composites showed a monotonic increase with increasing coating thickness. A chemical attack of hydrogen or other ions (e.g. a C-H group) on the surface of SiC fibres during the coating process, owing to the formation of volatile hydrogen, lead to an increment of the surface defects of the fibres. This was confirmed by Wang et al. [35] in their work on the SiC coating of the carbon fibre. In the present study, the existing ˜30 nm carbon on the surface of KD-I fibre [36] made the fibre easy to be attacked. Deposition of non-stoichiometric SiC, causing a decrease in strength. During the CVD process, a small amount of free silicon or carbon always existed [35]. The existence of free silicon, either disordered the structure of SiC and formed a new source of cracks or attacked the carbon on fibre surface resulting in properties degeneration of the KD-I fibre. The effect of residual stress. The different thermal expansion coefficient between KD-I SiC fibre and CVD SiC coating, which are 3 × 10-6 K-1 (RT ˜ 1000 °C) and 4.6 × 10-6 K-1 (RT ˜ 1000 °C), respectively, could cause residual stress

Joining of pressureless-sintered SiC to stainless steel using Ag-Cu alloy and insert-metals

International Nuclear Information System (INIS)

Yano, Toyohiko; Takada, Naohiro; Iseki, Takayoshi

1987-01-01

Brazing of pressureless-sintered SiC to stainless steel using Ag-28 wt% Cu alloy was studied. In SiC plate joined to stainless steel rod (6 mm in diameter) using an Ag-Cu alloy powder containing 1.5 wt% Ti, the bond strength increased with decreasing brazing temperature and holding time. When the increased size of stainless steel plate (10 x 10 x 4 mm), joining was unsuccessful by the method mentioned above and even with Ti insert-metal. However, simultaneous use of Ti and Mo as insert-metal gave a good bonding in the order SiC/Ti/Mo/stainless steel, because of relaxation of residual stress due to thermal expansion mismatch. The shear strength was 30 - 50 MPa. A thin layer, probably Ti 3 SiC 2 , was observed at the interface between SiC and brazing filler immediately after melting. But with increasing both temperature and time, Ti 5 Si 3 (C) and TiC x were formed if Ti was continuously provided from the brazing filler. Since the interface of Ti 3 SiC 2 and either Ti 5 Si 3 (C) or TiC x seemed to be brittle, the formation of Ti 5 Si 3 (C) and TiC x decreased the bond strength. At lower temperature and short time, a high bond strength is expected when Ti was inserted in contact with SiC. (author)

Fabrication and characterization of laminated Ti-(TiB+La2O3/Ti composite

Directory of Open Access Journals (Sweden)

Yuanfei Han

2015-10-01

Full Text Available The incorporation of ceramic particulate reinforcements into titanium alloys can improve the specific strength and specific stiffness, while inevitably reduce the plasticity and ductility. In this study, in situ synthesized multilayer Ti-(TiB+La2O3/Ti composite was designed by learning from the microstructure of nature biological materials with excellent mechanical properties. The Ti-(TiB+La2O3/Ti composite with unique characteristic of laminated structure was prepared by combined powder metallurgy and hot rolling. The method has the synthesize advantages with in-situ reaction of Ti and LaB6 at high temperature and controllability of reinforcements size and constituent phases in composites. The result shows that the pores in the as sintered laminated structure composite completely disappeared after hot rolling at 1050 °C. The agglomerated reinforcement particles were well dispersed and distributed uniformly along the rolling direction. The thickness of pure Ti layer and (TiB+La2O3/Ti composite layer decreased from 1 mm to about 200 μm. Meanwhile, the grains size was refined obviously after rolling deformation. The room temperature tensile test indicates that the elongation of the laminated Ti-(TiB+La2O3/Ti composite improved from 13% to 17% in comparison with the uniform (TiB+La2O3/Ti composite, while the tensile strength had little change. It provides theoretical and experimental basis for fabricating the novel high performance laminated Ti-(TiB+La2O3/Ti composites.

Residual stress in ceramics and ceramic composites

International Nuclear Information System (INIS)

Oden, M.

1992-01-01

Residual stresses in Si 3 N 4 and SiC have been measured with X-ray diffraction after grinding and thermal shock. The produced surface stresses are compressive after both treatments. The stresses show a strong dependence on the quenching temperature up to a certain temperature when cracks relax the stresses. The influence of the amount of reinforcing phase on the residual stress state in a Al 2 O 3 /SiC whisker composite was investigated and correlated to a modified Eshelby model. The agreement is excellent. The composite was quenched in liquid He (4K) and the stress state measured after show no relaxation of stresses, indicating elastic behaviour. An in situ strain measurement as a function of temperature conducted on a Al 2 O 3 /SiC whisker composite and a SiC/TiB 2 particle composite show very good agreement with the Eshelby model for the Al 2 O 3 /SiC system but not agreement for the SiC/TiB 2 system. The reason is believed to be stress relaxation during sample preparation. (au) (53 refs., 24 figs., 14 tabs.)

FE simulation of the indentation deformation of SiC modified vinylester composites in respect to their abrasive wear performance

Directory of Open Access Journals (Sweden)

2008-10-01

Full Text Available The abrasive sliding friction and wear behaviours of silicon carbide (SiC filled vinylester (VE composites were investigated. The average grain size of the incorporated SiC particles was varied, holding the volume content of them in every case at 16 vol%. Mechanical properties (hardness, compression modulus, yield stress of the filled and neat VE were determined. The tribological properties were investigated in block (composite – on – ring (steel test configuration. The steel counter bodies were covered with abrasive papers of different graining. Coefficient of friction (COF and specific wear rate of the VE + SiC composites were determined. It was observed that the wear resistance increases with increasing average filler grain size and with decreasing abrasiveness of the counter surface. The COF of the VE + SiC composites is independent of the size of the incorporated particles, but it is strongly influenced by the abrasiveness of the counter body. The worn surfaces of the VE + SiC systems were analysed in scanning electron microscope (SEM to deduce the typical wear mechanisms. The size effect of the SiC filler particles onto the abrasive wear characteristics was investigated by assuming that the roughness peaks of the abrasive paper and the indenter of the microhardness test cause similar micro scaled contact deformations in the composites. Therefore FE method was used to simulate the micro scaled deformation process in the VE + SiC systems during microindentation tests. The FE results provided valuable information on how to explain the size effect of the incorporated SiC filler.

Friction Stir Processing of Copper-Coated SiC Particulate-Reinforced Aluminum Matrix Composite

Directory of Open Access Journals (Sweden)

Chih-Wei Huang

2018-04-01

Full Text Available In the present work, we proposed a novel friction stir processing (FSP to produce a locally reinforced aluminum matrix composite (AMC by stirring copper-coated SiC particulate reinforcement into Al6061 alloy matrix. Electroless-plating process was applied to deposit the copper surface coating on the SiC particulate reinforcement for the purpose of improving the interfacial adhesion between SiC particles and Al matrix. The core-shell SiC structure provides a layer for the atomic diffusion between aluminum and copper to enhance the cohesion between reinforcing particles and matrix on one hand, the dispersion of fine copper in the Al matrix during FSP provides further dispersive strengthening and solid solution strengthening, on the other hand. Hardness distribution and tensile results across the stir zone validated the novel concept in improving the mechanical properties of AMC that was realized via FSP. Optical microscope (OM and Transmission Electron Microscopy (TEM investigations were conducted to investigate the microstructure. Energy dispersive spectrometer (EDS, electron probe micro-analyzer (EPMA, and X-ray diffraction (XRD were explored to analyze the atomic inter-diffusion and the formation of intermetallic at interface. The possible strengthening mechanisms of the AMC containing Cu-coated SiC particulate reinforcement were interpreted. The concept of strengthening developed in this work may open a new way of fabricating of particulate reinforced metal matrix composites.

Molecular dynamics simulation of damage cascade creation in SiC composites containing SiC/graphite interface

Energy Technology Data Exchange (ETDEWEB)

Wallace, Joseph; Chen, Di; Wang, Jing; Shao, Lin, E-mail: lshao@tamu.edu

2013-07-15

Silicon carbide composites have been investigated for their use as structural materials for advanced nuclear reactor designs. Although the composites have significantly enhanced mechanical properties and structure integrity, there is little known about the behavior of defects in the presence of a graphite-silicon carbide interface. In this study, molecular dynamics simulations have been used to model defect creation and clustering in a composite containing a SiC/graphite interface. Evolution of displacements as a function of time were studied and compared to bulk SiC. The results show that the first a few SiC atomic layers closest to the interface are easily damaged. However, beyond these first few atomic layers the system appears to be unaffected by the SiC interface.

Effect of Reactant Concentration on the Microstructure of SiC Nano wires Grown In Situ within SiC Fiber Preforms

International Nuclear Information System (INIS)

Kim, Weon Ju; Kang, Seok Min; Park, Ji Yeon; Ryu, Woo Seog

2006-01-01

Silicon carbide fiber-reinforced silicon carbide matrix (SiC f /SiC) composites are considered as advanced materials for control rods and other in-core components of high-temperature gas cooled reactors. Although the carbon fiber-reinforced carbon matrix (C f /C) composites are more mature and have advantages in cost, manufacturability and some thermomechanical properties, the SiC f /SiC composites have a clear advantage in irradiation stability, specifically a lower level of swelling and retention of mechanical properties. This offers a lifetime component for control rod application to HTGRs while the Cf/C composites would require 2-3 replacements over the reactor lifetime. In general, the chemical vapor infiltration (CVI) technique has been used most widely to produce SiC f /SiC composites. Although the technique produces a highly pure SiC matrix, it requires a long processing time and inevitably contains large interbundle pores. The present authors have recently developed 'whisker growing-assisted process,' in which one-dimensional SiC nano structures with high aspect ratios such as whiskers, nano wires and nano rods are introduced into the fiber preform before the matrix infiltration step. This novel method can produce SiC f /SiC composites with a lower porosity and an uniform distribution of pores when compared with the conventional CVI. This would be expected to increase mechanical and thermal properties of the SiC f /SiC composites. In order to take full advantage of the whisker growing strategy, however, a homogeneous growth of long whiskers is required. In this study, we applied the atmospheric pressure CVI process without metallic catalysts for the growth of SiC nano wires within stacked SiC fiber fabrics. We focused on the effect of the concentration of a reactant gas on the growth behavior and microstructures of the SiC nano wires and discussed a controlling condition for the homogenous growth of long SiC nano wires

Strength and conductivity of unidirectional copper composites reinforced by continuous SiC fibers

International Nuclear Information System (INIS)

Kimmig, S.; Allen, I.; You, J.H.

2013-01-01

A SiC long fiber-reinforced copper composite offers a beneficial combination of high strength and high thermal conductivity at elevated temperatures. Both properties make the composite a promising material for the heat sink of high-heat-flux components. In this work, we developed a novel Cu/SiC f composite using the Sigma fiber. Based on HIP technique, a metallurgical process was established for fabricating high quality specimens using a TiC interface coating. Extensive tensile tests were conducted on the unidirectionally reinforced composite at 20 °C and 300 °C for a wide range of fiber volume fraction (V f ). In this paper, a large amount of test data is presented. The transversal thermal conductivity varies from 260 to 130 W/mK at 500 °C as V f is increased from 13% to 37%. The tensile strength reached up to 1246 MPa at 20 °C for V f = 37.6%, where the fracture strain was limited to 0.8%. The data of both elastic modulus and ultimate strength exhibited a good agreement with the rule-of-mixture predictions indicating a high quality of the materials. The strength of the composite with the Sigma fibers turned out to be superior to those of the SCS6 fibers at 300 °C, although the SCS6 fiber actually has a higher strength than the Sigma fiber. The fractographic pictures of tension test and fiber push-out test manifested a sufficient interfacial bonding

Effect of re-melting on particle distribution and interface formation in SiC reinforced 2124Al matrix composite

Energy Technology Data Exchange (ETDEWEB)

Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

2013-12-15

The interface between metal matrix and ceramic reinforcement particles plays an important role in improving properties of the metal matrix composites. Hence, it is important to find out the interface structure of composite after re-melting. In the present investigation, the 2124Al matrix with 10 wt.% SiC particle reinforced composite was re-melted at 800 °C and 900 °C for 10 min followed by pouring into a permanent mould. The microstructures reveal that the SiC particles are distributed throughout the Al-matrix. The volume fraction of SiC particles varies from top to bottom of the composite plate and the difference increases with the decrease of re-melting temperature. The interfacial structure of re-melted 2124Al–10 wt.%SiC composite was investigated using scanning electron microscopy, an electron probe micro-analyzer, a scanning transmission electron detector fitted with scanning electron microscopy and an X-ray energy dispersive spectrometer. It is found that a thick layer of reaction product is formed at the interface of composite after re-melting. The experimental results show that the reaction products at the interface are associated with high concentration of Cu, Mg, Si and C. At re-melting temperature, liquid Al reacts with SiC to form Al{sub 4}C{sub 3} and Al–Si eutectic phase or elemental Si at the interface. High concentration of Si at the interface indicates that SiC is dissociated during re-melting. The X-ray energy dispersive spectrometer analyses confirm that Mg- and Cu-enrich phases are formed at the interface region. The Mg is segregated at the interface region and formed MgAl{sub 2}O{sub 4} in the presence of oxygen. The several elements identified at the interface region indicate that different types of interfaces are formed in between Al matrix and SiC particles. The Al–Si eutectic phase is formed around SiC particles during re-melting which restricts the SiC dissolution. - Highlights: • Re-melted composite shows homogeneous particle

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process

Science.gov (United States)

Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

2017-11-01

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

Fabrication of fiber composites with a MAX phase matrix by reactive melt infiltration

International Nuclear Information System (INIS)

Lenz, F; Krenkel, W

2011-01-01

Due to the inherent brittleness of ceramics it is very desirable to increase the damage tolerance of ceramics. The ternary MAX phases are a promising group of materials with high fracture toughness. The topic of this study is the development of ceramic matrix composites (CMCs) with a matrix containing MAX phases, to achieve a damage tolerant structural composite material. For this purpose carbon fiber reinforced preforms with a carbon-titanium carbide matrix (C/C-TiC) were developed and infiltrated with silicon by a pressureless reactive melt infiltration. Finally liquid silicon caused the formation of SiC, TiSi 2 and Ti 3 SiC 2 in the matrix of the composite.

SiC fiber and yttria-stabilized zirconia composite thick thermal barrier coatings fabricated by plasma spray

Science.gov (United States)

Ma, Rongbin; Cheng, Xudong; Ye, Weiping

2015-12-01

Approximately 4 mm-thick SiC fiber/yttria-stabilized zirconia (YSZ) composite thermal barrier coatings (TBCs) were prepared by atmospheric plasma spray (APS). The composite coatings have a 'reinforced concrete frame structure', which can protect the coating from failure caused by increasing thickness of coating. The SiC fiber plays an important role in reducing the residual stress level of the composite coatings. The thermal conductivity (TC) value of the composite coatings is 0.632 W/m K, which is about 50% reduction compared to that of typical APS YSZ TBCs. And the composite coatings have higher fracture toughness and better thermal shock resistance than the YSZ TBCs.

Improvement of thermal conductivity of ceramic matrix composites for 4. generation nuclear reactors; Amelioration de la conductivite thermique des composites a matrice ceramique pour les reacteurs de 4. generation

Energy Technology Data Exchange (ETDEWEB)

Cabrero, J.

2009-11-15

This study deals with thermal conductivity improvement of SiCf/SiC ceramic matrix composites materials to be used as cladding material in 4. generation nuclear reactor. The purpose of the study is to develop a composite for which both the temperature and irradiation effect is less pronounced on thermal conductivity of material than for SiC. This material will be used as matrix in CMC with SiC fibers. Some TiC-SiC composites with different SiC volume contents were prepared by spark plasma sintering (SPS). The sintering process enables to fabricate specimens very fast, with a very fine microstructure and without any sintering aids. Neutron irradiation has been simulated using heavy ions, at room temperature and at 500 C. Evolution of the thermal properties of irradiated materials is measured using modulated photothermal IR radiometry experiment and was related to structural evolution as function of dose and temperature. It appears that such approach is reliable to evaluate TiC potentiality as matrix in CMC. Finally, CMC with TiC matrix and SiC fibers were fabricated and both mechanical and thermal properties were measured and compare to SiCf/SiC CMC. (author)

Layered Composite of TiC-TiB2 to Ti-6Al-4V in Graded Composition by Combustion Synthesis in High-gravity Field

International Nuclear Information System (INIS)

Huang Xuegang; Zhao Zhongmin; Zhang Long

2013-01-01

By taking combustion synthesis to prepare solidified TiB 2 matrix ceramic in high-gravity field, the layered composite of TiC-TiB 2 ceramic to Ti-6Al-4V substrate in graded composition was achieved. XRD, FESEM and EDS results showed that the bulk full-density solidified TiC-TiB 2 composite was composed of fine TiB 2 platelets, TiC irregular grains, a few of α-Al 2 O 3 inclusions and Cr alloy phases, and α'-Ti phases alternating with Ti-enriched carbides constituted the matrix of the joint in which fine TiB platelets were embedded, whereas some C, B atoms were also detected at the heat-affected zone of Ti-6A1-4V substrate. The layered composite of the solidified ceramic to Ti-6Al-4V substrate in graded composition with continuous microstructure was considered a result of fused joint and inter-diffusion between liquid ceramic and surface-molten Ti alloy, followed by TiB 2 -Ti peritectic reaction and subsequent eutectic reaction in TiC-TiB-Ti ternary system.

(FSP) of Al–TiC in situ composite

Indian Academy of Sciences (India)

An Al-5 wt% TiC composite was processed in situ using K2TiF6 and graphite in Al melt and subjected to FSP. Processing parameters for FSP were optimized to get a defect free stir zone and homogenize the particle distribution. It was found that a rotation speed > 800 rpm is needed. A rotation speed of 1000 rpm and a ...

Microstructure and fracture in SiC whisker reinforced 2124 aluminum composite

Science.gov (United States)

Nieh, T. G.; Raninen, R. A.; Chellman, D. J.

1985-01-01

The microstructures of extruded and hot-rolled 2124 Al-15 percent (by weight) SiC whisker composites have been investigated, experimentally. Among the specific factors studied were: the strength of the whisker-matrix interfaces; (2) the presence of oxides; (3) the presence of defective whiskers; (4) and the presence of distribution of intermetallic compounds, impurities in the SiC(w) powder, and microstructural inhomogeneities. Modifications in the microstructure of the SiC/AL composites due to hot rolling and extrusion are illustrated in a series of microphotographs. It was found that hot rolling along the axis of extrusion was associated with some types of whisker damage, while the whiskers still retain their original orientation. Hot-rolling perpendicular to the axis of extrusion, however, tended to rotate the whiskers and produced a nearly isotropic material. Whisker free zones were virtually eliminated or reduced in size by hot rolling. In situ Auger fractography of the composite showed that the interfacial bonding between the SiC and the Al matrix was good and that Al2O2 had no significant influence on the fracture mechanics of the composite.

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process.

Science.gov (United States)

Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

2017-11-25

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

Improvement of thermal conductivity of ceramic matrix composites for 4. generation nuclear reactors

International Nuclear Information System (INIS)

Cabrero, J.

2009-11-01

This study deals with thermal conductivity improvement of SiCf/SiC ceramic matrix composites materials to be used as cladding material in 4. generation nuclear reactor. The purpose of the study is to develop a composite for which both the temperature and irradiation effect is less pronounced on thermal conductivity of material than for SiC. This material will be used as matrix in CMC with SiC fibers. Some TiC-SiC composites with different SiC volume contents were prepared by spark plasma sintering (SPS). The sintering process enables to fabricate specimens very fast, with a very fine microstructure and without any sintering aids. Neutron irradiation has been simulated using heavy ions, at room temperature and at 500 C. Evolution of the thermal properties of irradiated materials is measured using modulated photothermal IR radiometry experiment and was related to structural evolution as function of dose and temperature. It appears that such approach is reliable to evaluate TiC potentiality as matrix in CMC. Finally, CMC with TiC matrix and SiC fibers were fabricated and both mechanical and thermal properties were measured and compare to SiCf/SiC CMC. (author)

Effects of Interface Coating and Nitride Enhancing Additive on Properties of Hi-Nicalon SiC Fiber Reinforced Reaction-Bonded Silicon Nitride Composites

Science.gov (United States)

Bhatt, Ramakrishana T.; Hull, David R.; Eldridge, Jeffrey I.; Babuder, Raymond

2000-01-01

Strong and tough Hi-Nicalon SiC fiber reinforced reaction-bonded silicon nitride matrix composites (SiC/ RBSN) have been fabricated by the fiber lay-up approach. Commercially available uncoated and PBN, PBN/Si-rich PBN, and BN/SiC coated SiC Hi-Nicalon fiber tows were used as reinforcement. The composites contained approximately 24 vol % of aligned 14 micron diameter SiC fibers in a porous RBSN matrix. Both one- and two-dimensional composites were characterized. The effects of interface coating composition, and the nitridation enhancing additive, NiO, on the room temperature physical, tensile, and interfacial shear strength properties of SiC/RBSN matrix composites were evaluated. Results indicate that for all three coated fibers, the thickness of the coatings decreased from the outer periphery to the interior of the tows, and that from 10 to 30 percent of the fibers were not covered with the interface coating. In the uncoated regions, chemical reaction between the NiO additive and the SiC fiber occurs causing degradation of tensile properties of the composites. Among the three interface coating combinations investigated, the BN/SiC coated Hi-Nicalon SiC fiber reinforced RBSN matrix composite showed the least amount of uncoated regions and reasonably uniform interface coating thickness. The matrix cracking stress in SiC/RBSN composites was predicted using a fracture mechanics based crack bridging model.

Development of the fabrication process of SiC composite by radiation beam

International Nuclear Information System (INIS)

Park, Ji Yeon; Kim, Weon Ju; Jung, Choong Hwan; Woo, Chang Hyeon; Ryu, Woo Seog

2006-01-01

In order to operate the nuclear system at high temperatures, core materials with a good irradiation resistance at high temperatures must be developed. SiC composite is one of candidates for high temperature structural materials. Among several fabrication processes, the PIP process includes the curing and pyrolysis process. Generally, the thermal oxidation curing method has some disadvantages; difficulty in the control of oxygen contents and volatilization of many constituents. To overcome these disadvantages and reduce the process time, a new and improved method like the beam curing process has been proposed as one of the effective methods for the fabrication of SiC composite. In this study, the electron beam curing method in the PIP process was optimized to develop SiCf/SiC composite with low oxygen contents. Using the electron beam curing method with full doses of 2∼10 MGy and the pyrolysis process at 1300∼1400 .deg. C, composite with the oxygen content of less than 1 wt% could be obtained. Additionally, if the slurry impregnation and curing/pyrolysis processes were repeated several times, dense composite could be produced

Vacuum brazing of high volume fraction SiC particles reinforced aluminum matrix composites

Science.gov (United States)

Cheng, Dongfeng; Niu, Jitai; Gao, Zeng; Wang, Peng

2015-03-01

This experiment chooses A356 aluminum matrix composites containing 55% SiC particle reinforcing phase as the parent metal and Al-Si-Cu-Zn-Ni alloy metal as the filler metal. The brazing process is carried out in vacuum brazing furnace at the temperature of 550°C and 560°C for 3 min, respectively. The interfacial microstructures and fracture surfaces are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy spectrum analysis (EDS). The result shows that adequacy of element diffusion are superior when brazing at 560°C, because of higher activity and liquidity. Dislocations and twins are observed at the interface between filler and composite due to the different expansion coefficient of the aluminum alloy matrix and SiC particles. The fracture analysis shows that the brittle fracture mainly located at interface of filler and composites.

Microstructure Characteristic of In-situ Ti/TiC Composites

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

TiC reinforced titanium composites has been produced with different Al content and C content by XDTM. The results have shown that TiC particles are of two different morphologies: coarse dendritical primary TiC and short bar-shape eutectic TiC. Al content has great effects on the morphology of TiC. With the increasing of Al content, the morphology of primary TiC changes from coarse developed dendrite into short bar-shape or plate-shape TiC with 35%Al. Meanwhile, the structure of the matrix changes from single Ti to Ti and Ti3Al, and to Ti3Al and TiAl. However, the C content has no influence on the microstructure of matrix. When the C content is less than 1.2%, the dendrite TiC disappears and only short bar-shape or plate-shape TiC exists in the composites. In addition, the effect of heat treatment on the morphology of TiC has also studied.

Fabrication and Mechanical Properties of SiCw(p/SiC-Si Composites by Liquid Si Infiltration using Pyrolysed Rice Husks and SiC Powders as Precursors

Directory of Open Access Journals (Sweden)

Dan Zhu

2014-03-01

Full Text Available Dense silicon carbide (SiC matrix composites with SiC whiskers and particles as reinforcement were prepared by infiltrating molten Si at 1550 °C into porous preforms composed of pyrolysed rice husks (RHs and extra added SiC powder in different ratios. The Vickers hardness of the composites showed an increase from 18.6 to 21.3 GPa when the amount of SiC added in the preforms was 20% (w/w, and then decreased to 17.3 GPa with the increase of SiC added in the preforms up to 80% (w/w. The values of flexural strength of the composites initially decreased when 20% (w/w SiC was added in the preform and then increased to 587 MPa when the SiC concentration reached 80% (w/w. The refinement of SiC particle sizes and the improvement of the microstructure in particle distribution of the composites due to the addition of external SiC played an effective role in improving the mechanical properties of the composites.

Improved thermoelectric performance of CdO by adding SiC fibers versus by adding SiC nanoparticles inclusions

Science.gov (United States)

Liang, S.; Li, Longjiang

2018-03-01

We report the improved thermoelectric (TE) performance of CdO by alloying with SiC fibers. In contrast to the lowered thermoelectric figure of merit (ZT) in a CdO matrix with SiC nanoparticle composites, an appreciable ZT value increment of about 36% (from 0.32 to 0.435) at 1000 K was obtained in the CdO matrix with SiC fiber composites. Both kinds of composites show substantially decreased thermal conductivity due to additional phonon scattering by the nano-inclusions. Compared to the very high electrical resistivity (ρ ˜ 140 μΩ m) for 5 at. % SiC nanoparticle composites, SiC fiber composites favorably maintained a very low ρ (˜30 μΩ m) even with 5 at. % SiC at 1000 K. We think the substantial difference of specific surface areas of these two nano-inclusions (30 m2/g for fibers vs 300 m2/g for nanoparticles) might play a crucial role to fine tune the TE performance. Larger interface could be inductive to diffusion and electron acceptor activation, which affect carrier mobility considerably. This work might hint at an alternative approach to improve TE materials' performance.

Fabrication of SiC Composites with Synergistic Toughening of Carbon Whisker and In Situ 3C-SiC Nanowire

Directory of Open Access Journals (Sweden)

Zhang Yunlong

2016-01-01

Full Text Available The SiC composites with synergistic toughening of carbon whisker and in situ 3C-SiC nanowire have been fabricated by hot press sinter technology and annealed treatment technology. Effect of annealed time on the morphology of SiC nanowires and mechanical properties of the Cw/SiC composites was surveyed in detail. The appropriate annealed time improved mechanical properties of the Cw/SiC composites. The synergistic effect of carbon whisker and SiC nanowire can improve the fracture toughness for Cw/SiC composites. The vapor-liquid-solid growth (VLS mechanism was proposed. TEM photo showed that 3C-SiC nanowire can be obtained with preferential growth plane ({111}, which corresponded to interplanar spacing about 0.25 nm.

Effect of LaB6 on the thermal shock property of MoSi2-SiC coating for carbon/carbon composites

International Nuclear Information System (INIS)

Li Ting; Li Hejun; Shi Xiaohong

2013-01-01

Highlights: ► LaB 6 -MoSi 2 -SiC and MoSi 2 -SiC multi-composition coatings were coated on C/C composites by pack cementation. ► The microstructure and thermal shock resistance of both coatings were investigated. ► The addition of LaB 6 can increase the compactness, flexural strength and fracture toughness of the MoSi 2 -SiC coating simultaneously. ► Both coatings bond well with the substrates before and after thermal cycling oxidation between 1773 K and room temperature. ► The LaB 6 -MoSi 2 -SiC coated C/C shows better thermal shock resistance than the MoSi 2 -SiC coated C/C. - Abstract: LaB 6 -MoSi 2 -SiC and MoSi 2 -SiC coatings were prepared on the surface of carbon/carbon composites by pack cementation method. The crystal structures of the coatings were measured by X-ray diffraction. The morphologies and element distributions were also analyzed by scanning electron microscopy and energy dispersive spectroscopy, respectively. The effect of LaB 6 on the microstructure and thermal shock resistance of MoSi 2 -SiC coating was investigated. The results indicated that the LaB 6 -MoSi 2 -SiC coating possessed a denser structure and superior thermal shock resistance. After 25 times of thermal cycling oxidation between 1773 K and room temperature, the weight losses of the LaB 6 -MoSi 2 -SiC and MoSi 2 -SiC coated samples were 0.627% and 2.019%, respectively.

Wear behavior of AA 5083/SiC nano-particle metal matrix composite: Statistical analysis

Science.gov (United States)

Hussain Idrisi, Amir; Ismail Mourad, Abdel-Hamid; Thekkuden, Dinu Thomas; Christy, John Victor

2018-03-01

This paper reports study on statistical analysis of the wear characteristics of AA5083/SiC nanocomposite. The aluminum matrix composites with different wt % (0%, 1% and 2%) of SiC nanoparticles were fabricated by using stir casting route. The developed composites were used in the manufacturing of spur gears on which the study was conducted. A specially designed test rig was used in testing the wear performance of the gears. The wear was investigated under different conditions of applied load (10N, 20N, and 30N) and operation time (30 mins, 60 mins, 90 mins, and 120mins). The analysis carried out at room temperature under constant speed of 1450 rpm. The wear parameters were optimized by using Taguchi’s method. During this statistical approach, L27 Orthogonal array was selected for the analysis of output. Furthermore, analysis of variance (ANOVA) was used to investigate the influence of applied load, operation time and SiC wt. % on wear behaviour. The wear resistance was analyzed by selecting “smaller is better” characteristics as the objective of the model. From this research, it is observed that experiment time and SiC wt % have the most significant effect on the wear performance followed by the applied load.

Effect of turning parameters on surface roughness of A356/5% SiC composite produced by electromagnetic stir casting

Energy Technology Data Exchange (ETDEWEB)

Dwivedi, S. P.; Kumar, Sudhir; Kumar, Ajay [Noida Institute of Engineering Technology, U.P (India)

2012-12-15

In the present investigation, A356 alloy 5 wt% SiC composite is fabricated by electromagnetic stir casting process. An attempt has been made to investigate the effect of CNC lathe process parameters like cutting speed, depth of cut, and feed rate on surface roughness during machining of A356 alloy 5 wt% SiC particulate metal-matrix composites in dry condition. Response surface methodology (Box Behnken Method) is chosen to design the experiments. The results reveal that cutting speed increases surface roughness decreases, whereas depth of cut and feed increase surface roughness increase. Optimum values of speed (190 m/min), feed (0.14 mm/rev) and depth of cut (0.20 mm) during turning of A356 alloy 5 wt% SiC composites to minimize the surface roughness (3.15>m) have been find out. The mechanical properties of A356 alloy 5 wt% SiC were also analyzed.

TiO2 and SiC nanostructured films, organized CNT structures

Indian Academy of Sciences (India)

sized nanostructured TiO2 films through hydrolysis of titanium tetra-isopropoxide. (TTIP) [9 ... structured TiO2 as a photocatalyst is as follows [15]:. TiO2(ns) ... The deposited films were easily detached from the silica tube and subjected to. SEM.

Fabrication and Mechanical Properties of TiC/TiAl Composites

Institute of Scientific and Technical Information of China (English)

YUE Yun-long; GONG Yan-sheng; WU Hai-tao; WANG Chuan-bin; ZHANG Lian-meng

2004-01-01

TiC/TiAl composites with different TiC content were fabricated by rapid heating technique ofspark plasma sintering (SPS). The effect of TiC particles on microstructure and mechanical properties of TiAl matrix was investigated. The results indicate that grain sizes of TiAl matrix decrease and mechanical properties are improved because of the addition of TiC particles. The composites display a 26.8% increase in bending strength when10wt% TiC is added and 43.8% improvement in fracture toughness when 5 wt % TiC is added compared to valuesof TiC-free materials. Grain-refinement and dispersion-strengthening were the main strengthening mechanism. Theimprovement of fracture toughness was due to the deflexion of TiC particles to the crack.

Microstructure of in-situ Synthesized (TiB+TiC)/Ti Composites Prepared by Hot-pressing

Institute of Scientific and Technical Information of China (English)

Zhenzhu ZHENG; Lin GENG; Honglin WANG; Weimin ZHOU; Hongyu XU

2003-01-01

In-situ 5 vol.pct TiB whiskers and TiC particulates reinforced Ti composites were fabricated by blending Ti powderand B4C particulates followed by reactive hot-pressing. The microstructure of the composites was investigated byusing differential scanning c

Joining of SiC ceramics and SiC/SiC composites

Energy Technology Data Exchange (ETDEWEB)

Rabin, B.H. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

1996-08-01

This project has successfully developed a practical and reliable method for fabricating SiC ceramic-ceramic joints. This joining method will permit the use of SiC-based ceramics in a variety of elevated temperature fossil energy applications. The technique is based on a reaction bonding approach that provides joint interlayers compatible with SiC, and excellent joint mechanical properties at temperatures exceeding 1000{degrees}C. Recent emphasis has been given to technology transfer activities, and several collaborative research efforts are in progress. Investigations are focusing on applying the joining method to sintered {alpha}-SiC and fiber-reinforced SiC/SiC composites for use in applications such as heat exchangers, radiant burners and gas turbine components.

Effect of heat treatment on microstructure and interface of SiC particle reinforced 2124 Al matrix composite

Energy Technology Data Exchange (ETDEWEB)

Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

2013-11-15

The microstructure and interface between metal matrix and ceramic reinforcement of a composite play an important role in improving its properties. In the present investigation, the interface and intermetallic compound present in the samples were characterized to understand structural stability at an elevated temperature. Aluminum based 2124 alloy with 10 wt.% silicon carbide (SiC) particle reinforced composite was prepared through vortex method and the solid ingot was deformed by hot rolling for better particle distribution. Heat treatment of the composite was carried out at 575 °C with varying holding time from 1 to 48 h followed by water quenching. In this study, the microstructure and interface of the SiC particle reinforced Al based composites have been studied using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA) associated with wavelength dispersive spectroscopy (WDS) and transmission electron microscopy (TEM) to identify the precipitate and intermetallic phases that are formed during heat treatment. The SiC particles are uniformly distributed in the aluminum matrix. The microstructure analyses of Al–SiC composite after heat treatment reveal that a wide range of dispersed phases are formed at grain boundary and surrounding the SiC particles. The energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy analyses confirm that finely dispersed phases are CuAl{sub 2} and CuMgAl{sub 2} intermetallic and large spherical phases are Fe{sub 2}SiAl{sub 8} or Al{sub 15}(Fe,Mn){sub 3}Si. It is also observed that a continuous layer enriched with Cu and Mg of thickness 50–80 nm is formed at the interface in between Al and SiC particles. EDS analysis also confirms that Cu and Mg are segregated at the interface of the composite while no carbide is identified at the interface. - Highlights: • The composite was successfully heat treated at 575°C for 1

Report on the Fracture Analysis of HfB(sub 2)-SiC and ZrB(sub 2)-SiC Composites; TOPICAL

International Nuclear Information System (INIS)

MECHOLSKY, JR. JOHN J.

2001-01-01

Hafnium diboride-silicon carbide (HS) and zirconium diboride-silicon carbide (ZS) composites are potential materials for high temperature, thermal shock applications such as for components on re-entry vehicles. In order to establish material constants necessary for evaluation of in situ fracture, bars fractured in four-point flexure were examined using fractographic principles. The fracture toughness was determined from measurements of the critical crack sizes and the strength values and the crack branching constants were established to use in forensic fractography for future in-flight tests. The fracture toughnesses range from about 13 MPam(sup 1/2) at room temperature to about 6 MPam(sup 1/2) at 1400 C for ZrB(sub 2)-Sic composites and from about 13 MPam(sup 1/2) at room temperature to about 4 MPam(sup 1/2) at 1400 C for HfB(sub 2)-SiC composites. Thus, the toughnesses of either the HS or ZS composites have the potential for use in thermal shock applications. Processing and manufacturing defects limited the strength of the test bars. However, examination of the microstructure on the fracture surfaces shows that the processing of these composites can be improved. There is potential for high toughness composites with high strength to be used in thermal shock conditions if the processing and handling are controlled

Compósitos SiCf /SiC utilizados em sistemas de proteção térmica SiCf /SiC composites for thermal protection systems

Directory of Open Access Journals (Sweden)

M. Florian

2005-09-01

Full Text Available Compósitos de carbeto de silício (SiC reforçado com fibras de carbeto de silício (SiCf são materiais candidatos em potencial para utilização em sistemas de proteção térmica em altas temperaturas devido principalmente à boa condutividade térmica na direção da fibra e muito baixa condutividade térmica na direção transversal à fibra, alta dureza, estabilidade térmica e à corrosão por oxidação. O compósito SiCf/SiC possui uma matriz de SiC reforçada com fibras contínuas policristalinas de SiC e é obtido por reações de conversão em altas temperaturas e atmosfera controlada, utilizando o compósito carbono/carbono como precursor. O processo de Reação Química em Vapor (CVR foi utilizado para a fabricação de compósitos SiCf/SiC com alta pureza na fase de SiC-beta. O compósito precursor de carbono/carbono foi fabricado com fibra de carbono não estabilizada e matriz carbonosa derivada da resina fenólica na forma de carbono isotrópico. O compósito convertido exibiu uma densidade de 1,75 g/cm³, com 40% de porosidade aberta e resistência à flexão de 80 MPa medida por ensaio flexão em 4 pontos. A área especifica medida pela técnica de BET é dependente da temperatura de conversão e das condições inicias do precursor de carbono, podendo chegar a 18 m²/g.Composites based on silicon carbide are potential candidate materials for thermal protection systems mainly due to its good thermal conductivity in fiber direction and very low transversal thermal conductivity, high hardness, corrosion and thermal resistance. SiCf/SiC composite presents a SiC matrix reinforced with SiC polycrystalline continuous fibers. The composite was obtained by conversion reactions at high temperature and controlled atmosphere from a carbon/carbon composite precursor. The CVR process was used to fabricate SiC /SiC composite with crystalline high-purity beta-SiC from a carbon-carbon precursor fabricated with non-stabilized carbon fiber and

Chemical vapor deposition of SiC on C-C composites as plasma facing materials for fusion application

International Nuclear Information System (INIS)

Kim, W. J.; Lee, M. Y.; Park, J. Y.; Hong, G. W.; Kim, J. I.; Choi, D. J.

2000-01-01

Because of the low activation and excellent mechanical properties at elevated temperatures, carbon-fiber reinforced carbon(C-C) composites have received much attention for plasma facing materials for fusion reactor and high-temperature structural applications such as aircrafts and space vehicles. These proposed applications have been frustrated by the lack of resistance to hydrogen erosion and oxidation on exposure to ambient oxidizing conditions at high temperature. Although Silicon Carbide (SiC) has shown excellent properties as an effective erosion-and oxidation-protection coating, many cracks are developed during fabrication and thermal cycles in use due to the Coefficients of Thermal Expansion(CTE) mismatch between SiC and C-C composite. In this study, we adopted a pyrolitic carbon as an interlayer between SiC and C-C substrate in order to minimize the CTE mismatch. The oxidation-protection performance of this composite was investigated as well

Micromechanics of fiber pull-out and crack bridging in SCS-6 SiC- CVD SiC composite system at high-temperature

International Nuclear Information System (INIS)

El-Azab, A.; Ghoniem, N.M.

1993-01-01

A micro mechanical model is developed to study fiber pull-out and crack bridging in fiber reinforced SiC-SiC composites with time dependent thermal creep. By analyzing the creep data for monolithic CVD SiC (matrix) and the SCS-6 SiC fibers in the temperature range 900-1250 degrees C, it is found that the matrix creep rates can be ignored in comparison to those of fibers. Two important relationships are obtained: (1) a time dependent relation between the pull-out stress and the relative sliding distance between the fiber and matrix for the purpose of analyzing pull-out experiments, and (2) the relation between the bridging stress and the crack opening displacement to be used in studying the mechanics and stability of matrix crack bridged by fibers at high temperatures. The present analysis can also be applied to Nicalon-reinforced CVD SiC matrix system since the Nicalon fibers exhibit creep characteristics similar to those of the SCS-6 fibers

Strengthening mechanisms in Ti-6Al-4V/TiC composites

International Nuclear Information System (INIS)

Johnson, A.J. Wagoner; Kumar, K.S.; Briant, C.L.

2004-01-01

In this study, the compressive behavior of Ti-6Al-4V/TiC composites considered for ballistic applications was examined at strain rates of 0.1, 1.0, and 10 s-1. As little as 1 vol% of particulate TiC provided nearly a 25% increase in strength in Ti-6Al-4V/TiC composites over that of the monolithic Ti-6Al-4V, while subsequent additions of TiC did not provide proportional benefit. The mechanisms responsible for such a significant increase in strength were investigated for the first time in this study. Microscopy (optical, SEM, TEM) aided in identifying the possible strengthening mechanisms that are typically important to the strength of metal matrix composites. These mechanisms include grain size and subgrain size refinement and an increase in dislocation density, all of which can occur during processing. Two other important mechanisms are thermal mismatch strains and load transfer from the matrix to the particle; the contribution of these mechanisms to the strength of the composite was evaluated using the Eshelby approach. A quantitative comparison of the mechanisms listed clearly showed that none of them was responsible for the large increase in strength with only 1vol%TiC in Ti-6Al-4V. The results from this study show for the first time that carbon in solution is, by far, the most potent strengthening mechanism in the Ti-6Al-4V/TiC particulate composites

Thermal conductivity analysis of SiC ceramics and fully ceramic microencapsulated fuel composites

International Nuclear Information System (INIS)

Lee, Hyeon-Geun; Kim, Daejong; Lee, Seung Jae; Park, Ji Yeon; Kim, Weon-Ju

2017-01-01

Highlights: • Thermal conductivity of SiC ceramics and FCM pellets was measured and discussed. • Thermal conductivity of FCM pellets was analyzed by the Maxwell-Eucken equation. • Effective thermal conductivity of TRISO particles applied in this study was assumed. - Abstract: The thermal conductivity of SiC ceramics and FCM fuel composites, consisting of a SiC matrix and TRISO coated particles, was measured and analyzed. SiC ceramics and FCM pellets were fabricated by hot press sintering with Al_2O_3 and Y_2O_3 sintering additives. Several factors that influence thermal conductivity, specifically the content of sintering additives for SiC ceramics and the volume fraction of TRISO particles and the matrix thermal conductivity of FCM pellets, were investigated. The thermal conductivity values of samples were analyzed on the basis of their microstructure and the arrangement of TRISO particles. The thermal conductivity of the FCM pellets was compared to that predicted by the Maxwell-Eucken equation and the thermal conductivity of TRISO coated particles was calculated. The thermal conductivity of FCM pellets in various sintering conditions was in close agreement to that predicted by the Maxwell-Eucken equation with the fitted thermal conductivity value of TRISO particles.

Toxicological consequences of TiO2, SiC nanoparticles and multi-walled carbon nanotubes exposure in several mammalian cell types: an in vitro study

International Nuclear Information System (INIS)

Barillet, Sabrina; Simon-Deckers, Angelique; Herlin-Boime, Nathalie; Mayne-L'Hermite, Martine; Reynaud, Cecile; Cassio, Doris; Gouget, Barbara; Carriere, Marie

2010-01-01

The development of nanotechnologies may lead to dissemination of potentially toxic nanoparticles in the environment. Toxicology of these nano-sized particles is thus attracting attention of public and governments worldwide. Our research is focused on the in vitro response of eukaryotic cells to nanoparticles exposure. For this purpose, we used cellular models of primary target organs (lung: A549 alveolar epithelial cells), or secondary target organs (liver: WIF-B9, Can-10 and kidneys: NRK-52E, LLC-PK1 proximal cells), i.e., organs exposed if nanoparticles are translocated through epithelial barriers. These cells were exposed to TiO 2 , SiC nanoparticles or multi-walled carbon nanotubes (MWCNT). The influence of nanoparticles physico-chemical characteristics on various toxicological endpoints (cytotoxicity, reactive oxygen species generation, genotoxicity) was specified. Our data demonstrate that nanoparticles toxicity depend on their size, morphology, and chemical composition, the finest, spherical shaped, and anatase TiO 2 nanoparticles being the more cytotoxic to NRK-52E cells, while SiC nanoparticles exert almost no cytotoxicity. MWCNT cytotoxicity neither depended on their length, nor on the presence of metal impurities. Nanoparticles cytotoxicity also depended on the exposed cell line. All the tested nanoparticles were uptaken by cells and caused intracellular reactive oxygen species generation. Relative to genotoxic effects, DNA strand breaks were detected in NRK-52E cells via the alkaline comet assay after exposure of cells to TiO 2 nanoparticles and to a lesser extent after exposure to MWCNT, but no double strand breaks were detected. The originality of this study lies on the panel of nanomaterials which were tested on a variety of cell lines. All these data may lead to a better understanding of nanomaterial toxicity and hazards for health.

Effect of TiO2 addition on reaction between SiC and Ni in SiC-Ni cermet spray coatings. Part 2. ; Development of SiC-based cermet spray coatings. SiC-Ni yosha himakuchu no SiC-Ni kaimen hanno ni oyobosu TiO2 tenka no koka. 2. ; SiC-ki sametto yosha himaku no kaihatsu

Energy Technology Data Exchange (ETDEWEB)

Nakamura, T [Kumano Technical College, Mie (Japan); Oki, S; Goda, S [Kinki Univ., Higashi-Osaka, Osaka (Japan). Faculty of Science and Technology

1992-09-30

The depression of the reaction between SiC and Ni, by adding TiO2 powder in spraying powder which has caused uniform dispersion in spray coating and reduction of TiO2 by the reaction during spraying, was studied. The mass ratio of the mixed components has been, SiC:Ni:TiO2=3:2:1. The spray coating was examined by electron prove microanalysis as well as X-ray diffractometry, centering mainly to the SiC-metal interface reaction. The formation of Ni-Si compounds have been depressed by the addition of TiO2 to spraying powder and by using plasma gas containing H2. Reason for this has been that the TiC formed in the SiC-Ni interface has depressed the reaction at the SiC-Ni interface. Further, TiO2 is reduced during spraying, and TiC is thought to be formed by the reaction between Ti and SiC or reaction between TiO2 and SiC. 8 refs., 6 figs., 1 tab.

Computational Modeling of Radiation Phenomenon in SiC for Nuclear Applications

Science.gov (United States)

Ko, Hyunseok

Silicon carbide (SiC) material has been investigated for promising nuclear materials owing to its superior thermo-mechanical properties, and low neutron cross-section. While the interest in SiC has been increasing, the lack of fundamental understanding in many radiation phenomena is an important issue. More specifically, these phenomena in SiC include the fission gas transport, radiation induced defects and its evolution, radiation effects on the mechanical stability, matrix brittleness of SiC composites, and low thermal conductivities of SiC composites. To better design SiC and SiC composite materials for various nuclear applications, understanding each phenomenon and its significance under specific reactor conditions is important. In this thesis, we used various modeling approaches to understand the fundamental radiation phenomena in SiC for nuclear applications in three aspects: (a) fission product diffusion through SiC, (b) optimization of thermodynamic stable self-interstitial atom clusters, (c) interface effect in SiC composite and their change upon radiation. In (a) fission product transport work, we proposed that Ag/Cs diffusion in high energy grain boundaries may be the upper boundary in unirradiated SiC at relevant temperature, and radiation enhanced diffusion is responsible for fast diffusion measured in post-irradiated fuel particles. For (b) the self-interstitial cluster work, thermodynamically stable clusters are identified as a function of cluster size, shape, and compositions using a genetic algorithm. We found that there are compositional and configurational transitions for stable clusters as the cluster size increases. For (c) the interface effect in SiC composite, we investigated recently proposed interface, which is CNT reinforced SiC composite. The analytical model suggests that CNT/SiC composites have attractive mechanical and thermal properties, and these fortify the argument that SiC composites are good candidate materials for the cladding

Mechanical Properties of SiC, Al2O3 Reinforced Aluminium 6061-T6 Hybrid Matrix Composite

Science.gov (United States)

Murugan, S. Senthil; Jegan, V.; Velmurugan, M.

2018-04-01

This paper contains the investigation of tensile, compression and impact characterization of SiC, Al2O3 reinforced Aluminium 6061-T6 matrix hybrid composite. Hybrid matrix composite fabrication was done by stir casting method. An attempt has been made by keeping Al2O3 percentage (7%) constant and increasing SiC percentage (10, 15, and 20%). After fabricating, the samples were prepared and tested to find out the various mechanical properties like tensile, compressive, and impact strength of the developed composites of different weight % of silicon carbide and Alumina in Aluminium alloy. The main objective of the study is to compare the values obtained and choose the best composition of the hybrid matrix composite from the mechanical properties point of view.

Influence of surface oxidation on the radiative properties of ZrB{sub 2}-SiC composites

Energy Technology Data Exchange (ETDEWEB)

Li, Ning, E-mail: lncaep@163.com [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, 621900 (China); Xing, Pifeng; Li, Cui [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, 621900 (China); Wang, Peng [School of Material Science and Engineering, Shandong University of Technology, Zibo 255049 (China); Jin, Xinxin [College of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040 (China); Zhang, Xinghong [Science and Technology on Advanced Composites in Special Environments Laboratory, Harbin Institute of Technology, Harbin 150001 (China)

2017-07-01

Highlights: • Surface component affected radiative properties of ZrB{sub 2}-SiC composites significantly. • Emissivity in long-wave range gradually increased with the thickness of oxide scale. • The surface temperature had a little effect on radiative properties of composites. • Influence of surface roughness on emissivity could be negligible. • Covering the surface with glass is a method for improving radiative properties. - Abstract: The spectral emissivities of ZrB{sub 2}-20 vol.% SiC composites with various surface components of ZrB{sub 2}/SiC (ZS1), silica-rich glass (ZS2) and porous zirconia (ZS3) were measured using infrared spectrometer in the wavelength range from 2.5 to 25.0 μm. The relationship between surface oxidation (associated with surface component, thickness of oxide scale, testing temperature as well as roughness) and the radiative properties of ZrB{sub 2}-SiC composites were investigated systematically. Surface component affected the radiative properties of composites significantly. The total emissivity of ZS1 varied from 0.22 to 0.81 accompanied with surface oxidation in the temperature range 300–900 °C. The emissivity of ZS2 was about 1.5 times as that of ZS3 under the same testing conditions. The oxide scale on specimen surface enhanced the radiative properties especially in terms of short-wave range, and the emissivity in the long-wave range gradually increased with the thickness of oxide scale within a certain range. The influence of testing temperature and surface roughness was also investigated. The testing temperature had a little effect on radiative properties, whereas effect of surface roughness could be negligible.

Mechanical characterization of SiC particulate & E-glass fiber reinforced Al 3003 hybrid metal matrix composites

Science.gov (United States)

Narayana, K. S. Lakshmi; Shivanand, H. K.

2018-04-01

Metal matrix composites constitute a class of low cost high quality materials which offer high performance for various industrial applications. The orientation of this research is towards the study of mechanical properties of as cast silicon carbide (SiC) particulates and Short E-Glass fibers reinforced Aluminum matrix composites (AMCs). The Hybrid metal matrix composite is developed by reinforcing SiC particulates of 100 microns and short E-Glass fibers of 2-3 mm length with Al 3003 in different compositions. The vortex method of stir casting was employed, in which the reinforcements were introduced into the vortex created by the molten metal by means of mechanical stirrer. The mechanical properties of the prepared metal matrix composites were analyzed. From the studies it was noticed that an improvement in mechanical properties of the reinforced alloys compared to unreinforced alloys.

Scanning and transmission electron microscopy study of the microstructural changes occurring in aluminium matrix composites reinforced with SiC particles during casting and welding: interface reactions

Science.gov (United States)

Urena; Gomez De Salazar JM; Gil; Escalera; Baldonedo

1999-11-01

Processing of aluminium matrix composites (AMCs), especially those constituted by a reactive system such as Al-SiC, presents great difficulties which limit their potential applications. The interface reactivity between SiC and molten Al generates an aluminium carbide which degrades the composite properties. Scanning and transmission electron microscopes equipped with energy-dispersive X-ray spectroscopes are essential tools for determining the structure and chemistry of the Al-SiC interfaces in AMCs and changes occurring during casting and arc welding. In the present work, an aluminium-copper alloy (AA2014) reinforced with three different percentages of SiC particles was subjected to controlled remelting tests, at temperatures in the range 750-900 degrees C for 10 and 30 min. Arc welding tests using a tungsten intert gas with power inputs in the range 850-2000 W were also carried out. The results of these studies showed that during remelting there is preferential SiC particle consumption with formation of Al4C3 by interface reaction between the solid SiC particle and the molten aluminium matrix. The formation of Al4C3 by the same mechanism has also been detected in molten pools of arc welded composites. However, in this case there was formation of an almost continuous layer of Al4C3, which protects the particle against further consumption, and formation of aciculate aluminium carbide on the top weld. Both are formed by fusion and dissolution of the SiC in molten aluminium followed by reaction and precipitation of the Al4C3 during cooling.

In-pile Hydrothermal Corrosion Evaluation of Coated SiC Ceramics and Composites

Energy Technology Data Exchange (ETDEWEB)

Carpenter, David [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Ang, Caen [Univ. of Tennessee, Knoxville, TN (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Linton, Kory D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-09-01

Hydrothermal corrosion accelerated by water radiolysis during normal operation is among the most critical technical feasibility issues remaining for silicon carbide (SiC) composite-based cladding that could provide enhanced accident-tolerance fuel technology for light water reactors. An integrated in-pile test was developed and performed to determine the synergistic effects of neutron irradiation, radiolysis, and pressurized water flow, all of which are relevant to a typical pressurized water reactor (PWR). The test specimens were chosen to cover a range of SiC materials and a variety of potential options for environmental barrier coatings. This document provides a summary of the irradiation vehicle design, operations of the experiment, and the specimen loading into the irradiation vehicle.

Infiltrated TiC/Cu composites

International Nuclear Information System (INIS)

Frage, N.; Froumin, N.; Rubinovich, L.; Dariel, M.P.

2001-01-01

One approach for the fabrication of ceramic-metal composites is based on the pressureless impregnation of a porous ceramic preform by a molten metal. Molten Cu does not react with TiC and the wetting angle is close to 90 o . Nonetheless, molten Cu readily impregnates partially sintered TiC preforms. A model that describes the dependence of the critical contact angle for spontaneous impregnation by molten metals in partially sintered preforms on the level of densification and on the morphology of the particles was developed. For high aspect ratios of the particles forming the preform, wetting angles close to 90 o still allow impregnation by the molten metal. The results of the model were confirmed by infiltration of partially sintered TiC preforms with molten Cu and by fabrication of the TiC/Cu composites with various ceramic-to metal ratios. Decreasing of the metal content in the composite from 50 vol.% to 10 vol.% leads to a hardness increase from 250 to 1800 HV, and to the decrease of the bending strength from 960 to 280 MPa. The resistivity of these TiC/Cu composites decreases from 142 ohm cm to 25 ohm cm. (author)

Thermal shock behavior of nano-sized SiC particulate reinforced AlON composites

Energy Technology Data Exchange (ETDEWEB)

Zhao, X.J. [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Ru, H.Q., E-mail: ruhq@smm.neu.edu.cn [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China); Chen, D.L., E-mail: dchen@ryerson.ca [Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Zhang, N.; Liang, B. [Key Laboratory of Advanced Materials Manufacturing Technology of Liaoning Province, Shenyang University, Shenyang, Liaoning 110044 (China)

2012-03-25

Highlights: Black-Right-Pointing-Pointer Addition of nano-SiC particles enhances residual strength and critical temperature. Black-Right-Pointing-Pointer Young's modulus decreases with increasing quenching temperature. Black-Right-Pointing-Pointer Linear relationship between residual strength and thermal shock times is obtained. Black-Right-Pointing-Pointer Rougher fracture surfaces in the SiC-AlON composites are observed. - Abstract: Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications. Thermal shock resistance is a major concern and an important performance index of high-temperature ceramics. While silicon carbide (SiC) particles have been proven to improve mechanical properties of AlON ceramic, the high-temperature thermal shock behavior was unknown. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of AlON ceramic and 8 wt% SiC-AlON composites over a temperature range between 175 Degree-Sign C and 275 Degree-Sign C. The residual strength and Young's modulus after thermal shock decreased with increasing quenching temperature and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. A linear relationship between the residual strength and thermal shock times was observed in both pure AlON and SiC-AlON composites. The addition of nano-sized SiC particles increased both residual strength and critical temperature from 200 Degree-Sign C in the monolithic AlON to 225 Degree-Sign C in the SiC-AlON composites due to the toughening effect, the lower coefficient of thermal expansion and higher thermal conductivity of SiC. The enhancement of the thermal shock resistance in the SiC-AlON composites was directly related to the change of fracture mode from intergranular cracking along with cleavage-type fracture in the AlON to a rougher fracture surface with ridge

Oxidation effects on the mechanical properties of SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

Science.gov (United States)

Bhatt, Ramakrishna T.

1989-01-01

The room temperature mechanical properties of SiC fiber reinforced reaction bonded silicon nitride composites were measured after 100 hrs exposure at temperatures to 1400 C in nitrogen and oxygen environments. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The results indicate that composites heat treated in a nitrogen environment at temperatures to 1400 C showed deformation and fracture behavior equivalent to that of the as-fabricated composites. Also, the composites heat treated in an oxidizing environment beyond 400 C yielded significantly lower tensile strength values. Specifically in the temperature range from 600 to 1000 C, composites retained approx. 40 percent of their as-fabricated strength, and those heat treated in the temperatures from 1200 to 1400 C retained 70 percent. Nonetheless, for all oxygen heat treatment conditions, composite specimens displayed strain capability beyond the matrix fracture stress; a typical behavior of a tough composite.

Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

Energy Technology Data Exchange (ETDEWEB)

Yu Shengwang, E-mail: bkdysw@yahoo.cn; Fan Pengwei; Tang Weizhong; Li Xiaojing; Hu Haolin; Hei Hongjun; Zhang Sikai; Lu Fanxiu

2011-11-01

SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH{sub 3}){sub 4}) diluted in H{sub 2} as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co{sub 2}Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.

Pressure dependence of morphology and phase composition of SiC films deposited by microwave plasma chemical vapor deposition on cemented carbide substrates

International Nuclear Information System (INIS)

Yu Shengwang; Fan Pengwei; Tang Weizhong; Li Xiaojing; Hu Haolin; Hei Hongjun; Zhang Sikai; Lu Fanxiu

2011-01-01

SiC films were deposited on cemented carbide substrates by employing microwave plasma chemical vapor deposition method using tetramethylsilane (Si(CH 3 ) 4 ) diluted in H 2 as the precursor. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and scratching technique were used to characterize morphology, composition, phases present and adhesion of the films. Experimental results show that the deposition pressure has great influence on morphologies and phase composition of the films. In sequence, SiC films with a cauliflower-like microstructure, granular films with terrace-featured SiC particles coexisting with Co 2 Si compound and clusters of nanometer SiC nanoplatelets appear as a function of the deposition pressure. In terms of plasma density and substrate temperature, this sequential appearance of microstructures of SiC films was explained. Adhesion tests showed that among the three types of films studied, the films with the terrace-featured SiC particles have relatively higher adhesion. Such knowledge will be of importance when the SiC films are used as interlayer between diamond films and cemented carbide substrates.

The topotactic transformation of Ti3SiC2 into a partially ordered cubic Ti(C0.67Si0.06) phase by the diffusion of Si into molten cryolite

International Nuclear Information System (INIS)

Barsoum, M.W.; El-Raghy, T.; Farber, L.; Amer, M.; Christini, R.; Adams

1999-01-01

Immersion of Ti 3 SiC 2 samples in molten cryolite at 960 C resulted in the preferential diffusion of Si atoms out of the basal planes to form a partially ordered, cubic phase with approximate chemistry Ti(C 0.67 , Si 0.06 ). The latter forms in domains, wherein the (111) planes are related by mirror planes; i.e., the loss of Si results in the de-twinning of the Ti 3 C 2 layers. Raman spectroscopy, X-ray diffraction, optical, scanning and transmission electron microscopy all indicate that the Si exists the structure topotactically, in such a way that the C atoms remain partially in their ordered position in the cubic phase

Nanocrystalline SiC and Ti₃SiC₂ Alloys for Reactor Materials: Diffusion of Fission Product Surrogates

Energy Technology Data Exchange (ETDEWEB)

Henager, Charles H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jiang, Weilin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2014-11-01

MAX phases, such as titanium silicon carbide (Ti₃SiC₂), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti₃SiC₂ has been suggested in the literature as a possible fuel cladding material. Prior to the application, it is necessary to investigate diffusivities of fission products in the ternary compound at elevated temperatures. This study attempts to obtain relevant data and make an initial assessment for Ti₃SiC₂. Ion implantation was used to introduce fission product surrogates (Ag and Cs) and a noble metal (Au) in Ti₃SiC₂, SiC, and a dual-phase nanocomposite of Ti₃SiC₂/SiC synthesized at PNNL. Thermal annealing and in-situ Rutherford backscattering spectrometry (RBS) were employed to study the diffusivity of the various implanted species in the materials. In-situ RBS study of Ti₃SiC₂ implanted with Au ions at various temperatures was also performed. The experimental results indicate that the implanted Ag in SiC is immobile up to the highest temperature (1273 K) applied in this study; in contrast, significant out-diffusion of both Ag and Au in MAX phase Ti₃SiC₂ occurs during ion implantation at 873 K. Cs in Ti₃SiC₂ is found to diffuse during post-irradiation annealing at 973 K, and noticeable Cs release from the sample is observed. This study may suggest caution in using Ti₃SiC₂ as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. Further studies of the related materials are recommended.

Micro-nano filler metal foil on vacuum brazing of SiCp/Al composites

Science.gov (United States)

Wang, Peng; Gao, Zeng; Niu, Jitai

2016-06-01

Using micro-nano (Al-5.25Si-26.7Cu)- xTi (wt%, x = 1.0, 1.5, 2.0, 2.5 and 3.0) foils as filler metal, the research obtained high-performance joints of aluminum matrix composites with high SiC particle content (60 vol%, SiCp/Al-MMCs). The effect of brazing process and Ti content on joint properties was investigated, respectively. The experimental results indicate that void free dense interface between SiC particle and metallic brazed seam with C-Al-Si-Ti product was readily obtained, and the joint shear strength enhanced with increasing brazing temperature from 560 to 580 °C or prolonging soaking time from 10 to 90 min. Sound joints with maximum shear strength of 112.5 MPa was achieved at 580 °C for soaking time of 90 min with (Al-5.25Si-26.7Cu)-2Ti filler, where Ti(AlSi)3 intermetallic is in situ strengthening phase dispersed in the joint and fracture occured in the filler metal layer. In this research, the beneficial effect of Ti addition into filler metal on improving wettability between SiC particle and metallic brazed seam was demonstrated, and capable welding parameters were broadened for SiCp/Al-MMCs with high SiC particle content.

Concentration of uranium on TiO-PAN and NaTiO-PAN composite absorbers

International Nuclear Information System (INIS)

Motl, Alois; Sebesta, Ferdinand; John, Jan; Spendlikova, Irena; Nemec, Mojmir

2013-01-01

Inorganic ion exchangers have been extensively tested for use in separation and concentration of uranium from Surface water. Except for separation of uranium from uranium -Contaminated waste water (e.g. waste water from mining and milling of uranium, Waste from nuclear fuel reprocessing) their main area of application has been foreseen to be their use for extraction of uranium from sea water which could partially cover future needs of uranium. Another perspective area of application is pre-concentration of uranium from natural waters followed by uranium determination via various specialized techniques such as TRLFS or AMS. Possibilities of uranium extraction from sea water have been subject of several international conferences (e.g. Topical meetings on the Recovery of Uranium from Seawater in 1980's, ACS National Meetings 2012 etc.) and are critically evaluated in a review by Bitte or recently by Kim. In the Czech Republic uranium-selective inorganic ion exchangers might be applied for treatment of various wastes from uranium industry, namely underground Water, uranium milling over-balance water, or acid waste water from underground uranium leaching and also like in other countries for determination of uranium isotopic composition focusing on anthropogenic and natural 236 U content. Among the best performing inorganic ion exchangers for the above listed purposes hydrated titanium dioxide (abbreviated as TiO) and sodium titanate (abbreviated as NaTiO) can be listed. Properties of TiO and NaTiO were reviewed by Lehto. From the point of view of ion-exchange, properties of hydrated titanium oxide and sodium titanate are very similar. The main disadvantage of these ion exchangers for industrial-scale application is their insufficient mechanical stability. To improve this property, the sorption materials can be embedded into a binding matrix. Modified polyacrylonitrile (PAN) has been proposed at the Czech Technical University in Prague as a universal binding matrix for

Preparation and Mechanical Properties of TiC-Fe Cermets and TiC-Fe/Fe Bilayer Composites

Science.gov (United States)

Zheng, Yong; Zhou, Yang; Li, Runfeng; Wang, Jiaqi; Chen, Lulu; Li, Shibo

2017-10-01

TiC-Fe cermets and TiC-Fe/Fe bilayer composites consisting of a pure Fe layer and a TiC-Fe cermets layer were fabricated by hot-pressing sintering. The pure Fe layer contributes to the toughness of composites, and the TiC-Fe cermets layer endows the composites with an improved tensile strength and hardness. The effect of TiC contents (30-60 vol.%) on the mechanical properties of TiC-Fe cermets and TiC-Fe/Fe bilayer composites was investigated. Among the TiC-Fe cermets, the 40 vol.% TiC-Fe cermets possessed the highest tensile strength of 581 MPa and Vickers hardness of 5.1 GPa. The maximum fracture toughness of 17.0 MPa m1/2 was achieved for the TiC-Fe cermets with 30 vol.% TiC. For the TiC-Fe/Fe bilayer composites, the 40 vol.% TiC-Fe/Fe bilayer composite owns the maximum tensile strength of 588 MPa, which is higher than that of 40 vol.% TiC-Fe cermets. In addition, the 33.5% increment of tensile strength of 30 vol.% TiC-Fe/Fe bilayer composite comparing with the 30 vol.% TiC-Fe cermets, which is attributed to the 30 vol.% TiC-Fe/Fe bilayer composite exhibited the largest interlaminar shear strength of 335 MPa. The bilayer composites are expected to be used as wear resistance components in some heavy wear conditions.

Sapphire/TiAl composites - structure and properties

International Nuclear Information System (INIS)

Povarova, K.B.; Antonova, A.V.; Mileiko, S.T.; Sarkissyan, N.S.

2001-01-01

Ti-Al-intermetallic-based alloys with lamellar microstructure, -γ(TiAl) +α 2 (Ti 3 Al) are characterized by a high melting point of 1460 o C, a low density of ∼3.9 g/cm 3 , a high gas corrosion resistance up to a temperature of about 900 o C, a high creep resistance up to a temperature of about 800 o C, and a sufficiently high fracture toughness at low temperatures, up to 30 Mpa x m 1/2 . Hence, they are considered as excellent matrices for fibres of high melting point. Unlike well-developed SiC/TiAl composites, which have an obvious upper limit for the usage temperature due to SiC/TiAl interaction, Sapphire/TiAl composites remain nearly unknown because fibres to be used in such composites have not been really available. At the present time, such fibres are developed in Solid State Physics Inst. of RAS. The results of preliminary creep tests of Al 2 O 3 /TiAl composites obtained by using pressure casting have shown that usage of such composite systems shifts the temperature limit for light structural materials in terms of creep resistance to, at least, 1050 o C: creep strength on 100 h time base reaches 120 MPa at that temperature. It occurs also that Sapphire-fibres/TiAl-matrix composite specimens have an increased gas corrosion resistance by more than one order of the magnitudes as compared with that of the matrix alloy. (author)

Effects of ultrasonic vibration on microstructure and mechanical properties of nano-sized SiC particles reinforced Al-5Cu composites.

Science.gov (United States)

Li, Jianyu; Lü, Shulin; Wu, Shusen; Gao, Qi

2018-04-01

Ultrasonic vibration (UV) treatment has been successfully applied to improve the particles distribution of nano-sized SiC particles (SiC p ) reinforced Al-5Cu alloy matrix composites which were prepared by combined processes of dry high energy ball milling and squeeze casting. When UV treatment is applied, the distribution of nano-sized SiC p has been greatly improved. After UV for 1 min, large particles aggregates are broken up into small aggregates due to effects of cavitation and the acoustic streaming. After UV for 5 min, all the particles aggregates are dispersed and the particles are uniformly distributed in the composites. Compared with the Al-5Cu matrix alloy, the ultimate tensile strength, yield strength and elongation of the 1 wt% nano-sized SiC p /Al-5Cu composites treated by UV for 5 min are 270 MPa, 173 MPa and 13.3%, which are increased by 7.6%, 6.8% and 29%, respectively. The improvements of mechanical properties after UV are attributed to the uniform distribution of nano particles, grain refinement of aluminum matrix alloy and reduction of porosity in the composites. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterization of laser deposited Ti6Al4V/TiC composite powders on a Ti6Al4V substrate

CSIR Research Space (South Africa)

Mahamood, RM

2014-01-01

Full Text Available This paper reports the material characterization of Ti6Al4V/TiC composite produced by laser metal deposition. The Ti6Al4V/TiC composites were deposited with a composition ratio of 50 wt.% Ti64l4V and 50 wt.% TiC. The depositions were achieved...

Identification of sigma and OMEGA phases in AA2009/SiC composites

Energy Technology Data Exchange (ETDEWEB)

Rodrigo, P., E-mail: pilar.rodrigo@urjc.e [Departamento de Ciencia e Ingenieria de Materiales, Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, c/Tulipan s/n, 28933 Mostoles, Madrid (Spain); Poza, P.; Utrilla, M.V.; Urena, A. [Departamento de Ciencia e Ingenieria de Materiales, Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, c/Tulipan s/n, 28933 Mostoles, Madrid (Spain)

2009-08-12

The microstructure evolution during ageing treatment at 170 and 190 deg. C of AA2009/SiC composites, reinforced with 15 vol.% particulates and whiskers, was studied by transmission electron microscopy. Besides theta' and S' phases, the typical hardening precipitates on Al-Cu-Mg alloys, it was found the presence of OMEGA and sigma (Al{sub 5}Cu{sub 6}Mg{sub 2}) phases in the matrix. sigma phase was only found in the matrix of particulate composite, while OMEGA phase appeared in both. This phase has not been previously observed in Al matrix composites based on conventional Al-Cu-Mg alloys.

Interfaces in Composites. Volume 170. Materials Research Society Symposium Proceedings Held in Boston, Massachusetts on 27-29 November 1989

Science.gov (United States)

1990-11-21

silar . In all cases the innermost phase was bWed on TiC,. soetimes with Nb substituting, esunmably. for the M. rinthe-r out the complex carbides of the...of SIC whisker / Al20 3 matrix composites was evaluated. Composites were fabricated with Silar SC-9 and Tateho SCW-I-S SiC whiskers. The properties...those of the Silar SC-9 whisker contained a substantial amount of SiOxCy and SiO2, in addition to the expected SIC. Table I summarizes the mechanical

Low modulus and bioactive Ti/α-TCP/Ti-mesh composite prepared by spark plasma sintering.

Science.gov (United States)

Guo, Yu; Tan, Yanni; Liu, Yong; Liu, Shifeng; Zhou, Rui; Tang, Hanchun

2017-11-01

A titanium mesh scaffold composite filled with Ti/α-TCP particles was prepared by spark plasma sintering (SPS). The microstructures and interfacial reactions of the composites were investigated by scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The compressive strength and elastic modulus were also measured. In vitro bioactivity and biocompatibility was evaluated by using simulated body fluid and cells culture, respectively. After high temperature sintering, Ti oxides, Ti x P y and CaTiO 3 were formed. The formation of Ti oxides and Ti x P y were resulted from the diffusion of O and P elements from α-TCP to Ti. CaTiO 3 was the reaction product of Ti and α-TCP. The composite of 70Ti/α-TCP incorporated with Ti mesh showed a high compressive strength of 589MPa and a low compressive modulus of 30GPa. The bioactivity test showed the formation of a thick apatite layer on the composite and well-spread cells attachment. A good combination of mechanical properties and bioactivity indicated a high potential application of Ti/α-TCP/Ti-mesh composite for orthopedic implants. Copyright © 2017. Published by Elsevier B.V.

Penetration resistance and ballistic-impact behavior of Ti/TiAl3 metal/intermetallic laminated composites (MILCs: A computational investigation

Directory of Open Access Journals (Sweden)

Jennifer S. Snipes

2016-06-01

Full Text Available A comprehensive computational engineering analysis is carried out in order to assess suitability of the Ti/TiAl3 metal/intermetallic laminated composites (MILCs for use in both structural and add-on armor applications. This class of composite materials consists of alternating sub-millimeter thick layers of Ti (the ductile and tough constituent and TiAl3 (the stiff and hard constituent. In recent years, this class of materials has been investigated for potential use in light-armor applications as a replacement for the traditional metallic or polymer-matrix composite materials. Within the computational analysis, an account is given to differing functional requirements for candidate materials when used in structural and add-on ballistic armor. The analysis employed is of a transient, nonlinear-dynamics, finite-element character, and the problem investigated involves normal impact (i.e. under zero obliquity angle of a Ti/TiAl3 MILC target plate, over a range of incident velocities, by a fragment simulating projectile (FSP. This type of analysis can provide more direct information regarding the ballistic limit of the subject armor material, as well as help with the identification of the nature and the efficacy of various FSP material-deformation/erosion and kinetic-energy absorption/dissipation phenomena and processes. The results obtained clearly revealed that Ti/TiAl3 MILCs are more suitable for use in add-on ballistic, than in structural armor applications.

Ab-initio calculation of EuO doped with 5% of (Ti, V, Cr and Fe): GGA and SIC approximation

Science.gov (United States)

Rouchdi, M.; Salmani, E.; Bekkioui, N.; Ez-Zahraouy, H.; Hassanain, N.; Benyoussef, A.; Mzerd, A.

2017-12-01

In this research, a simple theoretical method is proposed to investigate the electronic, magnetic and optical properties of Europium oxide (EuO) doped with 5% of (Ti, V, Cr and Fe). For a basic understanding of these properties, we employed Density-Functional Theory (DFT) based calculations with the Korringa-Kohn-Rostoker code (KKR) combined with the Coherent Potential Approximation (CPA). Also we investigated the half-metallic ferromagnetic behavior of EuO doped with 5% of (Ti, V, Cr and Fe) within the self-interaction-corrected Generalized Gradient Approximation (GGA-SIC). Our calculated results revealed that the Eu0.95TM0.05O is ferromagnetic with a high transition temperature. Moreover, the optical absorption spectra revealed that the half metallicity has been also predicted.

Mechanical properties of Nextel trademark 312 fiber-reinforced SiC matrix composites

International Nuclear Information System (INIS)

Vaidyanathan, K.R.; Sankar, J.; Kelkar, A.D.; Weaver, B.

1995-01-01

Vapor phase synthesis is emerging as a method for the preparation of near final-shape, ceramic matrix composites for advanced structural applications. Oxide fiber-reinforced silicon carbide matrix composites are currently being developed for these applications. The mechanical properties of Nextel trademark 312 fiber reinforced SiC matrix composites fabricated employing the forced-flow, thermal gradient chemical vapor infiltration process (FCVI) were evaluated at room temperature in pure tension. The composites were fabricated with a 0.15 μm pyrolytic carbon interface layer for improving the toughness of the composite system. Because of the available FCVI apparatus, only short length specimens (7--8 cm) could be fabricated. Room temperature tensile strengths were measured and compared to room temperature flexure strength results for the composite. Excellent toughness and composite behavior was obtained for the composite system. Fractography as well as possible factors responsible for the differences in tensile and flexural strengths for the composite system is presented in this paper

Microstructure development of in situ porous TiO/Cu composites

International Nuclear Information System (INIS)

Qin, Q.D.; Huang, B.W.; Li, W.; Shao, F.

2016-01-01

An in situ porous TiO/Cu composite is successfully prepared using powder metallurgy by the reaction of Ti_2CO and Cu powder. Ti_2CO powder is produced by the carbothermic reduction of titanium dioxide (TiO_2) at 1000 °C. Morphological examination of the composite shows that the porosity of composites lies in the range between 10.2% and 35.2%. As the volume fraction of TiO increases, the size of TiO becomes more fine. Scanning electron microscopy (SEM) of the fracture morphology indicates that TiO particles and the Cu matrix are connected by a Cu–Ti phase. - Highlights: • An porous TiO/Cu composite is successfully prepared by powder metallurgy technology. • The porosity of composites lies in the range between 10.2% and 35.2%. • The TiO particles and the Cu matrix are connected by a Cu-Ti phase.

NiTi-polyimide composites prepared using thermal imidization process

Czech Academy of Sciences Publication Activity Database

Vokoun, David; Sysel, P.; Heller, Luděk; Kadeřávek, L.; Svatuška, Michal; Goryczka, T.; Kafka, Vratislav; Šittner, Petr

2016-01-01

Roč. 25, č. 5 (2016), 1993-1999 ISSN 1059-9495 R&D Projects: GA ČR GC15-13174J; GA ČR GA14-15264S Institutional support: RVO:68378271 ; RVO:68378297 Keywords : actuator * composite * model * NiTi * polyimide * residual * stress Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.331, year: 2016

Microstructure development of in situ porous TiO/Cu composites

Energy Technology Data Exchange (ETDEWEB)

Qin, Q.D., E-mail: 58124812@qq.com [Department of Materials & Metallurgy Engineering, Guizhou Institute of Technology, No.1 Caiguan Road, Guiyang 550003 (China); 2011 Special Functional Materials Collaborative Innovation Center of Guizhou Province, No.1 Caiguan Road, Guiyang 550003 (China); Huang, B.W. [Department of Materials & Metallurgy Engineering, Guizhou Institute of Technology, No.1 Caiguan Road, Guiyang 550003 (China); 2011 Special Functional Materials Collaborative Innovation Center of Guizhou Province, No.1 Caiguan Road, Guiyang 550003 (China); Li, W. [Department of Materials Engineering, Zhengzhou Technology College, No. 81 Zhengshang Road, Zhengzhou, 450051 (China); Shao, F. [2011 Special Functional Materials Collaborative Innovation Center of Guizhou Province, No.1 Caiguan Road, Guiyang 550003 (China)

2016-07-05

An in situ porous TiO/Cu composite is successfully prepared using powder metallurgy by the reaction of Ti{sub 2}CO and Cu powder. Ti{sub 2}CO powder is produced by the carbothermic reduction of titanium dioxide (TiO{sub 2}) at 1000 °C. Morphological examination of the composite shows that the porosity of composites lies in the range between 10.2% and 35.2%. As the volume fraction of TiO increases, the size of TiO becomes more fine. Scanning electron microscopy (SEM) of the fracture morphology indicates that TiO particles and the Cu matrix are connected by a Cu–Ti phase. - Highlights: • An porous TiO/Cu composite is successfully prepared by powder metallurgy technology. • The porosity of composites lies in the range between 10.2% and 35.2%. • The TiO particles and the Cu matrix are connected by a Cu-Ti phase.

Structural comparison of sintering products made of "TiC + Ti" composite powders and "Ti + C" powder mixtures

Science.gov (United States)

Krinitcyn, Maksim G.; Pribytkov, Gennadii A.; Korosteleva, Elena N.; Firsina, Irina A.; Baranovskii, Anton V.

2017-12-01

In this study, powder composite materials comprised of TiC and Ti with different ratios are processed by sintering of Ti and C powder mixtures and self-propagating high-temperature synthesis (SHS) in "Ti+C" system followed by sintering. The microstructure and porosity of obtained composites are investigated and discussed. The dependence of porosity on sintering time is explained theoretically. Optimal regimes that enable to obtain the most homogeneous structure with the least porosity are described.

Annealing Effect on Mechanical Properties of Ti-Al Alloy/Pure Ti Harmonic-Structured Composite by MM/SPS Process

International Nuclear Information System (INIS)

Yoshida, R; Tsuda, T; Fujiwara, H; Miyamoto, H; Ameyama, K

2014-01-01

The Ti-Al alloy/pure Ti harmonic-structured composite was produced by mechanical milling and spark plasma sintering process for improvement of low ductility at room temperature of Ti-Al alloy. The harmonic-structured composite with the dispersed area having coarse grained titanium and the network area having fine-grained Ti-48mol%Al alloy demonstrates high strength and high ductility at room temperature. The annealing effect of the microstructure on the mechanical properties in the Ti-Al alloy/pure Ti harmonic-structured composite are investigated. The microstructure of the Ti-Al alloy/pure Ti harmonic-structured composite annealed at 873 K, 973 K and 1073 K are maintained the Ti-Al network structure and pure Ti dispersed regions, the average grain size of pure Ti dispersed region is only coarsen by annealing. The harmonic-structured composite annealed at 873 K, 973 K and 1073 K are maintained the high hardness. The tensile results reveal that the Ti-Al alloy/pure Ti harmonic- structured composite annealed at 873 K exhibits high strength and especially high ductility

Deposition characteristics of titanium coating deposited on SiC fiber by cold-wall chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Luo, Xian, E-mail: luo_shenfan@hotmail.com; Wu, Shuai; Yang, Yan-qing; Jin, Na; Liu, Shuai; Huang, Bin

2016-12-01

The deposition characteristics of titanium coating on SiC fiber using TiCl{sub 4}-H{sub 2}-Ar gas mixture in a cold-wall chemical vapor deposition were studied by the combination of thermodynamic analysis and experimental studies. The thermodynamic analysis of the reactions in the TiCl{sub 4}-H{sub 2}-Ar system indicates that TiCl{sub 4} transforms to titanium as the following paths: TiCl{sub 4} → TiCl{sub 3} → Ti, or TiCl{sub 4} → TiCl{sub 3} → TiCl{sub 2} → Ti. The experimental results show that typical deposited coating contains two distinct layers: a TiC reaction layer close to SiC fiber and titanium coating which has an atomic percentage of titanium more than 70% and that of carbon lower than 30%. The results illustrate that a carbon diffusion barrier coating needs to be deposited if pure titanium is to be prepared. The deposition rate increases with the increase of temperature, but higher temperature has a negative effect on the surface uniformity of titanium coating. In addition, appropriate argon gas flow rate has a positive effect on smoothing the surface morphology of the coating. - Highlights: • Both thermodynamic analysis and experimental studies were adopted in this work. • The transformation paths of TiCl{sub 4} to Ti is: TiCl{sub 4} → TiCl{sub 3} → Ti, or TiCl{sub 4} → TiCl{sub 3} → TiCl{sub 2} → Ti. • Typical deposited Ti coating on SiC fiber contained two distinct layers. • Deposition temperature is important on deposition rate and morphologies. • Appropriate argon gas flow rate has a positive effect on smoothing of the coating.

Fabrication of mullite-bonded porous SiC ceramics from multilayer-coated SiC particles through sol-gel and in-situ polymerization techniques

Science.gov (United States)

Ebrahimpour, Omid

particles and alumina nano powders were mixed in alumina sol to adjust the alumina weight to 35 wt%. Then, the desired amount of catalyst, which depends on the total surface area of the particles, was grafted onto the surface of the powders under an inert atmosphere. Consequently, the polymerization started from the surface of the substrate. The treated powders were characterized by SEM, XPS and TGA. In addition, the amount of pore-former was determined by TGA analysis. Porous SiC ceramics, which were fabricated by the novel process, consist of mullite, SiC, cristobalite and a small amount of alumina and TiO 2 as a result of reaction of TiCl4 with air. Furthermore, the effect of the sintering temperatures (1500°C, 1550°C and 1600°C) on the crystalline structure of the porous samples was investigated. Furthermore, it was proposed that converting TiCl4 to TiO2 acted as the sintering additive to form mullite at a lower sintering temperature. (Abstract shortened by UMI.).

Aging characteristic and mechanical properties of TiC/2618 composite

Institute of Scientific and Technical Information of China (English)

龙春光; 张厚安; 庞佑霞; 刘厚才

2001-01-01

TiC/2618 composite was prepared by XD method . The constituent and microstructure of the composite have been investigated by X-ray diffraction and TEM technique. The aging characteristics and mechanical properties at high and room temperatures were studied. The results show that: 1 ) it is possible to prepare multiple alloy matrix TiC/2618composite by XD method; 2) the TiC particles in TiC/2618 composite have the characteristics of fine size, clean appearance and a good bond with the matrix; 3) the aging law of the TiC/2618 composite has been changed by the addition of TiC particles. Two-peak value phenomenon has been observed when it was aged at 190 ℃; 4) TiC/2618 composite has better mechanical properties than those of the matrix both at room and high temperatures.

The role of TiB2 in strengthening TiB2 reinforced aluminium casting composites

International Nuclear Information System (INIS)

Chen, Z; Kang, H; Zhao, Y; Zheng, Y; Wang, T

2016-01-01

With an aim of developing high quality in situ TiB 2 reinforced aluminium foundry alloy based composites, the conventional direct synthesis method was modified into a two-step route. In step one we optimized the halide salt route to fabricate in situ TiB 2 particulate reinforced aluminium matrix composites and in step two we investigated the effects of the Al-5wt.% TiB 2 composite, as a “master composite”, on strengthening the practical foundry alloys. The in situ formed TiB 2 particles play two roles while strengthening the composites: (1) The grain refinement effect that improves the quality of the alloy matrix; and (2) The interactions between the hard particulates and the matrix add extra increment to the material strength. In different alloy systems, TiB 2 may play distinct roles in these two aspects (figure 1). Further analysis of the strengthening mechanisms shows that particle agglomeration behaviour during solidification is responsible for the latter one. The present work details the role of TiB 2 in strengthening TiB 2 reinforced aluminium casting composites. (paper)

Microstructure and mechanical properties of TiB2–TiC–WC composite ceramic tool materials

International Nuclear Information System (INIS)

Song, Jinpeng; Huang, Chuanzhen; Zou, Bin; Liu, Hanlian; Wang, Jun

2012-01-01

Highlights: ►Effect of sintering parameters on TiB 2 –TiC–WC composites has been investigated. ► Ni element was dispersed in the interface between WC and matrix grains. ► The fracture mode changed from intergranular fracture to transgranular fracture. ► The microstructure and mechanical properties of the composite were improved. -- Abstract: TiB 2 –TiC–WC composites with Ni as a sintering aid were fabricated by a hot-press technique at 1700 °C and 1650 °C for 1 h, respectively. The microstructure and mechanical properties were investigated. The composites were analyzed by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The matrix phases consisted of TiB 2 and TiC. No severe chemical reactions happened between the additive and matrix. The microstructure consisted of the fine WC grains and uniform matrix grains. When the proper WC content added to TiB 2 –TiC composites, the growth of matrix grains was inhibited and the mechanical properties of the composites were improved. The interface energy was strengthened by Ni that dispersed in the interfaces among WC grains and matrix grains, which made the fracture mode change from intergranular fracture to transgranular fracture. The transgranular fracture and the pulling out of WC grains played a predominant role in the propagating of cracks when WC content was 20 wt.% in TiB 2 –TiC–WC composites. The optimal mechanical properties of TiB 2 –TiC–20 wt.%WC composite were 955.71 MPa of flexural strength, 7.5 MPa m 1/2 of fracture toughness and 23.5 GPa of Vickers hardness.

Effects of nitrogen and carbon doping on properties and photocatalytic activity of TiO2-In2O3 composite

International Nuclear Information System (INIS)

Wu, Chung-Hsin; Wu, Jui-Tai; Lai, Chih-Hao; Chung, Wei-Yang; Kuo, Chao-Yin; Hong, Pui-Kwan Andy

2015-01-01

TiO 2 -In 2 O 3 (Ti-In) was synthesized by the sol-gel method and the composite was further doped with nitrogen and carbon to create Ti-In-N and Ti-In-C, respectively. The dye C.I. Reactive Red 2 (RR2) was used a model compound to be subjected to various composites and measured for removal by photocatalytic degradation and adsorption. Ti-In-N possessed a larger mean diameter than Ti-In-C, while the latter possessed a greater anatase content and surface area than the former. After N or C doping, the spectra of corresponding Ti-In-N and Ti-In-C showed absorption edges at longer wavelengths than the parent Ti-In. Ti-N-O and Ti-O-C bonds were found in Ti-In-N and Ti-In-C composites, respectively. Ti-In-N was more effective for RR2 photodegradation than Ti-In-C, and the Ti-In-C removed more RR2 by adsorption than Ti-In-N

Influence of surface morphology and UFG on damping and mechanical properties of composite reinforced with spinel MgAl{sub 2}O{sub 4}-SiC core-shell microcomposites

Energy Technology Data Exchange (ETDEWEB)

Singh, Subhash; Pal, Kaushik, E-mail: pl_kshk@yahoo.co.in

2017-01-15

Interface between ceramic particulate and matrix is known to control the response of the materials and functionality of the composite. Among numerous physical properties, grain structure of the materials has also played a significant role in defining the behaviour of metal matrix composites. Usually, silicon carbide (SiC) particles show poor interfacial wettability in aluminium melt. Herein, we were successfully synthesized magnesium oxide (MgO) and nanocrystalline magnesium aluminate (MgAl{sub 2}O{sub 4}) spinel coated silicon carbide (SiC) core-shell micro-composites through sol-gel technique to improve the wettability of dispersoids. Core-shell structures of submicron size were thoroughly investigated by various characterization techniques. Further, aluminium matrix composites incorporated with pristine SiC, MgO grafted SiC and MgAl{sub 2}O{sub 4} grafted SiC particles were fabricated by stir casting technique, respectively. Additionally, as-cast composites were processed via friction stir processing (FSP) technique to observe the influence of grain refinement on mechanical and damping properties. Electron back scattered diffraction (EBSD), Field emission scanning electron microscopy (FE-SEM) and X-ray energy dispersion spectroscopy (EDX) analysis were conducted for investigating grain size refinement, adequate dispersion, stability and de-agglomeration of encapsulated SiC particles in aluminium matrix. The mechanical as well as thermal cyclic (from − 100 to 400 °C) damping performance of the as-cast and friction stir processed composites were studied, respectively. Finally, the enhanced properties were attributable to reduced agglomeration, stabilization and proper dispersion of the tailored SiC particles Al matrix. - Highlights: •Synthesizing a novel coating layer of MgO and MgAl{sub 2}O{sub 4} spinel onto SiC particles •Significant improvement in UTS and hardness by reinforcing tailored SiC in Al •Significant grain refinements were obtained through

Characteristics of laser clad α-Ti/TiC+(Ti,W)C1-x/Ti2SC+TiS composite coatings on TA2 titanium alloy

Science.gov (United States)

Zhai, Yong-Jie; Liu, Xiu-Bo; Qiao, Shi-Jie; Wang, Ming-Di; Lu, Xiao-Long; Wang, Yong-Guang; Chen, Yao; Ying, Li-Xia

2017-03-01

TiC reinforced Ti matrix composite coating with Ti2SC/TiS lubricant phases in-situ synthesized were prepared on TA2 titanium alloy by laser cladding with different powder mixtures: 40%Ti-19.5%TiC-40.5%WS2, 40%Ti-25.2%TiC-34.8%WS2, 40%Ti-29.4%TiC-30.6%WS2 (wt%). The phase compositions, microstructure, microhardness and tribological behaviors and wear mechanisms of coatings were investigated systematically. Results indicate that the main phase compositions of three coatings are all continuous matrix α-Ti, reinforced phases of (Ti,W)C1-x and TiC, lubricant phases of Ti2SC and TiS. The microhardness of the three different coatings are 927.1 HV0.5, 1007.5 HV0.5 and 1052.3 HV0.5, respectively. Compared with the TA2 titanium alloy (approximately 180 HV0.5), the microhardness of coatings have been improved dramatically. The coefficients of friction and the wear rates of those coatings are 0.41 and 30.98×10-5 mm3 N-1 m-1, 0.30 and 18.92×10-5 mm3 N-1 m-1, 0.34 and 15.98×10-5 mm3 N-1 m-1, respectively. Comparatively speaking, the coating fabricated with the powder mixtures of 40%Ti-25.2%TiC-34.8%WS2 presents superior friction reduction and anti-wear properties and the main wear mechanisms of that are slight plastic deformation and adhesive wear.

Cold spraying SiC/Al metal matrix composites: effects of SiC contents and heat treatment on microstructure, thermophysical and flexural properties

Science.gov (United States)

Gyansah, L.; Tariq, N. H.; Tang, J. R.; Qiu, X.; Feng, B.; Huang, J.; Du, H.; Wang, J. Q.; Xiong, T. Y.

2018-02-01

In this paper, cold spray was used as an additive manufacturing method to fabricate 5 mm thick SiC/Al metal matrix composites with various SiC contents. The effects of SiC contents and heat treatment on the microstructure, thermophysical and flexural properties were investigated. Additionally, the composites were characterized for retention of SiC particulates, splat size, surface roughness and the progressive understanding of strengthening, toughening and cracking mechanisms. Mechanical properties were investigated via three-point bending test, thermophysical analysis, and hardness test. In the as-sprayed state, flexural strength increased from 95.3 MPa to 133.5 MPa, an appreciation of 40% as the SiC contents increased, and the main toughening and strengthening mechanisms were zigzag crack propagation and high retention of SiC particulates respectively. In the heat treatment conditions, flexural strength appreciated significantly compared to the as-sprayed condition and this was as a result of coarsening of pure Al splat. Crack branching, crack deflection and interface delamination were considered as the main toughening mechanisms at the heat treatment conditions. Experimental results were consistent with the measured CTE, hardness, porosity and flexural modulus.

Wettability between TiN,TiC Containing Carbon Composite Refractory and Molten Slag or Hot Metal

Institute of Scientific and Technical Information of China (English)

SHIYue－xun; LIYingand; 等

1994-01-01

In order to develop a new-type TiC-TiN containing carbon composite refractory so as to improve the service life of blast furnace hearth,the wettability between the carbon refractory and molten slag or metal has been mea-sured.It was indicated that the carbon refractory is wet-ted by slag(θ≤90°） when(TiC+TiN)>33.52%,The effects of TiN or TiC on wetting behavior are basi-cally identical.When the amount of TiC in the carbon com-posite refractory is greater than 60% it will be wetted by hot metal;therefore,the carbon composite refractory will be wetted by slag but not permeated by hot metal when the amount of TiC is restricted.

Long-term corrosion tests of Ti{sub 3}SiC{sub 2} and Ti{sub 2}AlC in oxygen containing LBE at temperatures up to 700 °C

Energy Technology Data Exchange (ETDEWEB)

Heinzel, A., E-mail: Annette.heinzel@kit.edu; Weisenburger, A.; Müller, G.

2016-12-15

Two MAX-phase materials, Ti{sub 3}SiC and Ti{sub 2}AlC, were tested at 550 °C, 650 °C and 700 °C up to 10 000 h in LBE (lead-bismuth-eutectic) containing of 10{sup −6} and 10{sup −8} wt% oxygen. It was found that secondary phases have a strong influence on corrosion effects. Ti{sub 3}SiC showed a surface disintegration at 550°C/10{sup −6} wt% oxygen after longer exposure, while a 4–7 μm thick TiO{sub 2} layer with Pb-Bi inclusions was detected on Ti{sub 2}AlC. However, Ti{sub 3}SiC is protected by a double layered oxide with an outer part of TiO{sub 2} and a mixed inner layer of SiO{sub 2} and TiO{sub 2} at the higher temperatures. Ti{sub 2}AlC formed a TiO{sub 2} surface layer containing Al{sub 2}O{sub 3}. Some defects could be observed on the Ti{sub 3}SiC surface in LBE containing 10{sup −8} wt% oxygen at 550 °C and 650 °C. The secondary phases between the Ti{sub 3}SiC grains showed strong oxidation at 700 °C. Due to the high Al solubility in LBE, Ti{sub 2}AlC experienced strong dissolution attack after longer exposure times at 650 and 700 °C.

Laser processing of in situ TiN/Ti composite coating on titanium.

Science.gov (United States)

Sahasrabudhe, Himanshu; Soderlind, Julie; Bandyopadhyay, Amit

2016-01-01

Laser remelting of commercially pure titanium (CP-Ti) surface was done in a nitrogen rich inert atmosphere to form in situ TiN/Ti composite coating. Laser surface remelting was performed at two different laser powers of 425 W and 475 W. At each power, samples were fabricated with one or two laser scans. The resultant material was a nitride rich in situ coating that was created on the surface. The cross sections revealed a graded microstructure. There was presence of nitride rich dendrites dispersed in α-Ti matrix at the uppermost region. The structure gradually changed with lesser dendrites and more heat affected α-Ti phase maintaining a smooth interface. With increasing laser power, the dendrites appeared to be larger in size. Samples with two laser scans showed discontinuous dendrites and more α-Ti phase as compared to the samples with one laser scan. The resultant composite of TiN along with Ti2N in α-Ti showed substantially higher hardness and wear resistance than the untreated CP-Ti substrate. Coefficient of friction was also found to reduce due to surface nitridation. Leaching of Ti(4+) ions during wear test in DI water medium was found to reduce due to laser surface nitriding. Copyright © 2015 Elsevier Ltd. All rights reserved.

Microstructure and kinetics of a functionally graded NiTi-TiC x composite produced by combustion synthesis

International Nuclear Information System (INIS)

Burkes, Douglas E.; Moore, John J.

2007-01-01

Production of a NiTi-TiC x functionally graded material (FGM) composite is possible through use of a combustion synthesis (CS) reaction employing the propagating mode (SHS). The NiTi-TiC x FGM combines the well-known and understood superelastic and shape memory capabilities of NiTi with the high hardness, wear and corrosion resistance of TiC x . The material layers were observed as functionally graded both in composition and porosity with distinct interfaces, while still maintaining good material interaction and bonding. XRD of the FGM composite revealed the presence of TiC x with equi-atomic NiTi and minor NiTi 2 and NiTi 3 phases. The TiC x particle size decreased with increasing NiTi content. Microindentation performed across the length of the FGM revealed a decrease in hardness as the NiTi content increased

Composition powders of the system TiC-TiB2

International Nuclear Information System (INIS)

Degrave, I.E.; Udalov, Yu.P.

2000-01-01

The ceramic composition on TiC-TiB 2 base is proposed for substitution of scarce and expensive tungsten carbide for manufacturing metallo-ceramic articles. The technology of TiC and TiB 2 powder production from the mixture of oxides and carbon-bearing reducing agents is developed. Saccharose is recommended to be used as a reductant. Carbon tetrachloride vapors are introduced into the reaction volume to accelerate the synthesis. The purification of the product from residual carbon is performed in high frequency glow discharge with the use of air as a plasma forming gas. Microstructural studies show that the product obtained constitutes submicron TiC particles in a TiB 2 matrix [ru

In situ synthesized TiB-TiN reinforced Ti6Al4V alloy composite coatings: microstructure, tribological and in-vitro biocompatibility.

Science.gov (United States)

Das, Mitun; Bhattacharya, Kaushik; Dittrick, Stanley A; Mandal, Chitra; Balla, Vamsi Krishna; Sampath Kumar, T S; Bandyopadhyay, Amit; Manna, Indranil

2014-01-01

Wear resistant TiB-TiN reinforced Ti6Al4V alloy composite coatings were deposited on Ti substrate using laser based additive manufacturing technology. Ti6Al4V alloy powder premixed with 5wt% and 15wt% of boron nitride (BN) powder was used to synthesize TiB-TiN reinforcements in situ during laser deposition. Influences of laser power, scanning speed and concentration of BN on the microstructure, mechanical, in vitro tribological and biological properties of the coatings were investigated. Microstructural analysis of the composite coatings showed that the high temperature generated due to laser interaction with Ti6Al4V alloy and BN results in situ formation of TiB and TiN phases. With increasing BN concentration, from 5wt% to 15wt%, the Young's modulus of the composite coatings, measured by nanoindentation, increased from 170±5GPa to 204±14GPa. In vitro tribological tests showed significant increase in the wear resistance with increasing BN concentration. Under identical test conditions TiB-TiN composite coatings with 15wt% BN exhibited an order of magnitude less wear rate than CoCrMo alloy-a common material for articulating surfaces of orthopedic implants. Average top surface hardness of the composite coatings increased from 543±21HV to 877±75HV with increase in the BN concentration. In vitro biocompatibility and flow cytometry study showed that these composite coatings were non-toxic, exhibit similar cell-materials interactions and biocompatibility as that of commercially pure titanium (CP-Ti) samples. In summary, excellent in vitro wear resistance, high stiffness and suitable biocompatibility make these composite coatings as a potential material for load-bearing articulating surfaces towards orthopaedic implants. © 2013 Elsevier Ltd. All rights reserved.

Shear stiffness in nanolaminar Ti3SiC2 challenges ab initio calculations

International Nuclear Information System (INIS)

Kisi, E H; Zhang, J F; Kirstein, O; Riley, D P; Styles, M J; Paradowska, A M

2010-01-01

Nanolaminates such as the M n+1 AX n (MAX) phases are a material class with ab initio derived elasticity tensors published for over 250 compounds. We have for the first time experimentally determined the full elasticity tensor of the archetype MAX phase, Ti 3 SiC 2 , using polycrystalline samples and in situ neutron diffraction. The experimental elastic constants show extreme shear stiffness, with c 44 more than five times greater than expected for an isotropic material. Such shear stiffness is quite rare in hexagonal materials and strongly contradicts the predictions of all published MAX phase elastic constants derived from ab initio calculations. It is concluded that second order properties such as elastic moduli derived from ab initio calculations require careful experimental verification. The diffraction technique used currently provides the only method of verification for the elasticity tensor for the majority of new materials where single crystals are not available. (fast track communication)

Phenomenological inelastic constitutive equations for SiC and SiC fibers under irradiation

International Nuclear Information System (INIS)

El-Azab, A.; Ghoniem, N.M.

1994-01-01

Experimental data on irradiation-induced dimensional changes and creep in β-SiC and SiC fibers is analyzed, with the objective of studying the constitutive behavior of these materials under high-temperature irradiation. The data analysis includes empirical representation of irradiation-induced dimensional changes in SiC matrix and SiC fibers as function of time and irradiation temperature. The analysis also includes formulation of simple scaling laws to extrapolate the existing data to fusion conditions on the basis of the physical mechanisms of radiation effects on crystalline solids. Inelastic constitutive equations are then developed for SCS-6 SiC fibers, Nicalon fibers and CVD SiC. The effects of applied stress, temperature, and irradiation fields on the deformation behavior of this class of materials are simultaneously represented. Numerical results are presented for the relevant creep functions under the conditions of the fusion reactor (ARIES IV) first wall. The developed equations can be used in estimating the macro mechanical properties of SiC-SiC composite systems as well as in performing time-dependent micro mechanical analysis that is relevant to slow crack growth and fiber pull-out under fusion conditions

AlTiN layer effect on mechanical properties of Ti-doped diamond-like carbon composite coatings

International Nuclear Information System (INIS)

Pang Xiaolu; Yang Huisheng; Gao Kewei; Wang Yanbin; Volinsky, Alex A.

2011-01-01

Ti/Ti-doped diamond-like carbon (DLC) and Ti/AlTiN/Ti-DLC composite coatings were deposited by magnetron sputtering on W18Cr4V high speed steel substrates. The effect of the AlTiN support layer on the properties of these composite coatings was investigated through microstructure and mechanical properties characterization, including hardness, elastic modulus, coefficient of friction and wear properties measured by scanning electron microscopy, Raman spectroscopy, scratch and ball-on-disk friction tests. Ti and AlTiN interlayers have a columnar structure with 50-80 nm grains. The hardness and elastic modulus of Ti/Ti-DLC and Ti/AlTiN/Ti-DLC coatings is 25.9 ± 0.4, 222.2 ± 6.3 GPa and 19.3 ± 1, 205.6 ± 6.7 GPa, respectively. Adhesion of Ti-DLC, Ti/AlTiN/Ti-DLC and AlTiN/Ti-DLC coatings expressed as the critical lateral force is 26.5 N, 38.2 N, and 47.8 N, respectively. Substrate coefficient of friction without coatings is 0.44, and it is 0.1 for Ti/Ti-DLC and Ti/AlTiN/Ti-DLC coatings. Wear resistance of Ti/AlTiN/Ti-DLC composite coatings is much higher than Ti/Ti-DLC coatings based on the wear track width of 169.8 and 73.2 μm, respectively, for the same experimental conditions.

Structure, phase composition and microhardness of vacuum-arc multilayered Ti/Al, Ti/Cu, Ti/Fe, Ti/Zr nano-structures with different periods

Energy Technology Data Exchange (ETDEWEB)

Demchishin, A.V., E-mail: ademch@meta.ua [Institute of Problems in Material Science, NASU, Kiev (Ukraine); Gnilitskyi, I., E-mail: iaroslav.gnilitskyi@unimore.it [DISMI – Department of Sciences and Methods for Engineering, University of Modena and Reggio Emilia, Reggio Emilia (Italy); Orazi, L., E-mail: leonardo.orazi@unimore.it [DISMI – Department of Sciences and Methods for Engineering, University of Modena and Reggio Emilia, Reggio Emilia (Italy); Ascari, A., E-mail: a.ascari@unibo.it [DIN – Department of Industrial Engineering, University of Bologna, Bologna (Italy)

2015-07-01

Highlights: • Multilayer coatings of Ti/Fe, Ti/Al, Ti/Cu and Ti/Zr are generated. • Microstructure and morphology of the different systems are investigated. • XR diffraction analysis was performed to investigate phases composition. • Effects of inter metallic phases on microhardess are investigated. • Correlations between parameters and layer thickness are outlined. - Abstract: The microstructure, phase composition and microhardness of multilayered Ti/Al, Ti/Cu, Ti/Fe and Ti/Zr condensates produced on stainless steel substrates via vacuum-arc evaporation of pure metals were studied. The sublayer periods (Λ) were regulated in the range 80–850 nm by varying the vacuum discharge current and the duration of the successive depositions of metallic plasma onto the substrates while maintaining the total deposition time constant. The regularity of the obtained nanostructures was investigated by scanning and transmission electron microscopy while phase compositions were identified with X-ray diffraction (XRD) analysis in order to evidence the presence of interdiffusion and the amount of intermetallics. Condensates cross sections were mechanically characterized by means of microhardness tests. Measurements were correlated to the periods and to the presence of intermetallics.

Structure, phase composition and microhardness of vacuum-arc multilayered Ti/Al, Ti/Cu, Ti/Fe, Ti/Zr nano-structures with different periods

International Nuclear Information System (INIS)

Demchishin, A.V.; Gnilitskyi, I.; Orazi, L.; Ascari, A.

2015-01-01

Highlights: • Multilayer coatings of Ti/Fe, Ti/Al, Ti/Cu and Ti/Zr are generated. • Microstructure and morphology of the different systems are investigated. • XR diffraction analysis was performed to investigate phases composition. • Effects of inter metallic phases on microhardess are investigated. • Correlations between parameters and layer thickness are outlined. - Abstract: The microstructure, phase composition and microhardness of multilayered Ti/Al, Ti/Cu, Ti/Fe and Ti/Zr condensates produced on stainless steel substrates via vacuum-arc evaporation of pure metals were studied. The sublayer periods (Λ) were regulated in the range 80–850 nm by varying the vacuum discharge current and the duration of the successive depositions of metallic plasma onto the substrates while maintaining the total deposition time constant. The regularity of the obtained nanostructures was investigated by scanning and transmission electron microscopy while phase compositions were identified with X-ray diffraction (XRD) analysis in order to evidence the presence of interdiffusion and the amount of intermetallics. Condensates cross sections were mechanically characterized by means of microhardness tests. Measurements were correlated to the periods and to the presence of intermetallics

Preparation of TiO2-SiO2 composite photocatalysts for environmental applications

Czech Academy of Sciences Publication Activity Database

Paušová, Š.; Krýsa, J.; Jirkovský, Jaromír; Prevot, V.; Mailhot, G.

2014-01-01

Roč. 89, č. 8 (2014), s. 1129-1135 ISSN 0268-2575 Institutional support: RVO:61388955 Keywords : photocatalysis * TiO2/SiO2 * composite Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.349, year: 2014

Microstructure and wear of in-situ Ti/(TiN + TiB) hybrid composite layers produced using liquid phase process

Energy Technology Data Exchange (ETDEWEB)

Yazdi, R., E-mail: ryazdi@ut.ac.ir; Kashani-Bozorg, S.F.

2015-02-15

Tungsten inert gas (TIG) technique was conducted on commercially pure (CP)-Ti substrate, which was coated with h-BN-based powder mixture prior to the treatment. The treated surfaces were evaluated and characterized by means of scanning electron microscope (SEM), X-ray diffraction analysis, and electron dispersive spectrometry (EDS). The microhardness and wear experiment were also performed by using a microhardness machine and pin-on-disk tribometer. As h-BN reacted with titanium, an in-situ hybrid composite layer was formed showing near stoichiometric dendrites of TiN, platelets of TiB and interdendritic regions of α′-Ti martensite crystal structures. The population level of TiN and TiB regions were found to increase using a pre-placed powder mixture with greater h-BN content. However, the fabricated layers exhibited cracking and porosity; these were minimized by adjusting arc energy density and h-BN content of powder mixture. The microhardness value of the fabricated hybrid composite layers was found to be in the range of ∼650 HV{sub 0.2}–1000 HV{sub 0.2}; this is three to five times higher than that of the untreated CP-Ti substrate. In addition, the in-situ hybrid composite layers exhibited superior wear behavior over CP-Ti substrate; this is attributed to the formation of newly formed ceramic phases in the solidified surface layers and good coherent interface between the composite layer and CP-substrate. Meanwhile, severe adhesive wear mechanism of CP-titanium surface changed to mild abrasive one as a result of surface treatment. - Highlights: • In-situ Ti/(TiN + TiB) hybrid composite layers were synthesized by TIG processing on commercially pure titanium. • The microstructure features were characterized by several methods. • Microhardness enhanced three to five times higher than that of the CP-Ti substrate after surface modification. • The fabricated composite layers improved wear resistance of CP-titanium. • Severe adhesive wear mechanism of

TiC-Maraging stainless steel composite: microstructure, mechanical and wear properties

Institute of Scientific and Technical Information of China (English)

Akhtar Farid; GUO Shiju; FENG Peizhong; Khadijah Ali Shah; Syed Javid Askari

2006-01-01

Particulate TiC reinforced 17-4PH and 465 maraging stainless steel matrix composites were processed by conventional powder metallurgy (P/M). TiC-maraging stainless steel composites with theoretical density ＞97% were produced using conventional P/M. The microstructure, and mechanical and wear properties of the composites were evaluated. The microstructure of the composites consisted of (core-rim structure) spherical and semi-spherical TiC particles depending on the wettability of the matrix with TiC particles. In TiC-maraging stainless steel composites, 465 stainless steel binder phase showed good wettability with TiC particles. Some microcracks appeared in the composites, indicating the presence of tensile stresses in the composites produced during sintering. The typical properties, hardness, and bend strength were reported for the composites. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was attributed to the aging reaction in maraging stainless steel. The specific wear behavior of the composites strongly depends on the content of TiC particles and their interparticle spacing, and on the heat treatment of the maraging stainless steel.

Influence of Ni-P Coated SiC and Laser Scan Speed on the Microstructure and Mechanical Properties of IN625 Metal Matrix Composites

Science.gov (United States)

Sateesh, N. H.; Kumar, G. C. Mohan; Krishna, Prasad

2015-12-01

Nickel based Inconel-625 (IN625) metal matrix composites (MMCs) were prepared using pre-heated nickel phosphide (Ni-P) coated silicon carbide (SiC) reinforcement particles by Direct Metal Laser Sintering (DMLS) additive manufacturing process under inert nitrogen atmosphere to obtain interface influences on MMCs. The distribution of SiC particles and microstructures were characterized using optical and scanning electron micrographs, and the mechanical behaviours were thoroughly examined. The results clearly reveal that the interface integrity between the SiC particles and the IN625 matrix, the mixed powders flowability, the SiC ceramic particles and laser beam interaction, and the hardness, and tensile characteristics of the DMLS processed MMCs were improved effectively by the use of Ni-P coated SiC particles.

Preparation, properties, and application characteristics of metastable layers of the Ti-Si-C-N system

International Nuclear Information System (INIS)

Fella, R.

1992-10-01

In the Ti-Si-C and Ti-Si-C-N systems, metastable layers were precipitated by means of non-reactive magnetron sputtering of hot-pressed two-phase TiC/SiC and TiN/SiC targets with 20 mole% and 50 mole% SiC. The preparation parameters were varied as follows: ion bombardment during precipitation (bias sputtering), substrate temperature, and annealing times when annealing amorphous 50%:50% TiC/SiC and 50%:50% TiN/SiC layers. Sputtering of targets containing 20% SiC was found to result in monophase fcc layers (NaCl structure). This was documented on the basis of X-ray and electron diffraction patterns. Direct precipitation of targets with 50 mole% SiC resulted in amorphous layers. Increasing the ion bombardment during accretion, raising the substrate temperature, and annealing amorphous 50%:50% TiC/SiC and 50%:50% TiN/SiC (layers precipitated directly) resulted in the crystallization of TiC and TiN nanocrystallites, respectively, imbedded in an amorphous SiC matrix. These crystallites were detected both by X-ray and by electron diffractions and by XPS studies. The XPS measurements of crystalline TiC and amorphous SiC reference layers demonstrated the existence of new kinds of carbon interface phases ('pseudocarbide layers') around TiC and amorphous SiC regions, respectively, which have a positive impact on the mechanical properties of the layers. The hardness of the layers can be correlated with the degrees of crystallization and texture. Adhesion and toughness are worse in SiC-bearing layers than PVD TiC and TiN layers, respectively. The application characteristics of the layers were determined by model wear tests relative to 100Cr6 by means of a pin/disk tribometer. N-bearing layers were found to have clearly higher friction coefficients and greater wear than layers without N. (orig.)

Fracture toughness of Ti-Al3Ti-Al-Al3Ti laminate composites under static and cyclic loading conditions

Science.gov (United States)

Patselov, A. M.; Gladkovskii, S. V.; Lavrikov, R. D.; Kamantsev, I. S.

2015-10-01

The static and cyclic fracture toughnesses of a Ti-Al3Ti-Al-Al3Ti laminate composite material containing at most 15 vol % intermetallic compound are studied. Composite specimens are prepared by terminating reaction sintering of titanium and aluminum foils under pressure. The fracture of the titanium layers is quasi-cleavage during cyclic crack growth and is ductile during subsequent static loading.

PHASE CONSTITUENTS AND MICROSTRUCTURE OF Ti3Al/Fe3Al + TiN/TiB2 COMPOSITE COATING ON TITANIUM ALLOY

OpenAIRE

JIANING LI; CHUANZHONG CHEN; CUIFANG ZHANG

2011-01-01

Laser cladding of the Fe3Al + B4C/TiN + Al2O3 pre-placed powders on the Ti-6Al-4V alloy can form the Ti3Al/Fe3Al + TiN/TiB2 composite coating, which improved the wear resistance of the Ti-6Al-4V alloy surface. In this study, the Ti3Al/Fe3Al + TiN/TiB2 composite coating has been researched by means of X-ray diffraction and scanning electron microscope. It was found that during the laser cladding process, Al2O3 can react with TiB2, leading to the formations of Ti3Al and B. This principle can be...

Advanced Environmental Barrier Coating and SA Tyrannohex SiC Composites Integration for Improved Thermomechanical and Environmental Durability

Science.gov (United States)

Zhu, Dongming; Halbig, Michael; Singh, Mrityunjay

2018-01-01

The development of 2700 degF capable environmental barrier coating (EBC) systems, particularly, the Rare Earth "Hafnium" Silicon bond coat systems, have significantly improved the temperature capability and environmental stability of SiC/SiC Ceramic Matrix Composite Systems. We have specifically developed the advanced 2700 degF EBC systems, integrating the EBC to the high temperature SA Tyrannohex SiC fiber composites, for comprehensive performance and durability evaluations for potential turbine engine airfoil component applications. The fundamental mechanical properties, environmental stability and thermal gradient cyclic durability performance of the EBC - SA Tyrannohex composites were investigated. The paper will particularly emphasize the high pressure combustion rig recession, cyclic thermal stress resistance and thermomechanical low cycle fatigue testing of uncoated and environmental barrier coated Tyrannohex SiC SA composites in these simulated turbine engine combustion water vapor, thermal gradients, and mechanical loading conditions. We have also investigated high heat flux and flexural fatigue degradation mechanisms, determined the upper limits of operating temperature conditions for the coated SA composite material systems in thermomechanical fatigue conditions. Recent progress has also been made by using the self-healing rare earth-silicon based EBCs, thus enhancing the SA composite hexagonal fiber columns bonding for improved thermomechanical and environmental durability in turbine engine operation environments. More advanced EBC- composite systems based on the new EBC-Fiber Interphases will also be discussed.

Investigation on Tribological Properties of the Pre-oxidized Ti2AlN/TiAl Composite

Science.gov (United States)

Wang, Daqun; Sun, Dongli; Han, Xiuli; Wang, Qing; Wang, Guangwei

2018-03-01

Different oxidation layers on the Ti2AlN/TiAl substrate which was fabricated by in situ synthesis were prepared through thermal oxidation process. The microstructure, phase identification and elements distribution of the oxidation layers were analyzed. The tribological performance of pre-oxidized composites against Si3N4 ball at 25 and 600 °C, as well as the effect of pre-oxidation layers on tribological performance was systematically investigated. The results show that, compared to Ti2AlN/TiAl, the pre-oxidized composites present more excellent tribological properties, especially the wear resistance at 600 °C. It is a significant finding that, different from severe abrasive wear and plastic deformation of Ti2AlN/TiAl, the tribo-films formed by the pre-oxidation layers on the worn surface of pre-oxidized composites weaken abrasive wear and suppress the development of plastic deformation to protect the underlying composite substrate from wear. Moreover, the stable cooperation on the interface between tribo-films and Si3N4 ball results in the relatively steady friction coefficient.

Experimental Studies on SiC and Rice Husk Ash Reinforced Al Alloy Composite

Directory of Open Access Journals (Sweden)

Shivaprakash Y. M.

2018-01-01

Full Text Available In this research work Aluminium alloy with Cu (4.5% as the major alloying element is used as the matrix in which SiC and Rice Husk Ash (RHA are dispersed to develop a hybrid composite. The dispersion is done by the motorized stir casting arrangement. The composite is fabricated by varying the proportions of the reinforcements in the base alloy. The composite specimens were tested for density changes, hardness and the wear. The microstructure images showed a uniform dispersion of the reinforcements in the matrix and this resulted in higher strength to weight ratio. The increase in strength of the composite is probably attributed to the increase in the dislocation density. Also, the abrasive wear resistance of the produced composite is found to be superior as compared to the matrix alloy because of the hard-ceramic particles in the reinforcements.

Correlations Between Arrangement of Reinforcing Particles and Mechanical Properties in Pressure Die Cast AlSi11-SiC Composites

Directory of Open Access Journals (Sweden)

Konopka Z.

2014-06-01

Full Text Available The work presents the investigation results concerning the structure of composite pressure die castings with AlSi11 alloy matrix reinforced with SiC particles. Examination has been held for composites containing 10 and 20 volume percent of SiC particles. The arrangement of the reinforcing particles within the matrix has been qualitatively assessed in specimens cut out of the castings. The index of distribution was determined on the basis of particle count in elementary measuring fields. The tensile strength, the yield point and elongation of the obtained composite were measured. Composite castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. The regression equation describing the change of the considered arrangement particles index and mechanical properties were found as a function of the pressure die casting parameters. The infuence of particle arrangement in composite matrix on mechanical properties these material was examined and the functions of correlations between values were obtained. The conclusion gives the analysis and the interpretation of the obtained results.

Stress-temperature-lifetime response of nicalon fiber-reinforced SiC composites in air

International Nuclear Information System (INIS)

Lin, Hua-Tay; Becher, P.F.

1996-01-01

Time-to-failure tests were conducted in four-point flexure and in air as a function of stress levels and temperatures to study the lifetime response of various Nicalon fiber-reinforced SiC (designated as Nic/SiC) composites with a graphitic interfacial coating. The results indicated that all of the Nic/SiC composites exhibit a similar stress-dependent failure at applied stress greater than a threshold value. In this case, the lifetimes of the composites increased with decrease in both stress level and test temperature. The lifetime of the composites appeared to be relatively insensitive to the thickness of graphitic interface layer and was enhanced somewhat by the addition of oxidation inhibitors. Electron microscopy and oxidation studies indicated that the life of the Nic/SiC composites was governed by the oxidation of the graphitic interfaces and the on of glass(es) in composites due to the oxidation of the fiber and matrix, inhibitor phases

A comparative study on the tensile and impact properties of Kevlar, carbon, and S-glass/epoxy composites reinforced with SiC particles

Science.gov (United States)

Bulut, Mehmet; Alsaadi, Mohamad; Erkliğ, Ahmet

2018-02-01

Present study compares the tensile and impact characteristics of Kevlar, carbon and glass fiber reinforced composites with addition of microscale silicon carbide (SiC) within the common matrix of epoxy. The variation of tensile and impact strength values was explored for different content of SiC in the epoxy resin by weight (0, 5, 10, 15 and 20 wt%). Resulting failure characteristics were identified by assisting Charpy impact tests. The influence of interfacial adhesion between particle and fiber/matrix on failure and tensile properties was discussed from obtained results and scanning electron microscopy (SEM) figures. It is concluded from results that the content of SiC particles, and fiber types used as reinforcement are major parameters those effecting on tensile and impact resistance of composites as a result of different interface strength properties between particle-matrix and particle-fiber.

TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

International Nuclear Information System (INIS)

Ghalamboran, Milad; Saedi, Yasin

2016-01-01

The fabrication method and characterization results of a TiO 2 -TiO 2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO 2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO 2 crystallites embedded in a matrix of nanometric TiO 2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant. (paper)

Electrochemical behaviour of TiO{sub 2} reinforced Al 7075 composite

Energy Technology Data Exchange (ETDEWEB)

Karunanithi, R., E-mail: karunaponni@gmail.com; Bera, Supriya; Ghosh, K.S., E-mail: ksghosh2001@yahoo.co.uk

2014-12-15

Graphical abstract: - Highlights: • Clustering of TiO{sub 2} particle and porosity increased with increasing TiO{sub 2}. • Coarse and numerous very fine η′ and η precipitates in T6 temper composite. • Shifting corrosion potential to noble direction with increasing TiO{sub 2}. • Corrosion is maximum for 30 vol.% TiO{sub 2} composite and least for 7075 alloy. • Pitting damage greater with the increasing TiO{sub 2}. - Abstract: Microstructures of sintered Al 7075 alloy and Al 7075 alloy reinforced with varying TiO{sub 2} composites exhibited uniform distribution of TiO{sub 2} particles, but clustering and porosity have increased with TiO{sub 2} content. TEM micrographs of the Al 7075 alloy and Al 7075 + TiO{sub 2} composite of peak aged T6 (PA) temper showed some coarse and numerous very fine η′ (MgZn{sub 2}) precipitates, and equilibrium η (MgZn{sub 2}) precipitates along the grain boundaries. Potentiodynamic electrochemical polarisation studies on the Al 7075 alloy of different tempers and Al 7075 + TiO{sub 2} composites in 3.5 wt.% NaCl solution showed that the corrosion potentials (E{sub corr}) have shifted towards noble direction with the addition of TiO{sub 2}, and there is an increase of corrosion current density (i{sub corr}) beyond 10 vol.% TiO{sub 2} in the composites. This is attributed to the increase in particle-matrix interface areas enhancing pitting corrosion. Optical micrographs of the corroded surface of 30% TiO{sub 2} composites exhibited maximum pitting damage.

Thermal effect of TiC in the Mo/TiC/SiC system at elevated temperature

International Nuclear Information System (INIS)

Roger, Jerome; Audubert, Fabienne; Le Petitcorps, Yann

2010-01-01

In this study, we examined the effect induced by the addition of a TiC interlayer on the stability of the Mo/SiC system at high temperature. Indeed, Mo/SiC couple is unstable at high temperature with formation of Mo 2 C and Mo 5 Si 3 C x phases. In order to limit the degradation of Mo mechanical properties, a TiC film was inserted between Mo and SiC. Samples used in this work were prepared on metallic wires substrates, SiC and TiC being deposited by CVD. The protection given by TiC layer was considered in the 1473-1673 K temperature range and for TiC thicknesses up to about 60 μm. From our results, TiC is not effective enough to mitigate C and Si atoms diffusion. Nevertheless, a notable reduction of the reaction extent is obtained at any temperatures. The so-observed effect depends on the TiC thickness and the temperature. In actual fact, TiC efficiency increases when temperature and/or TiC layer thickness increases without reaching a complete protection.

Aging Behaviour of 6061 Al-15 vol% SiC Composite in T4 and T6 Treatments

OpenAIRE

Melby Chacko; Jagannath Nayak

2014-01-01

The aging behaviour of 6061 Al-15 vol% SiC composite was investigated using Rockwell B hardness measurement. The composite was solutionized at 350°C and quenched in water. The composite was aged at room temperature (T4 treatment) and also at 140°C, 160°C, 180°C and 200°C (T6 treatment). The natural and artificial aging behaviour of composite was studied using aging curves determined at different temperatures. The aging period for peak aging for different temperatures was identified. The time ...

Silicon Carbide (SiC) Device and Module Reliability, Performance of a Loop Heat Pipe Subjected to a Phase-Coupled Heat Input to an Acceleration Field

Science.gov (United States)

2016-05-01

AFRL-RQ-WP-TR-2016-0108 SILICON CARBIDE (SiC) DEVICE AND MODULE RELIABILITY Performance of a Loop Heat Pipe Subjected to a Phase-Coupled...CARBIDE (SiC) DEVICE AND MODULE RELIABILITY Performance of a Loop Heat Pipe Subjected to a Phase-Coupled Heat Input to an Acceleration Field 5a...Shukla, K., “Thermo-fluid dynamics of Loop Heat Pipe Operation,” International Communications in Heat and Mass Transfer , Vol. 35, No. 8, 2008, pp

Application of the laser pyrolysis to the synthesis of SiC, TiC and ZrC pre-ceramics nano-powders

International Nuclear Information System (INIS)

Leconte, Y.; Maskrot, H.; Combemale, L.; Herlin-Boime, N.; Reynaud, C.

2007-01-01

Refractory carbide nano-structured ceramics appear to be promising materials for high temperature applications requiring hard materials such as nuclear energy industry. Such carbide materials are usually obtained with micrometric sizes from the high temperature carbo-reduction of an oxide phase in a raw mixture of C black and titania or zirconia. TiC and ZrC nano-powders were produced from an intimate mixture of oxide nano-grains with free C synthesized by laser pyrolysis from the decomposition of a liquid precursor. The temperature and the duration of the thermal treatment leading to the carburization were decreased, allowing the preservation of the nano-scaled size of the starting grains. A solution of titanium iso-prop-oxide was laser-pyrolyzed with ethylene as sensitizer in order to synthesize Ti/C/O powders. These powders were composed of crystalline TiO 2 nano-grains mixed with C. Annealing under argon enabled the formation of TiC through the carburization of TiO 2 by free C. The final TiC mean grain size was about 80 nm. Zr/O/C powders were prepared from a solution of zirconium butoxide and were composed of ZrO 2 crystalline nano-grains and free C. The same thermal treatment as for TiC, but at higher temperature, showed the formation of crystalline ZrC with a final mean grain size of about 40 nm. These two liquid routes of nano-particles synthesis are also compared to the very efficient gaseous route of SiC nano-powders synthesis from a mixture of silane and acetylene. (authors)

Nanoscale dynamic wetting and spreading of molten Ti alloy on 6H-SiC

International Nuclear Information System (INIS)

Tanaka, Shun-Ichiro; Iwamoto, Chihiro

2008-01-01

We have investigated nanoscale features at the reactive wetting front of the molten Ag-27.4 wt.% Cu-4.9 wt.% Ti on 6H-SiC using video movies recorded in situ on a high-temperature stage of a high-resolution transmission electron microscope and also proposed a model of a chemical reaction at each tip. One of the features of reactive wetting and spreading at 1073 K in 4 x 10 -5 Pa was the discontinuous motion of the tip, and the halting time depended on the thickness of an amorphous Si-O layer on SiC, which can be explained by the time needed for the decomposition of the layer by Ti atoms to form TiC nanoparticles since Ti atoms in the molten alloy sufficiently rapidly diffuse to the tip on the SiC surface. Molten Ti and TiC nanolayers preceded the Ti 5 Si 3 nanolayer at the tip. The reaction required to form the TiC nanolayer is also the rate-determining step for spreading. The contact angle of the tip increased up to 60-80 deg. when the tip halted, whereas the tip decreased down to 10 deg. on the nonbasal plane and 20 deg. on the basal plane of SiC when it traveled rapidly. The high traveling angle of the molten tip on the basal polar plane of SiC indicates a high interfacial energy between Ti and SiC(0 0 0 1)

Effect of different sintering aids on thermo-mechanical properties and oxidation of SiC fibers - Reinforced ZrB{sub 2} composites

Energy Technology Data Exchange (ETDEWEB)

Sciti, D., E-mail: diletta.sciti@istec.cnr.it [ISTEC-CNR, Institute of Science and Technology for Ceramics, National Research Council, Via Granarolo 64, I-48018 Faenza (Italy); Silvestroni, L. [ISTEC-CNR, Institute of Science and Technology for Ceramics, National Research Council, Via Granarolo 64, I-48018 Faenza (Italy); Saccone, G.; Alfano, D. [CIRA, Italian Aerospace Research Center, 81043 Capua (Italy)

2013-01-15

Reinforced zirconium diboride composites containing 15 vol% of Hi Nicalon SiC chopped fibers were hot pressed with addition of various sintering additives, Si{sub 3}N{sub 4}, ZrSi{sub 2} or MoSi{sub 2}. Depending on the sintering aid, different densification temperatures were set in the range 1650-1750 Degree-Sign C. Temperature and additive strongly influenced the matrix/fiber interface, which in turn had a strong impact on the mechanical properties and the oxidation behavior at 1650 Degree-Sign C. Even the workability, performed either by conventional machining or electro discharge machining, varied depending on the sintering additive and the secondary phases formed in the system. The system containing Si{sub 3}N{sub 4} turned out to have the highest mechanical properties, but intermediate oxidation resistance; the composite containing ZrSi{sub 2} had the lowest sintering temperature, but displayed the worst oxidation resistance, and finally the composite containing MoSi{sub 2} showed intermediate mechanical properties, but the highest oxidation resistance and lowest degree of damage upon machining. Preliminary measurements of thermal shock resistance by the water quenching method were also carried out. -- Highlights: Black-Right-Pointing-Pointer We produced SiC fibers reinforced ZrB{sub 2} using different sintering aids. Black-Right-Pointing-Pointer The sintering additives affected properties, oxidation and machinability. Black-Right-Pointing-Pointer The system containing Si{sub 3}N{sub 4} had the highest mechanical properties. Black-Right-Pointing-Pointer The composite containing MoSi{sub 2} had the highest oxidation resistance. Black-Right-Pointing-Pointer ZrB{sub 2}-SiC fibers have higher thermal shock resistance than ZrB{sub 2}-SiC particles.

Microstructure, thermal behavior and mechanical properties of squeeze cast SiC, ZrO2 or C reinforced ZA27 composites

International Nuclear Information System (INIS)

El-khair, M.T. Abou; Lotfy, A.; Daoud, A.; El-Sheikh, A.M.

2011-01-01

Research highlights: → ZA27 with 5% SiC, ZrO2 or C particles are synthesized by stirring then squeezed. → Particles refine the structure. 50 MPa decreases porosity% and increases density. → α and β nucleation temperatures of the composites are lower than those of the matrix. → Particles accelerate age hardening and increase peak hardness of the composites → Particles reduce the CTEs of composites compared to those of the matrix. - Abstract: ZA27 alloy based composites were synthesized by stirring method, followed by squeeze casting. Stir casting was employed successfully to incorporate 5 vol.% of various reinforcement particulates, namely, SiC, ZrO 2 or C. The porosity in the composites was decreased by squeeze pressure. The presence of particles and/or application of squeeze pressure during solidification resulted in considerable refinement in the structure of the composites. The microstructures, X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDXA) results indicated that no significant reactions occurred at the interface between the SiC or C particles and ZA27 alloy. However, in case of ZrO 2 reinforced ZA27, the ZrO 2 reacted with Cu present in the molten ZA27 alloy, forming Cu 5 Zr. Thermal analysis showed that both α and β nucleation and growth temperatures of the composites were lower than those of the ZA27 alloy. The presence of particles in the as-cast or squeezed composites led to not only an accelerated age hardening response, but also an increase in the peak hardness of the composites. The values of coefficient of thermal expansion (CTE) of the composites were drastically lower as compared to those of the ZA27 alloy. The tensile properties of the composites decreased as a result of the addition of the particles. Scanning electron microscope (SEM) pictures of the composites indicated that cracks mainly initiated at particle-matrix interface, propagated through the matrix and linked up with other cracks leading to failure of the

TiN/VN composites with core/shell structure for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Dong, Shanmu; Chen, Xiao [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Gu, Lin [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 9808577 (Japan); Zhou, Xinhong [Qingdao University of Science and Technology, Qingdao 266101 (China); Wang, Haibo; Liu, Zhihong; Han, Pengxian; Yao, Jianhua; Wang, Li [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Cui, Guanglei, E-mail: cuigl@qibebt.ac.cn [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Chen, Liquan [Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao 266101 (China); Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

2011-06-15

Research highlights: {yields} Vanadium and titanium nitride nanocomposite with core-shell structure was prepared. {yields} TiN/VN composites with different V:Ti molar ratios were obtained. {yields} TiN/VN composites can provide promising electronic conductivity and favorable capacity storage. -- Abstract: TiN/VN core-shell composites are prepared by a two-step strategy involving coating of commercial TiN nanoparticles with V{sub 2}O{sub 5}.nH{sub 2}O sols followed by ammonia reduction. The highest specific capacitance of 170 F g{sup -1} is obtained when scanned at 2 mV s{sup -1} and a promising rate capacity performance is maintained at higher voltage sweep rates. These results indicate that these composites with good electronic conductivity can deliver a favorable capacity performance.

Preparation and mechanical properties of in situ TiC{sub x}–Ni (Si, Ti) alloy composites

Energy Technology Data Exchange (ETDEWEB)

Wang, Wenjuan [Institute of Materials Science and Engineering, School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044 (China); Zhai, Hongxiang, E-mail: hxzhai@sina.com [Institute of Materials Science and Engineering, School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044 (China); Chen, Lin; Huang, Zhenying [Institute of Materials Science and Engineering, School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044 (China); Bei, Guoping; Baumgärtner, Christoph; Greil, Peter [Department of Materials Science (Glass and Ceramics), University of Erlangen-Nuernberg, Martensstr. 5, 91058 Erlangen (Germany)

2014-10-20

Novel in situ TiC{sub x} reinforced Ni (Si, Ti) alloy composites with superior mechanical properties were prepared at 1250 °C for 30 min by pressureless sintering Ti{sub 3}SiC{sub 2} (10 and 20 vol%) and Ni as precursors. The Ti{sub 3}SiC{sub 2} particles decomposed into substoichiometric TiC{sub x} phase, while the additional Si and partial Ti atoms derived from Ti{sub 3}SiC{sub 2} diffused into Ni matrix to form Ni (Si, Ti) alloy. The in situ formed TiC{sub x} phases are mainly dispersed on the grain boundaries of the Ni (Si, Ti) alloying, forming a strong skeleton and refining the microstructures of the metal matrix. The hardness, the yield stress σ{sub 0.2%} and ultimate compressive strength of 20.6 vol%TiC{sub x}–Ni(Si, Ti) composite can reach 2.15±0.04 GPa, 466.8±55.8 MPa and 733.3±78.4 MPa, respectively. The enhanced mechanical properties of TiC{sub x}–Ni(Si, Ti) composites are due to the in situ formation of TiC{sub x} skeleton, the refined microstructures of Ni (Si, Ti) alloys and solid solution effects as well as good wettability between TiC{sub x} and Ni (Si, Ti) matrix.

Manufacture and properties of AlON-TiN particulate composites

Energy Technology Data Exchange (ETDEWEB)

Zhang Zuotai; Wang Xidong; Zhang Mei; Li Wenchao [Dept. of Physical Chemistry of Metallurgy, Univ. of Science and Technology, Beijing, BJ (China)

2005-07-01

Dense aluminum oxynitride-titanium nitride (AlON-TiN) composites with 3{proportional_to}15 wt% TiN were fabricated by hot pressing technique. The effect of the content of a dispersion-toughening aid, TiN, on the mechanical properties, oxidation resistance and wear resistance were studied and related to the microstructure. The composites with a content of 15 wt% were characterized with the highest strength, 487 MPa, and the highest wear resistance properties. Oxidation behavior was studied and the results showed that AlON-TiN composites have excellent oxidation resistance. (orig.)

Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding

Science.gov (United States)

Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

2010-11-01

A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and 800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

Effect of Zirconium Addition on Microstructure and Mechanical Property of TiC/Ti6A14V Composites

Science.gov (United States)

Ma, Xuliang; Wang, Xiang; Li, Li; Gai, Pengtao; Zhu, Chengwu

TiC/Ti6A14V composites with different Zr additions were prepared successfully in a consumable vacuum arc furnace equipped with a water-cooled copper crucible and the effect of the Zr content on the microstructure and mechanical property of 15 vol.%TiC/Ti6A14V composites was investigated by XRD, SEM and hardness testing. The results show that when the level of Zr addition is less than 4 wt.%, the morphology of the primary TiC in the composites is dendrite, and the petal-shape, piece-shape or palpus-shape eutectic TiC separates out around the primary TiC. The average size of the primary TiC decreases and the amount of eutectic TiC increases gradually with increasing Zr content. The effects of Zr on morphology of the primary TiC weaken with further addition of Zr. And the hardness (HRC) of composites was obviously increased in the whole range of Zr addition. The refinement mechanism of Zr was attributed to the combined effects of increase in nucleation rate at the constitutionally supercooled zone ahead of the solidification front and reduction in growth rate.

Laser fabrication of Ti6Al4V/TiC composites using simultaneous powder and wire feed

International Nuclear Information System (INIS)

Wang, F.; Mei, J.; Jiang, H.; Wu, X.

2007-01-01

Composites of Ti-6Al-4V containing different volume fractions of TiC were manufactured using direct laser fabrication. Ti-6Al-4V wire and TiC powder were fed into the laser with the rate of powder feed being changed so that samples containing different volume fractions of TiC could be manufactured. Optical microscopy, scanning electron and transmission electron microscopy were used to characterise the microstructure of these samples. The room temperature tensile properties were measured also on some selected compositions together with their Young's moduli. In addition the change in wear resistance was studied as a function of TiC volume fraction using a standard wear test. These observations are discussed in terms of the advantages and difficulties of using simultaneous wire and powder feed systems and in terms of the value of this approach in obtaining data over a wide range of compositions for such a composite

Phase Constituents and Microstructure of Ti3Al/Fe3Al + TiN/TiB2 Composite Coating on Titanium Alloy

Science.gov (United States)

Li, Jianing; Chen, Chuanzhong; Zhang, Cuifang

Laser cladding of the Fe3Al + B4C/TiN + Al2O3 pre-placed powders on the Ti-6Al-4V alloy can form the Ti3Al/Fe3Al + TiN/TiB2 composite coating, which improved the wear resistance of the Ti-6Al-4V alloy surface. In this study, the Ti3Al/Fe3Al + TiN/TiB2 composite coating has been researched by means of X-ray diffraction and scanning electron microscope. It was found that during the laser cladding process, Al2O3 can react with TiB2, leading to the formations of Ti3Al and B. This principle can be used to improve the Fe3Al + B4C/TiN laser-cladded coating on the Ti-6Al-4V alloy. Furthermore, during the cladding process, C consumed the oxygen in Fe3Al + B4C /TiN + Al2O3 molten pool, which retarded the productions of the redundant metal oxides.

Study of the preparation of Cu-TiC composites by reaction of soluble Ti and ball-milled carbon coating TiC

Science.gov (United States)

Xu, Xuexia; Li, Wenbin; Wang, Yong; Dong, Guozhen; Jing, Shangqian; Wang, Qing; Feng, Yanting; Fan, Xiaoliang; Ding, Haimin

2018-06-01

In this work, Cu-TiC composites have been successfully prepared by reaction of soluble Ti and carbon coating TiC. Firstly, the ball milling of graphite and TiC mixtures is used to obtain the carbon coating TiC which has fine size and improved reaction activity. After adding the ball milled carbon coating TiC into Cu-Ti melts, the soluble Ti will easily react with the carbon coating to form TiC. This process will also improve the wettability between Cu melts and TiC core. As a result, besides the TiC prepared by reaction of soluble Ti and carbon coating, the ball milled TiC will also be brought into the melts. Some of these ball-milled TiC particles will go on being coated by the formed TiC from the reaction of Ti and the coating carbon and left behind in the composites. However, most of TiC core will be further reacted with the excessive Ti and be transformed into the newly formed TiC with different stoichiometry. The results indicate that it is a feasible method to synthesize TiC in Cu melts by reaction of soluble Ti and ball-milled carbon coating TiC.

The corrosion behavior of CVI SiC matrix in SiC{sub f}/SiC composites under molten fluoride salt environment

Energy Technology Data Exchange (ETDEWEB)

Wang, Hongda [Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); School of Graduate, University of Chinese Academy of Sciences, Beijing 100049 (China); Feng, Qian [Analysis and Testing Center, Donghua University, Shanghai 201600 (China); Wang, Zhen, E-mail: jeff@mail.sic.ac.cn [Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhou, Haijun; Kan, Yanmei; Hu, Jianbao [Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Dong, Shaoming, E-mail: smdong@mail.sic.ac.cn [Structural Ceramics and Composites Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

2017-04-15

High temperature corrosion behavior and microstructural evolution of designed chemical-vapor-infiltrated SiC matrix in SiC fiber reinforced SiC ceramic matrix composites in 46.5LiF-11.5NaF-42.0KF (mol. %) eutectic salt at 800 °C for various corrosion time was studied. Worse damage was observed as extending the exposure time, with the mass loss ratio increasing from 0.716 wt. % for 50 h to 5.914 wt. % for 500 h. The mass loss rate showed a trend of first decrease and then increase with the extended corrosion exposure. Compared with the near-stoichiometric SiC matrix layers, the O-contained boundaries between deposited matrix layers and the designed Si-rich SiC matrix layers were much less corrosion resistant and preferentially corroded. Liner relationship between the mass loss ratio and the corrosion time obtained from 50 h to 300 h indicated that the corrosion action was reaction-control process. Further corrosion would lead to matrix layer exfoliation and higher mass loss ratio.

Ammonia Sensing Behaviors of TiO2-PANI/PA6 Composite Nanofibers

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Fenglin Huang

2012-12-01

Full Text Available Titanium dioxide-polyaniline/polyamide 6 (TiO2-PANI/PA6 composite nanofibers were prepared by in situ polymerization of aniline in the presence of PA6 nanofibers and a sputtering-deposition process with a high purity titanium sputtering target. TiO2-PANI/PA6 composite nanofibers and PANI/PA6 composite nanofibers were fabricated for ammonia gas sensing. The ammonia sensing behaviors of the sensors were examined at room temperature. All the results indicated that the ammonia sensing property of TiO2-PANI/PA6 composite nanofibers was superior to that of PANI/PA6 composite nanofibers. TiO2-PANI/PA6 composite nanofibers had good selectivity to ammonia. It was also found that the content of TiO2 had a great influence on both the morphology and the sensing property of TiO2-PANI/PA6 composite nanofibers.

Trace element determination in presolar SiC grains by synchrotron x-ray fluorescence: Commencement of a coordinated multimethod study

International Nuclear Information System (INIS)

Knight, K.B.; Sutton, S.R.; Newville, M.; Davis, A.M.; Dauphas, N.; Lewis, R.S.; Amari, S.; Steele, I.M.; Savina, M.R.; Pellin, M.J.

2008-01-01

We determined trace element compositions of individual ∼1-3 ?m presolar SiC grains from 6 KJG grains and 26 additionally cleaned KJG grains from the Murchison CM chondrite using nondestructive synchrotron X-ray fluorescence (SXRF). Presolar SiC grains are robust remnants of stellar matter ejected from stars. They survived processing in the early solar system and retain the nucleosynthetic fingerprints of their stellar progenitors. As such, they represent unique physical probes of the interiors of stars. Presolar SiC grains are commonly analyzed by mass spectrometric techniques that determine isotopic compositions and, to some degree, elemental concentrations. These techniques, however, are destructive, and can be subject to matrix effects. Elemental composition data on presolar grains remain scarce and affected by contamination and analytical artifacts. In addition, contamination has plagued isotopic characterization of some elements such as Mo and Ba. We determined trace element compositions of individual ∼1-3 (micro)m presolar SiC grains from the Murchison CM chondrite using nondestructive synchrotron X-ray fluorescence (SXRF). Samples included the KJG fraction, and a second KJG fraction that underwent additional cleaning. As every cleaning step results in some grain loss, one goal of this study was to justify additional cleaning of grains. Six KJG grains and 26 additionally cleaned KJG grains were analyzed, with location and identities of individual grains noted for future correlated isotopic study.

Development of SiC Nanoparticles and Second Phases Synergistically Reinforced Mg-Based Composites Processed by Multi-Pass Forging with Varying Temperatures

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Kaibo Nie

2018-01-01

Full Text Available In this study, SiC nanoparticles were added into matrix alloy through a combination of semisolid stirring and ultrasonic vibration while dynamic precipitation of second phases was obtained through multi-pass forging with varying temperatures. During single-pass forging of the present composite, as the deformation temperature increased, the extent of recrystallization increased, and grains were refined due to the inhibition effect of the increasing amount of dispersed SiC nanoparticles. A small amount of twins within the SiC nanoparticle dense zone could be found while the precipitated phases of Mg17Al12 in long strips and deformation bands with high density dislocations were formed in the particle sparse zone after single-pass forging at 350 °C. This indicated that the particle sparse zone was mainly deformed by dislocation slip while the nanoparticle dense zone may have been deformed by twinning. The yield strength and ultimate tensile strength of the composites were gradually enhanced through increasing the single-pass forging temperature from 300 °C to 400 °C, which demonstrated that initial high forging temperature contributed to the improvement of the mechanical properties. During multi-pass forging with varying temperatures, the grain size of the composite was gradually decreased while the grain size distribution tended to be uniform with reducing the deformation temperature and extending the forging passes. In addition, the amount of precipitated second phases was significantly increased compared with that after multi-pass forging under a constant temperature. The improvement in the yield strength of the developed composite was related to grain refinement strengthening and Orowan strengthening resulting from synergistical effect of the externally applied SiC nanoparticles and internally precipitated second phases.

Self-ignition combustion synthesis of TiFe in hydrogen atmosphere

Energy Technology Data Exchange (ETDEWEB)

Wakabayashi, R. [Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan)], E-mail: ryuta@eng.hokudai.ac.jp; Sasaki, S. [Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan); Saita, I. [National Institute of Advanced Industrial Science and Technology (AIST), AIST Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan); Sato, M. [Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan); Uesugi, H. [Bio Coke Lab., Ltd., 5-34-20 Hirato, Totsuka-ku, Yokohama, Kanagawa 244-0802 (Japan); Akiyama, T. [Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan)

2009-07-08

This paper describes the self-ignition combustion synthesis (SICS) of highly active titanium iron (TiFe) in a high-pressure hydrogen atmosphere without employing an activation process. In the experiments, well-mixed powders of Ti and Fe in the molar ratio of 1:1 were uniformly heated up to 1085 deg. C, the eutectic temperature of Ti-Fe binary system, in pressurized hydrogen at 0.9 MPa. The electric source was disconnected immediately after the ignition between Ti and Fe, and the mixture was cooled naturally. In this study, the exothermic reaction Ti + Fe = TiFe + 40 kJ occurred at around 1085 deg. C after the hydrogenation and decomposition of Ti. X-ray diffraction analysis showed that the final product had only one phase-TiFeH{sub 0.06}-which can store hydrogen of 1.55 mass% under hydrogen pressure of 4 MPa. The product obtained by SICS contained considerably more hydrogen quickly as compared to the commercially available product; this fact can be explained by the porous structure of the obtained product, which was observed using a scanning electron microscope. In conclusion, the SICS of TiFe saved time and energy, yields products with high porosity and small crystals, enabled easy hydrogenation, and did not require activation processes.

Characteristics and in vitro biological assessment of (Ti, O, N)/Ti composite coating formed on NiTi shape memory alloy

International Nuclear Information System (INIS)

Sun Tao; Wang Langping; Wang Min; Tong, Ho-Wang; Lu, William W.

2011-01-01

In this investigation, plasma immersion ion implantation and deposition (PIIID) was used to fabricate a (Ti, O, N)/Ti coating on NiTi shape memory alloy (SMA) to improve its long-term biocompatibility and wear resistance. The surface morphology, composition and roughness of uncoated and coated NiTi SMA samples were examined. Energy dispersive X-ray elemental mapping of cross-sections of (Ti, O, N)/Ti coated NiTi SMA revealed that Ni was depleted from the surface of coated samples. No Ni was detected by X-ray photoelectron spectroscopy on the surface of coated samples. Furthermore, three-point bending tests showed that the composite coating could undergo large deformation without cracking or delamination. After 1 day cell culture, SaOS-2 cells on coated samples spread better than those on uncoated NiTi SMA samples. The proliferation of SaOS-2 cells on coated samples was significantly higher at day 3 and day 7 of cell culture.

Compositionally graded Ti6Al4V + TiC made by direct laser fabrication using powder and wire

International Nuclear Information System (INIS)

Wang, F.; Mei, J.; Wu Xinhua

2007-01-01

Ti6Al4V reinforced with TiC has been fabricated as compositionally graded material by direct laser fabrication using TiC powder and Ti6Al4V wire which were fed simultaneously into the laser focal point. The microstructure along the length of the sample has been characterised using X-ray diffraction and scanning electron microscopy. The results show that the composition along the length changes as expected from the imposed changes in feed rate when allowance is made for the different capture efficiency for the powder and the wire. Some unmelted TiC has been observed in regions where the TiC fraction was high, but along most of the length of the samples TiC was completely melted and formed primary TiC, eutectic TiC and secondary TiC. Some preliminary tribological properties of the compositionally graded material were obtained using a sliding wear test which showed that the tribological properties of Ti6Al4V are improved by the reinforced TiC particles with the optimum frictional behaviour being found with approximately 24 vol% of TiC

Fabrication of steel matrix composites locally reinforced with different ratios of TiC/TiB2 particulates using SHS reactions of Ni-Ti-B4C and Ni-Ti-B4C-C systems during casting

International Nuclear Information System (INIS)

Yang Yafeng; Wang Huiyuan; Liang Yunhong; Zhao Ruyi; Jiang Qichuan

2007-01-01

Steel matrix composites locally reinforced with different molar ratios of in situ TiC/TiB 2 particulates (2:1, 1:1 and 1:2, respectively) have been fabricated successfully utilizing the self-propagating high-temperature synthesis (SHS) reactions of Ni-Ti-B 4 C and Ni-Ti-B 4 C-C systems during casting. Differential thermal analysis (DTA) and X-ray diffraction (XRD) results reveal that the exothermic reactions of the Ni-Ti-B 4 C and Ni-Ti-B 4 C-C systems proceed in such a way that Ni initially reacts with B 4 C and Ti to form Ni 2 B and Ti 2 Ni compounds, respectively, with heat evolution at 1037 deg. C; Subsequently, the external heat and the evolved heat from these exothermic reactions promote the reactions forming TiC and TiB 2 at 1133 deg. C. In the composites reinforced with 1:2 molar ratio of TiC/TiB 2 , almost all TiB 2 grains have clubbed structures, while TiC grains exhibit near-spherical morphologies. Furthermore, TiB 2 grain sizes decrease, with the increase of TiC content. In particular, in the composites reinforced with 2:1 molar ratio of TiC/TiB 2 , it is difficult to find the clubbed TiB 2 grains. Macro-pores and blowholes are absent in the local reinforcing region of the composites reinforced with 1:1 and 1:2 molar ratios of TiC/TiB 2 , while a few macro-pores can be observed in the composite reinforced with 2:1 molar ratio of TiC/TiB 2 . Moreover, the densities of the composites reinforced with 1:1 and 1:2 molar ratios of TiC/TiB 2 are higher than that of the composite reinforced with 2:1 molar ratio of TiC/TiB 2 . The composite reinforced with 1:2 molar ratio of TiC/TiB 2 has the highest hardness and the best wear resistance

Microstructure and high temperature oxidation resistance of in-situ synthesized TiN/Ti_3Al intermetallic composite coatings on Ti6Al4V alloy by laser cladding process

International Nuclear Information System (INIS)

Liu, Hongxi; Zhang, Xiaowei; Jiang, Yehua; Zhou, Rong

2016-01-01

High temperature anti-oxidation TiN/Ti_3Al intermetallic composite coatings were fabricated with the powder and AlN powder on Ti6Al4V titanium alloy surface by 6 kW transverse-flow CO_2 laser apparatus. The chemical composition, morphology and microstructure of the TiN/Ti_3Al composite coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high temperature oxidation resistance of TiN/Ti_3Al coating, the isothermal oxidation test was performed in a high temperature resistance furnace at 600 °C and 800 °C, respectively. The result shows that the composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like or dendrites), with an even distribution in Ti_3Al matrix. It indicates that a physical and chemical reaction between Ti powder and AlN powder has completely occurred under the laser irradiation condition. In addition, the microhardness of the TiN/Ti3Al intermetallic composite coating is 3.4 times higher than that of the Ti6Al4V alloy substrate and reaches 844 HV_0_._2. The high temperature oxidation behavior test reveals that the high temperature oxidation resistance of TiN/Ti_3Al composite coating is much better than that of titanium alloy substrate. The excellent high temperature oxidation resistance of TiN/Ti_3Al intermetallic composite coating is attributed to the formation of reinforced phases TiN, Al_2O_3 and TiO_2. The laser cladding TiN/Ti_3Al intermetallic composite coating is anticipated to be a promising high temperature oxidation resistance coating for Ti6Al4V alloy. - Highlights: • In-situ TiN/Ti_3Al composite coating was synthesized on Ti6Al4V alloy by laser cladding. • The influence of Ti and AlN molar ratio on the microstructure of the coating was studied. • The TiN/Ti_3Al intermetallic coating is mainly composed of α-Ti, TiN and Ti_3Al phases. • The

Microstructure and Properties of (TiB2 + NiTi)/Ti Composite Coating Fabricated by Laser Cladding

Science.gov (United States)

Lin, Yinghua; Lei, Yongping; Fu, Hanguang; Lin, Jian

2015-10-01

Agglomerated TiB2 particle and network-like structure-reinforced titanium matrix composite coatings were prepared by laser cladding of the Ni + TiB2 + Ti preplaced powders on Ti-6Al-4V alloy. The network-like structure mainly consisted of NiTi and Ni3Ti. Through the experiment, it was found that the size of agglomerated particle gradually decreased with the increase of Ti content, but the number of the network-like structure first increased and then disappeared. In-situ reaction competition mechanism and the formation of network-like structure were discussed. The average micro-hardness gradually decreased with the increase of Ti content, but the average fracture toughness gradually increased. Meanwhile, the wear resistance of the coatings is higher than that of the substrate, but the wear loss of the coatings is gradually increased with the increase of Ti content.

Microstructure and mechanical properties of in situ TiC and Nd2O3 particles reinforced Ti-4.5 wt.%Si alloy composites

International Nuclear Information System (INIS)

Zhang, Xinjiang; Li, Yibin; Song, Guangping; Sun, Yue; Peng, Qingyu; Li, Yuxin; He, Xiaodong

2011-01-01

Highlights: → (TiC + Nd 2 O 3 )/Ti-4.5 wt.%Si composites were in situ synthesized. → The phase components and microstructures of the composites were investigated. → In situ reinforcements improve the mechanical properties of the matrix alloy. -- Abstract: (TiC + Nd 2 O 3 )/Ti-4.5 wt.%Si composites were in situ synthesized by a non-consumable arc-melting technology. The phases in the composites were identified by X-ray diffraction. Microstructures of the composites were observed by optical microscope and scanning electron microscope. The composite contains four phases: TiC, Nd 2 O 3 , Ti 5 Si 3 and Ti. The TiC and Nd 2 O 3 particles with dendritic and near-equiaxed shapes are well distributed in Ti-4.5 wt.%Si alloy matrix, and the fine Nd 2 O 3 particles exist in the network Ti + Ti 5 Si 3 eutectic cells and Ti matrix of the composites. The hardness and compressive strength of the composites are markedly higher than that of Ti-4.5 wt.%Si alloy. When the TiC content is fixed as 10 wt.% in the composites, the hardness is enhanced as the Nd 2 O 3 content increases from 8 wt.% to 13 wt.%, but the compressive strength peaks at the Nd 2 O 3 content of 8 wt.%.

Microstructure and mechanical properties of in situ casting TiC/Ti6Al4V composites through adding multi-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Ya, Bin; Zhou, Bingwen; Yang, Hongshuo; Huang, Bingkun; Jia, Fei; Zhang, Xingguo, E-mail: zxgwj@dlut.edu.cn

2015-07-15

Highlights: • Adding MWCNTs in situ casting fabricating TiC/Ti6Al4V composites is first reported. • The solidification process of in situ casting TiC/Ti6Al4V composites is discussed. • Microstructure shows remarkable correlations with adding MWCNTS. • Strength and plasticity show remarkable correlations with adding MWCNTs. - Abstract: In this study, multi-walled carbon nanotubes (MWCNTs) were added as carbon sources to fabricate in situ casting TiC/Ti6Al4V (TC4) composites. The effects of MWCNTs on the microstructure and mechanical properties are studied. The composites are analyzed by X-ray diffraction, field-emission scanning electron microscope and electron probe microanalysis. The fracture behavior of TiC/TC4 composites are also studied. Smaller size of TiC particles and grain compared with TC4-graphite composites can be observed. The tensile strength of TC4-MWCNTs composites is about 1110.1 MPa, which is higher than that of TC4-graphite composites, about 1003.6 MPa. Fracture behavior also was changed by adding MWCNTs in situ casting TiC/TC4 composites.

Synthesis and Characterization of MAX Ceramics (MAXCERs)

Science.gov (United States)

Nelson, Johnny Carl

This research has focused on the design and development of novel multifunctional MAX reinforced ceramics (MAXCERs). These MAXCERs were manufactured with 1-50 vol% ratios of ceramics to MAX phases. Chapter II reports on the synthesis and tribological behavior of Ti3SiC2 matrix composites by incorporating (1 and 6 vol%) Al2O3, (1 and 5 vol%) BN, and (1 and 5 vol%) B4C ceramic particulate additives in the matrix. All the composites were fabricated by pressureless sintering by using 1 wt% Ni as a sintering agent at 1550 °C for 2 hours. SEM and XRD studies showed that Al2O3 is relatively inert in the Ti3SiC 2 matrix whereas BN and B4C reacted significantly with the Ti3 SiC2 matrix to form TiB2. Detailed tribological studies showed that Ti3SiC2-1wt%Ni (baseline) samples showed dual type tribological behavior where the friction coefficient (micro) was low ( 0.2) during stage 1, thereafter micro increased sharply and transitioned into stage 2 ( 0.8). The addition of Al2O3 as an additive had little effect on the tribological behavior, but the addition of B4C and BN was able to enhance the tribological behavior by increasing the transition distance (TD). Chapter III reports on the synthesis and tribological behavior of TiB2 matrix composites by incorporating (10, 30, and 50 vol%) Ti3SiC2 ceramic particulate additives in the matrix. The fabrication parameters were similar to the Ti3SiC2 samples from Chapter II. There was minimal reaction between the TiB2 and the Ti3SiC2. Detailed tribological studies showed that TiB2 (baseline) and TiB2-10%Ti 3SiC2 samples showed an average micro of 0.29 and 0.28, respectively. TiB2-30%Ti3SiC2 and TiB 2-50%Ti3SiC2 showed dual-type tribological behavior where micro was low ( 0.25) during stage 1, thereafter micro increased gradually and transitioned into stage 2 ( 0.6). Low wear rates were seen for all samples.

Effect of clustering on the mechanical properties of SiC particulate-reinforced aluminum alloy 2024 metal matrix composites

International Nuclear Information System (INIS)

Hong, Soon-Jik; Kim, Hong-Moule; Huh, Dae; Suryanarayana, C.; Chun, Byong Sun

2003-01-01

Al 2024-SiC metal matrix composite (MMC) powders produced by centrifugal atomization were hot extruded to investigate the effect of clustering on their mechanical properties. Fracture toughness and tension tests were conducted on specimens reinforced with different volume fractions of SiC. A model was proposed to suggest that the strength of the MMCs could be estimated from the load transfer model approach that takes into consideration the extent of clustering. This model has been successful in predicting the experimentally observed strength and fracture toughness values of the Al 2024-SiC MMCs. On the basis of experimental observations, it is suggested that the strength of particulate-reinforced MMCs may be calculated from the relation: σ y =σ m V m +σ r (V r -V c )-σ r V c , where σ and V represent the yield strength and volume fraction, respectively, and the subscripts m, r, and c represent the matrix, reinforcement, and clusters, respectively

Microstructural studies and wear assessments of Ti/TiC surface composite coatings on commercial pure Ti produced by titanium cored wires and TIG process

Energy Technology Data Exchange (ETDEWEB)

Monfared, A., E-mail: amirmonfared25@yahoo.com [Department of Materials Science and Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Kokabi, A.H.; Asgari, S. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

2013-01-15

Tungsten Inert Gas (TIG) process and titanium cored wires filled with micro size TiC particles were employed to produce surface composite coatings on commercial pure Ti substrate for wear resistance improvement. Wire drawing process was utilized to produce several cored wires from titanium strips and titanium carbide powders. Subsequently, these cored wires were melted and coated on commercial pure Ti using TIG process. This procedure was repeated at different current intensities and welding travel speeds. Composite coating tracks were found to be affected by TIG heat input. The microstructural studies using optical and scanning electron microscopy supported by X-ray diffraction showed that the surface composite coatings consisted of {alpha} Prime -Ti, spherical and dendritic TiC particles. Also, greater volume fractions of TiC particles in the coatings were found at lower heat input. A maximum microhardness value of about 1100 HV was measured which is more than 7 times higher than the substrate material. Pin-on-disk wear tests exhibited a better performance of the surface composite coatings than the untreated material which was attributed to the presence of TiC particles in the microstructure. -- Highlights: Black-Right-Pointing-Pointer Ti/TiC composite coatings were produced on the CP-Ti. Black-Right-Pointing-Pointer Titanium cored wire and TIG process were employed for production of the coatings. Black-Right-Pointing-Pointer Decreasing heat input, increased the volume fraction of TiC in the coatings. Black-Right-Pointing-Pointer The maximum microhardness obtained in the lowest heat input. Black-Right-Pointing-Pointer The wear resistance of the coatings improved due to the formation of TiC particles.

Formation of Al3Ti/Mg composite by powder metallurgy of Mg–Al–Ti system

Directory of Open Access Journals (Sweden)

Zi R Yang et al

2008-01-01

Full Text Available An in situ titanium trialuminide (Al3Ti-particle-reinforced magnesium matrix composite has been successfully fabricated by the powder metallurgy of a Mg–Al–Ti system. The reaction processes and formation mechanism for synthesizing the composite were studied by differential scanning calorimetry (DSC, x-ray diffractometry (XRD, scanning electron microscopy (SEM and energy-dispersive x-ray spectroscopy (EDS. Al3Ti particles are found to be synthesized in situ in the Mg alloy matrix. During the reaction sintering of the Mg–Al–Ti system, Al3Ti particles are formed through the reaction of liquid Al with as-dissolved Ti around the Ti particles. The formed intermetallic particles accumulate at the original sites of the Ti particles. As sintering time increases, the accumulated intermetallic particles disperse and reach a relatively homogeneous distribution in the matrix. It is found that the reaction process of the Mg–Al–Ti system is almost the same as that of the Al–Ti system. Mg also acts as a catalytic agent and a diluent in the reactions and shifts the reactions of Al and Ti to lower temperatures. An additional amount of Al is required for eliminating residual Ti and solid-solution strengthening of the Mg matrix.

Formation of Al3Ti/Mg composite by powder metallurgy of Mg-Al-Ti system.

Science.gov (United States)

Yang, Zi R; Qi Wang, Shu; Cui, Xiang H; Zhao, Yu T; Gao, Ming J; Wei, Min X

2008-07-01

An in situ titanium trialuminide (Al 3 Ti)-particle-reinforced magnesium matrix composite has been successfully fabricated by the powder metallurgy of a Mg-Al-Ti system. The reaction processes and formation mechanism for synthesizing the composite were studied by differential scanning calorimetry (DSC), x-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Al 3 Ti particles are found to be synthesized in situ in the Mg alloy matrix. During the reaction sintering of the Mg-Al-Ti system, Al 3 Ti particles are formed through the reaction of liquid Al with as-dissolved Ti around the Ti particles. The formed intermetallic particles accumulate at the original sites of the Ti particles. As sintering time increases, the accumulated intermetallic particles disperse and reach a relatively homogeneous distribution in the matrix. It is found that the reaction process of the Mg-Al-Ti system is almost the same as that of the Al-Ti system. Mg also acts as a catalytic agent and a diluent in the reactions and shifts the reactions of Al and Ti to lower temperatures. An additional amount of Al is required for eliminating residual Ti and solid-solution strengthening of the Mg matrix.

Synthesis, Characterization, and NIR Reflectance of Highly Dispersed NiTiO3 and NiTiO3/TiO2 Composite Pigments

Directory of Open Access Journals (Sweden)

Yuping Tong

2016-01-01

Full Text Available The highly dispersed nanostructured NiTiO3 pigments and NiTiO3/TiO2 composite pigments can be synthesized at relative low temperature. The activation energy of crystal growth of NiTiO3 during calcinations via salt-assistant combustion method is 9.35 kJ/mol. The UV-vis spectra results revealed that the absorbance decreased with the increasing of calcinations temperature due to small size effect of nanometer particles. The optical data of NiTiO3 nanocrystals were analyzed at the near-absorption edge. SEM showed that the obtained NiTiO3 nanocrystals and NiTiO3/TiO2 nanocomposite were composed of highly dispersed spherical-like and spherical particles with uniform size distribution, respectively. The chromatic properties and diffuse reflectance of samples were investigated. The obtained NiTiO3/TiO2 composite samples have higher NIR reflectance than NiTiO3 pigments.

Effect of Pressurizing during Compaction and Sintering on the Formation of Reaction-Bonded SiC–Ti{sub 3}SiC{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Kim, Sun-Han; Jung, Yang-Il; Rhee, Young-Woo; Park, Dong-Jun; Park, Jung-Hwan; Park, Jeong-Yong; Kim, Hyun-Gil; Koo, Yang-Hyun [LWR Fuel Technology Division, KAERI, Daejeon (Korea, Republic of)

2016-05-15

A reaction-bonded SiC-Ti{sub 3}SiC{sub 2} ceramic composite was produced for use in a ceramic-metal composite cladding tube. The diffusion reaction between TiC and Si was investigated with respect to process pressure. The mole-fraction of TiC and Si was controlled to be 3:2 to obtain a Ti{sub 3}SiC{sub 2} phase in the ceramic composite. Sintering was conducted at 1450 °C where TiC particles could react with melted Si. SiC ceramic composites consisting of Ti{sub 3}SiC{sub 2} and TiSi{sub 2} matrix phases were obtained. The formation of the constituent phases was strongly related to the processing pressure. The number of second phases in the SiC-Ti{sub 3}SiC{sub 2} composite was controlled by adjusting the processing pressure. When the powder compacts were not pressurized, no Ti{sub 3}SiC{sub 2} phase was formed. However, the Ti{sub 3}SiC{sub 2} phase was formed under pressurizing during compaction and/or sintering. The higher the pressure the higher the purity of SiC-Ti{sub 3}SiC{sub 2}. The dual-phased SiC-Ti{sub 3}SiC{sub 2} composite, however, revealed the decreased resistance to high-temperature oxidation. It is suggested that the incorporation of TiSi{sub 2} in the composite increases the oxidation resistance as well as mechanical property.

Enhanced properties of nanostructured TiO2-graphene composites by rapid sintering

Science.gov (United States)

Shon, In-Jin; Yoon, Jin-Kook; Hong, Kyung-Tae

2018-01-01

Despite of many attractive properties of TiO2, the drawback of TiO2 ceramic is low fracture toughness for widely industrial application. The method to improve the fracture toughness and hardness has been reported by addition of reinforcing phase to fabricate a nanostructured composite. In this regard, graphene has been evaluated as an ideal second phase in ceramics. Nearly full density of nanostructured TiO2-graphene composite was achieved within one min using pulsed current activated sintering. The effect of graphene on microstructure, fracture toughness and hardness of TiO2-graphene composite was evaluated using Vickers hardness tester and field emission scanning electron microscopy. The grain size of TiO2 in the TiO2-x vol% (x = 0, 1, 3, and 5) graphene composite was greatly reduced with increase in addition of graphene. Both hardness and fracture toughness of TiO2-graphene composites simultaneously increased in the addition of graphene.

Nondestructive evaluation of ceramic and metal matrix composites for NASA's HITEMP and enabling propulsion materials programs

Science.gov (United States)

Generazio, Edward R.

1992-01-01

In a preliminary study, ultrasonic, x-ray opaque, and fluorescent dye penetrants techniques were used to evaluate and characterize ceramic and metal matrix composites. Techniques are highlighted for identifying porosity, fiber alignment, fiber uniformity, matrix cracks, fiber fractures, unbonds or disbonds between laminae, and fiber-to-matrix bond variations. The nondestructive evaluations (NDE) were performed during processing and after thermomechanical testing. Specific examples are given for Si3N4/SiC (SCS-6 fiber), FeCrAlY/Al2O3 fibers, Ti-15-3/SiC (SCS-6 fiber) materials, and Si3N4/SiC (SCS-6 fiber) actively cooled panel components. Results of this study indicate that the choice of the NDE tools to be used can be optimized to yield a faithful and accurate evaluation of advanced composites.

Synthesis and processing of nanostructured BN and BN/Ti composites

Science.gov (United States)

Horvath, Robert Steven

Superhard materials, such as cubic-BN, are widely used in machine tools, grinding wheels, and abrasives. Low density combined with high hardness makes c-BN and its composites attractive candidate materials for personnel and vehicular armor. However, improvements in toughness, and ballistic-impact performance, are needed to meet anticipated performance requirements. To achieve such improvements, we have targeted for development nanostructured c-BN, and its composites with Ti. Current research utilizes an experimental high pressure/high temperature (HPHT) method to produce these materials on a laboratory scale. Results from this work should transfer well into the industrial arena, utilizing high-tonnage presses used in the production of synthetic diamond and c-BN. Progress has been made in: (1) HPHT synthesis of cBN powder using Mg as catalyst; (2) HPHT consolidation of cBN powder to produce nanostructured cBN; (3) reactive-HPHT consolidation of mixed cBN/Ti powder to produce nanostructured Ti- or TiB2/TiN-bonded cBN; and (4) reactive-HPHT consolidation of mixed hBN/Ti powder to produce nanostructured Ti-bonded TiB2/TiN or TiB2/TiN. Even so, much remains to be done to lay a firm scientific foundation to enable the reproducible fabrication of large-area panels for armor applications. To this end, Rutgers has formed a partnership with a major producer of hard and superhard materials. The ability to produce hard and superhard nanostructured composites by reacting cBN or hBN with Ti under high pressure also enables multi-layered structures to be developed. Such structures may be designed to satisfy impedance-mismatch requirements for high performance armor, and possibly provide a multi-hit capability. A demonstration has been made of reactive-HPHT processing of multi-layered composites, consisting of alternating layers of superhard Ti-bonded cBN and tough Ti. It is noteworthy that the pressure requirements for processing Ti-bonded cBN, Ti-bonded TiB2/TiN, and their

Effect of consolidation techniques on the properties of Al matrix composite reinforced with nano Ni-coated SiC

Science.gov (United States)

Abolkassem, Shimaa A.; Elkady, Omayma A.; Elsayed, Ayman H.; Hussein, Walaa A.; Yehya, Hosam M.

2018-06-01

Al /Ni-SiC composite was prepared via powder metallurgy technique. SiC particles were coated with 10 wt% nano nickel by electroless deposition, then mixed by three percents (5, 10 and 15 wt%) with Al powder in a ball mill using 10:1 ball to powder ratio for 5 h. Three types of sintering techniques were used to prepare the composite. Uniaxial cold compacted samples were sintered in a vacuum furnace at 600 °C for 1 h. The second group was the vacuum sintered samples which were post-processed by hot isostatic press (HIP) at 600 °C for 1hr under the pressure of 190 MPa. The third group was the hot pressed samples that were consolidated at 550 °C under the uniaxial pressure of 840 MPa. The results showed that the hot pressed samples have the highest densification values (97-100%), followed by the HIP samples (94-98%), then come the vacuum sintered ones (92-96%). X-ray diffraction analysis (XRD) indicated the presence of Al and Al3Ni, which means that all SiC particles were encapsulated with nickel as short peaks for SiC were observed. Hardness results revealed that HIP samples have the highest hardness values. The magnetization properties were improved by increasing SiC/Ni percent, and HIP samples showed the highest magnetization parameter values.

Structure and mechanical properties of Ti-Si-C coatings deposited by magnetron sputtering

International Nuclear Information System (INIS)

Koutzaki, S.H.; Krzanowski, J.E.; Nainaparampril, J.J.

2001-01-01

Nanostructured coatings consisting of mixed carbide phases can provide a potential means to developing superhard coatings. Heterogeneous nanostructured coatings can be obtained by either deposition of multilayer structures or by depositing film compositions that undergo a natural phase separation due to thermodynamic immiscibility. In the present work, we have taken the latter approach, and deposited films by radio frequency cosputtering from dual carbide targets. We have examined a number of ternary carbide systems, and here we report the results obtained on Ti-Si-C films with a nominal (Ti 1-x Si x )C stoichiometry and with x≤0.31. It was found that the nanoindentation hardness increased with Si content, and the maximum hardness achieved was nearly twice that of sputter-deposited TiC. We further analyzed these films using high-resolution transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction. Since cubic SiC has an x-ray pattern almost identical to that of TiC, the extent of phase separation could not be determined by that method. However, XRD did demonstrate a general disordering of the films with increasing SiC content. In addition, a mottled structure was observed in high-resolution TEM images of the Si-containing films, confirming microstructural effects due to the Si additions

High-temperature fracture and fatigue resistance of a ductile β-TiNb reinforced γ-TiAl intermetallic composite

International Nuclear Information System (INIS)

Rao, K.T.V.; Ritchie, R.O.

1998-01-01

The high-temperature fatigue-crack propagation and fracture resistance of a model γ-TiAl intermetallic composite reinforced with 20 vol. % ductile β-TiNb particles is examined at elevated temperatures of 650 and 800 C and compared with behavior at room temperature. TiNb reinforcements are found to enhance the fracture toughness of γ-TiAl, even at high temperatures, from about 123 to ∼40 MPa m 1/2 , although their effectiveness is lower compared to room temperature due to the reduction in strength of TiNb particles. Under monotonic loading, crack-growth response in the composite is characterized by resistance-curve behavior arising from crack trapping, renucleation and resultant crack bridging effects attributable to the presence of TiNb particles. In addition, crack-tip blunting associated with plasticity increases the crack-initiation (matrix) toughness of the composite, particularly at 800 C, above the ductile-to-brittle transition temperature (DBTT) for γ-TiAl. High-temperature fatigue-crack growth resistance, however, is marginally degraded by the addition of TiNb particles in the C-R (edge) orientation, similar to observations made at room temperature; premature fatigue failure of TiNb ligaments in the crack wake diminishes the role of bridging under cyclic loading. Both fatigue and fracture resistance of the composite are slightly lower at 650 C (just below the DBTT for TiAl) compared to the behavior at ambient and 800 C. Overall, the beneficial effect of adding ductile TiNb reinforcements to enhance the room-temperature fracture and fatigue resistance of γ-TiAl alloys is retained up to 800 C, in air environments. There is concern, however, regarding the long-term environmental stability of these composite microstructures in unprotected atmospheres

Compressive performance and crack propagation in Al alloy/Ti{sub 2}AlC composites

Energy Technology Data Exchange (ETDEWEB)

Hanaor, D.A.H., E-mail: dorian.hanaor@sydney.edu.au [School of Civil Engineering, University of Sydney, Sydney, NSW 2006 (Australia); Hu, L. [Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011 (United States); Kan, W.H.; Proust, G. [School of Civil Engineering, University of Sydney, Sydney, NSW 2006 (Australia); Foley, M. [Australian Centre for Microscopy and Microanalysis, University of Sydney, Sydney, NSW 2006 (Australia); Karaman, I.; Radovic, M. [Department of Materials Science and Engineering, Texas A& M University, College Station, TX 77843 (United States)

2016-08-30

Composite materials comprising a porous Ti{sub 2}AlC matrix and Al 6061 alloy were fabricated by a current-activated pressure assisted melt infiltration process. Coarse, medium and fine meso-structures were prepared with Al alloy filled pores of differing sizes. Materials were subjected to uniaxial compressive loading up to stresses of 668 MPa, leading to the failure of specimens through crack propagation in both phases. As-fabricated and post-failure specimens were analysed by X-ray microscopy and electron microscopy. Quasi-static mechanical testing results revealed that compressive strength was the highest in the fine structured composite materials. While the coarse structured specimens exhibited a compressive strength of 80% relative to this. Reconstructed micro-scale X-ray tomography data revealed different crack propagation mechanisms. Large planar shear cracks propagated throughout the fine structured materials while the coarser specimens exhibited networks of branching cracks propagating preferentially along Al alloy-Ti{sub 2}AlC phase interfaces and through shrinkage pores in the Al alloy phase. Results suggest that control of porosity, compensation for Al alloy shrinkage and enhancement of the Al alloy-Ti{sub 2}AlC phase interfaces are key considerations in the design of high performance metal/Ti{sub 2}AlC phase composites.

Preparation of biomorphic SiC ceramic by carbothermal reduction of oak wood charcoal

International Nuclear Information System (INIS)

Qian Junmin; Wang Jiping; Jin Zhihao

2004-01-01

Highly porous silicon carbide (SiC) ceramic with woodlike microstructure has been prepared at 1400-1600 deg. C by carbothermal reduction reaction of charcoal/silica composites in static argon atmosphere. These composites were fabricated by infiltrating silica sol into a porous biocarbon template from oak wood using a vacuum/pressure infiltration process. The morphology of resulting porous SiC ceramic, as well as the conversion mechanism of wood to porous SiC ceramic, have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Experimental results show that the biomorphic cellular morphology of oak wood charcoal is remained in the porous SiC ceramic with high precision that consists of β-SiC with traces of α-SiC. Silica in the charcoal/silica composites exists in the cellular pores in form of fibers and rods. The SiC strut material is formed by gas-solid reaction between SiO (g) and C (s) during the charcoal-to-ceramic conversion. The densification of SiC strut material may occur at moderate temperatures and holding time

Preparation of biomorphic SiC ceramic by carbothermal reduction of oak wood charcoal

Energy Technology Data Exchange (ETDEWEB)

Qian Junmin; Wang Jiping; Jin Zhihao

2004-04-25

Highly porous silicon carbide (SiC) ceramic with woodlike microstructure has been prepared at 1400-1600 deg. C by carbothermal reduction reaction of charcoal/silica composites in static argon atmosphere. These composites were fabricated by infiltrating silica sol into a porous biocarbon template from oak wood using a vacuum/pressure infiltration process. The morphology of resulting porous SiC ceramic, as well as the conversion mechanism of wood to porous SiC ceramic, have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Experimental results show that the biomorphic cellular morphology of oak wood charcoal is remained in the porous SiC ceramic with high precision that consists of {beta}-SiC with traces of {alpha}-SiC. Silica in the charcoal/silica composites exists in the cellular pores in form of fibers and rods. The SiC strut material is formed by gas-solid reaction between SiO (g) and C (s) during the charcoal-to-ceramic conversion. The densification of SiC strut material may occur at moderate temperatures and holding time.

Fabrication of TiNi/CFRP smart composite using cold drawn TiNi wires

Science.gov (United States)

Xu, Ya; Otsuka, Kazuhiro; Toyama, Nobuyuki; Yoshida, Hitoshi; Jang, Byung-Koog; Nagai, Hideki; Oishi, Ryutaro; Kishi, Teruo

2002-07-01

In recent years, pre-strained TiNi shape memory alloys (SMA) have been used for fabricating smart structure with carbon fibers reinforced plastics (CFRP) in order to suppress microscopic mechanical damages. However, since the cure temperature of CFRP is higher than the reverse transformation temperatures of TiNi SMA, special fixture jigs have to be used for keeping the pre-strain during fabrication, which restricted its practical application. In order to overcome this difficulty, we developed a new method to fabricate SMA/CFRP smart composites without using special fixture jigs by controlling the transformation temperatures of SMA during fabrication. This method consists of using heavily cold-worked wires to increase the reverse transformation temperatures, and of using flash electrical heating of the wires after fabrication in order to decrease the reverse transformation temperatures to a lower temperature range again without damaging the epoxy resin around SMA wires. By choosing proper cold-working rate and composition of TiNi alloys, the reverse transformation temperatures were well controlled, and the TiNi/CFRP hybrid smart composite was fabricated without using special fixture jigs. The damage suppressing effect of cold drawn wires embedded in CFRP was confirmed.

Cu-TiB metal matrix composites prepared by powder metallurgy route

Directory of Open Access Journals (Sweden)

Guo Z.

2015-01-01

Full Text Available Titanium boride (TiB is characterized by good conductivity, high strength and high melting point. In this work, TiB was used to make Cu-TiB metal matrix composites (MMCs. Amounts of TiB added into Cu matrix were 2wt.%, 5wt.%, 10 wt.% and 15 wt.%. The samples were pressed at pressures of 500MPa, 600MPa, 700MPa and 800MPa and sintered at 820o and 920o, respectively. The properties of the sintered composites such as hardness and impact toughness were studied. Hardness and impact toughness of samples increased with increasing pressures and decreased with increasing contents of TiB. Composite with good mechanical properties and high conductivity was obtained from the sample containing 2wt.%TiB compacted at 800MPa and sintered at 920o. It was shown that 2wt.% TiB is a suitable content to make Cu-TiB MMCs with good mechanical properties and excellent conductivity.

Pressureless sintering of dense Si3N4 and Si3N4/SiC composites with nitrate additives

International Nuclear Information System (INIS)

Kim, J.Y.; Iseki, Takayoshi; Yano, Toyohiko

1996-01-01

The effect of aluminum and yttrium nitrate additives on the densification of monolithic Si 3 N 4 and a Si 3 N 4 /SiC composite by pressureless sintering was compared with that of oxide additives. The surfaces of Si 3 N 4 particles milled with aluminum and yttrium nitrates, which were added as methanol solutions, were coated with a different layer containing Al and Y from that of Si 3 N 4 particles milled with oxide additives. Monolithic Si 3 N 4 could be sintered to 94% of theoretical density (TD) at 1,500 C with nitrate additives. The sintering temperature was about 100 C lower than the case with oxide additives. After pressureless sintering at 1,750 C for 2 h in N 2 , the bulk density of a Si 3 N 4 /20 wt% SiC composite reached 95% TD with nitrate additives

Effect of nano-hydroxyapatite reinforcement in mechanically alloyed NiTi composites for biomedical implant

International Nuclear Information System (INIS)

Akmal, Muhammad; Raza, Ahmad; Khan, Muhammad Mudasser; Khan, M. Imran; Hussain, Muhammad Asif

2016-01-01

Equi-atomic NiTi alloy composites reinforced with 0, 2, 4 and 6 vol.% nano-hydroxyapatite (HA) were successfully synthesized using pressureless sintering. Pure Ni and Ti elements were ball milled for 10 h in order to produce a mechanically alloyed equi-atomic NiTi alloy (MA-NiTi). Mechanically alloyed NiTi and HA powders were blended, compacted and then sintered for 3 h at 1325 K. The sintered density varied inversely with volume percent of HA reinforcement. The X-Ray diffraction spectra and SEM images showed the formation of multiple phases like NiTi, NiTi 2 , Ni 3 Ti, and Ni 4 Ti 3 . The back scattered-SEM image analysis confirmed the presence of Ni-rich and Ti-rich phases with increasing HA content. The 6 vol.% HA reinforced composite showed Ni 3 Ti as the major phase having the highest hardness value which can be attributed to the presence of relatively harder phases along with higher HA content as a reinforcement. The composite of MA-NiTi with 2 vol.% HA manifested the most desirable results in the form of better sintering density mainly due to the minute decomposition of NiTi into other phases. Therefore, the 2 vol.% reinforced MA-NiTi composite can be exploited as a novel material for manufacturing biomedical implants. - Highlights: • NiTi-HA composites were synthesized using powder metallurgy route. • New phases such as NiTi 2 , Ni 3 Ti and Ni 4 Ti 3 were observed for sintered composites. • Mechanical properties enhanced with the increasing content of HA and new phases. • No martensitic transformation was observed for all composites by DSC analysis. • 2 vol.% HA composite is a novel candidate for biomedical implants.

Effect of nano-hydroxyapatite reinforcement in mechanically alloyed NiTi composites for biomedical implant

Energy Technology Data Exchange (ETDEWEB)

Akmal, Muhammad, E-mail: muhammad.akmal@giki.edu.pk [Faculty of Materials and Chemical Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640 (Pakistan); Raza, Ahmad, E-mail: ahmadrazac@yahoo.com [Faculty of Materials and Chemical Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640 (Pakistan); Khan, Muhammad Mudasser; Khan, M. Imran [Faculty of Materials and Chemical Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640 (Pakistan); Hussain, Muhammad Asif [Department of Chemical Engineering, Kangwon National University, Samcheok, 25913 (Korea, Republic of)

2016-11-01

Equi-atomic NiTi alloy composites reinforced with 0, 2, 4 and 6 vol.% nano-hydroxyapatite (HA) were successfully synthesized using pressureless sintering. Pure Ni and Ti elements were ball milled for 10 h in order to produce a mechanically alloyed equi-atomic NiTi alloy (MA-NiTi). Mechanically alloyed NiTi and HA powders were blended, compacted and then sintered for 3 h at 1325 K. The sintered density varied inversely with volume percent of HA reinforcement. The X-Ray diffraction spectra and SEM images showed the formation of multiple phases like NiTi, NiTi{sub 2}, Ni{sub 3}Ti, and Ni{sub 4}Ti{sub 3}. The back scattered-SEM image analysis confirmed the presence of Ni-rich and Ti-rich phases with increasing HA content. The 6 vol.% HA reinforced composite showed Ni{sub 3}Ti as the major phase having the highest hardness value which can be attributed to the presence of relatively harder phases along with higher HA content as a reinforcement. The composite of MA-NiTi with 2 vol.% HA manifested the most desirable results in the form of better sintering density mainly due to the minute decomposition of NiTi into other phases. Therefore, the 2 vol.% reinforced MA-NiTi composite can be exploited as a novel material for manufacturing biomedical implants. - Highlights: • NiTi-HA composites were synthesized using powder metallurgy route. • New phases such as NiTi{sub 2}, Ni{sub 3}Ti and Ni{sub 4}Ti{sub 3} were observed for sintered composites. • Mechanical properties enhanced with the increasing content of HA and new phases. • No martensitic transformation was observed for all composites by DSC analysis. • 2 vol.% HA composite is a novel candidate for biomedical implants.

Preparation and tribological properties of self-lubricating TiO2/graphite composite coating on Ti6Al4V alloy

International Nuclear Information System (INIS)

Mu, Ming; Zhou, Xinjian; Xiao, Qian; Liang, Jun; Huo, Xiaodi

2012-01-01

Highlights: ► A TiO 2 /graphite composite coating is produced on Ti alloy by one-step PEO process. ► The TiO 2 /graphite composite coating exhibits excellent self-lubricating behavior. ► The self-lubricating composite coating improves the wear resistance by comparison to the conventional PEO coating. - Abstract: One-step plasma electrolytic oxidation (PEO) process in a graphite-dispersed phosphate electrolyte was used to prepare a graphite-containing oxide composite coating on Ti6Al4V alloy. The composition and microstructure of the oxide coatings produced in the phosphate electrolytes with and without addition of graphite were analyzed by X-ray diffractometer (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The tribological properties of the uncoated Ti6Al4V alloy and oxide coatings were evaluated using a reciprocating ball-on-disk tribometer. Results showed that the graphite-containing oxide composite coating can be successfully produced on Ti6Al4V alloy in the graphite-dispersed phosphate electrolyte using PEO process. The graphite-containing oxide composite coating registered much lower friction coefficient and wear rate than the uncoated Ti6Al4V alloy and the oxide coating without graphite under dry sliding condition, exhibiting excellent self-lubricating property.

Microstructure and high temperature oxidation resistance of in-situ synthesized TiN/Ti{sub 3}Al intermetallic composite coatings on Ti6Al4V alloy by laser cladding process

Energy Technology Data Exchange (ETDEWEB)

Liu, Hongxi, E-mail: piiiliuhx@sina.com; Zhang, Xiaowei; Jiang, Yehua; Zhou, Rong

2016-06-15

High temperature anti-oxidation TiN/Ti{sub 3}Al intermetallic composite coatings were fabricated with the powder and AlN powder on Ti6Al4V titanium alloy surface by 6 kW transverse-flow CO{sub 2} laser apparatus. The chemical composition, morphology and microstructure of the TiN/Ti{sub 3}Al composite coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high temperature oxidation resistance of TiN/Ti{sub 3}Al coating, the isothermal oxidation test was performed in a high temperature resistance furnace at 600 °C and 800 °C, respectively. The result shows that the composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like or dendrites), with an even distribution in Ti{sub 3}Al matrix. It indicates that a physical and chemical reaction between Ti powder and AlN powder has completely occurred under the laser irradiation condition. In addition, the microhardness of the TiN/Ti3Al intermetallic composite coating is 3.4 times higher than that of the Ti6Al4V alloy substrate and reaches 844 HV{sub 0.2}. The high temperature oxidation behavior test reveals that the high temperature oxidation resistance of TiN/Ti{sub 3}Al composite coating is much better than that of titanium alloy substrate. The excellent high temperature oxidation resistance of TiN/Ti{sub 3}Al intermetallic composite coating is attributed to the formation of reinforced phases TiN, Al{sub 2}O{sub 3} and TiO{sub 2}. The laser cladding TiN/Ti{sub 3}Al intermetallic composite coating is anticipated to be a promising high temperature oxidation resistance coating for Ti6Al4V alloy. - Highlights: • In-situ TiN/Ti{sub 3}Al composite coating was synthesized on Ti6Al4V alloy by laser cladding. • The influence of Ti and AlN molar ratio on the microstructure of the coating was studied. • The TiN/Ti{sub 3}Al intermetallic

Optical Properties and Surface Morphology of Nano-composite PMMA: TiO2 Thin Films

International Nuclear Information System (INIS)

Lyly Nyl Ismail; Ahmad Fairoz Aziz; Habibah Zulkefle

2011-01-01

There are two nano-composite PMMA: TiO 2 solutions were prepared in this research. First solution is nano-composite PMMA commercially available TiO 2 nanopowder and the second solution is nano-composite PMMA with self-prepared TiO 2 powder. The self-prepared TiO 2 powder is obtained by preparing the TiO 2 sol-gel. Solvo thermal method were used to dry the TiO 2 sol-gel and obtained TiO 2 crystal. Ball millers were used to grind the TiO 2 crystal in order to obtained nano sized powder. Triton-X was used as surfactant to stabilizer the composite between PMMA: TiO 2 . Besides comparing the nano-composite solution, we also studied the effect of the thin films thickness on the optical properties and surface morphology of the thin films. The thin films were deposited by sol-gel spin coating method on glass substrates. The optical properties and surface characterization were measured with UV-VIS spectrometer equipment and atomic force microscopy (AFM). The result showed that nano-composite PMMA with self prepared TiO 2 give high optical transparency than nano-composite PMMA with commercially available TiO 2 nano powder. The results also indicate as the thickness is increased the optical transparency are decreased. Both AFM images showed that the agglomerations of TiO 2 particles are occurred on the thin films and the surface roughness is increased when the thickness is increased. High agglomeration particles exist in the AFM images for nano-composite PMMA: TiO 2 with TiO 2 nano powder compare to the other nano-composite solution. (author)

Biomimetic synthesis of cellular SiC based ceramics from plant ...

Indian Academy of Sciences (India)

Unknown

SiC based materials so derived can be used in structural applications and in designing high temperature filters and catalyst supports. Keywords. Biomimetic synthesis; carbonaceous biopreform; biomorphic Si–SiC ceramic composites; porous cellular SiC ceramics. 1. Introduction. In recent years, there has been tremendous ...

3D flexible NiTi-braided elastomer composites for smart structure applications

International Nuclear Information System (INIS)

Heller, L; Vokoun, D; Šittner, P; Finckh, H

2012-01-01

While outstanding functional properties of thin NiTi wires are nowadays well recognized and beneficially utilized in medical NiTi devices, development of 2D/3D wire structures made out of these NiTi wires remains challenging and mostly unexplored. The research is driven by the idea of creating novel 2D/3D smart structures which inherit the functional properties of NiTi wires and actively utilize geometrical deformations within the structure to create new/improved functional properties. Generally, textile technology provides attractive processing methods for manufacturing 2D/3D smart structures made out of NiTi wires. Such structures may be beneficially combined with soft elastomers to create smart deformable composites. Following this route, we carried out experimental work focused on development of 3D flexible NiTi-braided elastomer composites involving their design, laboratory manufacture and thermomechanical testing. We describe the manufacturing technology and structural properties of these composites; and perform thermomechanical tests on the composites, focusing particularly on quasistatic tensile properties, energy absorption, damping and actuation under tensile loading. Functional thermomechanical properties of the composites are discussed with regard to the mechanical properties of the components and architecture of the composites. It is found that the composites indeed inherit all important features of the thermomechanical behavior of NiTi wires but, due to their internal architecture, outperform single NiTi wires in some features such as the magnitude of recoverable strain, superelastic damping capacity and thermally induced actuation strain. (paper)

Microstructure and sliding wear characterization of Cu/TiB2 copper matrix composites fabricated via friction stir processing

Directory of Open Access Journals (Sweden)

I. Dinaharan

2017-09-01

Full Text Available The poor wear performance of copper is improved by reinforcing hard ceramic particles. The present work reports the fabrication of Cu/TiB2 (0, 6, 12, 18 vol.% copper matrix composites (CMCs using friction stir processing (FSP. TiB2 particles were initially packed together into a machined groove and were subjected to FSP under a constant set of process parameters. The microstructure was observed using optical, scanning and transmission electron microscopy. The wear behavior was examined using a pin-on-disc apparatus. The micrographs showed a homogeneous distribution of TiB2 particles without aggregation and segregation. The distribution of TiB2 particles was closely persistent across the stir zone. TiB2 particles were well bonded with the copper matrix without any interfacial reaction. Many TiB2 particles fractured during FSP. The grains in the composite were extensively refined because of dynamic recrystallization and pinning effect of TiB2 particles. The wear behavior under dry sliding condition was presented in detail.

Correlation between the electrical properties and the interfacial microstructures of TiAl-based ohmic contacts to p-type 4H-SiC

Science.gov (United States)

Tsukimoto, S.; Nitta, K.; Sakai, T.; Moriyama, M.; Murakami, Masanori

2004-05-01

In order to understand a mechanism of TiAl-based ohmic contact formation for p-type 4H-SiC, the electrical properties and microstructures of Ti/Al and Ni/Ti/Al contacts, which provided the specific contact resistances of approximately 2×10-5 Ω-cm2 and 7×10-5 Ω-cm2 after annealing at 1000°C and 800°C, respectively, were investigated using x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Ternary Ti3SiC2 carbide layers were observed to grow on the SiC surfaces in both the Ti/Al and the Ni/Ti/Al contacts when the contacts yielded low resistance. The Ti3SiC2 carbide layers with hexagonal structures had an epitaxial orientation relationship with the 4H-SiC substrates. The (0001)-oriented terraces were observed periodically at the interfaces between the carbide layers and the SiC, and the terraces were atomically flat. We believed the Ti3SiC2 carbide layers primarily reduced the high Schottky barrier height at the contact metal/p-SiC interface down to about 0.3 eV, and, thus, low contact resistances were obtained for p-type TiAl-based ohmic contacts.

Characterisation of phase composition, microstructure and microhardness of electroless nickel composite coating co-deposited with SiC on casting aluminium LM24 alloy substrate

OpenAIRE

Franco, M.; Sha, Wei; Malinov, Savko

2013-01-01

Electroless Ni-P (EN) and composite Ni-P-SiC (ENC) coatings were developed on cast aluminium alloy, LM24. The coating phase composition, microstructure and microhardness were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester, respectively, on as-plated and heat-treated specimens. The original microstructure of the Ni-P matrix is not affected by the inclusion of the hard particles SiC. No formation of Ni-Si phase was observed upto 500°C of ...

Pressureless sintering behavior and mechanical properties of ZrB2–SiC composites: effect of SiC content and particle size

Directory of Open Access Journals (Sweden)

Mehri Mashhadi

2015-10-01

Full Text Available In the present paper, ZrB2–SiC composites were prepared by pressureless sintering at temperatures of 2000–2200 °C for 1 h under argon atmosphere. In order to prepare composite samples, ZrB2 powder was milled for 2 h, then the reinforcing particles including of micron and nano-sized SiC powder were added. The mixtures were formed and, after the pyrolysis, they were sintered. Densification, microstructural and mechanical properties of ZrB2–SiC composites were investigated. The shrinkage of samples was measured both before and after the sintering, and the microstructure of samples was examined using scanning electron microscopy (SEM, equipped with EDS spectroscopy. Both mass fraction and size of SiC powder have a great effect on relative density, porosity, shrinkage, hardness and microstructure of these composites. The highest relative density and hardness were 98.12% and 15.02 GPa, respectively, in ZrB2–10 wt% SiCnano composite sintered at 2200 °C.

3D flexible NiTi-braided elastomer composites for smart structure applications

Czech Academy of Sciences Publication Activity Database

Heller, Luděk; Vokoun, David; Šittner, Petr; Finckh, H.

2012-01-01

Roč. 21, č. 4 (2012), s. 1-13 ISSN 0964-1726 R&D Projects: GA ČR GAP108/10/1296 EU Projects: European Commission(XE) 46559 - CERINKA; European Commission(XE) 19945 - UPWIND; European Commission(XE) 515813 - AVALON Institutional research plan: CEZ:AV0Z10100520 Keywords : NiTi * braided structures * composites Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.024, year: 2012

Structural, morphological and interfacial characterization of Al-Mg/TiC composites

International Nuclear Information System (INIS)

Contreras, A.; Angeles-Chavez, C.; Flores, O.; Perez, R.

2007-01-01

Morphological and structural characterization of Al-Mg/TiC composites obtained by infiltration process and wetting by the sessile drop technique were studied. Focusing at the interface, wetting of TiC substrates by molten Al-Mg-alloys at 900 deg. C was investigated. Electron probe microanalysis (EPMA) indicated that aluminum carbide (Al 4 C 3 ) is formed at the interface and traces of TiAl 3 in the wetting assemblies were detected. Scanning Electron Microscopy (SEM) observations show that TiC particles do not appear to be uniformly attacked to produce a continuous layer of Al 4 C 3 at the interface. Molten Al-Mg-alloys were infiltrated into TiC preforms with flowing argon at a temperature of 900 deg. C. In the composites no reaction phase was observed by SEM. Quantification of the Al phase in the composite was carried out by X-ray diffraction (XRD) and Rietveld analysis. Chemical mapping analyzed by SEM shows that the Al-Mg alloy surrounds TiC particles. In the composites with 20 wt.% of Mg the Al-Mg-β phase was detected through XRD

Amylose–halloysite–TiO{sub 2} composites: Preparation, characterization and photodegradation

Energy Technology Data Exchange (ETDEWEB)

Zheng, Pengwu; Du, Yuanyuan [School of Pharmacy, Jiangxi Science and Technology Normal University, 330013 Nanchang, Jiangxi (China); Chang, Peter R. [Bioproducts and Bioprocesses National Science Program, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2 Canada (Canada); Department of Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada); Ma, Xiaofei, E-mail: maxiaofei@tju.edu.cn [Chemistry Department, School of Science, Tianjin University, Tianjin 300072 (China)

2015-02-28

Highlights: • The amylose–HNT–TiO{sub 2} with high dispersion of TiO{sub 2} was fabricated. • The amylose–HNT–TiO{sub 2} was characterized. • The photodegradation of MB and 4-NP was investigated. - Abstract: A supramolecular structure was initially formed between amylose and halloysite (HNT) simply by using a mechanical force. Subsequently, amylose acted as a template for the growth of TiO{sub 2} nanoparticles. The thus-prepared amylose–HNT–TiO{sub 2} composite was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analyses, and transmission electron microscopy (TEM). In comparison to its counterpart HNT-TiO{sub 2} composite, the amylose–HNT–TiO{sub 2} composite exhibited better dispersion, a larger specific surface area, and photocatalytic activity that was more effective for the photodegradation/removal of methylene blue (MB) and the persistent organic pollutant 4-nitrophenol (4-NP) under UV irradiation. After four successive UV irradiation treatments, amylose–HNT–TiO{sub 2} removed about 90% of 4-NP or MB.

Synthesis of a TiBw/Ti6Al4V composite by powder compact extrusion using a blended powder mixture

Energy Technology Data Exchange (ETDEWEB)

Lu, Huiyang, E-mail: hl209@waikato.ac.nz [Waikato Center for Advanced Materials, School of Engineering, University of Waikato, Hamilton (New Zealand); Zhang, Deliang, E-mail: zhangdeliang@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai (China); Gabbitas, Brian, E-mail: briang@waikato.ac.nz [Waikato Center for Advanced Materials, School of Engineering, University of Waikato, Hamilton (New Zealand); Yang, Fei, E-mail: fyang@waikato.ac.nz [Waikato Center for Advanced Materials, School of Engineering, University of Waikato, Hamilton (New Zealand); Matthews, Steven, E-mail: S.Matthews@massey.ac.nz [School of Engineering and Advanced Technology, Massey University, Auckland (New Zealand)

2014-09-01

Highlights: • TiB/Ti6Al4V composites were prepared from extruded BE powders. • Different starting powders affected the morphologies of TiB whiskers formed in-situ. • A TiB/Ti6Al4V composite with TiB whiskers had good strength and ductility. • The strength and ductility achieved were superior to those obtained by other methods. - Abstract: A Ti–6 wt%Al–4 wt%V alloy (Ti6Al4V) matrix composite, reinforced by in situ synthesized TiB whiskers (TiBw) has been successfully fabricated by powder compact extrusion using a blended powder mixture. The microstructural characterization of the various extruded samples showed that the different starting powders, pre-alloyed powder plus boron powder or titanium plus Al–40V master alloy powder plus boron powder, had a significant effect on the morphology of the in situ synthesized TiB whiskers. It is also evident that the TiB whiskers affect the microstructural evolution of the Ti6Al4V matrix. The tensile test results indicated that the composite with a dispersion of fine TiB whiskers with high aspect ratios exhibited a high ultimate tensile stress (UTS) and yield stress (YS) of 1436 MPa and 1361 MPa, respectively, a reasonably good tensile ductility reflected by an elongation to fracture of 5.6% was also achieved. This is a significant improvement compared with as-extruded monolithic Ti6Al4V alloy produced in this study.

Synthesis of a TiBw/Ti6Al4V composite by powder compact extrusion using a blended powder mixture

International Nuclear Information System (INIS)

Lu, Huiyang; Zhang, Deliang; Gabbitas, Brian; Yang, Fei; Matthews, Steven

2014-01-01

Highlights: • TiB/Ti6Al4V composites were prepared from extruded BE powders. • Different starting powders affected the morphologies of TiB whiskers formed in-situ. • A TiB/Ti6Al4V composite with TiB whiskers had good strength and ductility. • The strength and ductility achieved were superior to those obtained by other methods. - Abstract: A Ti–6 wt%Al–4 wt%V alloy (Ti6Al4V) matrix composite, reinforced by in situ synthesized TiB whiskers (TiBw) has been successfully fabricated by powder compact extrusion using a blended powder mixture. The microstructural characterization of the various extruded samples showed that the different starting powders, pre-alloyed powder plus boron powder or titanium plus Al–40V master alloy powder plus boron powder, had a significant effect on the morphology of the in situ synthesized TiB whiskers. It is also evident that the TiB whiskers affect the microstructural evolution of the Ti6Al4V matrix. The tensile test results indicated that the composite with a dispersion of fine TiB whiskers with high aspect ratios exhibited a high ultimate tensile stress (UTS) and yield stress (YS) of 1436 MPa and 1361 MPa, respectively, a reasonably good tensile ductility reflected by an elongation to fracture of 5.6% was also achieved. This is a significant improvement compared with as-extruded monolithic Ti6Al4V alloy produced in this study

Al2TiO5-ZrTiO4-ZrO2 composites

International Nuclear Information System (INIS)

Parker, F.J.

1990-01-01

The characterization and properties of ceramic composites containing the phases Al 2 TiO 5 , ZrTiO 4 , and ZrO 2 are described. The low thermal expansions are apparently due to a combination of microcracking by the titanate phases and a contractive phase transformation by the ZrO 2 . The crystal chemistry and microstructure of the product are processing dependent. Although the composites represent a complex microcracking system, the low thermal expansions and high-temperature stability make them potential candidates for commercial application requiring thermal shock resistance

Dielectric property of NiTiO3 doped substituted ortho-chloropolyaniline composites

Directory of Open Access Journals (Sweden)

Mohana Lakshmi

2013-11-01

Full Text Available Ortho-chloropolyaniline (OCP-NiTiO3 composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO3. Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO3 particles. Surface morphology of OCP and OCP-NiTiO3 composites were studied using Scanning Electron Microscope (SEM. The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO3 composites have been investigated in the frequency range of 50 Hz – 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO3 particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.

Small Incision Cataract Surgery (SICS with Clear Corneal Incision and SICS with Scleral Incision – A Comparative Study

Directory of Open Access Journals (Sweden)

Md Shafiqul Alam

2014-01-01

Full Text Available Background: Age related cataract is the leading cause of blindness and visual impairment throughout the world. With the advent of microsurgical facilities simple cataract extraction surgery has been replaced by small incision cataract surgery (SICS with posterior chamber intra ocular lens implant, which can be done either with clear corneal incision or scleral incision. Objective: To compare the post operative visual outcome in these two procedures of cataract surgery. Materials and method: This comparative study was carried out in the department of Ophthalmology, Delta Medical College & Hospital, Dhaka, Bangladesh, during the period of January 2010 to December 2012. Total 60 subjects indicated for age related cataract surgery irrespective of sex with the age range of 40-80 years with predefined inclusion and exclusion criteria were enrolled in the study. Subjects were randomly and equally distributed in 2 groups; Group A for SICS with clear corneal incision and group B for SICS with scleral incision. Post operative visual out come was evaluated by determining visual acuity and astigmatism in different occasions and was compared between groups. Statistical analysis was done by SPSS for windows version12. Results: The highest age incidence (43.3% was found between 61 to 70 years of age group. Among study subjects 40 were male and 20 were female. Preoperative visual acuity and astigmatism were evenly distributed between groups. Regarding postoperative unaided visual outcome, 6/12 or better visual acuity was found in 19.98% cases in group A and 39.6% cases in group B at 1st week. At 6th week 6/6 vision was found in 36.3% in Group A and 56.1% in Group B and 46.2% in group A and 66% in group B without and with correction respectively. With refractive correction, 6/6 vision was attained in 60% subjects of group A and 86.67% of group B at 8th week. Post operative visual acuity was statistically significant in all occasions. Postoperative astigmatism of

In situ preparation of (TiB + TiC + Nd2O3)/Ti composites by powder metallurgy

International Nuclear Information System (INIS)

Lu Junqiang; Qin Jining; Lu Weijie; Liu Yang; Gu Jiajun; Zhang Di

2009-01-01

Titanium matrix composites reinforced with multiple ceramic particulates TiB, TiC and Nd 2 O 3 were prepared by powder metallurgy utilizing the chemical reactions among Ti, B 4 C, NdB 6 and oxygen in Ti powder. The thermodynamic feasibility of the in situ reaction has been calculated. The phases were identified by X-ray diffraction (XRD). The result shows that multiple ceramic phases TiB, TiC and Nd 2 O 3 particulates have been synthesized. The microstructures were examined by means of optical microscopy (OM), scanning electron microscopy (SEM), backscattered electron microscopy and transmission electron microscope (TEM). The results show that the reinforcements are distributed uniformly in the matrix alloy and grow in different shapes. TiB grows in needle shape; TiC and Nd 2 O 3 grow in equiaxed or near-equiaxed shapes. The addition of NdB 6 is beneficial to grain refinement, grain-boundary purification and porosity reduction

The development of SiC whisker fabrication technology for nuclear applications

International Nuclear Information System (INIS)

Kang, Thae Khapp; Kuk, Il Hiun; Kim, Chang Kyu; Lee, Jae Chun; Lee, Ho Jin; Park, Soon Dong; Im, Gyeong Soo

1991-02-01

Some important experiments for whisker growth reactions, fabrication processes, and experiments for fabricarion of whisker reinforced composites have been performed. In order to investigate growth reaction of SiC whiskers, a conventional carbothermic reaction was tested. Based on the results of carbothermic process, a new process called silicothermic reaction was planned and some basic experiments were performed. Reaction characteristics of silicon monoxide, core material for SiC whisker growth in both of the reactions were investigated for basic data. Additionally, a hydrofluoric acid leaching process was tested for developing SiC whisker recovery process, and powder metallurgy process and melt sqeeze process were tried to develop aluminum-SiC whisker composites. (Author)

Bulletin of Materials Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

The microstructure and mechanical properties of Ti3SiC2–SiC nanocomposite fabricated by in situ hot pressing (HP) synthesis process were studied. The results show that dense Ti3SiC2–SiC composite contained minor TiSi2 obtained by hot sintering at 1350°C for 1 h. The average grain size of Ti3SiC2 was 4 m in length, ...

Interface electron structure of Fe3Al/TiC composites

Institute of Scientific and Technical Information of China (English)

PANG Lai-xue; SUN Kang-ning; SUN Jia-tao; FAN Run-hua; REN Shuai

2006-01-01

Based on YU's solids and molecules emperical electron theory(EET), interface valence electron structure of TiC-Fe3Al composites was set up, and the valence electron density of different atomic states TiC and Fe3Al composites in various planes was determined. The results indicate that the electron density of (100)Fe3Al is consistent with that of (110)TiC in the first-class approximation, the absolute value of minimum electron density difference along the interface is 0.007 37 nm-2, and the relative value is 0.759%. (110)TiC//(100)Fe3Al preferred orientation is believed to benefit the formation of the cuboidal shape TiC. In the other hand, it shows that the particle growth is accompanied by the transport of electron, the deviation continuity of electron density intrinsically hinders the grain growth. The electron density of (100)TiC is not consistent with Fe3Al arbitrary crystallographic plane,thus it well explains that the increased titanium and carbon contents do not increase the size of large particles. The crystallographic orientation of (110)TiC//(100)FeAl will improve the mechanical properties. Therefore interface electron theory is an effective theoretical implement for designing excellent property of composites.

Synthesis and photocatalytic activity of poly(3-hexylthiophene)/TiO2 composites

International Nuclear Information System (INIS)

Muktha, B.; Mahanta, Debajyoti; Patil, Satish; Madras, Giridhar

2007-01-01

An heterogeneous conducting polymer composite, poly(3-hexylthiophene)/TiO 2 (P3HT/TiO 2 ), was synthesized. The photocatalytic activity of P3HT alone and the composite was investigated for the first time by degrading a common dye under UV exposure. It was shown that the photocatalytic activity of the nanocomposites was higher compared to either the polymer or TiO 2 alone. A simple mechanism was proposed to explain this observed synergetic effect. - Graphical abstract: Photocatalytic mechanism of the polymer composite with titania. A new heterogeneous conducting polymer composite with titania (P3HT/TiO 2 ) was synthesized and the photocatalytic activity this composite was investigated by degrading a common dye under UV exposure. It was shown that the nanocomposite exhibited synergetic photocatalytic catalytic activity compared to either the polymer or TiO 2 alone. The scheme of the possible mechanism of enhancement of photocatalytic degradation rate in a conducting polymer nanocomposite is shown in the figure

A nano lamella NbTi–NiTi composite with high strength

Energy Technology Data Exchange (ETDEWEB)

Jiang, Jiang [Jiangxi Key Laboratory of Advanced Copper and Tungsten Materials, Jiangxi Academy of Sciences, Nanchang 330029 (China); Institute of Applied Physics of Jiangxi Academy of Sciences, Nanchang 330029 (China); State Key Laboratory of Heavy Oil Processing and Department of Materials Science and engineering, China University of Petroleum, Beijing 102249 (China); Jiang, Daqiang [State Key Laboratory of Heavy Oil Processing and Department of Materials Science and engineering, China University of Petroleum, Beijing 102249 (China); School of Mechanical and Chemical Engineering, The University of Western Australia, WA 6009 (Australia); Hao, Shijie; Yu, Cun; Zhang, Junsong [State Key Laboratory of Heavy Oil Processing and Department of Materials Science and engineering, China University of Petroleum, Beijing 102249 (China); Ren, Yang [X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Lu, Deping; Xie, Shifang [Jiangxi Key Laboratory of Advanced Copper and Tungsten Materials, Jiangxi Academy of Sciences, Nanchang 330029 (China); Institute of Applied Physics of Jiangxi Academy of Sciences, Nanchang 330029 (China); Cui, Lishan, E-mail: lishancui63@126.com [State Key Laboratory of Heavy Oil Processing and Department of Materials Science and engineering, China University of Petroleum, Beijing 102249 (China)

2015-05-01

A hypereutectic Nb{sub 60}Ti{sub 24}Ni{sub 16} (at%) alloy was prepared by vacuum induction melting, and a nano lamellae NbTi–NiTi composite was obtained by hot-forging and wire-drawing of the ingot. Microscopic analysis showed that NbTi and NiTi nano lamellae distributed alternatively in the composite, and aligned along the wire axial direction, with a high volume fraction (~70%) of NbTi nano lamellae. In situ synchrotron X-ray diffraction analysis revealed that stress induced martensitic transformation occurred upon loading, which would effectively weaken the stress concentration at the interface and avoid the introduction of defects into the nano reinforced phase. Then the embedded NbTi nano lamellae exhibited a high elastic strain up to 2.72%, 1.5 times as high as that of the Nb nanowires embedded in a conventional plastic matrix, and the corresponding stress carried by NbTi was evaluated as 2.53 GPa. The high volume fraction of NbTi nano lamellae improved the translation of high strength from the nano reinforced phase into bulk properties of the composite, with a platform stress of ~1.7 GPa and a fracture strength of ~1.9 GPa.

SiC Nanoparticles Toughened-SiC/MoSi2-SiC Multilayer Functionally Graded Oxidation Protective Coating for Carbon Materials at High Temperatures

Science.gov (United States)

Abdollahi, Alireza; Ehsani, Naser; Valefi, Zia; Khalifesoltani, Ali

2017-05-01

A SiC nanoparticle toughened-SiC/MoSi2-SiC functionally graded oxidation protective coating on graphite was prepared by reactive melt infiltration (RMI) at 1773 and 1873 K under argon atmosphere. The phase composition and anti-oxidation behavior of the coatings were investigated. The results show that the coating was composed of MoSi2, α-SiC and β-SiC. By the variations of Gibbs free energy (calculated by HSC Chemistry 6.0 software), it could be suggested that the SiC coating formed at low temperatures by solution-reprecipitation mechanism and at high temperatures by gas-phase reactions and solution-reprecipitation mechanisms simultaneously. SiC nanoparticles could improve the oxidation resistance of SiC/MoSi2-SiC multiphase coating. Addition of SiC nanoparticles increases toughness of the coating and prevents spreading of the oxygen diffusion channels in the coating during the oxidation test. The mass loss and oxidation rate of the SiC nanoparticle toughened-SiC/MoSi2-SiC-coated sample after 10-h oxidation at 1773 K were only 1.76% and 0.32 × 10-2 g/cm3/h, respectively.

Preparation and characterization of photoactive composite kaolinite/TiO2

International Nuclear Information System (INIS)

Mamulova Kutlakova, K.; Tokarsky, J.; Kovar, P.; Vojteskova, S.; Kovarova, A.; Smetana, B.; Kukutschova, J.; Capkova, P.; Matejka, V.

2011-01-01

Preparation of nanocomposite kaolinite/TiO 2 , using hydrolysis of titanyl sulfate in the presence of kaolin was addressed. A variable (kaolin)/(titanyl sulfate) ratio has been used in order to achieve the desired TiO 2 content in prepared nanocomposites. Calcination of the composites at 600 deg, C led to the transformation of the kaolinite to metakaolinite and to origination of metakaolinite/TiO 2 composites. The prepared samples were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry and diffuse reflectance spectroscopy in the UV-VIS region. Structural ordering of TiO 2 on the kaolinite particle surface was modeled using empirical force field atomistic simulations in the Material Studio modeling environment. Photodegradation activity of the composites prepared was evaluated by the discoloration of Acid Orange 7 aqueous solution.

Preparation and solar-light photocatalytic activity of TiO2 composites: TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite

Science.gov (United States)

Li, Y.; Li, S. G.; Wang, J.; Li, Y.; Ma, C. H.; Zhang, L.

2014-12-01

Three TiO2 loaded composites, TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite, were prepared in order to improve the solar-light photocatalytic activity of TiO2. The results showed that the photocatalytic activity could obviously be enhanced by loading appropriate amount of inorganic mineral materials. Meanwhile, TiO2 content, heat-treatment temperature and heat-treatment time on the photocatalytic activity were reviewed. Otherwise, the effect of solar light irradiation time and dye concentration on the photocatalytic degradation of Acid Red B was investigated. Furthermore, the degradation mechanism and adsorption process were also discussed.

Effect of nano-CeO2 on microstructure properties of TiC/TiN+nTi(CN) reinforced composite coating

International Nuclear Information System (INIS)

Jianing, Li; Chuanzhong, Chen; Cuifang, Zhang

2012-01-01

TiC/TiN+TiCN reinforced composite coatings were fabricated on Ti-6Al-4V alloy by laser cladding, which improved surface performance of the substrate. Nano-CeO 2 was able to suppress crystallization and growth of the crystals in the laser-cladded coating to a certain extent. With the addition of proper content of nano-CeO 2 , this coating exhibited fine microstructure. In this study, the Al 3 Ti+TiC/TiN+nano-CeO 2 laser-cladded coatings were studied by means of X-ray diffraction and scanning electron microscope. The X-ray diffraction results indicated that the Al 3 Ti+TiC/TiN+nano-CeO 2 laser-cladded coating consisted of Ti 3 Al, TiC, TiN, Ti 2 Al 20 Ce, TiC 0.3 N 0.7 , Ce(CN) 3 and CeO 2 , this phase constituent was beneficial to increase the microhardness and wear resistance of Ti-6Al-6V alloy. (author)

Tensile Creep and Fatigue of Sylramic-iBN Melt-Infiltrated SiC Matrix Composites: Retained Properties, Damage Development, and Failure Mechanisms

Science.gov (United States)

Morscher, Greg; Gowayed, yasser; Miller, Robert; Ojard, Greg; Ahmad, Jalees; Santhosh, Unni; John, Reji

2008-01-01

An understanding of the elevated temperature tensile creep, fatigue, rupture, and retained properties of ceramic matrix composites (CMC) envisioned for use in gas turbine engine applications are essential for component design and life-prediction. In order to quantify the effect of stress, time, temperature, and oxidation for a state-of-the-art composite system, a wide variety of tensile creep, dwell fatigue, and cyclic fatigue experiments were performed in air at 1204 C for the SiC/SiC CMC system consisting of Sylramic-iBN SiC fibers, BN fiber interphase coating, and slurry-cast melt-infiltrated (MI) SiC-based matrix. Tests were either taken to failure or interrupted. Interrupted tests were then mechanically tested at room temperature to determine the residual properties. The retained properties of most of the composites subjected to tensile creep or fatigue were usually within 20% of the as-produced strength and 10% of the as-produced elastic modulus. It was observed that during creep, residual stresses in the composite are altered to some extent which results in an increased compressive stress in the matrix upon cooling and a subsequent increased stress required to form matrix cracks. Microscopy of polished sections and the fracture surfaces of specimens which failed during stressed-oxidation or after the room-temperature retained property test was performed on some of the specimens in order to quantify the nature and extent of damage accumulation that occurred during the test. It was discovered that the distribution of stress-dependent matrix cracking at 1204 C was similar to the as-produced composites at room temperature; however, matrix crack growth occurred over time and typically did not appear to propagate through thickness except at final failure crack. Failure of the composites was due to either oxidation-induced unbridged crack growth, which dominated the higher stress regime (> 179 MPa) or controlled by degradation of the fibers, probably caused by

Surface oxidation of porous ZrB2-SiC ceramic composites by continuous-wave ytterbium fibre laser

International Nuclear Information System (INIS)

Mahmod, Dayang Salyani Abang; Glandut, Nicolas; Khan, Amir Azam; Labbe, Jean-Claude

2015-01-01

Highlights: • Surface oxidation of ZrB 2 -SiC ceramic composites by Yb-fibre laser. • Round spiral laser pattern created for the surface oxidation. • Presence of laser-formed oxide scale and unaffected beneath regions. • Crazed but uncracked surface oxide. • A dense glassy SiO 2 -rich layer exhibited enhances oxidation resistance. - Abstract: Surface treatment of ceramic substrates by a laser beam can allow to incorporate interesting properties to these ceramics. In the present work, surface oxidation of ca. 30% porous ZrB 2 -SiC ceramic composites by using an ytterbium fibre laser was conducted. Oxidation of ceramic substrates through this process under ambient conditions has certain advantages compared to the classical oxidation method. A particular spiral laser pattern was created in order to produce an oxidized structure on ZrB 2 -SiC porous substrates. The laser parameters were as follows i.e., laser power of 50, 60 and 70 W, a beam diameter of 1.25 mm, velocity of 2 mm/s, acceleration and deceleration of 1 mm/s 2 . The microstructural and morphological changes in the laser-treated region was examined using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. At laser power of 70 W, the sample exhibits uniform oxidation. It revealed that the very porous bulk beneath remained unaffected and unoxidized because this laser-formed oxide scale protects the substrate from oxidation. The presence of oxidized and unaffected regions indicated a high degree of heat localization. The dense glassy SiO 2 -rich layer prevents the inward oxygen diffusion into the inner bulk hence enhances the oxidation resistance.

Preparation and properties of electrodeposited Ni-TiO2 composite coating

Directory of Open Access Journals (Sweden)

Sukhdev Singh Bhogal

2015-03-01

Full Text Available Mechanical properties of cutting tool like microhardness, coating adhesiveness & corrosion resistance are some important parameters, which affects the tool life and further indirectly affects the component cost. In this paper Ni-TiO2 composite coating was prepared through electrocodeposition in order to improve the mechanical properties of tungsten carbide cutting tools. Microhardness of Ni-TiO2 composite layer have been studied by varying input current density (mA, pH vale of electrolyte & particle concentration of TiO2 in electrolyte bath. Microstructure and phase structure of composite layer were investigated using atomic force microscope (AFM, scanning electronic microscope (SEM and X-ray diffraction (XRD. Surface morphology of Ni-TiO2 coated layer shows fine grained structures is obtained at low currents with higher microhardness of composite coating. Maximum microhardness 1483 HV of coated layer is found at 15mA of current and at 4.5 pH of watt’s solution. It has also been seen that with the increase of Ti, microhardness of the layer is also increases.  

Preparation of Ag deposited TiO2 (Ag/TiO2) composites and investigation on visible-light photocatalytic degradation activity in magnetic field

Science.gov (United States)

Zhang, L.; Ma, C. H.; Wang, J.; Li, S. G.; Li, Y.

2014-12-01

In this study, Ag deposited TiO2 (Ag/TiO2) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO2 (Ag/TiO2) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO2 (Ag/TiO2) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO2 (Ag/TiO2) composites and then contributed to the degradation of organic dyes.

Laminated Ti-Al composites: Processing, structure and strength

DEFF Research Database (Denmark)

Du, Yan; Fan, Guohua; Yu, Tianbo

2016-01-01

Laminated Ti-Al composite sheets with different layer thickness ratios have been fabricated through hot pressing followed by multi-pass hot rolling at 500 °C.The laminated sheets show strong bonding with intermetallic interface layers of nanoscale thickness between the layers of Ti and Al....... The mechanical properties of the composites with different volume fractions of Al from 10% to 67% show a good combination of strength and ductility. A constraint strain in the hot-rolled laminated structure between the hard and soft phases introduces an elastic-plastic deformation stage, which becomes more...

Sintering of Mo2FeB2 based cermet and its layered composites containing Sic fibers

International Nuclear Information System (INIS)

Rao, D.; Upadhyaya, G.S.

2001-01-01

In the present investigation Mo 2 FeB 2 based cermet (KH-C50) and its composites containing SiC fibers were sintered in two different atmospheres namely hydrogen and vacuum. It was observed that vacuum sintered samples have remarkably lower porosities than the hydrogen sintered ones. Two different sintering cycles were employed for each of the atmosphere and properties of the material were studied. Introduction of fibers in the composite imparts shrinkage anisotropy during sintering. Fiber containing cermets have rather poor densification and transverse rupture strength (TRS). TRS, macro and microhardness, and boride grain size measurements were also carried out for the cermets sintered in different atmospheres. (author)

SnTe-TiC-C composites as high-performance anodes for Li-ion batteries

Science.gov (United States)

Son, Seung Yeon; Hur, Jaehyun; Kim, Kwang Ho; Son, Hyung Bin; Lee, Seung Geol; Kim, Il Tae

2017-10-01

Intermetallic SnTe composites dispersed in a conductive TiC/C hybrid matrix are synthesized by high-energy ball milling (HEBM). The electrochemical performances of the composites as potential anodes for Li-ion batteries are evaluated. The structural and morphological characteristics of the SnTe-TiC-C composites with various TiC contents are investigated by X-ray diffraction (XRD) and high-resolution transmission electron microscopy, which reveal that SnTe and TiC are uniformly dispersed in a carbon matrix. The electrochemical performance is significantly improved by introducing TiC to the SnTe-C composite; higher TiC contents result in better performances. Among the prepared composites, the SnTe-TiC (30%)-C and SnTe-TiC (40%)-C electrodes exhibit the best electrochemical performance, showing the reversible capacities of, respectively, 652 mAh cm-3 and 588 mAh cm-3 after 400 cycles and high rate capabilities with the capacity retentions of 75.4% for SnTe-TiC (30%)-C and 82.2% for SnTe-TiC (40%)-C at 10 A g-1. Furthermore, the Li storage reaction mechanisms of Te or Sn in the SnTe-TiC-C electrodes are confirmed by ex situ XRD.

Thermal shock fatigue behavior of TiC/Al2O3 composite ceramics

Institute of Scientific and Technical Information of China (English)

SI Tingzhi; LIU Ning; ZHANG Qingan; YOU Xianqing

2008-01-01

The thermal shock fatigue behaviors of pure hot-pressed alumina and 30 wt. % TiC/Al2O3 composites were studied. The effect of TiC and Al2O3 starting particle size on the mechanical properties of the composites was discussed. Indentation-quench test was conducted to evaluate the effect of thermal fatigue temperature difference (ΔT) and number of thermal cycles (N) on fatigue crack growth (Δα). The mechanical properties and thermal fatigue resistance of TiC/Al2O3 composites are remarkably improved by the addition of TiC. The thermal shock fatigue of monolithic alumina and TiC/Al2O3 composites is due to a "true" cycling effect (thermal fatigue). Crack deflection and bridging are the predominant reasons for the improvement of thermal shock fatigue resistance of the composites.

Elaboration of silicon carbides nano particles (SiC): from the powder synthesis to the sintered ceramic

International Nuclear Information System (INIS)

Reau, A.

2008-01-01

Materials for the reactor cores of the fourth generation will need materials supporting high temperatures with fast neutrons flux. SiC f /SiC ceramics are proposed. One of the possible elaboration process is to fill SiC fiber piece with nano particles SiC powder and to strengthen by sintering. The aim of this thesis is to obtain a nano structured SiC ceramic as a reference for the SiC f /SiC composite development and to study the influence of the fabrication parameters. (A.L.B.)

Preparation of TiC/Ni3Al Composites by Upward Melt Infiltration

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

TiC/Ni3Al composites have been prepared using upward infiltration method. The densificstion was performed by both Ni3Al melt filling and TiC sintering during the infiltration. The dissolution of TiC in liquid Ni3Al has been evidenced by finding Ni3(Al,Ti)C after fast cooling in the TiC/Ni3Al composites. The dissolution may be responsible for the infiltration and sintering. Compared with downward infiltration, the upward infiltration brought about higher strength and fracture toughness and shorter infiltration time. TiC/20 vol. pct Ni3Al composite processed by upward infiltration had a flexural strength of 1476 Mpa with a statistic Weibull modulus of 20.2 and a fracture toughness of 20.4 Mpa(m). Better mechanical properties may be attributed to melt unidirectional movement in upward infiltration.

Synthesis of nano-TiO2/diatomite composite and its photocatalytic degradation of gaseous formaldehyde

Science.gov (United States)

Zhang, Guangxin; Sun, Zhiming; Duan, Yongwei; Ma, Ruixin; Zheng, Shuilin

2017-08-01

The TiO2/diatomite composite was synthesized through a mild hydrolysis of titanyl sulfate. The prepared composite was characterized by X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffused reflectance spectroscopy. The results demonstrate that the anatase TiO2 nanopartilces anchored on the surface of diatomite with Ti-O-Si bonds between diatomite and TiO2. The photodegradation of gaseous formaldehyde under UV irradiation by the TiO2/diatomite composite was studied under various operating conditions, including relative humidity, illumination intensity and catalyst amount, which have significant influence on the degradation process. The TiO2/diatomite composite exhibited better photocatalytic activity than pure TiO2, which could be attributed to the favorable nanoparticles dispersibility and strong formaldehyde adsorption capacity. In addition, the composite exhibited outstanding reusability over five cycles. The TiO2/diatomite composite shows great promising application foreground in formaldehyde degradation.

High-performance thermoelectric materials based on ternary TiO2/CNT/PANI composites.

Science.gov (United States)

Erden, Fuat; Li, Hui; Wang, Xizu; Wang, FuKe; He, Chaobin

2018-04-04

In the present work, we report the fabrication of high-performance thermoelectric materials using TiO2/CNT/PANI ternary composites. We showed that a conductivity of ∼2730 S cm-1 can be achieved for the binary CNT (70%)/PANI (30%) composite, which is the highest recorded value for the reported CNT/PANI composites. We further demonstrated that the Seebeck coefficient of CNT/PANI composites could be enhanced by incorporating TiO2 nanoparticles into the binary CNT/PANI composites, which could be attributed to lower carrier density and the energy scattering of low-energy carriers at the interfaces of TiO2/a-CNT and TiO2/PANI. The resulting TiO2/a-CNT/PANI ternary system exhibits a higher Seebeck coefficient and enhanced thermoelectric power. Further optimization of the thermoelectric power was achieved by water treatment and by tuning the processing temperature. A high thermoelectric power factor of 114.5 μW mK-2 was obtained for the ternary composite of 30% TiO2/70% (a-CNT (70%)/PANI (30%)), which is the highest reported value among the reported PANI based ternary composites. The improvement of thermoelectric performance by incorporation of TiO2 suggests a promising approach to enhance power factor of organic thermoelectric materials by judicial tuning of the carrier concentration and electrical conductivity.

Electrophoretic deposition of PEEK-TiO 2 composite coatings on stainless steel

KAUST Repository

Seuß, Sigrid

2012-03-01

Electrophoretic deposition (EPD) has been successfully used to deposit composite coatings composed of polyetheretherketone (PEEK) and titanium dioxide (TiO 2) nanoparticles on 316L stainless steel substrates. The suspensions of TiO2 nanoparticles and PEEK microparticles for EPD were prepared in ethanol. PEEK-TiO 2 composite coatings were optimized using suspensions containing 6wt% PEEK-TiO 2 in ethanol with a 3:1 ratio of PEEK to TiO 2 in weight and by applying a potential difference of 30 V for 1 minute. A heat-treatment process of the optimized PEEK-TiO 2 composite coatings was erformed at 335°C for 30 minutes with a heating rate of 10°Cmin -1 to densify the deposits. The EPD coatings were microstructurally evaluated by scanning electron microscopy (SEM). It was demonstrated that EPD is a convenient and rapid method to fabricate PEEK/TiO 2 coatings on stainless steel which are interesting for biomedical applications. © (2012) Trans Tech Publications, Switzerland.

Synthesis of visible-light responsive graphene oxide/TiO(2) composites with p/n heterojunction.

Science.gov (United States)

Chen, Chao; Cai, Weimin; Long, Mingce; Zhou, Baoxue; Wu, Yahui; Wu, Deyong; Feng, Yujie

2010-11-23

Graphene oxide/TiO(2) composites were prepared by using TiCl(3) and graphene oxide as reactants. The concentration of graphene oxide in starting solution played an important role in photoelectronic and photocatalytic performance of graphene oxide/TiO(2) composites. Either a p-type or n-type semiconductor was formed by graphene oxide in graphene oxide/TiO(2) composites. These semiconductors could be excited by visible light with wavelengths longer than 510 nm and acted as sensitizer in graphene oxide/TiO(2) composites. Visible-light driven photocatalytic performance of graphene oxide/TiO(2) composites in degradation of methyl orange was also studied. Crystalline quality and chemical states of carbon elements from graphene oxide in graphene oxide/TiO(2) composites depended on the concentration of graphene oxide in the starting solution. This study shows a possible way to fabricate graphene oxide/semiconductor composites with different properties by using a tunable semiconductor conductivity type of graphene oxide.

SYLRAMICTM SiC fibers for CMC reinforcement

International Nuclear Information System (INIS)

Jones, Richard E.; Petrak, Dan; Rabe, Jim; Szweda, Andy

2000-01-01

Dow Corning researchers developed SYLRAMIC SiC fiber specifically for use in ceramic-matrix composite (CMC) components for use in turbine engine hot sections where excellent thermal stability, high strength and high thermal conductivity are required. This is a stoichiometric SiC fiber with a high degree of crystallinity, high tensile strength, high tensile modulus and good thermal conductivity. Owing to the small diameter, this textile-grade fiber can be woven into 2-D and 3-D structures for CMC fabrication. These properties are also of high interest to the nuclear community. Some initial studies have shown that SYLRAMIC fiber shows very good dimensional stability in a neutron flux environment, which offers further encouragement. This paper will review the properties of SYLRAMIC SiC fiber and then present the properties of polymer impregnation and pyrolysis (PIP) processed CMC made with this fiber at Dow Corning. While these composites may not be directly applicable to applications of interest to this audience, we believe that the properties shown will give good evidence that the fiber should be suitable for high temperature structural applications in the nuclear arena

Elastic and thermo-physical properties of TiC, TiN, and their intermediate composition alloys using ab initio calculations

International Nuclear Information System (INIS)

Kim, Jiwoong; Kang, Shinhoo

2012-01-01

Highlights: ► Elastic properties of TiC, TiN and their alloys were calculated by ab initio calculations. ► Debye temperature and Gruneisen constant of TiC, TiN and their alloys were calculated as a function of nitrogen content. ► Thermo-physical properties were calculated as a function of nitrogen content. ► Thermal expansion of the alloys was fitted in different temperature range. - Abstract: The equilibrium lattice parameters, elastic properties, material brittleness, heat capacities, and thermal expansion coefficients of TiC, TiN, and their intermediate composition alloys (Ti(C 1−x N x ), x = 0.25, 0.5, and 0.75) were calculated using ab initio density functional theory (DFT) methods. We employed the Debye–Gruneisen model to calculate a finite temperature heat capacity and thermal expansion coefficient. The calculated elastic moduli and thermal expansion coefficients agreed well with the experimental data and with other DFT calculations. Accurate heat capacities of TiC, TiN, and their intermediate composition alloys were obtained by calculating not only the phonon contributions but also the electron contributions to the heat capacity. Our calculations indicated that the heat capacity differences between each composition originated mainly from the electronic contributions.

Fine filament NbTi superconductive composite

International Nuclear Information System (INIS)

Hong, S.; Grabinsky, G.; Marancik, W.; Pattanayak, D.

1986-01-01

The large superconducting magnet for the high energy physics accelerator requires fine filament composite to minimize the field error due to the persistent current in the filaments. New concepts toward the fine filament composite and its cable fabrication are discussed. Two-stage cables of fine wire with intermediate number of filaments were introduced. The first stage was six wires cables around one and in the second stage this was used to produce a Rutherford cable. The advantage of this process is in the ease of billet fabrication since the number of filaments in a single wire is within the range of easy billet fabrication. The disadvantage is in the cable fabrication. One of the major concerns in the fabrication of fine NbTi filaments composite in a copper matrix is the intermetallic compound formation during the extrusion and heat treatment steps. The hard intermetallic particles degrade the uniformity of the filaments and reduce the critical current density. The process of using Nb barrier between the filaments and copper matrix in order to prevent this CuTi intermetallic particle formation is described

Nanocrystalline SiC and Ti₃SiC₂ Alloys for Reactor Materials: Annual Report

Energy Technology Data Exchange (ETDEWEB)

Henager, Charles H. [pnnl; Alvine, Kyle J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Roosendaal, Timothy J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shin, Yongsoon [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nguyen, Ba Nghiep; Borlaug, Brennan A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jiang, Weilin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Arreguin, Shelly A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2015-01-15

A new dual-phase nanocomposite of Ti₃SiC₂/SiC is being synthesized using preceramic polymers, ceramic powders, and carbon nanotubes (CNTs) designed to be suitable for advanced nuclear reactors and perhaps as fuel cladding. The material is being designed to have superior fracture toughness compared to SiC, adequate thermal conductivity, and higher density than SiC/SiC composites. This annual report summarizes the progress towards this goal and reports progress in understanding certain aspects of the material behavior but some shortcomings in achieving full density or in achieving adequate incorporation of CNTs. The measured thermal conductivity is adequate and falls into an expected range based on SiC and Ti₃SiC₂. Part of this study makes an initial assessment for Ti₃SiC₂ as a barrier to fission product transport. Ion implantation was used to introduce fission product surrogates (Ag and Cs) and a noble metal (Au) in Ti₃SiC₂, SiC, and a synthesized at PNNL. The experimental results indicate that the implanted Ag in SiC is immobile up to the highest temperature (1273 K) applied in this study; in contrast, significant out-diffusion of both Ag and Au in MAX phase Ti₃SiC₂ occurs during ion implantation at 873 K. Cs in Ti₃SiC₂ is found to diffuse during post-irradiation annealing at 973 K, and noticeable Cs release from the sample is observed. This study may suggest caution in using Ti₃SiC₂ as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. Progress is reported in thermal conductivity modeling of SiC-based materials that is relevant to this research, as is progress in modeling the effects of CNTs on fracture strength of SiC-based materials.

Comparison of a novel TiO₂/diatomite composite and pure TiO₂ for the purification of phosvitin phosphopeptides.

Science.gov (United States)

Zhang, Yang; Li, Junhua; Niu, Fuge; Sun, Jun; Dou, Yuan; Liu, Yuntao; Su, Yujie; Zhou, Bei; Xu, Qinqin; Yang, Yanjun

2014-06-01

A novel TiO2/diatomite composite (TD) was prepared and then characterized by scanning electron microscope (SEM) and Fourier Transform Infrared (FTIR). The results of SEM showed that after modification, the porous surface of diatomite was covered with TiO2. Both diatomite and TD had clear disc-shaped structures with average grain diameters of around 25 μm. Then TD and pure TiO2 were applied in the purification of phosvitin phosphopeptides (PPPs) from the digest of egg yolk protein, and a comparative study of adsorption properties of PPPs on TD and TiO2 was performed. In the study of adsorption kinetics, the adsorption equilibrium of PPPs on TD and TiO2 fitted well with the Langmuir model, and the time needed to reach adsorption equilibrium were both around 10 min. The maximum dynamic adsorption capacity of TD (8.15 mg/g) was higher than that of TiO2 (4.96 mg/g). The results of repeated use showed that TD and TiO2 were very stable after being subjected to ten repeated adsorption-elution cycles, and TD could easily be separated from aqueous solution by filtration. On the other hand, the present synthetic technology of TD was very simple, cost-effective, organic solvent-free and available for large-scale preparation. Thus, this separation method not only brings great advantages in the purification of PPPs from egg yolk protein but also provides a promising purification material for the enrichment of phosphopeptides in proteomic researches. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced cycle stability of micro-sized Si/C anode material with low carbon content fabricated via spray drying and in situ carbonization

Energy Technology Data Exchange (ETDEWEB)

Wang, Dingsheng; Gao, Mingxia, E-mail: gaomx@zju.edu.cn; Pan, Hongge; Liu, Yongfeng; Wang, Junhua; Li, Shouquan; Ge, Hongwei

2014-08-01

Highlights: • Micro-sized Si/C composites were fabricated via. spray drying and carbonization. • Multi-morphology carbon was formed in the Si/C composites. • Si/C composite with 5.6 wt.% C provides significant improved cycling stability. • Multi-morphology carbon plays effective role in improving the electrochemical property. • The method provides potential for mass production of superior Si-based anode materials. - Abstract: Micro-sized Si/C composites with in situ introduced carbon of multi-morphology were fabricated via spray drying a suspension of commercial micro-sized Si and citric acid followed by a carbonization. Different ratios of Si to citric acid were used to optimize the composition and structure of the composites and thus the electrochemical performance. Carbon flakes including crooked and flat ones were well dispersed in between the Si particles, forming Si/C composites. Floc-like carbon layers and carbon fragments were also found to cover partially the Si particles. The Si/C composite with a low carbon content of 5.6 wt.% provides an initial reversible capacity of 2700 mA h/g and a capacity of 1860 mA h/g after 60 cycles at a current density of 100 mA/g as anode material for lithium-ion batteries (LIBs), which are much higher than those of pristine Si and the Si/C composites with higher carbon content. The mechanism of the enhancement of electrochemical performance of the micro-sized Si/C composite is discussed. The fabrication method and the structure design of the composites offer valuable potential in developing adaptable Si-based anode materials for industrial applications.

Early implementation of SiC cladding fuel performance models in BISON

Energy Technology Data Exchange (ETDEWEB)

Powers, Jeffrey J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2015-09-18

SiC-based ceramic matrix composites (CMCs) [5–8] are being developed and evaluated internationally as potential LWR cladding options. These development activities include interests within both the DOE-NE LWR Sustainability (LWRS) Program and the DOE-NE Advanced Fuels Campaign. The LWRS Program considers SiC ceramic matrix composites (CMCs) as offering potentially revolutionary gains as a cladding material, with possible benefits including more efficient normal operating conditions and higher safety margins under accident conditions [9]. Within the Advanced Fuels Campaign, SiC-based composites are a candidate ATF cladding material that could achieve several goals, such as reducing the rates of heat and hydrogen generation due to lower cladding oxidation rates in HT steam [10]. This work focuses on the application of SiC cladding as an ATF cladding material in PWRs, but these work efforts also support the general development and assessment of SiC as an LWR cladding material in a much broader sense.

Characteristics of hot-pressed fiber-reinforced ceramics with SiC matrix

Science.gov (United States)

Miyoshi, Tadahiko; Kodama, Hironori; Sakamoto, Hiroshi; Goto, Akihiro; Iijima, Shiroo

1989-11-01

Silicon carbide ceramics’ matrix composites with SiC or C filaments were fabricated through hot pressing, and the effects of the filament pullout on their fracture toughness were experimentally investigated. The C-rich coating layers on the SiC filaments were found to have a significant effect on the frictional stress at the filament/matrix interfaces, through assising the filamet pullout from the matrix. Although the coating layers were apt to burn out in the sintering process of SiC matrix compposites, a small addition of carbon to the raw materials was found to be effective for the retention of the layers on the fibers, thus increasing the fracture toughness of the composites. The fracture toughness of the C filament/SiC matrix composite increased with temperature due to the larger interfacial frictional stress at higher temperatures, because of the higher thermal expansion of the filament in the radial direction than that of the matrix.

Growth of BaTiO3-PVDF composite thick films by using aerosol deposition

Science.gov (United States)

Cho, Sung Hwan; Yoon, Young Joon

2016-01-01

Barium titanate (BaTiO3)-polyvinylidene fluoride (PVDF) composite thick films were grown by using aerosol deposition at room temperature with BaTiO3 and PVDF powders. To produce a uniform composition in ceramic and polymer composite films, which show a substantial difference in specific gravity, we used PVDF-coated BaTiO3 powders as the starting materials. An examination of the microstructure confirmed that the BaTiO3 were well distributed in the PVDF matrix in the form of a 0 - 3 compound. The crystallite size in the BaTiO3-PVDF composite thick films was 5 ˜ 50 times higher than that in pure BaTiO3 thick films. PVDF plays a role in suppressing the fragmentation of BaTiO3 powder during the aerosol deposition process and in controlling the relative permittivity.

Effect of preceramic and Zr coating on impregnation behaviors of SiC ceramic composite

Science.gov (United States)

Jung, Yang-Il; Kim, Sun-Han; Kim, Hyun-Gil; Park, Jeong-Yong; Koo, Yang-Hyun

2015-01-01

SiC fiber-reinforced ceramic composites were fabricated using a polymer impregnation and pyrolysis process. To develop the low temperature process, the pyrolysis was conducted at 600 °C in air. Both a microstructural observation and a mechanical test were utilized for the evaluation of the impregnation. For the impregnation, two kinds of polycarbosilane having a different degree of cross-linking were used. The level of cross-linking affected the ceramic yield of the composites. The cross-linking under oxygen containing atmosphere resulted in a dense matrix and high density of filling. However, tight bonding between the matrix and fibers in the fully dense composite samples, which was obtained using a cross-linking agent of divinylbenzene, turned out to be deteriorative on the mechanical properties. The physical isolation of fibers from matrix phase in the composites was very important to attain a mechanical ductility. The brittle fracture was alleviated by introducing an interphase coating with metallic Zr. The combination of forming the dense matrix and interphase coating should be a necessary condition for the SiCf/SiC fiber-reinforce composite, and it is practicable by controlling the process parameters.

Synthesis and characterization of MoS2/Ti composite coatings on Ti6Al4V prepared by laser cladding

Science.gov (United States)

Yang, Rongjuan; Liu, Zongde; Wang, Yongtian; Yang, Guang; Li, Hongchuan

2013-02-01

The MoS2/Ti composite coating with sub-micron grade structure has been prepared on Ti6Al4V by laser method under argon protection. The morphology, microstructure, microhardness and friction coefficient of the coating were examined. The results indicated that the molybdenum disulfide was decomposed during melting and resolidification. The phase organization of composite coating mainly consisted of ternary element sulfides, molybdenum sulfides and titanium sulfides. The friction coefficient of and the surface roughness the MoS2/Ti coating were lower than those of Ti6Al4V. The composite coating exhibits excellent adhesion to the substrates, less surface roughness, good wear resistance and harder surface.

Friction and wear behavior of TiC particle reinforced ZA43 matrix composites

Institute of Scientific and Technical Information of China (English)

谢贤清; 张荻; 刘金水; 吴人洁

2001-01-01

TiC/ZA43 composites were fabricated by XDTM and stirring-casting techniques. The tribology properties of the unreinforced ZA43 alloy and the composites were studied by using a block-on-ring apparatus. Experimental results show that the incorporation of TiC particles improves the microstructure of ZA43 matrix alloy. The coefficient of friction μ and the width of worn groove decrease with the increase of TiC volume fraction φ(TiC). The width of worn groove and μ of the composite during wear testing increase with increasing the applied load. Metallographic examinations reveal that unreinforced ZA43 alloy has deep ploughing grooves with obvious adhesion phenomenon, whereas TiC/ZA43 composites have smooth worn surface. Delamination formation is related to the fatigue cracks and the shear cracks on the surface.

Influence of TiB2 particles on machinability and machining parameter optimization of TiB2/Al MMCs

Directory of Open Access Journals (Sweden)

Ruisong JIANG

2018-01-01

Full Text Available In situ formed TiB2 particle reinforced aluminum matrix composites (TiB2/Al MMCs have some extraordinary properties which make them be a promising material for high performance aero-engine blade. Due to the influence of TiB2 particles, the machinability is still a problem which restricts the application of TiB2/Al MMCs. In order to meet the industrial requirements, the influence of TiB2 particles on the machinability of TiB2/Al MMCs was investigated experimentally. Moreover, the optimal machining conditions for this kind of MMCs were investigated in this study. The major conclusions are: (1 the machining force of TiB2/Al MMCs is bigger than that of non-reinforced alloy and mainly controlled by feed rate; (2 the residual stress of TiB2/Al MMCs is compressive while that of non-reinforced alloy is nearly neutral; (3 the surface roughness of TiB2/Al MMCs is smaller than that of non-reinforced alloy under the same cutting speed, but reverse result was observed when the feed rate increased; (4 a multi-objective optimization model for surface roughness and material removal rate (MRR was established, and a set of optimal parameter combinations of the machining was obtained. The results show a great difference from SiC particle reinforced MMCs and provide a useful guide for a better control of machining process of this material.

Hard TiCx/SiC/a-C:H nanocomposite thin films using pulsed high energy density plasma focus device

International Nuclear Information System (INIS)

Umar, Z.A.; Rawat, R.S.; Tan, K.S.; Kumar, A.K.; Ahmad, R.; Hussain, T.; Kloc, C.; Chen, Z.; Shen, L.; Zhang, Z.

2013-01-01

Highlights: •The energetic ions and electron beams are used to synthesize TiC x /SiC/a-C:H films. •As-deposited crystalline and hard nanocomposite TiC x /SiC/a-C:H films are synthesized. •Very high average deposition rates of 68 nm/shot are achieved using dense plasma focus. •The maximum hardness of 22 GPa is achieved at the surface of the film. -- Abstract: Thin films of TiC x /SiC/a-C:H were synthesized on Si substrates using a complex mix of high energy density plasmas and instability accelerated energetic ions of filling gas species, emanated from hot and dense pinched plasma column, in dense plasma focus device. The conventional hollow copper anode of Mather type plasma focus device was replaced by solid titanium anode for synthesis of TiC x /SiC/a-C:H nanocomposite thin films using CH 4 :Ar admixture of (1:9, 3:7 and 5:5) for fixed 20 focus shots as well as with different number of focus shots with fixed CH 4 :Ar admixture ratio 3:7. XRD results showed the formation of crystalline TiC x /SiC phases for thin film synthesized using different number of focus shots with CH 4 :Ar admixture ratio fixed at 3:7. SEM results showed that the synthesized thin films consist of nanoparticle agglomerates and the size of agglomerates depended on the CH 4 :Ar admixture ratio as well as on the number of focus shots. Raman analysis showed the formation of polycrystalline/amorphous Si, SiC and a-C for different CH 4 :Ar ratio as well as for different number of focus shots. The XPS analysis confirmed the formation of TiC x /SiC/a-C:H composite thin film. Nanoindentation results showed that the hardness and elastic modulus values of composite thin films increased with increasing number of focus shots. Maximum values of hardness and elastic modulus at the surface of the composite thin film were found to be about 22 and 305 GPa, respectively for 30 focus shots confirming the successful synthesis of hard composite TiC x /SiC/a-C:H coatings

Review of Research Work on Ti-BASED Composite Coatings

Science.gov (United States)

Gabbitas, Brian; Salman, Asma; Zhang, Deliang; Cao, Peng

The service life of industrial components is limited predominantly by Chemical corrosion/mechanical wear. The project is concerned with the investigation of the capability of Ti(Al,O)/Al2O3 coatings to improve the service life of tool steel (H13) used for dies in aluminium high pressure die casting. This paper gives a general review on the research work conducted at the University of Waikato on producing and evaluating the titanium/alumina based composite coatings. The powder feedstocks for making the composite coatings were produced by high energy mechanical milling of a mixture of Al and TiO2 powders in two different molar ratios followed by a thermal reaction process. The feedstocks were then thermally sprayed using a high velocity air-fuel (HVAF) technique on H13 steel substrates to produce a Ti(Al,O)/Al2O3 composite coatings. The performance of the coating was assessed in terms of thermal shock resistance and reaction kinetics with molten aluminium. The composite powders and coatings were characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD).

The Effect of Titanium Dioxide (TiO2) Nanoparticles on Hydroxyapatite (HA)/TiO2 Composite Coating Fabricated by Electrophoretic Deposition (EPD)

Science.gov (United States)

Amirnejad, M.; Afshar, A.; Salehi, S.

2018-05-01

Composite coatings of Hydroxyapatite (HA) with ceramics, polymers and metals are used to modify the surface structure of implants. In this research, HA/TiO2 composite coating was fabricated by electrophoretic deposition (EPD) on 316 stainless steel substrate. HA/TiO2 composite coatings with 5, 10 and 20 wt.% of TiO2, deposited at 40 V and 90 s as an optimum condition. The samples coated at this condition led to an adherent, continuous and crack-free coating. The influence of TiO2 content was studied by performing different characterization methods such as scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), corrosion resistance in simulated body fluid (SBF), coating's dissolution rate in physiological solution and bond strength to the substrate. The results showed that the higher amount of TiO2 in the composite coating led to increase in bond strength of coating to stainless steel substrate from 3 MPa for HA coating to 5.5 MPa for HA-20 wt.% TiO2 composite coating. In addition, it caused to reduction of corrosion current density of samples in the SBF solution from 18.92 μA/cm2 for HA coating to 6.35 μA/cm2 for HA-20 wt.% TiO2 composite coating.

The Effect of Titanium Dioxide (TiO2) Nanoparticles on Hydroxyapatite (HA)/TiO2 Composite Coating Fabricated by Electrophoretic Deposition (EPD)

Science.gov (United States)

Amirnejad, M.; Afshar, A.; Salehi, S.

2018-04-01

Composite coatings of Hydroxyapatite (HA) with ceramics, polymers and metals are used to modify the surface structure of implants. In this research, HA/TiO2 composite coating was fabricated by electrophoretic deposition (EPD) on 316 stainless steel substrate. HA/TiO2 composite coatings with 5, 10 and 20 wt.% of TiO2, deposited at 40 V and 90 s as an optimum condition. The samples coated at this condition led to an adherent, continuous and crack-free coating. The influence of TiO2 content was studied by performing different characterization methods such as scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), corrosion resistance in simulated body fluid (SBF), coating's dissolution rate in physiological solution and bond strength to the substrate. The results showed that the higher amount of TiO2 in the composite coating led to increase in bond strength of coating to stainless steel substrate from 3 MPa for HA coating to 5.5 MPa for HA-20 wt.% TiO2 composite coating. In addition, it caused to reduction of corrosion current density of samples in the SBF solution from 18.92 μA/cm2 for HA coating to 6.35 μA/cm2 for HA-20 wt.% TiO2 composite coating.

Microstructure, consolidation and mechanical behaviour of Mg/n-TiC composite

Directory of Open Access Journals (Sweden)

N. Vijay Ponraj

2016-09-01

Full Text Available In this work, the microstructure, consolidation and mechanical properties of pure magnesium, magnesium based composite containing with different fractions (5, 10, 15 wt% of Titanium carbide nanoparticles (n-TiC were fabricated via powder metallurgy technique. The fabricated composites exhibited homogeneous distribution of TiC with little porosity. Microstructure of the composite and powders was studied using X-ray diffraction, Scanning electron microscope, and Transmission electron microscope. Microstructural characterization of the materials exposed that the accumulation of nanosized titanium carbide reinforcement enhanced the homogenization during mechanical blending. The relative density, compressibility, green compressive strength, sinterability and hardness of the nanocomposites were also examined. The effect of reinforcement on the densification was studied and reported in terms of the relative density and consolidation behaviour of the Magnesium matrix with n-TiC was studied and best compacted fit obtained through the Heckel, Panelli Ambrosio Filho and Ge equations. The compressive strength of the composite significantly increases from 230 MPa to 389 MPa with content of n-TiC and sintering temperature. Experiments have been performed under different conditions of temperature, n-TiC Content, and compacting pressure.

[Preparation and catalytic activity of surface-modification CNTs/TiO2 composite photocatalysts].

Science.gov (United States)

Wang, Huan-Ying; Li, Wen-Jun; Chang, Zhi-Dong; Zhou, Hua-Lei; Guo, Hui-Chao

2011-09-01

A novel kind of carbon nanotubes/titanium dioxide (CNTs/TiO2) composite photocatalyst was prepared by a modified sol-gel method in which the nanoscaled TiO2 particles were uniformly deposited on the CNTs modified with poly(vinyl pyrrolidone) (PVP). The composites were characterized by a range of analytical techniques including high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show the successful covering of the CNTs with PVP, forming core-shell structure. The nanoscaled TiO2 particles were uniformly deposited on the surface of CNTs reducing the bare CNTs which avoid losing the absorption and scattering of photons. The combination of CNTs and TiO2 particles imply the enhanced interactions between the CNTs and TiO2 interface which possibly becomes heterojunction. The composites become mesoporous crystalline TiO2 (anatase) clusters after annealing at 500 degrees C, and the surface area increases obviously. The photocatalytic activities of surface modification CNTs/TiO2 (smCNTs/TiO2) composites are extremely enhanced from the results of the photodegradation of methylene blue (MB).

Effect of TiC addition on surface oxidation behavior of SKD11 tool steel composites

Science.gov (United States)

Cho, Seungchan; Jo, Ilguk; Kim, Heebong; Kwon, Hyuk-Tae; Lee, Sang-Kwan; Lee, Sang-Bok

2017-09-01

Titanium carbide (TiC) reinforced tool steel matrix composites were successfully fabricated by a liquid pressing infiltration process and research was subsequently conducted to investigate the composites' oxidation resistance. The mass gain of the tested TiC-SKD11 composite held at 700 °C for 50 h in an air environment decreased by about 60%, versus that of the SKD11, which indicates improved oxidation resistance. Improved oxidation resistance of the TiC-SKD11 composite originates from uniformly reinforced TiC, with a phase transition to thermodynamically stable, volume-expanded TiO2.

Ohmic Contacts to P-Type SiC

National Research Council Canada - National Science Library

Crofton, John

2000-01-01

Alloys of aluminum (Al) have previously been used as ohmic contacts to p-type SiC, however the characteristics and performance of these contacts is drastically affected by the type and composition of the Al alloy...

Cavitation resistance of surface composition "Steel-Ni-TiNi-TiNiZr-cBNCo", formed by High-Velocity Oxygen-Fuel spraying

Science.gov (United States)

Blednova, Zh. M.; Dmitrenko, D. V.; Balaev, E. U. O.

2018-01-01

The object of the study is a multilayered surface composition "Steel - a Multicomponent material with Shape Memory Effect - a wear-resistant layer" under conditions of cavitation effects in sea water. Multicomponent TiNi-based coatings with addition of alloying elements such as Zr in an amount up to 10% mass, allow to create a composite material with a gradient of properties at the interface of layers, which gives new properties to coatings and improves their performance significantly. The use of materials with shape memory effect (SME) as surface layers or in the composition of surface layered compositions allows to provide an effective reaction of materials to the influence of external factors and adaptation to external influences. The surface composite layer cBN-10%Co has high hardness and strength, which ensures its resistance to shock cyclic influences of collapsing caverns. The increased roughness of the surface of a solid surface composite in the form of strong columnar structures ensures the crushing of vacuum voids, redistributing their effect on the entire surface, and not concentrating them in certain zones. In addition, the gradient structure of the multilayer composite coating TiNi-Ti33Ni49Zr18-cBN-10%Co Co makes it possible to create conditions for the relaxation of stresses created by the variable impact load of cavitation caverns and the manifestation of compensating internal forces due to thermo-elastic martensitic transformations of SME materials. The cavitation resistance of the coating TiNi-Ti33Ni49Zr18-cBN-10%Co according to the criterion of mass wear is 15-20 times higher than that of the base material without coating and 10-12 times higher than that of the TiNi-TiNiZr coating. The proposed architecture of the multifunctional gradient composition, "steel-Ni-TiNi- Ti33Ni49Zr18-cBN-10%Co", each layer of which has its functional purpose, allows to increase the service life of parts operating under conditions of cavitation-fatigue loading in

Erosion behaviour of physically vapour-deposited and chemically vapour-deposited SiC films coated on molybdenum during oxygenated argon beam thinning

International Nuclear Information System (INIS)

Shikama, T.; Kitajima, M.; Fukutomi, M.; Okada, M.

1984-01-01

The erosion behaviour during bombardment with a 5 keV argon beam at room temperature was studied for silicon carbide (SiC) films of thickness of about 10 μm coated on molybdenum by physical vapour deposition (PVD) and chemical vapour deposition (CVD). The PVD SiC (plasma-assisted ion plating) exhibited a greater thinning rate than the CVD SiC film. Electron probe X-ray microanalysis revealed that the chemical composition of PVD SiC was changed to a composition enriched in silicon by the bombardment, and there was a notable change in its surface morphology. The CVD SiC retained its initial chemical composition with only a small change in its surface morphology. Auger electron spectroscopy indicated that silicon oxide was formed on the surface of PVD SiC by the bombardment. The greater thinning rate and easier change in chemical composition in PVD SiC could be attributed to its readier chemical reaction with oxygen due to its more non-uniform structure and weaker chemical bonding. Oxygen was present as one of the impurities in the argon beam. (Auth.)

Synthesis and photocatalytic properties of visible light responsive La/TiO2-graphene composites

International Nuclear Information System (INIS)

Khalid, N.R.; Ahmed, E.; Hong Zhanglian; Ahmad, M.

2012-01-01

Highlights: ► Synthesis of La/TiO 2 -graphene composites by two-step hydrothermal method. ► Efficient charge separation due to La doping and graphene incorporation. ► Enhanced photocatalytic activity of composite catalyst for MB degradation under visible-light. - Abstract: La/TiO 2 -graphene composites used as photocatalyst were prepared by two-step hydrothermal method. The as-prepared composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The results of optical properties of La/TiO 2 -graphene composites exhibit extended light absorption in visible-light region and possess better charge separation capability as compared to pure TiO 2 . The photocatalytic activity measurement demonstrate that La/TiO 2 -graphene composites exhibited an enhanced photocatalytic activity for methylene blue (MB) degradation under visible-light irradiation compared to pure TiO 2 , which was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of graphene and the large surface contact between graphene and La/TiO 2 nanoparticles.

Photodegradation of indigo carmine and methylene blue dyes in aqueous solution by SiC-TiO{sub 2} catalysts prepared by sol-gel

Energy Technology Data Exchange (ETDEWEB)

Gomez-Solis, Christian [Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, San Luis Potosi Av. Manuel Nava 6, San Luis Potosi, S.L.P. 78290 (Mexico); Juarez-Ramirez, Isaias, E-mail: isajua13@yahoo.com [Departamento de Ecomateriales y Energia, Facultad de Ingenieria Civil, Universidad Autonoma de Nuevo Leon, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Moctezuma, Edgar [Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, San Luis Potosi Av. Manuel Nava 6, San Luis Potosi, S.L.P. 78290 (Mexico); Torres-Martinez, Leticia M. [Departamento de Ecomateriales y Energia, Facultad de Ingenieria Civil, Universidad Autonoma de Nuevo Leon, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico)

2012-05-30

Highlights: Black-Right-Pointing-Pointer Photodegradation of organic dyes is possible using sol-gel SiC-TiO{sub 2} catalysts. Black-Right-Pointing-Pointer SiC-TiO{sub 2} makes a synergy effect that enhances its catalytic activity. Black-Right-Pointing-Pointer Sol-gel allows good dispersion and attachment of TiO{sub 2} particles on SiC surface. Black-Right-Pointing-Pointer SiC-TiO{sub 2} exhibits better activity than TiO{sub 2} (P25) on organic dyes degradation. Black-Right-Pointing-Pointer SiC-TiO{sub 2} catalysts are settled down and easily separated after photocatalysis. - Abstract: Indigo carmine and methylene blue dyes in aqueous solution were photodegraded using SiC-TiO{sub 2} catalysts prepared by sol-gel method. After thermal treatment at 450 Degree-Sign C, SiC-TiO{sub 2} catalysts prepared in this work showed the presence of SiC and TiO{sub 2} anatase phase. Those compounds showed specific surface area values around 22-25 m{sup 2} g{sup -1}, and energy band gap values close to 3.05 eV. In comparison with TiO{sub 2} (P25), SiC-TiO{sub 2} catalysts showed the highest activity for indigo carmine and methylene blue degradation, but this activity cannot be attributed to the properties above mentioned. Therefore, photocatalytic performance is due to the synergy effect between SiC and TiO{sub 2} particles caused by the sol-gel method used to prepare the SiC-TiO{sub 2} catalysts. TiO{sub 2} nanoparticles are well dispersed onto SiC surface allowing the transfer of electronic charges between SiC and TiO{sub 2} semiconductors, which avoid the fast recombination of the electron-hole pair during the photocatalytic process.

Facile synthesis of polyaniline/TiO2/graphene oxide composite for high performance supercapacitors