WorldWideScience

Sample records for carbide whisker composites

  1. Protective coating for alumina-silicon carbide whisker composites

    Science.gov (United States)

    Tiegs, Terry N.

    1989-01-01

    Ceramic composites formed of an alumina matrix reinforced with silicon carbide whiskers homogenously dispersed therein are provided with a protective coating for preventing fracture strength degradation of the composite by oxidation during exposure to high temperatures in oxygen-containing atmospheres. The coating prevents oxidation of the silicon carbide whiskers within the matrix by sealing off the exterior of the matrix so as to prevent oxygen transport into the interior of the matrix. The coating is formed of mullite or mullite plus silicon oxide and alumina and is formed in place by heating the composite in air to a temperature greater than 1200.degree. C. This coating is less than about 100 microns thick and adequately protects the underlying composite from fracture strength degradation due to oxidation.

  2. Silicon carbide whisker composites. (Latest citations from Engineered Materials abstracts). NewSearch

    Energy Technology Data Exchange (ETDEWEB)

    1994-11-01

    The bibliography contains citations concerning the manufacture and applications of silicon carbide whisker reinforced composites. Citations discuss the preparation of whiskers and the processing of composites containing the whiskers. Applications include aerospace engines, automotive components, engine components, and surgical implants. Physical properties such as bending strength, crack propagation, creep, fracture toughness, and stress strain curves are covered. Ceramic matrix, metal matrix, and carbon-carbon composites are examined. (Contains a minimum of 248 citations and includes a subject term index and title list.)

  3. Aluminum nitride-silicon carbide whisker composites: Processing, properties, and microstructural stability

    Energy Technology Data Exchange (ETDEWEB)

    Cross, M.T.

    1990-01-01

    Aluminum nitride -- silicon carbide whisker composites with up to 20 vol % whiskers were fabricated by pressureless sintering (1750{degree}--1800{degree}C) and by hot-pressing (1700{degree}--1800{degree}C). Silicon carbide whiskers were found to degrade depending on the type of protective powder bed used during sintering. Whiskers were found to degraded in high oxygen containing samples by reaction with sintering additives. Whisker degradation was also due to the formation of silicon carbide -- aluminum nitride solid solution. No whisker degradation was observed in hot-pressed samples. For these samples Young's modulus and fracture toughness were measured. A 33% increase in the fracture toughness was measured by the indentation technique for a 20 vol % whisker composite. Operative toughening mechanisms were investigated using scanning electron microscopy. Crack deflection and whisker bridging were the dominant mechanisms. It was also shown that load transfer from matrix to whiskers can be a contributing factor to toughening. 88 refs., 34 figs., 11 tabs.

  4. Silicon carbide whisker composites. (Latest citations from Engineered Materials abstracts). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-02-01

    The bibliography contains citations concerning the manufacture and applications of silicon carbide whisker reinforced composites. Citations discuss the preparation of whiskers and the processing of composites containing the whiskers. Applications include aerospace engines, automotive components, engine components, and surgical implants. Physical properties such as bending strength, crack propagation, creep, fracture toughness, and stress strain curves are covered. Ceramic matrix, metal matrix, and carbon-carbon composites are examined. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  5. Silicon carbide whisker reinforced composites and method for making same

    Science.gov (United States)

    Wei, G.C.

    1984-02-09

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties, especially increased fracture toughness. In the formation of these ceramic composites, the single-crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al/sub 2/O/sub 3/, mullite, or B/sub 4/C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600 to 1950/sup 0/C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m/sup 1/2/ which represents as much as a two-fold increase over that of the matrix material.

  6. Boron carbide whiskers produced by vapor deposition

    Science.gov (United States)

    1965-01-01

    Boron carbide whiskers have an excellent combination of properties for use as a reinforcement material. They are produced by vaporizing boron carbide powder and condensing the vapors on a substrate. Certain catalysts promote the growth rate and size of the whiskers.

  7. Effects of interfaces and preferred orientation on the electrical response of composites of alumina and silicon carbide whiskers

    Science.gov (United States)

    Bertram, Brian D.

    Ceramic-matrix composites of alumina and silicon carbide whiskers have recently found novel commercial application as electromagnetic absorbers. However, a detailed understanding of how materials issues influence the composite electrical response which underpins this application has been absent until now. In this project, such composites were electrically measured over a wide range of conditions and modeled in terms of various aspects of the microstructure in order to understand how they work. For this purpose, three types of composites were made by different methods from the same set of ceramic powder blends loaded with different volume fractions of whiskers. In doing so, the interfaces between whiskers, the preferred orientations of whiskers, and the structure of electrically-connected whisker clusters were varied. In Chapter 3, it shown that Schottky energy barriers form at the junctions of the wide-bandgap semiconductor whiskers when metal electrodes are applied for measurements. These barriers were characterized on the microscopic and macroscopic level, and the gap between these different scales was bridged. Also, a modeling approach was developed for the loading dependence of the composite non-linear response which results from the barriers. In Chapter 4, the effects of significantly different types of preferred orientation are elucidated and a strong structure-property correlation is established. The effects of other structural issues on the electrical response are uncovered as well, such as those pertaining to porosity in the ceramic and the interfaces between electrically-connected SiCw. In Chapter 5, the non-linear response model of Chapter 3 is adapted in the development of a new model for electrically-percolated clusters. This model demonstrates how loading and interfacial issues influence the cluster topology and may result in the cluster having a non-linear electrical response. In Chapter 6, the effects of various factors on the broadband frequency

  8. Silicon carbide whisker reinforced ceramic composites and method for making same

    Science.gov (United States)

    Wei, George C.

    1985-01-01

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  9. Radial furnace shows promise for growing straight boron carbide whiskers

    Science.gov (United States)

    Feingold, E.

    1967-01-01

    Radial furnace, with a long graphite vaporization tube, maintains a uniform thermal gradient, favoring the growth of straight boron carbide whiskers. This concept seems to offer potential for both the quality and yield of whiskers.

  10. R-Curve Behavior for Silicon Carbide Whisker Reinforced Aluminum Oxide Composites

    Science.gov (United States)

    1990-01-01

    In 1976, Cutler sold his process to Exxon Enterprises and Hulco Inc. The joint effort, called Silag Inc., resulted in a plant at Greer, S.C...designed solely to make SiC whiskers commercially. In 1982, Arco Metals purchased the company, renamed it Arco Metals/ Silag Operation, and since then has...frequently observed, resulting in a range of planar defect densities and a mixture of structural types. The fringe spacing rarely repeats more than once or

  11. Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics

    Science.gov (United States)

    Becher, Paul F.; Tiegs, Terry N.

    1987-01-01

    The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

  12. Continuous synthesis of silicon carbide whiskers

    Science.gov (United States)

    Choi, Heon-Jin; Lee, June-Gunn

    1995-04-01

    Experimental synthesis of SiC whiskers coupled with thermodynamic calculations revealed the preferred reaction routes for the efficient synthesis of SiC whiskers. This formed the basis for the design of a continuous reactor, which consists of a boat-train loaded with silica-carbon mixture and iron-coated graphite substrate above it in an alumina-tube reactor. High-quality SiC whiskers have been grown with diameters of 1-3 micron. The yield was about 30% based on the silicon input as SiO2 and output as SiC whiskers. This demonstrates the feasibility of continuous SiC whiskers production without the additional processes of purification and classification.

  13. Effect of thermal cycling on whisker-reinforced dental resin composites.

    Science.gov (United States)

    Xu, Hockin H K; Eichmiller, Frederick C; Smith, Douglas T; Schumacher, Gary E; Giuseppetti, Anthony A; Antonucci, Joseph M

    2002-09-01

    The mechanical properties of dental resin composites need to be improved in order to extend their use to high stress-bearing applications such as crown and bridge restorations. Recent studies used single crystal ceramic whiskers to reinforce dental composites. The aim of this study was to investigate the effects of thermal cycling on whisker-reinforced composites. It was hypothesized that the whisker composites would not show a reduction in mechanical properties or the breakdown of whisker-resin interface after thermal cycling. Silicon carbide whiskers were mixed with silica particles, thermally fused, then silanized and incorporated into resin to make flexural specimens. The filler mass fraction ranged from 0% to 70%. The specimens were thermal cycled in 5 degrees C and 60 degrees C water baths, and then fractured in three-point bending to measure strength. Nano-indentation was used to measure modulus and hardness. No significant loss in composite strength, modulus and hardness was found after 10(5) thermal cycles (family confidence coefficient=0.95; Tukey's multiple comparison test). The strength of whisker composite increased with filler level up to 60%, then plateaued when filler level was further increased to 70%; the modulus and hardness increased monotonically with filler level. The strength and modulus of whisker composite at 70% filler level were significantly higher than the non-whisker controls both before and after thermal cycling. SEM revealed no separation at the whisker-matrix interfaces, and observed resin remnants on the pulled-out whiskers, indicating strong whisker-resin bonding even after 10(5) thermal cycles. In conclusion, novel dental resin composites containing silica-fused whiskers possessed superior strength and modulus compared to non-whisker composites both before and after thermal cycling. The whisker-resin bonding appeared to be resistant to thermal cycling in water, so that no loss in composite strength or stiffness occurred after

  14. Inorganic-whisker-reinforced polymer composites synthesis, properties and applications

    CERN Document Server

    Sun, Qiuju

    2015-01-01

    Inorganic-Whisker-Reinforced Polymer Composites: Synthesis, Properties and Applications gives a comprehensive presentation of inorganic microcrystalline fibers, or whiskers, a polymer composite filler. It covers whisker synthesis, surface modification, applications for reinforcing polymer-matrix composites, and analysis of resulting filled polymer composites. It focuses on calcium carbonate whiskers as a primary case study, introducing surface treatment methods for calcium carbonate whiskers and factors that influence them.Along with calcium carbonate, the book discusses potassium titanate and

  15. Dental resin composites containing silica-fused whiskers--effects of whisker-to-silica ratio on fracture toughness and indentation properties.

    Science.gov (United States)

    Xu, Hockin H K; Quinn, Janet B; Smith, Douglas T; Antonucci, Joseph M; Schumacher, Gary E; Eichmiller, Frederick C

    2002-02-01

    Dental resin composites need to be strengthened in order to improve their performance in large stress-bearing applications such as crowns and multiple-unit restorations. Recently, silica-fused ceramic whiskers were used to reinforce dental composites, and the whisker-to-silica ratio was found to be a key microstructural parameter that determined the composite strength. The aim of this study was to further investigate the effects of whisker-to-silica ratio on the fracture toughness, elastic modulus, hardness and brittleness of the composite. Silica particles and silicon carbide whiskers were mixed at whisker:silica mass ratios of 0:1, 1:5. 1:2, 1:1, 2:1, 5:1, and 1:0. Each mixture was thermally fused, silanized and combined with a dental resin at a filler mass percentage of 60%. Fracture toughness was measured with a single-edge notched beam method. Elastic modulus and hardness were measured with a nano-indentation system. Whisker:silica ratio had significant effects on composite properties. The composite toughness (mean+/-SD; n = 9) at whisker:silica = 2:1 was (2.47+/-0.28) MPa m(1/2), significantly higher than (1.02+/-0.23) at whisker:silica = 0:1, (1.13+/-0.19) of a prosthetic composite control, and (0.95+/-0.11) of an inlay/onlay composite control (Tukey's at family confidence coefficient = 0.95). Elastic modulus increased monotonically and hardness plateaued with increasing the whisker:silica ratio. Increasing the whisker:silica ratio also decreased the composite brittleness, which became about 1/3 of that of the inlay:onlay control. Electron microscopy revealed relatively flat fracture surfaces for the controls, but much rougher ones for the whisker composites, with fracture steps and whisker pullout contributing to toughness. The whiskers appeared to be well-bonded with the matrix, probably due to the fused silica producing rough whisker surfaces. Reinforcement with silica-fused whiskers resulted in novel dental composites that possessed fracture toughness

  16. Performance of Potassium Titanate Whisker Reinforced PPESK Composites

    Institute of Scientific and Technical Information of China (English)

    Minjie QU; Xigao JIAN; Wei HE; Gongxiong LIAO

    2004-01-01

    A group of poly (phthalazinone ether sulfone ketone)/potassium-titanate-whisker (PPSEK/whisker) composites was prepared by coprecipitation from solution. The whisker surface was modified using titanate coupling agent prior to blending. The tensile, impact, morphology and thermal properties of the moulded composites were investigated.The measurements showed that the tensile strength and impact strength of the composites increased with increasing whiskers content up to 10 to 20 phr, thereafter they showed a decrease in the whiskers content reached 40 phr.At the same time, the modulus of the composites increased with increasing whiskers content. Scanning electron microscopy studies revealed that the whiskers within the composites were dispersed uniformly by treated with coupling agent. Finally, thermogravimetric analysis showed that the heat resistance of the composites tended to increase with increasing whisker content. The results were analysed and discussed in terms of established models of the behaviour of short-fiber reinforced composites.

  17. Optimal Structure Design and Model Fitting of Silicon Carbide Whisker/Silicon Carbide Particle/Polypropylene Composites%碳化硅晶须/碳化硅颗粒/聚丙烯复合材料的结构优化设计和模型拟合

    Institute of Scientific and Technical Information of China (English)

    郭培荣; 张炜巍

    2012-01-01

    Polypropylene (PP) matrix thermal conductivity composites were prepared by mixing/mould pressing method with PP as an resin matrix,single silicon carbide whisker(SiC w)&silicon carbide particle (SiCp) and hybrid SiCw/SiCpas the thermal conductive fillers.Results showed that the thermal conductivity increased with the increasing content of thermal conductive fillers SiCw/SiCp.The thermal conductivity of the PP composites filled with hybrid SiC w/SiC p possessed better thermal conductivity than that of the composites filled with single SiCw or SiCp.The thermal conductivity coefficient A.was 0.856 W/(m o K) with 50 wt% hybrid SiC w/SiC p,about 5 times higher than that of the neat PP.Both the tensile and impact strength of the composites increased firstly,but decreased with excessive addition of SiC w/SiC p.The mechanical properties were optimal with 10 wt% hybrid SiCw/SiCp.The SiC w was much easier to form the thermal conductivity chains and network than that of SiCp.%以聚丙烯(PP)为基体,以单一碳化硅晶须( SiCw)、碳化硅颗粒(SiCp)和混杂SiCw/SiCp为导热填料,共混/模压制备PP基导热复合材料.结果表明:同等用量下,混杂SiCw/SiCp填充PP具有比单一SiCw或SiCp填充PP更佳的导热性能,且随SiCw/SiCp用量的增加而增加;当SiCw/SiCp质量分数为50%时,导热性能最佳,其导热系数为0.856 W/(m· K),为纯PP的5倍多.PP的拉伸强度与冲击强度随SiCw/SiCp用量的增加先增加后降低,当混杂SiCw/SiCp质量分数为10%时,力学性能最佳.相比SiCp而言,SiCw更易在PP中形成导热网链.

  18. Silicon Whisker and Carbon Nanofiber Composite Anode Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Physical Sciences Inc. (PSI) proposes to develop a silicon whisker and carbon nanofiber composite anode for lithium ion batteries on a Phase I program. This anode...

  19. Silicon Whisker and Carbon Nanofiber Composite Anode Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Physical Sciences Inc. (PSI) has successfully developed a silicon whisker and carbon nanofiber composite anode for lithium ion batteries on a Phase I program. PSI...

  20. Silicon carbide reinforced silicon carbide composite

    Science.gov (United States)

    Lau, Sai-Kwing (Inventor); Calandra, Salvatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    2001-01-01

    This invention relates to a process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  1. Composition Comprising Silicon Carbide

    Science.gov (United States)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

    2012-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  2. Performance of Silicon carbide whisker reinforced ceramic inserts on Inconel 718 in end milling process

    Science.gov (United States)

    Reddy, M. M.; Joshua, C. X. H.

    2016-03-01

    An experimental investigation is planned in order to study the machinability of Inconel 718 with silicon carbide whisker reinforced ceramic inserts in end milling process. The relationship between the cutting speed, feed rate, and depth of cut against the response factors are studied to show the level of significance of each parameter. The cutting parameters are optimized by using Taguchi method. Implementing analysis of variance, the parameter which influences the surface roughness the most is determined to be the cutting speed, followed by the feed rate and depth of cut. Meanwhile, the optimal cutting condition is determined to have high cutting speed, low feed rate, and high depth of cut in the range of selected parameters.

  3. PREDICTION OF MECHANICAL PROPERTY OF WHISKER REINFORCED METAL MATRIX COMPOSITE: PART-Ⅰ. MODEL AND FORMULATION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on study of strain distribution in whisker reinforced metal matrix composites, an explicit precise stiffness tensor is derived. In the present theory, the effect of whisker orientation on the macro property of composites is considered, but the effect of random whisker position and the complicated strain field at whisker ends are averaged. The derived formula is able to predict the stiffness modulus of composites with arbitrary whisker orientation under any loading condition. Compared with the models of micro-mechanics, the present theory is competent for modulus prediction of actual engineering composites. The verification and application of the present theory are given in a subsequent paper published in the same issue.

  4. Titanium Carbide-Graphite Composites

    Science.gov (United States)

    1991-11-08

    titanium carbide , titanium carbide with free graphite, titanium carbide /vanadium carbide alloy with free graphite, and titanium carbide with...from melts. The test pins were drawn across hot pressed titanium carbide wear plates with 5 newtons of normal force. The lowest friction coefficient at...22 C was 0.12 obtained with pure titanium carbide . The lowest friction coefficient at 900 C was 0.19 obtained with titanium carbide with boron and

  5. Strengthening and toughening of poly(L-lactide) composites by surface modified MgO whiskers

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Wei [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Luo, Binghong, E-mail: tluobh@jnu.edu.cn [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Qin, Xiaopeng; Li, Cairong [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Liu, Mingxian; Ding, Shan [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Zhou, Changren, E-mail: tcrz9@jnu.edu.cn [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China)

    2015-03-30

    Highlights: • The grafted PLLA chain on the surface of g-MgO whisker was ruled out by FTIR spectroscopy and TG/DTG analyses. • The excellent dispersion of g-MgO whiskers and the strong interfacial adhesion of g-MgO whiskers/PLLA composite were proved by FSEM. • Comparing to MgO particles and MgO whiskers, fibrous-like g-MgO whiskers are the most effective reinforcing and toughening fillers for PLLA. - Abstract: To improve both the strength and toughness of poly(L-lactide) (PLLA), fibrous-like MgO whiskers with diameters of 0.15–1 μm and lengths of 15–110 μm were prepared, and subsequently surface modified with L-lactide to obtain grafted MgO whiskers (g-MgO whiskers). The structures and properties of MgO whiskers and g-MgO whiskers were studied. Then, a series of MgO whiskers/PLLA and g-MgO whiskers/PLLA composites were prepared by solution casting method, for comparison, MgO particles/PLLA composite was prepared too. The resulting composites were evaluated in terms of hydrophilicity, crystallinity, dispersion of whiskers, interfacial adhesion and mechanical performance by means of polarized optical microscopy (POM), contact angle measurement, field emission scanning electron microscope (FSEM), transmission electron microscopy (TEM) and tensile testing. The results revealed that the crystallization rate and hydrophilicity of PLLA were improved by the introduction of MgO whiskers and g-MgO whiskers. The g-MgO whiskers can disperse more uniformly in and show stronger interfacial adhesion with the matrix than MgO whiskers as a result of the surface modification. Due to the bridge effect of the whiskers and the excellent interfacial adhesion between g-MgO whiskers and PLLA, g-MgO whiskers/PLLA composites exhibited remarkably higher strength, modulus and toughness compared to the pristine PLLA, MgO particles/PLLA and MgO whiskers/PLLA composites.

  6. Product technology and market assessment for silicon carbide whisker reinforced alumina heat-exchanger tubes. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Loutfy, R.O.; Withers, J.C. [Materials and Electrochemical Research Corp., Tucson, AZ (United States); Chakravarti, D. [Arizona Univ., Tucson, AZ (United States)

    1993-10-01

    This report describes a study designed to develop an assessment of key performance features, desirable technical specifications and market potential for silicon carbide whisker-reinforced alumina (henceforth SCWRA) tubes for heat exchanger applications in a number of industries. The results of the first stage of a Delphi study conducted in the US market are presented. The second phase of the study is in progress. The first stage results suggest that there is a small market for SCWRA tubes in heat exchanger applications. The market is expected to grow steadily during the 1990`s. With appropriate performance specifications and competitive pricing, growth should come from (a) new applications that permit recovery in cases that were previously infeasible and (b) selective, partial substitution and replacement of current ceramics and metal/ceramic composites in existing applications. We identify key performance factors and detailed specifications needed in six designated industries (primary metals, fabricated metals, chemicals, glass, utility and incinerators). Reliability, durability and low maintenance costs emerge as critical performance factors across these industries. The data show that although ceramics are recognized as having better properties, enhancing reliability and durability and thus improving maintenance cost performance is a key priority. Such improvements, reflected in the objectives for SCWRA tubes, should facilitate adoption in both new and existing applications. At this time, we are unable to assess market size directly. However, expert judgment provided indices tracking the projected market for heat exchanger tubes from 1990 to 2005.

  7. Investigation into hemp fiber-and whisker-reinforced soy protein composites

    Institute of Scientific and Technical Information of China (English)

    Linxiang WANG; Rakesh KUMAR; Lina ZHANG

    2009-01-01

    Whiskers, designated as W, were prepared from hemp fibers. Both fibers and whiskers were characterized by Fourier transform infrared spectroscopy, thermogravi-metric analysis. Scanning electron microscopy and transmission electron microscopy were used to evaluate the dimensions of the fibers and whiskers, respectively.By incorporating different weight fraction of the fibers and whiskers into soy protein isolate, we prepared two different composites designated as SC and SC-W,respectively. Thiodiglycol was used as a plasticizer for the preparation of composites. The SC and SC-W composites were characterized and compared in terms of mechanical properties, volume fraction of porosity,and water uptake. The results indicated that there was not much significant difference in the properties of the composites. In fact, mechanical properties of fiber-reinforced composites were higher than whisker-reinforced composites at optimum weight fractions.This study can give us the idea about the judicious use of fibers or whiskers as reinforcement materials.

  8. Effects of incorporating nanosized calcium phosphate particles on properties of whisker-reinforced dental composites.

    Science.gov (United States)

    Xu, Hockin H K; Sun, Limin; Weir, Mike D; Takagi, Shozo; Chow, Laurence C; Hockey, Bernard

    2007-04-01

    Clinical data indicate that secondary caries and restoration fracture are the most common problems facing tooth restorations. Our ultimate goal was to develop mechanically-strong and caries-inhibiting dental composites. The specific goal of this pilot study was to understand the relationships between composite properties and the ratio of reinforcement filler/releasing filler. Nanoparticles of monocalcium phosphate monohydrate (MCPM) were synthesized and incorporated into a dental resin for the first time. Silicon carbide whiskers were fused with silica nanoparticles and mixed with the MCPM particles at MCPM/whisker mass ratios of 1:0, 2:1, 1:1, 1:2, and 0:1. The composites were immersed for 1-56 days to measure Ca and PO4 release. When the MCPM/whisker ratio was changed from 0:1 to 1:2, the composite flexural strength (mean +/- SD; n = 5) decreased from 174 +/- 26 MPa to 138 +/- 9 MPa (p < 0.05). A commercial nonreleasing composite had a strength of 112 +/- 14 MPa. When the MCPM/whisker ratio was changed from 1:2 to 1:1, the Ca concentration at 56 days increased from 0.77 +/- 0.04 mmol/L to 1.74 +/- 0.06 mmol/L (p < 0.05). The corresponding PO4 concentration increased from 3.88 +/- 0.21 mmol/L to 9.95 +/- 0.69 mmol/L (p < 0.05). Relationships were established between the amount of release and the MCPM volume fraction v(MCPM) in the resin: [Ca]= 42.9 v(MCPM) (2.7), and [PO4] = 48.7 v(MCPM) (1.4). In summary, the method of combining nanosized releasing fillers with reinforcing fillers yielded Ca- and PO4-releasing composites with mechanical properties matching or exceeding a commercial stress-bearing, nonreleasing composite. This method may be applicable to the use of other Ca-PO4 fillers in developing composites with high stress-bearing and caries-preventing capabilities, a combination not yet available in any dental materials.

  9. Dental composite resins containing silica-fused ceramic single-crystalline whiskers with various filler levels.

    Science.gov (United States)

    Xu, H H

    1999-07-01

    Currently available direct-filling composite resins are susceptible to fracture and hence are not recommended for use in large stress-bearing posterior restorations involving cusps. The glass fillers in composites provide only limited reinforcement because of the brittleness and low strength of glass. The aim of the present study was to use ceramic single-crystalline whiskers as fillers to reinforce composites, and to investigate the effect of whisker filler level on composite properties. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whiskers, thereby improving retention in the matrix. The composite flexural strength, elastic modulus, hardness, and degree of polymerization conversion were measured as a function of whisker filler mass fraction, which ranged from 0% to 70%. Selected composites were polished simulating clinical procedures, and the surface roughness was measured with profilometry. The whisker composite with a filler mass fraction of 55% had a flexural strength (mean +/- SD; n = 6) of 196+/-10 MPa, significantly higher than 83+/-14 MPa of a microfill and 120+/-16 MPa of a hybrid composite control (family confidence coefficient = 0.95; Tukey's multiple comparison). The composite modulus and hardness increased monotonically with filler level. The flexural strength first increased, then plateaued with increasing filler level. The degree of conversion decreased with increasing filler level. The whisker composite had a polished surface roughness similar to that of a conventional hybrid composite (p>0.1; Student's t). To conclude, ceramic whisker reinforcement can significantly improve the mechanical properties of composite resins; the whisker filler level plays a key role in determining composite properties; and the reinforcement mechanisms appear to be crack pinning by whiskers and friction from whisker pullout resisting crack propagation.

  10. Effect of deformation temperature on the hot compressive behavior of metal matrix composites with misaligned whiskers

    Institute of Scientific and Technical Information of China (English)

    LI Aibin; MENG Qingyuan; GENG Lin; DENG Chunfeng; YAN Yiwu

    2007-01-01

    A multi-inclusion cell model is used to investigate the effect of deformation temperature and whisker rotation on the hot compressive behavior of metal matrix composites with misaligned whiskers. Numerical results show that deformation temperature influences the work-hardening behavior of the matrix and the rotation behavior of the whiskers. With increasing temperature, the work hardening rate of the matrix decreases, but the whisker rotation angle increases. Both whisker rotation and the increase of deformation temperature can induce reductions in the load supported by whisker and the load transferred from matrix to whisker. Additionally, it is found that during large strain deformation at higher temperatures, the enhancing of deformation temperature can reduce the effect of whisker rotation. Meanwhile, the stress-strain behavior of the composite is rather sensitive to deformation temperature. At a relatively lower temperature (150℃), the composite exhibits work hardening due to the matrix work hardening, but at relatively higher temperatures (300℃ and above),the composite shows strain softening due to whisker rotation. It is also found that during hot compression at higher temperatures, the softening rate of the composite decreases with increasing temperature. The predicted stress-strain behavior of the composite is approximately in agreement with the experimental results.

  11. Influence of Special Silica on the In—Situ Growth of Silicon Carbide Whiskers in Al2O3—C Refractories

    Institute of Scientific and Technical Information of China (English)

    WANGTian-ming; DOUShu-ju; 等

    1996-01-01

    In this paper,the influence of special silicas on the in-situ growth of silicon carbide whiskers in Al2O3-C refractories has been stud-ied.The microstructures of the products have been analyzed by means of SEM,and it is found that the whiskers grew better by adding some special silicas,Silica ② shows the best result because the VLS mechanism made the whiskers grow as long as 40μm and could be expected to greatly improve the mechnical properties of the refractories.

  12. Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

    Science.gov (United States)

    Singh, M.; Levine, S. R.

    1995-01-01

    A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

  13. Investigation of Creep Phenomenon in Metal Matrix Composites with Whiskers

    Directory of Open Access Journals (Sweden)

    Vahid Monfared

    2012-09-01

    Full Text Available A new mathematical model based on the exponential, logarithmic and polynomial (mixed functions is presented for determination of some unknowns such as displacement rate in outer surface of unit cell and strain rate of short fiber (whisker composites with elastic fiber in steady state creep under axial loading. In addition, effective factor or effect coefficient is introduced for determination of creep displacement rate in outer surface. Also, radial, axial displacement rates, equivalent and shear stresses will be determined by new method. Aim of this study is using the mathematical modeling instead of time consuming and costly experimental methods. On the other hand, unknowns are determined by polynomial, exponential and logarithmic functions instead of some theories, simply. These analytical results are then validated by the Finite Element Analysis (FEA. Interestingly, good agreements are found between analytical and numerical predictions for creep strain rate and displacement rate.

  14. Wear properties of potassium titanate whiskers-reinforced Al-12Si alloy composites

    Directory of Open Access Journals (Sweden)

    Wu Shenqing

    2010-02-01

    Full Text Available Potassium titanate (K2O·6TiO2 whiskers-reinforced Al-12Si alloy composites were prepared by the squeeze casting technique. Wear properties of the composites were investigated by pin-on-disc tests under dry conditions. The experimental results showed that K2O·6TiO2 whiskers can effectively reinforce the matrix alloy and improve the wear resistance of the composite when the volume fraction of whiskers is low at 10 vol%. However, the composites with a high volume fraction of whiskers showed lower wear resistance than the Al-12Si alloy. The main wear mechanism of the composites is clarified as de-lamination and abrasive wear.

  15. Wear and mechanical properties of nano-silica-fused whisker composites.

    Science.gov (United States)

    Xu, H H K; Quinn, J B; Giuseppetti, A A

    2004-12-01

    Resin composites must be improved if they are to overcome the high failure rates in large stress-bearing posterior restorations. This study aimed to improve wear resistance via nano-silica-fused whiskers. It was hypothesized that nano-silica-fused whiskers would significantly improve composite mechanical properties and wear resistance. Nano-silicas were fused onto whiskers and incorporated into a resin at mass fractions of 0%-74%. Fracture toughness (mean +/- SD; n = 6) was 2.92 +/- 0.14 MPa.m(1/2) for whisker composite with 74% fillers, higher than 1.13 +/- 0.19 MPa.m(1/2) for a prosthetic control, and 0.95 +/- 0.11 MPa.m(1/2) for an inlay/onlay control (Tukey's at 0.95). A whisker composite with 74% fillers had a wear depth of 77.7 +/- 6.9 mum, less than 118.0 +/- 23.8 microm of an inlay/onlay control, and 172.5 +/- 15.4 microm of a prosthetic control (p hardness, modulus, strength, and toughness, with R = 0.95-0.97. Novel nano-silica-fused whisker composites possessed high toughness and wear resistance with smooth worn surfaces, and may be useful in large stress-bearing restorations.

  16. Preparation and Electromechanical Properties of PVDF Matrix Piezoelectric Composites Containing Highly Oriented BaTiO3 Whiskers

    Institute of Scientific and Technical Information of China (English)

    Xuetao LUO; Lifu CHEN; Xiaojun CHEN; Qianjun HUANG

    2004-01-01

    The piezoelectric composites containing highly oriented BaTiO3 whiskers as active phase and PVDF as matrix have been prepared by micro-hole extrusion and orientation in carried fibers. The morphology of oriented BaTiO3 whiskers and microstructure of the composites were observed by SEM. As for its electromechanical properties, it is found that the dielectric constant, piezoelectric constant and remnant of polarization in the BaTiO3 whisker-PVDF composite are considerably higher than that in the BaTiO3 powders-PVDF composite, while the loss factors follow the opposite trend. For the BaTiO3 whisker-PVDF composite, the values of ε, d33 and Pr parallel to the whisker orientation (normal specimen) are much higher than that perpendicular to the whisker orientation (parallel specimen). The significant effects of the connective passages of active phase on electromechanical properties of the piezoelectric composites has also been investigated.

  17. Thermo-Mechanical Characterization of Silicon Carbide-Silicon Carbide Composites at Elevated Temperatures Using a Unique Combustion Facility

    Science.gov (United States)

    2009-09-10

    F THERMO-MECHANICAL CHARACTERIZATION OF SILICON CARBIDE - SILICON CARBIDE COMPOSITES AT ELEVATED...MECHANICAL CTERIZATION OF SILICON CARBIDE -SILIC BIDE COMPOSITES AT LEVATED TEMPER S USING A UNIQUE COMBUSTION FACILITY DISSERTATI N Ted T. Kim...THERMO-MECHANICAL CHARACTERIZATION OF SILICON CARBIDE - SILICON CARBIDE COMPOSITES AT ELEVATED TEMPERATURES USING A UNIQUE COMBUSTION FACILITY

  18. Diamond-silicon carbide composite and method

    Science.gov (United States)

    Zhao, Yusheng

    2011-06-14

    Uniformly dense, diamond-silicon carbide composites having high hardness, high fracture toughness, and high thermal stability are prepared by consolidating a powder mixture of diamond and amorphous silicon. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPam.sup.1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness.

  19. Influence of CaCO3 Whisker Content on Mechanical and Tribological Properties of Polyetheretherketone Composites

    Institute of Scientific and Technical Information of China (English)

    Youxi LIN; Chenghui GAO; Ning LI

    2006-01-01

    The mechanical and tribological properties of polyetheretherketone(PEEK)composites filled with CaCO3 whisker in various content of 0~45%(wt pct)were investigated. The composite specimens were prepared by compression molding. Tribological testing of composites in dry wear mode against carbon steel ring was carried out on a MM200 block-on-ring apparatus. Data on neat PEEK were also included for comparison. It was observed that inclusion of CaCO3 whisker affected the most mechanical properties and the friction and wear in a beneficial way. With an increase in CaCO3 whisker content, friction coefficient continuously decreased but the trends in wear performance varied. The specific wear rate showed minima as 1.28×10-6 mm3/Nm for 15% CaCO3 whisker inclusion followed by a slow increase for further CaCO3 whisker addition. In terms of friction applications, when the tribological and mechanical properties are combined, the optimal content of CaCO3 whisker in the filled PEEK should be recommended as 15% to 20%. Fairly good correlations are observed in friction coefficient vs bending modulus and wear rate vs bending strength, confirming that the bending properties prove to be the most important tribology controlling parameters in the present work.

  20. Whisker-reinforced dental core buildup composites: effect of filler level on mechanical properties.

    Science.gov (United States)

    Xu, H H; Smith, D T; Schumacher, G E; Eichmiller, F C

    2000-12-15

    The strength and toughness of dental core buildup composites in large stress-bearing restorations need to be improved to reduce the incidence of fracture due to stresses from chewing and clenching. The aims of the present study were to develop novel core buildup composites reinforced with ceramic whiskers, to examine the effect of filler level, and to investigate the reinforcement mechanisms. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whisker surface for improved retention in the matrix. Filler level was varied from 0 to 70%. Flexural strength, compressive strength, and fracture toughness of the composites were measured. A nano-indentation system was used to measure elastic modulus and hardness. Scanning electron microscopy (SEM) was used to examine the fracture surfaces of specimens. Whisker filler level had significant effects on composite properties. The flexural strength in MPa (mean +/- SD; n = 6) increased from (95+/-15) for the unfilled resin to (193+/- 8) for the composite with 50% filler level, then slightly decreased to (176+/-12) at 70% filler level. The compressive strength increased from (149+/-33) for the unfilled resin to (282+/-48) at 10% filler level, and remained equivalent from 10 to 70% filler level. Both the modulus and hardness increased monotonically with filler level. In conclusion, silica particle-fused ceramic single-crystalline whiskers significantly reinforced dental core buildup composites. The reinforcement mechanisms appeared to be crack deflection and bridging by the whiskers. Whisker filler level had significant effects on the flexural strength, compressive strength, elastic modulus, and hardness of composites.

  1. Process for making silicon carbide reinforced silicon carbide composite

    Science.gov (United States)

    Lau, Sai-Kwing (Inventor); Calandra, Salavatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    1998-01-01

    A process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  2. Carbides composite surface layers produced by (PTA)

    Energy Technology Data Exchange (ETDEWEB)

    Tajoure, Meloud, E-mail: Tajoore2000@yahoo.com [MechanicalEng.,HIHM,Gharian (Libya); Tajouri, Ali, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com [Materials and Metallurgical Eng., UOT, Tripoli (Libya); Akreem, Mosbah, E-mail: makreem@yahoo.com [Industrial Research Centre,Tripoli (Libya)

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  3. Preparation of mullite whiskers reinforced SiC/Al2O3 composites by microwave sintering

    Directory of Open Access Journals (Sweden)

    Wei Li

    2016-12-01

    Full Text Available Mullite whiskers reinforced SiC/Al2O3 composites were prepared by microwave sintering in a microwave chamber with TE666 resonant mode. Original SiC particles were coated with SiO2 using sol-gel processing and mixed with Al2O3 particles. Mullite was formed in the reaction between SiO2 and Al2O3. The isostatically pressed cylindrical pellets were sintered from 1350 °C to 1600 °C for 30 min. Physical and chemical responses were investigated by detecting changes in reflected power during the microwave sintering process. XRD was carried out to characterize the samples and showed that mullite could be formed at 1200 °C. Bridging of mullite whiskers between Al2O3 and SiC particles was observed by SEM and is due to a so-called local hot spot effect, which was the unique feature for microwave sintering. The optimized microwave sintering temperature was 1500 °C corresponding to the maximum amount of mullite whiskers within SiC/Al2O3 composites. The high electro-magnetic field enhanced the decomposition of mullite at higher temperatures above 1550 °C. The mechanical properties of mullite whiskers reinforced SiC/Al2O3 composites are much better than the SiC/Al2O3 composites without mullite whiskers.

  4. Whisker Orientation Function and Elastic Modulus of the as-cast 20%SiCw/Mg Composite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The relationship between the plane-orientation function and the space-orientation function of whiskers in whisker-reinforced metal matrix composites was analyzed theoretically. The actual orientation of whiskers in the as-cast 20%SiCw/Mg composite (SiCw content in volume fraction) were investigated, and the elastic modulus of the composite was measured with an ultrasonic velocity analyzer. Results show that there is an evident difference be-tween the plane-orientation function and the space-orientation function of whiskers and the space-orientation function can represent the actual condition of the composite. Only by using the space-orientation function of whiskers, the difference of elastic modulus of the as-cast composite in different directions can be explained reasonably.

  5. Effect of cellulose whisker content on the properties of poly(ethylene-co-vinyl acetate)/cellulose composites.

    Science.gov (United States)

    Elanthikkal, Silviya; Gopalakrishnapanicker, Unnikrishnan; Varghese, Soney; Guthrie, James T; Francis, Tania

    2013-06-20

    The reinforcing effect of cellulose whiskers, produced from banana waste fibres, has been investigated using poly(ethylene-co-vinyl acetate) [EVA]/cellulose whisker composites. Cellulose whiskers, approximately 300 nm long and 30 nm wide, were obtained via a sulphuric acid hydrolysis method. The effects of the cellulose whisker loading on the thermal properties, mechanical properties and on the morphological features of the composites have been investigated. EVA copolymer with a vinyl acetate segment content of 40% has been used for composite fabrication. The developed composites showed superior thermal and mechanical properties relative to that of the EVA copolymer alone. Three theoretical models, namely the Halpin-Tsai model, the Kerner model and the Nicolais-Narkis model have been employed to provide a basis for the comparison of the results with the observations from the tensile investigations.

  6. STRAIN REGULARITY IN REINFORCERS OFSHORT-FIBER/ WHISKER REINFORCED COMPOSITE AND ITS APPLICATION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    If the reinforcers were spheroids or ellipsoids, and their volume fraction was no more than 10%, their interactions could be neglected so that the elastic modulus of the composites could be predicted accurately[1~4]. However, in practical short-fiber/whisker reinforced metal matrix composites, the volume fraction of reinforcers is as high as 15%~40%. Additionally, the shape of reinforcers is usually far much more complicated than that of spheroids or ellipsoids and their distribution is irregular. The distance between reinforcers is usually as small as their diameter, so that it is difficult to cut out a unit cell with only a singular reinforcer included. For this kind of engineering composites, accurate prediction of effective elastic moduli is still an open problem until now[5].  In Refs.[6, 7], based on the study of strain distribution in whisker reinforced composites, the ratio of the root-mean-square strain of reinforcers to the macro linear strain along the same direction is defined as deformation characteristic parameter λf. An explicit precise stiffness tensor is derived by introducing λf and distribution density function of reinforcers, which is able to predict the stiffness modulus of composites with arbitrary whisker orientation under any loading condition. However, accurate prediction of the present theory depends on the value of λf.  In the present paper, the relation between λf and the microstructure geometrical and physical parameters of the composite will be investigated with a shear lag model[8] and network model[9] in order to derive a regressive formula for λf. As an example of verification, the tensile stress-strain curve of a whisker reinforced metal matrix composite will be predicted and compared with experiments.

  7. The mechanical behavior dependence on the TiB whisker realignment during hot-working in titanium matrix composites

    Science.gov (United States)

    Ma, Fengcang; Liu, Ping; Li, Wei; Liu, Xinkuan; Chen, Xiaohong; Zhang, Ke; Pan, Deng; Lu, Weijie

    2016-10-01

    Low-cost TiB whiskers reinforced titanium matrix composite (TMCs) was fabricated with enhanced mechanical performances using in situ technologies and hot working. Morphologies observation indicates that needle-like TiB whiskers with a hexagonal transverse section grow along the [010] direction due to B27 crystal structure and its growth mechanism. Mechanical properties tests show that the mechanical behavior of the TiB whiskers reinforced TMCs is dependent on the deformation amplitudes applied in hot-working. The improvement in yield strength by hot-working is attributed to the TiB whiskers realignment and the refinement of microstructure. Models are constructed to evaluate the realignment of TiB whisker during deformation and the increase in yield strength of the composite at elevated temperatures. These models clarify the alignment effect of TiB whiskers under various deformation amplitudes applied in hot-workings and reveals the yield strength dependence on TiB whiskers orientation.

  8. PREDICTION OF MECHANICAL PROPERTY OF WHISKER REINFORCED METAL MATRIX COMPOSITE:PART-Ⅱ. VERIFICATION & APPLICATION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The present paper continues the discussion in Part-I. Model and Formulation. Based on the theory proposed in Part-I, the formulae predicting stiffness moduli of the composites in some typical cases of whisker orientations and loading conditions are derived and compared with theoretical representatives in literatures, experimental measurement and commonly-used empirical formulae. It seems that (1) with whisker reinforcing and matrix-hardening considered, the present prediction is in well agreement with the experimental measurement; (2) the present theory can predict accurate moduli with the proper pre-calculated parameters; (3) the upper-bound and lower-bound of the present theory are just the predictions of equal strain theory and equal stress theory; (4) the present theory provides a physical explanation and theoretical base for the present commonly-used empirical formulae. Compared with the microscopic mechanical theories, the present theory is competent for modulus prediction of practical engineering composite in accuracy and simplicity.

  9. STRAIN REGULARITY IN REINFORCERS OF SHORT-FIBER/ WHISKER REINFORCED COMPOSITE AND ITS APPLICATION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on the study of strain distribution in short-fiber/whisker reinforced metal matrix composites, a deformation characteristic parameter λ is defined as the ratio of the root-mean-square strain of reinforcers to the macro-linear strain along the same direction. Quantitative relation between λ and microstructure parameters of the composite is obtained. As an example of applying and verifying λ, the stress-strain curve of [AlBO]w/Al composite under tensile loading is predicted and favorably compared with experiments. By using λ, the stiffness modulus of the composite with arbitrary reinforcer orientation under any loading condition is predicted from the microstructure parameters of material.

  10. Poly(Butylene Terephthalate Based Composites Containing Alumina Whiskers: Influence of Filler Functionalization on Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Pietro Russo

    2014-01-01

    Full Text Available Poly(butylene terephthalate (PBT is one of the most widely used semicrystalline thermoplastics polyester because of its superior thermal and mechanical properties, high dimensional stability and excellent processability. In this research PBT-based nanocomposites, including various amounts (up to 10 wt% of commercial alumina whiskers, have been prepared by using a Brabender internal chamber mixer and analysed in terms of morphological features and dielectric properties. Specific attention has been focused on the effect of the filler functionalization considering 3-glycidoxy propylmethoxysilane (GPS or 3-methacryloxypropyltrimethoxysilane (MPS as coupling agents. Tests, performed on compounds filled with neat and functionalized alumina whiskers, show a clear dependence of relative dielectric permittivity εr, invariance of dissipation factor (tgδ, and a sensible increase of volume electrical resistivity (ρv with the filler’s content and are encouraging for a future introduction of such composites in many electrical applications.

  11. Mullite Whiskers and Mullite-whisker Felt

    Science.gov (United States)

    Talmy, Inna G.; Haught, Deborah A.

    1993-01-01

    The Naval Surface Warfare Center has developed processes for the preparation of mullite (3(Al2O3)(dot)2(SiO2)) whiskers and mullite-whisker felt. Three patents on the technology were issued in 1990. The processes are based on chemical reactions between AlF3, Al2O3, and SiO2. The felt is formed in-situ during the processing of shaped powdered precursors. It consists of randomly oriented whiskers which are mutually intergrown forming a rigid structure. The microstructure and properties of the felt and size of the whiskers can be modified by varying the amount of Al2O3 in the starting mixture. Loose mullite whiskers can be used as a reinforcement for polymer-, metal-, and ceramic-matrix composites. The felt can be used as preforms for fabricating composite materials as well as for thermal insulation and high temperature, chemically stable filters for liquids (melts) and gases.

  12. Carbide-reinforced metal matrix composite by direct metal deposition

    Science.gov (United States)

    Novichenko, D.; Thivillon, L.; Bertrand, Ph.; Smurov, I.

    Direct metal deposition (DMD) is an automated 3D laser cladding technology with co-axial powder injection for industrial applications. The actual objective is to demonstrate the possibility to produce metal matrix composite objects in a single-step process. Powders of Fe-based alloy (16NCD13) and titanium carbide (TiC) are premixed before cladding. Volume content of the carbide-reinforced phase is varied. Relationships between the main laser cladding parameters and the geometry of the built-up objects (single track, 2D coating) are discussed. On the base of parametric study, a laser cladding process map for the deposition of individual tracks was established. Microstructure and composition of the laser-fabricated metal matrix composite objects are examined. Two different types of structures: (a) with the presence of undissolved and (b) precipitated titanium carbides are observed. Mechanism of formation of diverse precipitated titanium carbides is studied.

  13. Effect of surface treatment of hydroxyapatite whiskers on the mechanical properties of bis-GMA-based composites

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Hongquan; Zhang Ming, E-mail: htmzhang@polyu.edu.h [Department of Health Technology and Informatics, Hong Kong Polytechnic University (Hong Kong)

    2010-10-01

    The mechanical properties of bis-GMA-based composites filled with hydroxyapatite (HA) particles or whiskers are characterized in this paper. The inherent properties of reinforcements, the bonding strength of the filler-matrix interface and their dispersibility in a polymer matrix were intimately associated with the mechanical performance of the composites. Silanization of both particles and whiskers effectively improved the bonding of the filler-matrix interface, their dispersibility in matrix monomers and filler loading. The particle- and whisker-filled composites showed highly significant differences in both flexural strength and fracture toughness. HA whiskers prepared by hydrothermal homogeneous precipitation had superior dispersibility and wettability in the polymer matrix; no aggregation and entanglement were found in both the products before and after silanization and the resin composites. These features conferred the whiskers having good interface bonding with the polymer matrix and superior reinforcing and toughening effects. For the particulate filler, the addition of HA led to a decrease in the flexural strength for both silane-treated and untreated fillers. Cracks propagated easily through the micropores and voids in the HA aggregates, leading to lower flexural strength and low toughness. However, silanization of HA did not show obvious effects on the elastic modulus of the composites.

  14. Characterization of silicon-silicon carbide ceramic derived from carbon-carbon silicon carbide composites

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Vijay K. [Indian Institute of Technology, Varanasi (India). Dept. of Mechanical Engineering; Krenkel, Walter [Univ. of Bayreuth (Germany). Dept. of Ceramic Materials Engineering

    2013-04-15

    The main objective of the present work is to process porous silicon - silicon carbide (Si - SiC) ceramic by the oxidation of carboncarbon silicon carbide (C/C - SiC) composites. Phase studies are performed on the oxidized porous composite to examine the changes due to the high temperature oxidation. Further, various characterization techniques are performed on Si- SiC ceramics in order to study the material's microstructure. The effects of various parameters such as fiber alignment (twill weave and short/chopped fiber) and phenolic resin type (resol and novolak) are characterized.

  15. Investigation into ramie whisker reinforced arylated soy protein composites

    CSIR Research Space (South Africa)

    Kumar, R

    2010-03-01

    Full Text Available of SW and SW-B composites, such as their morphologies, mechanical properties, thermal stability, optical transmittance, and water uptake, are discussed. The results indicated substantial improvement in the water resistance, thermal stability...

  16. Preparation and Tribological Properties of Ni-P Electroless Composite Coating Containing Potassium Titanate Whisker

    Institute of Scientific and Technical Information of China (English)

    Yaxu JIN; Lin HUA

    2007-01-01

    Nickel-phosphorus (Ni-P) composite coatings containing potassium titanate (K2Ti6O13) whiskers (PTWs) were prepared by electroless plating. The surface morphology and component of coatings were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively before and after wear test. The tribological performance was evaluated using a pin-on-disk wear tester under dry conditions. It is found that the Ni-P-PTWs composite coatings exhibit higher wear resistance than Ni-P and Ni-P-SiC electroless coatings. The favorable effects of PTWs on the tribological properties of the composite coatings are attributed to the super-strong mechanical properties and the specific tunneling structures of PTWs. The PTWs greatly reinforce the structure of the Ni-P-based composite coatings and thereby greatly reduce the adhesive and plough wear of Ni-P-PTWs composite coatings.

  17. A whisker-like carbon composite for the immobilization of laccase and its bioelectrochemistry

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel mesoporous carbon/whisker-like carbon (MCWC) composite was used for the immobilization of laccase (Lac) and its bioelectrochemical behaviors were studied.It was confirmed by XPS that Lac was strongly adsorbed on the surface of the MCWC composite.The cyclic voltammetric results showed that the immobilized Lac underwent a direct quasi-reversible electrochemical reaction.The value of the electron transfer rate constant ks was estimated to be 0.770 s-1,indicating a reasonably fast electron transfer between the immobilized Lac and the underlying electrode.The surface concentration (I-) of Lac was estimated to be 2.730 × 10-12 mol/cm2.Further experimental results showed that the immobilized Lac displayed an appreciable electrocatalytic activity to the electrochemical reduction of O2.These properties could be attributed to the particular structure of loosely packed nanometer-scale carbon whiskers and the existence of a large amount of oxygen-containing groups.The immo- bilization method and the novel carrier (MCWC) may find new applications in fabricating the biocatalysts for biofuel cells.

  18. SYNTHESIS OF SiC WHISKER AND ITS APPLICATION IN COMPOSITE MATERIALS

    Institute of Scientific and Technical Information of China (English)

    王启宝; 郭梦熊

    1997-01-01

    The SiC whiskers (SiCw) synthesized from rice hulls is studied in this paper. The properties of the application in the composite materials are tested, and also compared with the SiCw produced in US and Japan, the results indicate that the SiCw produced by this method is mainly straight crystals with multi nodes on face, the main type is β-SiC. It has many advantages such as high strength and excellent oxidation resistance to high temperature. The Si3N4 ceramic composite materials reinforced and toughened with the SiCw, δRT∫ of the material is (856±22)MPa, δ1300℃t is approximately (418.5±14.2) MPa and KIC is approximately (11.3±1.0) MPa·m1/2. Besides, the application of the SiCw in the engineering materials of mining is forecasted.

  19. Polymer grafted hydroxyapatite whisker as a filler for dental composite resin with enhanced physical and mechanical properties.

    Science.gov (United States)

    Liu, Fengwei; Wang, Ruili; Cheng, Yanhua; Jiang, Xiaoze; Zhang, Qinghong; Zhu, Meifang

    2013-12-01

    The objective of this study was to investigate the effect of surface graft polymerization of hydroxyapatite whisker (HW) on physical and mechanical properties of dental composite resin. Poly bisphenol A glycidyl methacrylate (Poly(Bis-GMA)) was grafted onto silanized hydroxyapatite whisker (SHW) via solution polymerization and the amount of the Poly(Bis-GMA) on the surface was effectively controlled by polymerization time. The obtained poly(Bis-GMA) grafted hydroxyapatite whisker (PGHW) with different polymer contents was filled into a resin matrix respectively, meanwhile the composites with HW and with SHW served as controls. Monomer conversion was characterized by Fourier transform infrared spectroscopy (FTIR) and volume shrinkage of the composite resin was measured with a density tester. Mechanical properties were tested with a universal testing machine. The results indicated that the composite filled with PGHW-1h (graft ratio of poly(Bis-GMA): 8.5 wt.%) showed lower shrinkage and better mechanical properties, improving flexural strength by 6.5% and 11.9% compared with SHW filled composite and HW filled composite, respectively. However, PGHW with higher graft ratios aggregated seriously and formed defects in the composite, leading to deterioration of mechanical properties. It was revealed that the poly(Bis-GMA) on the surface of PGHW acted as a functional transition layer and enhanced interfacial compatibility and interaction between whisker and resin matrix, which facilitated the dispersion of PGHW in the composite and decreased the composite shrinkage. Thus, the graft polymerization of Bis-GMA on the surface of filler might be a promising modification method for the fabrication of dental materials.

  20. Fabrication of Carbon Nanotube - Chromium Carbide Composite Through Laser Sintering

    Science.gov (United States)

    Liu, Ze; Gao, Yibo; Liang, Fei; Wu, Benxin; Gou, Jihua; Detrois, Martin; Tin, Sammy; Yin, Ming; Nash, Philip; Tang, Xiaoduan; Wang, Xinwei

    2016-03-01

    Ceramics often have high hardness and strength, and good wear and corrosion resistance, and hence have many important applications, which, however, are often limited by their poor fracture toughness. Carbon nanotubes (CNTs) may enhance ceramic fracture toughness, but hot pressing (which is one typical approach of fabricating CNT-ceramic composites) is difficult to apply for applications that require localized heat input, such as fabricating composites as surface coatings. Laser beam may realize localized material sintering with little thermal effect on the surrounding regions. However, for the typical ceramics for hard coating applications (as listed in Ref.[1]), previous work on laser sintering of CNT-ceramic composites with mechanical property characterizations has been very limited. In this paper, research work has been reported on the fabrication and characterization of CNT-ceramic composites through laser sintering of mixtures of CNTs and chromium carbide powders. Under the studied conditions, it has been found that laser-sintered composites have a much higher hardness than that for plasma-sprayed composites reported in the literature. It has also been found that the composites obtained by laser sintering of CNTs and chromium carbide powder mixtures have a fracture toughness that is ~23 % higher than the material obtained by laser sintering of chromium carbide powders without CNTs.

  1. Characterization of the mechanical behaviors and bioactivity of tetrapod ZnO whiskers reinforced bioactive glass/gelatin composite scaffolds.

    Science.gov (United States)

    Guo, Weihuang; Zhao, Fujian; Wang, Yudong; Tang, Jieyin; Chen, Xiaofeng

    2017-04-01

    The purpose of this study is to construct bone tissue engineering scaffold with high porosity, good mechanical properties, and biological activities. Bioactive glass/gelatin composite scaffolds with different amounts of tetrapod zinc oxide whiskers were produced. The morphology, mechanical properties and in vitro bioactivity of the composite scaffolds were investigated. Results showed that, the composite scaffolds had open pores with a high degree of interconnectivity, and the porosity was higher than 80%. With the amount of ZnO whiskers increased, the mechanical properties of scaffolds increased. However, the reinforcing effect began to decrease when the addition is higher than 2wt%, which was resulted by the aggregation of the ZnO whiskers. In vitro test showed that, the composite scaffolds processed good biodegradability, and in vitro apatite-forming ability. The release of zinc ions retarded the growth of the HCA, so the HCA deposited on the scaffolds with ZnO was amorphous and worm-like. Furthermore, the composite scaffolds had good biocompatibility assessed by in vitro cell tests using rMSCs. All results are promising for the application of the composite scaffolds in bone repair. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Influence of nanometric silicon carbide on phenolic resin composites properties

    Indian Academy of Sciences (India)

    GEORGE PELIN; CRISTINA-ELISABETA PELIN; ADRIANA STEFAN; ION DINC\\u{A}; ANTON FICAI; ECATERINA ANDRONESCU; ROXANA TRUSC\\u{A}

    2016-06-01

    This paper presents a preliminary study on obtaining and characterization of phenolic resin-based composites modified with nanometric silicon carbide. The nanocomposites were prepared by incorporating nanometric silicon carbide (nSiC) into phenolic resin at 0.5, 1 and 2 wt% contents using ultrasonication to ensure uniform dispersion of the nanopowder, followed by heat curing of the phenolic-based materials at controlled temperature profile up to 120$^{\\circ}$C. The obtained nanocomposites were characterized by FTIR spectroscopy and scanning electron microscopy analysis and evaluated in terms of mechanical, tribological and thermal stability under load. The results highlight the positive effect of the nanometric silicon carbide addition in phenolic resin on mechanical, thermo-mechanical and tribological performance, improving their strength, stiffness and abrasive properties. The best results were obtained for 1 wt% nSiC, proving that this value is the optimum nanometric silicon carbide content. The results indicate that these materials could be effectively used to obtain ablative or carbon–carbon composites in future studies.

  3. Prussian Blue Modified Solid Carbon Nanorod Whisker Paste Composite Electrodes: Evaluation towards the Electroanalytical Sensing of H2O2

    Directory of Open Access Journals (Sweden)

    Carolin Siimenson

    2012-01-01

    Full Text Available Metallic impurity free solid carbon nanorod “Whiskers” (SCNR Whiskers, a derivative of carbon nanotubes, are explored in the fabrication of a Prussian Blue composite electrode and critically evaluated towards the mediated electroanalytical sensing of H2O2. The sensitivity and detection limits for H2O2 on the paste electrodes containing 20% (w/w Prussian Blue, mineral oil, and carbon nanorod whiskers were explored and found to be 120 mA/(M cm2 and 4.1 μM, respectively, over the concentration range 0.01 to 0.10 mM. Charge transfer constant for the 20% Prussian Blue containing SCNR Whiskers paste electrode was calculated, for the reduction of Prussian Blue to Prussian White, to reveal a value of 1.8±0.2 1/s (α=0.43, N=3. Surprisingly, our studies indicate that these metallic impurity-free SCNR Whiskers, in this configuration, behave electrochemically similar to that of an electrode constructed from graphite.

  4. Thermal Properties of Polyimide Composites with Nanostructured Silicon Carbide

    Directory of Open Access Journals (Sweden)

    Alyona Igorevna Wozniak

    2016-12-01

    Full Text Available A series of polyimide composites reinforced with different loadings of silicon carbide (SiC nanoparticles are prepared by in-situ polymerization technique. The polyimide (PI matrix resin is derived from 4,4’-oxydianiline (4,4’-ODA and pyromelliticdianhydride (PMDA. The dispersions of SiC nanoparticles are prepared via ultrasonic irradiation or mechanical homogenization. In this method, the SiC nanoparticles are dispersed in diamine solution followed by polymerization with dianhydride. The composites obtained under sonication were found to have lower thermal properties than composites prepared under homogenization.

  5. Effect of hydroxyapatite whisker surface graft polymerization on water sorption, solubility and bioactivity of the dental resin composite.

    Science.gov (United States)

    Liu, Fengwei; Jiang, Xiaoze; Bao, Shuang; Wang, Ruili; Sun, Bin; Zhu, Meifang

    2015-08-01

    The aim of this study was to investigate the effect of poly bisphenol A glycidyl methacrylate (poly(Bis-GMA)) grafted hydroxyapatite whisker (PGHW) on water sorption, solubility and bioactivity of the dental resin composite. PGHW with different graft ratios was synthesized, by controlling grafting time, and filled into a dental resin matrix respectively. Fracture surface of the resin composites showed that PGHW-matrix interfacial compatibility and bonding were enhanced, and lower amounts of poly(Bis-GMA) on PGHW-1h (graft ratio: 8.5 wt.%) could facilitate the dispersion of PGHW-1 h in the composite. The PGHW-1h filled resin composite absorbed the lowest amount of water (27.16 μg/mm(3), 7 d), whereas the untreated hydroxyapatite whisker (HW) filled resin composite absorbed the highest. PGHW with higher graft ratios induced the decrease of the monomer conversion in the resulting composite, therefore, the PGHW-18 h (graft ratio: 32.8 wt.%) filled resin composite had the highest solubility. In vitro bioactivity of the studied resin composites in simulated body fluid (SBF) showed that a dense and continuous apatite layer was formed on the surface of the resin composite, and the surface graft polymerization on the whisker did not significantly affect the apatite forming ability of the resin composite. It was revealed that graft polymerization of an appropriate amount of Bis-GMA onto HW could be an effective method to improve the interfacial properties and stability in water of the dental resin composite without compromising the bioactivity. Copyright © 2015. Published by Elsevier B.V.

  6. Thermal properties of wood-derived silicon carbide and copper-silicon carbide composites

    Science.gov (United States)

    Pappecena, Kristen E.

    Wood-derived ceramics and composites have been of interest in recent years due to their unique microstructures, which lead to tailorable properties. The porosity and pore size distribution of each wood type is different, which yields variations in properties in the resultant materials. The thermal properties of silicon carbide ceramics and copper-silicon carbide composites derived from wood were studied as a function of their pore structures. Wood was pyrolyzed at temperatures ranging from 300-2400°C to yield porous carbon. The progression toward long-range order was studied as a function of pyrolyzation temperature. Biomorphic silicon carbide (bioSiC) is a porous ceramic material resulting from silicon melt infiltration of these porous carbon materials. BioSiC has potential applicability in many high temperature environments, particularly those in which rapid temperature changes occur. To understand the behavior of bioSiC at elevated temperatures, the thermal and thermo-mechanical properties were studied. The thermal conductivity of bioSiC from five precursors was determined using flash diffusivity at temperatures up to 1100°C. Thermal conductivity results varied with porosity, temperature and orientation, and decreased from 42-13 W/mK for porosities of 43-69%, respectively, at room temperature. The results were compared with to object-oriented finite-element analysis (OOF). OOF was also used to model and understand the heat-flow paths through the complex bioSiC microstructures. The thermal shock resistance of bioSiC was also studied, and no bioSiC sample was found to fail catastrophically after up to five thermal shock cycles from 1400°C to room temperature oil. Copper-silicon carbide composites have potential uses in thermal management applications due to the high thermal conductivity of each phase. Cu-bioSiC composites were created by electrodeposition of copper into bioSiC pores. The detrimental Cu-SiC reaction was avoided by using this room temperature

  7. SiC whisker reinforced MoSi2 composite prepared by spark plasma sintering from COSHS-ed powder

    Institute of Scientific and Technical Information of China (English)

    XU Jian-guang; ZHANG Hou-an; JIANG Guo-jian; ZHANG Bao-lin; LI Wen-lan

    2006-01-01

    SiC whisker reinforced MoSi2 composite powder was synthesized by a novel process,referred to the literature as chemical oven self-propagating high temperature synthesis(COSHS). The as-prepared SiCw/MoSi2 composite powder was rapidly sintered by spark plasma sintering(SPS) process. The sintering temperature and pressure were 1 723 K at heating rate of 100 K/min and 40 MPa,respectively. The microstructure and mechanical properties of the composite were investigated. Relative densities of the monolithic material and composite are 95% and 99.3%,respectively. SEM micrographs of SiCw/MoSi2 composite show that SiC whiskers homogeneously distribute in MoSi2 matrix. The composite containing SiC whisker has higher Vicker hardness than monolithic MoSi2. Especially the room-temperature fracture toughness of the composite is higher than that of MoSi2,from 3.6 MPa -m1/2 for MoSi2 to 7.7 MPa-m1/2 for composite with 15% SiC(volume fraction),increased by 113.9%. The morphology of propagation of crack and fractured surface of composite reveal the mechnaism to improve fracture toughness of MoSi2 matrix. The results show that the in-situ SiCw/MoSi2 composite powder prepared by COSHS technique can be successfully sinterded through SPS process and significant improvement of low temperature fracture toughness can be achieved.

  8. Status of silicon carbide composites for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Snead, L.L. [Oak Ridge National Laboratory, TN (United States); Jones, R.H. [Pacific Northwest National Laboratory, Richland, WA (United States); Kohyama, A. [Kyoto Univ. (Japan)] [and others

    1996-04-01

    An effort is now underway to design an irradiation creep experiment involving SiC composites and SiC fibers. In order to successfully design such an experiment, it is necessary to review and assess the available data for monolithic SiC to establish the possible bounds of creep behavior for the composite. The data available show that monolithic SiC will indeed creep at a higher rate under irradiation compared to that of thermal creep, and surprisingly, it will do so in a temperature-dependant manner that is typical of metals.

  9. Investigation on the Effects of Titanium Diboride Particle Size on Radiation Shielding Properties of Titanium Diboride Reinforced Boron Carbide-Silicon Carbide Composites

    OpenAIRE

    A.O. Addemir; A.C. Akarsu; A.B. Tugrul; B. Buyuk

    2012-01-01

    Composite materials have wide application areas in industry. Boron Carbide is an important material for nuclear technology. Silicon carbide is a candidate material in the first wall and blankets of fusion power plants. Titanium diboride reinforced boron carbide-silicon carbide composites which were produced from different titanium diboride particle sizes and ratios were studied for searching of the behaviour against the gamma ray. Cs-137 gamma radioisotope was used as gamma source in the expe...

  10. Dynamic consolidation of aluminum-silicon carbide composites

    Energy Technology Data Exchange (ETDEWEB)

    Rabin, B.H.; Korth, G.E.; Williamson, R.L.

    1990-01-01

    Dynamic consolidation was investigated as a potential method for producing P/M metal matrix composites. In this study, 2124 aluminum powders were mixed with silicon carbide particulate and consolidated using explosives. Numerical simulations were performed to provide insight into the consolidation process and to aid in the selection of experimental conditions. The microstructure of the as-consolidated product was dependent upon processing variables. Careful control of the shock parameters allowed full density, crack free composites to be achieved in cylindrical geometries. Although full density was obtained, low fracture strengths suggested a lack of interparticle bonding, probably resulting from the limited ability to redistribute surface oxides during consolidation. 10 refs., 9 figs.

  11. Electric Heating Property from Butyl Rubber-Loaded Boron Carbide Composites

    Institute of Scientific and Technical Information of China (English)

    MENG Dechuan; WANG Ninghui; LI Guofeng

    2014-01-01

    We researched the electric heating property from butyl rubber-loaded boron carbide composite. The effects of boron carbide content on bulk resistivity, voltage-current characteristic, thermal conductivity and thermal stability of boron carbide/butyl rubber (IIR) polymer composite were introduced. The analysis results indicated that the bulk resistivity decreased greatly with increasing boron carbide content, and when boron carbide content reached to 60%, the bulk resistivity achieved the minimum. Accordingly, electric heating behavior of the composite is strongly dependent on boron carbide content as well as applied voltage. The content of boron carbide was found to be effective in achieving high thermal conductivity in composite systems. The thermal conductivity of the composite material with added boron carbide was improved nearly 20 times than that of the pure IIR. The thermal stability test showed that, compared with pure IIR, the thermal stable time of composites was markedly extended, which indicated that the boron carbide can significantly improve the thermal stability of boron carbide/IIR composite.

  12. Microstructural Evolution of Chloride-Cleaned Silicon Carbide Aluminum Composites

    Science.gov (United States)

    Adeosun, S. O.; Akpan, E. I.; Gbenebor, O. P.; Balogun, S. A.

    2016-02-01

    This study examines the synergy between reinforcement surface modifications on the evolution of microstructures of AA6011-silicon carbide particle (SiCp) composites in multidirectional solidification. Silicon carbide particles (SiCp) were cleaned with ammonium chloride, tin(II) chloride, sodium chloride, and palladium(II) chloride and used as reinforcement to cast AA6011-SiCp composites by applying the stir casting method. A scanning electron microscope and x-ray diffractometer were used to investigate the morphology and phases present, respectively, in the composite material. Results show that wetting agents were effective as they inhibited the formation of Al4C3 in all modified composites. The modified SiCp was found to have varying effects on the morphology, dendrite arm size and direction, size and configuration of AlFeSi, and the amount of eutectic silicon depending on the concentration of the reagent and cleaning time. The highest effect was shown by the use of 40 g/L of tin(II) chloride. The composites had short dendritic arms, good interfacial interaction, and only a few crystals of AlFeSi.

  13. Si3N4/SiC/环氧树脂纳米导热复合材料的制备%Preparation of silicon nitride/silicon carbide whisker/epoxy resin thermal conductive nanocomposites

    Institute of Scientific and Technical Information of China (English)

    王明明; 张炜巍

    2012-01-01

    The epoxy resin thermal conductive composites were prepared with micro-silicon nitride/nano-silicon carbide whisker (Si3N4/SiC) hybrid fillers modified with silane coupling agent of KH -560.The influence of epoxy resin type, con tent and ratio of S3,N4/SiC,and surface modification on the thermal conductivity,mechanical ant! dielectric properties of the epoxy resin were investigated.The thermal conductivity of the epoxy resin composites increased with increasing the content of Si3N4/SIC hybrid fillers.And the thermal conductivity coefficient was 0.98 W/mK for 50 wt% Si3N4/SiC hybrid fillers (mass fraction, Si3N4/SiC =3/1).The dielectric constant of the epoxy resin composites increased with increasing the content of Si3/N4SiC hybrid fillers,however,the flexural and impact strength of the composites increased firstly,but decreased with excessive addition of Si3N4/SiC hybrid fillers.%以硅烷偶联剂KH-560改性的微米氮化硅/纳米碳化硅晶须(Si3N4/SiCw)为导热填料,浇注制备Si3N4/SiC/环氧树脂纳米导热复合材料.研究了环氧树脂种类、Si3N4/SiCw用量、复配比及表面改性对环氧树脂导热、力学和介电性能的影响.结果表明,环氧树脂的热导率随Si3N4/SiCw用量的增加而增大,当改性Si3N4/SiCw用量为50%[m(Si3N4) /m(SiCw)]=3/1时,环氧树脂的热导率为0.98 W/(m· K);复合材料的介电常数随Si3N4/SiCw用量的增加而增大,而力学性能则先增加后降低.

  14. Effects of in situ synthesized mullite whisker on mechanical properties of Al2O3-SiC composite by microwave sintering

    Science.gov (United States)

    Dang, Xudan; Wei, Meng; Fan, Bingbing; Guan, Keke; Zhang, Rui; Long, Weimin; Zhang, Hongsong

    2017-06-01

    In situ synthesis of mullite whisker was introduced to Al2O3-SiC composite by microwave sintering. The effects of sintering parameters (sintering temperature, holding time and SiC particle size) on thermal shock resistance of Al2O3-SiC composite were also studied in this paper. Original SiC particles coated with SiO2 by a sol-gel method were reacted with Al2O3 particles, resulting in the in situ growth of mullite. The phase composition was identified by x-ray diffraction (XRD). The bridging of mullite whisker between Al2O3 and SiC particles was observed by scanning electron microscopy (SEM) analysis. The thermal shock resistance of samples was investigated through the combination of water quenching and three-point bending methods. The results show that the thermal shock resistance of Al2O3-SiC composite with mullite whisker reinforced remarkably, indicating better mechanical properties than the Al2O3-SiC composite without mullite whisker. Finally, the optimum process parameters (the sintering temperature of 1500 °C, the holding time of 30 min, and the SiC particle size of 5 µm) for toughening Al2O3-SiC composite by in situ synthesized mullite whisker were obtained.

  15. Synergistically toughening effect of SiC whiskers and nanoparticles in Al2O3-based composite ceramic cutting tool material

    Science.gov (United States)

    Liu, Xuefei; Liu, Hanlian; Huang, Chuanzhen; Wang, Limei; Zou, Bin; Zhao, Bin

    2016-06-01

    In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiCnp advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vol% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730±95 MPa and fracture toughness is 5.6±0.6 MPa·m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.

  16. Synergistically toughening effect of SiC whiskers and nanoparticles in Al2O3-based composite ceramic cutting tool material

    Science.gov (United States)

    Liu, Xuefei; Liu, Hanlian; Huang, Chuanzhen; Wang, Limei; Zou, Bin; Zhao, Bin

    2016-09-01

    In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiCnp advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vol% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730±95 MPa and fracture toughness is 5.6±0.6 MPa·m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.

  17. Research on Diamond Enhanced Tungsten Carbide Composite Button

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    At the present, the cutters used in button bits and rock bits are mainly cobalt tungsten carbide in our country. Because of its low abrasive resistance, the bit service life and drilling efficiency was very low when the hard and extremely hard formations were being drilled. Owing to its high abrasive resistance, the diamond composite material is widely used in drilling operations. However, its toughness against impact is too low to be used in percussion drilling, only can it be used in rotary drilling. In ...

  18. Experience-based learning on determining the frictional coefficients of thermoset polymers incorporated with silicon carbide whiskers and chopped carbon fibers at different temperatures

    Science.gov (United States)

    Harrison, Edward; Alamir, Mohammed; Alzahrani, Naif; Asmatulu, Ramazan

    2017-04-01

    High temperature applications of materials have been increasing for various industrial applications, such as automobile brakes, clutches and thrust pads. The big portion of these materials are made out of the polymeric materials with various reinforcements. In the present study, high temperature polymeric materials were incorporated with SiC whiskers and chopped carbon fibers at 0, 5, 10 and 20wt.% and molded into desired size and shape prior to the curing process. These inclusions were selected because of their high mechanical strengths and thermal conductivity values to easily dissipate the frictional heat energy and sustain more external loads. The method of testing involves a metal ramp with an adjustable incline to find the coefficients of static and kinetic frictions by recording time and the angle of movement at various temperatures (e.g., -10°C and 50°C). The test results indicated that increasing the inclusions made drastic improvements on the coefficients of static and kinetic frictions. The undergraduate students were involved in the project and observed all the details of the process during the laboratory studies, as well as data collection, analysis and presentation. This study will be useful for the future trainings of the undergraduate engineering students on the composite, automobile and other manufacturing industries.

  19. Stress envelope of silicon carbide composites at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Nozawa, Takashi, E-mail: nozawa.takashi67@jaea.go.jp [Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan); Kim, Sunghun [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Ozawa, Kazumi; Tanigawa, Hiroyasu [Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan)

    2014-10-15

    To identify a comprehensive stress envelope, i.e., strength anisotropy map, of silicon carbide fiber-reinforced silicon carbide matrix composite (SiC/SiC composite) for practical component design, tensile and compressive tests were conducted using the small specimen test technique specifically tailored for high-temperature use. In-plane shear properties were, however, estimated using the off-axial tensile method and assuming that the mixed mode failure criterion, i.e., Tsai–Wu criterion, is valid for the composites. The preliminary test results indicate no significant degradation to either proportional limit stress (PLS) or fracture strength by tensile loading at temperatures below 1000 °C. A similarly good tolerance of compressive properties was identified at elevated temperatures, except for a slight degradation in PLS. With the high-temperature test data of tensile, compressive and in-plane shear properties, the stress envelopes at elevated temperatures were finally obtained. A slight reduction in the design limit was obvious at elevated temperatures when the compressive mode is dominant, whereas a negligibly small impact on the design is expected by considering the tensile loading case.

  20. FORMATION MECHANISM OF TITANIUM CARBIDE CRYSTAL IN LASER SYNTHESIZED METAL-CERAMIC COMPOSITE COATING

    OpenAIRE

    BAOSHUAI DU; ZHONGWEN. ZHANG; XINHONG WANG; ZENGDA ZOU

    2011-01-01

    In situ titanium carbide reinforced iron-based composite coating was deposited on mild carbon steel using laser surface engineering (LSE) with ferrotitanium and graphite as precursor. The microstructure and phase constituents of the deposited coating were characterized. Formation mechanism of titanium carbide crystal in the composite coating was elucidated by correlating the morphology of titanium carbide and the thermal cycle experienced by the precursor during the laser treatment. It was de...

  1. EFFECTS OF HEAT TREATMENT ON THE THERMAL EXPANSION BEHAVIOR OF SiC WHISKER REINFORCED ALUMINUM COMPOSITE

    Institute of Scientific and Technical Information of China (English)

    M. Hu; W.D. Fei; W.L. Li; C.K. Yao

    2001-01-01

    The thermal expansion behaviors of SiC whisker reinforced commercially pure aluminum composites subjected to different heat treatments were studied. The results indicated that the thermal expansion behaviors were greatly affected by heat treatment.To explain the results, the microstructures and thermal mismatch stresses in the matrix of the composite were examined by the transmission electron microscope and Xray diffraction, respectively. The dislocation density and thermal mismatch stresses in the matrix of the composites water quenched from 600°C are much higher than that of the composite slowly cooled from 600°C. The analysis suggested that the coefficients of thermal expansion (CTE) are closely related to the change of thermal mismatch stresses and yield strength of the matrix of the composite. The comparison of the coefficients of thermal expansion between experiments and calculations suggested that the temperature behaviors of CTE of SiCw/Al composite agree better with those of Kerner's model within lower temperature range.

  2. Investigations of Interface Properties in Copper-Silicon Carbide Composites

    Directory of Open Access Journals (Sweden)

    Chmielewski M.

    2017-06-01

    Full Text Available This paper analyses the technological aspects of the interface formation in the copper-silicon carbide composite and its effect on the material’s microstructure and properties. Cu-SiC composites with two different volume content of ceramic reinforcement were fabricated by hot pressing (HP and spark plasma sintering (SPS technique. In order to protect SiC surface from its decomposition, the powder was coated with a thin tungsten layer using plasma vapour deposition (PVD method. Microstructural analyses provided by scanning electron microscopy revealed the significant differences at metal-ceramic interface. Adhesion force and fracture strength of the interface between SiC particles and copper matrix were measured. Thermal conductivity of composites was determined using laser flash method. The obtained results are discussed with reference to changes in the area of metal-ceramic boundary.

  3. Minocycline-loaded cellulose nano whiskers/poly(sodium acrylate) composite hydrogel films as wound dressing.

    Science.gov (United States)

    Bajpai, S K; Pathak, V; Soni, Bhawna

    2015-08-01

    In this work, antibiotic drug Minocycline (Mic) loaded cellulose nano-whiskers (CNWs)/poly(sodium acrylate) hydrogel films were prepared and investigated for their drug releasing capacity in physiological buffer solution (PBS) at 37 °C. The (CNWs)/poly(sodium acrylate) film, containing 9.7% (w/w) of CNWs, demonstrated Mic release of 2500 μg/g while the plain poly(acrylate) film showed 3100 μg/g of drug release. In addition, with the increase in the concentration of cross-linker N,N'-methylene bisacrylamide (MB) from to, the drug release from the resulting films decreased from 507 to 191 μg/g. The release exponent 'n' for films with different compositions was found in the range of 0.45 to 0.89, thus indicating non-Fickian release mechanism. The Schott model was employed to interpret the kinetic drug release data successfully. The film samples poly(SA) and CNWs/poly(SA) (both not containing drug) showed thrombus formation of 0.010±0.001 g and 0.007±0.001 g, respectively, thus showing the non-thrombogenic behavior. In percent Hemolysis, both of the film samples of 1.136±0.012 and 0.5±0.020, respectively, thus indicating non-hemolytic behavior. In addition, both of the film samples demonstrated protein adsorption of 49.02±0.59μ g/μL and 51.20±0.51 μg/μL per cm(2), thus revealing a fair degree of protein adsorption. Finally, the Mic-loaded films showed fair anti-fungal and antibacterial properties.

  4. Investigation on the Effects of Titanium Diboride Particle Size on Radiation Shielding Properties of Titanium Diboride Reinforced Boron Carbide-Silicon Carbide Composites

    Directory of Open Access Journals (Sweden)

    A.O. Addemir

    2012-03-01

    Full Text Available Composite materials have wide application areas in industry. Boron Carbide is an important material for nuclear technology. Silicon carbide is a candidate material in the first wall and blankets of fusion power plants. Titanium diboride reinforced boron carbide-silicon carbide composites which were produced from different titanium diboride particle sizes and ratios were studied for searching of the behaviour against the gamma ray. Cs-137 gamma radioisotope was used as gamma source in the experiments which has a single gamma-peak at 0.662 MeV. Gamma transmission technique was used for the measurements. The effects of titanium diboride particle size on radiation attenuation of titanium diboride reinforced boron carbide-silicon carbide composites were evaluated in related with gamma transmission and the results of the experiments were interpreted and compared with each other. Composite materials have wide application areas in industry. Boron Carbide is an important material for nuclear technology. Silicon carbide is a candidate material in the first wall and blankets of fusion power plants. Titanium diboride reinforced boron carbide-silicon carbide composites which were produced from different titanium diboride particle sizes and ratios were studied for searching of the behaviour against the gamma ray. Cs-137 gamma radioisotope was used as gamma source in the experiments which has a single gamma-peak at 0.662 MeV. Gamma transmission technique was used for the measurements. The effects of titanium diboride particle size on radiation attenuation of titanium diboride reinforced boron carbide-silicon carbide composites were evaluated in related with gamma transmission and the results of the experiments were interpreted and compared with each other. Composite materials have wide application areas in industry. Boron Carbide is an important material for nuclear technology. Silicon carbide is a candidate material in the first wall and blankets of fusion

  5. [Effect of amount of silane coupling agent on flexural strength of dental composite resins reinforced with aluminium borate whisker].

    Science.gov (United States)

    Zhu, Ming-yi; Zhang, Xiu-yin

    2015-06-01

    To evaluate the effect of amount of silane coupling agent on flexural strength of dental composite resins reinforced with aluminium borate whisker (ABW). ABW was surface-treated with 0%, 1%, 2%, 3% and 4% silan coupling agent (γ-MPS), and mixed with resin matrix to synthesize 5 groups of composite resins. After heat-cured at 120 degrees centigrade for 1 h, specimens were tested in three-point flexure to measure strength according to ISO-4049. One specimen was selected randomly from each group and observed under scanning electron microscope (SEM). The data was analyzed with SAS 9.2 software package. The flexural strength (117.93±11.9 Mpa) of the group treated with 2% silane coupling agent was the highest, and significantly different from that of the other 4 groups (α=0.01). The amount of silane coupling agent has impact on the flexural strength of dental composite resins reinforced with whiskers; The flexual strength will be reduced whenever the amount is higher or lower than the threshold. Supported by Research Fund of Science and Technology Committee of Shanghai Municipality (08DZ2271100).

  6. 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.

  7. Waste Polyethylene and the Calcium Sulfate Whisker Composite Materials%废旧聚乙烯/硫酸钙晶须复合材料

    Institute of Scientific and Technical Information of China (English)

    刘彤

    2012-01-01

    Using waste polyethylene ( PE) and calcium sulfale whisker us raw material, the method of molten extrusion blending was used to prepare the composite of wasLe polyethyloene ( PE ) and calcium sulfate whisker, ihe influence of silane coupling agent KH-590 modified and unmodified calcium sulfate whisker content on the waste PE/calcium sulfate whisker mechanics properties of composite materials was compared. The mechanism of calcium sulfate whisker enhanced waste PE was investigatecb, and the microscopic structure of waste PE/calcium sulfate whisker composite materials was observed. The results showed that,when calcium sulfate whisker dosage was 15 % .unmodified calcium sulfate whisker made the tensile strength and impact strength increased by 23. 1 % and 9. 1 % ,modified calcium sulfate whisker made the tensile strength,impact strength and hending strength increased by 26. 7 % , 15. 6 % and 5.3 % ,il could uniform distributed in waste PE and play the obvious%采用废旧聚乙烯(PE)与硫酸钙晶须为原料,通过熔融挤出共混制得废旧PE/硫酸钙晶须复合材料,比较了经硅烷偶联剂KH-590改性与未改性的硫酸钙晶须用量对废旧PE/硫酸钙晶须复合材料力学性能的影响,分析硫酸钙晶须增强度旧PE的机理和废旧PE/硫酸钙晶须复合材料的微观结构.结果表明:当硫酸钙晶须用量为15%时,未改性硫酸钙晶须使复合材料的拉伸强度、冲击强度提高了23.1%、9.1%;改性硫酸钙晶须使复合材料的拉伸强度、冲击强度、弯曲强度提高了26.7%、15.6%和5 3%,其在废旧PE中分布均匀,能起到明显的增强作用.

  8. Rapid Fabrication of Carbide Matrix/Carbon Fiber Composites

    Science.gov (United States)

    Williams, Brian E.; Bernander, Robert E.

    2007-01-01

    Composites of zirconium carbide matrix material reinforced with carbon fibers can be fabricated relatively rapidly in a process that includes a melt infiltration step. Heretofore, these and other ceramic matrix composites have been made in a chemical vapor infiltration (CVI) process that takes months. The finished products of the CVI process are highly porous and cannot withstand temperatures above 3,000 F (approx.1,600 C). In contrast, the melt-infiltration-based process takes only a few days, and the composite products are more nearly fully dense and have withstood temperatures as high as 4,350 F (approx.2,400 C) in a highly oxidizing thrust chamber environment. Moreover, because the melt- infiltration-based process takes much less time, the finished products are expected to cost much less. Fabrication begins with the preparation of a carbon fiber preform that, typically, is of the size and shape of a part to be fabricated. By use of low-temperature ultraviolet-enhanced chemical vapor deposition, the carbon fibers in the preform are coated with one or more interfacial material(s), which could include oxides. The interfacial material helps to protect the fibers against chemical attack during the remainder of the fabrication process and against oxidation during subsequent use; it also enables slippage between the fibers and the matrix material, thereby helping to deflect cracks and distribute loads. Once the fibers have been coated with the interfacial material, the fiber preform is further infiltrated with a controlled amount of additional carbon, which serves as a reactant for the formation of the carbide matrix material. The next step is melt infiltration. The preform is exposed to molten zirconium, which wicks into the preform, drawn by capillary action. The molten metal fills most of the interstices of the preform and reacts with the added carbon to form the zirconium carbide matrix material. The zirconium does not react with the underlying fibers because they

  9. Enhanced Sintering of Boron Carbide-Silicon Composites by Silicon

    Science.gov (United States)

    Zeng, Xiaojun; Liu, Weiliang

    2016-09-01

    Boron carbide (B4C)-silicon (Si) composites have been prepared by aqueous tape casting, laminating, and spark plasma sintering (SPS). The influences of silicon (Si) content on the phases, microstructure, sintering properties, and mechanical properties of the obtained B4C-Si composites are studied. The results indicate that the addition of Si powder can act as a sintering aid and contribute to the sintering densification. The addition of Si powder can also act as a second phase and contribute to the toughening for composites. The relative density of B4C-Si composites samples with adding 10 wt.% Si powder prepared by SPS at 1600 °C and 50 MPa for 8 min is up to 98.3%. The bending strength, fracture toughness, and Vickers hardness of the sintered samples are 518.5 MPa, 5.87 MPa m1/2, and 38.9 GPa, respectively. The testing temperature-dependent high-temperature bending strength and fracture toughness can reach a maximum value at 1350 °C. The B4C-Si composites prepared at 1600, 1650, and 1700 °C have good high-temperature mechanical properties. This paper provides a facile low-temperature sintering route for B4C ceramics with improved properties.

  10. Enhanced Sintering of Boron Carbide-Silicon Composites by Silicon

    Science.gov (United States)

    Zeng, Xiaojun; Liu, Weiliang

    2016-11-01

    Boron carbide (B4C)-silicon (Si) composites have been prepared by aqueous tape casting, laminating, and spark plasma sintering (SPS). The influences of silicon (Si) content on the phases, microstructure, sintering properties, and mechanical properties of the obtained B4C-Si composites are studied. The results indicate that the addition of Si powder can act as a sintering aid and contribute to the sintering densification. The addition of Si powder can also act as a second phase and contribute to the toughening for composites. The relative density of B4C-Si composites samples with adding 10 wt.% Si powder prepared by SPS at 1600 °C and 50 MPa for 8 min is up to 98.3%. The bending strength, fracture toughness, and Vickers hardness of the sintered samples are 518.5 MPa, 5.87 MPa m1/2, and 38.9 GPa, respectively. The testing temperature-dependent high-temperature bending strength and fracture toughness can reach a maximum value at 1350 °C. The B4C-Si composites prepared at 1600, 1650, and 1700 °C have good high-temperature mechanical properties. This paper provides a facile low-temperature sintering route for B4C ceramics with improved properties.

  11. Spark plasma sintering of tantalum carbide and graphene reinforced tantalum carbide composites

    Science.gov (United States)

    Kalluri, Ajith Kumar

    Tantalum carbide (TaC), an ultra-high temperature ceramic (UHTC), is well known for its exceptional properties such as high hardness (15-19 GPa), melting point (3950 °C), elastic modulus (537 GPa), chemical resistance, and thermal shock resistance. To make TaC to be the future material for hypersonic vehicles, it is required to improve its thermal conductivity, strength, and fracture toughness. Researchers have previously reinforced TaC ceramic with carbides of silicon and boron as well as carbon nanotubes (CNTs), however, these reinforcements either undergo chemical changes or induce defects in the matrix during processing. In addition, these reinforcements exhibit a very minimal improvement in the properties. In the present work, we attempted to improve TaC fracture toughness by reinforcing with graphene nano-platelets (GNPs) and processing through spark plasma sintering at high temperature of 2000 °C, pressure of 70 MPa, and soaking time of 10 min. In addition, we investigated the active densification mechanism during SPS of TaC powder and the effect of ball milling time on mechanical properties of sintered TaC. A relative density of >96% was achieved using SPS of monolithic TaC (<3 μm). Ball milling improved the sintering kinetics and improved the mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness). Activation energy (100 kJ/mol) and stress exponent (1.2) were obtained using the analytical model developed for power-law creep. Grain boundary sliding is proposed as active densification mechanism based on these calculations. Reinforcing GNPs (2-6 vol.% ) in the TaC matrix improved relative density (99.8% for TaC-6 vol.% GNP). Also ˜150% and ˜180% increase in flexural strength and fracture toughness, respectively, was observed for TaC-6 vol.% GNP composite. The significant improvement in these properties is attributed to improved densification and toughening mechanisms such as sheet pull-out and crack

  12. 碳化硅晶须流延浆料的制备%Preparation of Silicon Carbide Whisker Slurry for Tape Casting

    Institute of Scientific and Technical Information of China (English)

    解玉鹏; 王长昊; 杨雪; 刘文彦; 齐丽晶

    2015-01-01

    Effect of dispersant and binder on rheological properties of SiC whisker slurry was investigated by discussing dispersion and viscosity of SiCw slurry,and then fixed the preparation parameters of slurry. The re-sults indicated that the appropriate content of dispersant(2 wt%) can effectively weaken whiskers attraction, reduce whiskers cluster,and improve whiskers dispersion. Meanwhile,binder of 3 wt% was used to prepare ap-propriate viscosity of slurry. By optimizing process parameters,well dispersed slurry with good stability can be obtained to be suitable for tape casting.%通过分析浆料分散性和粘度等因素,研究分散剂和粘结剂等对碳化硅晶须浆料流变行为的影响,确定合适的浆料制备工艺参数。结果表明:选择合适剂量的分散剂(2 wt%)能够有效减弱晶须之间的吸引力,减少晶须团簇,提高晶须分散性。同时选择3 wt%的粘结剂能够得到粘度适宜的浆料。优化工艺参数,最终获得分散性及稳定性较好且适于流延的晶须浆料。

  13. Porous Silicon Carbide/Carbon Composite Microspherules for Methane Storage

    Institute of Scientific and Technical Information of China (English)

    Fengbo Li; Qingli Qian; Shufeng Zhang; Fang Yan; Guoqing Yuan

    2007-01-01

    Porous silicon carbide/carbon (SiC/C) microspherules were prepared by the controlled heating treatment of polymer and silica hybrid precursors over 1000 ℃ in Ar/H2 stream. The resultant SiC/C composite shows improved physical properties such as excellent mechanical strength, regular physical form, and high packing density. Such improvement overcomes the main inherent problems encountered when using activated carbons as absorbents without sacrificing porosity properties. N2 sorption analysis shows that the SiC/C composite has a BET surface area of 1793 m2/g and a pore volume of 0.92 ml/g. Methane adsorption isotherm is determined by the conventional volumetric method at 25 ℃ and up to 7.0 MPa. On volumetric basis, the SiC/C composite microspherules show methane storage of 145 (V/V) at 3.5 MPa and 25 ℃. The combination of excellent physical properties and porosity properties in this SiC/C composite lends a great possibility to develop a competitive storage system for natural gas.

  14. Advanced Measurements of Silicon Carbide Ceramic Matrix Composites

    Energy Technology Data Exchange (ETDEWEB)

    Farhad Farzbod; Stephen J. Reese; Zilong Hua; Marat Khafizov; David H. Hurley

    2012-08-01

    Silicon carbide (SiC) is being considered as a fuel cladding material for accident tolerant fuel under the Light Water Reactor Sustainability (LWRS) Program sponsored by the Nuclear Energy Division of the Department of Energy. Silicon carbide has many potential advantages over traditional zirconium based cladding systems. These include high melting point, low susceptibility to corrosion, and low degradation of mechanical properties under neutron irradiation. In addition, ceramic matrix composites (CMCs) made from SiC have high mechanical toughness enabling these materials to withstand thermal and mechanical shock loading. However, many of the fundamental mechanical and thermal properties of SiC CMCs depend strongly on the fabrication process. As a result, extrapolating current materials science databases for these materials to nuclear applications is not possible. The “Advanced Measurements” work package under the LWRS fuels pathway is tasked with the development of measurement techniques that can characterize fundamental thermal and mechanical properties of SiC CMCs. An emphasis is being placed on development of characterization tools that can used for examination of fresh as well as irradiated samples. The work discuss in this report can be divided into two broad categories. The first involves the development of laser ultrasonic techniques to measure the elastic and yield properties and the second involves the development of laser-based techniques to measurement thermal transport properties. Emphasis has been placed on understanding the anisotropic and heterogeneous nature of SiC CMCs in regards to thermal and mechanical properties. The material properties characterized within this work package will be used as validation of advanced materials physics models of SiC CMCs developed under the LWRS fuels pathway. In addition, it is envisioned that similar measurement techniques can be used to provide process control and quality assurance as well as measurement of

  15. Probing Structure and Composition of Nickel/Titanium Carbide Hybrid Interfaces at the Atomic Scale (Preprint)

    Science.gov (United States)

    2010-01-01

    The transition in structure and composition across the titanium carbide /nickel hybrid interface has been determined at near atomic resolution by...coupling high-resolution transmission electron microscopy with three-dimensional atom probe tomography. The titanium carbide phase adopts a rocksalt-type

  16. Ultrafine-grained Aluminm and Boron Carbide Metal Matrix Composites

    Science.gov (United States)

    Vogt, Rustin

    Cryomilling is a processing technique used to generate homogenously distributed boron carbide (B4C) particulate reinforcement within an ultrafine-grained aluminum matrix. The motivation behind characterizing a composite consisting of cryomilled aluminum B4C metal matrix composite is to design and develop a high-strength, lightweight aluminum composite for structural and high strain rate applications. Cryomilled Al 5083 and B4C powders were synthesized into bulk composite by various thermomechanical processing methods to form plate and extruded geometries. The effects of processing method on microstructure and mechanical behavior for the final consolidated composite were investigated. Cryomilling for extended periods of time in liquid nitrogen has shown to increase strength and thermal stability. The effects associated with cryomilling with stearic acid additions (as a process-control agent) on the degassing behavior of Al powders is investigated and results show that the liberation of compounds associated with stearic acid were suppressed in cryomilled Al powders. The effect of thermal expansion mismatch strain on strengthening due to geometrically necessary dislocations resulting from quenching is investigated and found not to occur in bulk cryomilled Al 5083 and B 4C composites. Previous cryomilled Al 5083 and B4C composites have exhibited ultrahigh strength associated with considerable strain-to-failure (>14 pct.) at high strain rates (>103/s) during mechanical testing, but only limited strain-to-failure (˜0.75 pct.) at quasi-static strain rates (10-3/s). The increased strain to failure at high strain rates is attributed to micro-flaw developments, including kinking, extensive axial splitting, and grain growth were observed after high strain rate deformation, and the significance of these mechanisms is considered.

  17. A complex reinforced polymer interposer with ordered Ni grid and SiC nano-whiskers polyimide composite based on micromachining technology

    Science.gov (United States)

    Liu, Yanmei; Sun, Yunna; Wang, Yan; Ding, Guifu; Sun, Bin; Zhao, Xiaolin

    2017-01-01

    A complex reinforced polymer interposer comprised with conductive Ni cylinders, ordered Ni grid and SiC nano-whiskers/Polyimide (PI) composite was proposed. The conductive Ni cylinders distributing in the middle of each Ni grid unite designed as the supporting structure were used as electric connecting component for the interposer and were insulated by the SiC nano-whiskers/PI composite. The comprehensive properties of the complex reinforced polymer interposer were improved by a complex reinforced mechanism: the improved thermal conductivity and mechanical strength by the Ni supporting structure and the reduced metal/polymer interfacial mismatch due to the SiC nano-whiskers/PI composite with the optimized mixture ratio. The above complex reinforced polymer interposer and a traditional reinforced polymer interposer only with Ni grid were fabricated using micro-machining technology for comparative analysis. The comprehensive properties of these two polymer interposers were analyzed respectively. Compared with the traditional design, the comprehensive properties of the proposed complex reinforced polymer interposer were improved further, such as, 21.3% increase for the Young modulus, 10.1% decrease for the coefficient of thermal expansion (CTE) and 54.9% increase for the thermal conductivity. Such complex reinforced mechanism based on the metal ordered grid and random nano-whiskers has potential to expand the applications of the polymer interposer. [Figure not available: see fulltext.

  18. Modal acoustic emission source determination in silicon carbide matrix composites

    Science.gov (United States)

    Morscher, G. N.

    2000-05-01

    Modal acoustic emission has been used to monitor damage accumulation in woven silicon carbide (SiC) fiber reinforced SiC matrix composites during tensile testing. There are several potential sources of damage in these systems including transverse matrix cracking, fiber/matrix interphase debonding and sliding, longitudinal cracks in between plies, and fiber breakage. In the past, it has been shown that modal AE is excellent at detecting when damage occurs and subsides, where the damage occurs along the length of the sample, and the loss in material stiffness as a consequence of damage accumulation. The next step is to determine the extent that modal AE can be used to identify specific physical sources. This study will discuss the status of this aim for this composite system. Individual events were analyzed and correlated to specific sources based on the characteristics of the received waveforms, e.g., frequency spectrum and energy, and when the event occurred during the stress-history of the tensile test. Post-test microstructural examination of the test specimens enabled some correlation between specific types of AE events and damage sources.

  19. Phase diagram of boron carbide with variable carbon composition

    Science.gov (United States)

    Yao, Sanxi; Gao, Qin; Widom, Michael

    2017-02-01

    Boron carbide exhibits intrinsic substitutional disorder over a broad composition range. The structure consists of 12-atom icosahedra placed at the vertices of a rhombohedral lattice, together with a 3-atom chain along the threefold axis. In the high-carbon limit, one or two carbon atoms can replace boron atoms on the icosahedra while the chains are primarily of type C-B-C. We fit an interatomic pair interaction model to density-functional-theory total energies to investigate the substitutional carbon disorder. Monte Carlo simulations with sampling improved by replica exchange and augmented by two-dimensional multiple histogram analysis predict three phases. The low-temperature, high-carbon-composition monoclinic C m structure disorders through a pair of phase transitions, first via an Ising-like transition to a monoclinic centrosymmetric state with space group C 2 /m , then via a first-order three-state Potts-like transition to the experimentally observed rhombohedral R 3 ¯m symmetry.

  20. Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

    Science.gov (United States)

    Ponomarev, V. I.; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I.

    2015-09-01

    Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide В15- х С х , (1.5 ≤ x ≤ 3) and its magnesium derivative C4B25Mg1.42. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from В12.9С2.1 to В12.4С2.6.

  1. 表面微结构对碳化硅晶须掺杂石墨阴极爆炸电子发射性能的影响%Influence of surface microstructure on explosive electron emission prop erties of graphite catho de dop ed by silicon carbide whiskers

    Institute of Scientific and Technical Information of China (English)

    华叶; 万红; 陈兴宇; 吴平; 白书欣

    2016-01-01

    Explosive emission cathode (EEC) is a pivotal component in high power microwave source (HPMS), of which the ultimate properties are significantly dependent on the quality of electron beams generated from the cathode. Short lifetime and poor emission uniformity are the persistent drawbacks of conventional field EEC. Improvement of cathode material by changing its compositions and modifying surface micromorphology, is a feasible way to solve this problem. Graphite is one of the frequently used materials for EECs due to its long life-time and sturdy performance under high voltage and repetition frequency. Meanwhile silicon carbide (SiC) whiskers are distinguished by high aspect ratio (ratio of height to diameter) and low work function which is in favor of the fast onset of electron emission. In this work, the novel composites, composed of SiC whiskers, pitch and major graphite powders, are prepared by the conventional mingling and sintering. The cathodes are installed on TPG1000 system with a parameterized pulse of 970 kV, 9.2 kA, and 50 ns. By analyzing the changes of the rise edge of measured diode current and output microwave pulse duration, the effects of material composition and surface micromorphology on electron emission properties for the cathode are disclosed in detail. The results, based on the comparison of emission properties between graphite cathodes with and without SiC whiskers doped, reveal that SiC whiskers play an important role in accelerating the field emission of cathode, which is demonstrated by the eclipse of displacement current peak on the rise edge of measured current waveform after doping. Meanwhile, the duration of output microwave pulse is enhanced by about 11% after doping, which could be explained by the lower expansion speed of Si plasma. Moreover, the surface micro-protrusions of graphite cathode doped by SiC whiskers are constantly “polished” by heating effect and cathode plasma as the number of emission pulses increases to 11000

  2. Effect of hydroxyapatite spheres, whiskers, and nanoparticles on mechanical properties of a model BisGMA/TEGDMA composite initially and after storage.

    Science.gov (United States)

    Lezaja, Maja; Veljovic, Djordje N; Jokic, Bojan M; Cvijovic-Alagic, Ivana; Zrilic, Milorad M; Miletic, Vesna

    2013-11-01

    This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (SphSi), whiskers (Wh), silicon-doped whiskers (WhSi), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and SphSi groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites.

  3. 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.

  4. [Effects of silicon carbide on the cure depth, hardness and compressive strength of composite resin].

    Science.gov (United States)

    Wang, Ke; Lin, Yi'na; Liu, Xiaoqing

    2009-08-01

    The hardness, compressive strength and cure depth are important indices of the composite resin. This investigation was made with regard to the effects of silicon carbide on the cure depth, hardness and compressive strength of the light-curing composite resin. Different amounts of silicon carbide were added to the light-curing composite resin, which accounted for 0 wt%, 1 wt%, 0.6 wt%, 0.3 wt%, 0.1 wt%, 0.05 wt% and 0.005 wt% of the composite resin, respectively. The hardness, compressive strength and cure depth of the six afore-mentioned groups of composite resin were measured by the vernier caliper, the vickers hardness tester and the tensile strength of machine, respectively. The results showed that silicon carbide improved the hardness and compressive strength of the light-curing composite resin,when the concentration was 0.05 wt%. And the cure depth was close to that of control.

  5. Novel Manufacturing Process for Unique Mixed Carbide Refractory Composites Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This STTR Phase I project will establish the feasibility of an innovative manufacturing process to fabricate a range of unique hafnium/silicon based carbide...

  6. Growth of single phase Bi sub 2 Sr sub 2 CaCu sub 2 O sub x whiskers using optimized starting compositions for glassy precursors

    CERN Document Server

    Sugimata, E; Kume, E; Sakai, S

    2003-01-01

    Single phase Bi sub 2 Sr sub 2 CaCu sub 2 O sub x whiskers were grown by optimized starting compositions for glassy precursors. The most optimal starting composition ratio and the composition after the whisker growth were found to be Bi : Sr : Ca : Al = 0.96 : 1.10 : 0.37 : 1.21 : 0.61 and Bi sub 2 sub . sub 2 sub 5 Sr sub 2 sub . sub 0 sub 9 Ca sub 0 sub . sub 8 sub 7 Cu sub 2 sub . sub 0 sub 0 O sub x , respectively. From the results of R-T characteristics, it was determined that there was no intergrowth of the Bi sub 2 Sr sub 2 Ca sub 2 Cu sub 3 O sub x phase. (author)

  7. Analysis of the Coupling Effects of TiB Whiskers and TiC Particles on the Fracture Toughness of (TiB + TiC)/TC4 Composites: Experiment and Modeling

    Science.gov (United States)

    Lu, Weijie; Guo, Xianglong; Meng, Jialin; Wang, Fangqiu; Wang, Liqiang; Zhang, Di

    2015-08-01

    (TiB + TiC)/TC4 composites reinforced with different amounts of TiB whiskers and TiC particles are produced by common casting and hot forging technology. Then the fracture toughness of (TiB + TiC)/TC4 composites is analyzed by experiment and modeling. The experimental results indicate that not only reinforcement volume fraction but also the mole ratio between TiB whiskers and TiC particles can influence the fracture toughness of (TiB + TiC)/TC4 composites. Microstructure observations are carried out to examine the behavior of TiB whiskers and TiC particles in the fracture process. An analytical expression for predicting the fracture toughness of (TiB + TiC)/TC4 composites is built up. In particular, the coupling influences of TiB whiskers and TiC particles on the elastic modulus, yield strength, and fracture strain of TMCs are revealed in the modeling process. The results indicate that when TiB and TiC particles are coexisting in the TMCs, the fracture toughness of (TiB + TiC)/TC4 composites increases with the increase of the TiB whiskers aspect ratio, TiC particles volume fraction and size; however, with the increase of TiB whiskers volume fraction, the fracture toughness decreases. The breakage of TiB whiskers is the main reason for the fracture of TMCs. The acting mechanism of TiC particles on the fracture of TMCs transfers from blocking crack propagation and interfacial debonding to breakage with the increase of size, which can decrease the fracture toughness of (TiB + TiC)/TC4 composites. Considering the broken fraction of TiB whiskers, the fracture toughness of (TiB + TiC)/TC4 composites can be reasonably predicted.

  8. Temperature-dependent transformation from whisker- to nanoparticle-strengthened composite interface in the Al{sub 2}O{sub 3}/Ag-based alloy system and mechanical properties of the joints

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yifeng; Cao, Jian, E-mail: cao_jian@hit.edu.cn; Wang, Zhijie; Chen, Zhe; Song, Xiaoguo; Feng, Jicai

    2015-11-15

    Al{sub 4}B{sub 2}O{sub 9}-whisker-coated Al{sub 2}O{sub 3} ceramics were bonded by AgCu–4.5 wt.%Ti alloy in vacuum. The microstructure of the whisker-coated Al{sub 2}O{sub 3} joints was investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A continuous (Cu,Al){sub 3}Ti{sub 3}O layer formed against the alloy at lower bonding temperatures, and a complex transition zone bordering the whiskers was observed, which consisted of Ag nanoparticles, titanium oxides, TiB{sub 2}, (Cu,Al){sub 3}Ti{sub 3}O nanoparticles and possible Ag{sub 3}Al. As the bonding temperature increased, the Al{sub 2}O{sub 3}/AgCuTi interface was found to transform from whisker- to nanoparticle-strengthened composite region. Bend test results revealed that both the whiskers grown on Al{sub 2}O{sub 3} and the dispersive nanoscale products in the alloy played positive roles in improving the joint properties. The maximum bend strength of the whisker-coated Al{sub 2}O{sub 3} joints was 313 MPa at the bonding temperature of 820 °C. - Highlights: • Al{sub 4}B{sub 2}O{sub 9}-whisker-coated Al{sub 2}O{sub 3} ceramics were bonded by AgCu–4.5 wt.%Ti alloy in vacuum. • Microstructures of whisker-coated Al{sub 2}O{sub 3} joints were investigated in detail. • Both whiskers and the dispersive nanoscale products can improve the joint properties. • The maximum bend strength of the whisker-coated Al{sub 2}O{sub 3} joints was 313 MPa.

  9. Laser deposition of Inconel 625/tungsten carbide composite coatings by powder and wire feedstock

    OpenAIRE

    Abioye, Taiwo E.

    2014-01-01

    There is an increasing global demand to extend the life span of down-hole drilling tools in order to improve operation effectiveness and efficiency of oil and gas production. Laser cladding of tungsten carbide/Ni-based alloy metal matrix composite (MMC) coatings is currently being utilised for this purpose. However, the effect of tungsten carbide dissolution on the corrosion performance of the MMC coatings has not been completely understood. In this work, a study was carried out in which lase...

  10. Evaluation of titanium carbide metal matrix composites deposited via laser cladding

    Science.gov (United States)

    Cavanaugh, Daniel Thomas

    Metal matrix composites have been widely studied in terms of abrasion resistance, but a particular material system may behave differently as particle size, morphology, composition, and distribution of the hardening phase varies. The purpose of this thesis was to understand the mechanical and microstructural effects of combining titanium carbide with 431 series stainless steel to create a unique composite via laser cladding, particularly regarding wear properties. The most predominant effect in increasing abrasion resistance, measured via ASTM G65, was confirmed to be volume fraction of titanium carbide addition. Macrohardness was directly proportional to the amount of carbide, though there was an overall reduction in individual particle microhardness after cladding. The reduction in particle hardness was obscured by the effect of volume fraction carbide and did not substantially contribute to the wear resistance changes. A model evaluating effective mean free path of the titanium carbide particles was created and correlated to the measured data. The model proved successful in linking theoretical mean free path to overall abrasion resistance. The effects of the titanium carbide particle distributions were limited, while differences in particle size were noticeable. The mean free path model did not correlate well with the particle size, but it was shown that the fine carbides were completely removed by the coarse abrasive particles in the ASTM G65 test. The particle morphology showed indications of influencing the wear mode, but no statistical reduction was observed in the volume loss figures. Future studies may more specifically focus on particle morphology or compositional effects of the carbide particles.

  11. Non-oxidic nanoscale composites: single-crystalline titanium carbide nanocubes in hierarchical porous carbon monoliths.

    Science.gov (United States)

    Sonnenburg, Kirstin; Smarsly, Bernd M; Brezesinski, Torsten

    2009-05-07

    We report the preparation of nanoscale carbon-titanium carbide composites with carbide contents of up to 80 wt%. The synthesis yields single-crystalline TiC nanocubes 20-30 nm in diameter embedded in a hierarchical porous carbon matrix. These composites were generated in the form of cylindrical monoliths but can be produced in various shapes using modern sol-gel and nanocasting methods in conjunction with carbothermal reduction. The monolithic material is characterized by a combination of microscopy, diffraction and physisorption. Overall, the results presented in this work represent a concrete design template for the synthesis of non-oxidic nanoscale composites with high surface areas.

  12. Composite materials and bodies including silicon carbide and titanium diboride and methods of forming same

    Science.gov (United States)

    Lillo, Thomas M.; Chu, Henry S.; Harrison, William M.; Bailey, Derek

    2013-01-22

    Methods of forming composite materials include coating particles of titanium dioxide with a substance including boron (e.g., boron carbide) and a substance including carbon, and reacting the titanium dioxide with the substance including boron and the substance including carbon to form titanium diboride. The methods may be used to form ceramic composite bodies and materials, such as, for example, a ceramic composite body or material including silicon carbide and titanium diboride. Such bodies and materials may be used as armor bodies and armor materials. Such methods may include forming a green body and sintering the green body to a desirable final density. Green bodies formed in accordance with such methods may include particles comprising titanium dioxide and a coating at least partially covering exterior surfaces thereof, the coating comprising a substance including boron (e.g., boron carbide) and a substance including carbon.

  13. Titanium carbide/carbon composite nanofibers prepared by a plasma process

    Energy Technology Data Exchange (ETDEWEB)

    El Mel, A A; Gautron, E; Angleraud, B; Granier, A; Tessier, P Y [Universite de Nantes, CNRS, Institut des Materiaux Jean Rouxel, UMR 6502, 2 rue de la Houssiniere BP 32229-44322 Nantes cedex 3 (France); Choi, C H [Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)

    2010-10-29

    The incorporation of metal or metal carbide nanoparticles into carbon nanofibers modifies their properties and enlarges their field of application. The purpose of this work is to report a new non-catalytic and easy method to prepare organized metal carbide-carbon composite nanofibers on nanopatterned silicon substrates prepared by laser interference lithography coupled with deep reactive ion etching. Titanium carbide-carbon composite nanofibers were grown on the top of the silicon lines parallel to the substrate by a hybrid plasma process combining physical vapor deposition and plasma enhanced chemical vapor deposition. The prepared nanofibers were analyzed by scanning electron microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. We demonstrate that the shape, microstructure and the chemical composition of the as-grown nanofibers can be tuned by changing the plasma conditions.

  14. Titanium carbide/carbon composite nanofibers prepared by a plasma process.

    Science.gov (United States)

    El Mel, A A; Gautron, E; Choi, C H; Angleraud, B; Granier, A; Tessier, P Y

    2010-10-29

    The incorporation of metal or metal carbide nanoparticles into carbon nanofibers modifies their properties and enlarges their field of application. The purpose of this work is to report a new non-catalytic and easy method to prepare organized metal carbide-carbon composite nanofibers on nanopatterned silicon substrates prepared by laser interference lithography coupled with deep reactive ion etching. Titanium carbide-carbon composite nanofibers were grown on the top of the silicon lines parallel to the substrate by a hybrid plasma process combining physical vapor deposition and plasma enhanced chemical vapor deposition. The prepared nanofibers were analyzed by scanning electron microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. We demonstrate that the shape, microstructure and the chemical composition of the as-grown nanofibers can be tuned by changing the plasma conditions.

  15. The Effects of Carbide Characteristics on the Performance of Tungsten Carbide-Based Composite Overlays, Deposited by Plasma-Transferred Arc Welding

    Science.gov (United States)

    Fisher, G.; Wolfe, T.; Meszaros, K.

    2013-06-01

    In Alberta, there are huge quantities of ore processed to remove bitumen from oil sands deposits. The scale of production generates very aggressive tribocorrosive conditions during the mining, extraction, and upgrading processes. It is common to apply tungsten carbide-based composite overlays to improve the reliability and extend service lives of equipment and components. The performance of the applied overlays is largely dependent on the selection of the carbide type and the wear environment. This paper will evaluate overlays containing macrocrystalline, angular eutectic, and spherical eutectic tungsten carbides and discuss the performance of the overlays with a focus on carbide properties and the interactions between the service conditions and the composite material. This discussion will demonstrate how effective selection of protective materials can improve the reliability of oil sands equipment.

  16. Electrocatalytic Activity of Tungsten Trioxide Micro-spheres, Tungsten Carbide Microspheres and Multi-walled Carbon Nanotube-tungsten Carbide Composites

    Institute of Scientific and Technical Information of China (English)

    LU Hongzhi; YAN Taining

    2009-01-01

    Tungsten trioxide micropheres were prepared by spray pyrolysis, and tungsten carbidemicrospheres were produced by spray pyrolysis-low temperature reduction and carbonization technology.Multi-walled carbon nanotube-tungsten carbide composites were prepared by the continuous reductionand carbonization process using multi-walled carbon nanotubes (MWCNTs) and WO_3 precursor by mo-lecular level mixing and calcination. The morphology and structure of the samples were characterized byscanning electron microscope and transmission electron microscope. Furthermore, the crystal phase was identified by X-ray diffraction. The electrocatalytic activity of the sample was analyzed by means of me-thanol oxidation. Tungsten carbide microspheres were catalytic active for methanol oxidation reaction.Nevertheless tungsten trioxide microspheres and multi-walled carbon nanotube-tungsten carbide compos-ites were not catalytic active for methanol oxidation reaction. These results indicate that tungsten carbide micropheres are promising catalyst for methanol oxidation.

  17. ELASTO-PLASTIC DEFORMATION OF COMPOSITE POWDERS WITH LAYERED CARBON AND CARBIDE-FORMING ELEMENT COATING

    Directory of Open Access Journals (Sweden)

    V. Kovalevsky

    2012-01-01

    Full Text Available Coating structure formation under magnetron spraying of titanium and carbon cathodes and combined cathodes, namely cobalt (EP 131 – nickel, tungsten – carbon have been investigated under conditions of carbide separate synthesis within the temperature range of 650–1200 °C. Usage of cobalt and nickel particles as matrix material leads to their rapid thermal expansion under heating during sintering process in the dilatometer. Subsequent plastic deformation of sintered samples provides obtaining a composite powder material that is a composite with framing structure of cobalt, titanium and tungsten carbides in the coatings.

  18. Effect of microstructure on the high temperature strength of nitride bonded silicon carbide composite

    Indian Academy of Sciences (India)

    J Rakshit; P K Das

    2002-10-01

    Four compositions of nitride bonded SiC were fabricated with varying particle size of SiC of ∼ 9.67, ∼ 13.79, ∼ 60 and their mixture with Si of ∼ 4.83 particle size. The green density and hence the open porosity of the shapes were varied between 1.83 to 2.09 g/cc and 33.3 to 26.8 vol.%, respectively. The effect of these parameters on room temperature and high temperature strength of the composite up to 1300°C in ambient condition were studied. The high temperature flexural strength of the composite of all compositions increased at 1200 and 1300°C because of oxidation of Si3N4 phase and blunting crack front. Formation of Si3N4 whisker was also observed. The strength of the mixture composition was maximum.

  19. Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Ponomarev, V. I., E-mail: ksv17@ism.ac.ru; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I. [Russian Academy of Sciences, Institute of Structural Macrokinetics and Materials Science (Russian Federation)

    2015-09-15

    Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide B{sub 15–x}C{sub x}, (1.5 ≤ x ≤ 3) and its magnesium derivative C{sub 4}B{sub 25}Mg{sub 1.42}. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from B{sub 12.9}C{sub 2.1} to B{sub 12.4}C{sub 2.6}.

  20. Machining studies of die cast aluminum alloy-silicon carbide composites

    Science.gov (United States)

    Sornakumar, Thambu; Kathiresan, Marimuthu

    2010-10-01

    Metal matrix composites (MMCs) with high specific stiffness, high strength, improved wear resistance, and thermal properties are being increasingly used in advanced structural, aerospace, automotive, electronics, and wear applications. Aluminum alloy-silicon carbide composites were developed using a new combination of the vortex method and the pressure die-casting technique in the present work. Machining studies were conducted on the aluminum alloy-silicon carbide (SiC) composite work pieces using high speed steel (HSS) end-mill tools in a milling machine at different speeds and feeds. The quantitative studies on the machined work piece show that the surface finish is better for higher speeds and lower feeds. The surface roughness of the plain aluminum alloy is better than that of the aluminum alloy-silicon carbide composites. The studies on tool wear show that flank wear increases with speed and feed. The end-mill tool wear is higher on machining the aluminum alloy-silicon carbide composites than on machining the plain aluminum alloy.

  1. Studies of the composition and reactivity of carbon species generated through laser vaporization of graphite, tantalum carbide and tungsten carbide

    Energy Technology Data Exchange (ETDEWEB)

    Ortman, B.J.

    1987-01-01

    Vapor compositions above graphite, tantalum carbide, and tungsten carbide together with the chemical reactions of C/sub 1/, C/sub 2/ and C/sub 3/ were studied by the techniques of CW laser vaporization, matrix isolation, and FTIR spectroscopy. The carbon species were scavenged by cocondensing reactive gases (N/sub 2/, H/sub 2/, O/sub 2/, CO and H/sub 2/O) with the vapors of graphitic samples in argon or nitrogen matrices. Products were identified from their infrared spectra. Photolysis and annealing studies were also conducted to detect reaction intermediates, formation of carbon clusters, and metastable C/sub 1/, C/sub 2/, and C/sub 3/ adducts with the added reactants. From these experiments, CO was shown to be potentially the most useful scavenger molecule, since it reacted with both C/sub 1/ and C/sub 2/ to form C/sub 2/O and C/sub 3/O, respectively. CO also reacted with C/sub 3/ to form an adduct, which rearranges upon photolysis to form C/sub 4/O, a previously unknown molecule. Its identity was confirmed by isotopic studies and comparison of its vibrations to those of related molecules, C/sub 3/O, C/sub 2/O, and CO.

  2. Aluminum-titanium hydride-boron carbide composite provides lightweight neutron shield material

    Science.gov (United States)

    Poindexter, A. M.

    1967-01-01

    Inexpensive lightweight neutron shield material has high strength and ductility and withstands high internal heat generation rates without excessive thermal stress. This composite material combines structural and thermal properties of aluminum, neutron moderating properties of titanium hydride, and neutron absorbing characteristics of boron carbide.

  3. Reinforcement of calcium sulfate and magnesium sulfate whiskers to dental composite resin%CaSO4和MgSO4晶须填料对牙科复合树脂抗弯强度的影响

    Institute of Scientific and Technical Information of China (English)

    何峰; 徐玲玲; 谢海峰; 朱烨; 章非敏

    2010-01-01

    目的 观察CaSO4晶须和MgSO4晶须对复合树脂的抗弯强度的影响.方法 制备CaSO4晶须和MgSO4晶须,以硬脂酸钠改性剂表面改性,随后分别按质量分数为1%、10%、20%、30%混合添加到复合树脂中,固化后评价其三点抗弯强度,扫描电镜观察断面形态.结果 添加2种晶须的质量分数在10%及以下时,复合树脂的三点抗弯强度均下降,质量分数为20%和30%时,MgsO4晶须组的三点抗弯强度增加.结论 添加适当比例的MgSO4晶须可以提高复合树脂的三点抗弯强度.%Objective The aim of this study was to evaluate the effect of calcium sulphate and magnesium sulfate whiskers on the flexture strengths of dental composite resin.Methods Calcium sulfate whiskers and magnesium sulfate whiskers were prepared.Seven groups of composite resin specimens were prepared including one control group and six groups using either calcium sulfate whiskers or magnesium sulfate whiskers comprising 1%,10%,20%,30% of the material by weight.Before mixing with resin,both whiskers were surface modified by Sodium stearate.The standard resin samples with dimensions of 25 mm×2 mm×2 mm were prepared according to the ISO-10477 criterion(eight for each group),and their flexure strengths were measured by a universal testing machine.The fracture surfaces of selected specimens were examined by a scan electron microscope.Results Neither mixture improved the flexure strength of composite resin when the adding proportions of calcium sulfate and whiskers magnesium sulfate whiskers were under 10%.However,when the adding proportions were 20 wt % and 30 wt%,magnesium sulfate whiskers excerted positive effects.Concluson Appropriate proportions of magnesium sulfate crystal whisker would increase the flexure strength of dental composite resin.

  4. Molybdenum isotopic composition of single silicon carbides from supernovae.

    Energy Technology Data Exchange (ETDEWEB)

    Amari, S.; Clayton, R. N.; Davis, A. M.; Lewis, R. S.; Pellin, M. J.

    1999-02-03

    Presolar silicon carbide grains form in a variety of types of stars, including asymptotic giant branch red giant stars and supernovae. The dominant mechanisms of heavy element nucleosynthesis, the s-process and r-process, are thought to occur in AGB stars and supernovae, respectively. We have previously reported that mainstream SiC grains have strong enrichments in the s-process isotopes of Sr, Zr and Mo. We report here the first measurements of Mo isotopes in X-type SiC grains, which have previously been identified as having formed from supernova ejecta.

  5. Microstructure of alumina-matrix composites reinforced with nanometric titanium and titanium carbide dispersions

    OpenAIRE

    Elizabeth Refugio-García; David Hernández-Silva; Eduardo Terrés-Rojas; José Amparo Rodríguez-García; Enrique Rocha-Rangel

    2012-01-01

    The synthesis of alumina (Al2O3)-composites having different amount of very fine titanium and titanium carbide reinforcement-particles has been explored. Two experimental steps have been set for the synthesis; the first step consisted of the pressureless-sintering of Al2O3-titanium powders which were thoroughly mixed under high energy ball-milling and through the second step it was induced the formation of titanium carbide during different times at 500 ºC by the cementation packing process. S...

  6. Effects of calcium sulfate and magnesium sulfate whiskers on Vickers Hardness of dental composite resin%硫酸钙和硫酸镁晶须对复合树脂维氏硬度的影响

    Institute of Scientific and Technical Information of China (English)

    何峰; 张莘; 王晓菲; 章非敏; 谢海峰

    2011-01-01

    Objects The aim of this study was to evalue the effects of calcium sulphate and magnesium sulfate whiskers on the Vickers Hardness of dental composite resin. Methods Calcium suffate and magnesium sulfate whiskers were prepared and were surface modified by sodium stearate. Eight groups of composite resin specimens were prepared: one control group, and seven groups using either surface modified calcium sulfate whiskers or magnesium sulfate whiskers comprising 1%, 10% , 20%, 30% of the material by weight. The standard resin samples were prepared, and their Vickers Hardness values were measured. Results With 20% and 30% calcium sulphate or magnesium sulfate whiskers, surface hardness improved. The more magnesium sulfate whiskers was added, the higher surface hardness values presented. Conclusons Appropriate proportions of calcium sulphate and magnesium sulfate whisker would increase the surface hardness of dental composite resin.%目的 探讨硫酸钙和硫酸镁晶须对复合树脂的维氏硬度的影响.方法 制备硫酸钙和硫酸镁晶须,以硬脂酸钠改性剂表面改性,随后分别按1%、10%、20%、30%的比例混合入复合树脂中,固化后测量各组试件表面维氏硬度.结果 两种晶须的添加比例为20%和30%时,树脂的表面维氏硬度均增加,硫酸镁晶须添加量多时树脂表面硬度相应增加.结论 添加适当比例的硫酸钙和硫酸镁镁晶须可以提高复合树脂的表面硬度.

  7. Abrasive Performance of Chromium Carbide Reinforced Ni3Al Matrix Composite Cladding

    Institute of Scientific and Technical Information of China (English)

    LI Shang-ping; LUO He-li; FENG Di; CAO Xu; ZHANG Xi-e

    2009-01-01

    The Microstructure and room temperature abrasive wear resistance of chromium carbide reinforced NiM3Al matrix composite cladding at different depth on nickel base alloy were investigated. The results showed that there is a great difference in microstructure and wear resistance of the Ni3 Al matrix composite at different depth. Three kinds of tests, designed for different load and abrasive size, were used to understand the wear behaviour of this material. Under all three wear conditions, the abrasion resistance of the composite cladding at the depth of 6 mm, namely NC-M2, was much higher than that of the composite cladding at the depth of 2 mm, namely NC-M1. In addition, the wear-resistant advantage of NC-M2 was more obvious when the size of the abrasive was small. The relative wear resistance of NC-M2 increased from 1.63 times to 2.05 times when the size of the abrasive decreased from 180 μm to 50μm. The mierostructure of the composite cladding showed that the size of chromium carbide particles, which was mainly influenced by cooling rate of melting pool, was a function of distance from the interface between the coating and substrate varied gradually. The chromium carbide particles near the interface were finer than that far from inter-face, which was the main reason for the different wear resistance of the composite cladding at different depth.

  8. Mechanical and Corrosion Behaviour of Zn-27Al Based Composites Reinforced with Groundnut Shell Ash and Silicon Carbide

    OpenAIRE

    K.K. Alaneme; B.O. Fatile; J.O. Borode

    2014-01-01

    The mechanical and corrosion behaviour of Zn-27Al alloy based composites reinforced with groundnut shell ash and silicon carbide was investigated. Experimental test composite samples were prepared by melting Zn-27Al alloy with pre-determined proportions of groundnut ash and silicon carbide as reinforcements using double stir casting. Microstructural examination, mechanical properties and corrosion behaviour were used to characterize the composites produced. The results show that hardness and ...

  9. Bibliography on Ceramic Matrix Composites and Reinforcing Whiskers, Platelets, and Fibers, 1970-1990

    Science.gov (United States)

    1993-08-01

    Saburo Shigaki, Yoshiki Rao, A. Srinivasa Cannon, W Roger Hirata, Yoshihiro Yoshimua, Masahiro Ceram. Int. Somiya, Shigeyuki 15 (3), 179-88, 1989...P. Chartier , T. Mullites and Mullite-Zirconia Composites Giry, J. P. Kubota, Y. Takagi, H. Mullite and Mullite Matrix Composites Government Industrial...Yong, J. A. 74 (1), 187-93, Jan 1991 Rawlings, R. D. Rogers , P. S. (AD D250 366) Mater. Sci. Technol. 7, 155-7, Feb 1991 7.1.0.48 (AD D250 906

  10. Structure and abrasive wear resistance of R6M5 steel-tungsten carbide composite coatings

    Science.gov (United States)

    Gnyusov, S. F.

    2012-09-01

    Features of the structure formation, composition, and abrasive wear resistance of R6M5 steel-tungsten carbide (R6M5-WC) composite coatings have been studied as dependent on the WC content. The introduction of ˜20 wt % WC into the hardening composition leads to an increase in the fraction of M6C carbide (in the form of eutectic inclusions with average size ˜5.9 μm at grain boundaries and dispersed ˜0.25 μm particles in the volume of grains), while a large proportion of metastable austenite (˜88 vol %) is still retained. The R6M5-WC coatings exhibit high abrasive wear resistance, which is ensured by the γ → α' martensite transformation during friction and a muiltimodal size distribution of hardening particles.

  11. High Temperature Joining and Characterization of Joint Properties in Silicon Carbide-Based Composite Materials

    Science.gov (United States)

    Halbig, Michael C.; Singh, Mrityunjay

    2015-01-01

    Advanced silicon carbide-based ceramics and composites are being developed for a wide variety of high temperature extreme environment applications. Robust high temperature joining and integration technologies are enabling for the fabrication and manufacturing of large and complex shaped components. The development of a new joining approach called SET (Single-step Elevated Temperature) joining will be described along with the overview of previously developed joining approaches including high temperature brazing, ARCJoinT (Affordable, Robust Ceramic Joining Technology), diffusion bonding, and REABOND (Refractory Eutectic Assisted Bonding). Unlike other approaches, SET joining does not have any lower temperature phases and will therefore have a use temperature above 1315C. Optimization of the composition for full conversion to silicon carbide will be discussed. The goal is to find a composition with no remaining carbon or free silicon. Green tape interlayers were developed for joining. Microstructural analysis and preliminary mechanical tests of the joints will be presented.

  12. Effects of cellulose whiskers on properties of soy protein thermoplastics.

    Science.gov (United States)

    Wang, Yixiang; Cao, Xiaodong; Zhang, Lina

    2006-07-14

    Environmentally-friendly SPI/cellulose whisker composites were successfully prepared using a colloidal suspension of cellulose whiskers, to reinforce soy protein isolate (SPI) plastics. The cellulose whiskers, having an average length of 1.2 microm and diameter of 90 nm, respectively, were prepared from cotton linter pulp by hydrolyzing with sulfuric acid aqueous solution. The effects of the whisker content on the morphology and properties of the glycerol-plasticized SPI composites were investigated by scanning electron microscopy, dynamic mechanical thermal analysis, differential scanning calorimetry, ultraviolet-visible spectroscopy, water-resistivity testing and tensile testing. The results indicated that, with the addition of 0 to 30 wt.-% of cellulose whiskers, strong interactions occurred both between the whiskers and between the filler and the SPI matrix, reinforcing the composites and preserving their biodegradability. Both the tensile strength and Young's modulus of the SPI/cellulose whisker composites increased from 5.8 to 8.1 MPa and from 44.7 to 133.2 MPa, respectively, at a relative humidity of 43%, following an increase of the whisker content from 0 to 30 wt.-%. Furthermore, the incorporation of the cellulose whiskers into the SPI matrix led to an improvement in the water resistance for the SPI-based composites.

  13. Feasibility of Electrochemical Deposition of Nickel/Silicon Carbide Fibers Composites over Nickel Superalloys

    Science.gov (United States)

    Ambrosio, E. P.; Abdul Karim, M. R.; Pavese, M.; Biamino, S.; Badini, C.; Fino, P.

    2017-02-01

    Nickel superalloys are typical materials used for the hot parts of engines in aircraft and space vehicles. They are very important in this field as they offer high-temperature mechanical strength together with a good resistance to oxidation and corrosion. Due to high-temperature buckling phenomena, reinforcement of the nickel superalloy might be needed to increase stiffness. For this reason, it was thought to investigate the possibility of producing composite materials that might improve properties of the metal at high temperature. The composite material was produced by using electrochemical deposition method in which a composite with nickel matrix and long silicon carbide fibers was deposited over the nickel superalloy. The substrate was Inconel 718, and monofilament continuous silicon carbide fibers were chosen as reinforcement. Chemical compatibility was studied between Inconel 718 and the reinforcing fibers, with fibers both in an uncoated condition, and coated with carbon or carbon/titanium diboride. Both theoretical calculations and experiments were conducted, which suggested the use of a carbon coating over the fibers and a buffer layer of nickel to avoid unwanted reactions between the substrate and silicon carbide. Deposition was then performed, and this demonstrated the practical feasibility of the process. Yield strength was measured to detect the onset of interface debonding between the substrate and the composite layer.

  14. Microstructure of alumina-matrix composites reinforced with nanometric titanium and titanium carbide dispersions

    Directory of Open Access Journals (Sweden)

    Elizabeth Refugio-García

    2012-12-01

    Full Text Available The synthesis of alumina (Al2O3-composites having different amount of very fine titanium and titanium carbide reinforcement-particles has been explored. Two experimental steps have been set for the synthesis; the first step consisted of the pressureless-sintering of Al2O3-titanium powders which were thoroughly mixed under high energy ball-milling and through the second step it was induced the formation of titanium carbide during different times at 500 ºC by the cementation packing process. SEM and EDS analysis of the microstructures obtained in both sintered and cemented bodies were performed in order to know the effect of the activated carbon used as cementing agent on the titanium for each studied composite. It was observed that a titanium carbide layer growth from the surface into the bulk and reaches different depth as the titanium content in the composites increases. On the other hand, the use of ductile titanium notably enhanced density level and fracture toughness of the composites.

  15. Polymerization kinetics of boron carbide/epoxy composites

    Energy Technology Data Exchange (ETDEWEB)

    Abenojar, J., E-mail: abenojar@ing.uc3m.es [Materials Performance Group, Materials Science and Engineering Department, IAAB, Universidad Carlos III de Madrid, Av. Universidad, 30, 28911 Leganés (Spain); Encinas, N. [Materials Performance Group, Materials Science and Engineering Department, IAAB, Universidad Carlos III de Madrid, Av. Universidad, 30, 28911 Leganés (Spain); Real, J.C. del [Department of Mechanical Engineering, Universidad Pontificia Comillas, C/ Alberto Aguilera 23, 28015 Madrid (Spain); Martínez, M.A. [Materials Performance Group, Materials Science and Engineering Department, IAAB, Universidad Carlos III de Madrid, Av. Universidad, 30, 28911 Leganés (Spain)

    2014-01-10

    Graphical abstract: - Highlights: • Conversion degree and rate reaction of the curing reaction increase with temperature. • At low temperature, the particles exhibit catalytic effect, similar to the OH groups. • At high temperature, B{sub 4}C micro-particles increase the n-order rate reaction. • The diffusion constant diminishes with temperature for all the studied materials. • The autocatalytic reaction is favored by the effect of 6% nanoparticles. - Abstract: This study employs Differential Scanning Calorimetry (DSC) technique and focuses on the curing kinetics and the activation energy of the commercial epoxy resin (which cures at room temperature for 12 h) filled with boron carbide particles (B{sub 4}C) in different amount (6 and 12 wt%) and particle size (60 nm, 7 and 23 μm). An isothermal dwell at different temperatures (25, 35 and 50 °C) was used for 180 min. Thereafter, the temperature is increased by 5 °C min{sup −1} up to 200 °C to complete the curing process. Conversion degree is calculated by combining both methods. The kinetic constant and the reaction order are calculated using Kamal's equation with diffusion control. Consequently, the activation energy is computed assuming Arrhenius’ equation.The results show a significant influence of the temperature on the reaction mechanism. Furthermore, polymerization kinetics is affected by B{sub 4}C additions depending on the amount and size of the added particles.

  16. Synthesis and Characterization of In-situ Copper-Niobium Carbide Composite

    Science.gov (United States)

    Zuhailawati, H.; Othman, R.; Bui, D. L.; Umemoto, M.

    2008-03-01

    In this work, synthesis of copper matrix composite powder reinforced by in situ niobium carbide particle was prepared by mechanical alloying of elemental powder and subsequent heat treatment. Elemental powders of Cu-Nb-C correspond to Cu-40wt%Nb-10%wtC composition was milled for 54 hours at room temperature in a planetary ball mill. The effect of heat treatment temperature on the formation of niobium carbide was analyzed. Characterization by X-ray diffraction was done on the milled powder and heat-treated powder in order to investigate NbC formation. Results indicate that NbC began to precipitate after mechanical alloying for about 54h with heat treatment temperature of 900 °C and 1000 °C.

  17. Versatile Boron Carbide-Based Visual Obscurant Compositions for Smoke Munitions

    Science.gov (United States)

    2015-04-17

    ignition and are safe to handle. KEYWORDS: Smoke, Obscurants, Pyrotechnics, Boron carbide, Sustainable chemistry ■ INTRODUCTION Visible obscuration...laced with soot and chlorinated organic compounds. Smoke grenades containing these “HC” compositions have been responsible for several smoke...Robert A. Gilbert, Jr. 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) U.S. Army

  18. Effect of thermomechanical treatments on the aging response of centrifugally cast silicon carbide/aluminum composites

    OpenAIRE

    May, Christopher William

    1992-01-01

    Approved for public release; distribution is unlimited Differential scanning calorimetry was conducted using centrifugally cast monolithic A3356 aluminum material and 26 volume present silicon carbide (SiC) particle reinforced A356 aluminum matrix composite material in as-cast, cast and rolled, and cast and extruded conditions. Electrical resistivity and matrix micro-hardness measurements during isothermal aging treatments were also conducted. The effects of thermo-mechanical processing ...

  19. Effect of thermomechanical treatments on the aging response of centrifugally cast silicon carbide/aluminum composites

    OpenAIRE

    May, Christopher William

    1992-01-01

    Approved for public release; distribution is unlimited Differential scanning calorimetry was conducted using centrifugally cast monolithic A3356 aluminum material and 26 volume present silicon carbide (SiC) particle reinforced A356 aluminum matrix composite material in as-cast, cast and rolled, and cast and extruded conditions. Electrical resistivity and matrix micro-hardness measurements during isothermal aging treatments were also conducted. The effects of thermo-mechanical processing ...

  20. Development of a reaction-sintered silicon carbide matrix composite

    Science.gov (United States)

    Sayano, A.; Sutoh, C.; Suyama, S.; Itoh, Y.; Nakagawa, S.

    SiC matrix composites reinforced with continuous SiC-based fibres using reaction sintering (RS) for matrix processing were produced and their mechanical and physical properties were studied. Mechanical behaviour of SiCf/SiC (RS) composites in tension and in flexure exhibits improved toughness and a non-catastrophic failure due to fibre crack bridging and pullout from the matrix, and the composites exhibit high thermal conductivity, high Young's modulus and reduced porosity. Moreover, SiCf/SiC (RS) composites showed improved thermal shock resistance in comparison to monolithic RS-SiC. SiC matrix processing by RS leads to reduced production times and lower costs when compared with other methods such as polymer impregnation and pyrolysis (PIP) or chemical vapour infiltration (CVI). Composite prototypes were also produced for feasibility demonstration, and it was verified that the method could be applied to produce large parts and complex shapes.

  1. Cortical control of whisker movement.

    Science.gov (United States)

    Petersen, Carl C H

    2014-01-01

    Facial muscles drive whisker movements, which are important for active tactile sensory perception in mice and rats. These whisker muscles are innervated by cholinergic motor neurons located in the lateral facial nucleus. The whisker motor neurons receive synaptic inputs from premotor neurons, which are located within the brain stem, the midbrain, and the neocortex. Complex, distributed neural circuits therefore regulate whisker movement during behavior. This review focuses specifically on cortical whisker motor control. The whisker primary motor cortex (M1) strongly innervates brain stem reticular nuclei containing whisker premotor neurons, which might form a central pattern generator for rhythmic whisker protraction. In a parallel analogous pathway, the whisker primary somatosensory cortex (S1) strongly projects to the brain stem spinal trigeminal interpolaris nucleus, which contains whisker premotor neurons innervating muscles for whisker retraction. These anatomical pathways may play important functional roles, since stimulation of M1 drives exploratory rhythmic whisking, whereas stimulation of S1 drives whisker retraction.

  2. Modeling tin whisker growth.

    Energy Technology Data Exchange (ETDEWEB)

    Weinberger, Christopher Robert

    2013-08-01

    Tin, lead, and lead-tin solders are the most commonly used solders due to their low melting temperatures. However, due to the toxicity problems, lead must now be removed from solder materials. This has lead to the re-emergence of the issue of tin whisker growth. Tin whiskers are a microelectronic packaging issue because they can lead to shorts if they grow to sufficient length. However, the cause of tin whisker growth is still not well understood and there is lack of robust methods to determine when and if whiskering will be a problem. This report summarizes some of the leading theories on whisker growth and attempts to provide some ideas towards establishing the role microstructure plays in whisker growth.

  3. Modeling tin whisker growth.

    Energy Technology Data Exchange (ETDEWEB)

    Weinberger, Christopher Robert

    2013-08-01

    Tin, lead, and lead-tin solders are the most commonly used solders due to their low melting temperatures. However, due to the toxicity problems, lead must now be removed from solder materials. This has lead to the re-emergence of the issue of tin whisker growth. Tin whiskers are a microelectronic packaging issue because they can lead to shorts if they grow to sufficient length. However, the cause of tin whisker growth is still not well understood and there is lack of robust methods to determine when and if whiskering will be a problem. This report summarizes some of the leading theories on whisker growth and attempts to provide some ideas towards establishing the role microstructure plays in whisker growth.

  4. 微发泡聚丙烯/晶须复合材料的发泡行为与力学性能%Foam Behavior and Mechanical Property of PP/Whisker Microcellular Foam Composites

    Institute of Scientific and Technical Information of China (English)

    龚维; 高家诚; 何力; 朱建华; 于杰; 何颖

    2011-01-01

    Modified MgSO4 and CaCO3 whisker was added into polypropylene. The microcellular foam PP/whisker composites were made under the condition of twice-open mold. The influence of different types of whisker on the foaming behavior and mechanical properties of PP composites was analyzed by dispersion of the whisker, cell size and cell density in matrix material. The results show that CaCO3 whisker has a little nucleation efficiency in foamed PP composites, the cell size of this microcellular PP composites is about 25.27μm, enhancement effect is poor in foamed PP composites. However, as for MgSO4 whisker, there is a little nucleation efficiency, the cell size of this microcellular PP composites is about 26.75 tm, enhancement effect is better, in foamed PP composites, tensile strength is 30.5 MPa. Owing to it's lower cost and better enhancement effect, MgSO4 whisker is an ideal filler used in foamed PP composites.%将改性的MgSO4和CaCO3晶须加入聚丙烯中,在二次开模条件下制备微发泡聚丙烯(PP)/晶须复合材料,通过晶须在基体中的分散性、泡孔直径大小分布和泡孔密度,分析了不同晶须对材料的发泡行为与力学性能的影响.结果表明,晶须具有一定成核效应,CaCO3晶须的泡孔尺寸25.27μm左右,填充增强效果差;MgSO4晶须的泡孔尺寸在26.75μm左右,填充增强效果好,拉伸强度提高到30.5 MPa,与未发泡PP拉伸强度30.8 MPa相近,说明MgSO4既能达到降低成本又能起到增强效果;MgSO4晶须是微发泡PP复合材料的理想一维填料.

  5. Dry Sliding Wear behaviour of Aluminium-Red mud- Tungsten Carbide Hybrid metal matrix composites

    Science.gov (United States)

    Devi Chinta, Neelima; Selvaraj, N.; Mahesh, V.

    2016-09-01

    Red mud is an industrial waste obtained during the processing of alumina by Bayer's process. An attempt has been made to utilize the solid waste by using it as the reinforcement material in metal matrix composites. Red mud received from NALCO has been subjected for sieve analysis and milled to 42 nanometers using high energy ball mill. Red mud is used as a reinforcement material in Pure Aluminium matrix composite at 2%, 4%, and 6% weight at 100 microns level as well as 42 nano meters along with 4%Tungsten carbide by weight. Micro and Nano structured red mud powders, Tungsten carbide powder and Aluminium is mixed in a V-Blender, compacted at a pressure of 40 bar and samples are prepared by conventional sintering with vacuum as medium. In this current work, dry sliding wear characteristics at normal and heat treatment conditions are investigated with optimal combination of Aluminium, Tungsten carbide and different weight fractions of micro and nano structured red mud powder.

  6. Composition and microstructure of beryllium carbide films prepared by thermal MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    He, Yu-dan; Luo, Jiang-shan; Li, Jia; Meng, Ling-biao; Luo, Bing-chi; Zhang, Ji-qiang; Zeng, Yong; Wu, Wei-dong, E-mail: wuweidongding@163.com

    2016-02-15

    Highlights: • Non-columnar-crystal Be{sub 2}C films were firstly prepared by thermal MOCVD. • Beryllium carbide was always the dominant phase in the films. • α-Be and carbon existed in films deposited below and beyond 400 °C, respectively. • Morphology evolved with temperatures and no columnar grains were characterized. • The preferred substrate temperature for depositing high quality Be{sub 2}C films was 400 °C. - Abstract: Beryllium carbide films without columnar-crystal microstructures were prepared on the Si (1 0 0) substrate by thermal metal organic chemical vapor deposition using diethylberyllium as precursor. The influence of the substrate temperature on composition and microstructure of beryllium carbide films was systematically studied. Crystalline beryllium carbide is always the dominant phase according to XRD analysis. Meanwhile, a small amount of α-Be phase exists in films when the substrate temperature is below 400 °C, and hydrocarbon or amorphous carbon exists when the temperature is beyond 400 °C. Surfaces morphology shows transition from domes to cylinders, to humps, and to tetraquetrous crystalline needles with the increase of substrate temperature. No columnar grains are characterized throughout the thickness as revealed from the cross-section views. The average densities of these films are determined to be 2.04–2.17 g/cm{sup 3}. The findings indicate the substrate temperature has great influences on the composition and microstructure of the Be{sub 2}C films grown by thermal MOCVD.

  7. Carbide Coatings for Nickel Alloys, Graphite and Carbon/Carbon Composites to be used in Fluoride Salt Valves

    Energy Technology Data Exchange (ETDEWEB)

    Nagle, Denis [Johns Hopkins Univ., Baltimore, MD (United States); Zhang, Dajie [Johns Hopkins Univ., Baltimore, MD (United States)

    2015-10-22

    The focus of this research was concerned with developing materials technology that supports the evolution of Generation IV Advanced High Temperature Reactor (AHTR) concepts. Specifically, we investigate refractory carbide coatings for 1) nickel alloys, and 2) commercial carbon-carbon composites (CCCs). Numerous compelling reasons have driven us to focus on carbon and carbide materials. First, unlike metals, the strength and modulus of CCCs increase with rising temperature. Secondly, graphite and carbon composites have been proven effective for resisting highly corrosive fluoride melts such as molten cryolite [Na₃AlF₆] at ~1000°C in aluminum reduction cells. Thirdly, graphite and carbide materials exhibit extraordinary radiation damage tolerance and stability up to 2000°C. Finally, carbides are thermodynamically more stable in liquid fluoride salt than the corresponding metals (i.e. Cr and Zr) found in nickel based alloys.

  8. Lightweight graphene nanoplatelet/boron carbide composite with high EMI shielding effectiveness

    Science.gov (United States)

    Tan, Yongqiang; Luo, Heng; Zhang, Haibin; Zhou, Xiaosong; Peng, Shuming

    2016-03-01

    Lightweight graphene nanoplatelet (GNP)/boron carbide (B4C) composites were prepared and the effect of GNPs loading on the electromagnetic interference (EMI) shielding effectiveness (SE) has been evaluated in the X-band frequency range. Results have shown that the EMI SE of GNP/B4C composite increases with increasing the GNPs loading. An EMI SE as high as 37 ˜ 39 dB has been achieved in composite with 5 vol% GNPs. The high EMI SE is mainly attributed to the high electrical conductivity, high dielectric loss as well as multiple reflections by aligned GNPs inside the composite. The GNP/B4C composite is demonstrated to be promising candidate of high-temperature microwave EMI shielding material.

  9. Lightweight graphene nanoplatelet/boron carbide composite with high EMI shielding effectiveness

    Directory of Open Access Journals (Sweden)

    Yongqiang Tan

    2016-03-01

    Full Text Available Lightweight graphene nanoplatelet (GNP/boron carbide (B4C composites were prepared and the effect of GNPs loading on the electromagnetic interference (EMI shielding effectiveness (SE has been evaluated in the X-band frequency range. Results have shown that the EMI SE of GNP/B4C composite increases with increasing the GNPs loading. An EMI SE as high as 37 ∼ 39 dB has been achieved in composite with 5 vol% GNPs. The high EMI SE is mainly attributed to the high electrical conductivity, high dielectric loss as well as multiple reflections by aligned GNPs inside the composite. The GNP/B4C composite is demonstrated to be promising candidate of high-temperature microwave EMI shielding material.

  10. Silicon carbide composite for light water reactor fuel assembly applications

    Science.gov (United States)

    Yueh, Ken; Terrani, Kurt A.

    2014-05-01

    The feasibility of using SiCf-SiCm composites in light water reactor (LWR) fuel designs was evaluated. The evaluation was motivated by the desire to improve fuel performance under normal and accident conditions. The Fukushima accident once again highlighted the need for improved fuel materials that can maintain fuel integrity to higher temperatures for longer periods of time. The review identified many benefits as well as issues in using the material. Issues perceived as presenting the biggest challenges to the concept were identified to be flux gradient induced differential volumetric swelling, fragmentation and thermal shock resistance. The oxidation of silicon and its release into the coolant as silica has been identified as an issue because existing plant systems have limited ability for its removal. Detailed evaluation using available literature data and testing as part of this evaluation effort have eliminated most of the major concerns. The evaluation identified Boiling Water Reactor (BWR) channel, BWR fuel water tube, and Pressurized Water Reactor (PWR) guide tube as feasible applications for SiC composite. A program has been initiated to resolve some of the remaining issues and to generate physical property data to support the design of commercial fuel components.

  11. Silicon carbide composite for light water reactor fuel assembly applications

    Energy Technology Data Exchange (ETDEWEB)

    Yueh, Ken, E-mail: kyueh@epri.com [Fuel Reliability Program, EPRI, 1300 West WT Harris Blvd, Charlotte, NC 28262 (United States); Terrani, Kurt A., E-mail: terranika@ornl.gov [Fusion and Materials for Nuclear Systems Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd. MS 6093, Oak Ridge, TN 37831 (United States)

    2014-05-01

    The feasibility of using SiC{sub f}–SiC{sub m} composites in light water reactor (LWR) fuel designs was evaluated. The evaluation was motivated by the desire to improve fuel performance under normal and accident conditions. The Fukushima accident once again highlighted the need for improved fuel materials that can maintain fuel integrity to higher temperatures for longer periods of time. The review identified many benefits as well as issues in using the material. Issues perceived as presenting the biggest challenges to the concept were identified to be flux gradient induced differential volumetric swelling, fragmentation and thermal shock resistance. The oxidation of silicon and its release into the coolant as silica has been identified as an issue because existing plant systems have limited ability for its removal. Detailed evaluation using available literature data and testing as part of this evaluation effort have eliminated most of the major concerns. The evaluation identified Boiling Water Reactor (BWR) channel, BWR fuel water tube, and Pressurized Water Reactor (PWR) guide tube as feasible applications for SiC composite. A program has been initiated to resolve some of the remaining issues and to generate physical property data to support the design of commercial fuel components.

  12. Research on rare earth and iron-rich diamond-enhanced tungsten carbide composite button

    Institute of Scientific and Technical Information of China (English)

    SHI Xiaoliang; SHAO Gangqin; DUAN Longchen; YUAN Runzhang

    2004-01-01

    At the present time in china, the binder used in tungsten carbide composite button is mainly cobalt, which is very expensive. In order to solve the problems, a new type of rare earth and iron-rich diamond-enhanced tungsten carbide with high abrasive resistance and high toughness against impact, which realizes to substitute ferrum for cobalt, has been developed. The key problems in making the button are to improve the mechanical properties of matrix and increase the welding strength between the diamond and the matrix. All these problems have been solved effectively by low temperature activation hot-press sintering, doping rare earth lanthanum in matrix and high sintering pressure. The properties of the button have been determined under laboratory conditions. The test results show that its hardness is more than 90 HRA, its abrasive resistance is 39 times more than that of conventional cemented tungsten carbide, and its toughness against impact is more than 200 J. All these data show the button has very good mechanical properties.

  13. Influence of yttrium oxide doping on the microstructures of alumina-niobium carbide composites

    Energy Technology Data Exchange (ETDEWEB)

    Rumbao, A.H.; Bressiani, J.C.; Bressiani, A.H.A. [IPEN - Inst. de Pesquisas Energeticas e Nucleares, Cidade Univ. - Sao Paulo, SP (Brazil)

    2003-07-01

    Ceramic cutting tools have been developed as an alternative material to cemented carbides based ones with the goal of improving cutting speeds and productivity. Among the vast variety of ceramics considered for prospective use as cutting tools materials the preference is given to the composites containing carbides as a second component, i.e., such materials as Al{sub 2}O{sub 3}-SiC, and Al{sub 2}O{sub 3}-TiC. In the present work, the influence of Y{sub 2}O{sub 3} additives on microstructure of Al{sub 2}O{sub 3}-NbC composite is studied in order to evaluate the applicability of this material for as ceramic cutting tools manufacturing. The amount of Y{sub 2}O{sub 3} additives varied in the ranged, 0-3 wt% in the Al{sub 2}O{sub 3}-NbC 20 wt% composition. Specimens were produced by consequent uniaxial and isostatic pressing followed by pressureless sintering in the flowing argon at 1750 C for 15 min in a graphite resistance furnace. The achieved densities were up to 99% TD. Microstructure evaluation in terms of grain size distribution were achieved by mean of QUANTIKOV software applied to scanning electron microscope (SEM) micrographs. Optimization of the materials composition in regard of achieving the high densities without compromising the microstructure formation are discussed. (orig.)

  14. Superficial roughness on composite surface, composite enamel and composite dentin junctions after different finishing and polishing procedures. Part I: roughness after treatments with tungsten carbide vs diamond burs.

    Science.gov (United States)

    Ferraris, Federico; Conti, Alessandro

    2014-01-01

    The aim of this study is to investigate different instruments for finishing composite restorations, as well as examining different surfaces and interfaces of the same restoration. The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations finishing between tungsten carbide and diamond burs, furthermore the null hypothesis is that there are no significant differences on roughness between finishing on composite surfaces (C), compositeenamel (CE) and composite-dentin (CD) interfaces. The study was performed on 28 teeth, and class V cavities were prepared on the extracted teeth. Restorations were done in Filtek XTE nanofilled composite (3M Espe) in a standardized method, to then be finished. A comparison was made in the phase 1 between tungsten carbide burs (16 blades), diamond burs (46 μm), with a similar shape by the same manufacturer (Komet). Each surface received 5 bur applications. Consequently, an analysis with a profilometer was performed. Phase 2 involved further confrontation of ulterior finishing with ultrafine tungsten carbide burs (30 blades) and with extra and ultrafine diamond burs (25 and 8 μm) (the same shape as previously mentioned). A second analysis was then performed with a profilometer. All measurements were taken on C surfaces, CE and CD interfaces. Statistical analyses were carried out with c2 test (a = 0.05). The finishing procedures with fine grit or toothing burs gave a better smoothness with tungsten carbide burs compared to diamond burs. While with the ultrafine grit no significant differences were noted between tungsten carbide and diamond burs on the CE and CD interfaces, the diamond bur left less superficial roughness on the C surfaces. With regards to the superficial roughness of the different areas of restoration, it can be concluded that: minor roughness was detected on C surfaces, while the CD interface had the most superficial roughness, regardless of whether the

  15. SOLIDIFICATION CHARACTERISTIC OF TITANIUM CARBIDE PARTICULATE REINFORCED ALUMINIUM ALLOY MATRIX COMPOSITES

    Directory of Open Access Journals (Sweden)

    N. FATCHURROHMAN

    2012-04-01

    Full Text Available In this research solidification characteristic of metal matrix composites consisted of titanium carbide particulate reinforced aluminium-11.8% silicon alloy matrix is performed. Vortex mixing and permanent casting method are used as the manufacturing method to produce the specimens. Temperature measurements during the casting process are captured and solidification graphs are plotted to represent the solidification characteristic. The results show, as volume fraction of particulate reinforcement is increased, solidification time is faster. Particulate reinforcement promotes rapid solidification which will support finer grain size of the casting specimen. Hardness test is performed and confirmed that hardness number increased as more particulate are added to the system.

  16. In Situ Synthesis Aluminum Borate Whiskers Reinforced TiB2 Matrix Composites for Application in Aluminum Reduction Cells

    Science.gov (United States)

    Zhang, Gang; Yang, Jianhong

    2013-11-01

    The TiB2 matrix ceramics reinforced by aluminum borate whiskers (Al18B4O33 w) had been prepared by the pressureless sintering method. The mechanical properties and densification behavior of the TiB2 matrix ceramics were investigated. The results showed that Al18B4O33 w was in situ synthesized by the reaction of boehmite (AlOOH) and TiB2 powders during the sintering process. Increasing the sintering temperature had benefited for densification of the TiB2 matrix ceramics. Al18B4O33 w could increase the flexural strength and Vicker's hardness. It is obtained that the maximum value Vicker's hardness with 1.81 GPa and flexural strength with 82 MPa for samples sintered at 1600°C.

  17. Development of high temperature materials for solid propellant rocket nozzle applications. [tantalum carbides-tungsten fiber composites

    Science.gov (United States)

    Manning, C. R., Jr.; Honeycutt, L., III

    1974-01-01

    Evaluation of tantalum carbide-tungsten fiber composites has been completed as far as weight percent carbon additions and weight percent additions of tungsten fiber. Extensive studies were undertaken concerning Young's Modulus and fracture strength of this material. Also, in-depth analysis of the embrittling effects of the extra carbon additions on the tungsten fibers has been completed. The complete fabrication procedure for the tantalum carbide-tungsten fiber composites with extra carbon additions is given. Microprobe and metallographic studies showed the effect of extra carbon on the tungsten fibers, and evaluation of the thermal shock parameter fracture strength/Young's Modulus is included.

  18. Niobium Carbide-Reinforced Al Matrix Composites Produced by High-Energy Ball Milling

    Science.gov (United States)

    Travessa, Dilermando Nagle; Silva, Marina Judice; Cardoso, Kátia Regina

    2017-06-01

    Aluminum and its alloys are key materials for the transportation industry as they contribute to the development of lightweight structures. The dispersion of hard ceramic particles in the Al soft matrix can lead to a substantial strengthening effect, resulting in composite materials exhibiting interesting mechanical properties and inspiring their technological use in sectors like the automotive and aerospace industries. Powder metallurgy techniques are attractive to design metal matrix composites, achieving a homogeneous distribution of the reinforcement into the metal matrix. In this work, pure aluminum has been reinforced with particles of niobium carbide (NbC), an extremely hard and stable refractory ceramic. Its use as a reinforcing phase in metal matrix composites has not been deeply explored. Composite powders produced after different milling times, with 10 and 20 vol pct of NbC were produced by high-energy ball milling and characterized by scanning electron microscopy and by X-ray diffraction to establish a relationship between the milling time and size, morphology, and distribution of the particles in the composite powder. Subsequently, an Al/10 pct NbC composite powder was hot extruded into cylindrical bars. The strength of the obtained composite bars is comparable to the commercial high-strength, aeronautical-grade aluminum alloys.

  19. WHISKER LAKE WILDERNESS, WISCONSIN.

    Science.gov (United States)

    Schulz, Klaus J.

    1984-01-01

    The mineral-resource potential of the Whisker Lake Wilderness in northeastern Wisconsin was evaluated. Only a strip along the southwest corner of the wilderness is assessed as having probable mineral-resource potential. If mineral deposits exist, they probably are of the massive sulfide type. The geologic terrain precludes the presence of fossil fuel resources. Sand and gravel and peat in swampy lowlands are the only resources of the Whisker lake Wilderness.

  20. The effect of fiber microstructure on evolution of residual stresses in silicon carbide/titanium aluminide composites

    Science.gov (United States)

    Pindera, Marek-Jerzy; Freed, Alan D.

    1992-01-01

    This paper examines the effect of the morphology of the SCS6 silicon carbide fiber on the evolution of residual stresses in SiC/Ti composites. A micromechanics model based on the concentric cylinder concept is presented which is used to calculate residual stresses in a SiC/Ti composite during axisymmetric cooling by a spatially uniform temperature change. The silicon carbide fiber is modeled as a layered material with five distinct transversely isotropic and orthotropic, elastic layers, whereas the titanium matrix is taken to be isotropic, with temperature-dependent elastoplastic properties. The results arc compared with those obtained based on the assumption that the silicon carbide fiber is isotropic and homogeneous.

  1. Processing and characterization of in-situ aluminum bronze titanium carbide composites

    Science.gov (United States)

    Pillai, Balathandan S.

    The present study was carried out to develop a process for manufacturing in-situ aluminum bronze titanium carbide (TiC) friction drums using the centrifugal casting method and to characterize the material under optimum performance. The in-situ method of manufacturing is based on the reactive gas injection technique (RGI). The gas used in this study is high purity methane (CH 4). It was found that the methane gas injection time into the molten bath of aluminum bronze alloyed with titanium promotes the formation of titanium carbide (TiC) in the bronze matrix. The maximum amount of TiC incorporated in the matrix was 3.1 wt.%. This lead to 11.5 wt.% incorporation of TiC in the inner diameter of centrifugal castings as carbide particles drifted towards this region due to the centrifugal forces and their relatively low density. The hardness and strength of these composites when compared with the as cast condition was improved by heat treatment. However, the alloy ductility was decreased at the expense of the strength. It was found that the wear resistance properties of the composites were superior to those of pure cast and heat treated aluminum bronze currently in use. Optical and Scanning Electron Microscopy indicated that the composite surfaces did not scratch deeply when wearing against a hardened 4340 steel. The wear resistance of the as cast aluminum bronze was inferior to that of heat treated one. Moreover, the heat treated aluminum bronze showed a lack of high abrasion resistance. The frictional coefficient was relatively low for the as cast aluminum bronze as a result of adhesive wear behavior for the load and speed chosen in this present investigation. The corrosion studies showed that these composites do not lead to improved corrosion resistance in marine water environments. Apparently, there is a galvanic corrosion of TiC to bronze. In addition, pitting was observed on the corroded surfaces and increased with the volume fraction of TiC. Model validation was

  2. Synthesis of silicon carbide-silicon nitride composite ultrafine particles using a carbon dioxide laser

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Masaaki; Maniette, Yves; Nakata, Yoshinori; Okutani, Takeshi (Government Industrial Development Lab., Hokkaido, Sapporo (Japan))

    1993-05-01

    The synthesis and the structure of silicon carbide-silicon nitride (SiC-Si[sub 3]N[sub 4]) composite ultrafine particles have been studied. SiC-Si[sub 3]N[sub 4] composite ultrafine particles were prepared by irradiating a SiH[sub 4], C[sub 2]H[sub 4], and NH[sub 3] gas mixture with a CO[sub 2] laser at atmospheric pressure. The composition of composite powders changed with the reactant gas flow rate. The carbon and nitrogen content of the powder could be controlled in a wide range from 0 to 30 wt%. The composite powder, which contained 25.3 wt% carbon and 5.8 wt% nitrogen, had a [beta]-SiC structure. As the nitrogen content increased, SiC decreased and amorphous phase, Si[sub 3]N[sub 4], Si appeared. The results of XPS and lattice constant measurements suggested that Si, C, and N atoms were intimately mixed in the composite particles.

  3. Thermal Transport in Refractory Carbides.

    Science.gov (United States)

    Thermal energy transport mechanisms in titanium carbide and zirconium carbide have been studied. Several compositions of vanadium carbide alloyed...with titanium carbide were used. The electronic component of the thermal conductivity exceeded the values computed using the classical value for L in

  4. Effect of TiC whisker addition on properties of YG1OF alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The cemented carbide material (YG10F) with different additions of TiC whisker (0%, 0.3%, 0.6%, mass fraction) was prepared by different techniques. The effect of TiC whisker addition on the density, microhardness and toughness of the experimental material was investigated. The results indicate that after the wet-milling for 8 h and sintering in vacuum at 1 440 ℃, the toughness of YG10F is remarkably improved and meanwhile higher microhardness is obtained by 0.3% TiC whisker addition. Preliminary analysis suggests that the main toughening mechanism of TiC whisker in YG10F is whisker pull-out and bridging phenomena.

  5. Analysis of alumina-based titanium carbide composites by laser-induced breakdown spectroscopy

    Science.gov (United States)

    Ahmad, Kaleem; Tawfik, Walid; Farooq, Wazirzada A.; Singh, Jagdish P.

    2014-06-01

    In this work, alumina (Al2O3) containing different volume % of titanium carbide (TiC) ranging from 0 to 30 were consolidated by the novel spark plasma sintering. The spectroscopic analysis of the plasma generated by irradiation of laser Nd:YAG (λ = 1,064 nm) on different concentrations of the composites in air atmospheric pressure was performed. The qualitative examination of the composites confirms the presence of aluminum, titanium, and carbon as major elements, while magnesium and sodium have been found as minor trace elements. Plasma parameters were estimated by assuming the LTE conditions for optically thin plasma. The electron density and temperature were evaluated by using the Stark broadening and intensity of selected aluminum emission lines, respectively. The addition of TiC to Al2O3 shows a linear behavior with plasma temperature corroborated by the calibration curve of Ti in the composites. The results suggest that calibration curve between plasma temperature and the composites can be used to estimate different concentrations of TiC in Al2O3 without analyzing the whole elements in the composites and thus opens up new applications of LIBS in ceramic industry.

  6. Au ion irradiation of various silicon carbide fiber-reinforced SiC matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Chaâbane, Nihed, E-mail: nihed.chaabane@cea.fr [CEA, INSTN/UEPTN, F-91191 Gif-sur-Yvette (France); Flem, Marion Le [CEA, DEN/DMN/SRMA, F-91191 Gif-sur-Yvette (France); Tanguy, Morgane [CEA, INSTN/UEPTN, F-91191 Gif-sur-Yvette (France); Urvoy, Stéphane [CEA, DEN/DMN/SRMA, F-91191 Gif-sur-Yvette (France); Sandt, Christophe; Dumas, Paul [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Serruys, Yves [CEA, DEN/DMN/SRMP, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France)

    2013-08-15

    Silicon carbide fiber-reinforced SiC matrix composites are promising candidates as fuel cladding for several concepts of Generation IV reactors and as structural materials for fusion reactors. The composites used in this study were composed of a SiC matrix obtained by chemical vapor infiltration associated with various fiber types (Tyranno Type-S, Tyranno SA Grade-3 and Hi-Nicalon Type-S) and with a PyC layer as the interphase. 12 MeV Au ions were used for irradiation up to 0.05 and 1 displacement per atom (dpa) fluences at room temperature and 800 °C. Analysis of both microstructure and composition of composites were performed by scanning electron microscopy (SEM), electron probe microanalysis and Raman spectroscopy. At room temperature and low fluence, Raman spectroscopy results showed that irradiation induces a disordered/distorted state into fibers and matrix. With increasing fluence, a total amorphization of these constituents occurs. The increase in the irradiation temperature leads to a damage recovery and partial recrystallization of samples. Image analysis performed from SEM micrographs highlights no significant change in fiber diameter and shape. However, SEM analysis suggests a longitudinal shrinkage of Tyranno Type-S fibers for the composite irradiated at 1 dpa at room temperature and 800 °C. These results are in complete agreement with conclusions from neutron irradiations suggesting an appropriate relevance of irradiations with 12 MeV Au.

  7. The composition of reaction substrates for TiC carbides synthesis and its influence on the thickness of iron casting composite layer

    Directory of Open Access Journals (Sweden)

    E. Olejnik

    2011-04-01

    Full Text Available The effect of reaction substrates for the TiC carbide synthesis on the composite layer thickness produced in cast iron was examined. It was found that, at a constant weight of the charge amounting to 0.5 kg, changing the weight of the, placed in mould, stoichiometric mixture of titanium carbide (from 0.01 to 0.04 kg changed the thickness of the composite layer from 1 to 15 mm. Carbides synthesis starts directly in mould induced by the temperature of molten alloy poured into this mould (1700 K. The TiC carbides formed in this reaction are later, i.e. during alloy solidification, acting as a base composite material. The size of TiC carbides obtained in the synthesis is from 1 to 10 μm. They occur in the layers as locally compact and coagulated forms. Microstructure, chemical composition and structure of the obtained materials were tested by scanning electron microscopy (SEM, X-ray microanalysis (EDS, and X-ray diffraction (XRD.

  8. Effects of modifying agents on surface modifications of magnesium oxide whiskers

    Science.gov (United States)

    Zhao, Yun; Liu, Bei; Yang, Jinjun; Jia, Junping; You, Chen; Chen, Minfang

    2016-12-01

    In this work, the MgO whiskers have been treated by several modifying agents including the mixture of DL-malic acid oligo-L-lactide (g), aluminate coupling agent (Al) and stearic acid (Sa). The morphologies, covering quantity, compositions and components of the whiskers before and after the modifications were investigated by SEM, TG, XRD and FT-IR, respectively. Comparisons have been made on the morphologies of modified whiskers by different modifiers tailoring. The results show that the MgO whiskers treated by stearic acid have superior performance to the others, especially in terms of uniform dispersion. In contrast, both the mixture of DL-malic acid oligo-L-lactide and aluminate coupling agent have the negative effects on whiskers' dispersibility. FT-IR reveals that the chemical bonds were formed between the whiskers and each modifying agent and the XRD testing demonstrate that the crystal structures of the modified whiskers were well maintained without significant change.

  9. The Mechanical Properties of Polyurethane Elastomer Reinforced and Toughened By CaSO4-Whisker

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    CaSO4 whisker reinforcing and toughening mechanisms for polyurethane elastomer were studied. The effects of dispersity of CaSO4 whisker and interfacial bonding state on reinforcement and toughness were discussed.The microanalyses showed that CaSO4 whisker reinforcing mechanism for polyurethane elastomer mainly was load transferring and its toughening mechanism involved crack deflection and whisker pullout.The results indicated that composites with 5%-10% CaSO4 whisker exhibited the best mechanical properties. Good bonding interface was formed between whisker and matrix after the surface of CaSO4 whisker was treated by silane coupling agent.The fairly improved strength and toughness are attributed to the better interfacial bonding state.

  10. Laser cladding in-situ carbide particle reinforced Fe-based composite coatings with rare earth oxide addition

    Institute of Scientific and Technical Information of China (English)

    吴朝锋; 马明星; 刘文今; 钟敏霖; 张红军; 张伟明

    2009-01-01

    Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into t...

  11. Synthesis of copper-niobium carbide composite powder by in situ processing

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Zuhailawati [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)], E-mail: zuhaila@eng.usm.my; Othman, Radzali; Long, Bui Duc [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Umemoto, Minoru [Department of Production Systems Engineering, Toyohashi University of Technology (Japan)

    2008-09-22

    The in situ formation of niobium carbide (NbC) particles was investigated during mechanical alloying process as well as subsequent heat-treatment. Initial starting powders of Cu, Nb and C were used with a composition of Cu-40 wt% Nb-10 wt% C which was corresponding to Cu-40 vol% NbC. A mixture of this powder system was milled in an argon atmosphere for four different durations, i.e., 15 h, 31 h, 42 h and 54 h. X-ray diffraction was used to verify the formation of NbC. No NbC was formed after the milling process. The in situ formation of NbC in a copper matrix only took place after heat-treatment at 900 deg. C. Longer milling time resulted in the formation of NbC phase with more intense X-ray diffraction peaks due to powder refinement.

  12. Wear and cutting performance of diamond composite material-a comparison with tungsten carbide

    Institute of Scientific and Technical Information of China (English)

    LI Xing-sheng; J. N. Boland

    2004-01-01

    A series of wear and rock cutting tests were undertaken to assess the wear and cutting performance of a thermally stable diamond composite (TSDC). The wear tests were conducted on a newly designed wear testing rig in which a rotating aluminium oxide grinding wheel is turned (also known as machined) by the testing tool element.The rock cutting tests were performed on a linear rock-cutting planer. The thrust and cutting forces acting on the tool were measured during these tests. A tungsten carbide element was also studied for comparative purposes. The wear coefficients of both materials were used to evaluate wear performance while cutting performance was assessed by tool wear and the rates of increase in forces with cutting distance.

  13. Whisker dynamics underlying tactile exploration.

    Science.gov (United States)

    Hires, S Andrew; Efros, Alexander L; Svoboda, Karel

    2013-06-05

    Rodents explore the world by palpating objects with their whiskers. Whiskers interact with objects, causing stresses in whisker follicles and spikes in sensory neurons, which are interpreted by the brain to produce tactile perception. The mechanics of the whisker thus couple self-movement and the structure of the world to sensation. Whiskers are elastic thin rods; hence, they tend to vibrate. Whisker vibrations could be a key ingredient of rodent somatosensation. However, the specific conditions under which vibrations contribute appreciably to the stresses in the follicle remain unclear. We present an analytical solution for the deformation of individual whiskers in response to a time-varying force. We tracked the deformation of mouse whiskers during a pole localization task to extract the whisker Young's modulus and damping coefficient. We further extracted the time course and amplitude of steady-state forces during whisker-object contact. We use our model to calculate the relative contribution of steady-state and vibrational forces to stresses in the follicle in a variety of active sensation tasks and during the passive whisker stimuli typically used for sensory physiology. Vibrational stresses are relatively more prominent compared with steady-state forces for short contacts and for contacts close to the whisker tip. Vibrational stresses are large for texture discrimination, and under some conditions, object localization tasks. Vibrational stresses are negligible for typical ramp-and-hold stimuli. Our calculation provides a general framework, applicable to most experimental situations.

  14. Thermal Properties of epoxy composites with silicon carbide and/or graphite

    Science.gov (United States)

    Kim, Jungsoo; Kim, Yang Do; Nam, Dae Geun; Bae, Jong-Seong; Yeum, Jeong Hyun; Oh, Weontae

    2016-02-01

    Epoxy composites were fabricated with a filler of silicon carbide (SiC) and/or graphite to improve the thermal conductivity and thereby enhance the transfer of the heat from the light-emitting diode (LED) to the heat sink. The two fillers (SiC and graphite) were each added either separately, within a content range of 10 - 50 wt.%, or together to give a combined total content of 40 - 60 wt.%. The effect of the filler addition on the thermal and the mechanical properties of the epoxy composites was examined. The filler-induced change on the structural properties was investigated by using a morphological analysis of the epoxy composites, and the thermal conductivity was analyzed by measuring the thermal diffusivity, heat specific, and density. To confirm the adhesive property with aluminum, which is mostly used as the heat sink material were tested, the mechanical properties by using a bonding test with a modified tensile test. The thermal and the mechanical properties were improved with increasing filler content in the epoxy composites. In the case of combined filler addition, graphite was more effective than SiC in increasing the thermal properties. However, excessive filler addition reduced the epoxy's natural adhesive property and hence degraded the mechanical properties.

  15. Additive Manufacturing of Silicon Carbide-Based Ceramic Matrix Composites: Technical Challenges and Opportunities

    Science.gov (United States)

    Singh, Mrityunjay; Halbig, Michael C.; Grady, Joseph E.

    2016-01-01

    Advanced SiC-based ceramic matrix composites offer significant contributions toward reducing fuel burn and emissions by enabling high overall pressure ratio (OPR) of gas turbine engines and reducing or eliminating cooling air in the hot-section components, such as shrouds, combustor liners, vanes, and blades. Additive manufacturing (AM), which allows high value, custom designed parts layer by layer, has been demonstrated for metals and polymer matrix composites. However, there has been limited activity on additive manufacturing of ceramic matrix composites (CMCs). In this presentation, laminated object manufacturing (LOM), binder jet process, and 3-D printing approaches for developing ceramic composite materials are presented. For the laminated object manufacturing (LOM), fiber prepreg laminates were cut into shape with a laser and stacked to form the desired part followed by high temperature heat treatments. For the binder jet, processing optimization was pursued through silicon carbide powder blending, infiltration with and without SiC nano powder loading, and integration of fibers into the powder bed. Scanning electron microscopy was conducted along with XRD, TGA, and mechanical testing. Various technical challenges and opportunities for additive manufacturing of ceramics and CMCs will be presented.

  16. Characterization of boron carbide particulate reinforced in situ copper surface composites synthesized using friction stir processing

    Energy Technology Data Exchange (ETDEWEB)

    Sathiskumar, R., E-mail: sathiscit2011@gmail.com [Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, 641 014 Tamil Nadu (India); Murugan, N., E-mail: murugan@cit.edu.in [Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, 641 014 Tamil Nadu (India); Dinaharan, I., E-mail: dinaweld2009@gmail.com [Department of Mechanical Engineering, V V College of Engineering, Tisaiyanvilai, 627 657 Tamil Nadu (India); Vijay, S.J., E-mail: vijayjoseph@karunya.edu [Centre for Research in Metallurgy (CRM), School of Mechanical Sciences, Karunya University, Coimbatore, 641 114 Tamil Nadu (India)

    2013-10-15

    Friction stir processing has evolved as a novel solid state technique to fabricate surface composites. The objective of this work is to apply the friction stir processing technique to fabricate boron carbide particulate reinforced copper surface composites and investigate the effect of B{sub 4}C particles and its volume fraction on microstructure and sliding wear behavior of the same. A groove was prepared on 6 mm thick copper plates and packed with B{sub 4}C particles. The dimensions of the groove was varied to result in five different volume fractions of B{sub 4}C particles (0, 6, 12, 18 and 24 vol.%). A single pass friction stir processing was done using a tool rotational speed of 1000 rpm, travel speed of 40 mm/min and an axial force of 10 kN. Metallurgical characterization of the Cu/B{sub 4}C surface composites was carried out using optical microscope and scanning electron microscope. The sliding wear behavior was evaluated using a pin-on-disk apparatus. Results indicated that the B{sub 4}C particles significantly influenced the area, dispersion, grain size, microhardness and sliding wear behavior of the Cu/B{sub 4}C surface composites. When the volume fraction of B{sub 4}C was increased, the wear mode changed from microcutting to abrasive wear and wear debris was found to be finer. Highlights: • Fabrication of Cu/B{sub 4}C surface composite by friction stir processing • Analyzing the effect of B{sub 4}C particles on the properties of Cu/B4C surface composite • Increased volume fraction of B{sub 4}C particles reduced the area of surface composite. • Increased volume fraction of B{sub 4}C particles enhanced the microhardness and wear rate. • B{sub 4}C particles altered the wear mode from microcutting to abrasive.

  17. 硫酸钙晶须在室温硫化硅橡胶中的应用%Application of Calcium Sulfate Whisker in Room Temperature Vulcanized Silicone Rubber Compounds

    Institute of Scientific and Technical Information of China (English)

    王锦成; 薛烨; 仓世娇; 杨科

    2011-01-01

    研究硫酸钙晶须制备方法和用量对室温硫化硫酸钙晶须/硅橡胶复合材料性能的影响.结果表明,当硫酸钙晶须用量为10份时,复合材料的物理性能总体提高显著.扫描电子显微镜分析结果显示,烟气脱硫法硫酸钙晶须杂质较多,在硅橡胶中分散不均匀;电石渣法硫酸钙晶须内部结构完整,在硅橡胶中分散均匀.随着硫酸钙晶须用量增大,硅橡胶的粘度增大.热重分析结果显示,与烟气脱硫法硫酸钙晶须相比,电石渣法硫酸钙晶须对复合材料热稳定性能的改善较明显.%The influence of preparation method and addition level of calcium sulfate whisker on theproperties of room temperature vulcanized silicone rubber/calcium sulfate whisker composite was investigated. The results showed that, as the addition level of calcium sulfate whisker was 10 phr,the physical properties of composite were improved significantly. The SEM analysis result showed that, the calcium sulfate whisker prepared by gas desulfurization method possessed more impurities,and was dispersed unevenly in silicone rubber;the calcium sulfate whisker prepared by carbide slag method had better integrated internal structure, and was dispersed uniformly in silicone rubber. As the addition level of calcium sulfate whisker increased,the viscosity of silicone rubber increased. The TG analysis result showed that,compared with gas desulfurization method,the calcium sulfate whisker prepared by carbide slag method provided the composite better thermal stability.

  18. Solid Oxide Membrane (SOM) Process for Facile Electrosynthesis of Metal Carbides and Composites

    Science.gov (United States)

    Zou, Xingli; Chen, Chaoyi; Lu, Xionggang; Li, Shangshu; Xu, Qian; Zhou, Zhongfu; Ding, Weizhong

    2017-02-01

    Metal carbides (MCs) and composites including TiC, SiC, TaC, ZrC, NbC, Ti5Si3/TiC, and Nb/Nb5Si3 have been directly electrosynthesized from their stoichiometric metal oxides/carbon (MOs/C) mixture precursors by an innovative solid oxide membrane (SOM)-assisted electrochemical process. MOs/C mixture powders including TiO2/C, SiO2/C, Ta2O5/C, ZrO2/C, Nb2O5/C, TiO2/SiO2/C, Nb2O5/SiO2 were pressed to form porous pellets and then served as cathode precursors. A SOM-based anode, made from yttria-stabilized zirconia (YSZ)-based membrane, was used to control the electroreduction process. The SOM electrochemical process was performed at 1273 K (1000 °C) and 3.5 to 4.0 V in molten CaCl2. The oxygen component contained in the MOs/C precursors was gradually removed during electroreduction process, and thus, MOs/C can be directly converted into MCs and composites at the cathode. The reaction mechanism of the electroreduction process and the characteristics of the obtained MCs and composites products were systematically investigated. The results show that the electrosynthesis process typically involves compounding, electroreduction, dissolution-electrodeposition, and in situ carbonization processes. The products can be predesigned and controlled to form micro/nanostructured MCs and composites. Multicomponent multilayer composites (MMCs) have also been tried to electrosynthesize in this work. It is suggested that the SOM-assisted electroreduction process has great potential to be used for the facile and green synthesis of various MCs and composites.

  19. Solid Oxide Membrane (SOM) Process for Facile Electrosynthesis of Metal Carbides and Composites

    Science.gov (United States)

    Zou, Xingli; Chen, Chaoyi; Lu, Xionggang; Li, Shangshu; Xu, Qian; Zhou, Zhongfu; Ding, Weizhong

    2016-09-01

    Metal carbides (MCs) and composites including TiC, SiC, TaC, ZrC, NbC, Ti5Si3/TiC, and Nb/Nb5Si3 have been directly electrosynthesized from their stoichiometric metal oxides/carbon (MOs/C) mixture precursors by an innovative solid oxide membrane (SOM)-assisted electrochemical process. MOs/C mixture powders including TiO2/C, SiO2/C, Ta2O5/C, ZrO2/C, Nb2O5/C, TiO2/SiO2/C, Nb2O5/SiO2 were pressed to form porous pellets and then served as cathode precursors. A SOM-based anode, made from yttria-stabilized zirconia (YSZ)-based membrane, was used to control the electroreduction process. The SOM electrochemical process was performed at 1273 K (1000 °C) and 3.5 to 4.0 V in molten CaCl2. The oxygen component contained in the MOs/C precursors was gradually removed during electroreduction process, and thus, MOs/C can be directly converted into MCs and composites at the cathode. The reaction mechanism of the electroreduction process and the characteristics of the obtained MCs and composites products were systematically investigated. The results show that the electrosynthesis process typically involves compounding, electroreduction, dissolution-electrodeposition, and in situ carbonization processes. The products can be predesigned and controlled to form micro/nanostructured MCs and composites. Multicomponent multilayer composites (MMCs) have also been tried to electrosynthesize in this work. It is suggested that the SOM-assisted electroreduction process has great potential to be used for the facile and green synthesis of various MCs and composites.

  20. Mechanical and Corrosion Behaviour of Zn-27Al Based Composites Reinforced with Groundnut Shell Ash and Silicon Carbide

    Directory of Open Access Journals (Sweden)

    K.K. Alaneme

    2014-06-01

    Full Text Available The mechanical and corrosion behaviour of Zn-27Al alloy based composites reinforced with groundnut shell ash and silicon carbide was investigated. Experimental test composite samples were prepared by melting Zn-27Al alloy with pre-determined proportions of groundnut ash and silicon carbide as reinforcements using double stir casting. Microstructural examination, mechanical properties and corrosion behaviour were used to characterize the composites produced. The results show that hardness and ultimate tensile strength of the hybrid composites decreased with increase in GSA content. Although the % Elongation somewhat decreased with increase the GSA content, the trend was not as consistent as that of hardness and tensile strength. The fracture toughness of the hybrid composites however, increased with increase in the GSA content of the composites. In 3.5 % NaCl solution, the composites were resistant to corrosion with some of the hybrid composite grades containing GSA exhibiting relatively superior corrosion resistance to the grades without GSA. In 0.3M H2SO4 solution, the composites were generally a bit more susceptible to corrosion (compared to 3.5 % NaCl solution, but the effect of GSA content on the corrosion resistance of the composites was not consistent for the Zn-27Al alloy based composites.

  1. A Study of Current Chopping Characteristics in Metal-Carbide Composite Contact Materials

    Science.gov (United States)

    Yamamoto, Atsushi; Kusano, Takashi; Okutomi, Tsutomu; Yokokura, Kunio; Homma, Mitsutaka

    To clarify the effect of carbides on current chopping characteristics chopping current was evaluated for various metalcarbide contact materials. As a result, it was found that the chopping current of metal-carbide contacts was related to the vapor pressure of metals and the work function of carbides. It was also found that the chopping current was reduced by the heat treatment when the melting point of contacts is lower than the temperature of heat teatment.

  2. Effect of Powder-Feeding Modes During Plasma Spray on the Properties of Tungsten Carbide Composite Coatings

    Science.gov (United States)

    Zhong, Yi-ming; Du, Xiao-dong; Wu, Gang

    2017-05-01

    A WC-reinforced composite coating was fabricated on the surface of 45 steel samples by plasma, cladding process with WC powder added to the molten pool synchronously or in the tail of the molten pool. The microstructure, phase composition, and element distribution in the coating were analyzed. The results show that the undissolved WC particles and crystallized carbide (WC, W2C) were distributed uniformly in the sub-eutectic matrix in both cases. Fewer of the WC particles are dissolved in the matrix when they are injected into the tail of the molten pool. There are fewer needle-like tungsten carbide formations seen in the composite coating fabricated by back-feeding process than in that formed by synchronous feeding. The former results in a finer microstructure and a higher concentration gradient of elements near the interface between the WC particles and the coating matrix.

  3. Matrix cracking and creep behavior of monolithic zircon and zircon silicon carbide fiber composites

    Science.gov (United States)

    Anandakumar, Umashankar

    In this study, the first matrix cracking behavior and creep behavior of zircon matrix silicon carbide fiber composites were studied, together with the fracture and creep behavior of the monolithic zircon. These behaviors are of engineering and scientific importance, and the study was aimed at understanding the deformation mechanisms at elevated temperatures. The first matrix cracking behavior of zircon matrix uniaxially reinforced with silicon carbide fiber (SCS-6) composites and failure behavior of monolithic zircon were studied as a function of temperature (25°C, 500°C, and 1200°C) and crack length in three point bending mode. A modified vicker's indentation technique was used to vary the initial crack length in monolithic and composite samples. The interfacial shear strength was measured at these temperatures from matrix crack saturation spacing. The composites exhibited steady state and non steady state behaviors at the three different temperatures as predicted by theoretical models, while the failure stress of zircon decreased with increasing stress. The intrinsic properties of the composites were used to numerically determine the results predicted by three different matrix cracking models based on a fracture mechanics approach. The analysis showed that the model based on crack bridging analysis was valid at 25°C and 500°C, while a model based on statistical fiber failure was valid at 1200°C. Microstructural studies showed that fiber failure in the crack wake occurred at or below the matrix cracking stress at 1200°C, and no fiber failure occurred at the other two temperatures, which validated the results predicted by the theoretical models. Also, it was shown that the interfacial shear stress corresponding to debonding determined the matrix cracking stress, and not the frictional shear stress. This study showed for the first time, the steady state and non-steady state matrix cracking behavior at elevated temperatures, the difference in behavior between

  4. Microstructure and wear properties of tungsten carbide reinforced steel matrix composites

    Institute of Scientific and Technical Information of China (English)

    YOU Xian-qing; SONG Xue-feng; REN Hao; MA Jian-guo; HUANG Man-ping; ZHANG Cheng-jun

    2005-01-01

    WC(27%) reinforced steel matrix composites were produced by using an electroslag melting casting technique. The microstructure of the material was characterized using scanning electron microscopy(SEM), optical microscopy and X-ray diffraction(XRD). Energy dispersive spectroscopy(EDS) and transmission electron micro-scopy were performed to investigate the interfacial composition between WC particle and steel matrix. The results reveal that the WC particles are partially melted into the steel substrate. At the same time, a reaction layer was detected along with the periphery of WC particle, which significantly enhances the bonding strength of the interface. A slipping wear (high stress abrasion) test was utilized to understand the wear behavior of this material. Abrasive experiment displays a better wear resistance than unreinforced steel matrix when coarse WC particles are dispersed into it. The coarse particles provide greater wear-resistance than the fine particles and operatively takes on the most applied loads. Additionally, the large particles have not been peeled during the wear process for a long time, which indicates the effect of interfacial reaction on wear behavior at the ambient temperature. A double carbide (Fe, W)3C is detected in the interface zone between particles and matrices using transmission electron microscopy.

  5. 600 Mesh Silicon Carbide Corona Protection Varnish with EPOXY/OMMT Nano-composite Adhesive

    Institute of Scientific and Technical Information of China (English)

    HU Chunxiu; ZHAO Yingnan; HOU Haibo; ZHANG Xiaohong

    2016-01-01

    A new corona protection varnish was prepared by using epoxy/montmorillonite nano-composite and pure epoxy resin as adhesives respectively. The adhesive with different amounts of organic montmorillonite (OMMT) was mixed with 1200 mesh silicon carbide (SiC) by different weight ratios. The surface states of the varnishes with various adhesives were observed by powerful optical microscope. Some properties of the varnishes were analyzed during the enduring time under 5kV/cm DC, such as the relation of change in nonlinear coefifcient, natural surface resistivity, and surface temperature variation. The results showed that the amounts of OMMT had little effect on the natural surface resistance of the varnish but had important inlfuence on the nonlinear property of the varnish. When the range of the OMMT content was 2wt% to 6wt%, the nonlinear coefifcient of all materials with epoxy/OMMT nano-composite adhesive was higher than that with pure epoxy resin adhesive. The surface temperature of the varnish with epoxy/OMMT nanocomposite adhesive was all lower than that with the pure epoxy resin adhesive under high electrical ifeld strength.

  6. Time-Dependent Stress Rupture Strength Degradation of Hi-Nicalon Fiber-Reinforced Silicon Carbide Composites at Intermediate Temperatures

    Science.gov (United States)

    Sullivan, Roy M.

    2016-01-01

    The stress rupture strength of silicon carbide fiber-reinforced silicon carbide composites with a boron nitride fiber coating decreases with time within the intermediate temperature range of 700 to 950 degree Celsius. Various theories have been proposed to explain the cause of the time-dependent stress rupture strength. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of silicon carbide fiber-reinforced silicon carbide composites. This is achieved through the development of a numerically based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time-marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time-dependent behavior.

  7. Synthesis of carbon fibre-reinforced, silicon carbide composites by soft-solution approach

    Indian Academy of Sciences (India)

    N Padmavathi; P Ghosal; N Eswara Prasad; J Subramanyam; K K Ray

    2012-08-01

    The aim of the present work centers on synthesizing and characterizing carbon fibre (Cf) reinforced, silicon carbide matrix composites which are considered to have potential applications in aerospace and automobile industry. A series of composites, namely the Cf-SiC, Cf-(SiC+ZrC), Cf-(SiC+ZrB2), and Cf-(SiC+ZrO2), have been prepared by a proposed soft-solution approach. This approach involves the use of water-soluble precursors of colloidal silica, sucrose, zirconium oxychloride, and boric acid as sources of silica, carbon, zirconia, and boron oxide, respectively to achieve the desired matrices through drying, carbonization and carbothermal reduction. The prepared powders and the composites were characterized by thermal analysis, X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses to assess the phase formation and microstructure of the materials, apart from assessment of their tensile properties. The study shows that the soft-solution process yields matrices with finer crystallite sizes, having homogeneous distribution of the constituent phases of either the powders or of the composite matrices. The role of the additional phases on the tensile properties of the composites has been discussed using consideration of thermal stresses at fibre-matrix interface; whereas the role of the carbothermal reduction temperature in determining these properties has been explained using the interfacial characteristics of the fibre-matrix. Addition of ZrO2 in the matrix of SiC has shown to improve the properties of Cf-SiC composites considerably. The results of this investigation unambiguously demonstrate that aqueous solution-based processing can be used for fabrication of these composites in relatively shorter time in an environmental friendly manner without using any expensive equipment. The approach is capable of yielding composites with different phases in the matrix by simple variation of

  8. High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures

    OpenAIRE

    Hu, Liangfa; O’Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

    2016-01-01

    The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow...

  9. High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures

    Science.gov (United States)

    Hu, Liangfa; O’Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

    2016-10-01

    The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42–83 μm, 77–276 μm, and 167–545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed.

  10. Ordered hierarchical mesoporous/microporous carbon derived from mesoporous titanium-carbide/carbon composites and its electrochemical performance in supercapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hai-Jing; Wang, Jie; Wang, Cong-Xiao; Xia, Yong-Yao [Department of Chemistry and Shanghai Key Laboratory of Molecular, Catalysis and Innovative Materials, Institute of New Energy, Fudan University, Shanghai (China)

    2011-11-15

    Novel ordered hierarchical mesoporous/microporous carbon (OHMMC) derived from mesoporous titanium-carbide/carbon composites was prepared for the first time by synthesizing ordered mesoporous nanocrystalline titanium-carbide/carbon composites, followed by chlorination of titanium carbides. The mesostructure and microstructure can be conveniently tuned by controlling the TiC contents of mesoporous TiC/C composite precursor, and chlorination temperature. By optimal condition, the OHMMC has a high surface area (1917 m{sup 2}g{sup -1}), large pore volumes (1.24 cm{sup 3}g{sup -1}), narrow mesopore-size distributions (centered at about 3 nm), and micropore size of 0.69 and 1.25 nm, and shows a great potential as electrode for supercapacitor applications: it exhibits a high capacitance of 146 Fg{sup -1} in noaqueous electrolyte and excellent rate capability. The ordered mesoporous channel pores are favorable for retention and immersion of the electrolyte, providing a more favorable path for electrolyte penetration and transportation to achieve promising rate capability performance. Meanwhile, the micropores drilled on the mesopore-walls can increase the specific surface area to provide more sites for charge storage. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Evaluation of drilling Al/B4C composites with carbide drills

    Directory of Open Access Journals (Sweden)

    Ali Rıza Motorcu

    2016-08-01

    Full Text Available In this study, cutting forces and torque was evaluated through Taguchi Method (TM in the drilling of the high density B4C particle reinforced composites, which were produced through powder metallurgy-hot pressing method, with coated and uncoated carbide drills. Cutting speed (18, 25 and 35 m/min, feed rate (0.08, 0.112 and 0.16 mm/rev, coating properties (coated and uncoated and the amounts of particle reinforcement (5%, 10% and 15% B4C were used as the control factors. It was observed that the increased feed rate and particle reinforcement increased the axial force and torque, and decreased the cutting speed. The uncoated drills had a better performance than the coated drills. The amount of B4C reinforcement was observed to be the most effective parameter on the axial force and torque with the contribution ratios of 96.6% and 49.1%, respectively. Moreover, the correlation coefficients (R2 of the first order predictive equations developed for the axial force and torque were calculated as 0.895 and 0.854, respectively.

  12. Radiation-tolerant joining technologies for silicon carbide ceramics and composites

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, Yutai, E-mail: katohy@ornl.gov [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States); Snead, Lance L.; Cheng, Ting; Shih, Chunghao; Lewis, W. Daniel [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States); Koyanagi, Takaaki; Hinoki, Tatsuya [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Henager, Charles H. [Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, WA 99352 (United States); Ferraris, Monica [Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino (Italy)

    2014-05-01

    Silicon carbide (SiC) for nuclear structural applications, whether in the monolithic ceramic or composite form, will require a robust joining technology capable of withstanding the harsh nuclear environment. This paper presents significant progress made towards identifying and processing irradiation-tolerant joining methods for nuclear-grade SiC. In doing so, a standardized methodology for carrying out joint testing has been established consistent with the small volume samples mandated by neutron irradiation testing. Candidate joining technologies were limited to those that provide low induced radioactivity and included titanium diffusion bonding, Ti–Si–C MAX-phase joining, calcia–alumina glass–ceramic joining, and transient eutectic-phase SiC joining. Samples of these joints were irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor at 500 or 800 °C, and their microstructure and mechanical properties were compared to pre-irradiation conditions. Within the limitations of statistics, all joining methodologies presented retained their joint mechanical strength to ∼3 dpa at 500 °C, thus indicating the first results obtained on irradiation-stable SiC joints. Under the more aggressive irradiation conditions (800 °C, ∼5 dpa), some joint materials exhibited significant irradiation-induced microstructural evolution; however, the effect of irradiation on joint strength appeared rather limited.

  13. Radiation-tolerant joining technologies for silicon carbide ceramics and composites

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, Yutai; Snead, Lance L.; Cheng, Ting; Shih, Chunghao; Lewis, W. Daniel; Koyanagi, Takaaki; Hinoki, Tatsuya; Henager, Charles H.; Ferraris, Monica

    2014-05-01

    Silicon carbide (SiC) for nuclear structural applications, whether in the monolithic ceramic or composite form, will require a robust joining technology capable of withstanding the harsh nuclear environment. This paper presents significant progress made towards identifying and processing irradiation-tolerant joining methods for nuclear-grade SiC. In doing so, a standardized methodology for carrying out joint testing has been established consistent with the small volume samples mandated by neutron irradiation testing. Candidate joining technologies were limited to those that provide low induced radioactivity and included titanium diffusion bonding, Ti–Si–C MAX-phase joining, calcia–alumina glass–ceramic joining, and transient eutectic-phase SiC joining. Samples of these joints were irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor at 500 or 800 °C, and their microstructure and mechanical properties were compared to pre-irradiation conditions. Within the limitations of statistics, all joining methodologies presented retained their joint mechanical strength to ~3 dpa at 500 °C, thus indicating the first results obtained on irradiation-stable SiC joints. Finally, under the more aggressive irradiation conditions (800 °C, ~5 dpa), some joint materials exhibited significant irradiation-induced microstructural evolution; however, the effect of irradiation on joint strength appeared rather limited.

  14. Polymer-derived silicon carbide fibers with near-stoichiometric composition and low oxygen content

    Energy Technology Data Exchange (ETDEWEB)

    Sacks, M.D.; Scheiffele, G.W.; Saleem, M.; Staab, G.A.; Morrone, A.A.; Williams, T.J. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering

    1995-10-01

    Fine-diameter ({approximately} 10--15 {micro}m), polymer-derived SiC fibers were characterized. The average tensile strength of the fibers was {approximately} 2.8 GPa, although some lots had average strengths exceeding 3.5 GPa. Microstructure observations showed that fibers had fine grain sizes (mostly {approximately} 0.05--0.2 {micro}m), high densities ({approximately} 3.1--3.2 g/cm{sup 3}), and small residual pore sizes ({le} 0.1 {micro}m). Elemental analysis showed that fibers had near-stoichiometric composition. Electron and X-ray diffraction analyses indicated that fibers were primarily beta silicon carbide, with a minor amount of the alpha phase. A small amount of graphitic carbon was detected in some samples using high resolution transmission electron microscopy. The residual oxygen content in the fibers was {le} 0.1 wt%. Fibers exhibited good thermomechanical stability, as heat treatment at 1,800 C for 4 h in argon resulted in only an {approximately} 8% decrease in strength.

  15. Columnar-to-Equiaxed Transition in Metal-Matrix Composites Reinforced with Silicon Carbide Particles

    Directory of Open Access Journals (Sweden)

    Alicia E. Ares

    2013-01-01

    Full Text Available The present work is focused on the study of the effect of directional heat extraction on the silicon-carbide (SiC distribution in zinc-aluminum matrix composites (MMCs and on the columnar-to-equiaxed (CET position in directionally solidified samples. To this end, a ZA-27 alloy matrix was reinforced with ceramic particles of SiC and vertically directionally solidified. The cooling rates, temperature gradients, and interphase velocities were then measured, and their influence on the solidification microstructure of the MMCs was analyzed. The recalescence detected and measured during the equiaxed transition was of the order of 3.5°C to 1.1°C. The values of the temperature gradients reached a minimum during the CET and were even negative in most cases (between −3.89 K and 0.06 K. The interphase velocities varied between 0.07 mm/s and 0.44 mm/s at the transition. Also, the presence of ceramic particles in ZA-27 alloys affected the thermodynamic local conditions and the kinetics of nucleation, producing a finer microstructure.

  16. Experimental & Theoretical Analysis of Composite (Polyester & Silicon-Carbide Cantilever Beam

    Directory of Open Access Journals (Sweden)

    Yousif K. Yousif

    2012-01-01

    Full Text Available A cantilever beam is made from composite material which is consist of (matrix: polyester and (particles: Silicon-Carbide with different volume fraction of particles. A force is applied at the free end of beam with different values. The experimental maximum deflection of beam which occurs at the point of the applied load is recorded. The deflection and slope of beam are analyzed by using FEM modeling. MATLAB paltform is built to assemble the equations, vector and matrix of FEM and solving the unknown variables (deflection and slope at each node. Also ANSYS platform is used to modeling beam in finite element and solve the problem. The numerical methods are used to compare the results with the theoretical and experimental data. A good agreement is observed between the above methods. The Increase in volume fraction of particles results in increasing the modulus of elasticity and decreasing the deflection of beam. An equation is suggested for modulus of elasticity as functions of volume fraction.

  17. Electrical response and functionality of polymer matrix-titanium carbide composites

    Directory of Open Access Journals (Sweden)

    2010-04-01

    Full Text Available The dielectric response and conductivity of polymer matrix-titanium carbide composites was examined by means of Broadband Dielectric Spectroscopy in the frequency range of 10–1–107 Hz and over the temperature range of 40–150°C, varying the filler content. Dielectric data were analyzed via the electric modulus formalism. Recorded relaxations were attributed to interfacial polarization, glass to rubber transition and local motions of polar side groups. Alternating current conductivity varies up to seven orders of magnitude with both frequency and temperature. Direct current conductivity increases with temperature, although the rate of its alteration does not remain constant in the examined temperature range. In the low temperature region (up to 60°C increases at a higher rate, while right afterwards approaches rather constant values. Finally, in the high temperature range (above 90°C conductivity raises again but at a lower rate. This behaviour adds functionality to the composites’ performance and could be exploited in developing self-current regulators.

  18. Two-Dimensional Titanium Carbide/RGO Composite for High-Performance Supercapacitors.

    Science.gov (United States)

    Zhao, Chongjun; Wang, Qian; Zhang, Huang; Passerini, Stefano; Qian, Xiuzhen

    2016-06-22

    Ti3C2Tx, a 2D titanium carbide in the MXenes family, is obtained from Ti3AlC2 through selective etching of the Al layer. Due to its good conductivity and high volumetric capacitance, Ti3C2Tx is regarded as a promising candidate for supercapacitors. In this paper, the fabrication of Ti3C2Tx/RGO composites with different proportions of Ti3C2Tx and RGO is reported, in which RGO acts as a conductive "bridge" to connect different Ti3C2Tx blocks and a matrix to alleviate the volume change during charge/discharge process. In addition, RGO nanosheets can serve as a second nanoscale current collector and support as well for the electrode. The electrochemical performance of the as-fabricated Ti3C2Tx/RGO electrodes, characterized by CV, GCD, and EIS, are also reported. A highest specific capacitance (Cs) of 154.3 F/g at 2 A/g is obtained at the Ti3C2Tx: RGO weight ratio of 7:1 combined with an outstanding capacity retention (124.7 F/g) after 6000 cycles at 4 A/g.

  19. The material performance of HSS (high speed steel) tools and its relation with chemical composition and carbide distribution

    Science.gov (United States)

    Darmawan, B.; Kusman, M.; Hamdani, R. A.

    2016-04-01

    The study aims to compare the performance of two types of material HSS (High Speed Steel) are widely used. It also will be the chemical composition and distribution of carbide particles therein. Two types of HSS are available in the market: HSS from Germany (Bohler) and HSS from China. This research employed the pure experimental design. It consists of two stages. The first, aims to test/operate lathe machines to determine the lifetime and performance of tools based on specified wear criteria. The second, characterization of microstructure using SEM-EDS was conducted. Firstly, grinding of toolss was done so that the toolss could be used for cutting metal in the turning process. Grinding processes of the two types of toolss were done at the same geometry, that is side rake angle (12°-18°), angle of keenness (60°-68°), and side relief angle (10°-12°). Likewise, machining parameters were set in the same machining conditions. Based on the results of the tests, it is found that to reach 0.2 mm wear point, toolss made of HSS from Germany needed 24 minutes, while toolss made of HSS from China needed 8 minutes. Next, microstructure tests using SEM/EDS were done. The results of the SEM tests indicate that the carbide particles of HSS from Germany were more evenly distributed than the carbide particles of HSS from China. Carbide compounds identified in HSS from China were Cr23C6 and Fe4Mo2C. Oxide impurity of Al2O3 was also found in the material. On the other hand, in HSS from Germany, no impurity and other carbide compounds were identified, except Cr23C6 and Fe4Mo2C, also Fe4W2C, and VC or V4C3.

  20. Coating effects on thermal properties of carbon carbon and carbon silicon carbide composites for space thermal protection systems

    Science.gov (United States)

    Albano, M.; Morles, R. B.; Cioeta, F.; Marchetti, M.

    2014-06-01

    Many are the materials for hot structures, but the most promising one are the carbon based composites nowadays. This is because they have good characteristics with a high stability at high temperatures, preserving their mechanical properties. Unfortunately, carbon reacts rapidly with oxygen and the composites are subjected to oxidation degradation. From this point of view CC has to be modified in order to improve its thermal and oxidative resistance. The most common solutions are the use of silicon carbide into the carbon composites matrix (SiC composites) to make the thermal properties increase and the use of coating on the surface in order to protect the composite from the space plasma effects. Here is presented an experimental study on coating effects on these composites. Thermal properties of coated and non coated materials have been studied and the thermal impact on the matrix and surface degradation is analyzed by a SEM analysis.

  1. Wear Characteristics of Hybrid Composites Based on Za27 Alloy Reinforced With Silicon Carbide and Graphite Particles

    Directory of Open Access Journals (Sweden)

    S. Mitrović

    2014-06-01

    Full Text Available The paper presents the wear characteristics of a hybrid composite based on zinc-aluminium ZA27 alloy, reinforced with silicon-carbide and graphite particles. The tested sample contains 5 vol.% of SiC and 3 vol.% Gr particles. Compocasting technique has been used to prepare the samples. The experiments were performed on a “block-on-disc” tribometer under conditions of dry sliding. The wear volumes of the alloy and the composite were determined by varying the normal loads and sliding speeds. The paper contains the procedure for preparation of sample composites and microstructure of the composite material and the base ZA27 alloy. The wear surface of the composite material was examined using the scanning electronic microscope (SEM and energy dispersive spectrometry (EDS. Conclusions were obtained based on the observed impact of the sliding speed, normal load and sliding distance on tribological behaviour of the observed composite.

  2. Reaction-Based SiC Materials for Joining Silicon Carbide Composites for Fusion Energy

    Energy Technology Data Exchange (ETDEWEB)

    Lewinsohn, Charles A.; Jones, Russell H.; Singh, M.; Serizawa, H.; Katoh, Y.; Kohyama, A.

    2000-09-01

    The fabrication of large or complex silicon carbide-fiber-reinforced silicon carbide (SiC/SiC) components for fusion energy systems requires a method to assemble smaller components that are limited in size by manufacturing constraints. Previous analysis indicates that silicon carbide should be considered as candidate joint materials. Two methods to obtain SiC joints rely on a reaction between silicon and carbon to produce silicon carbide. This report summarizes preliminary mechanical properties of joints formed by these two methods. The methods appear to provide similar mechanical properties. Both the test methods and materials are preliminary in design and require further optimization. In an effort to determine how the mechanical test data is influenced by the test methodology and specimen size, plans for detailed finite element modeling (FEM) are presented.

  3. Study on Processing Conditions of Aluminum Matrix Composites Reinforced with Boron Carbide Particles

    Institute of Scientific and Technical Information of China (English)

    Fu Xueying; Zhang Hong; Xi Huizhi; Yi Xiaosu

    2004-01-01

    Different pre-heating of boron carbide particles for reinforcement and different processing conditions were studied in this work. Being one of the most cost-effective industrial methods, conventional melt stir-casting route was utilized.Result showed that the boron carbide particles distributed well for a suitable pre-heating temperature and processed in air.No reaction product was found at the A1-B4C interfaces at the resolution limit of SEM used in that way.

  4. Structure and mechanical properties of a multilayer carbide-hardened niobium composite material fabricated by diffusion welding

    Science.gov (United States)

    Korzhov, V. P.; Ershov, A. E.; Stroganova, T. S.; Prokhorov, D. V.

    2016-04-01

    The structure, the bending strength, and the fracture mechanism of an artificial niobium-based composite material, which is fabricated by high-pressure diffusion welding of multilayer stacks assembled from niobium foils with a two-sided carbon coating, are studied. The microstructure of the composite material is found to consist of alternating relatively plastic layers of the solid solution of carbon in niobium and hardening niobium carbide layers. The room-temperature proportional limit of the developed composite material is threefold that of the composite material fabricated from coating-free niobium foils using the proposed technology. The proportional limit of the developed composite material and the stress corresponding to the maximum load at 1100°C are 500 and 560 MPa, respectively. The developed material is considered as an alternative to Ni-Al superalloys.

  5. Titanium Carbide: Nanotechnology, Properties, Application

    OpenAIRE

    Galevsky, G. V.; Rudneva, V. V.; Garbuzova, A. K.; Valuev, Denis Viktorovich

    2015-01-01

    The paper develops scientific and technological bases for fabrication of titanium carbide which is a nanocomponent of composite materials. The authors determine optimum technology specifications and the main titanium carbide properties: fineness of titaniferous raw materials, carbide-forming agent quantity, set temperature of plasma flow, tempering temperature, titanium carbide yield, productivity, specific surface, size and shape of particles. The paper includes equations to describe how the...

  6. Preparation and characterization of keratin-K2Ti6O13 whisker ...

    African Journals Online (AJOL)

    USER

    2010-05-10

    May 10, 2010 ... hexatitanate (K2Ti6O13) whiskers be used to reinforce keratin film. The effects of ... reinforced composite manufacturing Co., and the optical micrograph is .... on the mechanical properties of jute-polypropylene composites.

  7. Assessment of Silicon Carbide Composites for Advanced Salt-Cooled Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, Yutai [ORNL; Wilson, Dane F [ORNL; Forsberg, Charles W [ORNL

    2007-09-01

    The Advanced High-Temperature Reactor (AHTR) is a new reactor concept that uses a liquid fluoride salt coolant and a solid high-temperature fuel. Several alternative fuel types are being considered for this reactor. One set of fuel options is the use of pin-type fuel assemblies with silicon carbide (SiC) cladding. This report provides (1) an initial viability assessment of using SiC as fuel cladding and other in-core components of the AHTR, (2) the current status of SiC technology, and (3) recommendations on the path forward. Based on the analysis of requirements, continuous SiC fiber-reinforced, chemically vapor-infiltrated SiC matrix (CVI SiC/SiC) composites are recommended as the primary option for further study on AHTR fuel cladding among various industrially available forms of SiC. Critical feasibility issues for the SiC-based AHTR fuel cladding are identified to be (1) corrosion of SiC in the candidate liquid salts, (2) high dose neutron radiation effects, (3) static fatigue failure of SiC/SiC, (4) long-term radiation effects including irradiation creep and radiation-enhanced static fatigue, and (5) fabrication technology of hermetic wall and sealing end caps. Considering the results of the issues analysis and the prospects of ongoing SiC research and development in other nuclear programs, recommendations on the path forward is provided in the order or priority as: (1) thermodynamic analysis and experimental examination of SiC corrosion in the candidate liquid salts, (2) assessment of long-term mechanical integrity issues using prototypical component sections, and (3) assessment of high dose radiation effects relevant to the anticipated operating condition.

  8. Box-and-Whisker Plots.

    Science.gov (United States)

    Larsen, Russell D.

    1985-01-01

    Box-and-whisker plots (which give rapid visualization of batches of data) can be effectively used to present diverse collections of data used in traditional first-year chemistry courses. Construction of box-and-whisker plots and their use with bond energy data and data on heats of formation and solution are discussed. (JN)

  9. The application and research status of tin whisker formation in electric usage

    Science.gov (United States)

    Zhao, Heng; Liu, Qing-bin; Lan, Yuan-pei; Wang, Hua; Yao, Da-wei

    2017-05-01

    `Hair Like' crystalline structure grows from most pure tin or zinc finishes. Usually, the diameter of tin whisker is up to 10 mm and the length of tin whisker is typically 1 µm. In detail, the questions for tin whisker formation are classified into 6 categories: 1. Residual stress with in the tin plating; 2. Intermetallic Formation; 3. Externally Applied Compressive Stress; 4. Bending and Stretching; 5. Scratches and Nicks; 6. Coefficient of Thermal Expansion Mismatches. The result shows that, whisker formation could causes electrical short circuit (High current of whisker melting), debris contamination (Sensitive Optical and Micro Electrical Mechanical System) and metal vapor (Vaporize Damage). Thus, it is suggested that environmental tests and standards (Whisker Shape, Temperature, Pressure, Moisture, Thermal Cycling, and Electrical Field) are required for suppressing whisker formation. Nowadays, the new standards committee of Europe Union acts RoHS (Restriction of certain Hazardous Substances) and WEEE (Waste Electrical and Electronic Equipment) to restrict Pb usage. Thus, new compounds adding to alloys to suppress whiskers are required in electronic application area. In summary, the tin whisker formation is largely influenced by compositions and precipitations.

  10. Ballistic Evaluation of rolled Homogeneous Steel Armor with Tungsten Carbide and Titanium Carbide Facing.

    Science.gov (United States)

    1960-12-01

    LABORATORIES BALLISTIC EVALUATION OF ROLLED HMtOGE14EOUS STEEL ASWKR f VITH TUNGSTEN CARBIDE AND TITANIUM CARBIDE FACING (U) TECHNICAL REPORT NO. WAL...carbide steel and titanium carbide steel composite armor when attacked by cal. .40 H19B WC cores, cal. .0 AP W2 projectiles, ZOIN fragment simulating...determine the effectiveness of tungsten car- bide (WC) and titanium carbide (TIC) facing on steel armor for the defeat of steel and tungsten carbide

  11. Automatic generation of 2D micromechanical finite element model of silicon–carbide/aluminum metal matrix composites: Effects of the boundary conditions

    DEFF Research Database (Denmark)

    Qing, Hai

    2013-01-01

    Two-dimensional finite element (FE) simulations of the deformation and damage evolution of Silicon–Carbide (SiC) particle reinforced aluminum alloy composite including interphase are carried out for different microstructures and particle volume fractions of the composites. A program is developed...

  12. Standard specification for nuclear-grade aluminum oxide-boron carbide composite pellets

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This specification applies to pellets composed of mixtures of aluminum oxide and boron carbide that may be ultimately used in a reactor core, for example, in neutron absorber rods. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

  13. Cryogenic optical measurements of 12-segment-bonded carbon-fiber-reinforced silicon carbide composite mirror with support mechanism

    Science.gov (United States)

    Kaneda, Hidehiro; Nakagawa, Takao; Onaka, Takashi; Enya, Keigo; Makiuti, Sin'itirou; Takaki, Junji; Haruna, Masaki; Kume, Masami; Ozaki, Tsuyoshi

    2008-03-01

    A 720 mm diameter 12-segment-bonded carbon-fiber-reinforced silicon carbide (C/SiC) composite mirror has been fabricated and tested at cryogenic temperatures. Interferometric measurements show significant cryogenic deformation of the C/SiC composite mirror, which is well reproduced by a model analysis with measured properties of the bonded segments. It is concluded that the deformation is due mostly to variation in coefficients of thermal expansion among segments. In parallel, a 4-degree-of-freedom ball-bearing support mechanism has been developed for cryogenic applications. The C/SiC composite mirror was mounted on an aluminum base plate with the support mechanism and tested again. Cryogenic deformation of the mirror attributed to thermal contraction of the aluminum base plate via the support mechanism is highly reduced by the support, confirming that the newly developed support mechanism is promising for its future application to large-aperture cooled space telescopes.

  14. Boron carbide: Consistency of components, lattice parameters, fine structure and chemical composition makes the complex structure reasonable

    Science.gov (United States)

    Werheit, Helmut

    2016-10-01

    The complex, highly distorted structure of boron carbide is composed of B12 and B11C icosahedra and CBC, CBB and B□B linear elements, whose concentration depends on the chemical composition each. These concentrations are shown to be consistent with lattice parameters, fine structure data and chemical composition. The respective impacts on lattice parameters are estimated and discussed. Considering the contributions of the different structural components to the energy of the overall structure makes the structure and its variation within the homogeneity range reasonable; in particular that of B4.3C representing the carbon-rich limit of the homogeneity range. Replacing in B4.3C virtually the B□B components by CBC yields the hypothetical moderately distorted B4.0C (structure formula (B11C)CBC). The reduction of lattice parameters related is compatible with recently reported uncommonly prepared single crystals, whose compositions deviate from B4.3C.

  15. Photons transport through ultra-high molecular weight polyethylene based composite containing tungsten and boron carbide fillers

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, S.M. [National Research Center “Kurchatov Institute”, Moscow 123182 (Russian Federation); Kuznetsov, S.A. [Russian State Technological University “MATI”, Moscow 121552 (Russian Federation); Volkov, A.E.; Terekhin, P.N.; Dmitriev, S.V. [National Research Center “Kurchatov Institute”, Moscow 123182 (Russian Federation); Tcherdyntsev, V.V.; Gorshenkov, M.V. [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Boykov, A.A., E-mail: kink03@gmail.com [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation)

    2014-02-15

    Highlights: • The developed method for predicting X-ray properties of the polymer. • Higher content of the fillers results in an increase of mechanical properties. • X-ray defensive properties of the samples were investigated experimentally. -- Abstract: Polymers are a base for creating of composite materials with high mechanical and chemical properties. Using the heavy metals as filler in these composites can give them X-ray protective properties. These materials have high deactivation rates and can be used to create Personal Protective Equipment (PPE) used in aggressive environments. It was proposed a model for calculation of X-ray protection properties of the polymer-based nanocomposite materials with ultra-high molecular weight polyethylene (UHMWPE) matrix, filled with tungsten and boron carbide particles. X-ray protective properties were calculated in a wide range of filler content using the developed model. Results of calculations allow selecting most effective compounds of X-ray protective UHMWPE based composites.

  16. Titanium Carbide: Nanotechnology, Properties, Application

    Science.gov (United States)

    Galevsky, G. V.; Rudneva, V. V.; Garbuzova, A. K.; Valuev, D. V.

    2015-09-01

    The paper develops scientific and technological bases for fabrication of titanium carbide which is a nanocomponent of composite materials. The authors determine optimum technology specifications and the main titanium carbide properties: fineness of titaniferous raw materials, carbide-forming agent quantity, set temperature of plasma flow, tempering temperature, titanium carbide yield, productivity, specific surface, size and shape of particles. The paper includes equations to describe how the major specifications of the fabrication technique influence the content of titanium carbide and free carbon in the end product.

  17. Electrical Resistivity, Tribological Behaviour of Multiwalled Carbon Nanotubes and Nanoboron Carbide Particles Reinforced Copper Hybrid Composites for Pantograph Application

    Directory of Open Access Journals (Sweden)

    N. Selvakumar

    2016-01-01

    Full Text Available This work focuses on the influence and contribution of multiwalled carbon-nanotube (MWCNT–boron carbide (B4C to the mechanical and tribological properties of copper matrix composites. Different weight fractions of nano- B4C-containing fixed-weight fractions of MWCNT-reinforced copper composites were prepared using the entrenched cold-press sintering method of powder metallurgy. The wear losses of sintered Cu–MWCNT–B4C composites were investigated by conducting sliding tests in a pin-on-disc apparatus. The addition of reinforcements showed enhancements in the hardness and wear properties of the composites due to the uniform dispersion of the secondary reinforcement in the copper matrix and the self-lubricating effect of the MWCNTs. The effects of the nanoparticle distribution in the matrix, the worn surface morphology, and the elemental composition of the composites were characterized using high-resolution scanning electron microscopy and X-ray diffraction analysis. The electrical resistivity of the fabricated copper hybrid composite preforms was evaluated using a four-point probe tester. Our results highlight the use of experiential reinforcing limits of B4C on the wear and electrical and mechanical behaviour of copper composites.

  18. Structural Evaluation and Mechanical Properties of Aluminum/Tungsten Carbide Composites Fabricated by Continual Annealing and Press Bonding (CAPB) Process

    Science.gov (United States)

    Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Drummen, G. P. C.

    2014-12-01

    In the present work, a novel technique is introduced called continual annealing and press bonding (CAPB) for the manufacturing of a bulk aluminum matrix composite dispersed with 10 vol pct tungsten carbide particles (Al/WCp composite). The microstructural evolution and mechanical properties of the Al/WCp composite during various CAPB cycles were examined by scanning electron microscopy (SEM), wavelength dispersive X-ray spectroscopy (WDX), and tensile testing. The microstructure of the fabricated composite after fourteen cycles of CAPB showed homogenous distribution of the WC particles in the aluminum matrix and strong bonding between the various layers. According to WDX analysis, the manufactured Al/WCp composite did not evidence the presence of additional elements. The results indicated that the tensile strength of the composites increased with the number of CAPB cycles, and reached a maximum value of 140 MPa at the end of the fourteenth cycle, which was 1.6 times higher than the obtained value for annealed aluminum (raw material, 88 MPa). Even though the elongation of the Al/WCp composite was reduced during the initial cycles of CAPB process, it increased significantly during the final cycles. SEM observation of fracture surfaces showed that the rupture mode in the CAPB-processed Al/WCp composite was of the shear ductile rupture type.

  19. The advantages of a tapered whisker.

    Science.gov (United States)

    Williams, Christopher M; Kramer, Eric M

    2010-01-20

    The role of facial vibrissae (whiskers) in the behavior of terrestrial mammals is principally as a supplement or substitute for short-distance vision. Each whisker in the array functions as a mechanical transducer, conveying forces applied along the shaft to mechanoreceptors in the follicle at the whisker base. Subsequent processing of mechanoreceptor output in the trigeminal nucleus and somatosensory cortex allows high accuracy discriminations of object distance, direction, and surface texture. The whiskers of terrestrial mammals are tapered and approximately circular in cross section. We characterize the taper of whiskers in nine mammal species, measure the mechanical deflection of isolated felid whiskers, and discuss the mechanics of a single whisker under static and oscillatory deflections. We argue that a tapered whisker provides some advantages for tactile perception (as compared to a hypothetical untapered whisker), and that this may explain why the taper has been preserved during the evolution of terrestrial mammals.

  20. The advantages of a tapered whisker.

    Directory of Open Access Journals (Sweden)

    Christopher M Williams

    Full Text Available The role of facial vibrissae (whiskers in the behavior of terrestrial mammals is principally as a supplement or substitute for short-distance vision. Each whisker in the array functions as a mechanical transducer, conveying forces applied along the shaft to mechanoreceptors in the follicle at the whisker base. Subsequent processing of mechanoreceptor output in the trigeminal nucleus and somatosensory cortex allows high accuracy discriminations of object distance, direction, and surface texture. The whiskers of terrestrial mammals are tapered and approximately circular in cross section. We characterize the taper of whiskers in nine mammal species, measure the mechanical deflection of isolated felid whiskers, and discuss the mechanics of a single whisker under static and oscillatory deflections. We argue that a tapered whisker provides some advantages for tactile perception (as compared to a hypothetical untapered whisker, and that this may explain why the taper has been preserved during the evolution of terrestrial mammals.

  1. Mechanical Behaviour ofAl2014 Reinforced with Boron Carbide and Short Basalt Fiber Based Hybrid Composites

    Directory of Open Access Journals (Sweden)

    Ranganatha S R

    2016-09-01

    Full Text Available The present study was aimed at evaluating the effect of short Basalt Fiber and B4Con hardness and impact strength of Al 2014 Composites. These AMCs with individual and multiple reinforcement (hybrid MMCs are finding increased applications in aerospace, automobile, space, underwater and transportation applications. An effort is made to enhance the Hardness and Impact properties of AMCs by reinforcing Al2014 matrix with Varying Proportion of Short basalt fiber and Boron carbide by stir casting method. Aluminum alloy matrix varying proportions of boron carbide particulates and Short Basalt fibers were fabricated. The microstructure,hardness and impact strength properties of the fabricated AMCs were analyzed. The optical microstructure study revealed the homogeneous dispersion of B4C particles and Short Basalt fiber in the matrix. Based on the results obtained from the Hardness and Impact of the metal matrix composites it is observed that, the hardness and impact strength increases with increase in the amount of reinforcement‘s.

  2. Assessment of thermal shock induced damage in silicon carbide fibre reinforced glass matrix composites

    Directory of Open Access Journals (Sweden)

    Boccaccini, A. R.

    1998-09-01

    Full Text Available The development of microstructural damage in silicon carbide fibre (Nicalon™ reinforced glass matrix composite samples subjected to thermal shock was investigated by using a nondestructive forced resonance technique and fibre push out indentation tests. Thermal shock testing involved quenching samples in a water bath maintained at room temperature from a high temperature (650ºC. Changes in the Young's modulus and internal friction of the samples with increasing number of shocks were measured accurately by the forced resonance technique. Fibre push-out tests showed no significant changes in the properties of the fibre-matrix interface, indicating that damage in the composite was concentrated mainly in the development of matrix microcracking. It was also shown that the internal friction is a very sensitive parameter by which to detect the onset and development of such microcracking. A simple semi-empirical model is proposed to correlate the internal friction level with the microcracking density in the glass matrix. Finally, the relevance of detecting nondestructively the existence of microcracks in the glass matrix, before any significant interfacial degradation occurs, is emphasized, in conextion with the possibility of inducing a crack healing process by a thermal treatment (annealing, taking advantage of the viscous flow properties of the glass.

    El desarrollo de daño microestructural en materiales compuestos de matriz de vidrio reforzados con fibras de carburo de silicio (Nicalon™ sometidos a choque térmico fue investigado mediante la técnica no-destructiva de resonancia forzada y por mediciones de indentación "push-out" de fibras. Los ensayos de choque térmico involucraron el enfriamiento brusco en un baño de agua a temperatura ambiente de las piezas previamente calentadas a una temperatura elevada (650ºC. La técnica de resonancia forzada permitió medir cambios en el módulo de Young de elasticidad y en la fricci

  3. Microstructural and mechanical characterization of hybrid aluminum matrix composite containing boron carbide and Al-Cu-Fe quasicrystals

    Science.gov (United States)

    Khan, Mahmood; Zulfaqar, Muhammad; Ali, Fahad; Subhani, Tayyab

    2017-07-01

    Hybrid aluminum matrix composites containing particles of boron carbide and quasicrystals were manufactured to explore the combined effect of reinforcements on microstructural evolution and mechanical performance of the composites. The particles were incorporated at a loading of 6 wt% each making a total of 12 wt% reinforcement in pure aluminum. For comparison, two composites containing individually reinforced 12 wt% particles were also prepared along with a reference specimen of pure aluminum. Ball milling technique was employed to mix the composite constituents. The green bodies of composite powders were prepared by uniaxial pressing at room temperature followed by consolidation by pressureless sintering under inert atmosphere. The microstructural characterization was performed using scanning electron microscopy while phase identification was carried out by X-ray diffraction. The mechanical characterization was performed by Vickers hardness and compression tests. Hybrid composites showed increased compressive properties while the composites containing solely quasicrystals demonstrated improved hardness. The increase in mechanical performance was related to the microstructural evolution due to the presence and uniform dispersion of binary particles.

  4. Sensing Device with Whisker Elements

    Science.gov (United States)

    Hartmann, Mitra J. (Inventor); Solomon, Joseph H. (Inventor)

    2013-01-01

    A sensing device includes an elongated whisker element having a flexible cantilever region and a base region where a change in moment or curvature is generated by bending of the cantilever region when it contacts an object. One or more sensor elements cooperatively associated with the whisker element provide one or more output signals that is/are representative of two orthogonal components of change in moment or curvature at the whisker base region to permit determination of object distance, fluid velocity profile, or object contour (shape) with accounting for lateral slip of the whisker element and frictional characteristics of the object. Multiple sensing devices can be arranged in arrays in a manner to sense object contour without or with adjustment for lateral slip.

  5. Synthesis of AlN whiskers using cobalt oxide catalyst and their alignments for the improvement of thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Dang, Thi My Linh [Nano-Convergence Materials Center, Korea Institute of Ceramic Engineering and Technology, Soho-ro 10, Jinju-si, Kyeoungsangnam-do, 660-031 (Korea, Republic of); Electronic Materials Lab., School of Advanced Materials Science and Engineering, SungKyunKwan Univ., Suwon-si, Gyeonggi-do, 440-746 (Korea, Republic of); Yoon, Dae-Ho, E-mail: dhyoon@skku.edu [Electronic Materials Lab., School of Advanced Materials Science and Engineering, SungKyunKwan Univ., Suwon-si, Gyeonggi-do, 440-746 (Korea, Republic of); Kim, Chang-Yeoul, E-mail: cykim15@kicet.re.kr [Nano-Convergence Materials Center, Korea Institute of Ceramic Engineering and Technology, Soho-ro 10, Jinju-si, Kyeoungsangnam-do, 660-031 (Korea, Republic of)

    2016-08-15

    We synthesized one dimensional (1-D) AlN whiskers by using the cobalt oxide catalyst-assisted carbothermal reduction method. The formation of AlN whiskers is investigated by the thermo-gravimetric and differential thermal analysis, Fourier-transformed infrared spectra, X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy observations. It was found that Co{sub 3}O{sub 4} droplets on the surfaces of Al{sub 2}O{sub 3} acted as a catalyst for the growth of AlN whiskers by vapor-liquid-solid (VLS) mechanism. In addition, AlN whiskers/PVA composites aligned in parallel with the heat flow direction showed an excellent thermal conductivity about three times higher than those of the perpendicularly aligned whisker composites. - Highlights: • AlN whiskers with high aspect ratio were synthesized from Al{sub 2}O{sub 3}. • Co{sub 3}O{sub 4} droplets on the surface of Al{sub 2}O{sub 3} acts as a catalyst for the whisker growth. • AlN whiskers are aligned within PVA in perpendicular and parallel with heat flow. • AlN whisker/PVA composite in perpendicular alignment shows a excellent heat conductivity.

  6. Magnetically Induced Continuous CO2 Hydrogenation Using Composite Iron Carbide Nanoparticles of Exceptionally High Heating Power.

    Science.gov (United States)

    Bordet, Alexis; Lacroix, Lise-Marie; Fazzini, Pier-Francesco; Carrey, Julian; Soulantica, Katerina; Chaudret, Bruno

    2016-12-19

    The use of magnetic nanoparticles to convert electromagnetic energy into heat is known to be a key strategy for numerous biomedical applications but is also an approach of growing interest in the field of catalysis. The heating efficiency of magnetic nanoparticles is limited by the poor magnetic properties of most of them. Here we show that the new generation of iron carbide nanoparticles of controlled size and with over 80 % crystalline Fe2.2 C leads to exceptional heating properties, which are much better than the heating properties of currently available nanoparticles. Associated to catalytic metals (Ni, Ru), iron carbide nanoparticles submitted to magnetic excitation very efficiently catalyze CO2 hydrogenation in a dedicated continuous-flow reactor. Hence, we demonstrate that the concept of magnetically induced heterogeneous catalysis can be successfully applied to methanation of CO2 and represents an approach of strategic interest in the context of intermittent energy storage and CO2 recovery.

  7. Effect of stress ratio and frequency on fatigue crack growth rate of 2618 aluminium alloy silicon carbide metal matrix composite

    Indian Academy of Sciences (India)

    Nirbhay Singh; Ram Khelawan; G N Mathur

    2001-04-01

    Effect of stress ratio and frequency on the fatigue crack propagation of 2618 aluminium alloy–silicon carbide composite were investigated at ambient temperature. With the first set of specimens, the fatigue crack growth rates were studied at three frequencies of 1 Hz, 5 Hz and 10 Hz at a stress ratio of 0.1 whereas the effects of stress ratios of 0.1, 0.25 and 0.50 were studied with the second set of specimens. The study showed that the fatigue crack propagation behaviour of this metal matrix composite was influenced to an appreciable extent by the stress ratio, but not by the fatigue frequencies used in this investigation.

  8. High-dose neutron irradiation of Hi-Nicalon Type S silicon carbide composites. Part 2: Mechanical and physical properties

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, Yutai, E-mail: katohy@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Nozawa, Takashi [Japan Atomic Energy Agency, Rokkasho, Aomori-ken (Japan); Shih, Chunghao [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Ozawa, Kazumi [Japan Atomic Energy Agency, Rokkasho, Aomori-ken (Japan); Koyanagi, Takaaki; Porter, Wally; Snead, Lance L. [Oak Ridge National Laboratory, Oak Ridge, TN (United States)

    2015-07-15

    Nuclear-grade silicon carbide (SiC) composite material was examined for mechanical and thermophysical properties following high-dose neutron irradiation in the High Flux Isotope Reactor at a temperature range of 573–1073 K. The material was chemical vapor-infiltrated SiC-matrix composite with a two-dimensional satin weave Hi-Nicalon Type S SiC fiber reinforcement and a multilayered pyrocarbon/SiC interphase. Moderate (1073 K) to very severe (573 K) degradation in mechanical properties was found after irradiation to >70 dpa, whereas no evidence was found for progressive evolution in swelling and thermal conductivity. The swelling was found to recover upon annealing beyond the irradiation temperature, indicating the irradiation temperature, but only to a limited extent. The observed strength degradation is attributed primarily to fiber damage for all irradiation temperatures, particularly a combination of severe fiber degradation and likely interphase damage at relatively low irradiation temperatures.

  9. Electron beam induced growth of tin whiskers

    Energy Technology Data Exchange (ETDEWEB)

    Vasko, A. C.; Karpov, V. G. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Warrell, G. R.; Parsai, E. I.; Shvydka, Diana, E-mail: diana.shvydka@utoledo.edu [Department of Radiation Oncology, University of Toledo Health Science Campus, Toledo, Ohio 43614 (United States)

    2015-09-28

    We have investigated the influence of electron irradiation on tin whisker growth. Sputtered tin samples exposed to electron beam of 6 MeV energy exhibited fast whisker growth, while control samples did not grow any whiskers. The statistics of e-beam induced whiskers was found to follow the log-normal distribution. The observed accelerated whisker growth is attributed to electrostatic effects due to charges trapped in an insulating substrate. These results offer promise for establishing whisker-related accelerated life testing protocols.

  10. Nanoscale multilayered and porous carbide interphases prepared by pressure-pulsed reactive chemical vapor deposition for ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Jacques, S., E-mail: jacques@lcts.u-bordeaux1.fr [LCTS, University of Bordeaux 1, CNRS, Herakles-Safran, CEA, 3 allee de la Boetie, F-33600 Pessac (France); Jouanny, I.; Ledain, O.; Maillé, L.; Weisbecker, P. [LCTS, University of Bordeaux 1, CNRS, Herakles-Safran, CEA, 3 allee de la Boetie, F-33600 Pessac (France)

    2013-06-15

    In Ceramic Matrix Composites (CMCs) reinforced by continuous fibers, a good toughness is achieved by adding a thin film called “interphase” between the fiber and the brittle matrix, which acts as a mechanical fuse by deflecting the matrix cracks. Pyrocarbon (PyC), with or without carbide sub-layers, is typically the material of choice to fulfill this role. The aim of this work was to study PyC-free nanoscale multilayered carbide coatings as interphases for CMCs. Nanoscale multilayered (SiC–TiC){sub n} interphases were deposited by pressure-Pulsed Chemical Vapor Deposition (P-CVD) on single filament Hi-Nicalon fibers and embedded in a SiC matrix sheath. The thicknesses of the carbide interphase sub-layers could be made as low as a few nanometers as evidenced by scanning and transmission electron microscopy. By using the P-ReactiveCVD method (P-RCVD), in which the TiC growth involves consumption of SiC, it was not only possible to obtain multilayered (SiC–TiC){sub n} films but also TiC films with a porous multilayered microstructure as a result of the Kirkendall effect. The porosity in the TiC sequences was found to be enhanced when some PyC was added to SiC prior to total RCVD consumption. Because the porosity volume fraction was still not high enough, the role of mechanical fuse of the interphases could not be evidenced from the tensile curves, which remained fully linear even when chemical attack of the fiber surface was avoided.

  11. Thermal Properties Of Chitin Whiskers Reinforced PolyAcrylic Acid

    Directory of Open Access Journals (Sweden)

    Michael Ikpi Ofem

    2015-08-01

    Full Text Available ABSTRACT Thermal analysisTGA of samples of Chitin PAA and Chitin-PAA complexes containing different weight fractions of chitin whiskers were investigated. The activation energies Ea and other kinematic parameters amp916S amp916H and amp916G for the filler matrix and blend were calculated using the Coats and Redfern Broido and Horowitz and Metzger methods at the second and third stages of decomposition. The study showed that the kinetic parameters for the composites lie between the matrix and the filler. .At each filler loading level the activation energies changes in enthalpies entropies and Gibbs functions obtained using all three methods are comparable for the second region of decomposition. The pattern is such that the value of these energy parameters gradually decreased as filler loading decreases. The gradual increase in activation energy as filler increases is attributed to even dispersion of the whiskers and interfacial adhesion between the matrix and the chitin whiskers.

  12. Microstructural and Mechanical Study of Inconel 625 – Tungsten Carbide Composite Coatings Obtained by Powder Laser Cladding

    Directory of Open Access Journals (Sweden)

    Huebner J.

    2017-06-01

    Full Text Available This study focuses on the investigation of fine (~0.54 μm tungsten carbide particles effect on structural and mechanical properties of laser cladded Inconel 625-WC composite. Three powder mixtures with different Inconel 625 – WC weight ratio (10, 20 and 30 weight % of WC were prepared. Coatings were made using following process parameters: laser beam diameter ø ≈ 500 μm, powder feeder rotation speed – 7 m/min, scanning velocity – 10 m/min, laser power – 220 W changed to 320 W, distance between tracks – 1 mm changed to 0.8 mm. Microstructure and hardness were investigated. Coatings produced by laser cladding were crack and pore free, chemically and structurally homogenous. High cooling rate during cladding process resulted in fine microstructure of material. Hardness improved with addition of WC from 396.3 ±10.5 HV for pure Inconel 625, to 469.9 ±24.9 HV for 30 weight % of WC. Tungsten carbide dissolved in Inconel 625 which allowed formation of intergranular eutectic that contains TCP phases.

  13. STUDY ON CaSO4 WHISKER REINFORCING AND TOUGHENING MECHANISMS FOR POLYURETHANE ELASTOMER%CaSO4晶须补强增韧聚氨酯弹性体机理的研究

    Institute of Scientific and Technical Information of China (English)

    刘玲; 殷宁; 亢茂青; 王心葵

    2001-01-01

    The CaSO4 whisker/polyurethane elastomer composites with high strength and high toughness are fabricated.The CaSO4 whisker reinforcing and toughening mechanisms for polyurethane elastomer are studied.The observation of the fracture surface by SEM and TEM shows that CaSO4 whisker reinforcing mechanism for polyurethane elastomer is mainly load transfering,while its toughening mechanism involves crack deflection and whisker pullout.The effects of dispersity of CaSO4 whisker and the interfacial bonding state on reinforcement and toughness are discussed.The results indicate that composites with 5%~10% CaSO4 whisker exhibit the best mechanical properties among the materials tested.Good bonding interface is formed between whisker and matrix after the surface of CaSO4 whisker being treated by silane coupling agent(KH-550).Better interfacial bonding state contributes to strength and toughness being fairly improved.

  14. The preparation and performance of calcium carbide-derived carbon/polyaniline composite electrode material for supercapacitors

    Science.gov (United States)

    Zheng, Liping; Wang, Ying; Wang, Xianyou; Li, Na; An, Hongfang; Chen, Huajie; Guo, Jia

    Calcium carbide (CaC 2)-derived carbon (CCDC)/polyaniline (PANI) composite materials are prepared by in situ chemical oxidation polymerization of an aniline solution containing well-dispersed CCDC. The structure and morphology of CCDC/PANI composite are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N 2 sorption isotherms. It has been found that PANI was uniformly deposited on the surface and the inner pores of CCDC. The supercapacitive behaviors of the CCDC/PANI composite materials are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results show that the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than the conducting polymers. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F g -1 measured by cyclic voltammetry at 1 mV s -1. Besides, the capacitance retention of coin supercapacitor remained 80.1% after 1000 cycles.

  15. The preparation and performance of calcium carbide-derived carbon/polyaniline composite electrode material for supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Liping; Wang, Xianyou; Li, Na; An, Hongfang; Chen, Huajie [School of Chemistry, Key Laboratory of Environmentally Friendly Chemistry and Applications of Minister of Education, Xiangtan University, Hunan 411105 (China); Wang, Ying; Guo, Jia [School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Hubei 430073 (China)

    2010-03-15

    Calcium carbide (CaC{sub 2})-derived carbon (CCDC)/polyaniline (PANI) composite materials are prepared by in situ chemical oxidation polymerization of an aniline solution containing well-dispersed CCDC. The structure and morphology of CCDC/PANI composite are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N{sub 2} sorption isotherms. It has been found that PANI was uniformly deposited on the surface and the inner pores of CCDC. The supercapacitive behaviors of the CCDC/PANI composite materials are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results show that the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than the conducting polymers. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F g{sup -1} measured by cyclic voltammetry at 1 mV s{sup -1}. Besides, the capacitance retention of coin supercapacitor remained 80.1% after 1000 cycles. (author)

  16. Role of friction stir processing parameters on microstructure and microhardness of boron carbide particulate reinforced copper surface composites

    Indian Academy of Sciences (India)

    R Sathiskumar; N Murugan; I Dinaharan; S J Vijay

    2013-12-01

    Friction stir processing (FSP) was applied to fabricate boron carbide (B4C) particulate reinforced copper surface composites. The effect of FSP parameters such as tool rotational speed, processing speed and groove width on microstructure and microhardness was investigated. A groove was contrived on the 6mm thick copper plates and packed with B4C particles. FSP was carried out using five various tool rotational speeds, processing speeds and groove widths. Optical and scanning electron microscopies were employed to study the microstructure of the fabricated surface composites. The results indicated that the selected FSP parameters significantly influenced the area of surface composite, distribution of B4C particles and microhardness of the surface composites. Higher tool rotational speed and lower processing speed produced an excellent distribution of B4C particles and higher area of surface composite due to higher frictional heat, increased stirring and material tranportation. The B4C particles were bonded well to the copper matrix and refined the grains of copper due to the pinning effect of B4C particles. B4C particles retained the original size and morphology because of its small size and minimum sharp corners in the morphology.

  17. Spark plasma sintering of silicon carbide and multi-walled carbon nanotube reinforced zirconium diboride ceramic composite

    Energy Technology Data Exchange (ETDEWEB)

    Yadhukulakrishnan, Govindaraajan B.; Rahman, Arif; Karumuri, Sriharsha [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States); Stackpoole, Margaret M. [ELORET Corporation, Moffett Field, CA 94035 (United States); Kalkan, A. Kaan; Singh, Raman P. [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States); Harimkar, Sandip P., E-mail: sandip.harimkar@okstate.edu [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States)

    2012-08-30

    Highlights: Black-Right-Pointing-Pointer Dense SiC and carbon nanotube reinforced ZrB{sub 2} composites were spark plasma sintered. Black-Right-Pointing-Pointer SiC and carbon nanotube reinforcement favored the densification of ZrB{sub 2} composites. Black-Right-Pointing-Pointer SiC and carbon nanotube reinforcement resulted in toughening of ZrB{sub 2} composites. Black-Right-Pointing-Pointer Carbon nanotubes were retained in the spark plasma sintered ZrB{sub 2} composites. - Abstract: In this paper spark plasma sintering (SPS) of silicon carbide and multi-walled carbon nanotube reinforced zirconium diboride ultra-high temperature ceramic matrix composites is reported. Systematic investigations on the effect of reinforcement type (SiC and CNTs) and content (10-40 vol.% SiC and 2-6 vol.% CNTs) on densification behavior, microstructure development, and mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness) are presented. With the similar SPS processing parameters (1900 Degree-Sign C, 70 MPa pressure, and 15 min soaking time), near-full densification (>99% relative density) was achieved with 10-40% SiC (in ZrB{sub 2}-SiC) and 4-6% CNT (in ZrB{sub 2}-CNT) reinforced composites. The SiC and CNT reinforcement further improved the indentation fracture toughness of the composites through a range of toughening mechanisms, including particle shearing, crack deflection at the particle-matrix interface, and grain pull-outs for ZrB{sub 2}-SiC composites, and CNT pull-outs and crack deflection in ZrB{sub 2}-CNT composites.

  18. Rapid whisker movements in sleeping newborn rats

    National Research Council Canada - National Science Library

    Tiriac, Alexandre; Uitermarkt, Brandt D; Fanning, Alexander S; Sokoloff, Greta; Blumberg, Mark S

    2012-01-01

    .... The rodent whisker system, with its precise isomorphic mapping of individual whiskers to discrete brain areas, has been a key contributor to our understanding of somatotopic maps and developmental plasticity...

  19. Millisecond, micron precision multi-whisker detector.

    Science.gov (United States)

    Grady, Stephen K; Hoang, Thanh T; Gautam, Shree Hari; Shew, Woodrow L

    2013-01-01

    The neural mechanisms of somatosensory information processing in the rodent vibrissae system are a topic of intense debate and research. Certain hypotheses emphasize the importance of stick-slip whisker motion, high-frequency resonant vibrations, and/or the ability to decode complex textures. Other hypotheses focus on the importance of integrating information from multiple whiskers. Tests of the former require measurements of whisker motion that achieve high spatiotemporal accuracy without altering the mechanical properties of whiskers. Tests of the latter require the ability to monitor the motion of multiple whiskers simultaneously. Here we present a device that achieves both these requirements for two-dimensional whisker motion in the plane perpendicular to the whiskers. Moreover, the system we present is significantly less expensive (whiskers in response to an air puff.

  20. Mitigating tin whisker risks theory and practice

    CERN Document Server

    Handwerker, Carol A; Bath, Jasbir

    2016-01-01

    Discusses the growth mechanisms of tin whiskers and the effective mitigation strategies necessary to reduce whisker growth risks. This book covers key tin whisker topics, ranging from fundamental science to practical mitigation strategies. The text begins with a review of the characteristic properties of local microstructures around whisker and hillock grains to identify why these particular grains and locations become predisposed to forming whiskers and hillocks. The book discusses the basic properties of tin-based alloy finishes and the effects of various alloying elements on whisker formation, with a focus on potential mechanisms for whisker suppression or enhancement for each element. Tin whisker risk mitigation strategies for each tier of the supply chain for high reliability electronic systems are also described.

  1. Room-Temperature and High-Temperature Tensile Mechanical Properties of TA15 Titanium Alloy and TiB Whisker-Reinforced TA15 Matrix Composites Fabricated by Vacuum Hot-Pressing Sintering

    Directory of Open Access Journals (Sweden)

    Yangju Feng

    2017-04-01

    Full Text Available In this paper, the microstructure, the room-temperature and high-temperature tensile mechanical properties of monolithic TA15 alloy and TiB whisker-reinforced TA15 titanium matrix composites (TiBw/TA15 fabricated by vacuum hot-pressing sintering were investigated. The microstructure results showed that there were no obvious differences in the microstructure between monolithic TA15 alloy and TiBw/TA15 composites, except whether or not the grain boundaries contained TiBw. After sintering, the matrix microstructure presented a typical Widmanstätten structure and the size of primary β grain was consistent with the size of spherical TA15 titanium metallic powders. This result demonstrated that TiBw was not the only factor limiting grain coarsening of the primary β grain. Moreover, the grain coarsening of α colonies was obvious, and high-angle grain boundaries (HAGBs were distributed within the primary β grain. In addition, TiBw played an important role in the microstructure evolution. In the composites, TiBw were randomly distributed in the matrix and surrounded by a large number of low-angle grain boundaries (LAGBs. Globularization of α phase occurred prior, near the TiBw region, because TiBw provided the nucleation site for the equiaxed α phase. The room-temperature and high-temperature tensile results showed that TiBw distributed at the primary β grain boundaries can strengthen the grain boundary, but reduce the connectivity of the matrix. Therefore, compared to the monolithic TA15 alloy fabricated by the same process, the tensile strength of the composites increased, and the tensile elongation decreased. Moreover, with the addition of TiBw, the fracture mechanism was changed to a mixture of brittle fracture and ductile failure (composites from ductile failure (monolithic TA15 alloy. The fracture surfaces of TiBw/TA15 composites were the grain boundaries of the primary β grain where the majority of TiB whiskers distributed, i.e., the

  2. Local anodic oxidation on hydrogen-intercalated graphene layers: oxide composition analysis and role of the silicon carbide substrate.

    Science.gov (United States)

    Colangelo, Francesco; Piazza, Vincenzo; Coletti, Camilla; Roddaro, Stefano; Beltram, Fabio; Pingue, Pasqualantonio

    2017-03-10

    We investigate nanoscale local anodic oxidation (LAO) on hydrogen-intercalated graphene grown by controlled sublimation of silicon carbide (SiC). Scanning probe microscopy was used as a lithographic and characterization tool in order to investigate the local properties of the nanofabricated structures. The anomalous thickness observed after the graphene oxidation process is linked to the impact of LAO on the substrate. Micro-Raman (μ-Raman) spectroscopy was employed to demonstrate the presence of two oxidation regimes depending on the applied bias. We show that partial and total etching of monolayer graphene can be achieved by tuning the bias voltage during LAO. Finally, a complete compositional characterization was achieved by scanning electron microscopy and energy dispersive spectroscopy.

  3. Local anodic oxidation on hydrogen-intercalated graphene layers: oxide composition analysis and role of the silicon carbide substrate

    Science.gov (United States)

    Colangelo, Francesco; Piazza, Vincenzo; Coletti, Camilla; Roddaro, Stefano; Beltram, Fabio; Pingue, Pasqualantonio

    2017-03-01

    We investigate nanoscale local anodic oxidation (LAO) on hydrogen-intercalated graphene grown by controlled sublimation of silicon carbide (SiC). Scanning probe microscopy was used as a lithographic and characterization tool in order to investigate the local properties of the nanofabricated structures. The anomalous thickness observed after the graphene oxidation process is linked to the impact of LAO on the substrate. Micro-Raman (μ-Raman) spectroscopy was employed to demonstrate the presence of two oxidation regimes depending on the applied bias. We show that partial and total etching of monolayer graphene can be achieved by tuning the bias voltage during LAO. Finally, a complete compositional characterization was achieved by scanning electron microscopy and energy dispersive spectroscopy.

  4. Radial Distance Estimation with Tapered Whisker Sensors.

    Science.gov (United States)

    Ahn, Sejoon; Kim, DaeEun

    2017-07-19

    Rats use their whiskers as tactile sensors to sense their environment. Active whisking, moving whiskers back and forth continuously, is one of prominent features observed in rodents. They can discriminate different textures or extract features of a nearby object such as size, shape and distance through active whisking. There have been studies to localize objects with artificial whiskers inspired by rat whiskers. The linear whisker model based on beam theory has been used to estimate the radial distance, that is, the distance between the base of the whisker and a target object. In this paper, we investigate deflection angle measurements instead of forces or moments, based on a linear tapered whisker model to see the role of tapered whiskers found in real animals. We analyze how accurately this model estimates the radial distance, and quantify the estimation errors and noise sensitivity. We also compare the linear model simulation and nonlinear numerical solutions. It is shown that the radial distance can be estimated using deflection angles at two different positions on the tapered whisker. We argue that the tapered whisker has an advantage of estimating the radial distance better, as compared to an untapered whisker, and active sensing allows that estimation without the whisker's material property and thickness or the moment at base. In addition, we investigate the potential of passive sensing for tactile localization.

  5. Microstructure and wear behaviour of FeAl-based composites containing in-situ carbides

    Indian Academy of Sciences (India)

    RAVI KANT; UJJWAL PRAKASH; VIJAYA AGARWALA; V V SATYA PRASAD

    2016-12-01

    Iron aluminides containing carbon are promising materials for tribological applications. Because of graphite formation at higher ($>$20 wt%) Al-contents the addition of carbon to FeAl-based alloys has not been successful.The graphite precipitation may be avoided by addition of Zr or Ti. Dry sliding wear behaviour of FeAl based alloys containing 1–1.5wt% carbon with quaternary addition of Ti or Zr has been studied using ball-on-disk wear test. Effect of sliding speeds and applied loads is investigated and correlated with mechanical properties. Wear resistance of FeAl-based alloys is found to be significantly improved on addition of Ti/Zr. This is attributed to the high hardness of alloy carbides. The lower load-bearing capacity of graphite flakes in localized region was found to increase the wear rate of the alloy. The carbides such as Fe$_3$AlC$_{0.5}$, TiC and ZrC are embedded in the matrix after sliding wear without destruction or delamination. This significantly affects the wear resistance of FeAl-based alloys.

  6. Morphological evolution of primary TiC carbide in laser clad TiC reinforced FeAl intermetallic composite coating

    Institute of Scientific and Technical Information of China (English)

    陈瑶; 王华明

    2003-01-01

    The novel rapidly solidified TiC/FeAl composite coatings were fabricated by laser cladding on the substrate of 1Cr18Ni9Ti stainless steel, particular emphasis has been placed on the growth morphologies of TiC carbide and its growth mechanism under a constant solidification conditions. Results show that the growth morphology of TiC carbide strongly depends upon the nucleation process and mass transportation process of TiC forming elements in laser melt pool. With increasing amount of titanium and carbon in melt pool, the growth morphology of TiC carbide changes from block-like to star-like and well-developed dendrite. As the amount of titanium and carbon increases further, TiC carbide particles are found to be irregular polyhedral block. Although the growth morphologies of TiC are various,their advancing fronts are all faceted, illustrating that TiC carbide grows by the mechanism of lateral ledge growth.

  7. Heat and Mass Transfer in the Chemical Vapor Deposition of Silicon Carbide in a Porous Carbon-Carbon Composite Material for a Heat Shield

    Science.gov (United States)

    Reznik, S. V.; Mikhailovskii, K. V.; Prosuntsov, P. V.

    2017-03-01

    Physical and mathematical simulations of the chemical vapor deposition of silicon carbide in a porous carbon-carbon composite material in a chemical vapor deposition reactor for formation of a matrix of a carbon-ceramic composite material for a heat shield of an aerospace aircraft have been performed. Results of parametric calculations of the heat and mass transfer at the macro- and microlevels in representative elements of the microstructure of carbon-carbon composite materials different in residual porosity at different temperatures in the reaction zone of the reactor are presented. Features of compaction of the pore space of a carbon-carbon composite material by a silicon-carbide matrix depending on the technological parameters of the reaction medium were analyzed.

  8. Microstructure and Mechanical Behaviour of Stir-Cast Al-Mg-Sl Alloy Matrix Hybrid Composite Reinforced with Corn Cob Ash and Silicon Carbide

    Directory of Open Access Journals (Sweden)

    Oluwagbenga Babajide Fatile

    2014-10-01

    Full Text Available In this present study, the microstructural and mechanical behaviour of Al-Mg-Si alloy matrix composites reinforced with silicon carbide (SiC and Corn cob ash (An agro‑waste was investigated. This research work was aimed at assessing the suitability of developing low cost- high performance Al-Mg-Si hybrid composite. Silicon carbide (SiC particulates added with 0,1,2,3 and 4 wt% Corn cob ash (CCA were utilized to prepare 10 wt% of the reinforcing phase with Al-Mg-Si alloy as matrix using two-step stir casting method. Microstructural characterization, density measurement, estimated percent porosity, tensile testing, and micro‑hardness measurement were used to characterize the composites produced. From the results obtained, CCA has great potential to serve as a complementing reinforcement for the development of low cost‑high performance aluminum hybrid composites.

  9. Study of multi-carbide B4C-SiC/(Al, Si) reaction infiltrated composites by SEM with EBSD

    Science.gov (United States)

    Almeida, B. A.; Ferro, M. C.; Ravanan, A.; Grave, P. M. F.; Wu, H.-Y.; Gao, M.-X.; Pan, Y.; Oliveira, F. J.; Lopes, A. B.; Vieira, J. M.

    2014-03-01

    In the definition of conceptual developments and design of new materials with singular or unique properties, characterisation takes a key role in clarifying the relationships of composition, properties and processing that define the new material. B4C has a rare combination of properties that makes it suitable for a wide range of applications in engineering: high refractoriness, thermal stability, high hardness and abrasion resistance coupled to low density. However, the low self-diffusion coefficient of B4C limits full densification by sintering. A way to overturn this constraint is by using an alloy, for example Al-Si, forming composites with B4C. Multi-carbide B4C-SiC/(Al, Si) composites were produced by the reactive melt infiltration technique at 1200 - 1350 °C with up to 1 hour of isothermal temperature holds. Pressed preforms made from C-containing B4C were spontaneously infiltrated with Al-Si alloys of composition varying from 25 to 50 wt% Si. The present study involves the characterisation of the microstructure and crystalline phases in the alloys and in the composites by X-ray diffraction and SEM/EDS with EBSD. Electron backscatter diffraction is used in detail to look for segregation and spatial distribution of Si and Al containing phases during solidification of the metallic infiltrate inside the channels of the ceramic matrix when the composite cools down to the eutectic temperature (577 °C). It complements elemental maps of the SEM/EDS. The production of a flat surface by polishing is intrinsically difficult and the problems inherent to the preparation of EBSD qualified finishing in polished samples of such type of composites are further discussed.

  10. Annual Conference on Composites and Advanced Ceramic Materials, 12th, Cocoa Beach, FL, Jan. 17-22, 1988, Proceedings. Parts 1 and 2

    Energy Technology Data Exchange (ETDEWEB)

    1988-10-01

    The present conference discusses topics in the development status of advanced ceramics, the engineering applications of ceramic-matrix composites, modeling and theoretical considerations of engineering ceramics, the role of interfaces in ceramic-matrix composites, and polycrystalline oxide-matrix composites. Also discussed are glass- and glass-ceramic-matrix composites, carbide- and nitride-matrix composites, the synthesis methods as well as the properties and applications of ceramic matrix-reinforcing whiskers, fibers, and powders, and various SDI-related advanced ceramic materials for use in orbital systems.

  11. Compositional effects on mechanical properties of hafnium-carbide-strengthened molybdenum alloys

    Science.gov (United States)

    Witzke, W. R.

    1975-01-01

    The mechanical properties of swaged rod thermomechanically processed from arc melted Mo-2Re-Hf-C alloys containing as much as 0.9-mol% HfC were evaluated. The low-temperature ductilities of these alloys were not influenced by the amount of HfC present but by the amount of Hf in excess of stoichiometry. Maximum ductility occurred at 0.2- to 0.3-at.% excess Hf. At 0.3- to 0.5-mol% HfC, alloy strength varied directly with the Mo content of extracted carbide particles, both decreasing as the amount of excess Hf increased. Additions of 2-at.% Re had little effect on strength or ductility. Tensile and creep strengths of Mo-2Re-0.7Hf-0.5C alloy equaled or exceeded those of other high strength Mo alloys.

  12. Hertzian indentation of colloidally processed titanium carbide-nickel aluminide composites

    Science.gov (United States)

    Collier, R. Bradley

    Advanced cermets based on titanium carbide (TiC), with a ductile nickel aluminide (Ni3Al) binder, have shown significant promise for use in a variety of demanding wear environments, due to a combination of high strength and good corrosion behaviour. A unique feature of TiC-Ni3Al cermets is that they show increasing strength from room temperature up to ˜1,000°C, while current materials such as tungsten carbide/cobalt (WC/Co) show significant strength degradation above ˜500°C. In this thesis, aqueous colloidal forming methods have been applied to process TiC preforms. The mechanisms and effectiveness of suspension stabilization were examined using methods such as zeta potential analysis, rheological measurements, and sedimentation trials for two common dispersants; an ammonium salt of polymethacrylate (PMA-NH 4) and two molecular weights (l,800 and 10,000) of polyethylenimine (PEI). TiC preforms were prepared by slip casting suspensions of up to 50 vol. % solids content. After drying, the TiC-based cermets were processed by melt infiltration with the Ni3Al alloy (IC-50) at 1475°C.Ni 3Al content was varied between 20 and 50 vol. % using this approach, resulting in final densities that exceeded 98% of theoretical. These samples were subjected to Hertzian indentation testing with loads ranging from 250 -- 2000 N, using WC-Co spheres with sizes ranging from 1.191 to 2.38 mm. Indentation stress-strain curves were produced from the indentation data and compared to the calculated elastic Hertzian response. The bonded interface method was used to examine the subsurface deformation of the material under load. Significant deformation of the binder and the eventual fracture of the TiC grains were observed. The nature of the quasi-plasticity of TiC-Ni 3Al and the effects of binder content on surface and subsurface deformation is examined.

  13. Mechanism and optimization of titanium carbide-reinforced iron composite formation through carbothermal reduction of hematite and anatase

    Energy Technology Data Exchange (ETDEWEB)

    Hasniyati, Md Razi; Zuhailawati, Hussain, E-mail: zuhaila@eng.usm.my; Ramakrishnan, Sivakumar; Hamid, Sheikh Abdul Rezan Sheikh Abdul

    2014-02-25

    Highlights: • Reduction mechanism of Fe{sub 2}O{sub 3} and TiO{sub 2} mixture in formation Fe–TiC composite was discovered. • Factorial design is used to define interaction between calcination temperature and FeCl{sub 3} content. • Increasing FeCl{sub 3} content and calcination temperature increased the formation of Fe and TiC phases. • Microhardness and density of the sintered composite improved noticeably. -- Abstract: This study investigated an optimization of titanium carbide-reinforced iron composite fabricated using a combination of powder metallurgy and carbothermal reduction of hematite-anatase mixture using 2{sup k} factorial design. The composite formation mechanism is described as well. Powders of hematite, anatase and graphite with mole ratio of 1:1:6 were mixed for 1 h together with 0 wt%, 1 wt% and 5 wt% FeCl{sub 3}. The mixture was pressed at 5 MPa, calcined for 1 h at 1000 °C, 1100 °C or 1200 °C and sintered at 1200 °C. X-ray diffraction of the calcined powder showed that with increasing temperature TiO{sub 2} was reduced to TiC through formation of various suboxides (Ti{sub 3}O{sub 5} and Ti{sub 2}O{sub 3}). Scanning electron microscope observation of the sintered composite indicated that addition of FeCl{sub 3} enhanced the formation of TiC in iron matrix. Consequently, microhardness and density of the sintered composite improved noticeably. Based on microhardness, green density and sintered density measurements, design of experiment analysis suggested that an increase in both FeCl{sub 3} content and calcination temperature increased the percentage of hematite and anatase reduction.

  14. Methods for Producing High-Performance Silicon Carbide Fibers, Architectural Preforms, and High-Temperature Composite Structures

    Science.gov (United States)

    DiCarlo, James A. (Inventor); Yun, Hee-Mann (Inventor)

    2014-01-01

    Methods are disclosed for producing architectural preforms and high-temperature composite structures containing high-strength ceramic fibers with reduced preforming stresses within each fiber, with an in-situ grown coating on each fiber surface, with reduced boron within the bulk of each fiber, and with improved tensile creep and rupture resistance properties tier each fiber. The methods include the steps of preparing an original sample of a preform formed from a pre-selected high-strength silicon carbide ceramic fiber type, placing the original sample in a processing furnace under a pre-selected preforming stress state and thermally treating the sample in the processing furnace at a pre-selected processing temperature and hold time in a processing gas having a pre-selected composition, pressure, and flow rate. For the high-temperature composite structures, the method includes additional steps of depositing a thin interphase coating on the surface of each fiber and forming a ceramic or carbon-based matrix within the sample.

  15. Development of niobium aluminide-based composites with improved toughness using treated reinforcements

    Energy Technology Data Exchange (ETDEWEB)

    Woytera, S.A.; Bhagat, R.B.; Amateau, M.F. [Pennsylvania State Univ., University Park, PA (United States). Applied Research Lab.

    1996-03-01

    Many ordered intermetallic compounds exhibit attractive properties for high temperature structural aerospace applications. The major obstacles limiting the use of these materials are their low ductility and toughness at room temperature and poor creep resistance at elevated temperatures. In this investigation treated silicon carbide whisker and niobium particle reinforced niobium aluminide matrix composites have been fabricated by reaction hot pressing in vacuum. Elemental matrix powders react exothermally and form the niobium aluminide matrix in situ. A suitable hot pressing cycle has been established for the successful development of the niobium aluminide matrix, while reducing adverse reactions between the matrix and the reinforcements. The composites with treated reinforcements are expected to have high resistance to creep at elevated temperatures and they show relatively low hardness and higher toughness in comparison with the composites reinforced with untreated whiskers.

  16. Effect of alloying elements on the composition of carbide phases and mechanical properties of the matrix of high-carbon chromium-vanadium steel

    Science.gov (United States)

    Titov, V. I.; Tarasenko, L. V.; Utkina, A. N.

    2017-01-01

    Based on the results of phase physicochemical analysis of high-carbon chromium-vanadium steel, the predominant type of carbide that provides high wear resistance has been established, and its amount and amount of carbon in martensite have been determined. Data on the composition and the amount of carbide phase and on the chemical composition of the martensite of high-carbon steel have been obtained, which allows determination of the alloying-element concentration limits. The mechanical testing of heats of a chosen chemical composition has been carried out after quenching and low-temperature tempering. The tests have demonstrated benefits of new steel in wear resistance and bending strength with the fatigue strength being retained, compared to steels subjected to cementation. The mechanism of secondary strengthening of the steel upon high-temperature tempering has been revealed. High-temperature tempering can be applied to articles that are required to possess both high wear resistance and heat resistance.

  17. PYROLYTIC CARBIDE DEVELOPMENT PROGRAM

    Science.gov (United States)

    and injector design changes were made to improve the quality of the carbide produced. Niobium carbide and tantalum carbide coated nozzles are described...Additional data for pyrolytic niobium carbide and hafnium carbide is also presented. (Author)

  18. Composite uranium carbide targets at TRIUMF: Development and characterization with SEM, XRD, XRF and L-edge densitometry

    Science.gov (United States)

    Kunz, Peter; Bricault, Pierre; Dombsky, Marik; Erdmann, Nicole; Hanemaayer, Vicky; Wong, John; Lützenkirchen, Klaus

    2013-09-01

    The production of radioactive ion beams (RIB) from spallation targets by irradiation with a continuous 500 MeV proton beam, has been routine at TRIUMF for several years. Based on the experience with composite refractory carbide targets a procedure for the fabrication of UC2/C targets was developed. It includes the preparation of UC2 by carbothermal reduction of UO2, the slip-casting of fine-grained UC2/C slurry on graphite foil under inert gas atmosphere and the cutting of composite target discs which are stacked up to a lamellar structure. The thermal properties of such an arrangement are adequate to withstand the high power deposition of an intense, continuous proton beam and also beneficial for the fast release of short-lived radioactive isotopes. Molecular structure, particle size and the impact of sintering of the target discs were investigated via XRD and SEM. Thickness and mass distribution were measured with position-sensitive LIII-edge densitometry. The results confirm that the properties of the UC2/C target material are well suited for RIB production at TRIUMF while there is still room for improvement with regard to uniformity of mass distribution in target disc thickness.

  19. Capacitance of two-dimensional titanium carbide (MXene) and MXene/carbon nanotube composites in organic electrolytes

    Science.gov (United States)

    Dall'Agnese, Yohan; Rozier, Patrick; Taberna, Pierre-Louis; Gogotsi, Yury; Simon, Patrice

    2016-02-01

    Pseudocapacitive materials that store charges by fast redox reactions are promising candidates for designing high energy density electrochemical capacitors. MXenes - recently discovered two-dimensional carbides, have shown excellent capacitance in aqueous electrolytes, but in a narrow potential window, which limits both the energy and power density. Here, we investigated the electrochemical behavior of Ti3C2 MXene in 1M solution of 1-ethly-3-methylimidazolium bis- (trifluoromethylsulfonyl)-imide (EMITFSI) in acetonitrile and two other common organic electrolytes. This paper describes the use of clay, delaminated and composite Ti3C2 electrodes with carbon nanotubes in order to understand the effect of the electrode architecture and composition on the electrochemical performance. Capacitance values of 85 F g-1 and 245 F cm-3 were obtained at 2 mV s-1, with a high rate capability and good cyclability. In situ X-ray diffraction study reveals the intercalation of large EMI+ cations into MXene, which leads to increased capacitance, but may also be the rate limiting factor that determines the device performance.

  20. 纳米纤维素晶须/壳聚糖天然可降解复合膜的制备与性能%Preparation and Properties of Nanocellulose Whiskers/Chitosan Natural Biodegradable Composite Films

    Institute of Scientific and Technical Information of China (English)

    徐寅; 王家俊; 刘幸幸; 吴鲜鲜

    2011-01-01

    Natural biodegradable composite films are prepared from nanocellulose whiskers(NCW) as reinforcement and chitosan(CS) as matrix via solution casting technique. The structures of the films are characterized by SEM, FT-IR, and XRD; Dynamic mechanical properties, tensile performance under dry and wet conditions are also tested. The results show that the composite films exhibite good miscibility; NCW significantly increases films' storage modulus, tensile modulus and strength. NCW promises to further widen applications and areas of CS material.%以纳米纤维素晶须(NCW)为增强体、壳聚糖(CS)为基体,通过流延法制得天然可降解复合膜.通过电子显微镜( SEM)、红外光谱(FT-IR)、X射线衍射(XRD)等手段对复合膜进行结构表征,并对复合膜的动态力学性能、干湿态拉伸性能进行了测试.结果表明:NCW与CS具有很好的相容性;NCW的加入显著提高了CS膜的储能模量、拉伸模量和拉伸强度.NCW能够进一步拓宽CS材料的应用领域和价值.

  1. Fundamental studies of tin whiskering in microelectronics finishes

    Science.gov (United States)

    Pinol, Lesly Agnes

    , thinner substrates displayed a more rapid onset of whiskering immediately following metallization. Changes in wafer-level stress were not found to correlate with whiskering morphology (number, density, length) after 6 weeks of aging. This result points either to the irrelevance of macrostress in the substrate/film composite, or to a difference in whiskering mechanism for rigid substrates (whose stress gradient over time is significant) when compared with thinner, flexible substrates (whose stress is less variable with time). Organic contamination was found to have no appreciable effect when explicitly introduced. Furthermore, electron-beam evaporated films whiskered more readily than films deposited via electroplating from baths containing organic "brighteners." Beyond such findings, novel in themselves, our work is also unique in that we emphasize the "clean" deposition of tin (with chromium adhesion layers and copper underlayers) by vacuum-based physical vapor deposition, to circumvent the question of contamination entirely. By employing silicon substrates exclusively, we have distinguished ourselves from other works (which, for example, use copper coupons fabricated from rolled shim stock) because we have better sample-to-sample consistency in terms of material properties, machinability, and orientation.

  2. Ultrafine Molybdenum Carbide Nanoparticles Composited with Carbon as a Highly Active Hydrogen-Evolution Electrocatalyst.

    Science.gov (United States)

    Ma, Ruguang; Zhou, Yao; Chen, Yongfang; Li, Pengxi; Liu, Qian; Wang, Jiacheng

    2015-12-01

    The replacement of platinum with non-precious-metal electrocatalysts with high efficiency and superior stability for the hydrogen-evolution reaction (HER) remains a great challenge. Herein, we report the one-step synthesis of uniform, ultrafine molybdenum carbide (Mo2C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo2C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1-3 layers) showed superior HER activity in acidic media, with a very low onset potential of -6 mV, a small Tafel slope of 41 mV dec(-1), and a large exchange current density of 0.179 mA cm(-2), as well as good stability during operation for 12 h. These excellent properties are similar to those of state-of-the-art 20% Pt/C and make the catalyst one of the most active acid-stable electrocatalysts ever reported for HER.

  3. Effect of temper on seawater corrosion of an aluminum-silicon carbide composite alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Z.; Abdul Aleem, B.J. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia)

    1996-11-01

    The corrosion behavior of annealed (O), as-fabricated (F), and naturally age-hardened (T4) aluminum alloy Al 6013 with 20 vol% silicon carbide in particulate form was investigated in 3.5 wt% sodium chloride and in Arabian Gulf water. Of the three tempers, T4 showed the lowest corrosion rate (0.04 mpy and 2.61 mpy) in deaerated and aerated NaCl, respectively. The corrosion rate in seawater was slightly higher. Predominant forms of corrosion were pitting and intergranular corrosion. Formation of corrosion chimneys was observed. X-ray diffraction Fourier transform infrared spectroscopy and energy dispersive spectroscopy showed intermetallic formation and the presence of a gelatinous film of aluminum hydroxide of bayrite type. The higher corrosion resistance of the T4 temper resulted from finer and more homogeneously distributed precipitates compared to tempers F and O. In view of the alloy`s good corrosion resistance and outstanding ultimate tensile strength, yield strength and specific modulus, it can be considered a strong competitor to Al 2024, Al 2014, and Al 6061, which are used mainly for structural applications.

  4. 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.

  5. Micromechanical analysis of a hybrid composite—effect of boron carbide particles on the elastic properties of basalt fiber reinforced polymer composite

    Science.gov (United States)

    Krishna Golla, Sai; Prasanthi, P.

    2016-11-01

    A fiber reinforced polymer (FRP) composite is an important material for structural application. The diversified application of FRP composites has become the center of attention for interdisciplinary research. However, improvements in the mechanical properties of this class of materials are still under research for different applications. The reinforcement of inorganic particles in a composite improves its structural properties due to their high stiffness. The present research work is focused on the prediction of the mechanical properties of the hybrid composites where continuous fibers are reinforced in a micro boron carbide particle mixed polypropylene matrix. The effectiveness of the addition of 30 wt. % of boron carbide (B4C) particle contributions regarding the longitudinal and transverse properties of the basalt fiber reinforced polymer composite at various fiber volume fractions is examined by finite element analysis (FEA). The experimental approach is the best way to determine the properties of the composite but it is expensive and time-consuming. Therefore, the finite element method (FEM) and analytical methods are the viable methods for the determination of the composite properties. The FEM results were obtained by adopting a micromechanics approach with the support of FEM. Assuming a uniform distribution of reinforcement and considering one unit-cell of the whole array, the properties of the composite materials are determined. The predicted elastic properties from FEA are compared with the analytical results. The results suggest that B4C particles are a good reinforcement for the enhancement of the transverse properties of basalt fiber reinforced polypropylene.

  6. Preparation of Chromium Oxide Coatings on Aluminum Borate Whiskers by a Hydrothermal Deposition Process

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Aluminum borate whiskers (9Al2O32B2O3) can be used to reinforce aluminum alloys to produce light and strong composites. However, the adverse interfacial reactions between the whiskers and the aluminum alloys inhibit their practical uses; therefore, a protective coating is needed on whiskers. In this work, aluminum borate whiskers were coated with chromium-coating deposits in a hydrothermal solution containing CrCl3, Na2C4H4O6, NaPH2O2, and H3BO3. The presence of the impurity P in the hydrothermal deposits can be avoided by reducing the amount of NaPH2O2 in the coating solution. Thermodynamic analysis was used to discuss the behavior of ions in the coating process. The subsequent heating of the hydrothermal products in air at 800 ℃ yielded smooth Cr2O3 films with a thickness of 0.060.07 μm.

  7. NASA Goddard Space Flight Center Tin Whisker (and Other Metal Whisker) Homepage

    Science.gov (United States)

    Brusse, Jay; Sampson, Mike; Leidecker, Henning; Kadesch, Jong

    2004-01-01

    This website provides information about tin whiskers and related research. The independent research performed during the past 50+ years is so vast that it is impractical to cover all aspects of tin whiskers in this one resource. Therefore, the absence of information in this website about a particular aspect of tin whiskers should NOT be construed as evidence of absence.

  8. NASA Goddard Space Flight Center Tin Whisker (and Other Metal Whisker) Homepage

    Science.gov (United States)

    Brusse, Jay; Sampson, Mike; Leidecker, Henning; Kadesch, Jong

    2004-01-01

    This website provides information about tin whiskers and related research. The independent research performed during the past 50+ years is so vast that it is impractical to cover all aspects of tin whiskers in this one resource. Therefore, the absence of information in this website about a particular aspect of tin whiskers should NOT be construed as evidence of absence.

  9. Whiskers and fibers of hydroxyapatite; Whiskers e fibras de hidroxiapatita

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, G.B.C.; Motisuke, M.; Zavaglia, C.A.C., E-mail: guicardoso@fem.unicamp.b [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Fac. de Engenharia Mecanica. Dept. de Engenharia de Materiais; Arruda, A.C.F. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Fac. de Engenharia Mecanica. Dept. de Engenharia de Petroleo

    2009-07-01

    Hydroxyapatite is a bioactive ceramic, which acts in tissue engineering by attracting bone cells. Occasionally it can be used as a biocompatible reinforcement. The mechanical role of this biomaterial can be defined depending of some characteristics analyzed by scanning electron microscope and X ray power diffraction. It can be classified in whiskers and fibers; each one has their own properties, which were discussed in this work. For its use as reinforcement it is necessary matrix with specific characteristics. (author)

  10. On the Strength of Silicon Carbide Particulate Reinforced Aluminium Alloy Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    Mingjiu ZHAO; Yue LIU; Liqing CHEN; Jing BI

    2004-01-01

    In the present study, the modified continuum model, quench strengthening and dislocation pile-up model was respectively used to estimate the yield strength of SiCp/Al composites. The experimental results showed that the modified shear lag model or quench strengthening model would underestimate the yield strength of SiCp/Al composites. However, the modified Hall-Petch correlation on the basis of the dislocation pile-up model, expressed as σcy = 244 + 371λ-1/2, fitted very well with the experimental data, which indicated that the strength increase of SiCp/Al composites might be due to the direct blocking of dislocation motion by the particulate-matrix interface.Namely, the dislocation pile-up is the most possible strengthening mechanism for SiCp/Al composites.

  11. Sodium sulfate corrosion of silicon carbide fiber-reinforced lithium aluminosilicate glass-ceramic matrix composites

    OpenAIRE

    1993-01-01

    Approved for public release; distribution is unlimited. Sodium sulfate hot corrosion of a SiC fiber-reinforced lithium aluminosilicate (LAS) glass-ceramic matrix composite was studied using Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD). Changes in the microstructural chemical composition of the specimens were investigated. The samples provided by Naval Air Warfare Center (NAWC), Warminster, PA were grouped as follows: (1) as-received, (2) Na2SO4 salt-coated and heat-treate...

  12. A Revival of Waste: Atmospheric Pressure Nitrogen Plasma Jet Enhanced Jumbo Silicon/Silicon Carbide Composite in Lithium Ion Batteries.

    Science.gov (United States)

    Chen, Bing-Hong; Chuang, Shang-I; Liu, Wei-Ren; Duh, Jenq-Gong

    2015-12-30

    In this study, a jumbo silicon/silicon carbide (Si/SiC) composite (JSC), a novel anode material source, was extracted from solar power industry cutting waste and used as a material for lithium-ion batteries (LIBs), instead of manufacturing the nanolized-Si. Unlike previous methods used for preventing volume expansion and solid electrolyte interphase (SEI), the approach proposed here simply entails applying surface modification to JSC-based electrodes by using nitrogen-atmospheric pressure plasma jet (N-APPJ) treatment process. Surface organic bonds were rearranged and N-doped compounds were formed on the electrodes through applying different plasma treatment durations, and the qualitative examinations of before/after plasma treatment were identified by X-ray photoelectron spectroscopy (XPS) and electron probe microanalyzer (EPMA). The surface modification resulted in the enhancement of electrochemical performance with stable capacity retention and high Coulombic efficiency. In addition, depth profile and scanning electron microscope (SEM) images were executed to determine the existence of Li-N matrix and how the nitrogen compounds change the surface conditions of the electrodes. The N-APPJ-induced rapid surface modification is a major breakthrough for processing recycled waste that can serve as anode materials for next-generation high-performance LIBs.

  13. Laser cladding of Inconel 625-based composite coatings reinforced by porous chromium carbide particles

    Science.gov (United States)

    Janicki, Damian

    2017-09-01

    Inconel 625/Cr3C2 composite coatings were produced via a laser cladding process using Cr3C2 reinforcing particles presenting an open porosity of about 60%. A laser cladding system used consisted of a direct diode laser with a rectangular beam spot and the top-hat beam profile, and an off-axis powder injection nozzle. The microstructural characteristics of the coatings was investigated with the use of scanning electron microscopy and X-ray diffraction. A complete infiltration of the porous structure of Cr3C2 reinforcing particles and low degree of their dissolution have been achieved in a very narrow range of processing parameters. Crack-free composite coatings having a uniform distribution of the Cr3C2 particles and their fraction up to 36 vol% were produced. Comparative erosion tests between the Inconel 625/Cr3C2 composite coatings and the metallic Inconel 625 coatings were performed following the ASTM G 76 standard test method. It was found that the composite coatings have a significantly higher erosion resistance to that of metallic coatings for both 30° and 90° impingement angles. Additionally, the erosion performances of composite coatings were similar for both the normal and oblique impact conditions. The erosive wear behaviour of composite coatings is discussed and related to the unique microstructure of these coatings.

  14. Reactividad entre whiskers de α-SiC y aluminio durante el procesado por vía líquida de materiales compuestos de matriz metálica

    Directory of Open Access Journals (Sweden)

    Ureña, A.

    1999-06-01

    Full Text Available The reactivity between α-SiC whiskers and an aluminium alloy (Al-Cu-Mg, both present in a metal matrix composite, has been studied when such matrix is in molten state. Using mainly transmission electron microscopy (TEM and electron microdiffraction (ED, the nature and morphology of the reaction products generated at the α-SiC/aluminium interface, when this last melts under different condition which simulate casting and welding procedures for metal matrix composites, have been characterised. Both the formation of Al4C3 aggregates with platelet morphology generated by dissolution-reaction mechanisms, and aciculate crystals of the same carbide form by complete dissolution of the α-SiC whiskers and later Al4C3 precipitation into the molten aluminium. Ternary Al-Si carbides with high chemical stability have been also identified by TEMED (β-Al4SiC4, being its formation related with higher energetic conditions than for the Al4C3.

    Se realiza un estudio de la reactividad entre whiskers de α-SiC y una aleación de aluminio en estado líquido (Al-Cu-Mg, que forman parte de un material compuesto de matriz metálica. Empleando fundamentalmente técnicas de microscopía electrónica de barrido (MEB y de transmisión (MET, junto con difracción de electrones (DE, se ha caracterizado la naturaleza y morfología de los productos de reacción que se generan en la intercara α-SiC/aluminio, cuando éste funde en diferentes condiciones que simulan procesos de fabricación y soldadura del material compuesto. Se ha observado tanto la formación de agregados de Al4C3 con morfología tabular producidos por mecanismos de disolución-reacción de los whiskers, como de cristales aciculares del mismo tipo de carburo formados por disolución total de α-SiC y precipitación en el aluminio fundido. Se ha determinado también que, en condiciones suficientemente energéticas, pueden llegar a formarse carburos ternarios de aluminio y silicio (β-Al4SiC4 que

  15. Effects of superfine refractory carbide additives on microstructure and mechanical properties of TiB{sub 2}–TiC+Al{sub 2}O{sub 3} composite ceramic cutting tool materials

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Bin, E-mail: zou20011110@163.com [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High Efficiency and Clean Mechanical Manufacture, Shandong University, Ministry of Education (China); Ji, Wenbin; Huang, Chuanzhen; Wang, Jun [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High Efficiency and Clean Mechanical Manufacture, Shandong University, Ministry of Education (China); Li, Shasha [Shandong Special Equipment Inspection Institute, Jinan 250013 (China); Xu, Kaitao [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High Efficiency and Clean Mechanical Manufacture, Shandong University, Ministry of Education (China)

    2014-02-05

    Highlights: • The superfine carbides determined the mechanical properties of composites. • Superfine HfC or TaC caused some oxide impurities in composites. • Superfine VC or NbC refined and homogenized the microstructure. • Failure of composites containing HfC or TaC was produced by larger grains. • Composite containing VC exhibited more bridging and transcrystalline failure. -- Abstract: A study to increase the mechanical properties of TiB{sub 2}–TiC+Al{sub 2}O{sub 3} composite ceramic cutting tool material by using superfine refractory carbide additives is presented. Four superfine refractory carbides are considered to investigate their effects on the phase composition, element distribution, grain size, fracture surface, crack propagation of the metal ceramic. The physicochemical properties of superfine carbides, such as chemical activities and atom radius, were found to have the significant effects on the microstructure and mechanical properties of the metal ceramic. Hafnium carbide (HfC) and Tantalum carbide (TaC) reduced the mechanical properties of the metal ceramic because of their poor solubility with the Ni binder phase and the formation of oxides. The mechanical properties of the metal ceramic were increased by the addition of superfine niobium carbide (NbC) and vanadium carbide (VC), and their optimum values were a flexural strength of 1100 ± 62 MPa, fracture toughness of 8.5 ± 0.8 MPa.m1/2 and hardness of 21.53 ± 0.36 GPa, respectively, when 3.2 wt% superfine VC was used.

  16. How do seal whiskers suppress vortex shedding

    Science.gov (United States)

    Rinehart, Aidan; Flaherty, Justin; Bunjavick, Joseph; Shyam, Vikram; Zhang, Wei

    2016-11-01

    Certain seal whiskers possess a unique geometry that significantly reduces the vortex-induced vibration; which has attracted great attention to understand how the unique shape re-organizes the wake structure and its potential for passive flow control. The shape of the whiskers can be described as an elliptical cross-section that is lofted along the length of the whisker. Along the entire length of the whisker the ellipse varies in major and minor axis as well as angle of incidence with respect to the axis of the whisker. Of particular interest in this study is to identify what effect the angle of incidence has on the flow structure around the whisker, which has been overlooked in the past. The study will analyze the wake structure behind various scaled-up whisker models using particle image velocimitry (PIV). These whisker models share common geometry dimensions except for the angle of incidence. Flow conditions are created in a water channel and a wind tunnel, covering a wide range of Reynolds number (a few hundreds to thousands), similar to the ambient flow environment of seals and to the targeted aero-propulsion applications. This study will help address knowledge gaps in understanding of how certain geometry features of seal whiskers influence the wake and establish best practices for its application as effective passive flow control strategy.

  17. Spark plasma sintering of mechanically alloyed in situ copper-niobium carbide composite

    Energy Technology Data Exchange (ETDEWEB)

    Long, B.D. [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Othman, R. [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Umemoto, M. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Zuhailawati, H., E-mail: zuhaila@eng.usm.m [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

    2010-09-03

    A Cu-NbC composite with high electrical conductivity and high microhardness was synthesized by mechanical alloying and densified using spark plasma sintering (SPS). Mixtures of Cu-NbC powders corresponding to volume fractions of 1, 5, 15 and 25 vol% NbC were milled in a high energy planetary mill under argon atmosphere for 30 h using ethanol as process control agent. The Cu-NbC as-milled powder was sintered using spark plasma sintering temperatures between 900 and 1000 {sup o}C. X-ray diffraction investigation showed that NbC started to form in the copper matrix during ball milling and the reaction between Nb and C was completed after 10 min of SPS sintering. Electrical conductivity and density of the Cu-15 vol% NbC composite increased with increasing sintering temperature. The results showed the superior properties of SPS-prepared Cu-NbC composite: electrical conductivity is almost 4 times higher and microhardness is 3.5 times higher than with normal sintering. A highest density of 98% and electrical conductivity of 45.6% IACS were obtained in the Cu-1 vol% NbC composite. The highest microhardness of 452.9 Hv was achieved in the Cu-25 vol% NbC composite.

  18. Electrochemical characterization of niobium carbide reinforced composites for the production of industrial gases

    Energy Technology Data Exchange (ETDEWEB)

    Silva, A.S.; Scatena, H. Jr.; Martinelli, A.E.; Alves, C. Jr. [Programa de Doutorado em Engenharia e Ciencias de Materiais, UFRN, Natal, RN (Brazil)

    2003-07-01

    The main goal of the present investigation is to analyze the use of Fe-NbC composites in the electrogeneration of industrial gases. The effect of the experimental parameters involved in the processing of PM composites on the performance of the resulting electrodes is also investigated. Cylindrical composite pellets were sintered varying their composition, sintering temperature and time, and compaction pressure. The resulting electrodes were characterized from the standpoint of their inherent electrical resistance, electrical resistance in NaOH 1M solution, and porosity. The electrical resistance of the composite electrode in solution was obtained from voltammetric tests carried out from -1V to 1.5V. The scan rate was set to 10mV/s. The results obtained up to this point showed that the sintering temperature has a major effect in determining the electrical resistance of the electrode in solution. Other manufacturing aspects have less important effects on that property. The onset of oxygen generation took place at approximately 0.6V (vs. Ag/AgCl) and the optimum potential at 100mA/cm{sup 2} was 0.94V. (orig.)

  19. Tin Whisker Testing and Modeling

    Science.gov (United States)

    2015-11-01

    contamination , and post-assembly contamination methods 40 5.2.3 Environmental exposure, whisker measurements and metallurgical analysis 42 5.3 Results and...The roughness is partly a result of the shrinkage of the liquid between the primary tin dendrites. The roughness tends to trap contamination , which...diameter, density, and distribution were measured. 5.2.3.3 Metallurgical analysis To examine contamination levels and distributions, as-received

  20. Developing scandium and zirconium containing aluminum boron carbide metal matrix composites for high temperature applications

    Science.gov (United States)

    Lai, Jing

    The study presented in this thesis focuses on developing castable, precipitation-strengthened Al--B4C metal matrix composites (MMCs) for high temperature applications. In the first part, B4C plates were immersed in liquid aluminum alloyed with Sc, Zr and Ti to investigate the interfacial reactions between B4C and liquid aluminum The influences of Sc, Zr and Ti on the interfacial microstructure in terms of individual and combined additions were examined. Results reveal that all three elements reacted with B4C and formed interfacial layers that acted as a diffusion barrier to limit the decomposition of B4C in liquid aluminum. The interfacial reactions and the reaction products in each system were identified. With the combined addition of Sc, Zr and Ti, most of the Ti was found to enrich at the interface, which not only offered appropriate protection of the B4C but also reduced the consumption of Sc and Zr at the interface. In the second part, Sc and Zr were introduced into Al-15vol.% B 4C composites presaturated by Ti, and eight experimental composites with different Sc and Zr levels were prepared via a conventional casting technique. It was found that Sc was involved in the interfacial reactions with B 4C that partially consume Sc. The Sc addition yielded considerable precipitation strengthening in the as-cast and peak aged conditions. To achieve an equivalent strengthening effect of Sc in binary Al-Sc alloys, approximately double the amount of Sc is required in Al-B4C composites. On the contrary, no major Zr reaction products were found at the interfaces and the major part of Zr remained in the matrix for the precipitation strengthening. The combination of Sc and Zr enhanced sthe precipitation strengthening. Two kinds of nanoscale precipitates, Al3Sc and Al3(Sc, Zr), were found in the as-cast microstructure and contributed to the increase in the matrix hardness. In the third part, all the experimental composites were isothermally aged at 300, 350, 400 and 450

  1. Formation of nanoscale titanium carbides in ferrite: an atomic study

    Science.gov (United States)

    Lv, Yanan; Hodgson, Peter; Kong, Lingxue; Gao, Weimin

    2016-03-01

    The formation and evolution of nanoscale titanium carbide in ferrite during the early isothermal annealing process were investigated via molecular dynamics simulation. The atomic interactions of titanium and carbon atoms during the initial formation process explained the atoms aggregation and carbides formation. It was found that the aggregation and dissociation of titanium carbide occurred simultaneously, and the composition of carbide clusters varied in a wide range. A mechanism for the formation of titanium carbide clusters in ferrite was disclosed.

  2. Carbothermal synthesis of silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Janney, M.A.; Wei, G.C.; Kennedy, C.R.; Harris, L.A.

    1985-05-01

    Silicon carbide powders were synthesized from various silica and carbon sources by a carbothermal reduction process at temperatures between 1500 and 1600/sup 0/C. The silica sources were fumed silica, methyltrimethoxysilane, and microcrystalline quartz. The carbon sources were petroleum pitch, phenolic resin, sucrose, and carbon black. Submicron SiC powders were synthesized. Their morphologies included equiaxed loosely-bound agglomerates, equiaxed hard-shell agglomerates, and whiskers. Morphology changed with the furnace atmosphere (argon, nitrogen, or nitrogen-4% hydrogen). The best sintering was observed in SiC derived from the fumed-silica-pitch and fumed-silica-sucrose precursors. The poorest sintering was observed in SiC derived from microcrystalline quartz and carbon black. 11 refs., 16 figs., 10 tabs.

  3. Research on Laser Cladded Nickel Based Nanometer Tungsten Carbide Composite Coating

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guang-jun; DAI Jian-qiang; WANG Hui-ping; YAN Min-jie; XI Wen-long; ZOU Chang-gu; GE Da-fang

    2004-01-01

    CO2 laser is adopted on the surface of austenitic stainless steel (1Cr18Ni9) to clad nickel based nanometer WC/Co composite coating. SEM, EDAX, XRD, AFM and Scratch Testers are adopted to conduct analysis and research on the microstructure, composition, phase and bonding strength of the coating. Results indicate that the microstructure of coating is metallurgically bonded with stainless steel base, eliminating porosities and cracks. The coating has a considerable quantity of nanometer particles visible with a granularity ≤ 100nm under a nanoscope atomic microscope. The bonding strength of the laser cladded coating is remarkably improved respectively compared with conventional hot-sprayed coating and spray welding. The nanometer effect of nanometer WC/Co introduced into the coating plays an important role in the laser cladding processes.

  4. Research on Laser Cladded Nickel Based Nanometer Tungsten Carbide Composite Coating

    Institute of Scientific and Technical Information of China (English)

    ZHANGGuang-jun; DAIJian-qiang; WANGHui-ping; YANMin-jie; XIWen-long; ZOUChang-gu; GEDa-fang

    2004-01-01

    CO2 laser is adopted on the surface of austenitic stainless steel (1Cr18Ni9) to clad nickel based nanometer WC/Co composite coating. SEM, EDAX, XRD, AFM and Scratch Testers are adopted to conduct analysis and research on the microstructure, composition, phase and bonding strength of the coating. Results indicate that the microstructure of coating is metallurgically bonded with stainless steel base, eliminating porosities and cracks. The coating has a considerable quantity of nanometer particles visible with a granularity ≤100nm under a nanoscope atomic microscope. The bonding strength of the laser cladded coating is remarkably improved respectively compared with conventional hot-sprayed coating and spray welding. The nanometer effect of nanometer WC/Co introduced into the coating plays an important role in the laser cladding processes.

  5. Aligned Carbon Nanotube Reinforced Silicon Carbide Composites by Chemical Vapor Infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Zhan Jun [University of Georgia, Athens, GA; Yang, Ying Chao [University of South Carolina, Columbia; Li, Kai Yuan [University of Georgia, Athens, GA; Tao, Xin Yong [University of South Carolina, Columbia; Eres, Gyula [ORNL; Howe, Jane Y [ORNL; Zhang, Li Tong [Northwestern Polytechnical University, Xi' an, China; Li, Xiao Dong [University of South Carolina, Columbia; Pan, Zhengwei [ORNL

    2011-01-01

    Owing to their exceptional stiffness and strength1 4, carbon nanotubes (CNTs) have long been considered to be an ideal reinforcement for light-weight, high-strength, and high-temperature-resistant ceramic matrix composites (CMCs)5 10. However, the research and development in CNT-reinforced CMCs have been greatly hindered due to the challenges related to manufacturing including poor dispersion, damages during dispersion, surface modification, densification and sintering, weak tube/matrix interfaces, and agglomeration of tubes at the matrix grain boundaries5,11. Here we report the fabrication of high-quality aligned CNT/SiC composites by chemical vapor infiltration (CVI), a technique that is being widely used to fabricate commercial continuous-filament CMCs12 15. Using the CVI technique most of the challenges previously encountered in the fabrication of CNT composites were readily overcome. Nanotube pullouts, an important toughening mechanism for CMCs, were consistently observed on all fractured CNT/SiC samples. Indeed, three-point bending tests conducted on individual CNT/SiC nanowires (diameters: 50 200 nm) using an atomic force microscope show that the CNT-reinforced SiC nanowires are about an order of magnitude tougher than the bulk SiC. The tube/matrix interface is so intimate and the SiC matrix is so dense that a ~50-nm-thick SiC coating can effectively protect the inside nanotubes from being oxidized at 1600 C in air. The CVI method may be extended to produce nanotube composites from a variety of matrix

  6. Diffusion Bonding of Silicon Carbide Particulate Reinforced 2024 A1 Composites

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@A study has been made on diffusion bonding of SiCp/2024Al composites by means of pure Al interlayer. In the condition of TB=843 K, PB=16 MPa, tB=-60 min, the diffusion bonded joint,with a shear strength of 235 MPa, was obtained when a 15μm thick interlayer was used. The results of the shear testing and SEM indicate that fracture of the joint presented characteristics of ductile rupture.

  7. Studies on Mechanical Behaviour of Aluminium/Nickel Coated Silicon Carbide Reinforced Functionally Graded Composite

    Directory of Open Access Journals (Sweden)

    A. Mohandas

    2017-06-01

    Full Text Available The aim of the work is to fabricate functionally graded aluminium (Al-Si6Cu/ nickel coated SiC metal matrix composite using centrifugal casting route. SiC particles (53-80 µm were coated with nickel using electroless coating technique to enhance the wettability with aluminium matrix. Several attempts were made to coat nickel on SiC by varying the process temperature (65 °C, 75 °C, and 85 °C to obtain a uniform coating. Silicon particles coated with nickel were characterised using EDS enabled Field Emission Scanning Electron Microscope and it was found that the maximum nickel coating on SiC occurred at a process temperature of 75°C. This nickel coated SiC particles were used as the reinforcement for the manufacture of functionally graded metal matrix composite and a cast specimen of dimensions 150×90×15 mm was obtained. To ensure the graded properties in the fabricated composites, microstructure (at a distance of 1, 7 and 14 mm and hardness (at a distance of 1, 3, 7, 10 and 14 mm from outer periphery taken in the radial direction was analysed using Zeiss Axiovert metallurgical microscope and Vickers micro hardness tester respectively. The microstructure reveals presence of more SiC particles at the outer periphery compared to inner periphery and the hardness test shows that the hardness also decreased from outer periphery (90 HV to inner periphery (78 HV.Tensile strength of specimen from outer zone (1-7mm and inner zone (8-14 mm of casting was also tested and found out a value of 153.3 Mpa and 123.3 Mpa for the outer zone and inner zone respectively. An important observation made was that the outer periphery of casting was particle rich and the inner periphery was particle deficient because of centrifugal force and variation in density between aluminium matrix and reinforcement. Functionally graded Al/SiC metal matrix composite could be extensively used in automotive industry especially in the manufacture of liners and brake drums.

  8. Influence of Interfacial Carbide Layer Characteristics on Thermal Properties of Copper-Diamond Composites (Postprint)

    Science.gov (United States)

    2014-04-01

    wettability of diamond is not an issue. Moreover, the solid-state processing can, in principle , be carried out at relatively low temperatures even for non...capacity. q was mea- sured using Archimedes ’ method, and D was measured with laser flash technique per ASTM E1461. The speci- mens for D measurement...respectively. The CTE of composites was measured with a push -rod dilatometer DIL 402 C (Manufacturer: NET- ZSCH-Gerätebau GmbH, Selb, Germany) per ASTM E228

  9. Rapid whisker movements in sleeping newborn rats.

    Science.gov (United States)

    Tiriac, Alexandre; Uitermarkt, Brandt D; Fanning, Alexander S; Sokoloff, Greta; Blumberg, Mark S

    2012-11-06

    Spontaneous activity in the sensory periphery drives infant brain activity and is thought to contribute to the formation of retinotopic and somatotopic maps. In infant rats during active (or REM) sleep, brainstem-generated spontaneous activity triggers hundreds of thousands of skeletal muscle twitches each day; sensory feedback from the resulting limb movements is a primary activator of forebrain activity. The rodent whisker system, with its precise isomorphic mapping of individual whiskers to discrete brain areas, has been a key contributor to our understanding of somatotopic maps and developmental plasticity. But although whisker movements are controlled by dedicated skeletal muscles, spontaneous whisker activity has not been entertained as a contributing factor to the development of this system. Here we report in 3- to 6-day-old rats that whiskers twitch rapidly and asynchronously during active sleep; furthermore, neurons in whisker thalamus exhibit bursts of activity that are tightly associated with twitches but occur infrequently during waking. Finally, we observed barrel-specific cortical activity during periods of twitching. This is the first report of self-generated, sleep-related twitches in the developing whisker system, a sensorimotor system that is unique for the precision with which it can be experimentally manipulated. The discovery of whisker twitching will allow us to attain a better understanding of the contributions of peripheral sensory activity to somatosensory integration and plasticity in the developing nervous system. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Electric field stimulated growth of Zn whiskers

    Energy Technology Data Exchange (ETDEWEB)

    Niraula, D.; McCulloch, J.; Irving, R.; Karpov, V. G. [Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Warrell, G. R.; Shvydka, Diana, E-mail: diana.shvydka@utoledo.edu [Department of Radiation Oncology, University of Toledo Health Science Campus, Toledo, Ohio 43614 (United States)

    2016-07-15

    We have investigated the impact of strong (∼10{sup 4} V/cm) electric fields on the development of Zn whiskers. The original samples, with considerable whisker infestation were cut from Zn-coated steel floors and then exposed to electric fields stresses for 10-20 hours at room temperature. We used various electric field sources, from charges accumulated in samples irradiated by: (1) the electron beam of a scanning electron microscope (SEM), (2) the electron beam of a medical linear accelerator, and (3) the ion beam of a linear accelerator; we also used (4) the electric field produced by a Van der Graaf generator. In all cases, the exposed samples exhibited a considerable (tens of percent) increase in whiskers concentration compared to the control sample. The acceleration factor defined as the ratio of the measured whisker growth rate over that in zero field, was estimated to approach several hundred. The statistics of lengths of e-beam induced whiskers was found to follow the log-normal distribution known previously for metal whiskers. The observed accelerated whisker growth is attributed to electrostatic effects. These results offer promise for establishing whisker-related accelerated life testing protocols.

  11. Electric field stimulated growth of Zn whiskers

    Science.gov (United States)

    Niraula, D.; McCulloch, J.; Warrell, G. R.; Irving, R.; Karpov, V. G.; Shvydka, Diana

    2016-07-01

    We have investigated the impact of strong (˜104 V/cm) electric fields on the development of Zn whiskers. The original samples, with considerable whisker infestation were cut from Zn-coated steel floors and then exposed to electric fields stresses for 10-20 hours at room temperature. We used various electric field sources, from charges accumulated in samples irradiated by: (1) the electron beam of a scanning electron microscope (SEM), (2) the electron beam of a medical linear accelerator, and (3) the ion beam of a linear accelerator; we also used (4) the electric field produced by a Van der Graaf generator. In all cases, the exposed samples exhibited a considerable (tens of percent) increase in whiskers concentration compared to the control sample. The acceleration factor defined as the ratio of the measured whisker growth rate over that in zero field, was estimated to approach several hundred. The statistics of lengths of e-beam induced whiskers was found to follow the log-normal distribution known previously for metal whiskers. The observed accelerated whisker growth is attributed to electrostatic effects. These results offer promise for establishing whisker-related accelerated life testing protocols.

  12. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-01

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties.

  13. Technology of Iron Carbide Synthesis

    Institute of Scientific and Technical Information of China (English)

    M.Bahgat

    2006-01-01

    Iron carbides are very promising metallurgical products and can be used for steelmaking process, where it plays as an alternative raw material with significant economic advantages. Also it has many other applications,e.g. catalysts, magnets, sensors. The present review investigates the different properties and uses of the iron carbides. The commercial production and the different varieties for the iron carbides synthesis (gaseous carburization, mechanochemical synthesis, laser pyrolysis, plasma pyrolysis, chemical vapor deposition and ion implantation) were reviewed. Also the effect of different factors on the carburization process like gas composition, raw material, temperature, reaction time, catalyst presence and sulfur addition was indicated.

  14. Correlated Strontium and Barium Isotopic Compositions of Acid-Cleaned Single Silicon Carbides from Murchison

    CERN Document Server

    Liu, Nan; Gallino, Roberto; Davis, Andrew M; Bisterzo, Sara; Gyngard, Frank; Kaeppeler, Franz; Cristallo, Sergio; Dauphas, Nicolas; Pellin, Michael J; Dillmann, Iris

    2015-01-01

    We present strontium, barium, carbon, and silicon isotopic compositions of 61 acid-cleaned presolar SiC grains from Murchison. Comparison with previous data shows that acid washing is highly effective in removing both strontium and barium contamination. For the first time, by using correlated $^{88}Sr$/$^{86}Sr$ and $^{138}Ba$/$^{136}Ba$ ratios in mainstream SiC grains, we are able to resolve the effect of $^{13}C$ concentration from that of $^{13}C$-pocket mass on s-process nucleosynthesis, which points towards the existence of large $^{13}C$-pockets with low $^{13}C$ concentration in AGB stars. The presence of such large $^{13}$R-pockets with a variety of relatively low $^{13}C$ concentrations seems to require multiple mixing processes in parent AGB stars of mainstream SiC grains.

  15. Experimental characterization and mechanical behaviour modelling of molybdenum-titanium carbide composite for high temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Cedat, D.; Libert, M.; Rey, C.; Clavel, M.; Schmitt, J.H. [Ecole Cent Paris, MSSMAT, F-92295 Chatenay Malabry (France); Le Flem, M. [CEA Saclay, DEN, DANS, DMN, SRMA, 91 - Gif-sur-Yvette (France); Fandeur, O. [CEA Saclay, DEN, DANS, DM2S, SEMT, LM2S, 91 - Gif-sur-Yvette (France)

    2009-03-15

    Simulations of the elastic-viscoplastic behaviour of ceramic-metal composite, over the temperature range 298-993 K, are performed on realistic aggregates built up from electron back scatter diffraction methods. Physical based constitutive models are developed in order to characterize the deformation behaviour of body centered cubic (bcc) metal and face centered cubic (fcc) ceramic under various temperatures. While the ceramic keeps elastic, the viscoplastic behaviour of the metal part is described with a dislocation - based model, implemented in the finite element code ABAQUS, in order to compute local strain and stress fields during compressive tests. It is shown that the adopted constitutive laws are able to give back local complex experimental evidence on weak points of the microstructure. (authors)

  16. CORRELATED STRONTIUM AND BARIUM ISOTOPIC COMPOSITIONS OF ACID-CLEANED SINGLE MAINSTREAM SILICON CARBIDES FROM MURCHISON

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Nan; Savina, Michael R.; Gallino, Roberto; Davis, Andrew M.; Bisterzo, Sara; Gyngard, Frank; Käppeler, Franz; Cristallo, Sergio; Dauphas, Nicolas; Pellin, Michael J.; Dillmann, Iris

    2015-04-08

    We present strontium, barium, carbon, and silicon isotopic compositions of 61 acid-cleaned presolar SiC grains from Murchison. Comparison with previous data shows that acid washing is highly effective in removing both strontium and barium contamination. For the first time, by using correlated Sr-88/Sr-86 and Ba-138/Ba-136 ratios in mainstream SiC grains, we are able to resolve the effect of C-13 concentration from that of C-13-pocket mass on s-process nucleosynthesis, which points toward the existence of large C-13 pockets with low C-13 concentrations in asymptotic giant branch stars. The presence of such large C-13 pockets with a variety of relatively low C-13 concentrations seems to require multiple mixing processes in parent asymptotic giant branch stars of mainstream SiC grains.

  17. CORRELATED STRONTIUM AND BARIUM ISOTOPIC COMPOSITIONS OF ACID-CLEANED SINGLE MAINSTREAM SILICON CARBIDES FROM MURCHISON

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Nan; Davis, Andrew M.; Dauphas, Nicolas; Pellin, Michael J. [Department of the Geophysical Sciences, The University of Chicago, Chicago, IL, 60637 (United States); Savina, Michael R. [Chicago Center for Cosmochemistry, Chicago, IL 60637 (United States); Gallino, Roberto; Bisterzo, Sara [Dipartimento di Fisica, Università di Torino, I-10125 Torino (Italy); Gyngard, Frank [Laboratory for Space Sciences, Washington University, St. Louis, MO 63130 (United States); Käppeler, Franz [Karlsruhe Institute of Technology, Institut für Kernphysik, Karlsruhe D-76021 (Germany); Cristallo, Sergio [INAF, Osservatorio Astronomico di Collurania, I-64100 Teramo (Italy); Dillmann, Iris, E-mail: lnsmile@uchicago.edu [TRIUMF, 4004 Wesbrook Mall, Vancouver BC V6T 2A3 (Canada)

    2015-04-10

    We present strontium, barium, carbon, and silicon isotopic compositions of 61 acid-cleaned presolar SiC grains from Murchison. Comparison with previous data shows that acid washing is highly effective in removing both strontium and barium contamination. For the first time, by using correlated {sup 88}Sr/{sup 86}Sr and {sup 138}Ba/{sup 136}Ba ratios in mainstream SiC grains, we are able to resolve the effect of {sup 13}C concentration from that of {sup 13}C-pocket mass on s-process nucleosynthesis, which points toward the existence of large {sup 13}C pockets with low {sup 13}C concentrations in asymptotic giant branch stars. The presence of such large {sup 13}C pockets with a variety of relatively low {sup 13}C concentrations seems to require multiple mixing processes in parent asymptotic giant branch stars of mainstream SiC grains.

  18. Research of Boron Carbide-Aluminum Composites%碳化硼-铝复合材料的研究进展

    Institute of Scientific and Technical Information of China (English)

    刘明朗; 韩增尧; 郎静; 马南钢; 吴骁行

    2011-01-01

    Boron carbide ceramics have the properties of high hardness, high melting point and low density, they will be more widely used if they can combine with Al to overcome their faults. Boron carbide-aluminum composites can be divided into aluminum matrix and boron carbide matrix according to the different matrix. The preparation process,interface reaction and wettability are presented in this paper, and the developing tendency of this materials is pointed out Finally, it is pointed out that this materails will be widely used in the fields of large area protection with the deepening of the research.%碳化硼陶瓷具有高硬度、高熔点、低密度的特点,将其与金属铝复合能克服自身缺陷,使其得到更广泛的应用.碳化硼-铝复合材料按照基体的不同可分为铝基和碳化硼基两大类,分别综述了其制备工艺、界面反应以及润湿性,并展望了其发展方向,最后指出,随着研究的深入该复合材料将在大面积防护领域得到广泛应用.

  19. Behavioral detection of passive whisker stimuli requires somatosensory cortex.

    Science.gov (United States)

    Miyashita, Toshio; Feldman, Daniel E

    2013-07-01

    Rodent whisker sensation occurs both actively, as whiskers move rhythmically across objects, and in a passive mode in which externally applied deflections are sensed by static, non-moving whiskers. Passive whisker stimuli are robustly encoded in the somatosensory (S1) cortex, and provide a potentially powerful means of studying cortical processing. However, whether S1 contributes to passive sensation is debated. We developed 2 new behavioral tasks to assay passive whisker sensation in freely moving rats: Detection of unilateral whisker deflections and discrimination of right versus left whisker deflections. Stimuli were simple, simultaneous multi-whisker deflections. Local muscimol inactivation of S1 reversibly and robustly abolished sensory performance on these tasks. Thus, S1 is required for the detection and discrimination of simple stimuli by passive whiskers, in addition to its known role in active whisker sensation.

  20. Tapered whiskers are required for active tactile sensation

    Science.gov (United States)

    Hires, Samuel Andrew; Pammer, Lorenz; Svoboda, Karel; Golomb, David

    2013-01-01

    Many mammals forage and burrow in dark constrained spaces. Touch through facial whiskers is important during these activities, but the close quarters makes whisker deployment challenging. The diverse shapes of facial whiskers reflect distinct ecological niches. Rodent whiskers are conical, often with a remarkably linear taper. Here we use theoretical and experimental methods to analyze interactions of mouse whiskers with objects. When pushed into objects, conical whiskers suddenly slip at a critical angle. In contrast, cylindrical whiskers do not slip for biologically plausible movements. Conical whiskers sweep across objects and textures in characteristic sequences of brief sticks and slips, which provide information about the tactile world. In contrast, cylindrical whiskers stick and remain stuck, even when sweeping across fine textures. Thus the conical whisker structure is adaptive for sensor mobility in constrained environments and in feature extraction during active haptic exploration of objects and surfaces. DOI: http://dx.doi.org/10.7554/eLife.01350.001 PMID:24252879

  1. Dry sliding friction and wear behaviors of Mg2B2O5 whisker reinforced 6061Al matrix composites%硼酸镁晶须增强6061铝基复合材料的干摩擦磨损行为

    Institute of Scientific and Technical Information of China (English)

    金培鹏; 陈庚; 韩丽; 王金辉

    2014-01-01

    The friction and wear properties of Mg2B2O5 whisker reinforced 6061Al matrix composite fabricated via power ultrasonic-stir casting process were investigated using a ball-on-disk wear-testing machine against a GCr45 steel counterface under dry sliding conditions. The reinforcements include as-received Mg2B2O5 whiskers and Mg2B2O5 whiskers coated with CuO and ZnO. The volume fraction of the composites is 2%. The relationship between the wear rate and the coefficient of friction was discussed. The results indicate that the wear rate of the Mg2B2O5 whiskers coated with ZnO reinforced aluminum matrix composites is the lowest among the materials. As the applied load and sliding speed steadily increase the coefficients of friction and wear rates of the as-received matrix alloy and the fabricated composites decrease. As the applied load and sliding speed increase, the wear mechanisms of the composites shift from a mild to a severe regime.%研究搅拌铸造工艺制备的硼酸镁晶须增强6061铝基复合材料在干滑动条件下的摩擦磨损性能。复合材料的体积分数为2%,根据增强体种类,材料分别记为:Al基体、Mg2B2O5w/6061Al、ZnO/Mg2B2O5w/6061Al和CuO/Mg2B2O5w/6061Al;讨论磨损速率和摩擦因数之间的关系。结果表明:在4种材料中,ZnO/Mg2B2O5w/6061Al复合材料的磨损率最低。随着载荷和滑动速度的增大,基体和复合材料的摩擦因数和磨损率降低,摩擦磨损机制由轻微磨损机制转向严重磨损机制。

  2. Modeling of burr size in drilling of aluminum silicon carbide composites using response surface methodology

    Directory of Open Access Journals (Sweden)

    Avinash A. Thakre

    2016-09-01

    Full Text Available Exit burrs produced during various machining processes degrade the product quality and functionality of different parts of assembly. It is essential to select the optimum tool geometry and process parameters for minimizing the burr formation during machining. In this paper, the effects of cutting speed, feed rate, point angle of drill bits and concentration of the reinforcements on the burrs produced were investigated. Response surface methodology has been adopted to create the quadratic model for the height and thickness of the burrs produced during drilling of AlSiC composites. Analysis of means and variance were used to find the significance of the process parameters on the responses and to find the optimum combination of parameters to minimize the burr formation. Feed rate, point angle and concentration of reinforcements in the matrix are found to be the significant factors. Both the responses were found to be minimum for lower feed rate, higher point angle and higher concentration of reinforcements. Scanning electron microscopy was used to understand the mechanism of burr formation.

  3. Microstructure and mechanical behavior of stir-cast Zn–27Al based composites reinforced with rice husk ash, silicon carbide, and graphite

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo Alaneme

    2017-04-01

    Full Text Available The microstructure and mechanical properties of Zn–27Al based composites reinforced with rice husk ash (RHA, silicon carbide (SiC, and graphite (Cg particles have been investigated. The Zn–27Al composites consisting of varied weight ratios of the reinforcing materials were produced using the stir casting process. Hardness test, tensile properties evaluation, fracture toughness determination, and microstructural examination, were used to characterize the composites produced. Results show that the microstructures of the composites are similar, consisting of the dendritic structure of the Zn–27Al alloy matrix with fine dispersion of the reinforcing particles. The hardness of the composites decreased with increase in the weight percent of RHA (and corresponding decrease in SiC weight percent in the reinforcement. The tensile strength and yield strength decreased slightly with increase in the weight ratio of RHA in the composites with a maximum of 8.5% and 9.6% reductions respectively observed for as much as 40% RHA (corresponding to 40% reduction in SiC in the hybrid reinforcement. Although some of the composite compositions containing RHA had slightly higher % elongation values compared with those without RHA, it was generally observed that the % elongation was invariant to the composite RHA content. The fracture toughness of the composites increases with increase in the weight percent of RHA with as much as a 20% increase obtained for as much as 40% RHA (corresponding to 40% reduction in SiC in the hybrid reinforcement.

  4. Study on the influence of rutile nano-TiO2 on performance of CaSO4 whisker/PP-R resin composite%金红石型纳米TiO2对CaSO4晶须/PP-R树脂复合材料性能的影响

    Institute of Scientific and Technical Information of China (English)

    邹敏; 王琪琳

    2009-01-01

    以金红石型纳米TiO2为添加剂改善了CaSO4晶须/PP-R树脂复合材料的各项性能,并研究了金红石型纳米TiO2对PP-R树脂的力学性能、耐热性能和紫外老化性能的影响.研究结果表明:由于纳米TiO2和CaSO4晶须的协同作用,添加纳米TiO2后可进一步提高CaSO4晶须/PP-R树脂复合材料的力学性能和耐热性能;金红石纳米TiO2的加入可以大幅度提高PP-R树脂的耐紫外老化性能,添加5%纳米TiO2后的CaSO4晶须/PP-R树脂复合材料经紫外辐射72 d后,其拉伸强度仅下降了0.36MPa,冲击强度仅下降了0.36kJ·m-2,熔融温度仅下降了5.4℃;而未添加纳米TiO2的CaSO4晶须/PP-R树脂复合材料的拉伸强度下降了1.96MPa,冲击强度下降了1.47kJ·m-2,熔融温度下降了18.6℃.%The performances of CaSO4 whisker/PP-R resin composites, such as the mechanics performance, heat performance and ultraviolet aging performance, had been improved by adding rutile nanometer titanium dioxide. The results showed that adding the rutile nano-TiO2 can improve the performances of CaSO4 whisker/PP-R resin composite farther than adding CaSO4 whisker only because of the cooperation of two stuffs. The results also showed the ultraviolet aging performance of CaSO4 whisker/PP-R resin composite adding 5% can be improved greatly. The rutile nano-TiO2/CaSO4 whisker/PP-R resin composite radiated by UV after 72days, it's tensile strength was 0. 36MPa, Intensity of impact was 0. 36KJ·m-2 and it' s softening point was 5. 4℃. But the CaSO4 whisker/PP-R resin composite radiated by UV after 72days, it's tensile strength was 1.96MPa, Intensity of impact was 1.46KJ·m-2 and it's softening point cut was 18. 6℃.

  5. Corrosion and wear behaviour of Al–Mg–Si alloy matrix hybrid composites reinforced with rice husk ash and silicon carbide

    OpenAIRE

    Kenneth Kanayo Alaneme; Tolulope Moyosore Adewale; Peter Apata Olubambi

    2014-01-01

    The corrosion and wear behaviour of Al–Mg–Si alloy matrix hybrid composites developed with the use of rice husk ash (RHA) and silicon carbide (SiC) particulates as reinforcements were investigated. RHA and SiC mixed in weight ratios 0:1, 1:3, 1:1, 3:1, and 1:0 were utilized to prepare 5, 7.5 and 10 wt% of the reinforcing phase with Al Mg Si alloy as matrix using double stir casting process. Open circuit corrosion potential (OCP) and potentiodynamic polarization measurements were used to study...

  6. Creep behavior and wear resistance of Al 5083 based hybrid composites reinforced with carbon nanotubes (CNTs) and boron carbide (B{sub 4}C)

    Energy Technology Data Exchange (ETDEWEB)

    Alizadeh, Ali [Faculty of Materials & Manufacturing Processes, Malek-e-Ashtar University of Technology, Tehran (Iran, Islamic Republic of); Abdollahi, Alireza, E-mail: alirezaabdollahi1366@gmail.com [Faculty of Materials & Manufacturing Processes, Malek-e-Ashtar University of Technology, Tehran (Iran, Islamic Republic of); Biukani, Hootan [Faculty of Engineering, South Tehran Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2015-11-25

    In the current research, aluminum based hybrid composite reinforced with boron carbide (B{sub 4}C) and carbon nanotubes (CNTs) was produced by powder metallurgy method. creep behavior, wear resistance, surface roughness, and hardness of the samples were investigated. To prepare the samples, Al 5083 powder was milled with boron carbide particles and carbon nanotubes using planetary ball mill under argon atmosphere with ball-to-powder weight ratio of 10:1 for 5 h. Afterwards, the milled powders were formed by hot press process at 380{sup °}C and then were sintered at 585{sup °}C under argon atmosphere for 2 h. There was shown to be an increase in hardness values of composite with an increase in B{sub 4}C content. The micrograph of worn surfaces indicate a delamination mechanism due to the presence of CNTs and abrasion mechanism in composite containing 10 vol.%B{sub 4}C. Moreover, it was shown that increasing B{sub 4}C content increases the wear resistance by 3 times under a load of 20 N and 10 times under a load of 10 N compared to CNTs-reinforced composite. surface roughness of the composite containing 5 vol.%CNT has shown to be more than other samples. The results of creep test showed that adding carbon nanotubes increases creep rate of Al 5083 alloy; however, adding B{sub 4}C decreases its creep rate. - Highlights: • Al 5083/(CNTs + B{sub 4}C) hybrid composite was produced by powder metallurgy method. • Creep behavior, wear resistance, surface roughness, and Hardness of samples were investigated. • Addition of CNTs to Al 5083 matrix reduces alloy hardness, wear resistance and creep strength. • By addition of B{sub 4}C and composite hybridization, creep strength and wear resistance increased. • Surface roughness of Al-5 vol.%CNT has shown to be more than other samples.

  7. Tactile object localization by anticipatory whisker motion.

    Science.gov (United States)

    Voigts, Jakob; Herman, David H; Celikel, Tansu

    2015-01-15

    Rodents use rhythmic protractions of their whiskers to locate objects in space. The amplitude of these protractions is reduced when whiskers contact objects, leading to a tendency of whiskers to only lightly touch the environment. While the impact of this process on the sensory input has been studied, little is known about how sensory input causes this change in the motor pattern. Here, using high-speed imaging of whisking in mice, we simultaneously measured whisker contacts and the resulting whisking motion. We found that mice precisely target their whisker protractions to the distance at which they expect objects. This modulation does not depend on the current sensory input and remains stable for at least one whisking cycle when there is no object contact or when the object position is changed. As a result, the timing and other information carried by whisker contacts encodes how well each protraction was matched to the object, functioning as an error signal. Whisker contacts can thus encode a mismatch between expected object locations and the actual environment. Copyright © 2015 the American Physiological Society.

  8. The probabilistic distribution of metal whisker lengths

    Energy Technology Data Exchange (ETDEWEB)

    Niraula, D., E-mail: Dipesh.Niraula@rockets.utoledo.edu; Karpov, V. G., E-mail: victor.karpov@utoledo.edu [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States)

    2015-11-28

    Significant reliability concerns in multiple industries are related to metal whiskers, which are random high aspect ratio filaments growing on metal surfaces and causing shorts in electronic packages. We derive a closed form expression for the probabilistic distribution of metal whisker lengths. Our consideration is based on the electrostatic theory of metal whiskers, according to which whisker growth is interrupted when its tip enters a random local “dead region” of a weak electric field. Here, we use the approximation neglecting the possibility of thermally activated escapes from the “dead regions,” which is later justified. We predict a one-parameter distribution with a peak at a length that depends on the metal surface charge density and surface tension. In the intermediate range, it fits well the log-normal distribution used in the experimental studies, although it decays more rapidly in the range of very long whiskers. In addition, our theory quantitatively explains how the typical whisker concentration is much lower than that of surface grains. Finally, it predicts the stop-and-go phenomenon for some of the whiskers growth.

  9. Modular fabrication and characterization of complex silicon carbide composite structures Advanced Reactor Technologies (ART) Research Final Report (Feb 2015 – May 2017)

    Energy Technology Data Exchange (ETDEWEB)

    Khalifa, Hesham [General Atomics, San Diego, CA (United States)

    2017-08-03

    Advanced ceramic materials exhibit properties that enable safety and fuel cycle efficiency improvements in advanced nuclear reactors. In order to fully exploit these desirable properties, new processing techniques are required to produce the complex geometries inherent to nuclear fuel assemblies and support structures. Through this project, the state of complex SiC-SiC composite fabrication for nuclear components has advanced significantly. New methods to produce complex SiC-SiC composite structures have been demonstrated in the form factors needed for in-core structural components in advanced high temperature nuclear reactors. Advanced characterization techniques have been employed to demonstrate that these complex SiC-SiC composite structures provide the strength, toughness and hermeticity required for service in harsh reactor conditions. The complex structures produced in this project represent a significant step forward in leveraging the excellent high temperature strength, resistance to neutron induced damage, and low neutron cross section of silicon carbide in nuclear applications.

  10. Investigation of Infiltrated and Sintered Titanium Carbide

    Science.gov (United States)

    1952-04-01

    taneive investigations in this field during the ’time preceding this contract, and concentrated their effort® On titanium carbide as the’ refractospy...component • The Basic work of this investigation consisted of? X, KpälfiCÄVtloh and refinement of cOmätrcial grades of titanium carbide hj...facilitate a comparison between the different methods» an investigation was then carried out with composite bodies* consisting of titanium carbide asd

  11. A study on in situ growth of TaC whiskers in Al{sub 2}O{sub 3} matrix powder for ceramic cutting tools

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Guolong [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High-efficiency and Clean Mechanical Manufacture (Shandong University), Ministry of Education (China); Huang, Chuanzhen, E-mail: chuanzhenh@sdu.edu.cn [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High-efficiency and Clean Mechanical Manufacture (Shandong University), Ministry of Education (China); Liu, Hanlian; Xu, Liang; Chong, Xuewen; Zou, Bin; Zhu, Hongtao [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High-efficiency and Clean Mechanical Manufacture (Shandong University), Ministry of Education (China)

    2012-08-15

    Graphical abstract: In situ growth of TaC whiskers (TaC{sub w}) was synthesized in an α-Al{sub 2}O{sub 3} matrix powder via a carbothermal reduction technique. The whiskers were 0.2–0.5 μm in diameter and 5–15 μm in length; they were straight and had smooth surfaces. Highlights: ► In situ growth of TaC whiskers was synthesized in an α-Al{sub 2}O{sub 3} matrix powder. ► The wet mixing method and 1450 °C were suitable for whiskers growth. ► The growth of TaC whiskers is not influenced by the Al{sub 2}O{sub 3} powder. ► The major impurities were TaC particles, nickel and unreacted carbon. -- Abstract: In situ growth of tantalum carbide (TaC) whiskers was synthesized in an α-Al{sub 2}O{sub 3} matrix powder via a carbothermal reduction technique within a temperature range of 1350–1500 °C in an argon atmosphere. The starting materials consisted of Ta{sub 2}O{sub 5}, C, Ni and NaCl powders. Different mixing methods and various reaction temperatures were employed. Most of the prepared whiskers were 0.2–0.5 μm in diameter and 5–15 μm in length. The reaction temperature of 1400–1450 °C was suitable for the growth of TaC whiskers and a wet mixing method was beneficial to increase the whisker yield. Some of the whiskers exhibited the needle shape while others exhibited the screw shape. The growth mechanism of the whiskers was a complex mechanism involving a helical screw dislocation mechanism and a vapor–liquid–solid process. No obvious influences of the Al{sub 2}O{sub 3} matrix powder on the growth of TaC whiskers were found and the major impurities in the obtained powder were TaC particles, nickel and unreacted carbon.

  12. Síntese de "whiskers" de CaSiO3 em fluxo salino para elaboração de biomateriais Synthesis of CaSiO3 "whiskers" in alkaline salt flux for biomaterials reinforcement

    Directory of Open Access Journals (Sweden)

    M. Motisuke

    2012-12-01

    Full Text Available Há tempos empregam-se "whiskers" cerâmicos como reforço de materiais nas mais diversas aplicações, porém os materiais com os quais estes são comumente fabricados (carbeto e nitreto de silício não permitem a sua utilização no campo dos biomateriais devido sua elevada toxicidade. Assim, torna-se interessante sintetizar "whiskers" biocompatíveis capazes de reforçar biomateriais cerâmicos e poliméricos sem prejudicar a saúde dos pacientes. Dessa forma, este trabalho tem como objetivo desenvolver e determinar os parâmetros limitantes de uma nova rota de síntese por fusão de sais de "whiskers" de CaSiO3, uma biocerâmica biocompatível, bioativa e reabsorvível. Este método é simples, barato e permite a produção em larga escala. Utilizou-se um fluxo de NaCl/KCl a 900 ºC para sintetizar "whiskers" de wollastonita, que foram caracterizados por difração de raios X e microscopia eletrônica de varredura. O método proposto mostrou-se eficiente, entretanto os tempos de patamar empregados não foram suficientes para garantir 100% de rendimento da reação de formação de CaSiO3, ocorrendo a formação de cristobalita.Materials reinforcement by ceramic whiskers has been employed for a long time in a variety of industrial applications. Nevertheless, the materials by which these whiskers are commonly made of (carbide and silicon nitride do not allow their use in biomaterials field due to their high toxicity. Then, it is of interest to synthesize ceramic whiskers which could reinforce biocompatible ceramic and polymeric biomaterials without harming the patients' health. In this manner, the aim of this work is to propose and analyze the limiting process variables of a new synthetic route to produce whiskers of CaSiO3 (wollastonite: a biocompatible, bioactive and readsorbable biomaterial. It was employed the molten salt synthesis at 900 ºC to grow wollastonite crystals which were characterized by X-ray diffraction and scanning electron

  13. Contact Whiskers for Millimeter Wave Diodes

    Science.gov (United States)

    Kerr, A. R.; Grange, J. A.; Lichtenberger, J. A.

    1978-01-01

    Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.

  14. 杂化碳化硅填充聚丙烯导热复合材料研究%Research of Hybrid Silicon Carbide Filled Polypropylene Composite Materials

    Institute of Scientific and Technical Information of China (English)

    梁曦锋; 徐睿杰

    2011-01-01

    Plastic was one of the indispensable materials in daily life,which often used to replace or mimic other material products.The general plastic PP was joined with the auxiliary packing such as SiC,PE wax,SiC whisker,and nano SiC,to improve PP's thermal conductivity.The formula was studied by changing the types and composition of packing and making products.The various performances,such as thermal conductivity,tensile properties,vicat softening point and melt index of products,were determined.%本文以PP塑料为基料,加入辅助填料以提高其热导率。本文分为两部分:一是研究并摸索出配方;二是对所得产品的性能进行测定,从而得出结论,通过加入SiC可有效提高热导率,但力学性能有所下降,熔融指数随填料填充量增加而降低。加入PE蜡可改善复合材料的流动性,加入第三组分杂化,可提高材料的热扩散系数。

  15. Spark Plasma Sintering of Aluminum-Magnesium-Matrix Composites with Boron Carbide and Tungsten Nano-powder Inclusions: Modeling and Experimentation

    Science.gov (United States)

    Dvilis, E. S.; Khasanov, O. L.; Gulbin, V. N.; Petyukevich, M. S.; Khasanov, A. O.; Olevsky, E. A.

    2016-03-01

    Spark-plasma sintering (SPS) is used to fabricate fully-dense metal-matrix (Al/Mg) composites containing hard ceramic (boron carbide) and refractory metal (tungsten) inclusions. The study objectives include the modeling (and its experimental verification) of the process of the consolidation of the composites consisted of aluminum-magnesium alloy AMg6 (65 wt.%), B4C powder (15 wt.%), and W nano-powder (20 wt.%), as well as the optimization of the composite content and of the SPS conditions to achieve higher density. Discrete element modeling of the composite particles packing based on the particle size distribution functions of real powders is utilized for the determination of the powder compositions rendering maximum mixture packing densities. Two models: a power-law creep model of the high temperature deformation of powder materials, and an empirical logarithmic pressure-temperature-relative density relationship are successfully applied for the description of the densification of the aluminum-magnesium metal matrix powder composite subjected to spark-plasma sintering. The elastoplastic properties of the sintered composite samples are assessed by nanoindentation.

  16. Space Shuttle Program Tin Whisker Mitigation

    Science.gov (United States)

    Nishimi, Keith

    2007-01-01

    The discovery of tin whiskers (TW) on space shuttle hardware led to a program to investigate and removal and mitigation of the source of the tin whiskers. A Flight Control System (FCS) avionics box failed during vehicle testing, and was routed to the NASA Shuttle Logistics Depot for testing and disassembly. The internal inspection of the box revealed TW growth visible without magnification. The results of the Tiger Team that was assembled to investigate and develop recommendations are reviewed in this viewgraph presentation.

  17. Morphology and properties of soy protein isolate thermoplastics reinforced with chitin whiskers.

    Science.gov (United States)

    Lu, Yongshang; Weng, Lihui; Zhang, Lina

    2004-01-01

    Environmentally friendly thermoplastic nanocomposites were successfully developed using a colloidal suspension of chitin whiskers as a filler to reinforce soy protein isolate (SPI) plastics. The chitin whiskers, having lengths of 500 +/- 50 nm and diameters of 50 +/- 10 nm on average, were prepared from commercial chitin by acid hydrolysis. The dependence of morphology and properties on the chitin whiskers content in the range from 0 to 30 wt % for the glycerol plasticized SPI nanocomposites was investigated by dynamic mechanical thermal analysis, scanning electron microscopy, swelling experiment, and tensile testing. The results indicate that the strong interactions between fillers and between the filler and SPI matrix play an important role in reinforcing the composites without interfering with their biodegradability. The SPI/chitin whisker nanocomposites at 43% relative humidity increased in both tensile strength and Young's modulus from 3.3 MPa for the SPI sheet to 8.4 MPa and from 26 MPa for the SPI sheet to 158 MPa, respectively. Further, incorporating chitin whisker into the SPI matrix leads to an improvement in water resistance for the SPI based nanocomposites.

  18. Microstructure and Mechanical Properties of CaCO3 Whisker-reinforced Cement

    Institute of Scientific and Technical Information of China (English)

    CAO Mingli; WEI Jianqiang

    2011-01-01

    Composite Portland cement (PC) played an important role in various kinds of construction engineering owing to low hydration heat,low-cost,and application of solid industrial waste,but its brittleness and low strength limited its use in stress-bearing locations.The aim of this study is to improve the toughness and fracture resistance by incorporating CaCO3 whisker in cement matrix.Effect of different content of calcium carbonate whiskers on the mechanical properties of PC was investigated.The results showed that the flexural strength,impact strength and split tensile strength were increased by 39.7%,39.25% and 36.34% at maximum,respectively.Microstructure and elements of the whiskers in hardened cement were observed and analyzed by SEM/EDS.The mechanisms of the reinforcement of CaCO3 whisker on cement were also discussed,and the conclusion was that the improvement could be correlated to energy-dissipating processes owing to crack bridging,crack deflection,and whisker pull-out at the crack tips.

  19. Computational-Experimental Processing of Boride/Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C

    Science.gov (United States)

    2015-09-16

    elements from the Hf family (i.e., Hf, Ti and Zr ) into a capillary to understand the effects of surface tension and viscosity during processing of melts...project primarily investigated computationally the infusion of liquid elements from the Hf family (i.e., Hf, Ti and Zr ) into a capillary to understand the... effects of surface tension and viscosity during processing of melts with a packed bed of B4C to form boride-carbide precipitates. Although the

  20. Analysis of whisker-toughened ceramic components - A design engineer's viewpoint

    Science.gov (United States)

    Duffy, Stephen F.; Manderscheid, Jane M.; Palko, Joseph L.

    1989-01-01

    The analysis of components fabricated from whisker-toughened ceramic matrix composites requires a departure from the 'factor-of-safety' design philosophy prevalent in the design of metallic structural component, which are more tolerant of flaws. A public-domain computer algorithm has been developed which, in conjunction with a general-purposed FEM program, can predict the fast-fracture reliability of a structural component under multiaxial loading conditions. The present version of the algorithm, designated 'Toughened Ceramics Analysis and Reliability Evaluation of Structures', accounts for material symmetry imposed by whisker orientation; the processes of crack deflection and crack pinning are also addressed.

  1. Nanocomposite polymer electrolytes based on poly(oxyethylene and cellulose whiskers

    Directory of Open Access Journals (Sweden)

    My Ahmed Saïd Azizi Samir

    2005-06-01

    Full Text Available Solid lithium-conducting nanocomposite polymer electrolytes based on poly(oxyethylene (POE were prepared from high aspect ratio cellulosic whiskers and lithium imide salt, LiTFSI. The cellulosic whiskers were extracted from tunicate -a sea animal- and consisted of slender parallelepiped rods that have an average length around 1 µm and a width close to 15 nm. High performance nanocomposite electrolytes were obtained. The filler provided a high reinforcing effect while a high level of ionic conductivity was retained with respect to unfilled polymer electrolytes. Cross-linking and plasticizing of the matrix as well as preparation of the composites from an organic medium were also investigated.

  2. Whisker/Cone growth on the thermal control surfaces experiment no. S0069

    Science.gov (United States)

    Zwiener, James M.; Coston, James E., Jr.; Miller, Edgar R.; Mell, Richard J.; Wilkes, Donald R.

    1995-01-01

    An unusual surface 'growth' was found during scanning electron microscope (SEM) investigations of the Thermal Control Surface Experiment (TCSE) S0069 front thermal cover. This 'growth' is similar to the cone type whisker growth phenomena as studied by G. K. Wehner beginning in the 1960's. Extensive analysis has identified the most probable composition of the whiskers to be a silicate type glass. Sources of the growth material are outgassing products from the experiment and orbital atomic oxygen, which occurs naturally at the orbital altitudes of the LDEF mission in the form of neutral atomic oxygen. The highly ordered symmetry and directionality of the whiskers are attributed to the long term (5.8 year) stable flight orientation of the LDEF.

  3. Nano-molybdenum carbide/carbon nanotubes composite as bifunctional anode catalyst for high-performance Escherichia coli-based microbial fuel cell.

    Science.gov (United States)

    Wang, Yaqiong; Li, Bin; Cui, Dan; Xiang, Xingde; Li, Weishan

    2014-01-15

    A novel electrode, carbon felt-supported nano-molybdenum carbide (Mo2C)/carbon nanotubes (CNTs) composite, was developed as platinum-free anode of high performance microbial fuel cell (MFC). The Mo2C/CNTs composite was synthesized by using the microwave-assisted method with Mo(CO)6 as a single source precursor and characterized by using X-ray diffraction and transmission electron microscopy. The activity of the composite as anode electrocatalyst of MFC based on Escherichia coli (E. coli) was investigated with cyclic voltammetry, chronoamperometry, and cell discharge test. It is found that the carbon felt electrode with 16.7 wt% Mo Mo2C/CNTs composite exhibits a comparable electrocatalytic activity to that with 20 wt% platinum as anode electrocatalyst. The superior performance of the developed platinum-free electrode can be ascribed to the bifunctional electrocatalysis of Mo2C/CNTs for the conversion of organic substrates into electricity through bacteria. The composite facilitates the formation of biofilm, which is necessary for the electron transfer via c-type cytochrome and nanowires. On the other hand, the composite exhibits the electrocatalytic activity towards the oxidation of hydrogen, which is the common metabolite of E. coli.

  4. Reactive diffusion between silicon and niobium carbide: Application to the in-situ synthesis of a silicon carbide-niobium disilicide composite

    Energy Technology Data Exchange (ETDEWEB)

    Kao, C.R. [National Central Univ., Chung Li (Taiwan, Province of China). Dept. of Chemical Engineering; Woodford, J.; Chang, Y.A. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering

    1996-10-01

    Reactive diffusion studies between NbC and Si were carried out at 1,300 C under a vacuum of 10{sup {minus}5} torr and a uniaxial pressure of 1 MPa. The annealing time ranged from 8 to 100 hours. The Si used was single crystal silicon; the NbC was hot-pressed powder compact. A NbSi{sub 2} + SiC two-phase reaction layer formed with NbSi{sub 2} as the matrix and SiC as discontinuous particles. The microstructure of the reaction product is homogeneous, dense, and fine. The NbSi{sub 2} grain size and SiC particle size are in the micron range. The growth of the reaction products follows parabolic kinetics. Extrapolation of the data to zero thickness suggests an apparent incubation time of 3.5 hours. However, for short annealing time (< 60 hours), the thickness data can be approximated by linear kinetics with an initial growth rate of about 2 {micro}m/hr. Based on these experimental observations, a growth mechanism for the reactive diffusion between Si single crystal and NbC powder compact is proposed. The authors propose that the nucleation sites for the SiC particles are at the voids of the NbC powder compact. This proposed nucleation mechanism offers a potential way of controlling the SiC particle size by changing the void size and void density of the NbC powder compact. This hypothesis, if proven to be true, will allow one to control mechanical properties of the composites by tailoring the SiC particles formed. It is also pointed out that the microstructure requires Si to be the dominant diffusing species and to diffuse through the reaction layer, while Nb and C only have to undergo local rearrangement.

  5. Cellulose whiskers: preparation, characterization and surface modification; Whiskers de celulose: preparacao, caracterizacao e modificacao de superficie

    Energy Technology Data Exchange (ETDEWEB)

    Taipina, Marcia O.; Ferrarezi, Marcia M.F.; Goncalves, Maria C., E-mail: maria@iqm.unicamp.br [Instituto de Quimica, Universidade Estadual de Campinas, Campinas, SP (Brazil)

    2011-07-01

    The main objectives of this work were to produce cellulose whiskers (from cotton fibers) by acid hydrolysis and subsequently modify the surface of these whiskers with 3-iso-cyanate-propyltrietoxy-silane. Cellulose whiskers structures were characterized by X-ray diffraction and Fourier transform infrared and their morphologies were investigated by scanning and transmission electron microscopy. Due to the hydrophilic nature of native cellulose, the formation of cellulose whisker nanocomposites is limited to water-soluble polymers. The applied methodology for surface modification of the whiskers allowed to obtain nanofibers with surface features more appropriate to allow the adhesion at fiber-matrix interface, which may result in a better performance of these fibers as reinforcing agents of hydrophobic polymer matrices. (author)

  6. In-situ fabricated TiB2 particle-whisker synergistically toughened Ti(C, N)-based ceramic cutting tool material

    Science.gov (United States)

    Liu, Hanlian; Shi, Qiang; Huang, Chuanzhen; Zou, Bin; Xu, Liang; Wang, Jun

    2015-03-01

    The mechanical properties of ceramic cutting tool materials can be modified by introducing proper content of nanoparticles or whiskers. However, the process of adding whiskers or nanoparticles has the disadvantages of high cost and health hazard as well as the agglomeration; although a new in-situ two-step sintering process can solve the above problems to some extent, yet the problems of low conversion ratio of the raw materials and the abnormal grain growth exist in this process. In this paper, an in-situ one-step synthesis technology is proposed, which means the growth of whiskers or nanoparticles and the sintering of the compact can be accomplished by one time in furnace. A kind of Ti(C, N)-based ceramic cutting tool material synergistically toughened by TiB2 particles and whiskers is fabricated with this new process. The phase compositions, relationships between microstructure and mechanical properties as well as the toughening mechanisms are analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composite which is sintered under a pressure of 32 MPa at a temperature of 1700°C in vacuum holding for 60 min can get the optimal mechanical properties. Its flexural strength, fracture toughness and Vickers hardness are 540 MPa, 7.81 MPa · m1/2 and 20.42 GPa, respectively. The composite has relatively high density, and the in-situ synthesized TiB2 whiskers have good surface integrity, which is beneficial for the improvement of the fracture toughness. It is concluded that the main toughening mechanisms of the present composite are whiskers pulling-out and crack deflection induced by whiskers, crack bridging by whiskers/particles and multi-scale particles synergistically toughening. This study proposes an in-situ one-step synthesis technology which can be well used for fabricating particles and whiskers synergistically toughened ceramic tool materials.

  7. In-situ Fabricated TiB2 Particle-whisker Synergistically Toughened Ti(C, N)-based Ceramic Cutting Tool Material

    Institute of Scientific and Technical Information of China (English)

    LIU Hanlian; SHI Qiang; HUANG Chuanzhen; ZOU Bin; XU Liang; WANG Jun

    2015-01-01

    The mechanical properties of ceramic cutting tool materials can be modified by introducing proper content of nanoparticles or whiskers. However, the process of adding whiskers or nanoparticles has the disadvantages of high cost and health hazard as well as the agglomeration;although a new in-situ two-step sintering process can solve the above problems to some extent, yet the problems of low conversion ratio of the raw materials and the abnormal grain growth exist in this process. In this paper, an in-situ one-step synthesis technology is proposed, which means the growth of whiskers or nanoparticles and the sintering of the compact can be accomplished by one time in furnace. A kind of Ti(C, N)-based ceramic cutting tool material synergistically toughened by TiB2 particles and whiskers is fabricated with this new process. The phase compositions, relationships between microstructure and mechanical properties as well as the toughening mechanisms are analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composite which is sintered under a pressure of 32 MPa at a temperature of 1700℃ in vacuum holding for 60 min can get the optimal mechanical properties. Its flexural strength, fracture toughness and Vickers hardness are 540 MPa, 7.81 MPa•m1/2 and 20.42 GPa, respectively. The composite has relatively high density, and the in-situ synthesized TiB2 whiskers have good surface integrity, which is beneficial for the improvement of the fracture toughness. It is concluded that the main toughening mechanisms of the present composite are whiskers pulling-out and crack deflection induced by whiskers, crack bridging by whiskers/particles and multi-scale particles synergistically toughening. This study proposes an in-situ one-step synthesis technology which can be well used for fabricating particles and whiskers synergistically toughened ceramic tool materials.

  8. Methods for fast, reliable growth of Sn whiskers

    Science.gov (United States)

    Bozack, M. J.; Snipes, S. K.; Flowers, G. N.

    2016-10-01

    We report several methods to reliably grow dense fields of high-aspect ratio tin whiskers for research purposes in a period of days to weeks. The techniques offer marked improvements over previous means to grow whiskers, which have struggled against the highly variable incubation period of tin whiskers and slow growth rate. Control of the film stress is the key to fast-growing whiskers, owing to the fact that whisker incubation and growth are fundamentally a stress-relief phenomenon. The ability to grow high-density fields of whiskers (103-106/cm2) in a reasonable period of time (days, weeks) has accelerated progress in whisker growth and aided in development of whisker mitigation strategies.

  9. Effect of particle size and percentages of Boron carbide on the thermal neutron radiation shielding properties of HDPE/B4C composite: Experimental and simulation studies

    Science.gov (United States)

    Soltani, Zahra; Beigzadeh, Amirmohammad; Ziaie, Farhood; Asadi, Eskandar

    2016-10-01

    In this paper the effects of particle size and weight percentage of the reinforcement phase on the absorption ability of thermal neutron by HDPE/B4C composites were investigated by means of Monte-Carlo simulation method using MCNP code and experimental studies. The composite samples were prepared using the HDPE filled with different weight percentages of Boron carbide powder in the form of micro and nano particles. Micro and nano composite were prepared under the similar mixing and moulding processes. The samples were subjected to thermal neutron radiation. Neutron shielding efficiency in terms of the neutron transmission fractions of the composite samples were investigated and compared with simulation results. According to the simulation results, the particle size of the radiation shielding material has an important role on the shielding efficiency. By decreasing the particle size of shielding material in each weight percentages of the reinforcement phase, better radiation shielding properties were obtained. It seems that, decreasing the particle size and homogeneous distribution of nano forms of B4C particles, cause to increase the collision probability between the incident thermal neutron and the shielding material which consequently improve the radiation shielding properties. So, this result, propose the feasibility of nano composite as shielding material to have a high performance shielding characteristic, low weight and low thick shielding along with economical benefit.

  10. Whisker sensory system - from receptor to decision.

    Science.gov (United States)

    Diamond, Mathew E; Arabzadeh, Ehsan

    2013-04-01

    One of the great challenges of systems neuroscience is to understand how the neocortex transforms neuronal representations of the physical characteristics of sensory stimuli into the percepts which can guide the animal's decisions. Here we present progress made in understanding behavioral and neurophysiological aspects of a highly efficient sensory apparatus, the rat whisker system. Beginning with the 1970s discovery of "barrels" in the rat and mouse brain, one line of research has focused on unraveling the circuits that transmit information from the whiskers to the sensory cortex, together with the cellular mechanisms that underlie sensory responses. A second, more recent line of research has focused on tactile psychophysics, that is, quantification of the behavioral capacities supported by whisker sensation. The opportunity to join these two lines of investigation makes whisker-mediated sensation an exciting platform for the study of the neuronal bases of perception and decision-making. Even more appealing is the beginning-to-end prospective offered by this system: the inquiry can start at the level of the sensory receptor and conclude with the animal's choice. We argue that rats can switch between two modes of operation of the whisker sensory system: (1) generative mode and (2) receptive mode. In the generative mode, the rat moves its whiskers forward and backward to actively seek contact with objects and to palpate the object after initial contact. In the receptive mode, the rat immobilizes its whiskers to optimize the collection of signals from an object that is moving by its own power. We describe behavioral tasks that rats perform in these different modes. Next, we explore which neuronal codes in sensory cortex account for the rats' discrimination capacities. Finally, we present hypotheses for mechanisms through which "downstream" brain regions may read out the activity of sensory cortex in order to extract the significance of sensory stimuli and, ultimately

  11. Rheocasting Al matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Girot, F.A.; Albingre, L.; Quenisset, J.M.; Naslain, R.

    1987-11-01

    A development status account is given for the rheocasting method of Al-alloy matrix/SiC-whisker composites, which involves the incorporation and homogeneous distribution of 8-15 vol pct of whiskers through the stirring of the semisolid matrix melt while retaining sufficient fluidity for casting. Both 1-, 3-, and 6-mm fibers of Nicalon SiC and and SiC whisker reinforcements have been experimentally investigated, with attention to the characterization of the resulting microstructures and the effects of fiber-matrix interactions. A thin silica layer is found at the whisker surface. 7 references.

  12. Imprecise Whisker Map in the Neonatal Rat Barrel Cortex.

    Science.gov (United States)

    Mitrukhina, Olga; Suchkov, Dmitry; Khazipov, Roustem; Minlebaev, Marat

    2015-10-01

    The somatosensory barrel cortex in rodents contains a topographic map of the facial whiskers where each cortical barrel is tuned to a corresponding whisker. However, exactly when this correspondence is established during development and how precise the functional topography of the whisker protomap is at birth, before the anatomical formation of barrels, are questions that remain unresolved. Here, using extracellular and whole-cell recordings from the barrel cortex of 0- to 7-day-old (P0-7; P0 = day of birth) rat pups in vivo, we report a low level of tuning to the principal whisker at P0-1, with multiple adjacent whiskers evoking large multi- and single-unit responses and excitatory postsynaptic currents in cortical neurons. Additionally, we found broad and largely overlapping projection fields (PFs) for neighboring whiskers in the barrel cortex at P0-1. Starting from P2-3, a segregated whisker map emerged, characterized by preferential single whisker tuning and segregated whisker PFs. These results indicate that the functional whisker protomap in the somatosensory cortex is imprecise at birth, that for 2-3 days after birth, whiskers compete for the cortical target territories, and that formation of a segregated functional whisker map coincides with emergence of the anatomical barrel map. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  13. Effects of neutron irradiation on mechanical properties of silicon carbide composites fabricated by nano-infiltration and transient eutectic-phase process

    Energy Technology Data Exchange (ETDEWEB)

    Koyanagi, Takaaki, E-mail: koyanagit@ornl.gov [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Ozawa, Kazumi [Materials Science and Technology Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States); Hinoki, Tatsuya; Shimoda, Kazuya [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Katoh, Yutai [Materials Science and Technology Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States)

    2014-05-01

    Unidirectional silicon carbide (SiC)-fiber-reinforced SiC matrix (SiC/SiC) composites fabricated by a nano-infiltration and transient eutectic-phase (NITE) process were irradiated with neutrons at 600 °C to 0.52 dpa, at 830 °C to 5.9 dpa, and at 1270 °C to 5.8 dpa. The in-plane and trans-thickness tensile and the inter-laminar shear properties were evaluated at ambient temperature. The mechanical characteristics, including the quasi-ductile behavior, the proportional limit stress, and the ultimate tensile strength, were retained subsequent to irradiation. Analysis of the stress–strain hysteresis loop indicated the increased fiber/matrix interface friction and the decreased residual stresses. The inter-laminar shear strength exhibited a significant decrease following irradiation.

  14. Understanding the movements of metal whiskers

    Science.gov (United States)

    Karpov, V. G.

    2015-06-01

    Metal whiskers often grow across leads of electric equipment causing short circuits and raising significant reliability issues. Their nature remains a mystery after several decades of research. It was observed that metal whiskers exhibit large amplitude movements under gentle air flow or, according to some testimonies, without obvious stimuli. Understanding the physics behind that movements would give additional insights into the nature of metal whiskers. Here, we quantitatively analyze possible mechanisms of the observed movements: (1) minute air currents; (2) Brownian motion due to random bombardments with the air molecules; (3) mechanically caused movements, such as (a) transmitted external vibrations, and (b) torque exerted due to material propagation along curved whiskers (the garden hose instability); (4) time dependent electric fields due to diffusion of ions; and (5) non-equilibrium electric fields making it possible for some whiskers to move. For all these mechanisms, we provide numerical estimates. Our conclusion is that the observed movements are likely due to the air currents or electric recharging caused by external light or similar factors.

  15. Silicon carbide sewing thread

    Science.gov (United States)

    Sawko, Paul M. (Inventor)

    1995-01-01

    Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems provide lightweight thermal insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

  16. Silicon Whisker and Carbon Nanofiber Composite Anode

    Science.gov (United States)

    Lang, Christopher M.

    2015-01-01

    Phase II Objectives: Demonstrate production levels of grams per batch; Achieve full cell anode capacity of greater than 1,000 mAh/g at a charge rate of 10 (C/10) and 0 degree C; Establish a full cell cycle life of over 300 cycles; Display an operating temperature of negative 30 degrees C to plus 30 degrees C; Demonstrate a rate capability of C/5 or higher; Deliver to NASA three 2.5 Ah cells (energy density greater than 220 Wh/kg); Exhibit the safety features of the anode and full cells; Design a 1 kWh prismatic battery pack.

  17. Thermal conductivity of boron carbides

    Science.gov (United States)

    Wood, C.; Emin, D.; Gray, P. E.

    1985-01-01

    Knowledge of the thermal conductivity of boron carbide is necessary to evaluate its potential for high-temperature thermoelectric energy conversion applications. Measurements have been conducted of the thermal diffusivity of hot-pressed boron carbide BxC samples as a function of composition (x in the range from 4 to 9), temperature (300-1700 K), and temperature cycling. These data, in concert with density and specific-heat data, yield the thermal conductivities of these materials. The results are discussed in terms of a structural model that has been previously advanced to explain the electronic transport data. Some novel mechanisms for thermal conduction are briefly discussed.

  18. Serviceability and Reinforcement of Low Content Whisker in Portland Cement

    Institute of Scientific and Technical Information of China (English)

    CAO Mingli; WEI Jianqiang; WANG Lijiu

    2011-01-01

    In order to explore the serviceability and reinforcement of CaCO3 whisker in portland cement matrix,the durability of CaCO3 whisker and effect of low whisker content(0%-4.0%)on the working performance and mechanical properties of portland cement were investigated.The experimental results show that CaCO3 whiskers have a good stability and serviceability in cement,and should not significantly alter the rheological properties of the cement paste.The flexural and compressive strength of portland cement reinforced by CaCO3 whiskers was increased by 33.3% and 12.83%,respectively.

  19. Use of Al{sub 4}C{sub 3} for fabrication of alumina–niobium carbide composites by combustion synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, C.L., E-mail: clyeh@fcu.edu.tw; Chen, Y.S.

    2014-03-15

    Highlights: • SHS with aluminothermic reduction was performed for formation of NbC and Nb{sub 2}C–Al{sub 2}O{sub 3} composites. • Al{sub 4}C{sub 3} prevents carbothermic reduction of Nb{sub 2}O{sub 5}, leading to improved product formation. • Optimum sample compositions were obtained for formation of NbC and Nb{sub 2}C–Al{sub 2}O{sub 3} composites. • Variations of combustion temperature and velocity with sample stoichiometry were presented. -- Abstract: Alumina–niobium carbide (Al{sub 2}O{sub 3}–NbC and Al{sub 2}O{sub 3}–Nb{sub 2}C) composites were synthesized by incorporating aluminothermic reduction of Nb{sub 2}O{sub 5} into a self-propagating combustion process. Starting materials of this study included Nb{sub 2}O{sub 5}, Al, Al{sub 4}C{sub 3} and carbon powders. Experimental evidence indicated that combustion temperature and flame-front velocity decreased with increasing elemental carbon in the reactant mixture. The use of Al{sub 4}C{sub 3} as the source of carbon was demonstrated to prevent carbothermic reduction of Nb{sub 2}O{sub 5}. As a result, the combustion exothermicity was increased and phase transformation and product densification were improved. According to the composition analysis, the carbon-free samples composed of Nb{sub 2}O{sub 5}:Al:Al{sub 4}C{sub 3} = 3:2:2 and 3:6:1 successfully produced NbC and Nb{sub 2}C–Al{sub 2}O{sub 3} composites, respectively, with very few minor phases.

  20. Corrosion and wear behaviour of Al–Mg–Si alloy matrix hybrid composites reinforced with rice husk ash and silicon carbide

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo Alaneme

    2014-01-01

    Full Text Available The corrosion and wear behaviour of Al–Mg–Si alloy matrix hybrid composites developed with the use of rice husk ash (RHA and silicon carbide (SiC particulates as reinforcements were investigated. RHA and SiC mixed in weight ratios 0:1, 1:3, 1:1, 3:1, and 1:0 were utilized to prepare 5, 7.5 and 10 wt% of the reinforcing phase with Al Mg Si alloy as matrix using double stir casting process. Open circuit corrosion potential (OCP and potentiodynamic polarization measurements were used to study the corrosion behaviour while coefficient of friction was used to assess the wear behaviour of the composites. The corrosion and wear mechanisms were established with the aid of scanning electron microscopy. The results show that the effect of RHA/SiC weight ratio on the corrosion behaviour of the composites in 3.5% NaCl solution was not consistent for the different weight percent of reinforcement (5, 7.5, and 10 wt% used in developing the Al–Mg–Si based composites. It was evident that for most cases the use of hybrid reinforcement of RHA and SiC resulted in improved corrosion resistance of the composites in 3.5% NaCl solution. Preferential dissolution of the more anodic Al–Mg–Si alloy matrix around the Al–Mg–Si matrix/RHA/SiC particle interfaces was identified as the primary corrosion mechanism. The coefficient of friction and consequently the wear resistance of the hybrid composites were comparable to that of the Al–Mg–Si alloy matrix reinforced with only SiC.

  1. Preparation and Dielectric Properties of Nanostructured ZnO Whiskers

    Institute of Scientific and Technical Information of China (English)

    SHI Xiao-Ling; YUAN Jie; ZHOU Wei; RONG Ji-Li; CAO Mao-Sheng

    2007-01-01

    By a novel controlled combustion synthesis method, a large number of nanostructured ZnO whiskers with different morphologies, such as tetra-needles, long-leg tetra-needles and multi-needles, are prepared without any additive in open air at high temperature. The morphologies and crystalline structures of the as-prepared ZnO nanostructured whiskers are investigated by SEM and XRD. The possible growth mechanism on the nanostructured ZnO whiskers is proposed. The experimental results indicate that the dielectric constants and losses of the nanostructured ZnO whiskers are very low, demonstrating that the nanostructured ZnO whiskers are low-loss materials for microwave absorption in X-band. However, obvious microwave absorption in nanostructured ZnO whiskers is observed. The quasi-microantenna model may be attributed to the microwave absorption of the ZnO whiskers.

  2. Growth Habit of the Basic Oxysulfate Magnesium Whisker

    Institute of Scientific and Technical Information of China (English)

    WU Jiansong; GAO Yimin

    2016-01-01

    The growth habit of the basic magnesium oxysulfate whisker was investigated based on the theoretical model of anion coordination polyhedron growth units. It is found that typical basic magnesium oxysulfate whisker growth is consistent with anion tetrahedral coordination incorporation rules. The growth units of basic magnesium oxysulfate whiskers are [Mg-(OH)4]2- and HSO4-. [Mg-(OH)4]2- is the favorable growth unit and whisker growth is in the direction of the [Mg-(OH)4]2- combination. A plurality of [Mg-(OH)4]2- s combine and become a larger dimensional growth unit in a one-dimensional direction. Then HSO4-and larger dimensional growth units connect as basic magnesium sulfate whiskers, according to the structural characteristics of the basic magnesium sulfate whisker, which can guide the synthesis of magnesium hydroxide whisker.

  3. NASA GSFC Tin Whisker Homepage http://nepp.nasa.gov/whisker

    Science.gov (United States)

    Shaw, Harry

    2000-01-01

    The NASA GSFC Tin Whisker Homepage provides general information and GSFC Code 562 experimentation results regarding the well known phenomenon of tin whisker formation from pure tin plated substrates. The objective of this www site is to provide a central repository for information pertaining to this phenomenon and to provide status of the GSFC experiments to understand the behavior of tin whiskers in space environments. The Tin Whisker www site is produced by Code 562. This www site does not provide information pertaining to patented or proprietary information. All of the information contained in this www site is at the level of that produced by industry and university researchers and is published at international conferences.

  4. NASA GSFC Tin Whisker Homepage http://nepp.nasa.gov/whisker

    Science.gov (United States)

    Shaw, Harry

    2000-01-01

    The NASA GSFC Tin Whisker Homepage provides general information and GSFC Code 562 experimentation results regarding the well known phenomenon of tin whisker formation from pure tin plated substrates. The objective of this www site is to provide a central repository for information pertaining to this phenomenon and to provide status of the GSFC experiments to understand the behavior of tin whiskers in space environments. The Tin Whisker www site is produced by Code 562. This www site does not provide information pertaining to patented or proprietary information. All of the information contained in this www site is at the level of that produced by industry and university researchers and is published at international conferences.

  5. Production of carbide-free thin ductile iron castings

    Institute of Scientific and Technical Information of China (English)

    M. Ashraf Sheikh

    2008-01-01

    The fast cooling rate of thin ductile iron castings requires special consideration to produce carbide-free castings. Extraor-dinary care was taken to select the charge to produce castings of 100-mm long round bars with 16-ram diameter. The castings show the presence of carbides in the bars. Seven melts were made with different temperatures and with different compositions to get rid of carbides. After chemical analyses, it was found that the extra purity of the charge with less than 0.008wt% sulfur in the castings was the cause of carbides. To remove the carbides fi'om the castings, sulfur should be added to the charge.

  6. Whisker encoding of mechanical events during active tactile exploration

    Science.gov (United States)

    Boubenec, Yves; Shulz, Daniel E.; Debrégeas, Georges

    2012-01-01

    Rats use their whiskers to extract a wealth of information about their immediate environment, such as the shape, position or texture of an object. The information is conveyed to mechanoreceptors located within the whisker follicle in the form of a sequence of whisker deflections induced by the whisker/object contact interaction. How the whiskers filter and shape the mechanical information and effectively participate in the coding of tactile features remains an open question to date. In the present article, a biomechanical model was developed that provides predictions of the whisker dynamics during active tactile exploration, amenable to quantitative experimental comparison. This model is based on a decomposition of the whisker profile into a slow, quasi-static sequence and rapid resonant small-scale vibrations. It was applied to the typical situation of a rat actively whisking across a solid object. Having derived the quasi-static sequence of whisker deformation, the resonant properties of the whisker were analyzed, taking into account the boundary conditions imposed by the whisker/surface contact. We then focused on two elementary mechanical events that are expected to trigger significant neural responses, namely (1) the whisker/object first contact and (2) the whisker detachment from the object. Both events were found to trigger a deflection wave propagating upward to the mystacial pad at constant velocity of ≈3–5 m/s. This yielded a characteristic mechanical signature at the whisker base, in the form of a large peak of negative curvature occurring ≈4 ms after the event has been triggered. The dependence in amplitude and lag of this mechanical signal with the main contextual parameters (such as radial or angular distance) was investigated. The model was validated experimentally by comparing its predictions to high-speed video recordings of shock-induced whisker deflections performed on anesthetized rats. The consequences of these results on possible tactile

  7. Whisker encoding of mechanical events during active tactile exploration

    Directory of Open Access Journals (Sweden)

    Yves eBoubenec

    2012-11-01

    Full Text Available Rats use their whiskers to extract a wealth of information about their immediate environment, such as the shape, position or texture of an object. The information is conveyed to mechanoreceptors located within the whisker follicle in the form of a sequence of whisker deflections induced by the whisker/object contact interaction. How the whiskers filter and shape the mechanical information and effectively participate in the coding of tactile features remains an open question to date. In the present article, a biomechanical model was developed that provides predictions of the whisker dynamics during active tactile exploration, amenable to quantitative experimental comparison. This model is based on a decomposition of the whisker profile into a slow, quasi-static sequence and rapid resonant small-scale vibrations. It was applied to the typical situation of a rat whisking across an object. Having derived the quasi-static sequence of whisker deformation, the resonant properties of the whisker were analyzed, taking into account the boundary conditions imposed by the whisker/surface contact. We then focused on two elementary mechanical events that are expected to trigger neural responses, namely (i the whisker/object first contact and (ii the whisker detachment from the object. Both events were found to trigger a deflection wave propagating upward to the mystacial pad at constant velocity of 3-5m/s. This yielded a characteristic mechanical signature at the whisker base, in the form of a large peak of negative curvature occurring 4ms after the event was triggered. The dependence in amplitude and lag of this mechanical signal with the main contextual parameters (such as radial or angular distance was investigated. The model was validated experimentally by comparing its predictions to high-speed video recordings of shock-induced whisker deflections performed on anesthetized rats. The consequences of these results on possible tactile encoding schemes are

  8. Research Progress on Aalcium Sulfate Whisker%硫酸钙晶须的研究进展

    Institute of Scientific and Technical Information of China (English)

    李桂璇; 谭建红; 李兵

    2016-01-01

    Calcium sulfate whisker is China’s excellent performance, with good market competitiveness and green environmental protection single crystal, which can be used in many aspects, but because of the complexity of preparation, the products are not enough. In order to have more products, the calcium sulfate whisker and process for preparation mechanism were briefly outlined, and in view of the different raw materials such as natural gypsum, halogen slag, carbide slag and different of preparation method such as atmospheric acidification method, hydrothermal method of calcium sulfate whiskers of preparation were described. The calcium sulfate whisker in the preparation, application development direction provided a reference of the future of calcium sulfate whisker deepen.%硫酸钙晶须是我国性能优良、具有很好市场竞争力且绿色环保的单晶体,可运用于多方面,但因其制备复杂,所以成品较少。为了能有更多成品得到使用,本文对硫酸钙晶须及其制备机理进行了简要的概述,同时针对不同的原料如天然石膏、卤渣、电石渣等及不同的制备方法如常压酸化法、水热法等对硫酸钙晶须的制备进行了表述,最后提出了硫酸钙晶须在制备、应用等方面发展的方向,为未来硫酸钙晶须的深化提供了一个参考。

  9. Fully printed, highly sensitive multifunctional artificial electronic whisker arrays integrated with strain and temperature sensors.

    Science.gov (United States)

    Harada, Shingo; Honda, Wataru; Arie, Takayuki; Akita, Seiji; Takei, Kuniharu

    2014-04-22

    Mammalian-mimicking functional electrical devices have tremendous potential in robotics, wearable and health monitoring systems, and human interfaces. The keys to achieve these devices are (1) highly sensitive sensors, (2) economically fabricated macroscale devices on flexible substrates, and (3) multifunctions beyond mammalian functions. Although highly sensitive artificial electronic devices have been reported, none have been fabricated using cost-effective macroscale printing methods and demonstrate multifunctionalities of artificial electronics. Herein we report fully printed high-sensitivity multifunctional artificial electronic whiskers (e-whisker) integrated with strain and temperature sensors using printable nanocomposite inks. Importantly, changing the composition ratio tunes the sensitivity of strain. Additionally, the printed temperature sensor array can be incorporated with the strain sensor array beyond mammalian whisker functionalities. The sensitivity for the strain sensor is impressively high (∼59%/Pa), which is the best sensitivity reported to date (>7× improvement). As the proof-of-concept for a truly printable multifunctional artificial e-whisker array, two- and three-dimensional space and temperature distribution mapping are demonstrated. This fully printable flexible sensor array should be applicable to a wide range of low-cost macroscale electrical applications.

  10. Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1994-01-01

    1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Boron by Titrimetry 7 to 13 Separation of Boron for Mass Spectrometry 14 to 19 Isotopic Composition by Mass Spectrometry 20 to 23 Separation of Halides by Pyrohydrolysis 24 to 27 Fluoride by Ion-Selective Electrode 28 to 30 Chloride, Bromide, and Iodide by Amperometric Microtitrimetry 31 to 33 Trace Elements by Emission Spectroscopy 34 to 46 1.3 The values stated in SI units are to be regarded as the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (F...

  11. Diffuse traumatic brain injury initially attenuates and later expands activation of the rat somatosensory whisker circuit concomitant with neuroplastic responses.

    Science.gov (United States)

    Hall, Kelley D; Lifshitz, Jonathan

    2010-04-06

    Traumatic brain injury can initiate an array of chronic neurological deficits, effecting executive function, language and sensorimotor integration. Mechanical forces produce the diffuse pathology that disrupts neural circuit activation across vulnerable brain regions. The present manuscript explores the hypothesis that the extent of functional activation of brain-injured circuits is a consequence of initial disruption and consequent reorganization. In the rat, enduring sensory sensitivity to whisker stimulation directs regional analysis to the whisker barrel circuit. Adult, male rats were subjected to midline fluid percussion brain or sham injury and evaluated between 1day and 42days post-injury. Whisker somatosensory regions of the cortex and thalamus maintained cellular composition as visualized by Nissl stain. Within the first week post-injury, quantitatively less cFos activation was elicited by whisker stimulation, potentially due to axotomy within and surrounding the whisker circuit as visualized by amyloid precursor protein immunohistochemistry. Over six weeks post-injury, cFos activation after whisker stimulation showed a significant linear correlation with time in the cortex (r(2)=0.545; p=0.015), non-significant correlation in the thalamus (r(2)=0.326) and U-shaped correlation in the dentate gyrus (r(2)=0.831), all eventually exceeding sham levels. Ongoing neuroplastic responses in the cortex are evidenced by accumulating growth associated protein and synaptophysin gene expression. In the thalamus, the delayed restoration of plasticity markers may explain the broad distribution of neuronal activation extending into the striatum and hippocampus with whisker stimulation. The sprouting of diffuse-injured circuits into diffuse-injured tissue likely establishes maladaptive circuits responsible for behavioral morbidity. Therapeutic interventions to promote adaptive circuit restructuring may mitigate post-traumatic morbidity. Copyright 2010 Elsevier B.V. All

  12. Effect of added silicon carbide nanowires and carbon nanotubes on mechanical properties of 0-3 natural rubber composites

    Science.gov (United States)

    Janyakunmongkol, Khantichai; Nhuapeng, Wim; Thamjaree, Wandee

    2016-01-01

    In this work, the mechanical properties of 0-3 nanocomposite materials containing silicon carbide nanowires (SiCNWs), carbon nanotubes (CNTs), and natural rubber were studied. The SiCNWs and CNTs were used as reinforcement fiber whereas natural rubber was used as the matrix phase. The chemical vapor depositions (CVD) was used for synthesizing the nanowire and nanotube phases. The volume fraction of reinforcement was varied from 0 to 10%. The nanophases were mixed in the natural rubber matrix and molded by the hand lay-up technique. The mechanical properties of the samples were examined and compared with those of neat natural rubber. From the results, it was found that the hardness and density of the samples increased with the quantities of nanophases. The nanocomposites with a volume fraction of 10% exhibited maximum hardness (50.5 SHORE A). The maximum tensile strength and extent of elongation at break of the samples were obtained from the 4% volume fraction sample, which were 16.13 MPa and 1,540%, respectively.

  13. Biological characteristics of the MG-63 human osteosarcoma cells on composite tantalum carbide/amorphous carbon films.

    Directory of Open Access Journals (Sweden)

    Yin-Yu Chang

    Full Text Available Tantalum (Ta is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC and TaC/amorphous carbon (a-C coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C, was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics.

  14. PIV Analysis of Wake Induced by Real Harbor Seal Whiskers

    Science.gov (United States)

    Bunjevac, Joseph; Rinehart, Aidan; Flaherty, Justin; Zhang, Wei

    2016-11-01

    Harbor Seals are able to accurately detect minute disturbances in the ambient flow using their whiskers, which is attributed to the exceptional capability of the whiskers to suppress vortex-induced vibrations in the wake. To explore potential applications for designing smart devices, such as high-sensitivity underwater flow sensors and drag reduction components, research has studied the role of key parameters of the whisker morphology on wake structure. Due to the inherent variation in size and angle of incidence along the length of whiskers, it is not well understood how a real seal whisker changes wake structure, in particular the vortex shedding behavior. This work aims to understand the flow around a single real seal whisker using Particle Image Velocimetry at low Reynolds numbers (i.e. a few hundred) in a water channel. Variations in flow structure are inspected between several different real whiskers and whisker models. The results will provide insights of the effects of the natural geometry of the harbor seal whiskers on wake flow compared to idealized whisker-like models.

  15. Carbide Transformations in Tempering of Complexly Alloyed White Cast Iron

    Science.gov (United States)

    Vdovin, K. N.; Gorlenko, D. A.; Zavalishchin, A. N.

    2015-07-01

    Variation of the chemical composition of all phases and structural components (metallic matrix, eutectic and secondary carbides) in complexly alloyed cast iron is studied after crystallization and different variants of tempering. It is shown that several groups of secondary carbides may be distinguished according to their morphology and chemical composition.

  16. Dry sliding wear of heat treated hybrid metal matrix composites

    Science.gov (United States)

    Naveed, Mohammed; Khan, A. R. Anwar

    2016-09-01

    In recent years, there has been an ever-increasing demand for enhancing mechanical properties of Aluminum Matrix Composites (AMCs), which are finding wide applications in the field of aerospace, automobile, defence etc,. Among all available aluminium alloys, Al6061 is extensively used owing to its excellent wear resistance and ease of processing. Newer techniques of improving the hardness and wear resistance of Al6061 by dispersing an appropriate mixture of hard ceramic powder and whiskers in the aluminium alloy are gaining popularity. The conventional aluminium based composites possess only one type of reinforcements. Addition of hard reinforcements such as silicon carbide, alumina, titanium carbide, improves hardness, strength and wear resistance of the composites. However, these composites possessing hard reinforcement do posses several problems during their machining operation. AMCs reinforced with particles of Gr have been reported to be possessing better wear characteristics owing to the reduced wear because of formation of a thin layer of Gr particles, which prevents metal to metal contact of the sliding surfaces. Further, heat treatment has a profound influence on mechanical properties of heat treatable aluminium alloys and its composites. For a solutionising temperature of 5500C, solutionising duration of 1hr, ageing temperature of 1750C, quenching media and ageing duration significantly alters mechanical properties of both aluminium alloy and its composites. In the light of the above, the present paper aims at developing aluminium based hybrid metal matrix composites containing both silicon carbide and graphite and characterize their mechanical properties by subjecting it to heat treatment. Results indicate that increase of graphite content increases wear resistance of hybrid composites reinforced with constant SiC reinforcement. Further heat treatment has a profound influence on the wear resistance of the matrix alloy as well as its hybrid composites

  17. Quantitative evaluation of carbides in nickel-base superalloy MAR-M247

    Science.gov (United States)

    Szczotok, A.

    2011-05-01

    It has been established that carbides in superalloys serve three functions. Fine carbides precipitated in the matrix give strengthening results. Carbides also can tie up certain elements that would otherwise promote phase instability during service. Grain boundary carbides prevent or retard grain-boundary sliding and strengthen the grain boundary, which depends significantly on carbide shape, size and distribution. Various types of carbides are possible, depending on superalloy composition and processing. In the paper optical and scanning electron microscopy investigations of carbides occurring in specimens of the polycrystalline nickel-base superalloy MAR-M247 were carried out. Conditions of carbides revealing and microstructure images acquisition have been described. Taking into consideration distribution and morphology of the carbides in matrix a method of quantitative description of Chinese script-like and blocky primary carbides on the basis of image analysis was proposed.

  18. Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel-tungsten composite coatings

    Science.gov (United States)

    Singh, Swarnima; Sribalaji, M.; Wasekar, Nitin P.; Joshi, Srikant; Sundararajan, G.; Singh, Raghuvir; Keshri, Anup Kumar

    2016-02-01

    Silicon carbide (SiC) reinforced nickel-tungsten (Ni-W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni-W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni-W-5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni-W-5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, Ecorr) compared to Ni-W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni-W-5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO4 and SiO2.

  19. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides.

    Science.gov (United States)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-14

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  20. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides

    Science.gov (United States)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-01

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  1. Properties of Doped GaSb Whiskers at Low Temperatures

    Science.gov (United States)

    Khytruk, Igor; Druzhinin, Anatoly; Ostrovskii, Igor; Khoverko, Yuriy; Liakh-Kaguy, Natalia; Rogacki, Krzysztof

    2017-02-01

    Temperature dependencies of GaSb whiskers' resistance doped with Te to concentration of 1.7 × 1018 cm-3 were measured in temperature range 1.5-300 K. At 4.2 K temperature, a sharp drop in the whisker resistance was found. The observed effect is likely connected with the contribution of two processes such as the electron localization in the whiskers and transition in superconducting state at temperature below 4.2 K. The whisker magnetoconductance is considered in the framework of weak antilocalization (WAL) model and connected with subsurface layers of the whiskers. The Shubnikov-de Haas (SdH) oscillatory effect is observed in high-quality n-type GaSb whiskers with tellurium doping concentration near the metal-insulator transition (MIT) for both longitudinal and transverse magnetoresistance.

  2. Spark plasma sintering of silicon carbide, multi-walled carbon nanotube and graphene reinforced zirconium diboride ceramic composite

    Science.gov (United States)

    Balaraman Yadhukulakrishnan, Govindaraajan

    Scope and Method of Study: Space vehicles re-entering the earth's atmosphere experience very high temperatures due to aerodynamic heating. Ultra-high temperature ceramics (UHTC) with melting point higher than 3200°C are promising materials for thermal protection systems of such space vehicles re-entering the earth's atmosphere. Among several UHTC systems ZrB2 based ceramic composites are particularly important for thermal protection systems due to their better mechanical and thermoelectric properties and high oxidation resistance. In this study spark plasma sintering of SiC, carbon nanotubes (CNT) and graphene nano platelets (GNP) reinforced ZrB2 ultra-high temperature ceramic matrix composites is reported. Findings and Conclusions: Systematic investigations on the effect of reinforcement type (SiC, CNTs and GNP) and content (10-40 vol.% SiC, 2-6 vol.% CNTs and 2-6 vol.% GNP) on densification behavior, microstructure development, and mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness) are reported. With the similar SPS parameters near-full densification (>99% relative density) was achieved with 10-40 vol.% SiC, 4-6 vol.% CNT reinforced composites. Highly dense composites were obtained in 4-6 vol.% GNP reinforced composites. The SiC, CNT and GNP reinforcement improved the indentation fracture toughness of the composites through a range of toughening mechanisms, including particle shearing, crack deflection at the particle-matrix interface, and grain pull-outs for ZrB2-SiC composites, CNT pull-outs and crack deflection in ZrB2-CNT composites and crack deflection, crack bridging and GNP sheet pull-out for ZrB2 -GNP composites.

  3. A Simple Model to Estimate the Yield Strength of Silicon Carbide Particulate Reinforced Aluminium Alloy Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In the present study, a modified Hall-Petch correlation on the basis of dislocation pile-up model was used to estimate the yield strength of SiCp/Al composites. The experimental results show that the modified Hall-Petch correlation expressed as σcy=244+371λ-1/2 fits very well with the experimental data, which indicated that the strength increase of SiCp/Al composites might be due to the direct blocking of dislocation motion by the particulate-matrix interface,namely, the dislocation pile-up is the most possible strengthening mechanism for SiCp/Al composites.

  4. Determination of composition and fluidity of an alloy for impregnating hard alloys on the basis of titanium carbide

    Directory of Open Access Journals (Sweden)

    A. Z. Issagulov

    2016-07-01

    Full Text Available In this paper optimum compositions of a metal bond of Cr – Ni - Co system are determined by mathematical planning methods. As a response function, value of bending strength at a temperature of 800 °C was used. On the basis of the developed planning matrix samples of required composition were made, bending strength and long-term strength are measured. A certain composition of alloy-bond and its quantity is found. Spiral tests were conducted to determine fluidity.

  5. EVALUATION OF LOCAL STRAIN EVOLUTION FROM METALLIC WHISKER FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, E.; Lam, P.

    2011-05-11

    Evolution of local strain on electrodeposited tin films upon aging has been monitored by digital image correlation (DIC) for the first time. Maps of principal strains adjacent to whisker locations were constructed via comparing pre- and post-growth scanning electron microscopy (SEM) images. Results showed that the magnitude of the strain gradient plays an important role in whisker growth. DIC visualized the dynamic growth process in which the alteration of strain field has been identified to cause growth of subsequent whiskers.

  6. Silica-templated synthesis of ordered mesoporous tungsten carbide/graphitic carbon composites with nanocrystalline walls and high surface areas via a temperature-programmed carburization route.

    Science.gov (United States)

    Wu, Zhangxiong; Yang, Yunxia; Gu, Dong; Li, Qiang; Feng, Dan; Chen, Zhenxia; Tu, Bo; Webley, Paul A; Zhao, Dongyuan

    2009-12-01

    Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature-programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA-15 or KIT-6), carburizing temperature (700-1000 degrees C), the PTA-loading amount, and the carburizing atmosphere (CH(4) or a CH(4)/H(2) mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC-phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74-169 m(2) g(-1)), large pore volumes (0.14-0.17 cm(3) g(-1)), narrow pore-size distributions (centered at about 3 nm), and very good oxidation resistance (up to 750 degrees C) have potential applications in fuel-cell catalysts and nanodevices.

  7. Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel–tungsten composite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Swarnima; Sribalaji, M. [Materials Science and Engineering, Indian Institute of Technology Patna, Navin Government Polytechnic Campus, Patliputra Colony, Patna, Bihar 800013 (India); Wasekar, Nitin P.; Joshi, Srikant; Sundararajan, G. [International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI) Hyderabad, Balapur P.O., Hyderabad, Andhra Pradesh 500005 (India); Singh, Raghuvir [CSIR-National Metallurgical Laboratory, Jamshedpur, Jharkhand 831007 (India); Keshri, Anup Kumar, E-mail: anup@iitp.ac.in [Materials Science and Engineering, Indian Institute of Technology Patna, Navin Government Polytechnic Campus, Patliputra Colony, Patna, Bihar 800013 (India)

    2016-02-28

    Graphical abstract: - Highlights: • Pulse electrodeposited Ni–W–SiC coating has been synthesized successfully. • Dome to turtle like structure has been observed on addition of SiC in Ni–W coating. • Formation of W(Ni) solid solution was observed on adding 5 g/l SiC in Ni–W coating. • Corrosion resistance improved for Ni–W–5 g/l SiC coating. • Texture formation and continuous barrier layer enhanced the corrosion resistance. - Abstract: Silicon carbide (SiC) reinforced nickel–tungsten (Ni–W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni–W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni–W–5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni–W–5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, E{sub corr}) compared to Ni–W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni–W–5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO{sub 4} and SiO{sub 2}.

  8. Conduction mechanism in boron carbide

    Science.gov (United States)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  9. Innovation Incubator: Whisker Labs Technical Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Sparn, Bethany F. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Frank, Stephen M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Earle, Lieko [National Renewable Energy Lab. (NREL), Golden, CO (United States); Scheib, Jennifer G. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-08-01

    The Wells Fargo Innovation Incubator (IN2) is a program to foster and accelerate startup companies with commercial building energy-efficiency and demand management technologies. The program is funded by the Wells Fargo Foundation and co-administered by the National Renewable Energy Laboratory (NREL). Whisker Labs, an Oakland, California-based company, was one of four awardees in the first IN2 cohort and was invited to participate in the program because of its novel electrical power sensing technology for circuit breakers. The stick-on Whisker meters install directly on the front face of the circuit breakers in an electrical panel using adhesive, eliminating the need to open the panel and install current transducers (CTs) on the circuit wiring.

  10. Centrifugal casting of ZA8 zinc alloy and composite A356/silicon carbide: Study and modeling of phases' and particles' segregation

    Science.gov (United States)

    Balout, Bahaa

    Centrifugation is a casting technology that allows the production of cylindrical and graduated parts with different mechanical properties through the section. The need for materials with good quality and specific mechanical properties has been driven this technology in order to produce different types of materials such as zinc alloys and graduated metal matrix composites reinforced by hard and wear resistant particles. The goal of this research project is to study and model the eutectic macrosegregation, the solidification speed, and the speeds of solidification fronts during centrifugal casting of ZA8 zinc-aluminum alloy in order to improve the part quality and increase its strength and field reliability. Moreover, the segregation of the particles during centrifugal casting of an aluminum matrix composite reinforced by silicon carbide particles (A356/SiC) is also studied to improve and control the graduation of the parts. The cooling rate, the speed, acceleration/deceleration, displacement, and segregation of the particles across the section will be modeled by discretization of Stokes' law in time in order to take into consideration the change in the centrifugal radius and melt viscosity during cooling process. This study will allow the control of the graduation degree of particles across the section in order to improve the properties and wear resistance of the composite. This composite can be used in systems where friction is critical and load is high (reinforcements of parts for the cylinders of pneumatic systems). The results show that the maximum macrosegregation zone of the eutectic across the casting section corresponds to the last point of solidification. The eutectic macrosegregation produced during centrifugal casting of thin walled part is a normal segregation which varies depending on the solidification speed and the ratio between the speeds of solidification fronts. On the other hand, it was found that the position and volume fraction of the particles

  11. The stochastic growth of metal whiskers

    Science.gov (United States)

    Subedi, Biwas; Niraula, Dipesh; Karpov, Victor G.

    2017-06-01

    The phenomenon of spontaneously growing metal whiskers (MWs) raises significant reliability concerns due to their related arcing and shorting in electric equipment. The growth kinetics of MWs remains poorly predictable. Here, we present a theory describing the earlier observed intermittent growth of MWs as caused by local energy barriers related to variations in the random electric fields generated by surface imperfections. We find the probabilistic distribution of MW stopping times, during which MW growth halts, which is important for reliability projections.

  12. Whisker Formation in Porosity in Al Alloys

    Science.gov (United States)

    Griffiths, William David; Elsayed, Ahmed; El-Sayed, Mahmoud Ahmed

    2016-12-01

    An examination of the fracture surfaces of tensile test bars from Al alloy castings held in the liquid state for up to 20 minutes revealed porosity which in some cases contained whisker-like features. Energy-dispersive X-ray analysis in a SEM suggested that these might be oxide whiskers forming in an oxide-related pore or double oxide film defect. Such entrainment defects (also known as bifilms) may entrap a small amount of the local atmosphere when they form and become incorporated into the liquid metal. This atmosphere may be predominantly air, which then subsequently reacts with the surrounding melt, firstly by reaction with oxygen and secondly by reaction with nitrogen. A CFD model of the heat distribution associated with the reactions between the interior atmosphere of a double oxide film defect and the surrounding liquid alloy suggested that highly localized increases in temperature, up to about 2000 K to 5000 K (1727 °C to 4727 °C), could occur, over a scale of a few hundred micrometers. Such localized increases in temperature might lead to the evaporation or disassociation of oxide within the pore, followed by condensation, to form the whisker structures observed. Hydrogen might also be expected to diffuse into the bifilm and may play a role in the chemical reactions associated with the development of the bifilm.

  13. Whisker-related afferents in superior colliculus.

    Science.gov (United States)

    Castro-Alamancos, Manuel A; Favero, Morgana

    2016-05-01

    Rodents use their whiskers to explore the environment, and the superior colliculus is part of the neural circuits that process this sensorimotor information. Cells in the intermediate layers of the superior colliculus integrate trigeminotectal afferents from trigeminal complex and corticotectal afferents from barrel cortex. Using histological methods in mice, we found that trigeminotectal and corticotectal synapses overlap somewhat as they innervate the lower and upper portions of the intermediate granular layer, respectively. Using electrophysiological recordings and optogenetics in anesthetized mice in vivo, we showed that, similar to rats, whisker deflections produce two successive responses that are driven by trigeminotectal and corticotectal afferents. We then employed in vivo and slice experiments to characterize the response properties of these afferents. In vivo, corticotectal responses triggered by electrical stimulation of the barrel cortex evoke activity in the superior colliculus that increases with stimulus intensity and depresses with increasing frequency. In slices from adult mice, optogenetic activation of channelrhodopsin-expressing trigeminotectal and corticotectal fibers revealed that cells in the intermediate layers receive more efficacious trigeminotectal, than corticotectal, synaptic inputs. Moreover, the efficacy of trigeminotectal inputs depresses more strongly with increasing frequency than that of corticotectal inputs. The intermediate layers of superior colliculus appear to be tuned to process strong but infrequent trigeminal inputs and weak but more persistent cortical inputs, which explains features of sensory responsiveness, such as the robust rapid sensory adaptation of whisker responses in the superior colliculus. Copyright © 2016 the American Physiological Society.

  14. Tensile Mechanical Properties and Strengthening Mechanism of Hybrid Carbon Nanotube and Silicon Carbide Nanoparticle-Reinforced Magnesium Alloy Composites

    National Research Council Canada - National Science Library

    Zhou, Xia; Su, Depeng; Wu, Chengwei; Liu, Liming

    2012-01-01

    .... The results showed that grains of the matrix in the AZ91/(CNT + SiC) composites were obviously refined after adding hybrid CNTs and SiC nanoparticles to the AZ91 alloy, and the room-temperature mechanical properties of AZ91/(CNT + SiC...

  15. Consolidation of dispersion strengthened copper-niobium carbide composite prepared by in situ and ex situ methods

    Energy Technology Data Exchange (ETDEWEB)

    Zuhailawati, H. [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang (Malaysia)], E-mail: zuhaila@eng.usm.my; Yong, T.L. [School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang (Malaysia)

    2009-04-15

    In this paper, Cu-20vol%NbC composite was prepared by in situ and ex situ processing methods. In in situ method, a mixture of Cu-Nb-C was mechanically alloyed in a high energy planetary mill while in ex situ method, a mixture of Cu-NbC powder was mixed in a low energy ball mill. Consolidation of the composite powder was systematically studied by pressing the powder at different compaction pressures, i.e. in the range of 350-650 MPa, followed with sintering at 900 deg. C for an hour. The presence of the NbC particle in copper matrix of the Cu-Nb-C sintered sample has been confirmed by X-ray diffraction and energy dispersive X-ray analysis. In situ composite has higher hardness and electrical conductivity than its counterpart due to a homogenous distribution of fine NbC particle and good NbC-Cu adhesion bonding. Higher compaction pressure has increased the hardness, electrical conductivity and density of the composites.

  16. Method Developed for the High-Temperature Nondestructive Evaluation of Fiber-Reinforced Silicon Carbide Ceramic Matrix Composites

    Science.gov (United States)

    Goldsby, Jon C.

    1998-01-01

    Ceramic matrix composites have emerged as candidate materials to allow higher operating temperatures (1000 to 1400 C) in gas turbine engines. A need, therefore, exists to develop nondestructive methods to evaluate material integrity at the material operating temperature by monitoring thermal and mechanical fatigue. These methods would also have potential as quality inspection tools. The goal of this investigation at the NASA Lewis Research Center is to survey and correlate the temperature-dependent damping and stiffness of advanced ceramic composite materials with imposed thermal and stress histories that simulate in-service turbine engine conditions. A typical sample size of 100 by 4 by 2 cubic millimeters, along with the specified stiffness and density, placed the fundamental vibration frequencies between 100 and 2000 Hz. A modified Forster apparatus seemed most applicable to simultaneously measure both damping and stiffness. Testing in vacuum reduced the effects of air on the measurements. In this method, a single composite sample is vibrated at its fundamental tone; then suddenly, the mechanical excitation is removed so that the sample's motion freely decays with time. Typical results are illlustrated in this paper.

  17. Study on the mechanism of surface modification of magnesium oxysulfate whisker

    Science.gov (United States)

    Dang, Li; Nai, Xueying; Zhu, Donghai; Jing, Yanwei; Liu, Xin; Dong, Yaping; Li, Wu

    2014-10-01

    Hydrophobic-lipophilic magnesium oxysulfate whisker (MOSw) was prepared by surface modification with lauric acid and the surface morphology of MOSw was examined with field emission scanning electron microscope (FESEM). X-ray powder diffraction (XRD) was used to characterize the crystalline degree of MOSw and modified MOSw (MOSw-LA). Both FESEM and XRD suggested that modification occurred on the surface of MOSw exclusively. The inexistence of physisorbed lauric acid was proved by Fouier transform infrared (FT-IR) spectroscopy. Thermogravimetric analyses ruled out the possibility that magnesium laurate (LA-Mg) physisorbed on the surface of MOSw-LA. Solid state 13C nuclear magnetic resonance (13C NMR) further verified the formation of COO-Mglauric acid was chemical adsorption taken place between lauric acid and Mgacid-base neutralization". This research provides a detailed explanation for a kind of surface modification, which may be further used in the performance of whisker/polymer matrix composites.

  18. Anatomical pathways involved in generating and sensing rhythmic whisker movements

    NARCIS (Netherlands)

    L.W.J. Bosman (Laurens); A.R. Houweling (Arthur); C.B. Owens (Cullen); N. Tanke (Nouk); O.T. Shevchouk (Olesya); N. Rahmati (Negah); W.H.T. Teunissen (Wouter); C. Ju (Chiheng); W. Gong (Wei); S.K.E. Koekkoek (Bas); C.I. de Zeeuw (Chris)

    2011-01-01

    textabstractThe rodent whisker system is widely used as a model system for investigating sensorimotor integration, neural mechanisms of complex cognitive tasks, neural development, and robotics. The whisker pathways to the barrel cortex have received considerable attention. However, many subcortical

  19. Anatomical pathways involved in generating and sensing rhythmic whisker movements

    NARCIS (Netherlands)

    L.W.J. Bosman (Laurens); A.R. Houweling (Arthur); C.B. Owens (Cullen); N. Tanke (Nouk); O.T. Shevchouk (Olesya); N. Rahmati (Negah); W.H.T. Teunissen (Wouter); C. Ju (Chiheng); W. Gong (Wei); S.K.E. Koekkoek (Bas); C.I. de Zeeuw (Chris)

    2011-01-01

    textabstractThe rodent whisker system is widely used as a model system for investigating sensorimotor integration, neural mechanisms of complex cognitive tasks, neural development, and robotics. The whisker pathways to the barrel cortex have received considerable attention. However, many subcortical

  20. Chemical Modification Methods of Nanoparticles of Silicon Carbide Surface

    Directory of Open Access Journals (Sweden)

    Anton S. Yegorov

    2015-09-01

    Full Text Available silicon carbide exhibits exceptional properties: high durability, high thermal conductivity, good heat resistance, low thermal expansion factor and chemical inactivity. Reinforcement with silicon carbide nanoparticles increases polymer’s tensile strength and thermal stability.Chemical methods of modification of the silicon carbide surface by means of variety of reagents from ordinary molecules to macromolecular polymers are reviewed in the review.The structure of silicon carbide surface layer and the nature of modificator bonding with the surface of SiC particles are reviewed. General examples of surface modification methodologies and composite materials with the addition of modified SiC are given.

  1. Carbides in Nodular Cast Iron with Cr and Mo

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2007-07-01

    Full Text Available In these paper results of elements microsegregation in carbidic nodular cast iron have been presented. A cooling rate in the centre of the cross-section and on the surface of casting and change of moulding sand temperature during casting crystallization and its self-cooling have been investigated. TDA curves have been registered. The linear distribution of elements concentration in an eutectic grain, primary and secondary carbides have been made. It was found, that there are two kinds of carbides: Cr and Mo enriched. A probable composition of primary and secondary carbides have been presented.

  2. HEAT-RESISTANT MATERIAL WITH SILICON CARBIDE AS A BASE,

    Science.gov (United States)

    A new high-temperature material, termed SG-60, is a silicon carbide -graphite composite in which the graphite is the thermostability carrier since it...is more heat-conducting and softer (heat conductivity of graphite is 0.57 cal/g-cm-sec compared with 0.02 cal/g-cm-sec for silicon carbide ) while... silicon carbide is the carrier of high-temperature strength and hardness. The high covalent bonding strength of the atoms of silicon carbide (283 kcal

  3. SILICON CARBIDE FOR SEMICONDUCTORS

    Science.gov (United States)

    This state-of-the-art survey on silicon carbide for semiconductors includes a bibliography of the most important references published as of the end...of 1964. The various methods used for growing silicon carbide single crystals are reviewed, as well as their properties and devices fabricated from...them. The fact that the state of-the-art of silicon carbide semiconductors is not further advanced may be attributed to the difficulties of growing

  4. Silicon Carbide Shapes.

    Science.gov (United States)

    Free-standing silicon carbide shapes are produced by passing a properly diluted stream of a reactant gas, for example methyltrichlorosilane, into a...reaction chamber housing a thin walled, hollow graphite body heated to 1300-1500C. After the graphite body is sufficiently coated with silicon carbide , the...graphite body is fired, converting the graphite to gaseous CO2 and CO and leaving a silicon carbide shaped article remaining.

  5. Influence of high sintering pressure on the microhardness and wear resistance of diamond powder and silicon carbide-based composites

    Directory of Open Access Journals (Sweden)

    Oleksandr Sergueevitch Osipov

    2004-06-01

    Full Text Available The work reported on here involved the development of several samples of "diamond-SiC" composite produced under sintering pressures of up to 9.0 GPa at temperatures of up to 1973 7K. The average size of the diamond micropowder crystals used was 40/28 µm. The sintering process was carried out in a 2500-ton hydraulic press equipped with an anvil-type high-pressure device having a toroidal work surface and a central concavity diameter of 20 mm. The microhardness and wear resistance of the samples were found to be dependent on the sintering pressure. The experimental results indicated that the maximum microhardness and minimum wear resistance coefficients of each compact were attained when the pressure applied during sintering exceeded 6.5 GPa. Based on the established values of pressure, this study served to identify the types of devices applicable for the manufacture of composite material inserts for a variety of rock drilling applications.

  6. Enhanced supercapacitive performance of delaminated two-dimensional titanium carbide/carbon nanotube composites in alkaline electrolyte

    Science.gov (United States)

    Yan, Pengtao; Zhang, Ruijun; Jia, Jin; Wu, Chao; Zhou, Aiguo; Xu, Jiang; Zhang, Xuesha

    2015-06-01

    MXenes, a new family of two-dimensional materials, are terminated by O, OH and F groups. The existence of the oxygen-containing functional groups indicates a potential application in supercapacitor based on a redox mechanism. However, the irreversible stacking of MXenes will lead to an insufficient utilization of these functional groups and thus a decrease in the supercapacitive performance. To solve the problem, we synthesized a composite material comprised of carbon nanotube (CNT) and Ti3C2 sheets (d-Ti3C2) delaminated from MXenes by ultrasonic stirring. The FTIR result suggests that the ultrasonication has no significant effect on the oxygen-containing functional groups. The resultant composites exhibit significantly higher volumetric capacitance and better capacitance retention (during 5-100 mv s-1) than d-Ti3C2. A highest volumetric capacitance of 393 F cm-3 at 5 mv s-1 in KOH electrolyte can be obtained when the weight ratio of d-Ti3C2 to CNT is 2:1. In addition, the volumetric capacitance has no significant degradation even after 10000 cycles in cycling stability test, showing an excellent cycling stability compared with metal oxides. These enhanced electrochemical performances can be ascribed to the introduction of CNTs, which impede the stacking of Ti3C2, enlarge the distance between Ti3C2 sheets and improve the electrical conductivity.

  7. Nanoscale Conductive Channels in Silicon Whiskers with Nickel Impurity

    Science.gov (United States)

    Yatsukhnenko, Serhii; Druzhinin, Anatoly; Ostrovskii, Igor; Khoverko, Yuriy; Chernetskiy, Mukhajlo

    2017-01-01

    The magnetization and magnetoresistance of Si whiskers doped with to boron concentrations corresponding to the metal-insulator transition (2 × 1018 cm-3 ÷ 5 × 1018 cm-3) were measured at high magnetic fields up to 14 T in a wide temperature range 4.2-300 K. Hysteresis of the magnetic moment was observed for Si p-type whiskers with nickel impurity in a wide temperature range 4.2-300 K indicating a strong interaction between the Ni impurities and the possibility of a magnetic cluster creation. The introduction of Ni impurity in Si whiskers leads to appearance and increase of the magnitude of negative magnetoresistance up to 10% as well as to the decrease of the whisker resistivity in the range of hopping conductance at low temperatures. The abovementioned effects were explained in the framework of appearance of magnetic polarons leading to modification of the conductive channels in the subsurface layers of the whiskers.

  8. Active carbon supported molybdenum carbides for higher alcohols synthesis from syngas

    DEFF Research Database (Denmark)

    Wu, Qiongxiao; Chiarello, Gian Luca; Christensen, Jakob Munkholt

    This work provides an investigation of the high pressure CO hydrogenation to higher alcohols on K2CO3 promoted active carbon supported molybdenum carbide. Both activity and selectivity to alcohols over supported molybdenum carbides increased significantly compared to bulk carbides in literatures....... spectroscopy were applied for determining the carburization temperature and evaluating the composition of the carbide clusters of different samples through determinations of the Mo-C and Mo-Mo coordination numbers....

  9. Barium Isotopic Composition of Mainstream Silicon Carbides from Murchison: Constraints for s-Process Nucleosynthesis in AGB Stars

    CERN Document Server

    Liu, Nan; Davis, Andrew M; Gallino, Roberto; Straniero, Oscar; Gyngard, Frank; Pellin, Michael J; Willingham, David G; Dauphas, Nicolas; Pignatari, Marco; Bisterzo, Sara; Cristallo, Sergio; Herwig, Falk

    2014-01-01

    We present barium, carbon, and silicon isotopic compositions of 38 acid-cleaned presolar SiC grains from Murchison. Comparison with previous data shows that acid washing is highly effective in removing barium contamination. Strong depletions in $\\delta$($^{138}$Ba/$^{136}$Ba) values are found, down to $-$400 permil, which can only be modeled with a flatter $^{13}$C profile within the $^{13}$C pocket than is normally used. The dependence of $\\delta$($^{138}$Ba/$^{136}$Ba) predictions on the distribution of $^{13}$C within the pocket in AGB models allows us to probe the $^{13}$C profile within the $^{13}$C pocket and the pocket mass in asymptotic giant branch (AGB) stars. In addition, we provide constraints on the $^{22}$Ne$(\\alpha,n)^{25}$Mg rate in the stellar temperature regime relevant to AGB stars, based on $\\delta$($^{134}$Ba/$^{136}$Ba) values of mainstream grains. We found two nominally mainstream grains with strongly negative $\\delta$($^{134}$Ba/$^{136}$Ba) values that cannot be explained by any of the...

  10. Structure and composition of zirconium carbide thin-film grown by ion beam sputtering for optical applications

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Amol, E-mail: modimh@rrcat.gov.in; Modi, Mohammed H., E-mail: modimh@rrcat.gov.in; Dhawan, Rajnish, E-mail: modimh@rrcat.gov.in; Lodha, G. S., E-mail: modimh@rrcat.gov.in [X-ray Optics Section, ISU Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India)

    2014-04-24

    Thin film of compound material ZrC was deposited on Si (100) wafer using ion beam sputtering method. The deposition was carried out at room temperature and at base pressure of 3×10{sup −5} Pa. X-ray photoelectron spectroscopy (XPS) measurements were performed for determining the surface chemical compositions. Grazing incidence x-ray reflectivity (GIXRR) measurements were performed to study the film thickness, roughness and density. From GIXRR curve roughness value of the film was found less than 1 nm indicating smooth surface morphology. Films density was found 6.51 g/cm{sup 3}, which is close to bulk density. Atomic force microscopy (AFM) measurements were performed to check the surface morphology. AFM investigation showed that the film surface is smooth, which corroborate the GIXRR data. Figure 2 of the original article PDF file, as supplied to AIP Publishing, contained a PDF processing error. This article was updated on 12 May 2014 to correct that error.

  11. SILICON CARBIDE DATA SHEETS

    Science.gov (United States)

    These data sheets present a compilation of a wide range of electrical, optical and energy values for alpha and beta- silicon carbide in bulk and film...spectrum. Energy data include energy bands, energy gap and energy levels for variously-doped silicon carbide , as well as effective mass tables, work

  12. Texture coding in the rat whisker system: slip-stick versus differential resonance.

    Directory of Open Access Journals (Sweden)

    Jason Wolfe

    2008-08-01

    Full Text Available Rats discriminate surface textures using their whiskers (vibrissae, but how whiskers extract texture information, and how this information is encoded by the brain, are not known. In the resonance model, whisker motion across different textures excites mechanical resonance in distinct subsets of whiskers, due to variation across whiskers in resonance frequency, which varies with whisker length. Texture information is therefore encoded by the spatial pattern of activated whiskers. In the competing kinetic signature model, different textures excite resonance equally across whiskers, and instead, texture is encoded by characteristic, nonuniform temporal patterns of whisker motion. We tested these models by measuring whisker motion in awake, behaving rats whisking in air and onto sandpaper surfaces. Resonant motion was prominent during whisking in air, with fundamental frequencies ranging from approximately 35 Hz for the long Delta whisker to approximately 110 Hz for the shorter D3 whisker. Resonant vibrations also occurred while whisking against textures, but the amplitude of resonance within single whiskers was independent of texture, contradicting the resonance model. Rather, whiskers resonated transiently during discrete, high-velocity, and high-acceleration slip-stick events, which occurred prominently during whisking on surfaces. The rate and magnitude of slip-stick events varied systematically with texture. These results suggest that texture is encoded not by differential resonant motion across whiskers, but by the magnitude and temporal pattern of slip-stick motion. These findings predict a temporal code for texture in neural spike trains.

  13. Barium isotopic composition of mainstream silicon carbides from Murchison: Constraints for s-process nucleosynthesis in asymptotic giant branch stars

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Nan; Davis, Andrew M.; Pellin, Michael J.; Dauphas, Nicolas [Department of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637 (United States); Savina, Michael R. [Chicago Center for Cosmochemistry, Chicago, IL 60637 (United States); Gallino, Roberto; Bisterzo, Sara [Dipartimento di Fisica, Università di Torino, I-10125 Torino (Italy); Straniero, Oscar; Cristallo, Sergio [INAF–Osservatorio Astronomico di Collurania, via Maggini snc, I-64100 Teramo (Italy); Gyngard, Frank [Laboratory for Space Sciences, Washington University, St. Louis, MO 63130 (United States); Willingham, David G. [Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Pignatari, Marco [Department of Physics, University of Basel, Basel CH-4056 (Switzerland); Herwig, Falk, E-mail: lnsmile@uchicago.edu [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P5C2 (Canada)

    2014-05-01

    We present barium, carbon, and silicon isotopic compositions of 38 acid-cleaned presolar SiC grains from Murchison. Comparison with previous data shows that acid washing is highly effective in removing barium contamination. Strong depletions in δ({sup 138}Ba/{sup 136}Ba) values are found, down to –400‰, which can only be modeled with a flatter {sup 13}C profile within the {sup 13}C pocket than is normally used. The dependence of δ({sup 138}Ba/{sup 136}Ba) predictions on the distribution of {sup 13}C within the pocket in asymptotic giant branch (AGB) models allows us to probe the {sup 13}C profile within the {sup 13}C pocket and the pocket mass in AGB stars. In addition, we provide constraints on the {sup 22}Ne(α, n){sup 25}Mg rate in the stellar temperature regime relevant to AGB stars, based on δ({sup 134}Ba/{sup 136}Ba) values of mainstream grains. We found two nominally mainstream grains with strongly negative δ({sup 134}Ba/{sup 136}Ba) values that cannot be explained by any of the current AGB model calculations. Instead, such negative values are consistent with the intermediate neutron capture process (i process), which is activated by the very late thermal pulse during the post-AGB phase and characterized by a neutron density much higher than the s process. These two grains may have condensed around post-AGB stars. Finally, we report abundances of two p-process isotopes, {sup 130}Ba and {sup 132}Ba, in single SiC grains. These isotopes are destroyed in the s process in AGB stars. By comparing their abundances with respect to that of {sup 135}Ba, we conclude that there is no measurable decay of {sup 135}Cs (t {sub 1/2} = 2.3 Ma) to {sup 135}Ba in individual SiC grains, indicating condensation of barium, but not cesium into SiC grains before {sup 135}Cs decayed.

  14. Anatomical Pathways Involved in Generating and Sensing Rhythmic Whisker Movements

    Science.gov (United States)

    Bosman, Laurens W. J.; Houweling, Arthur R.; Owens, Cullen B.; Tanke, Nouk; Shevchouk, Olesya T.; Rahmati, Negah; Teunissen, Wouter H. T.; Ju, Chiheng; Gong, Wei; Koekkoek, Sebastiaan K. E.; De Zeeuw, Chris I.

    2011-01-01

    The rodent whisker system is widely used as a model system for investigating sensorimotor integration, neural mechanisms of complex cognitive tasks, neural development, and robotics. The whisker pathways to the barrel cortex have received considerable attention. However, many subcortical structures are paramount to the whisker system. They contribute to important processes, like filtering out salient features, integration with other senses, and adaptation of the whisker system to the general behavioral state of the animal. We present here an overview of the brain regions and their connections involved in the whisker system. We do not only describe the anatomy and functional roles of the cerebral cortex, but also those of subcortical structures like the striatum, superior colliculus, cerebellum, pontomedullary reticular formation, zona incerta, and anterior pretectal nucleus as well as those of level setting systems like the cholinergic, histaminergic, serotonergic, and noradrenergic pathways. We conclude by discussing how these brain regions may affect each other and how they together may control the precise timing of whisker movements and coordinate whisker perception. PMID:22065951

  15. Anatomical pathways involved in generating and sensing rhythmic whisker movements

    Directory of Open Access Journals (Sweden)

    Laurens W.J. Bosman

    2011-10-01

    Full Text Available The rodent whisker system is widely used as a model system for investigating sensorimotor integration, neural mechanisms of complex cognitive tasks, neural development, and robotics. The whisker pathways to the barrel cortex have received considerable attention. However, many subcortical structures are paramount to the whisker system. They contribute to important processes, like filtering out salient features, integration with other senses and adaptation of the whisker system to the general behavioral state of the animal. We present here an overview of the brain regions and their connections involved in the whisker system. We do not only describe the anatomy and functional roles of the cerebral cortex, but also those of subcortical structures like the striatum, superior colliculus, cerebellum, pontomedullary reticular formation, zona incerta and anterior pretectal nucleus as well as those of level setting systems like the cholinergic, histaminergic, serotonergic and noradrenergic pathways. We conclude by discussing how these brain regions may affect each other and how they together may control the precise timing of whisker movements and coordinate whisker perception.

  16. Harbor seal whiskers synchronize with frequency of upstream wake

    Science.gov (United States)

    Beem, Heather; Triantafyllou, Michael

    2013-11-01

    Harbor seals are able to use their whiskers to track minute water movements, such as those left in the wake of a fish. The current study is a simple representation of what the whiskers experience as the seal chases a fish. A scaled whisker model (average cross-flow diameter: dw) is first tested in a towing tank by itself and then towed behind a larger cylinder (dc = 2 . 5dw), which serves as a wake generator. A flexing plate attached to the model base allows the whisker to freely vibrate in response to the flow. Measurements from strain gages on the plate are calibrated to tip deflections. While in the cylinder wake, the whisker vibrates with an amplitude up to ten times higher than it does on its own (A /dw = 0 . 15). Also, the whisker synchronizes with the vortex shedding frequency (fs =0/. 2 U dc) of the upstream cylinder over the range of reduced velocities tested, whereas on its own, the whisker oscillates around its own natural frequency in water. Seals may use the difference in vibration amplitude and frequency between these two cases to help detect the presence of a vortex wake.

  17. Graphite whiskers in CV3 meteorites.

    Science.gov (United States)

    Fries, Marc; Steele, Andrew

    2008-04-04

    Graphite whiskers (GWs), an allotrope of carbon that has been proposed to occur in space, have been discovered in three CV-type carbonaceous chondrites via Raman imaging and electron microscopy. The GWs are associated with high-temperature calcium-aluminum inclusion (CAI) rims and interiors, with the rim of a dark inclusion, and within an inclusion inside an unusual chondrule that bears mineralogy and texture indicative of high-temperature processing. Current understanding of CAI formation places their condensation, and that of associated GWs, relatively close to the Sun and early in the condensation sequence of protoplanetary disk materials. If this is the case, then it is a possibility that GWs are expelled from any young solar system early in its history, thus populating interstellar space with diffuse GWs. Graphite whiskers have been postulated to play a role in the near-infrared (near-IR) dimming of type Ia supernovae, as well as in the thermalization of both the cosmic IR and microwave background and in galactic center dimming between 3 and 9 micrometers. Our observations, along with the further possibility that GWs could be manufactured during supernovae, suggest that GWs may have substantial effects in observational astronomy.

  18. Mechanical properties and tribological behaviour of silicon carbide/carbon nano fibers nano composites; Propiedades mecanicas y tribologicas de materiales nanoestructurados de carburo de silicio/nanofibras de carbono

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, A.; Torrecillas, R.; Rocha, V. G.; Fernandez, A.; Bonache, V.; Salvador, M. D.

    2011-07-01

    The development of new ceramic/carbon nano structured materials is a very interesting option from the point of view of the automotive and aerospace industries. Its low density, high mechanical strength, high oxidation resistance and excellent friction behavior allows the use of these composites as functional materials. The aim of this study was to evaluate the influence of carbon nano fibers (CNFs) on the mechanical and tribological behavior of silicon carbide/CNFs nano composite obtained by spark plasma sintering technique. The tribological study was carried out in a ball-on-disk apparatus under dry sliding conditions (dry friction) and a fixed load of 15 N. The friction coefficient and wear rate were measured for each composite. Scanning electron microscope was used to analyze wear surface formed. The results show simultaneous improvement of wear behavior and mechanical properties of ceramic materials by incorporating of carbon nano fibers. (Author) 23 refs.

  19. A Nonlinear Viscous Model for Sn-Whisker Growth

    Science.gov (United States)

    Yang, Fuqian

    2016-12-01

    Based on the mechanism of the grain boundary fluid flow, a nonlinear viscous model for the growth of Sn-whiskers is proposed. This model consists of two units, one with a stress exponent of one and one with a stress exponent of n -1. By letting one of the constants be zero in the model, the constitutive relationship reduces to a linear flow relation or a power-law relation, representing the flow behavior of various metals. Closed-form solutions for the growth behavior of a whisker are derived, which can be used to predict the whisker growth and the stress evolution.

  20. Tactile Sensing with Whiskers of Various Shapes: Determining the Three-Dimensional Location of Object Contact Based on Mechanical Signals at the Whisker Base.

    Science.gov (United States)

    Huet, Lucie A; Rudnicki, John W; Hartmann, Mitra J Z

    2017-06-01

    Almost all mammals use their mystacial vibrissae (whiskers) as important tactile sensors. There are no sensors along the length of a whisker: all sensing is performed by mechanoreceptors at the whisker base. To use artificial whiskers as a sensing tool in robotics, it is essential to be able to determine the three-dimensional (3D) location at which a whisker has made contact with an object. With the assumption of quasistatic, frictionless, single-point contact, previous work demonstrated that the 3D contact point can be uniquely determined if all six components of force and moment are measured at the whisker base, but these measurements require a six-axis load cell. Here, we perform simulations to investigate the extent to which each of the 20 possible "triplet" combinations of the six mechanical signals at the whisker base uniquely determine 3D contact point location. We perform this analysis for four different whisker profiles (shapes): tapered with and without intrinsic curvature, and cylindrical with and without intrinsic curvature. We show that whisker profile has a strong influence on the particular triplet(s) of signals that uniquely map to the 3D contact point. The triplet of bending moment, bending moment direction, and axial force produces unique mappings for tapered whiskers. Four different mappings are unique for a cylindrical whisker without intrinsic curvature, but only when large deflections are excluded. These results inform the neuroscience of vibrissotactile sensing and represent an important step toward the development of artificial whiskers for robotic applications.

  1. Bio-Inspired PVDF-Based, Mouse Whisker Mimicking, Tactile Sensor

    Directory of Open Access Journals (Sweden)

    Mohsin Islam Tiwana

    2016-10-01

    Full Text Available The design and fabrication of a Polyvinylidene fluoride (PVDF based, mouse (or rodent whisker mimicking, tactile sensor is presented. Unlike previous designs reported in the literature, this sensor mimics the mouse whisker not only mechanically, but it also makes macro movements just like a real mouse whisker in a natural environment. We have developed a mathematical model and performed finite element analysis using COMSOL, in order to optimise the whisker to have the same natural frequency as that of a biological whisker. Similarly, we have developed a control system that enables the whisker mimicking sensor to vibrate at variable frequencies and conducted practical experiments to validate the response of the sensor. The natural frequency of the whisker can be designed anywhere between 35 and 110 Hz, the same as a biological whisker, by choosing different materials and physical dimensions. The control system of this sensor enables the whisker to vibrate between 5 and 236 Hz.

  2. Influence of nano-silica content on fiexural properties of the aluminum borate whisker and silica filler composite resins%纳米二氧化硅含量对硼酸铝晶须-二氧化硅熔附体填料复合树脂弯曲性能的影响

    Institute of Scientific and Technical Information of China (English)

    张文云; 袁艳波; 陈庆华; 肖玉鸿; 李星星

    2011-01-01

    目的 研究正硅酸乙酯(TEOS)水解所得纳米二氧化硅(Si02)含量对硼酸铝晶须(AIBw)与SiO2熔附体填料复合树脂弯曲性能的影响.方法 采用TEOS溶胶一凝胶法制得纳米SiO2,按不同比例通过高温烧结使其熔附于AIBw表面,制作试样并测试其弯曲强度和弯曲弹性模量;利用透射电镜(TEM)观察高温处理过程对晶须表面形态的影响以及不同比例的熔附体形貌.结果 AlBw-SiO2熔附体复合填料可显著提高牙科复合树脂的弯曲性能:AlBw和SiO2的质量比为3:1时牙科复合树脂的弯曲强度达(130.29±8.38)MPa.结论 TEOS溶胶-凝胶法水解所得的纳米SiO2含量可改善AlBw-SiO2熔附体填料复合树脂的弯曲性能.%Objective To discuss the influence of nano-silica content which was hydrolyzed by tetraethyl orthosioate(TEOS) on the aluminum borate whisker(AlBw) and silica filler composite resins on flexural properties.Methods The nanometer-size silicon dioxide (SiO2) particles were prepared by sol-gel method based on tetraethyl orthosioate.Different proportion of AlBw and SiO2 were fused and attached onto the surface of AlBw through high temperature,then polymerized with resin matrix after surface siliconization and their flexural strength and flexural modulus were determined.The effects of heat treatment to the surface morphology of AlBw and the shapes of the mixture at various proportions were characterized by TEM.Results The flexural properties of dental composite resins with AlBw-SiO2 compound as inorganic fillers were significantly improved.The flexural property of a new type of dental composite resins was (130.29±8.38) MPa, when the mass ratio of AlBw and nano-SiO2 particle was 3:1.Conclusion Nano-silica content which was hydrolyzed by tetraethyl orthosioate improved flexural properties of the aluminum borate whisker and silica filler composite resins.

  3. ADHERENCE AND PROPERTIES OF SILICON CARBIDE BASED FILMS ON STEEL

    OpenAIRE

    Lelogeais, M.; Ducarroir, M.; Berjoan, R.

    1991-01-01

    Coatings of silicon carbide with various compositions have been obtained in a r.f plasma assisted process using tetramethylsilane and argon as input gases. Some properties against mechanical applications of such deposits on steel have been investigated. Residual stresses and hardness are reported and discussed in relation with plasma parameters and deposit composition. By scratch testing, it was shown that the silicon carbide films on steel denote a good adherence when compared with previous ...

  4. In situ synthesis tungsten carbide reinforced ferrous matrix surface composites by laser cladding%激光熔覆原位合成碳化钨增强铁基表面复合材料的研究

    Institute of Scientific and Technical Information of China (English)

    陈莹莹; 李文戈; 吴培桂

    2011-01-01

    利用激光熔覆原位合成技术,在预置Ni涂层的45钢表面原位自生碳化钨陶瓷.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、显微硬度计等分析测试手段对碳化钨陶瓷增强相的组织形貌、物相组成、化学成分及力学性能等方面进行了研究.结果表明,熔覆区内的碳化物由过饱和固溶体共晶析出;涂层与基体问的结合为冶金结合;制备的表面复合材料的硬度高于基体,改性效果极为明显.%Multiphase tungsten carbide on 45 steel was fabricated by laser cladding cooperated with combustion synthesis. The microstructure,phase composition, element distribution and mechanical properties of tungsten carbide ceramic reinforcement phase were analyzed by XRD,SEM, EDS and microhardness tester, respectively. The results show that the laser cladding region supersaturated solid solution by eutectic precipitation. The coating and the substrate is metallurgical bonding. The hardness of composite is superior to substrate. In a word, the modification effect is remarkable.

  5. Growth and microstructure of AlN whiskers and dendrites

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    AlN whiskers or dendrites were synthesized with a sublimation-recrystallization method by using Al, AlN powders and some additives as raw materials. Whiskers with different sizes that featured high purity and good crystallinity were obtained by controlling temperature and gas supersaturation in the reaction container. The whiskers were described as long and straight single crystals of approximately 1-30 (m in diameter by the centimeter range in length. However, AlN dendrites were about 1 mm in diameter by 0.5 cm in length, and showed an obviously preferential growth orientation, i.e., perpendicular to and planes. It is concluded that the whiskers or dendrites grow via the vapor-solid mechanism.

  6. Proof of the WARM whisker conjecture for neuronal connections

    Science.gov (United States)

    Holmes, Mark; Kleptsyn, Victor

    2017-04-01

    This paper is devoted to the study of the so-called WARM reinforcement models that are generalisations of Pólya's urn. We show that in the graph setting, once the exponent α of the reinforcement function is greater than 2, the stable and critical equilibria can be supported only on spanning forests, and once α > 25 , on spanning whisker forests. Thus, we prove the whisker forests conjecture from Hofstad et al. [Ann. Appl. Probab. 26(4), 2494-2539 (2016)].

  7. Preparation and properties of ZnO nano-whiskers

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    By a novel controlled combustion synthesis method, a large amount of ZnO nano-whiskers with different morphologies like nanotetrapods, long-leg nanotetrapod and multipods, were prepared without any catalysts and additives in open air at high temperature. Their morphologies, structures and optical properties were in-vestigated by using SEM, XRD and PL spectrum. The possible growth mechanisms on the ZnO nano-whiskers were proposed in this paper.

  8. Low-temperature strain gauges based on silicon whiskers

    Directory of Open Access Journals (Sweden)

    Druzhinin A. A.

    2008-08-01

    Full Text Available To create low-temperature strain gauges based on p-type silicon whiskers tensoresistive characteristics of these crystals in 4,2—300 K temperature range were studied. On the basis of p-type Si whiskers with different resistivity the strain gauges for different materials operating at cryogenic temperatures with extremely high gauge factor at 4,2 K were developed, as well as strain gauges operating at liquid helium temperatures in high magnetic fields.

  9. Passive Wake Detection Using Seal Whisker-Inspired Sensing

    Science.gov (United States)

    2015-02-01

    119 20 3-14 (a) A Solidworks simulation of the strain induced on the flexure as the whisker deflects. (b) Close-up of the flexure...168 B-4 The twisted elliptical cylinder, as generated in Solidworks . . . . . . . 169 B-5 C l,v contours...blocks of machinable wax bolted together. A CNC tool path for the whisker geometry was created in MasterCAM from Solidworks and then routed out. (b) The

  10. Raman spectroscopic characterization of the core-rim structure in reaction bonded boron carbide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jannotti, Phillip; Subhash, Ghatu, E-mail: subhash@ufl.edu [Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States); Zheng, James Q.; Halls, Virginia [Program Executive Office—Soldier Protection and Individual Equipment, US Army, Fort Belvoir, Virginia 22060 (United States); Karandikar, Prashant G.; Salamone, S.; Aghajanian, Michael K. [M-Cubed Technologies, Inc., Newark, Delaware 19711 (United States)

    2015-01-26

    Raman spectroscopy was used to characterize the microstructure of reaction bonded boron carbide ceramics. Compositional and structural gradation in the silicon-doped boron carbide phase (rim), which develops around the parent boron carbide region (core) due to the reaction between silicon and boron carbide, was evaluated using changes in Raman peak position and intensity. Peak shifting and intensity variation from the core to the rim region was attributed to changes in the boron carbide crystal structure based on experimental Raman observations and ab initio calculations reported in literature. The results were consistent with compositional analysis determined by energy dispersive spectroscopy. The Raman analysis revealed the substitution of silicon atoms first into the linear 3-atom chain, and then into icosahedral units of the boron carbide structure. Thus, micro-Raman spectroscopy provided a non-destructive means of identifying the preferential positions of Si atoms in the boron carbide lattice.

  11. Fabrication of thorium bearing carbide fuels

    Science.gov (United States)

    Gutierrez, Rueben L.; Herbst, Richard J.; Johnson, Karl W. R.

    1981-01-01

    Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750.degree. C. and 2000.degree. C. were used during the reduction cycle. Sintering temperatures of 1800.degree. C. and 2000.degree. C. were used to prepare fuel pellet densities of 87% and >94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproducibility of chemicals and phase composition. Methods employing liquid techniques that form carbide microspheres or alloying-techniques which form alloys of thorium-uranium or thorium-plutonium suffer from limitation on the quantities processed of because of criticality concerns and lack of precise control of process conditions, respectively.

  12. Electroluminescence of Zn{sub 2}GeO{sub 4}:Mn through SiC whisker electric field enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Wagstaff, Brandon, E-mail: wagstabj@mcmaster.ca [McMaster University, Department of Engineering Physics, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L8 (Canada); Kitai, Adrian, E-mail: kitaia@mcmaster.ca [McMaster University, Department of Engineering Physics, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L8 (Canada); McMaster University, Department of Materials Science and Engineering, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L8 (Canada)

    2015-11-15

    Alternating current (AC) electroluminescence of thin film oxide phosphors is well known. However in this work electroluminescence of bulk oxide powder phosphors is achieved. A new type of AC Electroluminescent (ACEL) device has been created and developed by integrating SiC whiskers into a phosphor matrix composed of manganese-activated zinc germanate (Zn{sub 2}GeO{sub 4}:Mn{sup 2+}). The conductive SiC whiskers enhance the average electric field in specific regions of the phosphor such that localized breakdown of the phosphor occurs, thus emitting green light. This field enhancement allows light emission to occur in thick film oxide powder phosphors and is notably the first time that bright and reasonably efficient electroluminescence of zinc germanate has been observed without using expensive thin film deposition techniques. Light emission has been achieved in thick pressed pellets using surface-deposited electrodes and the brightness-voltage characteristics of light emission are shown to be consistent with field emission of carriers from the embedded whiskers. - Highlights: • A new electroluminescent phosphor, Zn{sub 2}GeO{sub 4}Mn{sup 2+}+SiC whiskers, is proposed. • A procedure is described to fabricate a solid sample of this composite material. • Under an AC voltage, green light is emitted only in samples containing the SiC whiskers. • A brightness of 25 Cd/m{sup 2} and efficiency of 0.25 Lm/W is observed 9.6×10{sup 6} V/m. • This is notably the first time that ACEL has been observed in bulk Zn{sub 2}GeO{sub 4}Mn{sup 2+}.

  13. Mirror Surface Grinding of Steel Bonded Carbides

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The steel bonded carbide, a composite material, is very difficult to be machined to a fine finish mirror surface. In this paper, an electrolytic in-process dressing (ELID) grinding with metallic bond super-hard abrasive wheel was developed for grinding steel bonded carbide GT35. Factors affecting ELID grinding performance were analyzed by an atomic force microscope (AFM). Based on the analysis of AFM topography of the fine ground mirror surface of the steel bonded carbide, a schematic diagram of the mechanism of micro-removal of the ground surface was described. The AFM topography also shows that the hard brittle carbide particles, on the surface of steel bonded carbide, were machined out by ductile cutting. Since the grinding cracks in the ground surface are due to temperature gradient, temperature distribution in the grinding area was analyzed by finite element method (FEM). Experimental results indicate that a good mirror surface with Ra<0.02pm can be obtained by the developed ELID grinding system.

  14. Tool flank wear model and parametric optimization in end milling of metal matrix composite using carbide tool: Response surface methodology approach

    Directory of Open Access Journals (Sweden)

    R. Arokiadass

    2012-04-01

    Full Text Available Highly automated CNC end milling machines in manufacturing industry requires reliable model for prediction of tool flank wear. This model later can be used to predict the tool flank wear (VBmax according to the process parameters. In this investigation an attempt was made to develop an empirical relationship to predict the tool flank wear (VBmax of carbide tools while machining LM25 Al/SiCp incorporating the process parameters such as spindle speed (N, feed rate (f, depth of cut (d and various % wt. of silicon carbide (S. Response surface methodology (RSM was applied to optimizing the end milling process parameters to attain the minimum tool flank wear. Predicted values obtained from the developed model and experimental results are compared, and error <5 percent is observed. In addition, it is concluded that the flank wear increases with the increase of SiCp percentage weight in the MMC.

  15. Synthesis of potassium hexatitanate whiskers using hydrothermal method

    Institute of Scientific and Technical Information of China (English)

    WANG Ju; LI Chun; LIANG Bin; WANG Xiaoqing

    2009-01-01

    High quality potassium hexatitanate whiskers were hydrothermally synthesized in one step under moderate temperature and pressure condi-tions. Effects of the titanium source and reaction conditions on the hydrothermal reaction rate, product phase component, and morphology of whiskers were investigated. The results show that the reactivity of hydrated titania, anatase TiO2, and rutile TiO2 with KOH decreases in turn, and with hydrated titania as titanium source, it is difficult to obtain potassium hexatitanate whiskers with good morphology. In contrast, uni-form potassium hexatitanate whiskers with a length of 10-20 μm and a diameter of 200-700 nm were obtained using anatase TiO2 as titanium source. The investigation demonstrates that the initial KOH concentration, annealing temperature and time, molar ratio of K2O/TiO2, etc. sig-nificantly affect the morphology of the as-synthesized whiskers. The optimized synthesis condition is as follows: anatase as a titanium source; 10 wt.% KOH solution; annealing temperature and time of 300℃ and 5 h, respectively; K2O/TiO2 molar ratio orS, etc. A rhombic potassium hexatitanate was prepared under the optimum condition and the whisker grew along the [110] direction. The reaction mechanism was dis-cussed.

  16. Tin Whisker Growth and Mitigation with a Nanocrysytalline Nickel Coating

    Science.gov (United States)

    Janiuk, Szymon

    Tin whiskers are a problem in the electronics industry since the EU banned the use of lead in Pb-Sn solders as part of the Restriction of Hazardous Substances (RoHS). The biggest concern with Sn whiskers is their ability to short-circuit electronics. High reliability applications such as the aerospace, defense, healthcare, and automotive industries are at most risk. This project explores Sn whisker mitigation and prevention with the use of nanocrystalline nickel coating over Sn surfaces. Sn was plated onto a pure Cu substrate using electroplating. A high temperature and high humidity condition, at 85°C and 85% RH, was effective at growing whiskers. A nNi coating was plated over Sn/Cu coupons. After subjecting the nNi/ Sn/Cu samples through 85°C/85% RH testing conditions, no whiskers were observed penetrating the surface. These results make nNi a viable material to use as a coating to prevent the growth of Sn whiskers in electronic assemblies.

  17. Supported molybdenum carbide for higher alcohol synthesis from syngas

    DEFF Research Database (Denmark)

    Wu, Qiongxiao; Christensen, Jakob Munkholt; Chiarello, Gian Luca

    2013-01-01

    Molybdenum carbide supported on active carbon, carbon nanotubes, and titanium dioxide, and promoted by K2CO3, has been prepared and tested for methanol and higher alcohol synthesis from syngas. At optimal conditions, the activity and selectivity to alcohols (methanol and higher alcohols) over...... supported molybdenum carbide are significantly higher compared to the bulk carbide. The CO conversion reaches a maximum, when about 20wt% Mo2C is loaded on active carbon. The selectivity to higher alcohols increases with increasing Mo2C loading on active carbon and reaches a maximum over bulk molybdenum...... carbide, while the selectivity to methanol follows the opposite trend. The effect of Mo2C loading on the alcohol selectivity at a fixed K/Mo molar ratio of 0.14 could be related to the amount of K2CO3 actually on the active Mo2C phase and the size, structure and composition of the supported carbide...

  18. 润滑条件下Mg2B2O5/6061Al基复合材料摩擦磨损性能研究%Friction and Wear Behaviors of Mg2B2O5 Whisker Reinforced 6061Al Matrix Composites under Lubricated Condition

    Institute of Scientific and Technical Information of China (English)

    陈庚; 金培鹏; 李丽荣; 郭娟

    2012-01-01

    采用自制的机械-超声混合搅拌设备制备出Mg2B2O5/6061Al铝基复合材料,复合材料的体积分数为2%.研究了载荷和滑动速度对基体以及复合材料的摩擦磨损性能的影响.实验结果表明,基体和复合材料摩擦系数总体上随着载荷和滑动速度的增加而减小.基体和复合材料的磨损率随载荷和滑动速度的增加而明显的增大,且基体和复合材料均存在一个临界载荷和临界滑动速度.当载荷和滑动速度到达临界值后,磨损率均急剧增大,此时试样摩擦磨损机制由微观疲劳磨损和磨粒磨损向粘着磨损与剥离磨损转变.%The fiiction and wear properties of MgAO, whisker reinforced 6061A1 matrix composites fabricated by power ultrasonic-stir casting process were investigated using a ball-on-disk wear-testing machine against a <3Cr45 steel counterface under lubricated conditions. The volume fraction of the composites was 2%. The relationship between the wear rate and the coefficient of friction was discussed. Results indicate that: as the applied load and sliding speed steadily increased, the fiiction coefficients of the matrix alloy and the fabricated composites decrease and the wear rate increases. Both of the applied load and sliding velocity of the matrix and composite have a critical value, when the applied load and sliding velocity reach the critical values, the wear rate increased sharply and the wear mechanisms of the composites shifted from mild to severe regime.

  19. Facial whisker pattern is not sufficient to instruct a whisker-related topographic map in the mouse somatosensory brainstem.

    Science.gov (United States)

    Laumonnerie, Christophe; Bechara, Ahmad; Vilain, Nathalie; Kurihara, Yukiko; Kurihara, Hiroki; Rijli, Filippo M

    2015-11-01

    Facial somatosensory input is relayed by trigeminal ganglion (TG) neurons and serially wired to brainstem, thalamus and cortex. Spatially ordered sets of target neurons generate central topographic maps reproducing the spatial arrangement of peripheral facial receptors. Facial pattern provides a necessary template for map formation, but may be insufficient to impose a brain somatotopic pattern. In mice, lower jaw sensory information is relayed by the trigeminal nerve mandibular branch, whose axons target the brainstem dorsal principal sensory trigeminal nucleus (dPrV). Input from mystacial whiskers is relayed by the maxillary branch and forms a topographic representation of rows and whiskers in the ventral PrV (vPrV). To investigate peripheral organisation in imposing a brain topographic pattern, we analysed Edn1(-/-) mice, which present ectopic whisker rows on the lower jaw. We found that these whiskers were innervated by mandibular TG neurons which initially targeted dPrV. Unlike maxillary TG neurons, the ectopic whisker-innervating mandibular neuron cell bodies and pre-target central axons did not segregate into a row-specific pattern nor target the dPrV with a topographic pattern. Following periphery-driven molecular repatterning to a maxillary-like identity, mandibular neurons partially redirected their central projections from dPrV to vPrV. Thus, while able to induce maxillary-like molecular features resulting in vPrV final targeting, a spatially ordered lower jaw ectopic whisker pattern is insufficient to impose row-specific pre-target organisation of the central mandibular tract or a whisker-related matching pattern of afferents in dPrV. These results provide novel insights into periphery-dependent versus periphery-independent mechanisms of trigeminal ganglion and brainstem patterning in matching whisker topography. © 2015. Published by The Company of Biologists Ltd.

  20. A kind of carbon whiskers in new structure and morphology

    Institute of Scientific and Technical Information of China (English)

    DONG; Jian

    2001-01-01

    [1]Endo, M., Saito, R., Dresselhaus, M. S. et al. From carbon fibers to nanotubes, in Carbon Nanotubes Preparations and Properties (ed. Ebbesen, T. W.), New York: CRC Press Inc., 1997, 54-66.[2]Baker, R. T. K., Baker, M. A., Harris, P. S. et al., Nucleation and growth of carbon deposits from the nickel catalyzed de-composition of acetylene, J.Catal., 1972, 26(7): 51.[3]Audier, M., Coulon, M., Kinetic and microscopic aspects of catalytic carbon growth, Carbon, 1985, 23(3): 317.[4]Oberlin, A., Endo, M., Koyama, T., High resolution microscope observations of graphitized carbon fibers, Carbon, 1976, 14(1): 133.[5]Bacon, R., Growth, structure, and properties of graphite whiskers, Journal of Applied Physics, 1960, 31(2): 283.[6]Murayama, H., Maeda, M., A novel form of filamentous graphite, Nature, 1990, 345(28): 791.[7]Pimpinelli, A., Villain, J., Physics of Crystal Growth, New York: Cambridge University Press, 1998, 62-64.[8]Minkoff, I., Solidification and Cast Structure, Chichester: Wiley, 1986, 42-47.[9]Pierson, H. O., Handbook of Carbon, Graphite, Diamond, and Fullerenes: Properties, Processing, and Applications, Park Ridge: Noyes Publications, 1993, 151.[10]Bennema, P., Spiral growth and surface roughing: Developments since Burton, Cabrera and Frank, Journal of Crystal Growth, 1984, 69(2): 182.

  1. Structure, function, and cortical representation of the rat submandibular whisker trident.

    Science.gov (United States)

    Thé, Lydia; Wallace, Michael L; Chen, Christopher H; Chorev, Edith; Brecht, Michael

    2013-03-13

    Although the neurobiology of rodent facial whiskers has been studied intensively, little is known about sensing in other vibrissae. Here we describe the under-investigated submandibular "whisker trident" on the rat's chin. In this three-whisker array, a unique unpaired midline whisker is laterally flanked by two slightly shorter whiskers. All three whiskers point to the ground and are curved backwards. Unlike other whiskers, the trident is not located on an exposed body part. Trident vibrissae are not whisked and do not touch anything over long stretches of time. However, trident whiskers engage in sustained ground contact during head-down running while the animal is exploring or foraging. In biomechanical experiments, trident whiskers follow caudal ground movement more smoothly than facial whiskers. Remarkably, deflection angles decrease with increasing ground velocity. We identified one putative trident barrel in the left somatosensory cortex and two barrels in the right somatosensory cortex. The elongated putative trident-midline barrel is the longest and largest whisker barrel, suggesting that the midline trident whisker is of great functional significance. Cortical postsynaptic air-puff responses in the trident representation show much less temporal precision than facial whisker responses. Trident whiskers do not provide as much high-resolution information about object contacts as facial whiskers. Instead, our observations suggest an idiothetic function: their biomechanics allow trident whiskers to derive continuous measurements about ego motion from ground contacts. The midline position offers unique advantages in sensing heading direction in a laterally symmetric manner. The changes in trident deflection angle with velocity suggest that trident whiskers might function as a tactile speedometer.

  2. Parallel pathways from motor and somatosensory cortex for controlling whisker movements in mice.

    Science.gov (United States)

    Sreenivasan, Varun; Karmakar, Kajari; Rijli, Filippo M; Petersen, Carl C H

    2015-02-01

    Mice can gather tactile sensory information by actively moving their whiskers to palpate objects in their immediate surroundings. Whisker sensory perception therefore requires integration of sensory and motor information, which occurs prominently in the neocortex. The signalling pathways from the neocortex for controlling whisker movements are currently poorly understood in mice. Here, we delineate two pathways, one originating from primary whisker somatosensory cortex (wS1) and the other from whisker motor cortex (wM1), that control qualitatively distinct movements of contralateral whiskers. Optogenetic stimulation of wS1 drove retraction of contralateral whiskers while stimulation of wM1 drove rhythmic whisker protraction. To map brainstem pathways connecting these cortical areas to whisker motor neurons, we used a combination of anterograde tracing using adenoassociated virus injected into neocortex and retrograde tracing using monosynaptic rabies virus injected into whisker muscles. Our data are consistent with wS1 driving whisker retraction by exciting glutamatergic premotor neurons in the rostral spinal trigeminal interpolaris nucleus, which in turn activate the motor neurons innervating the extrinsic retractor muscle nasolabialis. The rhythmic whisker protraction evoked by wM1 stimulation might be driven by excitation of excitatory and inhibitory premotor neurons in the brainstem reticular formation innervating both intrinsic and extrinsic muscles. Our data therefore begin to unravel the neuronal circuits linking the neocortex to whisker motor neurons. © 2014 The Authors. European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  3. A novel biomimetic whisker technology based on fiber Bragg grating and its application

    Science.gov (United States)

    Zhao, Chenlu; Jiang, Qi; Li, Yibin

    2017-09-01

    The paper describes a novel, biomimetic whisker-based sensing technology following the basic design of the facial whiskers of animals such as rats and mice. The sensor consists of a 3× 2 whisker array on each side of a robot. In experiments with the artificial whiskers, the motor drives rotating whiskers, and the center wavelength of a fiber Bragg grating pasted on the whisker will shift when the whisker touches an obstacle. The distance will be obtained by processing the wavelength shift data with algorithms. Then the shape recognition can be realized by postprocessing the distance data. The experimental results prove that the whisker array is capable of accurately gathering the distance and shape information of an object.

  4. Electro Conductive Alumina Nanocomposites From Different Alumina-Carbides Mixtures

    Directory of Open Access Journals (Sweden)

    Díaz Luis A.

    2016-01-01

    SiC whiskers reinforced electrically conductive ceramic compositions provide a fully dense material with optimal mechanical properties. The capability of electro-discharge machining obtains good surface quality, chip-free edges, dimensional accuracy and complex shapes. The fracture toughness is improved two to three fold over individual ceramic components. Strength and hardness is also increased. Some composites were tested as a cutting tool to machine IN-718 nickel-base superalloy industrial laminating cylinders. The composites were formed and electro-discharge machined to a standard size cutting insert.

  5. Salt flux synthesis of single and bimetallic carbide nanowires

    Science.gov (United States)

    Leonard, Brian M.; Waetzig, Gregory R.; Clouser, Dale A.; Schmuecker, Samantha M.; Harris, Daniel P.; Stacy, John M.; Duffee, Kyle D.; Wan, Cheng

    2016-07-01

    Metal carbide compounds have a broad range of interesting properties and are some of the hardest and highest melting point compounds known. However, their high melting points force very high reaction temperatures and thus limit the formation of high surface area nanomaterials. To avoid the extreme synthesis temperatures commonly associated with these materials, a new salt flux technique has been employed to reduce reaction temperatures and form these materials in the nanometer regime. Additionally, the use of multiwall carbon nanotubes as a reactant further reduces the diffusion distance and provides a template for the final carbide materials. The metal carbide compounds produced through this low temperature salt flux technique maintain the nanowire morphology of the carbon nanotubes but increase in size to ˜15-20 nm diameter due to the incorporation of metal in the carbon lattice. These nano-carbides not only have nanowire like shape but also have much higher surface areas than traditionally prepared metal carbides. Finally, bimetallic carbides with composition control can be produced with this method by simply using two metal precursors in the reaction. This method provides the ability to produce nano sized metal carbide materials with size, morphology, and composition control and will allow for these compounds to be synthesized and studied in a whole new size and temperature regime.

  6. Corrosion behaviour of groundnut shell ash and silicon carbide hybrid reinforced Al-Mg-Si alloy matrix composites in 3.5% NaCl and 0.3M H2SO4 solutions

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo ALANEME

    2015-05-01

    Full Text Available The corrosion behaviour of Al-Mg-Si alloy based composites reinforced with groundnut shell ash (GSA and silicon carbide (SiC was investigated. The aim is to assess the corrosion properties of Al-Mg-Si alloy based hybrid reinforced composites developed using different mix ratios of GSA (a cheaply processed agro waste derivative which served as partial replacement for SiC and SiC as reinforcing materials. GSA and SiC mixed in weight ratios 0:1, 1:3, 1:1, 3:1, and 1:0 were utilized to prepare 6 and 10 wt% of the reinforcing phase with Al‐Mg‐Si alloy as matrix using two‐step stir casting method. Mass loss and corrosion rate measurement was used to study the corrosion behaviour of the produced composites in 3.5% NaCl and 0.3M H2SO4 solutions. The results show that the Al-Mg-Si alloy based composites containing 6 and 10 wt% GSA and SiC in varied weight ratios were resistant to corrosion in 3.5% NaCl solution. The composites were however more susceptible to corrosion in 0.3M H2SO4 solution (in comparison with the 3.5% NaCl solution. It was noted that the Al-Mg-Si/6 wt% GSA-SiC hybrid composite grades containing GSA and SiC in weight ratio 1:3 and 3:1 respectively exhibited superior corrosion resistance in the 0.3M H2SO4 solution compared to other composites produced for this series. In the case of the Al-Mg-Si/10 wt% GSA-SiC hybrid composite grades, the corrosion resistance was relatively superior for the composites containing a greater weight ratio of GSA (75% and 100% in 0.3M H2SO4 solution.

  7. Sr{sub 1.98}Eu{sub 0.02}SiO{sub 4} luminescence whisker based on vapor-phase deposition: Facile synthesis, uniform morphology and enhanced luminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jian, E-mail: xujian@stu.xmu.edu.cn [Department of Materials Science and Engineering, Xiamen University, Xiamen 361005 (China); Hassan, Dhia A. [Department of Materials Science and Engineering, Xiamen University, Xiamen 361005 (China); Department of Chemistry, College of Education for Pure Science, University of Basrah, 61004 (Iraq); Zeng, Renjie; Peng, Dongliang [Department of Materials Science and Engineering, Xiamen University, Xiamen 361005 (China); Fujian Key Lab of Advanced Special Material, Xiamen University, Xiamen 361005 (China); Key Laboratory of High Performance Ceramic Fibers, Ministry of Education, Xiamen 361005 (China)

    2015-11-15

    Highlights: • For the first time, it is possible to obtain Sr{sub 1.98}Eu{sub 0.02}SiO{sub 4} whisker. • The whiskers are smooth and uniform with L/D ratio over 50. • Durability and thermal stability of the whisker are enhanced. - Abstract: A high performance strontium silicate phosphor has been successfully synthesized though a facile vapor-phase deposition method. The product consists of single crystal whiskers which are smooth and uniform, and with a sectional equivalent diameter of around 5 μm; the aspect ratio is over 50 and no agglomeration can be observed. X-ray diffraction result confirmed that the crystal structure of the whisker was α’-Sr{sub 2}SiO{sub 4}. The exact chemical composition was Sr{sub 1.98}Eu{sub 0.02}SiO{sub 4} which was analyzed by energy dispersive spectrometer and inductively coupled plasma-mass spectrometer. The whisker shows broad green emission with peak at 523 nm ranging from 470 to 600 nm (excited at 370 nm). Compared with traditional Sr{sub 2}SiO{sub 4}:Eu phosphor, durability (at 85% humidity and 85 °C) and thermal stability of the whisker are obviously improved. Moreover, growth mechanism of the Sr{sub 1.98}Eu{sub 0.02}SiO{sub 4} whiskers is Vapor–Liquid–Solid. On a macro-scale, the product is still powder which makes it suitable for the current packaging process of WLEDs.

  8. Study on fragmentation and dissolution behavior of carbide in a hot-rolled hypereutectic high chromium cast iron

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fei; Jiang, Yehua, E-mail: jiangyehua@kmust.edu.cn; Xiao, Han; Tan, Jun

    2015-01-05

    Highlights: • The method to prepare Carbon steel/High chromium iron is totally new. • High chromium iron can achieve small plastic deformation during hot rolling process. • Carbides in high chromium irons are crushed, refined obviously and becoming isolated, which is benefit to improve the impact toughness. • The carbide fragmentation and dissolution behavior of the hot-rolled HCCI were analyzed. - Abstract: A sandwich-structured composite containing a hypereutectic high chromium cast iron (HCCI) and low carbon steel (LCS) claddings was newly fabricated by centrifugal casting, then the blank was hot-rolled into composite plate. The carbide fragmentation and dissolution behavior of the hot-rolled HCCI were analyzed. During hot rolling, significant refinement of carbides was discovered in hot-rolled HCCI specimens. The carbides were broken and partly dissolved into the austenite matrix. The results show that carbides are firstly dissolved under the action of stress. There are grooves appeared at the boundaries of the carbides. The grooves reduce the cross section of the carbide. When the cross section of the carbide reaches to the required minimum critical cross section, the carbide breaks through the tensile force. After break, carbides continue to dissolve since more interfaces between the matrix and carbides are generated. The secondary carbides precipitated due to the dissolution are index as fcc and stacking faults parallel to the {1 1 1} are observed.

  9. Effect of composition of titanium in silver-copper-titanium braze alloy on dissimilar laser brazing of binder-less cubic boron nitride and tungsten carbide

    Science.gov (United States)

    Sechi, Yoshihisa; Nagatsuka, Kimiaki; Nakata, Kazuhiro

    2014-08-01

    Laser brazing with Ti as an active element in silver-copper alloy braze metal has been carried out for binder-less cubic boron nitride and tungsten carbide, using silver-copper- titanium braze alloys with titanium content that varied between 0.28 mass% and 1.68 mass%. Observations of the interface using electron probe microanalysis and scanning acoustic microscopy show that efficient interface adhesion between binder-less cubic boron nitride and the silver-copper-titanium braze alloy was achieved for the braze with a titanium content of 0. 28 mass%.

  10. Elastic modulus of SiCw/6061Al alloy composites as-squeeze-cast

    Institute of Scientific and Technical Information of China (English)

    姜传海; 吴建生; 王德尊

    2001-01-01

    By using the system of image analyzer connected with scanning electron microscope, the whisker orientation in the SiCw/6061Al alloy composite as-squeeze-cast was measured. According to the shear lag model and the actual distribution function of whisker in composite, the inhomogeneity of elastic modulus in composite was analyzed. With the method of ultrasonic velocity, the elastic modulus of composite was measured. The results showed that, the whiskers of composite are preferred in an orientation normal to the direction of squeeze cast. The higher the volume fraction of whisker, the more extent of preferred orientation of it, and the inhomogeneity of elastic modulus is mainly due to the differences of whisker distribution in composite.

  11. Heat-Resistance of the Powder Cobalt Alloys Reinforced by Niobium or Titanium Carbide

    Directory of Open Access Journals (Sweden)

    Cherepova, T.S.

    2016-01-01

    Full Text Available The characteristics of heat-resistance of powder cobalt alloys at 1100 °C were investigated. These alloys were developed for the protection of workers banding shelves GTE blades from wear. The alloys were prepared by hot pressing powders of cobalt, chromium, aluminum, iron and niobium or titanium carbides. The values of heat resistance alloys containing carbides between 30 and 70% (vol. depend on the type made of carbide alloys: alloys with titanium carbide superior in heat-resistant alloy of niobium carbide. The most significant factor affecting on the heat-resistant alloys, is porosity: with its increase the parameters decline regardless of the type and content of carbide. The optimum composition of powder heat resisting alloys of titanium carbide with a melting point above 1300 °C were determined for use in the aircraft engine.

  12. Formation mechanism of spheroidal carbide in ultra-low carbon ductile cast iron

    Directory of Open Access Journals (Sweden)

    Bin-guo Fu

    2016-09-01

    Full Text Available The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal carbide belonged to eutectic carbide and crystallized in the isolated eutectic liquid phase area. The formation process of the spheroidal carbide was related to the contact and the intersection between the primary dendrite and the secondary dendrite of austenite. The oxides of magnesium, rare earths and other elements can act as heterogeneous nucleation sites for the spheroidal carbide. It was also found that the amount of the spheroidal carbide would increase with an increase in carbon content. The cooling rate has an important influence on the spheroidal carbide under the same chemical composition condition.

  13. Whisker movements evoked by stimulation of single motor neurons in the facial nucleus of the rat

    NARCIS (Netherlands)

    L.J. Herfst (Lucas); M. Brecht (Michael)

    2008-01-01

    textabstractThe lateral facial nucleus is the sole output structure whose neuronal activity leads to whisker movements. To understand how single facial nucleus neurons contribute to whisker movement we combined single-cell stimulation and high-precision whisker tracking. Half of the 44 stimulated ne

  14. Effects of Conformal Coat on Tin Whisker Growth

    Science.gov (United States)

    Kadesch, Jong S.; Leidecker, Henning; Day, John H. (Technical Monitor)

    2000-01-01

    A whisker from a tin plated part was blamed for the loss of a commercial spacecraft in 1998. Although pure tin finishes are prohibited by NASA, tin plated parts, such as hybrids, relays and commercial off the shelf (COTS) parts, are something discovered to have been installed in NASA spacecraft. Invariably, the assumption is that a conformal coat will prevent the growth of, or short circuits caused by, tin whiskers. This study measures the effect a Uralane coating has on the initiation and growth of tin whiskers, on the ability of this coating to prevent a tin whisker from emerging from the coating, and on the ability to prevent shorting. A sample of fourteen brass substrates (1 inch by 4 inches by 1/16 inch) were plated by two separate processes: half of the specimens were 'bright' tin plated directly over the brass substrate and half received a copper flash over the brass substrate prior to 'bright' tin plating. Each specimen was coated on one half of the substrate with three bi-directional sprays of Uralane 5750 to a nominal thickness of 25 to 75 micrometers (1 to 3 mils). Several specimens of both types, Cu and non-Cu flashed, were placed in an oven maintained at 50 C as others' work suggests that this is the optimal temperature for whisker formation. The remaining specimens were maintained at room ambient conditions. The surfaces of each specimen have been regularly inspected using both optical (15 to 400x power) and Scanning Electronic Microscopy (SEM). Many types of growths, including needle-like whiskers, first appeared approximately three months after plating on the non-conformally coated sides of all specimens. At four months, 4 to 5 times more growth sites were observed on the coated side; however, the density of growth sites on the non-conformally coated side has since increased rapidly, and now, at one year, is about the same for both sides. The density of growth sites is estimated at 90/sq mm with 30 percent of the sites growing whiskers (needle

  15. Whisking and whisker kinematics during a texture classification task.

    Science.gov (United States)

    Zuo, Yanfang; Perkon, Igor; Diamond, Mathew E

    2011-11-12

    Rats explore objects by rhythmically whisking with their vibrissae. The goal of the present study is to learn more about the motor output used by rats to acquire texture information as well as the whisker motion evoked by texture contact. We trained four rats to discriminate between different grooved textures and used high-speed video to characterize whisker motion during the task. The variance in whisking parameters among subjects was notable. After whisker trimming, the animals changed their behaviour in ways that appear consistent with an optimization of whisker movement to compensate for lost information. These results lead to the intriguing notion that the rats use an information-seeking 'cognitive' motor strategy, instead of a rigid motor programme. Distinct stick/slip events occurred during texture palpation and their frequency increased in relation to the spatial frequency of the grooves. The results allow a preliminary assessment of three candidate texture-coding mechanisms-the number of grooves encountered during each touch, the temporal difference between groove contacts and the spatial pattern of groove contacts across the whiskers.

  16. Neuronal encoding of texture in the whisker sensory pathway.

    Directory of Open Access Journals (Sweden)

    Ehsan Arabzadeh

    2005-01-01

    Full Text Available A major challenge of sensory systems neuroscience is to quantify brain activity underlying perceptual experiences and to explain this activity as the outcome of elemental neuronal response properties. Rats make extremely fine discriminations of texture by "whisking" their vibrissae across an object's surface, yet the neuronal coding underlying texture sensations remains unknown. Measuring whisker vibrations during active whisking across surfaces, we found that each texture results in a unique "kinetic signature" defined by the temporal profile of whisker velocity. We presented these texture-induced vibrations as stimuli while recording responses of first-order sensory neurons and neurons in the whisker area of cerebral cortex. Each texture is encoded by a distinctive, temporally precise firing pattern. To look for the neuronal coding properties that give rise to texture-specific firing patterns, we delivered horizontal and vertical whisker movements that varied randomly in time ("white noise" and found that the response probabilities of first-order neurons and cortical neurons vary systematically according to whisker speed and direction. We applied the velocity-tuned spike probabilities derived from white noise to the sequence of velocity features in the texture to construct a simulated texture response. The close match between the simulated and real responses indicates that texture coding originates in the selectivity of neurons to elemental kinetic events.

  17. Fe3O4 nano-whiskers by ultrasonic-aided reduction in concentrated NaOH solution

    Institute of Scientific and Technical Information of China (English)

    Chenglong Yu; Xin Hao; Hongtao Jiang; Lili Wang

    2011-01-01

    Fe3O4 nano-whiskers were synthesized via ultrasonic-aided reduction of FeCl2·4H2O with N2H4·H2O in concentrated NaOH solution. Phase identification and morphology observation were conducted by X-ray diffraction (XRD) analysis,transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM). Face scanning energy dispersive spectrum (face scanning EDS) and two-dimensional fast Fourier transform (2DFFT) for element distribution were carried out for confirming composition homogeneity. From XRD and TEM,the synthesized Fe3O4 nano-whiskers are of cubic phase with average dimension of 20 nm × 200 nm (average aspect ratio of 10). FE-SEM shows that the nanowhiskers without dispersion are interconnected into a network at a scale of 20μm. 2DFFT of the distribution of Fe and O from face scanning EDS confirms the composition homogeneity of the synthesized Fe3O4. Hydrazine hydrate determines the formation of the nano-whiskers,while the possible mechanism is the preferred growth along certain orientation with the aid of ultrasonic treatment.

  18. 镍基合金碳化铬复合涂层材料的界面分析%Interfacial Analysis of Ni-based Alloy—Chromium Carbide Composite Coating

    Institute of Scientific and Technical Information of China (English)

    黄新波; 林化春

    2001-01-01

    This paper generates a concentration function combinin g A.Ficks second law of diffusion by means of polynomial curve,and develops an efficient solver to calculate the diffusion coefficient of every component prec isely.It states that interfacial diffusion which causes metallurgical bondage ha ppens between the Alloy Chromium Carbide Composite coating and the steel substrate.%利用多项式曲线拟合浓度函数,结合菲克扩散第二定律, 编制FORTRAN程序,快速准确地计算出各组元的扩散系数。证实真空熔烧所得镍基合金—— 碳化铬复合涂层与钢基体之间发生界面扩散,形成牢固的冶金结合。

  19. CARBON-CONTAINING COMPOSITES BASED ON METALS

    Directory of Open Access Journals (Sweden)

    VAGANOV V. E.

    2015-10-01

    Full Text Available Problem statement Among the developed technologies metal-composites production,a special place takes powder metallurgy, having fundamental differences from conventionally used foundry technologies. The main advantages of this technology are: the possibility of sensitive control, the structure and phase composition of the starting components, and ultimately the possibility of obtaining of bulk material in nanostructured state with a minimum of processing steps. The potential reinforcers metals include micro and nano-sized oxides, carbides, nitrides, whiskers. The special position is occupied with carbon nanostructures (CNS: С60 fullerenes, single-layer and multi-layer nanotubes, onions (spherical "bulbs", nano-diamonds and graphite,their properties are being intensively studied in recent years. These objects have a high thermal and electrical conductivity values, superelasticity, and have a strength approximate to the theoretical value, which can provide an obtaining composite nanomaterial with a unique set of physical and mechanical properties. In creation of a metal matrix composite nanomaterials (CM, reinforced by various CNS, a special attention should be given to mechanical activation processes (MA already at the stage of preparation of the starting components affecting the structure, phase composition and properties of aluminum-matrix composites. Purpose. To investigate the influence of mechanical activation on the structure and phase composition of aluminum-matrix composites. Conclusion. The results of the study of the structure and phase composition of the initial and mechanically activated powders and bulk-modified metal-composites are shown, depending on the type and concentration of modifying varieties CNS, regimes of MA and parameters of compaction. The study is conducted of tribological properties of Al-CNS OF nanostructured materials.

  20. Precipitation of the Carbides $M_{23}C_{6}$ under the Irradiation by High Energy Heavy Ions

    CERN Document Server

    Hofmann, A; Semina, V K; Kochanski, T

    2000-01-01

    Carbide M_{23}C_{6} precipitation process in chromium-nickel steels 12H18N9ô and 00H17N14í2 irradiated with high energy heavy Ar^{+6} ions at 625^{o}ó has been studied. It was found that ion irradiation accelerates carbide M_{23}C_{6} precipitation in comparison to thermal annealing. It was shown that composition of carbides formed by irradiation in 00H17N14í2 steel formed under irradiation differs from composition of carbides precipitated during thermal ageing.

  1. Plasma etching a ceramic composite. [evaluating microstructure

    Science.gov (United States)

    Hull, David R.; Leonhardt, Todd A.; Sanders, William A.

    1992-01-01

    Plasma etching is found to be a superior metallographic technique for evaluating the microstructure of a ceramic matrix composite. The ceramic composite studied is composed of silicon carbide whiskers (SiC(sub W)) in a matrix of silicon nitride (Si3N4), glass, and pores. All four constituents are important in evaluating the microstructure of the composite. Conventionally prepared samples, both as-polished or polished and etched with molten salt, do not allow all four constituents to be observed in one specimen. As-polished specimens allow examination of the glass phase and porosity, while molten salt etching reveals the Si3N4 grain size by removing the glass phase. However, the latter obscures the porosity. Neither technique allows the SiC(sub W) to be distinguished from the Si3N4. Plasma etching with CF4 + 4 percent O2 selectively attacks the Si3N4 grains, leaving SiC(sub W) and glass in relief, while not disturbing the pores. An artifact of the plasma etching reaction is the deposition of a thin layer of carbon on Si3N4, allowing Si3N4 grains to be distinguished from SiC(sub W) by back scattered electron imaging.

  2. Rheocasting Al Matrix Composites

    Science.gov (United States)

    Girot, F. A.; Albingre, L.; Quenisset, J. M.; Naslain, R.

    1987-11-01

    Aluminum alloy matrix composites reinforced by SiC short fibers (or whiskers) can be prepared by rheocasting, a process which consists of the incorporation and homogeneous distribution of the reinforcement by stirring within a semi-solid alloy. Using this technique, composites containing fiber volume fractions in the range of 8-15%, have been obtained for various fibers lengths (i.e., 1 mm, 3 mm and 6 mm for SiC fibers). This paper attempts to delineate the best compocasting conditions for aluminum matrix composites reinforced by short SiC (e.g Nicalon) or SiC whiskers (e.g., Tokamax) and characterize the resulting microstructures.

  3. 硫酸钙晶须改性氟橡胶复合材料的热稳定性%Thermal stability of calcium sulfate whisker modified fluororubber composites

    Institute of Scientific and Technical Information of China (English)

    李辉; 褚国红; 施强; 耿兵; 张书香

    2011-01-01

    The non-isothermal degradation behaviors of calcium sulfate whisker(CSW)/fluororubber(FPM) composites in nitrogen were investigated compared with those of anhydrous calcium sulfate(ACS)/(FPM) composites by TG and DTG.The kinetic parameters were evaluated by differential method and integral method.The results show that the apparent activation energy E of CSW/FPM composites calculated by differential method is 203.33 kJ·mol-1,higher than that of ACS/FPM composites(174.74kJ·mol-1) and the results suggest that CSW/FPM composites have better thermal stability.The thermal decomposition reaction orders are of the order of 1.The thermal decomposition apparent activation energy E increases with increasing mass loss.%采用热分析技术研究了在氮气气氛中硫酸钙晶须(CSW)/氟橡胶(FPM)复合材料的非等温热分解行为及其动力学,并与无水硫酸钙(ACS)/氟橡胶(FPM)复合材料进行了对比。通过Kissinger法和Ozawa法分别计算出其热分解活化能,且结果相近。结果表明:Kissinger法计算的CSW/FPM复合材料的热分解活化能为203.33 kJ.mol-1,高于ACS/FPM复合材料的热分解活化能(174.74 kJ.mol-1),具有较高的热稳定性;热分解反应级数约为1级。随着失重率的增大,热分解活化能增大。

  4. Synthesis of titanium nitride whiskers from potassium fluorotitanate (IV). Fukka chitan (IV) kariumu kara no chikka chitan whisker no gosei

    Energy Technology Data Exchange (ETDEWEB)

    Tabuchi, Mitsuharu; Kaneko, Yasunari; Iwasaki, Hiromichi (Ritsumeikan Univ., Kyoto (Japan). Faculty of Science and Engineering)

    1990-01-01

    TiN whiskers were formed by heating K {sub 2} TiF {sub 6} powder put on a graphite boat in flowing nitrogen gas. The boat was put inside a graphite tube laid in a furnace tube, and the whiskers were formed on the outer surface of the graphite tube. Firing conditions necessary for the synthesis of the whiskers were as follows; temperature of 1300 centigrade or higher, duration of 4 hours or more, nitrogen gas flow at the rate of 90 - 250 m/min. As for the chemical process leading to TiN compound, it was assumed that titanium fluorides such as TiF {sub 4} or TiF {sub 3}, which were formed by thermal decomposition of K {sub 3} TiF {sub 6} derived from K {sub 2} TiF {sub 6}, were defluorinated by reacting with alumina in the furnace tube. Observations of the whiskers by use of SEM and TEM demonstrated square or regular-hexagonal cross-sections of them and suggested the layer growth mechanism for the growth of whiskers having square cross-sections. 9 refs., 6 figs.

  5. 钛酸钾晶须/聚丙烯导热抗静电复合材料的制备与性能%Preparation and properties of thermally conductive and antistatic potassium titanate whiskers filled polypropylene composites

    Institute of Scientific and Technical Information of China (English)

    金亚旭; 于晓璞; 田玉明; 杨雯

    2012-01-01

    Conductive potassium titanate whiskers(PTWs) were used as a novel filler to prepare PTWs/ polypropylene(PP) composites by hot-press forming technology,for which the good thermally conductive and antistatic properties were obtained.The effects of PTWs content on thermal conductivity,volume resistivity,mechanical properties and formability of the PTWs/PP composites were investigated.The results show that with the increase of the PTWs content,thermal conductivity of the PTWs/PP composites increases whi1e volume resistivity decreases,besides,tensile and flexural strength of the PTWs/PP composites exhibits a tendency to increase firstly and then decrease,and the melt flow rate exhibits a tendency to increase.The PTWs/PP composite filled with 0.38% of PTWs presents the maximum thermal conductivity with the value of 0.5105 W·m-1·K-1 and the minimum volume resistivity of 109 Ω·cm,which meets the requirements for antistatic materials.%采用热压成型工艺制备了导电钛酸钾晶须(PTWs)/聚丙烯(PP)复合材料,研究了晶须用量对复合材料导热性能、抗静电性能和力学性能的影响。结果表明,随着PTWs用量的增加,PTWs/PP复合材料的热导率提高、体积电阻率和摩擦静电荷下降;材料的拉伸强度、弯曲强度均随PTWs用量的增加呈先增大后减小的趋势;而熔体流动速率则呈增大趋势。当PTWs体积分数达到0.38%时,材料的热导率达到最大值0.5105 W.m-1.K-1,电阻率降低到109Ω.cm以下,满足一般抗静电材料的要求。

  6. Encoding of whisker input by cerebellar Purkinje cells

    Science.gov (United States)

    Bosman, Laurens W J; Koekkoek, Sebastiaan K E; Shapiro, Joël; Rijken, Bianca F M; Zandstra, Froukje; van der Ende, Barry; Owens, Cullen B; Potters, Jan-Willem; de Gruijl, Jornt R; Ruigrok, Tom J H; De Zeeuw, Chris I

    2010-01-01

    The cerebellar cortex is crucial for sensorimotor integration. Sensorimotor inputs converge on cerebellar Purkinje cells via two afferent pathways: the climbing fibre pathway triggering complex spikes, and the mossy fibre–parallel fibre pathway, modulating the simple spike activities of Purkinje cells. We used, for the first time, the mouse whisker system as a model system to study the encoding of somatosensory input by Purkinje cells. We show that most Purkinje cells in ipsilateral crus 1 and crus 2 of awake mice respond to whisker stimulation with complex spike and/or simple spike responses. Single-whisker stimulation in anaesthetised mice revealed that the receptive fields of complex spike and simple spike responses were strikingly different. Complex spike responses, which proved to be sensitive to the amplitude, speed and direction of whisker movement, were evoked by only one or a few whiskers. Simple spike responses, which were not affected by the direction of movement, could be evoked by many individual whiskers. The receptive fields of Purkinje cells were largely intermingled, and we suggest that this facilitates the rapid integration of sensory inputs from different sources. Furthermore, we describe that individual Purkinje cells, at least under anaesthesia, may be bound in two functional ensembles based on the receptive fields and the synchrony of the complex spike and simple spike responses. The ‘complex spike ensembles’ were oriented in the sagittal plane, following the anatomical organization of the climbing fibres, while the ‘simple spike ensembles’ were oriented in the transversal plane, as are the beams of parallel fibres. PMID:20724365

  7. Muscular Basis of Whisker Torsion in Mice and Rats.

    Science.gov (United States)

    Haidarliu, Sebastian; Bagdasarian, Knarik; Shinde, Namrata; Ahissar, Ehud

    2017-09-01

    Whisking mammals move their whiskers in the rostrocaudal and dorsoventral directions with simultaneous rolling about their long axes (torsion). Whereas muscular control of the first two types of whisker movement was already established, the anatomic muscular substrate of the whisker torsion remains unclear. Specifically, it was not clear whether torsion is induced by asymmetrical operation of known muscles or by other largely unknown muscles. Here, we report that mystacial pads of newborn and adult rats and mice contain oblique intrinsic muscles (OMs) that connect diagonally adjacent vibrissa follicles. Each of the OMs is supplied by a cluster of motor end plates. In rows A and B, OMs connect the ventral part of the rostral follicle with the dorsal part of the caudal follicle. In rows C-E, in contrast, OMs connect the dorsal part of the rostral follicle to the ventral part of the caudal follicle. This inverse architecture is consistent with previous behavioral observations [Knutsen et al.: Neuron 59 (2008) 35-42]. In newborn mice, torsion occurred in irregular single twitches. In adult anesthetized rats, microelectrode mediated electrical stimulation of an individual OM that is coupled with two adjacent whiskers was sufficient to induce a unidirectional torsion of both whiskers. Torsional movement was associated with protracting movement, indicating that in the vibrissal system, like in the ocular system, torsional movement is mechanically coupled to horizontal and vertical movements. This study shows that torsional whisker rotation is mediated by specific OMs whose morphology and attachment sites determine rotation direction and mechanical coupling, and motor innervation determines rotation dynamics. Anat Rec, 300:1643-1653, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  8. Characterization of Silicon Carbide.

    Science.gov (United States)

    The various electrical and structural measurement techniques for silicon carbide are described. The electrical measurements include conductivity, resistivity, carrier concentration, mobility, doping energy levels, and lifetime. The structural measurements include polytype determination and crystalline perfection. Both bulk and epitaxial films are included.

  9. Curvature Optical Fiber Whiskers for Mobile Robot Guidance

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A novel optical fiber tactile sensory system is proposed forobstacle avoidance of mobile robot. The principle of this whisker-like tactile sensor is based on the geometric curvature changes of the optical fiber, which modulate the optical fiber′s light output. With high compliance of plastic optical fiber, the whiskers can produce only small flexing force upon mechanical contact with an obstacle. It can produce reliable proximity signals in extended tactile range, which can be translated into a larger stopping distance for the mobile robot. This sensor is lightweight, and of low cost to allow as many sensor, as necessary to be mounted on a robot.

  10. The effect of whisker movement on radial distance estimation: a case study in comparative robotics

    Directory of Open Access Journals (Sweden)

    Mathew H Evans

    2013-01-01

    Full Text Available Whisker movement has been shown to be under active control in certain specialist animals such as rats and mice. Though this whisker movement is well characterised, the role and effect of this movement on subsequent sensing is poorly understood. One method for investigating this phenomena is to generate artificial whisker deflections with robotic hardware under different movement conditions. A limitation of this approach is that assumptions must be made in the design of any artificial whisker actuators, which will impose certain restrictions on the whisker-object interaction. In this paper we present three robotic whisker platforms, each with different mechanical whisker properties and actuation mechanisms. A feature-based classifier is used to simultaneously discriminate radial distance to contact and contact speed for the first time. We show that whisker-object contact speed predictably affects deflection magnitudes, invariant of whisker material or whisker movement trajectory. We propose that rodent whisker control allows the animal to improve sensing accuracy by regulating contact speed induced touch-to-touch variability.

  11. The effect of whisker movement on radial distance estimation: a case study in comparative robotics

    Science.gov (United States)

    Evans, Mathew H.; Fox, Charles W.; Lepora, Nathan F.; Pearson, Martin J.; Sullivan, J. Charles; Prescott, Tony J.

    2013-01-01

    Whisker movement has been shown to be under active control in certain specialist animals such as rats and mice. Though this whisker movement is well characterized, the role and effect of this movement on subsequent sensing is poorly understood. One method for investigating this phenomena is to generate artificial whisker deflections with robotic hardware under different movement conditions. A limitation of this approach is that assumptions must be made in the design of any artificial whisker actuators, which will impose certain restrictions on the whisker-object interaction. In this paper we present three robotic whisker platforms, each with different mechanical whisker properties and actuation mechanisms. A feature-based classifier is used to simultaneously discriminate radial distance to contact and contact speed for the first time. We show that whisker-object contact speed predictably affects deflection magnitudes, invariant of whisker material or whisker movement trajectory. We propose that rodent whisker control allows the animal to improve sensing accuracy by regulating contact speed induced touch-to-touch variability. PMID:23293601

  12. Facile Synthesis of Electroconductive AZO@TiO2 Whiskers and Their Application in Textiles

    Directory of Open Access Journals (Sweden)

    Hui Ma

    2016-01-01

    Full Text Available The electroconductive AZO@TiO2 whiskers have been successfully prepared via coating Al doped ZnO onto TiO2 whisker. The orthogonal tests were employed to optimize the synthetic conditions. The crystallographic structure and the morphology of the AZO@TiO2 whiskers and the polypropylene nonwoven fabrics modified with AZO@TiO2 whiskers were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope, four-probe meter, and electrometer. The results showed the AZO@TiO2 whiskers exhibited good electroconductive performance. Moreover, the polypropylene nonwoven fabrics modified with AZO@TiO2 whiskers revealed excellent antistatic performance indicating wide application of AZO@TiO2 whiskers in the antistatic textiles.

  13. Rapid accurate isotopic measurements on boron in boric acid and boron carbide.

    Science.gov (United States)

    Duchateau, N L; Verbruggen, A; Hendrickx, F; De Bièvre, P

    1986-04-01

    A procedure is described whereby rapid and accurate isotopic measurements can be performed on boron in boric acid and boron carbide after fusion of these compounds with calcium carbonate. It allows the determination of the isotopic composition of boron in boric acid and boron carbide and the direct assay of boron or the (10)B isotope in boron carbide by isotope-dilution mass spectrometry.

  14. Nanosized Borides and Carbides for Electroplating. Metal-Matrix Coatings: Specifications, Performance Evaluation

    Science.gov (United States)

    Galevskiy, G. V.; Rudneva, V. V.; Galevskiy, S. G.; Il'yashchenko, D. P.; Kartsev, D. S.

    2016-04-01

    This paper summarizes experience of application of nano-sized carbides and borides of titanium and chromium, silicon carbide as components of electro-depositable coating compositions based on nickel, zinc, and chromium. Basic physical and mechanical properties of the coatings are determined. Technological and economic evaluation is completed; practicability of high-cost nano-diamonds substitution for nano-sized borides and carbides is justified.

  15. Nanosized Borides and Carbides for Electroplating. Metal-Matrix Coatings: Specifications, Performance Evaluation

    OpenAIRE

    Galevskiy, G. V.; Rudneva, V. V.; Galevskiy, S. G.; Ilyashchenko, Dmitry Pavlovich; Karthev, Dmitry Sergeevich

    2016-01-01

    This paper summarizes experience of application of nano-sized carbides and borides of titanium and chromium, silicon carbide as components of electro-depositable coating compositions based on nickel, zinc, and chromium. Basic physical and mechanical properties of the coatings are determined. Technological and economic evaluation is completed; practicability of high-cost nano-diamonds substitution for nano-sized borides and carbides is justified.

  16. Role of whiskers in sensorimotor development of C57BL/6 mice

    Science.gov (United States)

    Arakawa, Hiroyuki; Erzurumlu, Reha S.

    2015-01-01

    The mystacial vibrissae (whiskers) of nocturnal rodents play a major role in their sensorimotor behaviors. Relatively little information exists on the role of whiskers during early development. We characterized the contribution of whiskers to sensorimotor development in postnatal C57BL/6 mice. A comparison between intact and whisker-clipped mice in a battery of behavioral tests from postnatal day (P) 4 to 17 revealed that both male and female pups develop reflexive motor behavior even when the whiskers are clipped. Daily whisker trimming from P3 onwards results in diminished weight gain by P17, and impairment in whisker sensorimotor coordination behaviors, such as cliff avoidance and littermate huddling from P4 through P17, while facilitation of righting reflex at P4 and grasp response at P12. Since active whisker palpation does not start until 2 weeks of age, passive whisker touch during early neonatal stage must play a role in regulating these behaviors. Around the onset of exploratory behaviors (P12) neonatal whisker-clipped pups also display persistent searching movements when they encounter cage walls as a compensatory mechanism of sensorimotor development. Spontaneous whisker motion (whisking) is distinct from respiratory fluttering of whiskers. It is a symmetrical vibration of whiskers at a rate of approximately ∼8 Hz, and begins around P10. Oriented, bundled movements of whiskers at higher frequencies of ∼12 Hz during scanning object surfaces, i.e., palpation whisking, emerges at P14. The establishment of locomotive body coordination before eyes open accompanies palpation whisking, indicating an important role in the guidance of exploratory motor behaviors. PMID:25823761

  17. Understanding and predicting metallic whisker growth and its effects on reliability : LDRD final report.

    Energy Technology Data Exchange (ETDEWEB)

    Michael, Joseph Richard; Grant, Richard P.; Rodriguez, Mark Andrew; Pillars, Jamin; Susan, Donald Francis; McKenzie, Bonnie Beth; Yelton, William Graham

    2012-01-01

    Tin (Sn) whiskers are conductive Sn filaments that grow from Sn-plated surfaces, such as surface finishes on electronic packages. The phenomenon of Sn whiskering has become a concern in recent years due to requirements for lead (Pb)-free soldering and surface finishes in commercial electronics. Pure Sn finishes are more prone to whisker growth than their Sn-Pb counterparts and high profile failures due to whisker formation (causing short circuits) in space applications have been documented. At Sandia, Sn whiskers are of interest due to increased use of Pb-free commercial off-the-shelf (COTS) parts and possible future requirements for Pb-free solders and surface finishes in high-reliability microelectronics. Lead-free solders and surface finishes are currently being used or considered for several Sandia applications. Despite the long history of Sn whisker research and the recently renewed interest in this topic, a comprehensive understanding of whisker growth remains elusive. This report describes recent research on characterization of Sn whiskers with the aim of understanding the underlying whisker growth mechanism(s). The report is divided into four sections and an Appendix. In Section 1, the Sn plating process is summarized. Specifically, the Sn plating parameters that were successful in producing samples with whiskers will be reviewed. In Section 2, the scanning electron microscopy (SEM) of Sn whiskers and time-lapse SEM studies of whisker growth will be discussed. This discussion includes the characterization of straight as well as kinked whiskers. In Section 3, a detailed discussion is given of SEM/EBSD (electron backscatter diffraction) techniques developed to determine the crystallography of Sn whiskers. In Section 4, these SEM/EBSD methods are employed to determine the crystallography of Sn whiskers, with a statistically significant number of whiskers analyzed. This is the largest study of Sn whisker crystallography ever reported. This section includes a

  18. The aging response and creep of DRA composites

    Energy Technology Data Exchange (ETDEWEB)

    Bhagat, R.B.; House, M.B.; Meinert, K.C. (Pennsylvania State University, University Park (United States))

    1991-08-01

    The present discussion of results obtained by characterizations of the hardening rates of 6061 Al alloy/20-percent SiC whisker composites and 6061 Al alloy/15-percent Al2O3 particulate composites notes that, under identical aging conditions, the tensile strength of the former is about 65 percent higher than that of the latter. The whisker-reinforced composite's stiffness is, moreover, approximately 60 percent higher than that of the other material. At 350 C, the whisker-reinforced composite has 55 percent higher strength than the particulate-reinforced composite, by comparison with a 111 percent advantage at room temperature. The whisker composite also shows a two-orders-of-magnitude greater resistance to creep. 37 refs.

  19. Three Methods with Functions of Modification on Aluminum Borate Whisker and with Influence on Flexural Properties of Dental Composite Resins%三种方法对硼酸铝晶须表面改性作用及其对复合树脂性能的影响

    Institute of Scientific and Technical Information of China (English)

    袁艳波; 张文云; 陈庆华; 李星星; 肖玉鸿

    2012-01-01

    The present paper is aimed to discuss the influence of three different ways on modification of aluminum bo-rate whiskers (AlBw) and on flexural properties of dental composite resins. In Group A, AlBw and silicon dioxide (SiO2) nanoparticles were thermally fused directly under certain processes. In Group B, Si-0 network was formed on ' the surface of AlBw via the sol-gel process of tetraethoxysilane, then thermally fused with SiO2 nanoparticles to form AlBw-SiOz compound as inorganic fillers. In Group C, SiO2 nanoparticles were repaired by sol-gel method of tetrae-thoxysilane under certain processes, and were deposited in the surface of AlBw. The mixtures were fused with high temperature sintering method. The effects of the surface morphology of AlBw with different ways were characterized by TEM and SEM. Then the mixtures were polymerized with resin matrix after surface siliconization and their flexural strength and Young's modulus were determined. SEM was used to examine specimen fracture surfaces. The results showed that the flexural properties of dental composite resins were significantly improved after whiskers were modified. Different methods produce different effects. Flexural strength of the Group A is (95. 28±4. 53)MPa. The results of TEM and SEM revealed that the aggregation was obvious between AlBw and SitO2 nanoparticles. Flexural strength of the Group B was (123.14±17. 37)MPa. The results of TEM and SEM revealed that the dispersity was improved but SiO2 nanoparticles also reunited. AlBw were modified with nanometer-size SiO2 particles which were prepared by sol-gel method based on tetraethyl orthosioate(TEOS), the flexural properties of a new type of dental composite resins was (130. 29 ±8. 38)MPa. The results of TEM and SEM revealed that better dispersion between AlBw and SiO2 nanoparticles occurred. The SiO2 nanoparticles were fused and attached onto the surface of AlBw uniformly.%分别采用三种不同方法对硼酸铝晶须(AlBw)进行表面

  20. Box-and-Whisker Plots Applied to Food Chemistry

    Science.gov (United States)

    Ferreira, Joao E. V.; Miranda, Ricardo M.; Figueiredo, Antonio F.; Barbosa, Jardel P.; Brasil, Edykarlos M.

    2016-01-01

    Box-and-whisker plots or simply boxplots are powerful graphical representations that give an overview of a data set. In this work five different examples illustrate the applications of boxplots in food chemistry. The examples involve relative sweetness of sugars and sugar alcohols with respect to sucrose, the potassium content of fruits and…

  1. Box-and-Whisker Plots Applied to Food Chemistry

    Science.gov (United States)

    Ferreira, Joao E. V.; Miranda, Ricardo M.; Figueiredo, Antonio F.; Barbosa, Jardel P.; Brasil, Edykarlos M.

    2016-01-01

    Box-and-whisker plots or simply boxplots are powerful graphical representations that give an overview of a data set. In this work five different examples illustrate the applications of boxplots in food chemistry. The examples involve relative sweetness of sugars and sugar alcohols with respect to sucrose, the potassium content of fruits and…

  2. Silicium carbide-titanium carbide-compound materials: The influence of different production parameters on structure and mechanical properties. Siliciumcarbid-Titancarbid-Verbundwerkstoffe: Der Einfluss unterschiedlicher Herstellungsparameter auf Gefuege und mechanische Eigenschaften

    Energy Technology Data Exchange (ETDEWEB)

    Al-Robayie, J. (TU Berlin (Germany). Inst. fuer Nichtmetallische Werkstoffe); Hausner, H. (TU Berlin (Germany). Inst. fuer Nichtmetallische Werkstoffe)

    1993-03-01

    In order to improve brittle fracture behaviour of ceramic materials an tries to develop compound materials where a ceramic matrix may contain a second phase in the form of particles, whiskers or fibres. The mechanical characteristics thus obtained strongly depend on process engineering stages used during the production of this group of materials. This article describes results of studies obtained during developing TiC-particle reinforced silicium carbide materials. The influence of different process parameters on structure formation and thus mechanical properties is most important in this context. (orig./RHM)

  3. Effect of the silicon-carbide micro- and nanoparticle size on the thermo-elastic and time-dependent creep response of a rotating Al-SiC composite cylinder

    Science.gov (United States)

    Loghman, A.; Hammami, M.; Loghman, E.

    2017-05-01

    The history of stresses and creep strains of a rotating composite cylinder made of an aluminum matrix reinforced by silicon carbide particles is investigated. The effect of uniformly distributed SiC micro- and nanoparticles on the initial thermo-elastic and time-dependent creep deformation is studied. The material creep behavior is described by Sherby's constitutive model where the creep parameters are functions of temperature and the particle sizes vary from 50 nm to 45.9 μm. Loading is composed of a temperature field due to outward steady-state heat conduction and an inertia body force due to cylinder rotation. Based on the equilibrium equation and also stress-strain and strain-displacement relations, a constitutive second-order differential equation for displacements with variable and time-dependent coefficients is obtained. By solving this differential equation together with the Prandtl-Reuss relation and the material creep constitutive model, the history of stresses and creep strains is obtained. It is found that the minimum effective stresses are reached in a material reinforced by uniformly distributed SiC particles with the volume fraction of 20% and particle size of 50 nm. It is also found that the effective and tangential stresses increase with time at the inner surface of the composite cylinder; however, their variation at the outer surface is insignificant.

  4. Magnetic susceptibility and magnetoresistance of neutron-irradiated doped SI whiskers

    Energy Technology Data Exchange (ETDEWEB)

    Druzhinin, A.A., E-mail: druzh@polynet.lviv.ua [Lviv Polytechnic National University, S. Bandera Str., 12, Lviv 79013 (Ukraine); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw (Poland); Ostrovskii, I.P.; Khoverko, Yu.M. [Lviv Polytechnic National University, S. Bandera Str., 12, Lviv 79013 (Ukraine); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw (Poland); Rogacki, K. [International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw (Poland); Litovchenko, P.G.; Pavlovska, N.T. [Institute of Nuclear Researches, NAS of Ukraine, 47, Prospect Nauky, 03028 Kyiv (Ukraine); Pavlovskyy, Yu.V.; Ugrin, Yu.O. [Ivan Franko Drohobych State Pedagogical University, 24, Franko str., 82100 Drohobych (Ukraine)

    2015-11-01

    The effect of 8.6·10{sup 17} n/cm{sup 2} fast neutron irradiation on the magnetic susceptibility and magnetoresistance of Si whiskers with impurity concentration near metal–insulator transition (MIT) has been studied. Neutron irradiated specimens with boron concentration away of MIT are mainly diamagnetic with a small amount of paramagnetic centers originated from dangling bonds on the whisker surface. It has been established that at temperatures near 4.2 K, a significant contribution to the conductivity is made by light charge carriers of low concentration but with high mobility. The as grown whiskers with impurity concentration correspondent to MIT showed hysteresis loops in magnetization at temperature of liquid helium. Besides hysteresis loops in magnetoresistance was observed for whiskers under compression stress at low temperature up to 7 K. The possible reason of the effect can be magnetic interaction between impurities centers in subsurface region of the whisker with the orbital moment of dangle bounds in the whisker core–shell interstices. - Highlights: • Neutron irradiation influence on magnetic susceptibility of Si whiskers is studied. • Neutron irradiated Si whiskers with boron concentration away of MIT are diamagnetic. • Whiskers in the vicinity to MIT showed hysteresis loops in magnetoresistance. • Whiskers in the vicinity to MIT showed hysteresis loops in magnetic susceptibility.

  5. High-precision, three-dimensional tracking of mouse whisker movements with optical motion capture technology

    Directory of Open Access Journals (Sweden)

    Snigdha eRoy

    2011-06-01

    Full Text Available The mystacial vibrissae or whiskers in rodents are sensitive tactile hairs emerging from both sides of the face. Rats and mice actively move these whiskers during exploration. The neuronal mechanisms controlling whisker movements and the sensory representation of whisker tactile information are widely studied as a model for sensorimotor processing in mammals. Studies of the natural whisker movement patterns during exploration and tactile examination are still in their early stages. Tracking the movements of whiskers is technically challenging as they move relatively fast and are very thin, particularly in mice. Existing systems detect light-beam interruptions by the whiskers or use high-speed video to track whisker movements in one or two dimensions. Here we describe a method for tracking the movements of mouse whiskers in 3 dimensions (3D using using optical motion capture technology. Optical motion capture technology tracks the movements of small retro-reflective markers attached to whiskers of a head-fixed mouse with a spatial resolution of <0.5mm in all three dimensions and a temporal resolution of 5msec (200 fps. The system stores the 3D coordinates of the marker’s trajectories onto hard disk allowing a detailed analysis of movement trajectories bilateral coordination.

  6. Impedance spectroscopy of Si whiskers in the range of metal-insulator transition

    Directory of Open Access Journals (Sweden)

    A. O. Druzinin

    2013-12-01

    Full Text Available Introduction. The paper deals with investigation of impedance spectroscopy of Si whiskers with doping concentration in the vicinity to metal-insulator transition in the region of low (4,2 – 70 K temperature and frequency range 0,01 – 250x103 Hz. Experimental results. The silicon whiskers were grown by chemical vapour deposition method in closed bromine system. The whiskers of 40x10-6 m in diameter have boron concentration from 2×1018 to 2×1019 сm-3. The impedance spectroscopy of Si whiskers was investigated with use of Lock-in amplifier in the region of low (4,2 – 70 K temperature and frequency range 0,01 – 250 x 103 Hz. The investigations showed that in the range of zone conductance (T= 30 – 70 K the whisker impedance has inductive character, while at the range of impurity conductance (T = 4,2 – 20 K impedance changes to capacity character. The reduction of impurity concentration at dielectric side of metal-insulator transition leads to decrease of the whisker capacity in the range of low temperatures. Discussion. An inductive character of whisker impedance is explained skin-effect of conductance in thin whisker, while capacity character of the whisker impedance is connected with hopping conductance on impurity band. Conclusions. Character of changes of Si whisker impedance conductance is discussed in the frame of hopping conductance on impurity band, which takes place at low temperatures.

  7. Mitigation and Verification Methods for Sn Whisker Growth in Pb-Free Automotive Electronics

    Science.gov (United States)

    Hong, Won Sik; Oh, Chul Min; Kim, Do Seop

    2013-02-01

    This work describes mitigation methods against Sn whisker growth in Pb-free automotive electronics using a conformal coating technique, with an additional focus on determining an effective whisker assessment method. We suggest effective whisker growth conditions that involve temperature cycling and two types of storage conditions (high-temperature/humidity storage and ambient storage), and analyze whisker growth mechanisms. In determining an efficient mitigation method against whisker growth, surface finish and conformal coating have been validated as effective means. In our experiments, the surface finish of components comprised Ni/Sn, Ni/SnBi, and Ni/Pd. The effects of acrylic silicone, and rubber coating of components were compared with uncoated performance under high-temperature/humidity storage conditions. An effective whisker assessment method during temperature cycling and under various storage conditions (high temperature/humidity and ambient) is indicated for evaluating whisker growth. Although components were finished with Ni/Pd, we found that whiskers were generated at solder joints and that conformal coating is a useful mitigation method in this regard. Although whiskers penetrated most conformal coating materials (acrylic, silicone, and rubber) after 3500 h of high-temperature/humidity storage, the whisker length was markedly reduced due to the conformal coatings, with silicone providing superior mitigation over acrylic and rubber.

  8. Infrared thermal imaging of rat somatosensory cortex with whisker stimulation.

    Science.gov (United States)

    Suzuki, Takashi; Ooi, Yasuhiro; Seki, Junji

    2012-04-01

    The present study aims to validate the applicability of infrared (IR) thermal imaging for the study of brain function through experiments on the rat barrel cortex. Regional changes in neural activity within the brain produce alterations in local thermal equilibrium via increases in metabolic activity and blood flow. We studied the relationship between temperature change and neural activity in anesthetized rats using IR imaging to visualize stimulus-induced changes in the somatosensory cortex of the brain. Sensory stimulation of the vibrissae (whiskers) was given for 10 s using an oscillating whisker vibrator (5-mm deflection at 10, 5, and 1 Hz). The brain temperature in the observational region continued to increase significantly with whisker stimulation. The mean peak recorded temperature changes were 0.048 ± 0.028, 0.054 ± 0.036, and 0.097 ± 0.015°C at 10, 5, and 1 Hz, respectively. We also observed that the temperature increase occurred in a focal spot, radiating to encompass a larger region within the contralateral barrel cortex region during single-whisker stimulation. Whisker stimulation also produced ipsilateral cortex temperature increases, which were localized in the same region as the pial arterioles. Temperature increase in the barrel cortex was also observed in rats treated with a calcium channel blocker (nimodipine), which acts to suppress the hemodynamic response to neural activity. Thus the location and area of temperature increase were found to change in accordance with the region of neural activation. These results indicate that IR thermal imaging is viable as a functional quantitative neuroimaging technique.

  9. A mechanistic study on the synthesis of β-Sialon whiskers from coal fly ash

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, H.; Wang, P.Y. [Thermal Energy Research Centre, Shenyang Aerospace University, Shenyang 110136 (China); Yu, J.L., E-mail: jianglong.yu@newcastle.edu.au [Thermal Energy Research Centre, Shenyang Aerospace University, Shenyang 110136 (China); Chemical Engineering, University of Newcastle, Callaghan, NSW 2308 (Australia); Zhang, J. [Thermal Energy Research Centre, Shenyang Aerospace University, Shenyang 110136 (China)

    2015-05-15

    Graphical abstract: The appearance of bead-like whiskers indicated that the growth mechanism of the β-Sialon whiskers was different from the conventional one, in which a chain of droplets were formed and then consumed to participate in the formation of the whiskers. - Highlights: • β-Sialon whiskers were synthesized using waste fly ash by carbothemal reduction reaction under nitrogen atmosphere. • Rod-like β-Sialon whiskers with a diameter of 100–500 nm were formed. • Bead-like whiskers as intermediate morphology of the growing β-Sialon whiskers were found with increasing sintering time. • The growth mechanism of β-Sialon whiskers was different from the conventional VLS mechanism. • A chain of droplets were formed and participated in the formation of the whiskers. - Abstract: β-Sialon whiskers were produced at 1420 °C through carbothemal reduction reaction under nitrogen atmosphere using fly ash from coal-fired power plants. The effects of sintering time on the phase formation and morphology of the products were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) techniques. Rod-like β-Sialon whiskers with the diameter of 100–500 nm were successfully formed. With increasing sintering time, bead-like morphology during the growth process of the whiskers was found, and growth mechanism of β-Sialon whiskers was also discussed in detail. The growth mechanism proposed in this study was different from the conventional vapor–liquid–solid (VLS) mechanism.

  10. Effect of surface modified silicon carbide particles with Al{sub 2}O{sub 3} and nanocrystalline spinel ZnAl{sub 2}O{sub 4} on mechanical and damping properties of the composite

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-09-17

    In our proof-of-concept studies, pure aluminium metal matrix composites reinforced with alumina (Al{sub 2}O{sub 3}) and nanocrystalline spinel zinc aluminate (ZnAl{sub 2}O{sub 4}) coated silicon carbide (SiC) particles were fabricated by stir casting. Initially, we presented the results of an investigation on Al{sub 2}O{sub 3} and spinel ZnAl{sub 2}O{sub 4} coating layer on SiC particles of sub-micron size via facile sol–gel method. The amount and coverage of different coating crystals on SiC surface were studied through X-ray energy dispersion spectroscopy (EDX) analysis and transmission electron microscopy (TEM) analysis. Further, adequate dispersion, de-agglomeration and stability of coated SiC particles were investigated through Field emission scanning electron microscopy (FE-SEM) and elemental mapping of aluminium metal matrix composites. The room temperature mechanical properties and thermal cyclic damping behaviour of the composites were examined. The obtained results indicate that coating of SiC has a significant influence on the damping and mechanical properties and the resulting composite (ZnAl{sub 2}O{sub 4} coated SiC/Al) exhibited 60% higher stiffness (storage modulus) and 3.6 times increase in tensile strength, and 3.5 times increase in hardness respectively as compared to the pure aluminium. This is attributed to stabilization of the tailored SiC particles and improved interface bonding between coated particles and matrix.

  11. Characterisation of whisker control in the California sea lion (Zalophus californianus) during a complex, dynamic sensorimotor task.

    Science.gov (United States)

    Milne, Alyx O; Grant, Robyn A

    2014-10-01

    Studies in pinniped whisker use have shown that their whiskers are extremely sensitive to tactile and hydrodynamic signals. While pinnipeds position their whiskers on to objects and have some control over their whisker protractions, it has always been thought that head movements are more responsible for whisker positioning than the movement of the whiskers themselves. This study uses ball balancing, a dynamic sensorimotor skill that is often used in human and robotic coordination studies, to promote sea lion whisker movements during the task. For the first time, using tracked video footage, we show that sea lion whisker movements respond quickly (26.70 ms) and mirror the movement of the ball, much more so than the head. We show that whisker asymmetry and spread are both altered to help sense and control the ball during balancing. We believe that by designing more dynamic sensorimotor tasks we can start to characterise the active nature of this specialised sensory system in pinnipeds.

  12. Study of the Process of the Formation of Niobium Carbide on Graphite Particles,

    Science.gov (United States)

    fluid bed. Details were worked out specifically for the deposition of niobium carbide . Curves showing deposit thickness as function of process time and...temperature indicate a diffusion process. X-ray structural analyses established that a uniform deposit of niobium carbide , of nearly stoichiometric composition, was formed about the entire particle surfaces. (Author)

  13. Microstructures and Wear Performance of PTAW Deposited Ni-Based Coatings with Spherical Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Dewei Deng

    2015-10-01

    Full Text Available The Ni-based coatings with different content of spherical tungsten carbide were deposited by plasma transfer arc welding (PTAW method on 304 austenitic stainless steel sheets in this study. The microstructure and wear property of spherical tungsten carbide particle reinforced composite coatings were investigated by means of optical microscope, scanning electron microscope (SEM, X-ray diffraction (XRD, electron probe microanalysis (EPMA and sliding wear test. It is shown that the fraction of spherical tungsten carbides has an important influence on microstructure of Ni-based overlay. The Ni40 overlay consists of γ-Ni dendrites with interdendritic Ni-based eutectics, borides and carbides improving the wear resistance. In the case of composite coatings with different content of tungsten carbide, many new phases are observed, such as Ni2W4C and NiW. In addition, there are a large number of irregular structures in composite coatings, such as acicular structure and irregular stripe organization. The results of sliding wear test indicate that the mass loss of coatings is influenced by the content of tungsten carbide. The mass loss decreases with the increase of tungsten carbide fraction. At high load, the abrasive resistance of composite coating with 60 wt. % tungsten carbide is improved about 50-fold compared to that of Ni40 overlay.

  14. Influence of transformation temperature on carbide precipitation sequence during lower bainite formation

    Energy Technology Data Exchange (ETDEWEB)

    Caballero, F.G., E-mail: fgc@cenim.csic.es [Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC), Avda. Gregorio del Amo, 8, E-28040 Madrid (Spain); Miller, M.K. [Oak Ridge National Laboratory (ORNL), Materials Science and Technology Division, P.O. Box 2008, Oak Ridge, TN 37831-6139 (United States); Garcia-Mateo, C. [Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC), Avda. Gregorio del Amo, 8, E-28040 Madrid (Spain)

    2014-07-01

    The nature of different carbides formed during the lower bainite reaction at different transformation temperatures was determined by atom probe tomography in three steels with different carbon and silicon contents. It is known that steel composition and temperature alter the carbide precipitation sequence during low-temperature bainite formation. However, present results confirm that dislocations in lower bainite that are more prominent at the lower the transformation temperature, trap a substantial amount of carbon and hence, can influence the carbide precipitation sequence and, in particular, can determine where ε-carbide forms before the growth of cementite. - Highlights: • Identification of carbides in lower bainite using atom probe tomography. • Determination of carbon trapping at dislocations in lower bainite. • Carbide precipitation sequence during lower bainite formation.

  15. Microstructural studies of carbides in MAR-M247 nickel-based superalloy

    Science.gov (United States)

    Szczotok, A.; Rodak, K.

    2012-05-01

    Carbides play an important role in the strengthening of microstructures of nickel-based superalloys. Grain boundary carbides prevent or retard grain-boundary sliding and make the grain boundary stronger. Carbides can also tie up certain elements that would otherwise promote phase instability during service. Various types of carbides are possible in the microstructure of nickel-based superalloys, depending on the superalloy composition and processing. In this paper, scanning electron and scanning transmission electron microscopy studies of carbides occurring in the microstructure of polycrystalline MAR-M247 nickel-based superalloy were carried out. In the present work, MC and M23C6 carbides in the MAR-M247 microstructure were examined.

  16. Chemical Analysis Methods for Silicon Carbide

    Institute of Scientific and Technical Information of China (English)

    Shen Keyin

    2006-01-01

    @@ 1 General and Scope This Standard specifies the determination method of silicon dioxide, free silicon, free carbon, total carbon, silicon carbide, ferric sesquioxide in silicon carbide abrasive material.

  17. Whisker-Like Formations in Sn-3.0Ag-Pb Alloys

    Directory of Open Access Journals (Sweden)

    Koncz-Horváth D.

    2017-06-01

    Full Text Available In this study, different types of whisker-like formations of Sn-3.0Ag based alloy were presented. In the experimental process the amount of Pb element was changed between 1000 and 2000 ppm, and the furnace atmosphere and cooling rate were also modified. The novelty of this work was that whisker-like formations in macro scale size were experienced after an exothermic reaction. The whiskers of larger sizes than general provided opportunities to investigate the microstructure and the concentration nearby the whiskers. In addition, the whisker-like formations from Sn-Ag based bulk material did not only consist of pure tin but tin and silver phases. The whisker-like growth appeared in several forms including hillock, spire and nodule shaped formations in accordance with parameters. It was observed that the compound phases were clustered in many cases mainly at hillocks.

  18. Synthesis and characteristics of SiC whiskers with "rosary bead" morphology

    Institute of Scientific and Technical Information of China (English)

    Xian Jia; Xiaomei Ling

    2004-01-01

    SiC whiskers with ″rosary bead″ morphology were synthesized using suitable silicon source and carbon source through solid reaction at the temperature above 1537 K. The diameter and length of the SiC whiskers were about 0.1-1.0 μm and 20-100 μm,respectively. The largest diameter of their enlarged ends of the whiskers was about 0.2-1.0 μm, and it gradually and smoothly decreased to the size of the plain part of the whiskers. The results of X-ray diffraction analysis show that the crystalline structure of the obtained SiC whiskers is β-SiC. It is considered that the SiC whiskers grow via a vapor-solid mechanism.

  19. Chitosan whiskers from shrimp shells incorporated into dimethacrylate-based dental resin sealant.

    Science.gov (United States)

    Mahapoka, Ekamon; Arirachakaran, Pratanporn; Watthanaphanit, Anyarat; Rujiravanit, Ratana; Poolthong, Suchit

    2012-01-01

    A resin-based sealant containing chitosan whiskers was developed for use as a pit and fissure sealer. Chitosan whiskers were synthesized and then characterized using Fourier transform infrared spectrometry and transmission electron microscopy. The whiskers were next incorporated into dimethacrylate monomer at various ratios by weight and subsequently analyzed for their antimicrobial and physical properties. The dimethacrylate-based sealant containing chitosan whiskers had a greater antimicrobial activity than control sealant and they were comparable with antimicrobial commercial resin sealants. The inclusion of the whiskers did not reduce the curing depth or degree of double bond conversion and the reduction in hardness was minimal. In conclusion, a resin-based sealant containing chitosan whiskers can be considered an effective antimicrobial pit and fissure sealant.

  20. A radial map of multi-whisker correlation selectivity in the rat barrel cortex.

    Science.gov (United States)

    Estebanez, Luc; Bertherat, Julien; Shulz, Daniel E; Bourdieu, Laurent; Léger, Jean-François

    2016-11-21

    In the barrel cortex, several features of single-whisker stimuli are organized in functional maps. The barrel cortex also encodes spatio-temporal correlation patterns of multi-whisker inputs, but so far the cortical mapping of neurons tuned to such input statistics is unknown. Here we report that layer 2/3 of the rat barrel cortex contains an additional functional map based on neuronal tuning to correlated versus uncorrelated multi-whisker stimuli: neuron responses to uncorrelated multi-whisker stimulation are strongest above barrel centres, whereas neuron responses to correlated and anti-correlated multi-whisker stimulation peak above the barrel-septal borders, forming rings of multi-whisker synchrony-preferring cells.

  1. Fabrication of α-chitin whisker-reinforced poly(vinyl alcohol) nanocomposite nanofibres by electrospinning

    Science.gov (United States)

    Junkasem, Jirawut; Rujiravanit, Ratana; Supaphol, Pitt

    2006-09-01

    The present contribution reports, for the first time, the successful fabrication of α-chitin whisker-reinforced poly(vinyl alcohol) (PVA) nanocomposite nanofibres by electrospinning. The α-chitin whiskers were prepared from α-chitin flakes from shrimp shells by acid hydrolysis. The as-prepared chitin whiskers exhibited lengths in the range 231-969 nm and widths in the range 12-65 nm, with the average length and width being about 549 and 31 nm, respectively. Successful incorporation of the chitin whiskers within the as-spun PVA/chitin whisker nanocomposite nanofibres was verified by infrared spectroscopic and thermogravimetric methods. The incorporation of chitin whiskers within the as-spun nanocomposite fibre mats increased the Young's modulus by about 4-8 times over that of the neat as-spun PVA fibre mat.

  2. Fabrication of {alpha}-chitin whisker-reinforced poly(vinyl alcohol) nanocomposite nanofibres by electrospinning

    Energy Technology Data Exchange (ETDEWEB)

    Junkasem, Jirawut; Rujiravanit, Ratana; Supaphol, Pitt [Technological Center for Electrospun Fibers and the Petroleum and Petrochemical College, Chulalongkorn University, Soi Chula 12, Phyathai Road, Pathumwan, Bangkok 10300 (Thailand)

    2006-09-14

    The present contribution reports, for the first time, the successful fabrication of {alpha}-chitin whisker-reinforced poly(vinyl alcohol) (PVA) nanocomposite nanofibres by electrospinning. The {alpha}-chitin whiskers were prepared from {alpha}-chitin flakes from shrimp shells by acid hydrolysis. The as-prepared chitin whiskers exhibited lengths in the range 231-969 nm and widths in the range 12-65 nm, with the average length and width being about 549 and 31 nm, respectively. Successful incorporation of the chitin whiskers within the as-spun PVA/chitin whisker nanocomposite nanofibres was verified by infrared spectroscopic and thermogravimetric methods. The incorporation of chitin whiskers within the as-spun nanocomposite fibre mats increased the Young's modulus by about 4-8 times over that of the neat as-spun PVA fibre mat.

  3. Direct Electrochemical Preparation of Cobalt, Tungsten, and Tungsten Carbide from Cemented Carbide Scrap

    Science.gov (United States)

    Xiao, Xiangjun; Xi, Xiaoli; Nie, Zuoren; Zhang, Liwen; Ma, Liwen

    2017-02-01

    A novel process of preparing cobalt, tungsten, and tungsten carbide powders from cemented carbide scrap by molten salt electrolysis has been investigated in this paper. In this experiment, WC-6Co and NaCl-KCl salt were used as sacrificial anode and electrolyte, respectively. The dissolution potential of cobalt and WC was determined by linear sweep voltammetry to be 0 and 0.6 V ( vs Ag/AgCl), respectively. Furthermore, the electrochemical behavior of cobalt and tungsten ions was investigated by a variety of electrochemical techniques. Results of cyclic voltammetry (CV) and square-wave voltammetry show that the cobalt and tungsten ions existed as Co2+ and W2+ on melts, respectively. The effect of applied voltage, electrolysis current, and electrolysis times on the composition of the product was studied. Results showed that pure cobalt powder can be obtained when the electrolysis potential is lower than 0.6 V or during low current and short times. Double-cathode and two-stage electrolysis was utilized for the preparation of cobalt, tungsten carbide, and tungsten powders. Additionally, X-ray diffraction results confirm that the product collected at cathodes 1 and 2 is pure Co and WC, respectively. Pure tungsten powder was obtained after electrolysis of the second part. Scanning electron microscope results show that the diameters of tungsten, tungsten carbide, and cobalt powder are smaller than 100, 200, and 200 nm, respectively.

  4. Direct Electrochemical Preparation of Cobalt, Tungsten, and Tungsten Carbide from Cemented Carbide Scrap

    Science.gov (United States)

    Xiao, Xiangjun; Xi, Xiaoli; Nie, Zuoren; Zhang, Liwen; Ma, Liwen

    2016-10-01

    A novel process of preparing cobalt, tungsten, and tungsten carbide powders from cemented carbide scrap by molten salt electrolysis has been investigated in this paper. In this experiment, WC-6Co and NaCl-KCl salt were used as sacrificial anode and electrolyte, respectively. The dissolution potential of cobalt and WC was determined by linear sweep voltammetry to be 0 and 0.6 V (vs Ag/AgCl), respectively. Furthermore, the electrochemical behavior of cobalt and tungsten ions was investigated by a variety of electrochemical techniques. Results of cyclic voltammetry (CV) and square-wave voltammetry show that the cobalt and tungsten ions existed as Co2+ and W2+ on melts, respectively. The effect of applied voltage, electrolysis current, and electrolysis times on the composition of the product was studied. Results showed that pure cobalt powder can be obtained when the electrolysis potential is lower than 0.6 V or during low current and short times. Double-cathode and two-stage electrolysis was utilized for the preparation of cobalt, tungsten carbide, and tungsten powders. Additionally, X-ray diffraction results confirm that the product collected at cathodes 1 and 2 is pure Co and WC, respectively. Pure tungsten powder was obtained after electrolysis of the second part. Scanning electron microscope results show that the diameters of tungsten, tungsten carbide, and cobalt powder are smaller than 100, 200, and 200 nm, respectively.

  5. Titanium Matrix Composite Pressure Vessel Project

    Data.gov (United States)

    National Aeronautics and Space Administration — For over 15 years, FMW Composite Systems has developed Metal Matrix Composite manufacturing methodologies for fabricating silicon-carbide-fiber-reinforced titanium...

  6. Thermochemical Erosion of Hafnium Carbide Modified Carbon/Carbon Composite Throat in a Small Solid Rocket Motor%碳化铪改性炭/炭复合材料喉衬的热化学烧蚀

    Institute of Scientific and Technical Information of China (English)

    沈学涛; 李克智; 李贺军; 冯涛; 张磊磊; 王斌

    2011-01-01

    Thermochemical erosion of hafnium carbide (HfC) modified carbon/carbon (C/C) composite throat was investigated using a hot-fire testing system in a small solid rocket motor. Chemical composition of the equilibrium combustion products was calculated by NASA-CEA program based on the principle of free energy minimum. The reaction products between the oxidizing species and HfC in the C/C composites were also calculated by FactSage.The results show that H2O, CO2, and OH are the main oxidizing species to consume carbon and HfC and generate thermochemical erosion to the throat materials. The interface of the fibers and matrix is preferentially ablated, and then erosion extends to the fibers and matrix. The formation of cone-shaped fibers and shell-shaped matrix is attributed to the thermochemical erosion of the flame.%采用小型固体火箭发动机研究了碳化铪(HfC)改性炭/炭复合材料喉衬的热化学烧蚀.借助基于最小自由能原理的NASA-CEA程序计算了燃气组成,借助化学热力学软件FactSage计算了燃气组分与碳、HfC的化学反应.结果表明,燃气中的H2O、CO2和OH是碳和HfC的主要氧化组分,使材料发生热化学烧蚀;纤维-基体界面是烧蚀的薄弱环节,烧蚀沿着界面分别向碳纤维和基体方向推进.热化学作用(氧化)造成纤维变细,顶端呈锥状,基体变薄,呈壳状.

  7. Solid-state formation of titanium carbide and molybdenum carbide as contacts for carbon-containing semiconductors

    Science.gov (United States)

    Leroy, W. P.; Detavernier, C.; van Meirhaeghe, R. L.; Kellock, A. J.; Lavoie, C.

    2006-03-01

    Metal carbides are good candidates to contact carbon-based semiconductors (SiC, diamond, and carbon nanotubes). Here, we report on an in situ study of carbide formation during the solid-state reaction between thin Ti or Mo films and C substrates. Titanium carbide (TiC) was previously reported as a contact material to diamond and carbon nanotubes. However, the present study shows two disadvantages for the solid-state reaction of Ti and C. First, because Ti reacts readily with oxygen, a capping layer should be included to enable carbide formation. Second, the TiC phase can exist over a wide range of composition (about 10%, i.e., from Ti0.5C0.5 to Ti0.6C0.4), leading to significant variations in the properties of the material formed. The study of the Mo-C system suggests that molybdenum carbide (Mo2C) is a promising alternative, since the phase shows a lower resistivity (about 45% lower than for TiC), the carbide forms below 900 °C, and its formation is less sensitive to oxidation as compared with the Ti-C system. The measured resistivity for Mo2C is ρ=59 μΩ cm, and from kinetic studies an activation energy for Mo2C formation of Ea=3.15+/-0.15 eV was obtained.

  8. An Empirical Model for Estimating the Probability of Electrical Short Circuits from Tin Whiskers. Part 2

    Science.gov (United States)

    Courey, Karim; Wright, Clara; Asfour, Shihab; Onar, Arzu; Bayliss, Jon; Ludwig, Larry

    2009-01-01

    In this experiment, an empirical model to quantify the probability of occurrence of an electrical short circuit from tin whiskers as a function of voltage was developed. This empirical model can be used to improve existing risk simulation models. FIB and TEM images of a tin whisker confirm the rare polycrystalline structure on one of the three whiskers studied. FIB cross-section of the card guides verified that the tin finish was bright tin.

  9. Study of metal whiskers growth and mitigation technique using additive manufacturing

    Science.gov (United States)

    Gullapalli, Vikranth

    For years, the alloy of choice for electroplating electronic components has been tin-lead (Sn-Pb) alloy. However, the legislation established in Europe on July 1, 2006, required significant lead (Pb) content reductions from electronic hardware due to its toxic nature. A popular alternative for coating electronic components is pure tin (Sn). However, pure tin has the tendency to spontaneously grow electrically conductive Sn whisker during storage. Sn whisker is usually a pure single crystal tin with filament or hair-like structures grown directly from the electroplated surfaces. Sn whisker is highly conductive, and can cause short circuits in electronic components, which is a very significant reliability problem. The damages caused by Sn whisker growth are reported in very critical applications such as aircraft, spacecraft, satellites, and military weapons systems. They are also naturally very strong and are believed to grow from compressive stresses developed in the Sn coating during deposition or over time. The new directive, even though environmentally friendly, has placed all lead-free electronic devices at risk because of whisker growth in pure tin. Additionally, interest has occurred about studying the nature of other metal whiskers such as zinc (Zn) whiskers and comparing their behavior to that of Sn whiskers. Zn whiskers can be found in flooring of data centers which can get inside electronic systems during equipment reorganization and movement and can also cause systems failure. Even though the topic of metal whiskers as reliability failure has been around for several decades to date, there is no successful method that can eliminate their growth. This thesis will give further insights towards the nature and behavior of Sn and Zn whiskers growth, and recommend a novel manufacturing technique that has potential to mitigate metal whiskers growth and extend life of many electronic devices.

  10. Mechanical and thermal properties of denture PMMA reinforced with silanized aluminum borate whiskers.

    Science.gov (United States)

    Zhang, Xinjing; Zhang, Xiuyin; Zhu, Bangshang; Lin, Kaili; Chang, Jiang

    2012-01-01

    The aim of this study was to investigate the mechanical and thermal properties of denture polymethyl methacrylate (PMMA) reinforced with aluminum borate whiskers (ABWs). To improve bonding between ABWs and PMMA matrix, the surface of ABWs was modified with a silane coupling agent. Varied contents of silanized ABWs -ranging between 1 and 20 wt%- were mixed into the PMMA resin matrix to prepare ABW/PMMA composites, which were subjected to three-point bending test, Vickers hardness test, and thermal analysis. Silanized ABWs improved the flexural strength, surface hardness, and thermal stability of PMMA. Optimal amount of ABWs in the PMMA matrix was 5 wt%, which provided the ABW/PMMA with maximum reinforcement.

  11. Sintering behavior of alumina-niobium carbide ceramics from polymer-filler mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Acchar, W.; Wolff, D.M.B. [Programa de Doutorado em Engenharia e Ciencia dos Materiais-UFRN, Univ. Federal do Rio Grande do Norte, Natal, RN (Brazil); S. Dantas, A.C. da [Programa de Pos-graduacao em Engenharia Mecanica-UFRN, Univ. Federal do Rio Grande do Norte - Natal, RN (Brazil)

    2003-07-01

    Studies have been developed in the literature to obtain alternative ceramic cutting tools with better properties as tungsten carbide and silicon nitride. Results have showed that the addition of titanium carbide, tungsten carbide or niobium carbide has improved the wear resistance and hardness of alumina. This work presents a study about preparation and characterization of an alumina reinforced with niobium carbide. The composite material is produced using polymer-filler mixtures. Samples with 60 wt.% polysiloxane and a mixture of 40 wt.% of niobium and alumina powder were mixed, uniaxially pressed at 200 C and sintered in flowing argon at 1200 C, 1400 C and 1600 C. The composite materials were characterized by X-ray diffraction (XRD), density measurements, fracture strength and microstructural analysis. The 60 wt% polymer+40 wt% Nb showed the presence of new crystalline phases such as NbC, Nb{sub 5}Si{sub 3} and Nb{sub 3}Si. (orig.)

  12. Electronically induced contrast enhancement in whisker S1 cortical response fields.

    Science.gov (United States)

    von Kraus, Lee M; Francis, Joseph T

    2014-01-01

    The ability of an organism to specifically attend to relevant sensory information during learning and subsequent performance of a task is highly dependent on the release of the neurotransmitter Acetylcholine (ACh). Electrophysiological studies have shown that pairing endogenous ACh with specific visual or auditory stimuli induces long lasting enhancements of subsequent cortical responses to the previously paired stimulus. In this study we present data suggesting that similar effects can be elicited in the rat whisker sensory system. Specifically, we show that pairing whisker deflection with electrical stimulation of the magnocellular basal nucleus (BN: a natural source of cortical ACh) causes an increase in the center-surround contrast of the treated whisker's cortical response field (CRF). Meanwhile, deflections of whiskers distant from the treated whisker show overall increased response magnitudes, but non-significant changes in contrast between principle vs. surround barrel responses. Control trials, in which BN stimulation was not paired with whisker deflection, showed similar lack of contrast enhancement. These results indicate that BN stimulation, paired with incoming whisker information, selectively increases the paired whisker's CRF center-surround contrast, while unpaired BN stimulation causes a more general increases in S1 responsiveness, without contrast modulation. Enhanced control over whisker sensory pathway attentional mechanisms has the potential to facilitate a more effective transfer of desired information to the animal's neural processing circuitry, thereby allowing experimental evaluation of more complex behavior and cognition than was previously possible.

  13. Surface modification of magnesium hydroxide sulfate hydrate whiskers using a silane coupling agent by dry process

    Science.gov (United States)

    Zhu, Donghai; Nai, Xueying; Lan, Shengjie; Bian, Shaoju; Liu, Xin; Li, Wu

    2016-12-01

    In order to improve the compatibility of magnesium hydroxide sulfate hydrate (MHSH) whiskers with polymers, the surface of MHSH whiskers was modified using vinyltriethoxysilane (VTES) by dry process. The possible mechanism of the surface modification and the interfacial interactions between MHSH whiskers and VTES, as well as the effect of surface modification, were studied. Scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) analyses showed that the agglomerations were effectively separated and a thin layer was formed on the surface of the whiskers after modification. Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses showed that the VTES molecules were bound to the surface of MHSH whiskers after modification. Chemical bonds (Sisbnd Osbnd Mg) were formed by the reaction between Sisbnd OC2H5 or Sisbnd OH and the hydroxyl group of MHSH whiskers. The effect of surface modification was evaluated by sedimentation tests, contact angle measurements and thermogravimetric analysis (TGA). The results showed that the surface of MHSH whiskers was transformed from hydrophilic to hydrophobic, and the dispersibility and the compatibility of MHSH whiskers were significantly improved in the organic phase. Additionally, the thermal stability of the VTES-modified MHSH whiskers was improved significantly.

  14. Peripheral optogenetic stimulation induces whisker movement and sensory perception in head-fixed mice.

    Science.gov (United States)

    Park, Sunmee; Bandi, Akhil; Lee, Christian R; Margolis, David J

    2016-06-08

    We discovered that optical stimulation of the mystacial pad in Emx1-Cre;Ai27D transgenic mice induces whisker movements due to activation of ChR2 expressed in muscles controlling retraction and protraction. Using high-speed videography in anesthetized mice, we characterize the amplitude of whisker protractions evoked by varying the intensity, duration, and frequency of optogenetic stimulation. Recordings from primary somatosensory cortex (S1) in anesthetized mice indicated that optogenetic whisker pad stimulation evokes robust yet longer latency responses than mechanical whisker stimulation. In head-fixed mice trained to report optogenetic whisker pad stimulation, psychometric curves showed similar dependence on stimulus duration as evoked whisker movements and S1 activity. Furthermore, optogenetic stimulation of S1 in expert mice was sufficient to substitute for peripheral stimulation. We conclude that whisker protractions evoked by optogenetic activation of whisker pad muscles results in cortical activity and sensory perception, consistent with the coding of evoked whisker movements by reafferent sensory input.

  15. Influence of particle size composition on self-flowability of bauxite-silicon carbide shotcreting castables%粒度组成对高铝-碳化硅质湿式喷射料自流性的影响

    Institute of Scientific and Technical Information of China (English)

    姚金甫; 田守信; 王峰

    2011-01-01

    Bauxite-silicon carbide shotcreting castables was prepared with starting materials of sintered mullite,silicon carbide,alumina micropowder, silica fume, and binder of ultra-low cement. Influence of particle size composition on self-flowability of shotcreting castables was researched. The results show that: ( 1 ) shotcreting castables has good self-flowability and properties with 20% fine grain ≤ 1 mm;(2)self-flow castables has enough powder to get good self-flowability when powder content is 38%-41% and q value of Andreassen equation is 0.23-0.25; (3) powders with craggedness hillside contribution can give the castables good self-flowability and reasonable micropowder combination which result in a good bonding between particles and matrix,improving the pumping properties of castables.%以烧结莫来石M70(骨料和粉料)、碳化硅粉、氧化铝微粉、硅微粉、棕刚玉微粉等为原料,采用超低水泥结合体系,制备了高铝-碳化硅质湿式喷射料,研究了粒度组成对湿式喷射料自流性的影响.结果表明:≤1mm的细颗粒含量(w)为20%时,喷射料的自流性和性能较好;细粉含量(w)为38%~41%,Andreassen方程中q值在0.23~0.25之间时,能够确保自流料有足够的细粉以获得良好的自流性;采用山坡陡峭型粒度分布的一般细粉可使喷射料具有良好的自流性,合理的微粉组合可使颗粒和基质之间具有较好的结合性,有利于改善喷射料的泵送性能.

  16. ENTIRELY AQUEOUS SOLUTION-GEL ROUTE FOR THE PREPARATION OF ZIRCONIUM CARBIDE, HAFNIUM CARBIDE AND THEIR TERNARY CARBIDE POWDERS

    Directory of Open Access Journals (Sweden)

    Zhang Changrui

    2016-07-01

    Full Text Available An entirely aqueous solution-gel route has been developed for the synthesis of zirconium carbide, hafnium carbide and their ternary carbide powders. Zirconium oxychloride (ZrOCl₂.8H₂O, malic acid (MA and ethylene glycol (EG were dissolved in water to form the aqueous zirconium carbide precursor. Afterwards, this aqueous precursor was gelled and transformed into zirconium carbide at a relatively low temperature (1200 °C for achieving an intimate mixing of the intermediate products. Hafnium and the ternary carbide powders were also synthesized via the same aqueous route. All the zirconium, hafnium and ternary carbide powders exhibited a particle size of ∼100 nm.

  17. The cerebellum linearly encodes whisker position during voluntary movement.

    Science.gov (United States)

    Chen, Susu; Augustine, George J; Chadderton, Paul

    2016-01-19

    Active whisking is an important model sensorimotor behavior, but the function of the cerebellum in the rodent whisker system is unknown. We have made patch clamp recordings from Purkinje cells in vivo to identify whether cerebellar output encodes kinematic features of whisking including the phase and set point. We show that Purkinje cell spiking activity changes strongly during whisking bouts. On average, the changes in simple spike rate coincide with or slightly precede movement, indicating that the synaptic drive responsible for these changes is predominantly of efferent (motor) rather than re-afferent (sensory) origin. Remarkably, on-going changes in simple spike rate provide an accurate linear read-out of whisker set point. Thus, despite receiving several hundred thousand discrete synaptic inputs across a non-linear dendritic tree, Purkinje cells integrate parallel fiber input to generate precise information about whisking kinematics through linear changes in firing rate.

  18. Crystalline instability of Bi-2212 superconducting whiskers near room temperature

    Science.gov (United States)

    Cagliero, Stefano; Agostino, Angelo; Khan, Mohammad Mizanur Rahman; Truccato, Marco; Orsini, Francesco; Marinone, Massimo; Poletti, Giulio; Lascialfari, Alessandro

    2009-05-01

    We report new evidences for the thermodynamic instability of whisker crystals in the Bi-Sr-Ca-Cu-O (BSCCO) system. Annealing treatments at 90°C have been performed on two sets of samples, which were monitored by means of X-Rays Diffraction (XRD) and Atomic Force Microscopy (AFM) measurements, respectively. Two main crystalline domains of Bi2Sr2CuCa2O8+ x (Bi-2212) were identified in the samples by the XRD data, which underwent an evident crystalline segregation after about 60 hours. Very fast dynamics of the surface modifications was also described by the AFM monitoring. Two typologies of surface structures formed after about 3 annealing hours: continuous arrays of dome shaped bodies were observed along the edges of the whiskers, while in the central regions a dense texture of flat bodies was found. These modifications are described in terms of the formation of simple oxide clusters involving a degradation of the internal layers.

  19. 铝基碳化硼材料中子屏蔽性能的蒙特卡罗模拟%The Monte Carlo simulation of neutron shielding performance of boron carbide reinforced with aluminum composites

    Institute of Scientific and Technical Information of China (English)

    戴春娟; 刘希琴; 刘子利; 刘伯路

    2013-01-01

    Three groups of neutron shielding experiments were set up to study the shielding performance of B4C/Al composite, using the Monte-Carlo method. We have made the following changes: the content of boron carbide 20%-40%, neutron energy 200 eV-15 keV, material thickness 0.3-2 cm, so that we can draw the conclusions: the content of boron carbide and neutron transmission coefficient show a linear relation, with a big drop; under the same neutron energy, the neutron-shielding qualities of simulated specimens are for better than polyethylene boron carbide at the same content of B4C and water, copper, and concrete at the same thickness; an exponential decline relationship is exhibited by material thickness and neutron transmission coefficient, which change greatly with the increase in unit material thickness; the content of boron affects the thermal neutron transmission coefficient seriously. In the thermal neutron energy region, the change of per unit neutron energy(100 eV) has a big influence on neutron transmission coefficient. In the slow neutron energy region, the influence is small.%  采用蒙特卡罗方法,运用 MCNP4C 程序研究了碳化硼含量20%-40%、中子能量200 eV-15 keV、材料厚度0.3-2 cm 对 B4C/Al 复合材料中子屏蔽性能的影响.结果表明:碳化硼含量与中子透射系数呈一次线性下降关系;同含量的碳化硼, B4C/Al 材料的中子屏蔽效果要大大优于聚乙烯碳化硼材料;在等厚度条件下,模拟试样 B20等的中子屏蔽效果要优于水、铜、混凝土等常规屏蔽材料;材料厚度与中子透射系数呈指数下降关系,且单位厚度的增加对中子透射系数改变很大;含硼量对热中子透射系数影响很大;在热中子能区,中子每单位能量的变化对中子透射系数改变较大;在慢中子能区,中子每单位能量的变化对中子透射系数改变很小.

  20. Microstructure and wear resistance of TiC carbide-reinforced composite coating prepared by laser surface alloying%激光表面合金化制备TiC颗粒增强复合材料微观结构及磨擦学性能研究

    Institute of Scientific and Technical Information of China (English)

    许长庆; 李贵江

    2008-01-01

    To strengthen the wear resistance of AISI321 stainless steel, the TiC carbide-reinforced compos-ite coating was produced by laser surface alloying. The microstructure, microhardness, and wear resistance of the composite coatings were investigated using optical microscopy, X-ray diffraction (XRD) meter, scan-ning electron microscopy (SEM), microhardness tester, and sliding wear tester. The results show that the composite coating is metallurgically bonded to the substrate and the microstructure is fine and uniform. The hardness of the composite coating is up to 400 HV, which is 2.5 times that of the substrate. Under room temperature and oil lubrication condition, the sliding wear tests indicate the friction coefficient and weight loss of the composite coating are smaller than those of substrate. The worn surface of the composite coatings is much smoother than that of the substrate, without grooves and crater. The wear resistance of the material has been greatly improved by laser surface alloying.