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Sample records for high chromium cast

  1. Effect of Chromium on Microstructure and Properties of High Boron White Cast Iron

    NASA Astrophysics Data System (ADS)

    Liu, Zhongli; Chen, Xiang; Li, Yanxiang; Hu, Kaihua

    2008-03-01

    In this article, the effect of chromium on microstructure and properties of high boron white cast iron was studied. The results indicate that the microstructure of high boron white cast iron with different chromium content comprises a dendritic matrix and interdendritic eutectics, and the eutectic compound has a M2B-type chemical formula that does not change with the difference of chromium content. The increase of chromium not only increases the microhardness of boride, but also improves the morphology of boride, which is changed from continuous network to less continuous distribution. Moreover, with the chromium increase, martensite appears in the matrix under the as-cast condition, the appearance of which depends on the increase of chromium in the matrix and the uneven distribution of carbon in the matrix caused by chromium addition. After quenching in air, the matrixes of alloys all change to martensite. However, some secondary particles are found in the central area of the dendrite grains of alloys with higher chromium, and their existence is due to the difference of boron solubility in the matrix with different chromium content. In addition, the hardenability, hardness, and impact toughness are all improved with the increase in chromium.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Effects of heat treatment on wear resistance and fracture toughness of duo-cast materials composed of high-chromium white cast iron and low-chromium steel

    NASA Astrophysics Data System (ADS)

    Kim, Chang Kyu; Lee, Sunghak; Jung, Jae-Young

    2006-03-01

    The objective of this study is to investigate effects of heat treatment on wear resistance and fracture toughness in duo-cast materials composed of a high-chromium white cast iron and a low-chromium steel as a wear-resistant part and a ductile part, respectively. Different size, volume fraction, and distribution of M7C3 carbides were employed in the wear-resistant part by changing the amount of chromium, and the volume fraction of martensite in the austenitic matrix was varied by the heat treatment. In the alloys containing a small amount of chromium, an interdendritic structure of eutectic M7C3 carbides was formed, and led to the improvement of wear resistance and fracture toughness. After the heat treatment, the selective wear of the matrix and the cracking or spalled-off carbides were considerably reduced since the hardness difference between carbides and matrix decreased by the increase in the matrix hardness, thereby leading to the improvement of the wear resistance. However, the fracture toughness of the heat-treated alloys was lower than that of the as-cast alloys because the matrix containing a considerable amount of martensite did not effectively prevent the crack propagation.

  4. Effect of Heat Treatment on the Impact Toughness of `High-Chromium Cast Iron - Low Alloy Steel' Bimetal Components

    NASA Astrophysics Data System (ADS)

    Özdemir, Z.

    2017-03-01

    A bimetallic `low-alloy steel - high-chromium cast iron' composite obtained by successive sand casting is studied and shown to have good cohesion on the interface and no casting defects. The hardness and the impact toughness of the bimetal increase simultaneously. The microstructure is more homogeneous after diffusion annealing at 1040°C, rapid cooling, and 3-h tempering at 270°C.

  5. Solidification and solid-state transformation mechanisms in Si alloyed high-chromium white cast irons

    NASA Astrophysics Data System (ADS)

    Laird, George; Powell, Graham L. F.

    1993-04-01

    Chromium white cast irons are widely used in environments where severe abrasion resistance is a dominant requirement. To improve the wear resistance of these commercially important irons, the United States Bureau of Mines and CSIRO Australia are studying their solidification and solid-state transformation kinetics. A ternary Fe-Cr-C iron with 17.8 wt pct (pct) Cr and 3.0 pct C was compared with commercially available irons of similar Cr and C contents with Si contents between 1.6 and 2.2 pct. The irons were solidified and cooled at rates of 0.03 and 0.17 K · s-1 to 873 K. Differential thermal analysis (DTA) showed that Si depresses the eutectic reaction temperature and suggests that is has no effect upon the volume of eutectic carbides formed during solidification. Microprobe analysis revealed that austenite dendrites within the Si alloyed irons cooled at 0.03 and 0.17 K·s-1 had C and Cr contents that were lower than those of dendrites within the ternary alloy cooled at the same cooling rate and a Si alloyed iron that was water quenched from the eutectic temperature. These lower values were shown by image analysis to be the result of both solid-state growth (coarsening) of the eutectic carbides and some secondary carbide formation. Hardness measurements in the as-cast condition and after soaking in liquid nitrogen suggest an increase in the martensite start temperature as the Si content was increased. It is concluded that Si’s effect on increasing the size and volume fraction of eutectic carbides and increasing the matrix hardness should lead to improved wear resistance over regular high-chromium white cast irons.

  6. Diffusion zone between high-chromium cast iron and high-manganese steel during electric-slag facing

    SciTech Connect

    Ponomarenko, V.P.; Shvartser, A.Y.; Stroganova, G.V.

    1986-05-01

    The authors investigate extending the service lives of components by the method of electric-slag facing of working surfaces. Steel 45 was used in the annealed state. Electric-slag remelting was the method used to determine the bending strength. Metallographic examinations were conducted under an MIM-8m microscope, while x-ray analysis of the built-up and base metals were performed on a DRON-2 diffractometer. BAsic alloying elements, chromium and manganese were studied on a ''Cameca MS-46'' microanalyzer. During the electri-slag facing of a high-chromium cast iron containing 8% of Mn on high-manganese steel 11OG13L diffusion equalization of the manganese content occurs in the fusion zone. Diffusion displacement of carbon, chromium, and manganese from high-chromium cast iron into the high-manganese steel during electric-slag facing gies rise to a smooth change in the structure of the metal in the fusion zone, and to increased strength of the joint between the unlike materials investigated.

  7. Characterization of Microstructure and Mechanical Properties of High Chromium Cast Irons Using SEM and Nanoindentation

    NASA Astrophysics Data System (ADS)

    Chen, Ling; Iyengar, Srinivasan; Zhou, Jinming; Turba, Krystof; Ståhl, Jan-Eric

    2015-01-01

    The effects of composition changes and heat treatment on the microstructure and mechanical properties of high-chromium white cast irons were studied in order to characterize possible improvements in product performance and machinability. Materials characterization was performed using nanoindentation, SEM, and EDS techniques. Present results show that changes in carbon and silicon contents as well as heat treatment strongly affect the mechanical properties and their variation in the material. In the as-cast condition, the sample with relatively lower carbon and silicon contents has an austenite-martensite matrix and is much harder than the sample with relatively higher carbon and silicon contents having more eutectic carbides in a bainite matrix. Annealing leads to softening of the materials relative to the as-cast condition, with the relatively higher carbon-silicon material being marginally harder due to the presence of more eutectic carbides. A similar trend is seen after the hardening treatment, and the presence of primary carbide can restrict the extent of hardening due to the loss of alloying elements from the matrix.

  8. TiC reinforced cast chromium steels

    SciTech Connect

    Dogan, Omer N.; Rawers, James C.; Hawk, Jeffrey A.; Schrems, Karol K.

    2003-11-01

    A series of new titanium carbide reinforced cast chromium steels were developed for wear applications. Objective of the program was to enhance wear resistant alloys and, if possible, improve mechanical properties. The new steels which were melted in a vacuum induction furnace contained 12 Cr, 3-5 Ti, 1-2 C in weight percent. Alloying with Ti changed the precipitate microstructure from Cr carbide to TiC dispersed in a martensitic matrix. Yield strength and impact resistance improved with Ti alloying. Wear rates of the cast Cr/TiC steels, (determined from high- and low-stress abrasion tests, erosion test, and scratch tests) were generally lower than both the as-cast and heat-treated AISI type 440°C steel and were often further reduced by increasing the Ti alloy concentration. The exceptions were the erosion test for which all materials had similar wear rate.

  9. Phase Transformations and Microstructural Observations During Subcritical Heat Treatments of a High-Chromium Cast Iron

    NASA Astrophysics Data System (ADS)

    Karantzalis, A. E.; Lekatou, A.; Kapoglou, A.; Mavros, H.; Dracopoulos, V.

    2012-06-01

    In this study, Cr white iron of 18.23 wt.% was subjected to a series of subcritical heat treatments. At both temperatures of 350 and 450 °C, no precipitation of secondary carbides was observed, and the overall microstructure resembles to that of the as-cast condition. At 550 °C, hardness values increased slightly compared to the as-cast values. No evidence of secondary carbide formation was observed. At 650 and 750 °C, extensive-to-complete transformation to pearlite-ferrite structures has occurred. Some evidence of secondary carbide precipitation especially for prolonged treatment periods was not adequate to obstruct the hardness decrease due to the dominating effect of pearlitic-ferritic formation. At 850 °C, secondary carbide precipitation and martensite formation lead to high hardness values.

  10. Wear of Cast Chromium Steels With TiC Reinforcement

    SciTech Connect

    Dogan,O.N.; Hawk, J.A.; Tylczak, J.H.

    2001-10-01

    Wear resistance of a series of new titanium carbide reinforced cast chromium steels was investigated under various wear conditions. The steels which were melted in a vacuum induction furnace contained 12 Cr, 3-5 Ti, 1-2 C in weight percent. Microstructure of these materials was characterized using scanning electron microscopy, light optical microscopy, and X-ray diffraction. Microstructure of steels consisted of TiC phase dispersed in a martensitic matrix. High-stress and low-stress abrasion tests, and an erosion test, were utilized to understand the wear behavior of these materials under different environments. The steels were tested in as-cast and heat treated conditions. Wear rates of the cast Cr/TiC steels were compared to those of an AISI type 440C steel and P/M composites reinforced with TiC.

  11. Comprehensive study of the abrasive wear and slurry erosion behavior of an expanded system of high chromium cast iron and microstructural modification for enhanced wear resistance

    NASA Astrophysics Data System (ADS)

    Chung, Reinaldo Javier

    High chromium cast irons (HCCIs) have been demonstrated to be an effective material for a wide range of applications in aggressive environments, where resistances to abrasion, erosion and erosion-corrosion are required. For instance, machinery and facilities used in mining and extraction in Alberta's oil sands suffer from erosion and erosion-corrosion caused by silica-containing slurries, which create challenges for the reliability and maintenance of slurry pumping systems as well as other processing and handling equipment. Considerable efforts have been made to determine and understand the relationship between microstructural features of the HCCIs and their wear performance, in order to guide the material selection and development for specific service conditions with optimal performance. The focus was previously put on a narrow group of compositions dictated by ASTM A532. However, with recent advances in casting technology, the HCCI compositional range can be significantly expanded, which potentially brings new alloys that can be superior to those which are currently employed. This work consists of three main aspects of study. The first one is the investigation of an expanded system of white irons with their composition ranging from 1 to 6 wt.% C and 5 to 45 wt.% Cr, covering 53 alloys. This work has generated wear and corrosion maps and established correlation between the performance and microstructural features for the alloys. The work was conducted in collaboration with the Materials Development Center of Weir Minerals in Australia, and the results have been collected in a database that is used by the company to guide materials selection for slurry pump components in Alberta oil sands and in other mining operations throughout the world. The second part consists of three case studies on effects of high chromium and high carbon, respectively, on the performance of the HCCIs. The third aspect is the development of an approach to enhance the wear resistance of

  12. [On deffect of cobalt-chromium-nickel alloy for dental castings (author's transl)].

    PubMed

    Nasu, T; Hikichi, H; Noguchi, H

    1978-01-01

    We studied about castability and microporosity of cobalt-chromium-nickel alloy for dental casting in various methods of fusion and casting. The combinations of fusion and casting were induction fusion and centrifugal casting, arc discharge fusion and argon gas pressure casting and oxy-acetylene flame fusion and centrifugal casting. The following results were obtained. 1. The amount of microposity was smaller, when only mold temperature was low, and as mold temperature and casting temperature were high, castability was better. 2. The arc discharge fusion and argon gas pressure casting was the best method about castability and microporosity in three methods. Second method was the induction fusion and centrifugal casting. 3. In the induction fusion and centrifugal casting, blowing arong gas of 1 l/min to molten metal to protect the metal from oxidization improved the castability the best, but amount of microporosity was large, so that it was needed to lower the mold temperature in this condition. 4. The oxyacetylene flame fusion and centrifugal casting was not suitable for the casting of Co-Cr alloy "Regalloy No. 3", for the alloy was made for the induction fusion casting.

  13. Chromium at High Pressure

    NASA Astrophysics Data System (ADS)

    Jaramillo, Rafael

    2012-02-01

    Chromium has long served as the archetype of spin density wave magnetism. Recently, Jaramillo and collaborators have shown that Cr also serves as an archetype of magnetic quantum criticality. Using a combination of x-ray diffraction and electrical transport measurements at high pressures and cryogenic temperatures in a diamond anvil cell, they have demonstrated that the N'eel transition (TN) can be continuously suppressed to zero, with no sign of a concurrent structural transition. The order parameter undergoes a broad regime of exponential suppression, consistent with the weak coupling paradigm, before deviating from a BCS-like ground state within a narrow but accessible quantum critical regime. The quantum criticality is characterized by mean field scaling of TN and non mean field scaling of the transport coefficients, which points to a fluctuation-induced reconstruction of the critical Fermi surface. A comparison between pressure and chemical doping as means to suppress TN sheds light on different routes to the quantum critical point and the relevance of Fermi surface nesting and disorder at this quantum phase transition. The work by Jaramillo et al. is broadly relevant to the study of magnetic quantum criticality in a physically pure and theoretically tractable system that balances elements of weak and strong coupling. [4pt] [1] R. Jaramillo, Y. Feng, J. Wang & T. F. Rosenbaum. Signatures of quantum criticality in pure Cr at high pressure. Proc. Natl. Acad. Sci. USA 107, 13631 (2010). [0pt] [2] R. Jaramillo, Y. Feng, J. C. Lang, Z. Islam, G. Srajer, P. B. Littlewood, D. B. McWhan & T. F. Rosenbaum. Breakdown of the Bardeen-Cooper-Schrieffer ground state at a quantum phase transition. Nature 459, 405 (2009).

  14. Chromium.

    PubMed

    Barceloux, D G

    1999-01-01

    Chromium occurs primarily in the trivalent state (III), which is the most stable form, or in the hexavalent state (VI), which is a strong oxidizing agent. Elemental chromium (0) does not occur naturally on earth. Trivalent chromium (III) is an essential trace metal necessary for the formation of glucose tolerance factor and for the metabolism of insulin. Commercial applications of chromium compounds include tanning (III), corrosion inhibition, plating, glassware-cleaning solutions, wood preservatives (VI), manufacture of safety matches, metal finishing (VI), and the production of pigments (III, VI). Hexavalent chromium (VI) contaminated local soil when chromium waste slag was part of the fill material present in residential, public, and industrial areas. In some urban areas, about two-thirds of the chromium in air results from the emission of hexavalent chromium from fossil fuel combustion and steel production. The remaining chromium in air is the trivalent form. The residence time of chromium in air is < 10 days, depending on the particle size. Trivalent compounds generally have low toxicity and the gastrointestinal tract poorly absorbs these compounds. Hexavalent chromium is a skin and mucous membrane irritant and some of these hexavalent compounds are strong corrosive agents. Hexavalent chromium compounds also produce an allergic contact dermatitis characterized by eczema. Sensitivity to trivalent compounds is much less frequent, but some workers may react to high concentrations of these compounds. Hexavalent chromium is recognized by the International Agency for Research on Cancer and by the US Toxicology Program as a pulmonary carcinogen. The increased risk of lung cancer occurs primarily in workers exposed to hexavalent chromium dust during the refining of chromite ore and the production of chromate pigments. Although individual studies suggest the possibility of an excess incidence of cancer at sites outside the lung, the results from these studies are

  15. Welding of high chromium steels

    NASA Technical Reports Server (NTRS)

    Miller, W B

    1928-01-01

    A brief description is given of different groups of high chromium steels (rustless iron and stainless steels) according to their composition and more generally accepted names. The welding procedure for a given group will be much the same regardless of the slight variations in chemical composition which may exist within a certain group. Information is given for the tensile properties (yield point and ultimate strength) of metal sheets and welds before and after annealing on coupons one and one-half inches wide. Since welds in rustless iron containing 16 to 18 percent chromium and 7 to 12 percent nickel show the best combination of strength and ductility in the 'as welded' or annealed condition, it is considered the best alloy to use for welded construction.

  16. Solidification structure and abrasion resistance of high chromium white irons

    NASA Astrophysics Data System (ADS)

    Doğan, Ö. N.; Hawk, J. A.; Laird, G.

    1997-06-01

    Superior abrasive wear resistance, combined with relatively low production costs, makes high Cr white cast irons (WCIs) particularly attractive for applications in the grinding, milling, and pumping apparatus used to process hard materials. Hypoeutectic, eutectic, and hypereutectic cast iron compositions, containing either 15 or 26 wt pct chromium, were studied with respect to the macrostructural transitions of the castings, solidification paths, and resulting microstructures when poured with varying superheats. Completely equiaxed macrostructures were produced in thick section castings with slightly hypereutectic compositions. High-stress abrasive wear tests were then performed on the various alloys to examine the influence of both macrostructure and microstructure on wear resistance. Results indicated that the alloys with a primarily austenitic matrix had a higher abrasion resistance than similar alloys with a pearlitic/bainitic matrix. Improvement in abrasion resistance was partially attributed to the ability of the austenite to transform to martensite at the wear surface during the abrasion process.

  17. Effects of a Destabilization Heat Treatment on the Microstructure and Abrasive Wear Behavior of High-Chromium White Cast Iron Investigated Using Different Characterization Techniques

    NASA Astrophysics Data System (ADS)

    Gasan, Hakan; Erturk, Fatih

    2013-11-01

    The hypoeutectic white cast iron was subjected to various destabilization heat treatment temperatures of 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C) for 2 hours. The as-cast and destabilized specimens were characterized by optical metallography, classical direct comparison, and the Rietveld method. The volume fractions of carbides were measured by optical metallography. Moreover, the volume fractions of retained austenite and martensite were measured by the classical direct comparison method. Despite the limitations of optical metallography and the classical direct comparison method, the Rietveld method was successively and accurately applied to determine the volume fractions of all phases. In addition, the Rietveld analysis yielded certain results, such as the crystallographic properties of the phases that can be used to explain the relationship between the microstructural parameters and the wear behavior. Abrasive wear tests with different sliding speeds were carried out on the as-cast and destabilized alloys to identify the effect of microstructural parameters on the wear behavior. The results indicated that the morphologies of secondary carbides, the crystallographic properties of the phases, and the proper combination of the amount of martensite, retained austenite, and carbides were the principle parameters that affect the hardness and wear behavior of the alloy.

  18. High density tape casting system

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr. (Inventor)

    1989-01-01

    A system is provided for casting thin sheets (or tapes) of particles bound together, that are used for oxygen membranes and other applications, which enables the particles to be cast at a high packing density in a tape of uniform thickness. A slurry contains the particles, a binder, and a solvent, and is cast against the inside walls of a rotating chamber. Prior to spraying the slurry against the chamber walls, a solvent is applied to a container. The solvent evaporates to saturate the chamber with solvent vapor. Only then is the slurry cast. As a result, the slurry remains fluid long enough to spread evenly over the casting surface formed by the chamber, and for the slurry particles to become densely packed. Only then is the chamber vented to remove solvent, so the slurry can dry. The major novel feature is applying solvent vapor to a rotating chamber before casting slurry against the chamber walls.

  19. Solidification and solid state transformations during cooling of chromium-molybdenum white cast irons

    NASA Astrophysics Data System (ADS)

    Demello, J. D. B.; Durand-Charre, M.; Hamar-Thibault, S.

    1983-09-01

    Two series of Cr, Mo white cast irons were investigated by different techniques. Differential thermal analysis was carried out to determine the liquidus and eutectic temperatures. Unidirectional solidification was used to promote coarser structures easier to analyze. Furthermore, the microstructures of the sample, quenched during a slow unidirectional solidification, illustrate the behavior of the alloy during continuous cooling. The precipitates were characterized by scanning and transmission electron microscopy and microprobe analysis. The main findings are reported: (1) a correlation was found between the end of solidification and the chromium to carbon ratio; (2) the determination was made of the crystallization path; (3) in some high Cr/C ratio alloys a peritectic reaction occurs on the border of the grain giving a δ ferritic phase; (4) then this δ ferrite was found to decompose in a complex manner giving austenite and ferrite probably in a lamellar structure, then precipitates of M6C and Mo2C in the austenitic and ferritic phases, respectively; and (5) according to the kinetics of cooling, some alloys undergo martensitic and bainitic transformations.

  20. Protective claddings for high strength chromium alloys

    NASA Technical Reports Server (NTRS)

    Collins, J. F.

    1971-01-01

    The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

  1. Marginal accuracy of nickel chromium copings fabricated by conventional and accelerated casting procedures, produced with ringless and metal ring investment procedures: A comparative in vitro study

    PubMed Central

    Alex, Deepa; Shetty, Y. Bharath; Miranda, Glynis Anita; Prabhu, M. Bharath; Karkera, Reshma

    2015-01-01

    Background: Conventional investing and casting techniques are time-consuming and usually requires 2–4 h for completion. Accelerated nonstandard, casting techniques have been reported to achieve similar quality results in significantly less time, namely, in 30–40 min. During casting, it is essential to achieve compensation for the shrinkage of solidifying alloy by investment expansion. The metal casting ring restricts the thermal expansion of investment because the thermal expansion of the ring is lesser than that of the investment. The use of casting ring was challenged with the introduction of the ringless technique. Materials and Methods: A total of 40 test samples of nickel chromium (Ni-Cr) cast copings were obtained from the patterns fabricated using inlay casting wax. The 20 wax patterns were invested using metal ring and 20 wax patterns were invested using the ringless investment system. Of both the groups, 10 samples underwent conventional casting, and the other 10 underwent accelerated casting. The patterns were casted using the induction casting technique. All the test samples of cast copings were evaluated for vertical marginal gaps at four points on the die employing a stereo optical microscope. Results: The vertical marginal discrepancy data obtained were tabulated. Mean and standard deviations were obtained. Vertical discrepancies were analyzed using analysis of variance and Tukey honestly significantly different. The data obtained were found to be very highly significant (P < 0.001). Mean vertical gap was the maximum for Group II (53.64 μm) followed by Group IV (47.62 μm), Group I (44.83 μm) and Group III (35.35 μm). Conclusion: The Ni-Cr cast copings fabricated with the conventional casting using ringless investment system showed significantly better marginal fit than that of cast copings fabricated from conventional and accelerated casting with metal ring investment and accelerated casting using ringless investment since those copings had

  2. High-Density-Tape Casting System

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.

    1987-01-01

    Centrifuge packs solids from slurry into uniform, dense layer. New system produces tapes of nearly theoretical packing density. Centrifugal system used to cast thin tapes for capacitors, fuel cells, and filters. Cylindrical rotary casting chamber mounted on high-speed bearings and connected to motor. Liquid for vapor-pressure control and casting slurry introduced from syringes through rotary seal. During drying step, liquid and vapor vented through feed tubes or other openings. Laminated tapes produced by adding more syringes to cast additional layers of different materials.

  3. Chromium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effects of chromium (Cr) on glucose and insulin metabolism are well documented. Normal dietary intake of Cr appears to be suboptimal because several studies have reported beneficial effects of Cr in people with elevated blood glucose or type 2 diabetes eating conventional diets. Stresses that ...

  4. Effect of oxidation heat treatment on the bond strength between a ceramic and cast and milled cobalt-chromium alloys.

    PubMed

    Li, Jieyin; Ye, Xiuhua; Li, Bohua; Liao, Juankun; Zhuang, Peilin; Ye, Jiantao

    2015-08-01

    There is a dearth of dental scientific literature on the effect of different oxidation heat treatments (OHTs) (as surface pretreatments) on the bonding performance of cast and milled cobalt-chromium (CoCr) alloys. The objective of this study was to evaluate the effect of different OHTs on the bond strength between a ceramic and cast and milled CoCr alloys. Cobalt-chromium metallic specimens were prepared using either a cast or a milled method. Specimens were subjected to four different OHT methods: without OHT; OHT under normal atmospheric pressure; OHT under vacuum; and OHT under vacuum followed by sandblasting. The metal-ceramic bond strength was evaluated using a three-point bending test according to ISO9693. Scanning electron microscopy and energy-dispersive spectroscopy were used to study the specimens' microstructure and elemental composition. The bond strength was not affected by the CoCr manufacturing method. Oxidation heat treatment performed under normal atmospheric pressure resulted in the highest bond strength. The concentration of oxygen on the alloy surfaces varied with the different pretreatment methods in the following order: OHT under normal atmospheric pressure > OHT under vacuum > without OHT ≈ OHT under vacuum followed by sandblasting.

  5. Dry Sliding Wear Behaviours of Valve Seat Inserts Produced from High Chromium White Iron

    NASA Astrophysics Data System (ADS)

    Kalyon, Ali; Özyürek, Dursun; Günay, Mustafa; Aztekin, Hasan

    2015-11-01

    In this present study, wear behaviours of high chromium white iron valve seat inserts and tappets used in the automotive sector were investigated. Wear behaviours of three different rates of high chromium white cast irons (containing 10, 12 and 14% chromium) were examined under heavy service conditions. For that purpose, the produced valve seat inserts were characterized through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD) and hardness measurements. They were tested at a sliding speed of 1 ms-1, under 120 N load and for six different sliding distances (500, 1000, 1500, 2000, 2500, 3000 m) by using a standard wear apparatus (pin-on-disk type). The result showed that as the amount of Cr increased in the alloys, their hardness decreased. The decrease in the hardness were considered to be as the result of transformation of M7C3 carbides into M23C6 carbides in the structure. This decrease in hardness with increasing chromium content also increased the weight loss. Thus, it was determined that the white iron with 14% Cr (which had a greater amount of M23C6 carbides) was subjected to the highest wear.

  6. Effect of vanadium and chromium on the microstructural features of V-Cr-Mn-Ni spheroidal carbide cast irons

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Shimizu, K.; Cheiliakh, A. P.; Kozarevskaya, T. V.; Kusumoto, K.; Yamamoto, K.

    2014-11-01

    The objective of this investigation is to study the influence of vanadium (5.0wt%-10.0wt%) and chromium (0-9.0wt%) on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys' microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic (based on M7C3), pearlite, martensite, and austenite. Their combinations and area fraction (AF) ratios are reported to be influenced by the alloys' chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic (γ-Fe + M7C3), preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.

  7. A study of the structure and properties of high-strength bainite-carbide cast iron with globular graphite

    NASA Astrophysics Data System (ADS)

    Dhanapal, P.; Nazirudeen, S. S. Mohamed

    2012-03-01

    The structure and mechanical properties of two high-strength bainitic cast irons with carbon equivalent close to the eutectic one are studied. Additional alloying of one of the metals with chromium is used to obtain a bainite-carbide structure. The effect of the parameters of bainitic hardening on the hardness, impact toughness, and wear resistance of the metals is studied.

  8. Cast Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2003-01-01

    Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent dimensional stability, surface hardness and wear resistant properties.

  9. Boriding of high carbon high chromium cold work tool steel

    NASA Astrophysics Data System (ADS)

    Muhammad, W.

    2014-06-01

    High-carbon high-chromium cold work tool steels are widely used for blanking and cold forming of punches and dies. It is always advantageous to obtain an increased wear resistant surface to improve life and performance of these steels. In this connection boriding of a high-carbon high-chromium cold work die steel, D3, was conducted in a mixture of 30% B4C, 70% borax at 950 °C for two, four and six hours. Case depth of the borided layer obtained was between 40 to 80 μm. After boriding, the surface hardness achieved was between 1430 to 1544 HV depending upon the process time. X-ray diffraction studies confirmed the formation of a duplex compound layer consisting of FeB and Fe2B. It is generally considered that FeB is undesirable because of its inherent brittleness. Post boriding treatment (homogenization) transformed the compound layer into single-phase layer of Fe2B, while surface hardness decreased to 1345-1430 HV. Pin-on-disc wer test showed that wear resistance of the borided samples was superior as compared to non-borided material and increased with boriding time.

  10. The nature of temper brittleness of high-chromium ferrite

    SciTech Connect

    Sarrak, V.I.; Suvorova, S.O.; Golovin, I.S.; Mishin, V.M.; Kislyuk, I.V.

    1995-03-01

    The reasons for development of {open_quotes}475{degrees}C brittleness{close_quotes} of high-chromium ferritic steels are considered from the standpoint of fracture mechanics. It is shown that the general rise in the curve of temperature-dependent local flow stress has the decisive influence on the position of the ductile-to-brittle transformation temperature and the increase in it as the result of a hold at temperatures of development of brittleness. The established effect is related to the change in the parameters determining dislocation mobility, that is, the activation energy of dislocation movement in high-chromium ferrite and the resistance to microplastic deformation, both caused by processes of separation into layers of high-chromium ferrite and decomposition of the interstitial solid solution.

  11. A waterproof cast liner earns high marks.

    PubMed

    Selesnick, H; Griffiths, G

    1997-09-01

    Nondisplaced and stable fractures or severe sprains may be casted using fiberglass and a waterproof liner. Application of the liner is illustrated and described here. Allergic reactions, liner bulkiness, cast application and removal, and cost of materials have not proven to be problems. Among 337 patients fitted with this liner, odor, itching, and difficulties with drying were minimal, even though patients swam, bathed, or received hydrotherapy. Minor skin complications occurred in 5.9% of patients. Physician and patient satisfaction with the liner was high.

  12. Development of ductile high-strength chromium alloys, phase 2

    NASA Technical Reports Server (NTRS)

    Filippi, A. M.

    1973-01-01

    Strength and ductility were evaluated for chromium alloys dispersion hardened with the putative TaC, TaB, CbC, and CbB compounds. TaC and TaB proved to be the most potent strengtheners, but when combined, their effect far outweighed that produced individually. Tests at 1422 K (2100 F) on an alloy containing these two compounds at the combined level of 0.5 m/o revealed a 495 MN/sq m (70 ksi) tensile strength for wrought material, and a 100 hour rupture strength of 208 MN/sq m (30 ksi) when solution annealed and aged to maximize creep resistance. These levels of high temperature strength greatly exceed that reported for any other chromium-base alloy. The ductile-to-brittle transition temperature (DBTT) of the two phase strengthened alloy occurred at approximately 588 K (600 F) when heat treated to optimize creep strength and was not improved by fabrication to produce a wrought and recovered microstructure. The lowest DBTT measured on any of the alloys investigated was 422 K (300 F). Strengthening phases actually formed in Cr-Ta-B and Cr-Cb-B compositions are probable M2CrB2 (M=Ta or Cb) compounds of tetragonal crystal structure. The likely habit relationship between these compounds and chromium is postulated. Cube habit coherency was identified for TaC precipitation in chromium by electron microscopy. In another study, the maximum solubility of carbon in chromium was indicated to lie between 3/4 and 1 a/o and that of boron to be 1/2 a/o.

  13. Evaluation of finishing and polishing techniques on surface roughness of chromium-cobalt castings.

    PubMed

    Aydin, A K

    1991-06-01

    The effect of finishing and polishing techniques on surface roughness of a chromium-cobalt alloy was evaluated by means of a stylus profile instrumentation and scanning electron microscopy. Scanning electron micrographs, surface profile tracings, surface roughness recordings, and statistical analysis of data support the finding that the best surface finish is obtained when sandblasting, hard stone, medium abrasive disk, second sandblasting, electropolishing, hard rubber point, hard felt disk with pumice slurry, and felt disk and soft brush with polishing paste are used progressively. The results of this study indicate that the finishing procedure should be carried out in a logical, systematic sequence of steps.

  14. Reactor target from metal chromium for "pure" high-intensive artificial neutrino source

    NASA Astrophysics Data System (ADS)

    Gavrin, V. N.; Kozlova, Yu. P.; Veretenkin, E. P.; Logachev, A. V.; Logacheva, A. I.; Lednev, I. S.; Okunkova, A. A.

    2017-01-01

    The paper presents the first results of development of manufacturing technology of metallic chromium targets from highly enriched isotope 50Cr for irradiation in a high flux nuclear reactor to obtain a compact high intensity neutrino source with low content of radionuclide impurities and minimum losses of enriched isotope. The main technological stages are the hydrolysis of chromyl fluoride, the electrochemical reduction of metallic chromium, the hot isostatic pressing of chromium powder and the electrical discharge machining of chromium bars. The technological stages of hot isostatic pressing of chromium powder and of electrical discharge machining of Cr rods have been tested.

  15. Effect of storage time and framework design on the accuracy of maxillary cobalt-chromium cast removable partial dentures

    PubMed Central

    Viswambaran, M.; Sundaram, R. K.

    2015-01-01

    Statement of Problem: Inaccuracies in the fit of palatal major connectors may be related to distortion of the wax pattern due to prolonged storage time and faulty major connector design. Purpose: This in vitro study was carried out to find out the effect of storage time and major connector design on the accuracy of cobalt-chromium cast removable partial dentures (RPDs). Materials and Methods: A brass metal die with a Kennedy Class III, modification 1, the partially edentulous arch was used as a master die. Thirty-six refractory casts were fabricated from the master die. The refractory casts were divided into three groups (Group I: Anterior-posterior palatal bar, Group II: Palatal strap and Group III: Palatal plate) based on the design of maxillary major connector and subdivided into four groups (sub Group A: 01 h, sub Group B: 03 h, Sub Group C: 06 h, and sub Group D: 24 h) based on the storage time. For each group, 12 frameworks were fabricated. The influence of wax pattern storage time and the accuracy of the fit palatal major connector designs on the master die were compared. Casting defects (nodules/incompleteness) of the frameworks were also evaluated before finishing and polishing. Repeated measures analysis of variance was used to analyze the data. Results: The gap discrepancy was least in sub Group A (01 h) followed by sub Group B (03 h) and C (06 h) and most in sub Group D (24 h). Statistically significant differences (P < 0.05 in all locations L1–L5) in the fit of the framework were related to the design of the major connector. The gap discrepancy was least in Group I (anterior-posterior palatal bar) followed by Group II (palatal strap) and most in Group II (palatal plate). Conclusions: It is recommended that the wax patterns for RPD to be invested immediately on completion of the wax procedure. The selection of a major connector design is crucial for an accurate fit of RPD. PMID:26681850

  16. Casting accuracy of a nickel and beryllium-free cobalt-chromium alloy for crown and bridge prostheses and resin-bonded bridges.

    PubMed

    Hansson, O

    1985-01-01

    In the 1970's economic factors dictated the development of alternatives to gold alloys in dentistry in the USA and in Europe. A similar development has not occurred in Sweden because of different laws. Alloys that contain nickel and beryllium present a health hazard and are therefore of little interest to the Swedish market. A review of the literature shows that castings of base-metal alloys are less accurate than castings of conventional gold alloys and of low gold alloys. However, in long-span-bridges and in thin resin-bonded cast restorations, their physical and mechanical properties are superior to those of the gold alloys. In this study the casting accuracy of a nickel- and beryllium-free cobalt-chromium alloy, Neobond II Special, is investigated. Neobond II Special was found to be less accurate than Sjödings C-guld. The marginal discrepancies of the castings were small, however, when the castings were oversized. It also proved to be technique sensitive to conventional dental laboratory procedures. Thus, it seems difficult to get castings with an acceptable retention as well as small marginal discrepancies when using the base-metal alloy.

  17. The Role of Silicon in the Solidification of High-Cr Cast Irons

    NASA Astrophysics Data System (ADS)

    Bedolla-Jacuinde, A.; Rainforth, M. W.; Mejía, I.

    2013-02-01

    This work analyzes the effect of different additions of silicon (0 to 5.0 pct) on the structure of a high-Chromium white cast iron, with chromium content of 16.8 pct and carbon 2.56 pct. The alloys were analyzed in both as-cast and heat-treated conditions. Casting was undertaken in metallic molds that yielded solidification rates faster than in commercial processes. Nevertheless, there was some degree of segregation of silicon; this segregation resulted in a refinement in the microstructure of the alloy. Silicon also generated a greater influence on the structure by destabilizing the austenitic matrix, and promoted greater precipitation of eutectic carbides. Above 3 pct silicon, pearlite formation occurred in preference to martensite. After the destabilization heat treatment, the matrix structure of the irons up to 3 pct Si consisted of secondary carbides in a martensitic matrix with some retained austenite; higher Si additions produced a ferritic matrix. The different as-cast and heat-treated microstructures were correlated with selected mechanical properties such as hardness, matrix microhardness, and fracture toughness. Silicon additions increased matrix microhardness in the as-cast conditions, but the opposite phenomenon occurred in the heat-treated conditions. Microhardness decreased as silicon content was increased. Bulk hardness showed the same behavior. Fracture toughness was observed to increase up to 2 pct Si, and then decreased for higher silicon contents. These results are discussed in terms of the effect of eutectic carbides' size and the resulting matrix due to the silicon additions.

  18. Gamma titanium aluminide rendered castable by low chromium and high niobium additives

    SciTech Connect

    Shyh-Chin Huang.

    1993-05-25

    A castable composition is described comprising titanium, aluminum, chromium, and niobium in the following approximate composition: Ti-Al[sub 46]-[sub 48]Cr[sub 1-3]Nb[sub 6-14]; said alloy having been prepared by cast and HIP processing.

  19. An invitro analysis of elemental release and cytotoxicity of recast nickel-chromium dental casting alloys.

    PubMed

    Reddy, Nagam Raja; Abraham, Anandapandian Ponsekar; Murugesan, Krishnan; Matsa, Vasanthakumar

    2011-06-01

    Recasting of the casting alloys affects the composition and elemental release which may have cytotoxic effect different from the pure alloy in the surrounding tissues. An Invitro study was conducted to investigate the elemental release and their cytotoxic effects from commercially available Ni-Cr dental casting alloys, commonly used for fabricating fixed partial dentures. Three Ni-Cr alloys [Wiron 99(A), Ceramet (B), and Hi Nickel CB (C)] were tested. Alloy specimens (disks 3 × 5 mm) were casted and grouped as follows: Group I (A(1)/B(1)/C(1)): 100% pure alloy; Group II (A(2)/B(2)/C(2)): 50% new with 50% recast; and Group III (A(3)/B(3)/C(3)): 100% recast. Disks of each alloy type from each group were transferred to Dulbecco's modified eagle medium and left for 3 days at 37°C in an atmosphere of 5% CO(2). Ni, Cr, Co, Cu and Mo elemental release from metal alloys into culture medium was investigated using Inductively Coupled Plasma Mass Spectrometry. Cytotoxicity was tested using mouse fibroblast cells and MTT Assay. Controls consisted of 6 wells containing cells with no alloy specimens. Data were analyzed by two-way analysis of variance followed by t-test. The total amount of elements released in parts per billion for various casting groups were Group I, A(1)-6.572, B(1)-6.732, C(1)-8.407; Group II, A(2)-22.046, B(2)-26.450, C(2)-29.189; Group III, A(3)-84.554, B(3)-88.359, C(3)-92.264. More amounts of elements were released in Hi Nickel CB than Ceramet and Wiron 99 in all the three test groups. Percentage of viable cells from MTT analysis were Group I, A(1)-62.342, B(1)-61.322 C(1)-60.593, Group II, A(2)-58.699, B(2)-56.494, C(2)-52.688, Group III, A(3)-53.101, B(3)-52.195, C(3)-47.586. The viable cells present in the culture media were more in Wiron 99 than Ceramet and Hi Nickel CB. Elemental release increased with amount of recast alloy. Amongst the three alloys tested Hi Nickel CB had significantly higher elements released compared to Ceramet and Wiron 99

  20. Casting Technology.

    ERIC Educational Resources Information Center

    Wright, Michael D.; And Others

    1992-01-01

    Three articles discuss (1) casting technology as it relates to industry, with comparisons of shell casting, shell molding, and die casting; (2) evaporative pattern casting for metals; and (3) high technological casting with silicone rubber. (JOW)

  1. High-resolution airway morphometry from polyurethane casts

    NASA Astrophysics Data System (ADS)

    Neufeld, Gordon R.; Vargas, John; Hoford, John D.; Craft, Jeanne; Shroff, Sunil; McRae, Karen M.

    1995-05-01

    An airway cast was made and imbedded in a solid polyurethane block of a contrasting color. The block was sequentially milled and photographed. The sequential photographs were scanned to create an image database which was analyzed on VIDA; a multidimensional image analysis software package. The technique shows promise as a semi-automated process for generating a high resolution morphometric database from airway casts.

  2. High strength nickel-chromium-iron austenitic alloy

    DOEpatents

    Gibson, Robert C.; Korenko, Michael K.

    1980-01-01

    A solid solution strengthened Ni-Cr-Fe alloy capable of retaining its strength at high temperatures and consisting essentially of 42 to 48% nickel, 11 to 13% chromium, 2.6 to 3.4% niobium, 0.2 to 1.2% silicon, 0.5 to 1.5% vanadium, 2.6 to 3.4% molybdenum, 0.1 to 0.3% aluminum, 0.1 to 0.3% titanium, 0.02 to 0.05% carbon, 0.002 to 0.015% boron, up to 0.06 zirconium, and the balance iron. After solution annealing at 1038.degree. C. for one hour, the alloy, when heated to a temperature of 650.degree. C., has a 2% yield strength of 307 MPa, an ultimate tensile strength of 513 MPa and a rupture strength of as high as 400 MPa after 100 hours.

  3. High-valent imido complexes of manganese and chromium corroles.

    PubMed

    Edwards, Nicola Y; Eikey, Rebecca A; Loring, Megan I; Abu-Omar, Mahdi M

    2005-05-16

    The oxidation reaction of M(tpfc) [M = Mn or Cr and tpfc = tris(pentafluorophenyl)corrole] with aryl azides under photolytic or thermal conditions gives the first examples of mononuclear imido complexes of manganese(V) and chromium(V). These complexes have been characterized by NMR, mass spectrometry, UV-vis, EPR, elemental analysis, and cyclic voltammetry. Two X-ray structures have been obtained for Mn(tpfc)(NMes) and Cr(tpfc)(NMes) [Mes = 2,4,6-(CH(3))(3)C(6)H(2)]. Short metal-imido bonds (1.610 and 1.635 Angstroms) as well as nearly linear M-N-C angles are consistent with triple M triple-bond NR bond formation. The kinetics of nitrene [NR] group transfer from manganese(V) corroles to various organic phosphines have been defined. Reduction of the manganese(V) corrolato complex affords phosphine imine and Mn(III) with reaction rates that are sensitive to steric and electronic elements of the phosphine substrate. An analogous manganese complex with a variant corrole ligand containing bromine atoms in the beta-pyrrole positions, Mn(Br(8)tpfc)(NAr), has been prepared and studied. Its reaction with PEt(3) is 250x faster than that of the parent tpfc complex, and its Mn(V/IV) couple is shifted by 370 mV to a more positive potential. The EPR spectra of chromium(V) imido corroles reveal a rich signal at ambient temperature consistent with Cr(V) triple-bond NR (d(1), S = 1/2) containing a localized spin density in the d(xy) orbital, and an anisotropic signal at liquid nitrogen temperature. Our results demonstrate the synthetic utility of organic aryl azides in the preparation of mononuclear metal imido complexes previously considered elusive, and suggest strong sigma-donation as the underlying factor in stabilizing high-valent metals by corrole ligands.

  4. High strength cast aluminum alloy development

    NASA Astrophysics Data System (ADS)

    Druschitz, Edward A.

    The goal of this research was to understand how chemistry and processing affect the resulting microstructure and mechanical properties of high strength cast aluminum alloys. Two alloy systems were investigated including the Al-Cu-Ag and the Al-Zn-Mg-Cu systems. Processing variables included solidification under pressure (SUP) and heat treatment. This research determined the range in properties that can be achieved in BAC 100(TM) (Al-Cu micro-alloyed with Ag, Mn, Zr, and V) and generated sufficient property data for design purposes. Tensile, stress corrosion cracking, and fatigue testing were performed. CuAl2 and Al-Cu-Fe-Mn intermetallics were identified as the ductility limiting flaws. A solution treatment of 75 hours or longer was needed to dissolve most of the intermetallic CuAl 2. The Al-Cu-Fe-Mn intermetallic was unaffected by heat treatment. These results indicate that faster cooling rates, a reduction in copper concentration and a reduction in iron concentration might increase the ductility of the alloy by decreasing the size and amount of the intermetallics that form during solidification. Six experimental Al-Zn-Mg-Cu series alloys were produced. Zinc concentrations of 8 and 12wt% and Zn/Mg ratios of 1.5 to 5.5 were tested. Copper was held constant at 0.9%. Heat treating of the alloys was optimized for maximum hardness. Al-Zn-Mg-Cu samples were solution treated at 441°C (826°F) for 4 hours before ramping to 460°C (860°F) for 75 hours and then aged at 120°C (248°F) for 75 hours. X-ray diffraction showed that the age hardening precipitates in most of these alloys was the T phase (Mg32Zn 31.9Al17.1). Tensile testing of the alloys showed that the best mechanical properties were obtained in the lowest alloy condition. Chilled Al-8.2Zn-1.4Mg-0.9Cu solidified under pressure resulted in an alloy with a yield strength of 468MPa (68ksi), tensile strength of 525MPa (76ksi) and an elongation of 9%.

  5. Erosive Wear Behavior of High-Alloy Cast Iron and Duplex Stainless Steel under Mining Conditions

    NASA Astrophysics Data System (ADS)

    Yoganandh, J.; Natarajan, S.; Kumaresh Babu, S. P.

    2015-09-01

    Centrifugal pumps used in the lignite mines encounter erosive wear problems, leading to a disastrous failure of the pump casings. This paper attempts to evaluate the erosive wear resistance of Ni-Hard 4, high-chromium iron, and Cast CD4MCu duplex stainless steel (DSS), for mining conditions. The prepared test coupons were subjected to an erosion test by varying the impingement velocity and the angle of impingement, under two different pH conditions of 3 and 7, which pertained to the mining conditions. XRD analysis was carried out to confirm the phases present in the alloy. The eroded surface was subjected to SEM analysis to identify the erosion mechanisms. The surface degradation of Ni-Hard 4 and high-chromium iron came from a low-angle abrasion with a grooving and plowing mechanism at a low angle of impingement. At normal impingement, deep indentations resulted in lips and crater formations, leading to degradation of the surface in a brittle manner. A combined extrusion-forging mechanism is observed in the CD4MCu DSS surface at all the impingement angles.

  6. High-strength cast irons used for manufacturing parts of vaz passenger cars

    NASA Astrophysics Data System (ADS)

    Kitaigora, N. I.

    1996-10-01

    Methods for solving problems arising in the production of high-strength cast iron with stable properties and structure are considered. Results of introduction of new grades of high-strength cast iron instead of malleable cast iron and camshaft cast iron in the Volzhskii Automobile Plant are described.

  7. Effect of adhesive primers on bonding strength of heat cure denture base resin to cast titanium and cobalt-chromium alloy

    PubMed Central

    Kim, Su-Sung; Yang, Hong-So; Park, Sang-Won; Lim, Hyun-Pil

    2009-01-01

    STATEMENT OF PROBLEM The poor chemical bonding of a denture base resin to cast titanium framework often introduces adhesive failure and increases microleakage. PURPOSE This study evaluated the shear bond strengths of a heat cure denture base resin to commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy using two adhesive primers. MATERIAL AND METHODS Disks of commercially pure titanium, Ti-6Al-4V alloy and a cobalt-chromium alloy were cast. Specimens without the primer were also prepared and used as the controls. The shear bond strengths were measured on a screw-driven universal testing machine. RESULTS The primers significantly (P < .05) improved the shear bond strengths of the heat cure resin to all metals. However, the specimens primed with the Alloy primer® (MDP monomer) showed higher bond strength than those primed with the MR bond® (MAC-10 monomer) on titanium. Only adhesive failure was observed at the metal-resin interface in the non-primed specimens, while the primed specimens showed mixed failure of adhesive and cohesive failure. CONCLUSIONS The use of appropriate adhesive metal primers makes it possible not only to eliminate the need for surface preparation of the metal framework before applying the heat cure resins, but also reduce the need for retentive devices on the metal substructure. In particular, the Alloy primer®, which contains the phosphoric acid monomer, MDP, might be clinically more acceptable for bonding a heat cure resin to titanium than a MR bond®, which contains the carboxylic acid monomer, MAC-10. PMID:21165254

  8. Chromium incorporation into TiO{sub 2} at high pressure

    SciTech Connect

    Escudero, Alberto; Langenhorst, Falko

    2012-06-15

    Chromium incorporation into TiO{sub 2} up to 3 GPa at 1300 Degree-Sign C and 900 Degree-Sign C has been studied by XRD as well as TEM. A CaCl{sub 2} type TiO{sub 2} polymorph has been observed in the quenched samples from high pressure. Two different mechanisms of solubility occur in the recovered samples. Chromium replaces titanium on normal octahedral sites but it also occupies interstitial octahedral sites, especially in the samples recovered from higher pressures. Interstitial chromium is responsible for an orthorhombic distortion of the TiO{sub 2} rutile structure in the quenched samples and gives rise to a (1 1 0) twinned CaCl{sub 2}-structured polymorph. This phase is very likely the result of temperature quench at high pressure. The formation of this phase is directly related to the chromium content of the TiO{sub 2} grains. Chromium solubility in TiO{sub 2} increases with increasing the synthesis pressure. TiO{sub 2} is able to accommodate up to 15.3 wt% Cr{sub 2}O{sub 3} at 3 GPa and 1300 Degree-Sign C, compared to 5.7 wt% at atmospheric pressure at the same temperature. - Graphical abstract: Microstructure consisting of twins domains of recovered Cr-doped CaCl{sub 2} type TiO{sub 2} grains synthesised at high pressure. Highlights: Black-Right-Pointing-Pointer Chromium solubility in TiO{sub 2} increases at high pressure. Black-Right-Pointing-Pointer Chromium occupies substitutional and interstitial positions in the rutile structure. Black-Right-Pointing-Pointer Interstitial chromium causes a decrease of the rutile symmetry. Black-Right-Pointing-Pointer An orthorhombic CaCl{sub 2} type structure is observed in the quenched samples.

  9. Heat treatment in high Cr white cast iron Nb alloy

    NASA Astrophysics Data System (ADS)

    Farah, A. F.; Crnkovic, O. R.; Canale, L. C. F.

    2001-02-01

    Wear resistance of high Cr white cast irons can be improved by means of heat treatment. This type of cast iron alloy may present a microstructure with retained austenite. The amount of retained austenite changes with the applied heat treatment, which will have an influence on wear properties. The purpose of this work was to study the influence of several parameters such as quenching and tempering temperatures and subzero treatment in the wear performance of the high Cr white cast iron Nb alloy. In this way, the performance was evaluated using pin-on-disc abrasion test. The worn surface was examined by scanning electron microscopy, and the main wear mechanisms were identified. The microstructural characterization was also performed with carbide identification. This Fe alloy has proven to be good for applications in mining and alcohol-sugar industries.

  10. Conditions to obtain reliable high strength alumina via centrifugal casting

    SciTech Connect

    Huisman, W.; Graule, T.; Gauckler, L.J.

    1995-09-01

    Electrostatically stabilized alumina suspensions with high solids content of up to 58 vol% were consolidated into near-net-shape parts via centrifugal casting. High density green bodies showed excellent sintering kinetics leading to {ge} 99.5% of theoretical density (TD) at lowered temperatures compared to isostatic pressing. Four point bend strengths of 540 MPa with Weibull moduli of up to 24 were achieved using commercial {alpha}-alurnina powders.

  11. High temperature dissolution of chromium substituted nickel ferrite in nitrilotriacetic acid medium

    NASA Astrophysics Data System (ADS)

    Sathyaseelan, V. S.; Chandramohan, P.; Velmurugan, S.

    2016-12-01

    High temperature (HT) dissolution of chromium substituted nickel ferrite was carried out with relevance to the decontamination of nuclear reactors by way of chemical dissolution of contaminated corrosion product oxides present on stainless steel coolant circuit surfaces. Chromium substituted nickel ferrites of composition, NiFe(2-x)CrxO4 (x ≤ 1), was synthetically prepared and characterized. HT dissolution of these oxides was carried out in nitrilotriacetic acid medium at 160 °C. Dissolution was remarkably increased at 160 °C when compared to at 85 °C in a reducing decontamination formulation. Complete dissolution could be achieved for the oxides with chromium content 0 and 0.2. Increasing the chromium content brought about a marked reduction in the dissolution rate. About 40 fold decrease in rate of dissolution was observed when chromium was increased from 0 to 1. The rate of dissolution was not very significantly reduced in the presence of N2H4. Dissolution of oxide was found to be stoichiometric.

  12. Process to Continuously Melt, Refine and Cast High Quality Steel

    SciTech Connect

    2005-09-01

    The purpose of this project is to conduct research and development targeted at designing a revolutionary steelmaking process. This process will deliver high quality steel from scrap to the casting mold in one continuous process and will be safer, more productive, and less capital intensive to build and operate than conventional steelmaking. The new process will produce higher quality steel faster than traditional batch processes while consuming less energy and other resources.

  13. As-cast carbides in high-speed steels

    NASA Astrophysics Data System (ADS)

    Ding, Peidao; Shi, Gongqi; Zhou, Shouze

    1993-06-01

    The spatial distribution and structure of as-cast carbides and the effects of W, Mo, and V content on the morphology and amount of as-cast carbides in high-speed steels were studied systematically. It was shown that increasing the Mo and decreasing the W content led to a decrease in the amount of total eutectic carbide and an increase in the MC and M2C carbides. The eutectic morphology changed from skeletal to platelike when the content of Mo increased. The presence of V favored not only the formation of MC carbide but also the formation of M2C carbide and reduced the formation of M2C carbide. Increasing V led to an increase in the size of the eutectic carbides.

  14. Detonation initiation of heterogeneous melt-cast high explosives

    NASA Astrophysics Data System (ADS)

    Chuzeville, V.; Baudin, G.; Lefrançois, A.; Genetier, M.; Barbarin, Y.; Jacquet, L.; Lhopitault, J.-L.; Peix, J.; Boulanger, R.; Catoire, L.

    2017-01-01

    2,4,6-trinitrotoluene (TNT) is widely used in conventional and insensitive munitions as a fusible binder, commonly melt-cast with other explosives such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) or 3-nitro-1,2,4-triazol-one (NTO). In this paper, we study the shock-to-detonation transition phenomenon in two melt-cast high explosives (HE). We have performed plate impact tests on wedge samples to measure run-distance and time-to-detonation in order to establish the Pop-plot relation for several melt-cast HE. Highlighting the existence of the single curve buildup, we propose a two phase model based on a Zeldovich, Von-Neumann, Döring (ZND) approach where the deflagration fronts grow from the explosive grain boundaries. Knowing the grain size distribution, we calculate the deflagration velocities of the explosive charges as a function of shock pressure and explore the possible grain fragmentation.

  15. Palladium-chromium static strain gages for high temperatures

    NASA Technical Reports Server (NTRS)

    Lei, Jih-Fen

    1992-01-01

    An electrical resistance strain gage that can provide accurate static strain measurement to a temperature of 1500 F or above is being developed both in fine wire and thin film forms. The gage is designed to be temperature compensated on any substrate material. It has a dual element: the gage element is a special alloy, palladium-13wt percent chromium (PdCr), and the compensator element is platinum (Pt). Earlier results of a PdCr based wire gage indicated that the apparent strain of this gage can be minimized and the repeatability of the apparent strain can be improved by prestabilizing the gage on the substrate for a long period of time. However, this kind of prestabilization is not practical in many applications and therefore the development of a wire gage which is prestabilized before installation on the substrate is desirable. This paper will present our recent progress in the development of a prestabilized wire gage which can provide meaningful strain data for the first thermal cycle. A weldable PdCr gage is also being developed for field testing where conventional flame-spraying installation can not be applied. This weldable gage is narrower than a previously reported gage, thereby allowing the gage to be more resistant to buckling under compressive loads. Some preliminary results of a prestabilized wire gage flame-sprayed directly on IN100, an engine material, and a weldable gage spot-welded on IN100 and SCS-6/(beta)21-S Titanium Matrix Composite (TMC), a National Aero-Space Plane (NASP) structure material, will be reported. Progress on the development of a weldable thin film gage will also be addressed. The measurement technique and procedures and the lead wire effect will be discussed.

  16. A highly sensitive spectrophotometric determination of chromium using leuco Xylene cyanol FF.

    PubMed

    Revanasiddappa, H D; Kiran Kumar, T N

    2003-05-28

    A highly sensitive and selective spectrophotometric method was developed for the determination of trace amounts of chromium with leuco Xylene cynaol FF. The method is based on the oxidation of leuco Xylene cyanol FF (LXCFF) to its blue form of Xylene cyanol FF by chromium(VI) in sulphuric acid medium (pH 1.2-2.4), the absorbance of the formed dye is measured in an acetate buffer medium (pH 3.0-4.6) at 615 nm. The method obeys Beer's law in the concentration range of 0.05-0.45 mug ml(-l) chromium, having molar absorptivity and Sandell's sensitivity of 8.23x10(4) l mol(-1) cm(-l) and 0.00063 mug cm(-2), respectively. All the variables were studied in order to optimise the reaction conditions. The developed method has been successfully applied to the determination of chromium in steels, pharmaceutical samples, industrial effluents, natural water, and soil.

  17. Detecting defect in cast iron using high- TC SQUID

    NASA Astrophysics Data System (ADS)

    He, D. F.; Yoshizawa, M.; Oyama, Y.; Nakamura, M.

    2004-10-01

    For eddy-current NDE, due to the big permeability of ferromagnetic material, low testing frequency is needed to detect defects in it. SQUID has advantages in low frequency eddy current NDE. But the large magnetic field produced by ferromagnetic material often exceeds the dynamic range of general SQUID system. We developed a mobile high- TC SQUID system, with which, the dc and low-frequency magnetic field could be compensated well. Using our mobile SQUID system, the magnetic field produced by the cast iron could be compensated well and the defect in it could be successfully detected.

  18. High pressure die casting of Fe-based metallic glass

    PubMed Central

    Ramasamy, Parthiban; Szabo, Attila; Borzel, Stefan; Eckert, Jürgen; Stoica, Mihai; Bárdos, András

    2016-01-01

    Soft ferromagnetic Fe-based bulk metallic glass key-shaped specimens with a maximum and minimum width of 25.4 and 5 mm, respectively, were successfully produced using a high pressure die casting (HPDC) method, The influence of die material, alloy temperature and flow rate on the microstructure, thermal stability and soft ferromagnetic properties has been studied. The results suggest that a steel die in which the molten metal flows at low rate and high temperature can be used to produce completely glassy samples. This can be attributed to the laminar filling of the mold and to a lower heat transfer coefficient, which avoids the skin effect in the steel mold. In addition, magnetic measurements reveal that the amorphous structure of the material is maintained throughout the key-shaped samples. Although it is difficult to control the flow and cooling rate of the molten metal in the corners of the key due to different cross sections, this can be overcome by proper tool geometry. The present results confirm that HPDC is a suitable method for the casting of Fe-based bulk glassy alloys even with complex geometries for a broad range of applications. PMID:27725780

  19. High pressure die casting of Fe-based metallic glass

    NASA Astrophysics Data System (ADS)

    Ramasamy, Parthiban; Szabo, Attila; Borzel, Stefan; Eckert, Jürgen; Stoica, Mihai; Bárdos, András

    2016-10-01

    Soft ferromagnetic Fe-based bulk metallic glass key-shaped specimens with a maximum and minimum width of 25.4 and 5 mm, respectively, were successfully produced using a high pressure die casting (HPDC) method, The influence of die material, alloy temperature and flow rate on the microstructure, thermal stability and soft ferromagnetic properties has been studied. The results suggest that a steel die in which the molten metal flows at low rate and high temperature can be used to produce completely glassy samples. This can be attributed to the laminar filling of the mold and to a lower heat transfer coefficient, which avoids the skin effect in the steel mold. In addition, magnetic measurements reveal that the amorphous structure of the material is maintained throughout the key-shaped samples. Although it is difficult to control the flow and cooling rate of the molten metal in the corners of the key due to different cross sections, this can be overcome by proper tool geometry. The present results confirm that HPDC is a suitable method for the casting of Fe-based bulk glassy alloys even with complex geometries for a broad range of applications.

  20. Effect of silicon on the spheroidization of cementite in hypereutectoid high carbon chromium bearing steels

    NASA Astrophysics Data System (ADS)

    Kim, Kwan-Ho; Lee, Jae-Seung; Lee, Duk-Lak

    2010-12-01

    The effect of silicon on the spheroidization of cementite in hypereutectoid high carbon chromium bearing steels has been investigated on the basis of microstructural analysis and thermodynamic calculations. The results showed that an increase of silicon content in high carbon chromium bearing steels retards the spheoridization of cementite. The thermodynamic calculations revealed that the shrinkage of the austenite phase field in bearing steels with increasing silicon content gave rise to an increase of volume fraction of cementite at an annealing temperature, possibly resulting in incomplete spheroidization. Furthermore, due to the low solubility of silicon in cementite, an increase of silicon content can raise the activity or chemical potential of carbon atoms in austenite at the austenite/cementite interfaces. Consequently, the difference in chemical potential of carbon atoms at the interfaces would be reduced with increasing silicon content, causing a decrease of the driving force for their diffusion from cementite to austenite.

  1. Adipose tissue chromium and vanadium disbalance in high-fat fed Wistar rats.

    PubMed

    Tinkov, Alexey A; Popova, Elizaveta V; Polyakova, Valentina S; Kwan, Olga V; Skalny, Anatoly V; Nikonorov, Alexandr A

    2015-01-01

    The primary objective of the current study is to investigate the relationship between adipose tissue chromium and vanadium content and adipose tissue dysfunction in a model of diet-induced obesity. A total of 26 female Wistar rats were fed either standard or high-fat diet (31.6% of fat from total caloric content) for 3 months. High-fat-feeding resulted in 21 and 33% decrease in adipose tissue chromium and vanadium content, respectively. No change was seen in hair chromium or vanadium levels. Statistical analysis revealed a significant inverse correlation of adipose tissue Cr and V with animal morphometric parameters and adipocyte size. Significant inverse dependence was observed between adipose tissue Cr and V and serum leptin and proinflammatory cytokines' levels. At the same time, adipose tissue Cr and V levels were characterized by positive correlation between serum adiponectin and adiponectin/leptin ratio. Adipose tissue Cr and V were inversely correlated (p<0.05) with insulin and homeostatic model assessment insulin resistance index (HOMA-IR) levels. Cr and V concentrations were not correlated with serum glucose in either high-fat fed or control rats; however, both serum glucose and HOMA-IR levels were significantly higher in high-fat fed, compared to control, rats. The results allow to hypothesize that impairment of adipose tissue Cr and V content plays a certain role in the development of adipose tissue endocrine dysfunction in obesity.

  2. Metallographic problems of the production of parts from continuously cast high-speed steels

    NASA Astrophysics Data System (ADS)

    Supov, A. V.; Aleksandrova, N. M.; Paren'kov, S. A.; Kakabadze, R. V.; Pavlov, V. P.

    1998-09-01

    It has been assumed until recently that high-speed steels cannot be produced by the method of continuous casting. Numerous attempts to use this highly efficient technology for manufacturing such steels have failed because of breakage of the cast preforms. A solution was sought in improving the design of the continuous-casting machines (CCM), increasing the level of their automation, and using rational compositions of slag-forming mixtures (SFM). The idea was that a high-speed steel can be cast only in vertical CCM. The present work concerns regimes of secondary cooling under which the structures formed in high-speed steels provide a ductility sufficient for bending the continuously cast preform without failure. Steel R6M5 cast continuously in such a machine can easily be machined into hot-rolled preforms for sheets, wire, silver-steel rods, and other final products without a forging stage.

  3. Determination of hexavalent chromium in traditional Chinese medicines by high-performance liquid chromatography with inductively coupled plasma mass spectrometry.

    PubMed

    Li, Peng; Li, Li-Min; Xia, Jing; Cao, Shuai; Hu, Xin; Lian, Hong-Zhen; Ji, Shen

    2015-12-01

    An analytical method that combined high-performance liquid chromatography with inductively coupled plasma mass spectrometry has been developed for the determination of hexavalent chromium in traditional Chinese medicines. Hexavalent chromium was extracted using the alkaline solution. The parameters such as the concentration of alkaline and the extraction temperature have been optimized to minimize the interconversion between trivalent chromium and hexavalent chromium. The extracted hexavalent chromium was separated on a weak anion exchange column in isocratic mode, followed by inductively coupled plasma mass spectrometry determination. To obtain a better chromatographic resolution and sensitivity, 75 mM NH4 NO3 at pH 7 was selected as the mobile phase. The linearity of the proposed method was investigated in the range of 0.2-5.0 μg L(-1) (r(2) = 0.9999) for hexavalent chromium. The limits of detection and quantitation are 0.1 and 0.3 μg L(-1) , respectively. The developed method was successfully applied to the determination of hexavalent chromium in Chloriti lapis and Lumbricus with satisfactory recoveries of 95.8-112.8%.

  4. Twin-belt continuous caster with containment and cooling of the exiting cast product for enabling high-speed casting of molten-center product

    DOEpatents

    Dykes, Charles D.; Daniel, Sabah S.; Wood, J. F. Barry

    1990-02-20

    In continuously casting molten metal into cast product by a twin-belt machine, it is desirable to achieve dramatic increases in speed (linear feet per minute) at which cast product exits the machine, particularly in installations where steel cast product is intended to feed a downstream regular rolling mill (as distinct from a planetary mill) operating in tandem with the twin-belt caster. Such high-speed casting produces product with a relatively thin shell and molten interior, and the shell tends to bulge outwardly due to metallostatic head pressure of the molten center. A number of cooperative features enable high-speed, twin-belt casting: (1) Each casting belt is slidably supported adjacent to the caster exit pulley for bulge control and enhanced cooling of cast product. (2) Lateral skew steering of each belt provides an effective increase in moving mold length plus a continuity of heat transfer not obtained with prior art belt steering apparatus. (3) The exiting slab is contained and supported downstream from the casting machine to prevent bulging of the shell of the cast product, and (4) spray cooling is incorporated in the exit containment apparatus for secondary cooling of cast product.

  5. High-Throughput Production of Chromium(III) Complexes for Antibody Immobilization.

    PubMed

    Welch, Nicholas G; Scoble, Judith A; Easton, Christopher D; Williams, Charlotte C; Bradford, Barry J; Mamedova, Laman K; Pigram, Paul J; Muir, Benjamin W

    2016-10-05

    A robot-assisted high-throughput methodology was employed to produce chromium(III) complexes suitable for the surface modification of the commercially available PerkinElmer Optiplate96 well plate for use in enzyme-linked immunosorbent assays (ELISAs). The complexes were immobilized to the native functionality of the well plate and first screened using a horseradish-peroxidase-tagged (HRP) mouse antibody to quantify binding. The top "hits" were further assessed for their ability to present the antibody in a functional state using an ELISA. "Hits" from the second screen yielded four complexes capable of improving the signal intensity of the ELISA by greater than 500%. The metal/base ratio of these complexes was also investigated, and we isolated the most stable and reproducible candidate, [Cr(OH)6](3-), which was formed from chromium(III) perchlorate and pH adjusted with ethylenediamine. This chromium solution was employed in a clinically relevant setting for the detection of bovine TNFα producing up to a 200% increase in signal intensity.

  6. Chromium Extraction via Chemical Processing of Fe-Cr Alloys Fine Powder with High Carbon Content

    NASA Astrophysics Data System (ADS)

    Torres, D. M.; Navarro, R. C. S.; Souza, R. F. M.; Brocchi, E. A.

    2017-03-01

    Ferrous alloys are important raw materials for special steel production. In this context, alloys from the Fe-Cr system, with typical Cr weight fraction ranging from 0.45 to 0.95, are prominent, particularly for the stainless steel industry. During the process in which these alloys are obtained, there is considerable production of fine powder, which could be reused after suitable chemical treatment, for example, through coupling pyrometallurgical and hydrometallurgical processes. In the present study, the extraction of chromium from fine powder generated during the production of a Fe-Cr alloy with high C content was investigated. Roasting reactions were performed at 1073 K, 1173 K, and 1273 K (800 °C, 900 °C, and 1000 °C) with 300 pct (w/w) excess NaOH in an oxidizing atmosphere (air), followed by solubilization in deionized water, selective precipitation, and subsequent calcination at 1173 K (900 °C) in order to convert the obtained chromium hydroxide to Cr2O3. The maximum achieved Cr recovery was around 86 pct, suggesting that the proposed chemical route was satisfactory regarding the extraction of the chromium initially present. Moreover, after X-ray diffraction analysis, the final produced oxide has proven to be pure Cr2O3 with a mean crystallite size of 200 nm.

  7. Effect of Process Parameters, Casting Thickness, and Alloys on the Interfacial Heat-Transfer Coefficient in the High-Pressure Die-Casting Process

    NASA Astrophysics Data System (ADS)

    Guo, Zhi-Peng; Xiong, Shou-Mei; Liu, Bai-Cheng; Li, Mei; Allison, John

    2008-12-01

    The heat transfer at the metal-die interface is believed to have great influence on the solidification process and cast structure of the high-pressure die-casting (HPDC) process. The present article focused on the effects of process parameters, casting thickness, and alloys on the metal-die interfacial heat-transfer coefficient (IHTC) in the HPDC process. Experiment was carried out on a cold-chamber die-casting machine with two casting alloys AM50 and ADC12. A special casting, namely, “step-shape” casting, was used and cast against a H13 steel die. The IHTC was determined using an inverse approach based on the temperature measurements inside the die. Results show that the IHTC is different at different steps and changes as the solidification of the casting proceeds. Process parameters only influence the IHTC in its peak value, and for both AM50 and ADC12 alloys, a greater fast shot velocity leads to a greater IHTC peak value at steps 1 and 2. The initial die surface temperature has a more prominent influence on the IHTC peak values at the thicker steps, especially step 5. Results also show that a closer contact between the casting and die could be achieved when the casting alloy is ADC12 instead of AM50, which consequently leads to a higher IHTC.

  8. Two-phase chromium-niobium alloys exhibiting improved mechanical properties at high temperatures

    DOEpatents

    Liu, C.T.; Takeyama, Masao.

    1994-02-01

    The specification discloses chromium-niobium alloys which exhibit improved mechanical properties at high temperatures in the range of 1250 C and improved room temperature ductility. The alloys contain a Cr[sub 2]Nb-rich intermetallic phase and a Cr-rich phase with an overall niobium concentration in the range of from about 5 to about 18 at. %. The high temperature strength is substantially greater than that of state of the art nickel-based superalloys for enhanced high temperature service. Further improvements in the properties of the compositions are obtained by alloying with rhenium and aluminum; and additional rare-earth and other elements. 14 figures.

  9. Two-phase chromium-niobium alloys exhibiting improved mechanical properties at high temperatures

    DOEpatents

    Liu, Chain T.; Takeyama, Masao

    1994-01-01

    The specification discloses chromium-niobium alloys which exhibit improved mechanical properties at high temperatures in the range of 1250.degree. C. and improved room temperature ductility. The alloys contain a Cr.sub.2 Nb-rich intermetallic phase and a Cr-rich phase with an overall niobium concentration in the range of from about 5 to about 18 at. %. The high temperature strength is substantially greater than that of state of the art nickel-based superalloys for enhanced high temperature service. Further improvements in the properties of the compositions are obtained by alloying with rhenium and aluminum; and additional rare-earth and other elements.

  10. ToxCast Workflow: High-throughput screening assay data processing, analysis and management (SOT)

    EPA Science Inventory

    US EPA’s ToxCast program is generating data in high-throughput screening (HTS) and high-content screening (HCS) assays for thousands of environmental chemicals, for use in developing predictive toxicity models. Currently the ToxCast screening program includes over 1800 unique c...

  11. High-Throughput/High-Content Screening Assays with Engineered Nanomaterials in ToxCast

    EPA Science Inventory

    High-throughput and high-content screens are attractive approaches for prioritizing nanomaterial hazards and informing targeted testing due to the impracticality of using traditional toxicological testing on the large numbers and varieties of nanomaterials. The ToxCast program a...

  12. Commercialization of NASA's High Strength Cast Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2003-01-01

    In this paper, the commercialization of a new high strength cast aluminum alloy, invented by NASA-Marshall Space Flight Center, for high temperature applications will be presented. Originally developed to meet U.S. automotive legislation requiring low- exhaust emission, the novel NASA aluminum alloy offers dramatic improvement in tensile and fatigue strengths at elevated temperatures (450 F-750 F), which can lead to reducing part weight and cost as well as improving performance for automotive engine applications. It is an ideal low cost material for cast components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. NASA alloy also offers greater wear resistance, dimensional stability, and lower thermal expansion compared to conventional aluminum alloys, and the new alloy can be produced economically from sand, permanent mold and investment casting. Since 2001, this technology was licensed to several companies for automotive and marine internal combustion engines applications.

  13. Oxidation of Palladium-Chromium Alloys for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Piltch, Nancy D.; Jih-Fen, Lei; Zeller, Mary V.

    1994-01-01

    An alloy consisting of Pd with 13 wt % Cr is a promising material for high temperature applications. High temperature performance is degraded by the oxidation of the material, which is more severe in the fine wires and thin films used for sensor applications than in the bulk. The present study was undertaken to improve our understanding of the physical and chemical changes occurring at these temperatures and to identify approaches to limit oxidation of the alloy. The alloy was studied in both ribbon and wire forms. Ribbon samples were chosen to examine the role of grain boundaries in the oxidation process because of the convenience of handling for the oxidation studies. Wire samples 25 microns in diameter which are used in resistance strain gages were studied to correlate chemical properties with observed electrical, physical, and structural properties. Overcoating the material with a metallic Cr film did prevent the segregation of Pd to the surface; however, it did not eliminate the oxidation of the alloy.

  14. Removal of High Concentration Chromium by a Foam-separating Technique Using Casein Proteins as a Foaming Reagent

    NASA Astrophysics Data System (ADS)

    Sugimoto, Futoshi

    Foam separation of high concentration chromium in leather tanning wastewater was investigated using casein protein as a foaming reagent5mL of5w/v% ammonium acetate buffer was added to the sample chromium water. After adjusting the pH to 9.0,4g/L concentrations of casein and gelatin solution were added to recovery the coagulating flocs of chromium resulting foam separation. The sample water containing chromium flocs was incased in reactor, then mixed with distilled water and 1mL of ethanol to sum 200mL total. The foam separation was performed at time intervals of 3min with an air flow rate of 300mL/min. With casein reagent, the removal rate of chromium was not influenced by the presence of NaCl, however, the rate decreased tendency using with the use of gelatin. The proposed method, utilizing 4g/L of casein solution with water, was not influenced by the presence of calcium (<34mM), magnesium (<1mM), carbonate (<0.5mM), bicarbonate (<1.2mM) nor sulfate (<350mM) ions, and is ideal for foam separation in chromium concentrations of about 100mgCr/L.

  15. Predictive Model of Rat Reproductive Toxicity from ToxCast High Throughput Screening

    EPA Science Inventory

    The EPA ToxCast research program uses high throughput screening for bioactivity profiling and predicting the toxicity of large numbers of chemicals. ToxCast Phase‐I tested 309 well‐characterized chemicals in over 500 assays for a wide range of molecular targets and cellular respo...

  16. Low Cost Al-Si Casting Alloy As In-Situ Composite for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2000-01-01

    A new aluminum-silicon (Al-Si) alloy has been successfully developed at NASA- Marshall Space Flight Center (MSFC) that has significant improvement in tensile and fatigue strength at elevated temperatures (500 F-700 F). The alloy offers a number of benefits such as light weight, high hardness, low thermal expansion and high surface wear resistance. In hypereutectic form, this alloy is considered as an in-situ Al-Si composite with tensile strength of about 90% higher than the auto industry 390 alloy at 600 F. This composite is very economically produced by using either conventional permanent steel molds or die casting. The projected material cost is less than $0.90 per pound, and automotive components such as pistons can be cast for high production rate using conventional casting techniques with a low and fully accounted cost. Key Words: Metal matrix composites, In-situ composite, aluminum-silicon alloy, hypereutectic alloy, permanent mold casting, die casting.

  17. Development of Advanced Coating Techniques for Highly-durable Casting Dies

    NASA Astrophysics Data System (ADS)

    Tanaka, S.; Takagi, M.; Mano, T.

    2013-03-01

    In order to improve the durability of aluminum die-casting molds, we applied microstructure-controlled PVD coating techniques. Single-layer and multilayer films consisting of chromium nitride (CrN) or titanium aluminum nitride (TiAlN) were prepared using an ion plating process. Structures of multilayer films were observed using transmission electron microscopy. Pin-shaped mold steel specimens coated with each of the films were soaked in the molten aluminum alloy at 953 K different periods of time, and the amount of weight loss due to erosion was evaluated. The weight losses for the multilayer CrN and TiAlN specimens were found to be less than those for the single-layer specimens. As a practical test, five specimens of core pins used in aluminum die casting of automobile parts were coated with multilayer films, and the number of maintenance operations required to remove aluminum alloy remaining on the specimen surfaces after several thousand castings was counted and compared with six control specimens (core pins treated using a commercial salt bath diffusion process). The number of maintenance operations for CrN- and TiAlN-based multilayer-coated core pins was found to be lower than for the control specimens.

  18. Correlation of microstructure and fracture toughness in high-chromium white iron hardfacing alloys

    SciTech Connect

    Lee, S.; Choo, S.H.; Kim, N.J.; Baek, E.R.; Ahn, S.

    1996-12-01

    A correlation is made of microstructure and fracture toughness in hypereutectic high-chromium white iron hardfacing alloys. In order to investigate the matrix effect of these alloys, in particular, four different matrices such as pearlite, austenite, and a mixture of pearlite and austenite were employed by changing the ratio of Mn/Si, while the total volume fraction of carbides was fixed. The hardfacing alloys were deposited twice on a mild steel plate by the self-shielding flux-cored arc-welding method. Fracture toughness was increased by increasing the volume fraction of austenite in the matrix, whereas hardness and abrasion resistance were nearly constant. In situ observation of the fracture process showed that cracks initiated at large primary carbides tended to be blocked at the austenitic matrix. This suggested that fracture toughness was controlled mainly by the amount of austenite in the matrix, thereby yielding the better toughness in the hardfacing alloy having the austenitic matrix. Considering both abrasion resistance and fracture toughness, therefore, the austenitic matrix was preferred for the high-chromium white iron hardfacing alloys.

  19. Preparation, heat treatment, and mechanical properties of the uranium-5 weight percent chromium eutectic alloy

    SciTech Connect

    Townsend, A. B.

    1980-10-01

    The eutectic alloy of uranium-5 wt % chromium (U-5Cr) was prepared from high-purity materials and cast into 1-in.-thick ingots. This material was given several simple heat treatments, the mechanical properties of these heat-treated samples were determined; and the microstructure was examined. Some data on the melting point and transformation temperatures were obtained.

  20. A comparison of low-chromium and high-chromium reduced-activation steels for fusion applications

    SciTech Connect

    Klueh, R.L.; Maziasz, P.J.; Alexander, D.J.

    1996-11-01

    Ferritic steels have been considered candidate structural materials for first wall and blanket structures for fusion power plants since the late 1970s. The first steels considered in the United States were the conventional Cr-Mo steels Sandvik HT9 (nominally 12Cr-1Mo-0.25V-0.5W-0.5Ni-0.2C, here designated l2Cr-1MoVW), modified 9Cr-1Mo steel (9Cr-1Mo-0.2V-0.06Nb-0. IC, designated 9Cr-1MoVNb) and, to a lesser extent, 2 1/4Cr-1Mo steel (2.25Cr-Mo-0.1C). All compositions are in wt. %. The normalized-and-tempered 9 and 12Cr steels had a tempered martensite microstructure, and the normalized-and-tempered 2 1/4 Cr steel had a tempered bainite microstructure. This report describes chromium steels tested in normalized and tempered conditions. Miniature tensile and Charpy specimens were tested.

  1. Achieving High Strength and High Ductility in Friction Stir-Processed Cast Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Yuan, Wei; Panigrahi, Sushanta K.; Mishra, Rajiv S.

    2013-08-01

    Friction stir processing (FSP) is emerging as an effective tool for microstructural modification and property enhancement. As-cast AZ91 magnesium alloy was friction stir processed with one-pass and two-pass to examine the influence of processing conditions on microstructural evolution and corresponding mechanical properties. Grain refinement accompanied with development of strong basal texture was observed for both processing conditions. Ultrafine-grained (UFG) AZ91 was achieved under two-pass FSP with fine precipitates distributed on the grain boundary. The processed UFG AZ91 exhibited a high tensile strength of ~435 MPa (117 pct improvement) and tensile fracture elongation of ~23 pct. The promising combination of strength and ductility is attributed to the elimination of casting porosity, and high density of fine precipitates in an UFG structure with quite low dislocation density. The effects of grain size, precipitate, and texture on deformation behavior have been discussed.

  2. Formation of Superhexagonal Chromium Hydride by Exposure of Chromium Thin Film to High Temperature, High Pressure Hydrogen in a Ballistic Compressor.

    NASA Astrophysics Data System (ADS)

    Pan, Yi.

    This dissertation describes a novel, non-equilibrium method which was used to synthesize a new chromium hydride phase. Single crystal, body centered cubic Cr thin films were prepared by vacuum evaporation. These films were exposed to high temperature (close to the melting point of Cr), high pressure hydrogen gas in a ballistic compressor. This was followed by rapid cooling (>10^5^ circC/s) to room temperature. Using the transmission electron microscope (TEM), second phase particles of superhexagonal structure, which has lattice constant A = 4.77A and C/A = 1.84, are found in the films. This structure has a volume per Cr atom slightly larger than that of hexagonal closed packed CrH, so that the superhexagonal structure may contain more hydrogen than the hexagonal close packed CrH. The superhexagonal particles have a definite orientation relationship with the matrix: (021) _{rm sh} // (001) _{rm b} and (212)_{rm sh} // (110)_{rm b} . The superhexagonal structure is quite stable in air and at room temperature, but decomposes to body centered cubic Cr when bombarded by the electron beam in the TEM. No such particles were observed in Cr films exposed to pure argon under similar conditions in the ballistic compressor. Positive identification of hydrogen content was obtained by high-temperature vacuum extraction in a discharge tube. After vacuum extraction, hydrogen spectrum was observed, and the intensity of electron diffraction from superhexagonal structure decreased. Using an energy dispersive spectrometer with the capability of detecting elements down to atomic number six (carbon), no changes in composition of the films were found by comparing the characteristic x-ray spectra of the same film before and after exposure to hot, dense hydrogen in the ballistic compressor. This result suggests that this non-equilibrium method may be used for other metal-hydrogen system to obtain new structural phases that are of scientific or technological interest.

  3. SENSITIVITY OF HANFORD IMMOBILIZED HIGH LEVEL WASTE (IHLW) GLASS MASS TO CHROMIUM & ALUMINUM PARTITIONING ASSUMPTIONS

    SciTech Connect

    CERTA, P.J.

    2004-06-07

    The strategy for the treatment of the Hanford Site tank wastes involves water and caustic washing of the tank waste sludges to reduce sludge mass and the corresponding mass of high-level waste (HLW) glass that will be generated by the Waste Treatment and Immobilization Plant (WTP). During fiscal year (FY) 2003 CH2M HILL Hanford Group, Inc. (CH2M HILL) developed revised water wash and caustic leach factors for chromium (RPP-10222) and aluminum (RPP-11079) to estimate the waste treatment behavior of the tank waste compositions. Subsequently, the U.S. Department of Energy, Office of River Protection (ORP) requested that CH2M HILL evaluate the potential impacts to the HLW glass mass due to these revised water wash and caustic leach factors. ORP plans to use the results of this study in conjunction with separate information regarding the process impacts of implementing oxidative leaching at the WTP to determine whether oxidative leaching is adequate to mitigate potential increases in HLW glass production or whether additional strategies are required. The purpose of this sensitivity study of immobilized HLW glass mass to chromium and aluminum partitioning assumptions was to: (1) Identify the impacts of the revised water wash and caustic leach factors for chromium and aluminum on the mass of HLW glass. (2) Understand the effect of oxidative leaching on the mass of HLW glass. (3) Identify the major influences for HLW glass mass and waste blending. (4) Characterize the degree of pretreatment (water washing, caustic leaching, and oxidative leaching) assumed for different source tanks. (5) Identify candidate tanks for opportunistic sampling and testing to confirm the inventory and better understand the behavior of chromium during retrieval, staging, and subsequent processing. The study concluded that: (1) Application of the revised chromium and aluminum wash and leach factors will increase the HLW glass mass by about 60 to 100 percent (using the relaxed glass properties model

  4. Application of High-Temperature Mold Materials to Die Cast Copper Motor Rotor for Improved Efficiency

    SciTech Connect

    John G. Cowie; Edwin F. Brush, Jr.; Dale T. Peters; Stephen P. Midson; Darryl J. Van Son

    2003-05-01

    The objective of the study, Application of High-Temperature Mold Materials to Die Cast Copper Motor Rotor for Improved Efficiency, was to support the Copper Development Association (CDA) in its effort to design, fabricate and demonstrate mold technologies designed to withstand the copper motor rotor die casting environment for an economically acceptable life. The anticipated result from the compiled data and tests were to: (1) identify materials suitable for die casting copper, (2) fabricate motor rotor molds and (3) supply copper rotor motors for testing in actual compressor systems. Compressor manufacturers can apply the results to assess the technical and economical viability of copper rotor motors.

  5. LandCast 2050 High-Resolution Population Projection

    SciTech Connect

    2014-01-01

    The LandCast 2050 data set is an empirically-informed spatial distribution of projected population of the contiguous U.S. for 2050 compiled on a 30" x 30" latitude/longitude grid. Population projections of county level numbers were developed using a modified version of the U.S. Census's projection methodology - with the U.S. Census's official projection as the benchmark. Projected census counts were apportioned to each grid cell based on locally adaptive likelihood coefficients, which are based on land cover, slope, road proximity, distances to larger cities, a moving average of current population, and other data sets. The LandCast data set was developed as part of Oak Ridge National Laboratory (ORNL) Global Population Project for estimating ambient populations at risk.

  6. LandCast 2030 High-Resolution Population Projection

    SciTech Connect

    2014-01-01

    The LandCast 2030 data set is an empirically-informed spatial distribution of projected population of the contiguous U.S. for 2030 compiled on a 30" x 30" latitute/longitude grid. Population projections of county level numbers were developed using a modified version of the U.S. Census's projection methodology - with the U.S. Census's official projection as the benchmark. Projected census counts were apportioned to each grid cell based on locally adaptive likelihood coefficients, which are based on land cover, slope, road proximity, distances to larger cities, a moving average of current population, and other data sets. The LandCast 2030 data set was developed as part of Oak Ridge National Laboratory (ORNL) Global Population Project for estimating ambient populations at risk.

  7. Quenching of cast iron with a high copper content

    NASA Astrophysics Data System (ADS)

    Stepanova, Natalia; Bataev, Anatoly; Razumakov, Aleksey

    2015-10-01

    The structure, hardness, and microhardness of hypoeutectic white cast iron alloyed with copper after quenching at 1000 and 1120°C is studied. Features of cupric inclusion separation are detected and its size distribution is shown. After quenching the structure consists of martensite, residual austenite, and vermicular graphite. A decrease in the size and volume fraction of globular cupric inclusions is detected, along with the complete dissolution of nanoscale cupric inclusions, which are located in the ferrite of pearlite colonies. The result of these structural changes is a 30% increase in iron hardness. Cast iron quenching at 1120° C is followed by an increase in the austenite volume fraction to 69%. This effect is due to a decrease in the volume fraction of graphite and a corresponding increase in the carbon content in γ-Fe. Cupric inclusions are located mainly along boundaries of austenitic grains.

  8. Impact of chromium histidinate on high fat diet induced obesity in rats

    PubMed Central

    2011-01-01

    Background Chromium (Cr) is an essential trace element that has garnered interest for use as a weight loss aid, but its molecular mechanism in obesity is not clear. In this study, an attempt has been made to investigate the effects of chromium histidinate (CrHis) on glucose transporter-2 (GLUT-2), nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), nuclear factor-kappa B (NF-κB p65) and the oxidative stress marker 4-hydroxynonenal adducts (HNE) expressions in liver of rats fed high fat diet (HFD). Methods Male Wistar rats (n = 40, 8 wk-old) were divided into four groups. Group I was fed a standard diet (12% of calories as fat); Group II was fed a standard diet and supplemented with 110 μg CrHis/kg BW/d; Group III was fed a HFD (40% of calories as fat); Group IV was fed HFD and supplemented with 110 μg CrHis/kg BW/d. Results Rats fed HFD possessed greater serum insulin (40 vs.33 pmol/L) and glucose (158 vs. 143 mg/dL) concentration and less liver Cr (44 vs.82 μg/g) concentration than rats fed the control diet. However, rats supplemented with CrHis had greater liver Cr and serum insulin and lower glucose concentration in rats fed HFD (P < 0.05). The hepatic nuclear factor-kappa B (NF-κB p65) and HNE were increased in high fat group compared to control group, but reduced by the CrHis administration (P < 0.05). The levels of hepatic Nrf2 and HO-1 were increased by supplementation of CrHis (P < 0.05). Conclusion These findings demonstrate that supplementation of CrHis is protective against obesity, at least in part, through Nrf2-mediated induction of HO-1 in rats fed high fat diet. PMID:21539728

  9. Modeling of chromium in ground water

    SciTech Connect

    Shen, Huiying; Nikolaidis, N.P.

    1995-12-01

    National Chromium is a metal-plating facility located in Putnam, Connecticut that has been in operation for 55 years. Chromium has dripped onto the wooden floor and leached into the groundwater. The process that affect the fate and transport of chromium in groundwater are aqueous complexation, adsorption/desorption, precipitation/dissolution, and solute transport. In addition, field data and laboratory studies using soil samples from this site indicate that a predominant retardation process is diffusion into the soil matrix. While aqueous complexation usually takes seconds or less, the time scales of chromium diffusion in soil matrix is years. A three-dimensional multicomponent solute transport model has been developed to study the fate, speciation and transport of chromium. The model has been applied to the National Chromium site in a hind casting to study (1) the interaction among the processes, (2) the implication of chromium diffusion in soil matrix on remediation technologies, and (3) the time scales of remediation.

  10. Eutectic modification in a low-chromium white cast iron by a mixture of titanium, rare earths, and bismuth: I. Effect on microstructure

    NASA Astrophysics Data System (ADS)

    Bedolla-Jacuinde, A.; Aguilar, S. L.; Hernández, B.

    2005-04-01

    The present work studies the effect of small additions of a mixture of Ti, rare earths (RE), and Bi on the eutectic solidification of a low-Cr white cast iron (WCI) commercially designed as Ni-Hard Class I Type B according to the ASTM A532. For this purpose, systematic additions of a mixture of ferrotitanium-rare earths-bismuth (Fe-Ti-RE-Bi) up to 2% were made to a low-Cr WCI. By means of these additions, a modified carbide structure was obtained. Eutectic carbides changed from a highly interconnected ledeburite structure to more isolated, finer blocky structure. This microstructural change caused variations in the mechanical behavior of the WCI. The decrease in size and reduced connectivity of the eutectic carbides increased fracture toughness as well as wear resistance under dry sliding conditions. The effect of the admixture on the microstructure and mechanical properties is discussed in terms of the segregation and refining effects of the elements that comprise the mixture.

  11. Study of Chromium-Frit-Type Coatings for High-Temperature Protection of Molybdenum

    NASA Technical Reports Server (NTRS)

    Moore, D G; Bolz, L H; Pitts, J W; Harrison, W N

    1951-01-01

    The achievement of more compact and efficient power plants for aircraft is dependent, among other factors, on the perfection of heat-resisting materials that are superior to those in current use. Molybdenum is one of the high-melting metals (melting point, 4750 F). It is fairly abundant and also can be worked into many of the shapes required in modern power plants. To permit its widespread use at elevated temperatures, however, some means must first be found to prevent its rapid oxidation. The application of a protective coating is one method that might be used to achieve this goal. In the present work, a number of chromium-frit-type coatings were studied. These were bonded to molybdenum specimens by firing in controlled atmospheres to temperatures in the range of 2400 to 2700 F.

  12. Oral administration of the high-chromium yeast improve blood plasma variables and pancreatic islet tissue in diabetic mice.

    PubMed

    Liu, Lu; Jin, Wen; Lv, Jia-Ping

    2010-12-01

    The in vivo effects of oral administration of the high-chromium yeast to healthy and diabetic mice are described. Given that these complexes are proposed to function by potentiating the actions of insulin and activating the insulin receptor kinase, changes in lipid and carbohydrate metabolism would be expected. After 15 weeks administration (500 μg Cr/kg body mass) to healthy mice, abnormal metabolism and pathological change were not observed. After 15 weeks of treatment (0-1,000 μg Cr/kg body mass) of diabetic mice, the effect of high-chromium yeast on blood lipids and blood glycosylated hemoglobin (GHb) of diabetes are not consistent. High-chromium yeast results in a lowering (P < 0.05) of GHb and triglyceride, lowering (P < 0.01) of total cholesterol, and restoration (P < 0.01) of insulin; these results are in stark contrast to those of diabetic mice of administration of normal yeast, which have no effect on these parameters and serve as control group. The histopathological analysis of pancreas islet shows that high-chromium yeast could profoundly protect the impaired pancreatic islet and β-cells from inflammatory infiltration and fibrosis.

  13. Study on objective functions for the slow shot phase in high-pressure die casting

    NASA Astrophysics Data System (ADS)

    Frings, Markus; Behr, Marek; Elgeti, Stefanie

    2016-10-01

    High-pressure die casting is an important process in the field of aluminum processing. Especially during the slow shot phase, the process parameters immensely influence the cast part quality. At the current state of the art, the appropriate process parameters are identified based on running-in trials and significant experience. To translate this experience into a mathematical framework is the aim of this work. The idea is to shift the running-in trials to the computer—now in the form of a numerical optimization. In view of the optimization, this paper presents a selection of objective functions. These are assessed with the respect to (1) their suitability as an overall quality measure of the casting process and (2) the extent to which they reflect the goals of the casting process.

  14. A Review of Mold Flux Development for the Casting of High-Al Steels

    NASA Astrophysics Data System (ADS)

    Wang, Wanlin; Lu, Boxun; Xiao, Dan

    2016-02-01

    Mold flux plays key roles during the continuous casting process of molten steel, which accounts for the quality of final slabs. With the development of advanced high strength steels (AHSS), certain amounts of Al have been added into steels that would introduce severe slag/metal interaction problems during process of continuous casting. The reaction is between Al and SiO2 that is the major component in the mold flux system. Intensive efforts have been conducted to optimize the mold flux and a CaO-Al2O3-based mold flux system has been proposed, which shows the potential to be applied for the casting process of AHSS. The latest developments for this new mold flux system were summarized with the aim to offer technical guidance for the design of new generation mold flux system for the casting of AHSS.

  15. Heat and corrosion resistant cast CF8C stainless steel with improved high temperature strength and ductility

    DOEpatents

    Maziasz, Philip J.; McGreevy, Tim; Pollard, Michael James; Siebenaler, Chad W.; Swindeman, Robert W.

    2010-08-17

    A CF8C type stainless steel alloy and articles formed therefrom containing about 18.0 weight percent to about 22.0 weight percent chromium and 11.0 weight percent to about 14.0 weight percent nickel; from about 0.05 weight percent to about 0.15 weight percent carbon; from about 2.0 weight percent to about 10.0 weight percent manganese; and from about 0.3 weight percent to about 1.5 weight percent niobium. The present alloys further include less than 0.15 weight percent sulfur which provides high temperature strength both in the matrix and at the grain boundaries without reducing ductility due to cracking along boundaries with continuous or nearly-continuous carbides. The disclosed alloys also have increased nitrogen solubility thereby enhancing strength at all temperatures because nitride precipitates or nitrogen porosity during casting are not observed. The solubility of nitrogen is dramatically enhanced by the presence of manganese, which also retains or improves the solubility of carbon thereby providing additional solid solution strengthening due to the presence of manganese and nitrogen, and combined carbon.

  16. Heat and corrosion resistant cast CF8C stainless steel with improved high temperature strength and ductility

    DOEpatents

    Maziasz, Philip J.; McGreevy, Tim; Pollard, Michael James; Siebenaler, Chad W.; Swindeman, Robert W.

    2006-12-26

    A CF8C type stainless steel alloy and articles formed therefrom containing about 18.0 weight percent to about 22.0 weight percent chromium and 11.0 weight percent to about 14.0 weight percent nickel; from about 0.05 weight percent to about 0.15 weight percent carbon; from about 2.0 weight percent to about 10.0 weight percent manganese; and from about 0.3 weight percent to about 1.5 weight percent niobium. The present alloys further include less than 0.15 weight percent sulfur which provides high temperature strength both in the matrix and at the grain boundaries without reducing ductility due to cracking along boundaries with continuous or nearly-continuous carbides. The disclosed alloys also have increased nitrogen solubility thereby enhancing strength at all temperatures because nitride precipitates or nitrogen porosity during casting are not observed. The solubility of nitrogen is dramatically enhanced by the presence of manganese, which also retains or improves the solubility of carbon thereby providing additional solid solution strengthening due to the presence of manganese and nitrogen, and combined carbon.

  17. Solidification Microstructure of AISI M2 High Speed Steel Manufactured by the Horizontal Continuous Casting Process

    NASA Astrophysics Data System (ADS)

    Zhou, X. F.; Fang, F.; Jiang, J. Q.

    2011-01-01

    In the present work, AISI M2 high speed steel is produced by the horizontal continuous casting process. The difference of solidification microstructure in ingots by mould casting and continuous casting has been examined by means of scanning electron microscope (SEM), electron back-scatter diffraction (EBSD), transmission electron microscope (TEM) and high resolution electron microscope (HREM). The results show that the as-cast structure consists of iron matrix and networks of M2C eutectic carbides, which are greatly refined in the continuous casting ingot compared to the case of ingot by mould casting. Meanwhile, the morphology of M2C eutectic carbides changes from the plate-like shape into the fibrous one. Micro-twining and stacking faults are observed in the plate-like M2C, whereas they are rarely identified in the fibrous M2C. Based on the characteristic of morphology and microstructure, it is expected that the plate-like M2C is a faceted phase while the fibrous M2C is a non-faceted phase.

  18. Chromium in metabolic and cardiovascular disease.

    PubMed

    Hummel, M; Standl, E; Schnell, O

    2007-10-01

    Chromium is an essential mineral that appears to have a beneficial role in the regulation of insulin action, metabolic syndrome, and cardiovascular disease. There is growing evidence that chromium may facilitate insulin signaling and chromium supplementation therefore may improve systemic insulin sensitivity. Tissue chromium levels of subjects with diabetes are lower than those of normal control subjects, and a correlation exists between low circulating levels of chromium and the incidence of type 2 diabetes. Controversy still exists as to the need for chromium supplementation. However, supplementation with chromium picolinate, a stable and highly bioavailable form of chromium, has been shown to reduce insulin resistance and to help reduce the risk of cardiovascular disease and type 2 diabetes. Since chromium supplementation is a safe treatment, further research is necessary to resolve the confounding data. The existing data suggest to concentrate future studies on certain forms as chromium picolinate and doses as at least 200 mcg per day.

  19. Photocatalytic removal of hexavalent chromium by newly designed and highly reductive TiO2 nanocrystals.

    PubMed

    Chen, Gongde; Feng, Ji; Wang, Wenshou; Yin, Yadong; Liu, Haizhou

    2017-01-01

    Hexavalent chromium Cr(VI), a highly toxic oxyanion, widely occurs in drinking water supplies. This study designed and synthesized a new type of highly reductive TiO2 nanocrystals for photochemical Cr(VI) removal, via the thermal hydrolysis of TiCl4 in the presence of diethylene glycol (DEG). Surface analyses and hydroxyl radical measurements suggested that DEG was chemically bonded on TiO2 surface that resulted in an internal hole-scavenging effect and a high electron-releasing capacity, making it advantageous to conventional TiO2 materials. Upon UV irradiation, the synthesized TiO2 photocatalyst exhibited fast Cr(VI) reduction kinetics in diverse water chemical conditions. Fast elimination of Cr(VI) was achieved on a time scale of seconds in drinking water matrices. The removal of Cr(VI) by reductive TiO2 exhibited a three-stage kinetic behavior: an initial fast-reaction phase, a lag phase resulting from surface precipitation of Cr(OH)3(s), and a final reaction phase due to surface regeneration from oxidation-reduction induced ripening process. The lag phase disappeared in acidic conditions that prevented the formation of Cr(OH)3(s). The catalyst exhibited extremely high electron-releasing capacity that can be reused for multiple cycles of Cr(VI) removal in drinking water treatment.

  20. High Yield Strength Cast Steel With Improved Weldability

    DTIC Science & Technology

    1991-05-01

    TABLE 2 AIM COMPOSITIONS OF AIR-MELT INDUCTION HEATS (Wt. Percent) C Mn Si Cr Ni MO Cu Cb V HEAT 0.05 0.85 0.50 1.50 4.50 0.40 - - - 1089 HEAT 0.05 0.85...0.75 1.00 0.20 1.50 0.40 - 1093 Heate 1089 and 1090 were low carbon, higher nickel variations of HY-80 . Heat 1091 was a low carbon variation of HY-130...Several 1" cubes were saw cut from one of the test blocks cast in Heats 1089 , 1090, 1091, and 1092, These samples were hardened by austenitizing at

  1. Fabrication of Unique Magnetic Bionanocomposite for Highly Efficient Removal of Hexavalent Chromium from Water

    NASA Astrophysics Data System (ADS)

    Zhong, Yunlei; Qiu, Xun; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-08-01

    Biotreatment of hexavalent chromium has attracted widespread interest due to its cost effective and environmental friendliness. However, the difficult separation of biomass from aqueous solution and the slow hexavalent chromium bioreduction rate are bottlenecks for biotechnology application. In this approach, a core-shell structured functional polymer coated magnetic nanocomposite was prepared for enriching the hexavalent chromium. Then the nanocomposite was connected to the bacteria via amines on bacterial (Bacillus subtilis ATCC-6633) surface. Under optimal conditions, a series of experiments were launched to degrade hexavalent chromium from the aqueous solution using the as-prepared bionanocomposite. Results showed that B. subtilis@Fe3O4@mSiO2@MANHE (BFSM) can degrade hexavalent chromium from the water more effectively (a respectable degradation efficiency of about 94%) when compared with pristine B. subtilis and Fe3O4@mSiO2@MANHE (FSM). Moreover, the BFSM could be separated from the wastewater by magnetic separation technology conveniently due to the Fe3O4 core of FSM. These results indicate that the application of BFSM is a promising strategy for effective treating wastewater containing hexavalent chromium.

  2. Fabrication of Unique Magnetic Bionanocomposite for Highly Efficient Removal of Hexavalent Chromium from Water

    PubMed Central

    Zhong, Yunlei; Qiu, Xun; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-01-01

    Biotreatment of hexavalent chromium has attracted widespread interest due to its cost effective and environmental friendliness. However, the difficult separation of biomass from aqueous solution and the slow hexavalent chromium bioreduction rate are bottlenecks for biotechnology application. In this approach, a core-shell structured functional polymer coated magnetic nanocomposite was prepared for enriching the hexavalent chromium. Then the nanocomposite was connected to the bacteria via amines on bacterial (Bacillus subtilis ATCC-6633) surface. Under optimal conditions, a series of experiments were launched to degrade hexavalent chromium from the aqueous solution using the as-prepared bionanocomposite. Results showed that B. subtilis@Fe3O4@mSiO2@MANHE (BFSM) can degrade hexavalent chromium from the water more effectively (a respectable degradation efficiency of about 94%) when compared with pristine B. subtilis and Fe3O4@mSiO2@MANHE (FSM). Moreover, the BFSM could be separated from the wastewater by magnetic separation technology conveniently due to the Fe3O4 core of FSM. These results indicate that the application of BFSM is a promising strategy for effective treating wastewater containing hexavalent chromium. PMID:27502074

  3. High concentrations of chromium in lung tissue from lung cancer patients

    SciTech Connect

    Anttila, S.; Kokkonen, P.; Paeaekkoe PRai; Rainio, P.; Kalliomaeki, P.L.P.; Pallon, J.; Malmqvist, K.; Pakarinen, P.; Naentoe, V.Su.; Sutinen, S.

    1989-02-01

    The pulmonary chromium content was determined by plasma atomic emission spectrometer (DCP-AES) from 53 lung cancer and 43 control patients, and compared with smoking habits, severity of emphysema and occupational history. The chromium content from the lung cancer patients was higher than that from the smoking (P less than 0.025) or nonsmoking control patients (6.4 +/- 4.3, 4.0 +/- 4.0, and 2.2 +/- 0.6 microgram/g dry weight, respectively). A positive correlation between the pulmonary chromium and smoking time (P less than 0.025) and the severity of emphysema (P less than 0.001) was found in the control but not in the cancer patients. The difference in the pulmonary chromium content was greatest between those lung cancer and control patients who were light smokers or had mild emphysema. This group of lung cancer patients included subjects with occupational exposure to chromium. The possibility of occupational cancer should be considered especially with light smokers. The grade of emphysema and metals such as chromium accumulating from tobacco could serve as objective indicators of smoking.

  4. A high-performance flow-field structured iron-chromium redox flow battery

    NASA Astrophysics Data System (ADS)

    Zeng, Y. K.; Zhou, X. L.; An, L.; Wei, L.; Zhao, T. S.

    2016-08-01

    Unlike conventional iron-chromium redox flow batteries (ICRFBs) with a flow-through cell structure, in this work a high-performance ICRFB featuring a flow-field cell structure is developed. It is found that the present flow-field structured ICRFB reaches an energy efficiency of 76.3% with a current density of 120 mA cm-2 at 25 °C. The energy efficiency can be as high as 79.6% with an elevated current density of 200 mA cm-2 at 65 °C, a record performance of the ICRFB in the existing literature. In addition, it is demonstrated that the energy efficiency of the battery is stable during the cycle test, and that the capacity decay rate of the battery is 0.6% per cycle. More excitingly, the high performance of the flow-field structured battery significantly lowers the capital cost at 137.6 kWh-1, which is 28.2% lower than that of the conventional ICRFB for 8-h energy storage.

  5. High Density Die Casting (HDDC): new frontiers in the manufacturing of heat sinks

    NASA Astrophysics Data System (ADS)

    Sce, Andrea; Caporale, Lorenzo

    2014-07-01

    Finding a good solution for thermal management problems is every day more complex. due to the power density and the required performances. When a solution suitable for high volumes is needed. die-casting and extrusion are the most convenient technologies. However designers have to face the well-known limitations for those processes. High Density Die Casting (HDDC) is a process under advanced development. in order to overcome the extrusion and traditional die casting limits by working with alloys having much better thermal performances than the traditional die-casting process. while keeping the advantages of a flexible 3D design and a low cost for high volumes. HDDC offers the opportunity to design combining different materials (aluminium and copper. aluminium and stainless steel) obtaining a structure with zero porosity and overcoming some of die-casting limits. as shown in this paper. A dedicated process involving embedded heat pipes is currently under development in order to offer the possibility to dramatically improve the heat spreading.

  6. Development of low-temperature high-strength integral steel castings for offshore construction by casting process engineering

    NASA Astrophysics Data System (ADS)

    Lim, Sang-Sub; Mun, Jae-Chul; Kim, Tae-Won; Kang, Chung-Gil

    2014-12-01

    In casting steels for offshore construction, manufacturing integral casted structures to prevent fatigue cracks in the stress raisers is superior to using welded structures. Here, mold design and casting analysis were conducted for integral casting steel. The laminar flow of molten metal was analyzed and distributions of hot spots and porosities were studied. A prototype was subsequently produced, and air vents were designed to improve the surface defects caused by the release of gas. A radiographic test revealed no internal defects inside the casted steel. Evaluating the chemical and mechanical properties of specimens sampled from the product revealed that target values were quantitatively satisfied. To assess weldability in consideration of repair welding, the product was machined with grooves and welded, after which the mechanical properties of hardness as well as tensile, impact, and bending strengths were evaluated. No substantive differences were found in the mechanical properties before and after welding.

  7. Characterization of Ni-Cr alloys using different casting techniques and molds.

    PubMed

    Chen, Wen-Cheng; Teng, Fu-Yuan; Hung, Chun-Cheng

    2014-02-01

    This study differentiated the mechanical properties of nickel-chromium (Ni-Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni-Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500 rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, "casting mold," significantly influenced all mechanical properties. The graphite mold casting of the Ni-Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni-Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties.

  8. Laser beam hardening of cast carbon steels, plain cast irons, and high-speed steels

    NASA Astrophysics Data System (ADS)

    Bylica, Andrzej; Adamiak, Stanislaw; Bochnowski, Wojciech; Dziedzic, Andrzej

    2000-11-01

    The examinations of the structure, hardness and abrasion resistance of surface layer of Fe-C alloys having the contents of carbon up to 4% and high-speed steel: 6-5-2, 4- 4-2-5+C after laser hardening are presented in the paper. They are compared with the properties obtained after conventional hardening. Laser of impulse operation - YAG:Nd and of continuous operation - CO2 were used. Analysis of structure was carried out based on metallographic and fractographic examinations as well as on X-ray properties, parameters of laser and conventional heat treatment of steels were defined.

  9. The carcinogenicity of chromium

    PubMed Central

    Norseth, Tor

    1981-01-01

    The carcinogenicity of chromium compounds is reviewed with specific attention to the gaps in knowledge for risk estimation and research needs. The most important problems at present are whether trivalent chromium compounds cause cancer, and whether there is a difference in cancer causing effects between the soluble and the slightly soluble hexavalent compounds in the practical exposure situation. Dose estimates for risk estimation based on epidemiological investigations are also lacking. Present evidence indicates that the trivalent chromium compounds do not cause cancer although high concentrations in some in vitro systems have shown genetic toxicity. Hexavalent chromium compounds cause cancer in humans, in experimental animals and exert genetic toxicity in bacteria and in mammalian cells in vitro. Epidemiological evidence and animal experiments indicate that the slightly soluble hexavalent salts are the most potent carcinogens, but proper identification and characterization of exposure patterns in epidemiological work are lacking. Workers also tend to have mixed exposures. Soluble and slightly soluble salts are equally potent genotoxic agents in vitro. Further work for establishing dose estimates for risk evaluation in epidemiological work is important. In vitro systems should be applied for further identification of the mechanism of the carcinogenic effects, and animal experiments are urgent for comparison of the carcinogenic potency of the different hexavalent salts. Hexavalent chromium salts must be regarded as established carcinogens, and proper action should be taken in all industries with regard to such exposure. At present the carcinogenic risk to the general population caused by chromium compounds seems to be negligible, chromium in cigarettes, however, is an uncertainty in this respect. The amount of chromium and the type of chromium compounds inhaled from cigarettes is not known. PMID:7023928

  10. Ultrasound Velocity Measurements in High-Chromium Steel Under Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Lunev, Aleksey; Bochkareva, Anna; Barannikova, Svetlana; Zuev, Lev

    2016-04-01

    In the present study, the variation of the propagation velocity of ultrasound in the plastic deformation of corrosion-resistant high-chromium steel 40X13 with ferrite-carbide (delivery status), martensitic (quenched) and sorbitol (after high-temperature tempering) structures have beem studied/ It is found that each state shows its view of the loading curve. In the delivery state diagram loading is substantially parabolic throughout, while in the martensitic state contains only linear strain hardening step and in the sorbitol state the plastic flow curve is three-step. The velocity of ultrasonic surface waves (Rayleigh waves) was measured simultaneously with the registration of the loading curve in the investigated steel in tension. It is shown that the dependence of the velocity of ultrasound in active loading is determined by the law of plastic flow, that is, the staging of the corresponding diagram of loading. Structural state of the investigated steel is not only changing the type of the deformation curve under uniaxial tension, but also changes the nature of ultrasound speed of deformation.

  11. High Throughput Genotoxicity Profiling of the US EPA ToxCast Chemical Library

    EPA Science Inventory

    A key aim of the ToxCast project is to investigate modern molecular and genetic high content and high throughput screening (HTS) assays, along with various computational tools to supplement and perhaps replace traditional assays for evaluating chemical toxicity. Genotoxicity is a...

  12. Using high-content imaging data from ToxCast to analyze toxicological tipping points (TDS)

    EPA Science Inventory

    Translating results obtained from high-throughput screening to risk assessment is vital for reducing dependence on animal testing. We studied the effects of 976 chemicals (ToxCast Phase I and II) in HepG2 cells using high-content imaging (HCI) to measure dose and time-depende...

  13. High content screening of ToxCast compounds using Vala Sciences’ complex cell culturing systems (SOT)

    EPA Science Inventory

    US EPA’s ToxCast research program evaluates bioactivity for thousands of chemicals utilizing high-throughput screening assays to inform chemical testing decisions. Vala Sciences provides high content, multiplexed assays that utilize quantitative cell-based digital image analysis....

  14. Strong correlations and the search for high-Tc superconductivity in chromium pnictides and chalcogenides

    NASA Astrophysics Data System (ADS)

    Pizarro, J. M.; Calderón, M. J.; Liu, J.; Muñoz, M. C.; Bascones, E.

    2017-02-01

    Undoped iron superconductors accommodate n =6 electrons in five d orbitals. Experimental and theoretical evidence shows that the strength of correlations increases with hole doping, as the electronic filling approaches half filling with n =5 electrons. This evidence delineates a scenario in which the parent compound of iron superconductors is the half-filled system, in analogy to cuprate superconductors. In cuprates the superconductivity can be induced upon electron or hole doping. In this work we propose to search for high-Tc superconductivity and strong correlations in chromium pnictides and chalcogenides with n <5 electrons. By means of ab initio slave-spin and multiorbital random-phase-approximation calculations we analyze the strength of the correlations and the superconducting and magnetic instabilities in these systems with the main focus on LaCrAsO. We find that electron-doped LaCrAsO is a strongly correlated system with competing magnetic interactions, with (π ,π ) antiferromagnetism and nodal d -wave pairing being the most plausible magnetic and superconducting instabilities, respectively.

  15. Influence of Basicity on High-Chromium Vanadium-Titanium Magnetite Sinter Properties, Productivity, and Mineralogy

    NASA Astrophysics Data System (ADS)

    Zhou, Mi; Yang, Songtao; Jiang, Tao; Xue, Xiangxin

    2015-05-01

    The effect of basicity on high-chromium vanadium-titanium magnetite (V-Ti-Cr) sintering was studied via sintering pot tests. The sinter rate, yield, and productivity were calculated before determining sinter strength (TI) and reduction degradation index (RDI). Furthermore, the effect of basicity on V-Ti-Cr sinter mineralogy was clarified using metallographic microscopy, x-ray diffraction, and scanning electron microscopy-energy-dispersive x-ray spectroscopy. The results indicate that increasing basicity quickly increases the sintering rate from 25.4 mm min-1 to 28.9 mm min-1, yield from 75.3% to 87.2%, TI from 55.4% to 64.8%, and productivity from 1.83 t (m2 h)-1 to 1.94 t (m2 h)-1 before experiencing a slight drop. The V-Ti-Cr sinter shows complex mineral composition, with main mineral phases such as magnetite, hematite, silicate (dicalcium silicate, Ca-Fe olivine, glass), calcium and aluminum silico-ferrite (SFCA/SFCAI) and perovskite. Perovskite is notable because it lowers the V-Ti sinter strength and RDI. The well intergrowths between magnetite and SFCA/SFCAI, and the decrease in perovskite and secondary skeletal hematite are the key for improving TI and RDI. Finally, a comprehensive index was calculated, and the optimal V-Ti-Cr sinter basicity also for industrial application was 2.55.

  16. Irradiation-induced impurity segregation and ductile-to-brittle transition temperature shift in high chromium ferritic/martensitic steels

    NASA Astrophysics Data System (ADS)

    Lu, Z.; Faulkner, R. G.; Flewitt, P. E. J.

    2007-08-01

    A model is presented to predict irradiation-induced impurity segregation and its contribution to the ductile-to-brittle transition temperature (DBTT) shift in high chromium ferritic steels. The hardening contribution (dislocation loops, voids and precipitates) is also considered in this study. The predicted results are compared with the experimental DBTT shifts data for irradiated 9Cr1MoVNb and 12Cr1MoVW steels with different grain sizes.

  17. Modeling of different zones of as-cast structure of high carbon steel ingots

    NASA Astrophysics Data System (ADS)

    Chen, Zhiye; Arnsfeld, Sonja; Senk, Dieter

    2012-07-01

    Ingot casting technology has been expanded to large parts during the last decades. As the ingot sizes increase, higher quality of the as-cast semi-products is demanded, with regard to the control of casting defects like macrosegregation and structure inhomogeneity. In order to investigate macrosegregation and to estimate the as-cast structure, theoretical study and simulation work on ingot solidification are carried out at the Department of Ferrous Metallurgy of RWTH Aachen University (IEHK). A solidification model has been developed, and based on that, modeling of the structure morphology has been performed. A proper coupling of the developed solidification model with experimental results from IEHK is under investigation. This solidification model is a two-phase FVM model applied for high carbon steel with 0.6 wt.% [C]. The temperature and concentration fields of the solid and liquid phases have been calculated and these results can provide information for further prediction of the solidification structure such as CET (Columnar to Equiaxed Transition) zone and casting defects in an ingot. The structure morphology model introduces a shape factor of grains as the quantitative criterion for identification of the structure morphology. It focuses on the interaction between nuclei density and resulting macroscopic structure, and can calculate the strictly columnar zone, CET zone with mainly columnar characteristics and enclosed equiaxed crystals, and the pure equiaxed zone. The results will be presented, and the correlation of CET zone with development of macrosegregation in the inner part of an ingot will be discussed.

  18. A high resolution finite volume method for efficient parallel simulation of casting processes on unstructured meshes

    SciTech Connect

    Kothe, D.B.; Turner, J.A.; Mosso, S.J.; Ferrell, R.C.

    1997-03-01

    We discuss selected aspects of a new parallel three-dimensional (3-D) computational tool for the unstructured mesh simulation of Los Alamos National Laboratory (LANL) casting processes. This tool, known as {bold Telluride}, draws upon on robust, high resolution finite volume solutions of metal alloy mass, momentum, and enthalpy conservation equations to model the filling, cooling, and solidification of LANL castings. We briefly describe the current {bold Telluride} physical models and solution methods, then detail our parallelization strategy as implemented with Fortran 90 (F90). This strategy has yielded straightforward and efficient parallelization on distributed and shared memory architectures, aided in large part by new parallel libraries {bold JTpack9O} for Krylov-subspace iterative solution methods and {bold PGSLib} for efficient gather/scatter operations. We illustrate our methodology and current capabilities with source code examples and parallel efficiency results for a LANL casting simulation.

  19. Characterization of pores in high pressure die cast aluminum using active thermography and computed tomography

    NASA Astrophysics Data System (ADS)

    Maierhofer, Christiane; Myrach, Philipp; Röllig, Mathias; Jonietz, Florian; Illerhaus, Bernhard; Meinel, Dietmar; Richter, Uwe; Miksche, Ronald

    2016-02-01

    Larger high pressure die castings (HPDC) and decreasing wall thicknesses are raising the issue of casting defects like pores in aluminum structures. Properties of components are often strongly influenced by inner porosity. As these products are being established more and more in lightweight construction (e.g. automotive and other transport areas), non-destructive testing methods, which can be applied fast and on-site, are required for quality assurance. In this contribution, the application of active thermography for the direct detection of larger pores is demonstrated. The analysis of limits and accuracy of the method are completed by numerical simulation and the method is validated using computed tomography.

  20. High-Throughput Exposure Potential Prioritization for ToxCast Chemicals

    EPA Science Inventory

    The U.S. EPA must consider lists of hundreds to thousands of chemicals when prioritizing research resources in order to identify risk to human populations and the environment. High-throughput assays to identify biological activity in vitro have allowed the ToxCastTM program to i...

  1. High-Throughput Models for Exposure-Based Chemical Prioritization in the ExpoCast Project

    EPA Science Inventory

    The United States Environmental Protection Agency (U.S. EPA) must characterize potential risks to human health and the environment associated with manufacture and use of thousands of chemicals. High-throughput screening (HTS) for biological activity allows the ToxCast research pr...

  2. High Throughput Prioritization for Integrated Toxicity Testing Based on ToxCast Chemical Profiling

    EPA Science Inventory

    The rational prioritization of chemicals for integrated toxicity testing is a central goal of the U.S. EPA’s ToxCast™ program (http://epa.gov/ncct/toxcast/). ToxCast includes a wide-ranging battery of over 500 in vitro high-throughput screening assays which in Phase I was used to...

  3. tcpl: The ToxCast Pipeline for High-Throughput Screening Data

    EPA Science Inventory

    Motivation: The large and diverse high-throughput chemical screening efforts carried out by the US EPAToxCast program requires an efficient, transparent, and reproducible data pipeline.Summary: The tcpl R package and its associated MySQL database provide a generalized platform fo...

  4. Evaluation of food-relevant chemicals in the ToxCast high-throughput screening program

    EPA Science Inventory

    There are thousands of chemicals that are directly added to or come in contact with food, many of which have undergone little to no toxicological evaluation. The ToxCast high-throughput screening (HTS) program has evaluated over 1,800 chemicals in concentration-response across ~8...

  5. The direct strip casting concept: A low-cost, high-productivity solution for flat products of all steel grades

    SciTech Connect

    Reichelt, W.; Urlau, U.; Burstroem, E.; Nystroem, R.

    1996-12-31

    The Direct Strip Casting concept is characterized by a high degree of flexibility as regards the types of steel to be cast, at the same time guaranteeing a high production rate and low investment costs. It has been planned to cast strips of all steel grades with a thickness of approx. 10 mm. These strips will not be directly transferred to a cold rolling mill but will undergo two or three hot passes before being wound into a coil. A comparison of the economic feasibility of the DSC process with other near net shape casting processes shows that this process is suitable for small as well as large production rates (up to million tpy/strand) because of the low investment and operating costs. Casting and rolling tests performed in a pilot casting machine and in a casting machine for laboratory purposes show potentially that: the crucial element of the DSC process, the belt caster, is sufficiently stable to attain the required final strip geometry already at the time of casting; the hot shaping envisaged in the DSC concept is sufficient to remove a lack of symmetry that may arise during casting; and the rolling passes envisaged in the DSC concept are necessary and yet at the same time adequate for achieving material properties, for example, sufficiently high r-values for deep drawing grades.

  6. Dispersion modeling of particulate matter containing hexavalent chromium during high winds in southern Iraq.

    PubMed

    Zannetti, Paolo; Daly, Aaron D; Freedman, Frank R

    2015-02-01

    The aim of this paper is to describe a scientific methodology (i.e., the combination of different well-established modeling techniques) and its application to a real case scenario of contaminated dust emissions in high winds. This scenario addresses potential air pollution problems at the water treatment plant (WTP) at Qarmat-Ali, Basra, Iraq, during 2003. Workplace practices at the WTP before 2003 resulted in sodium dichromate contamination in the area. Looting at the site in early 2003 also contributed to this contamination. Individuals who were assigned to provide security at the site in 2003 have claimed adverse health effects caused by exposure to dust containing hexavalent chromium [Cr(VI)]. This report presents our modeling study with respect to these claims in relation to (1) amount of Cr(VI) present in the soil, (2) wind erosion episodes, and (3) possible long-term (e.g., annual average) Cr(VI) concentrations inhaled by different people while at the site. Our modeling approach included (1) the analysis of Cr(VI) soil measurements to assess the degree of contamination in different areas of the plant at different times; (2) the use of DUSTRAN model equations to calculate the emission rate of particulate matter (PM) less than 10 µm in diameter (PM10) during high-wind episodes; (3) the use of the U.S. Environmental Protection Agency (EPA) AERMOD modeling system to estimate Cr(VI) concentrations at the site; and (4) the calculation of modeling results in the form of both contour lines of average Cr(VI) concentrations at the site, and specific concentration values for selected individuals, based upon their recollection of their visits to the site.

  7. High lubricious surface of cobalt-chromium-molybdenum alloy prepared by grafting poly(2-methacryloyloxyethyl phosphorylcholine).

    PubMed

    Kyomoto, Masayuki; Iwasaki, Yasuhiko; Moro, Toru; Konno, Tomohiro; Miyaji, Fumiaki; Kawaguchi, Hiroshi; Takatori, Yoshio; Nakamura, Kozo; Ishihara, Kazuhiko

    2007-07-01

    Osteolysis caused by wear particles from polyethylene in artificial hip joints is of great concern. Various bearing couple combinations, bearing material improvements, and surface modifications have been attempted to reduce such wear particles. With the aim of reducing the wear and developing a novel artificial hip-joint system, we created a highly lubricious metal-bearing material: A 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer was grafted onto the surface of the cobalt-chromium-molybdenum (Co-Cr-Mo) alloy. For ensuring the long-term retention of poly(MPC) on the Co-Cr-Mo alloy, we used a 4-methacryloxyethyl trimellitate anhydride (4-META) intermediate layer and photo-induced graft polymerization technique to create a strong bonding between the Co-Cr-Mo substrate and the poly(MPC) chain via the 4-META layer. The Co-Cr-Mo alloy was pretreated with nitric acid and O(2) plasma to facilitate efficient interaction between the 4-META carboxyl group and the surface hydroxyl group on the Cr oxide passive layer of the Co-Cr-Mo alloy. After MPC grafting, the MPC unit peaks were clearly observed in the Fourier-transform infrared spectroscopy with attenuated total reflection (FT-IR/ATR) and X-ray photoelectron spectroscopy (XPS) spectra of the Co-Cr-Mo surface. Tribological studies with a pin-on-plate machine revealed that surface MPC grafting markedly lowered the friction coefficient. We concluded that the grafted poly(MPC) layer successfully provided high lubricity to the Co-Cr-Mo surface.

  8. Effect of Different Casting Parameters on the Cleanliness of High Manganese Steel Ingots Compared to High Carbon Steel

    NASA Astrophysics Data System (ADS)

    von Schweinichen, Petrico; Chen, Zhiye; Senk, Dieter; Lob, Alexander

    2013-12-01

    The increasing demand for excellent steel properties has led to the creation of new steel grades such as high manganese TWIP and TRIP steels which are scientifically examined in Germany within the international research framework of the SFB 761 "Steel-ab initio." The production of these high-technology products, utilizing mainly the ingot-casting method, leads to new challenges in the prevention of cast defects. At RWTH Aachen University, a systematic investigation of the solidification process as it relates to shrinkage cavity, macrosegregation, cleanliness, and surface imperfections in as-cast ingots is being conducted. A particular attention was devoted to the effects of such casting parameters as superheat, pouring rate, hot top, and stirring conditions on the solidification and cleanliness of low carbon alloyed and high manganese alloyed steels. The experimental results show that rising manganese content leads to a higher amount and larger size of inclusions while rising carbon content enhances the inclusion generation in the same way. It was found that a bottom teeming system combined with an inert gas atmosphere produces the best quality and that if casting is performed with a runner-system, it is important to use a SiO2-free refractory to avoid oxidizing the Mn content of the melt to MnO inclusions by redox-reactions.

  9. New developments on optimizing properties of high-Zn aluminium cast alloys

    NASA Astrophysics Data System (ADS)

    Krajewski, W. K.; Buras, J.; Krajewski, P. K.; Greer, A. L.; Schumacher, P.; Haberl, K.

    2016-07-01

    Foundry alloys with Al-based matrices have a wide range of uses in today's global economy and there is a high demand for castings of Al alloys, including Al-Zn alloys. In this paper, investigations on the grain refinement of high-Zn aluminium cast alloys are presented. Aluminium alloys with relatively high zinc content have a tendency to be coarse-grained, especially in the case of castings with low cooling rates such as are found in sand moulds. The coarse-grained structure degrades the plasticity, specifically the elongation. Therefore, for aluminium alloys of high (10-30 wt.%) zinc content, inoculation is attractive, aiming to break up the primary dendrites of the a-phase solid solution of zinc in aluminium. Such dendrites are the principal microstructural component in these alloys. On the other hand, a finer grain structure usually reduces the damping (e.g. as measured by attenuation of ultrasound) in these alloys. In the present investigations, a binary sand-cast Al-20 wt.% Zn alloy was inoculated with different additions of AlTi3C0.15 (TiCAl) and ZnTi-based master alloys. The sand-cast samples were subjected to mechanical-property measurements (tensile strength and elongation), image analysis to determine grain size, and measurements of the attenuation of 1 MHz ultrasound. It is found that both of the master alloys used cause significant refinement of the a-AlZn primary dendrites and change their morphology from linear-branched to semi-globular, increase the elongation by about 40%, and decrease the attenuation coefficient by about 25% in comparison with the initial alloy without inoculation.

  10. Semi-solid processing of high-chromium tool steel to obtain microstructures without carbide network

    NASA Astrophysics Data System (ADS)

    Jirková, H.; Aišman, D.; Rubešová, K.; Opatová, K.; Mašek, B.

    2017-02-01

    Treatment of high-alloy tool steels that involves transition to the semi-solid state can transform the sharp-edged primary carbides which usually form during solidification. These carbides severely impair toughness and are virtually impossible to eliminate by conventional treatment routes. Upon classical semi-solid processing which dissolves these carbides, the resulting microstructure consists of polyhedral and super-saturated austenite embedded in lamellar austenite-carbide network. This type of microstructure reflects in the mechanical properties, predominantly in material behaviour under tensile loading. Such a network, however, can be removed by appropriate thermomechanical treatment. In the present experiment, various procedures involving heating to the semi-solid state were tested on X210Cr12 tool steel. The feedstock was heated to the temperature range of 1220 – 1280 °C. The heating was followed by procedures involving either water quenching to the forming temperature, room temperature or temperature from the range from 500 °C to 1000 °C followed by reheating to the forming temperature. It was found that the development of the lamellar network strongly depends on the temperature of heating to semi-solid state. Thermomechanical treatment produced microstructures in which the matrix consisted of a mixture of polyhedral austenite grains and the M-A constituent. In addition, the initial lamellar eutectic network was partially or even completely melted and substituted with a mixture of very fine recrystallized austenite grains and precipitates of chromium carbides. Some fine M7C3 carbides were present in the austenitic-martensitic matrix as well. When appropriate processing parameters were chosen, very good mechanical properties were obtained, among them a hardness of 860 HV10.

  11. Formation of high overburden dumps in open-casts

    SciTech Connect

    S.G. Molotilov; V.K. Norri

    2007-09-15

    The specificity of formation of high overburden dumps in opencast excavations and ravines is considered. It is proposed to exercise high dumping and deformation control in piled rocks by using a new dumping complex supporting high efficiency and safety of dumping operations.

  12. Evaluation of Compatibility of ToxCast High-Throughput/High-Content Screening Assays with Engineered Nanomaterials

    EPA Science Inventory

    High-throughput and high-content screens are attractive approaches for prioritizing nanomaterial hazards and informing targeted testing due to the impracticality of using traditional toxicological testing on the large numbers and varieties of nanomaterials. The ToxCast program a...

  13. ToxCast Assay Network (TCAN) Viewer: A Visualization Tool for High-throughput Assay Chemical Data (SOT)

    EPA Science Inventory

    USEPA’s ToxCast program has generated high-throughput bioactivity screening (HTS) data on thousands of chemicals. The ToxCast program has described and annotated the HTS assay battery with respect to assay design and target information (e.g., gene target). Recent stakeholder and ...

  14. Supplementary chromium(III) propionate complex does not protect against insulin resistance in high-fat-fed rats.

    PubMed

    Król, Ewelina; Krejpcio, Zbigniew; Iwanik, Katarzyna

    2014-02-01

    Improper eating habits such as high-fat or high-carbohydrate diets are responsible for metabolic changes resulting in impaired glucose tolerance, hyperinsulinemia, insulin resistance, and ultimately diabetes. Although the essentiality of trivalent chromium for humans has been recently questioned by researchers, pharmacological dosages of this element can improve insulin sensitivity in experimental animals and diabetic subjects. The aim of the study was to assess the preventive potential of the supplementary chromium(III) propionate complex (CrProp) in rats fed a high-fat diet. The experiment was conducted on 32 male Wistar rats divided into four groups and fed the following diets: the control (C, AIN-93G), high-fat diets (HF, 40% energy from fat), and a high-fat diet supplemented with CrProp at dosages of 10 and 50 mg Cr/kg diet (HF + Cr10 and HF + Cr50, respectively). After 8 weeks, high-fat feeding led to an increased body mass, hyperinsulinemia, insulin resistance, a decreased serum urea concentration, accumulation of lipid droplets in hepatocytes, and increased renal Fe and splenic Cu contents. Supplementary CrProp in both dosages did not alleviate these changes but increased renal Cr content and normalized splenic Cu content in high-fat-fed rats. Supplementary CrProp does not prevent the development of insulin resistance in rats fed a high-fat diet.

  15. Effects of chromium and nitrogen content on the microstructures and mechanical properties of as-cast Co-Cr-Mo alloys for dental applications.

    PubMed

    Yoda, Keita; Suyalatu; Takaichi, Atsushi; Nomura, Naoyuki; Tsutsumi, Yusuke; Doi, Hisashi; Kurosu, Shingo; Chiba, Akihiko; Igarashi, Yoshimasa; Hanawa, Takao

    2012-07-01

    The microstructure and mechanical properties of as-cast Co-(20-33)Cr-5Mo-N alloys were investigated to develop ductile Co-Cr-Mo alloys without Ni addition for dental applications that satisfy the requirements of the type 5 criteria in ISO 22674. The effects of the Cr and N contents on the microstructure and mechanical properties are discussed. The microstructures were evaluated using scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD), and electron back-scattered diffraction pattern analysis. The mechanical properties were evaluated using tensile testing. The proof strength and elongation of N-containing 33Cr satisfied the type 5 criteria in ISO 22674. ε-phase with striations was formed in the N-free (20-29)Cr alloys, while there was slight formation of ε-phase in the N-containing (20-29)Cr alloys, which disappeared in N-containing 33Cr. The lattice parameter of the γ-phase increased with increasing Cr content (i.e. N content) in the N-containing alloys, although the lattice parameter remained almost the same in the N-free alloys because of the small atomic radius difference between Co and Cr. Compositional analyses by EDS and XRD revealed that in the N-containing alloys Cr and Mo were concentrated in the cell boundary, which became enriched in N, stabilizing the γ-phase. The mechanical properties of the N-free alloys were independent of the Cr content and showed low strength and limited elongation. Strain-induced martensite was formed in all the N-free alloys after tensile testing. On the other hand, the proof strength, ultimate tensile strength, and elongation of the N-containing alloys increased with increasing Cr content (i.e. N content). Since formation of ε-phase after tensile testing was confirmed in the N-containing alloys the deformation mechanism may change from strain-induced martensite transformation to another form, such as twinning or dislocation slip, as the N content increases. Thus the N

  16. Evaluation and Comparison of High-Level Microwave Oven Disinfection with Chemical Disinfection of Dental Gypsum Casts

    PubMed Central

    Meghashri, K; Kumar, Prasanna; Prasad, D Krishna; Hegde, Rakshit

    2014-01-01

    Background: The aim of this study was to evaluate and compare microwave disinfection with chemical disinfection of dental gypsum casts. Materials and Methods: A total of 120 casts were prepared from a silicone mold using Type III dental stone. Of the 120 casts, 60 casts were contaminated with 1 ml suspension of Staphylococcus aureus and 60 casts were contaminated with 1 ml suspension of Pseudomonas aeruginosa. Then, the casts were disinfected with microwave irradiation and chemical disinfection using the microwave oven and 0.5% sodium hypochlorite. Bacteriologic procedures were performed; the cfu/ml for each cast was calculated as a weighted mean. The results were analyzed using Kruskal-Wallis test and Mann-Whitney test. Results: The untreated casts showed Brain heart infusion broth counts of 106 log cfu/ml compared to irradiated and chemically disinfected casts, in which 105 log reduction of cfu/ml was seen. These results satisfied the requirements of current infection control guidelines for the dental laboratory. The results obtained for chemical disinfection were in equivalence with microwave disinfection. Conclusions: Within the limitation of this in vitro study, it was found that microwave disinfection of casts for 5 min at 900 W gives high-level disinfection that complies with the current infection control guidelines for the dental laboratory and microwave disinfection method is an effective and validated method as chemical disinfection. How to cite the article: Meghashri K, Kumar P, Prasad DK, Hegde R. Evaluation and comparison of high-level microwave oven disinfection with chemical disinfection of dental gypsum casts. J Int Oral Health 2014;6(3):56-60 . PMID:25083033

  17. Flexural Strength and Toughness of Austenitic Stainless Steel Reinforced High-Cr White Cast Iron Composite

    NASA Astrophysics Data System (ADS)

    Sallam, H. E. M.; Abd El-Aziz, Kh.; Abd El-Raouf, H.; Elbanna, E. M.

    2013-12-01

    Flexural behavior of high-Cr white cast iron (WCI) reinforced with different shapes, i.e., I- and T-sections, and volume fractions of austenitic stainless steel (310 SS) were examined under three-point bending test. The dimensions of casted beams used for bending test were (50 × 100 × 500 mm3). Carbon and alloying elements diffusion enhanced the metallurgical bond across the interface of casted beams. Carbon diffusion from high-Cr WCI into 310 SS resulted in the formation of Cr-carbides in 310 SS near the interface and Ni diffusion from 310 SS into high-Cr WCI led to the formation of austenite within a network of M7C3 eutectic carbides in high-Cr WCI near the interface. Inserting 310 SS plates into high-Cr WCI beams resulted in a significant improvement in their toughness. All specimens of this metal matrix composite failed in a ductile mode with higher plastic deformation prior to failure. The high-Cr WCI specimen reinforced with I-section of 310 SS revealed higher toughness compared to that with T-section at the same volume fraction. The presence of the upper flange increased the reinforcement efficiency for delaying the crack growth.

  18. Melt-cast organic glasses as high-efficiency fast neutron scintillators

    DOE PAGES

    Carlson, Joseph S.; Feng, Patrick L.

    2016-06-24

    In this work we report a new class of organic-based scintillators that combines several of the desirable attributes of existing crystalline, liquid, and plastic organic scintillators. The prepared materials may be isolated in single crystalline form or melt-cast to produce highly transparent glasses that have been shown to provide high light yields of up to 16,000 photons/MeVee, as evaluated against EJ-200 plastic scintillators and solution-grown trans-stilbene crystals. The prepared organic glasses exhibit neutron/gamma pulse-shape discrimination (PSD) and are compatible with wavelength shifters to reduce optical self-absorption effects that are intrinsic to pure materials such as crystalline organics. In conclusion, themore » combination of high scintillation efficiency, PSD capabilities, and facile scale-up via melt-casting distinguishes this new class of amorphous materials from existing alternatives.« less

  19. Melt-cast organic glasses as high-efficiency fast neutron scintillators

    SciTech Connect

    Carlson, Joseph S.; Feng, Patrick L.

    2016-06-24

    In this work we report a new class of organic-based scintillators that combines several of the desirable attributes of existing crystalline, liquid, and plastic organic scintillators. The prepared materials may be isolated in single crystalline form or melt-cast to produce highly transparent glasses that have been shown to provide high light yields of up to 16,000 photons/MeVee, as evaluated against EJ-200 plastic scintillators and solution-grown trans-stilbene crystals. The prepared organic glasses exhibit neutron/gamma pulse-shape discrimination (PSD) and are compatible with wavelength shifters to reduce optical self-absorption effects that are intrinsic to pure materials such as crystalline organics. In conclusion, the combination of high scintillation efficiency, PSD capabilities, and facile scale-up via melt-casting distinguishes this new class of amorphous materials from existing alternatives.

  20. Eutectic modification in a low-chromium white cast iron by a mixture of titanium, rare earths, and bismuth: Part II. effect on the wear behavior

    NASA Astrophysics Data System (ADS)

    Bedolla-Jacuinde, A.; Aguilar, S. L.; Maldonado, C.

    2005-06-01

    In this work, we studied the wear behavior of a low-Cr white cast iron (WCI) modified with ferrotitanium-rare earths-bismuth (Fe-Ti-RE-Bi) up to 2%. These additions modified the eutectic carbide structure of the alloy from continuous ledeburite into a blocky, less interconnected carbide network. The modified structure was wear tested under pure sliding conditions against a hardened M2 steel counter-face using a load of 250 N. It was observed that wear resistance increased as the modifier admixture increased. The modified structure had smaller more isolated carbides than the WCI with no Fe-Ti-RE-Bi additions. It was observed that large carbides fracture during sliding, which destabilizes the structure and causes degradation in the wear behavior. A transition from abrasive to oxidative wear after 20 km sliding occurred for all alloys. In addition, the modified alloys exhibited higher values of hardness and fracture toughness. These results are discussed in terms of the modified eutectic carbide microstructure.

  1. Ultra-high vacuum compatible induction-heated rod casting furnace

    NASA Astrophysics Data System (ADS)

    Bauer, A.; Neubauer, A.; Münzer, W.; Regnat, A.; Benka, G.; Meven, M.; Pedersen, B.; Pfleiderer, C.

    2016-06-01

    We report the design of a radio-frequency induction-heated rod casting furnace that permits the preparation of polycrystalline ingots of intermetallic compounds under ultra-high vacuum compatible conditions. The central part of the system is a bespoke water-cooled Hukin crucible supporting a casting mold. Depending on the choice of the mold, typical rods have a diameter between 6 mm and 10 mm and a length up to 90 mm, suitable for single-crystal growth by means of float-zoning. The setup is all-metal sealed and may be baked out. We find that the resulting ultra-high vacuum represents an important precondition for processing compounds with high vapor pressures under a high-purity argon atmosphere up to 3 bars. Using the rod casting furnace, we succeeded to prepare large high-quality single crystals of two half-Heusler compounds, namely, the itinerant antiferromagnet CuMnSb and the half-metallic ferromagnet NiMnSb.

  2. Ultra-high vacuum compatible induction-heated rod casting furnace.

    PubMed

    Bauer, A; Neubauer, A; Münzer, W; Regnat, A; Benka, G; Meven, M; Pedersen, B; Pfleiderer, C

    2016-06-01

    We report the design of a radio-frequency induction-heated rod casting furnace that permits the preparation of polycrystalline ingots of intermetallic compounds under ultra-high vacuum compatible conditions. The central part of the system is a bespoke water-cooled Hukin crucible supporting a casting mold. Depending on the choice of the mold, typical rods have a diameter between 6 mm and 10 mm and a length up to 90 mm, suitable for single-crystal growth by means of float-zoning. The setup is all-metal sealed and may be baked out. We find that the resulting ultra-high vacuum represents an important precondition for processing compounds with high vapor pressures under a high-purity argon atmosphere up to 3 bars. Using the rod casting furnace, we succeeded to prepare large high-quality single crystals of two half-Heusler compounds, namely, the itinerant antiferromagnet CuMnSb and the half-metallic ferromagnet NiMnSb.

  3. Direct determination of chromium in infant formulas employing high-resolution continuum source electrothermal atomic absorption spectrometry and solid sample analysis.

    PubMed

    Silva, Arlene S; Brandao, Geovani C; Matos, Geraldo D; Ferreira, Sergio L C

    2015-11-01

    The present work proposed an analytical method for the direct determination of chromium in infant formulas employing the high-resolution continuum source electrothermal atomic absorption spectrometry combined with the solid sample analysis (SS-HR-CS ET AAS). Sample masses up to 2.0mg were directly weighted on a solid sampling platform and introduced into the graphite tube. In order to minimize the formation of carbonaceous residues and to improve the contact of the modifier solution with the solid sample, a volume of 10 µL of a solution containing 6% (v/v) H2O2, 20% (v/v) ethanol and 1% (v/v) HNO3 was added. The pyrolysis and atomization temperatures established were 1600 and 2400 °C, respectively, using magnesium as chemical modifier. The calibration technique was evaluated by comparing the slopes of calibration curves established using aqueous and solid standards. This test revealed that chromium can be determined employing the external calibration technique using aqueous standards. Under these conditions, the method developed allows the direct determination of chromium with limit of quantification of 11.5 ng g(-1), precision expressed as relative standard deviation (RSD) in the range of 4.0-17.9% (n=3) and a characteristic mass of 1.2 pg of chromium. The accuracy was confirmed by analysis of a certified reference material of tomato leaves furnished by National Institute of Standards and Technology. The method proposed was applied for the determination of chromium in five different infant formula samples. The chromium content found varied in the range of 33.9-58.1 ng g(-1) (n=3). These samples were also analyzed employing ICP-MS. A statistical test demonstrated that there is no significant difference between the results found by two methods. The chromium concentrations achieved are lower than the maximum limit permissible for chromium in foods by Brazilian Legislation.

  4. Turbine component casting core with high resolution region

    DOEpatents

    Kamel, Ahmed; Merrill, Gary B.

    2014-08-26

    A hollow turbine engine component with complex internal features can include a first region and a second, high resolution region. The first region can be defined by a first ceramic core piece formed by any conventional process, such as by injection molding or transfer molding. The second region can be defined by a second ceramic core piece formed separately by a method effective to produce high resolution features, such as tomo lithographic molding. The first core piece and the second core piece can be joined by interlocking engagement that once subjected to an intermediate thermal heat treatment process thermally deform to form a three dimensional interlocking joint between the first and second core pieces by allowing thermal creep to irreversibly interlock the first and second core pieces together such that the joint becomes physically locked together providing joint stability through thermal processing.

  5. Application of high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for determination of chromium compounds in the air at the workplace.

    PubMed

    Stanislawska, Magdalena; Janasik, Beata; Wasowicz, Wojciech

    2013-12-15

    The toxicity and bioavailability of chromium species are highly dependable on the form or species, therefore determination of total chromium is insufficient for a complete toxicological evaluation and risk assessment. An analytical method for determination of soluble and insoluble Cr (III) and Cr (VI) compounds in welding fume at workplace air has been developed. The total chromium (Cr) was determined by using quadruple inductively coupled plasma mass spectrometry (ICP-MS) equipped with a dynamic reaction cell (DRC(®)). Soluble trivalent and hexavalent chromium compounds were determined by high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). A high-speed, reversed-phase CR C8 column (PerkinElmer, Inc., Shelton, CT, USA) was used for the speciation of soluble Cr (III) and soluble Cr (VI). The separation was accomplished by interaction of the chromium species with the different components of the mobile phase. Cr (III) formed a complex with EDTA, i.e. retained on the column, while Cr (VI) existed in the solutions as dichromate. Alkaline extraction (2% KOH and 3% Na2CO3) and anion exchange column (PRP-X100, PEEK, Hamilton) were used for the separation of the total Cr (VI). The results of the determination of Cr (VI) were confirmed by the analysis of the certified reference material BCR CRM 545 (Cr (VI) in welding dust). The results obtained for the certified material (40.2±0.6 g kg(-1)) and the values recorded in the examined samples (40.7±0.6 g kg(-1)) were highly consistent. This analytical method was applied for the determination of chromium in the samples in the workplace air collected onto glass (Whatman, Ø 37 mm) and membrane filters (Sartorius, 0.8 μm, Ø 37 mm). High performance liquid chromatography with inductively coupled plasma mass spectrometry is a remarkably powerful and versatile technique for determination of chromium species in welding fume at workplace air.

  6. Secondary Al-Si-Mg High-pressure Die Casting Alloys with Enhanced Ductility

    NASA Astrophysics Data System (ADS)

    Bösch, Dominik; Pogatscher, Stefan; Hummel, Marc; Fragner, Werner; Uggowitzer, Peter J.; Göken, Mathias; Höppel, Heinz Werner

    2015-03-01

    Al-Si-Mg-based secondary cast alloys are attractive candidates for thin-walled high-pressure die castings for applications in the transport industry. The present study investigates the effect of manganese additions at high cooling rates on microstructure, mechanical properties, and on the dominating fracture mechanisms of alloy AlSi10Mg with an elevated iron concentration. Systematic variations of the Mn content from 0.20 to 0.85 wt pct at a constant Fe content of 0.55 wt pct illustrate the key changes in type, phase fraction, and shape of the Fe-containing intermetallic phases, and the corresponding influence on the alloy's ductility. For high-pressure die casting (HPDC), an optimal range of the Mn content between 0.40 and 0.60 wt pct, equivalent to a Mn/Fe ratio of approximately 1, has been identified. At these Mn and Fe contents, the high cooling rates obtained in HPDC result in the formation of fine and homogeneously distributed α-Al15(Fe,Mn)3Si2 phase, and crack initiation is transferred from AlFeSi intermetallics to eutectic silicon. The study interprets the microstructure-property relationship in the light of thermodynamic calculations which reveal a significant increase in undercooling of the α-Al15(Fe,Mn)3Si2 phase with increased Mn content. It concludes that the interdependence of the well-defined Mn/Fe ratio and the high cooling rate in HPDC can generate superior ductility in secondary AlSi10Mg cast alloys.

  7. The effects of chromium complex and level on glucose metabolism and memory acquisition in rats fed high-fat diet.

    PubMed

    Sahin, Kazim; Tuzcu, Mehmet; Orhan, Cemal; Agca, Can A; Sahin, Nurhan; Guvenc, Mehmet; Krejpcio, Zbigniew; Staniek, Halina; Hayirli, Armagan

    2011-11-01

    Conditions in which glucose metabolism is impaired due to insulin resistance are associated with memory impairment. It was hypothesized that supplemental chromium (Cr) may alleviate insulin resistance in type 2 diabetes and consequently improve memory acquisition, depending upon its source and level. In a complete randomized design experiment, male Wistar rats (n=60; weighing 200-220 g) were fed either normal (8%, normal diet (ND)) or high-fat (40%, high-fat diet (HFD)) diet and supplemented with Cr as either chromium-glycinate (CrGly) or chromium-acetate (CrAc) at doses of 0, 40, or 80 μg/kg body weight (BW) via drinking water from 8 to 20 weeks of age. Feeding HFD induced type 2 diabetes, as reflected by greater glucose/insulin ratio (2.98 vs. 2.74) comparing to feeding ND. Moreover, HFD rats had greater BW (314 vs. 279 g) and less serum (53 vs. 68 μg/L) and brain (14 vs. 24 ng/g) Cr concentrations than ND rats. High-fat diet caused a 32% reduction in expressions of glucose transporters 1 and 3 (GLUTs) in brain tissue and a 27% reduction in mean percentage time spent in the target quadrant and a 38% increase in spatial memory acquisition phase (SMAP) compared with ND. Compared with supplemental Cr as CrAc, CrGly was more effective to ameliorate response variables (i.e., restoration of tissue Cr concentration, enhancement of cerebral GLUTs expressions, and reduction of the glucose/insulin ratio and SMAP) in a dose-response manner, especially in rats fed HFD. Supplemental Cr as CrGly may have therapeutic potential to enhance insulin action and alleviate memory acquisition in a dose-dependent manner, through restoring tissue Cr reserve and enhancing cerebral GLUTs expressions.

  8. High temperature reflectance of hyperpure slip cast silica. [for Outer Planet Entry Probe reflective heat shields

    NASA Technical Reports Server (NTRS)

    Dillow, C. F.; Schmitt, R. J.; Blome, J. C.

    1976-01-01

    An experimental program to optically characterize hyperpure slip cast silica at elevated temperatures is described. This sintered ceramic material is being used in the development of a reflective heat shield for the Outer Planet Entry Probe. A unique high temperature integrating sphere reflectometer is described and reflectance data in the spectral range 0.23-2.3 micron are presented at temperatures up to 1427 C in air and helium environments. Kubelka-Munk (K-M) scattering and absorptance coefficients (K and S), using the Reichman extension of the K-M theory, are presented as is a unique method of obtaining K and S from the Reichman equations using only reflectance data. The hyperpure slip cast silica material was found to retain its high diffuse reflectance at temperatures up to 1204 C, with slight degradation occurring at higher temperatures.

  9. Flexible high power-per-weight perovskite solar cells with chromium oxide-metal contacts for improved stability in air

    NASA Astrophysics Data System (ADS)

    Kaltenbrunner, Martin; Adam, Getachew; Głowacki, Eric Daniel; Drack, Michael; Schwödiauer, Reinhard; Leonat, Lucia; Apaydin, Dogukan Hazar; Groiss, Heiko; Scharber, Markus Clark; White, Matthew Schuette; Sariciftci, Niyazi Serdar; Bauer, Siegfried

    2015-10-01

    Photovoltaic technology requires light-absorbing materials that are highly efficient, lightweight, low cost and stable during operation. Organolead halide perovskites constitute a highly promising class of materials, but suffer limited stability under ambient conditions without heavy and costly encapsulation. Here, we report ultrathin (3 μm), highly flexible perovskite solar cells with stabilized 12% efficiency and a power-per-weight as high as 23 W g-1. To facilitate air-stable operation, we introduce a chromium oxide-chromium interlayer that effectively protects the metal top contacts from reactions with the perovskite. The use of a transparent polymer electrode treated with dimethylsulphoxide as the bottom layer allows the deposition--from solution at low temperature--of pinhole-free perovskite films at high yield on arbitrary substrates, including thin plastic foils. These ultra-lightweight solar cells are successfully used to power aviation models. Potential future applications include unmanned aerial vehicles--from airplanes to quadcopters and weather balloons--for environmental and industrial monitoring, rescue and emergency response, and tactical security applications.

  10. Flexible high power-per-weight perovskite solar cells with chromium oxide-metal contacts for improved stability in air.

    PubMed

    Kaltenbrunner, Martin; Adam, Getachew; Głowacki, Eric Daniel; Drack, Michael; Schwödiauer, Reinhard; Leonat, Lucia; Apaydin, Dogukan Hazar; Groiss, Heiko; Scharber, Markus Clark; White, Matthew Schuette; Sariciftci, Niyazi Serdar; Bauer, Siegfried

    2015-10-01

    Photovoltaic technology requires light-absorbing materials that are highly efficient, lightweight, low cost and stable during operation. Organolead halide perovskites constitute a highly promising class of materials, but suffer limited stability under ambient conditions without heavy and costly encapsulation. Here, we report ultrathin (3 μm), highly flexible perovskite solar cells with stabilized 12% efficiency and a power-per-weight as high as 23 W g(-1). To facilitate air-stable operation, we introduce a chromium oxide-chromium interlayer that effectively protects the metal top contacts from reactions with the perovskite. The use of a transparent polymer electrode treated with dimethylsulphoxide as the bottom layer allows the deposition-from solution at low temperature-of pinhole-free perovskite films at high yield on arbitrary substrates, including thin plastic foils. These ultra-lightweight solar cells are successfully used to power aviation models. Potential future applications include unmanned aerial vehicles-from airplanes to quadcopters and weather balloons-for environmental and industrial monitoring, rescue and emergency response, and tactical security applications.

  11. Inelastic properties of high-strength cast iron with strained graphite

    NASA Astrophysics Data System (ADS)

    Petrushin, G. D.; Petrushina, A. G.; Golovin, S. A.

    2011-05-01

    The effect of the habit of graphite inclusions of deformed high-strength cast iron on the dissipation of the energy of fluctuations in the amplitude-independent and dependent ranges of internal friction is studied. The values of the factor of shape and of the degree of deformation of graphite inclusions in deformed iron are computed. A mathematical model predicting the effect of plastic deformation of graphite inclusions on the characteristics of the dissipation of energy in grayed iron is suggested.

  12. Fatigue behaviour of friction stir processed AZ91 magnesium alloy produced by high pressure die casting

    SciTech Connect

    Cavaliere, P. . E-mail: pasquale.cavaliere@unile.it; De Marco, P.P.

    2007-03-15

    The room temperature fatigue properties of AZ91 magnesium alloy produced by high pressure die casting (HPDC) as cast, heat treated, friction stir processed (FSP) and FSP and heat treated were studied. The fatigue properties of the material were evaluated for the HPDC magnesium alloy in the as-received state and after a solution treatment at 415 deg. C for 2 h and an ageing treatment at 220 deg. C for 4 h. The heat treatment resulted in a significant increase in the fatigue properties of the HPDC material, while no significance influence of heat treatment was recorded in the FSP condition. The morphology of fracture surfaces was examined by employing a field emission gun scanning electron microscope (FEGSEM)

  13. Low-strain plasticity in a high pressure die cast Mg-Al alloy

    NASA Astrophysics Data System (ADS)

    Vanna Yang, K.; Cáceres, C. H.; Nagasekhar, A. V.; Easton, M. A.

    2012-03-01

    The Kocks-Mecking method was used to compare the strain-hardening behavior at low strains of high pressure die cast Mg-9 mass% Al alloy and gravity cast fine grained pure Mg specimens. The alloy specimens exhibited a rounded flow curve in contrast with the pure metal's for which macroscopic yielding occurred at a well-defined stress. Microhardness mapping of the cross-section of an alloy specimen showed a surface layer, or skin, with hardness values ˜20 HV above those of the centre or core region. On the assumption that the core strain hardens at the same rate as the pure Mg specimen, it was estimated that ˜20% of the alloy specimen's cross-section was still elastic when the core reached full plasticity. The micromechanics of the elasto-plastic transition in the alloy specimens are discussed.

  14. Microstructural study of surface melted and chromium surface alloyed ductile iron

    NASA Astrophysics Data System (ADS)

    Sohi, M. Heydarzadeh; Ebrahimi, M.; Ghasemi, H. M.; Shahripour, A.

    2012-07-01

    In this study, ductile iron was surface melted and chromium surface alloyed via pre-placing of ferrochromium powder with different thicknesses and subsequently surface melting by tungsten inert gas (TIG) process. Optical and scanning electron microscopy, as well as micro-hardness testing and X-ray diffraction analysis were used for characterization of the treated samples. Surface melting and chromium surface alloying resulted in formation of ledeburitic structure and high chromium white cast iron in the treated layers, respectively. It was also noticed that hardness of the treated layers was considerably higher than that of the base material. Increasing thickness of ferrochromium layer increased the amount of M7C3 carbides and hardness of the alloyed layer.

  15. Speciation, Dissolution, and Redox Reactions of Chromium Relevant to Pretreatment and Separation of High-Level Tank Wastes

    SciTech Connect

    Clark Sue B.; Dhanpat Rai; Linfeng Rao

    2005-04-20

    Chromium, one of the problematic elements in tank sludges, is considered the most important constituent in defining the total volume of high-level radioactive waste (HLW) glass. Current sludge washing processes (e.g. caustic leaching, 3 M NaOH) are not effective in removing Cr. This inefficient removal would result in production of an unacceptably large volume of HLW glass and thus a tremendous increase in the cost of waste disposal. This proposed research seeks to develop fundamental data for chromium (Cr) reactions that are not currently available but are essential for developing effective methodologies for removing Cr form high-level waste (HLW). Our objectives are to study (1) the dissolution of several solid phases (e.g., CrOOH, Cr2O3(c), Cr(OH)3, and Fe and Cr, binary hydroxides, identified to be important from sludge leaching studies) in highly alkaline solutions and in the presence of other electrolytes (e.g., carbonate, phosphate, sulfate, nitrite), and (2) the effect of the nature of Cr solid phases and aqueous species on their redox reactivity with a variety of potential oxidants (e.g., H2o2, persulfate, O2, and ferrate). This information will provide critical support for developing enhanced pretreatment strategies for removing Cr from HLW and will achieve a major cost reduction HLW disposal.

  16. Modeling of microstructure evolution of magnesium alloy during the high pressure die casting process

    NASA Astrophysics Data System (ADS)

    Wu, Mengwu; Xiong, Shoumei

    2012-07-01

    Two important microstructure characteristics of high pressure die cast magnesium alloy are the externally solidified crystals (ESCs) and the fully divorced eutectic which form at the filling stage of the shot sleeve and at the last stage of solidification in the die cavity, respectively. Both of them have a significant influence on the mechanical properties and performance of magnesium alloy die castings. In the present paper, a numerical model based on the cellular automaton (CA) method was developed to simulate the microstructure evolution of magnesium alloy during cold-chamber high pressure die casting (HPDC) process. Modeling of dendritic growth of magnesium alloy with six-fold symmetry was achieved by defining a special neighbourhood configuration and calculating of the growth kinetics from complete solution of the transport equations. Special attention was paid to establish a nucleation model considering both of the nucleation of externally solidified crystals in the shot sleeve and the massive nucleation in the die cavity. Meanwhile, simulation of the formation of fully divorced eutectic was also taken into account in the present CA model. Validation was performed and the capability of the present model was addressed by comparing the simulated results with those obtained by experiments.

  17. Cytotoxicity and oxidative mechanisms of different forms of chromium.

    PubMed

    Bagchi, Debasis; Stohs, Sidney J; Downs, Bernard W; Bagchi, Manashi; Preuss, Harry G

    2002-10-30

    Chromium exists mostly in two valence states in nature: hexavalent chromium [chromium(VI)] and trivalent chromium [chromium(III)]. Chromium(VI) is commonly used in industrial chrome plating, welding, painting, metal finishes, steel manufacturing, alloy, cast iron and wood treatment, and is a proven toxin, mutagen and carcinogen. The mechanistic cytotoxicity of chromium(VI) is not completely understood, however, a large number of studies demonstrated that chromium(VI) induces oxidative stress, DNA damage, apoptotic cell death and altered gene expression. Conversely, chromium(III) is essential for proper insulin function and is required for normal protein, fat and carbohydrate metabolism, and is acknowledged as a dietary supplement. In this paper, comparative concentration- and time-dependent effects of chromium(VI) and chromium(III) were demonstrated on increased production of reactive oxygen species (ROS) and lipid peroxidation, enhanced excretion of urinary lipid metabolites, DNA fragmentation and apoptotic cell death in both in vitro and in vivo models. Chromium(VI) demonstrated significantly higher toxicity as compared with chromium(III). To evaluate the role of p53 gene, the dose-dependent effects of chromium(VI) were assessed in female C57BL/6Ntac and p53-deficient C57BL/6TSG p53 mice on enhanced production of ROS, lipid peroxidation and DNA fragmentation in hepatic and brain tissues. Chromium(VI) induced more pronounced oxidative damage in multiple target organs in p53 deficient mice. Comparative studies of chromium(III) picolinate and niacin-bound chromium(III), two popular dietary supplements, reveal that chromium(III) picolinate produces significantly more oxidative stress and DNA damage. Studies have implicated the toxicity of chromium picolinate in renal impairment, skin blisters and pustules, anemia, hemolysis, tissue edema, liver dysfunction; neuronal cell injury, impaired cognitive, perceptual and motor activity; enhanced production of hydroxyl

  18. Development of analytical procedures for determination of total chromium by quadrupole ICP-MS and high-resolution ICP-MS, and hexavalent chromium by HPLC-ICP-MS, in different materials used in the automotive industry.

    PubMed

    Séby, F; Gagean, M; Garraud, H; Castetbon, A; Donard, O F X

    2003-10-01

    A European directive was recently adopted limiting the use of hazardous substances such as Pb, Hg, Cd, and Cr(VI) in vehicle manufacturing. From July 2003 a maximum of 2 g Cr(VI) will be authorised per vehicle in corrosion-preventing coatings of key components. As no standardised procedures are available to check if produced vehicles are in agreement with this directive, the objective of this work was to develop analytical procedures for total chromium and Cr(VI) determination in these materials. The first step of this study was to optimise digestion procedures for total chromium determination in plastic and metallic materials by inductively coupled plasma mass spectrometry (ICP-MS). High resolution (HR) ICP-MS was used to examine the influence of polyatomic interferences on the detection of the (52)Cr(+) and (53)Cr(+) isotopes. If there was strong interference with m/ z 52 for plastic materials, it was possible to use quadrupole ICP-MS for m/ z 53 if digestions were performed with HNO(3)+H(2)O(2). This mixture was also necessary for digestion of chromium from metallic materials. Extraction procedures in alkaline medium (NH(4)(+)/NH(3) buffer solution at pH 8.9) assisted by sonication were developed for determining Cr(VI) in four different corrosion-preventing coatings by HPLC-ICP-MS. After optimisation and validation with the only solid reference material certified for its Cr(VI) content (BCR 545; welding dusts), the efficiency of this extraction procedure for screw coatings was compared with that described in the EN ISO 3613 standard generally used in routine laboratories. For coatings comprising zinc and aluminium passivated in depth with chromium oxides the extraction procedure developed herein enabled determination of higher Cr(VI) concentrations. This was also observed for the screw covered with a chromium passivant layer on zinc-nickel. For coating comprising a chromium passivant layer on alkaline zinc the standardized extraction procedure was more efficient

  19. Effect of Shot Peening on the High-Cycle Fatigue Behavior of High-Strength Cast Iron with Nodular Graphite

    NASA Astrophysics Data System (ADS)

    Benam, Amir Sadighzadeh

    2017-01-01

    The effect of shot peening treatment on high-cycle fatigue of high-strength cast iron with globular graphite is studied. The fatigue curves are plotted, the microhardness and the surface roughness are measured. An analysis of fracture surfaces is performed, and the thickness of the hardened layer is determined. The shot peening is shown to affect favorably the fatigue resistance of the iron but to worsen the condition of the surface.

  20. Urinary casts

    MedlinePlus

    ... blood cell (WBC) casts are more common with acute kidney infections. Your provider will tell you more about your results. Risks There are no risks with this test. Alternative Names Hyaline casts; Granular casts; Renal tubular epithelial casts; Waxy casts; Casts in the ...

  1. In-depth study of mold heat transfer for the high speed continuous casting process

    NASA Astrophysics Data System (ADS)

    Jeong, Heetae; Hwang, Jong-Yeon; Cho, Jung-Wook

    2016-03-01

    Mold heat transfer during the commercial high speed continuous casting up to 7 m/min was investigated in order to clarify the influence of various operating conditions such as casting speed, mold flux, mold thickness, thickness and height of mold coated layer and so on. A simple, but practical formula of heat flux has been derived in terms of those operating conditions by analyzing the heat flux data obtained in CEM® (Compact Endless Casting and Rolling Mill) caster based on simplified one dimensional heat transfer model. Especially, impact of mold parameters such as mold thickness, mold coated layer thickness and its height on the heat flux can be linearly expressed in the empirical formula derived. Heat flux ratio (HR), the ratio of the narrow face heat flux to the wide face one, is one of the important indicators to evaluate whether the solidified shell is evenly robust or not. Averaged HR in CEM® caster is around 0.87, which varies according to the caster specifications and operating conditions. It is suggested that the mold taper should be adjusted to maintain the HR as close to 0.87 as possible.

  2. High-Temperature Low-Cycle Fatigue Property of Heat-Resistant Ductile-Cast Irons

    NASA Astrophysics Data System (ADS)

    Kim, Yoon-Jun; Jang, Ho; Oh, Yong-Jun

    2009-09-01

    This study examined the high-temperature degradation behavior of two types of heat-resistant Si-Mo ductile cast iron (Fe-3.4C-3.7Si-0.4Mo and Fe-3.1C-4.5Si-1.0Mo) with particular attention paid to the mechanical properties and overall oxidation resistance. Tension and low-cycle fatigue properties were examined at 600 °C and 800 °C. The mechanical tests and metallographic and fractographic analyses showed that cast iron containing higher Si and Mo contents had a higher tensile strength and longer fatigue life at both temperatures than cast iron with lower levels due to the phase transformations of pearlite and carbide. The Coffin-Manson type equation was used to assess the fatigue mechanism suggesting that the higher Si-Mo alloy was stronger but less ductile than the lower Si-Mo alloy at 600 °C. However, similar properties for both alloys were observed at 800 °C because of softening and oxidation effects. Analysis of the isothermal oxidation behavior at those temperatures showed that mixed Fe2SiO4 layers were formed and the resulting scaling kinetics was much faster for low Si-Mo containing iron. With increasing temperature, subsurface degradation such as decarburization, voids, and cracks played a significant role in the overall oxidation resistance.

  3. Assessment of Computer Simulation Software and Process Data for High Pressure Die Casting of Magnesium

    SciTech Connect

    Sabau, Adrian S; Hatfield, Edward C; Dinwiddie, Ralph Barton; Kuwana, Kazunori; Viti, Valerio; Hassan, Mohamed I; Saito, Kozo

    2007-09-01

    Computer software for the numerical simulation of solidification and mold filling is an effective design tool for cast structural automotive magnesium components. A review of commercial software capabilities and their validation procedures was conducted. Aside form the software assessment, the program addressed five main areas: lubricant degradation, lubricant application, gate atomization, and heat transfer at metal mold interfaces. A test stand for lubricant application was designed. A sensor was used for the direct measurement of heat fluxes during lubricant application and casting solidification in graphite molds. Spray experiments were conducted using pure deionized water and commercial die lubricants. The results show that the sensor can be used with confidence for measuring heat fluxes under conditions specific to the die lube application. The data on heat flux was presented in forms suitable for use in HPDC simulation software. Severe jet breakup and atomization phenomena are likely to occur due to high gate velocities in HPDC. As a result of gate atomization, droplet flow affects the mold filling pattern, air entrapment, skin formation, and ensuing defects. Warm water analogue dies were designed for obtaining experimental data on mold filling phenomena. Data on break-up jet length, break-up pattern, velocities, and droplet size distribution were obtained experimentally and was used to develop correlations for jet break-up phenomena specific to die casting gate configurations.

  4. Stabilized chromium oxide film

    DOEpatents

    Nyaiesh, A.R.; Garwin, E.L.

    1986-08-04

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150A are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  5. Stabilized chromium oxide film

    DOEpatents

    Garwin, Edward L.; Nyaiesh, Ali R.

    1988-01-01

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150.ANG. are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  6. High-capacity adsorption of dissolved hexavalent chromium using amine-functionalized magnetic corn stalk composites.

    PubMed

    Song, Wen; Gao, Baoyu; Zhang, Tengge; Xu, Xing; Huang, Xin; Yu, Huan; Yue, Qinyan

    2015-08-01

    Easily separable amine-functionalized magnetic corn stalk composites (AF-MCS) were employed for effective adsorption and reduction of toxic hexavalent chromium [Cr(VI)] to nontoxic Cr(III). The saturated magnetization of AF-MCS reached 6.2emu/g, and as a result, it could be separated from aqueous solution by a magnetic process for its superparamagnetism. The studies of various factors influencing the sorption behavior indicated that the optimum AF-MCS dosage for Cr(VI) adsorption was 1g/L, and the maximum adsorption capacity was observed at pH 3.0. The chromium adsorption perfectly fitted the Langmuir isotherm model and pseudo second order kinetic model. Furthermore, characterization of AF-MCS was investigated by means of XRD, SEM, TEM, FT-IR, BET, VSM and XPS analysis to discuss the uptake mechanism. Basically, these results demonstrated that AF-MCS prepared in this work has shown its merit in effective removal of Cr(VI) and rapid separation from effluents simultaneously.

  7. Influence of pH on the survival of Dictyosphaerium chlorelloides populations living in aquatic environments highly contaminated with chromium.

    PubMed

    Pereira, María; Bartolomé, M Carmen; Sánchez-Fortún, Sebastián

    2013-12-01

    The accommodation of photosynthetic organisms to adverse conditions, such as pH changes in the aquatic environment, and their response to aquatic pollutants is essential to develop future biosensors. The present study reports the ability of both Cr(VI)-sensitive and tolerant Dyctiosphaerium chlorelloides strains to live in aqueous solutions highly contaminated with hexavalent chromium under varying ranges of pH, by the determination of chromium toxic effects on these strains. Studies of cell growth, photosynthetic quantum yield and gross photosynthesis rate show that both D. chlorelloides strains are able to survive in alkaline and moderately acidified (pH 4.25) aquatic environments. Below this pH value cell populations from both strains exposed for short periods of time to Cr(VI) showed alterations in the three parameters studied. There were no significant differences comparing the response of both strains at pH change in the culture medium. However, Cr(VI)-tolerant strain exhibits a better fit to maintain cell growth than Cr(VI)-sensitive strain when both were subjected to pH 4.25 in the culture medium. The absence of significant differences in photosynthetic activity results for both strains suggests that the lower sensitivity exhibited by Cr(VI)-tolerant strain would be due to cellular morphological changes rather than changes in cellular activity.

  8. High cycle fatigue life improvement of polycrystalline alpha-iron modified by silver, chromium, aluminium, and yttrium ion implantation

    SciTech Connect

    Wang, H.W.; Yang, D.Z.; Shi, W.D.; Patu, S.

    1995-06-15

    Body-centered cubic (bcc) metals are at least of parallel significance to fcc ones. Work on bcc metal`s fatigue modification by ion implantation is rare. The asymmetry deformation and high SFE characteristics in the microplasticity of bcc metals make the fatigue process more complex. The authors have chosen polycrystalline alpha-iron as the target metal to be implanted with silver, chromium, aluminium, and yttrium ions, which are mutually immiscible, limited soluble without precipitation, and soluble with precipitation in iron, respectively. This work aims at providing a systematic investigation on different mechanisms dominant in fatigue. This brief report is on the high cycle fatigue (HCF) property improvement by these metallic ion implantations, which is part of a series of reports both on HCF and low cycle fatigue (LCF) modifications by each individual ion implantation.

  9. Effect of Destabilization Heat Treatments on the Microstructure of High-Chromium Cast Iron: A Microscopy Examination Approach

    NASA Astrophysics Data System (ADS)

    Karantzalis, A. E.; Lekatou, A.; Diavati, E.

    2009-11-01

    A 18.22 wt.% Cr white iron has been subjected to various destabilization heat treatments. Destabilization at 800 °C caused gradual precipitation of M23C6 secondary carbide particles with time leading to a gradual increase in the bulk hardness. At 900, 1000, and 1100 °C, an initial sharp increase in bulk hardness with time occurred, reaching a plateau that was followed by a slightly decreasing trend. The combination of martensite formed, stoichiometry, and morphology of the secondary carbides present (mostly M7C3) are responsible for the obtained values of hardness. At 1100 °C, severe dissolution of the secondary carbides and consequent stabilization of the austenitic phase took place. Maximum hardness values were obtained for destabilization at 1000 °C. The correlation between bulk hardness and microstructural features was elaborated.

  10. Updates on EPA’s High-Throughput Exposure Forecast (ExpoCast) Research Project (CPCP)

    EPA Science Inventory

    Recent research advances by the ORD ExpoCast project (CSS Rapid Exposure and Dosimetry) are presented to the computational toxicology community in the context of prioritizing chemicals on a risk-basis using joint ExpoCast and ToxCast predictions. Recent publications by Wambaugh e...

  11. Repeatability of tensile properties in high pressure die-castings of an Al-Mg-Si-Mn alloy

    NASA Astrophysics Data System (ADS)

    Yang, Hailin; Ji, Shouxun; Watson, Douglas; Fan, Zhongyun

    2015-09-01

    High pressure die-castings of an Al-Mg-Si-Mn alloy have been assessed in terms of the repeatability of the mechanical properties including yield strength, ultimate tensile strength and elongation by the normal standard deviations method and by the Weibull statistical model with three parameters. It was found that the round samples had the maximum Weibull modulus, indicating the best repeatability. The machined samples exhibited the second best of Weibull modulus. Among the square samples, the 2 mm and 5 mm thick samples had the lowest and the highest Weibull modulus respectively, indicating that the repeatability for the castings was influenced by the wall thickness. The microstructural uniformity and porosity levels are critical factors in determining the repeatability of the high pressure die-castings. A less segregation in the microstructure could uniform the stress distribution in the die-castings and a less porosity in the casting could reduce the sources for brittle fracture. These improved the repeatability in casting production.

  12. Effect of prior deformation on microstructural development and Laves phase precipitation in high-chromium stainless steel.

    PubMed

    Hsiao, Z-W; Chen, D; Kuo, J-C; Lin, D-Y

    2017-04-01

    This study investigated the influence of deformation on precipitation behaviour and microstructure change during annealing. Here, the prior deformation of high-chromium stainless steel was tensile deformation of 3%, 6% and 10%, and the specimens were then annealed at 700˚C for 10 h. The specimens were subsequently analyzed using backscattered electron image and electron backscattering diffraction measurements with SEM. Compared with the deformation microstructure, the grains revealed no preferred orientation. The precipitates of TiN and NbC were formed homogenously in the grain interior and at grain boundaries after annealing. Fine Laves phase precipitates were observed in grains and along subgrain boundaries as the deformation increased. Furthermore, the volume fraction of Laves phase increased, but the average particle diameter of precipitate was reduced as the deformation increased.

  13. High glucose and ketosis (acetoacetate) increases, and chromium niacinate decreases, IL-6, IL-8, and MCP-1 secretion and oxidative stress in U937 monocytes.

    PubMed

    Jain, Sushil K; Rains, Justin L; Croad, Jennifer L

    2007-10-01

    Elevated blood levels of the proinflammatory cytokines interleukin-6 (IL-6), interleukin-8 (IL-8), and MCP-1 (monocyte chemoattractant protein-1) increase insulin resistance and the risk of cardiovascular disease (CVD). There is no previous study that has examined the effect of ketosis and trivalent chromium on IL-6, IL-8, or MCP-1 secretion in any cell type or in human or animal model. The authors examined the hypothesis that ketosis increases and trivalent chromium decreases the levels of cytokines and oxidative stress in diabetes using a U937 monocyte cell culture model. Cells were cultured with control, high glucose (HG), and acetoacetate (AA) in the absence or presence (0.5-10 microM) of CrCl(3), chromium picolinate (Cr-P), or chromium niacinate (Cr-N) at 37 degrees C for 24 h. The data show a significant stimulation of IL-6, IL-8, and MCP-1 secretion and an increase in oxidative stress in cells treated with HG or AA. The effect of HG on cytokine secretion was reduced by Cr-N, and to a lesser extent by CrCl(3) and Cr-P. The effect of HG on oxidative stress was reduced by Cr-N and CrCl 3, but not by Cr-P. Similarly, Cr-N decreased the cytokine secretion in HG + AA-treated cells. Cr-N significantly decreased standard oxidant (H(2)O(2)) induced cytokine secretion, which suggests that reduction of cytokine secretion by Cr-N is in part mediated by its antioxidative effect. In a cell culture model, Cr-N appears to be the most effective form of chromium in inhibiting oxidative stress and proinflammatory cytokine secretion by monocytes. This study suggests that chromium niacinate supplementation may be useful in reducing vascular inflammation and the risk of CVD in diabetes.

  14. High Wear Resistance of White Cast Iron Treated by Novel Process: Principle and Mechanism

    NASA Astrophysics Data System (ADS)

    Jia, Xiaoshuai; Zuo, Xunwei; Liu, Yu; Chen, Nailu; Rong, Yonghua

    2015-12-01

    Based on microstructure desired, a novel process is proposed to treat Fe-2.4C-12.0Cr (mass pct) white cast iron balls, that is, destabilizing heat treatment following multicycle quenching and sub-critical treatment (De-MQ-Sct) process, and such a complex process is simply performed by alternate water quenching and air cooling. For comparison, the white cast iron balls also were treated by conventional normalization (NOR) process and Oil-quenching process, respectively. The partitioning of carbon from martensite to retained austenite during De-MQ-Sct process promotes the interaction between carbide precipitation and martensitic transformation, while this interaction is a unique effect only produced by multicycle quenching linking destabilizing and sub-critical treatments, which leads to more and finer secondary carbides and more carbon-enriched austenite in De-MQ-Sct sample than those in NOR or Oil-quenching sample. The average hardness of 60 HRC and impact toughness of 12.6 J/cm2 are obtained in De-MQ-Sct white cast iron balls, which are much higher than those in NOR and Oil-quenching ones. The wear behaviours measured by pin-on-disk wear tests indicate that the weight loss of De-MQ-Sct sample is only about one third of the NOR sample and one half of the Oil-quenching sample. Microstructural characterization reveals that high wear resistance related to hardness and toughness of the De-MQ-Sct balls are mainly attributed to the considerable fine secondary carbides and stable carbon-enriched retained austenite.

  15. Microstructure evolution of eutectic Al-Cu strips by high-speed twin-roll strip casting process

    NASA Astrophysics Data System (ADS)

    Sahoo, Seshadev; Ghosh, Sudipto

    2015-10-01

    In the present investigation, microstructural evolutions of functionally graded eutectic Al-Cu strips prepared by high-speed twin-roll strip caster at different casting speeds and liquid melt superheats were studied. The as-cast sample was subjected to scanning electron microscope to study the evolution of microstructure of the strip at different casting speeds and liquid melt superheats. At different casting speeds, non-equilibrium eutectic structure observed on the Al-Cu eutectic strip consists of lamellar as well as wavy structure with a distinct boundary. The lamellar microstructure consists of alternating layers of well-bonded α-Al phase and θ-Al2Cu phase. The globular flowery structure within the eutectic matrix was observed on the strip at different liquid melt superheats. The microhardness of the as-cast strip was studied by Vickers hardness tester, and it was found that hardness value increases with increasing casting speed and decreases with increasing liquid melt superheat.

  16. Development of Cast Alumina-forming Austenitic Stainless Steel Alloys for use in High Temperature Process Environments

    SciTech Connect

    Muralidharan, Govindarajan; Yamamoto, Yukinori; Brady, Michael P; Pint, Bruce A; Pankiw, Roman; Voke, Don

    2015-01-01

    There is significant interest in the development of alumina-forming, creep resistant alloys for use in various industrial process environments. It is expected that these alloys can be fabricated into components for use in these environments through centrifugal casting and welding. Based on the successful earlier studies on the development of wrought versions of Alumina-Forming Austenitic (AFA) alloys, new alloy compositions have been developed for cast products. These alloys achieve good high-temperature oxidation resistance due to the formation of protective Al2O3 scales while multiple second-phase precipitation strengthening contributes to excellent creep resistance. This work will summarize the results on the development and properties of a centrifugally cast AFA alloy. This paper highlights the strength, oxidation resistance in air and water vapor containing environments, and creep properties in the as-cast condition over the temperature range of 750°C to 900°C in a centrifugally cast heat. Preliminary results for a laboratory cast AFA composition with good oxidation resistance at 1100°C are also presented.

  17. Ductile and High Strength White Cast Iron of Ultrafine Interconnected Network Morphology

    NASA Astrophysics Data System (ADS)

    Ho, C. M.; Kui, H. W.

    2011-12-01

    Fe100- x C x melts ( x = 18 to 24) can be cast under B2O3 flux into solids of interconnected network morphology, with a wavelength in the submicron range. There are two major constituent subnetworks, which are a brittle Fe3C subnetwork and a ductile αFe subnetwork. The Fe100- x C x network alloys, therefore, are white cast iron of novel microstructure. Fe100- x C x specimens of x = 18 to 21 are ductile and the yield strength can be as large as ~3200 MPa. Fe100- x C x specimens of x = 22 to 24 are in the regime of a ductile-to-brittle transition. The compressive strength is high, at ~2700 MPa. Microstructural analysis indicates that the ultrafine network morphology and the ductile αFe subnetwork are responsible for the ductility exhibited in Fe100- x C x network alloys of x = 17 to 21. They are also responsible for the high compressive strength in Fe100- x C x network alloys of x = 22 to 24.

  18. Interpretation of high-temperature tensile properties by thermodynamically calculated equilibrium phase diagrams of heat-resistant austenitic cast steels

    NASA Astrophysics Data System (ADS)

    Jung, Seungmun; Sohn, Seok Su; Choi, Won-Mi; Lee, Byeong-Joo; Oh, Yong-Jun; Jang, Seongsik; Lee, Sunghak

    2017-01-01

    High-temperature tensile properties of three heat-resistant austenitic cast steels fabricated by varying W, Mo, and Al contents were interpreted by thermodynamically calculated equilibrium phase diagrams of austenite, ferrite, and carbides as well as microstructural analyses. A two-step calculation method was adopted to cast steel microstructures below the liquid dissolution temperature because the casting route was not an equilibrium state. Thermodynamically calculated fractions of equilibrium phases were well matched with experimentally measured fractions. Ferrites existed at room and high temperatures in both equilibrium phase diagrams and actual microstructures, which has not been reported in previous researches on austenitic cast steels. In the W2Mo1Al1 steel, 38% and 12% of ferrite existed in the equilibrium phase diagram and actual microstructure, respectively, and led to the void initiation and coalescence at ferrites and consequently to the serious deterioration of high-temperature strengths. The present equilibrium phase diagrams, besides detailed microstructural analyses, effectively evaluated the high-temperature performance by estimating high-temperature equilibrium phases, and provided an important idea on whether ferrite were formed or not in the heat-resistant austenitic cast steels.

  19. Near-anode focusing phenomenon caused by the high anolyte concentration in the electrokinetic remediation of chromium(VI)-contaminated soil.

    PubMed

    Li, Dong; Xiong, Zhen; Nie, Yang; Niu, Yuan-Yuan; Wang, Li; Liu, Yuan-Yuan

    2012-08-30

    The effects of the concentration and the low pH value of anolyte on the electrokinetic remediation (EKR) of chromium-contaminated soil were investigated using chromium-spiked kaolin-gypsum soil. Results of visual observation and X-ray fluorescence analysis show that high anolyte concentrations could cause an ion-induced potential gradient well trapping effect on the soil near the anode, and consequently cause a focusing phenomenon (FP) without chemical precipitation. This FP significantly prolonged the remediation duration and reduced chromium removal. The low pH value of soil aggravated the FP, resulting in a quasi-dead zone near the anode caused by the reduction in soil resistance, rather than the adsorption of chromium (VI) ions. The high anolyte concentration also resulted in high energy consumption. The FP and low pH value collectively decreased the energy efficiency by more than 96%. This kind of FP can be predicted via the online monitoring of the potential gradient profiles of the soil between the electrodes in the EKR.

  20. Myoneural necrosis following high-frequency electrical stimulation of the cast-immobilized rabbit hindlimb

    NASA Technical Reports Server (NTRS)

    Friden, J.; Lieber, R. L.; Myers, R. R.; Powell, H. C.; Hargens, A. R.

    1989-01-01

    The morphological and physiological effects of 4 weeks of high-frequency electrical stimulation (1 h/day, 5 days/week) on cast-immobilized rabbit hindlimbs were investigated in the tibialis anterior muscle and peroneal nerve. In 2 out of 6 animals, high-frequency stimulation with immobilization caused muscle fiber death, internalization of muscle fiber nuclei, connective tissue proliferation, inflammatory response, altered fiber size distribution and variable staining intensities. The fast-twitch fibers were predominantly affected. Two of six peripheral nerves subjected to immobilization and stimulation showed severe damage. Tetanic forces were significantly reduced in the affected muscles. Therefore, the immobilization and high-frequency stimulation may be detrimental to myoneural structure and function and, thus, this combination of therapies should be applied conservatively.

  1. CF8C-Plus: A New High Temperature Austenitic Casting for Advanced Power Systems

    SciTech Connect

    Shingledecker, John P; Maziasz, Philip J; Evans, Neal D; Santella, Michael L

    2006-01-01

    A new cast austenitic stainless steel, CF8C plus, has been developed by Oak Ridge National Laboratory and Caterpillar for a wide range of transportation and energy applications. CF8C plus steel has improved high temperature tensile, creep, fatigue, and creep-fatigue properties compared with standard CF8C steel. Changes to the CF8C steel composition, including additions of Mn and N, result in changes to the solidification behaviour and final microstructure of the alloy, which directly relate to the improved mechanical properties. Additionally, CF8C plus is a relatively inexpensive steel which exhibits good castability. The mechanical properties of the alloy have generated significant interest for the production/design of cast components for diesel engine turbochargers and other exhaust components, natural gas reciprocating engines for distributed power, and turbine end covers and casings for land based turbines. In the present paper, the microstructural evolution of CF8C and CF8C plus are presented in more detail, and the mechanical properties of the alloys are compared with each other and other engineering alloys.

  2. Microstructure and Properties of Cast B-Bearing High Speed Steel

    NASA Astrophysics Data System (ADS)

    Fu, Hanguang; Ma, Shengqiang; Hou, Jianqiang; Lei, Yongping; Xing, Jiandong

    2013-04-01

    Microstructure, mechanical properties, and wear resistance of B-bearing high-speed steel (HSS) roll material containing 0.90-1.00% C, 1.3-1.5% B, 0.8-1.5% W, 0.8-1.5% Mo, 4.6-5.0% Cr, 1.0-1.2% V, and 0.15-0.20% Ti were studied by means of the optical microscopy (OM), the scanning electron microscopy (SEM), x-ray diffraction (XRD), hardness, impact toughness, and pin-on-disk abrasion tests. The results showed that as-cast structure of B-bearing HSS consisted of α-Fe-, M23(B,C)6-, M3(B0.7C0.3)-, and M2(B,C)-type borocarbides, a small quantity of retained austenite, and a small amount of TiC. The hardness and impact toughness values of as-cast B-bearing HSS reached 65-67 HRC and 80-85 kJ/cm2, respectively. There were many M23(B,C)6-precipitated phases in the matrix after tempering, and then, with increasing temperature, the amount of precipitated phases increased considerably. Hardness of B-bearing HSS gradually decreased with the increasing tempering temperature, and the change of tempering temperature had no obvious effect on impact toughness. B-bearing HSS tempered at 500 °C has excellent wear resistance, which can be attributed to the effect of boron.

  3. High temperature performance of nickel aluminide castings for furnace fixtures and components

    SciTech Connect

    Orth, J.E.; Sikka, V.K.

    1996-10-01

    Materials are often the key to technological advancement. To remain competitive and create new markets, modern heat treating industries must utilize these technological advances to increase production and process efficiencies. These challenges are frequently met by increasing process temperatures and minimizing down time for maintenance and unscheduled repairs. This requirement has frequently been a challenge in the past since an increase in the process temperature typically results in a decrease in the life of the furnace fixtures and components. Nickel aluminide intermetallic alloys, based on the Ni{sub 3}Al composition and structure, are a new class of materials for use in the heat treating industries. These alloys provide excellent strength at elevated temperatures combined with very good resistance to carburization (in reducing and oxidizing environments) and high temperature oxidation. The mechanical and physical properties of cast nickel aluminide alloys are presented and compared to other commercially available cast and wrought heat resistant alloys. The advances in the development of these alloys are also discussed.

  4. Method for fabricating ceramic filaments and high density tape casting method

    NASA Technical Reports Server (NTRS)

    Collins, Jr., Earl R. (Inventor)

    1990-01-01

    An apparatus and method is disclosed for fabricating mats of ceramic material comprising preparing a slurry of ceramic particles in a binder/solvent, charging the slurry into a vessel, forcing the slurry from the vessel into spinneret nozzles, discharging the slurry from the nozzles into the path of airjets to enhance the sinuous character of the slurry exudate and to dry it, collecting the filaments on a moving belt so that the filaments overlap each other thereby forming a mat, curing the binder therein, compressing and sintering the mat to form a sintered mat, and crushing the sintered mat to produce filament shaped fragments. A process is also disclosed for producing a tape of densely packed, bonded ceramic particles comprising forming a slurry of ceramic particles and a binder/solvent, applying the slurry to a rotating internal molding surface, applying a large centrifugal force to the slurry to compress it and force excess binder/solvent from the particles, evaporating solvent and curing the binder thereby forming layers of bonded ceramic particles and cured binder, and separating the binder layer from the layer of particles. Multilayers of ceramic particles are cast in an analogous manner on top of previously formed layers. When all of the desired layers have been cast the tape is fired to produce a sintered tape. For example, a three-layer tape is produced having outer layers of highly compressed filament shaped fragments of strontium doped lanthanum (LSM) particles and a center layer of yttria stabilized zicronia (YSZ) particles.

  5. Evaluation of food-relevant chemicals in the ToxCast high ...

    EPA Pesticide Factsheets

    There are thousands of chemicals that are directly added to or come in contact with food, many of which have undergone little to no toxicological evaluation. The ToxCast high-throughput screening (HTS) program has evaluated over 1,800 chemicals in concentration-response across ~820 assay endpoints and continues to grow; with all data completely available to the public, this resource serves as a unique opportunity to evaluate the bioactivity of chemicals in vitro. This study investigated the chemical landscape of the food-relevant chemical universe using cheminformatics analyses, and subsequently evaluated the bioactivity of food-relevant chemicals included in the ToxCast HTS program. Initially, a list of 9,437 food-relevant chemicals was compiled by comprehensively mining publicly available sources for direct food additives, food contact substances, indirect food additives, and pesticides. Of these food-relevant chemicals, 4,638 were associated with curated structure definition files amenable to defining physical/chemical features used to generate chemical fingerprints. Clustering was conducted based on the chemical fingerprints using a self-organizing map approach. This revealed that pesticides, food contact substances, and direct food additives generally clustered apart from one another, supporting that these categories reflect not only different uses but also distinct chemistries. Subsequently, 967 of the 9,437 food-relevant chemicals were identified in the T

  6. Effects of Pore Distributions on Ductility of Thin-Walled High Pressure Die-Cast Magnesium

    SciTech Connect

    Choi, Kyoo Sil; Li, Dongsheng; Sun, Xin; Li, Mei; Allison, John

    2013-06-01

    In this paper, a microstructure-based three-dimensional (3D) finite element modeling method is adopted to investigate the effects of porosity in thin-walled high pressure die-cast (HPDC) Magnesium alloys on their ductility. For this purpose, the cross-sections of AM60 casting samples are first examined using optical microscope and X-ray tomography to obtain the general information on the pore distribution features. The experimentally observed pore distribution features are then used to generate a series of synthetic microstructure-based 3D finite element models with different pore volume fractions and pore distribution features. Shear and ductile damage models are adopted in the finite element analyses to induce the fracture by element removal, leading to the prediction of ductility. The results in this study show that the ductility monotonically decreases as the pore volume fraction increases and that the effect of ‘skin region’ on the ductility is noticeable under the condition of same local pore volume fraction in the center region of the sample and its existence can be beneficial for the improvement of ductility. The further synthetic microstructure-based 3D finite element analyses are planned to investigate the effects of pore size and pore size distribution.

  7. Development of high-cycle fatigue design curves for a cast aluminum alloy

    NASA Technical Reports Server (NTRS)

    Cooper, R. A.

    1979-01-01

    Life prediction curves for rocket engine pump parts were developed from the results of high-cycle fatigue tests run on cast-aluminum specimens. Notched and smooth specimens were cyclically tested at different mean stress levels at -320 F (78 K). The notch size and mean stress enveloped the design operating conditions. Local stress computed in the groove of the notched specimen was used to represent its fatigue strength. The von Mises criterion was used to determine effective cyclic stresses. The Goodman rule was applied to determine equivalent reversed alternating stresses. The procedure permitted the notched and smooth data sets to each be described by a single curve. High-cycle fatigue life curves were provided for the stress state, mean stress, and stress concentration spanned by the data.

  8. Structure and properties of wear-resistant white cast irons

    NASA Astrophysics Data System (ADS)

    Gol'dshtein, Ya. E.; Khismatullina, N. S.; Gol'dshtein, V. A.; Mosina, V. I.

    1986-08-01

    The favorable combined effect of vanadium and chromium on the wear resistance of white cast iron is manifested when their contents are 2...6 and 0...12%, respectively. In this case, the optimal vanadium content in cast iron operating under complex conditions of shock and bending loads can be determined from the equation % V=3+1/3 (% Cr) for a chromium content of not more than 12%.

  9. Short-duration gas nitriding of parts made of high-strength cast iron in the gaz joint-stock company

    NASA Astrophysics Data System (ADS)

    Starostin, V. N.; Pytyaeva, E. I.; Pershina, V. V.

    1998-10-01

    Castings of high-strength iron are use very widely. The range of automobile parts cast from iron with globular graphite is widening. It includes crankshafts and camshafts, flywheels, crankcases, various engine parts, etc. In order to increase hardness of the surface layer, the wear resistance, and the service life of parts made of high-strength cast iron, they are often subjected to nitriding. The present work is aimed at studying the nitriding process for parts made of VCh70 and VCh85 high-strength cast iron.

  10. High-performance epoxy casting resins for SMD-LED packaging

    NASA Astrophysics Data System (ADS)

    Bogner, Georg; Debray, Alexandra; Hoehn, Klaus

    2000-04-01

    In order to come up with high volume SMD-LED production encompassing 1.9 billion devices for current fiscal year we did basic exploratory work to establish structure-processing- property relations for robust epoxy casting resin packages with identical ppm level of one. Bisphenol A-based epoxy casting resins (DGEBA) with acidic ester modified Hexahydrophthalic anhydride (HHPA) hardeners using strictly controlled high-grade raw materials were formulated and thermally transferred to highly transparent polyester networks. For 1 mm thick samples transparency in the 400 to 800 nm region is above 90%. Thermal aging tests for 6 weeks at 120 degrees Celsius reveal only slight discoloration with a color distance of 2. To avoid significant light losses within the LED operating life of 100,000 hrs stress on mechanically sensitive light-emitting chips was reduced by matching glass transition temperature Tg and E-modulus to 115 degrees Celsius and 2,800 MPa, respectively. Total chloride content below 1,000 ppm imply low corrosion potential. Further, resin composition, epoxy-hardener mixing ratio as well as curing profile were adapted to materialize fast curing for demand quantities while introducing effective low stress moieties in the final structure. Low internal stress, superior thermal shock and crack resistance were derived from supreme fracture toughness: KIC and GIC values were 1.350 MPam1/2 and 560 J/m2. With favorable water absorption behavior LED-packages withstand all soldering processes including TTW (through the wave) soldering. Thus, SMD-LEDs fulfill electronic industry standard JEDEC LEVEL 2.

  11. An Investigation into the Accuracy of Two Currently Available Dental Impression Materials in the Construction of Cobalt-Chromium Frameworks for Removable Partial Dentures.

    PubMed

    Dubal, Rajesh Kumar; Friel, Tim; Taylor, Philip D

    2015-03-01

    This study investigated the suitability of irreversible hydrocolloid as an impression material for cobalt-chromium framework construction. Scans of casts derived from (1) alginate and (2) addition-cured polyvinylsiloxane impressions were superposed on to a control. The differences within and between groups were compared at fixed landmarks. The investigation revealed a high degree of scan coincidence within and between groups. However, certain features, such as undercuts, resulted in a lower degree of scan coincidence. Irreversible hydrocolloid appears to be a viable alternative to addition-cured polyvinyl-siloxane as an impression material for cobalt-chromium framework construction.

  12. Grain Coarsening of Cast Magnesium Alloys at High Cooling Rate: A New Observation

    NASA Astrophysics Data System (ADS)

    Ali, Yahia; You, Guoqiang; Pan, Fusheng; Zhang, Ming-Xing

    2017-01-01

    Most studies in the area of grain refinement have always taken for granted that higher cooling rate results in finer grains. However, when microstructural variation of the as-cast Mg with cooling rate was investigated using a specially designed V-shaped copper mold, the results were different. Although fast cooling during solidification led to microstructural refining in pure Mg, grain coarsening was observed at a higher cooling rate in Mg alloys that were inoculation treated with 1.0wt pctZr and 1.4wt pctCaO, and in the Mg-Al binary alloys. It is considered that the grain coarsening at higher cooling rate was attributed to the smaller constitutional undercooling zone formed at fast cooling due to the high temperature gradient in the three Mg alloys. These results can help in redefining the role of cooling rate in the grain refinement process.

  13. 3D CFD Simulation of Horizontal Spin Casting of High Speed Steel Roll

    NASA Astrophysics Data System (ADS)

    Redkin, Konstantin; Balakin, Boris; Hrizo, Christopher; Vipperman, Jeffrey; Garcia, Isaac; University Of Pittsburgh Team; Whemco Collaboration; University Of Bergen Collaboration

    2013-11-01

    The present paper reports some preliminary results on the multiphase modeling of the melt behavior in the horizontal spinning chamber. Three-dimensional (3D) computational fluid dynamics (CFD) model of the high speed steel (HSS) melt was developed in a novel way on the base of volume-of-fluid technique. Preliminary 3D CFD of the horizontal centrifugal casting process showed that local turbulences can take place depending on the geometrical features of the ``feeding'' arm (inlet), its position relative to the chamber, pouring rates and temperatures. The distribution of the melt inside the mold is directly related to the melt properties (viscosity and diffusivity), which depend on the temperature and alloy composition. The predicted liquid properties, used in the modeling, are based on actual chemical composition analysis performed on different heats. Acknowledgement of WHEMCO and United Rolls Inc. for supporting the program. Special appreciation for Kevin Marsden.

  14. In-Situ Observation of Horizontal Centrifugal Casting using a High-Speed Camera

    NASA Astrophysics Data System (ADS)

    Esaka, Hisao; Kawai, Kohsuke; Kaneko, Hiroshi; Shinozuka, Kei

    2012-07-01

    In order to understand the solidification process of horizontal centrifugal casting, experimental equipment for in-situ observation using transparent organic substance has been constructed. Succinonitrile-1 mass% water alloy was filled in the round glass cell and the glass cell was completely sealed. To observe the movement of equiaxed grains more clearly and to understand the effect of movement of free surface, a high-speed camera has been installed on the equipment. The most advantageous point of this equipment is that the camera rotates with mold, so that one can observe the same location of the glass cell. Because the recording rate could be increased up to 250 frames per second, the quality of movie was dramatically modified and this made easier and more precise to pursue the certain equiaxed grain. The amplitude of oscillation of equiaxed grain ( = At) decreased as the solidification proceeded.

  15. On Some Features of Chromium Carbide Diffusion Layer Formation

    NASA Astrophysics Data System (ADS)

    Glowacki, Z.; Kaluba, W.

    1982-05-01

    The formation of chromium carbide diffusion layers on iron-carbon alloys was studied in this investigation. The investigation was carried out on graphite, plain carbon steels, gray cast iron, and white cast iron. The carbide layers were obtained by the powder pack method. To distinguish the effect of iron from the chromizing medium on the layer morphology, high purity iron and chromium powders were used as the components of the powder mixture. The samples were chromized in the temperature range of 870 to 1373 K for five to 1500 minutes. Phase composition of the layers was examined by X-ray diffraction method. To assess chromium and iron distribution in the layers, an electron micro-probe was employed. Microstructure of the layers was examined with the aid of light and electron microscopes. Both replica and thin foil methods were used in this work. The original method of thin foil preparation was used to show the M7C3 layer substructure and to define its crystallographic orientation. It was found that formation of the carbide layer began at temperatures below A1 transformation, when the samples were heated to a normal chromizing temperature. It was proved that M3C appearance in the layer depends on both chromizing temperature and amount of carbon in the alloy. The Fe : Cr ratio in the chromized medium was found to affect the microstructure and thickness of the layers strongly. The needle-shaped grains of the M7C3 layer showed particular crystallographic orientation, i.e., [0001] M7C3 crystallographic direction was perpendicular to the diffusion front. The new data on microstructure of the carbide layers were obtained by thin foil method. The growth direction of the carbide layer was defined, which allowed the suggestion of the diffusion model for the carbide layer formation.

  16. Chromium in rivers impacted by tannery wastes determined by high performance liquid chromatography - inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Pereira de Abreu, M.-H.; Vignati, D.; Dominik, J.

    2003-05-01

    The total chromium concentrations by ICP-MS and HPLC-ICP-MS and the redox chromium species have been determined in rivers impacted by untreated wastes from tanneries at Fès (Morocco). The results obtained by two ICP-MS analysis methods showed significantly different chromium values at m/z 53. The higher values obtained with external calibration, can be attributed to matrix effects, especially ^{37}Cl ^{16}O at m/z 53. This is confirmed on the chromatograms by the presence of a peak at 100s with the anomalous ^{52}Cr/^{53}Cr isotopic ratio. The hexavalent chromium was not detected. Two trivalent chromium monomer species, Cr(OH)(H2O)5^{2+} and Cr(H2O)6^{3+}, were present in low concentrations. We suppose that the major part of chromium occurred as Cr(III) polymeric species which were not retained on the column. These Cr(III) forms are usually complexed with Cl^- or/and SO4^{2-}, used as tanning agents.

  17. Influence of nitrogen admixture to argon on the ion energy distribution in reactive high power pulsed magnetron sputtering of chromium

    NASA Astrophysics Data System (ADS)

    Breilmann, W.; Maszl, C.; Hecimovic, A.; von Keudell, A.

    2017-04-01

    Reactive high power impulse magnetron sputtering (HiPIMS) of metals is of paramount importance for the deposition of various oxides, nitrides and carbides. The addition of a reactive gas such as nitrogen to an argon HiPIMS plasma with a metal target allows the formation of the corresponding metal nitride on the substrate. The addition of a reactive gas introduces new dynamics into the plasma process, such as hysteresis, target poisoning and the rarefaction of two different plasma gases. We investigate the dynamics for the deposition of chromium nitride by a reactive HiPIMS plasma using energy- and time-resolved ion mass spectrometry, fast camera measurements and temporal and spatially resolved optical emission spectroscopy. It is shown that the addition of nitrogen to the argon plasma gas significantly changes the appearance of the localized ionization zones, the so-called spokes, in HiPIMS plasmas. In addition, a very strong modulation of the metal ion flux within each HiPIMS pulse is observed, with the metal ion flux being strongly suppressed and the nitrogen molecular ion flux being strongly enhanced in the high current phase of the pulse. This behavior is explained by a stronger return effect of the sputtered metal ions in the dense plasma above the racetrack. This is best observed in a pure nitrogen plasma, because the ionization zones are mostly confined, implying a very high local plasma density and consequently also an efficient scattering process.

  18. Method of reforming gasoline to raise the octane thereof utilizing low valence chromium composited with non-oxidizing high surface area support

    SciTech Connect

    Gleim, W.K.T.

    1984-05-15

    This invention relates to a method of reforming gasoline to raise the octane number thereof utilizing a novel catalyst comprising a low valence chromium metallic component composited with a non-oxidizing high surface area support. The low valence metallic component is present in divalent form or as a combination of the metallic state and the divalent form-preferably as a chloride and/or bromide. The preferred support is a high surface area coke.

  19. Root uptake and reduction of hexavalent chromium by aquatic macrophytes as assessed by high-resolution X-ray emission.

    PubMed

    Espinoza-Quiñones, Fernando R; Martin, Neiva; Stutz, Guillermo; Tirao, German; Palácio, Soraya M; Rizzutto, Márcia A; Módenes, Aparecido N; Silva, Fernando G; Szymanski, Nayara; Kroumov, Alexander D

    2009-09-01

    Aquatic macrophytes Salvinia auriculata, Pistia stratiotes and Eichhornia crassipes were chosen to investigate the Cr(VI) reduced by root-based biosorption in a chromium uptake experiment, using a high-resolution XRF technique. These plants were grown in hydroponics medium supplied with non-toxic Cr concentrations during a 27-day metal uptake experiment. The high-resolution Cr-Kbeta fluorescence spectra for dried root tissues and Cr reference material (100% Cr, Cr(2)O(3), and CrO(3)) were measured using an XRF spectrometer. For all species of aquatic plant treated with Cr(VI), the energy of the Cr-Kbeta(2,5) line was shifted around 8 eV below the same spectral line identified for the Cr(VI) reference, but it was also near to the line identified for the Cr(III) reference. Moreover, there was a lack of the strong Cr-Kbeta'' line assigned to the Cr(VI) reference material within the Cr(VI)-treated plant spectra, suggesting the reduction of Cr(VI) for other less toxic oxidation states of Cr. As all Cr-Kbeta spectra of root tissue species were compared, the peak energies and lineshape patterns of the Cr-Kbeta(2,5) line are coincident for the same aquatic plant species, when they were treated with Cr(III) and Cr(VI). Based on the experimental evidence, the Cr(VI) reduction process has happened during metal biosorption by these plants.

  20. Chromium Ions Improve Moisure Resistance of Epoxy Resins

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; St. Clair, T. L.; Stoakley, D. M.; Singh, J. J.; Sprinkle, D. R.

    1986-01-01

    Broad spectrum of thermosetting epoxy resins used on commercial and military aircraft, primarily as composite matrices and adhesives. In new technique, chromium-ion containing epoxy with improved resistance to moisture produced where chromium ions believed to prevent absorption of water molecules by coordinating themselves to hydroxyl groups on epoxy chain. Anticipated that improved epoxy formulation useful as composite matrix resin, adhesive, or casting resin for applications on commercial and advanced aircraft. Improvement made without sacrifice in mechanical properties of polymer.

  1. Cerium-Based, Intermetallic-Strengthened Aluminum Casting Alloy: High-Volume Co-product Development

    NASA Astrophysics Data System (ADS)

    Sims, Zachary C.; Weiss, D.; McCall, S. K.; McGuire, M. A.; Ott, R. T.; Geer, Tom; Rios, Orlando; Turchi, P. A. E.

    2016-07-01

    Several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanical properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.

  2. Cerium-based, intermetallic-strengthened aluminum casting alloy: High-volume co-product development

    DOE PAGES

    Sims, Zachary C.; Weiss, David; McCall, S. K.; ...

    2016-05-23

    Here, several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanicalmore » properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.« less

  3. tcpl: The ToxCast Pipeline for High-Throughput Screening ...

    EPA Pesticide Factsheets

    Motivation: The large and diverse high-throughput chemical screening efforts carried out by the US EPAToxCast program requires an efficient, transparent, and reproducible data pipeline.Summary: The tcpl R package and its associated MySQL database provide a generalized platform forefficiently storing, normalizing, and dose-response modeling of high-throughput and high-content chemicalscreening data. The novel dose-response modeling algorithm has been tested against millions of diversedose-response series, and robustly fits data with outliers and cytotoxicity-related signal loss.Availability: The tcpl package is freely available on the Comprehensive R Archive Network under theGPL-2 license. The tcpl R package and its associated MySQL database provide a generalized platform for efficiently storing, normalizing, and dose-response modeling of high-throughput and high-content chemical screening data. The novel dose-response modeling algorithm has been tested against millions of diverse dose-response series, and robustly fits data with outliers and cytotoxicity-related signal loss.

  4. Cerium-based, intermetallic-strengthened aluminum casting alloy: High-volume co-product development

    SciTech Connect

    Sims, Zachary C.; Weiss, David; McCall, S. K.; McGuire, Michael A.; Ott, Ryan T.; Geer, Tom; Rios, Orlando; Turchi, P. A. E.

    2016-05-23

    Here, several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanical properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.

  5. Systematic Microstructural and Corrosion Performance Evaluation of CK-3MCuN and CN-3MN High Molybdenum Stainless Steel Castings

    SciTech Connect

    C.D. Lundin; S. Wen; W. Liu; G. Zhou

    2001-10-01

    High molybdenum austenitic stainless steel castings are widely accepted for their high strength, excellent weldability, and good corrosion resistance over a wide range of temperatures in highly oxidizing aqueous and gaseous media in chemical processing and other environments. With their desirable performance, high molybdenum austenitic stainless steel castings are increasingly applied in industry in a similar manner as wrought materials. In general, cast and wrought stainless and high alloy steels are anticipated to possess equivalent resistance to corrosive media, and they are frequently used in conjunction with each other. However, alloying element segregation usually is more evident in castings than in wrought counterparts. Segregation of alloying elements can lead to the formation of secondary phases, such as sigma. Mechanical properties and especially the corrosion resistance of castings may be affected by the secondary phases. In addition, improper heat treatment procedures c an also lead to the formation of carbides and secondary phases in high alloy and austenitic stainless steels.

  6. Microstructure and surface properties of chromium-doped diamond-like carbon thin films fabricated by high power pulsed magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wu, Zhongzhen; Tian, Xiubo; Gui, Gang; Gong, Chunzhi; Yang, Shiqin; Chu, Paul K.

    2013-07-01

    High power pulsed magnetron sputtering (HPPMS) has attracted much interest due to the large plasma density and high ionization rate of sputtered materials. It is expected to produce a highly ionized C flux from a graphite target but unfortunately, the ionization rate of carbon is still very small and the discharge on a solid carbon target is unstable as well. In this work, a stable discharged chromium target is used in the preparation of chromium-doped diamond-like carbon (Cr-DLC) films in HPPMS in reactive C2H2 gas, but the unstable graphite. The chromium concentration in the Cr-DLC films is limited by surface poisoning due to reactive gas. Less than 2% of Cr is incorporated into the DLC films at C2H2 flow rate of 5 sccm or higher. However, as a result of the high ionization rate of the reactive gas in HPPMS, intense ion bombardment of the substrate is realized. The films show a smooth surface and a dense structure with a large sp3 concentration. As the C2H2 flow increase, the sp3 fraction increase and the sp3 to sp2 ratio increase to 0.75 at a C2H2 flow rate of 10 sccm. Compared to the substrate, the Cr-DLC films have lower friction and exhibit excellent corrosion resistance.

  7. Influence of chromium on the mechanical properties and microstructure of weld metal from a high-strength SMA electrode

    SciTech Connect

    Surian, E.; Trotti, J. ); Cassanelli, A. ); Vedia, L.A. De )

    1994-03-01

    In the present work, the influence of Cr on mechanical properties and microstructure of weld metal from a high-strength SMA electrode is analyzed by considering 12 experimental low-alloy low-hydrogen iron powder AWS E10018, E11018, E12018-M type covered electrodes. These electrodes were manufactured to obtain in the weld deposits Cr contents ranging from 0 to 1.8%, with two different Mn levels for each Cr content, maintaining the amount of other elements at a fixed value. All-weld-metal specimens and production type single V-groove welds were mechanically tested in the as-welded and stress-relieved conditions, and a metallographic study was conducted. Chromium was found to be deleterious to toughness with only a minor influence due to Mn variations. A postweld heat treatment led in all cases to a reduction of toughness. Increasing Cr content in the welds produced a higher proportion of acicular ferrite and a general refinement of the microstructure.

  8. Suppressing the chromium disproportionation reaction in O3-type layered cathode materials for high capacity sodium-ion batteries

    DOE PAGES

    Cao, Ming -Hui; Wang, Yong; Shadike, Zulipiya; ...

    2017-02-14

    Chromium-based layered cathode materials suffer from the irreversible disproportionation reaction of Cr4+ to Cr3+ and Cr6+, which hinders the reversible multi-electron redox of Cr ions in layered cathodes, and limits their capacity and reversibility. To address this problem, a novel O3-type layer-structured transition metal oxide of NaCr1/3Fe1/3Mn1/3O2 (NCFM) was designed and studied as a cathode material. A high reversible capacity of 186 mA h g–1 was achieved at a current rate of 0.05C in a voltage range of 1.5 to 4.2 V. X-ray diffraction revealed an O3 → (O3 + P3) → (P3 + O3'') → O3'' phase-transition pathway formore » NCFM during charge. X-ray absorption, X-ray photoelectron and electron energy-loss spectroscopy measurements revealed the electronic structure changes of NCFM during Na+ deintercalation/intercalation processes. It is confirmed that the disproportionation reaction of Cr4+ to Cr3+ and Cr6+ can be effectively suppressed by Fe3+ and Mn4+ substitution. Lastly, these results demonstrated that the reversible multi-electron oxidation/reduction of Cr ions can be achieved in NCFM during charge and discharge accompanied by CrO6 octahedral distortion and recovery.« less

  9. Chromium Reaction Mechanisms for Speciation using Synchrotron in-Situ High-Temperature X-ray Diffraction.

    PubMed

    Low, Fiona; Kimpton, Justin; Wilson, Siobhan A; Zhang, Lian

    2015-07-07

    We use in situ high-temperature X-ray diffraction (HT-XRD), ex-situ XRD and synchrotron X-ray absorption near edge structure spectroscopy (XANES) to derive fundamental insights into mechanisms of chromium oxidation during combustion of solid fuels. To mimic the real combustion environment, mixtures of pure eskolaite (Cr(3+)2O3), lime (CaO) and/or kaolinite [Al2Si2O5(OH)4] have been annealed at 600-1200 °C in air versus 1% O2 diluted by N2. Our results confirm for the first time that (1) the optimum temperature for Cr(6+) formation is 800 °C for the coexistence of lime and eskolaite; (2) upon addition of kaolinite into oxide mixture, the temperature required to produce chromatite shifts to 1000 °C with a remarkable reduction in the fraction of Cr(6+). Beyond 1000 °C, transient phases are formed that bear Cr in intermediate valence states, which convert to different species other than Cr(6+) in the cooling stage; (3) of significance to Cr mobility from the waste products generated by combustion, chromatite formed at >1000 °C has a glassy disposition that prevents its water-based leaching; and (4) Increasing temperature facilitates the migration of eskolaite particles into bulk lime and enhances the extent to which Cr(3+) is oxidized, thereby completing the oxidation of Cr(3+) to Cr(6+) within 10 min.

  10. Suppressing the chromium disproportionation reaction in O3-type layered cathode materials for high capacity sodium-ion batteries

    SciTech Connect

    Cao, Ming-Hui; Wang, Yong; Shadike, Zulipiya; Yue, Ji-Li; Hu, Enyuan; Bak, Seong-Min; Zhou, Yong-Ning; Yang, Xiao-Qing; Fu, Zheng-Wen

    2017-01-01

    Chromium-based layered cathode materials suffer from the irreversible disproportionation reaction of Cr4+ to Cr3+ and Cr6+, which hinders the reversible multi-electron redox of Cr ions in layered cathodes, and limits their capacity and reversibility. To address this problem, a novel O3-type layer-structured transition metal oxide of NaCr1/3Fe1/3Mn1/3O2 (NCFM) was designed and studied as a cathode material. A high reversible capacity of 186 mA h g-1 was achieved at a current rate of 0.05C in a voltage range of 1.5 to 4.2 V. X-ray diffraction revealed an O3 → (O3 + P3) → (P3 + O3'') → O3'' phase-transition pathway for NCFM during charge. X-ray absorption, X-ray photoelectron and electron energy-loss spectroscopy measurements revealed the electronic structure changes of NCFM during Na+ deintercalation/intercalation processes. It is confirmed that the disproportionation reaction of Cr4+ to Cr3+ and Cr6+ can be effectively suppressed by Fe3+ and Mn4+ substitution. These results demonstrated that the reversible multi-electron oxidation/reduction of Cr ions can be achieved in NCFM during charge and discharge accompanied by CrO6 octahedral distortion and recovery.

  11. TiC reinforced cast Cr steels

    SciTech Connect

    Dogan, O.N.; Hawk, J.A.; Schrems, K.K.

    2006-06-01

    A new class of materials, namely TiC-reinforced cast chromium (Cr) steels, was developed for applications requiring high abrasion resistance and good fracture toughness. The research approach was to modify the carbide structure of commercial AISI 440C steel for better fracture resistance while maintaining the already high abrasion resistance. The new alloys contained 12Cr, 2.5–4.5Ti, and 1–1.5C (wt.%) and were melted in a vacuum induction furnace. Their microstructure was composed primarily of a martensitic matrix with a dispersion of TiC precipitates. Modification of TiC morphology was accomplished through changing the cooling rate during solidification. Wear rates of the TiC-reinforced Cr steels were comparable to that of AISI 440C steel, but the impact resistance was much improved.

  12. High-performance, extrusion-cast explosives with low sensitivity: Interim report No. 2

    SciTech Connect

    Scribner, K.J.; von Holtz, E.; Simpson, R.L.

    1989-01-10

    Lawrence Livermore National Laboratory (LLNL) has developed a class of explosives having both high performance for modern precision munitions and greater safety for reduced vulnerability of launch platforms (ships, planes, ammunition storage sites) to enemy fire or accidents. Known as extrusion-cast explosives (ECXs), they have demonstrated performance levels equivalent to the most powerful now available, but test results indicate they are far less sensitive than the conventional high-energy explosives. Specifically, in a sympathetic-detonation test, ECX that was immediately adjacent to a deliberately-detonated donor charge did not detonate in two of three tests, whereas Comp B did detonate sympathetically in this test. Also, this ECX provided performance equivalent to that of the high-performance explosive LX-14, when tested in the TOW (tube-launched, optically-sighted, wire-guided) missile. This report describes the performance, vulnerability, and processing (at this stage of development) of this class of explosives. 9 refs., 18 figs., 11 tabs.

  13. Microstructure and Creep Behavior of High-Pressure Die-Cast Magnesium Alloy AE44

    NASA Astrophysics Data System (ADS)

    Zhu, S. M.; Nie, J. F.; Gibson, M. A.; Easton, M. A.; Bakke, P.

    2012-11-01

    The microstructure and creep behavior of a high-pressure die-cast AE44 (Mg-4Al-4RE) alloy have been studied. The creep properties were evaluated at 423 K and 448 K (150 °C and 175 °C) under stresses in the range 90 to 110 MPa. The microstructures before and after creep were examined by transmission electron microscopy (TEM). After creep, AE44 exhibits anomalously high stress exponents ( n = 67 at 423 K [150 °C] and n = 41 at 448 K [175 °C]) and stress-dependant activation energies ranging from 221 to 286 kJ/mol. The dislocation substructure developed during creep is characterized by extensive nonbasal slip and isolated but well-defined subgrain boundaries. It is shown that the anomalously high stress exponents cannot be rationalized by the threshold stress approach that is commonly adopted in analyzing the creep behavior of dispersion-strengthened alloys or metal matrix composites. A comparison in creep resistance is also made between AE44 and AE42 (Mg-4Al-2RE).

  14. Fracture Toughness and Fatigue Crack Growth Behavior of As-Cast High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Seifi, Mohsen; Li, Dongyue; Yong, Zhang; Liaw, Peter K.; Lewandowski, John J.

    2015-08-01

    The fracture toughness and fatigue crack growth behavior of two as-vacuum arc cast high-entropy alloys (HEAs) (Al0.2CrFeNiTi0.2 and AlCrFeNi2Cu) were determined. A microstructure examination of both HEA alloys revealed a two-phase structure consisting of body-centered cubic (bcc) and face-centered cubic (fcc) phases. The notched and fatigue precracked toughness values were in the range of those reported in the literature for two-phase alloys but significantly less than recent reports on a single phase fcc-HEA that was deformation processed. Fatigue crack growth experiments revealed high fatigue thresholds that decreased significantly with an increase in load ratio, while Paris law slopes exhibited metallic-like behavior at low R with significant increases at high R. Fracture surface examinations revealed combinations of brittle and ductile/dimpled regions at overload, with some evidence of fatigue striations in the Paris law regime.

  15. High coercivity microcrystalline Nd-rich Nd-Fe-Co-Al-B bulk magnets prepared by direct copper mold casting

    NASA Astrophysics Data System (ADS)

    Zhao, L. Z.; Hong, Y.; Fang, X. G.; Qiu, Z. G.; Zhong, X. C.; Gao, X. S.; Liu, Z. W.

    2016-06-01

    High coercivity Nd25Fe40Co20Al15-xBx (x=7-15) hard magnets were prepared by a simple process of injection casting. Different from many previous investigations on nanocomposite compositions, the magnets in this work contain hard magnetic Nd2(FeCoAl)14B, Nd-rich, and Nd1+ε(FeCo)4B4 phases. The magnetic properties, phase evolution, and microstructure of the as-cast and annealed magnets were investigated. As the boron content increased from 7 to 11 at%, the intrinsic coercivity Hcj of the as-cast magnet increased from 816 to 1140 kA/m. The magnets annealed at 750 °C have shown more regular and smaller grains than the as-cast alloys, especially for the x=11 alloy. The high intrinsic coercivities for the annealed alloys with x=8~11 result from the presence of small-sized grains in the microstructure. The highest Hcj of 1427 kA/m was obtained for the heat treated alloy with x=10. This work provides an alternative approach for preparing fully dense Nd-rich bulk hard magnets with relatively good properties.

  16. Sealing micropores in thin castings

    NASA Technical Reports Server (NTRS)

    Mersereau, G. A.; Nitzschke, G. O.; Ochs, H. L.; Sutch, F. S.

    1981-01-01

    Microscopic pores in thin-walled aluminum castings are sealed by impregnation pretreatment. Technique was developed for investment castings used in hermetically sealed chassic for electronic circuitry. Excessively high leakage rates were previously measured in some chassis.

  17. An Application of Trapped-Air Analysis to Large Complex High-Pressure Magnesium Casting

    SciTech Connect

    Prindiville, J; Lee, S; Gokhale, A

    2004-07-08

    The usual method for simulating die-castings consists of a solidification analysis of the casting process - a computer calculation of heat transfer between the casting and the die components. The use of cyclic simulations, coupled with the geometric accuracy of the finite element method, has advanced this procedure to the point where it is routinely used for reliable prediction of shrinkage defects in die-castings. Filling analysis is also routinely used to get a glimpse of cavity filling and ensures that overflows are at their most effective location. When coupled with heat transfer, a filling analysis is also very effective in demonstrating the effects of heat loss in the fluid and how it consequentially can negatively affect filling.

  18. High-Throughput Screening in ToxCast/Tox21 (FutureToxII)

    EPA Science Inventory

    Addressing safety aspects of drugs and environmental chemicals relies extensively on animal testing. However, the quantity of chemicals needing assessment and challenges of species extrapolation require development of alternative approaches. The EPA’s ToxCast program addresses th...

  19. ToxCast: Using high throughput screening to identify profiles of biological activity

    EPA Science Inventory

    ToxCast, the United States Environmental Protection Agency’s chemical prioritization research program, is developing methods for utilizing computational chemistry and bioactivity profiling to predict potential for toxicity and prioritize limited testing resources (www.epa.gov/toc...

  20. Chromium - blood test

    MedlinePlus

    ... work in the following industries: Leather tanning Electroplating Steel manufacturing Decreased chromium level only occurs in people who receive all of their nutrition by vein (total parenteral nutrition or TPN) and do not get enough chromium.

  1. Chromium in diet

    MedlinePlus

    Chromium deficiency may be seen as impaired glucose tolerance. It occurs in older people with type 2 diabetes and in infants with protein-calorie malnutrition. Taking chromium supplements can help manage these conditions. However, ...

  2. Adverse Reactions to Metal on Polyethylene Implants: Highly destructive lesions related to elevated concentration of Cobalt and Chromium in synovial fluid.

    PubMed

    Eltit, Felipe; Assiri, Ali; Garbuz, Donald; Duncan, Clive; Masri, Bassam; Greidanus, Nelson; Bell, Robert; Sharma, Manju; Cox, Michael; Wang, Rizhi

    2017-03-07

    Adverse local tissue reactions (ALTR) are the primary cause of failure of metal on metal (MoM) hip implants, and fewer but not negligible number cases of non-modular metal on polyethylene (MoP) implants. In this study we analyzed 17 cases of MoP ALTR, and equal number of MoM, by histological observation, cobalt and chromium concentration in serum and synovial fluid and cytokine analysis in ALTR tissues. ALTRs in MoP are highly necrotic, affecting larger areas than MoM ALTRs. Degenerative changes in blood vessels' wall were seen in all MoP ALTRs. The concentration of cobalt and chromium was higher in synovial fluid but lower in serum of MoP patients compared to MoM patients. Elevated concentrations of chemokines were observed in ALTR tissues. We conclude that ALTRs in MoP systems are highly necrotizing lesions that seem to have a similar development to ALTRs in MoM. Alteration of vessels wall seems to have a role in the tissues necrosis, as well as the elevated concentration of cobalt and chromium in synovial fluid of MoP patients. Chemokines may be involved in the pathogenesis of ALTR and constitute possible diagnostic targets. This article is protected by copyright. All rights reserved.

  3. Mechanical Properties of Carbon Fiber-Reinforced Aluminum Manufactured by High-Pressure Die Casting

    NASA Astrophysics Data System (ADS)

    Kachold, Franziska; Singer, Robert

    2016-08-01

    Carbon fiber reinforced aluminum was produced by a specially adapted high-pressure die casting process. The MMC has a fiber volume fraction of 27%. Complete infiltration was achieved by preheating the bidirectional, PAN-based carbon fiber body with IR-emitters to temperatures of around 750 °C. The degradation of the fibers, due to attack of atmospheric oxygen at temperatures above 600 °C, was limited by heating them in argon-rich atmosphere. Additionally, the optimization of heating time and temperature prevented fiber degradation. Only the strength of the outer fibers is reduced by 40% at the most. The fibers in core of fiber body are nearly undamaged. In spite of successful manufacturing, the tensile strength of the MMC is below strength of the matrix material. Also unidirectional MMCs with a fiber volume fraction of 8% produced under the same conditions, lack of the reinforcing effect. Two main reasons for the unsatisfactory mechanical properties were identified: First, the fiber-free matrix, which covers the reinforced core, prevents effective load transfer from the matrix to the fibers. And second, the residual stresses in the fiber-free zones are as high as 100 MPa. This causes premature failure in the matrix. From this, it follows that the local reinforcement of an actual part is limited. The stress distribution caused by residual stresses and by loading needs to be known. In this way, the reinforcing phase can be placed and aligned accordingly. Otherwise delamination and premature failure might occur.

  4. Gypsum-bonded alumina dental investment for high-fusing casting.

    PubMed

    Yan, M; Takahashi, H

    1998-09-01

    In this study, we developed a new gypsum-bonded investment for high-fusing alloys. The investment was composed of gypsum as a binder and alumina as a refractory. Effects of type of alumina powder and gypsum content on characteristics of the gypsum-bonded alumina investment were investigated. Obtained characteristics of this experimental investment were as follows: fluidities ranged from 48.8 to 88.9 mm; setting times ranged from 21.2 to more than 120 minutes; setting expansions ranged from 0.4 to 1.3%; green strengths showed 0.5 to 4.5 MPa; fired strengths ranged from 0.2 to 1.7 MPa; thermal expansions after firing were -1.60 to 2.16%. Thermal expansion occurred because of the chemical reaction between Al2O3 and CaO decomposed from gypsum. These results suggest that this gypsum-bonded alumina investment with 20 or 25 mass% gypsum content possessed the fundamental properties for high-fusing alloy casting.

  5. Control of Crystal Morphology for Mold Flux During High-Aluminum AHSS Continuous Casting Process

    NASA Astrophysics Data System (ADS)

    GUO, Jing; SEO, Myung-Duk; SHI, Cheng-Bin; CHO, Jung-Wook; KIM, Seon-Hyo

    2016-08-01

    In the present manuscript, the efforts to control the crystal morphology are carried out aiming at improving the lubrication of lime-alumina-based mold flux for casting advanced high-strength steel with high aluminum. Jackson α factors for crystals of melt crystallization in multi-component mold fluxes are established and reasonably evaluated by applying thermodynamic databases to understand the crystal morphology control both in lime-alumina-based and lime-silica-based mold fluxes. The results show that Jackson α factor and supercooling are the most critical factors to determine the crystal morphology in a mold flux. Crystals precipitating in mold fluxes appear with different morphologies due to their different Jackson α factors and are likely to be more faceted with higher Jackson α factor. In addition, there is a critical supercooling degree for crystal morphology dendritic transition. When the supercooling over the critical value, the crystals transform from faceted shape to dendritic ones in morphology as the kinetic roughening occurs. Typically, the critical supercooling degrees for cuspidine dendritic transition in the lime-silica-based mold fluxes are evaluated to be between 0.05 and 0.06. Finally, addition of a small amount of Li2O in the mold flux can increase the Jackson α factor and decrease the supercooling for cuspidine precipitation; thus, it is favorable to enhance a faceted cuspidine crystal.

  6. [Bioremediation of chromium (VI) contaminated site by reduction and microbial stabilization of chromium].

    PubMed

    Zheng, Jia-Chuan; Zhang, Jian-Rong; Liu, Xi-Wen; Xu, Qian; Shi, Wei-Lin

    2014-10-01

    Chromium (VI) contaminated soil samples were collected from a chemical plant in Suzhou. Firstly, the reduced soil was prepared by adding reagent (Stone-sulfure reagent) into polluted soil to transfer most chromium (VI) into chromium (III), then a nutrient solution was introduced into the reduced soil, and the stabilized soil was obtained after 60 days culturing. The chromium (VI) content of the three kinds of soil was analyzed. The results showed that the chromium (VI) content in toxicity characteristic leaching liquid (TCLL) dropped by 96. 8% (from 8.26 mg · L(-1) to 0.26 mg · L(-1)), and the total chromium content dropped by 95.7% (from 14.66 mg · L(-1) to 0.63 mg · L(-1)) after bioremediation in 5% nutrient solution. Additionally, the durability of chromium stabilization was tested by potassium permanganate oxidation and sterilization of microbe-treated soil. After oxidation, the chromium (VI) content in TCLL of the reduced soil was increased from 8.26 mg · L(-1) to 14.68 mg · L(-1). However, the content after bioremediation was decreased to 2.68 mg · L(-1). The results of sterilization demonstrated that the death of microbe had no significant effect on the stabilization of chromium. Consequently, the research in this paper demonstrated the feasibility of bioremediation of chromium (VI) polluted soil through reduction followed by stabilization/soilidification, and provided a technique with low cost but high efficiency.

  7. Thoria stability in TD-NiCr at high temperatures in the presence of chromium in solution.

    NASA Technical Reports Server (NTRS)

    Dalal, H.; Grant, N. J.

    1973-01-01

    Study of the influence of chromium in solid solution on the coarsening of ThO2 in TD-NiCr. Comparisons were made of ThO2 coarsening in chromium-free TD-Ni and in TD-NiCr, which is known to be low in Cr2O3 as a contaminant. The results of these comparisons indicate that the presence of 20% Cr in solid solution in a nickel-base alloy does not lead to a more rapid coarsening of ThO2 at temperatures of at least 2462 deg F (1350 deg C).

  8. Characterization of microstructure, texture and magnetic properties in twin-roll casting high silicon non-oriented electrical steel

    SciTech Connect

    Li, Hao-Ze; Liu, Hai-Tao Liu, Zhen-Yu Lu, Hui-Hu; Song, Hong-Yu; Wang, Guo-Dong

    2014-02-15

    An Fe-6.5 wt.% Si-0.3 wt.% Al as-cast sheet was produced by twin-roll strip casting process, then treated with hot rolling, warm rolling and annealing. A detailed study of the microstructure and texture evolution at different processing stages was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. The initial as-cast strip showed strong columnar grains and pronounced < 001 >//ND texture. The hot rolled and warm rolled sheets were characterized by large amounts of shear bands distributed through the thickness together with strong < 110 >//RD texture and weak < 111 >//ND texture. After annealing, detrimental < 111 >//ND texture almost disappeared while beneficial (001)<210 >, (001)<010 >, (115)<5 − 10 1 > and (410) < 001 > recrystallization textures were formed, thus the magnetic induction of the annealed sheet was significantly improved. The recrystallization texture in the present study could be explained by preferred nucleation and grain growth mechanism. - Highlights: • A high silicon as-cast strip with columnar structure was produced. • A thin warm rolled sheet without large edge cracks was obtained. • Microstructure and texture evolution at each stage were investigated. • Beneficial (001)<210 >, (001)<010 >, (410)<001 > recrystallization textures were formed. • The magnetic induction of annealed sheet was significantly improved.

  9. Flower-like self-assembly of gold nanoparticles for highly sensitive electrochemical detection of chromium(VI)

    PubMed Central

    Ouyang, Ruizhuo; Bragg, Stefanie A.; Chambers, James Q.; Xue, Zi-Ling

    2012-01-01

    We report here the fabrication of a flower-like self-assembly of gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) as a highly sensitive platform for ultratrace Cr(VI) detection. Two AuNPs layers are used in the current approach, in which the first is electroplated on the GCE surface as anchors for binding to an overcoated thiol sol-gel film derived from 3-mercaptopropyltrimethoxysilane (MPTS). The second AuNPs layer is then self-assembled on the surface of the sol-gel film, forming flower-like gold nanoelectrodes enlarging the electrode surface. When functionalized by a thiol pyridinium, the fabricated electrode displays a well-defined peak for selective Cr(VI) reduction with an unusually large, linear concentration range of 10–1,200 ng L−1 and a low detection limit of 2.9 ng L−1. In comparison to previous approaches using MPTS and AuNPs on Au electrodes, the current work expands the use of AuNPs to the GCE. Subsequent functionalization of the secondary AuNPs by a thiol pyridinium and adsorption/preconcentration of Cr(VI) lead to the unusually large detection range and high sensitivity. The stepwise preparation of the electrode has been characterized by electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM), and IR. The newly designed electrode exhibits good stability, and has been successfully employed to measure chromium in a pre-treated blood sample. The method demonstrates acceptable fabrication reproducibility and accuracy. PMID:22444528

  10. Frictional and structural characterization of ion-nitrided low and high chromium steels

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1985-01-01

    Low Cr steels AISI 41410, AISI 4340, and high Cr austenitic stainless steels AISI 304, AISI 316 were ion nitrided in a dc glow discharge plasma consisting of a 75 percent H2 - 25 percent N2 mixture. Surface compound layer phases were identified, and compound layer microhardness and diffusion zone microhardness profiles were established. Distinct differences in surface compound layer hardness and diffusion zone profiles were determined between the low and high Cr alloy steels. The high Cr stainless steels after ion nitriding displayed a hard compound layer and an abrupt diffusion zone. The compound layers of the high Cr stainless steels had a columnar structure which accounts for brittleness when layers are exposed to contact stresses. The ion nitrided surfaces of high and low Cr steels displayed a low coefficient of friction with respect to the untreated surfaces when examined in a pin and disk tribotester.

  11. Correlation of microstructure and thermal-fatigue properties of centrifugally cast high-speed steel rolls

    NASA Astrophysics Data System (ADS)

    Kim, Chang Kyu; Park, Jong Il; Ryu, Jae Hwa; Lee, Sunghak

    2004-02-01

    This is a study of thermal-fatigue properties in centrifugally cast high-speed steel (HSS) rolls. The thermal-fatigue mechanism was investigated, with special focus on the roll microstructure and the increase in tensile stress which led the specimens to fracture when it reached the tensile strength. The thermal-fatigue test results indicated that the thermal-fatigue life decreased with increasing maximum temperature of the thermal-fatigue cycle. The results were then interpreted based on the amount of carbides and the cyclic-softening phenomenon associated with the exposed time to elevated temperatures. The coarse intercellular carbides on the specimen surface acted as fatigue-crack initiation sites as they cleaved at a low stress level to form cracks. The roll having the lowest matrix hardness and the smallest amount of intercellular carbides, thus, showed better thermal fatigue properties than the other rolls. For the improvement of the thermal-fatigue properties of the rolls, this study suggests a homogeneous distribution of carbides by reducing the carbide segregation formed along the solidification cell boundary and by optimizing the roll compositions.

  12. Quantitative Characterization of Inclusions in Continuously Cast High-Carbon Steel

    NASA Astrophysics Data System (ADS)

    Faraji, Masoumeh; Wilcox, David P.; Thackray, Richard; Howe, Andrew A.; Todd, Iain; Tsakiropoulos, Panos

    2015-12-01

    Existing standards for the characterization of the size, morphology, chemistry, and distribution of inclusions in steels using different techniques are briefly reviewed in this work. Strengths and shortfalls of different methods are discussed, and a combination of different criteria is used to quantitatively characterize the inclusions in a continuously cast high-carbon steel. It is shown that the main elements in the inclusions for the studied steel were Mn, S, Ti, Al, and oxygen and that alongside MnS and some Al2O3 inclusions many non-metallic inclusions appeared in complex forms, consisting of silicates, sulfides, and different types of oxides. Duplex inclusions, mainly cores of Al2O3, or SiO2 surrounded by MnS were the most common complex multiphase inclusions in this steel. An industrial approach was used to classify the inclusions into thirteen different oxide types. Based upon this approach, data are presented according to the chemistry of inclusions using diagrams featuring different quantitative parameters. Furthermore, it is shown that the number of oxides per unit area and the size of oxides, respectively, decreased and increased with increasing distance from the surface of the bloom which had solidified at the highest cooling rate.

  13. Surface hardening of a ductile-cast iron roll using high-energy electron beams

    NASA Astrophysics Data System (ADS)

    Suh, Dongwoo; Lee, Sunghak; Koo, Yangmo; Kwon, Soon-Ju

    1997-07-01

    The effects of high-energy electron beam irradiation on surface hardening and microstructural modification in a ductile cast iron (DCI) roll are investigated in this study. The DCI roll samples were irradiated by using an electron accelerator (1.4 MeV), and then their microstructures and hardnesses were examined. Upon irradiation, the unirradiated microstructure containing graphites and the tempered bainite matrix was changed to martensite, ledeburite, and retained austenite, together with the complete or partial dissolution of graphites. This microstructural modification improved greatly the surface hardness due to transformation of martensite whose amount and type were determined by heat input during irradiation. In order to investigate these complex microstructures, a simulation test including thermal cycles of abrupt heating and quenching was carried out. The simulation results indicated that the irradiated surface was heated up to about 1100 °C to 1200 °C and then quenched to room temperature, which was enough to obtain surface hardening through martensitic transformation. Thermal analysis of the irradiated surface layer was also carried out using a finite difference method to understand the surface hardening of the DCI roll and to compare with the simulation test results.

  14. Numerical Simulation of Dendritic Growth of Continuously Cast High Carbon Steel

    NASA Astrophysics Data System (ADS)

    Wang, Weiling; Luo, Sen; Zhu, Miaoyong

    2015-01-01

    Considering the influence of the latent heat released during the solidification of high carbon liquid steel, a cellular automaton (CA) model coupled with the heat transfer was developed to investigate the growth of equiaxed dendrites which is controlled by the solute diffusion during the continuous casting process. Additionally, the growth of columnar dendrites and primary dendrite arm spacings were predicted and measured. The results show that the CA model is able to describe the growth behavior of equiaxed dendrites, especially at 5 K to 7 K melt undercoolings, and the approach adjusting the cooling medium temperature is reliable to keep the undercooling condition stable for equiaxed dendrites although its hysteresis is reinforced as the pre-set undercooling increases. With the increase of the melt undercooling, the growth of equiaxed dendrites becomes faster, and the thickness of dendritic arms increases slightly, however, the thickness of the diffusion layer in front of dendritic tips keeps constant. The growth of thin and tiny columnar dendrites will be confined due to the competition and absorbed by neighboring strong columnar dendrites, giving rise to the coarsening of columnar dendrites, which is observed both from the experimental observation and the numerical simulation. With the decrease of the cooling intensity, columnar dendrites get sparser, primary dendrite arm spacings increase, and secondary dendritic arms become undeveloped.

  15. Strengthening Micromechanisms in Cold-Chamber High-Pressure Die-Cast Mg-Al Alloys

    NASA Astrophysics Data System (ADS)

    Yang, Kun V.; Cáceres, Carlos H.; Easton, Mark A.

    2014-08-01

    The contributions from grain boundary, solid solution, and dispersion strengthening to the yield strength of cast-to-shape specimens were calculated for seven binary alloys with compositions ranging from very dilute (0.5 mass pct Al) to concentrated (12 mass pct Al). Experimentally and theoretically determined parameters were used to explicitly account for the different microstructures at the skin and core regions of specimens' cross sections. Microhardness maps were used to identify the specimens' skin. The specimens' strength was calculated as the weighted addition of the respective strengths of skin and core. The calculated strengths reproduced well the experimental values for the dilute alloys but underestimated the strength of the most concentrated alloys by as much as ~35 MPa. It is argued that the presence of the percolating network of Mg17Al12 eutectic intermetallic, particularly in the skin region, in conjunction with highly efficient dispersion hardening due to the convoluted shape of the intermetallics, accounts for the shortfall in the calculated strength.

  16. Cradle-to-Gate Impact Assessment of a High-Pressure Die-Casting Safety-Relevant Automotive Component

    NASA Astrophysics Data System (ADS)

    Cecchel, Silvia; Cornacchia, Giovanna; Panvini, Andrea

    2016-09-01

    The mass of automotive components has a direct influence on several aspects of vehicle performance, including both fuel consumption and tailpipe emissions, but the real environmental benefit has to be evaluated considering the entire life of the products with a proper life cycle assessment. In this context, the present paper analyzes the environmental burden connected to the production of a safety-relevant aluminum high-pressure die-casting component for commercial vehicles (a suspension cross-beam) considering all the phases connected to its manufacture. The focus on aluminum high-pressure die casting reflects the current trend of the industry and its high energy consumption. This work shows a new method that deeply analyzes every single step of the component's production through the implementation of a wide database of primary data collected thanks to collaborations of some automotive supplier companies. This energy analysis shows significant environmental benefits of aluminum recycling.

  17. Chromium regulation of multiple gene expression in rats with high-fructose diet-induced metabolic syndrome

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chromium (Cr) supplementation alleviates the metabolic syndrome, glucose intolerance, depression, excess body fat, and type 2 diabetes. However, not all studies have reported beneficial effects of Cr. Molecular evidence is lacking on the effects of Cr. The objective of this study was to investigate ...

  18. Computer Simulation and Experimental Validation on the Oxidation and Sulfate Corrosion Resistance of Novel Chromium Based High Temperature Alloys

    SciTech Connect

    Yang, Shizhong

    2013-02-28

    This report summarizes our recent works of ab initio molecular dynamics inter-atomic potentials development on dilute rare earth element yttrium (Y) etc. doped chromium (Cr) alloy systems, its applications in oxidation and corrosion resistance simulation, and experiment validation on the candidate systems. The simulation methods, experimental validation techniques, achievements already reached, students training, and future improvement are briefly introduced.

  19. Detection of highly toxic elements (lead and chromium) in commercially available eyeliner (kohl) using laser induced break down spectroscopy

    NASA Astrophysics Data System (ADS)

    Gondal, M. A.; Dastageer, M. A.; Al-Adel, F. F.; Naqvi, A. A.; Habibullah, Y. B.

    2015-12-01

    A sensitive laser induced breakdown spectroscopic system was developed and optimized for using it as a sensor for the detection of trace levels of lead and chromium present in the cosmetic eyeliner (kohl) of different price ranges (brands) available in the local market. Kohl is widely used in developing countries for babies as well adults for beautification as well eyes protection. The atomic transition lines at 405.7 nm and 425.4 nm were used as the marker lines for the detection of lead and chromium respectively. The detection system was optimized by finding the appropriate gate delay between the laser excitation and the data acquisition system and also by achieving optically thin plasma near the target by establishing the local thermodynamic equilibrium condition. The detection system was calibrated for these two hazardous elements and the kohl samples under investigation showed 8-15 ppm by mass of lead and 4-9 ppm by mass of Chromium, which are higher than the safe permissible levels of these elements. The limits of detection of the LIBS system for lead and chromium were found to be 1 and 2 ppm respectively.

  20. Development of Low-Noise High Value Chromium Silicide Resistors for Cryogenic Detector Applications

    NASA Technical Reports Server (NTRS)

    Jhabvala, Murzy; Babu, Sachi; Monroy, Carlos; Darren, C.; Krebs, Carolyn A. (Technical Monitor)

    2001-01-01

    Extremely high sensitivity detectors, such as silicon bolometers are required in many NASA missions for detection of photons from the x-ray to the far infrared regions. Typically, these detectors are cooled to well below the liquid helium (LHe) temperature (4.2 K) to achieve the maximum detection performance. As photoconductors, they are generally operated with a load resistor and a pre-set bias voltage, which is then coupled to the input gate of a source-follower Field Effect Transistor (FET) circuit. It is imperative that the detector system signal to noise performance be limited by the noise of the detector and not by the noise of the external components. The load resistor value is selected to optimize the detector performance. These two criteria tend to be contradictory in that these detectors require load resistors in the hundreds of megaohms, which leads to a higher Johnson noise. Additionally, the physical size of the resistor must be small for device integration as required by such missions as the NASA High Resolution Airborne Wide-Band Camera (HAWC) instrument and the Submillimeter High Angular Resolution Camera (SHARC) for the Caltech Submillimeter Observatory (CSO). We have designed, fabricated and characterized thin film resistors using a CrSi/TiW/Al metal system on optical quality quartz substrates. The resistor values range from 100 megaohms to over 650 megaohms and are Johnson noise limited at LHe temperatures. The resistor film is sputtered with a sheet resistance ranging from 300 ohms to 1600 ohms and the processing sequence developed for these devices allows for chemically fine tuning the sheet resistance in-situ. The wafer fabrication process was of sufficiently high yield (>80%) providing clusters of good resistors for integrated multiple detector channels, a very important feature in the assembly of these two instruments.

  1. Palladium-chromium static strain gage for high temperature propulsion systems

    NASA Technical Reports Server (NTRS)

    Lei, Jih-Fen

    1991-01-01

    The present electrical strain gage for high temperature static strain measurements is in its fine-wire and thin-film forms designed to be temperature-compensated on any substrate material. The gage element is of Pd-Cr alloy, while the compensator is of Pt. Because the thermally-induced apparent strain of this compensated wire strain gage is sufficiently small, with good reproducibility between thermal cycles to 800 C, output figures can be corrected within a reasonable margin of error.

  2. Highly active chromium-based selective ethylene tri-/tetramerization catalysts supported by PNPO phosphazane ligands.

    PubMed

    Zhou, Yusheng; Wu, Hongfei; Xu, Sheng; Zhang, Xuejun; Shi, Min; Zhang, Jun

    2015-05-28

    Novel Cr(iii) catalysts supported by PNPO phosphazane ligands of the type Ph2PN(R)P(Ph)OAr have been prepared, all of which, upon activation with MMAO-3A, are highly active in ethylene tri-/tetramerization with considerable selectivity. The effect of ligand substitution on the catalytic performance has been examined. The Cr precatalyst supported by the PNPO phosphazane ligand with an N-cyclohexyl achieved high activity of 316.7 kg (g Cr h(-1))(-1) and a high total selectivity of 85.1% towards valuable 1-hexene (45.7%) and 1-octene (39.4%) using chlorobenzene as the solvent at 35 bar and 40 °C. In methylcyclohexane, the precatalyst supported by [Ph2PN((i)Pr)P(Ph)OPh] exhibited a higher 1-octene selectivity (54.0%) with a considerable activity of 73.3 kg (g Cr h(-1))(-1) at 35 bar and 40 °C. With the fine-tuned ligand backbone, such a PNPO phosphazane-based catalyst system provides a mode for precise understanding of the impact of ligand variations on catalytic performance.

  3. Chromium adsorption by lignin

    SciTech Connect

    Lalvani, S.B.; Huebner, A.; Wiltowski, T.S.

    2000-01-01

    Hexavalent chromium is a known carcinogen, and its maximum contamination level in drinking water is determined by the US Environmental Protection Agency (EPA). Chromium in the wastewaters from plating and metal finishing, tanning, and photographic industries poses environmental problems. A commercially available lignin was used for the removal of hexavalent as well as trivalent chromium from aqueous solution. It is known that hexavalent chromium is present as an anionic species in the solution. It was found that lignin can remove up to 63% hexavalent and 100% trivalent chromium from aqueous solutions. The removal of chromium ions was also investigated using a commercially available activated carbon. This absorbent facilitated very little hexavalent and almost complete trivalent chromium removal. Adsorption isotherms and kinetics data on the metal removal by lignin and activated carbon are presented and discussed.

  4. The Electrodeposition of Low Contraction Chromium Using High/Low Current Pulsing

    DTIC Science & Technology

    1993-03-01

    5200.22-M, Industrial Security Manual, Section 11-19 or DoD 5200.1- R , Information Security Program Regulation, Chapter IX. For unclassified, limited...Reducto-N PrOlec • 10704-ON). Weasinanon, OC 20503 1. AGENCY USE ONLY (Leave bldnk) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED March 1993 Final 4...C- 󈧅/30 A’M2 20 (c) ’S 40 ;0 20 30 •4 0 6P -C? 1 ME r ’ Figure 3. The effects of high/low current pulse plating on the (a) CCE, (b) hardness, and (c

  5. Phase transformation and long-term service of high-temperature martensitic chromium steels

    NASA Astrophysics Data System (ADS)

    Kalashnikov, I. S.; Tarasenko, L.; Acselrad, O.; Pereira, L. C.; Shalkevich, A.; Soboleva, G.

    2000-02-01

    Martensitic high Cr (10 - 16%) steels alloyed with Ni (Co), Mo, W, V, and N are widely used in constructions subjected to cyclic loads at temperatures up to 600 degrees Celsius, in general after quenching from 1100 - 1150 degrees Celsius followed by tempering at 650 - 690 degrees Celsius. Due to long term service exposure at high temperatures, different microstructural changes take place, such as second-phases precipitation, formation of low-angle grain boundaries, as well as internal damage caused by cyclic loads and creep. Specific phase diagrams are presented that can be used to define time periods for reliable operation of parts with given composition, based on the time required for the appearance of second phase particles known to be detrimental to mechanical strength and performance. Restoring thermal treatments to be applied after long time exposure at service conditions, aiming at increasing service life, are also presented and discussed. The combined use of the diagrams and the restoring treatment ensures prediction of a reliable service-life period for components made of these steels.

  6. Phase transformation and long-term service of high-temperature martensitic chromium steels

    NASA Astrophysics Data System (ADS)

    Kalashnikov, I. S.; Tarasenko, L.; Acselrad, O.; Pereira, L. C.; Shalkevich, A.; Soboleva, G.

    2001-02-01

    Martensitic high Cr (10 - 16%) steels alloyed with Ni (Co), Mo, W, V, and N are widely used in constructions subjected to cyclic loads at temperatures up to 600 degrees Celsius, in general after quenching from 1100 - 1150 degrees Celsius followed by tempering at 650 - 690 degrees Celsius. Due to long term service exposure at high temperatures, different microstructural changes take place, such as second-phases precipitation, formation of low-angle grain boundaries, as well as internal damage caused by cyclic loads and creep. Specific phase diagrams are presented that can be used to define time periods for reliable operation of parts with given composition, based on the time required for the appearance of second phase particles known to be detrimental to mechanical strength and performance. Restoring thermal treatments to be applied after long time exposure at service conditions, aiming at increasing service life, are also presented and discussed. The combined use of the diagrams and the restoring treatment ensures prediction of a reliable service-life period for components made of these steels.

  7. Corrosion behavior of high-nickel and chromium alloys in natural Baltic seawater

    SciTech Connect

    Birn, J.; Janik-Czachor, M.; Wolowik, A.; Szummer, A.

    1999-10-01

    Effect of Cl{sup {minus}} ion concentration (O M sodium chloride [NaCl] to 2 M NaCl) and temperature (25 C to 75 C) on stability of the passive state of high-Ni and Cr alloys: NI-1 ({approximately} 16% Mo), CR-2 ({approximately} 6.2% Mo), and NI-3 (3.5% Mo) were investigated in acidic and neutral electrolytes in strictly controlled electrochemical conditions. The anodic behavior of the alloys appeared to depend mostly upon Mo content in the alloy. Thus, the NI-1 was the most stable alloy under the applied experimental conditions. The other alloys were also quite resistant, undergoing pitting only at elevated temperatures, at high anodic potentials, and at a chloride concentration not lower than 1 M. In natural Baltic seawater, these alloys did not exhibit any tendency to pitting, in qualitative agreement with the accelerated electrochemical tests. Complementary microscopic and surface analytical (AES) investigations were carried out to correlate the anodic and corrosion behavior of these materials with their composition and structure, and the composition of the passivating films formed at their surfaces.

  8. High resolution lung airway cast segmentation with proper topology suitable for computational fluid dynamic simulations.

    PubMed

    Carson, James P; Einstein, Daniel R; Minard, Kevin R; Fanucchi, Michelle V; Wallis, Christopher D; Corley, Richard A

    2010-10-01

    Developing detailed lung airway models is an important step towards understanding the respiratory system. While modern imaging and airway casting approaches have dramatically improved the potential detail of such models, challenges have arisen in image processing as the demand for greater detail pushes the image processing approaches to their limits. Airway segmentations with proper topology have neither loops nor invalid voxel-to-voxel connections. Here we describe a new technique for segmenting airways with proper topology and apply the approach to an image volume generated by magnetic resonance imaging of a silicone cast created from an excised monkey lung.

  9. Conventionally cast and forged copper alloy for high-heat-flux thrust chambers

    NASA Technical Reports Server (NTRS)

    Kazaroff, John M.; Repas, George A.

    1987-01-01

    The combustion chamber liner of the space shuttle main engine is made of NARloy-Z, a copper-silver-zirconium alloy. This alloy was produced by vacuum melting and vacuum centrifugal casting; a production method that is currently now available. Using conventional melting, casting, and forging methods, NASA has produced an alloy of the same composition called NASA-Z. This report compares the composition, microstructure, tensile properties, low-cycle fatigue life, and hot-firing life of these two materials. The results show that the materials have similar characteristics.

  10. Fabrication of Unidirectional Fiber Reinforced 6061 Aluminum Alloy Using High Pressure Squeeze Casting

    DTIC Science & Technology

    1988-12-01

    soiidfication front as a funct:on of t:me. Suoerim csea cni t2s ine are ooin:s tlat reoresent t",e exact solution at the corresoonaing t:mes as cotainea from the...Bomoay, (1981). Nomoto, M., "Mechanical Properties of Squeeze Castings in Al- Cu Alloys," Journal Japan Institute Light Metals, Vol. 30 (1980), pp 212-216...5. KaneKo, Y., Murakami, H., Kuroda, K. and Nagazaki, S., "Squeeze Casting of Aluminum," Foundry Trade Journal , Vol. 148 (1980), pp 397-411. 6

  11. Chitosan-derived carbonaceous material for highly efficient adsorption of chromium (VI) from aqueous solution.

    PubMed

    Shen, Feng; Su, Jialei; Zhang, Xiao; Zhang, Keqiang; Qi, Xinhua

    2016-10-01

    A carbonaceous adsorbent for effectively removing Cr(VI) was synthesized by facile hydrothermal carbonization of chitosan (HTC-chitosan). The prepared HTC-chitosan exhibited good stability in acid solution while the amine groups were retained completely after simple and green hydrothermal carbonization treatment. Structure characteristics of the HTC-chitosan as well as its adsorption behaviors for Cr(VI) in aqueous solution were investigated. Under optimal conditions, the adsorption capacity of the HTC-chitosan for Cr(VI) reached as high as 388.60mgg(-1), which was much higher than that of other materials reported previously. The prepared HTC-chitosan adsorbent could be reused at least five times with adsorption efficiency more than 92%. These results indicate that HTC-chitosan exhibited great superiority for Cr(VI) adsoption from aqueous solution both in terms of the preparation process and adsorption performance.

  12. Neodymium-rich precipitate phases in a high-chromium ferritic/martensitic steel

    NASA Astrophysics Data System (ADS)

    Shen, Yinzhong; Zhou, Xiaoling; Shang, Zhongxia

    2016-05-01

    Neodymium being considered as nitride forming element has been used in a design of advanced ferritic/martensitic (FM) steels for fossil fired power plants at service temperatures of 630 °C to 650 °C to effectively improve the creep strength of the steels. To fully understand the characteristics of neodymium precipitates in high-Cr FM steels, precipitate phases in an 11Cr FM steel with 0.03 wt% addition of Nd have been investigated by transmission electron microscopy. Three neodymium phases with a face-centered cubic crystal structure and different composition were observed in the steel. They consisted of neodymium carbonitride with an average lattice parameter of 1.0836 nm, Nd-rich carbonitride mainly containing Mn, and Nd-rich MN nitride mainly containing Mn and Co. Other three Nd-rich and Nd-containing phases, which appear to be Nd-Co-Cr/Nd-rich intermetallic compounds and Cr-Fe-rich nitride containing Nd, were also detected in the steel. Nd-relevant precipitates were found to be minor phases compared with M23C6 and Nb/V/Ta-rich MX phases in the steel. The content of Nd in other precipitate phases was very low. Most of added Nd is considered to be present as solid solution in the matrix of the steel.

  13. New chemistry for the placement of chromium(III)/polymer gels in high-temperature reservoirs

    SciTech Connect

    Lockhart, T.P.; Albonico, P.

    1994-11-01

    Coordination chemistry concepts have been used in the development of Cr[sup +3]/polymer solutions that meet the delayed-gelation requirements for in-depth treatment of high-temperature reservoirs. Use of the malonate complex of Cr[sup +3], Cr(malonate)[sub 3], provides gelation delays at elevated temperature much greater than those obtained with either the hydrated Cr[sup +3] ion or Cr(acetate)[sub 3]. Inclusion of additional, uncomplexed malonate ions in the formulations provides a means for further, and predictable, extension of the gelation time. The gelation delays obtained over the temperature range of 90 to 135 C are equal to or greater than those that can be achieved with the best gelation delay technologies described previously. The dependence of the gelation time on temperature, pH, and the Cr[sup +3] and malonate ion concentrations has been investigated. Preliminary results indicate that the thermal decomposition of the delaying ligand, malonate, plays an important role in determining the gelation rate. The use of a Cr[sup +3] complex of relatively low toxicity rather than the carcinogenic Cr[sup +6] ion to control gelation rate is an attractive feature of the new technology.

  14. Mechanical behavior and brittle-ductile transition of high-chromium martensitic steel

    NASA Astrophysics Data System (ADS)

    Odnobokova, M. V.; Kipelova, A. Yu.; Belyakov, A. N.; Kaibyshev, R. O.

    2016-04-01

    The article presents data on the static tensile tests and dynamic impact-toughness tests of a highchromium martensitic 10Kh9V1M1FBR steel (0.12 wt % C, 9.8 wt % Cr, 0.93 wt % W, 1.01 wt % Mo, 0.2 wt % V, 0.05 wt % Nb, 0.05 wt % N, 0.003 wt % B, 0.36 wt % Mn, 0.2 wt % Ni, 0.06 wt % Si, 0.01 wt % P, 0.008 wt % S, 0.02 wt % Cu, 0.1 wt % Co, 0.015 wt % Al, and the remainder is Fe) in the temperature range from 20 to-196°C. In the case of static loading, a reduction in the temperature leads to an increase in the strength characteristics; upon a drop in the temperature from 20 to-100°C, the plasticity also increases. This is connected with the fact that the ductile fracture remains the basic mechanism down to cryogenic temperatures. The brittle-ductile transition related to the transition from ductile intragranular fracture to quasibrittle one is observed at-45°C. The steel exhibits high impact toughness to the temperature of-60°C ( KCV -60 = 95 J/cm2), at which the fraction of the ductile component in fracture is equal to 20%. At 80°C, the impact toughness decreases down to critical values (30 J/cm2), which correlates with the decrease in the fraction of the ductile component on the fracture surface down to 1%. The further decrease in the impact toughness down to 10 J/cm2 at-196°C is related to the transition from intragranular to intergranular brittle fracture.

  15. Direct oxidation of guanine and 7,8-dihydro-8-oxoguanine in DNA by a high-valent chromium complex: a possible mechanism for chromate genotoxicity.

    PubMed

    Sugden, K D; Campo, C K; Martin, B D

    2001-09-01

    Intracellular reductive activation of the human carcinogen chromate, Cr(VI), is a necessary step in the formation of DNA lesions that lead to cancer. Reductive activation forms the transient metastable high-valent oxidation state of Cr(V) as a precursor to the final intracellularly stable oxidation state, Cr(III). In this study, we have used a model high-valent Cr(V) complex, N,N'-ethylenebis(salicylideneanimato)oxochromium(V), Cr(V)-Salen, to probe the mechanism of interaction between this oxidation state of chromium and DNA. This interaction was found to be specific toward the oxidation of the nucleic acid base guanine in unmodified single- and double-stranded oligonucleotides as measured by an increased level of DNA strand cleavage at these sites following piperidine treatment. Replacement of a single guanine residue in DNA with a more readily oxidized 7,8-dihydro-8-oxoguanine (8-oxo-G) base allowed for site-specific oxidation at this modified site within the DNA strand by the Cr(V)-Salen complex. HPLC and ESI-mass spectrometry were used to identify the modified guanine base lesions formed in the reaction of this high-valent chromium complex with the 8-oxo-G-containing DNA substrate. Two of these modified base lesions, identified as guanidinohydantoin and spiroiminodihydantoin, were found in the reaction of the Cr(V)-Salen complex with 8-oxo-G-modified DNA, while only one, spiroiminodihydantoin, was formed from oxidation of the 8-oxo-G nucleoside. A primer extension assay using the exo(-) Klenow fragment demonstrated polymerase arrest at the site of these base modifications as well as a high degree of misincorporation of adenine opposite the site of modification. These results suggest that mutations arising from G --> T transversions would predominate with these lesions. The mechanism of damage and base oxidation products for the interaction between high-valent chromium and DNA described herein may be relevant to the in vivo formation of DNA damage leading to

  16. [Chromium and insulin resistance].

    PubMed

    Kleefstra, N; Bilo, H J; Bakker, S J; Houweling, S T

    2004-01-31

    Since as early as the 50s of the last century, it has been known that chromium is essential for normal glucose metabolism. Too little chromium in the diet may lead to insulin resistance. However, there is still no standard against which chromium deficiency can be established. Nevertheless, chromium supplements are becoming increasingly popular. Various systematic reviews have been unable to demonstrate any effects of chromium on glycaemic regulation (possibly due partly to the low dosages used), but there is a slight reduction in body weight averaging 1 kg. In a double-blind randomised placebo-controlled trial in a Chinese population with type-2 diabetes mellitus, supplementation with 1000 micrograms of chromium led to a fall in the glycosylated haemoglobin level (HbA1c) by 2%. Toxic effects of chromium are seldom seen; recently, however, the safety of one of the dosage forms of chromium, chromium picolinate, has been questioned. One should be aware that individual patients with type-2 diabetes mellitus may have an increased risk of hypoglycaemic episodes when taking chromium supplements as self-medication.

  17. High-Throughput Physiologically Based Toxicokinetic Models for ToxCast Chemicals

    EPA Science Inventory

    Physiologically based toxicokinetic (PBTK) models aid in predicting exposure doses needed to create tissue concentrations equivalent to those identified as bioactive by ToxCast. We have implemented four empirical and physiologically-based toxicokinetic (TK) models within a new R ...

  18. Nanomaterial (NM) bioactivity profiling by ToxCast high-throughput screening (HTS)

    EPA Science Inventory

    Rapidly increasing numbers of new NMs and their uses demand efficient tests of NM bioactivity for safety assessment. The EPA’s ToxCast program uses HTS assays to prioritize for targeted testing, identify biological pathways affected, and aid in linking NM properties and potential...

  19. Fatigue studies of high-palladium dental casting alloys: Part I. Fatigue limits and fracture characteristics.

    PubMed

    Li, D; Brantley, W A; Mitchell, J C; Daehn, G S; Monaghan, P; Papazoglou, E

    2002-04-01

    The fatigue limits and fracture characteristics for a Pd-Cu-Ga alloy and a Pd-Ga alloy were studied. The alloys were cast into tensile test bars with gauge diameter of 3 mm and gauge length of 15 mm, and the surfaces of the castings were neither air-abraded nor polished after removal from the investment. Specimens were prepared from all-new metal (not previously melted), a combination of 50% new metal and 50% old metal (previously melted one time) and 100% old metal. The cast bars were subjected to heat treatment simulating the complete firing cycles for dental porcelain, and fatigued in air at room temperature under uniaxial tension-compression stress at 10 Hz and a ratio of tensile stress amplitude to compressive stress amplitude (R-ratio) of -1. The alloy microstructures and fracture surfaces were examined with a scanning electron microscope (SEM). Results showed that the fatigue limits at 2 x 10(6)cycles of the Pd-Cu-Ga and Pd-Ga alloys were approximately 0.20 and 0.15 of their 0.1% yield strength (YS) in tension, respectively. The fatigue resistance for specimens from both alloys containing 50% old metal and 50% new metal was comparable to that of specimens containing all-new metal, although this decreased dramatically for Pd-Cu-Ga alloy specimens containing all-old metal. The fatigue resistance of the Pd-Cu-Ga alloy subjected to heat treatment simulating the porcelain firing cycles was not adversely affected by remnants of the original as-cast dendritic microstructure that remained in the relatively large test specimens. A longer heat treatment than recommended by the manufacturer for the porcelain firing cycles is needed to completely eliminate the as-cast dendritic structure in these specimens. The Pd-Cu-Ga alloy exhibited superior fatigue resistance to the Pd-Ga alloy, which has an equiaxed-grain microstructure and lower yield strength.

  20. Melt spun and suction cast Nd-Fe-Co-B-Nb hard magnets with high Nd contents

    NASA Astrophysics Data System (ADS)

    Cui, X. H.; Liu, Z. W.; Zhong, X. C.; Yu, H. Y.; Zeng, D. C.

    2012-04-01

    Nd-Fe-Co-B-Nb alloys with Nd contents of 9-9.5 at % were prepared by melt spinning and suction casting. It was found from the melt spun ribbon samples that Nb addition enhanced the glass forming ability and Co addition improved the thermal stability. Larger values of Jr and (BH)max were obtained for the ribbon samples than for the bulk ones due to the finer crystalline structure in the former. Nanocrystallite with amorphous structure was found in the suction cast rod samples. The as-cast Nd9Fe71.5B15.5Nb4 rod in a diameter of 2 mm exhibited the best hard magnetic behavior. A remanence of 0.59 T, a coercivity of 1154 kA/m, and a maximum energy product of 54.2 kJ/m3 have been obtained after heat treatment. The distribution of nonmagnetic FeNb phase plays a key role in the improvement of coercivity. Current work suggests that large size Nd2Fe14B/Fe3B nanocomposite magnets with high Nd contents and good magnetic properties can be obtained using a nanocrystalline precursor instead of bulk metallic glass.

  1. Predicting Stress vs. Strain Behaviors of Thin-Walled High Pressure Die Cast Magnesium Alloy with Actual Pore Distribution

    SciTech Connect

    Choi, Kyoo Sil; Barker, Erin; Cheng, Guang; Sun, Xin; Forsmark, Joy; Li, Mei

    2016-01-06

    In this paper, a three-dimensional (3D) microstructure-based finite element modeling method (i.e., extrinsic modeling method) is developed, which can be used in examining the effects of porosity on the ductility/fracture of Mg castings. For this purpose, AM60 Mg tensile samples were generated under high-pressure die-casting in a specially-designed mold. Before the tensile test, the samples were CT-scanned to obtain the pore distributions within the samples. 3D microstructure-based finite element models were then developed based on the obtained actual pore distributions of the gauge area. The input properties for the matrix material were determined by fitting the simulation result to the experimental result of a selected sample, and then used for all the other samples’ simulation. The results show that the ductility and fracture locations predicted from simulations agree well with the experimental results. This indicates that the developed 3D extrinsic modeling method may be used to examine the influence of various aspects of pore sizes/distributions as well as intrinsic properties (i.e., matrix properties) on the ductility/fracture of Mg castings.

  2. Structure and properties of cast and splat-quenched high-entropy Al-Cu-Fe-Ni-Si alloys

    NASA Astrophysics Data System (ADS)

    Bashev, V. F.; Kushnerov, O. I.

    2017-01-01

    The effect of the composition and cooling rate of the melt on the microhardness, phase composition, and fine-structure parameters of as-cast and splat-quenched (SQ) high-entropy (HE) Al-Cu-Fe-Ni-Si alloys was studied. The quenching was performed by conventional splat-cooling technique. The cooling rate was estimated to be 106 K/s. Components of the studied HE alloys were selected taking into account both criteria for designing and estimating their phase composition, which are available in the literature and based on the calculations of the entropy and enthalpy of mixing, and the difference between atomic radii of components as well. According to X-ray diffraction data, the majority of studied Al-Cu-Fe-Ni-Si compositions are two-phase HE alloys, the structure of which consists of disordered solid solutions with bcc and fcc structures. At the same time, the Al0.5CuFeNi alloy is single-phase in terms of X-ray diffraction and has an fcc structure. The studied alloys in the as-cast state have a dendritic structure, whereas, after splat quenching, the uniform small-grained structure is formed. It was found that, as the volume fraction of bcc solid solution in the studied HE alloys increases, the microhardness increases; the as-cast HE Al-Cu-Fe-Ni-Si alloys are characterized by higher microhardness compared to that of splat-quenched alloys. This is likely due to the more equilibrium multiphase state of as-cast alloys.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  4. Pulsed-field ionization spectroscopy of high Rydberg states (n=50-200) of bis(ɛ6-benzene)chromium

    NASA Astrophysics Data System (ADS)

    Choi, Kyo-Won; Choi, Sunyoung; Baek, Sun Jong; Kim, Sang Kyu

    2007-01-01

    The ionization behavior of the high Rydberg states of bis(η6-benzene)chromium in the presence of ac and/or dc fields has been explored. The application of an ac scrambling field at the time of laser excitation lengthens the lifetime of the Rydberg state by almost two orders of magnitude. The lifetime enhancement by the scrambling field is much more effective for n <100 than it is for n >100 Rydberg states. The pulsed-field ionization of Rydberg states of n <100 shows the typical diabatic ionization behavior for low n. The two distinct ionization behaviors observed for the relatively low (n=50-100) and high (n=100-200) Rydberg states suggest that the former originate from the optically accessed nf Rydberg series, whereas the latter are due to np Rydberg series. Based on the understanding of the ionization behavior of bis(η6-benzene)chromium, the accurate ionization potential is deduced to give IP =5.4665±0.0003eV. Optimization of the various electric field conditions greatly enhances the spectral sensitivity of the mass-analyzed threshold ionization (MATI) spectroscopy. The high-resolution MATI spectrum of the title molecule obtained here provides precise cationic vibrational frequencies for many skeletal and benzene ring modes. A number of vibrational modes are newly identified, and the ambiguity regarding to some mode assignments is now clearly resolved through the Frank-Condon analysis based on ab initio calculations.

  5. Heat treatment giving a stable high temperature micro-structure in cast austenitic stainless steel

    DOEpatents

    Anton, Donald L.; Lemkey, Franklin D.

    1988-01-01

    A novel micro-structure developed in a cast austenitic stainless steel alloy and a heat treatment thereof are disclosed. The alloy is based on a multicomponent Fe-Cr-Mn-Mo-Si-Nb-C system consisting of an austenitic iron solid solution (.gamma.) matrix reinforced by finely dispersed carbide phases and a heat treatment to produce the micro-structure. The heat treatment includes a prebraze heat treatment followed by a three stage braze cycle heat treatment.

  6. Chromium-51 calibrating neutrino source

    SciTech Connect

    Demchenko, N.F.; Karasev, V.I.; Karelin, E.A.

    1993-12-31

    The problem for measurement of the sun neutrino flux is resolved at the specially made Baksansk neutrino telescope and calls for calibration of registration system. For this a man made neutrino source is required with the known yield of particles and intensity comparable with the intensity of the measured subject. The most suitable radionuclide for production of this source is chromium-51 the radionuclide decay of which is accompanied with neutrino radiation. At the Research Institute of Atomic Reactors (in Dimitrovgrad) the production technology is developed as well as the closed chromium-51 neutrino source is made of 4 x 10{sup 5} Ci activity. The parts of active source made in the form of core of metallic isotope-enriched chromium were irradiated in the high flux neutron trap of the SM-2 reactor. The sources were subsequently assembled at the shield cells with remote equipment application. The source was certificated as a special form radioactive material. Due to low half-life of chromium-51 (T 1/2 - 27 hours) all the operations on assembly, certification and delivery of source to the Baksansk Laboratory were performed at the earliest possible date (less than 3 days).

  7. Evaluation of food-relevant chemicals in the ToxCast high-throughput screening program.

    PubMed

    Karmaus, Agnes L; Filer, Dayne L; Martin, Matthew T; Houck, Keith A

    2016-06-01

    Thousands of chemicals are directly added to or come in contact with food, many of which have undergone little to no toxicological evaluation. The landscape of the food-relevant chemical universe was evaluated using cheminformatics, and subsequently the bioactivity of food-relevant chemicals across the publicly available ToxCast highthroughput screening program was assessed. In total, 8659 food-relevant chemicals were compiled including direct food additives, food contact substances, and pesticides. Of these food-relevant chemicals, 4719 had curated structure definition files amenable to defining chemical fingerprints, which were used to cluster chemicals using a selforganizing map approach. Pesticides, and direct food additives clustered apart from one another with food contact substances generally in between, supporting that these categories not only reflect different uses but also distinct chemistries. Subsequently, 1530 food-relevant chemicals were identified in ToxCast comprising 616 direct food additives, 371 food contact substances, and 543 pesticides. Bioactivity across ToxCast was filtered for cytotoxicity to identify selective chemical effects. Initiating analyses from strictly chemical-based methodology or bioactivity/cytotoxicity-driven evaluation presents unbiased approaches for prioritizing chemicals. Although bioactivity in vitro is not necessarily predictive of adverse effects in vivo, these data provide insight into chemical properties and cellular targets through which foodrelevant chemicals elicit bioactivity.

  8. Clean Metal Casting

    SciTech Connect

    Makhlouf M. Makhlouf; Diran Apelian

    2002-02-05

    The objective of this project is to develop a technology for clean metal processing that is capable of consistently providing a metal cleanliness level that is fit for a given application. The program has five tasks: Development of melt cleanliness assessment technology, development of melt contamination avoidance technology, development of high temperature phase separation technology, establishment of a correlation between the level of melt cleanliness and as cast mechanical properties, and transfer of technology to the industrial sector. Within the context of the first task, WPI has developed a standardized Reduced Pressure Test that has been endorsed by AFS as a recommended practice. In addition, within the context of task1, WPI has developed a melt cleanliness sensor based on the principles of electromagnetic separation. An industrial partner is commercializing the sensor. Within the context of the second task, WPI has developed environmentally friendly fluxes that do not contain fluorine. Within the context of the third task, WPI modeled the process of rotary degassing and verified the model predictions with experimental data. This model may be used to optimize the performance of industrial rotary degassers. Within the context of the fourth task, WPI has correlated the level of melt cleanliness at various foundries, including a sand casting foundry, a permanent mold casting foundry, and a die casting foundry, to the casting process and the resultant mechanical properties. This is useful in tailoring the melt cleansing operations at foundries to the particular casting process and the desired properties of cast components.

  9. Compound-specific hydrogen isotope analysis of heteroatom-bearing compounds via gas chromatography-chromium-based high-temperature conversion (Cr/HTC)-isotope ratio mass spectrometry.

    PubMed

    Renpenning, Julian; Kümmel, Steffen; Hitzfeld, Kristina L; Schimmelmann, Arndt; Gehre, Matthias

    2015-09-15

    The traditional high-temperature conversion (HTC) approach toward compound-specific stable isotope analysis (CSIA) of hydrogen for heteroatom-bearing (i.e., N, Cl, S) compounds has been afflicted by fractionation bias due to formation of byproducts HCN, HCl, and H2S. This study presents a chromium-based high-temperature conversion (Cr/HTC) approach for organic compounds containing nitrogen, chlorine, and sulfur. Following peak separation along a gas chromatographic (GC) column, the use of thermally stable ceramic Cr/HTC reactors at 1100-1500 °C and chemical sequestration of N, Cl, and S by chromium result in quantitative conversion of compound-specific organic hydrogen to H2 analyte gas. The overall hydrogen isotope analysis via GC-Cr/HTC-isotope ratio mass spectrometry (IRMS) achieved a precision of better than ± 5 mUr along the VSMOW-SLAP scale. The accuracy of GC-Cr/HTC-IRMS was validated with organic reference materials (RM) in comparison with online EA-Cr/HTC-IRMS and offline dual-inlet IRMS. The utility and reliability of the GC-Cr/HTC-IRMS system were documented during the routine measurement of more than 500 heteroatom-bearing organic samples spanning a δ(2)H range of -181 mUr to 629 mUr.

  10. Cast Aluminum Structures Technology (CAST) Phase VI. Technology Transfer.

    DTIC Science & Technology

    1980-04-01

    system and ultimately fill the mold cavity to produce a casting. The fluidity of a given metal is measured with standard fluidity test molds. One...showed that the pouring temperature for large, thin-wall aluminum castings must be (1) high enough to provide sufficient fluidity for complete filling of...castings should have the following specific characteristics: good flowability , permeability, tensile strength, and compressive strength; high hot

  11. MOLDS FOR CASTING PLUTONIUM

    DOEpatents

    Anderson, J.W.; Miley, F.; Pritchard, W.C.

    1962-02-27

    A coated mold for casting plutonium comprises a mold base portion of a material which remains solid and stable at temperatures as high as the pouring temperature of the metal to be cast and having a thin coating of the order of 0.005 inch thick on the interior thereof. The coating is composed of finely divided calcium fluoride having a particle size of about 149 microns. (AEC)

  12. Development of a High Chromium Ni-Base Filler Metal Resistant to Ductility Dip Cracking and Solidification Cracking

    NASA Astrophysics Data System (ADS)

    Hope, Adam T.

    Many nuclear reactor components previously constructed with Ni-based alloys containing 20 wt% Cr have been found to be susceptible to stress corrosion cracking. The nuclear power industry now uses high chromium (˜30wt%) Ni-based filler metals to mitigate stress corrosion cracking. Current alloys are plagued with weldability issues, either solidification cracking or ductility dip cracking (DDC). Solidification cracking is related to solidification temperature range and the DDC is related to the fraction eutectic present in the microstructure. It was determined that an optimal alloy should have a solidification temperature range less than 150°C and at least 2% volume fraction eutectic. Due to the nature of the Nb rich eutectic that forms, it is difficult to avoid both cracking types simultaneously. Through computational modeling, alternative eutectic forming elements, Hf and Ta, have been identified as replacements for Nb in such alloys. Compositions have been optimized through a combination of computational and experimental techniques combined with a design of experiment methodology. Small buttons were melted using commercially pure materials in a copper hearth to obtain the desired compositions. These buttons were then subjected to a gas tungsten arc spot weld. A type C thermocouple was used to acquire the cooling history during the solidification process. The cooling curves were processed using Single Sensor Differential Thermal Analysis to determine the solidification temperature range, and indicator of solidification cracking susceptibility. Metallography was performed to determine the fraction eutectic present, an indicator of DDC resistance. The optimal level of Hf to resist cracking was found to be 0.25 wt%. The optimal level of Ta was found to be 4 wt%. gamma/MC type eutectics were found to form first in all Nb, Ta, and Hf-bearing compositions. Depending on Fe and Cr content, gamma/Laves eutectic was sometimes found in Nb and Ta-bearing compositions, while

  13. Synthesis, physical properties and application of the zero-valent iron/titanium dioxide heterocomposite having high activity for the sustainable photocatalytic removal of hexavalent chromium in water.

    PubMed

    Petala, Eleni; Baikousi, Maria; Karakassides, Michael A; Zoppellaro, Giorgio; Filip, Jan; Tuček, Jiří; Vasilopoulos, Konstantinos C; Pechoušek, Jiří; Zbořil, Radek

    2016-04-21

    A magnetic photocatalytic material composed of nanoscale zero-valent iron (nZVI) homogeneously distributed over a mesoporous nanocrystalline TiO2 matrix has been prepared by a multistage chemical process, including sol-gel technique, wet impregnation, and chemical reduction. X-ray powder diffraction and Raman spectroscopy were used for the structural and chemical characterization of the magnetic photocatalyst, while bulk magnetization measurements and scanning/transmission electron microscopy were employed to determine the physical and textural properties of the photocatalyst. The synthesized nZVI@TiO2 photocatalyst shows very high efficiency in the removal of hexavalent chromium, Cr(vi), from water. The degradation rate follows a pseudo-first-order kinetic model. Most importantly, the remarkable efficiency of the photocatalyst is found to be due to the synergistic contributions of both counterparts, nZVI and TiO2, as validated by comparative experiments with neat TiO2 and nZVI@TiO2 under UV-C irradiation and without irradiation. New insights into the mechanism of synergistic degradation of chromium(vi) and suppressed oxidation of nZVI particles in the composite material are proposed and therein discussed.

  14. Effects of silver and group 2 fluorides addition to plasma sprayed chromium carbide high temperature solid lubricant for foil gas bearing to 650 deg C

    NASA Technical Reports Server (NTRS)

    Wagner, R. C.; Sliney, H. E.

    1984-01-01

    A new self-lubricating coating composition of nickel aluminide-bonded chromium carbide formulated with silver and Group II fluorides was developed in a research program on high temperature solid lubricants. One of the proposed applications for this new coating composition is as a wide temperature spectrum solid lubricant for complaint foil gas bearings. Friction and wear properties were obtained using a foil gas bearing start/stop apparatus at temperatures from 25 to 650 C. The journals were Inconel 718. Some were coated with the plasma sprayed experimental coating, others with unmodified nickel aluminide/chromium carbide as a baseline for comparison. The addtitional components were provided to assist in achieving low friction over the temperature range of interest. Uncoated, preoxidized Inconel X-750 foil bearings were operated against these surfaces. The foils were subjected to repeated start/stop cycles under a 14-kPa (2-psi) bearing unit loading. Sliding contact occurred during lift-off and coastdown at surface velocities less than 6 m/s (3000 rpm). Testing continued until 9000 start/stop cycles were accumulated or until a rise in starting torque indicated the journal/bearing had failed. Comparison in coating performance as well as discussions of their properties and methods of application are given.

  15. Sodium sulfur container with chromium/chromium oxide coating

    DOEpatents

    Ludwig, Frank A.; Higley, Lin R.

    1981-01-01

    A coating of chromium/chromium oxide is disclosed for coating the surfaces of electrically conducting components of a sodium sulfur battery. This chromium/chromium oxide coating is placed on the surfaces of the electrically conducting components of the battery which are in contact with molten polysulfide and sulfur reactants during battery operation.

  16. A facile and simple high-performance polydimethylsiloxane casting based on self-polymerization dopamine

    NASA Astrophysics Data System (ADS)

    Chen, Xing; Zhang, Lu-lu; Sun, Jian-hai; Li, Hui; Cui, Da-fu

    2014-09-01

    We present a new and facile method for polydimethylsiloxane (PDMS) casting by dip-coating the master molds in an aqueous solution of dopamine. A poly(dopamine) film formed by self-polymerization of dopamine is used as the surface anti-adhesion coating for PDMS de-molding. Different master molds, such as metal, silicon and PDMS replica, were used to verify the feasibility of this proposed PDMS casting method. The poly(dopamine) coatings at various fabrication conditions were studied by using surface plasmon resonance technology. We found that it is very easy to form repeated poly(dopamine) coatings with similar thicknesses and density at fairly flexible conditions of self-polymerization. The water contact angles of the PDMS master molds and the positive PDMS replicas were studied after the PDMS master molds were immersed in the dopamine coating solution for different times. The de-molding process was then measured by surface plasmon resonance technology. The surface morphology of the master molds and the PDMS replicas were characterized by using scanning electron microscopy and atomic force microscopy. Results demonstrate that the poly(dopamine) coating exhibits a strong release property in the PDMS de-molding process and has good stickiness after PDMS de-molding a dozen times. The package performances of the PDMS replicas were detected and compared by bonding experiments. PDMS replicas after a second round of de-molding present a little higher package performance than that of the PDMS replicas with an anti-sticking agent of silane. The biochemical properties of PDMS replicas were studied through fluorescence immunoassay experiments. The PDMS replicas present similar biochemical properties to the bare PDMS. This biomimetic surface modification method of dopamine for PDMS casting has a great potential for preparing microdevices for various biological and clinical applications.

  17. Possible adverse effect of chromium in occupational exposure of tannery workers.

    PubMed

    Kornhauser, Carlos; Wróbel, Katarzyna; Wróbel, Kazimierz; Malacara, Juan Manuel; Nava, Laura Eugenia; Gómez, Leobardo; González, Rita

    2002-04-01

    Our aim was to investigate the adverse effects of occupational exposure to trivalent chromium. We measured chromium and iron levels in serum and urine and hemoglobin levels in tannery workers and unexposed persons. We studied three groups of subjects. Group 1 included 15 non-smoking male tannery workers highly exposed to chromium from tanning and retanning departments. Group 2 included 14 non-smoking male tannery workers with moderate chromium exposure from dying, drying and finishing departments. Group 3 included 11 healthy, non-smoking male subjects without direct chromium exposure. Higher serum chromium levels were observed in groups 1 and 2 with respect to group 3 (mean values respectively: 0.43; 0.25 and 0.13 microg x l(-1)). Urine chromium levels in group 1 were higher than those in controls (mean values: 1.78 and 1.35 microg x l(-1)). In group 1 an inverse association was found between serum chromium and urine iron (-0.524), urine chromium and hemoglobin (-0.594) and between the urine chromium to iron ratio and hemoglobin (-0.693, p<0.05). The results suggest a chromium adverse effect on iron metabolism, possibly associated with excessive body chromium accumulation. In conclusion, chromium urine test could be recommended for diagnosis of chromium adverse effect on iron metabolism. Further studies are needed to quantify the relationship between urine chromium and hemoglobin metabolism.

  18. Casting of undoped CdTe crystals with high electrical resistivity

    NASA Astrophysics Data System (ADS)

    Rudolph, P.; Kawasaki, S.; Yamashita, S.; Usuki, Y.; Konagaya, Y.; Matada, S.; Yamamoto, S.; Fukuda, T.

    1995-04-01

    Undoped semi-insulating CdTe crystals with an as-grown shape similar to the device profile for radiation detection has been grown by casting and subsequent unidirectional solidification. Crystals with maximum electrical resistivity of 5.7 × 10 10 Ω · cm and an average value 5 × 10 9 Ω · cm have been grown in a die of uncoated fused silica. Neither Cd source nor an inert gas overpressure was employed in the growth container. No additional preparation steps were required before the analysis of their detection behaviour. First measurements of the integral X-ray response have been carried out.

  19. Molecular determinants of caste differentiation in the highly eusocial honeybee Apis mellifera

    PubMed Central

    Barchuk, Angel R; Cristino, Alexandre S; Kucharski, Robert; Costa, Luciano F; Simões, Zilá LP; Maleszka, Ryszard

    2007-01-01

    Background In honeybees, differential feeding of female larvae promotes the occurrence of two different phenotypes, a queen and a worker, from identical genotypes, through incremental alterations, which affect general growth, and character state alterations that result in the presence or absence of specific structures. Although previous studies revealed a link between incremental alterations and differential expression of physiometabolic genes, the molecular changes accompanying character state alterations remain unknown. Results By using cDNA microarray analyses of >6,000 Apis mellifera ESTs, we found 240 differentially expressed genes (DEGs) between developing queens and workers. Many genes recorded as up-regulated in prospective workers appear to be unique to A. mellifera, suggesting that the workers' developmental pathway involves the participation of novel genes. Workers up-regulate more developmental genes than queens, whereas queens up-regulate a greater proportion of physiometabolic genes, including genes coding for metabolic enzymes and genes whose products are known to regulate the rate of mass-transforming processes and the general growth of the organism (e.g., tor). Many DEGs are likely to be involved in processes favoring the development of caste-biased structures, like brain, legs and ovaries, as well as genes that code for cytoskeleton constituents. Treatment of developing worker larvae with juvenile hormone (JH) revealed 52 JH responsive genes, specifically during the critical period of caste development. Using Gibbs sampling and Expectation Maximization algorithms, we discovered eight overrepresented cis-elements from four gene groups. Graph theory and complex networks concepts were adopted to attain powerful graphical representations of the interrelation between cis-elements and genes and objectively quantify the degree of relationship between these entities. Conclusion We suggest that clusters of functionally related DEGs are co-regulated during

  20. Assessment of ToxCast Phase II for Mitochondrial Liabilities Using a High-Throughput Respirometric Assay.

    PubMed

    Wills, Lauren P; Beeson, Gyda C; Hoover, Douglas B; Schnellmann, Rick G; Beeson, Craig C

    2015-08-01

    Previous high-throughput screens to identify mitochondrial toxicants used immortalized cell lines and focused on changes in mitochondrial membrane potential, which may not be sufficient and do not identify different types of mitochondrial dysfunction. Primary cultures of renal proximal tubule cells (RPTC) were examined with the Seahorse Extracellular Flux Analyzer to screen 676 compounds (5 μM; 1 h) from the ToxCast Phase II library for mitochondrial toxicants. Of the 676 compounds, 19 were classified as cytotoxicants, 376 were electron transport chain (ETC) inhibitors, and 5 were uncouplers. The remaining 276 compounds were examined after a 5-h exposure to identify slower acting mitochondrial toxicants. This experiment identified 3 cytotoxicants, 110 ETC inhibitors, and 163 compounds with no effect. A subset of the ToxCast Phase II library was also examined in immortalized human renal cells (HK2) to determine differences in susceptibility to mitochondrial toxicity. Of the 131 RPTC ETC inhibitors tested, only 14 were ETC inhibitors in HK2 cells. Of the 5 RPTC uncouplers, 1 compound was an uncoupler in HK2 cells. These results demonstrate that 73% (491/676) of the compounds in the ToxCast Phase II library compounds exhibit RPTC mitochondrial toxicity, overwhelmingly ETC inhibition. In contrast, renal HK2 cells are markedly less sensitive and only identified 6% of the compounds as mitochondrial toxicants. We suggest caution is needed when studying mitochondrial toxicity in immortalized cell lines. This information will provide mechanisms and chemical-based criteria for assessing and predicting mitochondrial liabilities of new drugs, consumer products, and environmental agents.

  1. Assessment of ToxCast Phase II for Mitochondrial Liabilities Using a High-Throughput Respirometric Assay

    PubMed Central

    Wills, Lauren P.; Beeson, Gyda C.; Hoover, Douglas B.; Schnellmann, Rick G.; Beeson, Craig C.

    2015-01-01

    Previous high-throughput screens to identify mitochondrial toxicants used immortalized cell lines and focused on changes in mitochondrial membrane potential, which may not be sufficient and do not identify different types of mitochondrial dysfunction. Primary cultures of renal proximal tubule cells (RPTC) were examined with the Seahorse Extracellular Flux Analyzer to screen 676 compounds (5 μM; 1 h) from the ToxCast Phase II library for mitochondrial toxicants. Of the 676 compounds, 19 were classified as cytotoxicants, 376 were electron transport chain (ETC) inhibitors, and 5 were uncouplers. The remaining 276 compounds were examined after a 5-h exposure to identify slower acting mitochondrial toxicants. This experiment identified 3 cytotoxicants, 110 ETC inhibitors, and 163 compounds with no effect. A subset of the ToxCast Phase II library was also examined in immortalized human renal cells (HK2) to determine differences in susceptibility to mitochondrial toxicity. Of the 131 RPTC ETC inhibitors tested, only 14 were ETC inhibitors in HK2 cells. Of the 5 RPTC uncouplers, 1 compound was an uncoupler in HK2 cells. These results demonstrate that 73% (491/676) of the compounds in the ToxCast Phase II library compounds exhibit RPTC mitochondrial toxicity, overwhelmingly ETC inhibition. In contrast, renal HK2 cells are markedly less sensitive and only identified 6% of the compounds as mitochondrial toxicants. We suggest caution is needed when studying mitochondrial toxicity in immortalized cell lines. This information will provide mechanisms and chemical-based criteria for assessing and predicting mitochondrial liabilities of new drugs, consumer products, and environmental agents. PMID:25926417

  2. Development of high-emittance scales on thoriated nickel-chromium-aluminum-base alloys. [produced by high temperature oxidation

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wright, I. G.; Wilcox, B. A.

    1973-01-01

    The surface regions of a DSNiCrAl alloy have been doped, by a pack diffusion process, with small amounts of Mn, Fe, or Co, and the effect of these dopants on the total normal emissivity of the scales produced by subsequent high temperature oxidation has been measured. While all three elements lead to a modest increase in emissivity, (up to 23% greater than the undoped alloy) only the change caused by manganese is thermally stable. However, this increased emissivity is within 85 percent of that of TDNiCr oxidized to form a chromia scale. The maganese-doped alloy is some 50 percent weaker than undoped DSNiCrAl after the doping treatment, and approximately 30 percent weaker after oxidation.

  3. Heat and corrosion resistant cast CN-12 type stainless steel with improved high temperature strength and ductility

    DOEpatents

    Mazias, Philip J.; McGreevy, Tim; Pollard,Michael James; Siebenaler, Chad W.; Swindeman, Robert W.

    2007-08-14

    A cast stainless steel alloy and articles formed therefrom containing about 0.5 wt. % to about 10 wt. % manganese, 0.02 wt. % to 0.50 wt. % N, and less than 0.15 wt. % sulfur provides high temperature strength both in the matrix and at the grain boundaries without reducing ductility due to cracking along boundaries with continuous or nearly-continuous carbides. Alloys of the present invention also have increased nitrogen solubility thereby enhancing strength at all temperatures because nitride precipitates or nitrogen porosity during casting are not observed. The solubility of nitrogen is dramatically enhanced by the presence of manganese, which also retains or improves the solubility of carbon thereby providing additional solid solution strengthening due to the presence of manganese and nitrogen, and combined carbon. Such solution strengthening enhances the high temperature precipitation-strengthening benefits of fine dispersions of NbC. Such solid solution effects also enhance the stability of the austenite matrix from resistance to excess sigma phase or chrome carbide formation at higher service temperatures. The presence of sulfides is substantially eliminated.

  4. Melting and casting of FeAl-based cast alloy

    SciTech Connect

    Sikka, V.K.; Wilkening, D.; Liebetrau, J.; Mackey, B.

    1998-11-01

    The FeAl-based intermetallic alloys are of great interest because of their low density, low raw material cost, and excellent resistance to high-temperature oxidation, sulfidation, carburization, and molten salts. The applications based on these unique properties of FeAl require methods to melt and cast these alloys into complex-shaped castings and centrifugal cast tubes. This paper addresses the melting-related issues and the effect of chemistry on the microstructure and hardness of castings. It is concluded that the use of the Exo-Melt{trademark} process for melting and the proper selection of the aluminum melt stock can result in porosity-free castings. The FeAl alloys can be melted and cast from the virgin and revert stock. A large variation in carbon content of the alloys is possible before the precipitation of graphite flakes occurs. Titanium is a very potent addition to refine the grain size of castings. A range of complex sand castings and two different sizes of centrifugal cast tubes of the alloy have already been cast.

  5. Trivalent chromium, in atherosclerosis and diabetes.

    PubMed

    Mossop, R T

    1991-11-01

    The known effects of trivalent chromium (Cr) in lowering blood levels of low density lipoproteins (LDL), raising high density lipoproteins (HDL) and improving glucose tolerance are summarised. Chromium deficiency cannot easily be established by direct means, but can be inferred by the reversal of symptoms and signs following the administration of trivalent chromium. This evidence can be supported by knowledge or suspicion of a deficiency in the diet, common in those who use highly refined cereal foods. It is considered that the beneficial effects of chromium repletion are now so well established and the trivalent form is so free of toxicity that it should now be used in clinical medicine for the benefit of those with some forms of diabetes and its complications and those suffering from atherosclerosis. Of perhaps more importance is the public health aspect, since most chromium is discarded in the cereal refinement process, we now have added evidence for a return to the diets in which complex carbohydrates predominated. In those who refuse or are unable to do this, possibly the addition of chromium to their drinking water may be of value.

  6. High-Strength Aluminum Casting Alloy for High-Temperature Applications (MSFC Center Director's Discretionary Fund Final Project No. 97-10)

    NASA Technical Reports Server (NTRS)

    Lee, J. A.

    1998-01-01

    A new aluminum-silicon alloy has been successfully developed at Marshall Space Flight Center that has a significant improvement in tensile strength at elevated temperatures (550 to 700 F). For instance, the new alloy shows in average tensile strength of at least 90 percent higher than the current 390 aluminum piston alloy tested at 500 F. Compared to conventional aluminum alloys, automotive engines using the new piston alloy will have improved gas mileage, and may produce less air pollution in order to meet the future U.S. automotive legislative requirements for low hydrocarbon emissions. The projected cost for this alloy is less than $0.95/lb, and it readily allows the automotive components to be cast at a high production volume with a low, fully accounted cost. It is economically produced by pouring molten metal directly into conventional permanent steel molds or die casting.

  7. Replacement of Ni by Mn in High-Ni-Containing Austenitic Cast Steels used for Turbo-Charger Application

    NASA Astrophysics Data System (ADS)

    Jung, Seungmun; Jo, Yong Hee; Jeon, Changwoo; Choi, Won-Mi; Lee, Byeong-Joo; Oh, Yong-Jun; Kim, Gi-Yong; Jang, Seongsik; Lee, Sunghak

    2017-02-01

    High-temperature tensile properties of austenitic cast steels fabricated by replacing Ni by Mn in a 20 wt pct Ni-containing steel were investigated. In a steel where 8 wt pct Ni was replaced by 9.2 wt pct of Mn, 17.4 and 9.8 pct of ferrite existed in equilibrium phase diagrams and actual microstructures, respectively, because a role of Mn as an austenite stabilizer decreased, and led to deterioration of high-temperature properties. When 2 to 6 wt pct Ni was replaced by 2.3 to 6.9 wt pct Mn, high-temperature properties were comparable to those of the 20 wt pct Ni-containing steel because ferrites were absent, which indicated the successful replacement of 6 wt pct Ni by Mn, with cost reduction of 27 pct.

  8. A Winning Cast

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Howmet Research Corporation was the first to commercialize an innovative cast metal technology developed at Auburn University, Auburn, Alabama. With funding assistance from NASA's Marshall Space Flight Center, Auburn University's Solidification Design Center (a NASA Commercial Space Center), developed accurate nickel-based superalloy data for casting molten metals. Through a contract agreement, Howmet used the data to develop computer model predictions of molten metals and molding materials in cast metal manufacturing. Howmet Metal Mold (HMM), part of Howmet Corporation Specialty Products, of Whitehall, Michigan, utilizes metal molds to manufacture net shape castings in various alloys and amorphous metal (metallic glass). By implementing the thermophysical property data from by Auburn researchers, Howmet employs its newly developed computer model predictions to offer customers high-quality, low-cost, products with significantly improved mechanical properties. Components fabricated with this new process replace components originally made from forgings or billet. Compared with products manufactured through traditional casting methods, Howmet's computer-modeled castings come out on top.

  9. Casting larger polycrystalline silicon ingots

    SciTech Connect

    Wohlgemuth, J.; Tomlinson, T.; Cliber, J.; Shea, S.; Narayanan, M.

    1995-08-01

    Solarex has developed and patented a directional solidification casting process specifically designed for photovoltaics. In this process, silicon feedstock is melted in a ceramic crucible and solidified into a large grained semicrystalline silicon ingot. In-house manufacture of low cost, high purity ceramics is a key to the low cost fabrication of Solarex polycrystalline wafers. The casting process is performed in Solarex designed casting stations. The casting operation is computer controlled. There are no moving parts (except for the loading and unloading) so the growth process proceeds with virtually no operator intervention Today Solarex casting stations are used to produce ingots from which 4 bricks, each 11.4 cm by 11.4 cm in cross section, are cut. The stations themselves are physically capable of holding larger ingots, that would yield either: 4 bricks, 15 cm by 15 an; or 9 bricks, 11.4 cm by 11.4 an in cross-section. One of the tasks in the Solarex Cast Polycrystalline Silicon PVMaT Program is to design and modify one of the castings stations to cast these larger ingots. If successful, this effort will increase the production capacity of Solarex`s casting stations by 73% and reduce the labor content for casting by an equivalent percentage.

  10. High cycle fatigue of weld repaired cast Ti-6AI-4V

    NASA Astrophysics Data System (ADS)

    Hunter, G. B.; Hodi, F. S.; Eagar, T. W.

    1982-09-01

    In order to determine the effects of weld repair on fatigue life of titanium-6Al-4V castings, a series of specimens was exposed to variations in heat treatment, weld procedure, HIP cycle, cooling rate, and surface finish. The results indicate that weld repair is not detrimental to HCF properties as fatigue cracks were located primarily in the base metal. Fine surface finish and large colony size are the primary variables improving the fatigue life. The fusion zone resisted fatigue crack initiation due to a basketweave morphology and thin grain boundary alpha. Multipass welds were shown not to affect fatigue life when compared with single pass welds. A secondary HIP treatment was not detrimental to fatigue properties, but was found to be unnecessary.

  11. Cast dielectric composite linear accelerator

    DOEpatents

    Sanders, David M.; Sampayan, Stephen; Slenes, Kirk; Stoller, H. M.

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  12. Machine Casting of Ferrous Alloys.

    DTIC Science & Technology

    possible today. Extensive work was conducted on casting of semi-solid alloys when highly fluid (’ Rheocasting ’) and when thixotropically gelled...Thixocasting’). In initial phases of the program, copper base alloys and cast iron alloys were prepared with special non-dendritic Rheocast structure by batch...processing. Compatibility studies were carried out to select materials suitable for preparing cast iron with the Rheocast structure. Design

  13. High-temperature low cycle fatigue behavior of a gray cast iron

    SciTech Connect

    Fan, K.L. He, G.Q.; She, M.; Liu, X.S.; Lu, Q.; Yang, Y.; Tian, D.D.; Shen, Y.

    2014-12-15

    The strain controlled low cycle fatigue properties of the studied gray cast iron for engine cylinder blocks were investigated. At the same total strain amplitude, the low cycle fatigue life of the studied material at 523 K was higher than that at 423 K. The fatigue behavior of the studied material was characterized as cyclic softening at any given total strain amplitude (0.12%–0.24%), which was attributed to fatigue crack initiation and propagation. Moreover, this material exhibited asymmetric hysteresis loops due to the presence of the graphite lamellas. Transmission electron microscopy analysis suggested that cyclic softening was also caused by the interactions of dislocations at 423 K, such as cell structure in ferrite, whereas cyclic softening was related to subgrain boundaries and dislocation climbing at 523 K. Micro-analysis of specimen fracture appearance was conducted in order to obtain the fracture characteristics and crack paths for different strain amplitudes. It showed that the higher the temperature, the rougher the crack face of the examined gray cast iron at the same total strain amplitude. Additionally, the microcracks were readily blunted during growth inside the pearlite matrix at 423 K, whereas the microcracks could easily pass through pearlite matrix along with deflection at 523 K. The results of fatigue experiments consistently showed that fatigue damage for the studied material at 423 K was lower than that at 523 K under any given total strain amplitude. - Highlights: • The low cycle fatigue behavior of the HT250 for engine cylinder blocks was investigated. • TEM investigations were conducted to explain the cyclic deformation response. • The low cycle fatigue cracks of HT250 GCI were studied by SEM. • The fatigue life of the examined material at 523 K is higher than that at 423 K.

  14. Microstructural effects on high-cycle fatigue-crack initiation in A356.2 casting alloy

    SciTech Connect

    Zhang, B.; Poirier, D.R.; Chen, W.

    1999-10-01

    The effects of various microconstituents on crack initiation and propagation in high-cycle fatigue (HCF) were investigated in an aluminum casting alloy (A356.2). Fatigue cracking was induced in both axial and bending loading conditions at strain/stress ratios of {minus}1, 0.1, and 0.2. The secondary dendrite arm spacing (SDAS) and porosity (maximum size and density distribution) were quantified in the directionally solidified casting alloy. Using scanning electron microscopy, the authors observed that cracks initiate at near-surface porosity, at oxides, and within the eutectic microconstituents, depending on the SDAS. When the SDAS is greater than {approximately}25 to 28{micro}m, the fatigue cracks initiate from surface and subsurface porosity. When the SDAS is less than {approximately}25 to 28{micro}m, the fatigue cracks initiate from the interdendritic eutectic constituents, where the silicon particles are segregated. Fatigue cracks initiated at oxide inclusions whenever they were near the surface, regardless of the SDAS. The fatigue life of a specimen whose crack initiated at a large eutectic constituent was about equal to that when the crack initiated at a pore or oxide of comparable size.

  15. Interfacial characteristics of diamond/aluminum composites with high thermal conductivity fabricated by squeeze-casting method

    SciTech Connect

    Jiang, Longtao; Wang, Pingping; Xiu, Ziyang; Chen, Guoqin; Lin, Xiu; Dai, Chen; Wu, Gaohui

    2015-08-15

    In this work, aluminum matrix composites reinforced with diamond particles (diamond/aluminum composites) were fabricated by squeeze casting method. The material exhibited a thermal conductivity as high as 613 W / (m · K). The obtained composites were investigated by scanning electron microscope and transmission electron microscope in terms of the (100) and (111) facets of diamond particles. The diamond particles were observed to be homogeneously distributed in the aluminum matrix. The diamond{sub (111)}/Al interface was found to be devoid of reaction products. While at the diamond{sub (100)}/Al interface, large-sized aluminum carbides (Al{sub 4}C{sub 3}) with twin-crystal structure were identified. The interfacial characteristics were believed to be responsible for the excellent thermal conductivity of the material. - Graphical abstract: Display Omitted - Highlights: • Squeeze casting method was introduced to fabricate diamond/Al composite. • Sound interfacial bonding with excellent thermal conductivity was produced. • Diamond{sub (111)}/ aluminum interface was firstly characterized by TEM/HRTEM. • Physical combination was the controlling bonding for diamond{sub (111)}/aluminum. • The growth mechanism of Al{sub 4}C{sub 3} was analyzed by crystallography theory.

  16. Stress-induced martensitic transformation and impact toughness of cast irons and high-carbon Fe-Ni-C steel

    NASA Astrophysics Data System (ADS)

    Zhang, M.-X.; Kelly, P. M.

    2001-11-01

    The relationship between the impact toughness and stress-induced martensitic transformation, which occurs during the impact process, has been studied in white cast irons and an Fe-Ni-C alloy at different temperatures. The experimental results have shown that in the brittle white cast irons, the stress-induced martensitic transformation makes a positive contribution to the impact toughness, and lowering the stability of austenite increases the toughness. In contrast, the transformation makes a negative contribution to the toughness of high-carbon austenitic steels, and lowering the stability of austenite decreases the toughness. The present work supports the early theory[1] that the magnitude of the toughness change depends on the fracture properties of the new phase and the energy being dissipated during the transformation process. Using the crystallographic model for the stress-induced martensitic transformation, which was originally developed in ceramics and was then refined and extended to irons and steels, the effect of the stress-induced martensitic transformation on the impact toughness can be predicted.

  17. Effect of ferrite on cast stainless steels

    SciTech Connect

    Nadezhdin, A.; Cooper, K. ); Timbers, G. . Kraft Pulp Division)

    1994-09-01

    Premature failure of stainless steel castings in bleach washing service is attributed to poor casting quality high porosity and to a high ferrite content, which makes the castings susceptible to corrosion by hot acid chloride solutions. A survey of the chemical compositions and ferrite contents of corrosion-resistant castings in bleach plants at three pulp mills found high [delta]-ferrite levels in the austenitic matrix due to the improper balance between austenite and ferrite stabilizers.

  18. Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.

    PubMed

    Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

    2016-03-24

    In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA.

  19. Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties

    PubMed Central

    Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

    2016-01-01

    In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

  20. Development of Secondary Recrystallization in high permeability grain oriented Silicon steel produced by Thin Slab Casting and Rolling process

    NASA Astrophysics Data System (ADS)

    Fan, L. F.; Liu, S. M.; Guo, F.; He, J. Z.; Lu, B.; Dong, R. F.

    2017-02-01

    Texture evolution during high temperature annealing process in high permeability grain oriented(Hi-B)silicon steel, produced by Thin Slab Casting and Rolling(TSCR) process, was investigated using macro-/microtexture analysis. Goss texture appears in ODF at 800°C, the intensity of Goss texture is very weak until 950°CGoss grains grow abnormally during 980°C∼1000°C, grain size reached centimeter level at 1000°C instead of Primary Grains, Goss grains were obtained fully at 1020°C, Secondary recrystallization completed at 1040°C The deviation angle of Goss grain orientation decreases gradually with increasing temperature, and it reached the minimum at 1040°C.

  1. The Effects of Austenitizing Conditions on the Microstructure and Wear Resistance of a Centrifugally Cast High-Speed Steel Roll

    NASA Astrophysics Data System (ADS)

    Kang, Minwoo; Lee, Young-Kook

    2016-07-01

    The influences of austenitizing conditions on the microstructure and wear resistance of a centrifugally cast high-speed steel roll were investigated through thermodynamic calculation, microstructural analysis, and high-temperature wear tests. When the austenitizing temperature was between 1323 K and 1423 K (1050 °C and 1150 °C), coarse eutectic M2C plates were decomposed into a mixture of MC and M6C particles. However, at 1473 K (1200 °C), the M2C plates were first replaced by both new austenite grains and MC particles without M6C particles, and then remaining M2C particles were dissolved during the growth of MC particles. The wear resistance of the HSS roll was improved with increasing austenitizing temperature up to 1473 K (1200 °C) because the coarse eutectic M2C plates, which are vulnerable to crack propagation, changed to disconnected hard M6C and MC particles.

  2. Effects of combined dietary chromium(III) propionate complex and thiamine supplementation on insulin sensitivity, blood biochemical indices, and mineral levels in high-fructose-fed rats.

    PubMed

    Król, Ewelina; Krejpcio, Zbigniew; Michalak, Sławomir; Wójciak, Rafał W; Bogdański, Paweł

    2012-12-01

    Insulin resistance is the first step in glucose intolerance and the development of type 2 diabetes mellitus, thus effective prevention strategies should also include dietary interventions to enhance insulin sensitivity. Nutrients, such as microelement chromium(III) and thiamine, play regulatory roles in carbohydrate metabolism. The objective of this study was to evaluate the insulin-sensitizing potential of the combined supplementary chromium(III) propionate complex (CrProp) and thiamine in insulin resistance animal model (rats fed a high-fructose diet). The experiment was carried out on 40 nine-week-old male Wistar rats divided into five groups (eight animals each). Animals were fed ad libitum: the control diet (AIN-93 M) and high-fructose diets with and without a combination of two levels of CrProp (0.1 and 1 mg Cr/kg body mass/day) and two levels of thiamine (0.5 and 10 mg/kg body mass/day) for 8 weeks. At the end of the experiment rats were sacrificed to collect blood and internal organs for analyses of blood biochemical and hematologic indices as well as tissular microelement levels that were measured using appropriate methods. It was found that both supplementary CrProp and thiamine (given alone) have significant insulin-sensitizing and moderate blood-lipid-lowering properties, while the combined supplementation with these agents does not give synergistic effects in insulin-resistant rats. CrProp given separately increased kidney Cu and Cr levels, while thiamine alone increased hepatic Cu contents and decreased renal Zn and Cu contents.

  3. Chromium coatings to reduce radiation buildup. Final report

    SciTech Connect

    Galbraith, G.T.; Asay, R.H.; Asay, D.J.

    1995-12-01

    For the past several years, the Electric Power Research Institute (EPRI) has been intensively investigating new methods to mitigate radiation buildup on out-of-core surfaces in light water reactors to reduce occupational radiation exposure. As a result of this work, a new surface preconditioning method termed stabilized chromium has been developed for pretreatment of reactor piping and other components. This treatment method has been shown to be highly effective in retarding radiation buildup. Initial coupon tests of stabilized chromium treatment, an EPRI patented process, showed very favorable results. EPRI is now sponsoring additional development and testing of this preconditioning technique. The specific goals of this project were to investigate the effects of various chromium plating bath compositions, define acceptable chromium plating parameters, and demonstrate the benefit of stabilized chromium treatment by preconditioning actual plant components. Presently, two steam generator manway diaphragms installed at Millstone-2 have been treated with stabilized chromium and are being exposed to primary coolant. After exposure for one fuel cycle the stabilized chromium surfaces had approximately ten times less activity buildup than electropolished-only reference surfaces. Two pipes in the residual heat removal system of Diablo Canyon Unit 2 have also been treated with stabilized and non-stabilized chromium. Initial gamma spectroscopy measurements of these pipes showed the pipe treated with stabilized chromium had the lowest activity buildup. Additional tests of stabilized and non-stabilized chromium films applied to coupon specimens were also conducted at the Doel-2 reactor to evaluate the effect of chromium film thickness on activity buildup. These tests showed thin stabilized chromium films (ca. 3,000 {angstrom}) to be highly effective in retarding activity buildup with reduction factors ranging from 100--150 in comparison to electropolished-only coupons.

  4. Simultaneous Effect of Plunger Motion Profile, Pressure, and Temperature on the Quality of High-Pressure Die-Cast Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Fiorese, Elena; Bonollo, Franco

    2016-12-01

    High-pressure die casting has been used widely to manufacture a large variety of products with high dimensional accuracy and productivity. Although this process has a considerably lower cycle time than the other metal forming processes, it is not yet optimized, due to the complexity of the process and the number of parameters to be controlled. Hence, the identification of the parameters affecting quality of castings is the current challenge toward efficient and effective production. In their previous work, the authors proposed and validated some novel kinematic parameters of the plunger, which explain and forecast both the static mechanical properties and the internal quality of castings. The present work extends such an approach by including two other meaningful parameters, which describe the effect of upset pressure and temperature on the final outcome. These parameters are here formulated and have been validated by means of a statistically significant sample manufactured with different plunger motion profiles, upset pressures, and temperatures of the melt and die. The quality of the castings was assessed through static mechanical properties and density measurements. As further proof, internal defects were analyzed on the fracture surfaces of some meaningful castings.

  5. Elasto-Plastic-Creep Constitutive Equation of an Al-Si-Cu High-Pressure Die Casting Alloy for Thermal Stress Analysis

    NASA Astrophysics Data System (ADS)

    Motoyama, Yuichi; Shiga, Hidetoshi; Sato, Takeshi; Kambe, Hiroshi; Yoshida, Makoto

    2016-11-01

    Accurate simulation of residual stress and deformation is necessary to optimize the design and lifetime of casting components. Therefore, the recovery and strain-rate dependence of the stress-strain curve have been incorporated into empirical constitutive equations to improve the thermal stress analysis accuracy. Nevertheless, these equations present several difficulties related to the determination of material constants and their physical bases. This study suggested an empirical elasto-plastic-creep constitutive equation incorporating these phenomena. To determine the material parameters used in this constitutive equation, this study investigated tensile test methods to obtain stress-strain curves that most closely resemble those during or immediately after casting for the Al-Si-Cu high-pressure die-casting alloy JIS ADC 12 (A383.0), which exhibits natural aging. Results show that solution heat treatment with subsequent cooling to the test temperature should be applied to obtain stress-strain curves used for the thermal stress analysis of high-pressure die casting process of this alloy. The yield stresses obtained using the conventional heating method were 50-64 pct higher than those of the method described above. Therefore, the conventional method is expected to overestimate the overestimation of the predicted residual stress in die castings. Evaluation of the developed equation revealed that it can represent alloy recovery and strain-rate dependence.

  6. Enhancing high throughput toxicology - development of putative adverse outcome pathways linking US EPA ToxCast screening targets to relevant apical hazards.

    EPA Science Inventory

    High throughput toxicology programs, such as ToxCast and Tox21, have provided biological effects data for thousands of chemicals at multiple concentrations. Compared to traditional, whole-organism approaches, high throughput assays are rapid and cost-effective, yet they generall...

  7. Cool Cast Facts

    MedlinePlus

    ... moving. The outer layer is usually made of plaster or fiberglass. Fiberglass casts are made of fiberglass, ... color! These casts are lighter and stronger than plaster casts. Plaster casts are usually white and made ...

  8. The Effects of High Dietary Doses of Chromium(III) Complex with Propionic Acid on Nutritional and Selected Blood Indices in Healthy Female Rats.

    PubMed

    Staniek, Halina; Krejpcio, Zbigniew; Wieczorek, Daria

    2016-05-01

    People taking dietary supplements are usually determined to lose weight, supplement nutrition or reduce the risk of illness and negative effects of their state of health. Chromium(III) supplementation influence body composition and mass, glucose and lipid metabolism and it enhance insulin action. This fact could be of general interest because diabetes mellitus is an increasing health problem in many countries. The study describes the effects of high dietary doses of chromium(III) complex with propionic acid [Cr3] (from 100 to 1000 mg Cr · kg(-1) diet) on the organisms of healthy female rats, with special regard to overall nutritional, carbohydrate, lipid and blood biochemical and morphological and haematological indices. The study was carried out on 30 10-week-old female Wistar rats, which were divided into five equal groups (six animals in each): the control group and four groups of tested animals which had free access to the diet supplemented with 100, 200, 500 and 1000 mg Cr · kg(-1) (equivalent of 10, 20, 50 and 100 mg Cr · kg body weight (b.w.) · day(-1)), given as [Cr3O(O2CCH2CH3)6(H2O)3]⋅NO3, also known as Cr3, for 4 weeks. There were no significant differences in body mass gains, feeding efficiency ratio, internal organ masses or blood serum glucose concentrations, except for some changes in the serum triglycerides concentration, which decreased in the rats that received 500 and 1000 mg Cr · kg(-1) diet, as opposed to the group treated with 200 mg Cr · kg(-1) diet. The dietary supplementation of Cr3 for 4 weeks at doses of 100 to 1000 mg Cr · kg(-1) diet did not affect overall nutritional indices and most blood biochemical, morphological and haematological indices.

  9. Improvements in high temperature (>700° C) performance of lean chromium stainless steels for power plant efficiency

    SciTech Connect

    Dunning, John S.; Alman, David E.

    2002-01-01

    The Albany Research Center has broad experience in developing oxidation resistant lean chromium alloys. Using alloy design principles, a baseline composition of Fe-16Cr-16Ni-2Mn-1Mo was selected, to which a total of 5 wt% Si and Al additions can be made and retain a fully austenitic microstructure. Cyclic oxidation tests in air for 1000 hours were carried out on alloys with Si only or combined Si and Al additions in the temperature range 700? C to 800? C. Oxidation resistance of alloys with Si only additions were outstanding, particularly at 800? C (i.e., these alloys possessed weight gains 4 times less than a standard type-304 alloy). In addition, Si alloys pre-oxidized at 800? C, showed a zero weight gain in subsequent testing for 1000 hours at 700? C. SEM and ESCA analysis of the oxide films and base material at the oxide/base metal interface were conducted to study potential rate controlling mechanisms. The mechanical properties of the alloys, further modified with carbide forming elements, were also evaluated in this temperature range.

  10. Flexible supercapacitors based on low-cost tape casting of high dense carbon nanofibers

    NASA Astrophysics Data System (ADS)

    Daraghmeh, Allan; Hussain, Shahzad; Servera, Llorenç; Xuriguera, Elena; Blanes, Mireia; Ramos, Francisco; Cornet, Albert; Cirera, Albert

    2017-02-01

    This experimental study, reports the use of flexible tape casting of dense carbon nanofiber (CNFs) alone and in hybrid structure with MnO2 for supercapacitor applications. Different electrolyte concentrations of potassium hydroxide (KOH) were tested and it was founded that mild concentrated electrolyte, like 9 M KOH, provides higher specific capacitance 38 F g‑1 at a scan rate of 5 mV s‑1. Electrochemical impedance spectroscopy (EIS) measurements explain that the solution resistance and the charge transfer resistance is higher for 3 M KOH concentrations and lower for 6 M KOH concentrations. Afterwards a novel, fast and simple method is adopted to achieve a hybrid nanostructure of CNFs/MnO2 with various KMnO4 ratios. The hybrid supercapacitor, having loaded a mass of 0.0003 g MnO2 as a thin film, delivers a highest specific capacitance of 812 F g‑1 at a scan rate 5 mV s‑1. Charge/discharge cycling stability at current density of 7.9 A g‑1 demonstrates larger specific capacitance 303 F g‑1 and stability. Furthermore, the hybrid supercapacitor can deliver specific energy (72.4 Wh kg‑1) at specific power (3.44 kW kg‑1). Specific surface area increase from 68 m2 g‑1 for CNFs to 240 m2 g‑1 for CNFs/MnO2.

  11. Casting Characteristics of Aluminum Die Casting Alloys

    SciTech Connect

    Makhlouf M. Makhlouf; Diran Apelian

    2002-02-05

    The research program investigates the casting characteristics of selected aluminum die casting alloys. Specifically, the alloys' tendencies towards die soldering and sludge formation, and the alloys' fluidity and machinability are evaluated. It was found that: When the Fe and Mn contents of the alloy are low; caution has to be taken against possible die soldering. When the alloy has a high sludge factor, particularly a high level of Fe, measures must be taken to prevent the formation of large hardspots. For this kind of alloy, the Fe content should be kept at its lowest allowable level and the Mn content should be at its highest possible level. If there are problems in die filling, measures other than changing the alloy chemistry need to be considered first. In terms of alloy chemistry, the elements that form high temperature compounds must be kept at their lowest allowable levels. The alloys should not have machining problems when appropriate machining techniques and machining parameters are used.

  12. ToxCast Dashboard

    EPA Pesticide Factsheets

    The ToxCast Dashboard helps users examine high-throughput assay data to inform chemical safety decisions. To date, it has data on over 9,000 chemicals and information from more than 1,000 high-throughput assay endpoint components.

  13. Extrusion cast explosive

    DOEpatents

    Scribner, Kenneth J.

    1985-01-01

    Improved, multiphase, high performance, high energy, extrusion cast explosive compositions, comprising, a crystalline explosive material; an energetic liquid plasticizer; a urethane prepolymer, comprising a blend of polyvinyl formal, and polycaprolactone; a polyfunctional isocyanate; and a catalyst are disclosed. These new explosive compositions exhibit higher explosive content, a smooth detonation front, excellent stability over long periods of storage, and lower sensitivity to mechanical stimulants.

  14. Casting and Angling.

    ERIC Educational Resources Information Center

    Little, Mildred J.; Bunting, Camille

    The self-contained packet contains background information, lesson plans, 15 transparency and student handout masters, drills and games, 2 objective examinations, and references for teaching a 15-day unit on casting and angling to junior high and senior high school students, either as part of a regular physical education program or as a club…

  15. Lost-Soap Aluminum Casting.

    ERIC Educational Resources Information Center

    Mihalow, Paula

    1980-01-01

    Lost-wax casting in sterling silver is a costly experience for the average high school student. However, this jewelry process can be learned at no cost if scrap aluminum is used instead of silver, and soap bars are used instead of wax. This lost-soap aluminum casting process is described. (Author/KC)

  16. Project CAST.

    ERIC Educational Resources Information Center

    Charles County Board of Education, La Plata, MD. Office of Special Education.

    The document outlines procedures for implementing Project CAST (Community and School Together), a community-based career education program for secondary special education students in Charles County, Maryland. Initial sections discuss the role of a learning coordinator, (including relevant travel reimbursement and mileage forms) and an overview of…

  17. Paper Casting.

    ERIC Educational Resources Information Center

    Arrasjid, Dorine A.

    1980-01-01

    Describes an art project, based on the work of artist Chew Teng Beng, in the molding of wet paper on a plaster cast to create embossed paper designs. The values of such a project are outlined, including a note that its tactile approach makes it suitable to visually handicapped students. (SJL)

  18. CASTING FURNACES

    DOEpatents

    Ruppel, R.H.; Winters, C.E.

    1961-01-01

    A device is described for casting uranium which comprises a crucible, a rotatable table holding a plurality of molds, and a shell around both the crucible and the table. The bottom of the crucible has an eccentrically arranged pouring hole aligned with one of the molds at a time. The shell can be connected with a vacuum.

  19. Effective bioleaching of chromium in tannery sludge with an enriched sulfur-oxidizing bacterial community.

    PubMed

    Zeng, Jing; Gou, Min; Tang, Yue-Qin; Li, Guo-Ying; Sun, Zhao-Yong; Kida, Kenji

    2016-10-01

    In this study, a sulfur-oxidizing community was enriched from activated sludge generated in tannery wastewater treatment plants. Bioleaching of tannery sludge containing 0.9-1.2% chromium was investigated to evaluate the effectiveness of the enriched community, the effect of chromium binding forms on bioleaching efficiency, and the dominant microbes contributing to chromium bioleaching. Sludge samples inoculated with the enriched community presented 79.9-96.8% of chromium leaching efficiencies, much higher than those without the enriched community. High bioleaching efficiencies of over 95% were achieved for chromium in reducible fraction, while 60.9-97.9% were observed for chromium in oxidizable and residual fractions. Acidithiobacillus thiooxidans, the predominant bacteria in the enriched community, played an important role in bioleaching, whereas some indigenous heterotrophic species in sludge might have had a supporting role. The results indicated that A. thiooxidans-dominant enriched microbial community had high chromium bioleaching efficiency, and chromium binding forms affected the bioleaching performance.

  20. Antiferromagnetism in chromium

    NASA Astrophysics Data System (ADS)

    Jaramillo, Rafael

    I present two experimental studies of the spin density wave antiferromagnetic order in elemental Chromium. The first addresses the response of the magnetic ground state to applied pressure. The spin and charge order parameters are probed at high pressure and low temperature in a diamond anvil cell using monochromatic X-ray diffraction. We find that the magnetism is suppressed exponentially with pressure, providing a canonical example of a weak-coupling, mean-field ground state, before terminating at a quantum phase transition. We confirm the harmonic relationship between the spin and charge degrees of freedom in the low temperature regime, and we identify the microscopic coupling between pressure and magnetism. The discovery of the long-sought-after quantum critical regime sets the stage for a complete study of antiferromagnetic quantum criticality in this clean model system. The second study addresses the thermodynamics and transport properties of antiferromagnetic domain structure. We find a robust thermal hysteresis in the longitudinal and Hall resistivities of sub-mm bulk Cr samples. The temperature limits of the hysteresis are correlated with domain wall fluctuations and freezing. The persistent sign of the hysteresis and the macroscopic return point memory warrant a new understanding of domain wall energetics. By combining electrical transport and X-ray microdiffraction measurements we are able to pinpoint the effects of antiferromagnetic domain walls on electron transport.

  1. Predicting the Influence of Pore Characteristics on Ductility of Thin-Walled High Pressure Die Casting Magnesium

    SciTech Connect

    Sun, Xin; Choi, Kyoo Sil; Li, Dongsheng

    2013-06-10

    In this paper, a two-dimensional microstructure-based finite element modeling method is adopted to investigate the effects of porosity in thin-walled high pressure die casting Mg materials on their ductility. For this purpose, the cross-sections of AM50 and AM60 casting samples are first examined using optical microscope to obtain the overall information on the pore characteristics. The experimentally quantified pore characteristics are then used to generate a series of synthetic microstructures with different pore sizes, pore volume fractions and pore size distributions. Pores are explicitly represented in the synthetic microstructures and meshed out for the subsequent finite element analysis. In the finite element analysis, an intrinsic critical strain value is used for the Mg matrix material, beyond which work-hardening is no longer permissible. With no artificial failure criterion prescribed, ductility levels are predicted for the various microstructures in the form of strain localization. Mesh size effect study is also conducted, from which a mesh size dependent critical strain curve is determined. A concept of scalability of pore size effects is then presented and examined with the use of the mesh size dependent critical strain curve. The results in this study show that, for the regions with lower pore size and lower volume fraction, the ductility generally decreases as the pore size and pore volume fraction increase whereas, for the regions with larger pore size and larger pore volume fraction, other factors such as the mean distance between the pores begin to have some substantial influence on the ductility. The results also indicate that the pore size effects may be scalable for the models with good-representative pore shape and distribution with the use of the mesh size dependent critical strain curve.

  2. Mineral of the month: chromium

    USGS Publications Warehouse

    Papp, John F.

    2005-01-01

    Chromium is one of the most indispensable industrial metals and it plays an essential but hidden role in daily life. Chromium is used in many consumer and building products, and it contributes to a clean, efficient and healthy environment.

  3. Type 2 Diabetic Rats on Diet Supplemented With Chromium Malate Show Improved Glycometabolism, Glycometabolism-Related Enzyme Levels and Lipid Metabolism

    PubMed Central

    Feng, Weiwei; Zhao, Ting; Mao, Guanghua; Wang, Wei; Feng, Yun; Li, Fang; Zheng, Daheng; Wu, Huiyu; Jin, Dun; Yang, Liuqing; Wu, Xiangyang

    2015-01-01

    Our previous study showed that chromium malate improved the regulation of blood glucose in mice with alloxan-induced diabetes. The present study was designed to evaluate the effect of chromium malate on glycometabolism, glycometabolism-related enzymes and lipid metabolism in type 2 diabetic rats. Our results showed that fasting blood glucose, serum insulin level, insulin resistance index and C-peptide level in the high dose group had a significant downward trend when compared with the model group, chromium picolinate group and chromium trichloride group. The hepatic glycogen, glucose-6-phosphate dehydrogenase, glucokinase, Glut4, phosphor-AMPKβ1 and Akt levels in the high dose group were significantly higher than those of the model, chromium picolinate and chromium trichloride groups. Chromium malate in a high dose group can significantly increase high density lipoprotein cholesterol level while decreasing the total cholesterol, low density lipoprotein cholesterol and triglyceride levels when compared with chromium picolinate and chromium trichloride. The serum chromium content in chromium malate and chromium picolinate group is significantly higher than that of the chromium trichloride group. The results indicated that the curative effects of chromium malate on glycometabolism, glycometabolism-related enzymes and lipid metabolism changes are better than those of chromium picolinate and chromium trichloride. Chromium malate contributes to glucose uptake and transport in order to improved glycometabolism and glycometabolism-related enzymes. PMID:25942313

  4. Type 2 diabetic rats on diet supplemented with chromium malate show improved glycometabolism, glycometabolism-related enzyme levels and lipid metabolism.

    PubMed

    Feng, Weiwei; Zhao, Ting; Mao, Guanghua; Wang, Wei; Feng, Yun; Li, Fang; Zheng, Daheng; Wu, Huiyu; Jin, Dun; Yang, Liuqing; Wu, Xiangyang

    2015-01-01

    Our previous study showed that chromium malate improved the regulation of blood glucose in mice with alloxan-induced diabetes. The present study was designed to evaluate the effect of chromium malate on glycometabolism, glycometabolism-related enzymes and lipid metabolism in type 2 diabetic rats. Our results showed that fasting blood glucose, serum insulin level, insulin resistance index and C-peptide level in the high dose group had a significant downward trend when compared with the model group, chromium picolinate group and chromium trichloride group. The hepatic glycogen, glucose-6-phosphate dehydrogenase, glucokinase, Glut4, phosphor-AMPKβ1 and Akt levels in the high dose group were significantly higher than those of the model, chromium picolinate and chromium trichloride groups. Chromium malate in a high dose group can significantly increase high density lipoprotein cholesterol level while decreasing the total cholesterol, low density lipoprotein cholesterol and triglyceride levels when compared with chromium picolinate and chromium trichloride. The serum chromium content in chromium malate and chromium picolinate group is significantly higher than that of the chromium trichloride group. The results indicated that the curative effects of chromium malate on glycometabolism, glycometabolism-related enzymes and lipid metabolism changes are better than those of chromium picolinate and chromium trichloride. Chromium malate contributes to glucose uptake and transport in order to improved glycometabolism and glycometabolism-related enzymes.

  5. Application of Targeted Functional Assays to Assess a Putative Vascular Disruption Developmental Toxicity Pathway Informed By ToxCast High-Throughput Screening Data

    EPA Science Inventory

    Chemical perturbation of vascular development is a putative toxicity pathway which may result in developmental toxicity. EPA’s high-throughput screening (HTS) ToxCast program contains assays which measure cellular signals and biological processes critical for blood vessel develop...

  6. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

    Santella, M.L.; Sikka, V.K.

    1998-03-10

    A filler metal alloy used as a filler for welding cast nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and cast in copper chill molds. 3 figs.

  7. A hemi-metallocene chromium catalyst with trimethylaluminum-free methylaluminoxane for the synthesis of disentangled ultra-high molecular weight polyethylene.

    PubMed

    Romano, Dario; Ronca, Sara; Rastogi, Sanjay

    2015-02-01

    Recently, it has been shown that by using a single-site catalytic system having titanium as a metallic center, it is possible to tailor the entanglement density in the amorphous region of a semi-crystalline ultra-high molecular weight polyethylene (UHMWPE). This route provides the possibility to make high-modulus, high-strength uniaxially and biaxially drawn tapes and films, without using any solvent during processing. In this publication, it is shown that a single-site catalyst having chromium as metallic center, proposed by Enders and co-workers, can also be tuned to provide control on the entanglement density during synthesis of the UHMWPE. However, to achieve the goal some modifications during the synthesis are required. The synthesized polymers can be processed in the solid state below the equilibrium melting temperature, resulting in uniaxially drawn tapes having tensile strength and modulus greater than 3.5 N/tex and 200 N/tex, respectively. Rheological studies have been performed to follow the increase in entanglement density in melt state with time.

  8. [Adaptation of the bank vole (Clethrionomys glareolus Schreber) to conditions of biogeochemical province with abnormally high content of nickel, cobalt and chromium].

    PubMed

    Mikheeva, E V; Zhigal'skiĭ, O A; Mamina, V P; Baĭtimirova, E A

    2006-01-01

    Morphophysiological characteristics and peculiarities of adrenal gland of bank vole (Clethrionomys glareolus) were studied in the area of natural biogeochemical province with abnormally high content of nickel, cobalt and chromium. The control population inhabited area with usual content of these elements. We used 4-factor analysis of variance to estimate the influence of geochemical conditions, phase of population cycle, sex and reproductive state on the morphophysiological characteristics of animals and functional activity of adrenal gland. Animals from area with high concentration of Ni, Co and Cr show an increase in relative mass of adrenal glands, fascicular zone of adrenal cortex, size of cells and their nuclei. All these changes can be considered as an evidence of increased secretion of glucocorticoids. It is shown that phase of population cycle influences fatness of animals, size of nuclei, cells and adrenal cortex. Females in comparison with males are characterized with higher indexes of liver and adrenal gland, as well as morphometric indexes of adrenal cortex. The maturation of animals is accompanied with increase in body mass, fatness and relative mass of adrenal glands, the size of cortex zone, nuclei and cells themselves. It is supposed that the effect of "geochemical factor" results in intensification of glucocorticoid secretion of adrenal costex, thus increasing non-specific resistance of animals inhabiting area with high concentration of heavy metals. Such factors as "phase of population cycle", "sex" and "reproductive state", influence mineralocorticoid activity, glucocorticoid and androgenic functions of adrenal cortex. Some factors show synergetic effect.

  9. High concentrations of hexavalent chromium in drinking water alter iron homeostasis in F344 rats and B6C3F1 mice.

    PubMed

    Suh, Mina; Thompson, Chad M; Kirman, Christopher R; Carakostas, Michael C; Haws, Laurie C; Harris, Mark A; Proctor, Deborah M

    2014-03-01

    Hexavalent chromium [Cr(VI)] induces hematological signs of microcytic anemia in rodents. Considering that Cr(VI) can oxidize ferrous (Fe(2+)) to ferric (Fe(3+)) iron, and that only the former is transported across the duodenum, we hypothesize that, at high concentrations, Cr(VI) oxidizes Fe(2+) in the lumen of the small intestine and perturbs iron absorption. Herein we report that 90-day exposure to Cr(VI) in drinking water resulted in dose-dependent decreases in Fe levels in the duodenum, liver, serum, and bone marrow. Toxicogenomic analyses from the duodenum indicate responses consistent with Fe deficiency, including significant induction of divalent metal transporter 1 (DMT1, Slc11a2) and transferrin receptor 1 (TFR1, Tfr1). In addition, at ⩾20mg Cr(VI)/L in drinking water, Cr RBC:plasma ratios in rats were increased and exceeded unity, indicating saturation of reductive capacity and intracellular absorption of Cr(VI) into red blood cells (RBCs). These effects occurred in both species but were generally more severe in rats. These data suggest that high concentrations of Cr(VI) in drinking limit Fe absorption and alter iron homeostasis. Furthermore, some effects observed at high doses in recent Cr(VI) chronic and subchronic bioassays may be explained, at least in part, by iron deficiency and disruption of homeostasis.

  10. Casting methods

    SciTech Connect

    Marsden, Kenneth C.; Meyer, Mitchell K.; Grover, Blair K.; Fielding, Randall S.; Wolfensberger, Billy W.

    2012-12-18

    A casting device includes a covered crucible having a top opening and a bottom orifice, a lid covering the top opening, a stopper rod sealing the bottom orifice, and a reusable mold having at least one chamber, a top end of the chamber being open to and positioned below the bottom orifice and a vacuum tap into the chamber being below the top end of the chamber. A casting method includes charging a crucible with a solid material and covering the crucible, heating the crucible, melting the material, evacuating a chamber of a mold to less than 1 atm absolute through a vacuum tap into the chamber, draining the melted material into the evacuated chamber, solidifying the material in the chamber, and removing the solidified material from the chamber without damaging the chamber.

  11. Casting alloys.

    PubMed

    Wataha, John C; Messer, Regina L

    2004-04-01

    Although the role of dental casting alloys has changed in recent years with the development of improved all-ceramic materials and resin-based composites, alloys will likely continue to be critical assets in the treatment of missing and severely damaged teeth. Alloy shave physical, chemical, and biologic properties that exceed other classes of materials. The selection of the appropriate dental casting alloy is paramount to the long-term success of dental prostheses,and the selection process has become complex with the development of many new alloys. However, this selection process is manageable if the practitioner focuses on the appropriate physical and biologic properties, such as tensile strength, modulus of elasticity,corrosion, and biocompatibility, and avoids dwelling on the less important properties of alloy color and short-term cost. The appropriate selection of an alloy helps to ensure a longer-lasting restoration and better oral health for the patient.

  12. High Integrity Castings: Proceedings of the Conference on Advances in High Integrity Castings Held in Conjunction with the 1988 World Materials Congress, Chicago, Illinois, USA, 24-30 September 1988

    DTIC Science & Technology

    1988-01-01

    tough competitor to wrought products with the design flexibility of a casting. Solidification models to aid in decreasing the lead time from concept...Technical Center, Livonia, MI; J. R. Keough, Atmosphere Group, Inc., Wixom, M/ Heat Transfer - Solidification Kinetics Modeling of Casting Solidification...34Diffusion Models for Hot Pressing with Surface Energy and Pressure Effects as Driving Forces", Journal of Applied Physics, Vol. 41, No. 12, Nov. 1970

  13. Correlation of microstructure with the wear resistance and fracture toughness of white cast iron alloys

    NASA Astrophysics Data System (ADS)

    Filipovic, M.; Kamberovic, Z.; Korac, M.; Gavrilovski, M.

    2013-05-01

    The objective of this investigation was to set down (on the basis of the results obtained by the examination of white cast iron alloys with different contents of alloying elements) a correlation between chemical composition and microstructure, on one hand, and the properties relevant for this group of materials, i.e., wear resistance and fracture toughness, on the other. Experimental results indicate that the volume fraction of the eutectic carbide phase (M3C or M7C3) have an important influence on the wear resistance of white iron alloys under low-stress abrasion conditions. Besides, the martensitic or martensite-austenitic matrix microstructure more adequately reinforced the eutectic carbides, minimizing cracking and removal during wear, than did the austenitic matrix. The secondary carbides which precipitate in the matrix regions of high chromium iron also influence the abrasion behaviour. The results of fracture toughness tests show that the dynamic fracture toughness in white irons is determined mainly by the properties of the matrix. The high chromium iron containing 1.19 wt% V in the as-cast condition, showed the greater fracture toughness when compared to other experimental alloys. The higher toughness was attributed to strengthening during fracture, since very fine secondary carbide particles were present mainly in an austenitic matrix.

  14. CASTING APPARATUS

    DOEpatents

    Gray, C.F.; Thompson, R.H.

    1958-09-23

    An apparatus is described for casting small quantities of uranlum. It consists of a crucible having a hole in the bottom with a mold positioned below. A vertical rcd passes through the hole in the crucible and has at its upper end a piercing head adapted to break the oxide skin encasing a molten uranium body. An air tight cylinder surrounds the crucible and mold, and is arranged to be evacuated.

  15. [Occupational exposure to chromium(VI) compounds].

    PubMed

    Skowroń, Jolanta; Konieczko, Katarzyna

    2015-01-01

    This article discusses the effect of chromium(VI) (Cr(VI)) on human health under conditions of acute and chronic exposure in the workplace. Chromium(VI) compounds as carcinogens and/or mutagens pose a direct danger to people exposed to them. If carcinogens cannot be eliminated from the work and living environments, their exposure should be reduced to a minimum. In the European Union the proposed binding occupational exposure limit value (BOELV) for chromium(VI) of 0.025 mg/m³ is still associated with high cancer risk. Based on the Scientific Commitee of Occupational Exposure Limits (SCOEL) document chromium(VI) concentrations at 0.025 mg/m³ increases the risk of lung cancer in 2-14 cases per 1000 exposed workers. Exposure to chromium(VI) compounds expressed in Cr(VI) of 0.01 mg Cr(VI)/m3; is responsible for the increased number of lung cancer cases in 1-6 per 1000 people employed in this condition for the whole period of professional activity.

  16. Phytotoxic lesions of chromium in maize.

    PubMed

    Sharma, D C; Sharma, C P; Tripathi, R D

    2003-04-01

    Chromium (Cr) is fairly abundant in the earth's crust and ranks fourth among the 29 elements of biological importance. Besides natural sources, Cr enters biotic components of the ecosystem in various ways. Of other major industrial sources, tanning and chrome-plating industries are prominent sources. Cr(VI) form of chromium is highly reactive and influences both plants and animals. Due to Mn present in soil, Cr(III) is oxidized to Cr(VI) which remains in soil for a long time and can affect plant growth and development. Since maize is an important food and fodder plant for human beings and cattle, a study was conducted to investigate the effects of Cr on some metabolic activities of maize (Zea mays L. cv. Ganga 5). Chromium caused visible lesions of interveinal chlorosis. Young leaves showed vein clearing. Also, a papery appearance was observed in leaves. Margins of leaves were curled and the leaves appeared pale at greater Cr exposure. Concentrations of both chlorophyll a and b were reduced by exposure to Cr, the activities of ribonuclease and phenyl phosphatase were greater while the activity of iron-porphyrin enzyme catalase was less and the activity of amylase was also much less in plants exposed to Cr. Chromium also caused retardation of soluble protein. Accumulation of Cr in roots was much at all the levels of chromium supply. Exposure to Cr resulted in reduction in grain production and quality.

  17. Embryo- and fetotoxicity of chromium in pregestationally exposed mice

    SciTech Connect

    Junaid, M.; Murthy, R.C.; Saxena, D.K.

    1996-10-01

    Chromium, an essential element in the human body required for proper carbohydrate, protein, and fat metabolism, is reported to impair gestational development of offspring of workers chronically exposed to this metal in the work place. Workers in chromium based industries can be exposed to concentrations two orders of magnitude higher than the general population. Among the general population, residents living near chromate production sites may be exposed to high levels of chromium (VI) in air or to elevated levels (40 - 50,000 ppm) of chromium in effluents. Shmitova reported afterbirth and puerperal hemorrhages in women industrially exposed to this metal and observed high chromium levels in blood and urine of pregnant women and in fetal and cord blood. Chromium readily passes the placental barrier and reaches the growing fetus. Exposure of mice to chromium during various gestational periods resulted in embryo and fetotoxic effects. This study looks at the role of body chromium accumulated pregestationally on embryo and fetal development and its subsequent transfer to feto-placental sites. 25 refs., 3 tabs.

  18. Effects of Alloying Elements on Microstructure, Hardness, Wear Resistance, and Surface Roughness of Centrifugally Cast High-Speed Steel Rolls

    NASA Astrophysics Data System (ADS)

    Ha, Dae Jin; Sung, Hyo Kyung; Park, Joon Wook; Lee, Sunghak

    2009-11-01

    A study was made of the effects of carbon, tungsten, molybdenum, and vanadium on the wear resistance and surface roughness of five high-speed steel (HSS) rolls manufactured by the centrifugal casting method. High-temperature wear tests were conducted on these rolls to experimentally simulate the wear process during hot rolling. The HSS rolls contained a large amount (up to 25 vol pct) of carbides, such as MC, M2C, and M7C3 carbides formed in the tempered martensite matrix. The matrix consisted mainly of tempered lath martensite when the carbon content in the matrix was small, and contained a considerable amount of tempered plate martensite when the carbon content increased. The high-temperature wear test results indicated that the wear resistance and surface roughness of the rolls were enhanced when the amount of hard MC carbides formed inside solidification cells increased and their distribution was homogeneous. The best wear resistance and surface roughness were obtained from a roll in which a large amount of MC carbides were homogeneously distributed in the tempered lath martensite matrix. The appropriate contents of the carbon equivalent, tungsten equivalent, and vanadium were 2.0 to 2.3, 9 to 10, and 5 to 6 pct, respectively.

  19. On-line hydrogen-isotope measurements of organic samples using elemental chromium: an extension for high temperature elemental-analyzer techniques.

    PubMed

    Gehre, Matthias; Renpenning, Julian; Gilevska, Tetyana; Qi, Haiping; Coplen, Tyler B; Meijer, Harro A J; Brand, Willi A; Schimmelmann, Arndt

    2015-01-01

    The high temperature conversion (HTC) technique using an elemental analyzer with a glassy carbon tube and filling (temperature conversion/elemental analysis, TC/EA) is a widely used method for hydrogen isotopic analysis of water and many solid and liquid organic samples with analysis by isotope-ratio mass spectrometry (IRMS). However, the TC/EA IRMS method may produce inaccurate δ(2)H results, with values deviating by more than 20 mUr (milliurey = 0.001 = 1‰) from the true value for some materials. We show that a single-oven, chromium-filled elemental analyzer coupled to an IRMS substantially improves the measurement quality and reliability for hydrogen isotopic compositions of organic substances (Cr-EA method). Hot chromium maximizes the yield of molecular hydrogen in a helium carrier gas by irreversibly and quantitatively scavenging all reactive elements except hydrogen. In contrast, under TC/EA conditions, heteroelements like nitrogen or chlorine (and other halogens) can form hydrogen cyanide (HCN) or hydrogen chloride (HCl) and this can cause isotopic fractionation. The Cr-EA technique thus expands the analytical possibilities for on-line hydrogen-isotope measurements of organic samples significantly. This method yielded reproducibility values (1-sigma) for δ(2)H measurements on water and caffeine samples of better than 1.0 and 0.5 mUr, respectively. To overcome handling problems with water as the principal calibration anchor for hydrogen isotopic measurements, we have employed an effective and simple strategy using reference waters or other liquids sealed in silver-tube segments. These crimped silver tubes can be employed in both the Cr-EA and TC/EA techniques. They simplify considerably the normalization of hydrogen-isotope measurement data to the VSMOW-SLAP (Vienna Standard Mean Ocean Water-Standard Light Antarctic Precipitation) scale, and their use improves accuracy of the data by eliminating evaporative loss and associated isotopic fractionation while

  20. On-line hydrogen-isotope measurements of organic samples using elemental chromium: An extension for high temperature elemental-analyzer techniques

    USGS Publications Warehouse

    Gehre, Matthias; Renpenning, Julian; Gilevska, Tetyana; Qi, Haiping; Coplen, Tyler B.; Meijer, Harro A.J.; Brand, Willi A.; Schimmelmann, Arndt

    2015-01-01

    The high temperature conversion (HTC) technique using an elemental analyzer with a glassy carbon tube and filling (temperature conversion/elemental analysis, TC/EA) is a widely used method for hydrogen isotopic analysis of water and many solid and liquid organic samples with analysis by isotope-ratio mass spectrometry (IRMS). However, the TC/EA IRMS method may produce inaccurate δ2H results, with values deviating by more than 20 mUr (milliurey = 0.001 = 1‰) from the true value for some materials. We show that a single-oven, chromium-filled elemental analyzer coupled to an IRMS substantially improves the measurement quality and reliability for hydrogen isotopic compositions of organic substances (Cr-EA method). Hot chromium maximizes the yield of molecular hydrogen in a helium carrier gas by irreversibly and quantitatively scavenging all reactive elements except hydrogen. In contrast, under TC/EA conditions, heteroelements like nitrogen or chlorine (and other halogens) can form hydrogen cyanide (HCN) or hydrogen chloride (HCl) and this can cause isotopic fractionation. The Cr-EA technique thus expands the analytical possibilities for on-line hydrogen-isotope measurements of organic samples significantly. This method yielded reproducibility values (1-sigma) for δ2H measurements on water and caffeine samples of better than 1.0 and 0.5 mUr, respectively. To overcome handling problems with water as the principal calibration anchor for hydrogen isotopic measurements, we have employed an effective and simple strategy using reference waters or other liquids sealed in silver-tube segments. These crimped silver tubes can be employed in both the Cr-EA and TC/EA techniques. They simplify considerably the normalization of hydrogen-isotope measurement data to the VSMOW-SLAP (Vienna Standard Mean Ocean Water-Standard Light Antarctic Precipitation) scale, and their use improves accuracy of the data by eliminating evaporative loss and associated isotopic fractionation while

  1. Chromium(III) and chromium(VI) surface treated galvanized steel for outdoor constructions: environmental aspects.

    PubMed

    Lindström, David; Hedberg, Yolanda; Odnevall Wallinder, Inger

    2010-06-01

    The long-term degradation of chromium(III) (Zn-Cr(III)) and chromium(VI)-based (Zn-Cr(VI)) surface treatments on galvanized steel and their capacities to hinder the release of zinc induced by atmospheric corrosion at nonsheltered urban and marine exposure conditions for 2 years are investigated. Compared to bare zinc sheet, both surface treatments revealed high corrosion protection abilities and capacities to hinder the release of zinc, still evident after 2 years of exposure. The zinc barrier properties of the thinner Zn-Cr(VI) (10 nm) treatment were during the first 100 days of urban exposure slightly improved compared with Zn-Cr(III) (35 nm). However, their long-term protection capacities were inverse. Released concentrations of total chromium correspond to annual release rates less than 0.000032 (Zn-Cr(III)) and 0.00014 g Cr m(-2) yr(-1) (Zn-Cr(VI)) after 1 year of urban exposure. Aging by indoor storage of the surface treatments prior to outdoor exposure reduced the released Cr concentrations from the surface treatments. No Cr(VI) was released from the aged surfaces but from the freshly exposed Zn-Cr(VI). Marine exposure conditions resulted in a faster reduction of chromate to chromium(III)oxide compared with urban conditions, and a significantly lower amount of both chromium(III) and chromium(VI) released from Zn-Cr(VI) at the marine site compared with the urban site.

  2. A combined arc-melting and tilt-casting furnace for the manufacture of high-purity bulk metallic glass materials.

    PubMed

    Soinila, E; Pihlajamäki, T; Bossuyt, S; Hänninen, H

    2011-07-01

    An arc-melting furnace which includes a tilt-casting facility was designed and built, for the purpose of producing bulk metallic glass specimens. Tilt-casting was chosen because reportedly, in combination with high-purity processing, it produces the best fatigue endurance in Zr-based bulk metallic glasses. Incorporating the alloying and casting facilities in a single piece of equipment reduces the amount of laboratory space and capital investment needed. Eliminating the sample transfer step from the production process also saves time and reduces sample contamination. This is important because the glass forming ability in many alloy systems, such as Zr-based glass-forming alloys, deteriorates rapidly with increasing oxygen content of the specimen. The challenge was to create a versatile instrument, in which high purity conditions can be maintained throughout the process, even when melting alloys with high affinity for oxygen. Therefore, the design provides a high-vacuum chamber to be filled with a low-oxygen inert atmosphere, and takes special care to keep the system hermetically sealed throughout the process. In particular, movements of the arc-melting electrode and sample manipulator arm are accommodated by deformable metal bellows, rather than sliding O-ring seals, and the whole furnace is tilted for tilt-casting. This performance of the furnace is demonstrated by alloying and casting Zr(55)Cu(30)Al(10)Ni(5) directly into rods up to ø 10 mm which are verified to be amorphous by x-ray diffraction and differential scanning calorimetry, and to exhibit locally ductile fracture at liquid nitrogen temperature.

  3. Effects of sodium hypochlorite and high pH buffer solution in electrokinetic soil treatment on soil chromium removal and the functional diversity of soil microbial community.

    PubMed

    Cang, Long; Zhou, Dong-Mei; Alshawabkeh, Akram N; Chen, Hai-Feng

    2007-04-02

    Effects of sodium hypochlorite (NaClO), applied as an oxidant in catholyte, and high pH buffer solution on soil Cr removal and the functional diversity of soil microbial community during enhanced electrokinetic treatments of a chromium (Cr) contaminated red soil are evaluated. Using pH control system to maintain high alkalinity of soil together with the use of NaClO increased the electrical conductivities of soil pore liquid and electroosmotic flux compared with the control (Exp-01). The pH control and NaClO improved the removal of Cr(VI) and total Cr from the soil. The highest removal percentages of soil Cr(VI) and total Cr were 96 and 72%, respectively, in Exp-04 when the pH value of the anolyte was controlled at 10 and NaClO was added in the catholyte. The alkaline soil environment and introduction of NaClO in the soil enhanced the desorption of Cr(VI) from the soil and promoted Cr(III) oxidation to mobile Cr(VI), respectively. However, the elevated pH and introduction of NaClO in the soil, which are necessary for improving the removal efficiency of soil Cr, resulted in a significantly adverse impact on the functional diversity of soil microbial community. It suggests that to assess the negative impact of extreme conditions for enhancing the extraction efficiencies of Cr on the soil properties and function is necessary.

  4. The Effect of Manganese Additions on the Reactive Evaporation of Chromium in Ni-Cr Alloys

    SciTech Connect

    Holcomb, Gordon R.; Alman, David E.

    2004-10-20

    Chromium is used as an alloy addition in stainless steels and nickel-chromium alloys to form protective chromium oxide scales. Chromium oxide undergoes reactive evaporation in high temperature exposures in the presence of oxygen and/or water vapor. The deposition of gaseous chromium species onto solid oxide fuel cell electrodes can reduce the efficiency of the fuel cell. Manganese additions to the alloy can reduce the activity of chromium in the oxide, either from solid solution replacement of chromium with manganese (at low levels of manganese) or from the formation of manganese-chromium spinels (at high levels of manganese). This reduction in chromium activity leads to a predicted reduction in chromium evaporation by as much as a factor of 35 at 800 C and 55 at 700 C. The results of evaporation loss measurements on nickel-chromium-manganese alloys are compared with the predicted reduction. Quantifying the effects of manganese additions on chromium evaporation should aid alloy development of metallic interconnects and balance-of-plant alloys.

  5. Fatigue characterization of high pressure die-cast magnesium AM60B alloy using experimental and computational investigations

    NASA Astrophysics Data System (ADS)

    Lu, You

    The object of the current dissertation is to foster fundamental advances in microstructure-fatigue characteristics of a high pressure die cast magnesium AM60B alloy. First, high cycle fatigue staircase experiments were conducted on specimens extracted from automobile instrument panels. The resulting fracture surfaces were then examined with scanning electron microscopic imaging to elucidate the fatigue crack initiation sites and propagation paths at different stages of the fatigue life. Due to the fact that the qualification of the crack initiation and propagation mechanisms through experiment alone is difficult, complementary micromechanical finite element simulations were conducted. Particularly, the effects of different applied loading conditions and the porosity morphology (e.g. pore shape, pore size, pore spacing, proximity to the free surface) on the maximum plastic shear strain range, as a driving force for crack initiation, were analyzed. Moreover, at the microstructually small crack (MSC) propagation stage, the shielding effects of beta-phase Mg17Al12 particles were systematically studied. Based on the distribution of the maximum principal stress within the particles and the maximum hydrostatic stress along the particle/matrix interfaces, the relative influence of the pre-damaged (fractured or debonded) particles and various particle cluster morphologies were carefully investigated. In the finite element simulations, the constitutive behaviours of AM60B alloy and the alpha-matrix were simulated by the advanced kinematic hardening law tuned with experimentally determined material parameters under cyclic loading.

  6. The influence of heat treatment on the high-stress abrasion resistance and fracture toughness of alloy white cast irons

    NASA Astrophysics Data System (ADS)

    Sare, I. R.; Arnold, B. K.

    1995-07-01

    The influence of a range of austenitizing and subcritical (tempering) heat treatments on the high-stress abrasion resistance and fracture toughness of four commercially significant grades of alloy white cast iron was investigated. Complementing an earlier study[1] on the influence of a more limited range of heat treatments on the gouging abrasion performance of the same alloys, the results showed that the effect of austenitizing temperature on high-stress abrasion pin test weight loss differed for each alloy. With increasing austenitizing temperature, these results ranged from a substantial improvement in wear performance and retention of hardness through to vir-tually no change in wear performance and substantial falls in hardness. Fracture toughness, however, increased markedly in all alloys with increasing austenitizing temperature. Tempering treatments in the range 400 °C to 600 °C, following hardening at the austenitizing temperature used commonly in industrial practice for each alloy, produced significant changes in both hard-ness and wear performance, but negligible changes in fracture toughness. Most importantly, the data showed that selection of the correct temperature for subcritical heat treatment to reduce the retained austenite content for applications involving repeated impact loading is critical if abrasion resistance is not to suffer.

  7. O on the Crystallization Behavior of Lime-Alumina-Based Mold Flux for Casting High-Al Steels

    NASA Astrophysics Data System (ADS)

    Lu, Boxun; Chen, Kun; Wang, Wanlin; Jiang, Binbin

    2014-08-01

    With the development of advanced high strength steel (AHSS), a large amount of aluminum was added into steels. The reaction between aluminum in the molten steel and silica based mold flux in the continuous-casting process would tend to cause a series of problems and influence the quality of slabs. To solve the above problems caused by the slag-steel reaction, nonreactive lime-alumina-based mold flux system has been proposed. In this article, the effect of Li2O and Na2O on the crystallization behavior of the lime-alumina-silica-based mold flux has been studied by using the single hot thermocouple technology (SHTT) and double hot thermocouple technology (DHTT). The results indicated that Li2O and Na2O in the above mold flux system play different roles as they behaved in traditional lime-silica based mold flux, which would tend to inhibit general mold flux crystallization by lowering the initial crystallization temperature and increasing incubation time, especially in the high-temperature region. However, when their content exceeds a critical value, the crystallization process of mold fluxes in low temperature zone would be greatly accelerated by the new phase formation of LiAlO2 and Na x Al y Si z O4 crystals, respectively. The crystalline phases precipitated in all samples during the experiments are discussed in the article.

  8. Chromium and aging

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aging is associated with increased blood glucose, insulin, blood lipids, and fat mass, and decreased lean body mass leading to increased incidences of diabetes and cardiovascular diseases. Improved chromium nutrition is associated with improvements in all of these variables. Insulin sensitivity de...

  9. Chromium(VI)

    Integrated Risk Information System (IRIS)

    TOXICOLOGICAL REVIEW OF HEXAVALENT CHROMIUM ( CAS No . 18540 - 29 - 9 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) August 1998 U.S . Environmental Protection Agency Washington , DC DISCLAIMER This document has been reviewed in accordance with U.S . Environme

  10. Final Report - Effects of High Spinel and Chromium Oxide Crystal Contents on Simulated HLW Vitrification in DM100 Melter Tests, VSL-09R1520-1, Rev. 0, dated 6/22/09

    SciTech Connect

    Kruger, Albert A.; Matlack, K. S.; Kot, W.; Pegg, I. L.; Chaudhuri, M.; Lutze, W.

    2013-11-13

    The principal objective of the work was to evaluate the effects of spinel and chromium oxide particles on WTP HLW melter operations and potential impacts on melter life. This was accomplished through a combination of crucible-scale tests, settling and rheological tests, and tests on the DM100 melter system. Crucible testing was designed to develop and identify HLW glass compositions with high waste loadings that exhibit formation of crystalline spinel and/or chromium oxide phases up to relatively high crystal contents (i.e., > 1 vol%). Characterization of crystal settling and the effects on melt rheology was performed on the HLW glass formulations. Appropriate candidate HLW glass formulations were selected, based on characterization results, to support subsequent melter tests. In the present work, crucible melts were formulated that exhibit up to about 4.4 vol% crystallization.

  11. Performance of iron-chromium-aluminum alloy surface coatings on Zircaloy 2 under high-temperature steam and normal BWR operating conditions

    NASA Astrophysics Data System (ADS)

    Zhong, Weicheng; Mouche, Peter A.; Han, Xiaochun; Heuser, Brent J.; Mandapaka, Kiran K.; Was, Gary S.

    2016-03-01

    Iron-chromium-aluminum (FeCrAl) coatings deposited on Zircaloy 2 (Zy2) and yttria-stabilized zirconia (YSZ) by magnetron sputtering have been tested with respect to oxidation weight gain in high-temperature steam. In addition, autoclave testing of FeCrAl-coated Zy2 coupons under pressure-temperature-dissolved oxygen coolant conditions representative of a boiling water reactor (BWR) environment has been performed. Four different FeCrAl compositions have been tested in 700 °C steam; compositions that promote alumina formation inhibited oxidation of the underlying Zy2. Parabolic growth kinetics of alumina on FeCrAl-coated Zy2 is quantified via elemental depth profiling. Autoclave testing under normal BWR operating conditions (288 °C, 9.5 MPa with normal water chemistry) up to 20 days demonstrates observable weight gain over uncoated Zy2 simultaneously exposed to the same environment. However, no FeCrAl film degradation was observed. The 900 °C eutectic in binary Fe-Zr is addressed with the FeCrAl-YSZ system.

  12. Effects of dietary chromium (III) picolinate on growth performance, respiratory rate, plasma variables, and carcass traits of pigs fed high-fat diets.

    PubMed

    Kim, Beob G; Lindemann, Merlin D; Cromwell, Gary L

    2010-02-01

    We investigated the effects of supplemental chromium (Cr) as Cr (III) picolinate on pigs fed high-fat diets (HFD) in a 56-day experiment. Thirty-two crossbred pigs (9.6 kg) were allotted to four treatments with four blocks and two pigs/pen. Treatments included: (1) low-fat diet (fat < 3.5%; LFD) with no Cr, (2) HFD (fat > 30%) with no Cr, (3) HFD with 1,000 ppb Cr, and (4) HFD with 2,000 ppb Cr. Pigs fed HFD gained weight faster, consumed less, and had lower feed:gain (p < 0.05). Pigs fed HFD had higher respiration rates than pigs fed LFD on d 41 (p < 0.05). Plasma insulin on d 14 linearly decreased with Cr (p = 0.05). Plasma cholesterol concentrations were higher in the pigs fed HFD than those fed LFD, but were largely unaffected by supplemental Cr. Consumption of HFD resulted in greater carcass weight, perirenal fat, and backfat measures (p < 0.01) compared with the LFD group. Cr resulted in linear reductions of hot carcass weight (p = 0.08) and average backfat (p < 0.05). The effects of Cr on carcass fat measures were more pronounced in castrated males than in females. These results indicate that Cr attenuates some effects of a HFD, mainly body fat accretion of pigs, and especially in castrated pigs.

  13. Highly sensitive surface-enhanced Raman scattering detection of hexavalent chromium based on hollow sea urchin-like TiO2@Ag nanoparticle substrate.

    PubMed

    Zhou, Wen; Yin, Bin-Cheng; Ye, Bang-Ce

    2017-01-15

    As one of the most toxic heavy metals, hexavalent chromium (Cr(VI)) has long been a concern due to its threats to human health and the environment. In this work, we develop a sensitive surface-enhanced Raman scattering (SERS) sensor for highly specific detection of Cr(VI) using hollow sea urchin-like TiO2@Ag nanoparticles (NPs). The TiO2@Ag NPs are functionalized with glutathione (GSH) and used as substrates with 2-mercaptopyridine (2-MPy) as a Raman reporter for a recyclable SERS-active sensor, enabling ultrasensitive detection of Cr(VI). Excellent SERS signals of 2-MPy reporters are detected when GSH complexation with Cr(VI) causes aggregation of the TiO2@Ag NPs. The developed sensor exhibits good linearity in the range from 10nM to 2μM for Cr(VI) with a detection limit of ca. 1.45nM. It features excellent selectivity to Cr(VI) over other interfering metal ions, and good application for quantitative analysis of Cr(VI) in water samples. Moreover, the proposed SERS sensor can be fully regenerated when exposed to UV light as a result of the self-cleaning ability of the substrates. In contrast to the traditional SERS detection, the present work shed new light on the design and synthesis of hierarchically self-assembled 3D substrate for SERS, catalysis and biosensor development.

  14. Application of a water cooling treatment and its effect on coal-based reduction of high-chromium vanadium and titanium iron ore

    NASA Astrophysics Data System (ADS)

    Yang, Song-tao; Zhou, Mi; Jiang, Tao; Guan, Shan-fei; Zhang, Wei-jun; Xue, Xiang-xin

    2016-12-01

    A water cooling treatment was applied in the coal-based reduction of high-chromium vanadium and titanium (V-Ti-Cr) iron ore from the Hongge region of Panzhihua, China. Its effects on the metallization ratio ( η), S removal ratio ( R S), and P removal ratio ( R P) were studied and analyzed on the basis of chemical composition determined via inductively coupled plasma optical emission spectroscopy. The metallic iron particle size and the element distribution of Fe, V, Cr, and Ti in a reduced briquette after water cooling treatment at 1350°C were determined and observed via scanning electron microscopy. The results show that the water cooling treatment improved the η, R S, and R P in the coal-based reduction of V-Ti-Cr iron ore compared to those obtained with a furnace cooling treatment. Meanwhile, the particle size of metallic iron obtained via the water cooling treatment was smaller than that of metallic iron obtained via the furnace cooling treatment; however, the particle size reached 70 μm at 1350°C, which is substantially larger than the minimum particle size required (20 μm) for magnetic separation. Therefore, the water cooling treatment described in this work is a good method for improving the quality of metallic iron in coal-based reduction and it could be applied in the coal-based reduction of V-Ti-Cr iron ore followed by magnetic separation.

  15. Prediction of Microporosity in Shrouded Impeller Castings

    SciTech Connect

    Viswanathan, S. Nelson, C.D.

    1998-09-01

    The purpose of this Cooperative Research and Development Agreement (CRADA) between the Oak Ridge National Laboratory (ORNL) and Morris Bean and Company was to link computer models of heat and fluid flow with previously developed quality criteria for the prediction of microporosity in a Al-4.5% Cu alloy shrouded impeller casting. The results may be used to analyze the casting process design for the commercial production of 206 o alloy shrouded impeller castings. Test impeller castings were poured in the laboratory for the purpose of obtaining thermal data and porosity distributions. Also, a simulation of the test impeller casting was conducted and the results validated with porosity measurements on the test castings. A comparison of the predicted and measured microporosity distributions indicated an excellent correlation between experiments and prediction. The results of the experimental and modeling studies undertaken in this project indicate that the quality criteria developed for the prediction of microporosity in Al-4.5% Cu alloy castings can accurately predict regions of elevated microporosity even in complex castings such as the shrouded impeller casting. Accordingly, it should be possible to use quality criteria for porosity prediction in conjunction with computer models of heat and fluid flow to optimize the casting process for the production of shrouded impeller castings. Since high levels of microporosity may be expected to result in poor fatigue properties, casting designs that are optimized for low levels of microporosity should exhibit superior fatigue life.

  16. Casting materials

    DOEpatents

    Chaudhry, Anil R.; Dzugan, Robert; Harrington, Richard M.; Neece, Faurice D.; Singh, Nipendra P.

    2011-06-14

    A foam material comprises a liquid polymer and a liquid isocyanate which is mixed to make a solution that is poured, injected or otherwise deposited into a corresponding mold. A reaction from the mixture of the liquid polymer and liquid isocyanate inside the mold forms a thermally collapsible foam structure having a shape that corresponds to the inside surface configuration of the mold and a skin that is continuous and unbroken. Once the reaction is complete, the foam pattern is removed from the mold and may be used as a pattern in any number of conventional casting processes.

  17. High spatial dynamics-photoluminescence imaging reveals the metallurgy of the earliest lost-wax cast object.

    PubMed

    Thoury, M; Mille, B; Séverin-Fabiani, T; Robbiola, L; Réfrégiers, M; Jarrige, J-F; Bertrand, L

    2016-11-15

    Photoluminescence spectroscopy is a key method to monitor defects in semiconductors from nanophotonics to solar cell systems. Paradoxically, its great sensitivity to small variations of local environment becomes a handicap for heterogeneous systems, such as are encountered in environmental, medical, ancient materials sciences and engineering. Here we demonstrate that a novel full-field photoluminescence imaging approach allows accessing the spatial distribution of crystal defect fluctuations at the crystallite level across centimetre-wide fields of view. This capacity is illustrated in archaeology and material sciences. The coexistence of two hitherto indistinguishable non-stoichiometric cuprous oxide phases is revealed in a 6,000-year-old amulet from Mehrgarh (Baluchistan, Pakistan), identified as the oldest known artefact made by lost-wax casting and providing a better understanding of this fundamental invention. Low-concentration crystal defect fluctuations are readily mapped within ZnO nanowires. High spatial dynamics-photoluminescence imaging holds great promise for the characterization of bulk heterogeneous systems across multiple disciplines.

  18. High spatial dynamics-photoluminescence imaging reveals the metallurgy of the earliest lost-wax cast object

    PubMed Central

    Thoury, M.; Mille, B.; Séverin-Fabiani, T.; Robbiola, L.; Réfrégiers, M.; Jarrige, J-F; Bertrand, L.

    2016-01-01

    Photoluminescence spectroscopy is a key method to monitor defects in semiconductors from nanophotonics to solar cell systems. Paradoxically, its great sensitivity to small variations of local environment becomes a handicap for heterogeneous systems, such as are encountered in environmental, medical, ancient materials sciences and engineering. Here we demonstrate that a novel full-field photoluminescence imaging approach allows accessing the spatial distribution of crystal defect fluctuations at the crystallite level across centimetre-wide fields of view. This capacity is illustrated in archaeology and material sciences. The coexistence of two hitherto indistinguishable non-stoichiometric cuprous oxide phases is revealed in a 6,000-year-old amulet from Mehrgarh (Baluchistan, Pakistan), identified as the oldest known artefact made by lost-wax casting and providing a better understanding of this fundamental invention. Low-concentration crystal defect fluctuations are readily mapped within ZnO nanowires. High spatial dynamics-photoluminescence imaging holds great promise for the characterization of bulk heterogeneous systems across multiple disciplines. PMID:27843139

  19. High spatial dynamics-photoluminescence imaging reveals the metallurgy of the earliest lost-wax cast object

    NASA Astrophysics Data System (ADS)

    Thoury, M.; Mille, B.; Séverin-Fabiani, T.; Robbiola, L.; Réfrégiers, M.; Jarrige, J.-F.; Bertrand, L.

    2016-11-01

    Photoluminescence spectroscopy is a key method to monitor defects in semiconductors from nanophotonics to solar cell systems. Paradoxically, its great sensitivity to small variations of local environment becomes a handicap for heterogeneous systems, such as are encountered in environmental, medical, ancient materials sciences and engineering. Here we demonstrate that a novel full-field photoluminescence imaging approach allows accessing the spatial distribution of crystal defect fluctuations at the crystallite level across centimetre-wide fields of view. This capacity is illustrated in archaeology and material sciences. The coexistence of two hitherto indistinguishable non-stoichiometric cuprous oxide phases is revealed in a 6,000-year-old amulet from Mehrgarh (Baluchistan, Pakistan), identified as the oldest known artefact made by lost-wax casting and providing a better understanding of this fundamental invention. Low-concentration crystal defect fluctuations are readily mapped within ZnO nanowires. High spatial dynamics-photoluminescence imaging holds great promise for the characterization of bulk heterogeneous systems across multiple disciplines.

  20. Hot deformation characteristics of as-cast high-Cr ultra-super-critical rotor steel with columnar grains

    NASA Astrophysics Data System (ADS)

    Ding, Zong-ye; Hu, Qiao-dan; Zeng, Long; Li, Jian-guo

    2016-11-01

    Isothermal hot compression tests of as-cast high-Cr ultra-super-critical (USC) rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s-1. The softening mechanism was dynamic recovery (DRV) at 950°C and the strain rate of 1 s-1, whereas it was dynamic recrystallization (DRX) under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ•mol-1. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate ( θ)-flow stress ( σ) and -∂ θ/∂ σ-σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s-1, with a power dissipation efficiency η greater than 31%.

  1. Extrusion cast explosive

    DOEpatents

    Scribner, K.J.

    1985-01-29

    Improved, multiphase, high performance, high energy, extrusion cast explosive compositions, comprising, a crystalline explosive material; an energetic liquid plasticizer; a urethane prepolymer, comprising a blend of polyvinyl formal, and polycaprolactone; a polyfunctional isocyanate; and a catalyst are disclosed. These new explosive compositions exhibit higher explosive content, a smooth detonation front, excellent stability over long periods of storage, and lower sensitivity to mechanical stimulants. 1 fig.

  2. Extrusion cast explosive

    DOEpatents

    Scribner, K.J.

    1985-11-26

    Disclosed is an improved, multiphase, high performance, high energy, extrusion cast explosive compositions, comprising, a crystalline explosive material; an energetic liquid plasticizer; a urethane prepolymer, comprising a blend of polyvinyl formal, and polycaprolactone; a polyfunctional isocyanate; and a catalyst. These new explosive compositions exhibit higher explosive content, a smooth detonation front, excellent stability over long periods of storage, and lower sensitivity to mechanical stimulants. 1 fig.

  3. High temperature support apparatus and method of use for casting materials

    DOEpatents

    Clark, Roger F; Cliber, James A; Stoddard, Nathan G; Gerber, Jesse I; Roberts, Raymond J; Wilmerton, Mark A

    2015-02-10

    This invention relates to a system and a method of use for large ceramic member support and manipulation at elevated temperatures in non-oxidizing atmospheres, such as using carbon-carbon composite materials for producing high purity silicon in the manufacture of solar modules. The high temperature apparatus of this invention includes one or more support ribs, one or more cross braces in combination with the one or more support ribs, and a shaped support liner positionable upon the one or more support ribs and the one or more cross braces.

  4. Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2009-01-01

    In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

  5. Effect of Al2O3 on the Crystallization of Mold Flux for Casting High Al Steel

    NASA Astrophysics Data System (ADS)

    Zhou, Lejun; Wang, Wanlin; Zhou, Kechao

    2015-06-01

    In order to lower the weight of automotive bodies for better fuel-efficiency and occupant safety, the demand for high Al-containing advanced high strength steel, such as transformation-induced plasticity and twinning-induced plasticity steel, is increasing. However, high aluminum content in steels would tend to significantly affect the properties of mold flux during the continuous casting process. In this paper, a kinetic study of the effect of Al2O3 content on the crystallization behavior of mold flux was conducted by using the single hot thermocouple technique and the Johnson-Mehl-Avrami model combined with the Arrhenius Equation. The results suggested that Al2O3 behaves as an amphoteric oxide in the crystallization process of mold flux. The precipitated phases of mold flux change from cuspidine (Ca4Si2O7F2) into nepheline (NaAlSiO4) and CaF2, and then into gehlenite (Ca2Al2SiO7) with the increase of Al2O3 content. The kinetics study of the isothermal crystallization process indicated that the effective crystallization rate ( k) and Avrami exponent ( n) also first increased and then decreased with the increase of Al2O3 content. The values for the crystallization activation energy of mold flux with different Al2O3 contents were E R0.8A7 = 150.76 ± 17.89 kJ/mol, E R0.8A20 = 136.43 ± 6.48 kJ/mol, E R0.8A30 = 108.63 ± 12.25 kJ/mol and E R0.8A40 = 116.15 ± 8.17 kJ/mol.

  6. Slip-Cast Superconductive Parts

    NASA Technical Reports Server (NTRS)

    Wise, Stephanie A.; Buckley, John D.; Vasquez, Peter; Buck, Gregory M.; Hicks, Lana P.; Hooker, Matthew W.; Taylor, Theodore D.

    1993-01-01

    Complex shapes fabricated without machining. Nonaqueous slip-casting technique used to form complexly shaped parts from high-temperature superconductive materials like YBa(2)Cu(3)O(7-delta). Such parts useful in motors, vibration dampers, and bearings. In process, organic solvent used as liquid medium. Ceramic molds made by lost-wax process used instead of plaster-of-paris molds, used in aqueous slip-casting but impervious to organic solvents and cannot drain away liquid medium. Organic-solvent-based castings do not stick to ceramic molds as they do to plaster molds.

  7. Chromium(II) and chromium(II) tri-tert-butoxysiloxy complexes

    SciTech Connect

    Terry, K.W.; Gantzel, P.K.; Tilley, T.D. )

    1993-11-10

    The authors have been exploring the structure, bonding, and chemistry of transition-metal and main-group complexes that possess oxygen-rich alkoxysiloxy ligands such as [minus]OSi(O[sup t]Bu)[sub 3]. A primary focus of these studies is the development of molecular, single-source precursors to homogeneous, ultrapure metal silicates. The authors have found that titanium, zirconium, hafnium, and aluminum derivatives of [minus]OSi(O[sup t]Bu)[sub 3] thermally decompose at low temperatures (100-200[degrees]C) with elimination of isobutylene and water to give metal-containing silicates. Previous observations suggested the possible use of this methodology in new syntheses of supported catalysts, particularly since chemical reactivities and selectivities are known to be very sensitive to the size and shape of the supported metal catalyst particles. Silica- and aluminosilica-supported chromium catalysts are used widely for the catalytic polymerization of ethylene. To examine alkoxysiloxy derivatives of chromium as precursors to chromium-supported catalysts, the authors have begun to explore synthetic routes to Cr-OSi(O[sup t]Bu)[sub 3] complexes. On the basis of previously reported routes to siloxide and alkoxide complexes of chromium, approaches based on either the silanol HOSi(O[sup t]Bu)[sub 3] or alkali metal derivatives MOSi(O[sup t]Bu)[sub 3] (M = Li, Na, K) as starting materials seem possible. The authors report two siloxide complexes which result from the reaction of Cr(NEt[sub 2])[sub 4] with HOSi(O[sup t]Bu)[sub 3]. While this reaction does not provide a high yield of a single product that can be used in a convenient route to chromium silicate materials, it does offer the opportunity to closely compare analogous chromium(II) and chromium(III) siloxide complexes Cr[OSi(O[sup t]Bu)[sub 3

  8. Mechanical and structural properties of solution-cast high-amylose maize starch films.

    PubMed

    Koch, Kristine; Gillgren, Thomas; Stading, Mats; Andersson, Roger

    2010-01-01

    Environmental issues have forced the introduction of sustainable solutions such as annually renewable resources being used as a raw material for packaging and disposables. This paper examined the effects of time and temperature during manufacturing and plasticiser content on the molecular structure of high-amylose maize starch films. It also analysed how manufacturing conditions, plasticiser content and molecular structure of the films affected their material properties. It was found that increased time or temperature increased the degradation of amylose and of amylopectin, which in turn negatively affected film cohesiveness. However, neither time nor temperature had any effect on tensile properties.

  9. Effect of chromium picolinate and melatonin either in single or in a combination in high carbohydrate diet-fed male Wistar rats.

    PubMed

    Doddigarla, Zephy; Ahmad, Jamal; Parwez, Iqbal

    2016-01-01

    This study is designed to know the effects of chromium picolinate (CrPic) and melatonin (Mel) each alone and in a combination on high carbohydrate diet-fed (HCD-fed) male Wistar rats that exhibit insulin resistance (IR), hyperglycemia, and oxidative stress. Wistar rats have been categorized into five groups. Each group consisted of six male Wistar rats, control rats (group I), HCD (group II), HCD + CrPic (group III), HCD + Mel (group IV), and HCD + CrPic + Mel (group V). Insignificant differences were observed in serum levels of superoxide dismutase, nitric oxide, and zinc in group III, group IV, and group V when each group was compared with group II rats respectively. Significant differences were observed in group III, group IV, and group V when each group was compared with group II in homeostasis model assessment-estimated IR (P < 0.05, <0.0.05, <0.05), and in the levels of blood glucose (P < 0.05, <0.0.05, <0.05), total cholesterol (P < 0.05, <0.001, <0.001), triacylglycerols (<0.05, <0.001, <0.001), high density lipoprotein cholesterol (P < 0.05, <0.001, <0.001), malondialdehyde (P < 0.05, <0.05, <0.001), catalase (P <0.05, <0.05, <0.05), glutathione (P < 0.05, <0.05, <0.05), Mel (P < 0.05, <0.05, <0.001), and copper (P < 0.05, <0.05, < 0.001). In view of these results, HCD-fed male Wistar rats that are destined to attain IR and T2DM through diet can be prevented by giving CrPic and Mel administration in alone or in a combination.

  10. Studies of chromium gettering

    SciTech Connect

    Simpkins, J.E.; Mioduszewski, P.; Stratton, L.W.

    1982-01-01

    Preliminary results have shown that hydrogen pumping by chromium is a surface effect. Unlike with titanium, the getter material used in many present day tokamaks, there is no significant diffusion into the bulk. Additional experiments have been carried out to measure the basic characteristics of chromium films for gases of interest in tokamak research. These gases include deuterium, oxygen and nitrogen. A vacuum system is described which allowed precise control of the test gas, a constant wall temperature and determination of the projected getter surface area. A quadrupole mass spectrometer, rather than simply a total pressure gauge, was utilized to measure the partial pressure of the test gas as well as the residual gas composition in the system. A quartz crystal monitor was used to measure film thickness. Pumping speeds and sticking coefficients are given as a function of surface coverage for each test gas. A comparison will be made with titanium films deposited in the same vacuum system and under similar conditions.

  11. [Application to dental casting machine of the rapid heating infrared image furnace (author's transl)].

    PubMed

    Etchu, Y; Noguchi, H

    1980-10-01

    The authors tried to manufacture a casting machine in dentistry by application of the infrared image furnace with a high heating speed and an easy control of a heating temperature. This machine melts an alloy in a carbon crucible set in the furnace, held in the horizontal position. Then, the furnace is turned to the vertical position to drop a melted alloy on the casting mold, and the alloy is cast in the mold by the pressure of Argon gas. The functions of trial casting machine were follows. 1. The trial casting machine was capable of heating to 1250 degrees C within one minute under 4 kW electric power. 2. The castability of the 20% Au-Pd-Ag commercial alloy cast in all casting conditions by the trial casting machine was higher than that of Thermotrol D-2 automatic centrifugal casting machine. 3. Castings of the trial casting machine showed higher tensile strength and elongation than those of the centrifugal casting machine, and the deviation of values got by the trial casting machine was small. In particular, some casting of the trial casting machine showed three times or over elongation values as compared with those of the centrifugal casting machine. 4. When casting conditions (casting temperature, casting pressure) of the trial casting machine changed, the physical properties of castings did not change so much. However, when the mold was not prevented from heating by the furnace in casting, the elongation of castings increased.

  12. Transmission and Reflection Terahertz Spectroscopy of Insensitive Melt-Cast High-Explosive Materials

    NASA Astrophysics Data System (ADS)

    Palka, Norbert; Szala, Mateusz

    2016-10-01

    Currently, artillery shells and grenades that are introduced into the market are based on melt-castable insensitive high explosives (IHEs), which do not explode while they run a risk of impact, heat or shrapnel. Particles of explosives (such as hexogen, nitroguanidine and nitrotriazolone) are suspended in different proportions in a matrix of 2.4-dinitroanisole. In this paper, we investigated samples of commonly used IHEs: PAX-41, IMX-104 and IMX-101, whose internal structures were determined by a scanning electron microscope. Terahertz time domain spectroscopy was applied in both transmission and reflection configurations. At first, the complex refraction indices of four pure constituents creating IHEs were determined and became the basis of further calculations. Next, the experimentally determined transmission and reflection spectra of IHEs and pure constituents were compared with theoretical considerations. The influence of the grain size of constituent material and scattering on the reflection spectra was analysed, and good agreement between the experimental and theoretical data was achieved.

  13. Studies of chromium gettering

    NASA Astrophysics Data System (ADS)

    Simpkins, J. E.; Mioduszewski, P.; Stratton, L. W.

    1982-12-01

    Preliminary results have shown that hydrogen pumping by chromium is a surface effect. Unlike with titanium, the getter material used in many present day tokamaks, there is no significant diffusion into the bulk. This feature, which would minimize the tritium inventory, makes chromium a viable alternate to titanium gettering for future tokamaks. Additional experiments have been carried out to measure the basic characteristics of chromium films for gases of interest in tokamak research. These gases include deuterium, oxygen and nitrogen. A vacuum system is described which allowed precise control of the test gas, a constant wall temperature and determination of the projected getter surface area. A quadrupole mass spectrometer, rather than simply a total pressure gauge, was utilized to measure the partial pressure of the test gas as well as the residual gas composition in the system. A quartz crystal monitor was used to measure film thickness. Pumping speeds and sticking coefficients are given as a function of surface coverage for each test gas. A comparison will be made with titanium films deposited in the same vacuum system and under similar conditions.

  14. Visualizing taste papillae in vivo with scanning electron microscopy of a high resolution cast.

    PubMed

    Myers, W E; Hettinger, T P; D'Ambrosio, J A; Wendt, S L; Pearson, C B; Barry, M A; Frank, M E

    1995-02-01

    A method using polyvinylsiloxane (PVS), a high-resolution dental impression material, to obtain negative images of lingual surfaces is described. Epoxy-resin tongue replicas made from these impressions were examined with scanning electron microscopy (SEM). This method has been developed to visualize structural details of the tongue surface of living human beings and laboratory animals. The utility of the method is demonstrated with hamster tongues, which have well-defined fungiform papillae with single taste pores, and human tongues, which have more variable surface structures. Replicas made from PVS impressions of tongues of living hamsters were compared with the same tongues after fixation. The replicas contained much of the detail present in fixed tongues. With SEM, it was possible to identify individual fungiform papillae, which contained depressions with the size and the location of hamster taste pores. Individual papillae could also be recognized in human-tongue replicas, but taste pores could not be identified with certainty. These replicas provide permanent, three-dimensional records of tongue topography that could be used to document changes due to trauma, disease and aging.

  15. Superior mechanical performance of highly porous, anisotropic nanocellulose-montmorillonite aerogels prepared by freeze casting.

    PubMed

    Donius, Amalie E; Liu, Andong; Berglund, Lars A; Wegst, Ulrike G K

    2014-09-01

    Directionally solidified nanofibrillated cellulose (NFC)-sodium-montmorillonite (MMT) composite aerogels with a honeycomb-like pore structure were compared with non-directionally frozen aerogels with equiaxed pore structure and identical composition and found to have superior functionalities. To explore structure-property correlations, three different aerogel compositions of 3wt% MMT, and 0.4wt%, 0.8wt%, and 1.2wt% NFC, respectively, were tested. Young׳s modulus, compressive strength and toughness were found to increase with increasing NFC content for both architectures. The modulus increased from 25.8kPa to 386kPa for the isotropic and from 2.13MPa to 3.86MPa for the anisotropic aerogels, the compressive yield strength increased from 3.3kPa to 18.0kPa for the isotropic and from 32.3kPa to 52.5kPa for the anisotropic aerogels, and the toughness increased from 6.3kJ/m(3) to 24.1kJ/m(3) for the isotropic and from 22.9kJ/m(3) to 46.2kJ/m(3) for the anisotropic aerogels. The great range of properties, which can be achieved through compositional as well as architectural variations, makes these aerogels highly attractive for a large range of applications, for which either a specific composition, or a particular pore morphology, or both are required. Finally, because NFC is flammable, gasification experiments were performed, which revealed that the inclusion of MMT increased the heat endurance and shape retention functions of the aerogels dramatically up to 800°C while the mechanical properties were retained up to 300°C.

  16. Machine Casting of Ferrous Alloys

    DTIC Science & Technology

    1976-08-01

    high- lights of the earlier reports and much detail about Rheocast - ing and the casting of aluminum containing superalloys by Hitchiner’s patented...Augmented Hipo-v Procer-s EVALUATION OF RHEOCASTING WITH TFT: CTA PROCESS fU.S. Pat. 3,863,706) . Introduction to Rheocasting ... Rheocasting ...Drawing of suspension Bomb Lug. 13 Apparatus used to CLA pour Rheocast aluminum. 14 collection of parts cast by CLA process in semi- solid 35 5 aluminum

  17. Prediction of Part Distortion in Die Casting

    SciTech Connect

    R. Allen Miller

    2005-03-30

    The die casting process is one of the net shape manufacturing techniques and is widely used to produce high production castings with tight tolerances for many industries. An understanding of the stress distribution and the deformation pattern of parts produced by die casting will result in less deviation from the part design specification, a better die design and eventually more productivity and cost savings. This report presents methods that can be used to simulate the die casting process in order to predict the deformation and stresses in the produced part and assesses the degree to which distortion modeling is practical for die casting at the current time. A coupled thermal-mechanical finite elements model was used to simulate the die casting process. The simulation models the effect of thermal and mechanical interaction between the casting and the die. It also includes the temperature dependant material properties of the casting. Based on a designed experiment, a sensitivity analysis was conducted on the model to investigate the effect of key factors. These factors include the casting material model, material properties and thermal interaction between casting and dies. To verify the casting distortion predictions, it was compared against the measured dimensions of produced parts. The comparison included dimensions along and across the parting plane and the flatness of one surface.

  18. Environmental biochemistry of chromium.

    PubMed

    Losi, M E; Amrhein, C; Frankenberger, W T

    1994-01-01

    Chromium is a d-block transitional element with many industrial uses. It occurs naturally in various crustal materials and is discharged to the environment as industrial waste. Although it can occur in a number of oxidation states, only 3+ and 6+ are found in environmental systems. The environmental behavior of Cr is largely a function of its oxidation state. Hexavalent Cr compounds (mainly chromates and dichromates) are considered toxic to a variety of terrestrial and aquatic organisms and are mobile in soil/water systems, much more so than trivalent Cr compounds. This is largely because of differing chemical properties: Hexavalent Cr compounds are strong oxidizers and highly soluble, while trivalent Cr compounds tend to form relatively inert precipitates at near-neutral pH. The trivalent state is generally considered to be the stable form in equilibrium with most soil/water systems. A diagram of the Cr cycle in soils and water is given in Fig. 6 (Bartlett 1991). This illustration provides a summary of environmentally relevant reactions. Beginning with hexavalent Cr that is released into the environment as industrial waste, there are a number of possible fates, including pollution of soil and surface water and leaching into groundwater, where it may remain stable and, in turn, can be taken up by plants or animals, and adsorption/precipitation, involving soil colloids and/or organic matter. Herein lies much of the environmental concern associated with the hexavalent form. A portion of the Cr(VI) will be reduced to the trivalent form by inorganic electron donors, such as Fe2+ and S2-, or by bioprocesses involving organic matter. Following this conversion, Cr3+ can be expected to precipitate as oxides and hydroxides or to form complexes with numerous ligands. This fraction includes a vast majority of global Cr reserves. Soluble Cr3+ complexes, such as those formed with citrate, can undergo oxidation when they come in contact with manganese dioxide, thus reforming

  19. Advanced Casting Technology

    DTIC Science & Technology

    1982-08-01

    water , aged 5 hrs on 155 C. Fig. 15 Time required for 19 mm thick test slab casting, poured in sand, to cool...fraction rare earth could be solution treated, quenched and artificially aged to give high tensile properties at room temperature, which were well...Strength. MagnesiumrZincrRare. Earth . Alloys In parallel with the development of silver containing alloy systems, further improvements were obtained

  20. Shadow of a Large Disc Casts New Light on the Formation of High Mass Stars

    NASA Astrophysics Data System (ADS)

    2004-05-01

    Massive Star Observed that Forms through a Rotating Accretion Disc Summary Based on a large observational effort with different telescopes and instruments, mostly from the European Southern Observatory (ESO), a team of European astronomers [1] has shown that in the M 17 nebula a high mass star [2] forms via accretion through a circumstellar disc, i.e. through the same channel as low-mass stars. To reach this conclusion, the astronomers used very sensitive infrared instruments to penetrate the south-western molecular cloud of M 17 so that faint emission from gas heated up by a cluster of massive stars, partly located behind the molecular cloud, could be detected through the dust. Against the background of this hot region a large opaque silhouette, which resembles a flared disc seen nearly edge-on, is found to be associated with an hour-glass shaped reflection nebula. This system complies perfectly with a newly forming high-mass star surrounded by a huge accretion disc and accompanied by an energetic bipolar mass outflow. The new observations corroborate recent theoretical calculations which claim that stars up to 40 times more massive than the Sun can be formed by the same processes that are active during the formation of stars of smaller masses. PR Photo 15a/04: Stellar cluster and star-forming region M 17 (also available without text inside photo) PR Photo 15b/04: Silhouette disc seen in M 17 PR Photo 15c/04: Rotation of the disc in M 17. PR Photo 15d/04: Bipolar reflection nebula and silhouette disc of a young, massive star in M 17 PR Photo 15e/04: Optical spectrum of the bipolar nebula. PR Video 03/04: Zooming in onto the disc. The M 17 region ESO PR Photo 15a/04 ESO PR Photo 15a/04 [Preview - JPEG: 400 x 497 pix - 271k] [Normal - JPEG: 800 x 958 pix - 604k] ESO PR Photo 15a1/04 ESO PR Photo 15a/04 (without text within photo) [Preview - JPEG: 400 x 480 pix - 275k] [Normal - JPEG: 800 x 959 pix - 634k] [High-Res - JPEG: 3000 x 3597 pix - 3.8M] [Full-Res - JPEG

  1. INCONEL 690 CORROSION IN WTP (WASTE TREATMENT PLANT) HLW (HIGH LEVEL WASTE) GLASS MELTS RICH IN ALUMINUM & BISMUTH & CHROMIUM OR ALUMINUM/SODIUM

    SciTech Connect

    KRUGER AA; FENG Z; GAN H; PEGG IL

    2009-11-05

    Metal corrosion tests were conducted with four high waste loading non-Fe-limited HLW glass compositions. The results at 1150 C (the WTP nominal melter operating temperature) show corrosion performance for all four glasses that is comparable to that of other typical borosilicate waste glasses, including HLW glass compositions that have been developed for iron-limited WTP streams. Of the four glasses tested, the Bi-limited composition shows the greatest extent of corrosion, which may be related to its higher phosphorus content. Tests at higher suggest that a moderate elevation of the melter operating temperature (up to 1200 C) should not result in any significant increase in Inconel corrosion. However, corrosion rates did increase significantly at yet higher temperatures (1230 C). Very little difference was observed with and without the presence of an electric current density of 6 A/inch{sup 2}, which is the typical upper design limit for Inconel electrodes. The data show a roughly linear relationship between the thickness of the oxide scale on the coupon and the Cr-depletion depth, which is consistent with the chromium depletion providing the material source for scale growth. Analysis of the time dependence of the Cr depletion profiles measured at 1200 C suggests that diffusion of Cr in the Ni-based Inconel alloy controls the depletion depth of Cr inside the alloy. The diffusion coefficient derived from the experimental data agrees within one order of magnitude with the published diffusion coefficient data for Cr in Ni matrices; the difference is likely due to the contribution from faster grain boundary diffusion in the tested Inconel alloy. A simple diffusion model based on these data predicts that Inconel 690 alloy will suffer Cr depletion damage to a depth of about 1 cm over a five year service life at 1200 C in these glasses.

  2. Anti-diabetic activity of chromium picolinate and biotin in rats with type 2 diabetes induced by high-fat diet and streptozotocin.

    PubMed

    Sahin, Kazim; Tuzcu, Mehmet; Orhan, Cemal; Sahin, Nurhan; Kucuk, Osman; Ozercan, Ibrahim H; Juturu, Vijaya; Komorowski, James R

    2013-07-28

    The objective of the present study was to evaluate anti-diabetic effects of chromium picolinate (CrPic) and biotin supplementations in type 2 diabetic rats. The type 2 diabetic rat model was induced by high-fat diet (HFD) and low-dose streptozotocin. The rats were divided into five groups as follows: (1) non-diabetic rats fed a regular diet; (2) diabetic rats fed a HFD; (3) diabetic rats fed a HFD and supplemented with CrPic (80 μg/kg body weight (BW) per d); (4) diabetic rats fed a HFD and supplemented with biotin (300 μg/kg BW per d); (5) diabetic rats fed a HFD and supplemented with both CrPic and biotin. Circulating glucose, cortisol, total cholesterol, TAG, NEFA and malondialdehyde concentrations decreased (P< 0·05), but serum insulin concentrations increased (P< 0·05) in diabetic rats treated with biotin and CrPic, particularly with a combination of the supplements. Feeding a HFD to diabetic rats decreased PPAR-γ expression in adipose tissue and phosphorylated insulin receptor substrate 1 (p-IRS-1) expression of liver, kidney and muscle tissues, while the supplements increased (P< 0·001) PPAR-γ and p-IRS-1 expressions in relevant tissues. Expression of NF-κB in the liver and kidney was greater in diabetic rats fed a HFD, as compared with rats fed a regular diet (P< 0·01). The supplements decreased the expression of NF-κB in diabetic rats (P< 0·05). Results of the present study revealed that supplementing CrPic and biotin alone or in a combination exerts anti-diabetic activities, probably through modulation of PPAR-γ, IRS-1 and NF-κB proteins.

  3. Influence of Crucible Materials on High-temperature Properties of Vacuum-melted Nickel-chromium-cobalt Alloy

    NASA Technical Reports Server (NTRS)

    Decker, R F; Rowe, John P; Freeman, J W

    1957-01-01

    A study of the effect of induction-vacuum-melting procedure on the high-temperature properties of a titanium-and-aluminum-hardened nickel-base alloy revealed that a major variable was the type of ceramic used as a crucible. Reactions between the melt and magnesia or zirconia crucibles apparently increased high-temperature properties by introducing small amounts of boron or zirconium into the melts. Heats melted in alumina crucibles had relatively low rupture life and ductility at 1,600 F and cracked during hot-working as a result of deriving no boron or zirconium from the crucible.

  4. The effect of chromium picolinate on serum cholesterol and apolipoprotein fractions in human subjects.

    PubMed Central

    Press, R. I.; Geller, J.; Evans, G. W.

    1990-01-01

    Chromium has been implicated as a cofactor in the maintenance of normal lipid and carbohydrate metabolism. A deficiency of chromium results from diets low in biologically available chromium. Picolinic acid, a metabolite of tryptophan, forms stable complexes with transitional metal ions, which results in an improved bioavailability of the metal ion chromium. To determine whether or not chromium picolinate is effective in humans, 28 volunteer subjects were given either chromium tripicolinate (3.8 micromol [200 micrograms] chromium) or a placebo daily for 42 days in a double-blind crossover study. A 14-day period off capsules was used between treatments. Levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, and apolipoprotein B, the principal protein of the LDL fraction, decreased significantly while the subjects were ingesting chromium picolinate. The concentration of apolipoprotein A-I, the principal protein of the high-density lipoprotein (HDL) fraction, increased substantially during treatment with chromium picolinate. The HDL-cholesterol level was elevated slightly but not significantly during ingestion of chromium picolinate. Only apolipoprotein B, of the variables measured, was altered significantly during supplementation with the placebo. These observations show that chromium picolinate is efficacious in lowering blood lipids in humans. PMID:2408233

  5. Alternative Testing Strategy Example: Bioactivity Profilign of Diverse Engineering Nanomaterials via High-throughput Screening in ToxCast

    EPA Science Inventory

    Most of the over 2800 nanomaterials (NMs) in commerce lack hazard data. Efficient NM testing requires suitable toxicity tests for prioritization of NMs to be tested. The EPA’s ToxCast program is evaluating HTS assays to prioritize NMs for targeted testing. Au, Ag, CeO2, Cu(O2), T...

  6. NCCT ToxCast Program for Nanomaterial Prioritization: High-Throughput Screening, Consideration of Exposure, and Bioactivity Profiling/Modeling

    EPA Science Inventory

    Find relationships between bioactivities and NM characteristics or testing conditions. Recommend a dose metric for NMs in vitro studies. Establish associations to in vivo toxicity or pathways identified from testing of conventional chemicals with ToxCast HTS methods. May be abl...

  7. Thin Wall Iron Castings

    SciTech Connect

    J.F. Cuttino; D.M. Stefanescu; T.S. Piwonka

    2001-10-31

    Results of an investigation made to develop methods of making iron castings having wall thicknesses as small as 2.5 mm in green sand molds are presented. It was found that thin wall ductile and compacted graphite iron castings can be made and have properties consistent with heavier castings. Green sand molding variables that affect casting dimensions were also identified.

  8. Lipid peroxidation in workers exposed to hexavalent chromium.

    PubMed

    Huang, Y L; Chen, C Y; Sheu, J Y; Chuang, I C; Pan, J H; Lin, T H

    1999-02-26

    The aim of this study was to investigate whether exposure to hexavalent chromium induces lipid peroxidation in human. This study involved 25 chrome-plating factory workers and a reference group of 28 control subjects. The whole-blood and urinary chromium concentrations were determined by graphite furnace atomic absorption spectrophotometry. Malondialdehyde (MDA), the product of lipid peroxidation, was determined by high-performance liquid chromatography, and the activities of protective enzymes were measured by ultraviolet-visible spectrophotometry. In the chrome-plating workers, the mean concentrations of chromium in blood and urine were 5.98 microg/L and 5.25 microg/g creatinine, respectively; the mean concentrations of MDA in blood and urine were 1.7 micromol/L and 2.24 micromol/g creatinine. The concentrations of both chromium and MDA in blood and urine were significantly higher in the chromium-exposed workers. The activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) were not markedly different between control and exposed workers. Data suggest that MDA may be used as a biomarker for occupational chromium exposure. Antioxidant enzymic activities are not a suitable marker for chromium exposure.

  9. The Role of Indian Caste Identity and Caste Inconsistent Norms on Status Representation

    PubMed Central

    Sankaran, Sindhuja; Sekerdej, Maciek; von Hecker, Ulrich

    2017-01-01

    The Indian caste system is a complex social structure wherein social roles like one’s profession became ‘hereditary,’ resulting in restricted social mobility and fixed status hierarchies. Furthermore, we argue that the inherent property of caste heightens group identification with one’s caste. Highly identified group members would protect the identity of the group in situations when group norms are violated. In this paper, we were interested in examining the consequence of caste norm violation and how an individual’s status is mentally represented. High caste norms are associated with moral values while the lower caste norms are associated with immorality. We predicted a ‘black sheep effect,’ that is, when high caste individuals’ group identity (caste norm violation condition) is threatened their salient high caste identity would increase, thereby resulting in devaluing the status of their fellow in-group member if the latter is perceived as perpetrator. We presented participants with a social conflict situation of a victim and a perpetrator that is ‘Caste norm consistent’ (Lower caste individual as a perpetrator and higher caste individual as a victim) and vice versa ‘Caste norm inconsistent’ condition (higher caste individual as perpetrator and lower caste individual as a victim). Then, participants had to choose from nine pictorial depictions representing the protagonists in the story on a vertical line, with varying degrees of status distance. Results showed evidence for the black sheep effect and, furthermore, revealed that no other identity (religious, national, and regional) resulted in devaluing the status of fellow in-group member. These results help us understand the ‘black sheep’ effect in the context of moral norms and status representation and are discussed in the framework of the Indian society.

  10. Low cycle fatigue life of two nickel-base casting alloys in a hydrogen environment. [for high-pressure oxidizer turbopump turbine nozzles

    NASA Technical Reports Server (NTRS)

    Cooper, R. A.

    1976-01-01

    Samples of two nickel-base casting alloys, Mar-M-246 (a Martin Company alloy) and 713LC (a low-carbon modification of the alloy 713C developed by International Nickel Company) were tested as candidate materials for the high-pressure fuel and high-pressure oxidizer turbopump turbine nozzles. The samples were subjected to tensile tests and to low cycle fatigue tests in high-pressure hydrogen to study the influence of the hydrogen environment. The Mar-M-246 material was found to have a three times higher cyclic life in hydrogen than the 713LC alloy, and was selected as the nozzle material.

  11. Highly efficient removal of chromium(VI) by Fe/Ni bimetallic nanoparticles in an ultrasound-assisted system.

    PubMed

    Zhou, Xiaobin; Jing, Guohua; Lv, Bihong; Zhou, Zuoming; Zhu, Runliang

    2016-10-01

    Highly active Fe/Ni bimetallic nanocomposites were prepared by using the liquid-phase reduction method, and they were proven to be effective for Cr(VI) removal coupled with US irradiation. The US-assisted Fe/Ni bimetallic system could maintain a good performance for Cr(VI) removal at a wide pH range of 3-9. Based on the characterization of the Fe/Ni nanoparticles before and after reaction, the high efficiency of the mixed system could attribute to the synergistic effects of the catalysis of Ni(0) and US cavitation. Ni(0) could facilitate the Cr(VI) reduction through electron transfer and catalytic hydrogenation. Meanwhile, US could fluidize the Fe/Ni nanoparticles to increase the actual reactive surface area and clean off the co-precipitated Fe(III)-Cr(III) hydroxides to maintain the active sites on the surface of the Fe/Ni nanoparticles. Thus, compared with shaking, the US-assisted Fe/Ni system was more efficient on Cr(VI) removal, which achieved 94.7% removal efficiency of Cr(VI) within 10 min. The pseudo-first-order rate constant (kobs) in US-assisted Fe/Ni system (0.5075 min(-1)) was over 5 times higher than that under shaking (0.0972 min(-1)). Moreover, the Fe/Ni nanoparticles still have a good performance under US irradiation after 26 days aging as well as regeneration.

  12. Simulated spatial and temporal dependence of chromium concentration in pure Fe and Fesbnd 14%Cr under high dpa ion irradiation

    NASA Astrophysics Data System (ADS)

    Vörtler, K.; Mamivand, M.; Barnard, L.; Szlufarska, I.; Garner, F. A.; Morgan, D.

    2016-10-01

    In this work we develop an ab initio informed rate theory model to track the spatial and temporal evolution of implanted ions (Cr+) in Fe and Fesbnd 14%Cr during high dose irradiation. We focus on the influence of the specimen surface, the depth dependence of ion-induced damage, the damage rate, and the consequences of ion implantation, all of which influence the depth dependence of alloy composition evolving with continued irradiation. We investigate chemical segregation effects in the material by considering the diffusion of the irradiation-induced defects. Moreover, we explore how temperature, grain size, grain boundary sink strength, and defect production bias modify the resulting distribution of alloy composition. Our results show that the implanted ion profile can be quite different than the predicted SRIM implantation profile due to radiation enhanced transport and segregation.

  13. Effects of composition and testing conditions on oxidation behavior of four cast commercial nickel-base superalloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Probst, H. B.

    1974-01-01

    Four cast nickel-base superalloys were oxidized at 1000 and 1100 C for times up to 100 hr in static air and a Mach 1 gas stream. The oxidation resistance was judged by weight change, metal thickness loss, depletion-zone formation, and oxide formation and morphology. The alloys which formed mostly nickel aluminate (NiAl2O4) and aluminum oxide (Al2O3) (B-1900, VIA, and to a lesser extent 713C) were more oxidation resistant. Poorer oxidation resistance was associated with the appearance of chromium sesquioxide (Cr2O3) and chromite spinel (738X). Refractory metal content had little effect on oxidation resistance. Refractory metals appeared in the scale as tapiolite (NiM2O6, where M represents the refractory metal). Thermal cycling in static air appeared to supply sufficient data for the evaluation of oxidation resistance, especially for alloys which form oxides of low volatility. For alloys of higher chromium levels with high propensities toward forming a chromium-bearing scale of higher volatility, testing under conditions of high gas velocity is necessary to assess fully the behavior of the alloy.

  14. Relationship Between the 3D Porosity and β-Phase Distributions and the Mechanical Properties of a High Pressure Die Cast AZ91 Mg Alloy

    NASA Astrophysics Data System (ADS)

    Biswas, Somjeet; Sket, Federico; Chiumenti, Michele; Gutiérrez-Urrutia, Iván; Molina-Aldareguía, Jon M.; Pérez-Prado, Maria Teresa

    2013-09-01

    Currently, most magnesium lightweight components are fabricated by casting as this process is cost effective and allows forming parts with complex geometries and weak textures. However, cast microstructures are known to be heterogeneous and contain unpredictable porosity distributions, which give rise to a large variability in the mechanical properties. This work constitutes an attempt to correlate the microstructure and the mechanical behavior of a high pressure die cast (HPDC) Mg AZ91 alloy, aimed at facilitating process optimization. We have built a stairway-shaped die to fabricate alloy sections with different thicknesses and, thus, with a range of microstructures. The grain size distributions and the content of β-phase (Mg17Al12) were characterized by optical and electron microscopy techniques as well as by electron backscatter diffraction (EBSD). The bulk porosity distribution was measured by 3D computed X-ray microtomography. It was found that the through-thickness microhardness distribution is mostly related to the local area fraction of the β-phase and to the local area fraction of the pores. We correlate the tensile yield strength to the average pore size and the fracture strength and elongation to the bulk porosity volume fraction. We propose that this empirical approach might be extended to the estimation of mechanical properties in other HPDC Mg alloys.

  15. Chromium-induced toxic hepatitis.

    PubMed

    Lança, Sara; Alves, Amanda; Vieira, Ana Isabel; Barata, José; de Freitas, João; de Carvalho, Alvaro

    2002-12-01

    A clinical case of acute hepatitis in a patient undergoing an alternative medicine weight-reduction regimen is reported. Chromium polynicotinate had been ingested in combination with vegetable extracts over a 5-month period. Liver biopsy was compatible with toxic hepatitis and greatly elevated hepatic chromium levels were found (>10x normal). The clinical picture regressed following suspension of the medication.

  16. Chromium-rich lawsonite in high-Cr eclogites from the Făgăras Massif (South Carpathians)

    NASA Astrophysics Data System (ADS)

    Negulescu, E.; Săbău, G.

    2012-12-01

    Lawsonite is a relatively rare phase in natural rocks, because of its thermal decomposition during exhumation, and Cr-bearing lawsonite being restricted to only a few occurrences worldwide. Here we report Cr-lawsonite in eclogites hosted in a medium-grade metamorphic complex. Several high-Cr eclogite lenses occur in the Topolog Complex (Făgăras Massif) of dominantly gneissic-amphibolitic composition. High Cr contents are the result of emerald-green mm-sized nodules containing Cr-rich minerals, embedded in a gray-green matrix of kyanite, clinopyroxene, garnet, amphibole, zoisite, and rutile. Garnets occur as porphyroblasts or in coronas around clinopyroxene aggregates probably replacing former magmatic pyroxene. Relict gabbroic textures (sometimes pegmatoid) and whole rock geochemistry indicate a gabbroic cumulate origin. The REE pattern, displaying a slight positive Eu anomaly and a tea spoon-shaped LREE depletion is also indicative of a cumulate origin, as also noted by Pe Piper & Piper (2002) for the Othrys gabbro (as well as others in the Vourinos and Pindos ophiolitic suites) with the same unusual REE-pattern. The emerald-green Cr-rich nodules are unevenly distributed in the rock, and always enclosed in Cr-rich clinopyroxenes (up to 5.46% Cr2O3) which may exhibit Cr-diffusion haloes towards normal Cr-free matrix pyroxene. The nodules consist of diablastic chromite, rutile and Cr-rich kyanite of up to 15.67 wt% Cr2O3, Cr-bearing epidote, to which Cr-rich staurolite (up to 10.45% Cr2O3; XMg up to 0.68) and Cr-rich lawsonite (up to 9.17% Cr2O3) may exceptionally associate. Cr concentrations in kyanite and lawsonite are, to our knowledge, the highest reported so far. Cr-lawsonite was identified in a single sample, as small single phase inclusions armoured in Cr-kyanite. Equilibrium PT-conditions of 2.6 GPa and 610o C were derived from the garnet-mantled clinopyroxene aggregates using multi-equilibria calculation with the PTGIBBS routine of Brandelik & Massonne

  17. Structure and Properties of Chromium- and Zinc-Oxide Layers Formed on Zircaloy-2 in High-Temperature Water

    SciTech Connect

    Blajiev, Orlin L.; Matsuura, Chihiro; Hiroishi, Daisuke; Ishigure, Kenkichi

    2002-01-15

    The corrosion behavior of Zircaloy-2 in the presence of Zn was investigated. Zinc is a possible technological additive to be injected in the coolant to reduce the {sup 60}Co buildup. However, its influence on the cladding corrosion, alone or in combination with some typical corrosion impurities, as, for example, Cr, has not been considered so far. Because of this, the surface composition and electrochemical properties of Zircaloy specimens were investigated after their exposure to Zn{sup 2+}, CrO{sub 4}{sup 2-}, and CrO{sub 4}{sup 2-} + Zn{sup 2+} aqueous solutions at 250degC. It was found that zinc-containing phases did not deposit from solutions containing on Zn{sup 2+} ions. Amorphous Cr{sup 3+}-oxide and ZnCr{sub 2}O{sub 4} ferrite phases were found on the surface of the samples after their exposure to CrO{sub 4}{sup 2-} and CrO{sub 4}{sup 2-} + Zn{sup 2+} environments, respectively. The amounts of the deposited Cr and Zn + Cr strongly depended on the times of the preconditioning of the Zircaloy specimens in high-temperature water. The rate of the oxide precipitation declined with increasing exposure time to both the CrO{sub 4}{sup 2-} and CrO{sub 4}{sup 2-} + Zn{sup 2+} solutions. The electrochemical measurement showed that the limiting factor of the Cr and Zn + Cr deposition reaction was the reduction of Cr(VI) to Cr(III). The reduction completely depended on the resistance of ZrO{sub 2}, Cr, and Zn + Cr oxides, which increased with the time of preconditioning and exposure. A thermodynamic analysis based on oxide solubilities was applied to explain the different deposition pathways in the CrO{sub 4}{sup 2-} and CrO{sub 4}{sup 2-} + Zn{sup 2+} environments. In view of the decreasing deposition rate of the Zn - Cr-oxide phases, it could be concluded that their limited precipitation and presence do not have a significant adverse effect on the fuel cladding corrosion.

  18. Groundwater contaminant by hexavalent chromium

    SciTech Connect

    Parsons, C.

    1995-11-01

    Oxidation of trivalent chromium to hexavalent chromium has been investigated as a function of total manganese in soils as well as various incubation conditions. Chromium and manganese contents were analyzed by atomic absorption (graphite furnace and flame emission respectively) following acid digestion. Total hexavalent chromium generation capacity was determined by addition of 0.001 M CrCL3, incubation, and analysis by s-diphenyl carbazide. Samples were then leached with CaSO{sub 4} and MgSO{sub 4} and incubated in various environments (oven, freeze-drier, field moist, ultrafreeze) to test for geogenic generation of Cr(IV). The degree of geogenic generation of hexavalent chromium was compared with total Mn and Cr content as well as hexavalent generational capacity.

  19. SCIENCE AND TECHNOLOGY ACTIVITIES FOR CHROMIUM IN THE 100 AREAS

    SciTech Connect

    PETERSEN SW

    2009-07-02

    {sm_bullet} Primary Objective: Protect the Columbia River - Focus is control and treatment of contamination at or near the shoreline, which is influenced by bank storage {sm_bullet} Secondary Objective: Reduce hexavalent chromium to <48 parts per billion (ppb) in aquifer (drinking water standard) - Large plumes with isolated areas of high chromium concentrations (> 40,000 ppb), - Unknown source location(s); probably originating in reactor operation areas

  20. Analytical stress modeling of high-energy laser windows: Application to fusion-cast calcium fluoride windows

    NASA Astrophysics Data System (ADS)

    Klein, Claude A.

    2005-08-01

    The performance of a laser-window material must be assessed not only in terms of its ability to transmit high-power beams without generating undue optical distortion but also in terms of the constraints imposed by stress-related failure modes. In operational use, the stress field images the superposition of stresses originating from the mechanical load created by the pressure differential and the thermal load created by the laser beam. Here, we provide the tools to carry out an analysis of both pressure- and beam-induced stresses, and illustrate the procedure in the context of assessing the performance of a "model" window made of fusion-cast CaF2. The analysis assumes (a) operation on a time scale such that lateral heat diffusion can be ignored, and (b) cylindrically symmetric Gaussian beam shapes, which permit straightforward calculations of stress distributions that should be representative of worst case situations. Pressure-induced stresses strongly depend on the window's aspect ratio, which suggests increasing the thickness to minimize the stress, but considerations relating to the optical performance require minimum allowable thicknesses based on a Weibull statistical analysis of the fracture probability. Beam-induced stresses are best evaluated in terms of (a) thickness-averaged radial and azimuthal stresses, which increase linearly with exposure time and depend on radial distances through the truncation parameter, and (b) across-the-thickness stress deviations relative to the average stress, which are caused by surface absorption and reach steady-state configurations on a time scale much shorter than the characteristic time for lateral heat transport. The average stress is always compressive and equibiaxial in the central region of the window, but its azimuthal component turns tensile in the rim region, thus threatening the structural integrity through brittle fracture. In addition, the coating-induced stress results in on-axis surface compressions that may

  1. Effects of hot-rolling reduction on microstructure, texture and magnetic properties of high silicon steel produced by strip casting

    NASA Astrophysics Data System (ADS)

    Hou, D. Y.; Xu, H. J.; Jiao, H. T.; Zhao, C. W.; Xiong, W.; Yang, J. P.; Qiu, W. Z.; Xu, Y. B.

    2017-01-01

    Non-oriented Fe-7.1wt.% Si as-cast strips were produced by twin-roll strip casting process. Then the as-cast strips were hot rolled with different reductions, followed by warm rolling and final annealing. The microstructure, texture evolution and magnetic properties were investigated in detail. The texture of hot rolled sheets with 40% reduction showed strongest {001}<110> texture, whereas the dominated texture was turned into {110}<001> and {110}<112>as the reduction was increased to 56% and 68%. After warm rolling and annealing, the average grain size was decreased firstly and then increased with an increase in hot rolling reduction. In the case of 40% hot rolling reduction, the recrystallization texture was dominated by strong γ (<111>//ND) texture. With an increase in hot rolling reduction, the γ texture was gradually weakened while α (<110>//RD) texture was enhanced. In addition, relatively stronger {100} texture was presented in the sheet of 68% hot rolling reduction. The highest B50 value attained was 1.66 T and the lowest P10/400 was 24.26 W/kg at a reduction of 56%.

  2. Effect of chromium additions on the mechanical and physical properties and microstructure of Fe-Co-Ni-Cr-Mo-C ultra-high strength steel: Part I

    NASA Astrophysics Data System (ADS)

    Machmeier, P.; Matuszewski, T.; Jones, R.; Ayer, R.

    1997-06-01

    The effect of chromium additions to an Fe-14Co-10Ni-0.1Mo-0.16C (AF1410 based) secondary hardening steel was evaluated by mechanical and physical properties and by microstructural examination. This unique behavior was extended to encompass a large range of aging temperatures and times that may be encountered during commercial thermal treatment and/or welding. In the aging range of 482 to 550 °C, an increase in chromium from 2 to 3% in the AF1410 based steel resulted in a substantial strength decrease concomitant with an increase in toughness. This behavior is related to a peak hardening shift, early M2C carbide coarsening, and an increase in reverted austenite for the 1 wt% Cr increase. The increased aging kinetics resulting from the 3Cr steel caused a faster dissolution of Fe3C and rapid changes in chromium partitioning in the (Mo,Cr)2C carbide resulting in a coherency loss with a corresponding decrease in lattice parameter. The kinetics of the secondary hardening reaction, for the two steels, was determined by resistivity data for changes in aging parameters (time/temperature).

  3. Study of the structure and properties of metal of the major steam lines of a CCGT-420 unit made from high-chromium X10CrMoVNb9-1 (P91) steel

    NASA Astrophysics Data System (ADS)

    Grin', E. A.; Anokhov, A. E.; Pchelintsev, A. V.; Krüger, E.-T.

    2016-07-01

    The technology of manufacture of live steam lines and hot reheat lines at FINOW Rohrsysteme GmbH are discussed. These pipelines are designed for high-performance CCGT units and are made from high-chromium martensitic steel X10CrMoVNb9-1 (P91). The principles of certification and evaluation of conformance of thermal and mechanical equipment made from new construction materials with the TRCU 032-2013 technical regulation of the Customs Union are detailed. The requirements outlined in Russian and international regulatory documents regarding the manufacture of pipes and semifinished products for pipeline systems are compared. The characteristic features of high-chromium martensitic steel, which define the requirements for its heat treatment and welding, are outlined. The methodology and the results of a comprehensive analysis of metal of pipes, fittings, and weld joints of steam lines are presented. It is demonstrated that the short-term mechanical properties of metal (P91 steel) of pipes, bends, and weld joints meet the requirements of European standards and Russian technical specifications. The experimental data on long-term strength of metal of pipes from a live steam line virtually match the corresponding reference curve from the European standard, while certain experimental points for metal of bends of this steam line and metal of pipes and bends from a hot reheat line lie below the reference curve, but they definitely stay within the qualifying (20%) interval of the scatter band. The presence of a weakened layer in the heat-affected zone of weld joints of steel P91 is established. It is shown that the properties of this zone govern the short-term and long-term strength of weld joints in general. The results of synthesis and analysis of research data support the notion that the certification testing of steam lines and other equipment made from chromium steels should necessarily involve the determination of long-term strength parameters.

  4. Comparative study of two commercially pure titanium casting methods

    PubMed Central

    RODRIGUES, Renata Cristina Silveira; FARIA, Adriana Claudia Lapria; ORSI, Iara Augusta; de MATTOS, Maria da Gloria Chiarello; MACEDO, Ana Paula; RIBEIRO, Ricardo Faria

    2010-01-01

    The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior. Objective This study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure. Material and Methods 72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey's to compare materials and cast methods (α=0.05). Results Three of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (p<0.05) were observed only for the Co-Cr alloy with 0.25 mm and 0.50 mm undercuts. Significant differences were found for the 0.25 mm and 0.75 mm undercuts dependent on the material used. For the 0.50 mm undercut, significant differences were found when the materials were induction casted. Conclusion Although both casting methods produced satisfactory CP Ti RPD frameworks, the occurrence of porosities was greater in the plasma/vacuum-pressure than in the induction/centrifugation method, the latter resulting in higher clasp rigidity, generating higher retention force values. PMID:21085805

  5. Hexavalent chromium monitor

    DOEpatents

    Tao, Shiquan; Winstead, Christopher B.

    2005-04-12

    A monitor is provided for use in measuring the concentration of hexavalent chromium in a liquid, such as water. The monitor includes a sample cell, a light source, and a photodetector. The sample cell is in the form of a liquid-core waveguide, the sample cell defining an interior core and acting as a receiver for the liquid to be analyzed, the interior surface of the sample cell having a refractive index of less than 1.33. The light source is in communication with a first end of the sample cell for emitting radiation having a wavelength of about and between 350 to 390 nm into the interior core of the waveguide. The photodetector is in communication with a second end of the waveguide for measuring the absorption of the radiation emitted by the light source by the liquid in the sample cell. The monitor may also include a processor electronically coupled to the photodetector for receipt of an absorption signal to determine the concentration of hexavalent chromium in the liquid.

  6. Usefulness of gel-casting method in the fabrication of nonstoichiometric CaZrO{sub 3}-based electrolytes for high temperature application

    SciTech Connect

    Dudek, Magdalena

    2009-09-15

    Hydrogels obtained from lower toxicity monomers of N-(hydroxymethyl)acrylamide and N,N'-methylenebisacrylamide were applied to form nonstoichiometric CaZrO{sub 3}-based electrolytes. A coprecipitation-calcination method with ((NH{sub 4}){sub 2}C{sub 2}O{sub 4}) in concentrated NH{sub 3} aqueous solution was used to synthesise CaZrO{sub 3} involving 51 mol.% CaO (CZ-51) powder. The gas-tight CaZrO{sub 3}-based rods were prepared by the gel-casting method with 45 vol.% suspension and then sintered at 1500 deg. C-2 h. It was found that in low oxygen partial pressure, the nonstoichiometric CaZrO{sub 3} obtained by gel-casting method were pure oxide ion conductors. These samples exhibited comparable electrical conductivity values to isostatically compressed pellets starting from the same powder. The results of experiments on thermochemical stability of CZ-51 gel-cast shapes at high temperatures in air or gas mixtures involving 2-50 vol.% H{sub 2}, as well as the corrosion resistance in exhaust gases from a self-ignition engine were also presented and discussed. The thermal resistance of CaZrO{sub 3} obtained rods against molten nickel or iron was also examined. Based upon these investigations, it is evident that only in hydrogen-rich gas atmospheres can the stability of CaZrO{sub 3} shapes be limited due to the presence of CaO precipitation as a second phase. The nonstoichiometric CaZrO{sub 3} (CZ-51) gel-cast materials were also tested in solid galvanic cells, designed to study thermodynamic properties of oxide materials, important for SOFC and energy technology devices. In this way, the Gibbs energy of NiM{sub 2}O{sub 4}, M = Cr, Fe, at 650-1000 deg. C was determined. The CaZrO{sub 3} involving 51 mol.% CaO gel-cast sintered shapes seems to be promising solid electrolytes for electrochemical oxygen probes in control of metal processing and thermodynamic studies of materials important for the development of the energy industry.

  7. INTERIOR VIEW WITH CASTING MACHINE AND CASTING FOREMAN OBSERVING OPERATION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR VIEW WITH CASTING MACHINE AND CASTING FOREMAN OBSERVING OPERATION TO ENSURE MAXIMUM PRODUCTION AND QUALITY. - McWane Cast Iron Pipe Company, Pipe Casting Area, 1201 Vanderbilt Road, Birmingham, Jefferson County, AL

  8. Clean Cast Steel Technology, Phase IV

    SciTech Connect

    Charles E. Bates

    2003-02-24

    The objective of the Clean Cast Steel Technology Program was to improve casting product quality by removing or minimizing oxide defects and to allow the production of higher integrity castings for high speed machining lines. Previous research has concentrated on macro-inclusions that break, chip, or crack machine tool cutters and drills and cause immediate shutdown of the machining lines. The overall goal of the project is to reduce the amount of surface macro-inclusions and improve the machinability of steel castings. Macro-inclusions and improve the machinability of steel castings. Macro-inclusions have been identified by industrial sponsors as a major barrier to improving the quality and marketability of steel castings.

  9. Effect of tritium on corrosion behavior of chromium in 0.01 N sulfuric acid solution

    SciTech Connect

    Oyaidzu, M.; Isobe, K.; Hayashi, T.

    2015-03-15

    The effects of tritium on the corrosion behavior of chromium in 0.01 N sulfuric solution have been investigated in the present study. Electrochemical experiments have been carried our for pure chromium. At first, the concentration dependence of sulfuric acid solution on anodic polarization behavior of chromium was experimented, resulting in that 0.01 N one was found appropriate. The dependence of both dissolved oxygen and tritium concentration on anodic behavior of chromium were performed. It was found from that the self-passivation of chromium induced by dissolved oxygen was inhibited in tritiated solution resulting in the enhancement of the corrosion. As a consequence it is highly likely that the elution of chromium by highly oxidative radiolysis products would explain the passivation inhibitory effect of SUS304 stainless steel observed in tritiated solutions.

  10. Effects of dietary organic chromium and vitamin C supplementation on performance, immune responses, blood metabolites, and stress status of laying hens subjected to high stocking density.

    PubMed

    Mirfendereski, E; Jahanian, R

    2015-02-01

    The present study was carried out to investigate the effects of dietary supplementation of chromium-methionine (CrMet) and vitamin C (VC) on performance, immune response, and stress status of laying hens subjected to high stocking density. A total of 360 Hy-Line W-36 leghorn hens (at 26 wk old) were used in a 2×3×2 factorial arrangement that had 2 cage densities (5 and 7 hens per cage), 3 Cr levels (0, 500, and 1,000 ppb as CrMet), and 2 dietary VC levels (0 and 500 ppm as L-ascorbic acid). The trial lasted for 12 wk. The first 2 wk were for adaptation (26 to 28 wk of age), and the remaining 10 wk served as the main recording period. In addition to performance, immune response to Newcastle disease virus (NDV) was assessed at d 7 and 14 postvaccination. Also, the birds' stress status was evaluated by analyzing appropriate plasma metabolites. The results showed that hens in cages with higher stocking density had lower hen-day egg production, egg mass, and feed intake compared with those in normal density cages (P<0.05). Dietary CrMet supplementation caused significant increases in egg production and egg mass (P<0.01). There were significant Cr × VC interactions related to egg production and feed conversion efficiency (P<0.01); dietary CrMet supplementation was more effective in improving egg production and feed conversion ratio in VC-unsupplemented diets. Although plasma concentrations of triglycerides and high-density lipoproteins were not influenced by dietary treatments, supplemental CrMet decreased plasma cholesterol levels (P<0.05). Plasma insulin and glucose levels of hens kept at a density of 7 hens/cage were significantly higher than those of hens in normal cage density (P<0.01), and dietary CrMet supplementation decreased plasma concentrations of insulin (P<0.001) and glucose (P<0.01), with higher impacts in high stocking density-challenged hens. While high stocking density caused a marked increase in plasma corticosterone (P<0.01), both supplemental

  11. Novel template-casting technique for fabricating beta-tricalcium phosphate scaffolds with high interconnectivity and mechanical strength and in vitro cell responses.

    PubMed

    Liu, Yongxing; Kim, Joong-Hyun; Young, Daniel; Kim, Sungwoo; Nishimoto, Satoru K; Yang, Yunzhi

    2010-03-01

    A novel template-casting method was developed to produce completely interconnected, macroporous biodegradable beta-tricalcium phosphate (beta-TCP) scaffolds, whose architecture and chemistry can be fully manipulated by varying the templates and casting materials. The processing route includes preparation of beta-TCP slurry; casting and shaping into preformed templates comprised of paraffin beads; solidifying, drying; and sintering. Structural, chemical, and mechanical properties of the prepared macroporous scaffolds were characterized using micro computed tomography, scanning electron microscopy, x-ray diffractometry, Fourier transform infrared spectroscopy, and mechanical testing. Human embryonic palatal mesenchymal cells were used to evaluate cell proliferation within the scaffolds in vitro. The scaffolds consisted of interconnected macropores and solid struts, leading to a reticular network. Two groups of scaffolds with larger pores, approximately 600-800 microm and smaller pores approximately 350-500 microm, were demonstrated. The interconnected windows between neighboring macropores were 440 +/- 57 microm in diameter for the larger-pored scaffolds, and 330 +/- 50 microm for the smaller-pored scaffolds. The scaffolds were highly crystallized and composed dominantly of beta-tricalcium phosphate (beta-TCP) accompanied by minor phase of hydroxyapatite (HA). The hydroxyl group was clearly detected by FTIR on the scaffolds. High mechanical strength (9.3 MPa) was demonstrated by the completely interconnected scaffolds with approximately 79% porosity. The human embryonic palatal mesenchymal (HEPM) cells proliferated well on the smaller-pored and larger-pored scaffolds, exhibiting a significantly higher level of proliferation in the first 11 days of culture on the smaller pored scaffolds. High levels of differentiation were also evidenced in both pore sizes of scaffolds.

  12. Cool Cast Facts

    MedlinePlus

    ... outer layer is usually made of plaster or fiberglass. Fiberglass casts are made of fiberglass, which is a plastic that can be shaped. Fiberglass casts come in many different colors — if you' ...

  13. Plastic casting resin poisoning

    MedlinePlus

    Epoxy poisoning; Resin poisoning ... Epoxy and resin can be poisonous if they are swallowed or their fumes are breathed in. ... Plastic casting resins are found in various plastic casting resin products.

  14. Analyzing the Dynamics and Morphology of Cast-off Pattern at Different Speed Levels Using High-speed Digital Video Imaging.

    PubMed

    Kunz, Sebastian Niko; Adamec, Jiri; Grove, Christina

    2017-03-01

    During a bloodstain pattern analysis, one of the essential tasks is to distinguish between different kinds of applied forces as well as to estimate their level of intensity. In this study, high-speed digital imaging has been used to analyze the formation of cast-off patterns generated by a simulated backswing with a blood-bearing object. For this purpose, 0.5 mL blood was applied evenly over the last 5 cm of a blade simulant. Bloodstains were created through the controlled acceleration of a backswing at different speed levels between 1.1 m/sec and 3.8 m/sec. The flight dynamics of blood droplets were captured with an Olympus(®) i-Speed 3 high-speed digital camera with a Nikon(®) AF Nikkor 50 mm f/1.8 D lens and analyzed using the Olympus i-Speed 3 Viewer software. The video analysis showed that, during the backswing, blood droplets would move toward the lower end of the knifepoint and would be tangentially thrown off. These droplets impacted on the horizontal surface according to the arc of the swing. An increase in velocity led to longer cast-off patterns with distinct morphological characteristics. Under laboratory conditions, bloodstain pattern analysis allows certain conclusions about the intensity of a backswing and provides instructions on the position of the offender. However, due to the number of unknown variables at a crime scene, such interpretation of cast-off patterns is extremely limited and should be performed with extreme caution.

  15. Chromium isotopes as indicators of hexavalent chromium reduction

    SciTech Connect

    Johnson, Thomas M.

    2012-03-20

    This is the final report for a university research project which advanced development of a new technology for identifying chemical reduction of hexavalent chromium contamination in groundwater systems. Reduction renders mobile and toxic hexavalent chromium immobile and less toxic. The new method uses stable isotope ratio measurements, which are made using multicollector ICP-mass spectrometry. The main objectives of this project were completed during the project period and two peer-reviewed articles were published to disseminate the information gained.

  16. Effects of magnesia and potassium sulfate on gypsum-bonded alumina dental investment for high-fusing casting.

    PubMed

    Yan, M; Takahashi, H

    1998-12-01

    The purpose of this study was to improve the characteristics of gypsum-bonded alumina investments using magnesia and potassium sulfate as chemical additives. Magnesia content improved fluidity, delayed setting reaction, increased green strength, and decreased setting expansion, when mixed with distilled water. When the investment was mixed with potassium sulfate, the setting time and setting expansion were reduced, and the thermal expansion increased, however, the green strength decreased. Therefore, the investment with a small amount of magnesia mixed with potassium sulfate was considered a suitable composition, having adequate setting behavior, enough green strength and sufficient compensate expansion for casting.

  17. Is chromium pharmacologically relevant?

    PubMed

    Vincent, John B

    2014-10-01

    Recent research, combined with reanalysis of previous results, has revealed that chromium can no longer be considered an essential trace element. Clinical studies are ambiguous at best as to whether Cr has a pharmacological effect in humans. Observed effects of Cr on rodent models of insulin resistance and diabetes are best interpreted in terms of a pharmacological role for Cr. Studies on the effects of Cr on rat models of diabetes are reviewed herein and suggest Cr increases insulin sensitivity in peripheral tissues of the rodent models. The lack of effects in human studies may stem from humans receiving a comparably smaller dose than the rodent models. However, given the different responses to Cr in the rodent models, humans could potentially have different responses to Cr.

  18. LLNL casting technology

    SciTech Connect

    Shapiro, A.B.; Comfort, W.J. III

    1994-01-01

    Competition to produce cast parts of higher quality, lower rejection rate, and lower cost is a fundamental factor in the global economy. To gain an edge on foreign competitors, the US casting industry must cut manufacturing costs and reduce the time from design to market. Casting research and development (R&D) are the key to increasing US compentiveness in the casting arena. Lawrence Livermore National Laboratory (LLNL) is the home of a wide range of R&D projects that push the boundaries of state-of-the art casting. LLNL casting expertise and technology include: casting modeling research and development, including numerical simulation of fluid flow, heat transfer, reaction/solidification kinetics, and part distortion with residual stresses; special facilities to cast toxic material; extensive experience casting metals and nonmetals; advanced measurement and instrumentation systems. Department of Energy (DOE) funding provides the leverage for LLNL to collaborate with industrial partners to share this advanced casting expertise and technology. At the same time, collaboration with industrial partners provides LLNL technologists with broader insights into casting industry issues, casting process data, and the collective, experience of industry experts. Casting R&D is also an excellent example of dual-use technology; it is the cornerstone for increasing US industrial competitiveness and minimizing waste nuclear material in weapon component production. Annual funding for casting projects at LLNL is $10M, which represents 1% of the total LLNL budget. Metal casting accounts for about 80% of the funding. Funding is nearly equally divided between development directed toward US industrial competitiveness and weapon component casting.

  19. Method for fabricating cermets of alumina-chromium systems

    DOEpatents

    Morgan, Chester S.

    1983-01-01

    Cermet insulators resistant to thermal and mechanical shock are prepared from alumina-chromium systems by providing an Al.sub.2 O.sub.3 material of about 0.5 to 7.0 micron size with a solid-hydrocarbon overcoating by slurring an effective amount of said solid hydrocarbon in a solvent mixture containing said Al.sub.2 O.sub.3 and thereafter evaporating said solvent, contacting said coated Al.sub.2 O.sub.3 with a solution of chromium precursor compound, heating the resulting mixture in a reducing environment to a temperature above the decomposition temperature of said chromium precursor compound but less than the melting temperature of the Al.sub.2 O.sub.3 or chromium for sufficient duration to yield a particulate compound having chromium essentially dispersed throughout the Al.sub.2 O.sub.3, and then densifying said particulate to provide said cermet characterized by a theoretical density in excess of 96% and having 0.1 to 10.0 vol.% elemental chromium metal present therein as a dispersed phase at the boundaries of the Al.sub.2 O.sub.3 material. Cermet components prepared thereby are useful in high temperature equipment, advanced heat engines, and nuclear-related equipment applications where electrical or thermal insulators are required.

  20. Centrifugal slip casting of components

    SciTech Connect

    Steinlage, G.A.; Roeder, R.K.; Trumble, K.P.; Bowman, K.J.

    1996-05-01

    Research in layered and functionally gradient materials has emerged because of the increasing demand for high-performance engineering materials. Many techniques have been used to produce layered and functionally gradient components. Common examples include thermal spray processing, powder processing, chemical and physical vapor deposition, high-temperature or combustion synthesis, diffusion treatments, microwave processing and infiltration. Of these techniques, powder processing routes offer excellent microstructural control and product quality, and they are capable of producing large components. Centrifugal slip casting is a powder-processing technique combining the effects of slip casting and centrifugation. In slip casting, consolidation takes place as fluid is removed by the porous mold. Particles within the slip move with the suspending fluid until reaching the mold wall, at which point they are consolidated. In centrifugation, particles within the slip move through the fluid at a rate dependent upon the gravitational force and particle drag.

  1. Effect of Some Parameters on the Cast Component Properties in Hot Chamber Die Casting

    NASA Astrophysics Data System (ADS)

    Singh, Rupinder; Singh, Harvir

    2016-04-01

    Hot chamber die casting process is designed to achieve high dimensional accuracy for small products by forcing molten metal under high pressure into reusable moulds, called dies. The present research work is aimed at study of some parameters (as a case study of spring adjuster) on cast component properties in hot chamber die casting process. Three controllable factors of the hot chamber die casting process (namely: pressure at second phase, metal pouring temperature and die opening time) were studied at three levels each by Taguchi's parametric approach and single-response optimization was conducted to identify the main factors controlling surface hardness, dimensional accuracy and weight of the casting. Castings were produced using aluminium alloy, at recommended parameters through hot chamber die casting process. Analysis shows that in hot chamber die casting process the percentage contribution of second phase pressure, die opening time, metal pouring temperature for surface hardness is 82.48, 9.24 and 6.78 % respectively. While in the case of weight of cast component the contribution of second phase pressure is 94.03 %, followed by metal pouring temperature and die opening time (4.58 and 0.35 % respectively). Further for dimensional accuracy contribution of die opening time is 76.97 %, metal pouring temperature is 20.05 % and second phase pressure is 1.56 %. Confirmation experiments were conducted at an optimal condition showed that the surface hardness, dimensional accuracy and weight of the castings were improved significantly.

  2. Studies on copper alloys containing chromium on the copper side phase diagram

    NASA Technical Reports Server (NTRS)

    Doi, T.

    1984-01-01

    Specimens were prepared from vacuum melted alloys of high purity vacuum melted copper and electrolytic chromium. The liquidus and eutectic point were determined by thermal analysis. The eutectic temperature is 1974.8 F and its composition is 1.28 wt% of chromium. The determination of solid solubility of chromium in copper was made by microscopic observation and electrical resistivity measurement. The solubility of chromium in solid copper is 0.6 wt% at 1050 F, 0.4 wt% at 1000 F, 0.25 wt% at 950 F, 0.17 wt% at 900 F, and 0.30 wt% at 840 F.

  3. Distribution, origin and fate of chromium in soils in Guanajuato, Mexico.

    PubMed

    Armienta, M A; Rodríguez, R; Ceniceros, N; Juárez, F; Cruz, O

    1996-01-01

    Total, hexavalent and trivalent chromium were determined in surface and 30-cm depth soil samples from a highly chromium-polluted area in Guanajuato state, central México. Four samples were also analyzed by a sequential extraction procedure. Nearly 0.9 km(2) out of the 8 km(2) area sampled was polluted with chromium, at concentrations up to 12960 mg kg(-1), mostly as Cr(III). Concentrations of Cr(VI) were lower than 0.5 mg kg(-1) in most sampled points, with the exception of one, where the concentration was found to be 65.14 mg kg(-1). Chromiumcontaining dust from a chromate factory accounted for most of the contamination. The highest concentrations of hexavalent chromium in soil, were in the bottom sediments of an abandoned water reservoir used to store polluted water from a well, before use of the water in the factory process. Tannery wastes, dust from a sanitary landfill of chromate compounds and the transport of chromium products are the sources of chromium at other sites. Chromium is fixed preferentially in the hydrous Fe and Mn oxides in the more polluted soils. Less polluted soils have a high proportion of chromium associated with the sulfide and organic fraction. Cr(III) is retained preferentially in the superficial soil layer. Variations in the physical characteristics of the soil, relative abundance of the various soil components and characteristics of the contaminant source, give rise to differences in chromium soil concentrations with depth.

  4. Dimensionally Controlled Lithiation of Chromium Oxide

    SciTech Connect

    Fister, Tim T.; Hu, Xianyi; Esbenshade, Jennifer; Chen, Xiao; Wu, Jinsong; Dravid, Vinayak; Bedzyk, Michael; Long, Brandon; Gewirth, Andrew A.; Shi, Bing; Schlepütz, Christian M.; Fenter, Paul

    2016-01-12

    Oxide conversion reactions are an alternative approach for high capacity lithium ion batteries but are known to suffer from structural irreversibility associated with the phase separation and reconstitution of reduced metal species and Li2O. In particular, the morphology of the reduced metal species is thought to play a critical role in the electrochemical properties of a conversion material. Here we use a model electrode with alternating layers of chromium and chromium oxide to better understand and control these phase changes in real-time and at molecular length scales. Despite lacking crystallinity at the atomic scale, this superstructure is observed (with X-ray reflectivity, XR) to lithiate and delithiate in a purely one-dimensional manner, preserving the layered structure. The XR data show that the metal layers act as nucleation sites for the reduction of chromium in the conversion reaction. Irreversibility during delithiation is due to the formation of a ternary phase, LiCrO2, which can be further delithiated at higher potentials. The results reveal that the combination of confining lithiation to nanoscale sheets of Li2O and the availability of reaction sites in the metal layers in the layered structure is a strategy for improving the reversibility and mass transport properties that can be used in a wide range of conversion materials.

  5. Fabrication of chitosan-magnetite nanocomposite strip for chromium removal

    NASA Astrophysics Data System (ADS)

    Sureshkumar, Vaishnavi; Kiruba Daniel, S. C. G.; Ruckmani, K.; Sivakumar, M.

    2016-02-01

    Environmental pollution caused by heavy metals is a serious threat. In the present work, removal of chromium was carried out using chitosan-magnetite nanocomposite strip. Magnetite nanoparticles (Fe3O4) were synthesized using chemical co-precipitation method at 80 °C. The nanoparticles were characterized using UV-visible spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction spectrometer, atomic force microscope, dynamic light scattering and vibrating sample magnetometer, which confirm the size, shape, crystalline nature and magnetic behaviour of nanoparticles. Atomic force microscope revealed that the particle size was 15-30 nm and spherical in shape. The magnetite nanoparticles were mixed with chitosan solution to form hybrid nanocomposite. Chitosan strip was casted with and without nanoparticle. The affinity of hybrid nanocomposite for chromium was studied using K2Cr2O7 (potassium dichromate) solution as the heavy metal solution containing Cr(VI) ions. Adsorption tests were carried out using chitosan strip and hybrid nanocomposite strip at different time intervals. Amount of chromium adsorbed by chitosan strip and chitosan-magnetite nanocomposite strip from aqueous solution was evaluated using UV-visible spectroscopy. The results confirm that the heavy metal removal efficiency of chitosan-magnetite nanocomposite strip is 92.33 %, which is higher when compared to chitosan strip, which is 29.39 %.

  6. Chromium (VI)-induced oxidative stress, apoptotic cell death and modulation of p53 tumor suppressor gene.

    PubMed

    Bagchi, D; Bagchi, M; Stohs, S J

    2001-06-01

    Chromium (VI) is a widely used industrial chemical, extensively used in paints, metal finishes, steel including stainless steel manufacturing, alloy cast irons, chrome, and wood treatment. On the contrary, chromium (III) salts such as chromium polynicotinate, chromium chloride and chromium picolinate, are used as micronutrients and nutritional supplements, and have been demonstrated to exhibit a significant number of health benefits in rodents and humans. However, the cause for the hexavalent chromium to induce cytotoxicity is not entirely understood. A series of in vitro and in vivo studies have demonstrated that chromium (VI) induces an oxidative stress through enhanced production of reactive oxygen species (ROS) leading to genomic DNA damage and oxidative deterioration of lipids and proteins. A cascade of cellular events occur following chromium (VI)-induced oxidative stress including enhanced production of superoxide anion and hydroxyl radicals, increased lipid peroxidation and genomic DNA fragmentation, modulation of intracellular oxidized states, activation of protein kinase C, apoptotic cell death and altered gene expression. In this paper, we have demonstrated concentration- and time-dependent effects of sodium dichromate (chromium (VI) or Cr (VI)) on enhanced production of superoxide anion and hydroxyl radicals, changes in intracellular oxidized states as determined by laser scanning confocal microscopy, DNA fragmentation and apoptotic cell death (by flow cytometry) in human peripheral blood mononuclear cells. These results were compared with the concentration-dependent effects of chromium (VI) on chronic myelogenous leukemic K562 cells and J774A.1 murine macrophage cells. Chromium (VI)-induced enhanced production of ROS, as well as oxidative tissue and DNA damage were observed in these cells. More pronounced effect was observed on chronic myelogenous leukemic K562 cells and J774A.1 murine macrophage cells. Furthermore, we have assessed the effect of a

  7. Morphological castes in a vertebrate

    PubMed Central

    O'Riain, M. J.; Jarvis, J. U. M.; Alexander, R.; Buffenstein, R.; Peeters, C.

    2000-01-01

    Morphological specialization for a specific role has, until now, been assumed to be restricted to social invertebrates. Herein we show that complete physical dimorphism has evolved between reproductives and helpers in the eusocial naked mole-rat. Dimorphism is a consequence of the lumbar vertebrae lengthening after the onset of reproduction in females. This is the only known example of morphological castes in a vertebrate and is distinct from continuous size variation between breeders and helpers in other species of cooperatively breeding vertebrates. The evolution of castes in a mammal and insects represents a striking example of convergent evolution for enhanced fecundity in societies characterized by high reproductive skew. Similarities in the selective environment between naked mole-rats and eusocial insect species highlight the selective conditions under which queen/worker castes are predicted to evolve in animal societies. PMID:11087866

  8. Evaluation of aquatic toxicities of chromium and chromium-containing effluents in reference to chromium electroplating industries.

    PubMed

    Baral, A; Engelken, R; Stephens, W; Farris, J; Hannigan, R

    2006-05-01

    This study evaluated aquatic toxicities of chromium and chromium-containing laboratory samples representative of effluents from chromium electroplating industries, and compared the aquatic environmental risks of hexavalent and trivalent chromium electroplating operations. Trivalent chromium electroplating has emerged as an acceptable alternative to hazardous hexavalent chromium electroplating. This process substitution has reduced the human health impact in the workplace and minimized the production of hazardous sludge regulated under the Resource Conservation and Recovery Act (RCRA). The thrust behind this research was to investigate whether trivalent chromium electroplating operations have lower adverse impacts on standardized toxicity test organisms. Ceriodaphnia dubia and Pimephales promelas were used to investigate toxicities of trivalent chromium (Cr (III)), hexavalent chromium (Cr (VI)), and industrial effluents. In agreement with previous studies, Cr (III) was found to be less toxic than Cr (VI). Despite having several organic and inorganic constituents in the effluents obtained from trivalent chromium plating baths, they exhibited less adverse effects to C. dubia than effluents obtained from hexavalent chromium electroplating baths. Thus, transition from hexavalent to trivalent chromium electroplating processes may be justified. However, because of the presence of organic constituents such as formate, oxalate, and triethylene glycol in effluents, trivalent chromium electroplating operations may face additional regulatory requirements for removal of total organic carbon.

  9. Chromium deficiency during total parenteral nutrition.

    PubMed

    Freund, H; Atamian, S; Fischer, J E

    1979-02-02

    Chromium is required for maintenance of normal glucose tolerance. After complete bowel resection and five months of total parenteral nutrition, severe glucose intolerance, weight loss, and a metabolic encephalopathy-like confusional state developed in a patient. Serum chromium levels were at the lowest normal level. Supplementation of 150 microgram of chromium per day reversed the glucose intolerance, reduced insulin requirements, and resulted in weight gain and the disappearance of encephalopathy. The low levels of chromium and response to chromium supplementation suggest that chromium deficiency can arise in long-term total parenteral nutrition.

  10. Investigation of Total and Hexavalent Chromium in Filtered and Unfiltered Groundwater Samples at the Tucson International Airport Superfund Site.

    PubMed

    Tillman, Fred D; McCleskey, R Blaine; Hermosillo, Edyth

    2016-10-01

    Potential health effects from hexavalent chromium in groundwater have recently become a concern to regulators at the Tucson International Airport Area Superfund site. In 2016, the U.S. Geological Survey sampled 46 wells in the area to characterize the nature and extent of chromium in groundwater, to understand what proportion of total chromium is in the hexavalent state, and to determine if substantial differences are present between filtered and unfiltered chromium concentrations. Results indicate detectable chromium concentrations in all wells, over 75 % of total chromium is in the hexavalent state in a majority of wells, and filtered and unfiltered results differ substantially in only a few high-turbidity total chromium samples.

  11. Investigation of total and hexavalent chromium in filtered and unfiltered groundwater samples at the Tucson International Airport Superfund Site

    USGS Publications Warehouse

    Tillman, Fred; McCleskey, R. Blaine; Hermosillo, Edyth

    2016-01-01

    Potential health effects from hexavalent chromium in groundwater have recently become a concern to regulators at the Tucson International Airport Area Superfund site. In 2016, the U.S. Geological Survey sampled 46 wells in the area to characterize the nature and extent of chromium in groundwater, to understand what proportion of total chromium is in the hexavalent state, and to determine if substantial differences are present between filtered and unfiltered chromium concentrations. Results indicate detectable chromium concentrations in all wells, over 75 % of total chromium is in the hexavalent state in a majority of wells, and filtered and unfiltered results differ substantially in only a few high-turbidity total chromium samples.

  12. Mathematical Modeling of High-Temperature Constitutive Equations and Hot Processing Maps for As-Cast SA508-3 Steel

    NASA Astrophysics Data System (ADS)

    Sui, Dashan; Wang, Tao; Zhu, Lingling; Gao, Liang; Cui, Zhenshan

    2016-11-01

    The hot deformation behavior and hot workability characteristics of as-cast SA508-3 steel were studied by modeling the constitutive equations and developing hot processing maps. The isothermal compression experiments were carried out at temperatures of 950°C, 1050°C, 1150°C, and 1250°C and strain rates of 0.001 s-1, 0.01 s-1, 0.1 s-1, and 1 s-1 respectively. The two-stage flow stress models were established through the classical theories on work hardening and softening, and the solution of activation energy for hot deformation was 355.0 kJ mol-1 K-1. Based on the dynamic material model, the power dissipation and instability maps were developed separately at strains of 0.2, 0.4, 0.6 and 0.8. The power dissipation rate increases with both the increase of temperature and the decrease of strain rate, and the instable region mainly appears on the conditions of low temperature and high strain rate. The optimal hot working parameters for as-cast SA508-3 steel are 1050-1200°C/0.001-0.1 s-1, with about 25-40% peak efficiency of power dissipation.

  13. Effect of Hydrostatic Pressure on the 3D Porosity Distribution and Mechanical Behavior of a High Pressure Die Cast Mg AZ91 Alloy

    NASA Astrophysics Data System (ADS)

    Sket, Federico; Fernández, Ana; Jérusalem, Antoine; Molina-Aldareguía, Jon M.; Pérez-Prado, María Teresa

    2015-09-01

    A limiting factor of high pressure die cast (HPDC) Mg alloys is the presence of porosity, which has a detrimental effect on the mechanical strength and gives rise to a large variability in the ductility. The application of hydrostatic pressure after casting is known to be beneficial to improve the mechanical response of HPDC Mg alloys. In this study, a combined experimental and simulation approach has been developed in order to investigate the influence of pressurization on the 3D porosity distribution and on the mechanical behavior of an HPDC Mg AZ91 alloy. Examination of about 10,000 pores by X-ray computed microtomography allowed determining the effect of hydrostatic pressure on the bulk porosity volume fraction, as well as the change in volume and geometry of each individual pore. The evolution of the 3D porosity distribution and mechanical behavior of a sub-volume containing 200 pores was also simulated by finite element analysis. Both experiments and simulations consistently revealed a decrease in the bulk porosity fraction and a bimodal distribution of the individual volume changes after the application of the pressure. This observation is associated with pores containing internal pressure as a result of the HPDC process. Furthermore, a decrease in the complexity factor with increasing volume change is observed experimentally and predicted by simulations. The pressure-treated samples have consistently higher plastic flow strengths.

  14. Processing of IN-718 Lattice Block Castings

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.

    2002-01-01

    Recently a low cost casting method known as lattice block casting has been developed by JAM Corporation, Wilmington, Massachusetts for engineering materials such as aluminum and stainless steels that has shown to provide very high stiffness and strength with only a fraction of density of the alloy. NASA Glenn Research Center has initiated research to investigate lattice block castings of high temperature Ni-base superalloys such as the model system Inconel-718 (IN-718) for lightweight nozzle applications. Although difficulties were encountered throughout the manufacturing process , a successful investment casting procedure was eventually developed. Wax formulation and pattern assembly, shell mold processing, and counter gravity casting techniques were developed. Ten IN-718 lattice block castings (each measuring 15-cm wide by 30-cm long by 1.2-cm thick) have been successfully produced by Hitchiner Gas Turbine Division, Milford, New Hampshire, using their patented counter gravity casting techniques. Details of the processing and resulting microstructures are discussed in this paper. Post casting processing and evaluation of system specific mechanical properties of these specimens are in progress.

  15. Chromium recovery from exhausted baths generated in plating processes and its reuse in the tanning industry.

    PubMed

    Torras, Josep; Buj, Irene; Rovira, Miquel; de Pablo, Joan

    2012-03-30

    Chromium plating used for functional purposes provides an extremely hard, wear and corrosion resistant layer by means of electrolytic deposition. Typical layer thicknesses range between 2.5 and 500 μm. Chromium electroplating baths contain high concentrations of Cr(VI) with chromium trioxide (CrO(3)) as the chromium source. When because of technical or economic reasons a bath gets exhausted, a waste containing mainly chromium as dichromate as well as other heavy metals is generated. Chromium may then be purified for use in other industrial processes with different requirements. In this work, a sustainable system for using galvanic wastes as reagents in the leather tanning industry, thus reducing quantity of wastes to be treated, is presented. Metal cations present in the chromium exhausted bath were precipitated with NaOH. Then, the solution containing mainly soluble Cr(VI) was separated. By means of sodium sulphite in acidic conditions, Cr(VI) was reduced to Cr(III) as chromium (III) sulphate. From chromium (III) sulphate a basic Cr(III) sulphate may be obtained, which is one of most used compounds in the tanning industry. Cr(III) concentration in the final solution allows its reuse without concentration, but with a slight dilution.

  16. Activated carbons and low cost adsorbents for remediation of tri- and hexavalent chromium from water.

    PubMed

    Mohan, Dinesh; Pittman, Charles U

    2006-09-21

    Hexavalent chromium is a well-known highly toxic metal, considered a priority pollutant. Industrial sources of Cr(VI) include leather tanning, cooling tower blowdown, plating, electroplating, anodizing baths, rinse waters, etc. The most common method applied for chromate control is reduction of Cr(VI) to its trivalent form in acid (pH approximately 2.0) and subsequent hydroxide precipitation of Cr(III) by increasing the pH to approximately 9.0-10.0 using lime. Existing overviews of chromium removal only cover selected technologies that have traditionally been used in chromium removal. Far less attention has been paid to adsorption. Herein, we provide the first review article that provides readers an overview of the sorption capacities of commercial developed carbons and other low cost sorbents for chromium remediation. After an overview of chromium contamination is provided, more than 300 papers on chromium remediation using adsorption are discussed to provide recent information about the most widely used adsorbents applied for chromium remediation. Efforts to establish the adsorption mechanisms of Cr(III) and Cr(VI) on various adsorbents are reviewed. Chromium's impact environmental quality, sources of chromium pollution and toxicological/health effects is also briefly introduced. Interpretations of the surface interactions are offered. Particular attention is paid to comparing the sorption efficiency and capacities of commercially available activated carbons to other low cost alternatives, including an extensive table.

  17. Determination of total chromium in tanned leather samples used in car industry.

    PubMed

    Zeiner, Michaela; Rezić, Iva; Ujević, Darko; Steffan, Ilse

    2011-03-01

    Despite the high competition of synthetic fibers leather is nowadays still widely used for many applications. In order to ensure a sufficient stability of the skin matrix against many factors, such as microbial degradation, heat and sweat, a tanning process is indispensable. Using chromium (III) for this purpose offers a multitude of advantages, thus this way of tanning is widely applied. During the use of chromium tanned leather as clothing material as well as for decoration/covering purposes, chromium is extracted from the leather and may then cause nocuous effects to human skin, e.g. allergic reactions. Thus the knowledge of the total chromium content of leather samples expected to come into prolonged touch with human skin is very important. In car industry leather is used as cover for seats, steering wheel and gearshift lever The chromium contents often chromium tanned leather samples used in car industry were determined. First all samples were dried at 65 degrees C overnight and then cut in small pieces using a ceramic knife, weighed and analyzed by inductively coupled plasma--optical emission spectrometry (ICP-OES) after acidic microwave assisted digestion. The total chromium amounts found were in the range from 19 mg/g up to 32 mg/g. The extraction yield of chromium from leather samples in sweat is approximately 2-7%. Thus especially during long journeys in summer chromium can be extracted in amounts which may cause nocuous effects for example on the palm of the hands or on the back.

  18. The removal of hexavalent chromium from water by ferrous sulfate

    SciTech Connect

    Lin, C.J.J.; Vesilind, P.A.

    1995-12-31

    The redox reaction of hexavalent chromium and ferrous sulfate is investigated in his study. Hexavalent chromium, a highly toxic and mobile anion, could exist in raw water used as a public water supply due to the industrial chromium contamination of natural water or due to natural oxidation of trivalent chromium. Ferrous sulfate is one of the widely used coagulants in water treatment plants and has good reducing ability. Because of its reducing capacity, ferrous sulfate can be applied to remove hexavalent chromium from water. The required contact time to reach equilibrium, the effectiveness of Cr(VI) reduction at different initial pH, and the required ferrous sulfate dosage for complete reduction are investigated. The redox reaction can be completed within 10 minutes, allowing 30 mg/L of hexavalent chromium to react with stoichiometric dosage of ferrous sulfate in deionized water, regardless of the initial pH. The pH of the solution is depressed during the progress of the reaction due to the hydrolysis of the produced Fe(III) and Cr(III) ions from the reaction. Dissolved oxygen in water is found to interfere with the redox reaction by consuming ferrous ions when the initial pH of solutions is high. In deionized water, complete Cr(VI) reduction can be achieved by applying excess ferrous sulfate under the condition of this study. It is also achievable when the raw water from Durham Water Treatment Plant is used as the reaction medium, without additional dosage of ferrous sulfate. Based on the results, simultaneous removal of hexavalent chromium in water treatment by applying ferrous sulfate as the coagulant is theoretically feasible.

  19. Graphite Formation in Cast Iron

    NASA Technical Reports Server (NTRS)

    Stefanescu, D. M.

    1985-01-01

    In the first phase of the project it was proven that by changing the ratio between the thermal gradient and the growth rate for commercial cast iron samples solidifying in a Bridgman type furnace, it is possible to produce all types of graphite structures, from flake to spheroidal, and all types of matrices, from ferritic to white at a certain given level of cerium. KC-135 flight experiments have shown that in a low-gravity environment, no flotation occurs even in spheroidal graphite cast irons with carbon equivalent as high as 5%, while extensive graphite flotation occurred in both flake and spheroidal graphite cast irons, in high carbon samples solidified in a high gravity environment. This opens the way for production of iron-carbon composite materials, with high carbon content (e.g., 10%) in a low gravity environment. By using KC-135 flights, the influence of some basic elements on the solidification of cast iron will be studied. The mechanism of flake to spheroidal graphite transition will be studied, by using quenching experiments at both low and one gravity for different G/R ratios.

  20. The contemporary anthropogenic chromium cycle.

    PubMed

    Johnson, Jeremiah; Schewel, Laura; Graedel, T E

    2006-11-15

    Chromium is an essential engineering metal used in stainless and alloy steels, chemicals, and refractory products. Using material flow analysis, all major anthropogenic chromium flows are characterized for the year 2000, from mining through discard, on three spatial levels: fifty-four countries, nine world regions, and the planet. Included is the first detailed quantification of chromium in internationally traded finished products and diverse waste streams. Findings include (1) 78% of chromium flow entering final use is added as a net addition to stock on the global level; most countries are close to this figure; (2) the majority of mining occurs in Africa (2400 Gg Cr/yr) and the Commonwealth of Independent States (1090 Gg Cr/yr), while the major end-users are Asia, Europe, and North America at 1150, 1140, and 751 Gg Cr/yr, respectively; (3) waste flows of chromium are the greatest in Europe (420 Gg Cr/yr), Asia (370 Gg Cr/yr), and North America (290 Gg Cr/yr), but the composition of these waste flows varies greatly among the world regions; (4) releases of chromium by the global system, which total 2630 Gg Cr/yr, are nearly evenly divided among tailings, ferrochromium slag, downgraded scrap, and post-consumer losses; (5) many countries have a heavy foreign dependence on chromium in the all forms, as is demonstrated for the United States. The findings relating to in-use stock changes and finished product trade are relevant to industry, allowing for more accurate planning for future scrap availability. The quantification of releases due to discards and dissipation hold environmental and human health relevance, while the full life cycle international trade assessment addresses local scarcity.

  1. Identification of a cast iron alloy containing nonstrategic elements

    NASA Technical Reports Server (NTRS)

    Cooper, C. V.; Anton, D. L.; Lemkey, F. D.; Nowotny, H.; Bailey, R. S.; Favrow, L. H.; Smeggil, J. G.; Snow, D. B.

    1989-01-01

    A program was performed to address the mechanical and environmental needs of Stirling engine heater head and regenerator housing components, while reducing the dependence on strategic materials. An alloy was developed which contained no strategic elemental additions per se. The base is iron with additions of manganese, molybdenum, carbon, silicon, niobium, and ferro-chromium. Such an alloy should be producible on a large scale at very low cost. The resulting alloy, designated as NASAUT 4G-Al, contained 15 Mn, 15 Cr, 2 Mo, 1.5 C, 1.0 Si, 1.0 Nb (in weight percent) with a balance of Fe. This alloy was optimized for chemistry, based upon tensile strength, creep-rupture strength, fracture behavior, and fatigue resistance up to 800 C. Alloys were also tested for environmental compatibility. The microstructure and mechanic properties (including hardness) were assessed in the as-cast condition and following several heat treatments, including one designed to simulate a required braze cycle. The alloy was fabricated and characterized in the form of both equiaxed and columnar-grained castings. The columnar grains were produced by directional solidification, and the properties were characterized in both the longitudinal and transverse orientations. The NASAUT 4G-Al alloy was found to be good in cyclic-oxidation resistance and excellent in both hydrogen and hot-corrosion resistance, especially in comparison to the baseline XF-818 alloy. The mechanical properties of yield strength, stress-rupture life, high-cycle-fatigue resistance, and low-cycle-fatigue resistance were good to excellent in comparison to the current alloy for this application, HS-31 (X-40), with precise results depending in a complex manner on grain orientation and temperature. If required, the ductility could be improved by lowering the carbon content.

  2. Mare Chromium Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This crater, located in Mare Chromium, shows evidence of exterior modification, with little interior modification. While the rim is still visible, the ejecta blanket has been removed or covered. There is some material at the bottom of the crater, but the interior retains the bowl shape from the initial formation of the crater.

    Image information: VIS instrument. Latitude -34.4, Longitude 174.4 East (185.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  3. Microbial exudate promoted dissolution and transformation of chromium containing minerals

    NASA Astrophysics Data System (ADS)

    Saad, E. M.; Sun, J.; Tang, Y.

    2015-12-01

    Because of its utility in many industrial processes, chromium has become the second most common metal contaminant in the United States. The two most common oxidation states of chromium in nature are Cr(III), which is highly immobile, and Cr(VI), which is highly mobile and toxic. In both natural and engineered environments, the most common remediation of Cr(VI) is through reduction, which results in chromium sequestration in the low solubility mixed Cr(III)-Fe(III) (oxy)hydroxide phases. Consequently, the stability of these minerals must be examined to assess the fate of chromium in the subsurface. We examined the dissolution of mixed Cr(III)-Fe(III) (oxy)hydroxides in the presence of common microbial exudates, including the siderophore desferrioxamine B (DFOB; a common organic ligand secreted by most microbes with high affinity for ferric iron and other trivalent metal ions) and oxalate (a common organic acid produced by microbes). The solids exhibited incongruent dissolution with preferential leaching of Fe from the solid phase. Over time, this leads to a more Cr rich mineral, which is known to be more soluble than the corresponding mixed mineral phase. We are currently investigating the structure of the reacted mineral phases and soluble Cr(III) species, as well as the potential oxidation and remobilization of the soluble Cr species. Results from this study will provide insights regarding the long term transport and fate of chromium in the natural environment in the presence of microbial activities.

  4. Improved Slip Casting Of Ceramic Models

    NASA Technical Reports Server (NTRS)

    Buck, Gregory M.; Vasquez, Peter; Hicks, Lana P.

    1994-01-01

    Improved technique of investment slip casting developed for making precise ceramic wind-tunnel models. Needed in wind-tunnel experiments to verify predictions of aerothermodynamical computer codes. Ceramic materials used because of their low heat conductivities and ability to survive high temperatures. Present improved slip-casting technique enables casting of highly detailed models from aqueous or nonaqueous solutions. Wet shell molds peeled off models to ensure precise and undamaged details. Used at NASA Langley Research Center to form superconducting ceramic components from nonaqueous slip solutions. Technique has many more applications when ceramic materials developed further for such high-strength/ temperature components as engine parts.

  5. Correlation of microstructure and fracture toughness in three high-speed steel rolls

    SciTech Connect

    Lee, S.; Sohn, K.S.; Lee, C.G.; Jung, B.I.

    1997-01-01

    The objective of this study is to clarify the fracture characteristics of high-speed steel (HSS) rolls in terms of microstructural factors such as matrix phase and primary carbide particles. Three HSS rolls with different chromium contents were fabricated by centrifugal casting, and the effect of the chromium addition was investigated through microstructural analysis, fracture-mechanism study, and toughness measurement. The hard and brittle primary carbides, as well as the eutectic carbides (ledeburites), were segregated in the intercellular regions and dominated overall properties. Observation of the fracture process revealed that these primary carbides cleaved first to form microcracks at low stress-intensity factor levels and that the microcracks then readily propagated along the intercellular networks. The addition of chromium to a certain level yielded microstructural modification, including the homogeneous distribution of primary carbides, thereby leading to enhancement of fracture toughness of the HSS rolls.

  6. The effect of casting temperature on the fatigue properties of cast nickel aluminide alloys

    SciTech Connect

    Gieseke, B.; Sikka, V.K.

    1991-01-01

    The results of high cycle fatigue tests at 650{degree}C on several cast Ni{sub 3}Al alloys are reported and compared to cast IN-713C. These alloys include IC-221M and several variations to the IC-221M composition. The effect of casting temperature is investigated using castings poured at three different temperatures spanning a 56{degree}C range. The results show that IC-221M cast at the highest temperature has the best fatigue strength, exceeding that for IN-713C. In these alloys, crack initiation occurs at shrinkage microporosity and the effect of casting temperature on porosity is related to the observed differences in fatigue lives. 11 refs., 4 figs.

  7. Biomaterials by freeze casting.

    PubMed

    Wegst, Ulrike G K; Schecter, Matthew; Donius, Amalie E; Hunger, Philipp M

    2010-04-28

    The functional requirements for synthetic tissue substitutes appear deceptively simple: they should provide a porous matrix with interconnecting porosity and surface properties that promote rapid tissue ingrowth; at the same time, they should possess sufficient stiffness, strength and toughness to prevent crushing under physiological loads until full integration and healing are reached. Despite extensive efforts and first encouraging results, current biomaterials for tissue regeneration tend to suffer common limitations: insufficient tissue-material interaction and an inherent lack of strength and toughness associated with porosity. The challenge persists to synthesize materials that mimic both structure and mechanical performance of the natural tissue and permit strong tissue-implant interfaces to be formed. In the case of bone substitute materials, for example, the goal is to engineer high-performance composites with effective properties that, similar to natural mineralized tissue, exceed by orders of magnitude the properties of its constituents. It is still difficult with current technology to emulate in synthetic biomaterials multi-level hierarchical composite structures that are thought to be the origin of the observed mechanical property amplification in biological materials. Freeze casting permits to manufacture such complex, hybrid materials through excellent control of structural and mechanical properties. As a processing technique for the manufacture of biomaterials, freeze casting therefore has great promise.

  8. Glovebox Advanced Casting System Casting Optimization

    SciTech Connect

    Fielding, Randall Sidney

    2016-03-01

    Casting optimization in the GACS included three broad areas; casting of U-10Zr pins, incorporation of an integral FCCI barrier, and development of a permanent crucible coating. U-10Zr casting was improved over last year’s results by modifying the crucible design to minimize contact with the colder mold. Through these modifications casting of a three pin batch was successful. Incorporation of an integral FCCI barrier also was optimized through furnace chamber pressure changes during the casting cycle to reduce gas pressures in the mold cavities which led to three full length pins being cast which incorporated FCCI barriers of three different thicknesses. Permanent crucible coatings were tested against a base case; 1500°C for 10 minutes in a U-20Pu-10Zr molten alloy. None of the candidate coating materials showed evidence of failure upon initial visual examination. In all areas of work a large amount of characterization will be needed to fully determine the effects of the optimization activities. The characterization activities and future work will occur next year.

  9. Effect of a high temperature and hydrostatic pressure on the structure and the properties of a high-strength cast AM5 (the 201.2 alloy type) aluminum alloy

    NASA Astrophysics Data System (ADS)

    Akopyan, T. K.; Padalko, A. G.; Belov, N. A.; Shurkin, P. K.

    2016-07-01

    The phase-transition temperatures of a high-strength cast AM5 aluminum alloy are determined at atmospheric pressure and an excess pressure of 100 MPa using differential barothermic analysis (DBA) and classical differential thermal analysis (DTA). An excess pressure of 100 MPa is shown to increase the critical temperatures of the alloy by 12-17°C (including an increase in the solidus temperature by 12°C), which makes it possible to increase the hot isostatic pressing (HIP) temperature above the temperature of heating for quenching. The following three barothermal treatment schedules at p = 100 MPa and τ = 3 h, which have different isothermal holding temperatures, are chosen to study the influence of HIP on the structure and the properties of alloy AM5 castings: HIP1 ( t 1 = 505 ± 2°C), HIP2 ( t 2 = 520 ± 2°C), and HIP3 ( t 3 = 540 ± 2°C). High-temperature HIP treatment is found to increase the casting density and improve the morphology of secondary phases additionally, which ensures an increase in the plasticity of the alloy. In particular, the plasticity of the alloy after heat treatment according to schedule HIP3 + T6 (T6 means artificial aging to achieve the maximum strength) increases by a factor of ˜1.5.

  10. Chromium-Makes stainless steel stainless

    USGS Publications Warehouse

    Kropschot, S.J.; Doebrich, Jeff

    2010-01-01

    Chromium, a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point, is a silvery white, hard, and bright metal plating on steel and other material. Commonly known as chrome, it is one of the most important and indispensable industrial metals because of its hardness and resistance to corrosion. But it is used for more than the production of stainless steel and nonferrous alloys; it is also used to create pigments and chemicals used to process leather.

  11. Chromium-induced kidney disease

    SciTech Connect

    Wedeen, R.P. ); Qian, Lifen )

    1991-05-01

    Kidney disease is often cited as one of the adverse effects of chromium, yet chronic renal disease due to occupational or environmental exposure to chromium has not been reported. Occasional cases of acute tubular necrosis (ATN) following massive absorption of chromate have been described. Chromate-induced ATN has been extensively studied in experimental animals following parenteral administration of large doses of potassium chromate (hexavalent). The chromate is selectively accumulated in the convoluted proximal tubule where necrosis occurs. An adverse long-term effect of low-dose chromium exposure on the kidneys is suggested by reports of low molecular weight (LMW) proteinuria in chromium workers. Excessive urinary excretion of {beta}{sub 2}-microglobulin, a specific proximal tubule brush border protein, and retinol-binding protein has been reported among chrome palters and welders. However, LMW proteinuria occurs after a variety of physiologic stresses, is usually reversible, and cannot by itself be considered evidence of chromic renal disease. Chromate-induced ATN and LMW proteinuria in chromium workers, nevertheless, raise the possibility that low-level, long-term exposure may produce persistent renal injury. The absence of evidence of chromate-induced chromic renal disease cannot be interpreted as evidence of the absence of such injury.

  12. [Biological monitoring in chromium-plating industry].

    PubMed

    Madsen, S W; Krue, S; Bonde, J P

    1992-05-25

    The purpose of the present investigation was to evaluate the role of biological monitoring as a means of surveillance of exposure in the Danish chromium-plating industry. We collected spot urine samples from 47 employees in five electro-plating plants near Aarhus and compared the results wide 40 non-exposed workers. We found no increase of chromium in urine during a work shift (mean = 0.11 nmol chromium/mmol creatinine, p = .46). The mean urine chromium value among the chromium workers was twice the mean value of the referent population (p = 0.001). There was, however, a considerable overlap between the two populations. All of the urine chromium values were much lower than the proposed American biological exposure indices. The results do not indicate any need for implementation of biological monitoring in the Danish chromium-plating industry, but longitudinal studies concerning possible accumulation of chromium at present occupational exposure levels should be carried out.

  13. Chromium recovery from tannery sludge with saponin and oxidative remediation.

    PubMed

    Kiliç, Eylem; Font, Joaquim; Puig, Rita; Colak, Selime; Celik, Deniz

    2011-01-15

    Two new methods for treatment of tannery sludge were studied to achieve cost-effective and environmentally acceptable remediation solutions for high chromium containing tannery sludge. Quillaja bark saponin, a plant derived biosurfactant, was applied to dewatered tannery sludge for chromium recovery and a comparative assessment with H(2)O(2) oxidative treatment method is presented. Tannery sludge samples were treated on a laboratory scale with saponin in the pH range 2-3. The effects of various factors like time, concentration of saponin, pH, and temperature on the extraction of chromium were studied. The treatment with saponin extracted 24% of Cr from tannery sludge at a pH around2, performing multiple wash of 6h, at 33 °C. On the other hand, the H(2)O(2) treatment, which include Cr(III) oxidation to Cr(VI) and extraction with sulfuric acid solution at pH 2, enabled to extract 70% of chromium within less than 4h at room temperature (21 °C). The results indicate that the extraction efficiency of saponin was strongly dependent on the organic matter content of the sample, which affects chromium mobility by its high adsorption capacity. On the other hand hydrogen peroxide treatment is effective and the duration of the process is short and requires cheap chemicals and moderate conditions.

  14. Low-chromium reduced-activation ferritic steels for fusion

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.; Kenik, E.A.

    1996-04-01

    Development of reduced-activation ferritic steels has concentrated on high-chromium (8-10 wt% Cr) steels. However, there are advantages for a low-chromium steel, and initial ORNL studies on reduced-activation steels were on compositions with 2.25 to 12% Cr. Those studies showed an Fe-2.25Cr-2W-0.25V-0.1C (2 1/4Cr-2WV) steel to have the highest strenglth of the steels studied. Although this steel had the best strength, Charpy impact properties were inferior to those of an Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) and an Fe-2.25Cr-2W-0.1C (2 1/4Cr-2W) steel. Therefore, further development of the low-chromium Cr-W steels was required. These results indicate that it is possible to develop low-chromium reduced-activation ferritic steels that have tensile and impact properties as good or better than those of high-chromium (7-9% Cr) steels. Further improvement of properties should be possible by optimizing the composition.

  15. Diffusion of Chromium in Alpha Cobalt-Chromium Solid Solutions

    NASA Technical Reports Server (NTRS)

    Weeton, John W

    1951-01-01

    Diffusion of chromium in cobalt-chromium solid solutions was investigated in the range 0 to 40 atomic percent at temperatures of 1360 degrees, 1300 degrees, 1150 degrees, and 10000 degrees c. The diffusion coefficients were found to be relatively constant within the composition range covered by each specimen. The activation heat of diffusion was determined to be 63,000 calories per mole. This value agrees closely with the value of 63,400 calories per mole calculated by means of the Dushman-Langmuir equation.

  16. Improving Metal Casting Process

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Don Sirois, an Auburn University research associate, and Bruce Strom, a mechanical engineering Co-Op Student, are evaluating the dimensional characteristics of an aluminum automobile engine casting. More accurate metal casting processes may reduce the weight of some cast metal products used in automobiles, such as engines. Research in low gravity has taken an important first step toward making metal products used in homes, automobiles, and aircraft less expensive, safer, and more durable. Auburn University and industry are partnering with NASA to develop one of the first accurate computer model predictions of molten metals and molding materials used in a manufacturing process called casting. Ford Motor Company's casting plant in Cleveland, Ohio is using NASA-sponsored computer modeling information to improve the casting process of automobile and light-truck engine blocks.

  17. Precipitating Chromium Impurities in Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Salama, A. M.

    1982-01-01

    Two new treatments for silicon wafers improve solar-cell conversion efficiency by precipitating electrically-active chromium impurities. One method is simple heat treatment. Other involves laser-induced damage followed by similar heat treatment. Chromium is one impurity of concern in metallurgical-grade silicon for solar cells. In new treatment, chromium active centers are made electrically inactive by precipitating chromium from solid solution, enabling use of lower grade, lower cost silicon in cell manufacture.

  18. SLIP CASTING METHOD

    DOEpatents

    Allison, A.G.

    1959-09-01

    S>A process is described for preparing a magnesium oxide slip casting slurry which when used in conjunction with standard casting techniques results in a very strong "green" slip casting and a fired piece of very close dimensional tolerance. The process involves aging an aqueous magnestum oxide slurry, having a basic pH value, until it attains a specified critical viscosity at which time a deflocculating agent is added without upsetting the basic pH value.

  19. Erosive Wear Behavior of Nickel-Based High Alloy White Cast Iron Under Mining Conditions Using Orthogonal Array

    NASA Astrophysics Data System (ADS)

    Yoganandh, J.; Natarajan, S.; Babu, S. P. Kumaresh

    2013-09-01

    Nihard Grade-4, a nickel-bearing cast iron widely used in slurry pumps and hydrodynamic components, is evaluated for its erosive wear response under mining conditions using a statistical approach. Experiments were conducted by varying the factors namely velocity, slurry concentration, angle of impingement, and pH in three levels, using L9 orthogonal array. Analysis of variance was used to rank the factors influencing erosive wear. The results indicate that velocity is the most influencing factor followed by the angle of impingement, slurry concentration, and pH. Interaction effects of velocity, slurry concentration, angle of impingement, and pH on erosion rate have been discussed. Wear morphology was also studied using SEM characterization technique. At lower angle (30°) of impingement, the erosion of material is by micro fracture and shallow ploughing with the plastic deformation of the ductile austenitic matrix. At the normal angle (90°) of impingement, the material loss from the surface is found because of deep indentation, forming protruded lips which are removed by means of repeated impact of the erodent.

  20. High performance anode-supported tubular solid oxide fuel cells fabricated by a novel slurry-casting method

    NASA Astrophysics Data System (ADS)

    Duan, Nan-Qi; Yan, Dong; Chi, Bo; Pu, Jian; Jian, Li

    2015-02-01

    Tubular solid oxide fuel cells were fabricated and evaluated for their microstructure and electrochemical performance. The tubular substrate was prepared by casting NiO-Y2O3 stabilized ZrO2 (YSZ) slurry on the inner wall of a plastic mold (tube). The wall thickness and uniformity were controlled by slurry viscosity and rotation speed of the tube. The cells consisted of Ni-YSZ functional anode, YSZ electrolyte and (La0.8Sr0.2)0.95MnO3-δ (LSM)-YSZ cathode prepared in sequence on the substrate by dip-coating and sintering. Their dimension was 50 mm in length, 0.8 mm in thickness and 10.5 mm in outside diameter. The peak power density of the cell at temperatures between 650 and 850°C was in the range from 85 to 522 mW cm-2 and was greatly enhanced to the range from 308 to 1220 mW cm-2 by impregnating PdO into LSM-YSZ cathode. During a cell testing at 0.7 A cm-2 and 750°C for 282 h, the impregnated PdO particles grew by coalescence, which increased the cathode polarization resistance and so that decreased the cell performance. According to the degradation tendency, the cell performance will be stabilized in a longer run.

  1. High performance anode-supported tubular solid oxide fuel cells fabricated by a novel slurry-casting method.

    PubMed

    Duan, Nan-Qi; Yan, Dong; Chi, Bo; Pu, Jian; Jian, Li

    2015-02-02

    Tubular solid oxide fuel cells were fabricated and evaluated for their microstructure and electrochemical performance. The tubular substrate was prepared by casting NiO-Y2O3 stabilized ZrO2 (YSZ) slurry on the inner wall of a plastic mold (tube). The wall thickness and uniformity were controlled by slurry viscosity and rotation speed of the tube. The cells consisted of Ni-YSZ functional anode, YSZ electrolyte and (La0.8Sr0.2)0.95MnO(3-δ) (LSM)-YSZ cathode prepared in sequence on the substrate by dip-coating and sintering. Their dimension was 50 mm in length, 0.8 mm in thickness and 10.5 mm in outside diameter. The peak power density of the cell at temperatures between 650 and 850°C was in the range from 85 to 522 mW cm(-2) and was greatly enhanced to the range from 308 to 1220 mW cm(-2) by impregnating PdO into LSM-YSZ cathode. During a cell testing at 0.7 A cm(-2) and 750°C for 282 h, the impregnated PdO particles grew by coalescence, which increased the cathode polarization resistance and so that decreased the cell performance. According to the degradation tendency, the cell performance will be stabilized in a longer run.

  2. High performance anode-supported tubular solid oxide fuel cells fabricated by a novel slurry-casting method

    PubMed Central

    Duan, Nan-Qi; Yan, Dong; Chi, Bo; Pu, Jian; Jian, Li

    2015-01-01

    Tubular solid oxide fuel cells were fabricated and evaluated for their microstructure and electrochemical performance. The tubular substrate was prepared by casting NiO-Y2O3 stabilized ZrO2 (YSZ) slurry on the inner wall of a plastic mold (tube). The wall thickness and uniformity were controlled by slurry viscosity and rotation speed of the tube. The cells consisted of Ni-YSZ functional anode, YSZ electrolyte and (La0.8Sr0.2)0.95MnO3-δ (LSM)-YSZ cathode prepared in sequence on the substrate by dip-coating and sintering. Their dimension was 50 mm in length, 0.8 mm in thickness and 10.5 mm in outside diameter. The peak power density of the cell at temperatures between 650 and 850°C was in the range from 85 to 522 mW cm−2 and was greatly enhanced to the range from 308 to 1220 mW cm−2 by impregnating PdO into LSM-YSZ cathode. During a cell testing at 0.7 A cm−2 and 750°C for 282 h, the impregnated PdO particles grew by coalescence, which increased the cathode polarization resistance and so that decreased the cell performance. According to the degradation tendency, the cell performance will be stabilized in a longer run. PMID:25640168

  3. A high precision instrument to measure angular and binocular deviation introduced by aircraft windscreens by using a shadow casting technique

    SciTech Connect

    Shivananju, B. N.; Yamdagni, S.; Vasu, R. M.; Asokan, S.

    2012-12-15

    Objects viewed through transparent sheets with residual non-parallelism and irregularity appear shifted and distorted. This distortion is measured in terms of angular and binocular deviation of an object viewed through the transparent sheet. The angular and binocular deviations introduced are particularly important in the context of aircraft windscreens and canopies as they can interfere with decision making of pilots especially while landing, leading to accidents. In this work, we have developed an instrument to measure both the angular and binocular deviations introduced by transparent sheets. This instrument is especially useful in the qualification of aircraft windscreens and canopies. It measures the deviation in the geometrical shadow cast by a periodic dot pattern trans-illuminated by the distorted light beam from the transparent test specimen compared to the reference pattern. Accurate quantification of the shift in the pattern is obtained by cross-correlating the reference shadow pattern with the specimen shadow pattern and measuring the location of the correlation peak. The developed instrument is handy to use and computes both angular and binocular deviation with an accuracy of less than {+-}0.1 mrad ( Almost-Equal-To 0.036 mrad) and has an excellent repeatability with an error of less than 2%.

  4. Influence of high doses γ-irradiation on oxygen permeability of linear low-density polyethylene and cast polypropylene films

    NASA Astrophysics Data System (ADS)

    Klepac, Damir; Ščetar, Mario; Baranović, Goran; Galić, Kata; Valić, Srećko

    2014-04-01

    Linear low density polyethylene (PE-LLD) and cast polypropylene (PPcast) films were irradiated in a 60Co γ-source. The total irradiation dose varied from 0 kGy (unirradiated samples) to 200 kGy. Oxygen transport was investigated by a manometric method and the structural changes were studied by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Free radicals decay as a function of time was monitored by electron spin resonance (ESR) spectroscopy. The results show that the γ-irradiation reduces oxygen permeability coefficient in both films. The reduction was associated with an increase in crystallinity. DSC thermograms revealed a decrease in PPcast melting point with increasing irradiation dose, indicating higher degradation compared to PE-LLD. The observed peak in FTIR spectra for both samples at 1716 cm-1 corresponds to the stretching of the carbonyl and carboxylic groups which arise from the reaction of oxygen with the free radicals produced in the polymer matrix as a result of irradiation.

  5. A review of chromium, molybdenum, and tungsten alloys

    NASA Technical Reports Server (NTRS)

    Klopp, W. D.

    1975-01-01

    The mechanical properties of chromium, molybdenum, and tungsten alloys are reviewed with particular emphasis on high-temperature strength and low-temperature ductility. Precipitate strengthening is highly effective at 0.4 to 0.8 times the melting temperature in these metals, with HfC being most effective in tungsten and molybdenum, and Ta(B,C) most effective in chromium. Low-temperature ductility can be improved by alloying to promote rhenium ductilizing or solution softening. The low-temperature mechanical properties of these alloys appear related to electronic interactions rather than to the usual metallurgical considerations.

  6. Spectroscopic characteristics of chromium-doped mullite glass-ceramics

    SciTech Connect

    Wojtowicz, A.J.; Meng, W.; Lempicki, A.; Beall, G.H.; Hall, D.W.

    1988-06-01

    The chromium (3+) ion has been widely used as an optical activator in solid-state, tunable laser materials. High octahedral field-stabilization energy and resistance against both oxidation and reduction minimize the dependence of chromium (3+) on the solid-state host matrix. However, the high sensitivity of electronic structure on crystal field strength makes the appropriate choice of host the condition for success. Characteristics of chromium-doped mullite ceramics are discussed with reference to possible laser applications. Dominant features are attributed to large and inherent spectroscopic inhomogeneity of mullite. The spectroscopic data are analyzed using a generalized McCumber theory. The peak-stimulated emission cross section is 0.54 x 10 to the -20 sq cm. This together with preliminary single-pass measurements, indicate that gain for mullite is about 2.6 times smaller than gain for alexandrite.

  7. Optimization of heat transfer by adjusting power ratios between top and side heaters for casting high-performance multi-crystalline silicon ingots

    NASA Astrophysics Data System (ADS)

    Chen, Wenliang; Wu, Zhiyong; Zhong, Genxiang; Ding, Junjing; Yu, Yunyang; Zhou, Xucheng; Huang, Xinming

    2016-10-01

    Numerical simulations were applied to analyze the effects of the power ratios between top and side heaters on the crystal-melt (c-m) interface and the thermal stress distribution during the solidification process. The simulation results showed that among the different increase velocities of the power ratio, increasing the power ratio uniformly provided a most favorable solidification process: a slightly convex c-m interface shape and low thermal stress were obtained. The optimized design was implemented in casting experiments, which showed that the high-performance multi-crystalline silicon ingot had a vertical columnar structure and a lower dislocation density. The average conversion efficiency of solar cells was about 0.08% higher with this design (18.24%) than with the original design (18.16%).

  8. Tea tree oil concentration in follicular casts after topical delivery: determination by high-performance thin layer chromatography using a perfused bovine udder model.

    PubMed

    Biju, S S; Ahuja, Alka; Khar, Roop K

    2005-02-01

    Tea tree oil, a popular antimicrobial agent is recommended for the treatment of acne vulgaris, a disease of the pilosebaceous unit. Tea tree oil formulations (colloidal bed, microemulsion, multiple emulsion, and liposomal dispersion containing 5% w/w tea tree oil) were applied to bovine udder skin. The follicular uptake of tea tree oil upon application was determined by a cyanoacrylate method. Tea tree oil was determined by quantifying terpinen-4-ol content using high-performance thin layer chromatography. The accumulation of tea tree oil in the follicular casts was 0.43 +/- 0.01, 0.41 +/- 0.009, 0.21 +/- 0.006, and 0.16 +/- 0.005 percentage by weight (milligram oil/gram of sebum plug) for microemulsion, liposomal dispersion, multiple emulsion, and colloidal bed, respectively. This is the first study of its kind to quantify tea tree oil concentration in the follicles.

  9. Evolution of halictine castes

    NASA Astrophysics Data System (ADS)

    Knerer, Gerd

    1980-03-01

    Social halictine bees have female castes that range from species with no size differences to those with a discrete bimodality. Female caste differences are inversely correlated with the number of males produced in the first brood. It is proposed that the sexual dimorphism of solitary forms is being usurped by the female caste system of species in the process of turning social. Thus, caste differences and summer male suppression are greatest in the social species originating from solitary precursors with distinct sexual dimorphism, and are least in species evolving from solitary ancestors with a continuous sexual polymorphism.

  10. Cast Aluminum Bonding Study

    DTIC Science & Technology

    1988-05-01

    fabricated using P?-’r;est11 bur)ld II19 te(hnll I Oly with 6 cIsL nqs. The cast a lumi num alloy used was A357 . The sur- face preparation was phosphoric acid...from a cast aluminum alloy designated A357 . The bonding surfaces of the adherends were prepared using PAA. One primer and two adhesives considered...System, Cast Aluminum Lap Shear 18 11 Bond Area of 350°F Adhesive System, Cast Aluminum Lap Shear 19 vi LIST OF TABLES TABLE PAGE 1 A357 Chemical

  11. Increasing the structural complexity of chromium(IV) oxides by high-pressure and high-temperature reactions of CrO2.

    PubMed

    Castillo-Martínez, E; Arévalo-López, A M; Ruiz-Bustos, R; Alario-Franco, M A

    2008-10-06

    This work presents an overview of a series of increasingly complex oxides synthesized from CrO 2, under high-pressure and high-temperature conditions, having Cr (4+) in octahedral coordination. Although the emphasis is on the structure and microstructure of the compounds as obtained from X-ray diffraction and transmission electron microscopy and diffraction, attention is also given to their interesting electronic and magnetic properties. The study is complemented with an electron energy loss spectroscopic analysis of the different phases. These are the cubic perovskite SrCrO 3, the orthorhombic perovskite CaCrO 3, the solid solution Sr 1-xCa xCrO 3, the Ruddlesden-Popper-type Sr 3Cr 2O 7, the family CrSr 2RECu 2O 8 (RE = rare earth), a compositionally modulated perovskite "PbCrO 3", and the misfit layer oxide SrO 2[CrO 2] 1.85.

  12. Influence of Cr and W alloying on the fiber-matrix interfacial shear strength in cast and directionally solidified sapphire NiAl composites

    NASA Technical Reports Server (NTRS)

    Asthana, R.; Tiwari, R.; Tewari, S. N.

    1995-01-01

    Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys reinforced with sapphire fibers.

  13. Development of Alkaline Oxidative Dissolution Methods for Chromium (III) Compounds Present in Hanford Site Tank Sludges

    SciTech Connect

    NN Krot; VP Shilov; AM Fedoseev; NA Budantseva; MV Nikonov; AB Yusov; AYu Garnov; IA Charushnikova; VP Perminov; LN Astafurova; TS Lapitskaya; VI Makarenkov

    1999-07-02

    The high-level radioactive waste sludge in the underground storage tanks at the Hanford Site contains various chromium(III)solid phases. Dissolution and removal of chromium from tank waste sludges is desirable prior to high-level waste vitrification because increased volume is required to incorporate the residual chromium. Unfortunately, dissolution of chromium from the sludge to form Cr(OH){sub 4}{sup {minus}} through treatment with heated NaOH solution (also used to dissolve aluminum phases and metathesize phosphates to sodium salts) generally has been unsuccessful in tests with both simulated and genuine Hanford waste sludges. Oxidative dissolution of the Cr(III) compounds to form soluble chromate has been proposed as an alternative chromium solid phase dissolution method and results of limited prior testing have been reported.

  14. Anthropogenic Chromium Emissions in China from 1990 to 2009

    PubMed Central

    Cheng, Hongguang; Zhou, Tan; Li, Qian; Lu, Lu; Lin, Chunye

    2014-01-01

    An inventory of chromium emission into the atmosphere and water from anthropogenic activities in China was compiled for 1990 through to 2009. We estimate that the total emission of chromium to the atmosphere is about 1.92×105t. Coal and oil combustion were the two leading sources of chromium emission to the atmosphere in China, while the contribution of them showed opposite annual growth trend. In total, nearly 1.34×104t of chromium was discharged to water, mainly from six industrial categories in 20 years. Among them, the metal fabrication industry and the leather tanning sector were the dominant sources of chromium emissions, accounting for approximately 68.0% and 20.0% of the total emissions and representing increases of15.6% and 10.3% annually, respectively. The spatial trends of Cr emissions show significant variation based on emissions from 2005 to 2009. The emission to the atmosphere was heaviest in Hebei, Shandong, Guangdong, Zhejiang and Shanxi, whose annual emissions reached more than 1000t for the high level of coal and oil consumption. In terms of emission to water, the largest contributors were Guangdong, Jiangsu, Shandong and Zhejiang, where most of the leather production and metal manufacturing occur and these four regions accounted for nearly 47.4% of the total emission to water. PMID:24505309

  15. [Occupational exposure to hexavalent chromium during aircraft painting].

    PubMed

    Gherardi, M; Gatto, M P; Gordiani, A; Paci, E; Proietto, A

    2007-01-01

    Hygienists are interested in hexavalent chromium due to its genotoxic and carcinogenic effect on humans. The use of products containing hexavalent chromium is decreasing in many industrial fields because of the substitution with less-toxic compounds. In the aeronautical industry, however, the chromate are added to primer paint as a corrosion inhibitor of aircrafts surfaces: so hexavalent chromium compounds are available in many primers with a composition ranging from 10% to 13%. The application of these primers by using electrostatic guns potentially exposes painting and coating workers at high concentrations of aerosols containing Cr(VI). The aim of the present study is the evaluation of professional exposure to hexavalent chromium during aircraft painting, by adopting both environmental personal sampling and biological monitoring. To valuate workers exposure levels the personal measurements results have been compared with the exposure limit values (TLV-TWA) and the urinary chromium contents with the biological exposure indices (IBE). Moreover the strategy of coupling environmental sampling with biological monitoring seems to be a useful instrument to measure the validity of the individual protection devices.

  16. Nickel and chromium isotopes in Allende inclusions

    NASA Technical Reports Server (NTRS)

    Birck, J. L.; Lugmair, G. W.

    1988-01-01

    High-precision nickel and chromium isotopic measurements were carried out on nine Allende inclusions. It is found that Ni-62, Ni-64, excesses are present in at least three of the samples. The results suggest that the most likely mechanism for the anomalies is a neutron-rich statistical equilibrium process. An indication of elevated Ni-60 is found in almost every inclusion measured. This effect is thought to be related to the decay of now extinct Fe-60. An upper limit of 1.6 X 10 to the -6th is calculated for the Fe-60/Fe-56 ratio at the time these Allende inclusions crystallized.

  17. Tape casting of magnesium oxide.

    SciTech Connect

    Ayala, Alicia; Corral, Erica L.; Loehman, Ronald E.; Bencoe, Denise Nora; Reiterer, Markus; Shah, Raja A.

    2008-02-01

    A tape casting procedure for fabricating ceramic magnesium oxide tapes has been developed as a method to produce flat sheets of sintered MgO that are thin and porous. Thickness of single layer tapes is in the range of 200-400 {micro}m with corresponding surface roughness values in the range of 10-20 {micro}m as measured by laser profilometry. Development of the tape casting technique required optimization of pretreatment for the starting magnesium oxide (MgO) powder as well as a detailed study of the casting slurry preparation and subsequent heat treatments for sintering and final tape flattening. Milling time of the ceramic powder, plasticizer, and binder mixture was identified as a primary factor affecting surface morphology of the tapes. In general, longer milling times resulted in green tapes with a noticeably smoother surface. This work demonstrates that meticulous control of the entire tape casting operation is necessary to obtain high-quality MgO tapes.

  18. A Predictive Framework for Thermomechanical Fatigue Life of High Silicon Molybdenum Ductile Cast Iron Based on Considerations of Strain Energy Dissipation

    NASA Astrophysics Data System (ADS)

    Avery, Katherine R.

    Isothermal low cycle fatigue (LCF) and anisothermal thermomechanical fatigue (TMF) tests were conducted on a high silicon molybdenum (HiSiMo) cast iron for temperatures up to 1073K. LCF and out-of-phase (OP) TMF lives were significantly reduced when the temperature was near 673K due to an embrittlement phenomenon which decreases the ductility of HiSiMo at this temperature. In this case, intergranular fracture was predominant, and magnesium was observed at the fracture surface. When the thermal cycle did not include 673K, the failure mode was predominantly transgranular, and magnesium was not present on the fracture surface. The in-phase (IP) TMF lives were unaffected when the thermal cycle included 673K, and the predominant failure mode was found to be transgranular fracture, regardless of the temperature. No magnesium was present on the IP TMF fracture surfaces. Thus, the embrittlement phenomenon was found to contribute to fatigue damage only when the temperature was near 673K and a tensile stress was present. To account for the temperature- and stress-dependence of the embrittlement phenomenon on the TMF life of HiSiMo cast iron, an original model based on the cyclic inelastic energy dissipation is proposed which accounts for temperature-dependent differences in the rate of fatigue damage accumulation in tension and compression. The proposed model has few empirical parameters. Despite the simplicity of the model, the predicted fatigue life shows good agreement with more than 130 uniaxial low cycle and thermomechanical fatigue tests, cyclic creep tests, and tests conducted at slow strain rates and with hold times. The proposed model was implemented in a multiaxial formulation and applied to the fatigue life prediction of an exhaust manifold subjected to severe thermal cycles. The simulation results show good agreement with the failure locations and number of cycles to failure observed in a component-level experiment.

  19. Laser surface texturing of cast iron steel: dramatic edge burr reduction and high speed process optimisation for industrial production using DPSS picosecond lasers

    NASA Astrophysics Data System (ADS)

    Bruneel, David; Kearsley, Andrew; Karnakis, Dimitris

    2015-07-01

    In this work we present picosecond DPSS laser surface texturing optimisation of automotive grade cast iron steel. This application attracts great interest, particularly in the automotive industry, to reduce friction between moving piston parts in car engines, in order to decrease fuel consumption. This is accomplished by partially covering with swallow microgrooves the inner surface of a piston liner and is currently a production process adopting much longer pulse (microsecond) DPSS lasers. Lubricated interface conditions of moving parts require from the laser process to produce a very strictly controlled surface topography around the laser formed grooves, whose edge burr height must be lower than 100 nm. To achieve such a strict tolerance, laser machining of cast iron steel was investigated using an infrared DPSS picosecond laser (10ps duration) with an output power of 16W and a repetition rate of 200 kHz. The ultrashort laser is believed to provide a much better thermal management of the etching process. All studies presented here were performed on flat samples in ambient air but the process is transferrable to cylindrical geometry engine liners. We will show that reducing significantly the edge burr below an acceptable limit for lubricated engine production is possible using such lasers and remarkably the process window lies at very high irradiated fluences much higher that the single pulse ablation threshold. This detailed experimental work highlights the close relationship between the optimised laser irradiation conditions as well as the process strategy with the final size of the undesirable edge burrs. The optimised process conditions are compatible with an industrial production process and show the potential for removing extra post)processing steps (honing, etc) of cylinder liners on the manufacturing line saving time and cost.

  20. Method of improving fatigue life of cast nickel based superalloys and composition

    DOEpatents

    Denzine, Allen F.; Kolakowski, Thomas A.; Wallace, John F.

    1978-03-14

    The invention consists of a method of producing a fine equiaxed grain structure (ASTM 2-4) in cast nickel-base superalloys which increases low cycle fatigue lives without detrimental effects on stress rupture properties to temperatures as high as 1800.degree. F. These superalloys are variations of the basic nickel-chromium matrix, hardened by gamma prime [Ni.sub.3 (Al, Ti)] but with optional additions of cobalt, tungsten, molybdenum, vanadium, columbium, tantalum, boron, zirconium, carbon and hafnium. The invention grain refines these alloys to ASTM 2 to 4 increasing low cycle fatigue life by a factor of 2 to 5 (i.e. life of 700 hours would be increased to 1400 to 3500 hours for a given stress) as a result of the addition of 0.01% to 0.2% of a member of the group consisting of boron, zirconium and mixtures thereof to aid heterogeneous nucleation. The alloy is vacuum melted and heated to 250.degree.-400.degree. F. above the melting temperature, cooled to partial solidification, thus resulting in said heterogeneous nucleation and fine grains, then reheated and cast at about 50.degree.-100.degree. F. of superheat. Additions of 0.1% boron and 0.1% zirconium (optional) are the preferred nucleating agents.

  1. Cast segment evaluation

    NASA Technical Reports Server (NTRS)

    Diem, H. G.; Studhalter, W. R.

    1971-01-01

    Evaluation program to determine feasibility of fabricating segmented rocket engine thrust chambers using low cost, lightweight castings extends state of the art in areas of casting size and complexity, and in ability to provide thin sections and narrow, deep, cooling channels. Related developments are discussed.

  2. Higher Education's Caste System

    ERIC Educational Resources Information Center

    Iannone, Ron

    2004-01-01

    In this article, the author discusses the history of the present caste system in higher education. He shows how the public's perception of this caste system is based on image and not usually on the quality of teaching and curriculum in colleges and universities. Finally, he discusses a model for accessibility to higher education and how higher…

  3. A cast orientation index.

    PubMed

    Ivanhoe, J R; Mahanna, G K

    1994-12-01

    This article describes a technique that allows multiple master casts to be precisely oriented to the same path of insertion and withdrawal. This technique is useful in situations where multiple fixed prosthodontic preparations require surveyed restorations and a single master cast is not available.

  4. Effect of casting method on castability of titanium and dental alloys.

    PubMed

    Watanabe, I; Woldu, M; Watanabe, K; Okabe, T

    2000-09-01

    Titanium, once considered to be difficult to cast because of its relatively high melting point (1670 +/- 50 degrees C) and strong chemical affinity, can now be acceptably cast using newly developed casting apparatus. The objectives of this study were to examine the castability of commercially pure (CP) titanium using an ultra high-speed centrifugal casting machine and a pressure difference-type casting unit and to compare the castability of titanium with that of conventional dental casting alloys. To determine castability, two types of patterns were used: a mesh pattern of 22 x 24 mm cut polyether thread sieve, and a saucer pattern (24 mm diameter) perforated to create four T-shaped ends. The casting equipment significantly affected the mold filling of both patterns (p < 0.001). The castability indices obtained from both patterns of CP titanium cast in the centrifugal casting machine were significantly (p < 0.05) better than the indices of the castings produced in the pressure-difference casting unit. The radiographs of the saucer pattern cast in the centrifugal casting machine showed some pores that were fewer and smaller in size than the pores found in castings made in the pressure-difference unit. When the ultra high-speed centrifugal casting machine was used with the manufacturer's recommended mold material, the castability of titanium was similar to that of gold alloy or Ni-Cr alloy cast by conventional means.

  5. Use of chitosan for chromium removal from exhausted tanning baths.

    PubMed

    Cesaro, Raffaele; Fabbricino, Massimiliano; Lanzetta, Rosa; Mancino, Anna; Naviglio, Biagio; Parrilli, Michelangelo; Sartorio, Roberto; Tomaselli, Michele; Tortora, Gelsomina

    2008-01-01

    A novel approach, based on chitosan heavy-metal sequestrating ability, is proposed for chromium(III) removal from spent tanning liquor. Experimental results, obtained at lab-scale using real wastewater, are presented and discussed. Resulting efficiencies are extremely high, and strongly dependent on chitosan dose and pH value. Comparative analyses with other polysaccharides is also carried out showing that amine groups are more efficient than carboxyl and sulphate ones. Chromium recovery from sorption complexes and chitosan regeneration is finally proposed to optimize the whole process.

  6. Chromium boron surfaced nickel-iron base alloys

    NASA Technical Reports Server (NTRS)

    Rashid, James M. (Inventor); Friedrich, Leonard A. (Inventor); Freling, Melvin (Inventor)

    1984-01-01

    Chromium boron diffusion coatings on nickel iron alloys uniquely provide them with improvement in high cycle fatigue strength (up to 30%) and erosion resistance (up to 15 times), compared to uncoated alloy. The diffused chromium layer extends in two essential concentration zones to a total depth of about 40.times.10.sup.-6 m, while the succeeding boron layer is limited to 50-90% of the depth of the richest Cr layer nearest the surface. Both coatings are applied using conventional pack diffusion processes.

  7. Nickel and chromium cycles: Stocks and flows project part IV

    NASA Astrophysics Data System (ADS)

    Reck, Barbara K.; Gordon, Robert B.

    2008-07-01

    Nickel and chromium are essential ingredients in alloys increasingly important for energy-efficient, environmentally friendly modern technology. Quantitative assessment of the flows of these metals through the world economy from resource extraction to final disposal informs resource policy, energy planning, environmental science, and waste management. This article summarizes the worldwide technological cycles of nickel and chromium in 2000. Stainless steel is the major use of these metals, but they serve numerous other special needs, as in superalloys for high-temperature service, as plating materials, and in coinage. Because they are used primarily in alloys, novel recycling issues arise as their use becomes more widespread.

  8. Removal of chromium from synthetic plating waste by zero-valent iron and sulfate-reducing bacteria.

    PubMed

    Guha, Saumyen; Bhargava, Puja

    2005-01-01

    Experiments were conducted to evaluate the potential of zero-valent iron and sulfate-reducing bacteria (SRB) for reduction and removal of chromium from synthetic electroplating waste. The zero-valent iron shows promising results as a reductant of hexavalent chromium (Cr+6) to trivalent chromium (Cr+3), capable of 100% reduction. The required iron concentration was a function of chromium concentration in the waste stream. Removal of Cr+3 by adsorption or precipitation on iron leads to complete removal of chromium from the waste and was a slower process than the reduction of Cr+6. Presence SRB in a completely mixed batch reactor inhibited the reduction of Cr+6. In a fixed-bed column reactor, SRB enhanced chromium removal and showed promising results for the treatment of wastes with low chromium concentrations. It is proposed that, for waste with high chromium concentration, zero-valent iron is an efficient reductant and can be used for reduction of Cr+6. For low chromium concentrations, a SRB augmented zero-valent iron and sand column is capable of removing chromium completely.

  9. Chromium(III), insoluble salts

    Integrated Risk Information System (IRIS)

    TOXICOLOGICAL REVIEW OF TRIVALENT CHROMIUM ( CAS No . 16065 - 83 - 1 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) August 1998 U.S . Environmental Protection Agency Washington , DC DISCLAIMER This document has been reviewed in accordance with U.S . Environmen

  10. Chromium in the environment of Finland.

    PubMed

    Mukherjee, A B

    1998-06-30

    This paper focuses upon the use, import and release of chromium to the environment of Finland. In addition, the behavior of trivalent and hexavalent chromium in soils has been briefly reviewed. In Finland, consumption of chromium compounds occurs in the following pattern: stainless steel > leather tanning > metal plating > chemicals. The emission of chromium has decreased from 114 t in 1979 to 28 t in 1995. The highest release of chromium continues to be from ferrochromium and stainless steel plants. From these facilities, 85% of slag and dusts are used by a secondary facility to recover valuable metal. In the industrial areas, the oxidizing behavior of chromium (III) is still unknown. In this study, the leachability of chromium (VI) to ground water and its effects on terrestrial and aquatic species in Finland are discussed.

  11. [Worldwide cancer mortality among chromium platers].

    PubMed

    Hara, Toshiyuki; Takahashi, Ken

    2012-12-01

    The elevated risk of lung cancer among chromate-producing workers has been confirmed by many epidemiological studies. Although chromium has been most used in the chromium plating industry and many platers are employed in small-scale factories, cancer studies have been documented in only a few investigations. We have conducted several prospective cohort studies in Japanese chromium platers and recently extended them through 2003. We additionally surveyed epidemiological studies among chromium platers carried out in other parts of the world. Occupational chromium exposure through chromium plating work may be a risk factor for mortality not only from lung cancer but also malignant lymphoma and brain tumor. The age at first exposure to chromium may be a more important factor than the duration of exposure for an increased risk of lung cancer and malignant lymphoma.

  12. Ecophysiological responses of young mangrove species Rhizophora apiculata (Blume) to different chromium contaminated environments.

    PubMed

    Nguyen, Kim Linh; Nguyen, Hoang Anh; Richter, Otto; Pham, Minh Thinh; Nguyen, Van Phuoc

    2017-01-01

    Many mangrove forests have suffered from the contaminated environments near industrial areas. This study addresses the question how these environments influence the renewal of mangrove forests. To this end ecophysiological responses of the young mangrove species Rhizophora apiculata (Blume) grown under combinations of the factors heavy metals (here chromium), nutrition and soil/water environment were analyzed. We tested the hypothesis that soil/water conditions and nutrient status of the soil strongly influence the toxic effect of chromium. Seedlings of R. apiculata were grown in three different soil/water environments (natural saline soil with brackish water, salt-leached soil with fresh water and salt-leached-sterilized soil with fresh water) treated with different levels of chromium and NPK fertilizer. The system was inundated twice a day as similar to natural tidal condition in the mangrove wetland in the south of Vietnam. The experiments were carried out for 6months. Growth data of root, leaf and stem, root cell number and stomata number were recorded and analyzed. Results showed that growth of R. apiculata is slower in natural saline soil/water condition. The effect of chromium and of nutrients respectively depends on the soil/water condition. Under high concentrations of chromium, NPK fertilizer amplifies the toxic effect of chromium. Stomata density increases under chromium stress and is largest under the combination of chromium and salty soil/water condition. From the data a nonlinear multivariate regression model was derived capturing the toxicity threshold of R. apiculata under different treatment combinations.

  13. Stability of chromium (III) sulfate in atmospheres containing oxygen and sulfur

    NASA Technical Reports Server (NTRS)

    Jacob, K. T.; Rao, B. D.; Nelson, H. G.

    1978-01-01

    The stability of chromium sulfate in the temperature range from 880 K to 1040 K was determined by employing a dynamic gas-solid equilibration technique. The solid chromium sulfate was equilibrated in a gas stream of controlled SO3 potential. Thermogravimetric and differential thermal analyses were used to follow the decomposition of chromium sulfate. X-ray diffraction analysis indicated that the decomposition product was crystalline Cr2O3 and that the mutual solubility between Cr2(SO4)3 and Cr2O3 was negligible. Over the temperature range investigated, the decomposition pressure were significantly high so that chromium sulfate is not expected to form on commercial alloys containing chromium when exposed to gaseous environments containing oxygen and sulfur (such as those encountered in coal gasification).

  14. The use of trivalent chromium bath to obtain a solar selective black chromium coating

    NASA Astrophysics Data System (ADS)

    Survilienė, S.; Češūnienė, A.; Juškėnas, R.; Selskienė, A.; Bučinskienė, D.; Kalinauskas, P.; Juškevičius, K.; Jurevičiūtė, I.

    2014-06-01

    Black chromium coatings were electrodeposited from a trivalent chromium bath using a ZnO additive as a second main component. Black chromium was electrodeposited on steel and copper plates and substrates plated with bright nickel prior to black chromium electrodeposition. The black chromium coatings were characterized by XRD and SEM. The XRD data suggest that the phase structure of black chromium may be defined as a zinc solid solution in chromium or a chromium solid solution in zinc depending on the chromium/zinc ratio in the deposit. The role of substrate finish was evaluated through the corrosion resistance and reflectance of black chromium. According to corrosion tests the samples plated with bright nickel prior to black chromium deposition have shown the highest corrosion resistance. The electrodeposited black chromium possesses good optical properties for the absorption of solar energy. The absorption coefficient of black chromium was found to be over 0.99 for the samples obtained without the Ni undercoat and below 0.99 for those obtained with the use of Ni undercoat. However, the use of nickel undercoat before black chromium plating is recommended because it remarkably improves the corrosion resistance of samples.

  15. ALUMINUM AND CHROMIUM LEACHING WORKSHOP WHITEPAPER

    SciTech Connect

    McCabe, D; Jeff Pike, J; Bill Wilmarth, B

    2007-04-25

    A workshop was held on January 23-24, 2007 to discuss the status of processes to leach constituents from High Level Waste (HLW) sludges at the Hanford and Savannah River Sites. The objective of the workshop was to examine the needs and requirements for the HLW flowsheet for each site, discuss the status of knowledge of the leaching processes, communicate the research plans, and identify opportunities for synergy to address knowledge gaps. The purpose of leaching of non-radioactive constituents from the sludge waste is to reduce the burden of material that must be vitrified in the HLW melter systems, resulting in reduced HLW glass waste volume, reduced disposal costs, shorter process schedules, and higher facility throughput rates. The leaching process is estimated to reduce the operating life cycle of SRS by seven years and decrease the number of HLW canisters to be disposed in the Repository by 1000 [Gillam et al., 2006]. Comparably at Hanford, the aluminum and chromium leaching processes are estimated to reduce the operating life cycle of the Waste Treatment Plant by 20 years and decrease the number of canisters to the Repository by 15,000-30,000 [Gilbert, 2007]. These leaching processes will save the Department of Energy (DOE) billions of dollars in clean up and disposal costs. The primary constituents targeted for removal by leaching are aluminum and chromium. It is desirable to have some aluminum in glass to improve its durability; however, too much aluminum can increase the sludge viscosity, glass viscosity, and reduce overall process throughput. Chromium leaching is necessary to prevent formation of crystalline compounds in the glass, but is only needed at Hanford because of differences in the sludge waste chemistry at the two sites. Improving glass formulations to increase tolerance of aluminum and chromium is another approach to decrease HLW glass volume. It is likely that an optimum condition can be found by both performing leaching and improving

  16. [Blood and urine chromium: compared values between chromium exposed workers and common people].

    PubMed

    Provenzani, A; Verso, M G; Picciotto, D

    2008-01-01

    Aim of present study is the valutation and quantification of chromium in blood and urine. We compared 3 groups of persons formed by building workers, in particular masons, because cement contains potassium chromate that is dangerous for health, and by common people: urban population and outside the town population. In fact, exposure to CrVI risk is high for people who live near chromate industries. We maked a medical examination, blood and instrumental tests, chromium measuring in blood (recent exposure indicator) and urine (recent and previous indicator). Then we used statistical methods to estimate obtained values of blood and urine chromium among professional exposed people and common people. At the end we think that preventive measures in working environment reduced exposure to CrVI but environmental exposure (for example road dust from catalytic converter erosion, from brake lining erosion, cement dust and tobacco smoke), in the last years, has increased. So there are no difference between urban population and outside the town population and there are also no difference with professional exposed people for work prevention according to law in force, that let down professional risk using safe limits.

  17. A Double-blind, Randomized Pilot Trial of Chromium Picolinate for Binge Eating Disorder: Results of the Binge Eating and Chromium (BEACh) Study

    PubMed Central

    Brownley, Kimberly A.; Holle, Ann Von; Hamer, Robert M.; Via, Maria La; Bulik, Cynthia M.

    2015-01-01

    Objective Chromium treatment has been shown to improve mood, appetite, and glucose regulation in various psychiatric and medical patient populations. The authors propose that chromium may be useful in the treatment of binge eating disorder (BED). Method Twenty-four overweight adults with BED were enrolled in a 6-month double-blind placebo-controlled trial and randomly assigned to receive either 1000mcg chromium/day (“high dose”; n=8) or 600mcg chromium/day (“moderate dose”; n=9) as chromium picolinate or placebo (n=7). Mixed linear regression models were used to estimate mean change in binge frequency and related psychopathology, weight, symptoms of depression, and fasting glucose. Results Fasting glucose was significantly reduced in both chromium groups compared to the placebo group; similarly, numerically, but not significantly, greater reductions in binge frequency, weight, and symptoms of depression were observed in those treated with chromium versus placebo, although statistical power was limited in this pilot trial. For fasting glucose, the findings suggest a dose response with larger effects in the high dose compared to moderate dose group. Conclusion These initial findings support further larger trials to determine chromium’s efficacy in maintaining normal glucose regulation, reducing binge eating and related psychopathology, promoting modest weight loss, and reducing symptoms of depression in individuals with BED. Studies designed to link the clinical effects of chromium with changes in underlying insulin, serotonin, and dopamine pathways may be especially informative. If efficacious, chromium supplementation may provide a useful, low-cost alternative to or augmentation strategy for selective serotonin reuptake inhibitors, which have partial efficacy in BED. ClinicalTrials.gov NCT00904306. PMID:23751236

  18. Fatigue Properties of Cast Magnesium Wheels

    NASA Astrophysics Data System (ADS)

    Li, Zhenming; Luo, Alan A.; Wang, Qigui; Peng, Liming; Zhang, Peng

    2016-08-01

    This paper investigates the fatigue properties and deformation behavior of a newly developed Mg-2.96Nd-0.21Zn-0.39Zr magnesium alloy wheel in both as-cast and T6 conditions. Compared with the as-cast alloy, the T6-treated alloy shows a significant increase in fatigue strength and cyclic stress amplitude. This is believed to be attributed to the change of defect type from porosity to oxides and the increased matrix strength in the T6 (peak-aged) condition. For the as-cast alloy wheel, fatigue failure mainly originated from the cast defects including porosity, oxide film, and inclusion at or near the sample surface. In the T6-treated alloy, however, oxides and inclusions or slip bands initiate the fatigue cracks. Solution treatment appears to reduce or eliminate the shrinkage porosity because of grain growth and dissolution of as-cast eutectic phases in the grain boundaries. The cyclic stress amplitude of the as-cast alloy increases with increasing the number of cycles, while the T6-treated alloy shows cyclic softening after the stress reaches a maximum value. The Coffin-Manson law and Basquin equation can be used to evaluate the life of low cycle fatigue. The developed long crack model and multi-scale fatigue (MSF) models can be used to predict high-cycle fatigue life of the Mg-2.96Nd-0.21Zn-0.39Zr alloys with or without casting defects.

  19. Effectiveness of Haemodiafiltration with Heat Sterilized High-Flux Polyphenylene HF Dialyzer in Reducing Free Light Chains in Patients with Myeloma Cast Nephropathy

    PubMed Central

    2015-01-01

    Introduction In cases of myeloma cast nephropathy in need of haemodialysis (HD), reduction of free light chains using HD with High-Cut-Off filters (HCO-HD), in combination with chemotherapy, may be associated with better renal recovery. The aim of the present study is to evaluate the effectiveness of haemodiafiltration (HDF) in reducing free light chain levels using a less expensive heat sterilized high-flux polyphenylene HF dialyzer (HF-HDF). Methods In a single-centre prospective cohort study, 327 dialysis sessions were performed using a 2.2 m2 heat sterilized high-flux polyphenylene HF dialyzer (Phylther HF22SD), a small (1.1m2) or large (2.1 m2) high-cut-off (HCO) dialyzer (HCOS and HCOL) in a cohort of 16 patients presenting with dialysis-dependent acute cast nephropathy and elevated free light chains (10 kappa, 6 lambda). The outcomes of the study were the mean reduction ratio (RR) of kappa and lambda, the proportion of treatments with an RR of at least 0.65, albumin loss and the description of patient outcomes. Statistical analysis was performed using linear and logistic regression through generalized estimating equation analysis so as to take into account repeated observation within subjects and adjust for session duration. Results There were no significant differences in the estimated marginal mean of kappa RR, which were respectively 0.67, 0.69 and 0.70 with HCOL-HD, HCOS-HDF and HF-HDF (P = 0.950). The estimated marginal mean of the proportions of treatments with a kappa RR ≥0.65 were 68%, 63% and 71% with HCOL-HD, HCOS-HDF and HF-HDF, respectively (P = 0.913). The estimated marginal mean of lambda RR were higher with HCOL-HDF (0.78), compared to HCOL-HD and HF-HDF (0.62, and 0.61 respectively). The estimated marginal mean proportion of treatments with a lambda RR ≥0.65 were higher with HCOL-HDF (81%), compared to 57% in HF-HDF (P = 0.042). The median albumin loss were 7, 21 and 63 g/session with HF-HDF, HCOL-HD and HCOL-HDF respectively (P = 0

  20. Remediation of soils contaminated with chromium using citric and hydrochloric acids: the role of chromium fractionation in chromium leaching.

    PubMed

    Cheng, Shu-Fen; Huang, Chin-Yuan; Tu, Yao-Ting

    2011-01-01

    Acid washing is a common method for soil remediation, but is not always efficient for chromium-contaminated soil. Both soil particle size and the forms of chromium existing in the soil affect the efficiency of soil washing. Laboratory batch and column dissolution experiments were conducted to determine the efficiencies of citric and hydrochloric acids as agents to extract chromium from soils contaminated with chromium. The effects of soil particle size and chromium fractionation on Cr leaching were also investigated. About 90% of chromium in the studied soil existed either in residual form or bound to iron and manganese oxides, and Cr fraction distributions were similar for all soil particle sizes. Almost all exchangeable and carbonate-bound chromium was removed by washing once with 0.5 M HCl, whereas organic chromium was more effectively removed by washing with citric acid rather than with HCl solution of the same concentration. For chromium fractions that were either bound to Fe-Mn oxides or existed as residual forms, the efficiencies of acid washing were usually 20% or less, except for 0.5 M HCl solution, which had much higher efficiencies. Separation of the soil sample by particle size before the separate washing of the soil fractions had little improvement on the chromium removal.