Disorder and defects are not intrinsic to boron carbide

Science.gov (United States)

Mondal, Swastik; Bykova, Elena; Dey, Somnath; Ali, Sk Imran; Dubrovinskaia, Natalia; Dubrovinsky, Leonid; Parakhonskiy, Gleb; van Smaalen, Sander

2016-01-01

A unique combination of useful properties in boron-carbide, such as extreme hardness, excellent fracture toughness, a low density, a high melting point, thermoelectricity, semi-conducting behavior, catalytic activity and a remarkably good chemical stability, makes it an ideal material for a wide range of technological applications. Explaining these properties in terms of chemical bonding has remained a major challenge in boron chemistry. Here we report the synthesis of fully ordered, stoichiometric boron-carbide B13C2 by high-pressure-high-temperature techniques. Our experimental electron-density study using high-resolution single-crystal synchrotron X-ray diffraction data conclusively demonstrates that disorder and defects are not intrinsic to boron carbide, contrary to what was hitherto supposed. A detailed analysis of the electron density distribution reveals charge transfer between structural units in B13C2 and a new type of electron-deficient bond with formally unpaired electrons on the C-B-C group in B13C2. Unprecedented bonding features contribute to the fundamental chemistry and materials science of boron compounds that is of great interest for understanding structure-property relationships and development of novel functional materials.

The All Boron Carbide Diode Neutron Detector: Experiment and Modeling Approach

International Nuclear Information System (INIS)

Sabirianov, Ildar F.; Brand, Jennifer I.; Fairchild, Robert W.

2008-01-01

Boron carbide diode detectors, fabricated from two different polytypes of semiconducting boron carbide, will detect neutrons in reasonable agreement with theoretical expectations. The performance of the all boron carbide neutron detector differs, as expected, from devices where a boron rich neutron capture layer is distinct from the diode charge collection region (i.e. a conversion layer solid state detector). Diodes were fabricated from natural abundance boron (20% 10 B and 80% 11 B.) directly on the metal substrates and metal contacts applied to the films as grown. The total boron depth was on the order of 2 microns. This is clearly not a conversion-layer configuration. The diodes were exposed to thermal neutrons generated from a paraffin moderated plutonium-beryllium source in moderated and un-moderated, as well as shielded and unshielded experimental configurations, where the expected energy peaks at at 2.31 MeV and 2.8 MeV were clearly observed, albeit with some incomplete charge collection typical of thinner diode structures. The results are compared with other boron based thin film detectors and literature models. (authors)

Oxidation of boron carbide at high temperatures

International Nuclear Information System (INIS)

Steinbrueck, Martin

2005-01-01

The oxidation kinetics of various types of boron carbides (pellets, powder) were investigated in the temperature range between 1073 and 1873 K. Oxidation rates were measured in transient and isothermal tests by means of mass spectrometric gas analysis. Oxidation of boron carbide is controlled by the formation of superficial liquid boron oxide and its loss due to the reaction with surplus steam to volatile boric acids and/or direct evaporation at temperatures above 1770 K. The overall reaction kinetics is paralinear. Linear oxidation kinetics established soon after the initiation of oxidation under the test conditions described in this report. Oxidation is strongly influenced by the thermohydraulic boundary conditions and in particular by the steam partial pressure and flow rate. On the other hand, the microstructure of the B 4 C samples has a limited influence on oxidation. Very low amounts of methane were produced in these tests

Preparation of fiber reinforced titanium diboride and boron carbide composite bodies

International Nuclear Information System (INIS)

Newkirk, L.R.; Riley, R.E.; Sheinberg, H.; Valencia, F.A.; Wallace, T.C.

1979-01-01

A process is described for uniformly infiltrating woven carbon cloth with either titanium diboride or boron carbide at reduced pressure (15 to 25 torr). The effects of deposition temperature on the uniformity of penetration and on coating rate are described for temperatures from 750 to 1000 0 C and deposit loadings from 20 to 43 vol. %. For the boron carbides, boron composition is discussed and evidence is presented suggesting that propene is the dominant rate controlling reactant

Study and optimization of the carbothermic reduction process for obtaining boron carbide

International Nuclear Information System (INIS)

Castro, A.R.M. de.

1989-01-01

Boron carbide - B sub(4)C - is a ceramic material of technological importance due to its hardness and high chemical and thermal stabilities. Moreover, its high neutron capture cross section makes it suitable for application as neutron absorber in nuclear technology. The process for obtaining carbothermally derived boron carbide has been studied in two steps: firstly, the parameters of the boric acid → boron oxide dehydration reaction have been defined; secondly, the optimization of the carbothermal reduction reaction using boron oxide has been undertaken looking for boron carbide having low level of free carbon. The starting materials as well as the main products have been studied by chemical and spectrographic analyses, X-ray diffractometry, granulometric classification and scanning electron microscopy. The optimization of the carbothermic reduction process allowed for the development and set up of a fabrication procedure yielding high quality B sub(4) C powders, starting from low cost and easily available (in the Brazilian market) raw materials. (author)

Electronic and vibrational hopping transport in boron carbides

International Nuclear Information System (INIS)

Emin, D.

1991-01-01

General concepts of hopping-type transport and localization are reviewed. Disorder, electronic correlations and atomic displacements, effects ignored in electronic band structure calculations, foster localization of electronic charge carriers. Examples are given that illustrate the efficacy of these effects in producing localization. This introduction is followed by a brief discussion of the relation between hopping-type transport and localization. The fundamentals of the formation, localization, and hopping transport of small polarons and/or bipolarons is then described. Electronic transport in boron carbides is presented as an example of the adiabatic hopping of small bipolarons. Finally, the notion of vibrational hopping is introduced. The high-temperature thermal diffusion in boron carbides is presented as a potential application of this idea

Effect of boron on the microstructure and mechanical properties of carbidic austempered ductile iron

International Nuclear Information System (INIS)

Peng Yuncheng; Jin Huijin; Liu Jinhai; Li Guolu

2011-01-01

Highlights: → Boron are applied to carbidic austempered ductile iron (CADI). → Boron microalloying CADI is a new high hardenability of wear-resistant cast iron. → Addition of boron to CADI significantly improves hardenability. → Effect of boron on the CADI grinding ball were investigated. → Optimum property is obtained when boron content at 0.03 wt%. - Abstract: Carbidic austempered ductile iron (CADI) castings provide a unique combination of high hardness and toughness coupled with superior wear resistance properties, but their hardenability restricts their range of applications. The purpose of this study was to investigate the influence of boron on the microstructure and mechanical properties of CADI. The experimental results indicate that the CADI comprises graphite nodules, which are dispersive boron-carbides that are distributed in the form of strips, and the matrix is a typical ausferritic matrix. Microscopic amounts of boron can improve the hardenability of CADI, but higher boron content reduces the hardenability and toughness of CADI. The results are discussed in the context of the influence of boron content on the microstructure and mechanical properties of grinding balls.

Anomalous Seebeck coefficient in boron carbides

International Nuclear Information System (INIS)

Aselage, T.L.; Emin, D.; Wood, C.; Mackinnon, I.D.R.; Howard, I.A.

1987-01-01

Boron carbides exhibit an anomalously large Seebeck coefficient with a temperature coefficient that is characteristic of polaronic hopping between inequivalent sites. The inequivalence in the sites is associated with disorder in the solid. The temperature dependence of the Seebeck coefficient for materials prepared by different techniques provides insight into the nature of the disorder

Production of boron carbide powder by carbothermal synthesis of ...

Indian Academy of Sciences (India)

TECS

weight armour plates etc (Alizadeh et al 2004). It can also be used as a reinforcing material for ceramic matrix composites. It is an excellent neutron absorption material in nuclear industry due to its high neutron absorption co- efficient (Sinha et al 2002). Boron carbide can be prepared by reaction of elemental boron and ...

Sintering of nano crystalline α silicon carbide by doping with boron ...

Indian Academy of Sciences (India)

Sinterable nano silicon carbide powders of mean particle size (37 nm) were prepared by attrition milling and chemical processing of an acheson type alpha silicon carbide having mean particle size of 0.39 m (390 nm). Pressureless sintering of these powders was achieved by addition of boron carbide of 0.5 wt% together ...

Erosion wear of boron carbide ceramic nozzles by abrasive air-jets

International Nuclear Information System (INIS)

Deng Jianxin

2005-01-01

Boron carbide nozzles were produced by hot pressing. The erosion wear of this nozzle caused by abrasive particle impact was investigated by abrasive air-jets. Silica, silicon carbide and alumina powders with different hardness were used as the erodent abrasive particles. Results showed that the hardness of the erodent particles played an important role with respect to the erosion wear of the boron carbide nozzles. As the hardness of the erodent particles increases, there is a dramatic increase in erosion rate of the nozzles. The nozzle entrance area suffered from severe abrasive impact under large impact angles, and generated maximum tensile stresses. The wear mechanisms of boron carbide nozzle at this area appeared to be entirely brittle in nature with the evidence of large scale-chipping, and exhibited a brittle fracture induced removal process. While at the nozzle center wall section, most of the particles traveled parallel to the nozzle wall, and showed minimum tensile stresses. The wear mode in this area of the nozzle changed from impact to sliding erosion, and the wear mechanisms appeared to be the lateral cracking owing to a surface fatigue fracture mechanism

Epithermal neutron activation analysis using a boron carbide irradiation filter

International Nuclear Information System (INIS)

Ehmann, W.D.; Brueckner, J.

1980-01-01

The use of boron carbide as a thermal neutron filter in epithermal neutron activation (ENAA) analysis has been investigated. As compared to the use of a cadmium filter, boron provides a greater reduction of activities from elements relatively abundant in terrestrial rocks and fossil fuels, such as Na, La, Sc and Fe. These elements have excitation functions which follow the 1/v law in the 1 to 10 eV lower epithermal region. This enhances the sensitivity of ENAA for elements such as U, Th, Ba and etc. which have strong resonances in the higher epithermal region above 10 eV. In addition, a boron carbide filter has the advantages over cadmium of acquiring a relatively low level of induced activity which poses minimal radiation safety problems, when used for ENAA. (author)

Determination of soluble carbon in nuclear grade boron carbide

International Nuclear Information System (INIS)

Vega Bustillos, J.O.; Gomes, R.; Camaro, J.; Zorzetto, F.; Domingues, P.; Riella, H.

1990-05-01

The present work describes two different techniques (manometric and wet chemical) for the soluble carbon determination in nuclear grade boron carbide. The techniques are based on the reaction of the boron carbide with a sulfocromic mixture, generating CO 2 . The techniques differ on the mode they do the measurement of CO 2 produced. By wet chemical technique the CO 2 is absorved in a barium hydroxide solution and is determinated by titration. In the manometric technique the CO 2 gas is measured using a McLeod gauge. The gas produced by the latter technique is analysed by mass spectrometry. The details of the analytical technique and the data obtained are discussed. (author) [pt

Synergistic methods for the production of high-strength and low-cost boron carbide

Science.gov (United States)

Wiley, Charles Schenck

2011-12-01

Boron carbide (B4C) is a non-oxide ceramic in the same class of nonmetallic hard materials as silicon carbide and diamond. The high hardness, high elastic modulus and low density of B4C make it a nearly ideal material for personnel and vehicular armor. B4C plates formed via hot-pressing are currently issued to U.S. soldiers and have exhibited excellent performance; however, hot-pressed articles contain inherent processing defects and are limited to simple geometries such as low-curvature plates. Recent advances in the pressureless sintering of B4C have produced theoretically-dense and complex-shape articles that also exhibit superior ballistic performance. However, the cost of this material is currently high due to the powder shape, size, and size distribution that are required, which limits the economic feasibility of producing such a product. Additionally, the low fracture toughness of pure boron carbide may have resulted in historically lower transition velocities (the projectile velocity range at which armor begins to fail) than competing silicon carbide ceramics in high-velocity long-rod tungsten penetrator tests. Lower fracture toughness also limits multi-hit protection capability. Consequently, these requirements motivated research into methods for improving the densification and fracture toughness of inexpensive boron carbide composites that could result in the development of a superior armor material that would also be cost-competitive with other high-performance ceramics. The primary objective of this research was to study the effect of titanium and carbon additives on the sintering and mechanical properties of inexpensive B4C powders. The boron carbide powder examined in this study was a sub-micron (0.6 mum median particle size) boron carbide powder produced by H.C. Starck GmbH via a jet milling process. A carbon source in the form of phenolic resin, and titanium additives in the form of 32 nm and 0.9 mum TiO2 powders were selected. Parametric studies of

Boron Carbide: Stabilization of Highly-Loaded Aqueous Suspensions, Pressureless Sintering, and Room Temperature Injection Molding

Science.gov (United States)

Diaz-Cano, Andres

Boron carbide (B4C) is the third hardest material after diamond and cubic boron nitride. It's unique combination of properties makes B4C a highly valuable material. With hardness values around 35 MPa, a high melting point, 2450°C, density of 2.52 g/cm3, and high chemical inertness, boron carbide is used in severe wear components, like cutting tools and sandblasting nozzles, nuclear reactors' control rots, and finally and most common application, armor. Production of complex-shaped ceramic component is complex and represents many challenges. Present research presents a new and novel approach to produce complex-shaped B4C components. Proposed approach allows forming to be done at room temperatures and under very low forming pressures. Additives and binder concentrations are kept as low as possible, around 5Vol%, while ceramics loadings are maximized above 50Vol%. Given that proposed approach uses water as the main solvent, pieces drying is simple and environmentally safe. Optimized formulation allows rheological properties to be tailored and adjust to multiple processing approaches, including, injection molding, casting, and additive manufacturing. Boron carbide samples then were pressureless sintered. Due to the high covalent character of boron carbide, multiples sintering aids and techniques have been proposed in order to achieve high levels of densification. However, is not possible to define a clear sintering methodology based on literature. Thus, present research developed a comprehensive study on the effect of multiple sintering aids on the densification of boron carbide when pressureless sintered. Relative densities above 90% were achieved with values above 30MPa in hardness. Current research allows extending the uses and application of boron carbide, and other ceramic systems, by providing a new approach to produce complex-shaped components with competitive properties.

Functionalization and cellular uptake of boron carbide nanoparticles

DEFF Research Database (Denmark)

Mortensen, M. W.; Björkdahl, O.; Sørensen, P. G.

2006-01-01

In this paper we present surface modification strategies of boron carbide nanoparticles, which allow for bioconjugation of the transacting transcriptional activator (TAT) peptide and fluorescent dyes. Coated nanoparticles can be translocated into murine EL4 thymoma cells and B16 F10 malignant...

Electrical Characterization of Irradiated Semiconducting Amorphous Hydrogenated Boron Carbide

Science.gov (United States)

Peterson, George Glenn

Semiconducting amorphous partially dehydrogenated boron carbide has been explored as a neutron voltaic for operation in radiation harsh environments, such as on deep space satellites/probes. A neutron voltaic device could also be used as a solid state neutron radiation detector to provide immediate alerts for radiation workers/students, as opposed to the passive dosimetry badges utilized today. Understanding how the irradiation environment effects the electrical properties of semiconducting amorphous partially dehydrogenated boron carbide is important to predicting the stability of these devices in operation. p-n heterojunction diodes were formed from the synthesis of semiconducting amorphous partially dehydrogenated boron carbide on silicon substrates through the use of plasma enhanced chemical vapor deposition (PECVD). Many forms of structural and electrical measurements and analysis have been performed on the p-n heterojunction devices as a function of both He+ ion and neutron irradiation including: transmission electron microscopy (TEM), selected area electron diffraction (SAED), current versus voltage I(V), capacitance versus voltage C(V), conductance versus frequency G(f), and charge carrier lifetime (tau). In stark contrast to nearly all other electronic devices, the electrical performance of these p-n heterojunction diodes improved with irradiation. This is most likely the result of bond defect passivation and resolution of degraded icosahedral based carborane structures (icosahedral molecules missing a B, C, or H atom(s)).

Pulverization of boron element and proportions of boron carbide in boron; Broyage de bore element et dosage de carbure de bore dans le bore

Energy Technology Data Exchange (ETDEWEB)

Lang, F M; Finck, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1956-07-01

It is possible to reduce boron element into fine powder by means of a mortar and pestle made of sintered boron carbide, the ratio of boron carbide introduced being less than one per cent. Boron element at our disposal is made of sharp edged, dark brown, little grains of average size greater than 5 {mu}. Grain sizes smaller than 1{mu} are required for applying thin layers of such boron. (author) [French] Il est possible de pulveriser finement du bore element au moyen de mortier et pilon en carbure de bore fritte, le taux de carbure de bore introduit etant inferieur a 1 pour cent. Le bore element dont nous disposons est constitue de petits grains brun fonce, a aretes vives, de dimension moyenne superieure a 5 {mu}. L'application de ce bore en couches minces demande des grains de dimensions inferieures a 1 {mu}. (aute0008.

Irradiation damage in boron carbide: point defects, clusters and helium bubbles

International Nuclear Information System (INIS)

Stoto, T.; Zuppiroli, L.

1986-06-01

Boron carbide is a refractory hard and light material of interest in nuclear technology (fission and also fusion). Transmission electron microscopy was used to examine the properties of radiation induced damage. Firstly, the production of point defects and their clustering was studied in samples irradiated by 1 MeV electron in a high voltage electron microscope at selected temperatures from 12 K to 1000 K. Secondly, conventional transmission electron microscopy was used to understand the production of helium bubbles in neutron irradiated boron carbide and their role in the generation of microcracks. Finally, the interaction between point defects and bubbles was also examined

Friction and wear performance of diamond-like carbon, boron carbide, and titanium carbide coatings against glass

International Nuclear Information System (INIS)

Daniels, B.K.; Brown, D.W.; Kimock, F.M.

1997-01-01

Protection of glass substrates by direct ion beam deposited diamond-like carbon (DLC) coatings was observed using a commercial pin-on-disk instrument at ambient conditions without lubrication. Ion beam sputter-deposited titanium carbide and boron carbide coatings reduced sliding friction, and provided tribological protection of silicon substrates, but the improvement factor was less than that found for DLC. Observations of unlubricated sliding of hemispherical glass pins at ambient conditions on uncoated glass and silicon substrates, and ion beam deposited coatings showed decreased wear in the order: uncoated glass>uncoated silicon>boron carbide>titanium carbide>DLC>uncoated sapphire. Failure mechanisms varied widely and are discussed. Generally, the amount of wear decreased as the sliding friction decreased, with the exception of uncoated sapphire substrates, for which the wear was low despite very high friction. There is clear evidence that DLC coatings continue to protect the underlying substrate long after the damage first penetrates through the coating. The test results correlate with field use data on commercial products which have shown that the DLC coatings provide substantial extension of the useful lifetime of glass and other substrates. copyright 1997 Materials Research Society

Reaction of boron carbide with molybdenum disilicide

International Nuclear Information System (INIS)

Novikov, A.V.; Melekhin, V.F.; Pegov, V.S.

1989-01-01

The investigation results of interaction in the B 4 C-MoSi 2 system during sintering in vacuum are presented. Sintering of boron carbide with molybdenum disilicide is shown to lead to the formation of MoB 2 , SiC, Mo 5 Si 3 compounds, the presence of carbon-containing covering plays an important role in sintering

Determination of boron in graphite, boron carbide and glass by ICP-MS, ICP-OES and conventional wet chemical methods

International Nuclear Information System (INIS)

Venkatesh, K.; Kamble, Granthali S.; Venkatesh, Manisha; Kumar, Sanjukta A.; Reddy, A.V.R.

2014-01-01

Boron is an important element of interest in nuclear reactor materials due to its high neutron absorption cross section (σ 0 =3837 barns for 10 B). In the present paper, R and D work and routinely used methods have been described for the analysis of case samples (1) Graphite where boron is present at trace levels, (2) Boron Carbide having boron concentration of about 80% and (3) Glass containing 4-6 % boron. (author)

Method of accurate thickness measurement of boron carbide coating on copper foil

Science.gov (United States)

Lacy, Jeffrey L.; Regmi, Murari

2017-11-07

A method is disclosed of measuring the thickness of a thin coating on a substrate comprising dissolving the coating and substrate in a reagent and using the post-dissolution concentration of the coating in the reagent to calculate an effective thickness of the coating. The preferred method includes measuring non-conducting films on flexible and rough substrates, but other kinds of thin films can be measure by matching a reliable film-substrate dissolution technique. One preferred method includes determining the thickness of Boron Carbide films deposited on copper foil. The preferred method uses a standard technique known as inductively coupled plasma optical emission spectroscopy (ICPOES) to measure boron concentration in a liquid sample prepared by dissolving boron carbide films and the Copper substrates, preferably using a chemical etch known as ceric ammonium nitrate (CAN). Measured boron concentration values can then be calculated.

Method for fabricating boron carbide articles

International Nuclear Information System (INIS)

Ardary, Z.; Reynolds, C.

1980-01-01

Described is a method for fabricating an essentially uniformly dense boron carbide article of a length-to-diameter or width ratio greater than 2 to 1 comprising the steps of providing a plurality of article segments to be joined together to form the article with each of said article segments having a length-to-diameter or width ratio less than 1.5 to 1. Each segment is fabricated by hot pressing a composition consisting of boron carbide powder at a pressure and temperature effective to provide the article segment with a density greater than about 85% of theoretical density, providing each article segment with parallel planar end surfaces, placing a plurality of said article segments in a hot-pressing die in a line with the planar surfaces of adjacent article segments being disposed in intimate contact, and hot pressing the aligned article segments at a temperature and pressure effective to provide said article with a density over the length thereof in the range of about 94 to 98 percent theoretical density and greater than the density provided in the discrete hot pressing of each of the article segments and to provide a bond between adjacent article segments with said bond being at least equivalent in hardness, strength and density to a remainder of said article

Equations of state and melting curve of boron carbide in the high-pressure range of shock compression

Energy Technology Data Exchange (ETDEWEB)

Molodets, A. M., E-mail: molodets@icp.ac.ru; Golyshev, A. A.; Shakhrai, D. V. [Russian Academy of Sciences, Institute for Problems in Chemical Physics (Russian Federation)

2017-03-15

We have constructed the equations of state for crystalline boron carbide B{sub 11}C (C–B–C) and its melt under high dynamic and static pressures. A kink on the shock adiabat for boron carbide has been revealed in the pressure range near 100 GPa, and the melting curve with negative curvature in the pressure range 0–120 GPa has been calculated. The results have been used for interpreting the kinks on the shock adiabat for boron carbide in the pressure range of 0–400 GPa.

Size-scaling of tensile failure stress in boron carbide

Energy Technology Data Exchange (ETDEWEB)

Wereszczak, Andrew A [ORNL; Kirkland, Timothy Philip [ORNL; Strong, Kevin T [ORNL; Jadaan, Osama M. [University of Wisconsin, Platteville; Thompson, G. A. [U.S. Army Dental and Trauma Research Detachment, Greak Lakes

2010-01-01

Weibull strength-size-scaling in a rotary-ground, hot-pressed boron carbide is described when strength test coupons sampled effective areas from the very small (~ 0.001 square millimeters) to the very large (~ 40,000 square millimeters). Equibiaxial flexure and Hertzian testing were used for the strength testing. Characteristic strengths for several different specimen geometries are analyzed as a function of effective area. Characteristic strength was found to substantially increase with decreased effective area, and exhibited a bilinear relationship. Machining damage limited strength as measured with equibiaxial flexure testing for effective areas greater than ~ 1 mm2 and microstructural-scale flaws limited strength for effective areas less than 0.1 mm2 for the Hertzian testing. The selections of a ceramic strength to account for ballistically-induced tile deflection and to account for expanding cavity modeling are considered in context with the measured strength-size-scaling.

Analytical chemistry methods for boron carbide absorber material. [Standard

Energy Technology Data Exchange (ETDEWEB)

DELVIN WL

1977-07-01

This standard provides analytical chemistry methods for the analysis of boron carbide powder and pellets for the following: total C and B, B isotopic composition, soluble C and B, fluoride, chloride, metallic impurities, gas content, water, nitrogen, and oxygen. (DLC)

Lattice dynamics of {alpha} boron and of boron carbide; Proprietes vibrationnelles du bore {alpha} et du carbure de bore

Energy Technology Data Exchange (ETDEWEB)

Vast, N

1999-07-01

The atomic structure and the lattice dynamics of {alpha} boron and of B{sub 4}C boron carbide have been studied by Density Functional Theory (D.F.T.) and Density Functional Perturbation Theory (D.F.P.T.). The bulk moduli of the unit-cell and of the icosahedron have been investigated, and the equation of state at zero temperature has been determined. In {alpha} boron, Raman diffusion and infrared absorption have been studied under pressure, and the theoretical and experimental Grueneisen coefficients have been compared. In boron carbide, inspection of the theoretical and experimental vibrational spectra has led to the determination of the atomic structure of B{sub 4}C. Finally, the effects of isotopic disorder have been modeled by an exact method beyond the mean-field approximation, and the effects onto the Raman lines has been investigated. The method has been applied to isotopic alloys of diamond and germanium. (author)

Determination of isotopic composition of boron in boron carbide by TIMS and PIGE: an inter-comparison study

International Nuclear Information System (INIS)

Sasibhushan, K.; Rao, R.M.; Parab, A.R.; Alamelu, D.; Aggarwal, S.K.; Acharya, R.; Chhillar, S.; Pujari, P.K.

2015-01-01

The paper reports a comparison of results on the determination of isotopic composition of boron in boron carbide (B 4 C) samples by Thermal Ionisation Mass Spectrometry (TIMS) and Particle Induced Gamma ray Spectrometry (PIGE). B 4 C samples having varying boron isotopic composition (natural, enriched with respect to 10 B) and their synthetic mixtures) have been analysed by both the techniques. The 10 B atom% was found to be in the range of 20-67%. (author)

Boron carbide synthesis by carbothermic reduction of boron oxide

International Nuclear Information System (INIS)

Castro, A.R.M. de; Paschoal, J.O.A.

1988-01-01

Boron carbide (B 4 C) is a ceramic material of technological applications due to its extreme hardness and high chemical as well as thermal stability. Some parameters of the process for obtaining B 4 C by carbothermic reduction of B 2 O 3 have been determined. The starting powders and the final products have been analysed by chemical, spectrographic and X-ray diffraction methods. The results show that the B 4 C obtained by the carbothermic reduction process is suitable for applications with a definite determination of the free carbon content. (author) [pt

Evidence for multiple polytypes of semiconducting boron carbide (C2B10) from electronic structure

International Nuclear Information System (INIS)

Lunca-Popa, Petru; Brand, J I; Balaz, Snjezana; Rosa, Luis G; Boag, N M; Bai Mengjun; Robertson, B W; Dowben, P A

2005-01-01

Boron carbides fabricated via plasma enhanced chemical vapour deposition from different isomeric source compounds with the same C 2 B 10 H 12 closo-icosahedral structure result in materials with very different direct (optical) band gaps. This provides compelling evidence for the existence of multiple polytypes of C 2 B 10 boron carbide and is consistent with electron diffraction results

Superconductivity in heavily boron-doped silicon carbide

Directory of Open Access Journals (Sweden)

Markus Kriener, Takahiro Muranaka, Junya Kato, Zhi-An Ren, Jun Akimitsu and Yoshiteru Maeno

2008-01-01

Full Text Available The discoveries of superconductivity in heavily boron-doped diamond in 2004 and silicon in 2006 have renewed the interest in the superconducting state of semiconductors. Charge-carrier doping of wide-gap semiconductors leads to a metallic phase from which upon further doping superconductivity can emerge. Recently, we discovered superconductivity in a closely related system: heavily boron-doped silicon carbide. The sample used for that study consisted of cubic and hexagonal SiC phase fractions and hence this led to the question which of them participated in the superconductivity. Here we studied a hexagonal SiC sample, free from cubic SiC phase by means of x-ray diffraction, resistivity, and ac susceptibility.

Manufacturing method for boron carbide/carbon composite neutron shielding material

International Nuclear Information System (INIS)

Inoue, Takenori; Ukai, Shigeharu; Maruyama, Tadashi; Suya, Kiyoshi; Sunami, Yoshihiko.

1994-01-01

A less volatile binder pitch which is melted upon heating is used as a binder. Raw materials mainly comprising 60 to 85% by volume of a boron carbide powder and 15 to 40% by volume of a binder pitch are mixed, molded under pressure and heating at 480 to 600degC, then baked under non-pressurization, further impregnated with pitch under a reduced pressure and then baked again. The volume percentage of each of the materials is calculated based on the volume obtained by dividing the blending weight for each of raw materials with the intrinsic density respectively. The binding property relative to the boron carbide powder is improved by using a pitch having satisfactory melting performance and reduction of strength is decreased. Moreover, if the binder pitch is baked at about 2,000degC, it is easily converted into a graphitized tissues to have excellent slidability and fabricability. With such procedures, high bending strength and high heat conductivity can be ensured while keeping high boron content and neutron absorbing performance. (T.M.)

Studies on the influence of surface pre-treatments on electroless copper coating of boron carbide particles

International Nuclear Information System (INIS)

Deepa, J.P.; Resmi, V.G.; Rajan, T.P.D.; Pavithran, C.; Pai, B.C.

2011-01-01

Boron carbide is one of the hard ceramic particles which find application as structural materials and neutron shielding material due to its high neutron capture cross section. Copper coating on boron carbide particle is essential for the synthesis of metal-ceramic composites with enhanced sinterability and dispersibility. Surface characteristics of the substrate and the coating parameters play a foremost role in the formation of effective electroless coating. The effect of surface pre-treatment conditions and pH on electroless copper coating of boron carbide particles has been studied. Surface pre-treatement of B 4 C when compared to acid treated and alkali treated particles were carried out. Uniform copper coating was observed at pH 12 in alkali treated particles when compared to others due to the effective removal of inevitable impurities during the production and processing of commercially available B 4 C. A threshold pH 11 was required for initiation of copper coating on boron carbide particles. The growth pattern of the copper coating also varies depending on the surface conditions from acicular to spherical morphology.

Defects in boron carbide: First-principles calculations and CALPHAD modeling

International Nuclear Information System (INIS)

Saengdeejing, Arkapol; Saal, James E.; Manga, Venkateswara Rao; Liu Zikui

2012-01-01

The energetics of defects in B 4+x C boron carbide and β-boron are studied through first-principles calculations, the supercell phonon approach and the Debye–Grüneisen model. It is found that suitable sublattice models for β-boron and B 4+x C are B 101 (B,C) 4 and B 11 (B,C) (B,C,Va) (B,Va) (B,C,Va), respectively. The thermodynamic properties of B 4+x C, β-boron, liquid and graphite are modeled using the CALPHAD approach based on the thermochemical data from first-principles calculations and experimental phase equilibrium data in the literature. The concentrations of various defects are then predicted as a function of carbon composition and temperature.

High resolution imaging of boron carbide microstructures

International Nuclear Information System (INIS)

MacKinnon, I.D.R.; Aselage, T.; Van Deusen, S.B.

1986-01-01

Two samples of boron carbide have been examined using high resolution transmission electron microscopy (HRTEM). A hot-pressed B 13 C 2 sample shows a high density of variable width twins normal to (10*1). Subtle shifts or offsets of lattice fringes along the twin plane and normal to approx.(10*5) were also observed. A B 4 C powder showed little evidence of stacking disorder in crystalline regions

Boron carbide-coated carbon material, manufacturing method therefor and plasma facing material

International Nuclear Information System (INIS)

Suzuki, Takayuki; Kikuchi, Yoshihiro; Hyakki, Yasuo.

1997-01-01

The present invention concerns a plasma facing material suitable to a thermonuclear device. The material comprises a carbon material formed by converting the surface of a carbon fiber-reinforced carbon material comprising a carbon matrix and carbon fibers to a boron carbide, the material has a surface comprising vertically or substantially vertically oriented carbon fibers, and the thickness of the surface converted to boron carbide is reduced in the carbon fiber portion than in the carbon matrix portion. Alternatively, a carbon fiber-reinforced carbon material containing carbon fibers having a higher graphitizing degree than the carbon matrix is converted to boron carbide on the surface where the carbon fibers are oriented vertically or substantially vertically. The carbon fiber-reinforced material is used as a base material, and a resin material impregnated into a shaped carbon fiber product is carbonized or thermally decomposed carbon is filled as a matrix. The material of the present invention has high heat conduction and excellent in heat resistance thereby being suitable to a plasma facing material for a thermonuclear device. Electric specific resistivity of the entire coating layer can be lowered, occurrence of arc discharge is prevented and melting can be prevented. (N.H.)

Design of boron carbide-shielded irradiation channel of the outer irradiation channel of the Ghana Research Reactor-1 using MCNP.

Science.gov (United States)

Abrefah, R G; Sogbadji, R B M; Ampomah-Amoako, E; Birikorang, S A; Odoi, H C; Nyarko, B J B

2011-01-01

The MCNP model for the Ghana Research Reactor-1 was redesigned to incorporate a boron carbide-shielded irradiation channel in one of the outer irradiation channels. Extensive investigations were made before arriving at the final design of only one boron carbide covered outer irradiation channel; as all the other designs that were considered did not give desirable results of neutronic performance. The concept of redesigning a new MCNP model, which has a boron carbide-shielded channel is to equip the Ghana Research Reactor-1 with the means of performing efficient epithermal neutron activation analysis. After the simulation, a comparison of the results from the original MCNP model for the Ghana Research Reactor-1 and the new redesigned model of the boron carbide shielded channel was made. The final effective criticality of the original MCNP model for the GHARR-1 was recorded as 1.00402 while that of the new boron carbide designed model was recorded as 1.00282. Also, a final prompt neutron lifetime of 1.5245 × 10(-4)s was recorded for the new boron carbide designed model while a value of 1.5571 × 10(-7)s was recorded for the original MCNP design of the GHARR-1. Copyright © 2010 Elsevier Ltd. All rights reserved.

Experimental determination of boron and carbon thermodynamic activities in the carbide phase of the boron-carbon system

International Nuclear Information System (INIS)

Froment, A.K.

1990-01-01

- The boron-carbon phase diagram presents a single phase area ranging from 9 to 20 atomic percent of carbon. The measurement of carbon activity, in this range of composition, has been measured according to the following methods: - quantitative analysis of the methane-hydrogen mixture in equilibrium with the carbide, - high temperature mass spectrometry measurements. The first method turned out to be a failure; however, the apparatus used enabled the elaboration of a B 4 C composition pure phase from a two-phase (B 4 C + graphite) industrial product. The results obtained with the other two methods are consistent and lead to a law expressing the increase of the carbon activity in relation with the amount of this element; the high temperature mass spectrometry method has also made it possible to measure the boron activity which decreases when the carbon activity increases, but with a variation of amplitude much lower, according to the theoretical calculations. These results are a first step towards the knowledge of the boron carbide thermodynamical data for compositions different from B 4 C [fr

Role of intericosahedral chains on the hardness of sputtered boron carbide films

International Nuclear Information System (INIS)

Jacobsohn, L.G.; Averitt, R.D.; Wetteland, C.J.; Schulze, R.K.; Nastasi, M.; Daemen, L.L.; Jenei, Z.; Asoka-Kumar, P.

2004-01-01

The relationship between the structure and mechanical properties of sputter-deposited boron carbide films was investigated. Changes in the structure induced by annealing were characterized in terms of chemical composition, chemical bonding, and concentrations of defects and trapped impurities. The creation of intericosahedral chains for higher annealing temperatures was revealed by infrared and Raman measurements, and the intensity of the infrared band at 1500 cm-1 was found to be related to the hardness. The presence of residual trapped Ar atoms and of open-volume defects is insensitive to relatively high annealing temperatures and does not influence the recovery of the hardness. Our results suggest postdeposition annealing as a pathway to enhance the mechanical properties of boron carbide films

Electron microscopy study of radiation effects in boron carbide

International Nuclear Information System (INIS)

Stoto, T.

1987-03-01

Boron carbide is a disordered non-stoechiometric material with a strongly microtwinned polycristallyne microstructure. This ceramic is among the candidate materials for the first wall coating in fusion reactor and is used as a neutron absorber in the control rods of fast breeder reactors. The present work deals with the nature of radiation damage in this solid. Because of helium internal production, neutron irradiated boron carbide is affected by swelling and by a strong microcracking which can break up a pellet in fine powder. These processes are rather intensitive to the irradiation parameters (temperature, flux and even neutron spectrum). Transmission electron microscopy of samples irradiated by the fast neutrons of a reactor, the electrons of a high voltage electron microscope and of samples implanted with helium ions was used to understand the respective roles of helium and point defects in the processes of swelling and microcracking. The design of an irradiation chamber for helium implantation at controlled temperature from 600 to 1700 0 C was an important technical part of this work [fr

Helium behaviour in implanted boron carbide

Directory of Open Access Journals (Sweden)

Motte Vianney

2015-01-01

Full Text Available When boron carbide is used as a neutron absorber in nuclear power plants, large quantities of helium are produced. To simulate the gas behaviour, helium implantations were carried out in boron carbide. The samples were then annealed up to 1500 °C in order to observe the influence of temperature and duration of annealing. The determination of the helium diffusion coefficient was carried out using the 3He(d,p4He nuclear reaction (NRA method. From the evolution of the width of implanted 3He helium profiles (fluence 1 × 1015/cm2, 3 MeV corresponding to a maximum helium concentration of about 1020/cm3 as a function of annealing temperatures, an Arrhenius diagram was plotted and an apparent diffusion coefficient was deduced (Ea = 0.52 ± 0.11 eV/atom. The dynamic of helium clusters was observed by transmission electron microscopy (TEM of samples implanted with 1.5 × 1016/cm2, 2.8 to 3 MeV 4He ions, leading to an implanted slab about 1 μm wide with a maximum helium concentration of about 1021/cm3. After annealing at 900 °C and 1100 °C, small (5–20 nm flat oriented bubbles appeared in the grain, then at the grain boundaries. At 1500 °C, due to long-range diffusion, intra-granular bubbles were no longer observed; helium segregates at the grain boundaries, either as bubbles or inducing grain boundaries opening.

Evidence of amorphisation of B{sub 4}C boron carbide under slow, heavy ion irradiation

Energy Technology Data Exchange (ETDEWEB)

Gosset, D., E-mail: dominique.gosset@cea.fr [CEA, DEN, DMN-SRMA-LA2M, F-91191 Gif/Yvette (France); Miro, S. [CEA, DEN, DMN-SRMP-JANNUS, F-91191 Gif/Yvette (France); Doriot, S. [CEA, DEN, DMN-SRMA-LA2M, F-91191 Gif/Yvette (France); Victor, G. [CNRS-IN2P3-IPNL, F-69622 Villeurbanne (France); Motte, V. [CEA, DEN, DMN-SRMA-LA2M, F-91191 Gif/Yvette (France)

2015-12-15

Boron carbide is widely used either as armor-plate or neutron absorber. In both cases, a good structural stability is required. However, a few studies have shown amorphisation may occur in severe conditions. Hard impacts lead to the formation of amorphous bands. Some irradiations in electronic regime with H or He ions have also shown amorphisation of the material. Most authors however consider the structure is not drastically affected by irradiations in the ballistic regime. Here, we have irradiated at room temperature dense boron carbide pellets with Au 4 MeV ions, for which most of the damage is in the ballistic regime. This study is part of a program devoted to the behavior of boron carbide under irradiation. Raman observations have been performed after the irradiations together with transmission electron microscopy (TEM). Raman observations show a strong structural damage at moderate fluences (10{sup 14}/cm{sup 2}, about 0.1 dpa), in agreement with previous studies. On the other hand, TEM shows the structure remains crystalline up to 10{sup 15}/cm{sup 2} then partially amorphises. The amorphisation is heterogeneous, with the formation of nanometric amorphous zones with increasing density. It then appears short range and long range disorder occurs at quite different damage levels. Further experiments are in progress aiming at studying the structural stability of boron carbide and isostructural materials (α-B, B{sub 6}Si,…).

Evaluation of Aluminum-Boron Carbide Neutron Absorbing Materials for Interim Storage of Used Nuclear Fuel

International Nuclear Information System (INIS)

Wang, Lumin; Wierschke, Jonathan Brett

2015-01-01

The objective of this work was to understand the corrosion behavior of Boral® and Bortec® neutron absorbers over long-term deployment in a used nuclear fuel dry cask storage environment. Corrosion effects were accelerated by flowing humidified argon through an autoclave at temperatures up to 570°C. Test results show little corrosion of the aluminum matrix but that boron is leaching out of the samples. Initial tests performed at 400 and 570°C were hampered by reduced flow caused by the rapid build-up of solid deposits in the outlet lines. Analysis of the deposits by XRD shows that the deposits are comprised of boron trioxide and sassolite (H 3 BO 3 ). The collection of boron- containing compounds in the outlet lines indicated that boron was being released from the samples. Observation of the exposed samples using SEM and optical microscopy show the growth of new phases in the samples. These phases were most prominent in Bortec® samples exposed at 570°C. Samples of Boral® exposed at 570°C showed minimal new phase formation but showed nearly the complete loss of boron carbide particles. Boron carbide loss was also significant in Boral samples at 400°C. However, at 400°C phases similar to those found in Bortec® were observed. The rapid loss of the boron carbide particles in the Boral® is suspected to inhibit the formation of the new secondary phases. However, Material samples in an actual dry cask environment would be exposed to temperatures closer to 300°C and less water than the lowest test. The results from this study conclude that at the temperature and humidity levels present in a dry cask environment, corrosion and boron leaching will have no effect on the performance of Boral® and Bortec® to maintain criticality control.

Structural phase transitions in boron carbide under stress

International Nuclear Information System (INIS)

Korotaev, P; Pokatashkin, P; Yanilkin, A

2016-01-01

Structural transitions in boron carbide B 4 C under stress were studied by means of first-principles molecular dynamics in the framework of density functional theory. The behavior depends strongly on degree of non-hydrostatic stress. Under hydrostatic stress continuous bending of the three-atom C–B–C chain was observed up to 70 GPa. The presence of non-hydrostatic stress activates abrupt reversible chain bending, which is displacement of the central boron atom in the chain with the formation of weak bonds between this atom and atoms in the nearby icosahedra. Such structural change can describe a possible reversible phase transition in dynamical loading experiments. High non-hydrostatic stress achieved in uniaxial loading leads to disordering of the initial structure. The formation of carbon chains is observed as one possible transition route. (paper)

Dynamic Failure and Fragmentation of a Hot-Pressed Boron Carbide

Science.gov (United States)

Sano, Tomoko; Vargas-Gonzalez, Lionel; LaSalvia, Jerry; Hogan, James David

2017-12-01

This study investigates the failure and fragmentation of a hot-pressed boron carbide during high rate impact experiments. Four impact experiments are performed using a composite-backed target configuration at similar velocities, where two of the impact experiments resulted in complete target penetration and two resulted in partial penetration. This paper seeks to evaluate and understand the dynamic behavior of the ceramic that led to either the complete or partial penetration cases, focusing on: (1) surface and internal failure features of fragments using optical, scanning electron, and transmission electron microscopy, and (2) fragment size analysis using state-of-the-art particle-sizing technology that informs about the consequences of failure. Detailed characterization of the mechanical properties and the microstructure is also performed. Results indicate that transgranular fracture was the primary mode of failure in this boron carbide material, and no stress-induced amorphization features were observed. Analysis of the fragment sizes for the partial and completely penetrated experiments revealed a possible correlation between larger fragment sizes and impact performance. The results will add insight into designing improved advanced ceramics for impact protection applications.

Effect of material variables on the irradiation performance of boron carbide

International Nuclear Information System (INIS)

Basmajian, J.A.; Hollenberg, G.W.

1980-01-01

Boron carbide pellets were fabricated with variations in material parameters. These pellets were irradiated in the Experimental Breeder Reactor-II (EBR-II) to determine the effect of these variations on the performance. Helium release from the material and swelling of the pellets are the primary measures of performance. It was determined that material with a smaller grain size released more helium and swelled less. The pellets with boron-to-carbon ratios greater than 4 to 1 did not perform well. Iron additions improved the performance of the material while density variations had little effect

Sodium erosion of boron carbide from breached absorber pins

International Nuclear Information System (INIS)

Basmajian, J.A.; Baker, D.E.

1981-03-01

The purpose of the irradiation experiment was to provide an engineering demonstration of the irradiation behavior of breached boron carbide absorber pins. By building defects into the cladding of prototypic absorber pins, and performing the irradiation under typical FFTF operating conditions, a qualitative assessment of the consequences of a breach was achieved. Additionally, a direct comparison of pin behavior with that of the ex-reactor test could be made

The preparation method of solid boron solution in silicon carbide in the form of micro powder

International Nuclear Information System (INIS)

Pampuch, R.; Stobierski, L.; Lis, J.; Bialoskorski, J.; Ermer, E.

1993-01-01

The preparation method of solid boron solution in silicon carbide in the form of micro power has been worked out. The method consists in introducing mixture of boron, carbon and silicon and heating in the atmosphere of inert gas to the 1573 K

Novel semiconducting boron carbide/pyridine polymers for neutron detection at zero bias

Energy Technology Data Exchange (ETDEWEB)

Echeverria, Elena; Enders, A.; Dowben, P.A. [University of Nebraska-Lincoln, Department of Physics and Astronomy, Lincoln, NE (United States); James, Robinson; Chiluwal, Umesh; Gapfizi, Richard; Tae, Jae-Do; Driver, M. Sky; Kelber, Jeffry A. [University of North Texas, Department of Chemistry, Denton, TX (United States); Pasquale, Frank L. [University of North Texas, Department of Chemistry, Denton, TX (United States); Lam Research Corporation, PECVD Business Unit, Tualatin, OR (United States); Colon Santana, Juan A. [Center for Energy Sciences Research, Lincoln, NE (United States)

2014-09-19

Thin films containing aromatic pyridine moieties bonded to boron, in the partially dehydrogenated boron-rich icosahedra (B{sub 10}C{sub 2}H{sub X}), prove to be an effective material for neutron detection applications when deposited on n-doped (100) silicon substrates. The characteristic I-V curves for the heterojunction diodes exhibit strong rectification and largely unperturbed normalized reverse bias leakage currents with increasing pyridine content. The neutron capture generated pulses from these heterojunction diodes were obtained at zero bias voltage although without the signatures of complete electron-hole collection. These results suggest that modifications to boron carbide may result in better neutron voltaic materials. (orig.)

Structural modifications induced by ion irradiation and temperature in boron carbide B4C

Science.gov (United States)

Victor, G.; Pipon, Y.; Bérerd, N.; Toulhoat, N.; Moncoffre, N.; Djourelov, N.; Miro, S.; Baillet, J.; Pradeilles, N.; Rapaud, O.; Maître, A.; Gosset, D.

2015-12-01

Already used as neutron absorber in the current French nuclear reactors, boron carbide (B4C) is also considered in the future Sodium Fast Reactors of the next generation (Gen IV). Due to severe irradiation conditions occurring in these reactors, it is of primary importance that this material presents a high structural resistance under irradiation, both in the ballistic and electronic damage regimes. Previous works have shown an important structural resistance of boron carbide even at high neutron fluences. Nevertheless, the structural modification mechanisms due to irradiation are not well understood. Therefore the aim of this paper is to study structural modifications induced in B4C samples in different damage regimes. The boron carbide pellets were shaped and sintered by using spark plasma sintering method. They were then irradiated in several conditions at room temperature or 800 °C, either by favoring the creation of ballistic damage (between 1 and 3 dpa), or by favoring the electronic excitations using 100 MeV swift iodine ions (Se ≈ 15 keV/nm). Ex situ micro-Raman spectroscopy and Doppler broadening of annihilation radiation technique with variable energy slow positrons were coupled to follow the evolution of the B4C structure under irradiation.

In search of amorphization-resistant boron carbide

International Nuclear Information System (INIS)

Subhash, Ghatu; Awasthi, Amnaya P.; Kunka, Cody; Jannotti, Phillip; DeVries, Matthew

2016-01-01

Despite its superior mechanical properties, boron carbide suffers from amorphization, a pressure-induced phenomenon that disturbs crystalline order and likely reduces shear strength. Numerous experimental and computational studies have investigated the structure and origins of amorphization, yet strategies to mitigate this deleterious phenomenon elude. However, recent investigations have revealed three new research avenues for addressing this issue. First, we identify crystallographic cage spaces that may accommodate foreign atoms to potentially prevent structural collapse. Second, we propose polymorph-level tailoring through strict control of processing conditions. Finally, we demonstrate that reducing grain size to nanometer scale increases hardness and may counter amorphization.

Evaluation of Aluminum-Boron Carbide Neutron Absorbing Materials for Interim Storage of Used Nuclear Fuel

Energy Technology Data Exchange (ETDEWEB)

Wang, Lumin [Univ. of Michigan, Ann Arbor, MI (United States). Department of Nuclear Engineering and Radiological Science; Wierschke, Jonathan Brett [Univ. of Michigan, Ann Arbor, MI (United States). Department of Nuclear Engineering and Radiological Science

2015-04-08

The objective of this work was to understand the corrosion behavior of Boral® and Bortec® neutron absorbers over long-term deployment in a used nuclear fuel dry cask storage environment. Corrosion effects were accelerated by flowing humidified argon through an autoclave at temperatures up to 570°C. Test results show little corrosion of the aluminum matrix but that boron is leaching out of the samples. Initial tests performed at 400 and 570°C were hampered by reduced flow caused by the rapid build-up of solid deposits in the outlet lines. Analysis of the deposits by XRD shows that the deposits are comprised of boron trioxide and sassolite (H₃BO₃). The collection of boron- containing compounds in the outlet lines indicated that boron was being released from the samples. Observation of the exposed samples using SEM and optical microscopy show the growth of new phases in the samples. These phases were most prominent in Bortec® samples exposed at 570°C. Samples of Boral® exposed at 570°C showed minimal new phase formation but showed nearly the complete loss of boron carbide particles. Boron carbide loss was also significant in Boral samples at 400°C. However, at 400°C phases similar to those found in Bortec® were observed. The rapid loss of the boron carbide particles in the Boral® is suspected to inhibit the formation of the new secondary phases. However, Material samples in an actual dry cask environment would be exposed to temperatures closer to 300°C and less water than the lowest test. The results from this study conclude that at the temperature and humidity levels present in a dry cask environment, corrosion and boron leaching will have no effect on the performance of Boral® and Bortec® to maintain criticality control.

Electron microscopy of boron carbide before and after electron irradiation

International Nuclear Information System (INIS)

Stoto, T.; Zuppiroli, L.; Beauvy, M.; Athanassiadis, T.

1984-06-01

The microstructure of boron carbide has been studied by electron microscopy and related to the composition of the material. After electron irradiations in an usual transmission electron microscope and in a high voltage electron microscope at different temperatures and fluxes no change of these microstructures have been observed but a sputtering of the surface of the samples, which has been studied quantitatively [fr

Advanced Boron Carbide-Based Visual Obscurants for Military Smoke Grenades

Science.gov (United States)

2014-07-13

components on grenade burning time must be accounted for. Also, how these factors affect smoke cloud thickness and perceived visible obscuration...of Boron Carbide-Based Smoke Compositions. Propellants, Explos., Pyrotech. 2013, 38, 622-628. (30) Commission Internationale de l’Éclairage ( CIE ...volume, gives equation 2. Since αm is only a characteristic of the aerosol, it does not account for

High pressure synthesis and investigations of properties of boron allotropes and boron carbide

International Nuclear Information System (INIS)

Chuvashova, Irina

2017-01-01

This work aimed at the development of the high-pressure high-temperature (HPHT) synthesis of single crystals of boron allotropes and boron-rich compounds, which could be used further for precise investigations of their structures, properties, and behavior at extreme conditions. To summarize, the present work resulted in the HPHT synthesis of the first previously unknown non-icosahedral boron allotrope ζ-B. This finding confirmed earlier theoretical predictions, which stayed unproven for decades because of experimental challenges which couldn't be overcome until recently. Structural stability of α-B and β-B in the Mbar pressure range and B 13 C 2 up to 68 GPa was experimentally proven. Accurate measurements of the unit cell and B 12 icosahedra volumes of the stoichiometric boron carbide B 13 C 2 as a function of pressure led to conclusion that they undergo a similar reduction upon compression that is typical for covalently bonded solids. Neither 'molecular-like' nor 'inversed molecular-like' solid behavior upon compression was detected that has closed a long-standing scientific dispute. A comparison of the compressional behavior of B 13 C 2 with that of α-B and γ-B allotropes and B 4 C showed that it is determined by the types of bonding involved in the course of compression.

High pressure synthesis and investigations of properties of boron allotropes and boron carbide

Energy Technology Data Exchange (ETDEWEB)

Chuvashova, Irina

2017-06-12

This work aimed at the development of the high-pressure high-temperature (HPHT) synthesis of single crystals of boron allotropes and boron-rich compounds, which could be used further for precise investigations of their structures, properties, and behavior at extreme conditions. To summarize, the present work resulted in the HPHT synthesis of the first previously unknown non-icosahedral boron allotrope ζ-B. This finding confirmed earlier theoretical predictions, which stayed unproven for decades because of experimental challenges which couldn't be overcome until recently. Structural stability of α-B and β-B in the Mbar pressure range and B{sub 13}C{sub 2} up to 68 GPa was experimentally proven. Accurate measurements of the unit cell and B{sub 12} icosahedra volumes of the stoichiometric boron carbide B{sub 13}C{sub 2} as a function of pressure led to conclusion that they undergo a similar reduction upon compression that is typical for covalently bonded solids. Neither 'molecular-like' nor 'inversed molecular-like' solid behavior upon compression was detected that has closed a long-standing scientific dispute. A comparison of the compressional behavior of B{sub 13}C{sub 2} with that of α-B and γ-B allotropes and B{sub 4}C showed that it is determined by the types of bonding involved in the course of compression.

Structural models of increasing complexity for icosahedral boron carbide with compositions throughout the single-phase region from first principles

Science.gov (United States)

Ektarawong, A.; Simak, S. I.; Alling, B.

2018-05-01

We perform first-principles calculations to investigate the phase stability of boron carbide, concentrating on the recently proposed alternative structural models composed not only of the regularly studied B11Cp (CBC) and B12(CBC), but also of B12(CBCB) and B12( B4 ). We find that a combination of the four structural motifs can result in low-energy electron precise configurations of boron carbide. Among several considered configurations within the composition range of B10.5C and B4C , we identify in addition to the regularly studied B11Cp (CBC) at the composition of B4C two low-energy configurations, resulting in a new view of the B-C convex hull. Those are [B12 (CBC)]0.67[B12(B4)] 0.33 and [B12 (CBC)]0.67[ B12 (CBCB)]0.33, corresponding to compositions of B10.5C and B6.67C , respectively. As a consequence, B12(CBC) at the composition of B6.5C , previously suggested in the literature as a stable configuration of boron carbide, is no longer part of the B -C convex hull. By inspecting the electronic density of states as well as the elastic moduli, we find that the alternative models of boron carbide can provide a reasonably good description for electronic and elastic properties of the material in comparison with the experiments, highlighting the importance of considering B12(CBCB) and B12( B4 ), together with the previously proposed B11Cp (CBC) and B12(CBC), as the crucial ingredients for modeling boron carbide with compositions throughout the single-phase region.

Structural and electronic properties of boron-doped double-walled silicon carbide nanotubes

Energy Technology Data Exchange (ETDEWEB)

Behzad, Somayeh, E-mail: somayeh.behzad@gmail.co [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Moradian, Rostam [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Computational Physical Science Research Laboratory, Department of Nano Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Chegel, Raad [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of)

2010-12-01

The effects of boron doping on the structural and electronic properties of (6,0)-(14,0) double-walled silicon carbide nanotube (DWSiCNT) are investigated by using spin-polarized density functional theory. It is found that boron atom could be more easily doped in the inner tube. Our calculations indicate that a Si site is favorable for B under C-rich condition and a C site is favorable under Si-rich condition. Additionally, B-substitution at either single carbon or silicon atom site in DWSiCNT could induce spontaneous magnetization.

Structural and electronic properties of boron-doped double-walled silicon carbide nanotubes

International Nuclear Information System (INIS)

Behzad, Somayeh; Moradian, Rostam; Chegel, Raad

2010-01-01

The effects of boron doping on the structural and electronic properties of (6,0)-(14,0) double-walled silicon carbide nanotube (DWSiCNT) are investigated by using spin-polarized density functional theory. It is found that boron atom could be more easily doped in the inner tube. Our calculations indicate that a Si site is favorable for B under C-rich condition and a C site is favorable under Si-rich condition. Additionally, B-substitution at either single carbon or silicon atom site in DWSiCNT could induce spontaneous magnetization.

Structural and electronic properties of boron-doped double-walled silicon carbide nanotubes

Science.gov (United States)

Behzad, Somayeh; Moradian, Rostam; Chegel, Raad

2010-12-01

The effects of boron doping on the structural and electronic properties of (6,0)@(14,0) double-walled silicon carbide nanotube (DWSiCNT) are investigated by using spin-polarized density functional theory. It is found that boron atom could be more easily doped in the inner tube. Our calculations indicate that a Si site is favorable for B under C-rich condition and a C site is favorable under Si-rich condition. Additionally, B-substitution at either single carbon or silicon atom site in DWSiCNT could induce spontaneous magnetization.

Process for manufacturing boron carbide pellets that can be used for the realization, of the control rods of water reactors

International Nuclear Information System (INIS)

Ballagny, Alain; Brie, Michel.

1982-01-01

The subject of the invention is a process for manufacturing boron carbide pellets with a boron carbide content of not less than 68% by volume and having an open porosity. This process consists in (a) preparing a mix comprising boron carbide powder of which at least 90% of the particles are under 3 μ in size, and an organic binder that can be transformed into carbon by thermal treatment, (b) compressing the hot mix thus obtained to form unbaked pellets, under a pressure of 1000 to 6000 bars, at a temperature of 80 to 250 0 C and (c) submitting the unbaked pellets thus obtained to vacuum thermal treatment to transform this binder into porous carbon. The finished pellets are used in the control rods of water reactors [fr

Surface modification of the hard metal tungsten carbide-cobalt by boron ion implantation

International Nuclear Information System (INIS)

Mrotchek, I.

2007-01-01

In the present thesis ion beam implantation of boron is studied as method for the increasement of the hardness and for the improvement of the operational characteristics of cutting tools on the tungsten carbide-cobalt base. For the boron implantation with 40 keV energy and ∼5.10 17 ions/cm 2 fluence following topics were shown: The incoerporation of boron leads to a deformation and remaining strain of the WC lattice, which possesses different stregth in the different directions of the elementary cell. The maximum of the deformation is reached at an implantation temperature of 450 C. The segregation of the new phases CoWB and Co 3 W was detected at 900 C implantation temperature. At lower temperatures now new phases were found. The tribological characteristics of WC-Co are improved. Hereby the maxiaml effect was measured for implantation temperatures from 450 C to 700 C: Improvement of the microhardness by the factor 2..2.5, improvement of the wear resistance by the factor 4. The tribological effects extend to larger depths than the penetration depth of the boron implantation profile. The detected property improvements of the hard metal H3 show the possibility of a practical application of boron ion implantation in industry. The effects essential for a wer decreasement are a hardening of the carbide phase by deformation of the lattice, a hardening of the cobalt binding material and the phase boundaries because of the formation of a solid solution of the implanted boron atoms in Co and by this a blocking of the dislocation movement and the rupture spreading under load

Structural modifications induced by ion irradiation and temperature in boron carbide B{sub 4}C

Energy Technology Data Exchange (ETDEWEB)

Victor, G., E-mail: g.victor@ipnl.in2p3.fr [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); Pipon, Y.; Bérerd, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); Institut Universitaire de Technologie (IUT) Lyon-1, Université Claude Bernard Lyon 1, 69622 Villeurbanne Cedex (France); Toulhoat, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); CEA-DEN, Saclay, 91191 Gif-sur-Yvette (France); Moncoffre, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); Djourelov, N. [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee blvd, BG-1784 Sofia (Bulgaria); ELI-NP, IFIN-HH, 30 Reactorului Str, MG-6 Bucharest-Magurele (Romania); Miro, S. [CEA-DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Baillet, J. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); Pradeilles, N.; Rapaud, O.; Maître, A. [SPCTS, UMR CNRS 7315, Centre Européen de la céramique, University of Limoges (France); Gosset, D. [CEA, Saclay, DMN-SRMA-LA2M, 91191 Gif-sur-Yvette (France)

2015-12-15

Already used as neutron absorber in the current French nuclear reactors, boron carbide (B{sub 4}C) is also considered in the future Sodium Fast Reactors of the next generation (Gen IV). Due to severe irradiation conditions occurring in these reactors, it is of primary importance that this material presents a high structural resistance under irradiation, both in the ballistic and electronic damage regimes. Previous works have shown an important structural resistance of boron carbide even at high neutron fluences. Nevertheless, the structural modification mechanisms due to irradiation are not well understood. Therefore the aim of this paper is to study structural modifications induced in B{sub 4}C samples in different damage regimes. The boron carbide pellets were shaped and sintered by using spark plasma sintering method. They were then irradiated in several conditions at room temperature or 800 °C, either by favoring the creation of ballistic damage (between 1 and 3 dpa), or by favoring the electronic excitations using 100 MeV swift iodine ions (S{sub e} ≈ 15 keV/nm). Ex situ micro-Raman spectroscopy and Doppler broadening of annihilation radiation technique with variable energy slow positrons were coupled to follow the evolution of the B{sub 4}C structure under irradiation.

The irradiation behaviour of boron carbide/graphite between 800 and 1,1000C

International Nuclear Information System (INIS)

Hattenbach, K.; Hilgendorff, W.; Weiler, K.; Zimmermann, H.U.

1975-01-01

64 samples of boron carbide/graphite, a material used as burnable poison in high temperature reactors, were irradiated at temperatures between 800 and 1,100 0 C up to a fluence of 1-2 x 10 20 nvt. The following post-investigations were extended to dimensional measurements to determime a possible swelling or shrinking of the pellet, corrosion tests in completely desalinated water at 300 0 C, preparation of metallographic microsections to check for crack formation, determination of the helium hold back power and the thus involved gas chromatic analysis, as well as burn-up determinations by determining the boron 10/boron 11 ratio and the lithium concentration. (orig./LN) [de

Correlation for boron carbide helium release in fast reactors

International Nuclear Information System (INIS)

Basmajian, J.A.; Pitner, A.L.

1977-04-01

An empirical helium correlation for the helium release from boron carbide has been developed. The correlation provides a good fit to the experimental data in the temperature range from 800 to 1350 0 K, and burnup levels up to 80 x 10 20 captures/cm 3 . The correlation has the capability of extrapolation to 2200 0 K (3500 0 F) and 200 x 10 20 captures/cm 3 . In this range the helium release rate will not exceed the generation rate

Development of a process to recover boron carbide from nuclear reactor absorber rods

International Nuclear Information System (INIS)

Roth, C.; Lehnert, T.

1991-01-01

Boron carbide enriched with 10 B is used as a control rod in reactor engineering. At present spent rods are disposed of, although major amounts of 10 B are still 'unused'. The objective was to recover 10 B from the control rods by an energy and cost saving method in order to use it for making new control rods, thus saving raw materials and minimizing the radioactive waste volume. For this purpose, the well-known pyrohydrolysis process was taken and analysed for possible improvements. By mixing boron carbide with CO 2 as an oxidation-supporting agent, a lowering of the reaction temperature by 300deg C, and an increase in the oxidation speed by 350% were achieved. Since C0 2 is not consumed and can be circulated, the method for reprocessing spent control rods presented in this paper is both an economy-priced an energy-saving one. (orig.) With 98 refs., 9 tabs., 14 figs [de

Boron carbide in pile behaviour Rapsodie experience

International Nuclear Information System (INIS)

Kryger, B.; Colin, M.

1983-04-01

Results concerning boron carbide irradiation experiments performed in RAPSODIE up to 10 22 .cm - 3 capture density in the temperature range 600-1100 0 lead to the following main conclusions: initial density and grain size lowering contribute to swelling decrease but density is the major parameter for swelling limitation; swelling rate can vary in a wide range (ratio 1 to 3) according to combinations of density (1.8 to 2.3) and grain size (10 to 50 μm) values; a swelling balance reveals that the most important contribution to swelling should be a high density of helium small bubbles (<400 A); helium retention increases with density and grain size and decreases with temperature elevation. A diffusion law is proposed to describe the rate of helium release

Hydrothermal development and characterization of the wear-resistant boron carbide from Pandanus: a natural carbon precursor

Science.gov (United States)

Saritha Devi, H. V.; Swapna, M. S.; Ambadas, G.; Sankararaman, S.

2018-04-01

Boron carbide (B4C) is a prominent semiconducting material that finds applications in the field of science and technology. The excellent physical, thermal and electronic properties make it suitable as ceramic armor, wear-resistant, lens polisher and neutron absorber in the nuclear industry. The existing methods of synthesis of boron carbide involve the use of toxic chemicals that adversely affect the environment. In the present work, we report for the first time the use of the hydrothermal method, for converting the cellulose from Pandanus leaves as the carbon precursor for the synthesis of B4C. The carbon precursor is changed into porous functionalized carbon by treating with sodium borohydride (NaBH4), followed by treating with boric acid to obtain B4C. The samples are characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared, Raman, photoluminescent and Ultraviolet-Visible absorption spectroscopy. The formation of B4C from natural carbon source— Pandanus presents an eco-friendly, economic and non-toxic approach for the synthesis of refractory carbides.

Kerma factors in interaction of neutrons with boron carbide

International Nuclear Information System (INIS)

Bondarenko, I.M.

1979-01-01

Heat generation in neutron interactions with boron carbide B 10 ; B 11 and 12 C is calculated. Kerma-factors (kerma-kinetic energy released in materials) were calculated for neutron energies between 10 -4 eV and 15 MeV. No major simplifying assumptions are introduced, and the accuracy of the calculated kerma-factors depends only on availability and accuracy of the basic nuclear data. The ENDF/B-4 data and recent experimental information are used for the calculation of kerma-factors. Plots of these kerma-factors are presented in units of eVxb/atom and wtxsec/(cmxn) as a function of neutron energy

Effects of heat treatment on the microstructure of amorphous boron carbide coating deposited on graphite substrates by chemical vapor deposition

International Nuclear Information System (INIS)

Li Siwei; Zeng Bin; Feng Zude; Liu Yongsheng; Yang Wenbin; Cheng Laifei; Zhang Litong

2010-01-01

A two-layer boron carbide coating is deposited on a graphite substrate by chemical vapor deposition from a CH 4 /BCl 3 /H 2 precursor mixture at a low temperature of 950 o C and a reduced pressure of 10 KPa. Coated substrates are annealed at 1600 o C, 1700 o C, 1800 o C, 1900 o C and 2000 o C in high purity argon for 2 h, respectively. Structural evolution of the coatings is explored by electron microscopy and spectroscopy. Results demonstrate that the as-deposited coating is composed of pyrolytic carbon and amorphous boron carbide. A composition gradient of B and C is induced in each deposition. After annealing, B 4 C crystallites precipitate out of the amorphous boron carbide and grow to several hundreds nanometers by receiving B and C from boron-doped pyrolytic carbon. Energy-dispersive spectroscopy proves that the crystallization is controlled by element diffusion activated by high temperature annealing, after that a larger concentration gradient of B and C is induced in the coating. Quantified Raman spectrum identifies a graphitization enhancement of pyrolytic carbon. Transmission electron microscopy exhibits an epitaxial growth of B 4 C at layer/layer interface of the annealed coatings. Mechanism concerning the structural evolution on the basis of the experimental results is proposed.

Machinability of glass fiber reinforced plastic (GFRP) composite ...

African Journals Online (AJOL)

This paper deals with the study of machinability of GFRP composite tubes of different fiber orientation angle vary from 300 to 900. Machining studies were carried out on an all geared lathe using three different cutting tools: namely Carbide (K-20), Cubic Boron Nitride (CBN) and Poly-Crystalline Diamond (PCD). Experiments ...

Characterization of plastic and boron carbide additive manufactured neutron collimators

Science.gov (United States)

Stone, M. B.; Siddel, D. H.; Elliott, A. M.; Anderson, D.; Abernathy, D. L.

2017-12-01

Additive manufacturing techniques allow for the production of materials with complicated geometries with reduced costs and production time over traditional methods. We have applied this technique to the production of neutron collimators for use in thermal and cold neutron scattering instrumentation directly out of boron carbide. We discuss the design and generation of these collimators. We also provide measurements at neutron scattering beamlines which serve to characterize the performance of these collimators. Additive manufacturing of parts using neutron absorbing material may also find applications in radiography and neutron moderation.

Thermal expansion measurements on boron carbide and europium sesquioxide by laser interferometry

International Nuclear Information System (INIS)

Preston, S.D.

1980-01-01

A laser interferometer technique for measuring the absolute linear thermal expansion of small annular specimens is described. Results are presented for unirradiated boron carbide (B 4 C) and europia (Eu 2 O 3 ) up to 1000 0 C. Both compounds are neutron-absorbing materials of potential use in fast-reactor control rods and data on their thermophysical properties, in particular linear thermal expansion, are essential to the control rod designers. (author)

Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade boron carbide

CERN Document Server

American Society for Testing and Materials. Philadelphia

2004-01-01

1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade boron carbide powder and pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Total Carbon by Combustion and Gravimetry 7-17 Total Boron by Titrimetry 18-28 Isotopic Composition by Mass Spectrometry 29-38 Chloride and Fluoride Separation by Pyrohydrolysis 39-45 Chloride by Constant-Current Coulometry 46-54 Fluoride by Ion-Selective Electrode 55-63 Water by Constant-Voltage Coulometry 64-72 Impurities by Spectrochemical Analysis 73-81 Soluble Boron by Titrimetry 82-95 Soluble Carbon by a Manometric Measurement 96-105 Metallic Impurities by a Direct Reader Spectrometric Method 106-114

Kerma factors in interaction of neutrons with boron carbide

International Nuclear Information System (INIS)

Bondarenko, I.M.

1986-03-01

Heat generation in neutron interactions with boron carbide B 10 ; B 11 and 12 C is calculated. Kerma-factors (kerma-kinetic energy released in materials) were calculated for neutron energies between 10 -4 eV and 15 MeV. No major simplifying assumptions are introduced, and the accuracy of the calculated kerma-factors depends only on availability and accuracy of the basic nuclear data. The ENDF/B-4 data and recent experimental information are used for the calculation of kerma-factors. Plots of these kerma-factors are presented in units of eVxb/atom and wtxsec/(cmxn) as a function of neutron energy [fr

Sintering of beryllium oxide with 3-4 per cent elemental boron

International Nuclear Information System (INIS)

Pointud, R.; Rispal, Ch.; Le Garec, M.

1958-01-01

In order to manufacture a baffle absorbing neutrons of various energies, there was developed or mixture of a slower and an absorber. It is made by hot pressing impure beryllium containing boron carbide. The dense briquette has 100 x 100 x 50 mm and is machined on all her faces. She is of 2,85 density and about 3 to 4 per cent porosity, according to 5 per cent of boron. Difference of boron amount is lower than ten per cent between any two points of the briquette. (author) [fr

Synthesis, characterization and thermoelectric properties of metal borides, boron carbides and carbaborides; Synthese, Charakterisierung und thermoelektrische Eigenschaften ausgewaehlter Metallboride, Borcarbide und Carbaboride

Energy Technology Data Exchange (ETDEWEB)

Guersoy, Murat

2015-07-06

This work reports on the solid state synthesis and structural and thermoelectrical characterization of hexaborides (CaB{sub 6}, SrB{sub 6}, BaB{sub 6}, EuB{sub 6}), diboride dicarbides (CeB{sub 2}C{sub 2}, LaB{sub 2}C{sub 2}), a carbaboride (NaB{sub 5}C) and composites of boron carbide. The characterization was performed by X-ray diffraction methods and Rietveld refinements based on structure models from literature. Most of the compounds were densified by spark plasma sintering at 100 MPa. As high-temperature thermoelectric properties the Seebeck coefficients, electrical conductivities, thermal diffusivities and heat capacities were measured between room temperature and 1073 K. ZT values as high as 0.5 at 1273 K were obtained for n-type conducting EuB{sub 6}. High-temperature X-ray diffraction also confirmed its thermal stability. The solid solutions Ca{sub x}Sr{sub 1-x}B{sub 6}, Ca{sub x}Ba{sub 1-x}B{sub 6} and Sr{sub x}Ba{sub 1-x}B{sub 6} (x = 0, 0.25, 0.5, 0.75, 1) are also n-type but did not show better ZT values for the ternary compounds compared to the binaries, but for CaB{sub 6} the values of the figure of merit (ca. 0.3 at 1073 K) were significantly increased (ca. 50 %) compared to earlier investigations which is attributed to the densification process. Sodium carbaboride, NaB{sub 5}C, was found to be the first p-type thermoelectric material that crystallizes with the hexaboride-structure type. Seebeck coefficients of ca. 80 μV . K{sup -1} were obtained. Cerium diboride dicarbide, CeB{sub 2}C{sub 2}, and lanthanum diboride dicarbide, LaB{sub 2}C{sub 2}, are metallic. Both compounds were used as model compounds to develop compacting strategies for such layered borides. Densities obtained at 50 MPa were determined to be higher than 90 %. A new synthesis route using single source precursors that contain boron and carbon was developed to open the access to new metal-doped boron carbides. It was possible to obtain boron carbide, but metal-doping could not be

Structure prediction of boron-doped graphene by machine learning

Science.gov (United States)

M. Dieb, Thaer; Hou, Zhufeng; Tsuda, Koji

2018-06-01

Heteroatom doping has endowed graphene with manifold aspects of material properties and boosted its applications. The atomic structure determination of doped graphene is vital to understand its material properties. Motivated by the recently synthesized boron-doped graphene with relatively high concentration, here we employ machine learning methods to search the most stable structures of doped boron atoms in graphene, in conjunction with the atomistic simulations. From the determined stable structures, we find that in the free-standing pristine graphene, the doped boron atoms energetically prefer to substitute for the carbon atoms at different sublattice sites and that the para configuration of boron-boron pair is dominant in the cases of high boron concentrations. The boron doping can increase the work function of graphene by 0.7 eV for a boron content higher than 3.1%.

Compatibility of heat resistant alloys with boron carbide, 5

International Nuclear Information System (INIS)

Baba, Shinichi; Kurasawa, Toshimasa; Endow, Taichi; Someya, Hiroyuki; Tanaka, Isao.

1986-08-01

This paper includes an experimental result of out-of-pile compatibility and capsule design for irradiation test in Japan Materials Testing Reactor (JMTR). The compatibility between sheath material and neutron absorber materials for control rod devices (CRD) was examined for potential use in a very high temperature reactor (VHTR) which is under development at JAERI. The purpose of the compatibility tests are preliminary evaluation of safety prior to irradiation tests. Preliminary compatibility evaluation was concerned with three items as follows : 1) Lithium effects on the penetrating reaction of Incoloy 800H alloy in contact with a mixture of boronated graphite and lithium hydroxide powders, 2) Short term tensile properties of Incoloy 800H and Hastelloy XR alloy reacted with boronated graphite and fracture mode analysis, 3) Reaction behavior of both alloys under transient power conditions of a VHTR. It was clear that the reaction rate constant of the Incoloy 800H alloy was accelerated by doping lithium hydroxide into the boron carbide and graphite powder. The mechanical properties of Incoloy 800H and Hastelloy XR alloy reacted with boronated graphite were decreased. Ultimate tensile strength and tensile ductilities at temperatures over 850 deg C were reduced, but there was no change in the proof (yield) stress. Both alloys exhibited a brittle intergranular fracture mode during transient power conditions of a VHTR and also exhibited severe penetration. Irradiation capsules for compatibility test were designed to simulate three irradiation conditions of VHTR: 1) steady state for VHTR, 2) Transient power condition, 3) Service limited life of CRD. Capsule irradiation experiments have been carried out satisfactorily and thus confirm the validity of the capsule design procedure. (author)

Stochastic Distribution of Wear of Carbide Tools during Machining ...

African Journals Online (AJOL)

Journal of the Nigerian Association of Mathematical Physics ... The stochastic point model was used to determine the rate of wear distribution of the carbide tool ... Keywords: cutting speed, feed rate, machining time, tool life, reliability, wear.

Thick boron carbide coatings for protection of tokamak first wall and divertor

International Nuclear Information System (INIS)

Buzhinskij, O.I.; Semenets, Yu.M.

1999-01-01

A review of characteristics of various types of boron carbide coatings considered as candidate materials for protection of tokamak inner surfaces against high energy heat fluxes is presented. Such coatings are produced by various methods: chemical vapor deposition by means of chloride and fluoride techniques, gas conversion, plasma spray and reaction-sintering. Contrary to pure carbon materials, B 4 C has much lower chemical and high-temperature sputtering, is capable to oxygen gettering and lower hydrogen recycling. In contrast to thin boronization films, the thick coatings can resist high heat fluxes such as in tokamak divertors. Comparative analysis shows that coatings produced by the diffusion methods, such as fluoride CVD and gas conversion, are more resistent to heat loads, and one of the most promising candidates are the fluoride CVD coatings. (orig.)

The role of free carbon in the transport and magnetic properties of boron carbide

International Nuclear Information System (INIS)

Bandyopadhyay, A.K.; Beuneu, F.; Zuppiroli, L.; Beauvy, M.

1984-01-01

Boron carbide is a ceramic which has a wide field of application because of its mechanical and nuclear properties. This material is difficult to characterise due to the presence of different levels of disorder and inhomogeneities which are found in the usual available samples. The transport and magnetic properties of several samples of boron carbide have been measured from liquid helium to room temperature as a function of temperature and composition. We have attempted to attribute the different features of these properties to the different levels of disorder. The role of free carbon, in form of thin layers of graphite within the disordered semi-conducting matrix, was investigated in particular details, because it was either ignored or neglected by others. Free carbon is found to dominate the D.C. transport when its concentration is larger than 5%; while the principal features of the electron spin resonance (E.S.R.) line show a dominance of free carbon when the concentration is larger than 3.5%. Below these concentrations conductivities as well as spin relaxation rates do not depend very much on free carbon; neither these have been found to be correlated in a simple way to the stoichiometry. (author)

Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride

Directory of Open Access Journals (Sweden)

Kuruc Marcel

2014-12-01

Full Text Available Poly-crystalline cubic boron nitride (PCBN is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materials (such as glass and ceramics. This contribution investigates this advanced machining method during machining of PCBN.

Large-area homogeneous periodic surface structures generated on the surface of sputtered boron carbide thin films by femtosecond laser processing

Energy Technology Data Exchange (ETDEWEB)

Serra, R., E-mail: ricardo.serra@dem.uc.pt [SEG-CEMUC, Mechanical Engineering Department, University of Coimbra, Rua Luís Reis Santos, 3030-788 Coimbra (Portugal); Oliveira, V. [ICEMS-Instituto de Ciência e Engenharia de Materiais e Superfícies, Avenida Rovisco Pais no 1, 1049-001 Lisbon (Portugal); Instituto Superior de Engenharia de Lisboa, Avenida Conselheiro Emídio Navarro no 1, 1959-007 Lisbon (Portugal); Oliveira, J.C. [SEG-CEMUC, Mechanical Engineering Department, University of Coimbra, Rua Luís Reis Santos, 3030-788 Coimbra (Portugal); Kubart, T. [The Ångström Laboratory, Solid State Electronics, P.O. Box 534, SE-751 21 Uppsala (Sweden); Vilar, R. [Instituto Superior de Engenharia de Lisboa, Avenida Conselheiro Emídio Navarro no 1, 1959-007 Lisbon (Portugal); Instituto Superior Técnico, Avenida Rovisco Pais no 1, 1049-001 Lisbon (Portugal); Cavaleiro, A. [SEG-CEMUC, Mechanical Engineering Department, University of Coimbra, Rua Luís Reis Santos, 3030-788 Coimbra (Portugal)

2015-03-15

Highlights: • Large-area LIPSS were formed by femtosecond laser processing B-C films surface. • The LIPSS spatial period increases with laser fluence (140–200 nm). • Stress-related sinusoidal-like undulations were formed on the B-C films surface. • The undulations amplitude (down to a few nanometres) increases with laser fluence. • Laser radiation absorption increases with surface roughness. - Abstract: Amorphous and crystalline sputtered boron carbide thin films have a very high hardness even surpassing that of bulk crystalline boron carbide (≈41 GPa). However, magnetron sputtered B-C films have high friction coefficients (C.o.F) which limit their industrial application. Nanopatterning of materials surfaces has been proposed as a solution to decrease the C.o.F. The contact area of the nanopatterned surfaces is decreased due to the nanometre size of the asperities which results in a significant reduction of adhesion and friction. In the present work, the surface of amorphous and polycrystalline B-C thin films deposited by magnetron sputtering was nanopatterned using infrared femtosecond laser radiation. Successive parallel laser tracks 10 μm apart were overlapped in order to obtain a processed area of about 3 mm{sup 2}. Sinusoidal-like undulations with the same spatial period as the laser tracks were formed on the surface of the amorphous boron carbide films after laser processing. The undulations amplitude increases with increasing laser fluence. The formation of undulations with a 10 μm period was also observed on the surface of the crystalline boron carbide film processed with a pulse energy of 72 μJ. The amplitude of the undulations is about 10 times higher than in the amorphous films processed at the same pulse energy due to the higher roughness of the films and consequent increase in laser radiation absorption. LIPSS formation on the surface of the films was achieved for the three B-C films under study. However, LIPSS are formed under

Large-area homogeneous periodic surface structures generated on the surface of sputtered boron carbide thin films by femtosecond laser processing

International Nuclear Information System (INIS)

Serra, R.; Oliveira, V.; Oliveira, J.C.; Kubart, T.; Vilar, R.; Cavaleiro, A.

2015-01-01

Highlights: • Large-area LIPSS were formed by femtosecond laser processing B-C films surface. • The LIPSS spatial period increases with laser fluence (140–200 nm). • Stress-related sinusoidal-like undulations were formed on the B-C films surface. • The undulations amplitude (down to a few nanometres) increases with laser fluence. • Laser radiation absorption increases with surface roughness. - Abstract: Amorphous and crystalline sputtered boron carbide thin films have a very high hardness even surpassing that of bulk crystalline boron carbide (≈41 GPa). However, magnetron sputtered B-C films have high friction coefficients (C.o.F) which limit their industrial application. Nanopatterning of materials surfaces has been proposed as a solution to decrease the C.o.F. The contact area of the nanopatterned surfaces is decreased due to the nanometre size of the asperities which results in a significant reduction of adhesion and friction. In the present work, the surface of amorphous and polycrystalline B-C thin films deposited by magnetron sputtering was nanopatterned using infrared femtosecond laser radiation. Successive parallel laser tracks 10 μm apart were overlapped in order to obtain a processed area of about 3 mm 2 . Sinusoidal-like undulations with the same spatial period as the laser tracks were formed on the surface of the amorphous boron carbide films after laser processing. The undulations amplitude increases with increasing laser fluence. The formation of undulations with a 10 μm period was also observed on the surface of the crystalline boron carbide film processed with a pulse energy of 72 μJ. The amplitude of the undulations is about 10 times higher than in the amorphous films processed at the same pulse energy due to the higher roughness of the films and consequent increase in laser radiation absorption. LIPSS formation on the surface of the films was achieved for the three B-C films under study. However, LIPSS are formed under different

Surface structuring of boron doped CVD diamond by micro electrical discharge machining

Science.gov (United States)

Schubert, A.; Berger, T.; Martin, A.; Hackert-Oschätzchen, M.; Treffkorn, N.; Kühn, R.

2018-05-01

Boron doped diamond materials, which are generated by Chemical Vapor Deposition (CVD), offer a great potential for the application on highly stressed tools, e. g. in cutting or forming processes. As a result of the CVD process rough surfaces arise, which require a finishing treatment in particular for the application in forming tools. Cutting techniques such as milling and grinding are hardly applicable for the finish machining because of the high strength of diamond. Due to its process principle of ablating material by melting and evaporating, Electrical Discharge Machining (EDM) is independent of hardness, brittleness or toughness of the workpiece material. EDM is a suitable technology for machining and structuring CVD diamond, since boron doped CVD diamond is electrically conductive. In this study the ablation characteristics of boron doped CVD diamond by micro electrical discharge machining are investigated. Experiments were carried out to investigate the influence of different process parameters on the machining result. The impact of tool-polarity, voltage and discharge energy on the resulting erosion geometry and the tool wear was analyzed. A variation in path overlapping during the erosion of planar areas leads to different microstructures. The results show that micro EDM is a suitable technology for finishing of boron doped CVD diamond.

Comparative studies of electrochemical properties of carbon nanotubes and nanostructured boron carbide

Science.gov (United States)

Singh, Paviter; Kaur, Gurpreet; Singh, Kulwinder; Singh, Bikramjeet; Kaur, Manjot; Kumar, Manjeet; Bala, Rajni; Kumar, Akshay

2018-05-01

Boron carbide (B4C) and carbon nanotubes (CNTs) have the potential to act as electrocatalyst as these material show bifunctional behavior. B4C and CNTs were synthesized using solvothermal method. B4C display great catalytic activity as compared to CNTs. Raman spectra confirmed the formation of nanostructured carbon nanotubes. The observed onset potential was smaller 1.58 V in case of B4C as compared to CNTs i.e. 1.96 V in cyclic voltammetry. B4C material can emerge as a promising bifunctional electrocatalyst for battery applications.

Frequency mixing in boron carbide laser ablation plasmas

Science.gov (United States)

Oujja, M.; Benítez-Cañete, A.; Sanz, M.; Lopez-Quintas, I.; Martín, M.; de Nalda, R.; Castillejo, M.

2015-05-01

Nonlinear frequency mixing induced by a bichromatic field (1064 nm + 532 nm obtained from a Q-switched Nd:YAG laser) in a boron carbide (B4C) plasma generated through laser ablation under vacuum is explored. A UV beam at the frequency of the fourth harmonic of the fundamental frequency (266 nm) was generated. The dependence of the efficiency of the process as function of the intensities of the driving lasers differs from the expected behavior for four-wave mixing, and point toward a six-wave mixing process. The frequency mixing process was strongly favored for parallel polarizations of the two driving beams. Through spatiotemporal mapping, the conditions for maximum efficiency were found for a significant delay from the ablation event (200 ns), when the medium is expected to be a low-ionized plasma. No late components of the harmonic signal were detected, indicating a largely atomized medium.

Structure and properties of hot-pressed boron carbide ceramics

Energy Technology Data Exchange (ETDEWEB)

Koval' chenko, M S; Tkachenko, IU G; Koval' chuk, V V; Iurchenko, D Z; Satanin, S V [Institut Problem Materialovedeniia, Kiev (Ukrainian SSR)

1990-07-01

The microstructure and strength of B4C-TiB2-TiO{sub 2} ceramics samples, hot-compacted from a mixture of two types of B4C-TiO2-C powder, are examined. The two types are obtained by combining boric acid with either sucrose or carbon black. The grain-sizes of the two powders are found to be distinctly different from one another both before and after the grinding procedure and the degree of dispersion is not high. The strength tests show 600 MPa, the Vicker's hardness is 34.5 GPa, and the crack resistance coefficient of ceramics containing 15 percent TiB2 by mass is 5 MPa m exp 1/2. The use of soluble boron carbide powder helps achieve higher levels of strength and crack resistance. 5 refs.

Influence of edge radius of sintered-carbide tip on roughness of machined surface

Directory of Open Access Journals (Sweden)

Jiří Votava

2013-01-01

Full Text Available Increasing of cutting speed and thus increasing labour productivity is observed as a current trend in engineering production. This effort results to development of new cutting materials which are more capable to resist increased requirements on machined surface as well as operating life of the instrument. Nowadays, the most widely used materials used for cutting instruments are sintered carbides which are alloyed by other metals. The goal of this paper is to analyse change in quality of machined surface depending on the change of cutting conditions. For cutting operation, there were used a milling cutter high-speed steel 90 (HSS and removable sintered-carbide tips with different radius. Steel 12 050 hardened for 17 HRC was used as a machined material. Firstly, hardness of machined as well as machining materials was analysed. Further, metallographic analysis and measurement of microhardness of the individual structure phases was processed. Cutting conditions of both instruments were selected depending on the machined material. Surface roughness indicates the quality of machined surface.

Determination of nitrogen in boron carbide with the Leco UO-14 Nitrogen Determinator

International Nuclear Information System (INIS)

Gardner, R.D.; Ashley, W.H.; Henicksman, A.L.

1977-11-01

Use of various metals as fluxes for releasing nitrogen from boron carbide in the Leco Nitrogen Determinator was investigated. Metals such as iron, chromium, and molybdenum that wet the graphite crucible all promoted nitrogen release. Tin, copper, aluminum, and platinum did not wet the graphite and were of no value as fluxes. A procedure for sample handling and the resulting performance of the method are described. The precision at 0.06 to 0.6 percent nitrogen averaged 4 percent relative standard deviation

Deposition of multicomponent chromium carbide coatings using a non-conventional source of chromium and silicon with micro-additions of boron

Energy Technology Data Exchange (ETDEWEB)

Gonzalez Ruiz, Jesus Eduardo, E-mail: jesus.gonzalez@biomat.uh.cu [Biomaterials Center, University of Havana (Cuba); Rodriguez Cristo, Alejandro [Mechanical Plants Company, Road of the Sub-Plan, Farm La Cana, Santa Clara, Villa Clara (Cuba); Ramos, Adrian Paz [Department of Chemistry, Universite de Montreal, Quebec (Canada); Quintana Puchol, Rafael [Welding Research Center, Central University Marta Abreu of Las Villas, Villa Clara (Cuba)

2017-01-15

The chromium carbide coatings are widely used in the mechanical industry due to its corrosion resistance and mechanical properties. In this work, we evaluated a new source of chromium and silicon with micro-additions of boron on the deposition of multi-component coatings of chromium carbides in W108 steel. The coatings were obtained by the pack cementation method, using a simultaneous deposition at 1000 deg for 4 hours. The coatings were analyzed by X-ray diffraction, X-ray energy dispersive spectroscopy, optical microscopy, microhardness test method and pin-on-disc wear test. It was found that the coatings formed on W108 steel were mainly constituted by (Cr,Fe){sub 23}C{sub 6} , (Cr,Fe){sub 7} C{sub 3} , Cr{sub 5-x}Si{sub 3-x} C{sub x+z}, Cr{sub 3} B{sub 0,44}C{sub 1,4} and (or) Cr{sub 7} BC{sub 4} . The carbide layers showed thicknesses between 14 and 15 μm and maximum values of microhardness between 15.8 and 18.8 GPa. Also, the micro-additions of boron to the mixtures showed statistically significant influence on the thickness, microhardness and abrasive wear resistance of the carbide coatings. (author)

Effect of sintering temperature and boron carbide content on the wear behavior of hot pressed diamond cutting segments

Directory of Open Access Journals (Sweden)

Islak S.

2015-01-01

Full Text Available The aim of this study was to investigate the effect of sintering temperature and boron carbide content on wear behavior of diamond cutting segments. For this purpose, the segments contained 2, 5 and 10 wt.% B4C were prepared by hot pressing process carried out under a pressure of 35 MPa, at 600, 650 and 700 °C for 3 minutes. The transverse rupture strength (TRS of the segments was assessed using a three-point bending test. Ankara andesite stone was cut to examine the wear behavior of segments with boron carbide. Microstructure, surfaces of wear and fracture of segments were determined by scanning electron microscopy (SEM-EDS, and X-ray diffraction (XRD analysis. As a result, the wear rate decreased significantly in the 0-5 wt.% B4C contents, while it increased in the 5-10 wt.% B4C contents. With increase in sintering temperature, the wear rate decreased due to the hard matrix.

Microscopic origin of the composition-dependent change of the thermal conductivity in boron carbides

International Nuclear Information System (INIS)

Emin, D.; Howard, I.A.; Green, T.A.; Beckel, C.L.

1987-01-01

Large grain polycrystalline boron carbides have a high-temperature thermal conductivity which changes from being characteristic of a crystal to being glass-like as the carbon content is reduced from its maximal value. We relate this phenomenon, to compositional changes within the three-atom intericosahedral chains. With a reduction of the carbon concentration from its maximal concentration (20%), a carbon atom within some of the three-atoms (CBC) intericosahedral chains is replaced by a boron atom, thereby producing CBB chains. We estimate that the CBB chains are significantly softer than the CBC chains. Thus, with this reduction of carbon content the intericosahedral chains are inhomogeneously softened. This suppresses the coherent transport of heat through the chains. The remaining thermal transport occurs incoherently through vibrationally inequivalent structural units, i.e. ''phonon hopping.''

Optimizing Grain Boundary Complexions to Produce Dense Pressure-Less Sintered Boron Carbide (B4C)

Science.gov (United States)

2008-11-14

discontinuous distribution of the yttria. At this stage it is difficult to determine if the discontinuity is genuine or results from dewetting upon cooling...sample. However, the tendency of the film to form beads indicates a dewetting behavior. The weak interface between the yttria and the boron carbide...conform to the dewetting behavior. There is a possibility of a complexion transition as the sample is cooled down in the furnace. At high temperature the

Effect of the reinforced boron carbide particulate content of AA6061 alloy on formation of the passive film in seawater

International Nuclear Information System (INIS)

Katkar, V.A.; Gunasekaran, G.; Rao, A.G.; Koli, P.M.

2011-01-01

Highlights: → Presence of boron carbide increases the corrosion rate of A6061 alloy in seawater. → Increasing the B 4 C content decreases passive layer thickness. → Passive films formed on A6061 and its B 4 C composites are n-type semiconductors. - Abstract: The effect of boron carbide (B 4 C) reinforcement on the corrosion of AA6061 alloy was studied by investigating passive films formed in seawater. The higher passive current and its potential-dependence for these composites indicated formation of porous passive film. Electrochemical impedance spectroscopy (EIS) graph suggests that the alloy surface is partly or totally active. The formed passive film is n-type semiconductor junction in nature. The difference between corrosion potential (E corr ) and potential at zero charge (PZC) suggests that the chloride ions responsible for film breakdown exist within the passive film. A suitable mechanism is proposed for the passive film breakdown.

Growth of boron doped hydrogenated nanocrystalline cubic silicon carbide (3C-SiC) films by Hot Wire-CVD

Energy Technology Data Exchange (ETDEWEB)

Pawbake, Amit [School of Energy Studies, Savitribai Phule Pune University, Pune 411 007 (India); Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Mayabadi, Azam; Waykar, Ravindra; Kulkarni, Rupali; Jadhavar, Ashok [School of Energy Studies, Savitribai Phule Pune University, Pune 411 007 (India); Waman, Vaishali [Modern College of Arts, Science and Commerce, Shivajinagar, Pune 411 005 (India); Parmar, Jayesh [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Bhattacharyya, Somnath [Department of Metallurgical and Materials Engineering, IIT Madras, Chennai 600 036 (India); Ma, Yuan‐Ron [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Devan, Rupesh; Pathan, Habib [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Jadkar, Sandesh, E-mail: sandesh@physics.unipune.ac.in [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

2016-04-15

Highlights: • Boron doped nc-3C-SiC films prepared by HW-CVD using SiH{sub 4}/CH{sub 4}/B{sub 2}H{sub 6}. • 3C-Si-C films have preferred orientation in (1 1 1) direction. • Introduction of boron into SiC matrix retard the crystallanity in the film structure. • Film large number of SiC nanocrystallites embedded in the a-Si matrix. • Band gap values, E{sub Tauc} and E{sub 04} (E{sub 04} > E{sub Tauc}) decreases with increase in B{sub 2}H{sub 6} flow rate. - Abstract: Boron doped nanocrystalline cubic silicon carbide (3C-SiC) films have been prepared by HW-CVD using silane (SiH{sub 4})/methane (CH{sub 4})/diborane (B{sub 2}H{sub 6}) gas mixture. The influence of boron doping on structural, optical, morphological and electrical properties have been investigated. The formation of 3C-SiC films have been confirmed by low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy and high resolution-transmission electron microscopy (HR-TEM) analysis whereas effective boron doping in nc-3C-SiC have been confirmed by conductivity, charge carrier activation energy, and Hall measurements. Raman spectroscopy and HR-TEM analysis revealed that introduction of boron into the SiC matrix retards the crystallanity in the film structure. The field emission scanning electron microscopy (FE-SEM) and non contact atomic force microscopy (NC-AFM) results signify that 3C-SiC film contain well resolved, large number of silicon carbide (SiC) nanocrystallites embedded in the a-Si matrix having rms surface roughness ∼1.64 nm. Hydrogen content in doped films are found smaller than that of un-doped films. Optical band gap values, E{sub Tauc} and E{sub 04} decreases with increase in B{sub 2}H{sub 6} flow rate.

Surface modification of the hard metal tungsten carbide-cobalt by boron ion implantation; Oberflaechenmodifikation des Hartmetalls Wolframkarbid-Kobalt durch Bor-Ionenimplantation

Energy Technology Data Exchange (ETDEWEB)

Mrotchek, I.

2007-09-07

In the present thesis ion beam implantation of boron is studied as method for the increasement of the hardness and for the improvement of the operational characteristics of cutting tools on the tungsten carbide-cobalt base. For the boron implantation with 40 keV energy and {approx}5.10{sup 17} ions/cm{sup 2} fluence following topics were shown: The incoerporation of boron leads to a deformation and remaining strain of the WC lattice, which possesses different stregth in the different directions of the elementary cell. The maximum of the deformation is reached at an implantation temperature of 450 C. The segregation of the new phases CoWB and Co{sub 3}W was detected at 900 C implantation temperature. At lower temperatures now new phases were found. The tribological characteristics of WC-Co are improved. Hereby the maxiaml effect was measured for implantation temperatures from 450 C to 700 C: Improvement of the microhardness by the factor 2..2.5, improvement of the wear resistance by the factor 4. The tribological effects extend to larger depths than the penetration depth of the boron implantation profile. The detected property improvements of the hard metal H3 show the possibility of a practical application of boron ion implantation in industry. The effects essential for a wer decreasement are a hardening of the carbide phase by deformation of the lattice, a hardening of the cobalt binding material and the phase boundaries because of the formation of a solid solution of the implanted boron atoms in Co and by this a blocking of the dislocation movement and the rupture spreading under load.

Investigation of effects of boron additives and heat treatment on carbides and phase transition of highly alloyed duplex cast iron

International Nuclear Information System (INIS)

Tasgin, Yahya; Kaplan, Mehmet; Yaz, Mehmet

2009-01-01

The effect of boron additives and heat treatment on the microstructural morphology of the transition zone in a duplex cast iron, which has an outer shell of white cast iron (with a high Cr-content and containing boron additives) and an inner side composed of normal gray cast iron, has been investigated. For this purpose, two experimental materials possessing different compositions of white-gray duplex cast iron were produced. Subsequently, metallographic investigations were carried out to study the effect of heat treatment applied to the experimental materials by using the scanning electron microscopy technique, along with optical microscopy and energy dispersive X-ray spectroscopy. Moreover, the formation of various phases and carbide composites in the samples and their effects on the hardness were also investigated using X-ray diffraction techniques. The results of investigations, and hardness showed that addition of the elements Cr and B to high-alloyed white cast iron affected carbide formation significantly, while simultaneously hardening the microstructure, and consequently the carbide present in the transition area of white-gray cast iron was spread out and became thinner. However, B additives and heat treatment did not cause any damage to the transition region of high Cr-content duplex cast iron.

Surface impurity removal from DIII-D graphite tiles by boron carbide grit blasting

International Nuclear Information System (INIS)

Lee, R.L.; Hollerbach, M.A.; Holtrop, K.L.; Kellman, A.G.; Taylor, P.L.; West, W.P.

1993-11-01

During the latter half of 1992, the DIII-D tokamak at General Atomics (GA) underwent several modifications of its interior. One of the major tasks involved the removal of accumulated metallic impurities from the surface of the graphite tiles used to line the plasma facing surfaces inside of the tokamak. Approximately 1500 graphite tiles and 100 boron nitride tiles from the tokamak were cleaned to remove the metallic impurities. The cleaning process consisted of several steps: the removed graphite tiles were permanently marked, surface blasted using boron carbide (B 4 C) grit media (approximately 37 μm. diam.), ultrasonically cleaned in ethanol to remove loose dust, and outgassed at 1000 degrees C. Tests were done using, graphite samples and different grit blaster settings to determine the optimum propellant and abrasive media pressures to remove a graphite layer approximately 40-50 μm deep and yet produce a reasonably smooth finish. EDX measurements revealed that the blasting technique reduced the surface Ni, Cr, and Fe impurity levels to those of virgin graphite. In addition to the surface impurity removal, tritium monitoring was performed throughout the cleaning process. A bubbler system was set up to monitor the tritium level in the exhaust gas from the grit blaster unit. Surface wipes were also performed on over 10% of the tiles. Typical surface tritium concentrations of the tiles were reduced from about 500 dpm/100 cm 2 to less than 80 dpm/100 cm 2 following the cleaning. This tile conditioning, and the installation of additional graphite tiles to cover a high fraction of the metallic plasma facing surfaces, has substantially reduced metallic impurities in the plasma discharges which has allowed rapid recovery from a seven-month machine opening and regimes of enhanced plasma energy confinement to be more readily obtained. Safety issues concerning blaster operator exposure to carcinogenic metals and radioactive tritium will also be addressed

Fabrication and tribological response of aluminium 6061 hybrid composite reinforced with bamboo char and boron carbide micro-fillers

Science.gov (United States)

Chethan, K. N.; Pai, Anand; Keni, Laxmikant G.; Singhal, Ashish; Sinha, Shubham

2018-02-01

Metal matrix composites (MMCs) have a wide scope of industrial applications and triumph over conventional materials due to their light weight, higher specific strength, good wear resistance and lower coefficient of thermal expansion. The present study aims at establishing the feasibility of using Bamboo charcoal particulate and boron carbide as reinforcements in Al-6061 alloy matrix and to investigate their effect on the wear of composites taking into consideration the interfacial adhesion of the reinforcements in the alloy. Al-6061 alloy was chosen as a base metallic alloy matrix. Sun-dried bamboo canes were used for charcoal preparation with the aid of a muffle furnace. The carbon content in the charcoal samples was determined by EDS (energy dispersive spectroscopy). In present study, stir casting technique was used to prepare the samples with 1%, 2%, and 3% weight of bamboo charcoal and boron carbide with Al-6061. The fabricated composites were homogenised at 570°C for 6 hours and cooled at room temperature. Wear studies were carried out on the specimens with different speed and loads. It was found that wear rate and coefficient of friction decreased with increase in the reinforcement content.

On the use of Raman spectroscopy and instrumented indentation for characterizing damage in machined carbide ceramics

Science.gov (United States)

Groth, Benjamin Peter

Machining is a necessary post-processing step in the manufacturing of many ceramic materials. Parts are machined to meet specific dimensions, with tight tolerances, not attainable from forming alone, as well as to achieve a desired surface finish. However, the machining process is very harsh, often employing the use of high temperatures and pressures to achieve the wanted result. In the case of silicon carbide, a material with extremely high hardness and stiffness, machining is very difficult and requires machining conditions that are highly aggressive. This can leave behind residual stresses in the surface of the material, cause unwanted phase transformations, and produce sub-surface deformation that can lead to failure. This thesis seeks to determine the effect of various machining conditions on the Raman spectra and elastic properties of sintered silicon carbide materials. Sample sets examined included hot-pressed silicon carbide tiles with four different surface finishes, as well as "ideal" single crystal silicon carbide wafers. The surface finishes studied were as follows: an as-pressed finish; a grit blast finish; a harsh rotary ground finish; and a mirror polish. Each finish imparts a different amount, as well as type, of deformation to the sample and are each utilized for a specific application. The sample surfaces were evaluated using a combination of Raman spectroscopy, for phase identification and stress analysis, and nanoindentation, for obtaining elastic properties and imparting uniform controlled deformation to the samples. Raman spectroscopy was performed over each sample surface using 514- and 633-nm wavelength excitation, along with confocal and non-confocal settings to study depth variation. Surfaces stresses were determined using peak shift information extracted from Raman spectra maps, while other spectral variations were used to compare levels of machining damage. Elastic modulus, hardness, and plastic work of indentation maps were generated

Study of the machining of uranium carbide rods obtained by continuous casting under electronic bombardment

International Nuclear Information System (INIS)

Rousset, P.; Accary, A.

1965-01-01

The authors consider the various methods of machining uranium mono-carbide and compare them critically in the case of their application to uranium carbide obtained by fusion under an electronic bombardment and continuous casting. This study leads them to propose two mechanical machining methods: cylindrical rectification and center-less rectification, preceded by a preliminary roughing out of a cylinder, the latter appearing more suitable. A study of the machining yields as a function of the diameter of the rough bars and of the diameter of the finished rods has shown that an optimum value of the rough bar diameter exists for each value of the finished rod diameter. It is found that the yield increases as the diameter itself increases, this yield rising from 45 per cent to around 70 per cent as the diameter of the rough bars increases from 25-26 mm to 37-38 mm. (authors) [fr

Evaluation on machined surface of hardened stainless steel generated by hard turning using coated carbide tools with wiper geometry

International Nuclear Information System (INIS)

Noordin, M.Y.; Kurniawan, D.; Sharif, S.

2007-01-01

Hard turning has been explored to be the finish machining operation for parts made of hardened steel. Its feasibility is determined partially by the quality of the resulting machined surface. This study evaluates the surface integrity of martensitic stainless steel (48 HRC) resulting from hard turning using coated carbide tool with wiper geometry at various cutting speed and feed and compares to that obtained using coated carbide tool with conventional geometry. The wiper coated carbide tool is able to produce machined surface which is of finer finish (Ra is finer than 0.4 μm at most cutting parameters) and yet is similarly inducing only minor microstructural alteration compared to its conventional counterpart. From the view of the chip morphology where continuous type of chip is desired rather than sawtooth chip type, the wiper tool generates continuous chip at almost similar range of cutting parameters compared to the case when using conventional tool. Additionally, the use of wiper tool also induces the preferred compressive residual stress at the machined surface. (author)

Possibilities of Application of High Pressure Jet Assisted Machining in Hard Turning with Carbide Tools

Directory of Open Access Journals (Sweden)

G. Globočki Lakić

2017-06-01

Full Text Available High Pressure Jet Assisted Machining (HPJAM in turning is a hybrid machining method in which a high pressure jet of cooling and lubrication fluid, under high pressure (50 MPa, leads to the zone between the cutting tool edge and workpiece. An experimental study was performed to investigate the capabilities of conventional and high pressure cooling (HPC in the turning of hard-to-machine materials: hard-chromed and surface hardened steel Ck45 (58 HRc and hardened bearing steel 100Cr6 (62 HRc. Machining experiments were performed using coated carbide tools and highly cutting speed. Experimental measurements were performed for different input process parameters. The cooling capabilities are compared by monitoring of tool wear, tool life, cooling efficiency, and surface roughness. Connection between the tool wear and surface roughness is established. Experimental research show that the hard turning with carbide cutting tools and HP supply CLF provides numerous advantages from the techno-economic aspect: greater productivity, reduce of temperature in the cutting zone, improved control chip formation, extended tool life, low intensity of tool wear, surface roughness in acceptable limits, significant reduce of production costs related to the CLF.

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.

Detection of a leaking boron-carbide control rod in a TRIGA Mark I reactor

Energy Technology Data Exchange (ETDEWEB)

Blotcky, A J; Arsenault, L J [General Medical Research, Veterans Administration Hospital, Omaha (United States)

1974-07-01

During a routine quarterly inspection of the boron-carbide control rods of the Omaha Veterans Administration Hospital 18 kW Triga Mark I reactor, a pin hole leak was detected approximately 3 mm from the chamfered edge. The leak was found by observing bubbles when the rod was withdrawn from the reactor tank for visual observation, and could not be seen with the naked eye. This suggests that pin hole leaks could occur and not be visually detected in control rods and fuel elements examined underwater. A review of the rod calibrations showed that the leak had not caused a loss in rod worth. Slides will be presented showing the bubbles observed during the inspection, together with an unmagnified and magnified view of the pin hole. (author)

Detection of a leaking boron-carbide control rod in a TRIGA Mark I reactor

International Nuclear Information System (INIS)

Blotcky, A.J.; Arsenault, L.J.

1974-01-01

During a routine quarterly inspection of the boron-carbide control rods of the Omaha Veterans Administration Hospital 18 kW Triga Mark I reactor, a pin hole leak was detected approximately 3 mm from the chamfered edge. The leak was found by observing bubbles when the rod was withdrawn from the reactor tank for visual observation, and could not be seen with the naked eye. This suggests that pin hole leaks could occur and not be visually detected in control rods and fuel elements examined underwater. A review of the rod calibrations showed that the leak had not caused a loss in rod worth. Slides will be presented showing the bubbles observed during the inspection, together with an unmagnified and magnified view of the pin hole. (author)

Anodic solubility and electrochemical machining of hard alloys on the base of chromium and titanium carbides

Energy Technology Data Exchange (ETDEWEB)

Davydov, A D; Klepikov, A N; Malofeeva, A N; Moroz, I I

1985-01-01

The regularities of anodic behaviour and electrochemical machining (ECM) of the samples of three materials with the following compositions: 25% of Cr/sub 3/C/sub 2/, 15% of Ni, 70% of TiC, 25% of Ni, 5% of Cr, 70% of TiC, 15% of Ni, 15% of Mo are investigated. It is shown that the electrochemical method is applicable to hard alloys machining on the base of chromium and titanium carbides, the machining of which mechanically meets serious difficulties. The alloys machining rate by a mobile cathode constitutes about 0.5 mm/min.

Amorphisation of boron carbide under slow heavy ion irradiation

Energy Technology Data Exchange (ETDEWEB)

Gosset, D., E-mail: Dominique.gosset@cea.fr [CEA Saclay, DEN, DANS, DMN, SRMA, LA2M, Université Paris-Saclay, 91191, Gif/Yvette (France); Miro, S. [CEA Saclay, DEN, DANS, DMN, SRMP, Laboratoire JANNUS, Université Paris-Saclay, 91191, Gif/Yvette (France); Doriot, S. [CEA Saclay, DEN, DANS, DMN, SRMA, LA2M, Université Paris-Saclay, 91191, Gif/Yvette (France); Moncoffre, N. [CNRS/IN2P3/IPNL, 69622, Villeurbanne (France)

2016-08-01

Boron carbide B{sub 4}C is widely used as a neutron absorber in nuclear plants. Most of the post-irradiation examinations have shown that the structure of the material remains crystalline, in spite of very high atomic displacement rates. Here, we have irradiated B{sub 4}C samples with 4 MeV Au ions with different fluences at room temperature. Transmission electron microscopy (TEM) and Raman spectroscopy have been performed. The Raman analyses show a high structural disorder at low fluence, around 10{sup −2} displacements per atoms (dpa). However, the TEM observations show that the material remains crystalline up to a few dpa. At high fluence, small amorphous areas a few nanometers large appear in the damaged zone but the long range order is preserved. Moreover, the size and density of the amorphous zones do not significantly grow when the damage increases. On the other hand, full amorphisation is observed in the implanted zone at a Au concentration of about 0.0005. It can be inferred from those results that short range and long range damages arise at highly different fluences, that heavy ions implantation has drastic effects on the structure stability and that in this material self-healing mechanisms are active in the damaged zone.

Structural stability of boron carbide under pressure proven by spectroscopic studies up to 73 GPa

Energy Technology Data Exchange (ETDEWEB)

Chuvashova, Irina [Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth (Germany); Bayerisches Geoinstitut, University of Bayreuth (Germany); Gasharova, Biliana; Mathis, Yves-Laurent [IBPT, Karlsruhe Institute of Technology, Karlsruhe (Germany); Dubrovinsky, Leonid [Bayerisches Geoinstitut, University of Bayreuth (Germany); Dubrovinskaia, Natalia [Material Physics and Technology at Extreme Conditions, Laboratory of Crystallography, University of Bayreuth (Germany)

2017-11-17

Being a material of choice for lightweight armor applications, boron carbide has been intensively studied. Its behavior under pressure was investigated using both theoretical and experimental methods, such as powder X-ray diffraction and vibrational spectroscopy. As there is a discrepancy in experimental observations, in the presented work we studied vibrational properties of commercially available, ''nearly stoichiometric'' B{sub 4}C using IR and Raman spectroscopy up to 73 GPa. No phase transitions were found in the entire pressure range. Our results are at odds with the recent report of a phase transition in B{sub 4.3}C at about 40 GPa. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Neutron shielding behavior of thermoplastic natural rubber/boron carbide composites

Science.gov (United States)

Mat Zali, Nurazila; Yazid, Hafizal; Megat Ahmad, Megat Harun Al Rashid

2018-01-01

Many shielding materials have been designed against the harm of different types of radiation to the human body. Today, polymer-based lightweight composites have been chosen by the radiation protection industry. In the present study, thermoplastic natural rubber (TPNR) composites with different weight percent of boron carbide (B4C) fillers (0% to 30%) were fabricated as neutron shielding through melt blending method. Neutron attenuation properties of TPNR/B4C composites have been investigated. The macroscopic cross section (Σ), half value layer (HVL) and mean free path length (λ) of the composites have been calculated and the transmission curves have been plotted. The obtained results show that Σ, HVL and λ greatly depend on the B4C content. Addition of B4C fillers into TPNR matrix were found to enhance the macroscopic cross section values thus decrease the mean free path length (λ) and half value layer (HVL) of the composites. The transmission curves exhibited that the neutron transmission of the composites decreased with increasing shielding thickness. These results showed that TPNR/B4C composites have high potential for neutron shielding applications.

Fabrication of boron-phosphide neutron detectors

International Nuclear Information System (INIS)

Fitzsimmons, M.; Pynn, R.

1997-01-01

Boron phosphide is a potentially viable candidate for high neutron flux neutron detectors. The authors have explored chemical vapor deposition methods to produce such detectors and have not been able to produce good boron phosphide coatings on silicon carbide substrates. However, semi-conducting quality films have been produced. Further testing is required

Synthesis and characterization of boron incorporated diamond-like carbon thin films

International Nuclear Information System (INIS)

Zhang, L.L.; Yang, Q.; Tang, Y.; Yang, L.; Zhang, C.; Hu, Y.; Cui, X.

2015-01-01

Boron incorporated diamond-like carbon (B-DLC) (up to 8 wt.% boron) thin films were synthesized on silicon wafers using biased target ion beam deposition technique, where diamond-like carbon (DLC) was deposited by ion beam deposition and boron (B) was simultaneously incorporated by biased target sputtering of a boron carbide (B 4 C) target under different conditions. Pure DLC films and B–C films were also synthesized by ion beam deposition and biased target sputtering of B 4 C under similar conditions, respectively, as reference samples. The microstructure and mechanical properties of the synthesized films have been characterized by various technologies. It has been found that B exists in different states in B-DLC, including carbon-rich and B-rich boron carbides, boron suboxide and boron oxide, and the oxidation of B probably occurs during the film deposition. The incorporation of B into DLC leads to the increase of sp 3 bonded carbon in the films, the increase of both film hardness and elastic modulus, and the decrease of both surface roughness and friction coefficient. Furthermore, the content of sp 3 bonded carbon, film hardness and elastic modulus increase, and the film surface roughness and friction coefficient decrease with the increase of B-rich carbide in the B-DLC films. - Highlights: • Biased target ion beam deposition technique is promising to produce high quality DLC based thin films; • Boron exists in different states in B-DLC thin films; • The incorporation of B to DLC with different levels leads to improved film properties; • The fraction of sp 3 bonded C in B-DLC thin films increase with the increase of B-rich carbide content in the films

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...

Hybrid metallic nanocomposites for extra wear-resistant diamond machining tools

DEFF Research Database (Denmark)

Loginov, P.A.; Sidorenko, D.A.; Levashov, E.A.

2018-01-01

The applicability of metallic nanocomposites as binder for diamond machining tools is demonstrated. The various nanoreinforcements (carbon nanotubes, boron nitride hBN, nanoparticles of tungsten carbide/WC) and their combinations are embedded into metallic matrices and their mechanical properties...... are determined in experiments. The wear resistance of diamond tools with metallic binders modified by various nanoreinforcements was estimated. 3D hierarchical computational finite element model of the tool binder with hybrid nanoscale reinforcements is developed, and applied for the structure...

Study of boron carbide evolution under neutron irradiation

International Nuclear Information System (INIS)

Simeone, D.

1999-01-01

Owing to its high neutron efficiency, boron carbide (B 4 C) is used as a neutron absorber in control rods of nuclear plants. Its behaviour under irradiation has been extensively studied for many years. It now seems clear that brittleness of the material induced by the 10 B(n,α) 7 Li capture reaction is due to penny shaped helium bubbles associated to a high strain field around them. However, no model explains the behaviour of the material under neutron irradiation. In order to build such a model, this work uses different techniques: nuclear microprobe X-ray diffraction profile analysis and Raman and Nuclear Magnetic Resonance Spectroscopy to present an evolution model of B 4 C under neutron irradiation. The use of nuclear reactions produced by a nuclear microprobe such as the 7 Li(p,p'γ) 7 Li reaction, allows to measure lithium profile in B 4 C pellets irradiated either in Pressurised Water Reactors or in Fast Breeder Reactors. Examining such profiles enables us to describe the migration of lithium atoms out of B 4 C materials under neutron irradiation. The analysis of X-ray diffraction profiles of irradiated B 4 C samples allows us to quantify the concentrations of helium bubbles as well as the strain fields around such bubbles.Furthermore Raman spectroscopy studies of different B 4 C samples lead us to propose that under neutron irradiation. the CBC linear chain disappears. Such a vanishing of this CBC chain. validated by NMR analysis, may explain the penny shaped of helium bubbles inside irradiated B 4 C. (author)

Study on Surface Integrity of AISI 1045 Carbon Steel when machined by Carbide Cutting Tool under wet conditions

Directory of Open Access Journals (Sweden)

Tamin N. Fauzi

2017-01-01

Full Text Available This paper presents the evaluation of surface roughness and roughness profiles when machining carbon steel under wet conditions with low and high cutting speeds. The workpiece materials and cutting tools selected in this research were AISI 1045 carbon steel and canela carbide inserts graded PM25, respectively. The cutting tools undergo machining tests by CNC turning operations and their performances were evaluated by their surface roughness value and observation of the surface roughness profile. The machining tests were held at varied cutting speeds of 35 to 53 m/min, feed rate of 0.15 to 0.50 mm/rev and a constant depth of cut of 1 mm. From the analysis, it was found that surface roughness increased as the feed rate increased. Varian of surface roughness was suspected due to interaction between cutting speeds and feed rates as well as nose radius conditions; whether from tool wear or the formation of a built-up edge. This study helps us understand the effect of cutting speed and feed rate on surface integrity, when machining AISI 1045 carbon steel using carbide cutting tools, under wet cutting conditions.

Machining of high performance workpiece materials with CBN coated cutting tools

International Nuclear Information System (INIS)

Uhlmann, E.; Fuentes, J.A. Oyanedel; Keunecke, M.

2009-01-01

The machining of high performance workpiece materials requires significantly harder cutting materials. In hard machining, the early tool wear occurs due to high process forces and temperatures. The hardest known material is the diamond, but steel materials cannot be machined with diamond tools because of the reactivity of iron with carbon. Cubic boron nitride (cBN) is the second hardest of all known materials. The supply of such PcBN indexable inserts, which are only geometrically simple and available, requires several work procedures and is cost-intensive. The development of a cBN coating for cutting tools, combine the advantages of a thin film system and of cBN. Flexible cemented carbide tools, in respect to the geometry can be coated. The cBN films with a thickness of up to 2 μm on cemented carbide substrates show excellent mechanical and physical properties. This paper describes the results of the machining of various workpiece materials in turning and milling operations regarding the tool life, resultant cutting force components and workpiece surface roughness. In turning tests of Inconel 718 and milling tests of chrome steel the high potential of cBN coatings for dry machining was proven. The results of the experiments were compared with common used tool coatings for the hard machining. Additionally, the wear mechanisms adhesion, abrasion, surface fatigue and tribo-oxidation were researched in model wear experiments.

Phase Field Theory and Analysis of Pressure-Shear Induced Amorphization and Failure in Boron Carbide Ceramic

Directory of Open Access Journals (Sweden)

John D. Clayton

2014-07-01

Full Text Available A nonlinear continuum phase field theory is developed to describe amorphization of crystalline elastic solids under shear and/or pressure loading. An order parameter describes the local degree of crystallinity. Elastic coefficients can depend on the order parameter, inelastic volume change may accompany the transition from crystal to amorphous phase, and transitional regions parallel to bands of amorphous material are penalized by interfacial surface energy. Analytical and simple numerical solutions are obtained for an idealized isotropic version of the general theory, for an element of material subjected to compressive and/or shear loading. Solutions compare favorably with experimental evidence and atomic simulations of amorphization in boron carbide, demonstrating the tendency for structural collapse and strength loss with increasing shear deformation and superposed pressure.

Successive carbon- and boron saturation of KhVG steel in powder mixtures

Energy Technology Data Exchange (ETDEWEB)

Alimov, Yu A; Gordienko, S I

1975-01-01

Method of successive saturation of KhVG steel with carbon and boron in powder mixtures is described. After carbonization of steel in a charcoal carburator at 930 deg C during 3 hrs a domain of equiaxial large grains is formed there the latter representing carbides of Fe/sub 3/C and (Fe, M)/sub 3/C. The increase of duration of carbonization up to 5 hrs and above results in formation of a cement grid greatly impairing the mechanical properties of the metal. Carbonization is followed by borating in powdered technical boron carbide at 900 deg C for 4 hrs which ensures formation on the sample surface of a borated layer with depth up to 65 mkm covering the carbonized zone. As followed from metallographic and x-ray structural analysis, the borated layer consists of boride needles with complex composition (Fe, Cr, Mn)B. Oil hardening of carbonized KhVG steel from 850 deg C and low-temperature tempering at 180 deg C for 1 hr results in formation in the main metal of martensite-carbide structure and, respectively, in the decrease of the microhardness gradient between the diffusion layers, as compared with borated KhVG steel. Operation tests of strengthened matrices of preforming machines under the conditions of application of dynamic pressing forces up to 1500 kg Fce/cm/sup 2/ demonstrated that the cyclical strength of carboborated coverings is 2.0-3.0 times higher than that of borated ones. The method of carboborating is recommended for strengthening the details of stamp and press tools.

B4C solid target boronization of the MST reversed-field pinch

International Nuclear Information System (INIS)

Den Hartog, D.J.; Cekic, M.; Fiksel, G.; Hokin, S.A.; Kendrick, R.D.; Prager, S.C.; Stoneking, M.R.

1992-10-01

A solid rod of hot-pressed boron carbide is being used as the source of boron during boronization of MST. The most striking result of this procedure is the reduction in oxygen contamination of the plasma (O III radiation, characteristic of oxygen at the edge, falls by about a factor of 3 after boronization.). The radiated power fraction drops to about half its initial value. Particle reflux from the wall is also lowered, making density control simpler. The rod (12.7 mm diameter) is inserted into the edge plasma of normal high-power RFP discharges. B 4 C is ablated from the surface of the rod and deposited in a thin film (a-B/C:H) on the walls and limiters. The energy flux carried by ''superthermal'' (not ''runaway'') electrons at the edge of MST appears to enhance the efficient, non-destructive ablation of the boron carbide rod

Porosity determination of alumina and boron carbide ceramic samples by gamma ray transmission

International Nuclear Information System (INIS)

Moreira, Anderson Camargo; Appoloni, Carlos Roberto

2009-01-01

The aim of this work is to apply the Gamma Ray Transmission (GRT), a non destructive technique, for structural characterization of ceramic samples. With this technique, the porosity of Alumina (Al 2 O 3 ) and Boron Carbide (B 4 C) ceramic samples, in tablet format, was determined. The equipment employed is constituted by a 241 Am gamma ray source (59.6 keV and 100mCi), a 2''x2'' diameter NaI (Tl) scintillation detector coupled to a standard gamma ray transmission electronic and a micrometric and automated table for sample movement. The porosity profile of the samples shows a homogeneous porosity distribution, within the spatial resolution of the employed transmission system. The mean porosity determined for Al 2 O 3 and B 4 C were 17.8±1.3% and 3.87±0.43%, respectively. A statistical treatment of these results was performed and showed that the mean porosity values determinate by the GRT are the same as those supplied by the manufacturer. (author)

Properties of p-type amorphous silicon carbide window layers prepared using boron trifluoride

Energy Technology Data Exchange (ETDEWEB)

Gandia, J J [Inst. de Energias Renovables, CIEMAT, Madrid (Spain); Gutierrez, M T [Inst. de Energias Renovables, CIEMAT, Madrid (Spain); Carabe, J [Inst. de Energias Renovables, CIEMAT, Madrid (Spain)

1993-03-01

One set (A) of undoped and three sets (B, C and D) of doped hydrogenated amorphous silicon carbide samples have been made in the framework of a research plan for obtaining high quality p-type window layers by radiofrequency glow discharge of silane-based gas mixtures. The samples of sets A and B were made using different RF-power-density to mass-flow ratios for various methane percentages in the gas mixture. The best carbon incorporation in the amorphous silicon lattice was obtained at the highest RF-power density. The properties of sets C and D, prepared using different RF-power densities and silane and methane proportions have been analysed as functions of the concentration of boron trifluoride with respect to silane. In both cases, the optical gap E[sub G], after a slight initial decrease, remains at a value of approximately 2.1 eV without quenching in the doping ranges covered. The best conductivity obtained is 2x10[sup -7] ([Omega] cm)[sup -1]. IR spectra allow to associate these features with the structural quality of the films. (orig.)

Study of the processes of changing the crystal structure of boron carbide after the destruction of a nuclear reactor as a result of earthquake

International Nuclear Information System (INIS)

Mammadov, Kh.; Mirzayev, M.; Garibov, R.; Allahverdiyev, G.

2017-01-01

The territories of the Trans Caucasian Republics are characterized by high seismic activity. Therefore, the occurrence of cases of anthropogenic catastrophe including in the territories of nuclear reactors is not ruled out in case of natural disasters. Studies to create detectors based on B 4 C for recording ''cold'', ''hot'' and ''fast'' neutrons in order to increase the safety of nuclear reactors have been carried out in recent years. The B 4 C crystal structure is highly stable at relatively large intervals of temperature and pressure. The study of the thermo physical properties of samples of boron carbide irradiated with ionizing beams is interesting from the point of view to study of the stability of the structure and the stability of this compound. The thermal properties of B 4 C irradiated with ionizing γ radiation from a 60''Co source were investigated using the differential scanning calorimetric (DSC) methods. Upon irradiation with ionizing γ rays, a discrete change in the energy of the atoms occurs at the sites of the crystal lattice, the formation of active centers (radicals, ions, electrons), defects in the crystal lattice, the evaporation of crystalline hydrates, which are present in small amounts in bulk and crystalline compounds. The melting point of B 2 O 3 is 723 K, for boron 2348 K, for B 4 C 2623 K. The melting enthalpy for B 2 O 3 is 24.6 kJ/mol. With increasing temperature, the heat capacity and entropy of the non irradiated and irradiated B 4 C samples are increased. The nature of the change in the enthalpy and the Gibbs potential with increasing temperature depends on the presence of oxygen upon irradiation and during thermogravimetric analysis in the temperature range 298-1300 K. Changes in the values of thermodynamic functions occur due to the formation (under the influence of ionizing radiation) of excited atoms, active centers, defects in the crystal structure of

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.

Helium generation and diffusion in graphite and some carbides

International Nuclear Information System (INIS)

Holt, J.B.; Guinan, M.W.; Hosmer, D.W.; Condit, R.H.; Borg, R.J.

1976-01-01

The cross section for the generation of helium in neutron irradiated carbon was found to be 654 mb at 14.4 MeV and 744 mb at 14.9 MeV. Extrapolating to 14.1 MeV (the fusion reactor spectrum) gives 615 mb. The diffusion of helium in dense polycrystalline graphite and in pyrographite was measured and found to be D = 7.2 x 10 -7 m 2 s -1 exp (-80 kJ/RT). It is assumed that diffusion is primarily in the basal plane direction in crystals of the graphite. In polycrystalline graphite the path length is a factor of √2 longer than the measured distance due to the random orientation mismatch between successive grains. Isochronal anneals (measured helium release as the specimen is steadily heated) were run and maximum release rates were found at 200 0 C in polycrystalline graphite, 1000 0 C in pyrographite, 1350 0 C in boron carbide, and 1350 0 and 2400 0 C (two peaks) in silicon carbide. It is concluded that in these candidates for curtain materials in fusion reactors the helium releases can probably occur without bubble formation in graphites, may occur in boron carbide, but will probably cause bubble formation in silicon carbide. 7 figures

Effect of molybdenum, vanadium, boron on mechanical properties of high chromium white cast iron in as-cast condition

Science.gov (United States)

Nurjaman, F.; Sumardi, S.; Shofi, A.; Aryati, M.; Suharno, B.

2016-02-01

In this experiment, the effect of the addition carbide forming elements on high chromium white cast iron, such as molybdenum, vanadium and boron on its mechanical properties and microstructure was investigated. The high chromium white cast iron was produced by casting process and formed in 50 mm size of grinding balls with several compositions. Characterization of these grinding balls was conducted by using some testing methods, such as: chemical and microstructure analysis, hardness, and impact test. From the results, the addition of molybdenum, vanadium, and boron on high chromium white cast iron provided a significant improvement on its hardness, but reduced its toughness. Molybdenum induced fully austenitic matrix and Mo2C formation among eutectic M7C3 carbide. Vanadium was dissolved in the matrix and carbide. While boron was played a role to form fine eutectic carbide. Grinding balls with 1.89 C-13.1 Cr-1.32 Mo-1.36 V-0.00051 B in as-cast condition had the highest hardness, which was caused by finer structure of eutectic carbide, needle like structure (upper bainite) matrix, and martensite on its carbide boundary.

Boron carbide reinforced aluminium matrix composite: Physical, mechanical characterization and mathematical modelling

International Nuclear Information System (INIS)

Shirvanimoghaddam, K.; Khayyam, H.; Abdizadeh, H.; Karbalaei Akbari, M.; Pakseresht, A.H.; Ghasali, E.; Naebe, M.

2016-01-01

This paper investigates the manufacturing of aluminium–boron carbide composites using the stir casting method. Mechanical and physical properties tests to obtain hardness, ultimate tensile strength (UTS) and density are performed after solidification of specimens. The results show that hardness and tensile strength of aluminium based composite are higher than monolithic metal. Increasing the volume fraction of B_4C, enhances the tensile strength and hardness of the composite; however over-loading of B_4C caused particle agglomeration, rejection from molten metal and migration to slag. This phenomenon decreases the tensile strength and hardness of the aluminium based composite samples cast at 800 °C. For Al-15 vol% B_4C samples, the ultimate tensile strength and Vickers hardness of the samples that were cast at 1000 °C, are the highest among all composites. To predict the mechanical properties of aluminium matrix composites, two key prediction modelling methods including Neural Network learned by Levenberg–Marquardt Algorithm (NN-LMA) and Thin Plate Spline (TPS) models are constructed based on experimental data. Although the results revealed that both mathematical models of mechanical properties of Al–B_4C are reliable with a high level of accuracy, the TPS models predict the hardness and tensile strength values with less error compared to NN-LMA models.

Sintering of nano crystalline α silicon carbide by doping with boron ...

Indian Academy of Sciences (India)

Unknown

tions, they concluded that either reaction sintering or liquid phase .... α-6H silicon carbide single crystal by three different laboratories ... silicon carbide particles by the overall reaction .... layer displacement is likely to occur in such a manner as.

Study through potentiodynamic techniques of the corrosion resistance of different aluminium base MMC's with boron additions

International Nuclear Information System (INIS)

Abenojar, J.; Bautista, A.; Guzman, S.; Velasco, F.; Martinez, M.A.

2009-01-01

This paper compares a wrought aluminium with a PM aluminium and PM aluminium alloys with boron-base additions, containing boron carbide and Fe/B (obtained by mechanical alloying during 36 hours from a Fe-B 50% mixture by weight). The effect of sintering temperature for the Fe/B containing material and the effect of mechanical alloying for the boron carbide containing aluminium alloy on the corrosion resistance of those materials have been studied. Their behaviour is followed through cyclic anodic polarization curves in chloride media. In the Al+20%Fe/B composite, low sintering temperatures (650- 950 deg C) exert a negative effect. However, when the material was sintered at high temperature (1000-1100 deg C) its behaviour was very similar to the PM pure aluminium. The effect of mechanical alloying studied in aluminium with boron carbide was also important in corrosion resistance, finding a lower corrosion rate in the mechanically alloyed material. (author)

Natural precursor based hydrothermal synthesis of sodium carbide for reactor applications

Science.gov (United States)

Swapna, M. S.; Saritha Devi, H. V.; Sebastian, Riya; Ambadas, G.; Sankararaman, S.

2017-12-01

Carbides are a class of materials with high mechanical strength and refractory nature which finds a wide range of applications in industries and nuclear reactors. The existing synthesis methods of all types of carbides have problems in terms of use of toxic chemical precursors, high-cost, etc. Sodium carbide (Na2C2) which is an alkali metal carbide is the least explored one and also that there is no report of low-cost and low-temperature synthesis of sodium carbide using the eco-friendly, easily available natural precursors. In the present work, we report a simple low-cost, non-toxic hydrothermal synthesis of refractory sodium carbide using the natural precursor—Pandanus. The formation of sodium carbide along with boron carbide is evidenced by the structural and morphological characterizations. The sample thus synthesized is subjected to field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), ultraviolet (UV)—visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, and photoluminescent (PL) spectroscopic techniques.

The optical properties of boron carbide near boron K-edge inside periodical multilayers

Energy Technology Data Exchange (ETDEWEB)

Ksenzov, Dmitriy; Schlemper, Christoph; Pietsch, Ullrich [University of Siegen (Germany)

2010-07-01

Multilayer mirrors made for the use in the wavelength range near K-edge of boron (188 eV) are of great interest for X-ray fluorescence analysis of boron content in doped semiconductors, plasma diagnostics, astronomy and lithography. Moreover, multilayer mirrors composed by a metal and a low Z element like boron are used as optical elements in both the soft x-ray spectral range as well as at higher photon energies on 3rd generation synchrotron beamlines. Using an energy-resolved photon-in-photon-out method we reconstructed the optical data from energy dependence of both integrated peak intensity and FWHM of the 1st order ML Bragg peak measured at the UHV triple axis soft-x-ray reflectometer at BESSY II. The experiments clearly demonstrate that the peak shape of the ML Bragg peak is most sensitive to any kind of electronic excitation and recombination in solid. The soft-ray reflectivity can give detailed information for MLs with thickness up to several tens of nanometers. In addition, measurements close to a resonance edge probe the chemical state of the respective constituent accompanied with a high sensitivity of changes close to the sample surface.

Ultrasonically Assisted Single Point Diamond Turning of Optical Mold of Tungsten Carbide

Directory of Open Access Journals (Sweden)

Zhanjie Li

2018-02-01

Full Text Available To realize high efficiency, low/no damage and high precision machining of tungsten carbide used for lens mold, a high frequency ultrasonic vibration cutting system was developed at first. Then, tungsten carbide was precisely machined with a polycrystalline diamond (PCD tool assisted by the self-developed high frequency ultrasonic vibration cutting system. Tool wear mechanism was investigated in ductile regime machining of tungsten carbide. The cutter back-off phenomenon in the process was analyzed. The subsequent experimental results of ultra-precision machining with a single crystal diamond tool showed that: under the condition of high frequency ultrasonic vibration cutting, nano-scale surface roughness can be obtained by the diamond tool with smaller tip radius and no defects like those of ground surface were found on the machined surface. Tool wear mechanisms of the single crystal diamond tool are mainly abrasive wear and micro-chipping. To solve the problem, a method of inclined ultrasonic vibration cutting with negative rake angle was put forward according to force analysis, which can further reduce tool wear and roughness of the machined surface. The investigation was important to high efficiency and quality ultra-precision machining of tungsten carbide.

Effect of mechanical and thermal loading on boron carbide particles reinforced Al-6061 alloy

International Nuclear Information System (INIS)

Manjunatha, B.; Niranjan, H.B.; Satyanarayana, K.G.

2015-01-01

Metal Matrix Composites (MMC) considered as one of the ‘advanced materials’ have evoked growing interest during the last three decades due to their high performance and applications in strategic sectors. These composites exhibit unique and attractive properties over the monolithic alloys, but suffer from low ductility, which makes them not so attractive for some of the applications where high toughness is one of the design criteria. This limitation of MMCs has been overcome by resorting to various treatments such as mechanical and thermal loading. Considering very limited reports available on Al alloy reinforced with boron carbide (B 4 C) particles, this paper presents (i) preparation of Al-6061 alloy reinforced with 1.5–10 wt% B 4 C, (ii) subjecting them to mechanical and thermal treatments and (iii) characterization of all the above samples. Specific ultimate tensile strength and hardness of all the composites were higher than those of matrix. Also, these values increased with increasing amount of particles, with composites containing 8 wt% B 4 C showing the maximum values in all the three conditions. These observations are supported by the uniform distribution of particles in the matrix as observed in their microstructure

Natural cotton as precursor for the refractory boron carbide—a hydrothermal synthesis and characterization

Science.gov (United States)

Saritha Devi, H. V.; Swapna, M. S.; Raj, Vimal; Ambadas, G.; Sankararaman, S.

2018-01-01

Boron carbide (B4C) is an excellent covalent carbide that finds applications in industries and nuclear power plants. The present synthesis methods of boron carbide are expensive and involve the use of toxic chemicals that adversely affect environment. In the present work, we report for the first time the use of the hydrothermal method for converting the cellulose from cotton as the carbon precursor for B4C. The carbon precursor is converted into functionalized porous carbonaceous material by hydrothermal treatment followed by sodium borohydride. It is further treated with boric acid to make it a B4C precursor. The precursor is characterized by UV-visible diffuse reflectance, Raman, Fourier transform infrared, photoluminescent and energy dispersive spectroscopy. The morphology and structure analysis is carried out using field emission scanning electron microscopy and x-ray diffraction techniques. The results of structural and optical characterization of the sample synthesized are compared with the commercial B4C. The thermal stability of the sample is studied by thermogravimetric analysis. The sample annealed at 700 °C is found to be B4C devoid of amorphous carbon with a yield of 44.7%. The analysis reveals the formation of boron carbide from the sample.

Analysis of the influence of process conditions on the surface finish of ceramic materials manufactured by EDM; Analisis de la influencia de las condiciones de proceso sobre el acabado superficial de materiales ceramicos fabricados por electroerosion

Energy Technology Data Exchange (ETDEWEB)

Puertas-Arbizu, I.; Luis-Perez, C. J.

2004-07-01

Electrical discharge machining (EDM) is an emerging alternative versus some other manufacturing processes of conductive ceramic materials, such as: laser machining, electrochemical machining, abrasive water jet, ultrasonic machining and diamond wheel grinding. Due to its interest in the industrial field, in this work a study of the influence of process conditions on the surface aspect of three conductive ceramic materials: hot-pressed boron carbide (B{sub 4}C), reaction-bonded silicon carbide (SiSiC) and cobalt-bonded tungsten carbide (WC-Co) is carried out. These materials are to be electrical discharge machined under different machining conditions and in the particular case of finish stages (Ra{<=} 1 {mu}m). (Author)

Analysis of the influence of process conditions on the surface finish of ceramic materials manufactured by EDM

International Nuclear Information System (INIS)

Puertas-Arbizu, I.; Luis-Perez, C. J.

2004-01-01

Electrical discharge machining (EDM) is an emerging alternative versus some other manufacturing processes of conductive ceramic materials, such as: laser machining, electrochemical machining, abrasive water jet, ultrasonic machining and diamond wheel grinding. Due to its interest in the industrial field, in this work a study of the influence of process conditions on the surface aspect of three conductive ceramic materials: hot-pressed boron carbide (B 4 C), reaction-bonded silicon carbide (SiSiC) and cobalt-bonded tungsten carbide (WC-Co) is carried out. These materials are to be electrical discharge machined under different machining conditions and in the particular case of finish stages (Ra≤ 1 μm). (Author)

On the development of a dual-layered diamond-coated tool for the effective machining of titanium Ti-6Al-4V alloy

International Nuclear Information System (INIS)

Srinivasan, Balaji; Rao, Balkrishna C; Ramachandra Rao, M S

2017-01-01

This work is focused on the development of a dual-layered diamond-coated tungsten carbide tool for machining titanium Ti-6Al-4V alloy. A hot-filament chemical vapor deposition technique was used to synthesize diamond films on tungsten carbide tools. A boron-doped diamond interlayer was added to a microcrystalline diamond layer in an attempt to improve the interface adhesion strength. The dual-layered diamond-coated tool was employed in machining at cutting speeds in the range of 70 to 150 m min −1 with a lower feed and a lower depth of cut of 0.5 mm rev −1 and 0.5 mm, respectively, to operate in the transition from adhesion- to diffusion-tool-wear and thereby arrive at suitable conditions for enhancing tool life. The proposed tool was then compared, on the basis of performance under real-time cutting conditions, with commercially available microcrystalline diamond, nanocrystalline diamond, titanium nitride and uncoated tungsten carbide tools. The life and surface finish of the proposed dual-layered tool and uncoated tungsten carbide were also investigated in interrupted cutting such as milling. The results of this study show a significant improvement in tool life and finish of Ti-6Al-4V parts machined with the dual-layered diamond-coated tool when compared with its uncoated counterpart. These results pave the way for the use of a low-cost tool, with respect to, polycrystalline diamond for enhancing both tool life and machining productivity in critical sectors fabricating parts out of titanium Ti-6Al-4V alloy. The application of this coating technology can also be extended to the machining of non-ferrous alloys owing to its better adhesion strength. (paper)

Tritium release from fast neutron irradiated boron carbide

International Nuclear Information System (INIS)

Hollenberg, G.W.

1977-01-01

A high-energy neutron reaction with boron produces tritium. In the LMFBR control material, B 4 C, most of the tritium that is generated remains in the pellets. Potential retention mechanisms are discussed. 5 figures

Chemical erosion of sintered boron carbide due to H+ impact

International Nuclear Information System (INIS)

Davis, J.W.; Haasz, A.A.

1990-06-01

The production of hydrocarbons and boron hydrides due to H + bombardment of sintered B 4 C has been investigated as a function of sample temperature and incident ion energy. While hydrocarbon production was observed, the yields were approximately two orders of magnitude smaller than observed for graphite. There was no evidence to indicate the production of any volatile boron-containing compounds. (3 figs., 11 refs.)

High temperature synthesis of ceramic composition by directed reaction of molten titanium or zirconium with boron carbide

International Nuclear Information System (INIS)

Johnson, W.B.

1990-01-01

Alternative methods of producing ceramics and ceramic composites include sintering, hot pressing and more recently hot isostatic pressing (HIP) and self-propagating high temperature synthesis (SHS). Though each of these techniques has its advantages, each suffers from several restrictions as well. Sintering may require long times at high temperatures and for most materials requires sintering aids to get full density. These additives can, and generally do, change (often degrade) the properties of the ceramic. Hot pressing and hot isostatic pressing are convenient methods to quickly prepare samples of some materials to full density, but generally are expensive and may damage some types of reinforcements during densification. This paper focuses on the preparation and processing of composites prepared by the directed reaction of molten titanium or zirconium with boron carbide. Advantages and disadvantages of this approach when compared to traditional methods are discussed, with reference to specific examples. Examples of microstructure are properties of these materials are reported

Seebeck effect of some thin film carbides

International Nuclear Information System (INIS)

Beensh-Marchwicka, G.; Prociow, E.

2002-01-01

Several materials have been investigated for high-temperature thin film thermocouple applications. These include silicon carbide with boron (Si-C-B), ternary composition based on Si-C-Mn, fourfold composition based on Si-C-Zr-B and tantalum carbide (TaC). All materials were deposited on quartz or glass substrates using the pulse sputter deposition technique. Electrical conduction and thermoelectric power were measured for various compositions at 300-550 K. It has been found, that the efficiency of thermoelectric power of films containing Si-C base composition was varied from 0.0015-0.034 μW/cmK 2 . However for TaC the value about 0.093 μW/cmK 2 was obtained. (author)

Metalworking and machining fluids

Science.gov (United States)

Erdemir, Ali; Sykora, Frank; Dorbeck, Mark

2010-10-12

Improved boron-based metal working and machining fluids. Boric acid and boron-based additives that, when mixed with certain carrier fluids, such as water, cellulose and/or cellulose derivatives, polyhydric alcohol, polyalkylene glycol, polyvinyl alcohol, starch, dextrin, in solid and/or solvated forms result in improved metalworking and machining of metallic work pieces. Fluids manufactured with boric acid or boron-based additives effectively reduce friction, prevent galling and severe wear problems on cutting and forming tools.

Abrasive wear behavior of heat-treated ABC-silicon carbide

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiao Feng; Lee, Gun Y.; Chen, Da; Ritchie, Robert O.; De Jonghe, Lutgard C.

2002-06-17

Hot-pressed silicon carbide, containing aluminum, boron, and carbon additives (ABC-SiC), was subjected to three-body and two-body wear testing using diamond abrasives over a range of sizes. In general, the wear resistance of ABC-SiC, with suitable heat treatment, was superior to that of commercial SiC.

Microstructure evolution of SiC sintered bodies activated by boron and carbon

International Nuclear Information System (INIS)

Gubernat, A.; Stobierski, L.

2003-01-01

Investigation on the role of sintering aids on densification of silicon carbide indicate that boron and carbon modify mass transport mechanisms. It leads to changes of microstructure of polycrystalline silicon carbide. In the present work the influence of varying proportions of sintering aids on the material microstructure was studied. The microstructural changes were related to the changes of the selected properties of the resulting materials. (author)

Machine Learning methods in fitting first-principles total energies for substitutionally disordered solid

Science.gov (United States)

Gao, Qin; Yao, Sanxi; Widom, Michael

2015-03-01

Density functional theory (DFT) provides an accurate and first-principles description of solid structures and total energies. However, it is highly time-consuming to calculate structures with hundreds of atoms in the unit cell and almost not possible to calculate thousands of atoms. We apply and adapt machine learning algorithms, including compressive sensing, support vector regression and artificial neural networks to fit the DFT total energies of substitutionally disordered boron carbide. The nonparametric kernel method is also included in our models. Our fitted total energy model reproduces the DFT energies with prediction error of around 1 meV/atom. The assumptions of these machine learning models and applications of the fitted total energies will also be discussed. Financial support from McWilliams Fellowship and the ONR-MURI under the Grant No. N00014-11-1-0678 is gratefully acknowledged.

Nanomechanical and in situ TEM characterization of boron carbide thin films on helium implanted substrates: Delamination, real-time cracking and substrate buckling

Energy Technology Data Exchange (ETDEWEB)

Framil Carpeño, David, E-mail: david.framil-carpeno@auckland.ac.nz [Department of Chemical and Materials Engineering, The University of Auckland, 20 Symonds Street, Auckland 1010 (New Zealand); Ohmura, Takahito; Zhang, Ling [Strength Design Group, Structural Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Leveneur, Jérôme [National Isotope Centre, GNS Science, 30 Gracefield Road, Gracefield, Lower Hutt 5010 (New Zealand); Dickinson, Michelle [Department of Chemical and Materials Engineering, The University of Auckland, 20 Symonds Street, Auckland 1010 (New Zealand); Seal, Christopher [International Centre for Advanced Materials, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Kennedy, John [National Isotope Centre, GNS Science, 30 Gracefield Road, Gracefield, Lower Hutt 5010 (New Zealand); Hyland, Margaret [Department of Chemical and Materials Engineering, The University of Auckland, 20 Symonds Street, Auckland 1010 (New Zealand)

2015-07-15

Boron carbide coatings deposited on helium-implanted and unimplanted Inconel 600 were characterized using a combination of nanoindentation and transmission electron microscopy. Real-time coating, cracking and formation of slip bands were recorded using in situ TEM-nanoindentation, allowing site specific events to be correlated with specific features in their load–displacement curves. Cross-sections through the residual indent impression showed a correlation between pop-outs in the load–displacement curves and coating delamination, which was confirmed with cyclic indentation experiments. Inconel exhibits (-11-1) and (1-1-1) twin variants in its deformed region beneath the indenter, organized in bands with a ladder-like arrangement. The nanomechanical properties of the metal–ceramic coating combinations exhibit a marked substrate effect as a consequence of helium implantation.

Nanomechanical and in situ TEM characterization of boron carbide thin films on helium implanted substrates: Delamination, real-time cracking and substrate buckling

International Nuclear Information System (INIS)

Framil Carpeño, David; Ohmura, Takahito; Zhang, Ling; Leveneur, Jérôme; Dickinson, Michelle; Seal, Christopher; Kennedy, John; Hyland, Margaret

2015-01-01

Boron carbide coatings deposited on helium-implanted and unimplanted Inconel 600 were characterized using a combination of nanoindentation and transmission electron microscopy. Real-time coating, cracking and formation of slip bands were recorded using in situ TEM-nanoindentation, allowing site specific events to be correlated with specific features in their load–displacement curves. Cross-sections through the residual indent impression showed a correlation between pop-outs in the load–displacement curves and coating delamination, which was confirmed with cyclic indentation experiments. Inconel exhibits (-11-1) and (1-1-1) twin variants in its deformed region beneath the indenter, organized in bands with a ladder-like arrangement. The nanomechanical properties of the metal–ceramic coating combinations exhibit a marked substrate effect as a consequence of helium implantation

Electrophoretic deposits of boron on duralumin plates used for measuring neutron flux

International Nuclear Information System (INIS)

Lang, F.M.; Magnier, P.; Finck, C.

1956-01-01

Preparation of boron thin film deposits of around 1 mg per cm 2 on duralumin plates with a diameter of 8 cm. The boron coated plates for ionization chambers were originally prepared at the CEA by pulverization of boron carbides on sodium silicates. This method is not controlling precisely enough the quantity of boron deposit. Thus, an electrophoretic method is considered for a better control of the quantity of boron deposit in the scope of using in the future boron 10 which is costly and rare. The method described by O. Flint is not satisfying enough and a similar electrophoretic process has been developed. Full description of the method is given as well as explanation of the use of dried methanol as solvent, tannin as electrolyte and magnesium chloride to avoid alumina formation. (M.P.)

Method for producing polycrystalline boron nitride

International Nuclear Information System (INIS)

Alexeevskii, V.P.; Bochko, A.V.; Dzhamarov, S.S.; Karpinos, D.M.; Karyuk, G.G.; Kolomiets, I.P.; Kurdyumov, A.V.; Pivovarov, M.S.; Frantsevich, I.N.; Yarosh, V.V.

1975-01-01

A mixture containing less than 50 percent of graphite-like boron nitride treated by a shock wave and highly defective wurtzite-like boron nitride obtained by a shock-wave method is compressed and heated at pressure and temperature values corresponding to the region of the phase diagram for boron nitride defined by the graphite-like compact modifications of boron nitride equilibrium line and the cubic wurtzite-like boron nitride equilibrium line. The resulting crystals of boron nitride exhibit a structure of wurtzite-like boron nitride or of both wurtzite-like and cubic boron nitride. The resulting material exhibits higher plasticity as compared with polycrystalline cubic boron nitride. Tools made of this compact polycrystalline material have a longer service life under impact loads in machining hardened steel and chilled iron. (U.S.)

Structure and microhardness of alloy VT22 granules additionally doped with carbon and boron

International Nuclear Information System (INIS)

Sysoeva, N.V.; Polyakova, I.G.; Karpova, I.G.

1996-01-01

Aimed to improve heat resistance and strength of titanium base alloys due to carbon and boron additions (up to 0.3%) a study was made into regularities of phase decomposition in VT22 alloy during its rapid quenching from a liquid state on manufacturing granules 100-400 μm in size. Cooling rates on quenching were found to be sufficiently high to prevent precipitating carbides and borides. Subsequent annealing of granules promotes homogeneous precipitation of strengthening phases in the form of titanium carbides and borides, a reasonable amount of carbon and boron remaining in solid solution. An increase in microhardness of annealed granules reaches 20-25% compared to the standard alloy. 6 refs.; 2 figs.; 2 tabs

Characterization and evaluation of boron carbide for plate-impact conditions

International Nuclear Information System (INIS)

Holmquist, T. J.; Johnson, G. R.

2006-01-01

This article addresses the response of boron carbide (B 4 C) to high-velocity impact. The authors previously characterized this material in 1999, using the Johnson-Holmquist [AIP Conf. Proc. 309, 981 (1994)] (JH-2) model. Since then, there have been additional experimental data presented in the literature that better describe the hydrostatic pressure (including a phase change). In addition, a series of plate-impact experiments (one-dimensional, uniaxial strain) that used configurations that produced either a shock, a shock release, or a shock reshock was performed. These experiments provide material behavior regarding the damage, failed strength, and hydrostat for which previously there has been little or no data. Constitutive model constants were obtained for the Johnson-Holmquist-Beissel [J. Appl. Phys. 94, 1639 (2003)] model using some of these plate-impact experiments. Computations of all the experiments were performed and analyzed to better understand the material response. The analysis provided the following findings: (1) The material fails and loses strength when the Hugoniot elastic limit (HEL) is exceeded. (2) The material has significant strength after failure and gradually increases as the pressure increases. (3) The shear modulus does not degrade when the material fails (as has been postulated), but rather increases. (4) When the material is reloaded from an initial shocked (failed) state, the loading appears to be elastic, indicating the material is not on the yield surface after failure. To provide more insight into the behavior of B 4 C, the strength versus pressure response was compared to that of silicon carbide (SiC). The strength of SiC increases as the pressure increases beyond the HEL, probably due to pressure hardening or strain hardening. It appears that B 4 C does not experience any hardening effects and fails at the HEL. Although the HEL for B 4 C is higher than that of SiC, the hardening ability of SiC produces a similar maximum strength

Tribological and Wear Performance of Carbide Tools with TiB2 PVD Coating under Varying Machining Conditions of TiAl6V4 Aerospace Alloy

Directory of Open Access Journals (Sweden)

Jose Mario Paiva

2017-11-01

Full Text Available Tribological phenomena and tool wear mechanisms during machining of hard-to-cut TiAl6V4 aerospace alloy have been investigated in detail. Since cutting tool wear is directly affected by tribological phenomena occurring between the surfaces of the workpiece and the cutting tool, the performance of the cutting tool is strongly associated with the conditions of the machining process. The present work shows the effect of different machining conditions on the tribological and wear performance of TiB2-coated cutting tools compared to uncoated carbide tools. FEM modeling of the temperature profile on the friction surface was performed for wet machining conditions under varying cutting parameters. Comprehensive characterization of the TiB2 coated vs. uncoated cutting tool wear performance was made using optical 3D imaging, SEM/EDX and XPS methods respectively. The results obtained were linked to the FEM modeling. The studies carried out show that during machining of the TiAl6V4 alloy, the efficiency of the TiB2 coating application for carbide cutting tools strongly depends on cutting conditions. The TiB2 coating is very efficient under roughing at low speeds (with strong buildup edge formation. In contrast, it shows similar wear performance to the uncoated tool under finishing operations at higher cutting speeds when cratering wear predominates.

Characterizing the Effect of Laser Power on Laser Metal Deposited Titanium Alloy and Boron Carbide

Science.gov (United States)

Akinlabi, E. T.; Erinosho, M. F.

2017-11-01

Titanium alloy has gained acceptance in the aerospace, marine, chemical, and other related industries due to its excellent combination of mechanical and corrosion properties. In order to augment its properties, a hard ceramic, boron carbide has been laser cladded with it at varying laser powers between 0.8 and 2.4 kW. This paper presents the effect of laser power on the laser deposited Ti6Al4V-B4C composites through the evolving microstructures and microhardness. The microstructures of the composites exhibit the formation of α-Ti phase and β-Ti phase and were elongated towards the heat affected zone. These phases were terminated at the fusion zone and globular microstructures were found growing epitaxially just immediately after the fusion zone. Good bondings were formed in all the deposited composites. Sample A1 deposited at a laser power of 0.8 kW and scanning speed of 1 m/min exhibits the highest hardness of HV 432 ± 27, while sample A4 deposited at a laser power of 2.0 kW and scanning speed of 1 m/min displays the lowest hardness of HV 360 ± 18. From the hardness results obtained, ceramic B4C has improved the mechanical properties of the primary alloy.

Single-Crystal Tungsten Carbide in High-Temperature In-Situ Additive Manufacturing Characterization

Energy Technology Data Exchange (ETDEWEB)

Kolopus, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Boatner, Lynn A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-05-18

Nanoindenters are commonly used for measuring the mechanical properties of a wide variety of materials with both industrial and scientific applications. Typically, these instruments employ an indenter made of a material of suitable hardness bonded to an appropriate shaft or holder to create an indentation on the material being tested. While a variety of materials may be employed for the indenter, diamond and boron carbide are by far the most common materials used due to their hardness and other desirable properties. However, as the increasing complexity of new materials demands a broader range of testing capabilities, conventional indenter materials exhibit significant performance limitations. Among these are the inability of diamond indenters to perform in-situ measurements at temperatures above 600oC in air due to oxidation of the diamond material and subsequent degradation of the indenters mechanical properties. Similarly, boron carbide also fails at high temperature due to fracture. [1] Transition metal carbides possess a combination of hardness and mechanical properties at high temperatures that offer an attractive alternative to conventional indenter materials. Here we describe the technical aspects for the growth of single-crystal tungsten carbide (WC) for use as a high-temperature indenter material, and we examine a possible approach to brazing these crystals to a suitable mount for grinding and attachment to the indenter instrument. The use of a by-product of the recovery process is also suggested as possibly having commercial value.

The laser micro-machining system for diamond anvil cell experiments and general precision machining applications at the High Pressure Collaborative Access Team.

Science.gov (United States)

Hrubiak, Rostislav; Sinogeikin, Stanislav; Rod, Eric; Shen, Guoyin

2015-07-01

We have designed and constructed a new system for micro-machining parts and sample assemblies used for diamond anvil cells and general user operations at the High Pressure Collaborative Access Team, sector 16 of the Advanced Photon Source. The new micro-machining system uses a pulsed laser of 400 ps pulse duration, ablating various materials without thermal melting, thus leaving a clean edge. With optics designed for a tight focus, the system can machine holes any size larger than 3 μm in diameter. Unlike a standard electrical discharge machining drill, the new laser system allows micro-machining of non-conductive materials such as: amorphous boron and silicon carbide gaskets, diamond, oxides, and other materials including organic materials such as polyimide films (i.e., Kapton). An important feature of the new system is the use of gas-tight or gas-flow environmental chambers which allow the laser micro-machining to be done in a controlled (e.g., inert gas) atmosphere to prevent oxidation and other chemical reactions in air sensitive materials. The gas-tight workpiece enclosure is also useful for machining materials with known health risks (e.g., beryllium). Specialized control software with a graphical interface enables micro-machining of custom 2D and 3D shapes. The laser-machining system was designed in a Class 1 laser enclosure, i.e., it includes laser safety interlocks and computer controls and allows for routine operation. Though initially designed mainly for machining of the diamond anvil cell gaskets, the laser-machining system has since found many other micro-machining applications, several of which are presented here.

The laser micro-machining system for diamond anvil cell experiments and general precision machining applications at the High Pressure Collaborative Access Team

International Nuclear Information System (INIS)

Hrubiak, Rostislav; Sinogeikin, Stanislav; Rod, Eric; Shen, Guoyin

2015-01-01

We have designed and constructed a new system for micro-machining parts and sample assemblies used for diamond anvil cells and general user operations at the High Pressure Collaborative Access Team, sector 16 of the Advanced Photon Source. The new micro-machining system uses a pulsed laser of 400 ps pulse duration, ablating various materials without thermal melting, thus leaving a clean edge. With optics designed for a tight focus, the system can machine holes any size larger than 3 μm in diameter. Unlike a standard electrical discharge machining drill, the new laser system allows micro-machining of non-conductive materials such as: amorphous boron and silicon carbide gaskets, diamond, oxides, and other materials including organic materials such as polyimide films (i.e., Kapton). An important feature of the new system is the use of gas-tight or gas-flow environmental chambers which allow the laser micro-machining to be done in a controlled (e.g., inert gas) atmosphere to prevent oxidation and other chemical reactions in air sensitive materials. The gas-tight workpiece enclosure is also useful for machining materials with known health risks (e.g., beryllium). Specialized control software with a graphical interface enables micro-machining of custom 2D and 3D shapes. The laser-machining system was designed in a Class 1 laser enclosure, i.e., it includes laser safety interlocks and computer controls and allows for routine operation. Though initially designed mainly for machining of the diamond anvil cell gaskets, the laser-machining system has since found many other micro-machining applications, several of which are presented here

Effect of cutting parameters on sustainable machining performance of coated carbide tool in dry turning process of stainless steel 316

Science.gov (United States)

Bagaber, Salem A.; Yusoff, Ahmed Razlan

2017-04-01

The manufacturing industry aims to produce many products of high quality with relatively less cost and time. Different cutting parameters affect the machining performance of surface roughness, cutting force, and material removal rate. Nevertheless, a few studies reported on the effects of sustainable factors such as power consumed, cycle time during machining, and tool life on the dry turning of AISI 316. The present study aims to evaluate the machining performance of coated carbide in the machining of hard steel AISI 316 under the dry turning process. The influence of cutting parameters of cutting speed, feed rate, and depth of cut with their five (5) levels is established by a central composite design. Highly significant parameters were determined by analysis of variance (ANOVA), and the main effects of power consumed and time during machining, surface roughness, and tool wear were observed. Results showed that the cutting speed was proportional to power consumption and tool wear. Meanwhile, insignificant to surface roughness, feed rate most significantly affected surface roughness and power consumption followed by depth of cut.

Compatibility of heat resistant alloys with boron carbide, (4)

International Nuclear Information System (INIS)

Baba, Sinichi; Saruta, Toru; Ooka, Kiichi; Tanaka, Isao; Aoyama, Isao

1985-07-01

This paper relates to the compatibility test of control rod sheath (Hastelloy XR alloy) and neutron absorber (boronated graphite) for the VHTR, which has been researched and developed by JAERI. The irradiation was conducted by using the OGL-1 irradiation facility in the JMTR in order to study reaction behaviour between Hastelloy XR alloy and boronated graphite as well as to determine a reaction barrier performance of refractory metal foils Nb, Mo, W and Re. Irradiation conditions were as follows. Neutron dose : 4.05 x 10 22 m -2 (E 18 m -2 (E > 0.16 pJ, 1 Mev). Helium coolant : Average temperature 855 0 C, Pressure 2.94 MPa, Total impurity concentration 400 kBq/m 3 . Irradiation time : 5.0 Ms (1390 hours). Post-irradiation examinations i.e. visual inspection, dimensional inspection, weight measurement, metallography, hardness test, morphological observations by SEM and analysis of element distributions by EPMA were carried out. In the result, reaction products of Hastelloy XR alloy were observed in the ellipsoidal form locally. These results were same as those of the out-of-pile tests. Obvious irradiation effects were not detectable but a little accelarated increase in reaction depth of Hastelloy XR alloy by heat effect of specimens was observed. The refractory metal foils had a good performance of reaction barrier between Hastelloy XR alloy and boronated graphite. Furthermore, movement of Ni, Fe and Cr in the reaction area of Hastelloy XR alloy, difference in the reaction depth of B and C, irradiation effects on diffusion coefficient, lithium production and heat effect are discussed. (author)

Innovative boron nitride-doped propellants

Directory of Open Access Journals (Sweden)

Thelma Manning

2016-04-01

Full Text Available The U.S. military has a need for more powerful propellants with balanced/stoichiometric amounts of fuel and oxidants. However, balanced and more powerful propellants lead to accelerated gun barrel erosion and markedly shortened useful barrel life. Boron nitride (BN is an interesting potential additive for propellants that could reduce gun wear effects in advanced propellants (US patent pending 2015-026P. Hexagonal boron nitride is a good lubricant that can provide wear resistance and lower flame temperatures for gun barrels. Further, boron can dope steel, which drastically improves its strength and wear resistance, and can block the formation of softer carbides. A scalable synthesis method for producing boron nitride nano-particles that can be readily dispersed into propellants has been developed. Even dispersion of the nano-particles in a double-base propellant has been demonstrated using a solvent-based processing approach. Stability of a composite propellant with the BN additive was verified. In this paper, results from propellant testing of boron nitride nano-composite propellants are presented, including closed bomb and wear and erosion testing. Detailed characterization of the erosion tester substrates before and after firing was obtained by electron microscopy, inductively coupled plasma and x-ray photoelectron spectroscopy. This promising boron nitride additive shows the ability to improve gun wear and erosion resistance without any destabilizing effects to the propellant. Potential applications could include less erosive propellants in propellant ammunition for large, medium and small diameter fire arms.

ICP-MS determination of boron: method optimization during preparation of graphite reference material for boron

International Nuclear Information System (INIS)

Granthali, S.K.; Shailaja, P.P.; Mainsha, V.; Venkatesh, K.; Kallola, K.S.; Sanjukta, A.K.

2017-01-01

Graphite finds widespread use in nuclear reactors as moderator, reflector, and fuel fabricating components because of its thermal stability and integrity. The manufacturing process consists of various mixing, moulding and baking operations followed by heat-treatment between 2500 °C and 3000 °C. The high temperature treatment is required to drive the amorphous carbon-to-graphite phase transformation. Since synthetic graphite is processed at high temperature, impurity concentrations in the precursor carbon get significantly reduced due to volatilization. However boron may might partly gets converted into boron carbide at high temperatures in the carbon environment of graphite and remains stable (B_4C: boiling point 3500 °C) in the matrix. Literature survey reveals the use of various methods for determination of boron. Previously we have developed a method for determination of boron in graphite electrodes using inductively coupled plasma mass spectrometry (ICP-MS). The method involves removal of graphite matrix by ignition of the sample at 800°C in presence of saturated barium hydroxide solution to prevent the loss of boron. Here we are reporting a modification in the method by using calcium carbonate in place of barium hydroxide and using beryllium (Be) as an internal standard, which resulted in a better precession. The method was validated by spike recovery experiments as well as using another technique viz. Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The modified method was applied in evaluation of boron concentration in the graphite reference material prepared

Basic visualization experiments on eutectic reaction of boron carbide and stainless steel under sodium-cooled fast reactor conditions

International Nuclear Information System (INIS)

Yamano, Hidemasa; Suzuki, Tohru; Kamiyama, Kenji; Kudo, Isamu

2016-01-01

This paper describes basic visualization experiments on eutectic reaction and relocation of boron carbide (B 4 C) and stainless steel (SS) under a high temperature condition exceeding 1500degC as well as the importance of such behaviors in molten core during a core disruptive accident in a Generation-IV sodium-cooled fast reactor (750 MWe class) designed in Japan. At first, a reactivity history was calculated using an exact perturbation calculation tool taking into account expected behaviors. This calculation indicated the importance of a relocation behavior of the B 4 C-SS eutectic because its behavior has a large uncertainty in the reactivity history. To clarify this behavior, basic experiments were carried out by visualizing the reaction of a B 4 C pellet contacted with molten SS in a high temperature-heating furnace. The experiments have shown the eutectic reaction visualization as well as freezing and relocation of the B 4 C-SS eutectic in upper part of the solidified test piece due to the density separation. (author)

Anode performance of boron-doped graphites prepared from shot and sponge cokes

Science.gov (United States)

Liu, Tao; Luo, Ruiying; Yoon, Seong-Ho; Mochida, Isao

The structures and anode performances of graphitized pristine and boron-doped shot and sponge cokes have been comparatively studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and galvanostatic measurement. The results show that high degree of graphitization can be obtained by the substituted boron atom in the carbon lattice, and boron in the resultant boron-doped graphites mainly exist in the form of boron carbide and boron substituted in the carbon lattice. Both of boron-doped graphites from shot and sponge cokes obtain discharge capacity of 350 mAh g -1 and coulombic efficiency above 90%. Apart from commonly observed discharge plateau for graphite, boron-doped samples in this study also show a small plateau at ca. 0.06 V. This phenomenon can be explained that Li ion stores in the site to be void-like spaces that are produced by "molecular bridging" between the edge sites of graphene layer stack with a release of boron atoms substituted at the edge of graphene layer. The effect of the amount of boron dopant and graphitization temperature on the anode performance of boron-doped graphite are also investigated in this paper.

The conflicting roles of boron on the radiation response of precipitate-forming austenitic alloys

International Nuclear Information System (INIS)

Okita, T.; Sekimura, N.; Garner, F.

2007-01-01

Full text of publication follows: Boron is often a deliberately added solute to improve the radiation resistance of austenitic structural alloys, with boron exerting its greatest influence on carbide precipitation. However, boron also a source of helium via transmutation and therefore tends to accelerate the onset of void nucleation. These conflicting contributions of boron with respect to radiation resistance are not easily separated, but are sometimes utilized to mimic fusion-relevant gas generation rates when testing in surrogate fission spectra. In an earlier study the authors demonstrated that in simple model ternary alloys that boron additions tended to homogenize swelling somewhat via increased helium generation but not to exert any significant influence on the total swelling. In these easily swelling alloys void nucleation was not significantly influenced by additional helium or by boron's chemical effect, with boron remaining primarily in solution. In the current study, Fe-15Cr-16Ni-0.25 Ti-0.05C alloys with four levels of natural boron addition (0, 100, 500, 2500 appm) were irradiated side-by-side at ∼400 deg. C in the Fast Flux Test Facility under active temperature control in the Materials Open Test Assembly. Although three sets of irradiation conditions were explored, the boron variation was the only variable operating in each data set. The bulk swelling was measured using an immersion density technique and electron microscopy was employed to determine the details of void, dislocation and precipitate microstructure. It was found that by 100 appm B the strongest and most immediate effect of boron was to reduce swelling at all irradiation conditions explored, but the boron-induced increases in overall helium content were rather small over the 0-100 appm B range. This indicates that boron's primary effect was chemical in nature, expressed via its effect on precipitation. As the boron level was progressively increased, however, there was a reversal in

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.

A combination method for simulation of secondary knock-on atoms of boron carbide induced by neutron irradiation in SPRR-300

International Nuclear Information System (INIS)

Wu, Jian-Chun; Feng, Qi-Jie; Liu, Xian-Kun; Zhan, Chang-Yong; Zou, Yu; Liu, Yao-Guang

2016-01-01

A multiscale sequence of simulation should be used to predict properties of materials under irradiation. Binary collision theory and molecular dynamics (MDs) method are commonly used to characterize the displacement cascades induced by neutrons in a material. In order to reduce the clock time spent for the MD simulation of damages induced by high-energy primary knock-on atoms (PKAs), the damage zones were split into sub-cascade according to the sub-cascade formation criteria. Two well-known codes, Geant4 and TRIM, were used to simulate high-energy PKA-induced cascades in B_4C and then produce the secondary knock-on atom (SKA) energy spectrum. It has been found that both high-energy primary knock-on B and C atoms move a long range in the boron carbide. These atoms produce sub-cascades at the tip of trajectory. The energy received by most of the SKAs is <10 keV, which can be used as input to reduce the clock time spent for MD simulation.

Attenuation of Neutron and Gamma Radiation by a Composite Material Based on Modified Titanium Hydride with a Varied Boron Content

Science.gov (United States)

Yastrebinskii, R. N.

2018-04-01

The investigations on estimating the attenuation of capture gamma radiation by a composite neutron-shielding material based on modified titanium hydride and Portland cement with a varied amount of boron carbide are performed. The results of calculations demonstrate that an introduction of boron into this material enables significantly decreasing the thermal neutron flux density and hence the levels of capture gamma radiation. In particular, after introducing 1- 5 wt.% boron carbide into the material, the thermal neutron flux density on a 10 cm-thick layer is reduced by 11 to 176 factors, and the capture gamma dose rate - from 4 to 9 times, respectively. The difference in the degree of reduction in these functionals is attributed to the presence of capture gamma radiation in the epithermal region of the neutron spectrum.

Optical properties of boron carbide near the boron K edge evaluated by soft-x-ray reflectometry from a Ru/B4C multilayer

Energy Technology Data Exchange (ETDEWEB)

Ksenzov, Dmitriy; Panzner, Tobias; Schlemper, Christoph; Morawe, Christian; Pietsch, Ullrich

2009-12-10

Soft-x-ray Bragg reflection from two Ru/B4C multilayers with 10 and 63 periods was used for independent determination of both real and imaginary parts of the refractive index n = 1 -{delta} + i{beta} close to the boron K edge ({approx}188 eV). Prior to soft x-ray measurements, the structural parameters of the multilayers were determined by x-ray reflectometry using hard x rays. For the 63-period sample, the optical properties based on the predictions made for elemental boron major deviations were found close to the K edge of boron for the 10-period sample explained by chemical bonding of boron to B4C and various boron oxides.

Machinability and scratch wear resistance of carbon-coated WC inserts

Energy Technology Data Exchange (ETDEWEB)

Pazhanivel, B., E-mail: palcecri@yahoo.co.in; Kumar, T. Prem; Sozhan, G.

2015-03-15

Highlights: • Cemented WC inserts were coated with carbon by CVD. • The deposits were either loosely held MWCNTs or adherent carbides. • Co-efficient of friction (ramp load; 1–13 N); 0.2 and 0.1 μ, respectively, for the uncoated and carbide-coated inserts. • The carbide-coated insert exhibited better machinability and surface finish than a commercial TiCN-coated insert. - Abstract: In this work, cemented tungsten carbide (WC) inserts were coated with nanocarbons/carbides by chemical vapor deposition (CVD) and their machinability and scratch wear resistance were investigated. The hardness and surface conditions of the WC substrate were studied before and after coating. The CVD-generated nanocarbons on the insert surfaces were examined by SEM, FE-SEM and TEM. The electron microscopic images revealed that the carbons generated were multi-walled carbon nanotubes (MWCNTs) or carbides depending on the experimental conditions. In both the cases, the cutting edges of the inserts had dense deposits. Scratch wear test with the coated inserts showed that the co-efficient of friction was 0.1 μ as against 0.2 μ for the uncoated inserts under a ramp load of 1–13 N. The machinability characteristics of commercially available TiCN-coated inserts and the carbon-coated WC inserts were compared by using a CNC machine and a Rapid I vision inspection system. It was found that the carbide-coated inserts exhibited machinability with better surface finish comparable to that of the TiCN-coated inserts while the MWCNT-coated inserts showed inferior adhesion properties.

Response Surface Design Model to Predict Surface Roughness when Machining Hastelloy C-2000 using Uncoated Carbide Insert

International Nuclear Information System (INIS)

Razak, N H; Rahman, M M; Kadirgama, K

2012-01-01

This paper presents to develop of the response surface design model to predict the surface roughness for end-milling operation of Hastelloy C-2000 using uncoated carbide insert. Mathematical model is developed to study the effect of three input cutting parameters includes the feed rate, axial depth of cut and cutting speed. Design of experiments (DOE) was implemented with the aid of the statistical software package. Analysis of variance (ANOVA) has been performed to verify the fit and adequacy of the developed mathematical model. The result shows that the feed rate gave the more effect on the both prediction values of Ra compared to the cutting speed and axial depth of cut. SEM and EDX analyses were performed in different cutting conditions. It can be concluded that the feed rate and cutting force give the higher impact to influence the machining characteristics of surface roughness. Thus, the optimizing the cutting conditions are essential in order to improve the surface roughness in machining of Hastlelloy C-2000.

Recent developments in turning hardened steels - A review

Science.gov (United States)

Sivaraman, V.; Prakash, S.

2017-05-01

Hard materials ranging from HRC 45 - 68 such as hardened AISI H13, AISI 4340, AISI 52100, D2 STL, D3 STEEL Steel etc., need super hard tool materials to machine. Turning of these hard materials is termed as hard turning. Hard turning makes possible direct machining of the hard materials and also eliminates the lubricant requirement and thus favoring dry machining. Hard turning is a finish turning process and hence conventional grinding is not required. Development of the new advanced super hard tool materials such as ceramic inserts, Cubic Boron Nitride, Polycrystalline Cubic Boron Nitride etc. enabled the turning of these materials. PVD and CVD methods of coating have made easier the production of single and multi layered coated tool inserts. Coatings of TiN, TiAlN, TiC, Al2O3, AlCrN over cemented carbide inserts has lead to the machining of difficult to machine materials. Advancement in the process of hard machining paved way for better surface finish, long tool life, reduced tool wear, cutting force and cutting temperatures. Micro and Nano coated carbide inserts, nanocomposite coated PCBN inserts, micro and nano CBN coated carbide inserts and similar developments have made machining of hardened steels much easier and economical. In this paper, broad literature review on turning of hardened steels including optimizing process parameters, cooling requirements, different tool materials etc., are done.

Influencing factors and kinetics analysis on the leaching of iron from boron carbide waste-scrap with ultrasound-assisted method.

Science.gov (United States)

Li, Xin; Xing, Pengfei; Du, Xinghong; Gao, Shuaibo; Chen, Chen

2017-09-01

In this paper, the ultrasound-assisted leaching of iron from boron carbide waste-scrap was investigated and the optimization of different influencing factors had also been performed. The factors investigated were acid concentration, liquid-solid ratio, leaching temperature, ultrasonic power and frequency. The leaching of iron with conventional method at various temperatures was also performed. The results show the maximum iron leaching ratios are 87.4%, 94.5% for 80min-leaching with conventional method and 50min-leaching with ultrasound assistance, respectively. The leaching of waste-scrap with conventional method fits the chemical reaction-controlled model. The leaching with ultrasound assistance fits chemical reaction-controlled model, diffusion-controlled model for the first stage and second stage, respectively. The assistance of ultrasound can greatly improve the iron leaching ratio, accelerate the leaching rate, shorten leaching time and lower the residual iron, comparing with conventional method. The advantages of ultrasound-assisted leaching were also confirmed by the SEM-EDS analysis and elemental analysis of the raw material and leached solid samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Anode performance of boron-doped graphites prepared from shot and sponge cokes

Energy Technology Data Exchange (ETDEWEB)

Liu, Tao; Luo, Ruiying [School of Science, Beihang University, Beijing 100083 (China); Yoon, Seong-Ho; Mochida, Isao [Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)

2010-03-15

The structures and anode performances of graphitized pristine and boron-doped shot and sponge cokes have been comparatively studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and galvanostatic measurement. The results show that high degree of graphitization can be obtained by the substituted boron atom in the carbon lattice, and boron in the resultant boron-doped graphites mainly exist in the form of boron carbide and boron substituted in the carbon lattice. Both of boron-doped graphites from shot and sponge cokes obtain discharge capacity of 350 mAh g{sup -1} and coulombic efficiency above 90%. Apart from commonly observed discharge plateau for graphite, boron-doped samples in this study also show a small plateau at ca. 0.06 V. This phenomenon can be explained that Li ion stores in the site to be void-like spaces that are produced by ''molecular bridging'' between the edge sites of graphene layer stack with a release of boron atoms substituted at the edge of graphene layer. The effect of the amount of boron dopant and graphitization temperature on the anode performance of boron-doped graphite are also investigated in this paper. (author)

Polyethylene/boron-containing composites for radiation shielding

Energy Technology Data Exchange (ETDEWEB)

Shin, Ji Wook [Center for Materials Architecturing, Institute for Multi-Disciplinary Convergence of Materials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Department of Chemical and Biological Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Lee, Jang-Woo; Yu, Seunggun; Baek, Bum Ki; Hong, Jun Pyo [Center for Materials Architecturing, Institute for Multi-Disciplinary Convergence of Materials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Seo, Yongsok [School of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kim, Woo Nyon [Department of Chemical and Biological Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Hong, Soon Man, E-mail: smhong@kist.re.kr [Center for Materials Architecturing, Institute for Multi-Disciplinary Convergence of Materials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Koo, Chong Min, E-mail: koo@kist.re.kr [Center for Materials Architecturing, Institute for Multi-Disciplinary Convergence of Materials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of)

2014-06-01

Graphical abstract: - Highlights: • HDPE/silane-treated boron nitride (mBN) composites were fabricated. • The HDPE/mBN composites revealed a strong adhesion behavior at the interface of matrix/filler. • The HDPE/mBN composites show superior radiation shielding, thermoconductive and mechanical properties to the composites containing pristine BN and B{sub 4}C fillers. - Abstract: High-density polyethylene (HDPE) composites with modified boron nitride (mBN) fillers, functionalized with an organosilane, were fabricated through conventional melt-extrusion processing techniques. The properties and performances of these composites were compared with those of the composites containing pristine BN and boron carbide (B{sub 4}C) fillers. The silane functionalization of the BN fillers strongly improved the interfacial adhesion between the polymer matrix and the filler. As a result, the HDPE/mBN composites showed a better dispersion state of the filler particles, larger tensile modulus, greater effective thermal conductivity, and better neutron shielding property compared with the HDPE/BN and HDPE/B{sub 4}C composites.

Polyethylene/boron-containing composites for radiation shielding

International Nuclear Information System (INIS)

Shin, Ji Wook; Lee, Jang-Woo; Yu, Seunggun; Baek, Bum Ki; Hong, Jun Pyo; Seo, Yongsok; Kim, Woo Nyon; Hong, Soon Man; Koo, Chong Min

2014-01-01

Graphical abstract: - Highlights: • HDPE/silane-treated boron nitride (mBN) composites were fabricated. • The HDPE/mBN composites revealed a strong adhesion behavior at the interface of matrix/filler. • The HDPE/mBN composites show superior radiation shielding, thermoconductive and mechanical properties to the composites containing pristine BN and B 4 C fillers. - Abstract: High-density polyethylene (HDPE) composites with modified boron nitride (mBN) fillers, functionalized with an organosilane, were fabricated through conventional melt-extrusion processing techniques. The properties and performances of these composites were compared with those of the composites containing pristine BN and boron carbide (B 4 C) fillers. The silane functionalization of the BN fillers strongly improved the interfacial adhesion between the polymer matrix and the filler. As a result, the HDPE/mBN composites showed a better dispersion state of the filler particles, larger tensile modulus, greater effective thermal conductivity, and better neutron shielding property compared with the HDPE/BN and HDPE/B 4 C composites

Structure and photoluminescence of boron and nitrogen co-doped carbon nanorods

Energy Technology Data Exchange (ETDEWEB)

Wang, B.B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Gao, B. [College of Computer Science, Chongqing University, Chongqing 400044 (China); Chongqing Municipal Education Examinations Authority, Chongqing 401147 (China); Zhong, X.X., E-mail: xxzhong@sjtu.edu.cn [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Shao, R.W.; Zheng, K. [Institute of Microstructure and Properties of Advanced Materials, Beijing University of Technology, Beijing 100124 (China)

2016-07-15

Graphical abstract: Boron- and nitrogen- doped carbon nanorods. - Highlights: • The co-doping of nitrogen and boron in carbon nanorods. • The doping mechanism of nitrogen and boron in carbon nanorods by plasma. • Photoluminescence properties of nitrogen- and boron-doped carbon nanorods. - Abstract: Boron and nitrogen doped carbon nanorods (BNCNRs) were synthesized by plasma-enhanced hot filament chemical vapor deposition, where methane, nitrogen and hydrogen were used as the reaction gases and boron carbide was the boron source. The results of scanning electron microscopy, micro-Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy indicate that boron and nitrogen can be used as co-dopants in amorphous carbon nanorods. Combined with the characterization results, the doping mechanism was studied. The mechanism is used to explain the formation of different carbon materials by different methods. The photoluminescence (PL) properties of BNCNRs were studied. The PL results show that the BNCNRs generate strong green PL bands and weak blue PL bands, and the PL intensity lowered due to the doping of boron. The outcomes advance our knowledge on the synthesis and optical properties of carbon-based nanomaterials and contribute to the development of optoelectronic nanodevices based on nano-carbon mateirals.

Tantalum and niobium carbides obtention by carbothermic reduction of columbotantalite ores

International Nuclear Information System (INIS)

Gordo, E.; Garcia-Carcedo, F.; Torralba, J.M.

1998-01-01

Tantalum and niobium carbides are characterized by its high hardness and chemical corrosion resistance. Both carbides, but mainly TaC, are used in hard metals (sintered carbides), together with their carbides, to manufacture cutting tools and dies in special machining applications involving mechanical shock at high temperature. Its use as reinforcement of wear resistant materials through powder metallurgy techniques are being investigated. However, the use of TaC is usually limited because of its high cost. Therefore tantalum carbide with niobium content, which is cheaper, is used. In this work the obtention of complex tantalum and niobium carbides from a Spanish columbotantalite ore is studied through relatively cheap and simple process as it is carbothermic reduction. Concentration of the ore, its reduction and the characterization of products are described. (Author) 11 refs

Iron Carbides and Nitrides: Ancient Materials with Novel Prospects.

Science.gov (United States)

Ye, Zhantong; Zhang, Peng; Lei, Xiang; Wang, Xiaobai; Zhao, Nan; Yang, Hua

2018-02-07

Iron carbides and nitrides have aroused great interest in researchers, due to their excellent magnetic properties, good machinability and the particular catalytic activity. Based on these advantages, iron carbides and nitrides can be applied in various areas such as magnetic materials, biomedical, photo- and electrocatalysis. In contrast to their simple elemental composition, the synthesis of iron carbides and nitrides still has great challenges, particularly at the nanoscale, but it is usually beneficial to improve performance in corresponding applications. In this review, we introduce the investigations about iron carbides and nitrides, concerning their structure, synthesis strategy and various applications from magnetism to the catalysis. Furthermore, the future prospects are also discussed briefly. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Morphology study of refractory carbide powders

International Nuclear Information System (INIS)

Vavrda, J.; Blazhikova, Ya.

1982-01-01

Refractory carbides were investigated using JSM-U3 electron microscope of Joelco company at 27 KV accelerating voltage. Some photographs of each powder were taken with different enlargements to characterise the sample upon the whole. It was shown that morphological and especially topographic study of powders enables to learn their past history (way of fabrication and treatment). The presence of steps of compact particle fractures and cracks is accompanied by occurence of fine dispersion of carbides subjected to machining after facrication. On the contrary, the character of crystallographic surfaces and features of surface growth testify to the way of crystallization

Nanocomposites for Machining Tools

DEFF Research Database (Denmark)

Sidorenko, Daria; Loginov, Pavel; Mishnaevsky, Leon

2017-01-01

Machining tools are used in many areas of production. To a considerable extent, the performance characteristics of the tools determine the quality and cost of obtained products. The main materials used for producing machining tools are steel, cemented carbides, ceramics and superhard materials...

Sintering of beryllium oxide with 3-4 per cent elemental boron; Frittage de l'oxyde de beryllium a 3 et 5 pour cent de bore element

Energy Technology Data Exchange (ETDEWEB)

Pointud, R; Rispal, Ch; Le Garec, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

In order to manufacture a baffle absorbing neutrons of various energies, there was developed or mixture of a slower and an absorber. It is made by hot pressing impure beryllium containing boron carbide. The dense briquette has 100 x 100 x 50 mm and is machined on all her faces. She is of 2,85 density and about 3 to 4 per cent porosity, according to 5 per cent of boron. Difference of boron amount is lower than ten per cent between any two points of the briquette. (author) [French] Pour fabriquer un ecran absorbeur des neutrons d'energies diverses, on a realise l'association d'un element ralentisseur, Ie beryllium, et d'un element absorbant, le bore, par frittage sous charge d'une poudre mixte contenant de l'oxyde de beryllium technique et du carbure de bore technique. Le comprime obtenu est une brique de 100 x 100 x 50 mm, usinee sur toutes sur toutes surfaces, d'une densite de 2,85, porosite d'environ 3 a 4 pour cent pour une teneur en bore de 5 pour cent. L'heterogeneite en bore entre les differents points de cette brique est inferieure a 10 pour cent. (auteur)

Crack propagation and fracture in silicon carbide

International Nuclear Information System (INIS)

Evans, A.G.; Lange, F.F.

1975-01-01

Fracture mechanics and strength studies performed on two silicon carbides - a hot-pressed material (with alumina) and a sintered material (with boron) - have shown that both materials exhibit slow crack growth at room temperature in water, but only the hot-pressed material exhibits significant high temperature slow crack growth (1000 to 1400 0 C). A good correlation of the observed fracture behaviour with the crack growth predicted from the fracture mechanics parameters shows that effective failure predictions for this material can be achieved using macro-fracture mechanics data. (author)

Versatile Boron Carbide-Based Visual Obscurant Compositions for Smoke Munitions

Science.gov (United States)

2015-04-17

volatilize and disperse reaction products and inert diluents. Unlike the refractory oxides of common pyrotechnic fuels such as magnesium and aluminum, boron...peaks marked. [1] Akagi, R.; Ohtori, N.; Umesaki, N. Raman spectra of K2O–B2O3 glasses and melts. Journal of Non-Crystalline Solids. 2001

Standard specification for boron-Based neutron absorbing material systems for use in nuclear spent fuel storage racks

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

1.1 This specification defines criteria for boron-based neutron absorbing material systems used in racks in a pool environment for storage of nuclear light water reactor (LWR) spent-fuel assemblies or disassembled components to maintain sub-criticality in the storage rack system. 1.2 Boron-based neutron absorbing material systems normally consist of metallic boron or a chemical compound containing boron (for example, boron carbide, B4C) supported by a matrix of aluminum, steel, or other materials. 1.3 In a boron-based absorber, neutron absorption occurs primarily by the boron-10 isotope that is present in natural boron to the extent of 18.3 ± 0.2 % by weight (depending upon the geological origin of the boron). Boron, enriched in boron-10 could also be used. 1.4 The materials systems described herein shall be functional – that is always be capable to maintain a B10 areal density such that subcriticality Keff <0.95 or Keff <0.98 or Keff < 1.0 depending on the design specification for the service...

Effect of boron nitride coating on fiber-matrix interactions

International Nuclear Information System (INIS)

Singh, R.N.; Brun, M.K.

1987-01-01

Coatings can modify fiber-matrix reactions and consequently interfacial bond strengths. Commercially available mullite, silicon carbide, and carbon fibers were coated with boron nitride via low pressure chemical vapor deposition and incorporated into a mullite matrix by hot-pressing. The influence of fiber-matrix interactions for uncoated fibers on fracture morphologies was studied. These observations are related to the measured values of interfacial shear strengths

Silicon carbide layer structure recovery after ion implantation

International Nuclear Information System (INIS)

Violin, Eh.E.; Demakov, K.D.; Kal'nin, A.A.; Nojbert, F.; Potapov, E.N.; Tairov, Yu.M.

1984-01-01

The process of recovery of polytype structure of SiC surface layers in the course of thermal annealing (TA) and laser annealing (LA) upon boron and aluminium implantation is studied. The 6H polytype silicon carbide C face (0001) has been exposed to ion radiation. The ion energies ranged from 80 to 100 keV, doses varied from 5x10 14 to 5x10 16 cm -2 . TA was performed in the 800-2000 K temperature range. It is shown that the recovery of the structure of silicon carbide layers after ion implantation takes place in several stages. Considerable effect on the structure of the annealed layers is exerted by the implantation dose and the type of implanted impurity. The recovery of polytype structure is possible only under the effect of laser pulses with duration not less than the time for the ordering of the polytype in question

Application of in situ current normalized PIGE method for determination of total boron and its isotopic composition

International Nuclear Information System (INIS)

Chhillar, Sumit; Acharya, R.; Sodaye, S.; Pujari, P.K.

2014-01-01

A particle induced gamma-ray emission (PIGE) method using proton beam has been standardized for determination of isotopic composition of natural boron and enriched boron samples. Target pellets of boron standard and samples were prepared in cellulose matrix. The prompt gamma rays of 429 keV, 718 keV and 2125 keV were measured from 10 B(p,αγ) 7 Be, 10 B(p, p'γ) 10 B and 11 B(p, p'γ) 11 B nuclear reactions, respectively. For normalizing the beam current variations in situ current normalization method was used. Validation of method was carried out using synthetic samples of boron carbide, borax, borazine and lithium metaborate in cellulose matrix. (author)

Pilot production of 325 kg of uranium carbide

International Nuclear Information System (INIS)

Clozet, C.; Dessus, J.; Devillard, J.; Guibert, M.; Morlot, G.

1969-01-01

This report describes the pilot fabrication of uranium carbide rods to be mounted in bundles and assayed in two channels of the EL 4 reactor. The fabrication process includes: - elaboration of uranium carbide granules by carbothermic reduction of uranium dioxide; - electron bombardment melting and continuous casting of the granules; - machining of the raw ingots into rods of the required dimensions; finally, the rods will be piled-up to make the fuel elements. Both qualitative and quantitative results of this pilot production chain are presented and discussed. (authors) [fr

The Effect of Boron and Zirconium on the Structure and Tensile Properties of the Cast Nickel-Based Superalloy ATI 718Plus

Science.gov (United States)

Hosseini, Seyed Ali; Abbasi, Seyed Mehdi; Madar, Karim Zangeneh

2018-04-01

The effects of boron and zirconium on cast structure, hardness, and tensile properties of the nickel-based superalloy 718Plus were investigated. For this purpose, five alloys with different contents of boron and zirconium were cast via vacuum induction melting and then purified via vacuum arc remelting. Microstructural analysis by light-optical microscope and scanning electron microscope equipped with energy-dispersive x-ray spectroscopy and phase studies by x-ray diffraction analysis were performed. The results showed that boron and zirconium tend to significantly reduce dendritic arm spacing and increase the amount of Laves, Laves/gamma eutectic, and carbide phases. It was also found that boron led to the formation of B4C and (Cr, Fe, Mo, Ni, Ti)3B2 phases and zirconium led to the formation of intermetallic phases and ZrC carbide. In the presence of boron and zirconium, the hardness and its difference between dendritic branches and inter-dendritic spaces increased by concentrating such phases as Laves in the inter-dendritic spaces. These elements had a negative effect on tensile properties of the alloy, including ductility and strength, mainly because of the increase in the Laves phase. It should be noted that the largest degradation of the tensile properties occurred in the alloys containing the maximum amount of zirconium.

Boronization and Carburization of Superplastic Stainless Steel and Titanium-Based Alloys

Directory of Open Access Journals (Sweden)

Masafumi Matsushita

2011-07-01

Full Text Available Bronization and carburization of fine-grain superplastic stainless steel is reviewed, and new experimental results for fine grain Ti88.5Al4.5V3Fe2Mo2 are reported. In superplastic duplex stainless steel, the diffusion of carbon and boron is faster than in non-superplastic duplex stainless steel. Further, diffusion is activated by uniaxial compressive stress. Moreover, non-superplastic duplex stainless steel shows typical grain boundary diffusion; however, inner grain diffusion is confirmed in superplastic stainless steel. The presence of Fe and Cr carbides or borides is confirmed by X-ray diffraction, which indicates that the diffused carbon and boron react with the Fe and Cr in superplastic stainless steel. The Vickers hardness of the carburized and boronized layers is similar to that achieved with other surface treatments such as electro-deposition. Diffusion of boron into the superplastic Ti88.5Al4.5V3Fe2Mo2 alloy was investigated. The hardness of the surface exposed to boron powder can be increased by annealing above the superplastic temperature. However, the Vickers hardness is lower than that of Ti boride.

Sintering of beryllium oxide with 3-4 per cent elemental boron; Frittage de l'oxyde de beryllium a 3 et 5 pour cent de bore element

Energy Technology Data Exchange (ETDEWEB)

Pointud, R.; Rispal, Ch.; Le Garec, M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

In order to manufacture a baffle absorbing neutrons of various energies, there was developed or mixture of a slower and an absorber. It is made by hot pressing impure beryllium containing boron carbide. The dense briquette has 100 x 100 x 50 mm and is machined on all her faces. She is of 2,85 density and about 3 to 4 per cent porosity, according to 5 per cent of boron. Difference of boron amount is lower than ten per cent between any two points of the briquette. (author) [French] Pour fabriquer un ecran absorbeur des neutrons d'energies diverses, on a realise l'association d'un element ralentisseur, Ie beryllium, et d'un element absorbant, le bore, par frittage sous charge d'une poudre mixte contenant de l'oxyde de beryllium technique et du carbure de bore technique. Le comprime obtenu est une brique de 100 x 100 x 50 mm, usinee sur toutes sur toutes surfaces, d'une densite de 2,85, porosite d'environ 3 a 4 pour cent pour une teneur en bore de 5 pour cent. L'heterogeneite en bore entre les differents points de cette brique est inferieure a 10 pour cent. (auteur)

Optimization of Gas Composition Used in Plasma Chemical Vaporization Machining for Figuring of Reaction-Sintered Silicon Carbide with Low Surface Roughness.

Science.gov (United States)

Sun, Rongyan; Yang, Xu; Ohkubo, Yuji; Endo, Katsuyoshi; Yamamura, Kazuya

2018-02-05

In recent years, reaction-sintered silicon carbide (RS-SiC) has been of interest in many engineering fields because of its excellent properties, such as its light weight, high rigidity, high heat conductance and low coefficient of thermal expansion. However, RS-SiC is difficult to machine owing to its high hardness and chemical inertness and because it contains multiple components. To overcome the problem of the poor machinability of RS-SiC in conventional machining, the application of atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) to RS-SiC was proposed. As a highly efficient and damage-free figuring technique, AP-PCVM has been widely applied for the figuring of single-component materials, such as Si, SiC, quartz crystal wafers, and so forth. However, it has not been applied to RS-SiC since it is composed of multiple components. In this study, we investigated the AP-PCVM etching characteristics for RS-SiC by optimizing the gas composition. It was found that the different etching rates of the different components led to a large surface roughness. A smooth surface was obtained by applying the optimum gas composition, for which the etching rate of the Si component was equal to that of the SiC component.

Additive-assisted synthesis of boride, carbide, and nitride micro/nanocrystals

International Nuclear Information System (INIS)

Chen, Bo; Yang, Lishan; Heng, Hua; Chen, Jingzhong; Zhang, Linfei; Xu, Liqiang; Qian, Yitai; Yang, Jian

2012-01-01

General and simple methods for the syntheses of borides, carbides and nitrides are highly desirable, since those materials have unique physical properties and promising applications. Here, a series of boride (TiB 2 , ZrB 2 , NbB 2 , CeB 6 , PrB 6 , SmB 6 , EuB 6 , LaB 6 ), carbide (SiC, TiC, NbC, WC) and nitride (TiN, BN, AlN, MgSiN 2 , VN) micro/nanocrystals were prepared from related oxides and amorphous boron/active carbon/NaN 3 with the assistance of metallic Na and elemental S. In-situ temperature monitoring showed that the reaction temperature could increase quickly to ∼850 °C, once the autoclave was heated to 100 °C. Such a rapid temperature increase was attributed to the intense exothermic reaction between Na and S, which assisted the formation of borides, carbides and nitrides. The as-obtained products were characterized by XRD, SEM, TEM, and HRTEM techniques. Results in this report will greatly benefit the future extension of this approach to other compounds. - Graphical abstract: An additive-assisted approach is successfully developed for the syntheses of borides, carbides and nitrides micro/nanocrystals with the assistance of the exothermic reaction between Na and S. Highlights: ► An additive-assisted synthesis strategy is developed for a number of borides, carbides and nitrides. ► The reaction mechanism is demonstrated by the case of SiC nanowires. ► The formation of SiC nanowires is initiated by the exothermic reaction of Na and S.

Auger electron spectroscopy studies of boron carbide

International Nuclear Information System (INIS)

Madden, H.H.; Nelson, G.C.; Wallace, W.O.

1986-01-01

Auger electron spectroscopy has been used to probe the electronic structure of ion bombardment (IB) cleaned surfaces of B 9 C and B 4 C samples. The shapes of the B-KVV and C-KVV Auger lines were found to be relatively insensitive to the bulk stoichiometry of the samples. This indicates that the local chemical environments surrounding B and C atoms, respectively, on the surfaces of the IB cleaned samples do not change appreciably in going from B 9 C to B 4 C. Fracturing the sample in situ is a way of producing a clean representative internal surface to compare with the IB surfaces. Microbeam techniques have been used to study a fracture surface of the B 9 C material with greater spatial resolution than in our studies of IB surfaces. The B 9 C fracture surface was not homogeneous and contained both C-rich and B-rich regions. The C-KVV line for the C-rich regions was graphitic in shape. Much of the C-rich regions was found by IB to be less than 100 nm in thickness. The C-KVV line from the B-rich regions was carbidic and did not differ appreciably in shape from those recorded for the IB cleaned surfaces

Study of PVD AlCrN Coating for Reducing Carbide Cutting Tool Deterioration in the Machining of Titanium Alloys.

Science.gov (United States)

Cadena, Natalia L; Cue-Sampedro, Rodrigo; Siller, Héctor R; Arizmendi-Morquecho, Ana M; Rivera-Solorio, Carlos I; Di-Nardo, Santiago

2013-05-24

The manufacture of medical and aerospace components made of titanium alloys and other difficult-to-cut materials requires the parallel development of high performance cutting tools coated with materials capable of enhanced tribological and resistance properties. In this matter, a thin nanocomposite film made out of AlCrN (aluminum-chromium-nitride) was studied in this research, showing experimental work in the deposition process and its characterization. A heat-treated monolayer coating, competitive with other coatings in the machining of titanium alloys, was analyzed. Different analysis and characterizations were performed on the manufactured coating by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDXS), and X-ray diffraction (XRD). Furthermore, the mechanical behavior of the coating was evaluated through hardness test and tribology with pin-on-disk to quantify friction coefficient and wear rate. Finally, machinability tests using coated tungsten carbide cutting tools were executed in order to determine its performance through wear resistance, which is a key issue of cutting tools in high-end cutting at elevated temperatures. It was demonstrated that the specimen (with lower friction coefficient than previous research) is more efficient in machinability tests in Ti6Al4V alloys. Furthermore, the heat-treated monolayer coating presented better performance in comparison with a conventional monolayer of AlCrN coating.

Tool life of the edges coated with the c-BN+h-BN coatings with different structures during hard machinable steel machining

Directory of Open Access Journals (Sweden)

Kupczyk, M.

2005-12-01

Full Text Available In the presented paper the experimental results concerning the functional quality (durability during steel machining of thin, superhard coatings produced on the cutting edges are described. Differences among mentioned properties of coatings mainly result from a coating structure. But the structure of coatings results from deposition parameters Superhard boron nitride coatings were deposited on insert cutting edges made of cemented carbides by the pulse-plasma method applying different values of the discharge voltage. The comparative investigations of mentioned coatings have been concerned of tool life of edges during hard machinable material machining (nitriding steel hardened in oil. In these investigations for the purpose of additional increase of coatings adhesion to substrates an interfacial layers were applied.

En este trabajo se describen los resultados experimentales referentes a la calidad funcional (durabilidad durante el mecanizado del acero de recubrimientos delgados, de elevada dureza del filo de corte. Las diferencias en las propiedades de los recubrimientos se deben, principalmente, a la estructura del recubrimiento. No obstante, la estructura del recubrimiento está relacionada con los parámetros de la deposición. Recubrimientos de nitruro de boro de elevada dureza se depositaron sobre filos de corte insertados, fabricados con carburos cementados mediante el método de pulsos de plasma aplicando diferentes valores de voltaje de descarga. Las investigaciones comparativas de los mencionados recubrimientos han relacionado la vida del filo de la herramienta durante el mecanizado del material (acero nitrurado endurecido en aceite. En estas investigaciones se aplicaron capas interfaciales para aumentar la adherencia del recubrimiento.

Aqueous cutting fluid for machining fissionable materials

Science.gov (United States)

Duerksen, Walter K.; Googin, John M.; Napier, Jr., Bradley

1984-01-01

The present invention is directed to a cutting fluid for machining fissionable material. The cutting fluid is formed of glycol, water and boron compound in an adequate concentration for effective neutron attenuation so as to inhibit criticality incidents during machining.

Nanocomposites for Machining Tools

Directory of Open Access Journals (Sweden)

Daria Sidorenko

2017-10-01

Full Text Available Machining tools are used in many areas of production. To a considerable extent, the performance characteristics of the tools determine the quality and cost of obtained products. The main materials used for producing machining tools are steel, cemented carbides, ceramics and superhard materials. A promising way to improve the performance characteristics of these materials is to design new nanocomposites based on them. The application of micromechanical modeling during the elaboration of composite materials for machining tools can reduce the financial and time costs for development of new tools, with enhanced performance. This article reviews the main groups of nanocomposites for machining tools and their performance.

Precision machining commercialization

International Nuclear Information System (INIS)

1978-01-01

To accelerate precision machining development so as to realize more of the potential savings within the next few years of known Department of Defense (DOD) part procurement, the Air Force Materials Laboratory (AFML) is sponsoring the Precision Machining Commercialization Project (PMC). PMC is part of the Tri-Service Precision Machine Tool Program of the DOD Manufacturing Technology Five-Year Plan. The technical resources supporting PMC are provided under sponsorship of the Department of Energy (DOE). The goal of PMC is to minimize precision machining development time and cost risk for interested vendors. PMC will do this by making available the high precision machining technology as developed in two DOE contractor facilities, the Lawrence Livermore Laboratory of the University of California and the Union Carbide Corporation, Nuclear Division, Y-12 Plant, at Oak Ridge, Tennessee

Doping of silicon carbide by ion implantation

International Nuclear Information System (INIS)

Gimbert, J.

1999-01-01

It appeared that in some fields, as the hostile environments (high temperature or irradiation), the silicon compounds showed limitations resulting from the electrical and mechanical properties. Doping of 4H and 6H silicon carbide by ion implantation is studied from a physicochemical and electrical point of view. It is necessary to obtain n-type and p-type material to realize high power and/or high frequency devices, such as MESFETs and Schottky diodes. First, physical and electrical properties of silicon carbide are presented and the interest of developing a process technology on this material is emphasised. Then, physical characteristics of ion implantation and particularly classical dopant implantation, such as nitrogen, for n-type doping, and aluminium and boron, for p-type doping are described. Results with these dopants are presented and analysed. Optimal conditions are extracted from these experiences so as to obtain a good crystal quality and a surface state allowing device fabrication. Electrical conduction is then described in the 4H and 6H-SiC polytypes. Freezing of free carriers and scattering processes are described. Electrical measurements are carried out using Hall effect on Van der Panw test patterns, and 4 point probe method are used to draw the type of the material, free carrier concentrations, resistivity and mobility of the implanted doped layers. These results are commented and compared to the theoretical analysis. The influence of the technological process on electrical conduction is studied in view of fabricating implanted silicon carbide devices. (author)

The influence of Boron on creep-rupture behaviour of austenitic unstabilized and Nb-stabilized stainless steel X8CrNi 1613 in unirradiated and irradiated condition

International Nuclear Information System (INIS)

Sen, Susant Kumar.

1976-10-01

The present study deals with influence of boron on creep-rupture behaviour in unirradiated condition at 650 0 C along with precipitation behaviour, heat-treatment and recrystallization of unstabilized and stabilized steel. The results of creep-rupture tests on unirradiated specimens show that boron exerts a beneficial effect on the rupture life and ductility. Boron losses its beneficial effect on creep properties in unstabilized steel by prolong creeping. The magnitude of beneficial effect of Boron on creep properties depends upon the initial boron distribution which influences the number, size and distribution of the precipitates. Boron promotes the precipitation of type M 23 C 6 Carbides in the grain as well as at the grain boundary. Boron segregates in atomic form during slow cooling from austenitizing temperature. The recrystallization will be delayed by the presence of boron. The results of creep tests at 650 0 C shows that boron exerts a beneficial effect on creep life of irradiated steels. (orig./GSC) [de

Some problems connected with boron determination by atomic absorption spectroscopy and the sensitivity improvement

Directory of Open Access Journals (Sweden)

JELENA J. SAVOVIC

2001-08-01

Full Text Available Two atomizers were compared: an N2O–C2H2 flame and a stabilized U-shaped DC arc with aerosol supply. Both the high plasma temperature and the reducing atmosphere obtained by acetylene addition to the argon stream substantially increase the sensitivity of boron determination by atomic absorption spectroscopy (AAS when the arc atomizer is used. The results were compared with those for silicon as a control element. The experimental characteristic concentrations for both elements were compared with the computed values. The experimentally obtained characteristic concentration for boron when using the arc atomizer was in better agreement with the calculated value. It was estimated that the influence of stable monoxide formation on the sensitivity for both elements was about the same, but reduction of analyte and formation of non-volatile carbide particles was more important for boron, which is the main reason for the low sensitivity of boron determination using a flame atomizer. The use of an arc atomizer suppresses this interference and significantly improves the sensitivity of the determination.

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.

Effect of laser pulsed radiation on the properties of implanted layers of silicon carbide

International Nuclear Information System (INIS)

Violin, Eh.E.; Voron'ko, O.N.; Nojbert, F.; Potapov, E.N.

1984-01-01

Results are presented of investigation into pulsed laser radiation effects on the layers of GH polytype silicon carbide converted to amorphous state by implantation of boron and aluminium ions. The implantation doses were selected to be 5x10 16 for boron and 5x10 15 cm -2 for aluminium, with the ion energies being 60 and 80 keV, respectively. The samples annealed under nanosecond regime are stated to posseys neither photoluminescence (PL) nor cathodoluminescence (CL). At the same time the layers annealed in millisecond regime have a weak PL at 100 K and CL at 300 K. The PL and CL are observed in samples, laser-annealed at radiation energy density above 150-160 J/cm 2 in case of boron ion implantation and 100-120 J/cm 2 in case of aluminium ion implantation. Increasing the radiation energy density under the nanosecond regime of laser annealing results in the surface evaporation due to superheating of amorphous layers. Increasing the energy density above 220-240 J/cm 2 results in destruction of the samples

TEM Studies of Boron-Modified 17Cr-7Ni Precipitation-Hardenable Stainless Steel via Rapid Solidification Route

Science.gov (United States)

Gupta, Ankur; Bhargava, A. K.; Tewari, R.; Tiwari, A. N.

2013-09-01

Commercial grade 17Cr-7Ni precipitation-hardenable stainless steel has been modified by adding boron in the range 0.45 to 1.8 wt pct and using the chill block melt-spinning technique of rapid solidification (RS). Application of RS has been found to increase the solid solubility of boron and hardness of 17Cr-7Ni precipitation-hardenable stainless steel. The hardness of the boron-modified rapidly solidified alloys has been found to increase up to ~280 pct after isochronal aging to peak hardness. A TEM study has been carried out to understand the aging behavior. The presence of M23(B,C)6 and M2(B,C) borocarbides and epsilon-carbide in the matrix of austenite and ferrite with a change in heat treatment temperature has been observed. A new equation for Creq is also developed which includes the boron factor on ferrite phase stability. The study also emphasizes that aluminum only takes part in ferrite phase stabilization and remains in the solution.

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.

Benefits of Low Boron Core Design Concept for PWR

Energy Technology Data Exchange (ETDEWEB)

Daing, Aung Tharn; Kim, Myung Hyun [Kyung Hee University, Yongin (Korea, Republic of)

2009-10-15

Nuclear design study was carried out to develop low boron core (LBC) based on one of current PWR concepts, OPR-1000. Most of design parameters were the same with those of Ulchin unit-5 except extensive utilization of burnable poison (BP) pins in order to compensate reactivity increase in LBC. For replacement of reduced soluble boron concentration, four different kinds of integral burnable absorbers (IBAs) such as gadolinia, integral fuel burnable absorber (IFBA), erbia and alumina boron carbide were considered in suppressing more excess reactivity. A parametric study was done to find the optimal core options from many design candidates for fuel assemblies and cores. Among them, the most feasible core design candidate was chosen in accordance with general design requirements. In this paper, the feasibility and design change benefits of the most favorable LBC design were investigated in more detail through the comparison of neutronic and thermal hydraulic design parameters of LBC with the reference plant (REF). As calculation tools, the HELIOS/MASTER code package and the MATRA code were utilized. The main purpose of research herein is to estimate feasibility and capability of LBC which was mainly designed to mitigate boron dilution accident (BDA), and for reduction of corrosion products. The LBC design concept using lower boron concentration with an elevated enrichment in {sup 10}B allows a reduction in the concentration of lithium in the primary coolant required to maintain the optimum coolant pH. All in all, LBC with operation at optimum pH is expected to achieve some benefits from radiation source reduction of reduced corrosion product, the limitation of the Axial Offset Anomaly (AOA) and fuel cladding corrosion. Additionally, several merits of LBC are closely related to fluid systems and system related aspects, reduced boron and lithium costs, equipment size reduction for boric acid systems, elimination of heat tracing, and more aggressive fuel design concepts.

Benefits of Low Boron Core Design Concept for PWR

International Nuclear Information System (INIS)

Daing, Aung Tharn; Kim, Myung Hyun

2009-01-01

Nuclear design study was carried out to develop low boron core (LBC) based on one of current PWR concepts, OPR-1000. Most of design parameters were the same with those of Ulchin unit-5 except extensive utilization of burnable poison (BP) pins in order to compensate reactivity increase in LBC. For replacement of reduced soluble boron concentration, four different kinds of integral burnable absorbers (IBAs) such as gadolinia, integral fuel burnable absorber (IFBA), erbia and alumina boron carbide were considered in suppressing more excess reactivity. A parametric study was done to find the optimal core options from many design candidates for fuel assemblies and cores. Among them, the most feasible core design candidate was chosen in accordance with general design requirements. In this paper, the feasibility and design change benefits of the most favorable LBC design were investigated in more detail through the comparison of neutronic and thermal hydraulic design parameters of LBC with the reference plant (REF). As calculation tools, the HELIOS/MASTER code package and the MATRA code were utilized. The main purpose of research herein is to estimate feasibility and capability of LBC which was mainly designed to mitigate boron dilution accident (BDA), and for reduction of corrosion products. The LBC design concept using lower boron concentration with an elevated enrichment in 10 B allows a reduction in the concentration of lithium in the primary coolant required to maintain the optimum coolant pH. All in all, LBC with operation at optimum pH is expected to achieve some benefits from radiation source reduction of reduced corrosion product, the limitation of the Axial Offset Anomaly (AOA) and fuel cladding corrosion. Additionally, several merits of LBC are closely related to fluid systems and system related aspects, reduced boron and lithium costs, equipment size reduction for boric acid systems, elimination of heat tracing, and more aggressive fuel design concepts

The morphology of ceramic phases in B x C-SiC-Si infiltrated composites

International Nuclear Information System (INIS)

Hayun, S.; Frage, N.; Dariel, M.P.

2006-01-01

The present communication is concerned with the effect of the carbon source on the morphology of reaction bonded boron carbide (B 4 C). Molten silicon reacts strongly and rapidly with free carbon to form large, faceted, regular polygon-shaped SiC particles, usually embedded in residual silicon pools. In the absence of free carbon, the formation of SiC relies on carbon that originates from within the boron carbide particles. Examination of the reaction bonded boron carbide revealed a core-rim microstructure consisting of boron carbide particles surrounded by secondary boron carbide containing some dissolved silicon. This microstructure is generated as the outcome of a dissolution-precipitation process. In the course of the infiltration process molten Si dissolves some boron carbide until its saturation with B and C. Subsequently, precipitation of secondary boron carbide enriched with boron and silicon takes place. In parallel, elongated, strongly twinned, faceted SiC particles are generated by rapid growth along preferred crystallographic directions. This sequence of events is supported by X-ray diffraction and microcompositional analysis and well accounted for by the thermodynamic analysis of the ternary B-C-Si system. - Graphical abstract: Bright field TEM image of the rim area between two boron carbide grains

Plasma hot machining for difficult-to-cut materials, 1

International Nuclear Information System (INIS)

Kitagawa, Takeaki; Maekawa, Katsuhiro; Kubo, Akihiko

1987-01-01

Machinability of difficult-to-cut materials has been a great concern to manufacturing engineers since demands for new materials in the aerospace and nuclear industries are more and more increasing. The purpose of this study is to develop a hot machining to improve machinability of high hardness materials. A plasma arc is used for heating materials cut. The surface just after being heated is removed as a chip by tungsten carbide tools. The turning experiments of high hardness steels with aid of plasma arc heating show not only the decrease in cutting forces but also the following effectiveness: (1) The application of the plasma hot machining to the condition, under which a built-up edge (BUE) appears in turning 0.46%C steel, makes the BUE disappeared, bringing less flank wear. (2) In the case of 18%Mn steel cutting, deep groove wear on the end-cutting edge diminishes, and roughness of the machined surface is improved by the prevention from chatter. (3) Although the chilled cast iron has high hardness of above HB = 350, the plasma hot machining makes it possible to cut it with tungsten carbide tools having less chipping and flank wear. (author)

Study on the machinability characteristics of superalloy Inconel 718 during high speed turning

International Nuclear Information System (INIS)

Thakur, D.G.; Ramamoorthy, B.; Vijayaraghavan, L.

2009-01-01

The present paper is an attempt of an experimental investigation on the machinability of superalloy, Inconel 718 during high speed turning using tungsten carbide insert (K20) tool. The effect of machining parameters on the cutting force, specific cutting pressure, cutting temperature, tool wear and surface finish criteria were investigated during the experimentation. The machining parameters have been optimized by measuring forces. The effect of machining parameters on the tool wear was examined through SEM micrographs. During high speed turning acoustic emission signal were collected and analyzed to understand the effect of cutting parameters during online. The research work findings will also provide useful economic machining solution by utilizing economical tungsten carbide tooling during high speed processing of Inconel 718, which is otherwise usually machined by costly PCD or CBN tools. The present approach and results will be helpful for understanding the machinability of Inconel 718 during high speed turning for the manufacturing engineers

Design, Fabrication and Performance of Boron-Carbide Control Elements; Conception, Fabrication et Comportement de Lames de Commande en Carbure de Bore; Raschety, izgotovlenie i kharakteristiki reguliruyushchikh sterzhnej. Iz karbida Bora; Proyecto, Elaboracion y Rendimiento de Elementos de Control de Carburo de Boro

Energy Technology Data Exchange (ETDEWEB)

Brammer, H. A.; Jacobson, J. [General Electric Company, San Jose, CA (United States)

1964-06-15

A control blade design, incorporating boron-carbide (B{sub 4}C) in stainless-steel tubes, was introduced into service in boiling water reactors in April 1961. Since that time this blade has become the standard reference control element in General Electric boiling-water reactors, replacing the 2% boron-stainless-steel blades previously used. The blades consist of a sheathed, cruciform array of small vertical stainless-steel tubes filled with compacted boron-carbide powder. The boron-carbide powder is confined longitudinally into several independent compartments by swaging over ball bearings located inside the tubes. The development and use of boron-carbide control rods is discussed in five phases: 1. Summary of experience with boron-steel blades and reasons for transition to boron-carbide control; 2. Design of the boron-carbide blade, beginning with developmental experiments, including early measurements performed in the AEC ''Control Rod Material and Development Program'' at the Vallecitos Atomic Laboratory, through a description of the final control blade configuration; 3. Fabrication of the blades and quality control procedures; 4. Results of confirmatory pre-operational mechanical and reactivity testing; and 5. Post-operational experience with the blades, including information on the results of mechanical inspection and reactivity testing after two years of reactor service. (author) [French] Un modele de lame de commande en carbure de bore (B{sub 4}C) a ete mis en place dans des reacteurs a eau bouillante en avril 1961. Depuis lors, cette lame est devenue l 'element de commande temoin classique dans les reacteurs a eau bouillante de la General Electric et a remplace les lames en acier inoxydable a 2% de bore utilisees auparavant. Ces lames consistent en un assemblage gaine cruciforme comprenant de petits tubes d'acier inoxydable verticaux remplis de poudre de carbure de bore agglomeree. Dans le sens de la longueur, cette poudre est enfermee dans plusieurs

Resonant soft x-ray reflectivity of Me/B4C multilayers near the boron K edge

Energy Technology Data Exchange (ETDEWEB)

Ksenzov, Dmitriy; Schlemper, Christoph; Pietsch, Ullrich

2010-09-01

Energy dependence of the optical constants of boron carbide in the short period Ru/B4C and Mo/B4C multilayers (MLs) are evaluated from complete reflectivity scans across the boron K edge using the energy-resolved photon-in-photon-out method. Differences between the refractive indices of the B4Cmaterial inside and close to the surface are obtained from the peak profile of the first order ML Bragg peak and the reflection profile near the critical angle of total external reflection close to the surface. Where a Mo/B4C ML with narrow barrier layers appears as a homogeneous ML at all energies, a Ru/B4C ML exhibits another chemical nature of boron at the surface compared to the bulk. From evaluation of the critical angle of total external reflection in the energy range between 184 and 186 eV, we found an enriched concentration of metallic boron inside the Ru-rich layer at the surface, which is not visible in other energy ranges.

Electrophoretic deposits of boron on duralumin plates used for measuring neutron flux; Depots electrophoretiques de bore sur plaques de duralumin destines a des mesures de flux de neutrons

Energy Technology Data Exchange (ETDEWEB)

Lang, F M; Magnier, P; Finck, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1956-07-01

Preparation of boron thin film deposits of around 1 mg per cm{sup 2} on duralumin plates with a diameter of 8 cm. The boron coated plates for ionization chambers were originally prepared at the CEA by pulverization of boron carbides on sodium silicates. This method is not controlling precisely enough the quantity of boron deposit. Thus, an electrophoretic method is considered for a better control of the quantity of boron deposit in the scope of using in the future boron 10 which is costly and rare. The method described by O. Flint is not satisfying enough and a similar electrophoretic process has been developed. Full description of the method is given as well as explanation of the use of dried methanol as solvent, tannin as electrolyte and magnesium chloride to avoid alumina formation. (M.P.)

Manufacturing of a micro-tungsten carbide electrode using a supersonic-aided electrolysis process

International Nuclear Information System (INIS)

Weng, Feng-Tsai; Ho, Chi-Ting

2008-01-01

In this study, a novel micromachining technology for fabricating micro parts was described. The original diameter of a tungsten carbide rod was 3 mm, and it was first processed to a rod with a diameter of 50 µm by a precision-grinding process. It could then be machined to the desired diameter by a supersonic-aided electrolysis process. A high-aspect ratio of the micro-tungsten carbide rod was easily obtained by this process. The surface roughness of the sample that was processed by electrolysis with supersonic-aided agitation was compared with that of the sample obtained without agitation. The machined surface of the sample was smooth, and the reason may be that ionized particles in the anode could be removed by supersonic-aided agitation during the electrolysis process. A microelectrode with a tip of approximately 1 µm could be obtained by this process. (technical note)

OPTIMIZATION OF MACHINING PARAMETERS USING TAGUCHI APPROACH DURING HARD TURNING OF ALLOY STEEL WITH UNCOATED CARBIDE UNDER DRY CUTTING ENVIRONMENT

Directory of Open Access Journals (Sweden)

A. Das

2015-12-01

Full Text Available In today’s world of manufacturing by machining process two things are very important, one is productivity and the other one is quality. Quality of a product generally depends upon the surface finish and dimensional deviations. The productivity can be seen as a key economic indicator of innovation in terms of higher material removal rate with a less time and cost in machining industries. Taguchi method is a popular statistical technique for optimization of input parameters to get the best output results. Dry machining is a popular methodology for machining hard material and it has been accepted by many researchers to a great extent because of its low cost and safety. Many scientists have taken various input parameters and studied their effects on different output responses. In the present paper an attempt has been made to study the effect of input parameters such as cutting speed, feed rate and depth of cut on Surface roughness, Tool wear, Power consumption and Chip reduction co-efficient under dry condition using uncoated carbide insert. Signal to noise ratio has been used to select the optimal condition for various output responses. ANOVA table has been drawn for each output responses and finally mathematical model of multiple regression analysis has been prepared and authenticity of the statistical model have been checked by normal probability plot. It has been found from the experimental result that the power consumption and flank wear both were minimum at the cutting speed of 250 rpm and 400 rpm respectively. Chip reduction coefficient has been found minimum at a depth of cut of 0.3 mm and surface roughness was minimum at 0.1 mm/rev. feed rate.

Milling Machinability of TiC Particle and TiB Whisker Hybrid Reinforced Titanium Matrix Composites

Institute of Scientific and Technical Information of China (English)

Huan Haixiang; Xu Jiuhua; Su Honghua; Ge Yingfei; Liang Xinghui

2017-01-01

The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination.Polycrystalline diamond (PCD) tools with different grain sizes and geometries,and carbide tools with and without coatings were used in the experiments.Milling forces,milling temperatures,tool lifetimes,tool wear,and machined surface integrities were investigated.The PCD tool required a primary cutting force 15 ％ smaller than that of the carbide tool,while the uncoated carbide tool required a primary cutting force 10％ higher than that of the TiAlN-coated tool.A cutting force of 300 N per millimeter of the cutting edge (300 N/mm) was measured.This caused excessive tool chipping.The cutting temperature of the PCD tool was 20％-30％ lower than that of the carbide tool,while that of the TiAlN-coated tool was 12％ lower than that of the uncoated carbide tool.The cutting temperatures produced when using water-based cooling and minimal quantity lubrication (MQL) were reduced by 100 ℃ and 200 ℃,compared with those recorded with dry cutting,respectively.In general,the PCD tool lifetimes were 2-3 times longer than the carbide tool lifetimes.The roughness Ra of the machined surface was less than 0.6μm,and the depth of the machined surface hardened layer was in the range of 0.15-0.25 mm for all of the PCD tools before a flank wear land of 0.2 mm was reached.The PCD tool with a 0.8 mm tool nose radius,0° rake angle,10° flank angle,and grain size of (30+2)μm exhibited the best cutting performance.For this specific tool,a lifetime of 16 min can be expected.

Precision Surface Grinding of Silicon Carbide

Directory of Open Access Journals (Sweden)

Mohamed Konneh

2016-12-01

Full Text Available Silicon carbide (SiC is well known for its excellent material properties, high durability, high wear resistance, light weight and extreme hardness. Among the engineering applications of this material, it is an excellent candidate for optic mirrors used in an Airbone Laser (ABL device. However, the low fracture toughness and extreme brittleness characteristics of SiC are predominant factors for its poor machinability. This paper presents surface grinding of SiC using diamond cup wheels to assess the performance of diamond grits with respect to the roughness produced on the machined surfaces and also the morphology of the ground work-piece. Resin bonded diamond cup wheels of grit sizes 46 µm, 76 µm and 107 µm; depth of cut of 10 µm, 20 µm and 30 µm; and feed rate of 2 mm/min, 12 mm/min and 22 mm/min were used during this machining investigation. It has been observed that the 76 grit performs better in terms of low surface roughness value and morphology.

PVD-Alumina Coatings on Cemented Carbide Cutting Tools: A Study About the Effect on Friction and Adhesion Mechanism

Directory of Open Access Journals (Sweden)

S.E. Cordes

2012-03-01

Full Text Available Crystalline PVD γ-alumina coatings are interesting for machining operations due to their outstanding characteristics, such as high hot hardness, high thermal stability and low tendency to adhesion. In the present work (Ti,AlN/γ-Al2O3-coatings are deposited on cemented carbide by means of MSIP. Objectives of this work are to study the effects of coating and cutting fluid regarding friction in tribological tests and to study the wear mechanisms and cutting performance of γ-Al2O3-based coated cemented carbide cutting tools in machining operations of austenitic stainless steels. Based on the remarkable properties of the coating system the performance of the cutting tools is increasing significantly.

Tungsten carbide and tungsten-molybdenum carbides as automobile exhaust catalysts

International Nuclear Information System (INIS)

Leclercq, L.; Daubrege, F.; Gengembre, L.; Leclercq, G.; Prigent, M.

1987-01-01

Several catalyst samples of tungsten carbide and W, Mo mixed carbides with different Mo/W atom ratios, have been prepared to test their ability to remove carbon monoxide, nitric oxide and propane from a synthetic exhaust gas simulating automobile emissions. Surface characterization of the catalysts has been performed by X-ray photoelectron spectroscopy (XPS) and selective chemisorption of hydrogen and carbon monoxide. Tungsten carbide exhibits good activity for CO and NO conversion, compared to a standard three-way catalyst based on Pt and Rh. However, this W carbide is ineffective in the oxidation of propane. The Mo,W mixed carbides are markedly different having only a very low activity. 9 refs.; 10 figs.; 5 tabs

Structure and reactivity of boron-ate complexes derived from primary and secondary boronic esters.

Science.gov (United States)

Feeney, Kathryn; Berionni, Guillaume; Mayr, Herbert; Aggarwal, Varinder K

2015-06-05

Boron-ate complexes derived from primary and secondary boronic esters and aryllithiums have been isolated, and the kinetics of their reactions with carbenium ions studied. The second-order rate constants have been used to derive nucleophilicity parameters for the boron-ate complexes, revealing that nucleophilicity increased with (i) electron-donating aromatics on boron, (ii) neopentyl glycol over pinacol boronic esters, and (iii) 12-crown-4 ether.

Effect of fabrication process on physical and mechanical properties of tungsten carbide - cobalt composite: A review

Science.gov (United States)

Mahaidin, Ahmad Aswad; Jaafar, Talib Ria; Selamat, Mohd Asri; Budin, Salina; Sulaiman, Zaim Syazwan; Hamid, Mohamad Hasnan Abdul

2017-12-01

WC-Co, which is also known as cemented carbide, is widely used in metal cutting industry and wear related application due to their excellent mechanical properties. Manufacturing industries are focusing on improving productivity and reducing operational cost with machining operation is considered as one of the factors. Thus, machining conditions are becoming more severe and required better cutting tool bit with improved mechanical properties to withstand high temperature operation. Numerous studies have been made over the generation for further improvement of cemented carbide properties to meet the constant increase in demand. However, the results of these studies vary due to different process parameters and manufacturing technology. This paper summarizes the studies to improve the properties of WC-Co composite using different consolidation (powder size, mixing method, formulation, etc) and sintering parameters (temperature, time, atmosphere, etc).

Methods for separating boron from borated paraffin wax and its determination by ion chromatography

International Nuclear Information System (INIS)

Jeyakumar, S.

2015-01-01

Boron compounds are found to be useful in shielding against high-energy neutrons. In radiotherapy treatments, in order to protect occupational workers and patients from the undesirable neutron and gamma doses, paraffin wax containing B 4 C/boric acid is used. Low-level borate wastes generated from the nuclear power plants have been immobilized with paraffin wax using a concentrate waste drying system (CWDS). Borated paraffin waxes are prepared by mixing calculated amounts of either boric acid or boron carbide with the molten wax. This necessitates the determination of boron at different locations in order to check the homogeneous distribution of B over the borated wax. The determination of boron in nuclear materials is inevitable due to its high neutron absorption cross section. For the determination of boron in borated waxes, not many methods have been reported. A method based on the pyrohydrolysis extraction of boron and its quantification with ion chromatography was proposed for paraffin waxes borated with H 3 BO 3 and B 4 C. The B 4 C optimum pyrohydrolysis conditions were identified. Wax samples were mixed with U 3 O 8 , which prevents the sample from flare up, and also accelerates the extraction of boron. Pyrohydrolysis was carried out with moist O 2 at 950℃ for 60 and 90 min for wax with H 3 BO 3 and wax with B 4 C, respectively. Two simple methods of separation based on alkali extraction and melting wax in alkali were also developed exclusively for wax with H 3 BO 3 . In all the separations, the recovery of B was above 98%. During IC separation, B was separated as boron-mannitol anion complex. Linear calibration was obtained between 0.1 and 50 ppm of B, and LOD was calculated as 5 ppb (S/N=3). The reproducibility was better than 5% (RSD)

Microstructure and mechanical properties of a new type of austempered boron alloyed high silicon cast steel

Directory of Open Access Journals (Sweden)

Chen Xiang

2013-05-01

Full Text Available In the present paper, a new type of austempered boron alloyed high silicon cast steel has been developed, and its microstructures and mechanical properties at different temperatures were investigated. The experimental results indicate that the boron alloyed high silicon cast steel comprises a dendritic matrix and interdendritic eutectic borides in as-cast condition. The dendritic matrix is made up of pearlite, ferrite, and the interdendritic eutectic boride is with a chemical formula of M2B (M represents Fe, Cr, Mn or Mo which is much like that of carbide in high chromium white cast iron. Pure ausferrite structure that consists of bainitic ferrite and retained austenite can be obtained in the matrix by austempering treatment to the cast steel. No carbides precipitate in the ausferrite structure and the morphology of borides remains almost unchanged after austempering treatments. Secondary boride particles precipitate during the course of austenitizing. The hardness and tensile strength of the austempered cast steel decrease with the increase of the austempering temperature, from 250 篊 to 400 篊. The impact toughness is 4-11 J昪m-2 at room temperature and the impact fracture fractogragh indicates that the fracture is caused by the brittle fracture of the borides.

Corrosion resistant cemented carbide

International Nuclear Information System (INIS)

Hong, J.

1990-01-01

This paper describes a corrosion resistant cemented carbide composite. It comprises: a granular tungsten carbide phase, a semi-continuous solid solution carbide phase extending closely adjacent at least a portion of the grains of tungsten carbide for enhancing corrosion resistance, and a substantially continuous metal binder phase. The cemented carbide composite consisting essentially of an effective amount of an anti-corrosion additive, from about 4 to about 16 percent by weight metal binder phase, and with the remaining portion being from about 84 to about 96 percent by weight metal carbide wherein the metal carbide consists essentially of from about 4 to about 30 percent by weight of a transition metal carbide or mixtures thereof selected from Group IVB and of the Periodic Table of Elements and from about 70 to about 96 percent tungsten carbide. The metal binder phase consists essentially of nickel and from about 10 to about 25 percent by weight chromium, the effective amount of an anti-corrosion additive being selected from the group consisting essentially of copper, silver, tine and combinations thereof

Characterization of B4C-composite-reinforced aluminum alloy composites

Science.gov (United States)

Singh, Ram; Rai, R. N.

2018-04-01

Dry sliding wear tests conducted on Pin-on-disk wear test machine. The rotational speed of disc is ranging from (400-600rpm) and under loads ranging from (30-70 N) the contact time between the disc and pin is constant for each pin specimen of composites is 15 minute. In all manufacturing industries the uses of composite materials has been increasing globally, In the present study, an aluminum 5083 alloy is used as the matrix and 5% of weight percentage of Boron Carbide (B4C) as the reinforcing material. The composite is produced using stir casting technique. This is cost effective method. The aluminum 5083 matrix can be strengthened by reinforcing with hard ceramic particles like silicon carbide and boron carbide. In this experiment, aluminum 5083 alloy is selected as one of main material for making parts of the ship it has good mechanical properties, good corrosion resistance and it is can welded very easily and does have good strength. The samples are tested for hardness and tensile strength. The mechanical properties like Hardness can be increased by reinforcing aluminum 5083alloy 5% boron carbide (B4C) particles and tensile strength. Finally the Scanning Electron Microscope (SEM) analysis and EDS is done, which helps to study topography of composites and it produces images of a sample by scanning it with a focused beam of electrons and the presence of composition found in the matrix.

White light emission from engineered silicon carbide

DEFF Research Database (Denmark)

Ou, Haiyan

Silicon carbide (SiC) is a wide indirect bandgap semiconductor. The light emission efficiency is low in nature. But this material has very unique physical properties like good thermal conductivity, high break down field etc in addition to its abundance. Therefore it is interesting to engineer its...... light emission property so that to take fully potential applications of this material. In this talk, two methods, i.e. doping SiC heavily by donor-acceptor pairs and making SiC porous are introduced to make light emission from SiC. By co-doping SiC with nitrogen and boron heavily, strong yellow emission...... is demonstrated. After optimizing the passivation conditions, strong blue-green emission from porous SiC is demonstrated as well. When combining the yellow emission from co-doped SiC and blue-green from porous SiC, a high color rendering index white light source is achieved....

The coloring problem in the solid-state metal boride carbide ScB{sub 2}C{sub 2}. A theoretical analysis

Energy Technology Data Exchange (ETDEWEB)

Lassoued, Souheila [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques; Universite Kasdi Merbah-Ouargla (Algeria). Faculte des Mathematiques et des Sciences de la Matiere; Boucher, Benoit [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques; Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany); Boutarfaia, Ahmed [Universite Kasdi Merbah-Ouargla (Algeria). Faculte des Mathematiques et des Sciences de la Matiere; Gautier, Regis; Halet, Jean-Francois [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques

2016-08-01

The electronic properties of the layered ternary metal boride carbide ScB{sub 2}C{sub 2}, the structure of which consists of B/C layers made of fused five- and seven-membered rings alternating with scandium sheets, are analyzed. In particular, the respective positions of the B and C atoms (the so-called coloring problem) are tackled using density functional theory, quantum theory of atoms in molecules, and electron localizability indicator calculations. Results reveal that (i) the most stable coloring minimizes the number of B-B and C-C contacts and maximizes the number of boron atoms in the heptagons, (ii) the compound is metallic in character, and (iii) rather important covalent bonding occurs between the metallic sheets and the boron-carbon network.

Alkynyl substituted carboranes as precursors to boron carbide thin films, fibers and composites

International Nuclear Information System (INIS)

Johnson, S.E.; Yang, X.; Hawthorne, M.F.; Mackenzie, J.D.; Thorne, K.J.; Zheng, H.

1992-01-01

In this paper the use of alkynyl substituted derivatives of o-carborane as precursors to boron containing ceramics is described. These compounds undergo a thermally or photochemically induced polymerization to afford cross linked polyakynyl-o-carborane derivatives. The increase in molecular weight should allow for increased Tg's and the retention of modelled polymer preforms. In this report, these modification reactions are described. In addition, the retention of molded polymer preforms were analyzed after UV exposure and inert atmosphere pyrolysis

Obtainment, machining and wear of metal matrix composites processed by powder metallurgy

International Nuclear Information System (INIS)

Jesus, Edilson Rosa Barbosa de.

1998-01-01

The aim of this investigation was the obtainment of metal matrix composites (MMC) by the route of powder metallurgy, and the valuation of these materials with relation to their machining and wear characteristics. Firstly, were obtained pure commercial aluminium matrix composites materials, with 5, 10 and 15% volumetric fraction of silicon carbide particles. Was also obtained a material without reinforcement particles in order to verify by comparison, the influence of addition of reinforcement particles. The obtained materials were characterized physics (hydrostatic density), mechanics (hardness and tensile tests) and microstructurally (optical microscopy and scanning electron microscopy). The results showed a homogeneous distribution of reinforcement particles in the composite, and improvement in the mechanical properties, mainly tensile strength (UTS) in comparison to the unreinforced material. After, tests were made to verify the materials behavior during machining and to check the performance of several tool materials (cemented carbide, ceramics and polycrystalline diamond). In these tests, values of the cutting force were measured by instrumented tool-holders. Phenomena such as tool wear, built-up edge formation and mechanism of chip formation were also observed and evaluated. The results from the cemented carbide tool tests, were utilised for the machinability index determination of each material. These results were applied to the Taylor equation and the equation constants for each material and test conditions were determined. The results showed that the inclusion of silicon carbide particles made extremely difficult the machining of the composites, and only with diamond tool, satisfactory results were obtained. At last, wear tests were performed to verify the influence of the reinforcement particles in the characteristics of wear resistance of the materials. The results obtained were utilized in the wear coefficient determination for each material. The

Performance of PVD-Coated Carbide Tools When Turning Inconel 718 in Dry Machining

Directory of Open Access Journals (Sweden)

Gusri Akhyar Ibrahim

2011-01-01

Full Text Available Inconel 718 has found its niche in many industries, owing to its unique properties such as high oxidation resistance and corrosion resistance even at very high temperatures. Coated carbide tool with hard layer of PVD TiAlN is used to turn Inconel 718. Taguchi method with the orthogonal array L9 is applied in this experiment with the parameter cutting speed of 60–80 m/min, feed rate of 0.2–0.3 mm/rev, and depth of cut of 0.3–0.5 mm. The results show that depth of cut is a significant influence to the tool life. Cutting speed of 60 m/min, feed rate of 0.2 mm/rev, and depth of cut of 0.3 mm are the optimum parameters. The flank wear, crater wear, notch wear, and nose wear are the wear mechanisms on the carbide tool. Through the SEM, abrasion, attrition, and adhesion are the wear mechanisms which can be seen on the cutting tool.

Machinability of experimental Ti-Ag alloys.

Science.gov (United States)

Kikuchi, Masafumi; Takahashi, Masatoshi; Okuno, Osamu

2008-03-01

This study investigated the machinability of experimental Ti-Ag alloys (5, 10, 20, and 30 mass% Ag) as a new dental titanium alloy candidate for CAD/CAM use. The alloys were slotted with a vertical milling machine and carbide square end mills under two cutting conditions. Machinability was evaluated through cutting force using a three-component force transducer fixed on the table of the milling machine. The horizontal cutting force of the Ti-Ag alloys tended to decrease as the concentration of silver increased. Values of the component of the horizontal cutting force perpendicular to the feed direction for Ti-20% Ag and Ti-30% Ag were more than 20% lower than those for titanium under both cutting conditions. Alloying with silver significantly improved the machinability of titanium in terms of cutting force under the present cutting conditions.

Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Johnston, Jamin M.; Catledge, Shane A., E-mail: catledge@uab.edu

2016-02-28

Graphical abstract: - Highlights: • A detailed phase analysis after PECVD boriding shows WCoB, CoB and/or W{sub 2}CoB{sub 2}. • EDS of PECVD borides shows boron diffusion into the carbide grain structure. • Nanoindentation hardness and modulus of borides is 23–27 GPa and 600–780 GPa. • Scratch testing shows hard coating with cracking at 40N and spallation at 70N. - Abstract: Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W{sub 2}CoB{sub 2} with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

International Nuclear Information System (INIS)

Johnston, Jamin M.; Catledge, Shane A.

2016-01-01

Graphical abstract: - Highlights: • A detailed phase analysis after PECVD boriding shows WCoB, CoB and/or W_2CoB_2. • EDS of PECVD borides shows boron diffusion into the carbide grain structure. • Nanoindentation hardness and modulus of borides is 23–27 GPa and 600–780 GPa. • Scratch testing shows hard coating with cracking at 40N and spallation at 70N. - Abstract: Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W_2CoB_2 with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

Hot ductility behavior of a low carbon advanced high strength steel (AHSS) microalloyed with boron

International Nuclear Information System (INIS)

Mejia, I.; Bedolla-Jacuinde, A.; Maldonado, C.; Cabrera, J.M.

2011-01-01

Research highlights: → Effect of boron on the hot ductility behavior of a low carbon NiCrVCu AHSS. → Boron addition of 117 ppm improves hot ductility over 100% in terms of RA. → Hot ductility improvement is associated with segregation/precipitation of boron. → Typical hot ductility recovery at lower temperatures does not appear in this steel. → Hot ductility loss is associated with precipitates/inclusions coupled with voids. - Abstract: The current study analyses the influence of boron addition on the hot ductility of a low carbon advanced high strength NiCrVCu steel. For this purpose hot tensile tests were carried out at different temperatures (650, 750, 800, 900 and 1000 deg. C) at a constant true strain rate of 0.001 s -1 . Experimental results showed a substantial improvement in hot ductility for the low carbon advanced high strength steel when microalloyed with boron compared with that without boron addition. Nevertheless, both steels showed poor ductility when tested at the lowest temperatures (650, 750 and 800 deg. C), and such behavior is associated to the precipitation of vanadium carbides/nitrides and inclusions, particularly MnS and CuS particles. The fracture mode of the low carbon advanced high strength steel microalloyed with boron seems to be more ductile than the steel without boron addition. Furthermore, the fracture surfaces of specimens tested at temperatures showing the highest ductility (900 and 1000 deg. C) indicate that the fracture mode is a result of ductile failure, while in the region of poor ductility the fracture mode is of the ductile-brittle type failure. It was shown that precipitates and/or inclusions coupled with voids play a meaningful role on the crack nucleation mechanism which in turn causes a hot ductility loss. Likewise, dynamic recrystallization (DRX) which always results in restoration of ductility only occurs in the range from 900 to 1000 deg. C. Results are discussed in terms of boron segregation towards

Hot ductility behavior of a low carbon advanced high strength steel (AHSS) microalloyed with boron

Energy Technology Data Exchange (ETDEWEB)

Mejia, I., E-mail: imejia@umich.mx [Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio ' U' , Ciudad Universitaria, 58066 Morelia, Michoacan (Mexico); Bedolla-Jacuinde, A.; Maldonado, C. [Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio ' U' , Ciudad Universitaria, 58066 Morelia, Michoacan (Mexico); Cabrera, J.M. [Departament de Ciencia dels Materials i Enginyeria Metal.lurgica, ETSEIB - Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundacio CTM Centre Tecnologic, Av. de las Bases de Manresa 1, 08240 Manresa (Spain)

2011-05-25

Research highlights: {yields} Effect of boron on the hot ductility behavior of a low carbon NiCrVCu AHSS. {yields} Boron addition of 117 ppm improves hot ductility over 100% in terms of RA. {yields} Hot ductility improvement is associated with segregation/precipitation of boron. {yields} Typical hot ductility recovery at lower temperatures does not appear in this steel. {yields} Hot ductility loss is associated with precipitates/inclusions coupled with voids. - Abstract: The current study analyses the influence of boron addition on the hot ductility of a low carbon advanced high strength NiCrVCu steel. For this purpose hot tensile tests were carried out at different temperatures (650, 750, 800, 900 and 1000 deg. C) at a constant true strain rate of 0.001 s{sup -1}. Experimental results showed a substantial improvement in hot ductility for the low carbon advanced high strength steel when microalloyed with boron compared with that without boron addition. Nevertheless, both steels showed poor ductility when tested at the lowest temperatures (650, 750 and 800 deg. C), and such behavior is associated to the precipitation of vanadium carbides/nitrides and inclusions, particularly MnS and CuS particles. The fracture mode of the low carbon advanced high strength steel microalloyed with boron seems to be more ductile than the steel without boron addition. Furthermore, the fracture surfaces of specimens tested at temperatures showing the highest ductility (900 and 1000 deg. C) indicate that the fracture mode is a result of ductile failure, while in the region of poor ductility the fracture mode is of the ductile-brittle type failure. It was shown that precipitates and/or inclusions coupled with voids play a meaningful role on the crack nucleation mechanism which in turn causes a hot ductility loss. Likewise, dynamic recrystallization (DRX) which always results in restoration of ductility only occurs in the range from 900 to 1000 deg. C. Results are discussed in terms of

Ablation-resistant carbide Zr0.8Ti0.2C0.74B0.26 for oxidizing environments up to 3,000 °C

Science.gov (United States)

Zeng, Yi; Wang, Dini; Xiong, Xiang; Zhang, Xun; Withers, Philip J.; Sun, Wei; Smith, Matthew; Bai, Mingwen; Xiao, Ping

2017-06-01

Ultra-high temperature ceramics are desirable for applications in the hypersonic vehicle, rockets, re-entry spacecraft and defence sectors, but few materials can currently satisfy the associated high temperature ablation requirements. Here we design and fabricate a carbide (Zr0.8Ti0.2C0.74B0.26) coating by reactive melt infiltration and pack cementation onto a C/C composite. It displays superior ablation resistance at temperatures from 2,000-3,000 °C, compared to existing ultra-high temperature ceramics (for example, a rate of material loss over 12 times better than conventional zirconium carbide at 2,500 °C). The carbide is a substitutional solid solution of Zr-Ti containing carbon vacancies that are randomly occupied by boron atoms. The sealing ability of the ceramic's oxides, slow oxygen diffusion and a dense and gradient distribution of ceramic result in much slower loss of protective oxide layers formed during ablation than other ceramic systems, leading to the superior ablation resistance.

Machining NiTi micro-parts by micro-milling

International Nuclear Information System (INIS)

Weinert, K.; Petzoldt, V.

2008-01-01

The machinability of NiTi by milling has been examined using solid carbide end milling cutters. First results were obtained from machining simple slots applying TiAlN-coated tools with a diameter of 0.4 mm. The machining process was evaluated in terms of tool wear, cutting forces and machining quality. The tool wear and work piece quality was analysed with a scanning electron microscope and a white-light confocal microscope. Despite the poor machinability of NiTi good results concerning tool wear and shape accuracy of the milled slots were achieved. Essential for a good machining result is the application of minimum quantity lubrication. This clearly reduces NiTi adherences compared to dry machining. Work piece quality is improved and tool life is extended. Based on these results different structures could be produced by micro-milling

A comparison of tokamak operation with metallic getters (Ti, Cr, Be) and boronization

International Nuclear Information System (INIS)

Winter, J.

1990-07-01

In addition to discharge cleaning techniques, gettering of tokamaks has been used since 1975 as a powerful tool for controlling the impurity influx into fusion plasmas. High-Z metals like Ti and Cr, evaporated onto the walls of the fusion devices, have first been used. After the introduction of carbon as low Z plasma facing material for the large tokamaks new scenarios were developed, optimizing the low-Z aspect of wall materials. These are the boronization technique and the evaporation of Be in conjunction with the use of Be limiters. A review of the different getter techniques and of the observed results will be given, focussing on the comparison of the tokamak performance achieved with boronization and the use of beryllium. It is shown that in all cases of gettering the most important mechanism for the improved machine performance is the control of the oxygen impurity influx. Very similar results are found for the impurity control potential. The added benefit of boronization and Be gettering arises from the low Z of the materials. Both scenarios essentially lead to the same machine performance. Both render themselves as an option for future devices. (orig.)

Method and apparatus for coating thin foil with a boron coating

Science.gov (United States)

Lacy, Jeffrey L.

2018-01-16

An apparatus and a process is disclosed for applying a boron coating to a thin foil. Preferably, the process is a continuous, in-line process for applying a coating to a thin foil comprising wrapping the foil around a rotating and translating mandrel, cleaning the foil with glow discharge in an etching chamber as the mandrel with the foil moves through the chamber, sputtering the foil with boron carbide in a sputtering chamber as the mandrel moves through the sputtering chamber, and unwinding the foil off the mandrel after it has been coated. The apparatus for applying a coating to a thin foil comprises an elongated mandrel. Foil preferably passes from a reel to the mandrel by passing through a seal near the initial portion of an etching chamber. The mandrel has a translation drive system for moving the mandrel forward and a rotational drive system for rotating mandrel as it moves forward. The etching chamber utilizes glow discharge on a surface of the foil as the mandrel moves through said etching chamber. A sputtering chamber, downstream of the etching chamber, applies a thin layer comprising boron onto the surface of the foil as said mandrel moves through said sputtering chamber. Preferably, the coated foil passes from the mandrel to a second reel by passing through a seal near the terminal portion of the sputtering chamber.

Effect of heat treatments on machinability of gold alloy with age-hardenability at intraoral temperature.

Science.gov (United States)

Watanabe, I; Baba, N; Watanabe, E; Atsuta, M; Okabe, T

2004-01-01

This study investigated the effect of heat treatment on the machinability of heat-treated cast gold alloy with age-hardenability at intraoral temperature using a handpiece engine with SiC wheels and an air-turbine handpiece with carbide burs and diamond points. Cast gold alloy specimens underwent various heat treatments [As-cast (AC); Solution treatment (ST); High-temperature aging (HA), Intraoral aging (IA)] before machinability testing. The machinability test was conducted at a constant machining force of 0.784N. The three circumferential speeds used for the handpiece engine were 500, 1,000 and 1,500 m/min. The machinability index (M-index) was determined as the amount of metal removed by machining (volume loss, mm(3)). The results were analyzed by ANOVA and Scheffé's test. When an air-turbine handpiece was used, there was no difference in the M-index of the gold alloy among the heat treatments. The air-turbine carbide burs showed significantly (pmachinability of the gold alloy using the air-turbine handpiece. The heat treatments had a small effect on the M-index of the gold alloy machined with a SiC wheel for a handpiece engine.

Neutron absorbing article

International Nuclear Information System (INIS)

Naum, R.G.; Owens, D.P.; Dooker, G.I.

1981-01-01

A neutron-absorbing article suitable for use in spent fuel racks is described. It comprises boron carbide particles, diluent particles, and a phenolic polymer cured to a continuous matrix. The diluent may be silicon carbide, graphite, amorphous carbon, alumina, or silica. The combined boron carbide-diluent phase contains no more than 2 percent B 2 O 3 , and the neutron-absorbing article contains from 20 to 40 percent phenol resin. The ratio of boron carbide to diluent particles is in the range 1:9 to 9:1

Boron

Science.gov (United States)

Boron is an essential micronutrient element required for plant growth. Boron deficiency is wide-spread in crop plants throughout the world especially in coarse-textured soils in humid areas. Boron toxicity can also occur, especially in arid regions under irrigation. Plants respond directly to the...

Study of the machining of uranium carbide rods obtained by continuous casting under electronic bombardment; Etude de l'usinage de barreaux de carbure d'uranium obtenus par coulee continue sous bombardement electronique

Energy Technology Data Exchange (ETDEWEB)

Rousset, P; Accary, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

The authors consider the various methods of machining uranium mono-carbide and compare them critically in the case of their application to uranium carbide obtained by fusion under an electronic bombardment and continuous casting. This study leads them to propose two mechanical machining methods: cylindrical rectification and center-less rectification, preceded by a preliminary roughing out of a cylinder, the latter appearing more suitable. A study of the machining yields as a function of the diameter of the rough bars and of the diameter of the finished rods has shown that an optimum value of the rough bar diameter exists for each value of the finished rod diameter. It is found that the yield increases as the diameter itself increases, this yield rising from 45 per cent to around 70 per cent as the diameter of the rough bars increases from 25-26 mm to 37-38 mm. (authors) [French] Les auteurs envisagent les differentes methodes d'usinage du monocarbure d'uranium et se livrent a une etude critique de celles-ci, dans le cas de leur application a l'usinage de barreaux de carbure d'uranium obtenus par fusion sous bombardement electronique et coulee continue. Cette etude les conduit a proposer deux methodes d'usinage mecanique: la rectification cylindrique et la rectification 'centerless', precedee d'un ebauchage par carottage, la seconde paraissant la plus appropriee. L'etude des rendements d'usinage en fonction du diametre des barreaux bruts et du diametre des barreaux finis, a mis en evidence une valeur optimale du diametre des barreaux bruts pour chaque valeur du diametre des barreaux usines. Elle a montre que le rendement croit lorsque le diametre croit lui-meme, ce rendement passant d'environ 45 pour cent a environ 70 pour cent, lorsque le diametre des barreaux bruts passe de 25-26 mm a 37-38 mm.

Ceramic/polymer functionally graded material (FGM) lightweight armor system

Energy Technology Data Exchange (ETDEWEB)

Petrovic, J.J.; McClellan, K.J.

1998-12-31

This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Functionally graded material is an enabling technology for lightweight body armor improvements. The objective was to demonstrate the ability to produce functionally graded ceramic-polymer and ceramic-metal lightweight armor materials. This objective involved two aspects. The first and key aspect was the development of graded-porosity boron-carbide ceramic microstructures. The second aspect was the development of techniques for liquid infiltration of lightweight metals and polymers into the graded-porosity ceramic. The authors were successful in synthesizing boron-carbide ceramic microstructures with graded porosity. These graded-porosity boron-carbide hot-pressed pieces were then successfully liquid-infiltrated in vacuum with molten aluminum at 1,300 C, and with liquid polymers at room temperature. Thus, they were able to demonstrate the feasibility of producing boron carbide-aluminum and boron carbide-polymer functionally graded materials.

Dispersion toughened silicon carbon ceramics

Science.gov (United States)

Wei, G.C.

1984-01-01

Fracture resistant silicon carbide ceramics are provided by incorporating therein a particulate dispersoid selected from the group consisting of (a) a mixture of boron, carbon and tungsten, (b) a mixture of boron, carbon and molybdenum, (c) a mixture of boron, carbon and titanium carbide, (d) a mixture of aluminum oxide and zirconium oxide, and (e) boron nitride. 4 figures.

Development of new metal matrix composite electrodes for electrical discharge machining through powder metallurgy process

Directory of Open Access Journals (Sweden)

C. Mathalai Sundaram

2014-12-01

Full Text Available Electrical discharge machining (EDM is one of the widely used nontraditional machining methods to produce die cavities by the erosive effect of electrical discharges. This method is popular due to the fact that a relatively soft electrically conductive tool electrode can machine hard work piece. Copper electrode is normally used for machining process. Electrode wear rate is the major drawback for EDM researchers. This research focus on fabrication of metal matrix composite (MMC electrode by mixing copper powder with titanium carbide (TiC and Tungsten carbide (WC powder through powder metallurgy process, Copper powder is the major amount of mixing proportion with TiC and WC. However, this paper focus on the early stage of the project where powder metallurgy route was used to determine suitable mixing time, compaction pressure and sintering and compacting process in producing EDM electrode. The newly prepared composite electrodes in different composition are tested in EDM for OHNS steel.

Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

Science.gov (United States)

Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

2009-01-01

A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

Fabrication of uranium carbide/beryllium carbide/graphite experimental-fuel-element specimens

International Nuclear Information System (INIS)

Muenzer, W.A.

1978-01-01

A method has been developed for fabricating uranium carbide/beryllium carbide/graphite fuel-element specimens for reactor-core-meltdown studies. The method involves milling and blending the raw materials and densifying the resulting blend by conventional graphite-die hot-pressing techniques. It can be used to fabricate specimens with good physical integrity and material dispersion, with densities of greater than 90% of the theoretical density, and with a uranium carbide particle size of less than 10 μm

Reinforcement against crack propagation of PWR absorbers by development of boron-carbon-hafnium composites

International Nuclear Information System (INIS)

Provot, B.; Herter, P.

2000-01-01

In order to improve the mechanical behaviour of materials used as neutron absorbers in nuclear reactors, we have developed CERCER or CERMET composites with boron and hafnium. Thus a new composite B 4 C/HfB 2 has been especially studied. We have identified three kinds of degradation under irradiation (thermal gradient, swelling due to fission products and accidental corrosion) that induce imposed deformations cracking phenomena. Mechanical behaviour and crack propagation resistance have been studied by ball-on-three-balls and double torsion tests. A special device was developed to enable crack propagation and associated stress intensity factor measurements. Effects of structure and of a second phase are underline. First results show that these materials present crack initiation and propagation resistance much higher than pure boron carbide or hafnium diboride. We observe R-Curves effects, crack bridging or branching, crack arrests, and toughness increases that we can relate respectively to the composite structures. (author)

Performance evaluation of PCBN, coated carbide and mixed ceramic inserts in finish-turning of AISI D2 steel

Directory of Open Access Journals (Sweden)

M. Junaid Mir

2017-09-01

Full Text Available The present study compares the performance of three different cutting tools, viz., PCBN, mixed ceramic and coated carbide tool in finish turning of hardened D2 tool steel in terms of tool wear, surface roughness, and economic feasibility under dry cutting conditions. Results showed that tool life of PCBN inserts was better than mixed ceramic and coated carbide inserts. The flank wear of PCBN tools was observed to be lower than mixed ceramic and coated carbide inserts. The surface roughness achieved under all cutting conditions for mixed ceramic and coated-carbide inserts was comparable with that achieved with PCBN inserts and was below 1.6μm. Experimental results showed that the wear mechanism of ceramic tool is pre-dominantly abrasive wear at lower speeds and abrasive wear followed by adhesive wear at medium and higher speeds and for PCBN tools the dominant wear mechanism is abrasive wear and cratering at lower speeds followed by adhesive wear at higher speeds. For carbide tool the dominant wear mechanism was abrasive wear and cratering at lower speeds followed by adhesion and chipping at higher speeds. Obtained results revealed that PCBN tools can outperform both ceramic and carbide tools in terms of tool life under different machinability criteria used.

Nondestructive ultrasonic characterization of armor grade silicon carbide

Science.gov (United States)

Portune, Andrew Richard

Ceramic materials have traditionally been chosen for armor applications for their superior mechanical properties and low densities. At high strain rates seen during ballistic events, the behavior of these materials relies upon the total volumetric flaw concentration more so than any single anomalous flaw. In this context flaws can be defined as any microstructural feature which detriments the performance of the material, potentially including secondary phases, pores, or unreacted sintering additives. Predicting the performance of armor grade ceramic materials depends on knowledge of the absolute and relative concentration and size distribution of bulk heterogeneities. Ultrasound was chosen as a nondestructive technique for characterizing the microstructure of dense silicon carbide ceramics. Acoustic waves interact elastically with grains and inclusions in large sample volumes, and were well suited to determine concentration and size distribution variations for solid inclusions. Methodology was developed for rapid acquisition and analysis of attenuation coefficient spectra. Measurements were conducted at individual points and over large sample areas using a novel technique entitled scanning acoustic spectroscopy. Loss spectra were split into absorption and scattering dominant frequency regimes to simplify analysis. The primary absorption mechanism in polycrystalline silicon carbide was identified as thermoelastic in nature. Correlations between microstructural conditions and parameters within the absorption equation were established through study of commercial and custom engineered SiC materials. Nonlinear least squares regression analysis was used to estimate the size distributions of boron carbide and carbon inclusions within commercial SiC materials. This technique was shown to additionally be capable of approximating grain size distributions in engineered SiC materials which did not contain solid inclusions. Comparisons to results from electron microscopy

Alternative Process for Manufacturing of Thin Layers of Boron for Neutron Measurement

Energy Technology Data Exchange (ETDEWEB)

Auge, Gregoire; Partyka, Stanislas [Onet Technologies (France); Guerard, Bruno; Buffet, Jean-Claude [Institut Laue Langevin - ILL, Grenoble (France)

2015-07-01

Due to the worldwide shortage of helium 3, Boron-lined proportional counters are developed intensively by several groups. Up to now, thin boron containing layers for neutron detectors are essentially produced by sputtering of boron carbide (B{sub 4}C). This technology provides high quality films but it is slow and expensive. Our paper describes a novel and inexpensive technology for producing boron layers. This technology is based on chemical synthesis of boron 10 nanoparticles, and on electrophoretic deposition of these particles on metallic plates, or on metallic pieces with more complex shapes. The chemical synthesis consists in: - Heating boron 10 with lithium up to 700 deg. C under inert atmosphere: an intermetallic compound, LiB, is produced; - Hydrolysing this intermetallic compound: LiB + H{sub 2}O → B + Li{sup +} + OH{sup -} + 1/2H{sub 2}, where B is under the form of nanoparticles; - Purifying the suspension of boron nanoparticles in water, from lithium hydroxide, by successive membrane filtrations; - Evaporating the purified suspension, in order to get a powder of nanoparticles. The obtained nanoparticles have size around 300 nm, with a high porosity, of about 50%. This particle size is equivalent to about 150 nm massive particles. The nanoparticles are then put into suspension in a specific solvent, in order to perform deposition on metallic surfaces, by electrophoretic method. The solvent is chosen so that it is not electrolysed even under voltages of several tens of volts. An acid is dissolved into the solvent, so that the nanoparticles are positively charged. Deposition is performed on the cathode within about 10 min. The cathode could be an aluminium plate, or a nickel coated aluminium plate. Homogeneous deposition may also be performed on complex shapes, like grids in a Multigrid detector. A large volume of pieces, can be coated with a Boron-10 film in a few hours. The thickness of the layer can be adjusted according to the required neutron

Thermoelectric properties of boron and boron phosphide CVD wafers

Energy Technology Data Exchange (ETDEWEB)

Kumashiro, Y.; Yokoyama, T.; Sato, A.; Ando, Y. [Yokohama National Univ. (Japan)

1997-10-01

Electrical and thermal conductivities and thermoelectric power of p-type boron and n-type boron phosphide wafers with amorphous and polycrystalline structures were measured up to high temperatures. The electrical conductivity of amorphous boron wafers is compatible to that of polycrystals at high temperatures and obeys Mott`s T{sup -{1/4}} rule. The thermoelectric power of polycrystalline boron decreases with increasing temperature, while that of amorphous boron is almost constant in a wide temperature range. The weak temperature dependence of the thermal conductivity of BP polycrystalline wafers reflects phonon scattering by grain boundaries. Thermal conductivity of an amorphous boron wafer is almost constant in a wide temperature range, showing a characteristic of a glass. The figure of merit of polycrystalline BP wafers is 10{sup -7}/K at high temperatures while that of amorphous boron is 10{sup -5}/K.

Prediction of the wear and evolution of cutting tools in a carbide / titanium-aluminum-vanadium machining tribosystem by volumetric tool wear characterization and modeling

Science.gov (United States)

Kuttolamadom, Mathew Abraham

The objective of this research work is to create a comprehensive microstructural wear mechanism-based predictive model of tool wear in the tungsten carbide / Ti-6Al-4V machining tribosystem, and to develop a new topology characterization method for worn cutting tools in order to validate the model predictions. This is accomplished by blending first principle wear mechanism models using a weighting scheme derived from scanning electron microscopy (SEM) imaging and energy dispersive x-ray spectroscopy (EDS) analysis of tools worn under different operational conditions. In addition, the topology of worn tools is characterized through scanning by white light interferometry (WLI), and then application of an algorithm to stitch and solidify data sets to calculate the volume of the tool worn away. The methodology was to first combine and weight dominant microstructural wear mechanism models, to be able to effectively predict the tool volume worn away. Then, by developing a new metrology method for accurately quantifying the bulk-3D wear, the model-predicted wear was validated against worn tool volumes obtained from corresponding machining experiments. On analyzing worn crater faces using SEM/EDS, adhesion was found dominant at lower surface speeds, while dissolution wear dominated with increasing speeds -- this is in conformance with the lower relative surface speed requirement for micro welds to form and rupture, essentially defining the mechanical load limit of the tool material. It also conforms to the known dominance of high temperature-controlled wear mechanisms with increasing surface speed, which is known to exponentially increase temperatures especially when machining Ti-6Al-4V due to its low thermal conductivity. Thus, straight tungsten carbide wear when machining Ti-6Al-4V is mechanically-driven at low surface speeds and thermally-driven at high surface speeds. Further, at high surface speeds, craters were formed due to carbon diffusing to the tool surface and

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.

Porous silicon carbide (SIC) semiconductor device

Science.gov (United States)

Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

1996-01-01

Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

Alloy Design of Martensitic 9Cr-Boron Steel for A-USC Boiler at 650 °C — Beyond Grades 91, 92 and 122

Science.gov (United States)

Abe, Fujio; Tabuchi, M.; Tsukamoto, S.

Boundary hardening is shown to be the most important strengthening mechanism in creep of tempered martensitic 9% Cr steel base metal and welded joints at 650 °C. The enrichment of soluble boron near prior austenite grain boundaries (PAGBs) by the GB segregation is essential for the reduction of coarsening rate of M23C6 carbides near PAGBs, enhancing the boundary and sub-boundary hardening near PAGBs, and also for the change in α/γ transformation behavior in heat-affected-zone (HAZ) of welded joints during heating of welding, producing the same microstructure in HAZ as in the base metal. Excess addition of nitrogen to the 9Cr-boron steel promotes the formation of boron nitrides during normalizing heat treatment, which consumes most of soluble boron and degrades the creep strength. A NIMS 9Cr steel (MARBN; Martensitic 9Cr steel strengthened by boron and MX nitrides) with 120-150 ppm boron and 60-90 ppm nitrogen, where no boron nitride forms during normalizing heat treatment, exhibits not only much higher creep strength of base metal than Grades 91, 92 and 122 but also substantially no degradation in creep strength due to Type IV fracture in HAZ of welded joints at 650°C. The protective Cr2O3-rich scale forms on the surface of 9Cr steel by pre-oxidation treatment in Ar gas, which significantly improves the oxidation resistance in steam at 650°C.

Plasma spraying of zirconium carbide – hafnium carbide – tungsten cermets

Czech Academy of Sciences Publication Activity Database

Brožek, Vlastimil; Ctibor, Pavel; Cheong, D.-I.; Yang, S.-H.

2009-01-01

Roč. 9, č. 1 (2009), s. 49-64 ISSN 1335-8987 Institutional research plan: CEZ:AV0Z20430508 Keywords : Plasma spraying * cermet coatings * microhardness * zirconium carbide * hafnium carbide * tungsten * water stabilized plasma Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

LARGE AREA FILTERED ARC DEPOSITION OF CARBON AND BORON BASED HARD COATINGS

Energy Technology Data Exchange (ETDEWEB)

Bhattacharya, Rabi S.

2003-12-05

This document is a final report covering work performed under Contract No. DE-FG02-99ER82911 from the Department of Energy under a SBIR Phase II Program. Wear resistant, hard coatings can play a vital role in many engineering applications. The primary goal of this project was to develop coatings containing boron and carbon with hardness greater than 30 GPa and evaluate these coatings for machining applications. UES has developed a number of carbon and boron containing coatings with hardness in the range of 34 to 65 GPa using a combination of filtered cathodic arc and magnetron sputtering. The boron containing coatings were based on TiB2, TiBN, and TiBCN, while the carbon containing coatings ere TiC+C and hydrogen free diamond-like-carbon. Machining tests were performed with single and multilayer coated tools. The turning and milling tests were run at TechSolve Inc., under a subcontract at Ohio State University. Significant increases in tool lives were realized in end milling of H-13 die steel (8X) and titanium alloy (80%) using the TiBN coating. A multilayer TiBN/TiN performed the best in end-milling of highly abrasive Al-Si alloys. A 40% increase in life over the TiAlN benchmark coating was found. Further evaluations of these coatings with commercialization partners are currently in progress.

Experimental investigation on hard turning of AISI 4340 steel using cemented coated carbide insert

Science.gov (United States)

Pradeep Kumar, J.; Kishore, K. P.; Ranjith Kumar, M.; Saran Karthick, K. R.; Vishnu Gowtham, S.

2018-02-01

Hard turning is a developing technology that offers many potential advantages compared to grinding, which remains the standard finishing process for critical hardened surfaces. In this work, an attempt has been made to experimentally investigate hard turning of AISI 4340 steel under wet and dry condition using cemented coated carbide insert. Hardness of the workpiece material is tested using Brinell and Rockwell hardness testers. CNC LATHE and cemented coated carbide inserts of designation CNMG 120408 are used for conducting experimental trials. Significant cutting parameters like cutting speed, feed rate and depth of cut are considered as controllable input parameters and surface roughness (Ra), tool wear are considered as output response parameters. Design of experiments is carried out with the help of Taguchi’s L9 orthogonal array. Results of response parameters like surface roughness and tool wear under wet and dry condition are analysed. It is found that surface roughness and tool wear are higher under dry machining condition when compared to wet machining condition. Feed rate significantly influences the surface roughness followed by cutting speed. Depth of cut significantly influences the tool wear followed by cutting speed.

Metal Carbides for Biomass Valorization

Directory of Open Access Journals (Sweden)

Carine E. Chan-Thaw

2018-02-01

Full Text Available Transition metal carbides have been utilized as an alternative catalyst to expensive noble metals for the conversion of biomass. Tungsten and molybdenum carbides have been shown to be effective catalysts for hydrogenation, hydrodeoxygenation and isomerization reactions. The satisfactory activities of these metal carbides and their low costs, compared with noble metals, make them appealing alternatives and worthy of further investigation. In this review, we succinctly describe common synthesis techniques, including temperature-programmed reaction and carbothermal hydrogen reduction, utilized to prepare metal carbides used for biomass transformation. Attention will be focused, successively, on the application of transition metal carbide catalysts in the transformation of first-generation (oils and second-generation (lignocellulose biomass to biofuels and fine chemicals.

Neutron absorbing article

International Nuclear Information System (INIS)

Naum, R.G.; Owens, D.P.; Dooher, G.I.

1979-01-01

A neutron absorbing article, in flat plate form and suitable for use in a storage rack for spent fuel, includes boron carbide particles, diluent particles and a solid, irreversibly cured phenolic polymer cured to a continuous matrix binding the boron carbide and diluent particles. The total conent of boron carbide and diluent particles is a major proportion of the article and the content of cured phenolic polymer present is a minor proportion. By regulation of the ratio of boron carbide particles to diluent particles, normally within the range of 1:9 and 9:1 and preferably within the range of 1:5 to 5:1, the neutron absorbing activity of the product may be controlled, which facilitates the manufacture of articles of particular absorbing activities best suitable for specific applications

Tribo-mechanical and electrical properties of boron-containing coatings

Science.gov (United States)

Qian, Jincheng

The development of new hard protective coatings with advanced performance is very important for progress in a variety of scientific and industrial fields. Application of hard protective coatings can significantly improve the performance of parts and components, extend their service life, and save energy in many industrial applications including aerospace, automotive, manufacturing, and other industries. In addition, the multifunctionality of protective coatings is also required in many other application fields such as optics, microelectronics, biomedical, magnetic storage media, etc. Therefore, protective coatings with enhanced tribo-mechanical and corrosion properties as well as other functions are in demand. The coating characteristics can be adjusted by controlling the microstructure at different scales. For example, films with nanostructures, such as superlattice, nanocolumn, and nanocomposite systems, exhibit distinctive characteristics compared to single-phase materials. They show superior tribo-mechanical properties due to the presence of strong interfaces, and different functions can be achieved due to the multi-phase characteristics. Boron-containing materials with their excellent mechanical properties and interesting electronic characteristics are good candidates for functional hard protective coatings. For instance, cubic boron nitride (c-BN), boron carbide (B1-xCx), and titanium diboride (TiB 2) are well known for their high hardness, high thermal stability, and high chemical inertness. An interesting example is the boron carbon nitride (BCN) compound that possesses many attractive properties because its structure is similar to that of carbon (graphite and diamond) and of boron nitride (BN in hexagonal and cubic phases). The main goal of this work is to further develop the family of Boron-containing films including B1-xCx, Ti-B-C, and BCN films fabricated by magnetron sputtering, and to enhance their performance by controlling their microstructure on

Microstructural stability and mechanical properties of a boron modified Ni–Fe based superalloy for steam boiler applications

Energy Technology Data Exchange (ETDEWEB)

Wang, Changshuai, E-mail: cswang@imr.ac.cn; Guo, YongAn; Guo, Jianting; Zhou, Lanzhang, E-mail: lzz@imr.ac.cn

2015-07-15

Ni–Fe based superalloys are being considered as boiler materials in 700 °C advanced ultra-supercritical (A-USC) coal fired power plants due to their excellent oxidation and hot corrosion resistance, outstanding workability and low cost. In this paper, the microstructural stability and mechanical properties of a boron (B) modified Ni–Fe based superalloy designed for 700 °C A-USC during thermal exposure at 650–750 °C for up to 5000 h were investigated. The results show that adding boron has no apparent influence on the major precipitates, including spherical γ′ and blocky MC. However, the amount of M{sub 23}C{sub 6} decreases markedly after standard heat treatment. During long-term thermal exposure, the addition of boron has no influence on γ′ coarsening, η phase precipitation and primary MC degeneration, but decreases the growth rate of M{sub 23}C{sub 6} along grain boundary. The stress rupture life and ductility are obviously improved after the addition of B. Meanwhile, the yield strength of B-doped alloy almost keeps the same level as that without boron addition. The fracture surface characterization exhibits that the dimples increase significantly after adding boron. During long-term thermal exposure, the elongation of the alloy with B addition increases slightly, but, for the alloy without B addition, the elongation obviously increases. The improvement of the stress rupture life and ductility can be attributed to the increase of grain boundary strength and the optimization of M{sub 23}C{sub 6} carbide distribution at grain boundary.

Microstructural stability and mechanical properties of a boron modified Ni–Fe based superalloy for steam boiler applications

International Nuclear Information System (INIS)

Wang, Changshuai; Guo, YongAn; Guo, Jianting; Zhou, Lanzhang

2015-01-01

Ni–Fe based superalloys are being considered as boiler materials in 700 °C advanced ultra-supercritical (A-USC) coal fired power plants due to their excellent oxidation and hot corrosion resistance, outstanding workability and low cost. In this paper, the microstructural stability and mechanical properties of a boron (B) modified Ni–Fe based superalloy designed for 700 °C A-USC during thermal exposure at 650–750 °C for up to 5000 h were investigated. The results show that adding boron has no apparent influence on the major precipitates, including spherical γ′ and blocky MC. However, the amount of M 23 C 6 decreases markedly after standard heat treatment. During long-term thermal exposure, the addition of boron has no influence on γ′ coarsening, η phase precipitation and primary MC degeneration, but decreases the growth rate of M 23 C 6 along grain boundary. The stress rupture life and ductility are obviously improved after the addition of B. Meanwhile, the yield strength of B-doped alloy almost keeps the same level as that without boron addition. The fracture surface characterization exhibits that the dimples increase significantly after adding boron. During long-term thermal exposure, the elongation of the alloy with B addition increases slightly, but, for the alloy without B addition, the elongation obviously increases. The improvement of the stress rupture life and ductility can be attributed to the increase of grain boundary strength and the optimization of M 23 C 6 carbide distribution at grain boundary

Oxygen collection in the limiter shadow of TEXTOR depending on wall conditioning with boron

International Nuclear Information System (INIS)

Wienhold, P.; Seggern, J. v.; Kuenzli, H.

1991-01-01

One of the major consequences of the boronization of TEXTOR compared to the carbonized machine was the further and remaining decrease of the oxygen contamination of the plasma. This has lowered also the carbon chemical sputtering by a factor of two in spite of higher radiative power loads to the graphite limiters and made auxiliary heating up to 6 MW possible. The fact, that oxygen did not reoccur as it happened during operation with carbonized walls caused the suggestion of gettering by the formation of a stable bond to the boron. Therefore, a period (May/June 89) where different conditioning treatments with boron were applied to TEXTOR gave ideal circumstances for collection experiments in the SOL and the subsequent analysis of the deposits aiming at the understanding of this hypothesis. (author) 10 refs., 2 figs

Bulletin of Materials Science | News

Indian Academy of Sciences (India)

Home; Journals; Bulletin of Materials Science; Volume 25; Issue 3 ... Sintering of nano crystalline silicon carbide by doping with boron carbide ... of these powders was achieved by addition of boron carbide of 0.5 wt% together with carbon of 1 wt% at 2050°C at vacuum (3 mbar) for 15 min. ... pp 213-217 Alloys and Steels.

The Basics of Stellites in Machining Perspective

Directory of Open Access Journals (Sweden)

Md Shahanur Hasan

2016-12-01

Stellite 6 using coated carbide inserts is presented in this paper. Interesting facts on the residual stresses induced by machining processes in Stellite 6 are revealed and analysed. The microhardness variation of machined surfaces of stellite 6 using different tool geometries is investigated in this research review.  It is revealed that coated carbide inserts with a medium-size nose radius perform better in respect of hardness changes and heat generation, producing minimum phase changes on machined surfaces of stellite 6.

Neutron absorbing article and method for manufacture of such article

International Nuclear Information System (INIS)

McMurty, C.H.; Naum, R.G.; Owens, D.P.; Hortman, M.T.

1981-01-01

A neutron absorbing article is described which comprises boron carbide particles and an irreversibly-cured phenol aldehyde condensation polymer cured to a continuous matrix about the boron carbide particles. Such an article may be used in spent fuel storage racks. It can be manufactured by mixing together a curable phenolic resin with boron carbide particles, compacting the mixture to an article of desired shape, curing the resin at an elevated temperature, impregnating the cured article with curable phenolic resin in liquid state, and curing the article again

An experimental study of flank wear in the end milling of AISI 316 stainless steel with coated carbide inserts

Science.gov (United States)

Odedeyi, P. B.; Abou-El-Hossein, K.; Liman, M.

2017-05-01

Stainless steel 316 is a difficult-to-machine iron-based alloys that contain minimum of about 12% of chromium commonly used in marine and aerospace industry. This paper presents an experimental study of the tool wear propagation variations in the end milling of stainless steel 316 with coated carbide inserts. The milling tests were conducted at three different cutting speeds while feed rate and depth of cut were at (0.02, 0.06 and 01) mm/rev and (1, 2 and 3) mm, respectively. The cutting tool used was TiAlN-PVD-multi-layered coated carbides. The effects of cutting speed, cutting tool coating top layer and workpiece material were investigated on the tool life. The results showed that cutting speed significantly affected the machined flank wears values. With increasing cutting speed, the flank wear values decreased. The experimental results showed that significant flank wear was the major and predominant failure mode affecting the tool life.

Microstructural Study of Titanium Carbide Coating on Cemented Carbide

DEFF Research Database (Denmark)

Vuorinen, S.; Horsewell, Andy

1982-01-01

Titanium carbide coating layers on cemented carbide substrates have been investigated by transmission electron microscopy. Microstructural variations within the typically 5µm thick chemical vapour deposited TiC coatings were found to vary with deposit thickness such that a layer structure could...... be delineated. Close to the interface further microstructural inhomogeneities were obsered, there being a clear dependence of TiC deposition mechanism on the chemical and crystallographic nature of the upper layers of the multiphase substrate....

The effect of abrading and cutting instruments on machinability of dental ceramics.

Science.gov (United States)

Sakoda, Satoshi; Nakao, Noriko; Watanabe, Ikuya

2018-03-16

The aim was to investigate the effect of machining instruments on machinability of dental ceramics. Four dental ceramics, including two zirconia ceramics were machined by three types (SiC, diamond vitrified, and diamond sintered) of wheels with a hand-piece engine and two types (diamond and carbide) of burs with a high-speed air turbine. The machining conditions used were abrading speeds of 10,000 and 15,000 r.p.m. with abrading force of 100 gf for the hand-piece engine, and a pressure of 200 kPa and a cutting force of 80 gf for the air-turbine hand-piece. The machinability efficiency was evaluated by volume losses after machining the ceramics. A high-abrading speed had high-abrading efficiency (high-volume loss) compared to low-abrading speed in all abrading instruments used. The diamond vitrified wheels demonstrated higher volume loss for two zirconia ceramics than those of SiC and diamond sintered wheels. When the high-speed air-turbine instruments were used, the diamond points showed higher volume losses compared to the carbide burs for one ceramic and two zirconia ceramics with high-mechanical properties. The results of this study indicated that the machinability of dental ceramics depends on the mechanical and physical properties of dental ceramics and machining instruments. The abrading wheels show autogenous action of abrasive grains, in which ground abrasive grains drop out from the binder during abrasion, then the binder follow to wear out, subsequently new abrasive grains come out onto the instrument surface (autogenous action) and increase the grinding amount (volume loss) of grinding materials.

Design and simulation of thermal residual stresses of coatings on WC-Co cemented carbide cutting tool substrate

International Nuclear Information System (INIS)

Li, Anhai; Zhao, Jun; Zang, Jian; Zheng, Wei

2016-01-01

Large thermal residual stresses in coatings during the coating deposition process may easily lead to coating delamination of coated carbide tools in machining. In order to reduce the possibility of coating delamination during the tool failure process, a theoretical method was proposed and a numerical method was constructed for the coating design of WC-Co cemented carbide cutting tools. The thermal residual stresses of multi-layered coatings were analytically modeled based on equivalent parameters of coating properties, and the stress distribution of coatings are simulated by Finite element method (FEM). The theoretically calculated results and the FEM simulated results were verified and in good agreement with the experimental test results. The effects of coating thickness, tool substrate, coating type and interlayer were investigated by the proposed geometric and FEM model. Based on the evaluations of matchability of tool substrate and tool coatings, the basic principles of tool coating design were proposed. This provides theoretical basis for the selection and design of coatings of cutting tools in high-speed machining

Performance analysis of LMFBR control rods

International Nuclear Information System (INIS)

Pitner, A.L.; Birney, K.R.

1975-01-01

Control rods in the FFTF and LMFBR's will consist of pin bundles of stainless steel-clad boron carbide pellets. In the FFTF reference design, sixty-one pins of 0.474-inch diameter each containing a 36-inch stack of 0.362-inch diameter boron carbide pellets comprise a control rod. Reactivity control is provided by the 10 B (n,α) 7 Li reaction in the boron carbide. This reaction is accompanied by an energy release of 2.8 MeV, and heating from this reaction typically approaches 100 watts/cm 3 for natural boron carbide pellets in an LMFBR flux. Performance analysis of LMFBR control rods must include an assessment of the thermal performance of control pins. In addition, irradiation performance with regard to helium release, pellet swelling, and reactivity worth depletion as a function of service time must be evaluated

Análisis de la influencia de las condiciones de proceso sobre el acabado superficial de materiales cerámicos fabricados por electroerosión

Directory of Open Access Journals (Sweden)

Puertas-Arbizu, I.

2004-12-01

Full Text Available Electrical discharge machining (EDM is an emerging alternative versus some other manufacturing processes of conductive ceramic materials, such as: laser machining, electrochemical machining, abrasive water jet, ultrasonic machining and diamond wheel grinding. Due to its interest in the industrial field, in this work a study of the influence of process conditions on the surface aspect of three conductive ceramic materials: hot-pressed boron carbide (B₄C, reaction-bonded silicon carbide (SiSiC and cobalt-bonded tungsten carbide (WC-Co is carried out. These materials are to be electrical discharge machined under different machining conditions and in the particular case of finish stages (Ra ≤ 1 μm.

El mecanizado por electroerosión (en Inglés, Electrical Discharge Machining, EDM constituye una alternativa emergente frente a otros procesos de fabricación de materiales cerámicos conductores, tales como: mecanizado por láser, mecanizado electroquímico, chorro de agua con abrasivos, mecanizado por ultrasonidos y rectificado con muela de diamante. Debido a su interés en el ámbito industrial, en este trabajo se lleva a cabo un estudio de la influencia de las condiciones de operación sobre el aspecto superficial de tres materiales cerámicos conductores: carburo de boro prensado en caliente (B₄C, carburo de silicio infiltrado con silicio (SiSiC y carburo de wolframio en matriz metálica de cobalto (WC-Co, electroerosionados bajo diferentes condiciones de mecanizado y para el caso particular de regímenes de acabado (Ra ≤ 1 μm.

Production of neutron shielding material

International Nuclear Information System (INIS)

Roszler, J.J.

1979-01-01

A neutron-absorbing material consisting of a layer of boron carbide sandwiched between layers of aluminum is produced by constructing a rectangular box from aluminum plate leaving one end open. The box is filled with a uniform mixture of finely-divided boron carbide and anodized aluminum powders and the open end is sealed by welding an aluminum plate in place. The box is then heated to 800-850 deg F and rolled to reduce its thickness to the desired amount. The hot rolling bonds or sinters the particles of metal powder or boron carbide. (LL)

Boron-enhanced diffusion of boron from ultralow-energy boron implantation

International Nuclear Information System (INIS)

Agarwal, A.; Eaglesham, D.J.; Gossmann, H.J.; Pelaz, L.; Herner, S.B.; Jacobson, D.C.

1998-01-01

The authors have investigated the diffusion enhancement mechanism of BED (boron enhanced diffusion), wherein the boron diffusivity is enhanced three to four times over the equilibrium diffusivity at 1,050 C in the proximity of a silicon layer containing a high boron concentration. It is shown that BED is associated with the formation of a fine-grain polycrystalline silicon boride phase within an initially amorphous Si layer having a high B concentration. For 0.5 keV B + , the threshold implantation dose which leads to BED lies between 3 x 10 14 and of 1 x 10 15 /cm -2 . Formation of the shallowest possible junctions by 0.5 keV B + requires that the implant dose be kept lower than this threshold

Adsorption of boron from boron-containing wastewaters by ion exchange in a continuous reactor

International Nuclear Information System (INIS)

Yilmaz, A. Erdem; Boncukcuoglu, Recep; Yilmaz, M. Tolga; Kocakerim, M. Muhtar

2005-01-01

In this study, boron removal from boron-containing wastewaters prepared synthetically was investigated. The experiments in which Amberlite IRA 743, boron specific resin was used were carried out in a column reactor. The bed volume of resin, boron concentration, flow rate and temperature were selected as experimental parameters. The experimental results showed that percent of boron removal increased with increasing amount of resin and with decreasing boron concentration in the solution. Boron removal decreased with increasing of flow rate and the effect of temperature on the percent of total boron removal increased the boron removal rate. As a result, it was seen that about 99% of boron in the wastewater could be removed at optimum conditions

Design and Fabrication of Automatic Glass Cutting Machine

Science.gov (United States)

Veena, T. R.; Kadadevaramath, R. S.; Nagaraj, P. M.; Madhusudhan, S. V.

2016-09-01

This paper deals with the design and fabrication of the automatic glass or mirror cutting machine. In order to increase the accuracy of cut and production rate; and decrease the production time and accidents caused due to manual cutting of mirror or glass, this project aims at development of an automatic machine which uses a programmable logic controller (PLC) for controlling the movement of the conveyer and also to control the pneumatic circuit. In this machine, the work of the operator is to load and unload the mirror. The cutter used in this machine is carbide wheel with its cutting edge ground to a V-shaped profile. The PLC controls the pneumatic cylinder and intern actuates the cutter along the glass, a fracture layer is formed causing a mark to be formed below the fracture layer and a crack to be formed below the rib mark. The machine elements are designed using CATIA V5R20 and pneumatic circuit are designed using FESTO FLUID SIM software.

Optimization of cutting parameters in CNC turning of stainless steel 304 with TiAlN nano coated carbide cutting tool

Science.gov (United States)

Durga Prasada Rao, V.; Harsha, N.; Raghu Ram, N. S.; Navya Geethika, V.

2018-02-01

In this work, turning was performed to optimize the surface finish or roughness (Ra) of stainless steel 304 with uncoated and coated carbide tools under dry conditions. The carbide tools were coated with Titanium Aluminium Nitride (TiAlN) nano coating using Physical Vapour Deposition (PVD) method. The machining parameters, viz., cutting speed, depth of cut and feed rate which show major impact on Ra are considered during turning. The experiments are designed as per Taguchi orthogonal array and machining process is done accordingly. Then second-order regression equations have been developed on the basis of experimental results for Ra in terms of machining parameters used. Regarding the effect of machining parameters, an upward trend is observed in Ra with respect to feed rate, and as cutting speed increases the Ra value increased slightly due to chatter and vibrations. The adequacy of response variable (Ra) is tested by conducting additional experiments. The predicted Ra values are found to be a close match of their corresponding experimental values of uncoated and coated tools. The corresponding average % errors are found to be within the acceptable limits. Then the surface roughness equations of uncoated and coated tools are set as the objectives of optimization problem and are solved by using Differential Evolution (DE) algorithm. Also the tool lives of uncoated and coated tools are predicted by using Taylor’s tool life equation.

Surface/subsurface observation and removal mechanisms of ground reaction bonded silicon carbide

Science.gov (United States)

Yao, Wang; Zhang, Yu-Min; Han, Jie-cai; Zhang, Yun-long; Zhang, Jian-han; Zhou, Yu-feng; Han, Yuan-yuan

2006-01-01

Reaction Bonded Silicon Carbide (RBSiC) has long been recognized as a promising material for optical applications because of its unique combination of favorable properties and low-cost fabrication. Grinding of silicon carbide is difficult because of its high hardness and brittleness. Grinding often induces surface and subsurface damage, residual stress and other types of damage, which have great influence on the ceramic components for optical application. In this paper, surface integrity, subsurface damage and material removal mechanisms of RBSiC ground using diamond grinding wheel on creep-feed surface grinding machine are investigated. The surface and subsurface are studied with scanning electron microscopy (SEM) and optical microscopy. The effects of grinding conditions on surface and subsurface damage are discussed. This research links the surface roughness, surface and subsurface cracks to grinding parameters and provides valuable insights into the material removal mechanism and the dependence of grind induced damage on grinding conditions.

Doping of silicon carbide by ion implantation; Dopage du carbure de silicium par implantation ionique

Energy Technology Data Exchange (ETDEWEB)

Gimbert, J

1999-03-04

It appeared that in some fields, as the hostile environments (high temperature or irradiation), the silicon compounds showed limitations resulting from the electrical and mechanical properties. Doping of 4H and 6H silicon carbide by ion implantation is studied from a physicochemical and electrical point of view. It is necessary to obtain n-type and p-type material to realize high power and/or high frequency devices, such as MESFETs and Schottky diodes. First, physical and electrical properties of silicon carbide are presented and the interest of developing a process technology on this material is emphasised. Then, physical characteristics of ion implantation and particularly classical dopant implantation, such as nitrogen, for n-type doping, and aluminium and boron, for p-type doping are described. Results with these dopants are presented and analysed. Optimal conditions are extracted from these experiences so as to obtain a good crystal quality and a surface state allowing device fabrication. Electrical conduction is then described in the 4H and 6H-SiC polytypes. Freezing of free carriers and scattering processes are described. Electrical measurements are carried out using Hall effect on Van der Panw test patterns, and 4 point probe method are used to draw the type of the material, free carrier concentrations, resistivity and mobility of the implanted doped layers. These results are commented and compared to the theoretical analysis. The influence of the technological process on electrical conduction is studied in view of fabricating implanted silicon carbide devices. (author)

Boron reclamation

International Nuclear Information System (INIS)

Smith, R.M.

1980-07-01

A process to recover high purity 10 B enriched crystalline boron powder from a polymeric matrix was developed on a laboratory basis and ultimately scaled up to production capacity. The process is based on controlled pyrolysis of boron-filled scrap followed by an acid leach and dry sieving operation to return the powder to the required purity and particle size specifications. Typically, the recovery rate of the crystalline powder is in excess of 98.5 percent, and some of the remaining boron is recovered in the form of boric acid. The minimum purity requirement of the recovered product is 98.6 percent total boron

Real-time boronization in PBX-M using erosion of solid boronized targets

International Nuclear Information System (INIS)

Kugel, H.W.; Timberlake, J.; Bell, R.; LeBlanc, B.; Okabayashi, M.; Paul, S.; Tighe, W.; Hirooka, Y.

1994-11-01

Thirty one real-time boronizations were applied to PBX-M using the plasma erosion of solid target probes. More than 17 g of boron were deposited in PBX-M using this technique. The probes were positioned at the edge plasma to optimize vaporization and minimize spallation. Auger depth profile analysis of poloidal and toroidal deposition sample coupon arrays indicate that boron was transported by the plasma around the torus and deep into the divertors. During discharges with continuous real-time boronization, low-Z and high-Z impurities decreased rapidly as plasma surfaces were covered during the first 20-30 discharges. After boronization, a short-term improvement in plasma conditions persisted prior to significant boron erosion from plasma surfaces, and a longer term, but less significant improvement persisted as boron farther from the edge continued gettering. Real-time solid target boronization has been found to be very effective for accelerating conditioning to new regimes and maintaining high performance plasma conditions

Determination of emissivity coefficient of heat-resistant super alloys and cemented carbide

Directory of Open Access Journals (Sweden)

Kieruj Piotr

2016-12-01

Full Text Available This paper presents the analysis of emissivity engineering materials according to temperature. Experiment is concerned on difficult to machine materials, which may be turned with laser assisting. Cylindrical samples made of nickel-based alloys Inconel 625, Inconel 718, Waspaloy and tungsten-carbides based on cobalt matrix were analyzed. The samples’ temperature in contact method was compared to the temperature measured by non-contact pyrometers. Based on this relative, the value of the emissivity coefficient was adjusted to the right indication of pyrometers.

Fundamental Study on Electrical Discharge Machining

OpenAIRE

Uno, Yoshiyuki; Nakajima, Toshikatsu; Endo, Osamu

1989-01-01

The generation mechanism of crater in electrical discharge machining is analyzed with a single pulse discharge device for alloy tool steel, black alumina ceramics, cermet and cemented carbide, investigating the gap voltage, the discharge current, the shape of crater, the wear of electrode and so on. The experimental analysis makes it clear that the shape of crater has a characteristic feature for the kind of workpiece. The shape of electrode, which changes with the wear by an electric spark, ...

Ceramic silicon-boron-carbon fibers from organic silicon-boron-polymers

Science.gov (United States)

Riccitiello, Salvatore R. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

1993-01-01

Novel high strength ceramic fibers derived from boron, silicon, and carbon organic precursor polymers are discussed. The ceramic fibers are thermally stable up to and beyond 1200 C in air. The method of preparation of the boron-silicon-carbon fibers from a low oxygen content organosilicon boron precursor polymer of the general formula Si(R2)BR(sup 1) includes melt-spinning, crosslinking, and pyrolysis. Specifically, the crosslinked (or cured) precursor organic polymer fibers do not melt or deform during pyrolysis to form the silicon-boron-carbon ceramic fiber. These novel silicon-boron-carbon ceramic fibers are useful in high temperature applications because they retain tensile and other properties up to 1200 C, from 1200 to 1300 C, and in some cases higher than 1300 C.

Study of the machining of uranium carbide rods obtained by continuous casting under electronic bombardment; Etude de l'usinage de barreaux de carbure d'uranium obtenus par coulee continue sous bombardement electronique

Energy Technology Data Exchange (ETDEWEB)

Rousset, P.; Accary, A. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

The authors consider the various methods of machining uranium mono-carbide and compare them critically in the case of their application to uranium carbide obtained by fusion under an electronic bombardment and continuous casting. This study leads them to propose two mechanical machining methods: cylindrical rectification and center-less rectification, preceded by a preliminary roughing out of a cylinder, the latter appearing more suitable. A study of the machining yields as a function of the diameter of the rough bars and of the diameter of the finished rods has shown that an optimum value of the rough bar diameter exists for each value of the finished rod diameter. It is found that the yield increases as the diameter itself increases, this yield rising from 45 per cent to around 70 per cent as the diameter of the rough bars increases from 25-26 mm to 37-38 mm. (authors) [French] Les auteurs envisagent les differentes methodes d'usinage du monocarbure d'uranium et se livrent a une etude critique de celles-ci, dans le cas de leur application a l'usinage de barreaux de carbure d'uranium obtenus par fusion sous bombardement electronique et coulee continue. Cette etude les conduit a proposer deux methodes d'usinage mecanique: la rectification cylindrique et la rectification 'centerless', precedee d'un ebauchage par carottage, la seconde paraissant la plus appropriee. L'etude des rendements d'usinage en fonction du diametre des barreaux bruts et du diametre des barreaux finis, a mis en evidence une valeur optimale du diametre des barreaux bruts pour chaque valeur du diametre des barreaux usines. Elle a montre que le rendement croit lorsque le diametre croit lui-meme, ce rendement passant d'environ 45 pour cent a environ 70 pour cent, lorsque le diametre des barreaux bruts passe de 25-26 mm a 37-38 mm.

Study of boron carbide evolution under neutron irradiation; Contribution a l'etude de l'evolution du carbure de bore sous irradiation neutronique

Energy Technology Data Exchange (ETDEWEB)

Simeone, D. [CEA/Saclay, Dept. de Mecanique et de Technologie (DMT), 91 - Gif-sur-Yvette (France)]|[Universite Blaise Pascal, Clermont-Ferrand II, (CNRS), 63 - Aubiere (France)

1999-07-01

Owing to its high neutron efficiency, boron carbide (B{sub 4}C) is used as a neutron absorber in control rods of nuclear plants. Its behaviour under irradiation has been extensively studied for many years. It now seems clear that brittleness of the material induced by the {sup 10}B(n,{alpha}){sup 7}Li capture reaction is due to penny shaped helium bubbles associated to a high strain field around them. However, no model explains the behaviour of the material under neutron irradiation. In order to build such a model, this work uses different techniques: nuclear microprobe X-ray diffraction profile analysis and Raman and Nuclear Magnetic Resonance Spectroscopy to present an evolution model of B{sub 4}C under neutron irradiation. The use of nuclear reactions produced by a nuclear microprobe such as the {sup 7}Li(p,p'{gamma}){sup 7}Li reaction, allows to measure lithium profile in B{sub 4}C pellets irradiated either in Pressurised Water Reactors or in Fast Breeder Reactors. Examining such profiles enables us to describe the migration of lithium atoms out of B{sub 4}C materials under neutron irradiation. The analysis of X-ray diffraction profiles of irradiated B{sub 4}C samples allows us to quantify the concentrations of helium bubbles as well as the strain fields around such bubbles.Furthermore Raman spectroscopy studies of different B{sub 4}C samples lead us to propose that under neutron irradiation. the CBC linear chain disappears. Such a vanishing of this CBC chain. validated by NMR analysis, may explain the penny shaped of helium bubbles inside irradiated B{sub 4}C. (author)

Effect of machining parameters on surface integrity of silicon carbide ceramic using end electric discharge milling and mechanical grinding hybrid machining

International Nuclear Information System (INIS)

Ji, Renjie; Liu, Yonghong; Zhang, Yanzhen; Cai, Baoping; Li, Xiaopeng; Zheng, Chao

2013-01-01

A novel hybrid process that integrates end electric discharge (ED) milling and mechanical grinding is proposed. The process is able to effectively machine a large surface area on SiC ceramic with good surface quality and fine working environmental practice. The polarity, pulse on-time, and peak current are varied to explore their effects on the surface integrity, such as surface morphology, surface roughness, micro-cracks, and composition on the machined surface. The results show that positive tool polarity, short pulse on-time, and low peak current cause a fine surface finish. During the hybrid machining of SiC ceramic, the material is mainly removed by end ED milling at rough machining mode, whereas it is mainly removed by mechanical grinding at finish machining mode. Moreover, the material from the tool can transfer to the workpiece, and a combination reaction takes place during machining.

Joining elements of silicon carbide

International Nuclear Information System (INIS)

Olson, B.A.

1979-01-01

A method of joining together at least two silicon carbide elements (e.g.in forming a heat exchanger) is described, comprising subjecting to sufficiently non-oxidizing atmosphere and sufficiently high temperature, material placed in space between the elements. The material consists of silicon carbide particles, carbon and/or a precursor of carbon, and silicon, such that it forms a joint joining together at least two silicon carbide elements. At least one of the elements may contain silicon. (author)

Aspects of the chemistry of boron

International Nuclear Information System (INIS)

Moellinger, H.

1976-01-01

Crystal phases of elementary boron are reviewed as well as boron-sulphur, boron-selenum, boron-tellurium, and boron-nitrogen compounds, carboranes, and boron-carbohydrate complexes. A boron cadastre of rivers and lakes serves to illustrate the role of boron in environmental protection. Technically relevant boron compounds and their uses are mentioned. (orig.) 891 HK/orig. 892 MB [de

Use of Acoustic Emission and Pattern Recognition for Crack Detection of a Large Carbide Anvil.

Science.gov (United States)

Chen, Bin; Wang, Yanan; Yan, Zhaoli

2018-01-29

Large-volume cubic high-pressure apparatus is commonly used to produce synthetic diamond. Due to the high pressure, high temperature and alternative stresses in practical production, cracks often occur in the carbide anvil, thereby resulting in significant economic losses or even casualties. Conventional methods are unsuitable for crack detection of the carbide anvil. This paper is concerned with acoustic emission-based crack detection of carbide anvils, regarded as a pattern recognition problem; this is achieved using a microphone, with methods including sound pulse detection, feature extraction, feature optimization and classifier design. Through analyzing the characteristics of background noise, the cracked sound pulses are separated accurately from the originally continuous signal. Subsequently, three different kinds of features including a zero-crossing rate, sound pressure levels, and linear prediction cepstrum coefficients are presented for characterizing the cracked sound pulses. The original high-dimensional features are adaptively optimized using principal component analysis. A hybrid framework of a support vector machine with k nearest neighbors is designed to recognize the cracked sound pulses. Finally, experiments are conducted in a practical diamond workshop to validate the feasibility and efficiency of the proposed method.

Method of fabricating porous silicon carbide (SiC)

Science.gov (United States)

Shor, Joseph S. (Inventor); Kurtz, Anthony D. (Inventor)

1995-01-01

Porous silicon carbide is fabricated according to techniques which result in a significant portion of nanocrystallites within the material in a sub 10 nanometer regime. There is described techniques for passivating porous silicon carbide which result in the fabrication of optoelectronic devices which exhibit brighter blue luminescence and exhibit improved qualities. Based on certain of the techniques described porous silicon carbide is used as a sacrificial layer for the patterning of silicon carbide. Porous silicon carbide is then removed from the bulk substrate by oxidation and other methods. The techniques described employ a two-step process which is used to pattern bulk silicon carbide where selected areas of the wafer are then made porous and then the porous layer is subsequently removed. The process to form porous silicon carbide exhibits dopant selectivity and a two-step etching procedure is implemented for silicon carbide multilayers.

Process parameter optimization based on principal components analysis during machining of hardened steel

Directory of Open Access Journals (Sweden)

Suryakant B. Chandgude

2015-09-01

Full Text Available The optimum selection of process parameters has played an important role for improving the surface finish, minimizing tool wear, increasing material removal rate and reducing machining time of any machining process. In this paper, optimum parameters while machining AISI D2 hardened steel using solid carbide TiAlN coated end mill has been investigated. For optimization of process parameters along with multiple quality characteristics, principal components analysis method has been adopted in this work. The confirmation experiments have revealed that to improve performance of cutting; principal components analysis method would be a useful tool.

High-performance circular sawing of AISI 1045 steel with cermet and tungsten carbide inserts

International Nuclear Information System (INIS)

Abrao, A. M.; Rubio, J. C. Campos; Moreira, C.; Faria, P. E.

2014-01-01

This work investigated the influence of cutting speed and feed rate on cutting forces, surface roughness, and slot width circular sawing of AISI 1045 steel. The effects of tool material (cermet and tungsten carbide) and geometry (chip breaker flute and pre-cutting/postcutting teeth) were also investigated. Thrust and radial forces generally tended to decrease as the cutting speed increased and tended to increase with the feed rate. The lowest values of thrust and radial forces were obtained using a tungsten carbide saw ground with precutting and post-cutting teeth. With regard to the quality of the machined wall, the lowest surface roughness was obtained by applying the highest cutting speed and lowest feed rate and employing a cermet brazed saw. Under this condition, roughness values comparable to face turning and parting off operations were obtained. The cermet brazed saw was responsible for producing the narrowest slot widths.

Micro Electro Discharge Machining of Electrically Nonconductive Ceramics

International Nuclear Information System (INIS)

Schubert, A.; Zeidler, H.; Hackert, M.; Wolf, N.

2011-01-01

EDM is a known process for machining of hard and brittle materials. Due to its noncontact and nearly forceless behaviour, it has been introduced into micro manufacturing and through constant development it is now an important means for producing high-precision micro geometries. One restriction of EDM is its limitation to electrically conducting materials.Today many applications, especially in the biomedical field, make use of the benefits of ceramic materials, such as high strength, very low wear and biocompatibility. Common ceramic materials such as Zirconium dioxide are, due to their hardness in the sintered state, difficult to machine with conventional cutting techniques. A demand for the introduction of EDM to these materials could so far not be satisfied because of their nonconductive nature.At the Chemnitz University of Technology and the Fraunhofer IWU, investigations in the applicability of micro-EDM for the machining of nonconductive ceramics are being conducted. Tests are undertaken using micro-EDM drilling with Tungsten carbide tool electrodes and ZrO 2 ceramic workpieces. A starting layer, in literature often referred to as 'assisting electrode' is used to set up a closed electric circuit to start the EDM process. Combining carbon hydride based dielectric and a specially designed low-frequency vibration setup to excite the workpiece, the process environment can be held within parameters to allow for a constant EDM process even after the starting layer is machined. In the experiments a cylindrical 120 μm diameter Tungsten carbide tool electrode and Y 2 O 3 - and MgO- stabilized ZrO 2 worpieces are used. The current and voltage signals of the discharges within the different stages of the process (machining of the starting layer, machining of the base material, transition stage) are recorded and their characteristics compared to discharges in metallic material. Additionally, the electrode feed is monitored. The influences of the process parameters are

Characterization of Nanometric-Sized Carbides Formed During Tempering of Carbide-Steel Cermets

Directory of Open Access Journals (Sweden)

Matus K.

2016-06-01

Full Text Available The aim of this article of this paper is to present issues related to characterization of nanometric-sized carbides, nitrides and/or carbonitrides formed during tempering of carbide-steel cermets. Closer examination of those materials is important because of hardness growth of carbide-steel cermet after tempering. The results obtained during research show that the upswing of hardness is significantly higher than for high-speed steels. Another interesting fact is the displacement of secondary hardness effect observed for this material to a higher tempering temperature range. Determined influence of the atmosphere in the sintering process on precipitations formed during tempering of carbide-steel cermets. So far examination of carbidesteel cermet produced by powder injection moulding was carried out mainly in the scanning electron microscope. A proper description of nanosized particles is both important and difficult as achievements of nanoscience and nanotechnology confirm the significant influence of nanocrystalline particles on material properties even if its mass fraction is undetectable by standard methods. The following research studies have been carried out using transmission electron microscopy, mainly selected area electron diffraction and energy dispersive spectroscopy. The obtained results and computer simulations comparison were made.

Doped Boron Carbide-Based Polymers: Fundamental Studies of a Novel Class of Materials for Enhanced Neutron Detection

Science.gov (United States)

2016-03-01

heterojunction diodes fabricated from these films show no evidence of Schottky barrier formation or of significant leakage current in reverse bias [8...all of summer 2012 for this purpose. Related project work: measuring the electronic structure and the surface oxide of thorium oxide ThO2 with Tony...Detecting and Nanoelectronic Applications, Techon 2012. 4. “The History and Development of Boron Carbon Alloy Devices and Rare Earth Heterojunction

A technique to prepare boronated B72.3 monoclonal antibody for boron neutron capture therapy

International Nuclear Information System (INIS)

Ranadive, G.N.; Rosenzweig, H.S.; Epperly, M.W.

1993-01-01

B72.3 monoclonal antibody has been successfully boronated using mercaptoundecahydro-closo-dodecaborate (boron cage compound). The reagent was incorporated by first reacting the lysine residues of the antibody with m-maleimidobenzoyl succinimide ester (MBS), followed by Michael addition to the maleimido group by the mercapto boron cage compound to form a physiologically stable thioether linkage. Boron content of the antibody was determined by atomic absorption spectroscopy. For biodistribution studies, boronated antibody was radioiodinated with iodogen. 125 I-labeled and boronated B72.3 monoclonal antibody demonstrated clear tumor localization when administered via tail vein injections to athymic nude mice bearing LS174-T tumor xenografts. Boronated antibody was calculated to deliver 10 6 boron atoms per tumor cell. Although this falls short of the specific boron content originally proposed as necessary for boron neutron capture therapy (BNCT), recent calculations suggest that far fewer atoms of 10 B per tumor cell would be necessary to effect successful BNCT when the boron is targeted to the tumor cell membrane. (author)

Implantation of boron in silicon

International Nuclear Information System (INIS)

Hofker, W.K.

1975-01-01

The distribution versus depth of boron implanted in silicon and the corresponding electrical activity obtained after annealing are studied. The boron distributions are measured by secondary-ion mass spectrometry. Boron distributions implanted at energies in the range from 30 keV to 800 keV in amorphous and polycrystalline silicon are analysed. Moments of these distributions are determined by a curve-fitting programme and compared with moments calculated by Winterbon. Boron distributions obtained by implantations along a dense crystallographic direction in monocrystalline silicon are found to have penetrating tails. After investigation of some possible mechanisms of tail formation it is concluded that the tails are due to channelling. It was found that the behaviour of boron during annealing is determined by the properties of three boron fractions consisting of precipitated boron, interstitial boron and substitutional boron. The electrical activity of the boron versus depth is found to be consistent with the three boron fractions. A peculiar redistribution of boron is found which is induced by the implantation of a high dose of heavy ions and subsequent annealing. Different mechanisms which may cause the observed effects, such as thermal diffusion which is influenced by lattice strain and damage, are discussed. (Auth.)

New possibilities of the isotope distribution examination in irradiated absorbing materials using secondary ion mass spectrometry method

International Nuclear Information System (INIS)

Goncharenko, Y. D.; Evseev, L.A.; Risovany, V.D.

2005-01-01

The SIMS technique (with using a linear analysis and 2D surface imaging) has been to measure the radial distribution of the boron isotope ratio in the boron carbide pellets irradiated in the fast reactor. It was revealed that a radial distribution of isotope ratio in the boron carbide pellets is significantly different after irradiation in fast and thermal reactors. It was showed the advisability of using ion images for such examinations. (Author)

Stable carbides in transition metal alloys

International Nuclear Information System (INIS)

Piotrkowski, R.

1991-01-01

In the present work different techniques were employed for the identification of stable carbides in two sets of transition metal alloys of wide technological application: a set of three high alloy M2 type steels in which W and/or Mo were total or partially replaced by Nb, and a Zr-2.5 Nb alloy. The M2 steel is a high speed steel worldwide used and the Zr-2.5 Nb alloy is the base material for the pressure tubes in the CANDU type nuclear reactors. The stability of carbide was studied in the frame of Goldschmidt's theory of interstitial alloys. The identification of stable carbides in steels was performed by determining their metallic composition with an energy analyzer attached to the scanning electron microscope (SEM). By these means typical carbides of the M2 steel, MC and M 6 C, were found. Moreover, the spatial and size distribution of carbide particles were determined after different heat treatments, and both microstructure and microhardness were correlated with the appearance of the secondary hardening phenomenon. In the Zr-Nb alloy a study of the α and β phases present after different heat treatments was performed with optical and SEM metallographic techniques, with the guide of Abriata and Bolcich phase diagram. The α-β interphase boundaries were characterized as short circuits for diffusion with radiotracer techniques and applying Fisher-Bondy-Martin model. The precipitation of carbides was promoted by heat treatments that produced first the C diffusion into the samples at high temperatures (β phase), and then the precipitation of carbide particles at lower temperature (α phase or (α+β)) two phase field. The precipitated carbides were identified as (Zr, Nb)C 1-x with SEM, electron microprobe and X-ray diffraction techniques. (Author) [es

The study of high-boron steel and high-boron cast iron used for shield

International Nuclear Information System (INIS)

Pan Xuerong; Lu Jixin; Wen Yaozeng; Wang Zhaishu; Cheng Jiantin; Cheng Wen; Shun Danqi; Yu Jinmu

1996-12-01

The smelting, forging, heat-treatment technology and the mechanical properties of three kinds of high-boron steels (type 1: 0.5% boron; type 2: 0.5% boron and 4% or 2% nickel; type 3: 0.5% boron, 0.5% nickel and 0.5% molybdenum) were studied. The test results show that the technology for smelting, forging and heat-treatment (1050 degree C/0.5 h water cooled + 810 degree C/1 h oil cooled) in laboratory is feasible. Being sensitive to notch, the impact toughness of high-boron steel type 1 is not steady and can not meet the technology requirements on mechanical properties. The mechanical properties of both high-boron steel type 2 and type 3 can meet the technological requirements. The smelting technology of high-boron casting iron containing 0.5% boron was researched. The tests show that this casting iron can be smelted in laboratory and its properties can basically satisfy the technology requirements. (10 refs., 6 figs., 11 tab.)

High Speed Finish Turning of Inconel 718 Using PCBN Tools under Dry Conditions

Directory of Open Access Journals (Sweden)

José Luis Cantero

2018-03-01

Full Text Available Inconel 718 is a superalloy, considered one of the least machinable materials. Tools must withstand a high level of temperatures and pressures in a very localized area, the abrasiveness of the hard carbides contained in the Inconel 718 microstructure and the adhesion tendency during its machining. Mechanical properties along with the low thermal conductivity become an important issue for the tool wear. The finishing operations for Inconel 718 are usually performed after solution heat treatment and age hardening of the material to give the superalloy a higher level of hardness. Carbide tools, cutting fluid (at normal or high pressures and low cutting speed are the main recommendations for finish turning of Inconel 718. However, dry machining is preferable to the use of cutting fluids, because of its lower environmental impact and cost. Previous research has concluded that the elimination of cutting fluid in these processes is feasible when using hard carbide tools. Recent development of new PCBN (Polycrystalline Cubic Boron Nitride grades for cutting tools with higher tenacity has allowed the application of these tool grades in the finishing operations of Inconel 718. This work studies the performance of commercial PCBN tools from four different tool manufacturers as well as an additional grade with equivalent performance during finish turning of Inconel 718 under dry conditions. Wear tests were carried out with different cutting conditions, determining the evolution of machining forces, surface roughness and tool wear. It is concluded that it is not industrially viable the high-speed finishing of Inconel 718 in a dry environment.

Microsegregation in Nodular Cast Iron with Carbides

Directory of Open Access Journals (Sweden)

S. Pietrowski

2012-12-01

Full Text Available In this paper results of microsegregation in the newly developed nodular cast iron with carbides are presented. To investigate the pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen. The distribution of linear elements on the eutectic cell radius was examined. To investigate the microsegregation pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen.The linear distribution of elements on the eutectic cell radius was examined. Testing of the chemical composition of cast iron metal matrix components, including carbides were carried out. The change of graphitizing and anti-graphitizing element concentrations within eutectic cell was determined. It was found, that in cast iron containing Mo carbides crystallizing after austenite + graphite eutectic are Si enriched.

Microsegregation in Nodular Cast Iron with Carbides

Directory of Open Access Journals (Sweden)

Pietrowski S.

2012-12-01

Full Text Available In this paper results of microsegregation in the newly developed nodular cast iron with carbides are presented. To investigate the pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen. The distribution of linear elements on the eutectic cell radius was examined. To investigate the microsegregation pearlitic and bainitic cast iron with carbides obtained by Inmold method were chosen. The linear distribution of elements on the eutectic cell radius was examined. Testing of the chemical composition of cast iron metal matrix components, including carbides were carried out. The change of graphitizing and anti-graphitizing element concentrations within eutectic cell was determined. It was found, that in cast iron containing Mo carbides crystallizing after austenite + graphite eutectic are Si enriched.

Ceramic-bonded abrasive grinding tools

Science.gov (United States)

Holcombe, Jr., Cressie E.; Gorin, Andrew H.; Seals, Roland D.

1994-01-01

Abrasive grains such as boron carbide, silicon carbide, alumina, diamond, cubic boron nitride, and mullite are combined with a cement primarily comprised of zinc oxide and a reactive liquid setting agent and solidified into abrasive grinding tools. Such grinding tools are particularly suitable for grinding and polishing stone, such as marble and granite.

Ceramic-bonded abrasive grinding tools

Science.gov (United States)

Holcombe, C.E. Jr.; Gorin, A.H.; Seals, R.D.

1994-11-22

Abrasive grains such as boron carbide, silicon carbide, alumina, diamond, cubic boron nitride, and mullite are combined with a cement primarily comprised of zinc oxide and a reactive liquid setting agent and solidified into abrasive grinding tools. Such grinding tools are particularly suitable for grinding and polishing stone, such as marble and granite.

High temperature evaporation of titanium, zirconium and hafnium carbides

International Nuclear Information System (INIS)

Gusev, A.I.; Rempel', A.A.

1991-01-01

Evaporation of cubic nonstoichiometric carbides of titanium, zirconium and hafnium in a comparatively low-temperature interval (1800-2700) with detailed crystallochemical sample certification is studied. Titanium carbide is characterized by the maximum evaporation rate: at T>2300 K it loses 3% of sample mass during an hour and at T>2400 K titanium carbide evaporation becomes extremely rapid. Zirconium and hafnium carbide evaporation rates are several times lower than titanium carbide evaporation rates at similar temperatures. Partial pressures of metals and carbon over the carbides studied are calculated on the base of evaporation rates

Fine Structure Study of the Plasma Coatings B4C-Ni-P

Science.gov (United States)

Kornienko, E. E.; Bezrukova, V. A.; Kuz'min, V. I.; Lozhkin, V. S.; Tutunkova, M. K.

2017-12-01

The article considers structure of coatings formed of the B4C-Ni-P powder. The coatings were deposited using air-plasma spraying with the unit for annular injection of powder. The pipes from steel 20 (0.2 % C) were used as a substrate. The structure and phase composition of the coatings were studied by optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. It is shown that high-density composite coatings consisting of boron carbide particles distributed in the nickel boride metal matrix are formed using air-plasma spraying. The areas with round inclusions characterized by the increased amount of nickel, phosphorus and boron are located around the boron carbide particles. Boron oxides and nickel oxides are also present in the coatings. Thin interlayers with amorphous-crystalline structure are formed around the boron carbide particles. The thickness of these interlayers does not exceed 1 μm. The metal matrix material represents areas with nanocrystalline structure and columnar crystals.

Growth and characterization of thick cBN coatings on silicon and tool substrates

International Nuclear Information System (INIS)

Bewilogua, K.; Keunecke, M.; Weigel, K.; Wiemann, E.

2004-01-01

Recently some research groups have achieved progress in the deposition of cubic boron nitride (cBN) coatings with a thickness of 2 μm and more, which is necessary for cutting tool applications. In our laboratory, thick cBN coatings were sputter deposited on silicon substrates using a boron carbide target. Following a boron carbide interlayer (few 100 nm thick), a gradient layer with continuously increasing nitrogen content was prepared. After the cBN nucleation, the process parameters were modified for the cBN film growth to a thickness of more than 2 μm. However, the transfer of this technology to technically relevant substrates, like cemented carbide cutting inserts, required some further process modifications. At first, a titanium interlayer had to be deposited followed by a more than 1-μm-thick boron carbide layer. The next steps were identical to those on silicon substrates. The total coating thickness was in the range of 3 μm with a 0.5- to nearly 1-μm-thick cBN top layer. In spite of the enormous intrinsic stress, both the coatings on silicon and on cemented carbide exhibited a good adhesion and a prolonged stability in humid air. Oxidation experiments revealed a stability of the coating system on cemented carbide up to 700 deg. C and higher. Coated cutting inserts were tested in turning operations with different metallic workpiece materials. The test results will be compared to those of well-established cutting materials, like polycrystalline cubic boron nitride (PCBN) and oxide ceramics, considering the wear of coated tools

Tribological Characteristics of Tungsten Carbide Reinforced Arc Sprayed Coatings using Different Carbide Grain Size Fractions

Directory of Open Access Journals (Sweden)

W. Tillmann

2017-06-01

Full Text Available Tungsten carbide reinforced coatings play an important role in the field of surface engineering to protect stressed surfaces against wear. For thermally sprayed coatings, it is already shown that the tribological properties get mainly determined by the carbide grain size fraction. Within the scope of this study, the tribological characteristics of iron based WC-W2C reinforced arc sprayed coatings deposited using cored wires consisting of different carbide grain size fractions were examined. Microstructural characteristics of the produced coatings were scrutinized using electron microscopy and x-ray diffraction analyses. Ball-on-disk test as well as Taber Abraser and dry sand rubber wheel test were employed to analyze both the dry sliding and the abrasive wear behavior. It was shown that a reduced carbide grain size fraction as filling leads to an enhanced wear resistance against sliding. In terms of the Taber Abraser test, it is also demonstrated that a fine carbide grain size fraction results in an improved wear resistant against abrasion. As opposed to that, a poorer wear resistance was found within the dry sand rubber wheel tests. The findings show that the operating mechanisms for both abrasion tests affect the stressed surface in a different way, leading either to microcutting or microploughing.

High speed dry machining of MMCs with diamond tools

International Nuclear Information System (INIS)

Collins, J.L.

2001-01-01

The increasing use of metal matrix composites (MMCs) has raised new issues in their machining. Industrial demands for higher speed and dry machining of MMCs with improved component production to closer tolerances have driven the development of new tool materials. In particular, the wear characteristics of synthetic diamond tooling satisfy many of the requirements imposed in cutting these highly abrasive workpieces. The use of diamond tool materials, such as polycrystalline diamond (PCD), has resulted in tool life improvements which, allied with environmental considerations, show great potential for the development of dry cutting. This paper explores the wear characteristics of PCD, which is highly suited to the dry machining of particulate silicon carbide MMCs. Also, two further diamond tool materials are evaluated - chemical vapor deposition (CVD) thick layer diamond and synthetic single crystal diamond. Their suitability for the efficient machining of high volume fraction MMC materials is shown and their potential impact an the subsequent acceptance and integration of MMCs into engineering components is discussed. (author)

Influence of electrical discharge machining on the tribological characteristics of WC-Co alloys

International Nuclear Information System (INIS)

Casas, B.; Martinez, E.; Esteve, J.; Anglada, M.; Llanes, L.

2001-01-01

The influence of electrical discharge machining (EDM) on the abrasive wear resistance of two WC-10 % w tCo cemented carbides with different carbide grain size has been studied. Different surface finish conditions were evaluated corresponding to sequential EDM as well as grinding and polishing with diamond. The abrasive wear resistance was determined through microscratch measurements using a nano indentation system. Contrary to the results obtained from hardness measurements, this techniques allows to discern tribological differences among the distinct surface finish conditions studied. Finally, the abrasive wear resistance degradation associated with sequential EDM is discussed as a function of microstructure in terms of a damage parameters. (Author) 9 refs

Precipitation behavior of carbides in high-carbon martensitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Zhu, Qin-tian; Li, Jing; Shi, Cheng-bin; Yu, Wen-tao; Shi, Chang-min [University of Science and Technology, Beijing (China). State Key Laboratory of Advanced Metallurgy; Li, Ji-hui [Yang Jiang Shi Ba Zi Group Co., Ltd, Guangdong (China)

2017-01-15

A fundamental study on the precipitation behavior of carbides was carried out. Thermo-calc software, scanning electron microscopy, electron probe microanalysis, transmission electron microscopy, X-ray diffractometry and high-temperature confocal laser scanning microscopy were used to study the precipitation and transformation behaviors of carbides. Carbide precipitation was of a specific order. Primary carbides (M7C3) tended to be generated from liquid steel when the solid fraction reached 84 mol.%. Secondary carbides (M7C3) precipitated from austenite and can hardly transformed into M23C6 carbides with decreasing temperature in air. Primary carbides hardly changed once they were generated, whereas secondary carbides were sensitive to heat treatment and thermal deformation. Carbide precipitation had a certain effect on steel-matrix phase transitions. The segregation ability of carbon in liquid steel was 4.6 times greater that of chromium. A new method for controlling primary carbides is proposed.

Research of boron conversion coating in neutron detector with boron deposited GEM

International Nuclear Information System (INIS)

Ye Di; Sun Zhijia; Zhou Jianrong; Wang Yanfeng; Yang Guian; Xu Hong; Chen Yuanbai; Xiao Yu; Diao Xungang

2014-01-01

GEM is a flourishing new gas detector and nowadays its technology become more mature. It has outstanding properties, such as excellent position resolution, high counting rate, radiation resistance, simple and flexible signal readout, can be large-area detector, wide application range. Detector with boron deposited GEM uses multilayer GEM with deposited boron film as neutron conversion carrier which reads out the information of neutron shot from the readout electrode with gas amplification from every GEM layer. The detector is high performance which can meet the demands of neutron detector of a new generation. Boron deposited neutron conversion electrode with boron deposited cathode and GEM included is the core part of the detector. As boron is a high-melting-point metalloid (> 2 000 ℃), electroplating and thermal evaporation are inappropriate ways. So finding a way to deposit boron on electrode which can meet the demands become a key technology in the development of neutron detector with boron deposited GEM. Compared with evaporation, sputtering has features such as low deposition temperature, high film purity, nice adhesive, thus is appropriate for our research. Magnetron sputtering is a improved way of sputtering which can get lower sputtering air pressure and higher target voltage, so that we can get better films. Through deposit process, the research uses magnetron sputtering to deposit pure boron film on copper electrode and GEM film. This method can get high quality, nice adhere, high purity, controllable uniformity, low cost film with high speed film formation. (authors)

Transition metal carbide and boride abrasive particles

International Nuclear Information System (INIS)

Valdsaar, H.

1978-01-01

Abrasive particles and their preparation are discussed. The particles consist essentially of a matrix of titanium carbide and zirconium carbide, at least partially in solid solution form, and grains of crystalline titanium diboride dispersed throughout the carbide matrix. These abrasive particles are particularly useful as components of grinding wheels for abrading steel. 1 figure, 6 tables

Borides and vitreous compounds sintered as high-energy fuels

International Nuclear Information System (INIS)

Mota, J.M.; Abenojar, J.; Martinez, M.A.; Velasco, F.; Criado, A.J.

2004-01-01

Boron was chosen as fuel in view of its excellent thermodynamic values for combustion, as compared to traditional fuels. The problem of the boron in combustion is the formation of a surface layer of oxide, which delays the ignition process, reducing the performance of the rocket engine. This paper presents a high-energy fuel for rocket engines. It is composed of sintered boron (borides and carbides and vitreous compounds) with a reducing chemical agent. Borides and boron carbide were prepared since the combustion heat of the latter is similar to that of the amorphous boron (in: K.K. Kuo (Ed.), Boron-Based Solid Propellant and Solid Fuel, Vol. 427, CRC Press, Boca Raton, FL, 1993). Several chemical reducing elements were used, such as aluminum, magnesium, and coke. As the raw material for boron, different compounds were used: amorphous boron, boric acid and boron oxide

Note on boron toxicity in oats

Energy Technology Data Exchange (ETDEWEB)

Langille, W M; Mahoney, J F

1959-01-01

Boron was applied at the rate of 35 pounds per acre of borax to a field of oats. With the first noticeable growth there appeared a definite chlorotic condition of the oat seedlings on plots receiving boron treatments. Analysis of chlorotic tissue at 3 weeks after seeding indicated 110 ppm boron, while apparently healthy tissue contained 6.1 ppm boron at the same stage of growth. There was a rapid decline in the boron content of the oat tissue as the crop grew older. At maturity the oat tissue from the boron-treated plots contained an average of 14.15 ppm boron as compared with 4.10 boron from untreated areas. Boron toxicity had no harmful effect so far as yields were concerned, under the conditions of this experiment. 3 references.

Boron-11 MRI and MRS of intact animals infused with a boron neutron capture agent

International Nuclear Information System (INIS)

Kabalka, G.W.; Davis, M.; Bendel, P.

1988-01-01

Boron neutron capture therapy (BNCT) depends on the delivery of boron-containing drugs to a targeted lesion. Currently, the verification and quantification of in vivo boron content is a difficult problem. Boron-11 spectroscopy was utilized to confirm the presence of a dimeric sulfhydryl dodecaborane BNCT agent contained in an intact animal. Spectroscopy experiments revealed that the decay time of transverse magnetization of the boron-11 spins was less than 1 ms which precluded the use of a 2DFT imaging protocol. A back-projection protocol was developed and utilized to generate the first boron-11 image of a BNCT agent in the liver of an intact Fisher 344 rat

Point defects and transport properties in carbides

International Nuclear Information System (INIS)

Matzke, Hj.

1984-01-01

Carbides of transition metals and of actinides are interesting and technologically important. The transition-metal carbides (or carbonitrides) are extensively being used as hard materials and some of them are of great interest because of the high transition temperature for superconductivity, e.g. 17 K for Nb(C,N). Actinide carbides and carbonitrides, (U,Pu)C and (U,Pu)(C,N) are being considered as promising advanced fuels for liquid metal cooled fast breeder nuclear reactors. Basic interest exists in all these materials because of their high melting points (e.g. 4250 K for TaC) and the unusually broad range of homogeneity of nonstoichiometric compositions (e.g. from UCsub(0.9) to UCsub(1.9) at 2500 K). Interaction of point defects to clusters and short-range ordering have recently been studied with elastic neutron diffraction and diffuse scattering techniques, and calculations of energies of formation and interaction of point defects became available for selected carbides. Diffusion measurements also exist for a number of carbides, in particular for the actinide carbides. The existing knowledge is discussed and summarized with emphasis on informative examples of particular technological relevance. (Auth.)

Liquid phase sintering of carbides using a nickel-molybdenum alloy

International Nuclear Information System (INIS)

Barranco, J.M.; Warenchak, R.A.

1987-01-01

Liquid phase vacuum sintering was used to densify four carbide groups. These were titanium carbide, tungsten carbide, vanadium carbide, and zirconium carbide. The liquid phase consisted of nickel with additions of molybdenum of from 6.25 to 50.0 weight percent at doubling increments. The liquid phase or binder comprised 10, 20, and 40 percent by weight of the pressed powders. The specimens were tested using 3 point bending. Tungsten carbide showed the greatest improvement in bend rupture strength, flexural modulus, fracture energy and hardness using 20 percent binder with lesser amounts of molybdenum (6.25 or 12.5 wt %) added to nickel compared to pure nickel. A refinement in the carbide microstructure and/or a reduction in porosity was seen for both the titanium and tungsten carbides when the alloy binder was used compared to using the nickel alone. Curves depicting the above properties are shown for increasing amounts of molybdenum in nickel for each carbide examined. Loss of binder phase due to evaporation was experienced during heating in vacuum at sintering temperatures. In an effort to reduce porosity, identical specimens were HIP processed at 15 ksi and temperatures averaging 110 C below the sintering g temperature. The tungsten carbide and titanium carbide series containing 80 and 90 weight percent carbide phase respectively showed improvement properties after HIP while properties decreased for most other compositions

β-Rhombohedral Boron: At the Crossroads of the Chemistry of Boron and the Physics of Frustration [Boron: a frustrated element

Energy Technology Data Exchange (ETDEWEB)

Ogitsu, Tadashi [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schwegler, Eric [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Galli, Giulia [Univ. of California, Davis, CA (United States)

2013-05-08

In the periodic table boron occupies a peculiar, crossover position: on the first row, it is surrounded by metal forming elements on the left and by non-metals on the right. In addition, it is the only non-metal of the third column. Therefore it is perhaps not surprising that the crystallographic structure and topology of its stable allotrope at room temperature (β-boron) are not shared by any other element, and are extremely complex. The formidable intricacy of β- boron, with interconnecting icosahedra, partially occupied sites, and an unusually large number of atoms per unit cell (more than 300) has been known for more than 40 years. Nevertheless boron remains the only element purified in significant quantities whose ground state geometry has not been completely determined by experiments. However theoretical progress reported in the last decade has shed light on numerous properties of elemental boron, leading to a thorough characterization of its structure at ambient conditions, as well as of its electronic and thermodynamic properties. This review discusses in detail the properties of β-boron, as inferred from experiments and the ab-initio theories developed in the last decade.

Tungsten--carbide critical assembly

International Nuclear Information System (INIS)

Hansen, G.E.; Paxton, H.C.

1975-06-01

The tungsten--carbide critical assembly mainly consists of three close-fitting spherical shells: a highly enriched uranium shell on the inside, a tungsten--carbide shell surrounding it, and a steel shell on the outside. Ideal critical specifications indicate a rather low computed value of k/sub eff/. Observed and calculated fission-rate distributions for 235 U, 238 U, and 237 Np are compared, and calculated leakage neutrons per fission in various energy groups are given. (U.S.)

Plasma metallization of refractory carbide powders

International Nuclear Information System (INIS)

Koroleva, E.B.; Klinskaya, N.A.; Rybalko, O.F.; Ugol'nikova, T.A.

1986-01-01

The effect of treatment conditions in plasma on properties of produced metallized powders of titanium, tungsten and chromium carbides with the main particle size of 40-80 μm is considered. It is shown that plasma treatment permits to produce metallized powders of carbide materials with the 40-80 μm particle size. The degree of metallization, spheroidization, chemical and phase composition of metallized carbide powders are controlled by dispersivity of the treated material, concentration of a metal component in the treated mixtures, rate of plasma flow and preliminary spheroidization procedure

Damage to the edge of steel stampings and abrasive during ultrasonic hydroabrasive machining

International Nuclear Information System (INIS)

Dokuchaeva, V.A.; Chernov, A.P.

1976-01-01

Principles have been established explaining the fracture of abrasive material in the process of ultrasonic hydroabrasive treatment, and a method is proposed suitable for the calculation of steel barb erosion in the hydroabrasive flux. It is assumed that fracture occurs along the entire edge surface and that the losses caused by plastic deformation are small. Conclusion has been made as to the governing the change of the abrasive particle size in the time of treatment. It is shown that the most serious fracture takes place at initial stage of the treatment, terminating practically after 60 minutes of operation. Curves showing the distribution of boron carbide abrasive particles are presented

Boron-coated straws as a replacement for 3He-based neutron detectors

International Nuclear Information System (INIS)

Lacy, Jeffrey L.; Athanasiades, Athanasios; Sun, Liang; Martin, Christopher S.; Lyons, Tom D.; Foss, Michael A.; Haygood, Hal B.

2011-01-01

US and international government efforts to equip major seaports with large area neutron detectors, aimed to intercept the smuggling of nuclear materials, have precipitated a critical shortage of 3 He gas. It is estimated that the annual demand of 3 He for US security applications alone is more than the worldwide supply. This is strongly limiting the prospects of neutron science, safeguards, and other applications that rely heavily on 3 He-based detectors. Clearly, alternate neutron detection technologies that can support large sensitive areas, and have low gamma sensitivity and low cost must be developed. We propose a low-cost technology based on long copper tubes (straws), coated on the inside with a thin layer of 10 B-enriched boron carbide ( 10 B 4 C). In addition to the high abundance of boron on Earth and low cost of 10 B enrichment, the boron-coated straw (BCS) detector offers distinct advantages over conventional 3 He-based detectors, and alternate technologies such as 10 BF 3 tubes and 10 B-coated rigid tubes. These include better distribution inside moderator assemblies, many-times faster electronic signals, no pressurization, improved gamma-ray rejection, no toxic or flammable gases, and ease of serviceability. We present the performance of BCS detectors dispersed in a solid plastic moderator to address the need for portal monitoring. The design adopts the outer dimensions of currently deployed 3 He-based monitors, but takes advantage of the small BCS diameter to achieve a more uniform distribution of neutron converter throughout the moderating material. We show that approximately 63 BCS detectors, each 205 cm long, distributed inside the moderator, can match or exceed the detection efficiency of typical monitors fitted with a 5 cm diameter 3 He tube, 187 cm long, pressurized to 3 atm.

Boron-coated straws as a replacement for 3He-based neutron detectors

Science.gov (United States)

Lacy, Jeffrey L.; Athanasiades, Athanasios; Sun, Liang; Martin, Christopher S.; Lyons, Tom D.; Foss, Michael A.; Haygood, Hal B.

2011-10-01

US and international government efforts to equip major seaports with large area neutron detectors, aimed to intercept the smuggling of nuclear materials, have precipitated a critical shortage of 3He gas. It is estimated that the annual demand of 3He for US security applications alone is more than the worldwide supply. This is strongly limiting the prospects of neutron science, safeguards, and other applications that rely heavily on 3He-based detectors. Clearly, alternate neutron detection technologies that can support large sensitive areas, and have low gamma sensitivity and low cost must be developed. We propose a low-cost technology based on long copper tubes (straws), coated on the inside with a thin layer of 10B-enriched boron carbide ( 10B 4C). In addition to the high abundance of boron on Earth and low cost of 10B enrichment, the boron-coated straw (BCS) detector offers distinct advantages over conventional 3He-based detectors, and alternate technologies such as 10BF 3 tubes and 10B-coated rigid tubes. These include better distribution inside moderator assemblies, many-times faster electronic signals, no pressurization, improved gamma-ray rejection, no toxic or flammable gases, and ease of serviceability. We present the performance of BCS detectors dispersed in a solid plastic moderator to address the need for portal monitoring. The design adopts the outer dimensions of currently deployed 3He-based monitors, but takes advantage of the small BCS diameter to achieve a more uniform distribution of neutron converter throughout the moderating material. We show that approximately 63 BCS detectors, each 205 cm long, distributed inside the moderator, can match or exceed the detection efficiency of typical monitors fitted with a 5 cm diameter 3He tube, 187 cm long, pressurized to 3 atm.

Ligand sphere conversions in terminal carbide complexes

DEFF Research Database (Denmark)

Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.

2016-01-01

Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first...... example of a cationic terminal carbide complex, [RuC(Cl)(CH3CN)(PCy3)2]+, is described and characterized by NMR, MS, X-ray crystallography, and computational studies. The experimentally observed irregular variation of the carbide 13C chemical shift is shown to be accurately reproduced by DFT, which also...... demonstrates that details of the coordination geometry affect the carbide chemical shift equally as much as variations in the nature of the auxiliary ligands. Furthermore, the kinetics of formation of the sqaure pyramidal dicyano complex, trans-[RuC(CN)2(PCy3)2], from RuC has been examined and the reaction...

On the enhancement of corrosion in HTR graphite due to machining

International Nuclear Information System (INIS)

Hatton, D.; Harris, A.M.; Hall, J.A.

1975-09-01

A correlation is reported between bands of corrosion on the coolant surface of an inner sleeve from a Dragon reactor tubular interacting pin, and peaks in the axial profile of 60 Co along the pin. Tungsten has been observed at the corroded positions and it is postulated that these materials, deposited from a tungsten carbide tipped tool during machining, cause catalytic corrosion of the graphite. (author)

Crystallization of nodular cast iron with carbides

Directory of Open Access Journals (Sweden)

S. Pietrowski

2008-12-01

Full Text Available In this paper a crystallization process of nodular cast iron with carbides having a different chemical composition have been presented. It have been found, that an increase of molybdenum above 0,30% causes the ledeburutic carbides crystallization after (γ+ graphite eutectic phase crystallization. When Mo content is lower, these carbides crystallize as a pre-eutectic phase. In this article causes of this effect have been given.

Preparation and Fatigue Properties of Functionally Graded Cemented Carbides

International Nuclear Information System (INIS)

Liu Yong; Liu Fengxiao; Liaw, Peter K.; He Yuehui

2008-01-01

Cemented carbides with a functionally graded structure have significantly improved mechanical properties and lifetimes in cutting, drilling and molding. In this work, WC-6 wt.% Co cemented carbides with three-layer graded structure (surface layer rich in WC, mid layer rich in Co and the inner part of the average composition) were prepared by carburizing pre-sintered η-phase-containing cemented carbides. The three-point bending fatigue tests based on the total-life approach were conducted on both WC-6wt%Co functionally graded cemented carbides (FGCC) and conventional WC-6wt%Co cemented carbides. The functionally graded cemented carbide shows a slightly higher fatigue limit (∼100 MPa) than the conventional ones under the present testing conditions. However, the fatigue crack nucleation behavior of FGCC is different from that of the conventional ones. The crack nucleates preferentially along the Co-gradient and perpendicular to the tension surface in FGCC, while parallel to the tension surface in conventional cemented carbides

Boronated liposome development and evaluation

International Nuclear Information System (INIS)

Hawthorne, M.F.

1995-01-01

The boronated liposome development and evaluation effort consists of two separate tasks. The first is the development of new boron compounds and the synthesis of known boron species with BNCT potential. These compounds are then encapsulated within liposomes for the second task, biodistribution testing in tumor-bearing mice, which examines the potential for the liposomes and their contents to concentrate boron in cancerous tissues

Enhancement of thermal conductive pathway of boron nitride coated polymethylsilsesquioxane composite.

Science.gov (United States)

Kim, Gyungbok; Ryu, Seung Han; Lee, Jun-Tae; Seong, Ki-Hun; Lee, Jae Eun; Yoon, Phil-Joong; Kim, Bum-Sung; Hussain, Manwar; Choa, Yong-Ho

2013-11-01

We report here in the fabrication of enhanced thermal conductive pathway nanocomposites of boron nitride (BN)-coated polymethylsilsesquioxane (PMSQ) composite beads using isopropyl alcohol (IPA) as a mixing medium. Exfoliated and size-reduced boron nitride particles were successfully coated on the PMSQ beads and explained by surface charge differences. A homogeneous dispersion and coating of BN on the PMSQ beads using IPA medium was confirmed by SEM. Each condition of the composite powder was carried into the stainless still mould and then hot pressed in an electrically heated hot press machine. Three-dimensional percolation networks and conductive pathways created by exfoliated BN were precisely formed in the nanocomposites. The thermal conductivity of nanocomposites was measured by multiplying specific gravity, specific heat, and thermal diffusivity, based upon the laser flash method. Densification of the composite resulted in better thermal properties. For an epoxy reinforced composite with 30 vol% BN and PMSQ, a thermal conductivity of nine times higher than that of pristine PMSQ was observed.

Design and development of solid carbide step drill K34 for machining of CFRP and GFRP composite laminates

Science.gov (United States)

Rangaswamy, T.; Nagaraja, R.

2018-04-01

The Study focused on design and development of solid carbide step drill K34 to drill holes on composite materials such as Carbon Fiber Reinforced Plastic (CFRP) and Glass Fiber Reinforced Plastic (GFRP). The step drill K34 replaces step wise drilling of diameter 6.5mm and 9 mm holes that reduces the setup time, cutting speed, feed rate cost, delamination and increase the production rate. Several researchers have analyzed the effect of drilling process on various fiber reinforced plastic composites by carrying out using conventional tools and machinery. However, this process operation can lead to different kind of damages such as delamination, fiber pullout, and local cracks. To avoid the problems encountered at the time of drilling, suitable tool material and geometry is essential. This paper deals with the design and development of K34 Carbide step drill used to drill holes on CFRP and GFRP laminates. An Experimental study carried out to investigate the tool geometry, feed rate and cutting speed that avoids delamination and fiber breakage.

Plasma immersion ion implantation of boron for ribbon silicon solar cells

Directory of Open Access Journals (Sweden)

Derbouz K.

2013-09-01

Full Text Available In this work, we report for the first time on the solar cell fabrication on n-type silicon RST (for Ribbon on Sacrificial Template using plasma immersion ion implantation. The experiments were also carried out on FZ silicon as a reference. Boron was implanted at energies from 10 to 15 kV and doses from 1015 to 1016 cm-2, then activated by a thermal annealing in a conventional furnace at 900 and 950 °C for 30 min. The n+ region acting as a back surface field was achieved by phosphorus spin-coating. The frontside boron emitter was passivated either by applying a 10 nm deposited SiOX plasma-enhanced chemical vapor deposition (PECVD or with a 10 nm grown thermal oxide. The anti-reflection coating layer formed a 60 nm thick SiNX layer. We show that energies less than 15 kV and doses around 5 × 1015 cm-2 are appropriate to achieve open circuit voltage higher than 590 mV and efficiency around 16.7% on FZ-Si. The photovoltaic performances on ribbon silicon are so far limited by the bulk quality of the material and by the quality of the junction through the presence of silicon carbide precipitates at the surface. Nevertheless, we demonstrate that plasma immersion ion implantation is very promising for solar cell fabrication on ultrathin silicon wafers such as ribbons.

Influence of minimum quantity of lubricant (MQL on tool life of carbide cutting tools during milling process of steel AISI 1018

Directory of Open Access Journals (Sweden)

Diego Núñez

2017-03-01

Full Text Available Nowadays, high productivity of machining is an important issue to obtain economic benefits in the industry. This purpose could be reached with high cutting velocity and feed rate. However, the inherently behavior produce high temperatures in the interface of couple cutting tool/workpiece. Many cutting fluids have been developed to control temperature in process and increase tool life. The objective of this paper is to compare the carbide milling tool wear using different systems cutting fluids: flood and minimum quantity of lubrication (MQL. The values of carbide milling cutting tool wear was evaluate according with the standard ISO 8688-1 1989. The experimental results showed that using MQL reduces significantly (about 40% tool wear in milling AISI 1018 steel at industrial cutting conditions.

HCl removal using cycled carbide slag from calcium looping cycles

International Nuclear Information System (INIS)

Xie, Xin; Li, Yingjie; Wang, Wenjing; Shi, Lei

2014-01-01

Highlights: • Cycled carbide slag from calcium looping cycles is used to remove HCl. • The optimum temperature for HCl removal of cycled carbide slag is 700 °C. • The presence of CO 2 restrains HCl removal of cycled carbide slag. • CO 2 capture conditions have important effects on HCl removal of cycled carbide slag. • HCl removal capacity of carbide slag drops with cycle number rising from 1 to 50. - Abstract: The carbide slag is an industrial waste from chlor-alkali plants, which can be used to capture CO 2 in the calcium looping cycles, i.e. carbonation/calcination cycles. In this work, the cycled carbide slag from the calcium looping cycles for CO 2 capture was proposed to remove HCl in the flue gas from the biomass-fired and RDFs-fired boilers. The effects of chlorination temperature, HCl concentration, particle size, presence of CO 2 , presence of O 2 , cycle number and CO 2 capture conditions in calcium looping cycles on the HCl removal behavior of the carbide slag experienced carbonation/calcination cycles were investigated in a triple fixed-bed reactor. The chlorination product of the cycled carbide slag from the calcium looping after absorbing HCl is not CaCl 2 but CaClOH. The optimum temperature for HCl removal of the cycled carbide slag from the carbonation/calcination cycles is 700 °C. The chlorination conversion of the cycled carbide slag increases with increasing the HCl concentration. The cycled carbide slag with larger particle size exhibits a lower chlorination conversion. The presence of CO 2 decreases the chlorination conversions of the cycled carbide slag and the presence of O 2 has a trifling impact. The chlorination conversion of the carbide slag experienced 1 carbonation/calcination cycle is higher than that of the uncycled calcined sorbent. As the number of carbonation/calcination cycles increases from 1 to 50, the chlorination conversion of carbide slag drops gradually. The high calcination temperature and high CO 2

Lathe tool bit and holder for machining fiberglass materials

Science.gov (United States)

Winn, L. E. (Inventor)

1972-01-01

A lathe tool and holder combination for machining resin impregnated fiberglass cloth laminates is described. The tool holder and tool bit combination is designed to accommodate a conventional carbide-tipped, round shank router bit as the cutting medium, and provides an infinite number of cutting angles in order to produce a true and smooth surface in the fiberglass material workpiece with every pass of the tool bit. The technique utilizes damaged router bits which ordinarily would be discarded.

Biodistribution, toxicity and efficacy of a boronated porphyrin for boron neutron capture therapy

International Nuclear Information System (INIS)

Miura, Michiko; Micca, P.; Fairchild, R.; Slatkin, D.; Gabel, D.

1992-01-01

Boron-containing porphyrins may be useful for boron neutron capture therapy (BNCT) in the treatment of brain tumors. Porphyrins have been shown to accumulate in tumor tissue and to be essentially excluded from normal brain. However, problems of toxicity may prevent some boron-containing porphyrins from being considered for BNCT. The authors have synthesized the boronated porphyrin 2,4-bis-vinyl-o-nidocarboranyl-deuteroporphyrin IX (VCDP). Preliminary studies in tumor-bearing mice showed considerable uptake of boron at a total dose of 150 μg/gbw with low mortality. They now report that a total dose to mice of ∼ 275 μg VCDP/gbw administered in multiple intraperitoneal (ip) injections can provide 40-50μg B per gram of tumor with acceptable toxicity. Toxicity experiments and a preliminary trial of BNCT in mice given such doses are also reported

Influence of microwave sterilization on the cutting capacity of carbide burs.

Science.gov (United States)

Fais, Laiza Maria Grassi; Pinelli, Lígia Antunes Pereira; Adabo, Gelson Luis; Silva, Regina Helena Barbosa Tavares da; Marcelo, Caroline Canhizares; Guaglianoni, Dalton Geraldo

2009-01-01

This study compared the cutting capacity of carbide burs sterilized with microwaves and traditional sterilization methods. Sixty burs were divided into 5 groups according to the sterilization methods: dry heat (G1), autoclave (G2), microwave irradiation (G3), glutaraldehyde (G4) or control - no sterilization (G5). The burs were used to cut glass plates in a cutting machine set for twelve 2.5-min periods and, after each period, they were sterilized (except G5) following the protocol established for each group. The cutting capacity of the burs was determined by a weight-loss method. Data were analyzed statistically by Kruskal-Wallis and Dunn's test. The means of the cutting amount performed by each group after the 12 periods were G1 = 0.2167 +/- 0.0627 g; G2 = 0.2077 +/- 0.0231 g; G3 = 0.1980 +/- 0.0326 g; G4 = 0.1203 +/- 0.0459 g; G5 = 0.2642 +/- 0.0359 g. There were statistically significant differences among the groups (p<0.05); only dry heat sterilization was similar to the control. Sterilization by dry heat was the method that least affected the cutting capacity of the carbide burs and microwave sterilization was not better than traditional sterilization methods.

A New Boron Analysis Method

Energy Technology Data Exchange (ETDEWEB)

Weitman, J; Daaverhoeg, N; Farvolden, S

1970-07-01

In connection with fast neutron (n, {alpha}) cross section measurements a novel boron analysis method has been developed. The boron concentration is inferred from the mass spectrometrically determined number of helium atoms produced in the thermal and epithermal B-10 (n, {alpha}) reaction. The relation between helium amount and boron concentration is given, including corrections for self shielding effects and background levels. Direct and diffusion losses of helium are calculated and losses due to gettering, adsorption and HF-ionization in the release stage are discussed. A series of boron determinations is described and the results are compared with those obtained by other methods, showing excellent agreement. The lower limit of boron concentration which can be measured varies with type of sample. In e.g. steel, concentrations below 10-5 % boron in samples of 0.1-1 gram may be determined.

Two-channel neutron boron meter

International Nuclear Information System (INIS)

Chen Yongqing; Yin Guowei; Chai Songshan; Deng Zhaoping; Zhou Bin

1993-09-01

The two-channel neutron boron meter is a continuous on-line measuring device to measure boron concentration of primary cooling liquid of reactors. The neutron-leakage-compensation method is taken in the measuring mechanism. In the primary measuring configuration, the mini-boron-water annulus and two-channel and central calibration loop are adopted. The calibration ring and constant-temperature of boron-water can be remotely controlled by secondary instruments. With the microcomputer data processing system the boron concentration is automatically measured and calibrated in on-line mode. The meter has many advantages such as high accuracy, fast response, multi-applications, high reliability and convenience

Lattice vibrations in α-boron

International Nuclear Information System (INIS)

Richter, W.

1976-01-01

α-rhombohedral boron is the simplest boron modification, with only 12 atoms per unit cell. The boron atoms are arranged in B 12 icosahedra, which are centered at the lattice points of a primitive rhombohedral lattice. The icosahedra are slightly deformed, as the five-fold symmetry of the ideal icosahedron is incompatible with any crystal structure. The lattice dynamics of α-boron are discussed in terms of the model developed by Weber and Thorpe. (Auth.)

Boron Fullerenes: A First-Principles Study

Directory of Open Access Journals (Sweden)

Gonzalez Szwacki Nevill

2007-01-01

Full Text Available AbstractA family of unusually stable boron cages was identified and examined using first-principles local-density functional method. The structure of the fullerenes is similar to that of the B12icosahedron and consists of six crossing double-rings. The energetically most stable fullerene is made up of 180 boron atoms. A connection between the fullerene family and its precursors, boron sheets, is made. We show that the most stable boron sheets are not necessarily precursors of very stable boron cages. Our finding is a step forward in the understanding of the structure of the recently produced boron nanotubes.

Boron-containing thioureas for neutron capture therapy

International Nuclear Information System (INIS)

Ketz, H.

1993-01-01

Melanin is produced in large amounts in malignant melanotic melanomas. Because thiourea compounds are covalently incorporated into melanin during its biosynthesis, the preparation of boronated thiourea-derivatives is of particular interest for the BNCT (Boron Neutron Capture Therapy). Accumulation of boron in tumors by means of boronated thiourea-derivatives may therefore provide levels of 10 B which are useful for BNCT. In BNCT the tumor containing the boron compound is irradiated with epithermal neutrons to generate He- and Li-nuclei from the 10 B which can then destroy the tumor cells. Because of the short ranges of these particles (approximately one cell diameter) the damage will be almost exclusively confined to the tumor leaving normal tissue unharmed. High accumulation of 2-mercapto-1-methylimidazole (methimazole) in melanotic melanomas has been described in the literature. Boronated derivatives of methimazole were therefore synthesized. Boron was in the form of a boronic acid, a nido-carbonate and a mercaptoundeca hydro-closo-dodecaborate (BSH). The synthesis of the boron cluster derivatives of methimazole (nido-carborate- and BSH-derivatives) with 9 resp. 12 boron atoms in the molecule were expected to achieve higher concentrations of boron in the tumor than in the case of the boronic acid compound with its single boron atom. (orig.) [de

Tungsten carbide encapsulated in nitrogen-doped carbon with iron/cobalt carbides electrocatalyst for oxygen reduction reaction

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jie; Chen, Jinwei, E-mail: jwchen@scu.edu.cn; Jiang, Yiwu; Zhou, Feilong; Wang, Gang; Wang, Ruilin, E-mail: rl.wang@scu.edu.cn

2016-12-15

Graphical abstract: A hybrid catalyst was prepared via a quite green and simple method to achieve an one-pot synthesis of the N-doping carbon, tungsten carbides, and iron/cobalt carbides. It exhibited comparable electrocatalytic activity, higher durability and ability to methanol tolerance compared with commercial Pt/C to ORR. - Highlights: • A novel type of hybrid Fe/Co/WC@NC catalysts have been successfully synthesized. • The hybrid catalyst also exhibited better durability and methanol tolerance. • Multiple effective active sites of Fe{sub 3}C, Co{sub 3}C, WC, and NC help to improve catalytic performance. - Abstract: This work presents a type of hybrid catalyst prepared through an environmental and simple method, combining a pyrolysis of transition metal precursors, a nitrogen-containing material, and a tungsten source to achieve a one-pot synthesis of N-doping carbon, tungsten carbides, and iron/cobalt carbides (Fe/Co/WC@NC). The obtained Fe/Co/WC@NC consists of uniform Fe{sub 3}C and Co{sub 3}C nanoparticles encapsulated in graphitized carbon with surface nitrogen doping, closely wrapped around a plate-like tungsten carbide (WC) that functions as an efficient oxygen reduction reaction (ORR) catalyst. The introduction of WC is found to promote the ORR activity of Fe/Co-based carbide electrocatalysts, which is attributed to the synergistic catalysts of WC, Fe{sub 3}C, and Co{sub 3}C. Results suggest that the composite exhibits comparable electrocatalytic activity, higher durability, and ability for methanol tolerance compared with commercial Pt/C for ORR in alkaline electrolyte. These advantages make Fe/Co/WC@NC a promising ORR electrocatalyst and a cost-effective alternative to Pt/C for practical application as fuel cell.

Preparation of aluminum nitride-silicon carbide nanocomposite powder by the nitridation of aluminum silicon carbide

NARCIS (Netherlands)

Itatani, K.; Tsukamoto, R.; Delsing, A.C.A.; Hintzen, H.T.J.M.; Okada, I.

2002-01-01

Aluminum nitride (AlN)-silicon carbide (SiC) nanocomposite powders were prepared by the nitridation of aluminum-silicon carbide (Al4SiC4) with the specific surface area of 15.5 m2·g-1. The powders nitrided at and above 1400°C for 3 h contained the 2H-phases which consisted of AlN-rich and SiC-rich

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

International Nuclear Information System (INIS)

Nordell, Bradley J.; Karki, Sudarshan; Nguyen, Thuong D.; Rulis, Paul; Caruso, A. N.; Paquette, Michelle M.; Purohit, Sudhaunshu S.; Li, Han; King, Sean W.; Dutta, Dhanadeep; Gidley, David; Lanford, William A.

2015-01-01

Because of its high electrical resistivity, low dielectric constant (κ), high thermal neutron capture cross section, and robust chemical, thermal, and mechanical properties, amorphous hydrogenated boron carbide (a-B x C:H y ) has garnered interest as a material for low-κ dielectric and solid-state neutron detection applications. Herein, we investigate the relationships between chemical structure (atomic concentration B, C, H, and O), physical/mechanical properties (density, porosity, hardness, and Young's modulus), electronic structure [band gap, Urbach energy (E U ), and Tauc parameter (B 1/2 )], optical/dielectric properties (frequency-dependent dielectric constant), and electrical transport properties (resistivity and leakage current) through the analysis of a large series of a-B x C:H y thin films grown by plasma-enhanced chemical vapor deposition from ortho-carborane. The resulting films exhibit a wide range of properties including H concentration from 10% to 45%, density from 0.9 to 2.3 g/cm 3 , Young's modulus from 10 to 340 GPa, band gap from 1.7 to 3.8 eV, Urbach energy from 0.1 to 0.7 eV, dielectric constant from 3.1 to 7.6, and electrical resistivity from 10 10 to 10 15 Ω cm. Hydrogen concentration is found to correlate directly with thin-film density, and both are used to map and explain the other material properties. Hardness and Young's modulus exhibit a direct power law relationship with density above ∼1.3 g/cm 3 (or below ∼35% H), below which they plateau, providing evidence for a rigidity percolation threshold. An increase in band gap and decrease in dielectric constant with increasing H concentration are explained by a decrease in network connectivity as well as mass/electron density. An increase in disorder, as measured by the parameters E U and B 1/2 , with increasing H concentration is explained by the release of strain in the network and associated decrease in structural disorder. All of these correlations in a

Behavioral study of cnc-retrofitting kits for lathe machine

International Nuclear Information System (INIS)

Ahmad, I.

1999-01-01

The aim of this project is to develop a Computerized Numerical Controlled (CNC) retrofitting kit for a lathe machine, study its behavior and compare its performance with the retrofitting kit already designed and fabricated at (Pakistan Institute of Engineering and Applied Sciences (PIEAS). Design calculations were performed assuming 100 mm work piece diameter and 800 mm length of stock using tool materials HSS, uncoated carbide, coated carbide, ceramic and cermet tools for different materials. Also cutting, thrust and radial forces on a single point cutting tool were determined. Stepper motors of torque 972 oz-in were selected to drive the carriage and cross-slide in Z and X-directions respectively. Power screws were replaced with ball screws of 0.63 inch dia. (x-direction) and 1.26 in. dia. (Z-direction) which were locally manufactured in the workshop. Deep groove and Angular contact ball bearings were used to support the ball screw shafts against axial and radial loads. Flexible and plain couplings were developed to couple encoders and motors to the ball screw shafts respectively. Panel mount optical rotary encoders are being used for feedback control. Mechanical assembly is complete but due to unavailability of wiring diagram for motors, control electronics could not be accomplished. Therefore, machine could not be evaluated in terms of accuracy, repeatability and resolution using computer software. (author)

Nuclear fuel clad clothed with burnable poison and obtainment process

International Nuclear Information System (INIS)

Diez, P.; Netter, P.

1994-01-01

This clad has preferentially on its inner surface a boron compound such boron carbide or boron nitrogen deposited by Chemical Vapor Deposition or by Physical Vapor Deposition without any temperature elevation injurious to its mechanical properties. 3 figs

Processing and microstructural characterization of B4C-Al cermets

International Nuclear Information System (INIS)

Halverson, D.C.; Pyzik, A.J.; Aksay, I.A.

1985-01-01

Reaction thermodynamics and wetting studies were employed to evaluate boron carbide-aluminum cermets. Wetting phonomenon and interfacial reactions are characterized using ''macroscale'' and ''microscale'' techniques. Macroscale evaluation involved aluminium sessile drop studies on boron carbide substrates. Microscale evaluation involved the fabrication of actural cermet microstructures and their characterization through sem, x-ray diffraction, metallography, and electron microprobe. Contact-angle measurements and interfacial-reaction products are reported

Development of high toughness, high strength aluminide-bonded carbide ceramics

Energy Technology Data Exchange (ETDEWEB)

Becher, P.F.; Plucknett, K.P.; Tiegs, T.N. [Oak Ridge National Lab., TN (United States)] [and others

1997-04-01

Cemented carbides are widely used in applications where resistance to abrasion and wear are important, particularly in combination with high strength and stiffness. In the present case, ductile aluminides have been used as a binder phase to fabricate dense carbide cermets by either sintering of mixed powders or a melt-infiltration sintering process. The choice of an aluminide binder was based on the exceptional high temperature strength and chemical stability exhibited by these alloys. For example, TiC-based composites with a Ni{sub 3}Al binder phase exhibit improved oxidation resistance, Young`s moduli > 375 GPa, high fracture strengths (> 1 GPa) that are retained to {ge} 900{degrees}C, and fracture toughness values of 10 to 15 MPa{radical}m, identical to that measured in commercial cobalt-bonded WC with the same test method. The thermal diffusivity values at 200{degrees}C for these composites are {approximately} 0.070 to 0.075 cm{sup 2}/s while the thermal expansion coefficients rise with Ni3Al content from {approximately} 8 to {approximately}11 x 10{sup {minus}6}/{degrees}C over the range of 8 to 40 vol. % Ni{sub 3}Al. The oxidation and acidic corrosion resistances are quite promising as well. Finally, these materials also exhibit good electrical conductivity allowing them to be sectioned and shaped by electrical discharge machining (EDM) processes.

Boron-coated straws as a replacement for {sup 3}He-based neutron detectors

Energy Technology Data Exchange (ETDEWEB)

Lacy, Jeffrey L., E-mail: jlacy@proportionaltech.com [Proportional Technologies, Inc., 8022 El Rio Street, Houston, TX 77054 (United States); Athanasiades, Athanasios; Sun, Liang; Martin, Christopher S.; Lyons, Tom D.; Foss, Michael A.; Haygood, Hal B. [Proportional Technologies, Inc., 8022 El Rio Street, Houston, TX 77054 (United States)

2011-10-01

US and international government efforts to equip major seaports with large area neutron detectors, aimed to intercept the smuggling of nuclear materials, have precipitated a critical shortage of {sup 3}He gas. It is estimated that the annual demand of {sup 3}He for US security applications alone is more than the worldwide supply. This is strongly limiting the prospects of neutron science, safeguards, and other applications that rely heavily on {sup 3}He-based detectors. Clearly, alternate neutron detection technologies that can support large sensitive areas, and have low gamma sensitivity and low cost must be developed. We propose a low-cost technology based on long copper tubes (straws), coated on the inside with a thin layer of {sup 10}B-enriched boron carbide ({sup 10}B{sub 4}C). In addition to the high abundance of boron on Earth and low cost of {sup 10}B enrichment, the boron-coated straw (BCS) detector offers distinct advantages over conventional {sup 3}He-based detectors, and alternate technologies such as {sup 10}BF{sub 3} tubes and {sup 10}B-coated rigid tubes. These include better distribution inside moderator assemblies, many-times faster electronic signals, no pressurization, improved gamma-ray rejection, no toxic or flammable gases, and ease of serviceability. We present the performance of BCS detectors dispersed in a solid plastic moderator to address the need for portal monitoring. The design adopts the outer dimensions of currently deployed {sup 3}He-based monitors, but takes advantage of the small BCS diameter to achieve a more uniform distribution of neutron converter throughout the moderating material. We show that approximately 63 BCS detectors, each 205 cm long, distributed inside the moderator, can match or exceed the detection efficiency of typical monitors fitted with a 5 cm diameter {sup 3}He tube, 187 cm long, pressurized to 3 atm.

Obtainment, machining and wear of metal matrix composites processed by powder metallurgy; Obtencao, usinagem e desgaste de materiais compositos de matriz metalica processados via metalurgia do po

Energy Technology Data Exchange (ETDEWEB)

Jesus, Edilson Rosa Barbosa de. E-mail: erbjesus@usp.br

1998-07-01

The aim of this investigation was the obtainment of metal matrix composites (MMC) by the route of powder metallurgy, and the valuation of these materials with relation to their machining and wear characteristics. Firstly, were obtained pure commercial aluminium matrix composites materials, with 5, 10 and 15% volumetric fraction of silicon carbide particles. Was also obtained a material without reinforcement particles in order to verify by comparison, the influence of addition of reinforcement particles. The obtained materials were characterized physics (hydrostatic density), mechanics (hardness and tensile tests) and microstructurally (optical microscopy and scanning electron microscopy). The results showed a homogeneous distribution of reinforcement particles in the composite, and improvement in the mechanical properties, mainly tensile strength (UTS) in comparison to the unreinforced material. After, tests were made to verify the materials behavior during machining and to check the performance of several tool materials (cemented carbide, ceramics and polycrystalline diamond). In these tests, values of the cutting force were measured by instrumented tool-holders. Phenomena such as tool wear, built-up edge formation and mechanism of chip formation were also observed and evaluated. The results from the cemented carbide tool tests, were utilised for the machinability index determination of each material. These results were applied to the Taylor equation and the equation constants for each material and test conditions were determined. The results showed that the inclusion of silicon carbide particles made extremely difficult the machining of the composites, and only with diamond tool, satisfactory results were obtained. At last, wear tests were performed to verify the influence of the reinforcement particles in the characteristics of wear resistance of the materials. The results obtained were utilized in the wear coefficient determination for each material. The

Boron supplementation in broiler diets

Directory of Open Access Journals (Sweden)

EJ Fassani

2004-12-01

Full Text Available Boron supplementation in broiler feed is not a routine practice. However, some reports suggest a positive effect of boron on performance. This study assessed the effects of boron supplementation on broiler performance. Diets were based on maize and soybean meal, using boric acid P.A. as boron source. Six supplementation levels (0, 30, 60, 90, 120 and 150 ppm were evaluated using 1,440 one-day old males housed at a density of 30 chickens in each of 48 experimental plots of 3m². A completely randomized block design was used with 8 replicates. Feed intake, weight gain and feed conversion were assessed in the periods from 1 to 7 days, 1 to 21 days and 1 to 42 days of age, and viability was evaluated for the total 42-day rearing period. No performance variable was affected by boron supplementation (p>0.05 in the period from 1 to 7 days. The regression analysis indicated an ideal level of 37.4 ppm of boron for weight gain from 1 to 21 days (p0.05, although feed intake was reduced linearly with increased boron levels (p0.05. Ash and calcium percentages in the tibias of broilers and viability in the total rearing period were not affected by boron supplementation (p>0.05.

Three-dimensional studies of intergranular carbides in austenitic stainless steel.

Science.gov (United States)

Ochi, Minoru; Kawano, Rika; Maeda, Takuya; Sato, Yukio; Teranishi, Ryo; Hara, Toru; Kikuchi, Masao; Kaneko, Kenji

2017-04-01

A large number of morphological studies of intergranular carbides in steels have always been carried out in two dimensions without considering their dispersion manners. In this article, focused ion beam serial-sectioning tomography was carried out to study the correlation among the grain boundary characteristics, the morphologies and the dispersions of intergranular carbides in 347 austenitic stainless steel. More than hundred intergranular carbides were characterized in three dimensions and finally classified into three different types, two types of carbides probably semi-coherent to one of the neighboring grains with plate-type morphology, and one type of carbides incoherent to both grains with rod-type morphology. In addition, the rod-type carbide was found as the largest number of carbides among three types. Since large numbers of defects, such as misfit dislocations, may be present at the grain boundaries, which can be ideal nucleation sites for intergranular rod-type carbide precipitation. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved.For permissions, please e-mail: journals.permissions@oup.com.

Optical-optical double resonance, laser induced fluorescence, and revision of the signs of the spin-spin constants of the boron carbide (BC) free radical

Science.gov (United States)

Sunahori, Fumie X.; Nagarajan, Ramya; Clouthier, Dennis J.

2015-12-01

The cold boron carbide free radical (BC X 4Σ-) has been produced in a pulsed discharge free jet expansion using a precursor mixture of trimethylborane in high pressure argon. High resolution laser induced fluorescence spectra have been obtained for the B 4Σ--X 4Σ- and E 4Π-X 4Σ- band systems of both 11BC and 10BC. An optical-optical double resonance (OODR) scheme was implemented to study the finer details of both band systems. This involved pumping a single rotational level of the B state with one laser and then recording the various allowed transitions from the intermediate B state to the final E state with a second laser by monitoring the subsequent E-X ultraviolet fluorescence. In this fashion, we were able to prove unambiguously that, contrary to previous studies, the spin-spin constant λ is negative in the ground state and positive in the B 4Σ- excited state. It has been shown that λ″ expected based on a semiempirical second order perturbation theory calculation of the magnitude of the spin-spin constant. The OODR spectra have also been used to validate our assignments of the complex and badly overlapped E 4Π-X 4Σ- 0-0 and 1-0 bands of 11BC. The E-X 0-0 band of 10BC was found to be severely perturbed. The ground state main electron configuration is …3σ24σ25σ11π22π0 and the derived bond lengths show that there is a 0.03 Å contraction in the B state, due to the promotion of an electron from the 4σ antibonding orbital to the 5σ bonding orbital. In contrast, the bond length elongates by 0.15 Å in the E state, a result of promoting an electron from the 5σ bonding orbital to the 2π antibonding orbitals.

Nuclear magnetic resonance spectroscopy of boron compounds containing two-, three- and four-coordinate boron

International Nuclear Information System (INIS)

Wrackmeyer, B.

1988-01-01

The influence of boron chemistry on various areas of research in inorganic, organic and theoretical chemistry is well documented. In fact, many models presently employed to describe chemical bonding in general can be traced to attempts to understand bonding in boranes. The confirmation of many theoretical predictions in boron chemistry relies on direct and indirect structural information provided by various physical methods that - fortunately - became available almost at the same rate as that with which the interest in boron compounds was growing. Clearly, there has always been a strong link between the interest in synthesis and the application of physical methods. As in many other areas of chemistry, developments in boron chemistry have been greatly accelerated by NMR. 11 B NMR has been at the center of interest from the beginning, accompanied by routine 1 H NMR measurements, and occasional 14 N, 19 F and 31 P NMR work. In the last 12 years, we have seen an increasing number of 13 C NMR studies of boron compounds. The availability of multinuclear facilities for PFT NMR spectrometers stimulates the measurement of the NMR spectra of other nuclei, like 29 Si, 119 Sn or other metals, in order to obtain additional information. This paper is intended to serve several purposes: to update previous reviews on 11 B NMR of boron compounds, to demonstrate some applications of multinuclear NMR to boron chemistry; to attempt to incorporate new NMR parameters into the known data set; and to summarize the experimental facts required for obtaining the maximum information from NMR studies on boron compounds

Technics Research on Polycrystalline Cubic Boron Nitride Cutting Tools Dry Turning Ti-6AL-4V Alloy Based on Orthogonal Experimental Design

Directory of Open Access Journals (Sweden)

Jia Yunhai

2018-01-01

Full Text Available Ti-6Al-4V components are the most widely used titanium alloy products not only in the aerospace industry, but also for bio-medical applications. The machine-ability of titanium alloys is impaired by their high temperature chemical reactivity, low thermal conductivity and low modulus of elasticity. Polycrystalline cubic boron nitride represents a substitute tool material for turning titanium alloys due to its high hardness, wear resistance, thermal stability and hot red hardness. For determination of suitable cutting parameters in dry turning Ti-6AL-4V alloy by Polycrystalline cubic boron nitride cutting tools, the samples, 300mm in length and 100mm in diameter, were dry machined in a lathe. The turning suitable parameters, such as cutting speed, feed rate and cut depth were determined according to workpieces surface roughness and tools flank wear based on orthogonal experimental design. The experiment showed that the cutting speed in the range of 160~180 m/min, the feed rate is 0.15 mm/rev and the depth of cut is 0.20mm, ideal workpiece surface roughness and little cutting tools flank wear can be obtained.

The machinability of cast titanium and Ti-6Al-4V.

Science.gov (United States)

Ohkubo, C; Watanabe, I; Ford, J P; Nakajima, H; Hosoi, T; Okabe, T

2000-02-01

This study investigated the machinability (ease of metal removal) of commercially pure (CP) titanium and Ti-6Al-4V alloy. Both CP Ti and Ti-6Al-4V were cast into magnesia molds. Two types of specimens (with alpha-case and without alpha-case) were made for CP Ti and Ti-6Al-4V. Machinability (n = 5) was evaluated as volume loss (mm3) by cutting/grinding the 3.0 mm surface using fissure burs and silicon carbide (SiC) under two machining conditions: (1) two machining forces (100 or 300 gf) at two rotational speeds (15000 or 30000 rpm) for 1 min, and (2) constant machining force of 100 gf and rotational speed of 15000 rpm for 1, 2, 5, 10, and 30 min. As controls, conventionally cast Co-Cr and Type IV gold alloys were evaluated in the same manner as the titanium. When fissure burs were used, there was a significant difference in the machinability between CP titanium with alpha-case and without alpha-case. On the other hand, there was no appreciable difference in the amount of metal removed for each tested metal when using the SiC points.

Surface metallurgy of cemented carbide tools

International Nuclear Information System (INIS)

Chopra, K.L.; Kashyap, S.C.; Rao, T.V.; Rajagopalan, S.; Srivastava, P.K.

1983-01-01

Transition metal carbides, owing to their high melting point, hardness and wear resistance, are potential candidates for specific application in rockets, nuclear engineering equipment and cutting tools. Tungsten carbide sintered with a binder (either cobalt metal or a mixture of Co + TiC and/or TaC(NbC)) is used for cutting tools. The surface metallurgy of several commercially available cemented carbide tools was studied by Auger electron spectroscopy and X-ray photoelectron spectroscopy techniques. The tool surfaces were contaminated by adsorbed oxygen up to a depth of nearly 0.3 μm causing deterioration of the mechanical properties of the tools. Studies of fractured samples indicated that the tool surfaces were prone to oxygen adsorption. The fracture path passes through the cobalt-rich regions. The ineffectiveness of a worn cutting tool is attributed to the presence of excessive iron from the steel workpiece and carbon and oxygen in the surface layers of the tool. The use of appropriate hard coatings on cemented carbide tools is suggested. (Auth.)

Cell cycle dependence of boron uptake in various boron compounds used for neutron capture therapy

International Nuclear Information System (INIS)

Yoshida, F.; Matsumura, A.; Shibata, Y.; Yamamoto, T.; Nose, T.; Okumura, M.

2000-01-01

In neutron capture therapy, it is important that the tumor take boron in selectively. Furthermore, it is ideal when the uptake is equal in each tumor cell. Some indirect proof of differences in boron uptake among neoplastic cell cycles has been documented. However, no investigation has yet measured boron uptake directly. Using flow cytometry, in the present study cells were sorted by G0/G1 phase and G2/M phase, and the boron concentration of each fraction was measured with inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The results were that BSH (sodiumborocaptate) and BPA (p-boronophenylalanine) had higher rates of boron uptake in the G2/M group than in the G0/G1 group. However, in BPA the difference was more prominent, which revealed a 2.2-3.3 times higher uptake of boron in the G2/M group than in the G0/G1 group. (author)

Boron-Loaded Silicone Rubber Scintillators

Energy Technology Data Exchange (ETDEWEB)

Bell, Z.W.; Maya, L.; Brown, G.M.; Sloop, F.V.Jr

2003-05-12

Silicone rubber received attention as an alternative to polyvinyltoluene in applications in which the scintillator is exposed to high doses because of the increased resistance of the rubber to the formation of blue-absorbing color centers. Work by Bowen, et al., and Harmon, et al., demonstrated their properties under gamma/x-ray irradiation, and Bell, et al. have shown their response to thermal neutrons. This last work, however, provided an example of a silicone in which both the boron and the scintillator were contained in the rubber as solutes, a formulation which led to the precipitation of solids and sublimation of the boron component. In the present work we describe a scintillator in which the boron is chemically bonded to the siloxane and so avoids the problem of precipitation and loss of boron to sublimation. Material containing up to 18% boron, by weight, was prepared, mounted on photomultipliers, and exposed to both neutron and gamma fluxes. Pulse height spectra showing the neutron and photon response were obtained, and although the light output was found to be much poorer than from samples in which boron was dissolved, the higher boron concentrations enabled essentially 100% neutron absorption in only a few millimeters' thickness of rubber.

Tribology of carbide derived carbon films synthesized on tungsten carbide

Science.gov (United States)

Tlustochowicz, Marcin

Tribologically advantageous films of carbide derived carbon (CDC) have been successfully synthesized on binderless tungsten carbide manufactured using the plasma pressure compaction (P2CRTM) technology. In order to produce the CDC films, tungsten carbide samples were reacted with chlorine containing gas mixtures at temperatures ranging from 800°C to 1000°C in a sealed tube furnace. Some of the treated samples were later dechlorinated by an 800°C hydrogenation treatment. Detailed mechanical and structural characterizations of the CDC films and sliding contact surfaces were done using a series of analytical techniques and their results were correlated with the friction and wear behavior of the CDC films in various tribosystems, including CDC-steel, CDC-WC, CDC-Si3N4 and CDC-CDC. Optimum synthesis and treatment conditions were determined for use in two specific environments: moderately humid air and dry nitrogen. It was found that CDC films first synthesized at 1000°C and then hydrogen post-treated at 800°C performed best in air with friction coefficient values as low as 0.11. However, for dry nitrogen applications, no dechlorination was necessary and both hydrogenated and as-synthesized CDC films exhibited friction coefficients of approximately 0.03. A model of tribological behavior of CDC has been proposed that takes into consideration the tribo-oxidation of counterface material, the capillary forces from adsorbed water vapor, the carbon-based tribofilm formation, and the lubrication effect of both chlorine and hydrogen.

A system to deposit boron films (boronization) in the DIII-D tokamak

International Nuclear Information System (INIS)

Hodapp, T.R.; Jackson, G.L.; Phillips, J.; Holtrop, K.L.; Peterson, P.L.; Winters, J.

1992-01-01

A system has been added to the DIII-D tokamak to coat its plasma facing surfaces with a film of boron using diborane gas. The system includes special health and safety equipment for handling the diborane gas which is toxic and inflammable. The purpose f the boron film is to reduce the levels of impurity atoms in the DIII-D plasmas. Experiments following the application of the boron film in DIII-D have led to significant reductions in plasma impurity levels and the observation of a new, very high confinement regime

New possibilities using additive manufacturing with materials that are difficult to process and with complex structures

Science.gov (United States)

Olsson, Anders; Hellsing, Maja S.; Rennie, Adrian R.

2017-05-01

Additive manufacturing (or 3D printing) opens the possibility of creating new designs and manufacturing objects with new materials rapidly and economically. Particularly for use with polymers and polymer composites, simple printers can make high quality products, and these can be produced easily in offices, schools and in workshops and laboratories. This technology has opened a route for many to test ideas or to make custom devices. It is possible to easily manufacture complex geometries that would be difficult or even impossible to create with traditional methods. Naturally this technology has attracted attention in many fields that include the production of medical devices and prostheses, mechanical engineering as well as basic sciences. Materials that are highly problematic to machine can be used. We illustrate process developments with an account of the production of printer parts to cope with polymer fillers that are hard and abrasive; new nozzles with ruby inserts designed for such materials are durable and can be used to print boron carbide composites. As with other materials, complex parts can be printed using boron carbide composites with fine structures, such as screw threads and labels to identify materials. General ideas about design for this new era of manufacturing customised parts are presented.

New possibilities using additive manufacturing with materials that are difficult to process and with complex structures

International Nuclear Information System (INIS)

Olsson, Anders; Hellsing, Maja S; Rennie, Adrian R

2017-01-01

Additive manufacturing (or 3D printing) opens the possibility of creating new designs and manufacturing objects with new materials rapidly and economically. Particularly for use with polymers and polymer composites, simple printers can make high quality products, and these can be produced easily in offices, schools and in workshops and laboratories. This technology has opened a route for many to test ideas or to make custom devices. It is possible to easily manufacture complex geometries that would be difficult or even impossible to create with traditional methods. Naturally this technology has attracted attention in many fields that include the production of medical devices and prostheses, mechanical engineering as well as basic sciences. Materials that are highly problematic to machine can be used. We illustrate process developments with an account of the production of printer parts to cope with polymer fillers that are hard and abrasive; new nozzles with ruby inserts designed for such materials are durable and can be used to print boron carbide composites. As with other materials, complex parts can be printed using boron carbide composites with fine structures, such as screw threads and labels to identify materials. General ideas about design for this new era of manufacturing customised parts are presented. (invited comment)

Investigation of boron extraction process with aid magnesium hydroxide from mother liquor of boron production

International Nuclear Information System (INIS)

Balapanova, B.S.; Zhajmina, R.E.; Serazetdinov, D.Z.

1988-01-01

Conditions of boron - magnesium concentrate preparation from mother liquor by coprecipitation of borate - ions by magnesium hydroxide are investigated. It is shown that boron - magnesium concentrate and products of its heat treatment at 100 - 500 deg C in water are dissolved partially, and in ammonium citrate - practically completely. Suppositions are made on the composition of the product prepared, on the the structure of its crystal lattice and the processes taking place in it during heat treatment. The conclusion is made on the perspectiveness of processing of mother liquor of boron industry for boron - magnesium concentrate

Proceedings of the meeting for coordinating precision machining of optics research and requirements

International Nuclear Information System (INIS)

Saito, T.T.

1975-12-01

The meeting for ''Coordinating Precision Machining of Optics Research and Requirements'' on September 18, 1975, was sponsored by the Air Force Weapons Laboratory at Kirtland AFB, NM. These proceedings contain an introduction to the meeting including a brief description of the participants and the objectives. The developments and capabilities of Union Carbide Y-12 plant are described in detail. A short summary of the new Moore no. 5 machine at Bendix, Kansas City, Mo. is included as well as a description of using light scattering for roughness characterization at Rockwell International, Rocky Flats, Colorado. The executive summary of the meeting mentions some of the discussions that also followed. Important conclusions of the meeting were that a 5 y lead time is required to obtain a machine and acquire the necessary skills for precision machining, and that demands for diamond turning optics will be increasing

Vanadium carbide coatings: deposition process and properties

International Nuclear Information System (INIS)

Borisova, A.; Borisov, Y.; Shavlovsky, E.; Mits, I.; Castermans, L.; Jongbloed, R.

2001-01-01

Vanadium carbide coatings on carbon and alloyed steels were produced by the method of diffusion saturation from the borax melt. Thickness of the vanadium carbide layer was 5-15 μm, depending upon the steel grade and diffusion saturation parameters. Microhardness was 20000-28000 MPa and wear resistance of the coatings under conditions of end face friction without lubrication against a mating body of WC-2Co was 15-20 times as high as that of boride coatings. Vanadium carbide coatings can operate in air at a temperature of up to 400 o C. They improve fatigue strength of carbon steels and decrease the rate of corrosion in sea and fresh water and in acid solutions. The use of vanadium carbide coatings for hardening of various types of tools, including cutting tools, allows their service life to be extended by a factor of 3 to 30. (author)

Reactor irradiation effect on the physical-mechanical properties of zirconium carbides and niobium carbides

International Nuclear Information System (INIS)

Andrievskij, R.A.; Vlasov, K.P.; Shevchenko, A.S.; Lanin, A.G.; Pritchin, S.A.; Klyushin, V.V.; Kurushin, S.P.; Maskaev, A.S.

1978-01-01

A study has been made of the effect of the reactor radiation by a flux of neutrons 1.5x10 20 n/cm 2 (E>=1 meV) at radiation temperatures of 150 and 1100 deg C on the physico-mechanical properties of carbides of zirconium and niobium and their equimolar hard solution. A difference has been discovered in the behaviour of the indicated carbides under the effect of radiation. Under the investigated conditions of radiation the density of zirconium carbide is being decreased, while in the niobium carbide no actual volumetric changes occur. The increase of the lattice period in ZrC is more significant than in NbC. The electric resistance of ZrC is also changed more significantly than in the case of NbC, while for the microhardness a reverse relationship is observed. Strength and elasticity modulus change insignificantly in both cases. Resistance to crack formation shows a higher reduction for ZrC than for NbC, while the thermal strength shows an approximately similar increase. The equimolar hard solution of ZrC and NbC behaves to great extent similar to ZrC, although the change in electric resistance reminds of NbC while thermal strength changes differently. The study of the microstructure of the specimens has shown that radiation causes a large number of etching patterns-dislocations in NbC which are almost absent in ZrC

Joining of porous silicon carbide bodies

Science.gov (United States)

Bates, Carl H.; Couhig, John T.; Pelletier, Paul J.

1990-05-01

A method of joining two porous bodies of silicon carbide is disclosed. It entails utilizing an aqueous slip of a similar silicon carbide as was used to form the porous bodies, including the sintering aids, and a binder to initially join the porous bodies together. Then the composite structure is subjected to cold isostatic pressing to form a joint having good handling strength. Then the composite structure is subjected to pressureless sintering to form the final strong bond. Optionally, after the sintering the structure is subjected to hot isostatic pressing to further improve the joint and densify the structure. The result is a composite structure in which the joint is almost indistinguishable from the silicon carbide pieces which it joins.

An empirical model for parameters affecting energy consumption in boron removal from boron-containing wastewaters by electrocoagulation.

Science.gov (United States)

Yilmaz, A Erdem; Boncukcuoğlu, Recep; Kocakerim, M Muhtar

2007-06-01

In this study, it was investigated parameters affecting energy consumption in boron removal from boron containing wastewaters prepared synthetically, via electrocoagulation method. The solution pH, initial boron concentration, dose of supporting electrolyte, current density and temperature of solution were selected as experimental parameters affecting energy consumption. The obtained experimental results showed that boron removal efficiency reached up to 99% under optimum conditions, in which solution pH was 8.0, current density 6.0 mA/cm(2), initial boron concentration 100mg/L and solution temperature 293 K. The current density was an important parameter affecting energy consumption too. High current density applied to electrocoagulation cell increased energy consumption. Increasing solution temperature caused to decrease energy consumption that high temperature decreased potential applied under constant current density. That increasing initial boron concentration and dose of supporting electrolyte caused to increase specific conductivity of solution decreased energy consumption. As a result, it was seen that energy consumption for boron removal via electrocoagulation method could be minimized at optimum conditions. An empirical model was predicted by statistically. Experimentally obtained values were fitted with values predicted from empirical model being as following; [formula in text]. Unfortunately, the conditions obtained for optimum boron removal were not the conditions obtained for minimum energy consumption. It was determined that support electrolyte must be used for increase boron removal and decrease electrical energy consumption.

Conceptual design study of LMFBR core with carbide fuel

International Nuclear Information System (INIS)

Tezuka, H.; Hojuyama, T.; Osada, H.; Ishii, T.; Hattori, S.; Nishimura, T.

1987-01-01

Carbide fuel is a hopeful candidate for demonstration FBR(DFBR) fuel from the plant cost reduction point of view. High thermal conductivity and high heavy metal content of carbide fuel lead to high linear heat rate and high breeding ratio. We have analyzed carbide fuel core characteristics and have clarified the concept of carbide fuel core. By survey calculation, we have obtained a correlation map between core parameters and core characteristics. From the map, we have selected a high efficiency core whose features are better than those of an oxide core, and have obtained reactivity coefficients. The core volume and the reactor fuel inventory are approximately 20% smaller, and the burn-up reactivity loss is 50% smaller compared with the oxide fuel core. These results will reduce the capital cost. The core reactivity coefficients are similar to the conventional oxide DFBR's. Therefore the carbide fuel core is regarded as safe as the oxide core. Except neutron fluence, the carbide fuel core has better nuclear features than the oxide core

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.

Characterization of boron tolerant bacteria isolated from a fly ash dumping site for bacterial boron remediation.

Science.gov (United States)

Edward Raja, Chellaiah; Omine, Kiyoshi

2013-08-01

Boron is an essential micronutrient for plants, but can above certain concentrations be toxic to living organisms. A major environmental concern is the removal of boron from contaminated water and fly ash. For this purpose, the samples were collected from a fly ash dumping site, Nagasaki prefecture, Japan. The chemical characteristics and heavy metal concentration of the samples were performed by X-ray fluorescent analysis and leaching test. For bacterial analysis, samples were collected in sterile plastic sheets and isolation was carried out by serial dilution method. The boron tolerant isolates that showed values of maximum inhibitory concentration toward boron ranging from 100 to 260 mM level were screened. Based on 16S rRNA sequencing and phylogenetic analysis, the isolates were most closely related to the genera Bacillus, Lysinibacillus, Microbacterium and Ralstonia. The boron tolerance of these strains was also associated with resistant to several heavy metals, such as As (III), Cr (VI), Cd, Cu, Pb, Ni, Se (III) and Zn. Indeed, these strains were arsenic oxidizing bacteria confirmed by silver nitrate test. These strains exhibited their salt resistances ranging from 4 to 15 % were determined in Trypticase soy agar medium. The boron tolerant strains were capable of removing 0.1-2.0 and 2.7-3.7 mg l(-1) boron from the medium and fly ash at 168 h. Thus, we have successfully identified the boron tolerant and removal bacteria from a fly ash dumping site for boron remediation.

Boron uptake measurements in a rat model for Boron Neutron Capture Therapy of lung tumours

Energy Technology Data Exchange (ETDEWEB)

Bortolussi, S., E-mail: silva.bortolussi@pv.infn.i [Department of Nuclear and Theoretical Physics, University of Pavia, via Bassi 6, 27100 Pavia (Italy); National Institute of Nuclear Physics (INFN), Section of Pavia, via Bassi 6, 27100 Pavia (Italy); Bakeine, J.G. [Department of Nuclear and Theoretical Physics, University of Pavia, via Bassi 6, 27100 Pavia (Italy); Ballarini, F. [Department of Nuclear and Theoretical Physics, University of Pavia, via Bassi 6, 27100 Pavia (Italy); National Institute of Nuclear Physics (INFN), Section of Pavia, via Bassi 6, 27100 Pavia (Italy); Bruschi, P. [Department of Nuclear and Theoretical Physics, University of Pavia, via Bassi 6, 27100 Pavia (Italy); Gadan, M.A. [Department of Nuclear and Theoretical Physics, University of Pavia, via Bassi 6, 27100 Pavia (Italy); Comision Nacional de Energia Atomica, Buenos Aires (Argentina); Protti, N.; Stella, S. [Department of Nuclear and Theoretical Physics, University of Pavia, via Bassi 6, 27100 Pavia (Italy); National Institute of Nuclear Physics (INFN), Section of Pavia, via Bassi 6, 27100 Pavia (Italy); Clerici, A.; Ferrari, C.; Cansolino, L.; Zonta, C.; Zonta, A. [Department of Surgery, University of Pavia, via Ferrata 27100 Pavia (Italy); Nano, R. [Department of Animal Biology, University of Pavia, via Ferrata 27100 Pavia (Italy); Altieri, S. [Department of Nuclear and Theoretical Physics, University of Pavia, via Bassi 6, 27100 Pavia (Italy); National Institute of Nuclear Physics (INFN), Section of Pavia, via Bassi 6, 27100 Pavia (Italy)

2011-02-15

Lung carcinoma is the leading cause of cancer mortality in the Western countries. Despite the introduction over the last few years of new therapeutic agents, survival from lung cancer has shown no discernible improvement in the last 20 years. For these reasons any efforts to find and validate new effective therapeutic procedures for lung cancer are very timely. The selective boron uptake in the tumour with respect to healthy tissues makes Boron Neutron Capture Therapy a potentially advantageous option in the treatment of tumours that affect whole vital organs, and that are surgically inoperable. To study the possibility of applying BNCT to the treatment of diffuse pulmonary tumours, an animal model for boron uptake measurements in lung metastases was developed. Both healthy and tumour-bearing rats were infused with Boronophenylalanine (BPA) and sacrificed at different time intervals after drug administration. The lungs were extracted, and prepared for boron analysis by neutron autoradiography and {alpha}-spectroscopy. The boron concentrations in tumour and normal lung were plotted as a function of the time elapsed after BPA administration. The concentration in tumour is almost constant within the error bars for all the time intervals of the experiment (1-8 h), while the curve in normal lung decreases after 4 h from BPA infusion. At 4 h, the ratio of boron concentration in tumour to boron concentration in healthy lung is higher than 3, and it stays above this level up to 8 h. Also the images of boron distribution in the samples, obtained by neutron autoradiography, show a selective absorption in the metastases.

Fabrication of chamfered uranium-plutonium mixed carbide pellets

International Nuclear Information System (INIS)

Arai, Yasuo; Iwai, Takashi; Shiozawa, Kenichi; Handa, Muneo

1985-10-01

Chamfered uranium-plutonium mixed carbide pellets for high burnup irradiation test in JMTR were fabricated in glove boxes with purified argon gas. The size of die and punch in a press was decided from pellet densities and dimensions including the angle of chamfered parts. No chip or crack caused by adopting chamfered pellets was found in both pressing and sintering stages. In addition to mixed carbide pellets, uranium carbide pellets used as insulators were also successfully fabricated. (author)

Thermal neutron shield and method of manufacture

Science.gov (United States)

Brindza, Paul Daniel; Metzger, Bert Clayton

2013-05-28

A thermal neutron shield comprising concrete with a high percentage of the element Boron. The concrete is least 54% Boron by weight which maximizes the effectiveness of the shielding against thermal neutrons. The accompanying method discloses the manufacture of Boron loaded concrete which includes enriching the concrete mixture with varying grit sizes of Boron Carbide.

Influence of microwave sterilization on the cutting capacity of carbide burs

Directory of Open Access Journals (Sweden)

Laiza Maria Grassi Fais

2009-12-01

Full Text Available OBJECTIVE: This study compared the cutting capacity of carbide burs sterilized with microwaves and traditional sterilization methods. MATERIAL AND METHODS: Sixty burs were divided into 5 groups according to the sterilization methods: dry heat (G1, autoclave (G2, microwave irradiation (G3, glutaraldehyde (G4 or control - no sterilization (G5. The burs were used to cut glass plates in a cutting machine set for twelve 2.5-min periods and, after each period, they were sterilized (except G5 following the protocol established for each group. The cutting capacity of the burs was determined by a weight-loss method. Data were analyzed statistically by Kruskal-Wallis and Dunn's test. RESULTS: The means of the cutting amount performed by each group after the 12 periods were G1 = 0.2167 ± 0.0627 g; G2 = 0.2077 ± 0.0231 g; G3 = 0.1980 ± 0.0326 g; G4 = 0.1203 ± 0.0459 g; G5 = 0.2642 ± 0.0359 g. There were statistically significant differences among the groups (p<0.05; only dry heat sterilization was similar to the control. CONCLUSION: Sterilization by dry heat was the method that least affected the cutting capacity of the carbide burs and microwave sterilization was not better than traditional sterilization methods.

Hydrogen isotopes retention in divertor tiles of DIII-D tokamak

International Nuclear Information System (INIS)

Skorodumov, B.G.; Buzhinskij, O.I.; West, W.P.; Ulanov, V.G.

1996-01-01

The absolute concentration of hydrogen isotopes in graphite divertor tiles coated with boron carbide after the exposure in DIII-D during 16 operational weeks of the 1993 campaign was obtained using the 14 MeV neutron-induced recoil detection (NERD) method. It is shown that the absolute concentration of H in tile's surface layers correlates with thickness of the deposited layers. The graphite tile without boron carbide coating had a H concentration similar to that of the tile with the thickest deposited layer. Deuterium and tritium were not detected in any of the investigated tiles. The proposed method can be used for the determination of the thickness of coatings without sample destruction. Thus, the thickness of boron carbide coatings on the tiles obtained with this method varied from 80 to 115 μm, which corresponded well to electron microscope data. (orig.)

Laser-induced photochemical enrichment of boron isotopes

International Nuclear Information System (INIS)

Freund, S.M.; Ritter, J.J.

1976-01-01

A boron trichloride starting material containing both boron-10 isotopes and boron-11 isotopes is selectively enriched in one or the other of these isotopes by a laser-induced photochemical method involving the reaction of laser-excited boron trichloride with either H 2 S or D 2 S. The method is carried out by subjecting a low pressure gaseous mixture of boron trichloride starting material and the sulfide to infrared radiation from a carbon dioxide TE laser. The wave length of the radiation is selected so as to selectively excite one or the other of boron-10 BCl 3 molecules or boron-11 BCl 3 molecules, thereby making them preferentially more reactive with the sulfide. The laser-induced reaction produces both a boron-containing solid phase reaction product and a gaseous phase containing mostly unreacted BCl 3 and small amounts of sulfhydroboranes. Pure boron trichloride selectively enriched in one of the isotopes is recovered as the primary product of the method from the gaseous phase by a multi-step recovery procedure. Pure boron trichloride enriched in the other isotope is recovered as a secondary product of the method by the subsequent chlorination of the solid phase reaction product followed by separation of BCl 3 from the mixture of gaseous products resulting from the chlorination

A system to deposit boron films (boronization) in the DIII-D tokamak

International Nuclear Information System (INIS)

Hodapp, T.R.; Jackson, G.L.; Phillips, J.; Holtrop, K.L.; Petersen, P.I.; Winter, J.

1991-09-01

A system has been added to the D3-D tokamak to coat its plasma facing surfaces with a film of boron using diborane gas. The system includes special health and safety equipment for handling the diborane gas which is toxic and inflammable. The purpose of the boron film is to reduce the levels of impurity atoms in the D3-D plasmas. Experiments following the application of the boron film in D3-D have led to significant reductions in plasma impurity levels and the observation of a new, very high confinement regime. 9 refs., 1 fig

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.

Boron neutron capture therapy. Synthesis of boronated amines- and DNA intercalating agents for potential use in cancer therapy

International Nuclear Information System (INIS)

Ghaneolhosseini, H.

1998-01-01

Boron Neutron Capture Therapy is a binary cancer treatment modality, involving the delivery of a suitable boron compound to tumour cells followed by irradiation of the tumour by thermal neutrons. Boronated agents can selectively be delivered to tumour cells either directly with tumour-specific boron compounds, or by use of targeting strategies. However, the efficacy of this method would increase if the boron agents are localised in the cell nucleus rather than in the cell cytoplasm when neutron irradiation takes place. With these considerations in mind, some boronated DNA intercalating/interacting agents such as phenanthridine- acridine- spermidine- and naphthalimide derivatives were synthesised. Aminoalkyl-o-carboranes were synthesised in order to be used both for coupling to macromolecules and also for halogenation of their corresponding nido-derivatives. The amino groups were introduced using the Gabriel reagent N, N-dibenzyl iminodicarboxylate to provide 1-(aminomethyl)- and 1-(2-aminoethyl)-o-carboranes. The first attempt to achieve the possibility to accumulate a higher concentration of boron atoms in the cell nucleus was to synthesize carboranyl phenanthridinium analogues by reacting a p- or o-carboranyl moiety with phenanthridine, a chromophore with a planar aromatic ring system as DNA intercalator. Boronated acridine-spermidine, boronated diacridine, and boronated dispermidine were obtained in order to increase water solubility to avoid the interaction of these agents with non-DNA sides of the cell, especially membranes; and to enhance the feasibility of a higher DNA-binding constant and also decrease the DNA-drug dissociation rate. Finally, the synthesis of a boronated naphthalimide derivative was carried out by nucleophilic reaction of a primary aminoalkyl-p-carborane with naphthalic anhydride. Biological evaluations on DNA-binding, toxicity, and cellular binding with carboranyl phenanthridinium analogues, boronated acridine- and spermidine are described

Investigation on the Tribological Behavior of Arc-Sprayed and Hammer-Peened Coatings Using Tungsten Carbide Cored Wires

Science.gov (United States)

Tillmann, W.; Hagen, L.; Schröder, P.

2017-01-01

Due to their outstanding properties, WC-W2C iron-based cermet coatings are widely used in the field of wear protection. Regarding commonly used WC-W2C reinforced coating systems, it has been reported that their tribological behavior is mainly determined by the carbide grain size fraction. Although the manufacturing route for arc-sprayed WC-W2C cermet coatings is in an advanced state, there is still a lack of knowledge concerning the performance of cored wires with tungsten carbides as filling material and their related coating properties when post-treatment processes are used such as machine hammer peening (MHP). A major objective was to characterize WC-W2C FeCMnSi coatings, deposited with different carbide grain size fractions as a filling using cored wires, with respect to their tribological behavior. Moreover, deposits derived from cored wires with a different amount of hard phases are investigated. According to this, polished MHP surfaces are compared to as-sprayed and polished samples by means of metallographic investigations. With the use of ball-on-disk and dry rubber wheel tests, dry sliding and rolling wear effects on a microscopic level are scrutinized. It has been shown that the MHP process leads to a densification of the microstructure formation. For dry sliding experiments, the MHP coatings obtain lower wear resistances, but lower coefficients of friction than the conventional coatings. In view of abrasion tests, the MHP coatings possess an improved wear resistance. Strain hardening effects at the subsurface area were revealed by the mechanical response using nanoindentation. However, the MHP process has caused a cracking of embedded carbides, which favor breakouts, leading to advanced third-body wear.

Electrostatic design and beam transport for a folded tandem electrostatic quadrupole accelerator facility for accelerator-based boron neutron capture therapy

International Nuclear Information System (INIS)

Thatar Vento, V.; Bergueiro, J.; Cartelli, D.; Valda, A.A.; Kreiner, A.J.

2011-01-01

Within the frame of an ongoing project to develop a folded Tandem-Electrostatic-Quadrupole (TESQ) accelerator facility for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT), we discuss here the electrostatic design of the machine, including the accelerator tubes with electrostatic quadrupoles and the simulations for the transport and acceleration of a high intensity beam.

Hot flow behavior of boron microalloyed steels

International Nuclear Information System (INIS)

Lopez-Chipres, E.; Mejia, I.; Maldonado, C.; Bedolla-Jacuinde, A.; El-Wahabi, M.; Cabrera, J.M.

2008-01-01

This research work studies the effect of boron contents on the hot flow behavior of boron microalloyed steels. For this purpose, uniaxial hot-compression tests were carried out in a low carbon steel microalloyed with four different amounts of boron over a wide range of temperatures (950, 1000, 1050 and 1100 deg. C) and constant true strain rates (10 -3 , 10 -2 and 10 -1 s -1 ). Experimental results revealed that both peak stress and peak strain tend to decrease as boron content increases, which indicates that boron additions have a solid solution softening effect. Likewise, the flow curves show a delaying effect on the kinetics of dynamic recrystallization (DRX) when increasing boron content. Deformed microstructures show a finer austenitic grain size in the steel with higher boron content (grain refinement effect). Results are discussed in terms of boron segregation towards austenitic grain boundaries during plastic deformation, which increases the movement of dislocations, enhances the grain boundary cohesion and modificates the grain boundary structure

Boron-based nanostructures: Synthesis, functionalization, and characterization

Science.gov (United States)

Bedasso, Eyrusalam Kifyalew

Boron-based nanostructures have not been explored in detail; however, these structures have the potential to revolutionize many fields including electronics and biomedicine. The research discussed in this dissertation focuses on synthesis, functionalization, and characterization of boron-based zero-dimensional nanostructures (core/shell and nanoparticles) and one-dimensional nanostructures (nanorods). The first project investigates the synthesis and functionalization of boron-based core/shell nanoparticles. Two boron-containing core/shell nanoparticles, namely boron/iron oxide and boron/silica, were synthesized. Initially, boron nanoparticles with a diameter between 10-100 nm were prepared by decomposition of nido-decaborane (B10H14) followed by formation of a core/shell structure. The core/shell structures were prepared using the appropriate precursor, iron source and silica source, for the shell in the presence of boron nanoparticles. The formation of core/shell nanostructures was confirmed using high resolution TEM. Then, the core/shell nanoparticles underwent a surface modification. Boron/iron oxide core/shell nanoparticles were functionalized with oleic acid, citric acid, amine-terminated polyethylene glycol, folic acid, and dopamine, and boron/silica core/shell nanoparticles were modified with 3-(amino propyl) triethoxy silane, 3-(2-aminoethyleamino)propyltrimethoxysilane), citric acid, folic acid, amine-terminated polyethylene glycol, and O-(2-Carboxyethyl)polyethylene glycol. A UV-Vis and ATR-FTIR analysis established the success of surface modification. The cytotoxicity of water-soluble core/shell nanoparticles was studied in triple negative breast cancer cell line MDA-MB-231 and the result showed the compounds are not toxic. The second project highlights optimization of reaction conditions for the synthesis of boron nanorods. This synthesis, done via reduction of boron oxide with molten lithium, was studied to produce boron nanorods without any

Evaluation of Shielding Performance for Newly Developed Composite Materials

Science.gov (United States)

Evans, Beren Richard

This work details an investigation into the contributing factors behind the success of newly developed composite neutron shield materials. Monte Carlo simulation methods were utilized to assess the neutron shielding capabilities and secondary radiation production characteristics of aluminum boron carbide, tungsten boron carbide, bismuth borosilicate glass, and Metathene within various neutron energy spectra. Shielding performance and secondary radiation data suggested that tungsten boron carbide was the most effective composite material. An analysis of the macroscopic cross-section contributions from constituent materials and interaction mechanisms was then performed in an attempt to determine the reasons for tungsten boron carbide's success over the other investigated materials. This analysis determined that there was a positive correlation between a non-elastic interaction contribution towards a material's total cross-section and shielding performance within the thermal and epi-thermal energy regimes. This finding was assumed to be a result of the boron-10 absorption reaction. The analysis also determined that within the faster energy regions, materials featuring higher non-elastic interaction contributions were comparable to those exhibiting primarily elastic scattering via low Z elements. This allowed for the conclusion that composite shield success within higher energy neutron spectra does not necessitate the use elastic scattering via low Z elements. These findings suggest that the inclusion of materials featuring high thermal absorption properties is more critical to composite neutron shield performance than the presence of constituent materials more inclined to maximize elastic scattering energy loss.

Meeting the challenge of homogenous boron targeting of heterogeneous tumors for effective boron neutron capture therapy (BNCT)

International Nuclear Information System (INIS)

Heber, Elisa M.; Trivillin, Veronica A.; Itoiz, Maria E.; Rebagliati, J. Raul; Batistoni, Daniel; Kreimann, Erica L.; Schwint, Amanda E.; Nigg, David W.; Gonzalez, Beatriz N.

2006-01-01

BNCT is a tumor cell targeted radiation therapy. Inadequately boron targeted tumor populations jeopardize tumor control. Meeting the to date unresolved challenge of homogeneous targeting of heterogeneous tumors with effective boron carriers would contribute to therapeutic efficacy. The aim of the present study was to evaluate the degree of variation in boron content delivered by boronophenylalanine (BPA), GB-10 (Na 2 10 B 10 H 10 ) and the combined administration of (BPA+GB-10) in different portions of tumor, precancerous tissue around tumor and normal pouch tissue in the hamster cheek pouch oral cancer model. Boron content was evaluated by ICP-AES. The degree of homogeneity in boron targeting was assessed in terms of the coefficient of variation ([S.D./Mean]x100) of boron values. Statistical analysis of the results was performed by one-way ANOVA and the least significant difference test. GB-10 and GB-10 plus BPA achieved respectively a statistically significant 1.8-fold and 3.3-fold increase in targeting homogeneity over BPA. The combined boron compound administration protocol contributes to homogeneous targeting of heterogeneous tumors and would increase therapeutic efficacy of BNCT by exposing all tumor populations to neutron capture reactions in boron. (author)

Evaluation of three partially volatile neutron shields for high-performance shipping casks

International Nuclear Information System (INIS)

Rack, H.J.; Pearson, H.S.

1981-02-01

The thermal stability and mechanical behavior of three partially volatile candidate neutron shield materials have been evaluated. The results indicate that silicone based rubbers, impregnated with elemental boron or boron carbide, Boro-silicone 236 and Bisco NS-I respectively are more thermally stable than are borated beechwoods, e.g., Permali JN. Mechanical property measurements indicated however that the compressive strength of the borated beechwood is 10 to 48 times higher than that of the silicone-based rubbers. The compressive strengths of the borated beechwood and boron carbide impregnated silicone rubber were substantially more sensitive to test temperature than was the compressive strength of the boron impregnated silicone rubber. Finally the compressive strengths and energy absorbing capability of the boron impregnated silicone rubber is not affected by prior thermal exposure at 425 0 K for 1000h

Boron removal from geothermal waters by electrocoagulation

Energy Technology Data Exchange (ETDEWEB)

Yilmaz, A. Erdem [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering., 25240 Erzurum (Turkey)], E-mail: aerdemy@atauni.edu.tr; Boncukcuoglu, Recep [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering., 25240 Erzurum (Turkey); Kocakerim, M. Muhtar [Atatuerk University, Faculty of Engineering, Department of Chemical Engineering, 25240 Erzurum (Turkey); Yilmaz, M. Tolga; Paluluoglu, Cihan [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering., 25240 Erzurum (Turkey)

2008-05-01

Most of the geothermal waters in Turkey contain extremely high concentration of boron when they are used for irrigation. The use of geothermal waters for irrigation can results in excess amount deposition of boron in soil. On the other hand, a minimal boron concentration is required for irrigational waters. In this study, electrocoagulation (EC) was selected as a treatment process for the removal of boron from thermal waters obtained from Ilica-Erzurum in Turkey. Current density (CD), pH of solution and temperature of solution were selected as operational parameters. The results showed that boron removal efficiency increased from pH 4.0 to 8.0 and decreased at pH 10.0. Although boron removal efficiency was highest at pH 8.0, energy consumption was very high at this pH value compared to other pH intervals. Boron removal efficiency reached to 95% with increasing current density from 1.5 to 6.0 mA/cm{sup 2}, but energy consumption was also increased in this interval. At higher temperatures of solution, such as 313 and 333 K, boron removal efficiency increased. At optimum conditions, boron removal efficiency in geothermal water reached up to 95%.

Boron removal from geothermal waters by electrocoagulation

International Nuclear Information System (INIS)

Yilmaz, A. Erdem; Boncukcuoglu, Recep; Kocakerim, M. Muhtar; Yilmaz, M. Tolga; Paluluoglu, Cihan

2008-01-01

Most of the geothermal waters in Turkey contain extremely high concentration of boron when they are used for irrigation. The use of geothermal waters for irrigation can results in excess amount deposition of boron in soil. On the other hand, a minimal boron concentration is required for irrigational waters. In this study, electrocoagulation (EC) was selected as a treatment process for the removal of boron from thermal waters obtained from Ilica-Erzurum in Turkey. Current density (CD), pH of solution and temperature of solution were selected as operational parameters. The results showed that boron removal efficiency increased from pH 4.0 to 8.0 and decreased at pH 10.0. Although boron removal efficiency was highest at pH 8.0, energy consumption was very high at this pH value compared to other pH intervals. Boron removal efficiency reached to 95% with increasing current density from 1.5 to 6.0 mA/cm 2 , but energy consumption was also increased in this interval. At higher temperatures of solution, such as 313 and 333 K, boron removal efficiency increased. At optimum conditions, boron removal efficiency in geothermal water reached up to 95%

Removal of boron (B) from waste liquors.

Science.gov (United States)

Jiang, J Q; Xu, Y; Simon, J; Quill, K; Shettle, K

2006-01-01

This paper explores the use of electrocoagulation to remove boron from waste effluent in comparison with alum coagulation. In treating model test wastes, greater boron removals were achieved with electrocoagulation at low doses than conventional alum coagulation when reaction was undertaken for the same conditions (pH 8.5, and initial boron concentration was 500 mg/L). Al electrocoagulation can achieve good boron removal performance (68.3%) at a dose of 2.1 (as molar ratio of Al:B, and for current density of 62.1 A/m2), while alum coagulation can only achieve the maximum boron removal of 56% at a dose of 2.4. Also, Al electrocoagulation can remove 15-20% more boron than alum coagulation for the same dose compared in the treatment of both model test wastes and industry effluent. The estimation of running costs shows that to achieve 75% boron removal from industry waste effluent, i.e. removing 150 g of boron from 1 m3 of effluent, electrocoagulation was 6.2 times cheaper than alum coagulation. The economic advantage of electrocoagulation in the treatment of boron-containing waste effluent is thus significant.

Continued biological investigations of boron-rich oligomeric phosphate diesters (OPDs). Tumor-selective boron agents for BNCT

International Nuclear Information System (INIS)

Lee, Mark W.; Shelly, Kenneth; Kane, Robert R.; Hawthorne, M. Frederick

2006-01-01

Clinical success of Boron Neutron Capture Therapy will rely on the selective intracellular delivery of high concentrations of boron-10 to tumor tissue. In order for a boron agent to facilitate clinical success, the simultaneous needs of obtaining a high tumor dose, high tumor selectivity, and low systemic toxicity must be realized. Boron-rich oligomeric phosphate diesters (OPDs) are a class of highly water-soluble compounds containing up to 40% boron by weight. Previous work in our groups demonstrated that once placed in the cytoplasm of tumor cells, OPDs quickly accumulate within the cell nucleus. The objective of the current study was to determine the biodistribution of seven different free OPDs in BALB/c mice bearing EMT6 tumors. Fructose solutions containing between 1.4 and 6.4 micrograms of boron per gram of tissue were interveinously injected in mice seven to ten days after tumor implantation. At intervals during the study, animals were euthanized and samples of tumor, blood, liver, kidney, brain and skin were collected and analyzed for boron content using ICP-AES. Tumor boron concentrations of between 5 and 29 ppm were achieved and maintained over the 72-hour time course of each experiment. Several OPDs demonstrated high tumor selectivity with one oligomer exhibiting a tumor to blood ratio of 35:1. The apparent toxicity of each oligomer was assessed through animal behavior during the experiment and necropsy of each animal upon sacrifice. (author)

Micromanufacturing Of Hard To Machine Materials By Physical And Chemical Ablation Processes

International Nuclear Information System (INIS)

Schubert, A.; Edelmann, J.; Gross, S.; Meichsner, G.; Wolf, N.; Schneider, J.; Zeidler, H.; Hackert, M.

2011-01-01

Miniaturization leads to high requirements to the applied manufacturing processes especially in respect to the used hard to machine materials and the aims of structure size and geometrical accuracy. Traditional manufacturing processes reach their limits here. One alternative for these provide thermal and chemical ablation processes. These processes are applied for the production of different microstructures in different materials like hardened steel, carbides and ceramics especially for medical engineering and tribological applications.

SHB1/HY1 Alleviates Excess Boron Stress by Increasing BOR4 Expression Level and Maintaining Boron Homeostasis in Arabidopsis Roots

Directory of Open Access Journals (Sweden)

Qiang Lv

2017-05-01

Full Text Available Boron is an essential mineral nutrient for higher plant growth and development. However, excessive amounts of boron can be toxic. Here, we report on the characterization of an Arabidopsis mutant, shb1 (sensitive to high-level of boron 1, which exhibits hypersensitivity to excessive boron in roots. Positional cloning demonstrated that the shb1 mutant bears a point mutation in a gene encoding a heme oxygenase 1 (HO1 corresponding to the HY1 gene involved in photomorphogenesis. The transcription level of the SHB1/HY1 gene in roots is up-regulated under excessive boron stimulation. Either overexpressing SHB1/HY1 or applying the HO1 inducer hematin reduces boron accumulation in roots and confers high boron tolerance. Furthermore, carbon monoxide and bilirubin, catalytic products of HO1, partially rescue the boron toxicity-induced inhibition of primary root growth in shb1. Additionally, the mRNA level of BOR4, a boron efflux transporter, is reduced in shb1 roots with high levels of boron supplementation, and hematin cannot relieve the boron toxicity-induced root inhibition in bor4 mutants. Taken together, our study reveals that HO1 acts via its catalytic by-products to promote tolerance of excessive boron by up-regulating the transcription of the BOR4 gene and therefore promoting the exclusion of excessive boron in root cells.

Carbides crystalline structure of AISI M2 high-speed steel

International Nuclear Information System (INIS)

Serna, M.M.; Galego, E.; Rossi, J.L.

2005-01-01

The aim of this study was to identify the crystallographic structure of the extracted carbides of AISI M2 steel spray formed The structure determination of these carbides. The structure determination of these carbides is a very hard work. Since these structures were formed by atom migration it is not possible to reproduce them by a controlled process with a determined chemical composition. The solution of this problem is to obtain the carbide by chemical extraction from the steel. (Author)

Ternary carbide uranium fuels for advanced reactor design applications

International Nuclear Information System (INIS)

Knight, Travis; Anghaie, Samim

1999-01-01

Solid-solution mixed uranium/refractory metal carbides such as the pseudo-ternary carbide, (U, Zr, Nb)C, hold significant promise for advanced reactor design applications because of their high thermal conductivity and high melting point (typically greater than 3200 K). Additionally, because of their thermochemical stability in a hot-hydrogen environment, pseudo-ternary carbides have been investigated for potential space nuclear power and propulsion applications. However, their stability with regard to sodium and improved resistance to attack by water over uranium carbide portends their usefulness as a fuel for advanced terrestrial reactors. An investigation into processing techniques was conducted in order to produce a series of (U, Zr, Nb)C samples for characterization and testing. Samples with densities ranging from 91% to 95% of theoretical density were produced by cold pressing and sintering the mixed constituent carbides at temperatures as high as 2650 K. (author)

Structure and thermal expansion of NbC complex carbides

International Nuclear Information System (INIS)

Khatsinskaya, I.M.; Chaporova, I.N.; Cheburaeva, R.F.; Samojlov, A.I.; Logunov, A.V.; Ignatova, I.A.; Dodonova, L.P.

1983-01-01

Alloying dependences of the crystal lattice parameters at indoor temperature and coefficient of thermal linear exspansion within a 373-1273 K range are determined for complex NbC-base carbides by the method of mathematical expemental design. It is shown that temperature changes in the linear expansion coefficient of certain complex carbides as distinct from NbC have an anomaly (minimum) within 773-973 K caused by occurring reversible phase transformations. An increase in the coefficient of thermal linear expansion and a decrease in hardness of NbC-base tungsten-, molybdenum-, vanadium- and hafnium-alloyed carbides show a weakening of a total chemical bond in the complex carbides during alloying

Boron rates for triticale and wheat crops

Directory of Open Access Journals (Sweden)

Corrêa Juliano Corulli

2005-01-01

Full Text Available No reports are registered on responses to boron fertilization nutrient deficiency and toxicity in triticale crops. The aim of this study was to evaluate triticale response to different rates of boron in comparison to wheat in an hapludox with initial boron level at 0.08 mg dm-3 4 4 factorial design trial completely randomized blocks design (n = 4. Boron rates were 0; 0.62; 1.24 and 1.86 mg dm-3; triticale cultivars were IAC 3, BR 4 and BR 53 and IAPAR 38 wheat crop was used for comparison. The wheat (IAPAR 38 crop presented the highest boron absorption level of all. Among triticale cultivars, the most responsive was IAC 53, presenting similar characteristics to wheat, followed by BR 4; these two crops are considered tolerant to higher boron rates in soil. Regarding to BR 53, no absorption effect was observed, and the cultivars was sensitive to boron toxicity. Absorption responses differed for each genotype. That makes it possible to choose and use the best-adapted plants to soils with different boron rates.

An empirical model for parameters affecting energy consumption in boron removal from boron-containing wastewaters by electrocoagulation

Energy Technology Data Exchange (ETDEWEB)

Yilmaz, A. Erdem [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering, 25240 Erzurum (Turkey)]. E-mail: aerdemy@atauni.edu.tr; Boncukcuoglu, Recep [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering, 25240 Erzurum (Turkey); Kocakerim, M. Muhtar [Atatuerk University, Faculty of Engineering, Department of Chemical Engineering, 25240 Erzurum (Turkey)

2007-06-01

In this study, it was investigated parameters affecting energy consumption in boron removal from boron containing wastewaters prepared synthetically, via electrocoagulation method. The solution pH, initial boron concentration, dose of supporting electrolyte, current density and temperature of solution were selected as experimental parameters affecting energy consumption. The obtained experimental results showed that boron removal efficiency reached up to 99% under optimum conditions, in which solution pH was 8.0, current density 6.0mA/cm{sup 2}, initial boron concentration 100mg/L and solution temperature 293K. The current density was an important parameter affecting energy consumption too. High current density applied to electrocoagulation cell increased energy consumption. Increasing solution temperature caused to decrease energy consumption that high temperature decreased potential applied under constant current density. That increasing initial boron concentration and dose of supporting electrolyte caused to increase specific conductivity of solution decreased energy consumption. As a result, it was seen that energy consumption for boron removal via electrocoagulation method could be minimized at optimum conditions. An empirical model was predicted by statistically. Experimentally obtained values were fitted with values predicted from empirical model being as following;[ECB]=7.6x10{sup 6}x[OH]{sup 0.11}x[CD]{sup 0.62}x[IBC]{sup -0.57}x[DSE]{sup -0.}= {sup 04}x[T]{sup -2.98}x[t] Unfortunately, the conditions obtained for optimum boron removal were not the conditions obtained for minimum energy consumption. It was determined that support electrolyte must be used for increase boron removal and decrease electrical energy consumption.

An empirical model for parameters affecting energy consumption in boron removal from boron-containing wastewaters by electrocoagulation

International Nuclear Information System (INIS)

Yilmaz, A. Erdem; Boncukcuoglu, Recep; Kocakerim, M. Muhtar

2007-01-01

In this study, it was investigated parameters affecting energy consumption in boron removal from boron containing wastewaters prepared synthetically, via electrocoagulation method. The solution pH, initial boron concentration, dose of supporting electrolyte, current density and temperature of solution were selected as experimental parameters affecting energy consumption. The obtained experimental results showed that boron removal efficiency reached up to 99% under optimum conditions, in which solution pH was 8.0, current density 6.0mA/cm 2 , initial boron concentration 100mg/L and solution temperature 293K. The current density was an important parameter affecting energy consumption too. High current density applied to electrocoagulation cell increased energy consumption. Increasing solution temperature caused to decrease energy consumption that high temperature decreased potential applied under constant current density. That increasing initial boron concentration and dose of supporting electrolyte caused to increase specific conductivity of solution decreased energy consumption. As a result, it was seen that energy consumption for boron removal via electrocoagulation method could be minimized at optimum conditions. An empirical model was predicted by statistically. Experimentally obtained values were fitted with values predicted from empirical model being as following;[ECB]=7.6x10 6 x[OH] 0.11 x[CD] 0.62 x[IBC] -0.57 x[DSE] -0.04 x[T] -2.98 x[t] Unfortunately, the conditions obtained for optimum boron removal were not the conditions obtained for minimum energy consumption. It was determined that support electrolyte must be used for increase boron removal and decrease electrical energy consumption.

Low temperature study of nonstoichiometric titanium carbide

International Nuclear Information System (INIS)

Tashmetov, M.Yu.

2005-05-01

By low temperature neutron diffraction method was studied structure in nonstoichiometric titanium carbide from room temperature up to 12K. It is found of low temperature phase in titanium carbide- TiC 0.71 . It is established region and borders of this phase. It is determined change of unit cell parameter. (author)

Behaviour of a VVER-1000 fuel element with boron carbide/steel absorber tested under severe fuel damage conditions in the CORA facility (Results of experiment CORA-W2)

International Nuclear Information System (INIS)

Hagen, S.; Hofmann, P.; Noack, V.; Schanz, G.; Schumacher, G.; Sepold, L.

1994-10-01

The 'Severe Fuel Damage' (SFD) experiments of the Kernforschungszentrum Karlsruhe (KfK), Federal Republic of Germany, were carried out in the out-of-pile facility 'CORA' as part of the international Severe Fuel Damage (SFD) research. The experimental program was set up to provide information on the failure mechanisms of Light Water Reactor (LWR) fuel elements in a temperature range from 1200 C to 2000 C and in few cases up to 2400 C. Between 1987 and 1992 a total of 17 CORA experiments with two different bundle configurations, i.e. PWR (Pressurized Water Reactor) and BWR (Boiling Water Reactor) bundles were performed. These assemblies represented 'Western-type' fuel elements with the pertinent materials for fuel, cladding, grid spacer, and absorber rod. At the end of the experimental program two VVER-1000 specific tests were run in the CORA facility with identical objectives but with genuine VVER-type materials. The experiments, designated CORA-W1 and CORA-W2 were conducted on February 18, 1993 and April 21, 1993, respectively. Test bundle CORA-W1 was without absorber material whereas CORA-W2 contained one absorber rod (boron carbide/steel). As in the earlier CORA tests the test bundles were subjected to temperature transients of a slow heatup rate in a steam environment. The transient phases of the tests were initiated with a temperature ramp rate of 1 K/s. With these conditions a so-called small-break LOCA was simulated. The temperature escalation due to the exothermal zircon/niobium-steam reaction started at about 1200 C, leading the bundles to maximum temperatures of approximately 1900 C. The thermal response of bundle CORA-W2 is comparable to that of CORA-W1. In test CORA-W2, however, the temperature front moved faster from the top to the bottom compared to test CORA-W1 [de

Wear Mechanism of Chemical Vapor Deposition (CVD) Carbide Insert in Orthogonal Cutting Ti-6Al-4V ELI at High Cutting Speed

International Nuclear Information System (INIS)

Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.

2011-01-01

The performance of Chemical Vapor Deposition (CVD) carbide insert with ISO designation of CCMT 12 04 04 LF, when turning titanium alloys was investigated. There were four layers of coating materials for this insert i.e.TiN-Al2O3-TiCN-TiN. The insert performance was evaluated based on the insert's edge resistant towards the machining parameters used at high cutting speed range of machining Ti-6Al-4V ELI. Detailed study on the wear mechanism at the cutting edge of CVD carbide tools was carried out at cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev and depth of cut of 0.10-0.20 mm. Wear mechanisms such as abrasive and adhesive were observed on the flank face. Crater wear due to diffusion was also observed on the rake race. The abrasive wear occurred more at nose radius and the fracture on tool were found at the feed rate of 0.35 mm/rev and the depth of cut of 0.20 mm. The adhesion wear takes place after the removal of the coating or coating delaminating. Therefore, adhesion or welding of titanium alloy onto the flank and rake faces demonstrates a strong bond at the workpiece-tool interface.

A quantitative comparison between electrocoagulation and chemical coagulation for boron removal from boron-containing solution

International Nuclear Information System (INIS)

Yilmaz, A. Erdem; Boncukcuoglu, Recep; Kocakerim, M. Muhtar

2007-01-01

This paper provides a quantitative comparison of electrocoagulation and chemical coagulation approaches based on boron removal. Electrocoagulation process delivers the coagulant in situ as the sacrificial anode corrodes, due to a fixed current density, while the simultaneous evolution of hydrogen at the cathode allows for pollutant removal by flotation. By comparison, conventional chemical coagulation typically adds a salt of the coagulant, with settling providing the primary pollutant removal path. Chemical coagulation was carried out via jar tests using aluminum chloride. Comparison was done with the same amount of coagulant between electrocoagulation and chemical coagulation processes. Boron removal obtained was higher with electrocoagulation process. In addition, it was seen that chemical coagulation has any effect for boron removal from boron-containing solution. At optimum conditions (e.g. pH 8.0 and aluminum dose of 7.45 g/L), boron removal efficiencies for electrocoagulation and chemical coagulation were 94.0% and 24.0%, respectively

A quantitative comparison between electrocoagulation and chemical coagulation for boron removal from boron-containing solution

Energy Technology Data Exchange (ETDEWEB)

Yilmaz, A. Erdem [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering, 25240 Erzurum (Turkey)], E-mail: aerdemy@atauni.edu.tr; Boncukcuoglu, Recep [Atatuerk University, Faculty of Engineering, Department of Environmental Engineering, 25240 Erzurum (Turkey); Kocakerim, M. Muhtar [Atatuerk University, Faculty of Engineering, Department of Chemical Engineering, 25240 Erzurum (Turkey)

2007-10-22

This paper provides a quantitative comparison of electrocoagulation and chemical coagulation approaches based on boron removal. Electrocoagulation process delivers the coagulant in situ as the sacrificial anode corrodes, due to a fixed current density, while the simultaneous evolution of hydrogen at the cathode allows for pollutant removal by flotation. By comparison, conventional chemical coagulation typically adds a salt of the coagulant, with settling providing the primary pollutant removal path. Chemical coagulation was carried out via jar tests using aluminum chloride. Comparison was done with the same amount of coagulant between electrocoagulation and chemical coagulation processes. Boron removal obtained was higher with electrocoagulation process. In addition, it was seen that chemical coagulation has any effect for boron removal from boron-containing solution. At optimum conditions (e.g. pH 8.0 and aluminum dose of 7.45 g/L), boron removal efficiencies for electrocoagulation and chemical coagulation were 94.0% and 24.0%, respectively.

Extreme-Environment Silicon-Carbide (SiC) Wireless Sensor Suite

Science.gov (United States)

Yang, Jie

2015-01-01

Phase II objectives: Develop an integrated silicon-carbide wireless sensor suite capable of in situ measurements of critical characteristics of NTP engine; Compose silicon-carbide wireless sensor suite of: Extreme-environment sensors center, Dedicated high-temperature (450 deg C) silicon-carbide electronics that provide power and signal conditioning capabilities as well as radio frequency modulation and wireless data transmission capabilities center, An onboard energy harvesting system as a power source.

Oxide film assisted dopant diffusion in silicon carbide

Energy Technology Data Exchange (ETDEWEB)

Tin, Chin-Che, E-mail: cctin@physics.auburn.ed [Department of Physics, Auburn University, Alabama 36849 (United States); Mendis, Suwan [Department of Physics, Auburn University, Alabama 36849 (United States); Chew, Kerlit [Department of Electrical and Electronic Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kuala Lumpur (Malaysia); Atabaev, Ilkham; Saliev, Tojiddin; Bakhranov, Erkin [Physical Technical Institute, Uzbek Academy of Sciences, 700084 Tashkent (Uzbekistan); Atabaev, Bakhtiyar [Institute of Electronics, Uzbek Academy of Sciences, 700125 Tashkent (Uzbekistan); Adedeji, Victor [Department of Chemistry, Geology and Physics, Elizabeth City State University, North Carolina 27909 (United States); Rusli [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore)

2010-10-01

A process is described to enhance the diffusion rate of impurities in silicon carbide so that doping by thermal diffusion can be done at lower temperatures. This process involves depositing a thin film consisting of an oxide of the impurity followed by annealing in an oxidizing ambient. The process uses the lower formation energy of silicon dioxide relative to that of the impurity-oxide to create vacancies in silicon carbide and to promote dissociation of the impurity-oxide. The impurity atoms then diffuse from the thin film into the near-surface region of silicon carbide.

Oxide film assisted dopant diffusion in silicon carbide

International Nuclear Information System (INIS)

Tin, Chin-Che; Mendis, Suwan; Chew, Kerlit; Atabaev, Ilkham; Saliev, Tojiddin; Bakhranov, Erkin; Atabaev, Bakhtiyar; Adedeji, Victor; Rusli

2010-01-01

A process is described to enhance the diffusion rate of impurities in silicon carbide so that doping by thermal diffusion can be done at lower temperatures. This process involves depositing a thin film consisting of an oxide of the impurity followed by annealing in an oxidizing ambient. The process uses the lower formation energy of silicon dioxide relative to that of the impurity-oxide to create vacancies in silicon carbide and to promote dissociation of the impurity-oxide. The impurity atoms then diffuse from the thin film into the near-surface region of silicon carbide.

Study on the performance of fuel elements with carbide and carbide-nitride fuel

International Nuclear Information System (INIS)

Golovchenko, Yu.M.; Davydov, E.F.; Maershin, A.A.

1985-01-01

Characteristics, test conditions and basic results of material testing of fuel elements with carbide and carbonitride fuel irradiated in the BOR-60 reactor up to 3-10% burn-up at specific power rate of 55-70 kW/m and temperatures of the cladding up to 720 deg C are described. Increase of cladding diameter is stated mainly to result from pressure of swelling fuel. The influence of initial efficient porosity of the fuel on cladding deformation and fuel stoichiometry on steel carbonization is considered. Utilization of carbide and carbonitride fuel at efficient porosity of 20% at the given test modes is shown to ensure their operability up to 10% burn-up

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.

Effect of sintering temperature on the densification of B4C pellets

International Nuclear Information System (INIS)

Gomide, R.G.; Durazzo, M.; Riella, H.G.

1990-01-01

Boron is largely used in several types of nuclear reactors control and safety systems. In the majority of these applications sintered boron carbide pellets are used. Near stoichiometric B 4 C hardly densifies during pressureless sintering. As a starting point of an overall program to produce > 70% TD B 4 C pellets pressing parameters have been studied for further study of the influence of sintering temperature in the densification of this ceramic material. Dilatometric analyses show that sintering starts at 1760 0 C for the F 1200 ESK - type boron carbide powders. Moreover, the sintering experiments show that up to 92% TD pellets can be obtained. (author) [pt

“Investigations on the machinability of Waspaloy under dry environment”

Science.gov (United States)

Deepu, J.; Kuppan, P.; SBalan, A. S.; Oyyaravelu, R.

2016-09-01

Nickel based superalloy, Waspaloy is extensively used in gas turbine, aerospace and automobile industries because of their unique combination of properties like high strength at elevated temperatures, resistance to chemical degradation and excellent wear resistance in many hostile environments. It is considered as one of the difficult to machine superalloy due to excessive tool wear and poor surface finish. The present paper is an attempt for removing cutting fluids from turning process of Waspaloy and to make the processes environmentally safe. For this purpose, the effect of machining parameters such as cutting speed and feed rate on the cutting force, cutting temperature, surface finish and tool wear were investigated barrier. Consequently, the strength and tool wear resistance and tool life increased significantly. Response Surface Methodology (RSM) has been used for developing and analyzing a mathematical model which describes the relationship between machining parameters and output variables. Subsequently ANOVA was used to check the adequacy of the regression model as well as each machining variables. The optimal cutting parameters were determined based on multi-response optimizations by composite desirability approach in order to minimize cutting force, average surface roughness and maximum flank wear. The results obtained from the experiments shown that machining of Waspaloy using coated carbide tool with special ranges of parameters, cutting fluid could be completely removed from machining process

Raman spectroscopy of boron-doped single-layer graphene.

Science.gov (United States)

Kim, Yoong Ahm; Fujisawa, Kazunori; Muramatsu, Hiroyuki; Hayashi, Takuya; Endo, Morinobu; Fujimori, Toshihiko; Kaneko, Katsumi; Terrones, Mauricio; Behrends, Jan; Eckmann, Axel; Casiraghi, Cinzia; Novoselov, Kostya S; Saito, Riichiro; Dresselhaus, Mildred S

2012-07-24

The introduction of foreign atoms, such as nitrogen, into the hexagonal network of an sp(2)-hybridized carbon atom monolayer has been demonstrated and constitutes an effective tool for tailoring the intrinsic properties of graphene. Here, we report that boron atoms can be efficiently substituted for carbon in graphene. Single-layer graphene substitutionally doped with boron was prepared by the mechanical exfoliation of boron-doped graphite. X-ray photoelectron spectroscopy demonstrated that the amount of substitutional boron in graphite was ~0.22 atom %. Raman spectroscopy demonstrated that the boron atoms were spaced 4.76 nm apart in single-layer graphene. The 7-fold higher intensity of the D-band when compared to the G-band was explained by the elastically scattered photoexcited electrons by boron atoms before emitting a phonon. The frequency of the G-band in single-layer substitutionally boron-doped graphene was unchanged, which could be explained by the p-type boron doping (stiffening) counteracting the tensile strain effect of the larger carbon-boron bond length (softening). Boron-doped graphene appears to be a useful tool for engineering the physical and chemical properties of graphene.

Iron Carbides in Fischer–Tropsch Synthesis: Theoretical and Experimental Understanding in Epsilon-Iron Carbide Phase Assignment

International Nuclear Information System (INIS)

Liu, Xing-Wu; Cao, Zhi; Zhao, Shu; Gao, Rui

2017-01-01

As active phases in low-temperature Fischer–Tropsch synthesis for liquid fuel production, epsilon iron carbides are critically important industrial materials. However, the precise atomic structure of epsilon iron carbides remains unclear, leading to a half-century of debate on the phase assignment of the ε-Fe 2 C and ε’-Fe 2.2 C. Here, we resolve this decades-long question by a combining theoretical and experimental investigation to assign the phases unambiguously. First, we have investigated the equilibrium structures and thermal stabilities of ε-Fe x C, (x = 1, 2, 2.2, 3, 4, 6, 8) by first-principles calculations. We have also acquired X-ray diffraction patterns and Mössbauer spectra for these epsilon iron carbides, and compared them with the simulated results. These analyses indicate that the unit cell of ε-Fe 2 C contains only one type of chemical environment for Fe atoms, while ε’-Fe 2.2 C has six sets of chemically distinct Fe atoms.