The mechanism behind redox instability of anodes in high-temperature SOFCs

DEFF Research Database (Denmark)

Klemensø, Trine; Chung, Charissa; Larsen, Peter Halvor

2005-01-01

Bulk expansion of the anode upon oxidation is considered to be responsible for the lack of redox stability in high-temperature solid oxide fuel cells (SOFCs). The bulk expansion of nickel-yttria stabilized zirconia (YSZ) anode materials was measured by dilatometry as a function of sample geometry......, ceramic component, temperature, and temperature cycling. The strength of the ceramic network and the degree of Ni redistribution appeared to be key parameters of the redox behavior. A model of the redox mechanism in nickel-YSZ anodes was developed based on the dilatometry data and macro...

Excess free volume in metallic glasses measured by X-ray diffraction

International Nuclear Information System (INIS)

Yavari, Alain Reza; Moulec, Alain Le; Inoue, Akihisa; Nishiyama, Nobuyuki; Lupu, Nicoleta; Matsubara, Eiichiro; Botta, Walter Jose; Vaughan, Gavin; Di Michiel, Marco; Kvick, Ake

2005-01-01

In crystalline materials, lattice expansion as measured by diffraction methods differs from the expansion of the sample dimensions as measured by dilatometry, due to the contribution of thermal vacancies to the latter. We have found that in glassy materials and metallic glasses in particular, this is not the case for the contribution of free volume. These findings are the first direct experimental confirmation of simulation results indicating that atomic size holes are unstable in glasses such that free volume is dispersed randomly. This allows direct measurement of excess free volume in glasses using diffraction methods in place of dilatometry, which is difficult to use once the sample softens at the glass transition temperature T g and above. Quenched-in and deformation-induced free-volume ΔV f were measured by X-ray diffraction in transmission during heating using synchrotron light. The measured thermal expansion coefficients α th were the same as in dilatometry. The glass transition T g appeared as a break in the value of α th at T g . The 'change-of-slope method' was applied to the kinetics of relaxation to derive the activation energy for the free-volume annihilation process

Overlapping phase transformations on tempering of a low-alloy steel

International Nuclear Information System (INIS)

Valencia Morales, E; Galeano Alvarez, N.J; Vega Leiva, J; Castellanos L M; Villar C E; Antiquera Munoz J; Hernandez R J

2006-01-01

The kinetics of precipitation of the primary and independent carbides during tempering of a low-alloy steel are characterized by the application of the Kinetic Theory of the Overlapping Phase Transformations(KTOPT). It is based on the Avrami model and considers two simultaneous precipitation processes. The present set-up allows us to calculate the exponent of the Avrami equation for simultaneous reactions at different rates. Only the dilatometry curves on tempering are required. According to this new formulation, the treatment of the dilatometry records showed different mechanisms of nucleation and growth of the primary and independent carbides. These results are in agreement with the thin foil electron micrographs and hardness tests of the thermally treated samples (au)

Creep recovery of metallic glass Fe-Ni-B after longtime stress-annealing

NARCIS (Netherlands)

Jurikova, A; Csach, K; Miskuf, J; Ocelik, Vaclav

2004-01-01

The creep strain recovery of magnetic soft material - amorphous metallic glass Fe-Ni-B after a longtime stress-annealing at different temperatures below the crystallization temperature was described using differential scanning calorimetry and dilatometry. Several deformation energy accumulations

Bainite Formation in Medium-Carbon Low-Silicon Spring Steels Accounting for Chemical Segregation

NARCIS (Netherlands)

Goulas, C.; Mecozzi, M.G.; Sietsma, J.

2016-01-01

In this paper, the effect of chemical inhomogeneity on the isothermal bainite formation is investigated in medium-carbon low-silicon spring steel by dilatometry and microscopy. The analysis of the microstructure at different times during transformation shows that chemical segregation of

Characterization of nitrides in an AISI 1010 steel; Caracterizacion de nitruros en un acero AISI 1010

Energy Technology Data Exchange (ETDEWEB)

Naquid G, C. [Instituto Nacional de Investigaciones Nucleares, Gerencia de Ciencia de Materiales, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

1998-07-01

It was characterized the phase formation in the 1010 carbon steel nitrided in a plasma reactor nearby to eutectoid point. The microstructure and identification of these ones were evaluated by Optical microscopy (OM), Dilatometry and X-ray diffraction (XRD). (Author)

Characterization of nitrides in an AISI 1010 steel

International Nuclear Information System (INIS)

Naquid G, C.

1998-01-01

It was characterized the phase formation in the 1010 carbon steel nitrided in a plasma reactor nearby to eutectoid point. The microstructure and identification of these ones were evaluated by Optical microscopy (OM), Dilatometry and X-ray diffraction (XRD). (Author)

Competency Based Modular Experiments in Polymer Science and Technology.

Science.gov (United States)

Pearce, Eli M; And Others

1980-01-01

Describes a competency-based, modular laboratory course emphasizing the synthesis and characterization of polymers and directed toward senior undergraduate and/or first-year graduate students in science and engineering. One module, free-radical polymerization kinetics by dilatometry, is included as a sample. (CS)

Quantification of non-isothermal, multi-phase crystallization of isotactic polypropylene : the influence of shear and pressure

NARCIS (Netherlands)

Erp, van T.B.; Balzano, L.; Spoelstra, A.B.; Govaert, L.E.; Peters, G.W.M.

2012-01-01

Key issue in studying the crystallization process of semi-crystalline polymers, is the need for controlled (or known) boundary and initial conditions. Here dilatometry (PVT) is used to reveal the crystallization kinetics and the resulting morphology of isotactic polypropylene homopolymer as a

High-temperature Young’s moduli and dilatation behavior of silica refractories

Czech Academy of Sciences Publication Activity Database

Pabst, W.; Gregorová, E.; Kloužek, Jaroslav; Kloužková, A.; Zemenová, P.; Kohoutková, M.; Sedlářová, I.; Lang, K.; Kotouček, M.; Nevřivová, L.; Všianský, D.

2016-01-01

Roč. 36, č. 1 (2016), s. 209-220 ISSN 0955-2219 Institutional support: RVO:67985891 Keywords : silica refractories * Young’s modulus * elastic modulus * dilatation * dilatometry Subject RIV: JH - Ceramic s, Fire-Resistant Materials and Glass Impact factor: 3.411, year: 2016

In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

Directory of Open Access Journals (Sweden)

S. Hesamodin Talebi

2017-09-01

Full Text Available Phase transformations during non-isothermal tempering of bainitic or martensitic microstructures obtained after quenching of a medium-carbon low-alloy steel was studied. The microstructures correspond to different locations of an as-quenched large-sized forged ingot used as a die material in the automotive industry. High-resolution dilatometry experiments were conducted to simulate the heat treatment process, as well as to investigate different phenomena occurring during non-isothermal tempering. The microstructures were characterized using optical and scanning electron microscopy. Dilatometry analyses demonstrated that tempering behavior varied significantly from bainitic to martensitic microstructures. Retained austenite, which exists between bainitic ferrite sheaves, decomposes to lower bainite causing a remarkable volume increase. It was found that this decomposition finishes below 386 °C. By contrast, martensite tempering was accompanied with a volume decrease due to the decomposition of medium-carbon martensite to low carbon martensite and carbides.

Physical properties and microstructures of La_{1-{x}}Pr_{{x}}PO_4 monazite-ceramics

Science.gov (United States)

Thust, Anja; Hirsch, Antje; Haussühl, Eiken; Schrodt, Nadine; Loison, Lise; Schott, Petra; Peters, Lars; Roth, Georg; Winkler, Björn

2018-04-01

Synthetic La_{1-{x}}Pr_{{x}}PO_4 monazite-type powders and ceramics with 0 ≤ x ≤ 1 were analysed by scanning electron microscopy, high-temperature powder X-ray diffraction, dilatometry, and plane wave ultrasound spectroscopy. Ceramics were synthesised in a two-step sintering process at 1273 and 1573 K. Final densities were up to 99.3% of the theoretical densities. Each sample shows a homogeneous distribution of grain sizes, which increase with increasing sintering temperature. Grain sizes also depend on composition, with intermediate compositions yielding the largest grains. In-situ high-temperature powder X-ray diffraction shows that the volumetric thermal expansion coefficients of the monazite powders decrease with increasing Pr content. This behavior is not observed in dilatometry measurements of the bulk samples (ceramics) because their thermal expansion mainly depends on their density. Elastic properties show the same dependence on the density.

Characterization of structural relaxation in inorganic glasses using length dilatometry

Science.gov (United States)

Koontz, Erick

The processes that govern how a glass relaxes towards its thermodynamic quasi-equilibrium state are major factors in understanding glass behavior near the glass transition region, as characterized by the glass transition temperature (Tg). Intrinsic glass properties such as specific volume, enthalpy, entropy, density, etc. are used to map the behavior of the glass network below in and near the transition region. The question of whether a true thermodynamic second order phase transition takes place in the glass transition region is another pending question. Linking viscosity behavior to entropy, or viewing the glass configuration as an energy landscape are just a couple of the most prevalent methods used for attempting to understand the glass transition. The structural relaxation behavior of inorganic glasses is important for more than scientific reasons, many commercial glass processing operations including glass melting and certain forms of optical fabrication include significant time spent in the glass transition region. For this reason knowledge of structural relaxation processes can, at a minimum, provide information for annealing duration of melt-quenched glasses. The development of a predictive model for annealing time prescription has the potential to save glass manufacturers significant time and money as well as increasing volume throughput. In optical hot forming processes such as precision glass molding, molded optical components can significantly change in shape upon cooling through the glass transition. This change in shape is not scientifically predictable as of yet though manufacturers typically use empirical rules developed in house. The classification of glass behavior in the glass transition region would allow molds to be accurately designed and save money for the producers. The work discussed in this dissertation is comprised of the development of a dilatometric measurement and characterization method of structural relaxation. The measurement and characterization technique is comprised of three main components: experimental measurements, fitting of configurational length change, and description of glass behavior by analysis of fitting parameters. N-BK7 optical glass from Schott was used as the proof of concept glass but the main scientific interest was in three chalcogenide glasses: As40Se 60, As20Se80, and Ge17.9As19.7 Se62.4. The dilatometric experiments were carried out using a thermomechanical analyzer (TMA) on glass sample that were synthesized by the author, in all cases except N-BK7. Isothermal structural relaxation measurements were done on (12 mm tall x 3 mm x 3 mm) beams placed vertically in the TMA. The samples were equilibrated at a starting temperature (T 0) until structural equilibrium was reached then a temperature down step was initiated to the final temperature (T 1) and held isothermally until relaxation concluded. The configurational aspect of length relaxation, and therefore volume relaxation was extracted and fit with a Prony series. The Prony series parameters indicated a number of relaxation events occurring within the glass on timescales typically an order of magnitude apart in time. The data analysis showed as many as 4 discrete relaxation times at lower temperatures. The number of discrete relaxation decreased as the temperature increased until just one single relaxation was left in the temperature range just at or above Tg. In the case of N-BK7 these trends were utilized to construct a simple model that could be applied to glass manufacturing in the areas of annealing or PGM. A future development of a rather simple finite element model (FEM) would easily be able to use this model to predict the exponential-like, temperature and time dependent relaxation behaviors of the glass. The predictive model was not extended to the chalcogenide glass studied here, but could easily be applied to them in the future. The relaxation time trends versus temperature showed a definite region of transition between a low temperature state with many relaxations to a high temperature state with only a single relaxation. Evidence was found for the existence of a definitive transition of some kind in the range of Tg possibly relating the idea of a percolation temperature (T*) as defined by Carmi. The results of the measurements showed substantial support for both the Adam-Gibbs interpretation of decreasing entropy towards the Kauzmann temperature, while also displaying trends compatible with energy landscape theory and the idea of broken ergodicity of glass configuration below Tg. In addition effective relaxation energies were calculated and the energy needed for relaxation showed a definite upward trend with decreasing temperature also supporting the idea of reduced entropy and configurational freedom at lower temperatures. The effective relaxation energies are not purely thermodynamic in nature because they also characterize the effects of viscosity and the kinetics of the material that was relaxing. (Abstract shortened by UMI.).

Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in ?-Ti alloys

NARCIS (Netherlands)

Van Bohemen, S.M.C.; Sietsma, J.; Van der Zwaag, S.

2006-01-01

The formation mechanisms of two hcp ? phase morphologies in Ti-4.5Fe-6.8Mo-1.5Al have been investigated by optical microscopy (OM), atomic force microscopy (AFM), electron probe microanalysis (EPMA) and dilatometry. At relatively high temperatures primary ? forms predominantly on prior bcc ? grain

Method for analyzing passive silicon carbide thermometry with a continuous dilatometer to determine irradiation temperature

Science.gov (United States)

Campbell, Anne A.; Porter, Wallace D.; Katoh, Yutai; Snead, Lance L.

2016-03-01

Silicon carbide is used as a passive post-irradiation temperature monitor because the irradiation defects will anneal out above the irradiation temperature. The irradiation temperature is determined by measuring a property change after isochronal annealing, i.e., lattice spacing, dimensions, electrical resistivity, thermal diffusivity, or bulk density. However, such methods are time-consuming since the steps involved must be performed in a serial manner. This work presents the use of thermal expansion from continuous dilatometry to calculate the SiC irradiation temperature, which is an automated process requiring minimal setup time. Analysis software was written that performs the calculations to obtain the irradiation temperature and removes possible user-introduced error while standardizing the analysis. This method has been compared to an electrical resistivity and isochronal annealing investigation, and the results revealed agreement of the calculated temperatures. These results show that dilatometry is a reliable and less time-intensive process for determining irradiation temperature from passive SiC thermometry.

The effects of non-isothermal deformation on martensitic transformation in 22MnB5 steel

International Nuclear Information System (INIS)

Naderi, M.; Saeed-Akbari, A.; Bleck, W.

2008-01-01

In the present paper, the effects of process parameters on phase transformations during non-isothermal deformations are described and discussed. Non-isothermal high temperature compressive deformations were conducted on 22MnB5 boron steel by using deformation dilatometry. Cylindrical samples were uniaxially deformed at different strain rates ranging from 0.05 to 1.0 s -1 to a maximum compressive strain of 50%. Qualitative and quantitative investigations were carried out using surface hardness mapping data as well as dilatation curves. It was observed that a higher initial deformation temperatures resulted in a higher martensite fraction of the microstructure, while a variation in the martensite start temperature was negligible. Another conclusion was that by applying larger amounts of strain as well as higher force levels, not only the martensite start temperature, but also the amount of martensite was reduced. Moreover, it was concluded that using surface hardness mapping technique and dilatometry experiments were very reliable methods to quantify and qualify the coexisting phases

The effects of non-isothermal deformation on martensitic transformation in 22MnB5 steel

Energy Technology Data Exchange (ETDEWEB)

Naderi, M. [Department of Materials Science and Engineering, Faculty of Engineering, Arak University, Shariati Street, Arak (Iran, Islamic Republic of)], E-mail: malek.naderi@iehk.rwth-aachen.de; Saeed-Akbari, A.; Bleck, W. [Department of Ferrous Metallurgy, RWTH Aachen University, Aachen (Germany)

2008-07-25

In the present paper, the effects of process parameters on phase transformations during non-isothermal deformations are described and discussed. Non-isothermal high temperature compressive deformations were conducted on 22MnB5 boron steel by using deformation dilatometry. Cylindrical samples were uniaxially deformed at different strain rates ranging from 0.05 to 1.0 s{sup -1} to a maximum compressive strain of 50%. Qualitative and quantitative investigations were carried out using surface hardness mapping data as well as dilatation curves. It was observed that a higher initial deformation temperatures resulted in a higher martensite fraction of the microstructure, while a variation in the martensite start temperature was negligible. Another conclusion was that by applying larger amounts of strain as well as higher force levels, not only the martensite start temperature, but also the amount of martensite was reduced. Moreover, it was concluded that using surface hardness mapping technique and dilatometry experiments were very reliable methods to quantify and qualify the coexisting phases.

Microstructure Charaterization of a Hardened and Tempered Tool Steel: from Macro to Nano Scale

DEFF Research Database (Denmark)

Højerslev, Christian; Somers, Marcel A. J.; Carstensen, Jesper V.

2002-01-01

The microstructure of a conventionally heat treated PM AISI M3:2 tool steel, was characterised by a combination of light optical and electron microscopy, covering the range from micro to nano scale. Dilatometry and X-ray diffractometry were used for an overall macro characterisation of the phases...

Study of dimensional changes during redox cycling of oxygen carrier materials for chemical looping combustion

NARCIS (Netherlands)

Fossdal, A.; Darell, O.; Lambert, A.; Schols, E.; Comte, E.; Leenman, R.N.; Blom, R.

2015-01-01

Dimensional and phase changes of four candidate oxygen carrier materials for chemical looping combustion are investigated by dilatometry and high-temperature X-ray diffraction during four redox cycles. NiO/Ni2AlO4 does not exhibit significant dimensional changes during cycling, and it is shown that

Mechanical, Dielectric, and Spectroscopic Characteristics of "Micro/Nanocellulose + Oxide" Composites

Science.gov (United States)

Nedielko, Maksym; Hamamda, Smail; Alekseev, Olexander; Chornii, Vitalii; Dashevskii, Mykola; Lazarenko, Maksym; Kovalov, Kostiantyn; Nedilko, Sergii G.; Tkachov, Sergii; Revo, Sergiy; Scherbatskyi, Vasyl

2017-02-01

The set of composite materials that consist of micro/nanocellulose and complex K2Eu(MoO4)(PO4) luminescent oxide particles was prepared. The composites were studied by means of scanning electron microscopy, XRD analysis, dilatometry, differential scanning calorimetry and thermogravimetric analysis, and dielectric and luminescence spectroscopy.

Characterization of the interaction between glazes and ceramic bodies

Czech Academy of Sciences Publication Activity Database

Kavanová, M.; Kloužková, A.; Kloužek, Jaroslav

2017-01-01

Roč. 61, č. 3 (2017), s. 267-275 ISSN 0862-5468 Institutional support: RVO:67985891 Keywords : glazes * ceramic s * thermal analysis * coefficients of the thermal expansion * dilatometry Subject RIV: JH - Ceramic s, Fire-Resistant Materials and Glass OBOR OECD: Ceramic s Impact factor: 0.439, year: 2016

Kinetics of the subtransition in dipalmitoylphosphatidylcholine

International Nuclear Information System (INIS)

Tristram-Nagle, S.; Wiener, M.C.; Yang, C.P.; Nagle, J.F.

1987-01-01

The kinetics of the interconversions of the subgel and gel phases in dipalmitoylphosphatidylcholine have been studied by using differential dilatometry, differential scanning calorimetry (DSC), and neutral buoyancy centrifugation as a function of incubation temperature and deuteriation of the solvent. As seen by others, DSC scans show two peaks in the subgel transition region for incubation temperatures below 1 0 C. After incubation at 0.1 0 C, the DSC peak that occurs at the lower scanning temperature appears with an incubation half-time of 0.5 day and eventually converts into a peak at higher scanning temperature with an incubation half-time of 18 days. By varying the scanning rate, the authors show that these two peaks merge into one at slow scanning rates with a common equilibrium transition temperature of 13.8 0 C, in agreement with equilibrium calorimetry and dilatometry. For incubation temperatures above 4.6 0 C, only one peak appears in both scanning dilatometry and calorimetry. While the initial rate of subgel conversion is smaller at the higher incubation temperatures, after 300 h a higher percentage of the sample has converted to subgel than at the lower incubation temperatures. They suggest that higher incubation temperatures (near 5 0 C) are preferable for forming the stable subgel phase, and they present a colliding domain picture that indicates why this may be so. The results in D 2 O and the similarity of the kinetics of volume decrease with the kinetics of wide-angle diffraction lines also support the suggestion that the partial loss of interlamellar water plays a kinetic role in subgel formation

Kinetics of the subtransition in dipalmitoylphosphatidylcholine.

Science.gov (United States)

Tristram-Nagle, S; Wiener, M C; Yang, C P; Nagle, J F

1987-07-14

The kinetics of the interconversions of the subgel and gel phases in dipalmitoylphosphatidylcholine have been studied by using differential dilatometry, differential scanning calorimetry (DSC), and neutral buoyancy centrifugation as a function of incubation temperature and deuteriation of the solvent. As seen by others, DSC scans show two peaks in the subgel transition region for incubation temperatures below 1 degree C. After incubation at 0.1 degree C, the DSC peak that occurs at the lower scanning temperature appears with an incubation half-time of 0.5 day and eventually converts into a peak at higher scanning temperature with an incubation half-time of 18 days. By varying the scanning rate, we show that these two peaks merge into one at slow scanning rates with a common equilibrium transition temperature of 13.8 degrees C, in agreement with equilibrium calorimetry and dilatometry (delta V = 0.017 +/- 0.001 mL/g). For incubation temperatures above 4.6 degrees C, only one peak appears in both scanning dilatometry and calorimetry. While the initial rate of subgel conversion is smaller at the higher incubation temperatures, after 300 h a higher percentage of the sample has converted to subgel than at the lower incubation temperatures. We suggest that higher incubation temperatures (near 5 degrees C) are preferable for forming the stable subgel phase, and we present a colliding domain picture that indicates why this may be so. Our results in D2O and the similarity of the kinetics of volume decrease with the kinetics of wide-angle diffraction lines also support the suggestion that the partial loss of interlamellar water plays a kinetic role in subgel formation.

Residual stress in a M3:2 PM high speed steel; effect of mechanical loading

DEFF Research Database (Denmark)

Højerslev, Christian; Odén, Magnus; Carstensen, Jesper V.

2001-01-01

X-ray lattice strains were investigated in an AISI M3:2 PM high-speed steel in the as heat treated condition and after exposure to alternating mechanical load. The volume changes during heat treatment were monitored with dilatometry. Hardened and tempered AISI M3:2 steel consists of tempered lath...

Sol-Gel Processing Science Using a Sol-Gel Optics Research Facility (SGORF)

Science.gov (United States)

1989-09-10

Malaysia , Hong-Kong) where labor rates are perhaps one-tenth those of the U.S.. Figure 1 presents the trends of imports and exports of all optical... ACerS Annual Meeting, Washington, DC, May 1972. 2. W. A. Plummer, "Differential Dilatometry--A Powerful Tool," Corning Gla 33 Works, Corning, NY 14830

Electrochemical characterization of single-walled carbon nanotubes for electrochemical double layer capacitors using non-aqueous electrolyte

International Nuclear Information System (INIS)

Ruch, P.W.; Koetz, R.; Wokaun, A.

2009-01-01

Single-walled carbon nanotubes (SWCNTs) were investigated by cyclic voltammetry and electrochemical impedance spectroscopy in a non-aqueous electrolyte, 1 M Et 4 NBF 4 in acetonitrile, suitable for supercapacitors. Further, in situ dilatometry and in situ conductance measurements were performed on single electrodes and the results compared to an activated carbon, YP17. Both materials show capacitive behavior characteristic of high surface area electrodes for supercapacitors, with the maximum full cell gravimetric capacitance being 34 F/g for YP17 and 20 F/g for SWCNTs at 2.5 V with respect to the total active electrode mass. The electronic resistance of SWCNTs and activated carbon decreases significantly during charging, showing similarities of the two materials during electrochemical doping. The SWCNT electrode expands irreversibly during the first electrochemical potential sweep as verified by in situ dilatometry, indicative of at least partial debundling of the SWCNTs. A reversible periodic swelling and shrinking during cycling is observed for both materials, with the magnitude of expansion depending on the type of ions forming the double layer.

Viability of Pushrod Dilatometry Techniques for High Temperature In-Pile Measurements

Energy Technology Data Exchange (ETDEWEB)

J. E. Daw; J. L. Rempe; D. L. Knudson; K. G. Condie; J. C. Crepeau

2008-03-01

To evaluate the performance of new fuel, cladding, and structural materials for use in advanced and existing nuclear reactors, robust instrumentation is needed. Changes in material deformation are typically evaluated out-of-pile, where properties of materials are measured after samples were irradiated for a specified length of time. To address this problem, a series of tests were performed to examine the viability of using pushrod dilatometer techniques for in-pile instrumentation to measure deformation. The tests were performed in three phases. First, familiarity was gained in the use and accuracy of this system by testing samples with well defined thermal elongation characteristics. Second, high temperature data for steels, specifically SA533 Grade B, Class 1 (SA533B1) Low Alloy Steel and Stainless Steel 304 (SS304), found in Light Water Reactor (LWR) vessels, were aquired. Finally, data were obtained from a short pushrod in a horizontal geometry to data obtained from a longer pushrod in a vertical geometry, the configuration likely to be used for in-situ measurements. Results of testing show that previously accepted data for the structural steels tested, SA533B1 and SS304, are inaccurate at high temperatures (above 500 oC) due to extrpolation of high temperature data. This is especially true for SA533B1, as previous data do not account for the phase transformation of the material between 730 oC and 830 oC. Also, comparison of results for horizontal and vertical configurations show a maximum percent difference of 2.02% for high temperature data.

Characterization of MgMnxFe2-xO4 as a possible cathode material for electrochemical reduction of NOx

DEFF Research Database (Denmark)

Bræstrup, Frantz Radzik; Kammer Hansen, Kent

2009-01-01

Spinel-type oxides of MgMn x Fe2−x O4, x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, were synthesized as a solid state reaction and characterized with dilatometry and resistivity measurements up to 1000 °C. Results showed a general decrease of the linear expansion and an increase in conductivity as a function...

Density and atomic volume in liquid Al-Fe and Al-Ni binary alloys

Energy Technology Data Exchange (ETDEWEB)

Plevachuk, Yu. [Ivan Franko National Univ., Lviv (Ukraine). Dept. of Metal Physics; Egry, I.; Brillo, J.; Holland-Moritz, D. [Deutsches Zentrum fuer Luft- und Raumfahrt, Koeln (Germany). Inst. fuer Raumsimulation; Kaban, I. [Chemnitz Univ. of Technolgy (Germany). Inst. of Physics

2007-02-15

The density of liquid Al-Fe and Al-Ni binary alloys have been determined over a wide temperature range by a noncontact technique combining electromagnetic levitation and optical dilatometry. The temperature and composition dependences of the density are analysed. A negative excess volume correlates with the negative enthalpy of mixing, compound forming ability and chemical short-range ordering in liquid Al-Fe and Al-Ni alloys. (orig.)

Stability of solid oxide fuel cell materials

Energy Technology Data Exchange (ETDEWEB)

Armstrong, T.R.; Bates, J.L.; Chick, L.A. [Pacific Northwest Lab., Richland, WA (United States)

1996-04-01

Interconnection materials in a solid oxide fuel cell are exposed to both highly oxidizing conditions at the cathode and to highly reducing conditions at the anode. The thermal expansion characteristics of substituted lanthanum and yttrium chromite interconnect materials were evaluated by dilatometry as a function of oxygen partial pressures from 1 atm to 10{sup -18} atm, controlled using a carbon dioxide/hydrogen buffer.

Kaolin from Acoculco (Puebla, Mexico) as a raw material: mineralogical and thermal characterization

OpenAIRE

Garcia Vallès, Maite; Pi, T.; Alfonso, P.; Canet, C.; Martínez Manent, Salvador; Jiménez-Franco, A.; Tarragó Aymerich, Mariona; Hernández-Cruz, B.

2015-01-01

The present study determined the mineralogy and thermal properties of kaolin from Acoculco (Puebla), at the eastern Trans-Mexican Volcanic Belt and compared it with the nearby deposits of Agua Blanca (Hidalgo) and Huayacocotla (Veracruz). The mineralogy of the kaolins was determined by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Thermal behaviour was studied by differential thermal analysis, dilatometry and hot-stage microscopy. The Acoculco deposit is composed ...

Study of allotropic transformations in plutonium; Etude des transformations allotropiques du plutonium

Energy Technology Data Exchange (ETDEWEB)

Spriet, B [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1966-06-01

The allotropic transformations in plutonium have been studied by different methods: metallography, dilatometry, thermal analysis, resistivity measurements, examination with a hot stage microscope. In order to study the importance of the purity, purification process such as zone-melting or electro-diffusion have been developed. The characteristics of the {alpha} {r_reversible} {beta} transformation can be explained in terms of the influence of internal stresses on the transition temperature and on the transformation kinetics. Some particular characteristics of {delta} {yields} {gamma}, {gamma} {yields} {alpha}, {delta} {r_reversible} {epsilon}, {beta} {r_reversible} {gamma} and {delta} {yields} {alpha} transformations are also given. (author) [French] Les transformations, allotropiques du plutonium ont ete etudiees a l'aide de differentes methodes: metallographie, dilatometrie, analyse thermique, mesure de resistivite, examen au microscope a platine chauffante. Pour preciser l'influence de la purete, des procedes de purification comme la fusion de zone ou l'electrodiffusion ont ete mis au point. Les caracteres de la transformation {alpha} {r_reversible} {beta} s'expliquent par le role des contraintes internes sur la temperature de transition et la cinetique de transformation. Quelques particularites des transformations {delta} {yields} {gamma}, {gamma} {yields} {alpha}, {delta} {r_reversible} {epsilon}, {beta} {r_reversible} {gamma} et {delta} {yields} {alpha} sont egalement presentees. (auteur)

Initial sintering stage kinetics of CeO2 studied by stepwise isothermal dilatometry

International Nuclear Information System (INIS)

El Sayed Ali, M.; Toft Soerensen, O.

1985-02-01

The kinetics of the initial sintering stage of CeO 2 is studied by a new dilatometric technique in which the heating of the sample is controlled by its shrinkage rate. By this technique the shrinkage characteristically takes place in 'isothermal steps' which allows both the mechanism and its activation energy to be determined in a single experiment. The basic equations necessary to evaluate the shrinkage data are described, and using these equations on the curves recorded for CeO 2 it it shown that the controlling mechanism for the initial sintering stage for this oxides is grain-boundary diffusion of Ce 4+ -ions with an activation energy of 119.4 kcal/mole (5.2 eV). The corresponding diffusion coefficient is estimated to vary between 8.5 x 10 -17 - 3.1 x 10 -15 cm 2 /sec (1005 - 1099sup(o)C). (author)

Densification and crystalization kinetics of mullite diphasic gels from non_isothermal dilatometry experiments

Directory of Open Access Journals (Sweden)

Orgaz, Felipe

2008-12-01

Full Text Available Mullite (3 AI₂O₃_2 SiO₂ was processed by mixing silica and alumina colloids at pH below 3 in a high shear blender. The gels were sieved to ‹ 125 microns and cold isostatically pressed to form rods. The various processes involved during the sintering process such as condensation-polymerization and the competition between mullite crystallization and densification were analysed from constant heating rate equations and rate controlled sintering dilatometer experiments. Changes in the slopes permitted the identification of such processes and the activation energy for mullitization was calculated. Fast firing (20-30 K/min in the critical mullitization temperature range of 1230-1505^ºC and low heating rates (2-3 K/min in the viscous flow densification intervals of below 1230^ºC and higher than 1505 gives rise to near full density and fine grain microstructures of sintered mullite. Fast firing and high (0.5 to 1 % /min densification rate controlled processes seem to be the most suitable approaches to high density gel processed mullite. Amorphous silica is the rate controlling mechanism for the viscous flow densification process before alumina is solved and nucleation and crystallization of mullite appears. Deviations from the linear Frenkel model for viscous flow are also observed.

Mullita de composición (3Al₂O₃ -2 SiO₂ ha sido preparada mezclando coloides de sílice y alúmina en un mezclador de alta velocidad a pH inferior a 3. Los geles formados eran secados, tamizados por debajo de 125 micras y prensados isostáticamrente para formar varillas de unos 6 mm de diámetro. Los diferentes procesos que ocurren durante el proceso de sinterización, tales como polimerización- condensación y la competición entre cristalización y densificación, han sido analizados utilizando las ecuaciones de ecuaciones de velocidad de calentamiento constantte y experimentos de dilatometría utilizando un software que permite realizar ensayos a velocidad de contracción constante. Cambios en las pendientes han permitido la identificación de tales procesos y el calculo de la energia de activación para la formación de mullita. Calentamiento rápido (20-30 K/min en el rango critico de formación de mullita entre 1230-1505^ºC y bajas velocidades de calentamiento (2-3 K/min en las zonas de densificación por flujo viscoso daban lugar a mullitas sinterizadas con densidad cercana a la teórica y fina micro-estructura. Altas velocidades de densificación (o,5% a 1%/min son las mas adecuadas para sinterizar mullita de alta densidad. Flujo viscoso de la sílice amorfa es el mecanismo que controla la velocidad del proceso antes de disolver la alúmina y formar mullita por un proceso de nucleación y crecimiento. Se observan también desviaciones del modelo lineal de Frenkel para el flujo viscoso.

The Effects of Cr and Al Addition on Transformation and Properties in Low‐Carbon Bainitic Steels

OpenAIRE

Junyu Tian; Guang Xu; Mingxing Zhou; Haijiang Hu; Xiangliang Wan

2017-01-01

Three low‐carbon bainitic steels were designed to investigate the effects of Cr and Al addition on bainitic transformation, microstructures, and properties by metallographic method and dilatometry. The results show that compared with the base steel without Cr and Al addition, only Cr addition is effective for improving the strength of low‐carbon bainitic steel by increasing the amount of bainite. However, compared with the base steel, combined addition of Cr and Al has no significant effect o...

In Situ Techniques for the Investigation of the Kinetics of Austenitization of Supermartensitic Stainless Steel

DEFF Research Database (Denmark)

Nießen, Frank; Villa, Matteo; Apel, Daniel

2016-01-01

The austenitization and inter-critical annealing of X4CrNiMo16-5-1 (1.4418) supermartensitic stainless steel were investigated in-situ with synchrotron X-ray diffraction (XRD), dilatometry and differential scanning calorimetry (DSC) under isochronal heating conditions. Austenitization occurred...... of surface martensite formation on the XRD measurement. The applicable temperature range for DSC as well as the close proximity of the Ac1- and the Curietemperature limited the usage of the technique in the present case....

Studies of plutonium-iron and uranium-plutonium-iron alloys; Etudes d'alliages plutonium-fer et d'alliages uranium-plutonium-fer

Energy Technology Data Exchange (ETDEWEB)

Avivi, Ehud [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1964-01-15

We study the plutonium-iron system, by means of dilatometry, X rays and metallography, especially in the domain between PuFe{sub 2} and Fe. We determine the solubilities of Fe in PuFe{sub 2} and of Pu in Fe. We show the presence of an hexagonal PuFe{sub 2} phase and we propose a modification in the Pu-Fe phase diagram. Some low iron concentration U-Pu-Fe alloys have also been investigated. We characterise the different phases. We confirm that adding some iron lowers the quantity of the zeta U-Pu phase. We emphasize some characteristics of the alloys having the global concentration (U, Pu){sub 6} Fe. (authors) [French] On etudie par dilatometrie, rayons X et micrographie le systeme plutonium-fer, principalement dans la region comprise entre PuFe{sub 2} et Fe, On determine les solubilites du fer dans PuFe{sub 2}, et de Pu dans Fe. On met en evidence une phase PuFe{sub 2} hexagonale et on propose une modification du diagramme d'equilibre Pu-Fe. Certains alliages U-Pu-Fe a faibles concentrations en fer sont egalement etudies. On caracterise les phases en presence. On confirme que l'addition de fer diminue rapidement la quantite de phase U-Pu zeta. Enfin on revele certaines caracteristiques des alliages de composition globale (U, Pu){sub 6} Fe. (auteurs)

Thermal expansion characteristics of Fe–9Cr–0.12C–0.56Mn–0.24V–1.38W–0.06Ta (wt.%) reduced activation ferritic–martensitic steel

Energy Technology Data Exchange (ETDEWEB)

Subramanian, Raju, E-mail: sraju@igcar.gov.in [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603102 (India); Tripathy, Haraprasanna; Rai, Arun Kumar; Hajra, Raj Narayan; Saibaba, Saroja; Jayakumar, Tammana [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam 603102 (India); Rajendra Kumar, Ellappan [TBM Division, Institute for Plasma Research (IPR), Gandhi Nagar (India)

2015-04-15

Highlights: • Lattice & bulk thermal expansion of RAFM steel characterized by HTXRD and dilatometry. • Mean thermal expansion of α-ferrite is 1.48 × 10{sup −5} K{sup −1}; that of γ-austenite, 2.4 × 10{sup −5} K{sup −1}. • Magnetism makes a small negative contribution to overall thermal expansion. - Abstract: The lattice and bulk thermal expansion behavior of an Indian version of reduced activation ferritic–martensitic (INRAFM) steel has been quantified using high temperature X-ray diffraction and dilatometry. The lattice parameter of tempered α-ferrite phase exhibited a smooth quadratic increase with temperature, while that of γ-austenite remained fairly linear up to 1273 K. The results suggest that α-ferrite + Carbides → γ-austenite transformation occurs upon continuous heating in the temperature range, 1146 ⩽ T ⩽ 1173 K. Further, this transformation is found to be accompanied by a reduction in average atomic volume. The mean linear thermal expansion coefficients of tempered α-ferrite and γ-austenite phases are estimated to be about 1.48 × 10{sup −5} and 2.4 × 10{sup −5} K{sup −1} respectively. The magnetic contribution to relative thermal dilatation (Δl/l{sub 298}){sub mag} is found to be small and negative, as compared to phonon contribution.

Control of the γ-alumina to α-alumina phase transformation for an optimized alumina densification

Energy Technology Data Exchange (ETDEWEB)

Lamouri, S.; Hamidouche, M.; Bouaouadja, N.; Belhouchet, H.; Garnier, V.; Fantozzi, G.; Trelkat, J.F.

2017-07-01

In this work, we studied the aptitude to sintering green bodies using γ-Al2O3 transition alumina as raw powder. We focused on the influence of the heating rate on densification and microstructural evolution. Phase transformations from transition alumina γ→δ→θ→α-Al2O3 were studied by in situ X-rays diffraction from the ambient to 1200°C. XRD patterns revealed coexistence of various phase transformations during the heating cycle. DTA and dilatometry results showed that low heating rate leads to a significant reduction of the temperature of the α-Al2O3 alumina formation. Around 1190, 1217 and 1240°C were found when using 5, 10 and 20°C/min of heating rate, respectively. The activation energy for θ-Al2O3→α-Al2O3 transformation calculated by Kissinger and JMA equations using dilatometry method were 464.29 and 488.79kJ/mol, respectively and by DTA method were 450.72 and 475.49kJ/mol, respectively. In addition, the sintering of the green bodies with low heating rate promotes the rearrangement of the grains during θ-Al2O3→α-Al2O3 transformation, enhancing the relative density to 95% and preventing the development of a vermicular structure. (Author)

Low-Temperature Bainite: A Thermal Stability Study

Science.gov (United States)

Santajuana, Miguel A.; Rementeria, Rosalia; Kuntz, Matthias; Jimenez, Jose A.; Caballero, Francisca G.; Garcia-Mateo, Carlos

2018-06-01

The thermal stability of nanobainitic structures obtained by heat treating two different high-carbon high-silicon steels at temperatures between 200 °C and 600 °C has been investigated by means of three complementary techniques, i.e., field emission gun-scanning electron microscopy, X-ray diffraction, and high-resolution dilatometry. Three main stages have been established, each of them characterized by a distinctive microstructure. Furthermore, the nanocrystalline structure generated by the bainite reaction confers the steel with an extraordinary tempering resistance.

Ti₃SiC₂ Synthesis by Powder Metallurgical Methods

OpenAIRE

Kero, Ida; Antti, Marta-Lena; Odén, Magnus

2007-01-01

Titanium silicon carbide MAX phase was synthesised by a powder metallurgical method from ball milled TiC/Si powders of two different compositions, with TiC/Si ratios of 3:2 and 3:2.2 respectively. The cold pressed samples were analysed by dilatometry under flowing argon or sintered under vacuum for different times. The sintered samples were evaluated using x-ray diffraction (XRD). This study showed that titanium carbide was always present as a secondary phase and silicon carbide accompanied t...

Shape distortion and thermo-mechanical properties of dense SOFC components from green tape to sintered body

DEFF Research Database (Denmark)

Teocoli, Francesca; Esposito, Vincenzo; Ni, De Wei

stresses, which develop a camber in the final sintered body. To analyze the phenomena, shrinkage of SOFC components single layers and camber development of bi-layers were measured in-situ by optical dilatometry. In addition, a thoughtful investigation of the viscoelastic properties of individual layers......Sintering of ceramic materials is a critical process, especially when the components are shaped as multilayer. Microstructural changes and stresses take place in ceramics as single layer from the green stage to the densification stage, leading to shape distortion, delamination and cracks...

Bainitic transformation behavior studied by simultaneous neutron diffraction and dilatometric measurement

International Nuclear Information System (INIS)

Koo, Minseo; Xu, Pingguang; Tomota, Yo; Suzuki, Hiroshi

2009-01-01

Bainitic transformation behavior has firstly been observed using in situ neutron diffraction with an angular dispersive method for a hard bainite steel. The dilatometric measurement was carried out simultaneously with the neutron experiment where changes in (1 1 1) austenite and (1 1 0) ferrite diffraction profiles were monitored during heating, cooling and holding at a transformation temperature. The neutron experiments results agree with dilatometry results. They appear to have found that the austenite peak broadening occurs after the onset of bainitic transformation but not before.

PHOTOPOLYMERIZATION OF MMA INITIATED BY CYANINE DYE AND HEXAARYLBIIMIDAZOLE

Institute of Scientific and Technical Information of China (English)

无

1998-01-01

The photoinitiating system composed of 1-ethyl-3'-methyl thiacyanine bromide (C-I), 2-chlorohexaarylbiimidazole (o-Cl-HABI) and 3-mercapto-4-methyl-4H-1, 2, 4-triazole (MTA), which act as sensitizer, initiator and hydrogen-donor respectively, can be used to initiate the polymerization of methyl methacrylate (MMA). The kinetic study was carried out in trichloromathane solution at 30℃ by using dilatometry. The relation between the polymerization rate and the concentrations of C-I, o-Cl-HABI, MTA and MMA was studied.

Synthesis, growth, and studies (crystal chemistry, magnetic chemistry) of actinide-based intermetallic compounds and alloys with a 1.1.1 stoichiometry

International Nuclear Information System (INIS)

Kergadallan, Yann

1993-01-01

The first part of this research thesis reports the study of the synthesis and reactivity of intermetallic compounds with a 1.1.1 stoichiometry. It presents the thermal properties of 1.1.1 compounds: general presentation of physical transitions, and of solid solutions and formation heat, application to actinides (reactivity analysis from phase diagrams, techniques of crystal synthesis and crystal growth. It describes experimental techniques: synthesis, determination of fusion temperature by dilatometry, methods used for crystal growth, characterisation techniques (metallography, X ray diffraction on powders, dilatometry). It discusses the obtained results in terms of characterisation of synthesised samples, of crystal growth, and of measurements of fusion temperature. The second part addresses crystal chemistry studies: structure of compounds with a 1.1.1 stoichiometry (Laves structures, Zr, Ti and Pu compounds), techniques of analysis by X-ray diffraction (on powders and on single crystals), result interpretation (UNiX compounds, AnTAl compounds with T being a metal from group VIII, AnTGa compounds, AnNiGe compounds, distance comparison, structure modifications under pressure). The third part concerns physical issues. The author addresses the following topics: physical properties of intermetallic 1.1.1 compounds (magnetism of yttrium phases, behaviour of uranium-based Laves phases, analysis of pseudo-binary diagrams, physical characteristics of uranium-based 1.1.1 compounds, predictions of physical measurements), analysis techniques (Moessbauer spectroscopy, SQUID for Superconducting Quantum Interference Device), and result interpretation

Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

DEFF Research Database (Denmark)

Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

2008-01-01

form of the dispersion model. The development of hydration varied between the investigated cements; based on the measured data the degree of hydration after 24 h hydration at 20 C varied between 40 and 50%. This should be taken into account when comparing properties of concrete made from the different......Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...

Thermal expansion: Metallic elements and alloys. [Handbook

Science.gov (United States)

Touloukian, Y. S.; Kirby, R. K.; Taylor, R. E.; Desai, P. D.

1975-01-01

The introductory sections of the work are devoted to the theory of thermal expansion of solids and to methods for the measurement of the linear thermal expansion of solids (X-ray methods, high speed methods, interferometry, push-rod dilatometry, etc.). The bulk of the work is devoted to numerical data on the thermal linear expansion of all the metallic elements, a large number of intermetallics, and a large number of binary alloy systems and multiple alloy systems. A comprehensive bibliography is provided along with an index to the materials examined.

Kryogenbehandling: vejen til forståelse

DEFF Research Database (Denmark)

Stojko, Allan; Frandsen, Rasmus Berg; Somers, Marcel A.J.

2003-01-01

De mekaniske egenskaber for visse ståltyper kan påvirkes ved kryogenbehandling, dvs. en nedkøling til -196C efter austenitisering og før anløbning. Kuglelejestål, 100Cr6 (AISI E 52100), er blevet undersøgt med dilatometri, røntgendiffraktion (XRD) og transmissions elektron mikroskopi (TEM...... anløbningen var ca. 20 % mindre i det kryogenbehandlede 100Cr6 end i det konventionelt behandlede materiale. Spændingsmålinger med XRD antyder en mere homogen spændingsfordeling i kryogenbehandlet 100Cr6....

Linear thermal expansion coefficient of cast Fe-Ni invar and Fe-Ni-Co superinvar alloys

International Nuclear Information System (INIS)

Ogorodnikova, O.M.; Chermenskaya, E.V.; Rabinovich, S.V.; Grachev, S.V.

1999-01-01

Cast invar alloys Fe-Ni (28-35 wt. % Ni) are investigated using metallography, dilatometry and X-ray methods as soon as the crystallization is completed and again after low-temperature treatment resulting in martensitic transformation in low nickel alloys. Nickel distribution in a cast superinvar Fe-32% Ni-4% Co is studied by means of X-ray spectrum microanalysis. The results obtained permit the correction of model concepts about cast invars and the estimate of a coefficient of linear expansion depending on phase composition and nickel microsegregation [ru

A-Site Deficient (Pr0.6Sr0.4)(1-s)Fe0.8Co0.2O3-delta Perovskites as Solid Oxide Fuel Cell Cathodes

DEFF Research Database (Denmark)

Kammer Hansen, Kent

2009-01-01

Five A-site deficient (Pr0.6Sr0.4)1−sFe0.8Co0.2O3− perovskites (s=0.01, 0.05, 0.10, 0.15, and 0.20) were synthesized using the glycine-nitrate process. The perovskites were characterized with powder X-ray diffraction (XRD), dilatometry, four-point dc conductivity measurements, and electrochemical...... resistance more than 3 times lower than the weakly A-site deficient (Pr0.6Sr0.4)0.99Fe0.8Co0.2O3− perovskite. ©2009 The Electrochemical Society...

Thermal expansion and spontaneous magnetostriction of R2Co7 intermetallic compounds

International Nuclear Information System (INIS)

Andreev, A.V.; Bartashevich, M.I.; Deryagin, A.V.; Zadvorkin, S.M.; Tarasov, E.N.

1988-01-01

Thermal expansion of R 2 Co 7 (R=Y, Nd, Gd, Tb) single crystals was invesigated by the method of X-ray dilatometry. Anomalous of thermal expansion, taking place during magnetic ordering and spin reorientation were used to determine linear and volumetric magnetistriction deformations. Constants of anisotropic magnetostriction of all R 2 Co 7 compounds with nonzero orbital moment of rare earth ion were calculated on the basis of single-ion model according to deformation values and with account of temperature dependences of the magnitude and direction of magnetic moment

Defect Chemistry and Thermomechanical Properties of Ce0.8PrxTb0.2-xO2-delta

DEFF Research Database (Denmark)

Chatzichristodoulou, Christodoulos; Hendriksen, Peter Vang; Hagen, Anke

2010-01-01

of the partial molar enthalpy of reduction in the dopants, could successfully reproduce the experimentally determined oxygen nonstoichiometry. X-ray absorption near-edge spectroscopy measurements were performed at the Ce/Pr/Tb L3 and L2 edges. The valence state of each dopant was affected by the presence...... of the co-dopant. The redox properties strongly depended on the lattice strain energy and the mean metal-oxygen bond strength. The thermal and chemical expansion coefficients were determined by dilatometry. The strongly nonlinear behavior of the thermal expansion coefficient originated from the chemical...

Small-scale mechanical property characterization of ferrite formed during deformation of super-cooled austenite by nanoindentation

International Nuclear Information System (INIS)

Ahn, Tae-Hong; Um, Kyung-Keun; Choi, Jong-Kyo; Kim, Do Hyun; Oh, Kyu Hwan; Kim, Miyoung; Han, Heung Nam

2009-01-01

The mechanical properties of dynamically and statically transformed ferrites were analyzed using a nanoindentater-EBSD (Electron BackScattered Diffraction) correlation technique, which can distinguish indenting positions according to the grains in the specimen. The dilatometry and the band slope and contrast maps by EBSD were used to evaluate the volume fractions of two kinds of ferrite and pearlite. Fine ferrites induced by a dynamic transformation had higher nano-hardness than the statically transformed coarse ferrites. Transmission electron microscopy (TEM) showed the dynamic ferrites to have a higher dislocation density than the statically transformed ferrites.

Uso da técnica de dilatometria no estudo do efeito de diferentes aditivos na sinterização de Si3N4 Use of dilatometry to study the effect of different additives on the sintering of Si3N4

Directory of Open Access Journals (Sweden)

S. Ribeiro

2000-03-01

conducted using high temperature dilatometry and the results are presented in terms of the linear shrinkage and the rate of shrinkage. It was verified that the samples with higher additive content showed higher shrinkage as well as higher shrinkage rates. For samples doped with 14 and 21% of Y2O3/SiO2 additives, the shrinkage was 13,1 and 15,5% respectively and for samples doped with the same amounts of rare earth oxide concentrate/SiO2, 13,7 and 15,7% respectively. Furthermore, higher shrinkages and shrinkage rates have been observed for samples with pre-reacted disilicate additions, when compared to samples with separate oxide additions. In all cases, samples with rare earth oxide concentrate as sinter additive presented higher shrinkages and shrinkage rates in comparison to the correspondent samples with Y2O3 additions.

Sintering of hardmetals in different conditions: experimental results of 2-D dilatometry and computer simulations

International Nuclear Information System (INIS)

Gasik, M.; Zhang, B.; Kaskiala, M.; Yilkeraelae, J.

2001-01-01

Properties of WC-Co functionally gradated materials (FGM) manufactured by powder metallurgy from nanograin powders are studied. New optical system (a 2-D dilatometer) has been developed, using a high-resolution CCd camera and a dedicated software fro image processing. Sintering of WC-Co hard metals with different cobalt and grain growth inhibitors content was performed for various conditions (substrate, heating rate, temperature) and resulting anisotropy was measured. (author)

Study of the cooling process of an extruded aluminium profile

International Nuclear Information System (INIS)

Bouffioux, C.; Habraken, A.M.; Carton, M.; Lecomte-Beckers, J.

2004-01-01

The prediction of the final axial stresses and the residual strains of complex extruded aluminium profiles requires a good knowledge of the material behavior and of the industrial process. This paper is focused on the methods required to provide the whole set of data: material ones and process ones. Scanning differential calorimetry, dilatometry and diffusivity tests identify thermophysic material properties and hot tensile tests identify parameters of the elasto-visco-plastic Norton-Hoff law. The description of the industrial process and its simulations are described. Then a sensitivity analyzis provides the cooling key parameters causing the undesired final curvature during the industrial process

An improved method for determining the continuous cooling transformation diagram of C-Mn steels

Energy Technology Data Exchange (ETDEWEB)

Mesplont, C.; Cooman, B.C. de [Ghent Univ. (Belgium). Lab. for Iron and Steelmaking; Zhao, J.Z.; Vandeputte, S. [Ocas, Zelzate (Belgium)

2001-07-01

Dilatometry is often used to study the decomposition of austenite in steels, but the analysis of dilatometric data is often limited to the determination of transformation temperatures. The well-known lever rule is not applicable when more than one phase transformation occurs. A model accounting for the carbon partitioning effects was developed to extract the phase transformation kinetics of a C-Mn steel cooled using a wide range of cooling rates. The model is shown to be suitable to analyze the phase transformations in C-Mn steels and it can be used to obtain a detailed CCT diagram for those steels. (orig.)

The effect of materials properties on the Q of high Tc helical and coaxial resonators

International Nuclear Information System (INIS)

Peterson, G.E.; Fleming, D.A.; Johnson, D.W. Jr.; Rhodes, W.W.

1990-01-01

High T c helical and coaxial resonators have applications in U.H.F. radio receivers. We have employed a variety of techniques to study the superconducting materials used to form such resonators. These include, X-ray diffraction, SEM, density, dilatometry and sedigraph. We have correlated our data with resonator Q and frequency and have determined optimum conditions for highest Q. Our best resonators perform better than their all copper counterparts by a factor of 10 at 77K and at frequencies below 1,000 MHz. We have used these resonators in local oscillators and Butterworth filters in U.H.F. receivers

Thermophysical Properties of Heat Resistant Shielding Material

International Nuclear Information System (INIS)

Porter, W.D.

2004-01-01

This project was aimed at determining thermal conductivity, specific heat and thermal expansion of a heat resistant shielding material for neutron absorption applications. These data are critical in predicting the structural integrity of the shielding under thermal cycling and mechanical load. The measurements of thermal conductivity and specific heat were conducted in air at five different temperatures (-31 F, 73.4 F, 140 F, 212 F and 302 F). The transient plane source (TPS) method was used in the tests. Thermal expansion tests were conducted using push rod dilatometry over the continuous range from -40 F (-40 C) to 302 F (150 C)

Characterization of ceramic bodies to produce bricks from Campos Goytacazes, Brazil

International Nuclear Information System (INIS)

Almeida, L.L.P. de; Maia, F.S.; Petrucci, L.J.T.; Pessanha, E.M.; Paixao, L.P.

2010-01-01

This work has for objective to study comparatively the characteristics and technological properties of four typical ceramic bodies from the region of Campos dos Goytacazes-RJ used to fabricate red ceramics. The characterization techniques used were: X-ray fluorescence, X-ray diffraction, differential thermal analysis (DTA), thermogravimetric analysis (TGA) and dilatometry. Specimens were molded by extrusion and then fired at 750, 850 and 950 deg C. The evaluated firing properties were: linear shrinkage and water absorption. The results showed that the investigated ceramic bodies have similar chemical and mineralogical composition. It is also concluded that the bodies are adequate to produce bricks. (author)

Effects of co-sintering in self-standing CGO/YSZ and CGO/ ScYSZ dense bi-layers

DEFF Research Database (Denmark)

Teocoli, Francesca; Ni, De Wei; Brodersen, Karen

2014-01-01

-layers are critical due to the mismatch of thermo-mechanical and sintering properties among the materials. Despite the better sinteractivity of ScYSZ, the self-standing CGO/ScYSZ bilayer presents more challenges in terms of densification compared with the CGO/YSZ bi-layer. In particular, above 1200 C, ScYSZ and CGO......-standing bi-layered electrolyte system. The combined use of thermo-mechanical analysis, optical dilatometry, and scanning electron microscopy ensures a systematic characterization of both the individual layers and CGO/YSZ and CGO/ScYSZ bi-layered laminates. The results of the co-firing process of the bi...

Study of allotropic transformations in plutonium

International Nuclear Information System (INIS)

Spriet, B.

1966-06-01

The allotropic transformations in plutonium have been studied by different methods: metallography, dilatometry, thermal analysis, resistivity measurements, examination with a hot stage microscope. In order to study the importance of the purity, purification process such as zone-melting or electro-diffusion have been developed. The characteristics of the α ↔ β transformation can be explained in terms of the influence of internal stresses on the transition temperature and on the transformation kinetics. Some particular characteristics of δ → γ, γ → α, δ ↔ ε, β ↔ γ and δ → α transformations are also given. (author) [fr

Powder metallurgical processing of magnetostrictive materials based on rare earth-iron intermetallic compounds

International Nuclear Information System (INIS)

Malekzadeh, M.

1978-01-01

Procedures are described for fabrication of high density rare earth-iron magnetostrictive compounds by powder metallurgical techniques. The fabrication involves a sequence of steps which includes preparing the pre-alloyed compounds, pulverizing them into a fine powder, compacting in suitable sizes and shapes, and sintering. Samples prepared by these procedures are carefully characterized by scanning electron microscopy, x-ray diffraction, dilatometry, and magnetic measurements. Process steps are found to exert important influences upon densities, microstructure and magnetic properties attained after densification. Investigations on a number of these process steps, including milling time and medium, sintering, and magnetic powder alignment are described

Adsorption-Induced Deformation of Hierarchically Structured Mesoporous Silica-Effect of Pore-Level Anisotropy.

Science.gov (United States)

Balzer, Christian; Waag, Anna M; Gehret, Stefan; Reichenauer, Gudrun; Putz, Florian; Hüsing, Nicola; Paris, Oskar; Bernstein, Noam; Gor, Gennady Y; Neimark, Alexander V

2017-06-06

The goal of this work is to understand adsorption-induced deformation of hierarchically structured porous silica exhibiting well-defined cylindrical mesopores. For this purpose, we performed an in situ dilatometry measurement on a calcined and sintered monolithic silica sample during the adsorption of N 2 at 77 K. To analyze the experimental data, we extended the adsorption stress model to account for the anisotropy of cylindrical mesopores, i.e., we explicitly derived the adsorption stress tensor components in the axial and radial direction of the pore. For quantitative predictions of stresses and strains, we applied the theoretical framework of Derjaguin, Broekhoff, and de Boer for adsorption in mesopores and two mechanical models of silica rods with axially aligned pore channels: an idealized cylindrical tube model, which can be described analytically, and an ordered hexagonal array of cylindrical mesopores, whose mechanical response to adsorption stress was evaluated by 3D finite element calculations. The adsorption-induced strains predicted by both mechanical models are in good quantitative agreement making the cylindrical tube the preferable model for adsorption-induced strains due to its simple analytical nature. The theoretical results are compared with the in situ dilatometry data on a hierarchically structured silica monolith composed by a network of mesoporous struts of MCM-41 type morphology. Analyzing the experimental adsorption and strain data with the proposed theoretical framework, we find the adsorption-induced deformation of the monolithic sample being reasonably described by a superposition of axial and radial strains calculated on the mesopore level. The structural and mechanical parameters obtained from the model are in good agreement with expectations from independent measurements and literature, respectively.

The thermal expansion of hard magnetic materials of the Nd-Fe-B system

Science.gov (United States)

Savchenko, Igor; Kozlovskii, Yurii; Samoshkin, Dmitriy; Yatsuk, Oleg

2017-10-01

The results of dilatometric measurement of the thermal expansion of hard magnetic materials brands N35M, N35H and N35SH containing as a main component the crystalline phase of Nd2Fe14B type are presented. The temperature range from 200 to 750 K has been investigated by the method of dilatometry with an error of 1.5-2×10-7 K-1. The approximation dependences of the linear thermal expansion coefficient have been obtained. The character of changes of the thermal coefficient of linear expansion in the region of the Curie point has been specified, its critical indices and critical amplitudes have been defined.

Characterization of a red ceramic body used in the manufacture of ceramic bricks in the region of Campos dos Goytacazes, RJ, Brazil; Caracterizacao de massa ceramica vermelha utilizada na fabricacao de blocos ceramicos na regiao de Campos dos Goytacazes

Energy Technology Data Exchange (ETDEWEB)

Almeida, L.L.P. de; Petrucci, L.J.T.; Pessanha, E.M.; Paixao, L.P.; Maia, F.S. [Faetec, Campos dos Goytacazes, RJ (Brazil). Centro Vocacional Tecnologico. Ceramica

2010-07-01

This work aims at the physical and mineralogical characterization of a ceramic body, used industrially in the manufacture of ceramic bricks in the region of Campos dos Goytacazes. The clay was characterized by chemical composition, X-ray diffraction, dilatometry, differential thermal analysis and gravimetric. We test specimens were obtained by extrusion. The bodies were burned from 750 to 1000 deg C and then it was determined water absorption, linear shrinkage, loss on ignition and modulus of rupture. The results showed that the ceramic body consists mainly of kaolinite, quartz and feldspar is thus suitable for mass production of ceramic bricks in accordance with technical standards. (author)

Characterization of a red ceramic body used in the manufacture of ceramic bricks in the region of Campos dos Goytacazes, RJ, Brazil

International Nuclear Information System (INIS)

Almeida, L.L.P. de; Petrucci, L.J.T.; Pessanha, E.M.; Paixao, L.P.; Maia, F.S.

2010-01-01

This work aims at the physical and mineralogical characterization of a ceramic body, used industrially in the manufacture of ceramic bricks in the region of Campos dos Goytacazes. The clay was characterized by chemical composition, X-ray diffraction, dilatometry, differential thermal analysis and gravimetric. We test specimens were obtained by extrusion. The bodies were burned from 750 to 1000 deg C and then it was determined water absorption, linear shrinkage, loss on ignition and modulus of rupture. The results showed that the ceramic body consists mainly of kaolinite, quartz and feldspar is thus suitable for mass production of ceramic bricks in accordance with technical standards. (author)

Machine vision for high-precision volume measurement applied to levitated containerless material processing

International Nuclear Information System (INIS)

Bradshaw, R.C.; Schmidt, D.P.; Rogers, J.R.; Kelton, K.F.; Hyers, R.W.

2005-01-01

By combining the best practices in optical dilatometry with numerical methods, a high-speed and high-precision technique has been developed to measure the volume of levitated, containerlessly processed samples with subpixel resolution. Containerless processing provides the ability to study highly reactive materials without the possibility of contamination affecting thermophysical properties. Levitation is a common technique used to isolate a sample as it is being processed. Noncontact optical measurement of thermophysical properties is very important as traditional measuring methods cannot be used. Modern, digitally recorded images require advanced numerical routines to recover the subpixel locations of sample edges and, in turn, produce high-precision measurements

Production and mechanical properties of sintered carbides (hard steels WC-Co)

International Nuclear Information System (INIS)

Batalha, G.F.

1987-09-01

Densification and mechanical characteristics or WC-Co Cemented Carbides, were investigated by dilatometry, Hardness and bending tests, as a function of the two principal micro-structural parameters: the cobalt content and the particle size of carbide crystals. Vickers hardness of the studied compositions showed a linear variation with the increase of the cobalt content. By three point bending, the transverse rupture strenght increases with cobalt content, however, for larger grain size reaches a maximum, eventually reduced by brittle phases and incomplete dispersion. The results of brittle facture tests were statistically analised and fitted better to the 'Weakest Link Model' (Weibull distribution) than the 'Chain Model' (Gaussian distribution). (author) [pt

Real time neutron transmission investigation of the austenite-bainite transformation in grey iron

International Nuclear Information System (INIS)

Meggers, Kay; Priesmeyer, Hans G.; Trela, Walter J.; Bowman, Charles D.; Dahms, Michael

1994-01-01

The first successful application of a new method to investigate phase transformations in real time, like the decomposition of austenite into bainite in grey iron, is described. During the ongoing transformation, transmission spectra of thermal neutrons, which contain Bragg edges corresponding to the crystal structure of the transforming phases, are recorded. By evaluating the height of these Bragg edges, which is a measure of the volume fraction of the phase, at different transformation times, the transformation can be followed in-situ in a time resolved manner. The method is compared to other previously used methods (micrographs, dilatometry, diffraction techniques); also a summary and an outlook are given. ((orig.))

Thermo-physical characterization of the Fe_6_7Mo_6Ni_3_._5Cr_3_._5P_1_2C_5_._5B_2_._5 bulk metallic glass forming alloy

International Nuclear Information System (INIS)

Bochtler, Benedikt; Gross, Oliver; Gallino, Isabella; Busch, Ralf

2016-01-01

The iron-phosphorus based bulk metallic glass forming alloy Fe_6_7Mo_6Ni_3_._5Cr_3_._5P_1_2C_5_._5B_2_._5 is characterized with respect to its thermophysical properties, crystallization and relaxation behavior, as well as its viscosity. The alloy provides a high critical casting thickness of 13 mm, thus allowing for the casting of amorphous parts with a considerable size. Calorimetric measurements reveal the characteristic transformation temperatures, transformation enthalpies, and the specific heat capacity. The analyses show that no stable supercooled liquid region exists upon heating. The specific heat capacity data are used to calculate the enthalpy, entropy, and Gibbs free energy differences between the crystalline and the supercooled liquid state. The crystallization behavior of amorphous samples upon heating is analyzed by differential scanning calorimetry and X-ray diffraction, and a time-temperature-transformation diagram is constructed. Dilatometry is used to determine the thermal expansion behavior. The equilibrium viscosity below the glass transition as well as volume relaxation behavior are measured by three-point beam bending and dilatometry, respectively, to assess the kinetic fragility. With a kinetic fragility parameter of D* = 21.3, the alloy displays a rather strong liquid behavior. Viscosity above the melting point is determined using electromagnetic levitation in microgravity on a reduced gravity aircraft in cooperation with the German Aerospace Center (DLR). These high-temperature viscosity data are compared with the low-temperature three-point beam bending measurements. The alloy displays a strong liquid behavior at low temperatures and a fragile behavior at high temperatures. These results are analogous to the ones observed in several Zr-based bulk metallic glass forming liquids, indicating a strong to fragile liquid-liquid transition in the undercooled liquid, which is obscured by crystallization.

Study of uranium - 20 Wt per cent plutonium-niobium alloys (1963); Etude d'alliages U-Pu-Nb a 20 pour cent en poids de plutonium (1963)

Energy Technology Data Exchange (ETDEWEB)

Abgrall, J; Barthelemy, P; Boucher, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1963-07-01

U-Pu-Nb alloys containing 20 wt per cent Pu and 10 - 20 - 30 - 40 - 50 or 60 wt per cent Nb have been studied principally to determine the feasibility of their use as fuel element. The fabrication, casting and homogenisation presented certain difficulties due specially to niobium. The transformation temperatures, thermal expansion coefficients and nature of phases have been determined by thermal analysis, dilatometry, micrography and X Rays diffraction. For similar compositions, U-Pu-Mo and U-Pu-Nb alloys have many common points concerning the presence of zeta phase (up to 40 wt per cent Nb), the coefficients of expansion, the good behaviour during thermal cycling and the good resistance to air oxidation in spite of zeta phase. In consequence, irradiation tests in EL{sub 3} reactor (Saclay) will be carried out in the near future. (authors) [French] Les alliages a 20 pour cent de plutonium, 10 - 20 - 30 - 40 - 50 - 60 pour cent de niobium et le complement en uranium ont ete etudies du point de vue de leur possibilite d'emploi comme combustible. Les problemes d'elaboration, de mise en forme et d'homogeneisation sont presentes. Ils sont relativement delicats. On a determine par analyse thermique, dilatometrie, micrographie et diffraction des rayons X les temperatures de transformation a l'etat solide, les coefficients de dilatation et la nature des phases. Pour des teneurs analogues, on retrouve de nombreux points communs avec les alliages U-Pu-Mo: presence de la phase zeta des U-Pu a temperature moyenne, coefficients de dilatation analogues, bonne tenue en cyclage thermique et bonne resistance a l'oxydation dans l'air malgre la presence de la phase zeta. Des essais d'irradiation dans EL{sub 3} vont etre entrepris. (auteurs)

Study of uranium - 20 Wt per cent plutonium-niobium alloys (1963); Etude d'alliages U-Pu-Nb a 20 pour cent en poids de plutonium (1963)

Energy Technology Data Exchange (ETDEWEB)

Abgrall, J.; Barthelemy, P.; Boucher, R. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1963-07-01

U-Pu-Nb alloys containing 20 wt per cent Pu and 10 - 20 - 30 - 40 - 50 or 60 wt per cent Nb have been studied principally to determine the feasibility of their use as fuel element. The fabrication, casting and homogenisation presented certain difficulties due specially to niobium. The transformation temperatures, thermal expansion coefficients and nature of phases have been determined by thermal analysis, dilatometry, micrography and X Rays diffraction. For similar compositions, U-Pu-Mo and U-Pu-Nb alloys have many common points concerning the presence of zeta phase (up to 40 wt per cent Nb), the coefficients of expansion, the good behaviour during thermal cycling and the good resistance to air oxidation in spite of zeta phase. In consequence, irradiation tests in EL{sub 3} reactor (Saclay) will be carried out in the near future. (authors) [French] Les alliages a 20 pour cent de plutonium, 10 - 20 - 30 - 40 - 50 - 60 pour cent de niobium et le complement en uranium ont ete etudies du point de vue de leur possibilite d'emploi comme combustible. Les problemes d'elaboration, de mise en forme et d'homogeneisation sont presentes. Ils sont relativement delicats. On a determine par analyse thermique, dilatometrie, micrographie et diffraction des rayons X les temperatures de transformation a l'etat solide, les coefficients de dilatation et la nature des phases. Pour des teneurs analogues, on retrouve de nombreux points communs avec les alliages U-Pu-Mo: presence de la phase zeta des U-Pu a temperature moyenne, coefficients de dilatation analogues, bonne tenue en cyclage thermique et bonne resistance a l'oxydation dans l'air malgre la presence de la phase zeta. Des essais d'irradiation dans EL{sub 3} vont etre entrepris. (auteurs)

Effect of different strain distributions on the phase transformations in steel. Einfluss verschiedener Dehnungszustaende auf das Umwandlungsverhalten eines Stahls

Energy Technology Data Exchange (ETDEWEB)

Lyra, A.; Dahl, W. (Technische Hochschule Aachen (Germany, F.R.). Inst. fuer Eisenhuettenkunde)

1990-01-01

Using tensile specimens with two different geometries (notched and unnotched) and five cooling rates the anisothermal phase transformation of a 100 Cr 6 steel has been investigated under influence of different strain distributions inside the specimens. The nonhomogeneous distribution of plastic strain has been achieved by tensile testing at high temperatures (800deg C). Measurement of the transformation temperatures was carried out by dilatometry and differential thermal analysis (DTA). The results reveal that due to hot deformation the pearlitic transformation curves in the CCT-Diagram are dislocated to shorter times and higher temperatures compared with the underformed state. The extent of the displacement is however a function of the strain distribution inside the specimens. (orig.).

The thermal expansion of hard magnetic materials of the Nd-Fe-B system

Directory of Open Access Journals (Sweden)

Savchenko Igor

2017-01-01

Full Text Available The results of dilatometric measurement of the thermal expansion of hard magnetic materials brands N35M, N35H and N35SH containing as a main component the crystalline phase of Nd2Fe14B type are presented. The temperature range from 200 to 750 K has been investigated by the method of dilatometry with an error of 1.5-2×10-7 K-1. The approximation dependences of the linear thermal expansion coefficient have been obtained. The character of changes of the thermal coefficient of linear expansion in the region of the Curie point has been specified, its critical indices and critical amplitudes have been defined.

Chemically bonded ceramic matrix composites: Densification and conversion to diffusion bonding

International Nuclear Information System (INIS)

Johnson, B.R.; Guelguen, M.A.; Kriven, W.M.

1995-01-01

Chemically bonded ceramics appear to be a promising alternative route for near-net shape fabrication of multi-phase ceramic matrix composites (CMC's). The hydraulic (and refractory) properties of fine mono-calcium aluminate (CaAl 2 O 4 ) powders were used as the chemically bonding matrix phase, while calcia stabilized zirconia powders were the second phase material. Samples containing up to 70 wt% (55 vol%) zirconia have been successfully compacted and sintered. Various processing techniques were evaluated. Processing was optimized based on material properties, dilatometry and simultaneous thermal analysis (DTA/TGA). The physical characteristics of this novel CMC were characterized by hardness, density, and fracture toughness testing. Microstructures were evaluated by SEM and phase identification was verified using XRD

Nano silicon for lithium-ion batteries

International Nuclear Information System (INIS)

Holzapfel, Michael; Buqa, Hilmi; Hardwick, Laurence J.; Hahn, Matthias; Wuersig, Andreas; Scheifele, Werner; Novak, Petr; Koetz, Ruediger; Veit, Claudia; Petrat, Frank-Martin

2006-01-01

New results for two types of nano-size silicon, prepared via thermal vapour deposition either with or without a graphite substrate are presented. Their superior reversible charge capacity and cycle life as negative electrode material for lithium-ion batteries have already been shown in previous work. Here the lithiation reaction of the materials is investigated more closely via different electrochemical in situ techniques: Raman spectroscopy, dilatometry and differential electrochemical mass spectrometry (DEMS). The Si/graphite compound material shows relatively high kinetics upon discharge. The moderate relative volume change and low gas evolution of the nano silicon based electrode, both being important points for a possible future use in real batteries, are discussed with respect to a standard graphite electrode

Sintering of nanopowders of ZrO_2 (Y_2O_3): Effect of compaction pressure on densification

International Nuclear Information System (INIS)

Palmeira, Alexandre Alvarenga; Magnago, Roberto de Oliveira; Pereira, Glayce Cassaro; Bondioli, Marcelo Jose; Strecker, Kurt; Santos, Claudinei dos

2014-01-01

In this work studied the powders (nano) sintered of ZrO_2 (Y_2O_3) by dilatometry. Was identified the effect of compaction pressure variation in the final results of densification of materials. Powders were compacted at different compaction pressures. The compacts were subjected to temperatures of 1250°C to 1400°C with sintering levels ranging from 0 to 8 hours. Samples were characterized by X-ray diffraction and relative density using Archimedes method. The results were compared with powders (micro) of similar composition in order to compare the effect of particle size on densification parameters. The samples were further subjected to microstructural characterization in order to identify the average grain size of the sintering under each condition used in both materials. (author)

Characterization of grog of bricks; Caracterizacao de chamote de blocos de vedacao

Energy Technology Data Exchange (ETDEWEB)

Candido, V.S.; Pinheiro, R.M.; Monteiro, S.N.; Vieira, C.M.F. [Universidade Estadual do Norte Fluminense Darcy Ribeiro (LAMAV/CCT/UENF), Campos dos Goytacazes, RJ (Brazil). Lab. de Materiais Avancados

2010-07-01

This work aims to characterize a waste of red ceramic, grog, generated from the milling of defective pieces of bricks fired in a Hoffmann type furnace by a industry from Campos dos Goytacazes-RJ. The grog was tested for X-ray diffraction, X-ray fluorescence, thermogravimetric and differential thermal analysis, dilatometry, sieving and sedimentation by gravity and optical microscopy. The results indicated that the grog is predominantly constituted of quartz, muscovite mica and hematite. The presence of kaolinite indicates that the bricks were fired at low temperatures, below 600 deg C. Finally, the characterization results indicated that the grog presents itself as an alternative non plastic material to be used in mixtures with clays for the production of red ceramics. (author)

Characterization of grog of bricks

International Nuclear Information System (INIS)

Candido, V.S.; Pinheiro, R.M.; Monteiro, S.N.; Vieira, C.M.F.

2010-01-01

This work aims to characterize a waste of red ceramic, grog, generated from the milling of defective pieces of bricks fired in a Hoffmann type furnace by a industry from Campos dos Goytacazes-RJ. The grog was tested for X-ray diffraction, X-ray fluorescence, thermogravimetric and differential thermal analysis, dilatometry, sieving and sedimentation by gravity and optical microscopy. The results indicated that the grog is predominantly constituted of quartz, muscovite mica and hematite. The presence of kaolinite indicates that the bricks were fired at low temperatures, below 600 deg C. Finally, the characterization results indicated that the grog presents itself as an alternative non plastic material to be used in mixtures with clays for the production of red ceramics. (author)

Thermal analysis of rare earth gallates and aluminates

International Nuclear Information System (INIS)

O'Bryan, H.M.; Gallagher, P.K.; Berkstresser, G.W.; Brandle, C.D.

1990-01-01

Dilatometry, high-temperature x-ray diffraction, differential thermal analysis, and differential scanning calorimetry have been performed on LaGaO 3 , NdGaO 3 , PrGaO 3 , SmAlO 3 , and LaAlO 3 single crystals grown by the Czochralski technique. First order phase transitions have been located at 145 degree C for LaGaO 3 and 785 degree C for SmAlO 3 , and ΔH has been measured for the LaGaO 3 transition. Second order transitions have been identified for LaGaO 3 , PrGaO 3 , NdGaO 3 , and LaAlO 3 . The usefulness of these compounds as substrates for high temperature superconducting films is discussed in terms of thermal expansion matching

Synthesis and characterization of nanocomposite powders of calcium phosphate/titanium oxide for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Delima, S.A.; Camargo, N.H.A.; Souza, J.C.P.; Gemelli, E., E-mail: sarahamindelima@hotmail.com, E-mail: dem2nhac@joinville.udesc.br, E-mail: souzajulio@joinville.udesc.br, E-mail: gemelli@joinville.udesc.br [Universidade do Estado de Santa Catarina (UDESC), Joinville, SC (Brazil). Centro de Ciencias Tecnologicas

2009-07-01

The nanostructured bioceramics of calcium phosphate are current themes of research and they are becoming important as bone matrix in regeneration of tissues in orthopedic and dental applications. Nanocomposite powders of calcium phosphate, reinforced with nanometric particles of titanium oxide, silica oxide and alumina oxid ealpha, are being widely studied because they offer new microstructures, nanostructures and interconnected microporosity with high superficial area of micropores that contribute to osteointegration and osteoinduction processes. This study is about the synthesis of nanocomposites powders of calcium phosphate reinforced with 1%, 2%, 3% and 5% in volume of titanium oxide and its characterization through the techniques of X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Differential Thermal Analysis (DTA), Thermogravimetry (TG) and Dilatometry. (author)

The Influence of Vanadium on Ferrite and Bainite Formation in a Medium Carbon Steel

Science.gov (United States)

Sourmail, T.; Garcia-Mateo, C.; Caballero, F. G.; Cazottes, S.; Epicier, T.; Danoix, F.; Milbourn, D.

2017-09-01

The influence of vanadium additions on transformation kinetics has been investigated in a medium carbon forging steel. Using dilatometry to track transformation during continuous cooling or isothermal transformation, the impact of vanadium on both ferrite-pearlite and bainite has been quantified. Transmission electron microscopy and atom probe tomography have been used to establish whether vanadium was present in solid solution, or as clusters and precipitates. The results show that vanadium in solid solution has a pronounced retarding influence on ferrite-pearlite formation and that, unlike in the case of niobium, this effect can be exploited even during relatively slow cooling. The influence on bainite transformation was found to depend on temperature; an explanation in terms of the effect of vanadium on heterogeneous nucleation is tentatively proposed.

Influence of metallic additives on manganese ferrites sintering

Science.gov (United States)

Shevelev, S. A.; Luchnikov, P. A.; Yarullina, A. R.

2018-01-01

Influence of cuprum nanopowder additive received by electric explosion on the process of manganese ferrites MgFe2O4 consolidating at thermal sintering was researched by dilatometry method. Cuprum nanopowder at a rate of 5 mass % was added into the original commercial-grade powder of manganese ferrite MgFe2O4. Powder mixture was numerously blended with screening for better blending before pressing. Powder compacts were formed by cold one-axle static pressing. It was proved that introduction of cuprum additive caused shrinkage increase at final heating stage. There was abnormal compact enlarging at sintering in the air at isothermal stage; the specified process was not observed in vacuum. This difference can be explained by changes in conditions of gaseous discharge from volume of pores.

Analysis of thermal stability of ceramic engobes developed with marble reject; Analise da estabilidade termica de engobes ceramicos desenvolvidos com rejeito de marmore

Energy Technology Data Exchange (ETDEWEB)

Carlos, E.M.; Assis, R.B.; Sousa, R.F.; Galvao, A.C.P.; Mendes, J.U.L., E-mail: elionemoura@hotmail.com [Universidade Federal do Rio Grande do Norte (UFRN), RN (Brazil)

2014-07-01

Considering the technological growth and technical production in the ceramic industry, ceramic mass formulations were evaluated with addition of marble residue to substitute the quartz for obtaining of engobes. Five formulations were prepared varying the proportions of raw material, sieved at 200 mesh, ball mill homogenised, characterized by fluorescence (FRX) and X-ray diffraction (XRD). Samples were separated from the formulations for thermal analysis (TG / DSC) and dilatometry. The specimens were prepared in uniaxial press (25 Mpa). The FIII and FIV formulations presented satisfactory results, evidencing the potential of replacing quartz by the marble residue in ceramic formulation for engobes, minimizing the environmental impact by the undue discard of waste, reducing costs and increasing the range of raw materials for the coatings industry.

Characterization of microstructural strengthening in the heat-affected zone of a blast-resistant naval steel

Energy Technology Data Exchange (ETDEWEB)

Yu Xinghua, E-mail: yu.345@osu.edu [Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43221 (United States); Caron, Jeremy L. [Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43221 (United States)] [Welding and Joining Metallurgy Group, Welding Engineering Program, 1248 Arthur E. Adams Drive, Ohio State University, Columbus, OH 43221 (United States); Babu, S.S., E-mail: babu.13@osu.edu [Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43221 (United States) and Welding and Joining Metallurgy Group, Welding Engineering Program, 1248 Arthur E. Adams Drive, Ohio State University, Columbus, OH 43221 (United States); Lippold, John C. [Department of Materials Science and Engineering, Ohio State University, Columbus, OH 43221 (United States)] [Welding and Joining Metallurgy Group, Welding Engineering Program, 1248 Arthur E. Adams Drive, Ohio State University, Columbus, OH 43221 (United States); Isheim, Dieter; Seidman, David N. [Department of Materials Science and Engineering, Northwestern University, 2220 North Campus Drive, Evanston, IL 60208 (United States)] [Northwestern University Center for Atom-Probe Tomography, 2220 North Campus Drive, Evanston, IL 60208 (United States)

2010-10-15

The influence of simulated heat-affected zone thermal cycles on the microstructural evolution in a blast-resistant naval steel was investigated by dilatometry, microhardness testing, optical microscopy, electron backscatter diffraction and atom-probe tomography (APT) techniques. Coarsening of Cu precipitates were observed in the subcritical and intercritical heat-affected zones, with partial dissolution in the latter. A small number density of Cu precipitates and high Cu concentration in the matrix of the fine-grained heat-affected zone indicates the onset of Cu precipitate dissolution. Cu clustering in the coarse-grained heat-affected zone indicated the potential initiation of Cu reprecipitation during cooling. Segregation of Cu was also characterized by APT. The hardening and softening observed in the heat-affected zone regions was rationalized using available strengthening models.

Fabrication and properties of hot pressed bismuth tungstate

International Nuclear Information System (INIS)

Streicher, W.L.

1978-01-01

Bi 2 WO 6 is a synthetic polar material that is a possible candidate for energy conversion and detection systems. Previous research on this material has been concerned with crystal growth and sintering characteristics of polycrystalline compacts. This study involves itself with the fabrication of polycrystalline compacts by hot pressing techniques. Densities approaching theoretical crystal density were achieved by hot pressing at 850 0 C for one hour with pressures exceeding 35 MPa. Before hot pressing, the sintering range was determined by high temperature dilatometry of unfired Bi 2 WO 6 ceramics. Hot pressed discs were characterized by scanning electron microscopy, differential scanning calorimetry, and x-ray diffraction. Electrical properties were determined by dc resistivity, capacitance, and conductance measurements, ac poling, dc poling, and current-voltage measurements

Analysis of thermal stability of ceramic engobes developed with marble reject

International Nuclear Information System (INIS)

Carlos, E.M.; Assis, R.B.; Sousa, R.F.; Galvao, A.C.P.; Mendes, J.U.L.

2014-01-01

Considering the technological growth and technical production in the ceramic industry, ceramic mass formulations were evaluated with addition of marble residue to substitute the quartz for obtaining of engobes. Five formulations were prepared varying the proportions of raw material, sieved at 200 mesh, ball mill homogenised, characterized by fluorescence (FRX) and X-ray diffraction (XRD). Samples were separated from the formulations for thermal analysis (TG / DSC) and dilatometry. The specimens were prepared in uniaxial press (25 Mpa). The FIII and FIV formulations presented satisfactory results, evidencing the potential of replacing quartz by the marble residue in ceramic formulation for engobes, minimizing the environmental impact by the undue discard of waste, reducing costs and increasing the range of raw materials for the coatings industry

Synthesis and characterization of nanocomposite powders of calcium phosphate/titanium oxide for biomedical applications

International Nuclear Information System (INIS)

Delima, S.A.; Camargo, N.H.A.; Souza, J.C.P.; Gemelli, E.

2009-01-01

The nanostructured bioceramics of calcium phosphate are current themes of research and they are becoming important as bone matrix in regeneration of tissues in orthopedic and dental applications. Nanocomposite powders of calcium phosphate, reinforced with nanometric particles of titanium oxide, silica oxide and alumina oxid ealpha, are being widely studied because they offer new microstructures, nanostructures and interconnected microporosity with high superficial area of micropores that contribute to osteointegration and osteoinduction processes. This study is about the synthesis of nanocomposites powders of calcium phosphate reinforced with 1%, 2%, 3% and 5% in volume of titanium oxide and its characterization through the techniques of X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Differential Thermal Analysis (DTA), Thermogravimetry (TG) and Dilatometry. (author)

Thermal expansion of martensitic A15 superconductors: V3Si

International Nuclear Information System (INIS)

Finlayson, T.R.; Liu, M.; Smith, T.F.

1995-01-01

The martensite phase morphology of V 3 Si has been controlled by the application of appropriate stress fields to a single crystal. With this procedure, it is possible to transform the crystal to a single, tetragonal domain, enabling the thermal expansion coefficients for the tetragonal a and c axes to be measured, using high-resolution, capacitance dilatometry. Expansion anomalies were found at low temperatures, well below the superconducting critical temperature, for both the a and c axes. The tetragonality continues increasing on cooling at low temperatures, which, predicted by theory, should have been inhibited by the onset of superconductivity. In addition, anisotropy in thermal expansion is found up to 50 K, which is well above the conventional M s temperature of 21 K. (orig.)

Production of glass-ceramic materials obtained from sewage sludge treatment plant for urban wastewater in El-Sadat city (Egypt); Materiales vitroceramicos a partir de lodos procedentes de una estacion de depuracion de aguas residuales urbanas (en la Ciudad de El-Sadat, Egipto).

Energy Technology Data Exchange (ETDEWEB)

Garcia-Valles, M.; Aly, M. H.; El-Fadaly, E.; Hafez, H. S.; Nogues, J.; Martinez, S.

2011-07-01

Urban wastewater security is a source of significant volumes of sludge which is to be managed. This paper presents the possibility of applying a management process based on vitrification and by which, in addition to inert contaminants in sludge, you get a ceramic material with a significant added value. As a base of different analysis of the sludges, chemical (XRF), mineralogical (XRD) and thermal (DTA-TG), we obtain the original glass composition and its energy. By DTATG, dilatometry and SEM, it was determined the temperature of maximum nucleation rate, growth temperature and the morphology and size of developed nuclei, in this case are nano scale. Briefly, it was found as the management of municipal solid waste by vitrification as an alternative to landfills and incineration. (Author)

Redox transitions in strontium vanadates: Electrical conductivity and dimensional changes

International Nuclear Information System (INIS)

Macías, J.; Yaremchenko, A.A.; Frade, J.R.

2014-01-01

Highlights: • Electrical conductivity and thermal expansion of strontium vanadates are measured. • Conductivity of SrVO 3−δ is 10 6 –10 8 times higher compared to Sr 2 V 2 O 7 and Sr 3 V 2 O 8 . • Sr 2 V 2 O 7 transforms on reduction to SrVO 3−δ via (5Sr 3 V 2 O 8 + SrV 6 O 11 ) intermediate. • This process is kinetically stagnated due to good redox stability of Sr 3 V 2 O 8 . • Large volume changes on Sr 2 V 2 O 7 ↔ SrVO 3 transformation are confirmed by dilatometry. - Abstract: The reversibility of redox-induced phase transformations and accompanying electrical conductivity and dimensional changes in perovskite-type SrVO 3−δ , a parent material for a family of potential solid oxide fuel cell anode materials, were evaluated employing X-ray diffraction, thermal analysis, dilatometry and electrical measurements. At 873–1273 K, the electrical conductivity of SrVO 3−δ is metallic-like and 6–8 orders of magnitude higher compared to semiconducting V 5+ -based strontium pyrovanadate Sr 2 V 2 O 7 and strontium orthovanadate Sr 3 V 2 O 8 existing under oxidizing conditions. SrVO 3−δ is easily oxidized to a pyrovanadate phase at atmospheric oxygen pressure. Inverse reduction in 10%H 2 –90%N 2 atmosphere occurs in two steps through (5Sr 3 V 2 O 8 + SrV 6 O 11 ) intermediate. As Sr 3 V 2 O 8 is relatively stable even under reducing conditions, the perovskite phase and its high level of electrical conductivity cannot be recovered completely in a reasonable time span at temperatures ⩽1273 K. Dilatometric studies confirmed that SrVO 3 ↔ Sr 2 V 2 O 7 redox transformation is accompanied with significant dimensional changes. Their extent depends on the degree of phase conversion and, apparently, on microstructural features

The use of emanation thermal analysis for the evaluation of Fe2O3 reactivity

International Nuclear Information System (INIS)

Balek, V.

1977-01-01

The ETA method using 220 Rn was applied in studying the ZnO - Fe 2 O 3 reaction. The higher is the temperature at which the maximum is reached on the emanation vs. temperature curve of the mixture, the lower the indicated reactivity of Fe 2 O 3 used (temperature range 790 to 980 degC). The degree of order in the lattice of the ZnFe 2 O 4 formed may be judged from the emanation power at 850 to 1000 degC. Fe 2 O 3 pre-annealed to 1100 degC shows the lowest reactivity with ZnO. Associated with it is a lower capacity of forming the perfect ZnFe 2 O 4 structure. The ETA results are compared with those obtained by DTA and by dilatometry. (M.K.)

Substutited molybdates of bismuth on a basis of Bi13Mo5O34±δ: production and properties

Directory of Open Access Journals (Sweden)

Z. A. Mikhailovskaya

2014-11-01

Full Text Available The present work is devoted to the investigation of the methods of a synthesis and properties of the one of the most interesting one-dimensional oxygen –ion conductors, the Bi13Mo5O34±δ –based complex oxides. The general compositions of these bismuth molybdates are Bi13Mo5-хMeхO34-δ, and Bi13-yMeyMo5O34-δ, with Me = Mg, Ca, Sr, Ba (IIA group and Co, Fe, Ni (Fe triade. The samples have been synthesized using conventional ceramic technology. The powders and pellets of the bismuth molybdates were studied by X-Ray diffraction, scanning electron microscopy, laser dispersion, dilatometry, atom absorption and inductively-coupled plasma atomic emission spectrometry. Electrical conductivity has been studied using impedance spectroscopy method.

β → α isothermal transformation in pure and weakly alloyed uranium

International Nuclear Information System (INIS)

Aubert, H.; Lelong, C.

1966-01-01

The TTT diagrams describing the β → α isothermal transformation have been made by isothermal dilatometry for pure uranium and 21 alloys based on chromium, silicon, molybdenum, iron, aluminium, zirconium. The thermal cycle preceding the isothermal step influences the decomposition kinetics at temperature corresponding to the eutectoid and martensitic mechanisms, but not in the range where the bainitic transformation occurs. The stability of the β phase decreases with the chromium, molybdenum and silicon concentration: it is affected differently for each of the three transformation mechanisms. The ternary additions, even at very low concentration have a considerable effect on the stability. When the concentration decreases the martensitic mechanism is active at progressively higher temperature, diminishing to the point of disappearance the temperature range where the transformation is considered as being of the bainitic mode. (author) [fr

The kinetics and mechanism of bainite transformation in high strength steels

International Nuclear Information System (INIS)

Ali, A.; Bhadeshia, H.K.D.H.

1993-01-01

The kinetics and mechanism of bainite formation have been studied in high strength Fe-C-Si-Mn and Fe-C-Si-Ni steels using dilatometry, optical and transmission electron microscopy. In these silicon containing steels, carbide precipitation dies not accompany the growth of bainitic ferrite so that the mechanism of transformation can be readily interpreted. The work confirms that the volume fraction of bainite when the reaction stops, is far less that expected from equilibrium or para equilibrium considerations. In addition the bainite exhibits an invariant plane strain surface relief effect with a large shear component, and adopts a sheaf morphology. The results are demonstrated to be consistent with a displacive diffusion less transformation mechanism of bainite, in which the excess carbon is, subsequent to transformation, rejected into the residual austenite. (author)

Densification of Highly Defective Ceria by High Temperature Controlled Re-Oxidation

DEFF Research Database (Denmark)

Ni, De Wei; Glasscock, Julie; Pons, Aénor

2014-01-01

Highly enhanced densification and grain growth of Ce0.9Gd0.1O1.95-δ (CGO, gadolinium-doped ceria, with 10 mol% Gd) is achieved in low oxygen activity atmospheres. However, the material can suffer mechanical failures during cooling when the re-oxidation process is not controlled due to the large...... volume changes. In this work, the redox process of CGO is investigated using dilatometry, microscopy, electrochemical impedance spectroscopy and thermodynamic analysis. In addition, the conditions allowing controlled re-oxidation and cooling in order to preserve the mechanical integrity of the CGO...... component are defined: this can be achieved over a wide temperature range (800−1200◦C) by gradually increasing the oxygen content of the atmosphere. It is found that the electrical conductivity of the CGO, particularly at low temperature (oxidation...

Mechanical properties of refractory concretes for boilers; Propriedades mecanicas de concretos refratarios para caldeiras

Energy Technology Data Exchange (ETDEWEB)

Angioletto, E.; Pelisser, F.; Peterson, M.; Angioletto, E.; Rocha, M.R.; Arnt, A.B.C. [Universidade do Estado de Santa Catarina (UDESC), Criciuma, SC (Brazil)], E-mail: ean@unesc.net; Coelho, R. [Tractebel Energia, Florianpolis, SC (Brazil)

2010-07-01

Refractory concretes are used in extremely physically demanding conditions. An important example is concretes used as sealing systems in boilers, where their dimensional stability at high temperatures is fundamental to durability and has a strong impact on maintenance costs and system idleness. In this work, refractory concretes with different compositions were characterized and then tested by dilatometry, for compressive strength and in assays involving adherence between tensile concrete/metal inserts, simulating the fixing system in boilers. Analysis of the results showed that refractory concretes do not present retraction due to air during drying, eliminating the possibility of cracking. While casting the plate/prototype with metal inserts, satisfactory concrete/metal adherence was verified and surface cracking occurred that did not influence the tensile bond strength between the insert and the concrete. (author)

Cryogenic treatment of steel: from concept to metallurgical understanding

DEFF Research Database (Denmark)

Villa, Matteo; Somers, Marcel A. J.

2017-01-01

, the metallurgical understanding of the microstructural changes involved in cryogenic treatment of steel has remained poor. It is believed that the improvement in wear resistance is promoted by an enhanced precipitation of carbides during tempering, but no explanation has been given as to how this enhanced......Subjecting steel to cryogenic treatment to improve its properties was conceived in the 30ies of the previous century. The proof of concept that properties, in particular wear resistance, can indeed be improved importantly, was reported in the next decades. Despite many investigations...... precipitation can be obtained. In the last six years, the authors have applied in situ magnetometry, synchrotron X-Ray Diffraction and dilatometry to enlighten the phase transitions occurring in steels at cryogenic temperatures and to point out the connection between different treatment parameters...

Potential assessment of Sergipe and Alagoas clays in aggregates production for use in concrete; Avaliacao do potencial de argilas de Sergipe e Alagoas na producao de agregados para uso em concreto

Energy Technology Data Exchange (ETDEWEB)

Oliveira, H.A.; Santos, C.P.; Oliveira, R.M.P.B.; Jesus, E. de; Macedo, Z.S., E-mail: herbetalves148@gmail.com, E-mail: cochiran@hotmail.com, E-mail: rosaneboliveira@gmail.com, E-mail: edilsonjs@ufs.br, E-mail: zelia.macedo@gmail.com [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil)

2017-07-15

This study aims to characterize technologically three clays employed by ceramic industries in Sergipe state, Brazil. Its potential use for the production of calcined synthetic aggregate to substitute gravel in concrete production was evaluated. The characterization of the clays included particle size and plasticity analysis, X-ray diffraction, differential and thermogravimetric analyses, dilatometry, X-ray fluorescence, organic matter content, cation exchange capacity, specific area, and scanning electron microscopy. Ceramic bodies were uniaxially pressed under 30 MPa, into rectangular and cylindrical shapes. Ceramic bodies of individual clays and also ceramic formulations were fired and subsequently characterized to determine their water absorption, apparent density, compressive strength, and grain morphology. It was observed that, after firing at 1120 deg C, two formulations presented strength, water absorption and specific mass comparable to those of gravel used in concrete. (author)

Processing of Polypropylene-Organic Montmorillonite Nanocomposite by Equal Channel Multiangular Extrusion

Directory of Open Access Journals (Sweden)

V. A. Beloshenko

2016-01-01

Full Text Available By the example of polypropylene-organic montmorillonite composite (PP-OMMT, the abilities of the method of equal channel multiangular extrusion have been studied with respect to the modification of the structure and the properties of polymeric nanocomposites. With using X-ray structure analysis, TEM, DSC, and dilatometry, it has been demonstrated that this kind of processing provides an additional intercalation of the polymer into OMMT tactoids with the succeeding exfoliation and facilitates an increase in the aspect ratio, the degree of platelet orientation, the crystalline lamellar thickness, and a decrease in the dispersion of the crystallite thickness, as well as the formation of biaxial orientation of the OMMT and PP crystals. The observed structure rearrangements determine enhanced microhardness, ductility, and the heat distortion temperature of the PP-OMMT composite.

PHOTOPOLYMERIZATION INITIATED BY DIMETHYLAMINOCHALCONE/DIPHENYL-IODONIUM SALT COMBINATION SYSTEM SENSITIVE TO VISIBLE LIGHT

Institute of Scientific and Technical Information of China (English)

LI Jun; LI Miaozhen; SONG Huaihai; YANG Yongyuan; WANG Erjian

1993-01-01

Several dimethylamino-substituted chalcone (I.e.dimethylaminobenzal acetophenone) (DBA) derivatives with intramolecular charge transfer transition character were used as visible light sensitizers for radical photopolymerization initiated by iodonium salt (DPIO). Initiating radical species is produced from DBA sensitized photolysis of DPIO through the single electron transfer,accompanying the bleaching of DBA.The activity of DBA decreases as a function of substituent attached to phenyl ring in the order:DBA-2(OCH3)＞DBA-1(H)＞DBA-3(Cl).The kinetic study on photopolymerization of MMA was carried out in CH3CN solution at 30℃ by dilatometry.The polymerization rate was determined to be proportional to the concentration with exponents of 0.42,0.25 and 0.86 for DPIO,DBA-1and MMA,respectively.

A new method for determining the Curie temperature using a dilatometer

International Nuclear Information System (INIS)

Verma, A; Sundararaman, M; Singh, J B; Nalawade, S A

2010-01-01

Dilatometry is a tool used for the study of dimensional changes in materials as a function of temperature and also to identify phase transformations including magnetic transformations. In this paper, we describe two new methods that can be employed in an inductively heated dilatometer to determine the Curie temperature in metallic ferromagnetic materials. These methods are based on the fundamental magnetic properties of materials such as hysteresis loss and anomalous thermal conductivity changes near the Curie point. These methods have been used to determine the Curie point in nickel, iron and Co–5 at% Ni alloy. The values obtained match well with those reported in the literature. The effects of the geometry of the specimen and of the push-rod material on the measurement sensitivity of the transition temperature have been discussed

Sintering of nanopowders of ZrO{sub 2} (Y{sub 2}O{sub 3}): Effect of compaction pressure on densification; Sinterizacao de pos nanoparticulados de ZrO{sub 2} (Y{sub 2}O{sub 3}): efeito da pressao de compactacao na densificacao

Energy Technology Data Exchange (ETDEWEB)

Palmeira, Alexandre Alvarenga; Magnago, Roberto de Oliveira; Pereira, Glayce Cassaro [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Bondioli, Marcelo Jose; Strecker, Kurt [Universidade Federal Sao Joao Del-Rey (UFSJ), MG (Brazil); Santos, Claudinei dos [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil)

2014-06-15

In this work studied the powders (nano) sintered of ZrO{sub 2} (Y{sub 2}O{sub 3}) by dilatometry. Was identified the effect of compaction pressure variation in the final results of densification of materials. Powders were compacted at different compaction pressures. The compacts were subjected to temperatures of 1250°C to 1400°C with sintering levels ranging from 0 to 8 hours. Samples were characterized by X-ray diffraction and relative density using Archimedes method. The results were compared with powders (micro) of similar composition in order to compare the effect of particle size on densification parameters. The samples were further subjected to microstructural characterization in order to identify the average grain size of the sintering under each condition used in both materials. (author)

Structure of tetragonal martensite in the In95.42Cd4.58 cast alloy

Science.gov (United States)

Khlebnikova, Yu. V.; Egorova, L. Yu.; Rodionov, D. P.; Kazantsev, V. A.

2017-11-01

The structure of martensite in the In95.42Cd4.58 alloy has been studied by metallography, X-ray diffraction, dilatometry, and transmission electron microscopy. It has been shown that a massive structure built of colonies of tetragonal lamellar plates divided by a twin boundary {101}FCT is formed in the alloy under cooling below the martensite FCC → FCT transition temperature. The alloy recrystallizes after a cycle of FCT → FCC → FCT transitions with a decrease in the grain size by several times compared with the initial structure such fashion that the size of massifs and individual martensite lamella in the massif correlates with the change in the size of the alloy grain. Using thermal cycling, it has been revealed that the alloy tends to stabilize the high-temperature phase.

Potential assessment of Sergipe and Alagoas clays in aggregates production for use in concrete

International Nuclear Information System (INIS)

Oliveira, H.A.; Santos, C.P.; Oliveira, R.M.P.B.; Jesus, E. de; Macedo, Z.S.

2017-01-01

This study aims to characterize technologically three clays employed by ceramic industries in Sergipe state, Brazil. Its potential use for the production of calcined synthetic aggregate to substitute gravel in concrete production was evaluated. The characterization of the clays included particle size and plasticity analysis, X-ray diffraction, differential and thermogravimetric analyses, dilatometry, X-ray fluorescence, organic matter content, cation exchange capacity, specific area, and scanning electron microscopy. Ceramic bodies were uniaxially pressed under 30 MPa, into rectangular and cylindrical shapes. Ceramic bodies of individual clays and also ceramic formulations were fired and subsequently characterized to determine their water absorption, apparent density, compressive strength, and grain morphology. It was observed that, after firing at 1120 deg C, two formulations presented strength, water absorption and specific mass comparable to those of gravel used in concrete. (author)

Annealing behavior and shape memory effect in NiTi alloy processed by equal-channel angular pressing at room temperature

International Nuclear Information System (INIS)

Shahmir, Hamed; Nili-Ahmadabadi, Mahmoud; Wang, Chuan Ting; Jung, Jai Myun; Kim, Hyoung Seop; Langdon, Terence G.

2015-01-01

A martensitic NiTi shape memory alloy was processed successfully by equal-channel angular pressing (ECAP) for one pass at room temperature using a core–sheath billet design. The annealing behavior and shape memory effect of the ECAP specimens were studied followed by post-deformation annealing (PDA) at 673 K for various times. The recrystallization and structural evolution during annealing were investigated by differential scanning calorimetry, dilatometry, X-ray diffraction, transmission electron microscopy and microhardness measurements. The results indicate that the shape memory effect improves by PDA after ECAP processing. Annealing for 10 min gives a good shape memory effect which leads to a maximum in recoverable strain of 6.9 pct upon heating where this is more than a 25 pct improvement compared with the initial state

Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

Science.gov (United States)

Kahrobaee, Saeed; Kashefi, Mehrdad

2015-05-01

The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ɛ carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes.

The lanthanum gallate-based mixed conducting perovskite ceramics

Science.gov (United States)

Politova, E. D.; Stefanovich, S. Yu.; Aleksandrovskii, V. V.; Kaleva, G. M.; Mosunov, A. V.; Avetisov, A. K.; Sung, J. S.; Choo, K. Y.; Kim, T. H.

2005-01-01

The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O3- with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen.

Relaxation dynamics and transformation kinetics of deeply supercooled water: Temperature, pressure, doping, and proton/deuteron isotope effects.

Science.gov (United States)

Lemke, Sonja; Handle, Philip H; Plaga, Lucie J; Stern, Josef N; Seidl, Markus; Fuentes-Landete, Violeta; Amann-Winkel, Katrin; Köster, Karsten W; Gainaru, Catalin; Loerting, Thomas; Böhmer, Roland

2017-07-21

Above its glass transition, the equilibrated high-density amorphous ice (HDA) transforms to the low-density pendant (LDA). The temperature dependence of the transformation is monitored at ambient pressure using dielectric spectroscopy and at elevated pressures using dilatometry. It is found that near the glass transition temperature of deuterated samples, the transformation kinetics is 300 times slower than the structural relaxation, while for protonated samples, the time scale separation is at least 30 000 and insensitive to doping. The kinetics of the HDA to LDA transformation lacks a proton/deuteron isotope effect, revealing that this process is dominated by the restructuring of the oxygen network. The x-ray diffraction experiments performed on samples at intermediate transition stages reflect a linear combination of the LDA and HDA patterns implying a macroscopic phase separation, instead of a local intermixing of the two amorphous states.

In situ X-ray and neutron diffraction of the Ruddlesden-Popper compounds (RE2-xSrx)0.98(Fe0.8Co0.2)1-yMgyO4-δ (RE=La, Pr): Structure and CO2 stability

DEFF Research Database (Denmark)

Chatzichristodoulou, Christodoulos; Hauback, B.C.; Hendriksen, Peter Vang

2013-01-01

The crystal structure of the Ruddlesden-Popper compounds (La 1.0Sr1.0)0.98Fe0.8Co 0.2O4-δ and (La1.2Sr0.8) 0.98(Fe0.8Co0.2)0.8Mg 0.2O4-δ was investigated at 1000 °C in N 2 (aO2=1×10-4) by in-situ powder neutron diffraction. In-situ powder X-ray diffraction (PXD) was also employed to investigate....... The equivalent pseudo-cubic thermal and chemical expansion coefficients are in agreement with values determined by dilatometry. The chemical stability in CO2 containing environments of various Ruddlesden-Popper compounds with chemical formula (RE2-xSr x)0.98(Fe0.8Co0.2) 1-yMgyO4-δ (RE=La, Pr), as well...

Behavior of Eurofer97 reduced activation martensitic steel upon heating and continuous cooling

International Nuclear Information System (INIS)

Danon, A.; Alamo, A.

2002-01-01

The phase transformation behavior of the Eurofer97 steel (Fe9Cr1WVTa) has been investigated. The transformation temperatures upon heating and cooling were determined by dilatometry for different rates in the range 0.0028-100 deg. C/s. The prior austenitic grain size of Eurofer97, measured as a function of the austenitization temperature, does not change appreciably up to 1050 deg. C and then increases with increasing austenite temperature from 1050 up to 1200 deg. C. Continuous cooling transformation diagrams were determined for the austenitization temperatures of 980, 1060 and 1140 deg. C. They show a well-known form with two main phase fields, martensite and ferrite. Values of the critical cooling rates and ferrite start temperatures depend on the austenitization temperature. After thermal cycles samples were further characterized by optical microscopy, scanning electron microscopy and thermoelectric power measurements

Kinetics of anomalous multi-step formation of lath martensite in steel

DEFF Research Database (Denmark)

Villa, Matteo; Pantleon, Karen; Reich, Michael

2014-01-01

A steel containing 16wt.% Cr, 5wt.% Ni and 3wt.% Cu was transformed into martensite by applying isochronal, i.e. constant rate, cooling followed by isothermal holding. The formation of martensite was monitored with dilatometry. A series of retardations and accelerations of the transformation...... was observed during isochronal cooling for cooling rates ranging from 1.5 to 50Kmin−1. The cooling rate in the isochronal stage was observed to influence the transformation rate in the isothermal stage. Electron backscatter diffraction was applied to determine the morphology of the martensite, which...... was of lath type, and to investigate the microstructure of the material. No influence of the cooling rate on the scale of the microstructure was observed. The series of retardations and accelerations of the transformation is interpreted in terms of the combined effect of the strain and interfacial energy...

Synthesis and characterization of SnO2 doped with fluorine by the technique of polymeric precursors; Sintese e caracterizacao de SnO2 dopado com fluor pela tecnica dos precursores polimericos

Energy Technology Data Exchange (ETDEWEB)

Pereira, Gilberto J.; Lopes, Rafael Ialago, E-mail: gilbertop@fei.edu.br [Centro Universitario FEI, Sao Bernardo do Campo, SP (Brazil). Departamento de Engenharia de Materiais

2016-07-01

The present work deals with the synthesis of tin dioxide powders doped with fluorine and chlorine anions to evaluate the influence of these on the physico-chemical properties of SnO2, as well as to verify if the dopant does not make a solid solution with the material and its possible use as sintering additive. The samples were synthesized by Pechini method (polymer precursors) with tin oxalate as a source not contaminated with chlorine of this metal. Specific surface area characterization (BET method) and X-ray diffractometry (XRD) show that doping reduces the particle size of SnO2, being more effective at lower dopant levels. The dilatometry of the doped powders shows a reduction in the beginning and end temperatures of the sintering of the tin dioxide when compared with values in the literature.

Characterization of gadolinia doped ceria prepared with nanostructured powders

International Nuclear Information System (INIS)

Batista, R.M.; Muccillo, E.N.S.

2012-01-01

Gadolinia doped ceria is a potential material for application as solid electrolyte in solid oxide fuel cells that operate at intermediate temperatures. The performance of this kind of device is strongly influenced by the properties of the solid electrolyte, and then, by its microstructure. In this work the microstructure evolution of materials with surface area between 7 and 200 m 2 /g was investigated in detail. Cylindrical pellets were prepared by isostatic compaction and sintered in the 700 deg C to 1400 deg C temperature range. X-ray diffraction experiments were conducted to follow the crystallite growth. The microstructure evolution was accompanied by scanning electron microscopy. The densification was estimated by the geometric parameters of the samples and by dilatometry. The results revealed a fast sintering kinetics for materials with finer particle size, as expected. Different behaviors for crystallite growth were verified. (author)

Evaluation of strontium substituted lanthanum manganite-based solid oxide fuel cell cathodes using cone-shaped electrodes and electrochemical impedance spectroscopy

Directory of Open Access Journals (Sweden)

Kent Kammer Hansen

2018-05-01

Full Text Available Five La1-xSrxMnO3+d-based perovskites (x = 0, 0.05, 0.15, 0.25 and 0.50 were synthesized and investigated by powder XRD, dilatometry and electrochemical impedance spectroscopy measurements and cone-shaped electrode techniques. The thermal expansion coefficient increased with increasing strontium content. It was shown that the total polarization resistance was the lowest for the intermediate compound, La0.95Sr0.05MnO3+d. Two arcs were found in the impedance spectra. These arcs were attributed to two one-electron processes. The results indicate that either Mn(III is the catalytically active species or that the redox capacity is important for the activity of the compounds towards the reduction of oxygen in a solid oxide fuel cell. At higher temperatures, the oxide ionic conductivity may also play a role.

Formation and stabilization of reversed austenite in supermartensitic stainless steel

DEFF Research Database (Denmark)

Nießen, Frank; Grumsen, Flemming Bjerg; Hald, John

2017-01-01

of the reversed austenite phase fraction. Annealing at higher temperatures led to a gradual increase in hardness which was caused by formation of fresh martensite from reversed austenite. It was demonstrated that stabilization of reversed austenite is primarily based on chemical stabilization by partitioning......The formation and stabilization of reversed austenite upon inter-critical annealing was investigated in a X4CrNiMo16-5-1 (EN 1.4418) supermartensitic stainless steel by means of scanning electron microscopy, electron backscatter-diffraction, transmission electron microscopy, energy-dispersive X......-ray spectroscopy and dilatometry. The results were supported by thermodynamics and kinetics models, and hardness measurements. Isothermal annealing for 2 h in the temperature range of 475 to 650 °C led to gradual softening of the material which was related to tempering of martensite and the steady increase...

Synthesis and characterization of SnO2 doped with fluorine by the technique of polymeric precursors

International Nuclear Information System (INIS)

Pereira, Gilberto J.; Lopes, Rafael Ialago

2016-01-01

The present work deals with the synthesis of tin dioxide powders doped with fluorine and chlorine anions to evaluate the influence of these on the physico-chemical properties of SnO2, as well as to verify if the dopant does not make a solid solution with the material and its possible use as sintering additive. The samples were synthesized by Pechini method (polymer precursors) with tin oxalate as a source not contaminated with chlorine of this metal. Specific surface area characterization (BET method) and X-ray diffractometry (XRD) show that doping reduces the particle size of SnO2, being more effective at lower dopant levels. The dilatometry of the doped powders shows a reduction in the beginning and end temperatures of the sintering of the tin dioxide when compared with values in the literature

Phase transition and intramolecular hydrogen bonding in nitro derivatives of ortho-hydroxy acetophenones

Science.gov (United States)

Filarowski, A.; Kochel, A.; Koll, A.; Bator, G.; Mukherjee, S.

2006-03-01

The crystal structures of two ortho-hydroxy aryl ketones (5-chloro-3-nitro-2-hydroxyacetophenone, 5-methyl-3-nitro-2-hydroxyacetophenone and the complex 5-chloro-3-nitro-2-hydroxyacetophenone with 2-aminobenzoic acid (anthranilic acid)) were determined by X-ray diffraction. The existence of an intramolecular hydrogen bond of enol character between the hydroxyl and acetyl groups was found by the X-ray method. The enol character was also confirmed by DFT (B3LYP/6-31+G(d,p)) calculations. A phase transition was found at 138 K in 5-chloro-3-nitro-2-hydroxyacetophenone. This phase transition was investigated by differential scanning calorimetry (DSC), dilatometry, and the dielectric method. A study of the nitro-group dynamics in the ortho-hydroxy acetophenones was carried out with DFT (B3LYP/6-31+G(d,p)) calculations.

Relaxation dynamics and transformation kinetics of deeply supercooled water: Temperature, pressure, doping, and proton/deuteron isotope effects

Science.gov (United States)

Lemke, Sonja; Handle, Philip H.; Plaga, Lucie J.; Stern, Josef N.; Seidl, Markus; Fuentes-Landete, Violeta; Amann-Winkel, Katrin; Köster, Karsten W.; Gainaru, Catalin; Loerting, Thomas; Böhmer, Roland

2017-07-01

Above its glass transition, the equilibrated high-density amorphous ice (HDA) transforms to the low-density pendant (LDA). The temperature dependence of the transformation is monitored at ambient pressure using dielectric spectroscopy and at elevated pressures using dilatometry. It is found that near the glass transition temperature of deuterated samples, the transformation kinetics is 300 times slower than the structural relaxation, while for protonated samples, the time scale separation is at least 30 000 and insensitive to doping. The kinetics of the HDA to LDA transformation lacks a proton/deuteron isotope effect, revealing that this process is dominated by the restructuring of the oxygen network. The x-ray diffraction experiments performed on samples at intermediate transition stages reflect a linear combination of the LDA and HDA patterns implying a macroscopic phase separation, instead of a local intermixing of the two amorphous states.

Synthesis， Characterization and Inhibition Effects of Vanadium Substituted Dawson-type Heteropoly Acids(Mo， P)

Institute of Scientific and Technical Information of China (English)

YIN Yan-bing; YANG Yu-lin; FAN Rui-qing; ZHU Yang-qing; SUN Ji-ru

2011-01-01

Four new vanadium substituted Dawson-type heteropoly acids H7[P2Mo17VO62]·39H2O(1),H8[P2Mo16V2O62]·41H2O(2), H9[P2Mo15V3O62]·51H2O(3) and H8[P2Mo14V4O62H2]·45H2O(4) were prepared respectively. Their structures were determined by IR and ICP. The inhibition effects of vanadium substituted Dawson-type heteropoly acids(Mo, P) on free radical polymerization of methyl methacrylate(MMA) were investigated by dilatometry. The results show that the rate of the polymerization of MMA decreases and the inhibition effects of the four heteropoly acids reach the inhibitor performance of hydroquinone at a certain ratio.

Strain-enhanced sintering of iron powders

Energy Technology Data Exchange (ETDEWEB)

Amador, D.R.; Torralba, J.M. [Universidad Carlos III de Madrid, Departamento de Ciencias de Materiales e Ingenieria Metalurgica, Leganes, Madrid (Spain); Monge, M.A.; Pareja, R. [Universidad Carlos III de Madrid, Departamento de Fisica, Madrid (Spain)

2005-02-01

Sintering of ball-milled and un-milled Fe powders has been investigated using dilatometry, X-ray, density, and positron annihilation techniques. A considerable sintering enhancement is found in milled powders showing apparent activation energies that range between 0.44 and 0.80 eV/at. The positron annihilation results, combined with the evolution of the shrinkage rate with sintering temperature, indicate generation of lattice defects during the sintering process of milled and un-milled powders. The sintering enhancement is attributed to pipe diffusion along the core of moving dislocations in the presence of the vacancy excess produced by plastic deformation. Positron annihilation results do not reveal the presence of sintering-induced defects in un-milled powders sintered above 1200 K, the apparent activation energy being in good agreement with that for grain-boundary diffusion in {gamma}-Fe. (orig.)

Study of uranium - 20 Wt per cent plutonium-niobium alloys (1963)

International Nuclear Information System (INIS)

Abgrall, J.; Barthelemy, P.; Boucher, R.

1963-01-01

U-Pu-Nb alloys containing 20 wt per cent Pu and 10 - 20 - 30 - 40 - 50 or 60 wt per cent Nb have been studied principally to determine the feasibility of their use as fuel element. The fabrication, casting and homogenisation presented certain difficulties due specially to niobium. The transformation temperatures, thermal expansion coefficients and nature of phases have been determined by thermal analysis, dilatometry, micrography and X Rays diffraction. For similar compositions, U-Pu-Mo and U-Pu-Nb alloys have many common points concerning the presence of zeta phase (up to 40 wt per cent Nb), the coefficients of expansion, the good behaviour during thermal cycling and the good resistance to air oxidation in spite of zeta phase. In consequence, irradiation tests in EL 3 reactor (Saclay) will be carried out in the near future. (authors) [fr

A quantitative atom probe study of the Nb excess at prior austenite grain boundaries in a Nb microalloyed strip-cast steel

International Nuclear Information System (INIS)

Felfer, Peter J.; Killmore, Chris R.; Williams, Jim G.; Carpenter, Kristin R.; Ringer, Simon P.; Cairney, Julie M.

2012-01-01

Most modern HSLA steels rely on the effect of Nb in steels to achieve the properties desired for a specific application. While the role of Nb in forming precipitates has been well characterized, its role in a solid solution is less well understood due to the difficulty of obtaining quantitative experimental data. In the current work, site-specific atom probe tomography was used to quantify the amount of Nb present at prior austenite grain boundaries in a commercial strip-cast steel, produced via the Castrip ® process. This was compared to the amount of Nb found at ferrite–ferrite grain boundaries that had formed during the transformation from austenite to ferrite. With the interfacial excess Nb measured, thermodynamic calculations were carried out and compared to the change in transformation temperature obtained by dilatometry, with reference to a comparable Nb free, strip-cast steel.

Superior sinterability of nano-crystalline gadolinium doped ceria powders synthesized by co-precipitation method

International Nuclear Information System (INIS)

Hari Prasad, D.; Kim, H.-R.; Park, J.-S.; Son, J.-W.; Kim, B.-K.; Lee, H.-W.; Lee, J.-H.

2010-01-01

Reduced sintering temperature of doped ceria can greatly simplify the fabrication process of solid oxide fuel cells (SOFCs) by utilizing the co-firing of all cell components with a single step. In the present study, nano-crystalline gadolinium doped ceria (GDC) powders of high sinterability at lower sintering temperature has been synthesized by co-precipitation at room temperature. The successful synthesis of nano-crystalline GDC was confirmed by XRD, TEM and Raman spectroscopy analysis. Dilatometry studies showed that GDC prepared by this method can be fully densified (97% relative density) at a sintering temperature of 950 o C which is fairly lower than ever before. It has also been found that the sintered samples have a higher ionic conductivity of 1.64 x 10 -2 S cm -1 at 600 o C which is suitable for the intermediate temperature SOFC application.

Effects of additives on the sintering of UO2.Gd2O3 nuclear fuel

International Nuclear Information System (INIS)

Pagano Junior, Luciano

2009-01-01

The addition of 0.5wt% TiO 2 , Nb 2 O 5 , SiO 2 , Fe 2 O 3 and Al(OH) 3 in the UO 2 ·7%Gd 2 O 3 nuclear fuel and the effect on its sintering kinetics under a 99.999% H 2 atmosphere were investigated by stepwise isothermal dilatometry. This fuel, used as burnable poison in nuclear power plants, presents a diffusion barrier around 1573 K that impairs densification. The aid of the sintering additives TiO 2 , Al(OH) 3 , Nb 2 O 5 and Fe 2 O 3 turned out to be effective to obtain the required final density, unlike the effect observed for the SiO 2 -doped composition. The activation energy for the intermediate sintering stage was calculated by stepwise isothermal dilatometry method and a positive correlation with the sintered body density was found. The method was valid for part of the intermediate sintering stage, in the range from 1200 K to 1700 K for the doped compositions and with no additive, except for the SiO 2 -doped one, whose validity range was between 1500 K and 1900 K. The energy-density correlation was not valid for the SiO 2 -doped composition, whose effect was to reduce the final density. This anomalous behavior may be attributed to the intense loss of Si mass, probably due to lower oxides volatilization, during the initial sintering stage at temperatures lower than 1173 K. Similar loss, but no so intense, was observed for the Al(OH) 3 -doped composition in the temperature interval from 1173 K to 1573 K. The Si concentration decrease to residual values of dozens of parts per million may explain its anomalous behavior. The positive correlation between activation energy and sintered body density may be explained by the inhibitor role played by the TiO 2 , Nb 2 O 5 , Fe 2 O 3 and Al(OH) 3 additives on the diffusion mechanisms that enhance the coarsening regime. As a consequence, the densification mechanisms are favored in the competition for the surface free energy. The coarsening-densification transition temperature model, originally suggested for the UO 2

LiV2O4: A heavy fermion transition metal oxide

International Nuclear Information System (INIS)

Shinichiro, Kondo

1999-01-01

The format of this dissertation is as follows. In the remainder of Chapter 1, brief introductions and reviews are given to the topics of frustration, heavy fermions and spinels including the precedent work of LiV 2 O 4 . In Chapter 2, as a general overview of this work the important publication in Physical Review Letters by the author of this dissertation and collaborators regarding the discovery of the heavy fermion behavior in LiV 2 O 4 is introduced [removed for separate processing]. The preparation methods employed by the author for nine LiV 2 O 4 and two Li 1+x Ti 2-x O 4 (x = 0 and 1/3) polycrystalline samples are introduced in Chapter 3. The subsequent structural characterization of the LiV 2 O 4 and Li 1+x Ti 2-x O 4 samples was done by the author using thermogravimetric analysis (TGA), x-ray diffraction measurements and their structural refinements by the Rietveld analysis. The results of the characterization are detailed in Chapter 3. In Chapter 4 magnetization measurements carried out by the author are detailed. In Chapter 5, after briefly discussing the resistivity measurement results including the single-crystal work by Rogers et al., for the purpose of clear characterization of LiV 2 O 4 it is of great importance to introduce in the following chapters the experiments and subsequent data analyses done by his collaborators. Heat capacity measurements (Chapter 6) were carried out and analyzed by Dr. C.A. Swenson, and modeled theoretically by Dr. D.C. Johnston. In Chapter 7 a thermal expansion study using neutron diffraction by Dr. O. Chmaissem et al. and capacitance dilatometry measurements by Dr. C.A. Swenson are introduced. The data analyses for the thermal expansion study were mainly done by Dr. O. Chmaissem (for neutron diffraction) and Dr. C.A. Swendon (for dilatometry), with assistances by Dr. J.D. Jorgensen, Dr. D.C. Johnston, and S. Kondo the author of this dissertation. Chapter 8 describes nuclear magnetic resonance (NMR) measurements and

Influence of use of quartzite waste in moisture expansion of masses for ceramic tiles; Influencia do uso de residuo de quartzito na expansao por umidade de massas de revestimentos ceramicos planos

Energy Technology Data Exchange (ETDEWEB)

Medeiros, R.R.; Goncalves, W. P.; Cartaxo, J.M.; Ferreira, H.S.; Neves, G.A.; Ferreira, H.C., E-mail: rosinaldo.medeiros@ufrr.br, E-mail: wherllyson@yahoo.com.br, E-mail: julianamelo25@gmail.com, E-mail: hebersivini@gmail.com, E-mail: gelmires.neves@ufcg.edu.br, E-mail: heber.carlos@ufcg.edu.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais

2017-04-15

The moisture expansion (ME) is characterized as an increase in physical dimensions of ceramic body when in contact with water (liquid or vapor). The ME phenomenon may contribute to the appearance of serious pathology in ceramic tiles such as cracks, detachment or more severe damages. This work aimed to study the problem of ME in ceramic masses added with quartzite waste for use in tiles using the dilatometry and three-point flexural strength methods. The raw materials were processed and characterized by laser diffraction particle size analysis, plasticity, chemical analysis, thermogravimetric and differential thermal analysis, and X-ray diffraction. The results showed that the addition of quartzite waste generally elevated ME values for bodies fired at temperatures below 1100 °C. For bodies fired at 1200 °C the results indicated high mechanical performance and ME decrease, and the best results for additive formulations was 15% of quartzite. (author)

Colossal negative thermal expansion in reduced layered ruthenate.

Science.gov (United States)

Takenaka, Koshi; Okamoto, Yoshihiko; Shinoda, Tsubasa; Katayama, Naoyuki; Sakai, Yuki

2017-01-10

Large negative thermal expansion (NTE) has been discovered during the last decade in materials of various kinds, particularly materials associated with a magnetic, ferroelectric or charge-transfer phase transition. Such NTE materials have attracted considerable attention for use as thermal-expansion compensators. Here, we report the discovery of giant NTE for reduced layered ruthenate. The total volume change related to NTE reaches 6.7% in dilatometry, a value twice as large as the largest volume change reported to date. We observed a giant negative coefficient of linear thermal expansion α=-115 × 10 -6  K -1 over 200 K interval below 345 K. This dilatometric NTE is too large to be attributable to the crystallographic unit-cell volume variation with temperature. The highly anisotropic thermal expansion of the crystal grains might underlie giant bulk NTE via microstructural effects consuming open spaces in the sintered body on heating.

High-temperature magnetisation measurements on the pearlite transformation kinetics in nearly eutectoid steel

International Nuclear Information System (INIS)

Dijk, N.H. van; Offerman, S.E.; Klaasse, J.C.P.; Sietsma, J.; Zwaag, S. van der

2004-01-01

The isothermal transformation kinetics of the austenite to pearlite transformation in (nearly) eutectoid steel was studied by in situ magnetisation measurements at high temperatures. In eutectoid steel the high temperature austenite (γ-Fe) phase decomposes into pearlite, which consists of a lamellar structure of ferrite (α-Fe) and cementite (Fe 3 C). Below the Curie temperature of ferrite T C =1043 K the ferrite phase fraction can be probed by the magnetisation measurements. For our nearly eutectoid steel not only pearlite but also a small fraction of pro-eutectoid ferrite is formed. The transformation kinetics of the pearlite and the pro-eutectoid ferrite is studied by magnetisation measurements as a function of the isothermal transformation temperature and compared with the results from additional dilatometry measurements. The transformation kinetics was found to vary over four orders of magnitude over the range of transformation temperatures and was compared with model predictions

Comments on the equilibrium diagram of the Ti-Zr system

International Nuclear Information System (INIS)

Ruch, M.; Arias, D.

1993-01-01

The Ti-Zr system is a continuous series of solid solutions in both the α- and β-phases, with a congruent minimum at Ti-50at%Zr. The equilibrium diagram has been reviewed by Murray in 1981, who accepts the α/β temperature for this minimum determined by Farrar and Adler by metallographic techniques. Etchessahar and Debuigne measured by dilatometry a transformation temperature of (894 ±)K and (859±2)K for α/α + β and β/α + β respectively, and later in a high temperature Calvet microcalorimeter, 883K. Blacktop et al find that this value is consistent with their measurements of the α/β transformation temperature in Ti-40%Zr and Ti-60%Zr in a high temperature calorimeter. In the present work, the α/β transformation temperature was measured by several techniques. The effect of impurities is considered in both transformation temperature and microstructure of product phases

Production and characterization of a Fe-Ni alloy by aqueous coloidal processing and solid state reaction; Producao e caracterizacao de uma liga Fe-Ni obtida por processamento coloidal aquoso e reacao de estado solido

Energy Technology Data Exchange (ETDEWEB)

Vieira Junior, Luiz Eloi; Rodrigues Neto, Joao Batista; Klein, AloIsio Nelmo; Hotza, Dachamir, E-mail: eloi_junior@hotmail.com, E-mail: jbrn.ufsc@gmail.com, E-mail: a.n.klein@ufsc.br, E-mail: d.hotza@ufsc.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis, (Brazil); Moreno, Rodrigo, E-mail: rmoreno@icv.csic.es [Instituto de Ceramica y Vidrio (ICV/CSIC), Madri (Spain)

2016-10-15

Colloidal processing is a widely used technique to produce ceramic components. Several papers have been published in the last decade presenting the possibility to obtain aqueous concentrate stable suspension of metallic particles from their pH control and using dispersants. This paper aims to study the production of a steel with austenitic microstructure using elemental iron (Fe) and nickel (Ni) powders via colloidal route. For this, Zeta potential measurements were performed between pH 2 and 12 to Fe30Ni wt% composition. Aqueous suspensions reached solids concentrations of up to 45% v/v and processed by slip casting. The compacts were characterized by density (Archimedes), differential thermal analysis (DTA) and dilatometry. After sintering at 900°C to 1100°C/1h, the sintered bodies presented a microstructure with of annealing twins, porosity less than 10 %v/v approximate Vickers microhardness of 160 HV. (author)

Assessment of potential Rio Grande do Norte, Brazil, clays when subjected to high rates of heating; Avaliacao da potencialidade de argilas do Rio Grande do Norte quando submetidas a elevadas taxas de aquecimento

Energy Technology Data Exchange (ETDEWEB)

Filgueira, R L; Pereira, L M; Dutra, R P.S.; Nascimento, R M [Universidade Federal do Rio Grande do Norte (DEMat/CT/UFRN), Natal, RN (Brazil). Centro de Tecnologia. Dept. de Engenharia de Materiais

2009-07-01

In this work we study three clays of the state of Rio Grande do Norte, Brazil, to evaluate the potential them when subjected to high rates of heating. The samples were formed by pressing and subject to rates of 5 deg C / min, 10 deg C / min and 15 deg C / min, with temperature of 950 deg C. This study determined the technological properties of the samples. The mineralogical composition was identified by X-ray diffraction. The chemical composition was determined by Xray fluorescence. The Atterberg limits, were used to classify the samples on the plasticity. Were also performed: dilatometry, size analysis and scanning electron microscopy. The examination of the processing variables and the intrinsic characteristics of each material indicates that the RX clay showed the best results for the manufacture of blocks and tiles. The techniques used in this study were efficient and the initial objectives were achieved. (author)

Study on the welding continuous cooling transformation and weldability of SA508Gr4 steel for nuclear pressure vessels

International Nuclear Information System (INIS)

Bai, Qingwei; Ma, Yonglin; Xing, Shuqing; Chen, Zhongyi

2017-01-01

SA508Gr4 is a newly developed high-strength steel for nuclear reactor pressure vessels. Its welding characteristics remain largely unexplored. In this work, the simulated heat affected zone continuous cooling transformation (SH-CCT) diagram of SA508Gr4 steel was constructed and the high-temperature cooling phase compositions and the properties of the heat affected zone (HAZ) were characterized using dilatometry and microscopic tests. The results show that the phase transformation in the HAZ was divided into bainite and martensite transformation stages. When 4.6 ≤ t_8_/_5 (the HAZ cooling time from 800 C to 500 C) ≤ 15 s, lath-shaped martensite was fully developed, resulting in extensive hardening and cold cracking in the HAZ, while the cooling time required to form the bainite completely exceeds 1 200 s. Thus, to improve weld quality, preheating to 196 C or higher is recommended.

Finite element modeling of camber evolution during sintering of bi-layers

DEFF Research Database (Denmark)

Tadesse Molla, Tesfaye; Ni, De Wei; Bulatova, Regina

2014-01-01

The need for understanding the mechanisms and optimization of shape distortions during sintering of bilayers is necessary while producing structures with functionally graded architectures. A finite element model based on the continuum theory of sintering was developed to understand the camber...... developments during sintering of bilayers composed of La0.85Sr0.15MnO3 and Ce0.9Gd0.1O1.95 tapes. Free shrinkage kinetics of both tapes were used to estimate the parameters necessary for the finite element models. Systematic investigations of the factors affecting the kinetics of distortions such as gravity...... and friction as well as the initial geometric parameters of the bilayers were made using optical dilatometry experiments and the model. The developed models were able to capture the observed behaviors of the bilayers’ distortions during sintering. Finally, we present the importance of understanding and hence...

Mechanical and thermal expansion properties of β-eucryptite prepared by sol-gel methods and hot pressing

International Nuclear Information System (INIS)

Xia, L.; Wen, G.W.; Qin, C.L.; Wang, X.Y.; Song, L.

2011-01-01

Research highlights: → Dense LAS glass-ceramics were fabricated by sol-gel and hot pressing technique. → The LAS glass-ceramics have relative good mechanical properties. → The negative thermal expansion behavior of LAS glass-ceramics was investigated. -- Abstract: The microstructures, mechanical properties and thermal expansion behavior of monolithic lithium aluminosilicate glass-ceramics, prepared by sol-gel method and hot pressing, were investigated by using X-ray diffraction, scanning and transmission electron microscopies, three-point bend tests and dilatometry. β-eucryptite appeared as main phase in the monolithic lithium aluminosilicate glass-ceramics. The glass ceramics exhibited high relative densities and the average flexural strength and fracture toughness values were 154 MPa and 2.46 MPa m 1/2 , respectively. The lithium aluminosilicate glass-ceramics hot pressed 1300 and 1350 o C demonstrated negative coefficient of thermal expansion, which was affected by amount and type of crystalline phases.

Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

Directory of Open Access Journals (Sweden)

Pieczonka T.

2017-06-01

Full Text Available Aluminium oxide layer on aluminium particles cannot be avoided. However, to make the metal-metal contacts possible, this sintering barrier has to be overcome in some way, necessarily to form sintering necks and their development. It is postulated that the disruption of alumina layer under sintering conditions may originate physically and chemically. Additionally, to sinter successfully non alloyed aluminium powder in nitrogen, the operation of both types mechanism is required. It is to be noted that metallic aluminium surface has to be available to initiate reactions between aluminium and the sintering atmosphere, i.e. mechanical disruption of alumina film precedes the chemical reactions, and only then chemically induced mechanisms may develop. Dilatometry, gravimetric and differential thermal analyses, and microstructure investigations were used to study the sintering response of aluminium at 620°C in nitrogen, which is the only sintering atmosphere producing shrinkage.

Dimensional behavior of Ni-YSZ composites during redox cycling

DEFF Research Database (Denmark)

Pihlatie, Mikko; Kaiser, Andreas; Larsen, Peter Halvor

2009-01-01

The dimensional behavior of Ni-yttria-stabilized zirconia (YSZ) cermets during redox cycling was tested in dilatometry within the temperature range 600-1000 degrees C. The effect Of humidity oil redox stability was investigated at intermediate and low temperatures. We show that both the sintering...... of nickel depending on temperature of the initial reduction and the operating conditions, and the temperature of reoxidation are very important for the size of the dimensional change. Cumulative redox strain (CRS) is shown to be correlated with temperature. Measured maximum CRS after three redox cycles...... varies within 0.25-3.2% dL/L in dry gas and respective temperature range of 600-1000 degrees C. A high degree of redox reversibility was reached at low temperature. however. reversibility is lost at elevated temperatures. We found that at 850 degrees C, 6% steam and a very high p(H2O)/p(H2) ratio...

Study on the welding continuous cooling transformation and weldability of SA508Gr4 steel for nuclear pressure vessels

Energy Technology Data Exchange (ETDEWEB)

Bai, Qingwei; Ma, Yonglin; Xing, Shuqing; Chen, Zhongyi [Inner Mongolia Univ. of Science and Technology, Baotou (China). School of Material and Metallurgy; Kang, Xiaolan [Baotou Vocational and Technical College (China)

2017-02-15

SA508Gr4 is a newly developed high-strength steel for nuclear reactor pressure vessels. Its welding characteristics remain largely unexplored. In this work, the simulated heat affected zone continuous cooling transformation (SH-CCT) diagram of SA508Gr4 steel was constructed and the high-temperature cooling phase compositions and the properties of the heat affected zone (HAZ) were characterized using dilatometry and microscopic tests. The results show that the phase transformation in the HAZ was divided into bainite and martensite transformation stages. When 4.6 ≤ t{sub 8/5} (the HAZ cooling time from 800 C to 500 C) ≤ 15 s, lath-shaped martensite was fully developed, resulting in extensive hardening and cold cracking in the HAZ, while the cooling time required to form the bainite completely exceeds 1 200 s. Thus, to improve weld quality, preheating to 196 C or higher is recommended.

Thermal conductivity and expansion enhancement associated with formation of the superionic state in SrCl2

International Nuclear Information System (INIS)

Moore, J.P.; Weaver, F.J.; Graves, R.S.; McElroy, D.L.

1983-01-01

A second-order phase transition in SrCl 2 near 1000 K produces superionic conduction and is often called the Bredig transition. Fine-grained, 99% dense, SrCl 2 samples containing three volume percent TiO 2 to reduce radiant transport were used to measure the differential thermal expansion coefficient (α) by push-rod dilatometry and the thermal conductivity (lambda) by a radial heat flow method. Both properties show maxima near the Bredig transition. The peak α-value is over 75 x 10 -6 K -1 . The data obtained from the radial heat flow method show good agreement with earlier tests at low temperatures, and the high temperature results show a local enhancement of lambda if about 0.06 W/m.K. This enhancement cannot be attributed to electronic or radiant transport, but is due to a new mechanism of thermal diffusion of vacancy-anion interstitial pairs in the superionic state

Assessment of potential Rio Grande do Norte, Brazil, clays when subjected to high rates of heating

International Nuclear Information System (INIS)

Filgueira, R.L.; Pereira, L.M.; Dutra, R.P.S.; Nascimento, R.M.

2009-01-01

In this work we study three clays of the state of Rio Grande do Norte, Brazil, to evaluate the potential them when subjected to high rates of heating. The samples were formed by pressing and subject to rates of 5 deg C / min, 10 deg C / min and 15 deg C / min, with temperature of 950 deg C. This study determined the technological properties of the samples. The mineralogical composition was identified by X-ray diffraction. The chemical composition was determined by Xray fluorescence. The Atterberg limits, were used to classify the samples on the plasticity. Were also performed: dilatometry, size analysis and scanning electron microscopy. The examination of the processing variables and the intrinsic characteristics of each material indicates that the RX clay showed the best results for the manufacture of blocks and tiles. The techniques used in this study were efficient and the initial objectives were achieved. (author)

Studies of Fe-Co based perovskite cathodes with different A-site cations

DEFF Research Database (Denmark)

Kammer Hansen, K.

2006-01-01

Iron-cobalt based perovskite cathodes with different A-site cations ((Ln(0.6)Sr(0.4))(0.99)Fe0.8Co0.2O3-delta, where Ln is La, Pr, Sm or Gd) have been synthesised, characterised by a powder XRD, dilatometry, 4-point DC conductivity measurements, and electrochemical impedance spectroscopy (EIS......) on cone shaped electrodes. In addition to this scanning electron microscopy (SEM) was used to characterise the bars. XRD revealed that only the La-containing perovskite was hexagonal. The Pr and Sm perovskites were orthorhombic. The gadolinium-based perovskite was a two phase system consisting...... of an orthorhombic and a cubic perovskite phase. The thermal expansion coefficient (TEC) increased systematically with a decrease in the size of the A-site cation until the gadoliniurn-containing perovskite where the TEC decreases abruptly. The total electric conductivity was the highest for the La-based perovskite...

Sintering and Electrical Characterization of La and Nb Co‐doped SrTiO3 Electrode Materials for Solid Oxide Cell Applications

DEFF Research Database (Denmark)

Sudireddy, Bhaskar Reddy; Agersted, Karsten

2014-01-01

Single‐phase lanthanum and niobium co‐doped strontium titanate (Sr1–3x/2LaxTi0.9Nb0.1O3; x = 0–0.02) ceramics were prepared. Dilatometry in reducing atmosphere showed an increase in the sintering rate and sintered density with an increase in La amount. Microscopy of fractured surfaces of sintered...... samples showed that the average grain size increased drastically in reducing conditions with increasing La content (and associated A‐site vacancies). By incorporating 2 mol.% La, the electronic conductivity significantly improved from 80 to 135 S cm−1 at 1,000 °C, and even larger improvements were...... observed at lower temperatures. These observations demonstrate the flexibility in tailoring the microstructure and electronic transport properties by doping small amounts of La into the Nb‐doped SrTiO3 and show that Sr1–3x/2LaxTi0.9Nb0.1O3 is a potential electrode material for solid oxide cells....

Thermal expansion of organic superconductor κ-(D4-BEDT-TTF)2Cu{N(CN)2}Br. Isotopic effect

Science.gov (United States)

Dolbin, A. V.; Khlistuck, M. V.; Eselson, V. B.; Gavrilko, V. G.; Vinnikov, N. A.; Basnukaeva, R. M.; Konstantinov, V. A.; Nakazawa, Y.

2017-12-01

Linear thermal expansion coefficient (LTEC) of single crystal κ-(D4-BEDT-TTF)2Cu[N(CN)2]Br was studied across the crystal layers in the temperature range 2-290 K using the method of precise capacitive dilatometry. Below Tc = 11.6 K the LTEC of the sample had a small negative value, which is apparently due to the transition from the paramagnetic metal in the superconducting state. There was a bend of temperature dependence of the LTEC, which shows broad peak around 40 K and can be attributed to the elastic lattice anomaly around the end-point of Mott boundary. A sharp jump in the LTEC values and hysteresis was observed in the area of Tg ˜ 75-77 K, what is likely explained by the transition in a glass-like state. The isotope effect in the thermal expansion is discusses, which manifested itself in a shift of the phase transitions in comparison with fully deuterated BEDT-TTF sample.

The lanthanum gallate-based mixed conducting perovskite ceramics

International Nuclear Information System (INIS)

Politova, E.D.; Stefanovich, S.Yu.; Aleksandrovskii, V.V.; Kaleva, G.M.; Mosunov, A.V.; Avetisov, A.K.; Sung, J.S.; Choo, K.Y.; Kim, T.H.

2005-01-01

The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O 3-δ with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

The lanthanum gallate-based mixed conducting perovskite ceramics

Energy Technology Data Exchange (ETDEWEB)

Politova, E.D.; Stefanovich, S.Yu.; Aleksandrovskii, V.V.; Kaleva, G.M.; Mosunov, A.V.; Avetisov, A.K. [L.Ya. Karpov Institute of Physical Chemistry, Vorontsovo pole 10, 105064 Moscow (Russian Federation); Sung, J.S.; Choo, K.Y.; Kim, T.H. [Korea Institute of Energy Research, 71-2 Jang-dong Yooseong, Daejeon (Korea)

2005-01-01

The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O{sub 3-{delta}} with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Thermal expansion characteristics of Fe-9Cr-0.12C-0.56Mn-0.24V-1.38W-0.06Ta (wt.%) reduced activation ferritic-martensitic steel

Science.gov (United States)

Subramanian, Raju; Tripathy, Haraprasanna; Rai, Arun Kumar; Hajra, Raj Narayan; Saibaba, Saroja; Jayakumar, Tammana; Rajendra Kumar, Ellappan

2015-04-01

The lattice and bulk thermal expansion behavior of an Indian version of reduced activation ferritic-martensitic (INRAFM) steel has been quantified using high temperature X-ray diffraction and dilatometry. The lattice parameter of tempered α-ferrite phase exhibited a smooth quadratic increase with temperature, while that of γ-austenite remained fairly linear up to 1273 K. The results suggest that α-ferrite + Carbides → γ-austenite transformation occurs upon continuous heating in the temperature range, 1146 ⩽ T ⩽ 1173 K. Further, this transformation is found to be accompanied by a reduction in average atomic volume. The mean linear thermal expansion coefficients of tempered α-ferrite and γ-austenite phases are estimated to be about 1.48 × 10-5 and 2.4 × 10-5 K-1 respectively. The magnetic contribution to relative thermal dilatation (Δl/l298)mag is found to be small and negative, as compared to phonon contribution.

Sintering process optimization for multi-layer CGO membranes by in situ techniques

DEFF Research Database (Denmark)

Kaiser, Andreas; Prasad, A.S.; Foghmoes, Søren Preben Vagn

2013-01-01

The sintering of asymmetric CGO bi-layers (thin dense membrane on a porous support; Ce0.9Gd0.1O1.95-delta = CGO) with Co3O4 as sintering additive has been optimized by combination of two in situ techniques. Optical dilatometry revealed that bi-layer shape and microstructure are dramatically...... changing in a narrow temperature range of less than 100 degrees C. Below 1030 degrees C, a higher densification rate in the dense membrane layer than in the porous support leads to concave shape, whereas the densification rate of the support is dominant above 1030 degrees C, leading to convex shape. A fiat...... bi-layer could be prepared at 1030 degrees C, when shrinkage rates were similar. In situ van der Pauw measurements on tape cast layers during sintering allowed following the conductivity during sintering. A strong increase in conductivity and in activation energy E-a for conduction was observed...

Comparative study of ceramic tiles produced in the Town of Goytacazes / RJ (Brazil)

International Nuclear Information System (INIS)

Almeida, L.L.P. de; Pacheco, A.T.; Carreiro, R.S; Petrucci, L.J.T.

2011-01-01

The city of the Campos dos Goytacazes, situated in the region north of the state of Rio de Janeiro, presents characteristics place that it enter the producing greater of blocks and ceramic roofing tiles for the domestic market. This work makes a study enters four manufacturers of ceramic roofing tiles of the city of the Campos dos Goytacazes/RJ, to analysis comparatively its results according to in agreement the characterization submitted to dilatometry, Thermogravimetry, Differential Thermal Analysis and X-ray diffraction for the physical tests the tiles were collected after burning and the tests under Bylaw NBR 15310. The results had indicated a significant variation in the values of water absorption of each manufacturer. The same ones demonstrate that the ceramic roofing tiles of Campos of the Goytacazes present a uniformity in the results, being that it needs technological accompaniment during the manufacture process, to improve its properties and its quality for adequacy to the normative parameters of the ABNT. (author)

Properties of ceria doped with gadolinia via microwave-assisted hydrothermal synthesis

International Nuclear Information System (INIS)

Carregosa, J.D.C.; Oliveira, R.M.P.B.; Macedo, D.A.; Nascimento, R.M.

2016-01-01

The solid solution of CeO_2 doped with Gd"3"+ (CGO) is a promising candidate for electrolyte in Solid Oxide Full Cells (SOFCs) operating in intermediate and low temperatures. The reduction of the working temperature of these energy conversion devices is the great technological challenge to its marketing. In this work, nanocrystalline powders of Ce_1_-_xGd_xO_2_-_x_/_2 with x=0, x=0.1 e x=0.2 were obtained via microwave-hydrothermal synthesis at low temperature and times of synthesis (10 and 20 min at 120° C). The powders were analyzed by TG-DTA, DRX and dilatometry. The results showed characteristic peaks of the cubic fluorite-type structure, referring to the cerium oxide (CeO_2), without the presence of secondary peaks. It was also observed that the samples processed at levels of 10 and 20 minutes showed distinct behaviors in contrast to the concentrations of Gd"3"+. (author)

Kinetics of anomalous multi-step formation of lath martensite in steel

International Nuclear Information System (INIS)

Villa, Matteo; Pantleon, Karen; Reich, Michael; Kessler, Olaf; Somers, Marcel A.J.

2014-01-01

A steel containing 16 wt.% Cr, 5 wt.% Ni and 3 wt.% Cu was transformed into martensite by applying isochronal, i.e. constant rate, cooling followed by isothermal holding. The formation of martensite was monitored with dilatometry. A series of retardations and accelerations of the transformation was observed during isochronal cooling for cooling rates ranging from 1.5 to 50 K min −1 . The cooling rate in the isochronal stage was observed to influence the transformation rate in the isothermal stage. Electron backscatter diffraction was applied to determine the morphology of the martensite, which was of lath type, and to investigate the microstructure of the material. No influence of the cooling rate on the scale of the microstructure was observed. The series of retardations and accelerations of the transformation is interpreted in terms of the combined effect of the strain and interfacial energy introduced in the system during martensite formation, which stabilizes austenite, and autocatalytic nucleation of martensite

PHASE TRANSITION OF CaFeO2.5 AT HIGH TEMPERATURE

Directory of Open Access Journals (Sweden)

T Labii

2011-12-01

Full Text Available The numerous studies conducted on the structure of CaFeO2.5 showed that the material undergoes a series of transformations based on temperature. The first one appears around 700 K and indicates the evolution of the phasemagnetic material to a paramagnetic phase. At about 970 K the structure of CaFeO2.5 changes from rhombohedral to centered structure. Finally, around 1180 K it undergoes the transition to a structure that has been described as incommensurate modulated structure. We have observed the behavior of the material beyond this temperature by dilatometry, DSC and TGA. The tests conducted on a single crystal CaFeO2.5 confirm the changes already observed.For the first time there was a dilatometric anomaly (confirmed by DSC and TGA at 1310 K. This anomaly appears only in the crystallographic direction b which should probably be a  commensurate transformation of the material.

Properties of ceria doped with gadolinia via microwave-assisted hydrothermal synthesis; Propriedades de ceria dopada com gadolinia via sintese hidrotermal assistida por micro-ondas

Energy Technology Data Exchange (ETDEWEB)

Carregosa, J.D.C.; Oliveira, R.M.P.B. [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil); Macedo, D.A. [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil); Nascimento, R.M., E-mail: jdcovello@hotmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

2016-07-01

The solid solution of CeO{sub 2} doped with Gd{sup 3+} (CGO) is a promising candidate for electrolyte in Solid Oxide Full Cells (SOFCs) operating in intermediate and low temperatures. The reduction of the working temperature of these energy conversion devices is the great technological challenge to its marketing. In this work, nanocrystalline powders of Ce{sub 1-x}Gd{sub x}O{sub 2-x/2} with x=0, x=0.1 e x=0.2 were obtained via microwave-hydrothermal synthesis at low temperature and times of synthesis (10 and 20 min at 120° C). The powders were analyzed by TG-DTA, DRX and dilatometry. The results showed characteristic peaks of the cubic fluorite-type structure, referring to the cerium oxide (CeO{sub 2}), without the presence of secondary peaks. It was also observed that the samples processed at levels of 10 and 20 minutes showed distinct behaviors in contrast to the concentrations of Gd{sup 3+}. (author)

Sintered glass ceramic composites from vitrified municipal solid waste bottom ashes

International Nuclear Information System (INIS)

Aloisi, Mirko; Karamanov, Alexander; Taglieri, Giuliana; Ferrante, Fabiola; Pelino, Mario

2006-01-01

A glass ceramic composite was obtained by sinter-crystallisation of vitrified municipal solid waste bottom ashes with the addition of various percentages of alumina waste. The sintering was investigated by differential dilatometry and the crystallisation of the glass particles by differential thermal analysis. The crystalline phases produced by the thermal treatment were identified by X-ray diffraction analysis. The sintering process was found to be affected by the alumina addition and inhibited by the beginning of the crystal-phase precipitation. Scanning electron microscopy was performed on the fractured sintered samples to observe the effect of the sintering. Young's modulus and the mechanical strength of the sintered glass ceramic and composites were determined at different heating rates. The application of high heating rate and the addition of alumina powder improved the mechanical properties. Compared to the sintered glass ceramic without additives, the bending strength and the Young's modulus obtained at 20 deg. C/min, increased by about 20% and 30%, respectively

Effect of Ta content on martensitic transformation behavior of RuTa ultrahigh temperature shape memory alloys

International Nuclear Information System (INIS)

He Zhirong; Zhou Jingen; Furuya, Y.

2003-01-01

Effects of Ta content on martensitic transformation (MT) behavior of Ru 100-x Ta x (x=46-54 at.%) alloys have been investigated by differential scanning calorimetry, dilatometry, X-ray diffraction and optical microscopy. Ta content significantly affects the MT behavior of RuTa alloys. The one-stage reservible MT occurs in Ta-poor RuTa alloys with Ta content less than 49 at.%. The two-stage reservible MT takes place in near-equiatomic RuTa alloys. No reservible MT is observed in Ta-rich alloys with Ta content more then 52 at.% Ta. The MT temperatures and hysteresis of RuTa alloys decrease with increasing Ta content. The aged and thermal cycled processes are nearly no effect on the MT behavior of these alloys. The deforming way of RuTa alloys is twinning. The Ru 50 Ta 50 alloy is of the most excellent MT behavior among these RuTa alloys

Electrical Conductivity of Molten DyCl3-NaCl and DyCl3-KCl Systems: An Approach to Structural Interpretations of Rare Earth Chloride Melts

Science.gov (United States)

Iwadate, Yasuhiko; Ohkubo, Takahiro

2017-11-01

Electrical conductivities (κs) of molten DyCl3-NaCl and DyCl3-KCl systems were estimated by measuring the impedances of each mixture melt at any temperature and/or frequency. The molar volumes (Vms) were measured by dilatometry and represented as a polynomial empirical equation of temperature and composition. Due to both the properties, the molar conductivities (Λms) were calculated and their temperature and/or composition dependences were discussed from the standpoint of structural features as well. The κs increased curvilinearly with increasing temperature across the whole composition ranges. This trend was also applied to the Λms which was fitted by an Arrhenius-type equation. The relationship of Λms with melt composition was studied and the Λms were found to decrease with increasing composition of DyCl3. These findings were interpreted based on the results of structural science so far reported, and finally, the relationship between Λms and the structures of pure rare earth chloride melts was discussed.

Texture in low-alloyed uranium alloys

International Nuclear Information System (INIS)

Sariel, J.

1982-08-01

The dependence of the preferred orientation of cast and heat-treated polycrystalline adjusted uranium and uranium -0.1 w/o chromium alloys on the production process was studied. The importance of obtaining material free of preferred orientation is explained, and a survey of the regular methods to determine preferred orientation is given. Dilatometry, tensile testing and x-ray diffraction were used to determine the extent of the directionality of these alloys. Data processing showed that these methods are insufficient in a case of a material without any plastic forming, because of unreproducibility of results. Two parameters are defined from the results of Schlz's method diffraction test. These parameters are shown theoretically and experimentally (by extreme-case samples) to give the deviation from isotropy. Application of these parameters to the examined samples showes that cast material has preferred orientation, though it is not systematic. This preferred orientation was reduced by adequate heat treatments

Three-body abrasive wear behaviour of metastable spheroidal carbide cast irons with different chromium contents

Energy Technology Data Exchange (ETDEWEB)

Efremenko, Vasily; Pastukhova, Tatiana; Chabak, Yuliia; Efremenko, Alexey [Pryazovskyi State Technical Univ., Mariupol (Ukraine); Shimizu, Kazumichi; Kusumoto, Kenta [Muroran Institute of Technology, Hokkaido (Japan); Brykov, Michail [Zaporozhye National Technical Univ., Zaporozhye (Ukraine)

2018-02-15

The effect of heat treatment and chromium contents (up to 9.1 wt.%) on the wear resistance of spheroidal carbide cast iron (9.5 wt.% V) was studied using optical and scanning electron microscopy, X-ray diffractometry, dilatometry and three-body abrasive testing. It was found that quenching from 760 C and 920 C improved the alloys' wear resistance compared to the as-cast state due to the formation of metastable austenite transforming into martensite under abrasion. The wear characteristics of alloys studied are 1.6 - 2.3 times higher than that of reference cast iron (12 wt.% V) having stable austenitic matrix. Chromium addition decreases surface damage due to the formation of M{sub 7}C{sub 3} carbides, while it reduces wear resistance owing to austenite stabilization to abrasion-induced martensite transformation. The superposition of these factors results in decreasing the alloys' wear behaviour with chromium content increase.

Apparent molar volumes for dilute solutions of NaClO4 and [Co(en) 3](ClO4)3 in D2O and H2O at 278-318 K

International Nuclear Information System (INIS)

Bottomley, G.A.; Glossop, L.G.

1981-01-01

Apparent molar volumes for dilute solutions of NaClO 4 and [Co(en) 3 ](ClO 4 ) 3 in D 2 O and H 2 O were measured by using a dilatometry technique at 278, 298 and 318K. Comparison of limiting slopes with the Debye-Huckel predictions from the dielectric constant and compressibility of H 2 O and D 2 O is complicated by ion pairing. The apparent molar volumes for NaClO 4 were less in D 2 O than in H 2 O. The complex [Co(en) 3 ](ClO 4 ) 3 when studied in D 2 O had its amine protons exchanged by deuterium; this did not allow a direct comparison of the apparent molar volumes of the protonated complex in each solvent system, but revealed a large isotope effect. The apparent molar volumes of the [Co(en) 3 ](ClO 4 ) 3 showed a much larger temperature dependence than that of NaClO 4

Magnetic Levitation To Characterize the Kinetics of Free-Radical Polymerization.

Science.gov (United States)

Ge, Shencheng; Semenov, Sergey N; Nagarkar, Amit A; Milette, Jonathan; Christodouleas, Dionysios C; Yuan, Li; Whitesides, George M

2017-12-27

This work describes the development of magnetic levitation (MagLev) to characterize the kinetics of free-radical polymerization of water-insoluble, low-molecular-weight monomers that show a large change in density upon polymerization. Maglev measures density, and certain classes of monomers show a large change in density when monomers covalently join in polymer chains. MagLev characterized both the thermal polymerization of methacrylate-based monomers and the photopolymerization of methyl methacrylate and made it possible to determine the orders of reaction and the Arrhenius activation energy of polymerization. MagLev also made it possible to monitor polymerization in the presence of solids (aramid fibers, and carbon fibers, and glass fibers). MagLev offers a new analytical technique to materials and polymer scientists that complements other methods (even those based on density, such as dilatometry), and will be useful in investigating polymerizations, evaluating inhibition of polymerizations, and studying polymerization in the presence of included solid materials (e.g., for composite materials).

Structural mechanisms of high-temperature shape changes in titanium-nickel alloys after low-temperature thermomechanical treatment

International Nuclear Information System (INIS)

Prokoshkin, S.D.; Turenne, S.; Khmelevskaya, I.Yu.; Brailovski, V.; Trochu, F.

2000-01-01

High-Temperature Shape Memory Effect (HTSME) in Ti-Ni alloys and corresponding structural and internal stress changes were studied using dilatometry, in situ electron microscope and X-ray diffractometry. The HTSME induced by the Low Temperature Thermomechanical Treatment (LTMT) consists of two stages. The temperature range of the first stage is limited to 250 o C, while the second stage extends to 400-500 o C. The first stage is caused by the oriented reverse martensite transformation. The heterogeneous residual stress field causes a different thermal stability for the different martensite orientations. During the reverse transformation an anisotropic shift of martensite and austenite X-ray lines is observed that can be due to a relaxation of the orientated stresses and to changes in the martensite lattice. The second stage of HTSME is caused by internal stress relaxation during recovery and polygonization of austenite that are not typical shape memory mechanisms. The possible reasons for the martensite stabilization induced by LTMT will be discussed. (author)

Preparation and characterization of VB metal group glass for optical fiber communication devices

International Nuclear Information System (INIS)

Aranha, N.; Barbosa, L.C.; Garrido, F.M.S.; Alves, O.L.

1990-01-01

In this work was prepared the glass of composition Nb 2 O 5 (25.04%) - PbO (23.91%) - P 2 O 5 (34.25%) - K 2 O (16.80%) using a RF induction furnace at temperature of 1400 C for two hours under ambient atmosphere. The obtained glass are annealed at 300 C. The samples (powder and thin plates) was characterized by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and by determination of the thermal coefficient of expansion (dilatometry). Results shown the formation of a very homogeneous glass with a thermal coefficient of expansion (α) of 22.7.10 -6 C -1 . The ir bands suggest the formation of a phosphate glass with a good transmission in the region of 2.0-2.9 microns (5000-3400 cm -1 ). The transmission spectrum shows that the material is transparent in the region of 400-1000 nm with a cut-off at near 350nm. (author) [pt

LiV₂O₄: A heavy fermion transition metal oxide

Energy Technology Data Exchange (ETDEWEB)

Kondo, Shinichiro [Iowa State Univ., Ames, IA (United States)

1999-02-12

The format of this dissertation is as follows. In the remainder of Chapter 1, brief introductions and reviews are given to the topics of frustration, heavy fermions and spinels including the precedent work of LiV₂O₄. In Chapter 2, as a general overview of this work the important publication in Physical Review Letters by the author of this dissertation and collaborators regarding the discovery of the heavy fermion behavior in LiV₂O₄ is introduced [removed for separate processing]. The preparation methods employed by the author for nine LiV₂O₄ and two Li_1+xTi_2-xO₄ (x = 0 and 1/3) polycrystalline samples are introduced in Chapter 3. The subsequent structural characterization of the LiV₂O₄ and Li_1+xT_2-xO₄ samples was done by the author using thermogravimetric analysis (TGA), x-ray diffraction measurements and their structural refinements by the Rietveld analysis. The results of the characterization are detailed in Chapter 3. In Chapter 4 magnetization measurements carried out by the author are detailed. In Chapter 5, after briefly discussing the resistivity measurement results including the single-crystal work by Rogers et al., for the purpose of clear characterization of LiV₂O₄ it is of great importance to introduce in the following chapters the experiments and subsequent data analyses done by his collaborators. Heat capacity measurements (Chapter 6) were carried out and analyzed by Dr. C.A. Swenson, and modeled theoretically by Dr. D.C. Johnston. In Chapter 7 a thermal expansion study using neutron diffraction by Dr. O. Chmaissem et al. and capacitance dilatometry measurements by Dr. C.A. Swenson are introduced. The data analyses for the thermal expansion study were mainly done by Dr. O. Chmaissem (for neutron diffraction) and Dr. C.A. Swendon (for dilatometry), with assistances by Dr. J

New methods for removal of pollutants from exhaust gases

Energy Technology Data Exchange (ETDEWEB)

Braestrup, F.

2009-06-15

Different spinel-type oxides were investigated as possible cathode materials for the electrochemical reduction of NO{sub x} gases (NO and NO{sub 2}) in an all solid oxide electrochemical cell. Three different series of spinel-type oxides, with the following composition, were analyzed: Ni{sub 1-x}Mg{sub x}Fe{sub 2}O{sub 4} (x = 0.0, 0.3, 0.5, 0.6, 1.0), NiCr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0, 0.5, 1.0, 1.5, 2.0) and MgMn{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0). Furthermore were spinel-type oxides of ZnFe{sub 2}O{sub 4}, NiMn{sub 2}O{sub 4} and MnCo{sub 2}O{sub 4} also analyzed. The compounds were characterized with X-ray diffraction, dilatometry and resistivity measurements. Selected ones were also characterized with X-ray adsorption spectroscopy, thermogravimetry and neutron diffraction. Cone-shaped electrodes were fabricated for all of the materials and measurements were performed in different gases of NO, NO{sub 2}, O{sub 2} and mixtures of these. Cyclic voltammetry and electrochemical impedance spectroscopy were measured in the temperature range from 300 deg. C to 600 deg. C depending on materials. Current ratios of NO over O{sub 2} and NO{sub 2} over O{sub 2} showed that a number of spinels have high apparent selectivities with ratios of 20 or more. Electrodes having the highest cathodic activity were used to fabricate symmetrical cells and 3-electrode pellets. These were used for further characterization and measurements on gas conversion. The materials used for this purpose were MgFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} and results show that both materials can convert NO to NO{sub 2} and back again during polarization. However, the overall NO{sub x} level stayed almost unchanged during that process. A 3-electrode pellet with a ZnFe{sub 2}O{sub 4} electrode, was infiltrated with BaO improve the activity in NO, however, the gas conversion was still very low. The effect of BaO in NiMn{sub 2}O{sub 4} could not be determined as BaO reacted

Contribution to the study of the textures of uranium rods prepared by sintering-extrusion, and their consequences on the thermal cycling behaviour; Contribution a l'etude des textures de barreaux d'uranium mis en forme par frittage-extrusion et leurs consequences sur le comportement au cyclage thermique

Energy Technology Data Exchange (ETDEWEB)

Peix, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-11-01

Uranium rods prepared by sintering-extrusion in the {alpha} or {beta} phase (at various extrusion ratios) using slightly oxidised powders have been subjected to the thermal cycling test. At the same time, dilatometric and X-ray techniques have made it possible to determine the structures produced in these materials during their fabrication. A relationship is then proposed linking the texture to the increase in length on thermal cycling. 1. Two types of rods have been studied: Sintered-extruded in the {beta} phase: low density (88 per cent theoretical density), large grain-size and no preferential texture. Sintered-extruded in the {alpha} phase: high density (96 per cent theoretical density), fine grain with pronounced preferential texture. 2. After 1000 thermal cycles between 20 and 550 C, the increases in length are the following: 2 per cent for a uranium sintered-extruded in the {beta} phase (with surface cracking). between 14 and 56 per cent according to the extrusion ratio for on uranium sintered-extruded in the {alpha} phase (with no surface effects). 3. In the case of rods sintered-extruded in the {alpha} phase, determination of the pole figure using the Schulz reflection method showed the existence of two preferential orientations parallel to the direction of extrusion: one close to [100], the other close to [110]. By dilatometry it was then possible to measure quantitatively the proportion of each constituent in the overall texture and to show that an increase in the percentage of [100] occurs with increasing amounts of cold-working. 4. Finally, by comparing 2 and 3 it can be seen that the increases in length due to thermal cycling are connected to the percentage amounts of each component. It seems that the increases in length diminish as the percentage of [100] increases. On the other hand the behaviour of materials containing large amount of [110] is still far from clear. (author) [French] Des barreaux d'uranium realises par frittage-extrusion en phase

Modeling and experimental study of residual stresses in NOREM hardfacing coatings used in valve parts

International Nuclear Information System (INIS)

Beaurin, G.

2012-01-01

Hardfacing coatings are widely used on the surfaces of parts subjected to drastic loadings. Norem02 alloy, Fe-based, is used in PWR nuclear power plants on valves seating surfaces. Its microstructure consists of a dendritic austenite structure with ferrite islets and carbides. This work tends to demonstrate that for this alloy, metallurgical evolution during the welding process has very little influence on mechanical properties. Tensile behavior was characterized and completed by dilatometry tests in welding process temperature range until 1000 Celsius degrees, in order to identify an elastoplastic model with non linear kinematic hardening rule. Temperature, displacements, distortions and residual stresses were measured during the PTAW (Plasma Transferred Arc Welding) process and used to identify an equivalent thermal loading by solving an inverse problem. Finally, the numerical simulation of the whole process using the EDF FEM software Code-Aster is presented. Predicted temperatures are consistent with experimental ones. In the same way, predicted displacements, residual distortions and residual stresses at the end of the cooling phase are close to experimental measures, validating the modeling strategy presented in this work. (author)

Order-disorder transition and electrical conductivity of the brownmillerite solid-solutions system Ba sub 2 (In, M) sub 2 O sub 5 (M=Ga, Al)

CERN Document Server

Yamamura, H; Kakinuma, K; Mori, T; Haneda, H

1999-01-01

The brownmillerite solid-solution systems Ba sub 2 (In sub 1 sub - sub x M sub x) sub 2 O sub 5 (M=Ga, Al) were investigated by means of high-temperature X-ray diffraction (XRD), dilatometry, and electrical-conductivity measurements. XRD showed that the Ba sub 2 (In sub 1 sub - sub x Ga sub x) sub 2 O sub 5 system had orthorhombic symmetry in the composition range 0.0<=x<=0.2 and cubic symmetry in the range 0.3<=x. The Al system also changed to cubic symmetry from orthorhombic symmetry in the range 0.2<=x. While the orthorhombic phase showed an order-disorder transition in the electrical conductivity measurements, the transition temperature decreased with increasing the M content. The order-disorder transition temperature and the crystal-structure transition temperature were very different. Such a transition was not observed in the cubic phases, and their electrical conductivity were fairly low compared to those of the disordered cubic phase after the transition due to the heating process. These p...

Effect of the Configuration of a Bulky Aluminum Initiator on the Structure of Copolymers of l,l-Lactide with Symmetric Comonomer Trimethylene Carbonate

Directory of Open Access Journals (Sweden)

Marta Socka

2018-01-01

Full Text Available The effect of configuration of an asymmetric bulky initiator 2,2′-[1,1′-binaphtyl-2,2′-diyl- bis-(nitrylomethilidyne]diphenoxy aluminum isopropoxide (Ini on structure of copolymer of asymmetric monomer l,l-lactide (Lac with symmetric comonomer trimethylene carbonate (Tmc was studied using polarimetry, dilatometry, Size Exclusion Chromatography (SEC, and Carbon Nuclear Magnetic Resonance (13C NMR. When the S-enantiomer of Ini was used the distribution in copolymer chains at the beginning of polymerization is statistical, with alternacy tendency, changing next through a gradient region to homoblocks of Tmc. However, when R-Ini was used, the product formed was a gradient oligoblock one, with Tmc blocks prevailing at the beginning, changing to Lac blocks dominating at the end part of chains. Initiation of copolymerization with the mixture of both initiator enantiomers (S:R = 6:94 gave a multiblock copolymer of similar features but shorter blocks. Analysis of copolymerization progress required complex analysis of dilatometric data, assuming different molar volume contraction coefficients for units located in different triads. Comonomer reactivity ratios of studied copolymerizations were determined.

Assessment of polyphase sintered iron-cobalt-iron boride cermets

International Nuclear Information System (INIS)

Nowacki, J.; Pieczonka, T.

2004-01-01

Sintering of iron, cobalt and boron powders has been analysed. As a result iron-iron boride, Fe-Fe 2 B and iron/cobalt boride with a slight admixture of molybdenum, Fe - Co - (FeMoCo) 2 B cermets have been produced. Iron was introduced to the mixture as the Astalloy Mo Hoeganaes grade powder. Elemental amorphous boron powder was used, and formation of borides occurred both during heating and isothermal sintering periods causing dimensional changes of the sintered body. Dilatometry was chosen to control basic phenomena taking place during multiphase sintering of investigated systems. The microstructure and phase constituents of sintered compacts were controlled as well. The cermets produced were substituted to: metallographic tests, X-ray analysis, measurements of hardness and of microhardness, and of wear in the process of sliding dry friction. Cermets are made up of two phases; hard grains of iron - cobalt boride, (FeCo) 2 B (1800 HV) constituting the reinforcement and a relatively soft and plastic eutectic mixture Fe 2 B - Co (400-500 HV) constituting the matrix. (author)

Fatigue behavior of partially stabilized zirconia ceramics

International Nuclear Information System (INIS)

Ferber, M.K.; Hine, T.

1986-01-01

The time-dependent strength variations of two grades of MgO stabilized materials (Mg-PSZ) were measured as a function of temperature and applied stress level. The strength was determined using an interrupted fatigue (I.F.) test in which flexure samples were exposed at temperatures between 500 and 100 0 C for times up to 1008 h. During testing, the applied stress was maintained at a percentage of the short-term strength value measured at the same T. The resulting I.F. data gave evidence of both strengthening and weakening processes. The dominant mechanism at a given temperature was primarily dictated by the stress level. In the present investigation, the fatigue behavior for two grades of Mg-PSZ was evaluated by measuring the time-dependent strength variations as a function of temperature and applied stress level. Changes in microstructure resulting from the high-temperature exposure were determined from subsequent ceramographic, SEM and TEM studies. In addition, x-ray diffraction and dilatometry measurements were used to examine time-dependent variations in the phase assemblage

Bainitic Transformation and Properties of Low Carbon Carbide-Free Bainitic Steels with Cr Addition

Directory of Open Access Journals (Sweden)

Mingxing Zhou

2017-07-01

Full Text Available Two low carbon carbide-free bainitic steels (with and without Cr addition were designed, and each steel was treated by two kinds of heat treatment procedure (austempering and continuous cooling. The effects of Cr addition on bainitic transformation, microstructure, and properties of low carbon bainitic steels were investigated by dilatometry, metallography, X-ray diffraction, and a tensile test. The results show that Cr addition hinders the isothermal bainitic transformation, and this effect is more significant at higher transformation temperatures. In addition, Cr addition increases the tensile strength and elongation simultaneously for austempering treatment at a lower temperature. However, when the austempering temperature is higher, the strength increases and the elongation obviously decreases by Cr addition, resulting in the decrease in the product of tensile strength and elongation. Meanwhile, the austempering temperature should be lower in Cr-added steel than that in Cr-free steel in order to obtain better comprehensive properties. Moreover, for the continuous cooling treatment in the present study, the product of tensile strength and elongation significantly decreases with Cr addition due to more amounts of martensite.

The Effects of Cr and Al Addition on Transformation and Properties in Low‐Carbon Bainitic Steels

Directory of Open Access Journals (Sweden)

Junyu Tian

2017-01-01

Full Text Available Three low‐carbon bainitic steels were designed to investigate the effects of Cr and Al addition on bainitic transformation, microstructures, and properties by metallographic method and dilatometry. The results show that compared with the base steel without Cr and Al addition, only Cr addition is effective for improving the strength of low‐carbon bainitic steel by increasing the amount of bainite. However, compared with the base steel, combined addition of Cr and Al has no significant effect on bainitic transformation and properties. In Cr‐bearing steel, Al addition accelerates initial bainitic transformation, but meanwhile reduces the final amount of bainitic transformation due to the formation of a high‐temperature transformation product such as ferrite. Consequently, the composite strengthening effect of Cr and Al addition is not effective compared with individual addition of Cr in low‐carbon bainitic steels. Therefore, in contrast to high‐carbon steels, bainitic transformation in Cr‐bearing low‐carbon bainitic steels can be finished in a short time, and Al should not be added because Al addition would result in lower mechanical properties.

Thermal Expansion Anomaly and Spontaneous Magnetostriction of Y2Fe14Al3 Compound

International Nuclear Information System (INIS)

Yan-Ming, Hao; Xin-Yuan, Jiang; Chun-Jing, Gao; Yan-Zhao, Wu; Yan-Yan, Zhang

2009-01-01

The structure and magnetic properties of Y 2 Fe 14 Al 3 compound are investigated by means of x-ray diffraction and magnetization measurements. The Y 2 Fe 14 Al 3 compound has a hexagonal Th 2 Ni 17 -type structure. Negative thermal expansion is found in Y 2 Fe 14 Al 3 compound in the temperature range from 403 to 491K by x-ray dilatometry. The coefficient of the average thermal expansion is α-bar = –2.54 × 10 −5 K −1 . The spontaneous magnetostrictive deformations from 283 to 470K are calculated by means of the differences between the experimental values of the lattice parameters and the corresponding values extrapolated from the paramagnetic range. The result shows that the spontaneous volume magnetostrictive deformation ω S decreases from 5.74 × 10 −3 to nearly zero with temperature increasing from 283 to 470 K, the spontaneous linear magnetostrictive deformation λ c along the c-axis is larger than the spontaneous linear magnetostrictive deformation λ a in basal-plane in the same temperature below 350 K

Double Step Sintering Behavior Of 316L Nanoparticle Dispersed Micro-Sphere Powder

Directory of Open Access Journals (Sweden)

Jeon Byoungjun

2015-06-01

Full Text Available 316L stainless steel is a well-established engineering material and lots of components are fabricated by either ingot metallurgy or powder metallurgy. From the viewpoints of material properties and process versatility, powder metallurgy has been widely applied in industries. Generally, stainless steel powders are prepared by atomization processes and powder characteristics, compaction ability, and sinterability are quite different according to the powder preparation process. In the present study, a nanoparticle dispersed micro-sphere powder is synthesized by pulse wire explosion of 316L stainless steel wire in order to facilitate compaction ability and sintering ability. Nanoparticles which are deposited on the surface of micro-powder are advantageous for a rigid die compaction while spherical micro-powder is not to be compacted. Additionally, double step sintering behavior is observed for the powder in the dilatometry of cylindrical compact body. Earlier shrinkage peak comes from the sintering of nanoparticle and later one results from the micro-powder sintering. Microstructure as well as phase composition of the sintered body is investigated.

Sintering study of NiO-YSZ composite obtained by coprecipitation route; Estudo de sinterabilidade do composito de NiO-YSZ obtido pela rota de coprecipitacao

Energy Technology Data Exchange (ETDEWEB)

Yoshito, W K; Resitivo, T A.G.; Ussui, V; Lazar, D R.R.; Paschoal, J O.A., [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais

2009-07-01

NiO-YSZ composite is a widely used anode material for solid oxide fuel cell. The main purpose of the present work was the evaluation of the appropriate conditions of ceramic processing, by sintering behavior study of NiO-YSZ pressed powders, synthesized by hydroxide coprecipitation route. Using the empirical rate equation developed by Makipirtti-Meng, it was analyzed shrinkage rate in the temperature ranges of 900-1400 deg C as function of time. The powders were characterized by X-ray diffraction, scanning electron microscopy, gas adsorption, laser diffraction and helium picnometry. The microstructural characterization of the samples was evaluated by X-ray diffraction, scanning electron microscopy and relative density by the Archimedes method. It was found that activation energy value is 48,3 kJ.mol{sup -1} in the temperature range of 900-950 deg C and 604,83 kJ.mol{sup -1} for 1000-1200 deg C. These values correspond to the change that occurs in the microstructure during the heat treatment process. The sintering process was evaluated by the dilatometry date treatment. (author)

The effect of hydrothermal treatment on samaria and gadolinia doped ceria powders synthesized by coprecipitation

International Nuclear Information System (INIS)

Arakaki, Alexander Rodrigo; Yoshito, Walter Kenji; Ussui, Valter; Lazar, Dolores Ribeiro Ricci

2009-01-01

One of the main applications of ceria-based (CeO 2 ) ceramics is the manufacturing of Intermediate Temperature Solid Oxide Fuel Cells electrolytes. In order to improve ionic conductivity and densification of these materials various powder synthesis routes have been studied. In this work powders with composition Ce 0.8 (SmGd) 0.2 O 1.9h ave been synthesized by coprecipitation and hydrothermal treatment. A concentrate of rare earths containing 90wt% of CeO 2 and other containing 51% of Sm 2 O 3 and 30% of Gd 2 O 3 , both prepared from monazite processing, were used as precursor materials. The powders were characterized by X-ray diffraction, scanning and transmission electron microscopy, agglomerate size distribution by laser scattering and specific surface area by gas adsorption. Ceramic sinterability was evaluated by dilatometry and density measurements by Archimedes method. High specific surface area powders (~100m 2 /g) and cubic fluorite structure were obtained after hydrothermal treatment around 200 deg C. Ceramic densification was improved when compared to the one prepared from powders calcined at 800 deg C. (author)

Phase stability, oxygen nonstoichiometry, and superconductivity properties of Bi2Sr2CaCu2O8+δ and Bi1.8Pb0.4Sr2Ca2Cu3O10+δ

International Nuclear Information System (INIS)

Mozhaev, A.P.; Chernyaev, S.V.; Badun, Y.V.

1995-01-01

Phase stability of Bi 2 Sr 2 CaCu 2 O 8+δ (2212) and Bi 1.8 Pb 0.4 Sr 2 Ca 2 Cu 3 O 10+δ (2223) was studied by means of thermogravimetry, dilatometry, high-temperature resistivity, and the powder X-ray methods in the temperature range 700-1000 degrees and at P O2 = 1-10 -4.3 atm. The existence of a high-temperature (peritectic melting) boundary of phase stability was found. The temperatures of low-temperature phase decomposition were determined in air and under an oxygen atmosphere. The change in oxygen content was determined for the 2212 phase in the temperature range 700-860 degrees C and at P O2 = 0.21-10 -3.7 atm by iodometric analysis of quenched samples. It was found that in the single-phase region, the change in oxygen nonstoichiometry had an insignificant influence on T c . It was also shown that the slow cooling of samples led to a significant decrease in T c and transport j c due to partial phase decomposition

The influence of Fe2O3 in the humidity sensor performance of ZrO2:TiO2-based porous ceramics

International Nuclear Information System (INIS)

Cosentino, I.C.; Muccillo, E.N.S.; Muccillo, R.

2007-01-01

ZrO 2 :TiO 2 ceramics were prepared with different porosity values by two methods: (a) sintering at 1150, 1300 and 1500 deg. C, corresponding to the temperatures of the first, second and third sintering stages, according to dilatometry results; (b) adding Fe 2 O 3 (2.0 and 5.0 mol%) to ZrO 2 :TiO 2 powders before sintering. The ZrO 2 :TiO 2 specimens were characterized by X-ray diffraction, mercury porosimetry, scanning electron microscopy and impedance spectroscopy. The impedance spectroscopy analysis was carried out under different relative humidities. The bulk electrical resistivity in the low frequency region (10-100 Hz) decreases for increasing relative humidity. Increasing the sintering temperature from the first to the third sintering stage promoted grain growth, as expected, with consequent decrease of the intergranular porosity. The use of Fe 2 O 3 as sintering aid reduced the porosity of the specimens, but increased the electrical response under humid environments in comparison with specimens sintered without Fe 2 O 3

Structural, morphological and thermal properties of La1-xSrxMnO3 (x = 0.15 and 0.22) prepared by the polymeric precursor method

International Nuclear Information System (INIS)

Macedo, D.A; Cela, B.; Carvalho, W.M.; Martinelli, A.E.; Nascimento, R.M.; Paskocimas, C.A.

2009-01-01

Strontium-doped lanthanum manganite (La1 -x Sr x MnO 3 or LSM) is traditionally the most used material for cathodes in high temperature solid oxide fuel cell (800 deg C). This material shows excellent electrocatalytic activity for oxygen reduction and is chemical and thermal stable with the yttria-stabilized zirconia electrolyte (YSZ). In this work La 0.85 Sr 0.15 MnO 3 (LSM 15) and La 0.78 Sr 0.22 MnO 3 (LSM 22) were prepared by the polymeric precursor method, calcinated at 700 deg C for 2 h and characterized by X-ray diffraction, particle size analysis, scanning electronic microscopy and compacts' dilatometry. The synthesis method used provided the attainment of nanopowders with perovskite structure and particles sizes below 100 nm. The thermal expansion coefficients of LSM 15 and LSM 22 were found to be 12.2 x 10 -6 deg C -1 and 11.7 x 10 -6 deg C -1 respectively, which are very close to that of the YSZ. (author)

Microstructural Evolution and Mechanical Properties of Simulated Heat-Affected Zones in Cast Precipitation-Hardened Stainless Steels 17-4 and 13-8+Mo

Science.gov (United States)

Hamlin, Robert J.; DuPont, John N.

2017-01-01

Cast precipitation-hardened (PH) stainless steels 17-4 and 13-8+Mo are used in applications that require a combination of high strength and moderate corrosion resistance. Many such applications require fabrication and/or casting repair by fusion welding. The purpose of this work is to develop an understanding of microstructural evolution and resultant mechanical properties of these materials when subjected to weld thermal cycles. Samples of each material were subjected to heat-affected zone (HAZ) thermal cycles in the solution-treated and aged condition (S-A-W condition) and solution-treated condition with a postweld thermal cycle age (S-W-A condition). Dilatometry was used to establish the onset of various phase transformation temperatures. Light optical microscopy (LOM), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS) were used to characterize the microstructures, and comparisons were made to gas metal arc welds that were heat treated in the same conditions. Tensile testing was also performed. MatCalc thermodynamic and kinetic modeling software was used to predict the evolution of copper (Cu)-rich body center cubic precipitates in 17-4 and β-NiAl precipitates in 13-8+Mo. The yield strength was lower in the simulated HAZ samples of both materials prepared in the S-A-W condition when compared to their respective base metals. Samples prepared in the S-W-A condition had higher and more uniform yield strengths for both materials. Significant changes were observed in the matrix microstructure of various HAZ regions depending on the peak temperature, and these microstructural changes were interpreted with the aid of dilatometry results, LOM, SEM, and EDS. Despite these significant changes to the matrix microstructure, the changes in mechanical properties appear to be governed primarily by the precipitation behavior. The decrease in strength in the HAZ samples prepared in the S-A-W condition was attributed to the dissolution of precipitates

Heat treatment, microstructure and mechanical properties of a C–Mn–Al–P hot dip galvanizing TRIP steel

International Nuclear Information System (INIS)

Ding, Wei; Hedström, Peter; Li, Yan

2016-01-01

Heat treatments of a hot dip galvanizing TRIP (Transformation induced plasticity) steel with chemical composition 0.20C-1.50Mn-1.2Al-0.07P(mass%) were performed in a Gleeble 3500 laboratory equipment. The heat treatment process parameters were varied to investigate the effect of intercritical annealing temperature as well as isothermal bainitic transformation (IBT) temperature and time, on the microstructure and the mechanical properties. The microstructure was investigated using scanning electron microscopy, transmission electron microscopy and x-ray diffraction, while mechanical properties were evaluated by tensile testing. Furthermore, to generate a better understanding of the phase transformations during heat treatment, dilatometry trials were conducted. The desired microstructure containing ferrite, bainite, retained austenite and martensite was obtained after the heat treatments. It was further found that the IBT is critical in determining the mechanical properties of the steel, since it controls the fraction of bainite. With increasing bainite fraction, the fraction of retained austenite increases while the fraction of martensite decreases. The mechanical properties of the steel are excellent with a tensile strength above 780 MPa (expect in one case) and elongation above 22%.

Martensitic transformation in Eurofer-97 and ODS-Eurofer steels: A comparative study

International Nuclear Information System (INIS)

Zilnyk, K.D.; Oliveira, V.B.; Sandim, H.R.Z.; Möslang, A.; Raabe, D.

2015-01-01

Highlights: • Martensitic transformation of RAFM steels promotes significant grain fragmentation. • Austenite grain growth occurs in Eurofer-97 steel but not in ODS-Eurofer steel. • Boundary misorientation distribution of the as-quenched steels show two maxima peaks. • The amount of retained austenite varies from one steel to another. - Abstract: Reduced-activation ferritic–martensitic Eurofer-97 and ODS-Eurofer steels are potential candidates for structural applications in advanced nuclear reactors. Samples of both steel grades in the as-tempered condition were austenitized in vacuum for 1 h from 900 °C to 1300 °C followed by air cooling to room temperature. The microstructure was characterized by dilatometry, electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). Thermodynamic calculations provided by Thermo-Calc software were used to determine their transformation temperatures. Even having similar chemical composition, important changes were observed after martensitic transformation in these steels. Significant austenitic grain growth was observed in Eurofer-97 steel leading to the development of coarser martensitic packets. Contrastingly, austenitic grain growth was prevented in ODS-Eurofer steel due to fine and stable dispersion of Y-based particles

Plastic behavior of medium carbon vanadium microalloyed steel at temperatures near g « a transformation

Directory of Open Access Journals (Sweden)

Lourenço N.J.

2001-01-01

Full Text Available Dilatometric techniques were used to build the continuous cooling transformation (CCT diagram for a medium carbon microalloyed steel; the microstructure and hardness were determined at different cooling rates. The mechanical behavior of the steel in the austenite field and at temperatures approaching austenite to ferrite transformation was measured by means of hot torsion tests under isothermal and continuous cooling conditions. The no recrystallization temperatures, Tnr, and start of phase transformation, Ar3, were determined under continuous cooling condition using mean flow stress vs. inverse of absolute temperature diagrams. Interruption of static recrystallization within the interpass time in the austenite field indicated that the start of vanadium carbonitride precipitation occurred under 860 °C. Austenite transformation was found to start at around 710 °C, a temperature similar to that measured by dilatometry, suggesting that interphase precipitation delays the transformation of deformed austenite. Pearlite was observed at temperatures ranging from 650 °C to 600 °C, with the flow curves taking on a particular shape, i.e., stress rose sharply as strain was increased, reaching peak stress at low deformation, around 0.2, followed by an extensive softening region after peak stress.

Heat treatment, microstructure and mechanical properties of a C–Mn–Al–P hot dip galvanizing TRIP steel

Energy Technology Data Exchange (ETDEWEB)

Ding, Wei [School of Material and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Bayan Obo multimetallic resource comprehensive utilization Key lab, Inner Mongolia University of Science and Technology, Baotou 014010 (China); Hedström, Peter [Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Li, Yan [Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Bayan Obo multimetallic resource comprehensive utilization Key lab, Inner Mongolia University of Science and Technology, Baotou 014010 (China)

2016-09-30

Heat treatments of a hot dip galvanizing TRIP (Transformation induced plasticity) steel with chemical composition 0.20C-1.50Mn-1.2Al-0.07P(mass%) were performed in a Gleeble 3500 laboratory equipment. The heat treatment process parameters were varied to investigate the effect of intercritical annealing temperature as well as isothermal bainitic transformation (IBT) temperature and time, on the microstructure and the mechanical properties. The microstructure was investigated using scanning electron microscopy, transmission electron microscopy and x-ray diffraction, while mechanical properties were evaluated by tensile testing. Furthermore, to generate a better understanding of the phase transformations during heat treatment, dilatometry trials were conducted. The desired microstructure containing ferrite, bainite, retained austenite and martensite was obtained after the heat treatments. It was further found that the IBT is critical in determining the mechanical properties of the steel, since it controls the fraction of bainite. With increasing bainite fraction, the fraction of retained austenite increases while the fraction of martensite decreases. The mechanical properties of the steel are excellent with a tensile strength above 780 MPa (expect in one case) and elongation above 22%.

An extended analytical model for solid-state phase transformation upon continuous heating and cooling processes: Application in γ/α transformation

International Nuclear Information System (INIS)

Jiang, Y.-H.; Liu, F.; Song, S.-J.

2012-01-01

An extended analytical model is derived for non-isothermal solid-state phase transformation assuming interface-controlled growth mode, e.g. polymorphic or allotropic transformation. In the modeling, incorporation of thermodynamic factor into kinetics of nucleation and growth is performed, so that the model can be used to describe the transformation occurring either near or far from the equilibrium state. Furthermore, the effect of the initial transformation temperature is included through a special treatment for the “temperature integral”, so that the model can be used to depict the transformation during either continuous heating or continuous cooling. Numerical calculations demonstrate that the extended analytical model is accurate enough for practical use. On this basis, a general rate equation for non-isothermal (isochronal heating and cooling) transformation is derived. Applying the present model, the overall kinetic behavior of γ/α transformation in binary substitutional Fe-based alloys (e.g. Fe–Mn and Fe–Cu) upon cooling, measured by dilatometry, is described successfully. Compared with previous work, where a site saturation assumption is generally made, the prevalence of continuous nucleation deduced using the present model prediction seems more reasonable.

Order-disorder transition and electrical conductivity of the brownmillerite solid-solutions system Ba2(In, M)2O5 (M=Ga, Al)

International Nuclear Information System (INIS)

Yamamura, Hiroshi; Hamazaki, Hirohumi; Kakinuma, Katsuyoshi; Mori, Toshiyuki; Haneda, Hajime

1999-01-01

The brownmillerite solid-solution systems Ba 2 (In 1-x M x ) 2 O 5 (M=Ga, Al) were investigated by means of high-temperature X-ray diffraction (XRD), dilatometry, and electrical-conductivity measurements. XRD showed that the Ba 2 (In 1-x Ga x ) 2 O 5 system had orthorhombic symmetry in the composition range 0.0≤x≤0.2 and cubic symmetry in the range 0.3≤x. The Al system also changed to cubic symmetry from orthorhombic symmetry in the range 0.2≤x. While the orthorhombic phase showed an order-disorder transition in the electrical conductivity measurements, the transition temperature decreased with increasing the M content. The order-disorder transition temperature and the crystal-structure transition temperature were very different. Such a transition was not observed in the cubic phases, and their electrical conductivity were fairly low compared to those of the disordered cubic phase after the transition due to the heating process. These phenomena are discussed in terms of disordering of the tetrahedral site in the brownmillerite structure, which is occupied by the smaller Ga 3+ or Al 3+ rather than ny In 3+

Characterization of Iron and Steel Industry Slags to be Recycled under Ecological Aspects as a Recycling Concept for Waste Treatment

International Nuclear Information System (INIS)

Khalil, T.K.; Aly, H.F.; Bossert, J.

1999-01-01

The recycling and final disposal of different types of industrial waste play an important role in decreasing environmental pollution all over the world. Three different solid waste slags from steel industries situated in the Helwan area (Cairo-Egypt), namely blast furnace slags, oxygen converter slags arc furnace slags were studied. The morphology of the collected slag powders was examined using scanning electron microscopy (SEM). Surface characteristics of the slag powders were measured through nitrogen gas adsorption and application of the BET equation at 77 K. The thermal behaviour of the slag powders was studied with the help of differential thermal analysis (DTA) and thermogravimetry(TG)> Due to the presence of some changes in the DTA base lines, possibly as a result of phase transformations, X-ray diffraction was applied to identify these phases. The sintering behaviour of the compact slag powders after isostatic pressing was evaluated using dilatometry. The sintering and melting temperature of the studied samples were determined using heating microscopy. The effect of changing sintering temperature and of applying different isostatic pressures on the density and porosity of the slag powder compacts was investigated

Thermal-mechanical properties of a graphitic-nanofibers reinforced epoxy.

Science.gov (United States)

Salehi-Khojin, Amin; Jana, Soumen; Zhong, Wei-Hong

2007-03-01

We previously developed a series of reactive graphitic nanofibers (r-GNFs) reinforced epoxy (nano-epoxy) as composite matrices, which have shown good wetting and adhesion properties with continuous fiber. In this work, the thermal-mechanical properties of the nano-epoxy system containing EponTM Resin 828 and Epi-cure Curing Agent W were characterized. Results from three-point bending tests showed that the flexural strength and flexural modulus of this system with 0.30 wt% of reactive nanofibers were increased by 16%, and 21% respectively, over pure epoxy. Fracture toughness increased by ca. 40% for specimens with 0.50 wt% of r-GNFs. By dynamic mechanical analysis (DMA) test, specimens with 0.30 wt% of r-GNFs showed a significant increase in storage modulus E' (by ca. 122%) and loss modulus E" (by ca. 111%) with respect to that of pure epoxy. Also thermo-dilatometry analysis (TDA) was used to measure dimensional change of specimens as a function of temperature, and then, coefficients of thermal expansion (CTE) before and after glass transition temperature (Tg) were obtained. Results implied that nano-epoxy materials had good dimensional stability and reduced CTE values when compared to those of pure epoxy.

Microstructure and ductility of Fe28Cr16Co alloy with additions of silicon, molybdenum, titanium and aluminium

International Nuclear Information System (INIS)

Vodopivec, F.; Zvokelj, J.; Breskvar, B.; Gnidovec, D.; Rodic, A.; Torkar, M.

1994-01-01

The microstructure of several alloys with base composition Fe28Cr16Co and addition up to 1.5% silicon, 0.32% titanium, 2.34% molybdenum and 1% aluminium was investigated in the temperature range 500 to 1250 C by optical microscopy, hardness measurements and dilatometry. Also, ductility and wire drawing tests were carried out on some alloys. The addition of silicon, titanium, molybdenum or 0.13% Al does not prevent the formation of γ phase up to the temperature 1250 C and the formation of phase σ in the temperature range 700 to approximately 1000 C. The addition of 1% Al prevents the formation of phase σ and shifts the temperature of formation of phase γ to 1158 C. The addition of different elements does not affect significantly the spinodal decomposition of phase α. At increased temperature an interval of sufficient ductility for deformation by wire drawing was established. The ductility was greatly improved if the microstructure consisted of small inclusions of phase γ in a matrix of phase α, probably because the deformation by twinning was hindered. However, insufficient magnetic properties were obtained also after 80% of deformation. (orig.)

Non-isothermal kinetic analysis on the phase transformations of Fe–Co–V alloy

International Nuclear Information System (INIS)

Hasani, S.; Shamanian, M.; Shafyei, A.; Behjati, P.; Szpunar, J.A.

2014-01-01

Highlights: • We investigated, occurrence of different phase transformations in a FeCo- 7.15%wt V alloy upon heating to 1200 °C. • We investigated, the determination of the activation energy for these phase transformations by using five isoconversional methods. • We investigated, the calculation of the empirical kinetic triplets by using the invariant kinetic parameters method and fitting model. - Abstract: In this study, occurrence of different phase transformations was investigated in a FeCo-7 wt% V alloy upon heating to 1200 °C by the dilatometry method at different heating rates (5, 10, and 15 °C min −1 ). It was found that four phase transformations (including B2-type atomic ordering in α phase, first stage of polymorphic transformation (α → α r + γ), ordering to disordering, and second stage of polymorphic transformation (α r → γ) occur in this alloy up to 1200 °C. Two isoconversional methods, as Starink and Friedman, were used to determine variation of the activation energy with temperature, E(T). Moreover, the empirical kinetic triplets (E, A, and g(α)) were calculated by the invariant kinetic parameters (IKP) method and fitting model

[Preliminary study of bonding strength between diatomite-based dental ceramic and veneering porcelains].

Science.gov (United States)

Lu, Xiao-li; Gao, Mei-qin; Cheng, Yu-ye; Zhang, Fei-min

2015-04-01

In order to choose the best veneering porcelain for diatomite-based dental ceramic substrate, the bonding strength between diatomite-based dental ceramics and veneering porcelains was measured, and the microstructure and elements distribution of interface were analyzed. The coefficient of thermal expansion (CTE) of diatomite-based dental ceramics was detected by dilatometry. Three veneering porcelain materials were selected with the best CTE matching including alumina veneering porcelain (group A), titanium porcelain veneering porcelain (group B), and E-max veneering porcelain (group C). Shear bonding strength was detected. SEM and EDS were used to observe the interface microstructure and element distribution. Statistical analysis was performed using SPSS 17.0 software package. The CTE of diatomite-based dental ceramics at 25-500 degrees centigrade was 8.85×10-6K-1. The diatomite-based substrate ceramics combined best with group C. Shear bonding strength between group A and C and group B and C both showed significant differences(P<0.05). SEM and EDS showed that the interface of group C sintered tightly and elements permeated on both sides of the interface. The diatomite-based substrate ceramics combines better with E-max porcelain veneer.

Studies on tempering at different temperatures of the beta phase retained by water quenching in uranium-chromium alloys containing from 0,37 to 4 atoms of chromium percent (1963); Etude du revenu a differentes temperatures de la phase beta retenue par trempe a l'eau dans les alliages uranium-chrome contenant de 0,37 a 4 atomes pour cent de chrome (1963)

Energy Technology Data Exchange (ETDEWEB)

Degois, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1962-07-15

The author made a systematic study of the annealing of the beta phase retained by water-quenching in uranium-chromium alloys of concentrations between 0.37 and 4 of chromium percent. It is shown that alloys containing less than 1 atom per cent are transformed at temperatures between room temperature and 250 deg. C according to a bainitic process involving activation energies of the order of 14,500 cal/mole. Alloys containing more than 1 at. per cent are transformed at temperature between 400 and 650 deg. C by way of a germination and growth process involving an activation energy of the order of 33,000 cal/mole. The limit of solubility of chromium in beta uranium plays a fundamental part in the transformations of the alloys. The TTT curves of beta {yields} alpha transformation were drawn by the use of a thermo-dilatometer of very low inertia. The transformation law may be expressed 1 x = exp. (kt){sup n}; x represents the degree of progression of the transformation, k a coefficient dependent on the temperature, and n an exponent depending only on the composition of the alloy. A micrographic and crystallographic study confirmed the results found by dilatometry; in particular it was possible to measure the progression rates of the transformation. (author) [French] L'auteur a fait une etude systematique du revenu de la phase beta retenue par trempe a l'eau dans les alliages uranium-chrome de teneurs comprises entre 0,37 et 4 atomes pour cent de chrome. Il a montre que les alliages qui contiennent moins de 1 atome pour cent de chrome se transforment aux temperatures comprises entre la temperature ordinaire et 250 deg. C selon un processus bainitique mettant en jeu des energies d'activatlon de l'ordre de 14500 cal/mole. Les alliages qui renferment plus de 1 atome pour cent de chrome se transforment aux temperatures comprises entre 400 et 650 deg. C suivant un processus de germination et croissance mettant en jeu une energie d'activation de l'ordre de -33000 cal/mole. La

Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

International Nuclear Information System (INIS)

Kahrobaee, Saeed; Kashefi, Mehrdad

2015-01-01

The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ε carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes. - Highlights: • D2 steel parts were tempered at 200-650 °C to produce various microstructures. • Precipitation of ε and Fe 3 C carbides and spheroidization of carbides were detected. • Retained austenite decomposition and secondary hardening effect were determined. • Variations of electrical resistivity (ρ) and magnetic saturation (Bs) were studied. • Combined effects of ρ and Bs on the EC outputs were evaluated

Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

Energy Technology Data Exchange (ETDEWEB)

Kahrobaee, Saeed, E-mail: saeed.kahrobaee@yahoo.com; Kashefi, Mehrdad, E-mail: m-kashefi@um.ac.ir

2015-05-15

The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ε carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes. - Highlights: • D2 steel parts were tempered at 200-650 °C to produce various microstructures. • Precipitation of ε and Fe{sub 3}C carbides and spheroidization of carbides were detected. • Retained austenite decomposition and secondary hardening effect were determined. • Variations of electrical resistivity (ρ) and magnetic saturation (Bs) were studied. • Combined effects of ρ and Bs on the EC outputs were evaluated.

Thermal stability and phase transformations of martensitic Ti–Nb alloys

Directory of Open Access Journals (Sweden)

Matthias Bönisch, Mariana Calin, Thomas Waitz, Ajit Panigrahi, Michael Zehetbauer, Annett Gebert, Werner Skrotzki and Jürgen Eckert

2013-01-01

Full Text Available Aiming at understanding the governing microstructural phenomena during heat treatments of Ni-free Ti-based shape memory materials for biomedical applications, a series of Ti–Nb alloys with Nb concentrations up to 29 wt% was produced by cold-crucible casting, followed by homogenization treatment and water quenching. Despite the large amount of literature available concerning the thermal stability and ageing behavior of Ti–Nb alloys, only few studies were performed dealing with the isochronal transformation behavior of initially martensitic Ti–Nb alloys. In this work, the formation of martensites (α' and α'' and their stability under different thermal processing conditions were investigated by a combination of x-ray diffraction, differential scanning calorimetry, dilatometry and electron microscopy. The effect of Nb additions on the structural competition in correlation with stable and metastable phase diagrams was also studied. Alloys with 24 wt% Nb or less undergo a transformation sequence on heating from room temperature to 1155 K. In alloys containing >24 wt% Nb α'' martensitically reverts back to β0, which is highly unstable against chemical demixing by formation of isothermal ωiso. During slow cooling from the single phase β domain α precipitates and only very limited amounts of α'' martensite form.

Characterization of Ni{sub 5}3.5-Fe{sub 1}9.5-Ga{sub 2}7 Ni{sub 5}3.5 ferromagnetic shape memory alloy produced by powder metallurgy; Caracterizacion de la aleacion Ni{sub 5}3.5-Fe{sub 1}9.5-Ga{sub 2}7 con memoria de forma ferromagnetica producida por metalurgia de polvos

Energy Technology Data Exchange (ETDEWEB)

Olmos, L.; Alvarado-Hernandez, F.; Omar Jimenez, H.; Vergara-Hernandez, J.; Arroyo Albiter, M.; Ochoa-Gamboa, R. A.

2015-07-01

The main drawback of ferromagnetic shape memory alloys fabricated through casting methods are its brittleness. In order to overcome this disadvantage, powder metallurgy is an ideal technique for the consolidation of many engineering parts. This paper is focused on the study of the milling and sintering effects of metallic powders over the evolution of the crystalline phases responsibly for the shape memory effect of these materials. To achieve this objective, ferromagnetic shape memory alloy powders (Ni{sub 5}3.5-Fe{sub 1}9.5-Ga{sub 2}7) were prepared from a cast ingot by mechanical milling at two different times of 30 and 60 minutes. The evolution of the phases was investigated through high temperature X-ray diffraction (HTXRD), whereas sintering was analyzed with dilatometry tests. X-ray studies showed that four different phases can be present depending on the particle size and temperature at which the heat treatment was performed. Coarser powders showed a B2 structure along with a γ phase while the finer showed a L21 structure when treated below 1173 K. Furthermore, finer powders had a modulated M14 martensitic structure after sintering at temperatures above 1273 K. The sintering of powders was slow and a mass diffusion mechanism was not clearly observed. (Author)

The Effect of Simulated Thermomechanical Processing on the Transformation Behavior and Microstructure of a Low-Carbon Mo-Nb Linepipe Steel

Science.gov (United States)

Cizek, P.; Wynne, B. P.; Davies, C. H. J.; Hodgson, P. D.

2015-01-01

The present work investigates the transformation behavior of a low-carbon Mo-Nb linepipe steel and the corresponding transformation product microstructures using deformation dilatometry. The continuous cooling transformation (CCT) diagrams have been constructed for both the fully recrystallized austenite and that deformed in uniaxial compression at 1148 K (875 °C) to a strain of 0.5 for cooling rates ranging from 0.1 to about 100 K/s. The obtained microstructures have been studied in detail using electron backscattered diffraction complemented by transmission electron microscopy. Heavy deformation of the parent austenite has caused a significant expansion of the polygonal ferrite transformation field in the CCT diagram, as well as a shift in the non-equilibrium ferrite transformation fields toward higher cooling rates. Furthermore, the austenite deformation has resulted in a pronounced refinement in both the effective grain (sheaf/packet) size and substructure unit size of the non-equilibrium ferrite microstructures. The optimum microstructure expected to display an excellent balance between strength and toughness is a mix of quasi-polygonal ferrite and granular bainite (often termed "acicular ferrite") produced from the heavily deformed austenite within a processing window covering the cooling rates from about 10 to about 100 K/s.

Sintering behavior of LZSA glass-ceramics

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Oscar Rubem Klegues Montedo

2009-06-01

Full Text Available The LZSA glass-ceramic system (Li2O-ZrO2-SiO2-Al2O 3 shows interesting properties, such as good chemical resistance, low thermal expansion, high abrasion resistance, and a low dielectric constant. However, in order to obtain a high performance material for specific applications, the sintering behavior must be better understood so that the porosity may be reduced and other properties improved. In this context, a sintering investigation for a specific LZSA glass-ceramic system composition was carried out. A 18.8Li2O-8.3ZrO2-64.2SiO2-8.7Al 2O3 glass was prepared by melting the solids, quenching the melt in water, and grinding the resulting solid in order to obtain a powder (3.68 μm average particle diameter. Subsequently, the glass powder was characterized (chemical analysis and determination of thermal properties and the sintering behavior was investigated using optical non-contact dilatometry measurements. The results showed that the crystallization process strongly reduced the sintering in the temperature interval from 785 to 940 °C, and a maximum thermal shrinkage of 15.4% was obtained with operating conditions of 1020 °C and 180 minutes.

Predicting bioactive glass properties from the molecular chemical composition: glass transition temperature.

Science.gov (United States)

O'Donnell, Matthew D

2011-05-01

The glass transition temperature (T(g)) of inorganic glasses is an important parameter than can be used to correlate with other glass properties, such as dissolution rate, which governs in vitro and in vivo bioactivity. Seven bioactive glass compositional series reported in the literature (77 in total) were analysed here with T(g) values obtained by a number of different methods: differential thermal analysis, differential scanning calorimetry and dilatometry. An iterative least-squares fitting method was used to correlate T(g) from thermal analysis of these compositions with the levels of individual oxide and fluoride components in the glasses. When all seven series were fitted a reasonable correlation was found between calculated and experimental values (R(2)=0.89). When the two compositional series that were designed in weight percentages (the remaining five were designed in molar percentage) were removed from the model an improved fit was achieved (R(2)=0.97). This study shows that T(g) for a wide range in compositions (e.g. SiO(2) content of 37.3-68.4 mol.%) can be predicted to reasonable accuracy enabling processing parameters to be predicted such as annealing, fibre-drawing and sintering temperatures. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Experimental and Thermodynamic Study of Selected in-Situ Composites from the Fe-Cr-Ni-Mo-C System

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Wieczerzak K.

2016-06-01

Full Text Available The aim of the study was to synthesize and characterize the selected in-situ composites from the Fe-Cr-Ni-Mo-C system, additionally strengthened by intermetallic compounds. The project of the alloys was supported by thermodynamic simulations using Calculation of Phase Diagram approach via Thermo-Calc. Selected alloys were synthesized in an arc furnace in a high purity argon atmosphere using a suction casting unit. The studies involved a range of experimental techniques to characterize the alloys in the as-cast state, including optical emission spectrometry, light microscopy, scanning electron microscopy, electron microprobe analysis, X-ray diffraction and microhardness tests. These experimental studies were compared with the Thermo-Calc data and high resolution dilatometry. The results of investigations presented in this paper showed that there is a possibility to introduce intermetallic compounds, such as χ and σ, through modification of the chemical composition of the alloy with respect to Nieq and Creq. It was found that the place of intermetallic compounds precipitation strongly depends on matrix nature. Results presented in this paper may be successfully used to build a systematic knowledge about the group of alloys with a high volume fraction of complex carbides, and high physicochemical properties, additionally strengthened by intermetallic compounds.

Modeling and Analysis of Deformation for Spiral Bevel Gear in Die Quenching Based on the Hardenability Variation

Science.gov (United States)

Zhang, Yingtao; Wang, Gang; Shi, Wankai; Yang, Lin; Li, Zhichao

2017-07-01

Spiral bevel gears are widely used to transmit energy between intersecting axes. The strength and fatigue life of the gears are improved by carburizing and quenching. A die quenching process is used to control the deformation of the gear. The deformation is determined by the variations in the hardenability for a certain die quenching process. The relationship between hardenability, phase transformation and deformation needs to be studied to minimize deformation during the adjustment of the die quenching process parameters. In this paper, material properties for 22CrMoH steel are determined by the results of Jominy tests, dilatometry experiments and static mechanical property tests. The material models were built based on testing results under the consideration of hardenability variation. An finite element analysis model was developed to couple the phase transformation and deformation history of the complete carburizing and die quenching process for the spiral bevel gears. The final microstructures in the gear were bainite for low hardenability steel and a mixture of bainite and ferrite for high hardenability steel. The largest buckling deformation at the gear bottom surface is 0.375 mm at the outer circle for the low hardenability gear and 0.091 mm at the inner circle for the high hardenability gear.

EFFECTS OF MO ADDITION ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF CAST MICROALLOYED STEEL

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H. Torkamani

2017-09-01

Full Text Available In industry, the cost of production is an important factor and it is preferred to use conventional and low cost procedures for producing the parts. Heat treatment cycles and alloying additions are the key factors affecting the microstructure and mechanical properties of the cast steels. In this study an attempt was made to evaluate the influence of minor Mo addition on the microstructure and mechanical properties of conventionally heat treated cast micro-alloyed steels. The results of Jominy and dilatometry tests and also microstructural examinations revealed that Mo could effectively increase the hardenability of the investigated steel and change the microstructure features of the air-cooled samples. Acicular microstructure was the consequence of increasing the hardenability in Mo-added steel. Besides, it was found that Mo could greatly affect the isothermal bainitic transformation and higher fraction of martensite after cooling (from isothermal temperature was due to the Mo addition. The results of impact test indicated that the microstructure obtained in air-cooled Mo-added steel led to better impact toughness (28J in comparison with the base steel (23J. Moreover, Mo-added steel possessed higher hardness (291HV, yield (524MPa and tensile (1108MPa strengths compared to the base one.

Ash from a pulp mill boiler--characterisation and vitrification.

Science.gov (United States)

Ribeiro, Ana S M; Monteiro, Regina C C; Davim, Erika J R; Fernandes, M Helena V

2010-07-15

The physical, chemical and mineralogical characterisation of the ash resulting from a pulp mill boiler was performed in order to investigate the valorisation of this waste material through the production of added-value glassy materials. The ash had a particle size distribution in the range 0.06-53 microm, and a high amount of SiO(2) (approximately 82 wt%), which was present as quartz. To favour the vitrification of the ash and to obtain a melt with an adequate viscosity to cast into a mould, different amounts of Na(2)O were added to act as fluxing agent. A batch with 80 wt% waste load melted at 1350 degrees C resulting in a homogeneous transparent green-coloured glass with good workability. The characterisation of the produced glass by differential thermal analysis and dilatometry showed that this glass presents a stable thermal behaviour. Standard leaching tests revealed that the concentration of heavy metals in the leaching solution was lower than those allowed by the Normative. As a conclusion, by vitrification of batch compositions with adequate waste load and additive content it is possible to produce an ash-based glass that may be used in similar applications as a conventional silicate glass inclusively as a building ecomaterial. 2010 Elsevier B.V. All rights reserved.

Preparation, Characterization and application of Alumina Powder Produced by advanced Preparation Techniques

International Nuclear Information System (INIS)

Khalil, T.; Abou El Nour, F.; Bossert, J.; Ashor, A.H.

2000-01-01

Aluminum oxide powders were prepared by advanced chemical techniques. The morphology of the produced powders were examined using scanning electron microscopy (SEM). Surface characteristics of the powders were measured through nitrogen gas adsorption and application of the BET equation at 77 K, through the use of nitrogen gas adsorption at liquid nitrogen temperature and application of the Brunauer-Emett-Teller (BET) equation. The total surface area, total pore volume and pore radius of the powders were calculated through the construction of the plots relating the amount of nitrogen gas adsorbed V 1 and the thickness of the adsorbed layer t(V 1 -t plots). The thermal behaviour of the powders were studied with the help of differential thermal analysis (DTA) and thermogravimetry (TG). Due to the presence of some changes in the DTA base lines, possibly as a result of phase transformations, X-ray diffraction was applied to identify these phases. The sintering behaviour of the compact powders after isostatic pressing was evaluated using dilatometry. The sintering temperature of the studied samples were also determined using heating microscopy. The effect of changing sintering temperature and of applying different isostatic pressures on the density and porosity of the compacts was investigated

High density Gd-substituted yttrium iron garnets by coprecipitation

International Nuclear Information System (INIS)

Lamastra, Francesca Romana; Bianco, Alessandra; Leonardi, Federica; Montesperelli, Giampiero; Nanni, Francesca; Gusmano, Gualtiero

2008-01-01

Gadolinium-substituted yttrium iron garnets are ferrite materials of primary importance in microwave engineering. Stoichiometric powders of nominal composition Y 2.6 Gd 0.4 Fe 5 O 12 (i.e. Fe/(Y + Gd) = 1.67) were prepared by reverse strike coprecipitation of metal nitrates. In order to investigate the influence of composition on phase formation, non-stoichiometric powders were also synthesised. On the basis of DTA/TGA analysis, dried coprecipitates were calcined between 600 deg. C and 1200 deg. C and then characterised by ICP, XRD and HT-XRD. Amorphous coprecipitates crystallise around 700 deg. C in cubic garnet phase along with small amounts of YFeO 3 and/or α-Fe 2 O 3 . Only iron-rich garnets, either pure or Gd-substituted, calcined at 1200 deg. C or above display a single-phase cubic garnet. According to thermal dilatometry results, calcined powders were sintered in air up to 1470 deg. C. The microstructure of sintered ceramics is made up of fine grains, the average size ranging between 3 μm and 13 μm. Density of sintered bodies ranged from 88% to 98%. Ferromagnetic resonance linewidth (ΔH -3dB ) ranged between 4352.9 A m -1 and 4392.7 A m -1 , depending on composition and microstructure

Volume Recovery of Polymeric Glasses: Application of a Capacitance-based Measurement Technique

Science.gov (United States)

Sakib, Nazam; Simon, Sindee

Glasses, including polymeric glasses, are inherently non-equilibrium materials. As a consequence, the volume and enthalpy of a glass evolve towards equilibrium in a process termed structural recovery. Several open questions and new controversies remain unanswered in the field. Specifically, the presence of intermediate plateaus during isothermal structural recovery has been reported in recent enthalpy work. In addition, the dependence of the relaxation time on state variables and thermal history is unclear. Dilatometry is particularly useful for structural recovery studies because volume is an absolute quantity and volumetric measurements can be done in-situ. A capillary dilatometer, fitted with a linear variable differential transducer, was used previously to measure volume recovery of polymeric glass formers in our laboratory. To improve on the limitations associated with that methodology, including competition between the range of measurements versus the sensitivity, a capacitance-based technique has been developed following the work of Richert, 2010. The modification is performed by converting the glass capillary dilatometer into a cylindrical capacitor. For precision in capacitance data acquisition, an Andeen-Hagerling ultra-precision capacitance bridge (2550A, 1 kHz) is used. The setup will be tested by performing the signatures of structural recovery as described by Kovacs, 1963. Experiments are also planned to address the open questions in the field.

THERMAL EXPANSION BEHAVIOR OF THE Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF WITH Sm0.2Ce0.8O1.9

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M. AHMADREZAEI

2014-03-01

Full Text Available Nanostructured perovskite oxides of Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF were synthesized through the co-precipitation method. The thermal decomposition, phase formation and thermal expansion behavior of BSCF were characterized by thermogravimetric analysis, X-ray diffraction (XRD, and dilatometry, respectively. XRD peaks were indexed to a cubic perovskite structure with a Pm3m (221 space group. All the combined oxides produced the desired perovskite-phase BSCF. The microstructures were characterized by scanning electron microscopy (SEM and transmission electron microscopy (TEM. The TEM analysis showed that BSCF powders had uniform nanoparticle sizes and high homogeneity. The cross-sectional SEM micrograph of BSCF exhibited a continuous and no delaminated layer from the electrolyte-supported cell. The thermal expansion coefficient (TEC of BSCF was 16.2×10-6 K-1 at a temperature range of 600°C to 800°C. Additional experiments showed that the TEC of BSCF is comparable to that of Sm0.2Ce0.8O1.9 (SDC within the same temperature range. The results demonstrate that BSFC is a promising cathode material for intermediate-temperature solid-oxide fuel cells.

Lithium aluminosilicate reinforced with carbon nanofiber and alumina for controlled-thermal-expansion materials

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Amparo Borrell, Olga García-Moreno, Ramón Torrecillas, Victoria García-Rocha and Adolfo Fernández

2012-01-01

Full Text Available Materials with a very low or tailored thermal expansion have many applications ranging from cookware to the aerospace industry. Among others, lithium aluminosilicates (LAS are the most studied family with low and negative thermal expansion coefficients. However, LAS materials are electrical insulators and have poor mechanical properties. Nanocomposites using LAS as a matrix are promising in many applications where special properties are achieved by the addition of one or two more phases. The main scope of this work is to study the sinterability of carbon nanofiber (CNFs/LAS and CNFs/alumina/LAS nanocomposites, and to adjust the ratio among components for obtaining a near-zero or tailored thermal expansion. Spark plasma sintering of nanocomposites, consisting of commercial CNFs and alumina powders and an ad hoc synthesized β-eucryptite phase, is proposed as a solution to improving mechanical and electrical properties compared with the LAS ceramics obtained under the same conditions. X-ray diffraction results on phase compositions and microstructure are discussed together with dilatometry data obtained in a wide temperature range (−150 to 450 °C. The use of a ceramic LAS phase makes it possible to design a nanocomposite with a very low or tailored thermal expansion coefficient and exceptional electrical and mechanical properties.

Laser sintering of ceramics of Y2O3 pure e doped

International Nuclear Information System (INIS)

Oliveira, T.C. de; Goncalves, R.S.; Silva, R.S. da

2012-01-01

The Yttria (Y 2 O 3 ) is one of the most promising materials for refractory and optical applications due mainly to its high corrosion resistance, wide range of optical transmission and high melting point. However, due to its high melting point, ceramic bodies to obtain high density Y 2 O 3 high temperatures and require special sintering. Recently it has been proposed in the literature a new method of sintering in which a CO 2 laser, in continuous mode, is employed as the primary source of heat during sintering. Irradiation with laser light produces heating surface at elevated temperatures in a time interval of a few seconds, allowing to obtain dense ceramic bodies at elevated temperatures and with different properties from those sintered by conventional methods. In this paper, Y 2 O 3 powders of pure and doped with Mn, Ca and Zn were synthesized by the polymeric precursors and after calcination at 600 ° C/4h showed single phase. For the production and characterization of the samples used techniques DTA / TG, XRD Dilatometry, SEM and Radioluminescence. The sintered ceramics had a high relative density and strong dependence on the dopant used, which accelerate the densification process. Measures Radioluminescence showed characteristic peaks of Y 2 O 3 and dependence on the dopant used. (author)

Influence of the Mo and W additions on the microstructure evolution and mechanical properties in Si-Cr spring steels

International Nuclear Information System (INIS)

Ban, Deok Young; Lee, Sang Lae; Nam, Won Jong

1998-01-01

Effects of the Mo and W additions to Si-Cr spring steels on the microstructural evolution and mechanical properties in spring steels were investigated. It was found that the Mo and/or W addition does not change the behavior of tempered carbide at low temperatures, such as the precipitation of ε-carbide and the conversion of ε-carbide to cementite, via dilatometry tests and the observation of microstructure using TEM. However, it would reduce the coarsening rate of cementite at high temperature above 450 .deg. C, resulting in the smaller size of cementite particles due to the lower diffusion rate. Since the sag resistance depends on the distribution and the size of precipitates, steel C(0.2% W) showed the strongest sag resistance whereas steel A showed the weakest sag resistance, when tempered at 450 .deg. C. Also, an abundance of precipitates at 350 deg. C tempering exhibits the maximum loop area, i.e., the sag resistance for all the tested steels. The Mo and W additions to Si-Cr spring steels raised the ratio of loop area/tensile strength. Therefore, the Mo and W additions would be effective method to increase the sag resistance as well as strength in Si-Cr spring steels

Lithium aluminosilicate reinforced with carbon nanofiber and alumina for controlled-thermal-expansion materials

International Nuclear Information System (INIS)

Borrell, Amparo; García-Moreno, Olga; Torrecillas, Ramón; García-Rocha, Victoria; Fernández, Adolfo

2012-01-01

Materials with a very low or tailored thermal expansion have many applications ranging from cookware to the aerospace industry. Among others, lithium aluminosilicates (LAS) are the most studied family with low and negative thermal expansion coefficients. However, LAS materials are electrical insulators and have poor mechanical properties. Nanocomposites using LAS as a matrix are promising in many applications where special properties are achieved by the addition of one or two more phases. The main scope of this work is to study the sinterability of carbon nanofiber (CNFs)/LAS and CNFs/alumina/LAS nanocomposites, and to adjust the ratio among components for obtaining a near-zero or tailored thermal expansion. Spark plasma sintering of nanocomposites, consisting of commercial CNFs and alumina powders and an ad hoc synthesized β-eucryptite phase, is proposed as a solution to improving mechanical and electrical properties compared with the LAS ceramics obtained under the same conditions. X-ray diffraction results on phase compositions and microstructure are discussed together with dilatometry data obtained in a wide temperature range (−150 to 450 °C). The use of a ceramic LAS phase makes it possible to design a nanocomposite with a very low or tailored thermal expansion coefficient and exceptional electrical and mechanical properties.

Synthesis and thermophysical properties of AMoO4 (A = Ca, Sr, Ba)

International Nuclear Information System (INIS)

Maji, Binoy Kumar; Jena, Hrudananda; Asuvathraman, R.; Govindan Kutty, K.V.

2013-01-01

The alkaline earth molybdates AMoO 4 (A=Ca, Sr, Ba) belong to Scheelite type crystal structure with space group 14 1 /a, and are naturally occurring minerals. They are often found as secondary phases in irradiated oxide nuclear fuels as a product of fission product interaction. These compounds can also form as microcrystallites when the high-level nuclear waste is vitrified. As high temperature ceramics, they find applications as sensor materials, oxide ion conductors, etc. The thermophysical properties of these molybdates are essential for understanding their impact on the high temperature properties of the systems and devices containing them. In the present study, these compounds were synthesized by solid state reaction route in air at 823 K, and characterized by powder XRD and TG/DTA. The thermal expansion behavior was investigated by dilatometry in the temperature range of 300-800 K in air. The % thermal expansion of BaMoO 4 was found to be the lowest among the three compounds. The electrical conductivity of the compounds was measured by AC-impedance spectroscopy, and the conductivity was found to be in the range of 10 -4 S.cm -1 at 1073 K in air. The activation energy of electrical conduction was measured to be about 1.3 eV. (author)

A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements

Energy Technology Data Exchange (ETDEWEB)

Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland [Institute of Materials Physics, Graz University of Technology, A-8010 Graz (Austria)

2016-07-15

Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.

Breakdown of the Arrhenius Law in Describing Vacancy Formation Energies: The Importance of Local Anharmonicity Revealed by Ab initio Thermodynamics

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A. Glensk

2014-02-01

Full Text Available We study the temperature dependence of the Gibbs energy of vacancy formation in Al and Cu from T=0  K up to the melting temperature, fully taking into account anharmonic contributions. Our results show that the formation entropy of vacancies is not constant as often assumed but increases almost linearly with temperature. The resulting highly nonlinear temperature dependence in the Gibbs formation energy naturally explains the differences between positron annihilation spectroscopy and differential dilatometry data and shows that nonlinear thermal corrections are crucial to extrapolate high-temperature experimental data to T=0  K. Employing these corrections—rather than the linear Arrhenius extrapolation that is commonly assumed in analyzing experimental data—revised formation enthalpies are obtained that differ up to 20% from the previously accepted ones. Using the revised experimental formation enthalpies, we show that a large part of the discrepancies between DFT-GGA and unrevised experimental vacancy formation energies disappears. The substantial shift between previously accepted and the newly revised T=0  K formation enthalpies also has severe consequences in benchmarking ab initio methods against experiments, e.g., in deriving corrections that go beyond commonly used LDA and GGA exchange-correlation functionals such as the AM05 functional.

Microstructural and Mechanical Study of Press Hardening of Thick Boron Steel Sheet

Science.gov (United States)

Pujante, J.; Garcia-Llamas, E.; Golling, S.; Casellas, D.

2017-09-01

Press hardening has become a staple in the production of automotive safety components, due to the combination of high mechanical properties and form complexity it offers. However, the use of press hardened components has not spread to the truck industry despite the advantages it confers, namely affordable weight reduction without the use of exotic materials, would be extremely attractive for this sector. The main reason for this is that application of press hardened components in trucks implies adapting the process to the manufacture of thick sheet metal. This introduces an additional layer of complexity, mainly due to the thermal gradients inside the material resulting in though-thickness differences in austenitization and cooling, potentially resulting in complex microstructure and gradient of mechanical properties. This work presents a preliminary study on the press hardening of thick boron steel sheet. First of all, the evolution of the sheet metal during austenitization is studied by means of dilatometry tests and by analysing the effect of furnace dwell time on grain size. Afterwards, material cooled using different cooling strategies, and therefore different effective cooling rates, is studied in terms of microstructure and mechanical properties. Initial results from finite element simulation are compared to experimental results, focusing on the phase composition in through thickness direction. Results show that industrial-equivalent cooling conditions do not lead to gradient microstructures, even in extreme scenarios involving asymmetrical cooling.

Self-irradiation study of plutonium alloys

International Nuclear Information System (INIS)

Oudot, B.

2005-02-01

The plutonium is unstable and produces α or β decays depending on the isotope. These decays generate americium, uranium, helium and different kinds of structural defects. The effects of self-irradiation damage are observed at macroscopic scale, the mechanism occurs from atomic scale. In order to improve our understanding of the self-irradiation effects in PuGa alloys, a technique sensitive to the vacancies and vacancies clusters has been developed: the Positron Annihilation Spectroscopy (PAS). The swelling has been characterized by XRD at a microscopic scale and by dilatometry at a macroscopic scale. Swelling starts just after melting and reaches a saturation between 6 and 36 months depending on the degree of gallium homogeneity in the alloy. Swelling at saturation increases with the gallium content, but the absolute change in the cell parameters is constant during time. PAS showed that vacancies clusters develop immediately. Their concentration increase with time. A part of these clusters is stabilized by helium atoms and leads to the creation of bubbles, which contribution to swelling is negligible. The vacancies and vacancies clusters which are not stabilized by helium contribute to the swelling increase by mechanisms known for other materials. These mechanisms are based on a 'dislocation bias'. The presence of these dislocations can furthermore explain the low mean life time value of positrons at the saturation point. (author)

Si-substituted hydroxyapatite nanopowders: Synthesis, thermal stability and sinterability

International Nuclear Information System (INIS)

Bianco, Alessandra; Cacciotti, Ilaria; Lombardi, Mariangela; Montanaro, Laura

2009-01-01

Synthetic hydroxyapatites incorporating small amounts of Si have shown improved biological performances in terms of enhanced bone apposition, bone in-growth and cell-mediated degradation. This paper reports a systematic investigation on Si-substituted hydroxyapatite (Si 1.40 wt%) nanopowders produced following two different conventional wet methodologies: (a) precipitation of Ca(NO 3 ) 2 .4H 2 O and (b) titration of Ca(OH) 2 . The influence of the synthesis process on composition, thermal behaviour and sinterability of the resulting nanopowders is studied. Samples were characterised by electron microscopy, induced coupled plasma atomic emission spectroscopy, thermal analysis, infrared spectroscopy, N 2 adsorption measurements, X-ray diffraction and dilatometry. Semicrystalline Si-substituted hydroxyapatite powders made up of needle-like nanoparticles were obtained, the specific surface area ranged between 84 and 110 m 2 /g. Pure and Si-substituted hydroxyapatite nanopowders derived from Ca(NO 3 ) 2 .4H 2 O decomposed around 1000 deg. C. Si-substituted hydroxyapatite nanopowders obtained from Ca(OH) 2 were thermally stable up to 1200 deg. C and showed a distinct decreased thermal stability with respect to the homologous pure sample. Si-substituted hydroxyapatites exhibited higher sintering temperature and increased total shrinkage with respect to pure powders. Nanostructured dense ceramics were obtained by sintering at 1100 deg. C Si-substituted hydroxyapatites derived from Ca(OH) 2

Polymerization kinetics of monomers of importance in biomedicine investigated by γirradiation

International Nuclear Information System (INIS)

Bebe, S.; Monteiro, M.J.; Ganachaud, F.; Napper, D.H.; Gilbert, R.G.

1998-01-01

Gamma irradiation was used to initiate the polymerization of NIPAM in water below the LCST. Conversion as a function of time was followed with automated tracking dilatometry. The data were used to show that classical kinetics were obeyed. Relaxation experiments (i.e. where the dilatometer is removed from the γ source) then provide reliable values for the reactivity ratio, k i /k p , the ratio of the termination to propagation rate coefficients. It was found at a monomer concentration of 0.442 M, k i k p had a value of 8.1 at 27 deg C . This suggested that either k t was very low, perhaps because the radicals are constrained to some complexation or aggregation mechanism, or k p is extraordinarily high. Pulsed laser polymerizations (in conjunction with size exclusion chromatography, SEC) were performed to obtain accurate k p values for NIPAM in water over a temperature range below the LCST (2 - 27 deg C ). The main difficulty with most functional polymers is obtaining quantitative data from SEC. PNIPAM is no exception to the rule, and meticulous care in molecular weight analysis was necessary. Special insights were developed into sample preparation to obtain accurate molecular weight distributions (MWD). The value k p was found to be high, but not extraordinarily so, and hence the high value of k t must be due to a constrained polymer radical

Phase Transformations During Cooling of Automotive Steels

Science.gov (United States)

Padgett, Matthew C.

This thesis explores the effect of cooling rate on the microstructure and phases in advanced high strength steels (AHSS). In the manufacturing of automobiles, the primary joining mechanism for steel is resistance spot welding (RSW), a process that produces a high heat input and rapid cooling in the welded metal. The effect of RSW on the microstructure of these material systems is critical to understanding their mechanical properties. A dual phase steel, DP-600, and a transformation induced plasticity bainitic-ferritic steel, TBF-1180, were studied to assess the changes to their microstructure that take place in controlled cooling environments and in uncontrolled cooling environments, i.e. resistance spot welding. Continuous cooling transformation (CCT) diagrams were developed using strip specimens of DP-600 and TBF-1180 to determine the phase transformations that occur as a function of cooling rate. The resulting phases were determined using a thermal-mechanical simulator and dilatometry, combined with light optical microscopy and hardness measurements. The resulting phases were compared with RSW specimens where cooling rate was controlled by varying the welding time for two-plate welds. Comparisons were drawn between experimental welds of DP-600 and simulations performed using a commercial welding software. The type and quantity of phases present after RSW were examined using a variety of techniques, including light optical microscopy using several etchants, hardness measurements, and x-ray diffraction (XRD).

Sintering and thermal ageing studies of zirconia - yttria ceramics by impedance spectroscopy; Estudos de sinterizacao e de envelhecimento termico de ceramicas de zirconia - itria por espectroscopia de impedancia

Energy Technology Data Exchange (ETDEWEB)

Florio, Daniel Zanetti de

1998-07-01

ZrO{sub 2}:8 mol %Y{sub 2}O{sub 3} solid electrolyte ceramic pellets have been prepared with powders of three different origins: a Nissan (Japan) commercial powder, a powder obtained by the coprecipitation technique at IPEN, and the mixing of powder oxides (ZrO{sub 2} produced at a Pilot Plant at IPEN and 99.9% pure Y{sub 2}O{sub 3} of USA origin). These starting powders have been analysed by the following techniques: X-ray fluorescence for yttrium content, X-ray diffraction for structural phase content, sedimentation for particle size distribution, gas adsorption (BET) for surface area determination, and transmission electron microscopy for average particle size determination. Pressed ceramic pellets have been analysed by dilatometry to evaluate the sintering stages. Sintered pellets have been characterized by X-ray diffraction for phase analysis and scanning electron microscopy for grain morphology analysis. Impedance spectroscopy analysis have been carried out to follow thermal ageing of zirconia-yttria solid electrolyte at 600 deg C, the working temperature of permanent oxygen sensor, and to study sintering kinetics. The main results show that ageing at 600 deg C decreases the emf sensor response in the first 100 h to a steady value. Moreover, sintering studies by impedance spectroscopy allowed for finding correlations between electrical parameters, sintering kinetics and grain growth mechanisms. (author)

Sintering and thermal ageing studies of zirconia - yttria ceramics by impedance spectroscopy

International Nuclear Information System (INIS)

Florio, Daniel Zanetti de

1998-01-01

ZrO 2 :8 mol %Y 2 O 3 solid electrolyte ceramic pellets have been prepared with powders of three different origins: a Nissan (Japan) commercial powder, a powder obtained by the coprecipitation technique at IPEN, and the mixing of powder oxides (ZrO 2 produced at a Pilot Plant at IPEN and 99.9% pure Y 2 O 3 of USA origin). These starting powders have been analysed by the following techniques: X-ray fluorescence for yttrium content, X-ray diffraction for structural phase content, sedimentation for particle size distribution, gas adsorption (BET) for surface area determination, and transmission electron microscopy for average particle size determination. Pressed ceramic pellets have been analysed by dilatometry to evaluate the sintering stages. Sintered pellets have been characterized by X-ray diffraction for phase analysis and scanning electron microscopy for grain morphology analysis. Impedance spectroscopy analysis have been carried out to follow thermal ageing of zirconia-yttria solid electrolyte at 600 deg C, the working temperature of permanent oxygen sensor, and to study sintering kinetics. The main results show that ageing at 600 deg C decreases the emf sensor response in the first 100 h to a steady value. Moreover, sintering studies by impedance spectroscopy allowed for finding correlations between electrical parameters, sintering kinetics and grain growth mechanisms. (author)

The Investigation of Strain-Induced Martensite Reverse Transformation in AISI 304 Austenitic Stainless Steel

Science.gov (United States)

Cios, G.; Tokarski, T.; Żywczak, A.; Dziurka, R.; Stępień, M.; Gondek, Ł.; Marciszko, M.; Pawłowski, B.; Wieczerzak, K.; Bała, P.

2017-10-01

This paper presents a comprehensive study on the strain-induced martensitic transformation and reversion transformation of the strain-induced martensite in AISI 304 stainless steel using a number of complementary techniques such as dilatometry, calorimetry, magnetometry, and in-situ X-ray diffraction, coupled with high-resolution microstructural transmission Kikuchi diffraction analysis. Tensile deformation was applied at temperatures between room temperature and 213 K (-60 °C) in order to obtain a different volume fraction of strain-induced martensite (up to 70 pct). The volume fraction of the strain-induced martensite, measured by the magnetometric method, was correlated with the total elongation, hardness, and linear thermal expansion coefficient. The thermal expansion coefficient, as well as the hardness of the strain-induced martensitic phase was evaluated. The in-situ thermal treatment experiments showed unusual changes in the kinetics of the reverse transformation (α' → γ). The X-ray diffraction analysis revealed that the reverse transformation may be stress assisted—strains inherited from the martensitic transformation may increase its kinetics at the lower annealing temperature range. More importantly, the transmission Kikuchi diffraction measurements showed that the reverse transformation of the strain-induced martensite proceeds through a displacive, diffusionless mechanism, maintaining the Kurdjumov-Sachs crystallographic relationship between the martensite and the reverted austenite. This finding is in contradiction to the results reported by other researchers for a similar alloy composition.

Crack-resistant polyimide coating for high-capacity battery anodes

Science.gov (United States)

Li, Yingshun; Wang, Shuo; Lee, Pui-Kit; He, Jieqing; Yu, Denis Y. W.

2017-10-01

Electrode cracking is a serious problem that hinders the application of many next-generation high-capacity anode materials for lithium-ion batteries. Even though nano-sizing the material can reduce fracturing of individual particles, capacity fading is still observed due to large volume change and loss of contact in the electrode during lithium insertion and extraction. In this study, we design a crack-resistant high-modulus polyimide coating with high compressive strength which can hold multiple particles together during charge and discharge to maintain contact. The effectiveness of the coating is demonstrated on tin dioxide, a high-capacity large-volume-change material that undergoes both alloy and conversion reactions. The polyimide coating improves capacity retention of SnO2 from 80% to 100% after 80 cycles at 250 mA g-1. Stable capacity of 585 mAh g-1 can be obtained even at 500 mA g-1 after 300 cycles. Scanning electron microscopy and in-situ dilatometry confirm that electrode cracking is suppressed and thickness change is reduced with the coating. In addition, the chemically-stable polyimide film can separate the surface from direct contact with electrolyte, improving coulombic efficiency to ∼100%. We expect the novel strategy of suppressing electrode degradation with a crack-resistant coating can also be used for other alloy and conversion-based anodes.

Geological and technological characterization of the Late Jurassic-Early Cretaceous clay deposits (Jebel Ammar, northeastern Tunisia) for ceramic industry

Science.gov (United States)

Ben M'barek-Jemaï, Moufida; Sdiri, Ali; Ben Salah, Imed; Ben Aissa, Lassaad; Bouaziz, Samir; Duplay, Joelle

2017-05-01

Late Jurassic-Lower Cretaceous clays of the Jebel Ammar study site were used as raw materials for potential applications in ceramic industry. Physico-chemical characterization of the collected samples was performed using atomic absorption spectroscopy, X-ray diffraction, thermogravimetry and dilatometry (Bugot's curve). Geotechnical study was also undertaken by the assessment of plasticity and liquidity limits. It was found that high concentrations of silica, alumina with SiO2/Al2O3 ratio characterized the studied clays; its high amounts of CaO and Fe2O3 in the Late Jurassic clays indicated their calcareous nature. In addition, technological tests indicated moderate to low plasticity values for the Late Jurassic and Lower Cretaceous clays, respectively. Clay fraction (<2 μm) reached 50% of the natural clay in some cases. Mineralogical analysis showed that Jurassic clays were dominated by smectite, illite and kaolinite, as clay mineral species; calcite was the main associated mineral. Lower Cretaceous clays were mainly composed of abundant illite accompanied by well-crystallized smectite and kaolinite. Kaolinite gradually increased upwards, reaching 70% of the total clay fraction (i.e. <2 μm). Quartz, calcite and feldspar were the main non-clay minerals. Based on these analyses, the clays meet technological requirements that would allow their use in the ceramic industry and for the manufacturing of ceramic tiles.

Liquid phase sintered SiC. Processing and transformation controlled microstructure tailoring

Directory of Open Access Journals (Sweden)

V.A. Izhevskyi

2000-10-01

Full Text Available Microstructure development and phase formation processes during sintering of silicon carbide based materials with AlN-Y2O3, AlN-Yb2O3, and AlN-La2O3 sintering additives were investigated. Densification of the materials occurred by liquid-phase sintering mechanism. Proportion of alpha- and beta-SiC powders in the initial mixtures was a variable parameter, while the molar ratio of AlN/RE2O3, and the total amount of additives (10 vol. % were kept constant. Shrinkage behavior during sintering in interrelation with the starting composition of the material and the sintering atmosphere was investigated by high temperature dilatometry. Kinetics of b-SiC to a-SiC phase transformation during post-sintering heat treatment at temperatures 1900-1950 °C was studied, the degree of phase transformation being determined by quantitative x-ray analysis using internal standard technique. Evolution of microstructure resulting from beta-SiC to alpha-SiC transformation was followed up by scanning electron microscopy on polished and chemically etched samples. Transformation-controlled grain growth mechanism similar to the one observed for silicon nitride based ceramics was established. Possibility of in-situ platelet reinforced dense SiC-based ceramics fabrication with improved mechanical properties by means of sintering was shown.

Development of a Standard Methodology for the Quantitative Measurement of Steel Phase Transformation Kinetics and Dilation Strains Using Dilatometric Methods, QMST (TRP 0015)

Energy Technology Data Exchange (ETDEWEB)

Dr. Manish Metha; Dr. Tom Oakwood

2004-04-28

The purpose of this collaborative project was to develop a standard practice for obtaining and archiving quantitative steel transformation kinetic data and thermal strain data. Two families of dilatometric equipment were employed to develop this standard practice for testing bar product steels. These include high-speed quenching and deformation dilatometers and Gleeble{reg_sign} thermomechanical simulation instruments. Standard measurement, data interpretation and data reporting methods were developed and defined by the cross-industry QMST Consortium members consisting of steel-manufacturers, forgers, heat-treaters, modelers, automotive and heavy vehicle OEMs along with team expert technologists from the National Labs and academia. The team designed phase transformation experiments on two selected steel grades to validate the standard practices--a medium carbon grade SAE 1050 and an alloy steel SAE 8620. A final standard practice document was developed based on the two dilatometry methods, and was submitted to and approved by ASTM (available as A1033-04). The standard practice specifies a method for measuring austenite transformation under no elastic stress or plastic deformation. These methods will be an enabler for the development and electronic archiving of a quantitative database for process modeling using computer simulation software, and will greatly assist endusers in developing accurate process and product simulations during the thermo-mechanical processing of bar and rod product steels.

Simulation of distortion and residual stress in high pressure die casting – modelling and experiments

International Nuclear Information System (INIS)

Hofer, P; Kaschnitz, E; Schumacher, P

2012-01-01

Two individual high-pressure die-casting geometries were developed in order to study the influence of process parameters and different alloys on the distortion behaviour of castings. These geometries were a stress lattice and a V-shaped sample tending to form residual stress due to different wall thickness respectively by a deliberate massive gating system. In the experimental castings the influence of the most important process parameters such as die temperature and die opening time and the cooling regime was examined. The time evolution of process temperatures was measured using thermal imaging. The heat transfer coefficients were adapted to the observed temperature distributions. Castings were produced from the two alloys AlSi12 and AlSi10MnMg. The distortion of the castings was measured by means of a tactile measuring device. For the alloy AlSi10MnMg thermo-physical and thermo-mechanical data were obtained using differential scanning calorimetry, laser flash technique, dilatometry and tensile testing at elevated temperatures. These data were used for modelling the material behaviour of the AlSi10MnMg alloy in the numerical model while for the alloy AlSi12(Fe) literature data were used. Process and stress simulation were conducted using the commercial FEM software ANSYS Workbench. A survey on the results of the comparison between simulation and experiment is given for both alloys.

Effect of heat treatment and plastic deformation on the structure and the mechanical properties of nitrogen-bearing 04N9Kh2A steel

Science.gov (United States)

Blinov, V. M.; Bannykh, O. A.; Lukin, E. I.; Kostina, M. V.; Blinov, E. V.

2014-11-01

The effect of the conditions of heat treatment and plastic deformation on the structure and the mechanical properties of low-carbon martensitic nickel steel (9 wt % Ni) with an overequilibrium nitrogen content is studied. The limiting strain to failure of 04N9Kh2A steel is found to be 40% at a rolling temperature of 20°C and 80% at a rolling temperature of 900°C. Significant strengthening of the steel (σ0.2 = 1089 MPa) is obtained after rolling at a reduction of 40% at 20°C. The start and final temperatures of the α → γ transformation on heating and those of the γ → α transformation on cooling are determined by dilatometry. The specific features of the formation of the steel structure have been revealed as functions of the annealing and tempering temperatures. Electron-microscopic studies show that, after quenching from 850°C and tempering at 600°C for 1 h, the structure contains packet martensite with thin interlayers of retained austenite between martensite crystals. The strength of the nitrogen-bearing 04N9Kh2A steel after quenching from 850 and 900°C, cooling in water, and subsequent tempering at 500°C for 1 h is significantly higher than that of carboncontaining 0H9 steel used in cryogenic engineering.

Principles of TRIP Steel Optimization for Passive Damping Applications

Science.gov (United States)

Fraley, George Jay

Globally many historic structures of cultural significance which do not have systems to mitigate seismic damage are located in areas with heavy seismic activity. Efforts have been undertaken to develop strategies to retrofit such structures, however any intervention must be limited in size for aesthetic reasons. To contribute to this effort, ArcelorMittal aims to create steel-based solutions for passive energy dissipation through plastic deformation during cyclic loading. High-strength TRansformation-Induced Plasticity (TRIP) steels are proposed as an excellent candidate material for this application, due to the extreme combination of high strength and large ductility they are well-known to exhibit. To evaluate high-strength TRIP steels for passive damping applications, isothermal, fully-reversed, displacement-controlled Ultra-Low Cycle Fatigue (ULCF) experiments (Nf stainless steel 316, despite having a yield strength approximately four times larger. For a similar number of cycles to failure the high stability condition dissipated 2.4 times more energy than stainless steel 316 upon initial cycling. The stress-strain hysteresis curves and fatigue life data generated can be input into computational models of passive damping devices for initial concurrent material/device design iterations. Evidence of shear lips, large primary inclusions serving as fracture-initiation sites, and highly dimpled fracture surfaces confirmed for all failed specimens that ductile fracture mechanisms contribute to failure under ULCF conditions. For specimens failing in 10-11 cycles large protrusions aligned along the transverse direction were found, indicating that intergranular fracture may also be playing a role in ULCF failures for this alloy. To explore lower cost alternatives to fully-austenitic TRIP steels for passive-damping devices, austenite precipitation and its effect on uniaxial-tension mechanical properties in martensitic steels was investigated. Isothermal dilatometry

Study of 13Cr-4Ni-(Mo (F6NM Steel Grade Heat Treatment for Maximum Hardness Control in Industrial Heats

Directory of Open Access Journals (Sweden)

Massimo De Sanctis

2017-09-01

Full Text Available The standard NACE MR0175 (ISO 15156 requires a maximum hardness value of 23 HRC for 13Cr-4Ni-(Mo steel grade for sour service, requiring a double tempering heat treatment at temperature in the range 648–691 °C for the first tempering and 593–621 °C for the second tempering. Difficulties in limiting alloy hardness after the tempering of forged mechanical components (F6NM are often faced. Variables affecting the thermal behavior of 13Cr-4Ni-(Mo during single and double tempering treatments have been studied by means of transmission electron microscopy (TEM observations, X-ray diffraction measurements, dilatometry, and thermo-mechanical simulations. It has been found that relatively low Ac1 temperatures in this alloy induce the formation of austenite phase above 600 °C during tempering, and that the formed, reverted austenite tends to be unstable upon cooling, thus contributing to the increase of final hardness via transformation to virgin martensite. Therefore, it is necessary to increase the Ac1 temperature as much as possible to allow the tempering of martensite at the temperature range required by NACE without the detrimental formation of virgin martensite upon final cooling. Attempts to do so have been carried out by reducing both carbon (<0.02% C and nitrogen (<100 ppm levels. Results obtained herein show final hardness below NACE limits without an unacceptable loss of mechanical strength.

Study of rolled uranium annealing process; Etude du recuit de l'uranium lamine

Energy Technology Data Exchange (ETDEWEB)

Cabane, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1954-06-15

The dilatometric study of rolled uranium clearly shows not only the expansions or contractions induced by stress relief or diffusion of vacancies, but also the slope variations of the cooling curves, which are the best evidence of a texture change. Under the microscope, hard-rolled sheets appear as a mixture of two distinct structures; it is also possible by intermediate annealing to prepare homogeneous sheets of either structure, i.e. twinned or untwinned. All these sheets which have similar textures, undergo at first a primary recrystallization beginning at 320 deg C, then a texture change without any apparent crystal growth, at about 430 deg C. (author) [French] L'anisotropie de l'uranium {alpha} se manifeste fortement dans les coefficients de dilatation. Aussi la dilatometrie permet lle de reperer facilement les expansions ou contractions dues a des relachements de tensions ou a des disparitions de lacunes, ainsi que les variations de pente des courbes de refroidissement, qui constituent la plus importante manifestation d'un changement de texture. Au microscope, les toles fortement ecrouies apparaissent generalement formees d'un melange de deux structures differentes; on a pu aussi preparer des toles de structure homogene: les unes formees de cristaux macles, les autres apparemment depourvues de macles. Ces toles, qui ont toutes a peu pres la meme texture, subissent d'abord une recristallisation primaire a partir de 320 deg C, puis a 430 deg C environ, un changement de texture sans grossissement apparent de cristaux. (auteur)

Reactive sintering and microstructure development of tungsten carbide-AISI 304 stainless steel cemented carbides

Energy Technology Data Exchange (ETDEWEB)

Fernandes, C.M. [Department of Materials and Ceramics Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); CEMUC-Mechanical Engineering Department, University of Coimbra, Rua Luís Reis Santos, Pinhal de Marrocos, 3030-788 Coimbra (Portugal); Oliveira, F.J. [Department of Materials and Ceramics Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Senos, A.M.R., E-mail: anamor@ua.pt [Department of Materials and Ceramics Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)

2017-06-01

Sintering of WC-stainless steel (SS) composites within a typical binder range from 6 up to 15 wt% SS was investigated through constant heating rate dilatometry, in vacuum conditions, complemented by differential thermal analysis and by the study of the high temperature wetting behavior of SS on WC. The densification starts ∼900 °C with a typical densification curve for all compositions, where three distinct regions are discernible: the first one with a slow densification rate, followed by a second region where a sharp increase in the densification rate up to a maximum value dependent on the binder amount is observed and, finally, a third one with a slowdown of the densification rate until the end of the thermal cycle. The attained final density at 1450 °C is dependent on the binder amount, increasing proportionally to its initial content. The final microstructure presents a normal grain size distribution and appreciable amounts of eta-phase, besides the major WC phase and residual iron rich phase. The reactive densification behavior and the role of the liquid phase are interpreted accordingly with structural and kinetic data. - Highlights: • Sintering of WC-AISI304 composites starts ∼900 °C and involves three stages. • Densification is largely dominated by a reactive liquid phase sintering process. • Eta-phase constitutes a transient liquid phase during sintering. • Sintering cycles are dependent on the initial binder content.

In situ observation of self-propagating high temperature syntheses of Ta5Si3, Ti5Si3 and TiB2 by proton and X-ray radiography

Science.gov (United States)

Bernert, T.; Winkler, B.; Haussühl, E.; Trouw, F.; Vogel, S. C.; Hurd, A. J.; Smilowitz, L.; Henson, B. F.; Merrill, F. E.; Morris, C. L.; Mariam, F. G.; Saunders, A.; Juarez-Arellano, E. A.

2013-08-01

Self-propagating high temperature reactions of tantalum and titanium with silicon and titanium with boron were studied using proton and X-ray radiography, small-angle neutron scattering, neutron time-of-flight, X-ray and neutron diffraction, dilatometry and video recording. We show that radiography allows the observation of the propagation of the flame front in all investigated systems and the determination of the widths of the burning zones. X-ray and neutron diffraction showed that the reaction products consisted of ≈90 wt% of the main phase and one or two secondary phases. For the reaction 5Ti + 3Si → Ti5Si3 flame front velocities of 7.1(3)-34.2(4) mm/s were determined depending on the concentration of a retardant added to the starting material, the geometry and the green density of the samples. The flame front width was determined to be 1.17(4)-1.82(8) mm and depends exponentially on the flame front velocity. Similarly, for the reaction Ti + 2B → TiB2 flame front velocities of 15(2)-26.6(4) mm/s were determined, while for a 5Ta + 3Si → Ta5Si3 reaction the flame front velocity was 7.05(4) mm/s. The micro structure of the product phase Ta5Si3 shows no texture. From SANS measurements the dependence of the specific surface of the product phase on the particle sizes of the starting materials was studied.

Thermally Stable Ni-rich Austenite Formed Utilizing Multistep Intercritical Heat Treatment in a Low-Carbon 10 Wt Pct Ni Martensitic Steel

Science.gov (United States)

Jain, Divya; Isheim, Dieter; Zhang, Xian J.; Ghosh, Gautam; Seidman, David N.

2017-08-01

Austenite reversion and its thermal stability attained during the transformation is key to enhanced toughness and blast resistance in transformation-induced-plasticity martensitic steels. We demonstrate that the thermal stability of Ni-stabilized austenite and kinetics of the transformation can be controlled by forming Ni-rich regions in proximity of pre-existing (retained) austenite. Atom probe tomography (APT) in conjunction with thermodynamic and kinetic modeling elucidates the role of Ni-rich regions in enhancing growth kinetics of thermally stable austenite, formed utilizing a multistep intercritical ( Quench- Lamellarization- Tempering (QLT)-type) heat treatment for a low-carbon 10 wt pct Ni steel. Direct evidence of austenite formation is provided by dilatometry, and the volume fraction is quantified by synchrotron X-ray diffraction. The results indicate the growth of nm-thick austenite layers during the second intercritical tempering treatment (T-step) at 863 K (590 °C), with austenite retained from first intercritical treatment (L-step) at 923 K (650 °C) acting as a nucleation template. For the first time, the thermal stability of austenite is quantified with respect to its compositional evolution during the multistep intercritical treatment of these steels. Austenite compositions measured by APT are used in combination with the thermodynamic and kinetic approach formulated by Ghosh and Olson to assess thermal stability and predict the martensite-start temperature. This approach is particularly useful as empirical relations cannot be extrapolated for the highly Ni-enriched austenite investigated in the present study.

Quantification of the free volume in Zr45.0Cu39.3Al7.0Ag8.7 bulk metallic glasses subjected to plastic deformation by calorimetric and dilatometric measurements

International Nuclear Information System (INIS)

Zhang Yue; Hahn, Horst

2009-01-01

Zr 45.0 Cu 39.3 Al 7.0 Ag 8.7 bulk metallic glasses (BMGs) were prepared using suction casting technique. Plastic deformations were carried out by cold rolling and high-pressure torsion (HPT). The absolute contents of free volume in the as-cast, preheated and deformed samples were determined by differential scanning calorimetry (DSC) and dilatometry using the free volume model (FVM). The parameters required in the FVM are experimentally determined to be b = 0.107, β = 642.1 kJ/mol, D * = 10.3 and T 0 = 496.9 K, respectively. The equilibrium free volume determined by these parameters is in good agreement with that calculated from previous enthalpy relaxation experiments, showing the reliability of the values of the parameters. It is found that the content of free volume in the as-cast sample is 0.533% with respect to the atomic volume of the BMG. The free volume in the HPT deformed sample is determined to be 0.672%, which is the largest among all the samples. The excess free volume introduced by cold rolling is found to increase with the deformation strain and show weak strain rate dependent behavior. Finally, attempts are made to simulate the experimental DSC curve using a bimolecular kinetics in the flow defect model. However, the result shows that the kinetics of free volume may be more complicated than as described as a bimolecular process.

Characterization of morphology and kinetics of bainite transformation in a low alloy steel

International Nuclear Information System (INIS)

Gupta, C.; Dey, G.K.; Srivastav, D.; Chakravarthy, J.K.; Banerjee, S.

2005-01-01

Bainite transformation is ubiquitous in steels for pressure vessel applications in thermal and nuclear power plants. In this class of steels bainite is the dominant phase found in the microstructure, after industrial thermo-mechanical processing and heat treatment of pressure vessel component. The study of bainite transformation has been carried out using both isothermal and continuous cooling conditions. Previous studies have reported significant differences in the morphology and the type of bainite formed under these two conditions. Continuous cooling has been shown to result in a wider variety of bainite transformation products as compared with isothermal treatments. This has important implications for the technological properties of power plant components such as strength, toughness and hardenability. In the present study the cooling transformation characteristics of a new CrMo pressure vessel steel has been examined using dilatometry supplemented with TEM examination. The dilatometric data were analyzed to determine the activation energy and Avrami exponents. It was found that bainite with different morphologies formed over the cooling rates employed and were kinetically distinct. The dilatometric study along with TEM studies has shown that non-isothermal decomposition of austenite in this steel results in a complex microstructure containing an array of bainite morphologies. The bainitic ferrite plates are seen to be associated with various inter- and intra- plate constituents as the cooling rate changes. Despite this the transformation remains essentially bainitic over the range of cooling rates studied. Three different cooling rate regimes with distinctly different calculated Avrami exponents have been observed. (author)

Evaluation of mechanical properties and microstructural characterization of consolidated Cobalt-Chromium-Molybdenum obtained by selective laser melting and precision casting; Avaliação de propriedades mecânicas e caracterização microestrutural de consolidados de Cobalto-Cromo-Molibdênio obtidos por fusão seletiva a laser e fundição de precisão

Energy Technology Data Exchange (ETDEWEB)

Mergulhão, Marcello Vertamatti

2017-07-01

The objective of this work was to study the mechanical properties and microstructural characterization of specimens of the Co-Cr-Mo alloy obtained by additive manufacturing -selective laser melting (SLM) and precision casting aiming at the manufacture of dental prostheses. The following steps were carried out on Co-Cr-Mo gas-atomized powders: 1) investigation of the physical, chemical and thermal properties of atomized powders in different grain sizes (denominated: D1 <15 μm, D2 20-50 μm and D3 > 75 μm); 2) the consolidation of standard specimens via consolidation techniques; 3) characterization of consolidated by analysis of: cytotoxicity, porosity, X ray diffraction and dilatometry; 4) mechanical characterization of tensile, 3 point bending, hardness (macro and micro Vickers) tests and microstructural characterization (optical and scanning electron microscopy). In general, the results observed were: the grain size D2 (20-50 μm) is the one that best fits in the analysis of packaging, for the consolidation by SLM; the biocompatibility of the samples obtained a positive result for both processing techniques; the mechanical evaluation of the specimens shows that the SLM technique provides superior mechanical properties (yield stress, rupture stress, maximum stress, elongation and hardness), compared to those obtained by the precision casting technique; the microstructure obtained by the SLM process results in an ultrafine grains with high chemical homogeneity, differentiated by the gross dendritic microstructure in the casting process. In this way, the development of the present study evidenced superior quality in manufacturing customized dental components (copings) by SLM technique compared to precision casting. (author)

Glass-ceramics with multibarrier structure obtained from industrial waste

Energy Technology Data Exchange (ETDEWEB)

Berzina, L.; Cimdins, R.; Rozenstrauha, I. [Riga Tech. Univ. (Latvia). Fac. of Chem. Technol.; Bossert, J. [Technisches Inst.: Materialwissenschaft, Friedrich-Schiller-Univ., Jena (Germany); Kravtchenko, I. [Inst. for Problems of Material Science, Kiev (Ukraine)

1997-12-31

Recycling problem for various kind of waste is solved by processing the waste to ecological depositable products with multibarrier structure. In order to form a multibarrier structure the ecologically incompatible substances may be diluted and chemically bound until their recycling products gain a structure like natural mineral or glass (I. barrier). After that, remineralized materials are converted into a new product by melting or powder technology using an ecological compatible type of waste as a matrix phase (II. barrier). Waste which are treated this way could be applied to produce ceramic building materials and goods such as floor tiles, stone pavement and casting products. Industrial waste from the metallurgical factory in Latvia ``Liepajas metalurgs`` are metallurgical slag, filter dust, etching waste and sewage used in technologies. The main constituents of chemical compositions of these waste are: Fe, Ca, Si, Mg, Al, Mn etc. In some types of waste a small amount of ecologically risky elements such as Cr, Ni, Zr, Sn and Pb can occur. The combination of metallurgical waste with peat ashes from Riga thermal power station, oil shale ashes or glass waste under controlled sintering procedure gives bulk materials with surface or/and bulkcrystallization. The structure of glass-ceramics built this way may prevent the migration of ecologically risky elements into environment due to corrosion or friction. Physical-chemical properties and thermal behaviour (DTA, dilatometry, melting) of waste define the range of sintering for production of glass-ceramics (powder technology) and decorative glass-ceramic materials (melting and powder technology). (orig.) 5 refs.

Micro-nanocomposites Al2O3/ NbC/ WC and Al2O3/ NbC/ TaC

International Nuclear Information System (INIS)

Santos, Thais da Silva

2014-01-01

Alumina based ceramics belong to a class of materials designated as structural, which are widely used in cutting tools. Although alumina has good properties for application as a structural ceramics, composites with different additives have been produced with the aim of improving its fracture toughness and mechanical strength. New studies point out micro-nanocomposites, wherein the addition of micrometric particles should enhance mechanical strength, and nano-sized particles enhance fracture toughness. In this work, alumina based micro nanocomposites were obtained by including nano-sized NbC and micrometer WC particles at 2:1, 6:4, 10:5 and 15:10 vol% proportions, and also with the inclusion of nano-sized NbC and micrometer TaC particles at 2:1 vol% proportion. For the study of densification, micro-nanocomposites were sintered in a dilatometer with a heating rate of 20°C/min until a temperature of 1800°C in argon atmosphere. Based on the dilatometry results, specimens were sintered in a resistive graphite furnace under argon atmosphere between 1500°C and 1700°C by holding the sintering temperature for 30 minutes. Densities, crystalline phases, hardness and tenacity were determined, and micro-nanocomposites microstructures were analyzed. The samples Al 2 O 3 : NbC: TaC sintered at 1700 ° C achieved the greater apparent density (~ 95% TD) and the sample sintered at 1600 ° C showed homogeneous microstructure and increased hardness value (15.8 GPa) compared to the pure alumina . The compositions with 3% inclusions are the most promising for future applications. (author)

Evaluation of mechanical properties and microstructural characterization of consolidated Cobalt-Chromium-Molybdenum obtained by selective laser melting and precision casting

International Nuclear Information System (INIS)

Mergulhão, Marcello Vertamatti

2017-01-01

The objective of this work was to study the mechanical properties and microstructural characterization of specimens of the Co-Cr-Mo alloy obtained by additive manufacturing -selective laser melting (SLM) and precision casting aiming at the manufacture of dental prostheses. The following steps were carried out on Co-Cr-Mo gas-atomized powders: 1) investigation of the physical, chemical and thermal properties of atomized powders in different grain sizes (denominated: D1 <15 μm, D2 20-50 μm and D3 > 75 μm); 2) the consolidation of standard specimens via consolidation techniques; 3) characterization of consolidated by analysis of: cytotoxicity, porosity, X ray diffraction and dilatometry; 4) mechanical characterization of tensile, 3 point bending, hardness (macro and micro Vickers) tests and microstructural characterization (optical and scanning electron microscopy). In general, the results observed were: the grain size D2 (20-50 μm) is the one that best fits in the analysis of packaging, for the consolidation by SLM; the biocompatibility of the samples obtained a positive result for both processing techniques; the mechanical evaluation of the specimens shows that the SLM technique provides superior mechanical properties (yield stress, rupture stress, maximum stress, elongation and hardness), compared to those obtained by the precision casting technique; the microstructure obtained by the SLM process results in an ultrafine grains with high chemical homogeneity, differentiated by the gross dendritic microstructure in the casting process. In this way, the development of the present study evidenced superior quality in manufacturing customized dental components (copings) by SLM technique compared to precision casting. (author)

Microstrain temperature evolution in β-eucryptite ceramics: Measurement and model

International Nuclear Information System (INIS)

Bruno, G.; Garlea, V.O.; Muth, J.; Efremov, A.M.; Watkins, T.R.; Shyam, A.

2012-01-01

Mechanisms of microcracking and stress release in β-eucryptite ceramics were investigated by applying a combination of neutron diffraction (ND), dilatometry and the Integrity Factor Model (IFM). It was observed that the macroscopic thermal expansion of solid samples closely follows the lattice thermal expansion as a function of temperature, and both are dominated by microcracks closing (during heating) and opening (during cooling). Analogous experiments on powders showed that the stresses that manifest peak shift are indeed relieved by comminution, and that the resulting lattice thermal expansion can be considered as unconstrained. By means of Rietveld refinement of the ND data, the evolution with temperature of peak width parameters linked to strain distributions along the basal, pyramidal and axial planes could also be extracted. The peak width parameters S HKL correlated well with the strains calculated by peak shift and with the model results. Furthermore, while the peak shifts showed that the powders are basically stress free, the S HKL showed a strong evolution of the peak width. Powders carry, therefore, a measurable strain distribution inside the particles, owing to the thermal expansion anisotropy of the crystallites. The IFM allowed this behavior to be rationalized, and the effect of microcracking on thermal expansion to be quantified. Experimental data allowed accurate numerical prediction of microcracking on cooling and of the evolution of microstresses. They also allowed the derivation of the material elastic modulus from bulk thermal expansion curves through the IFM concept. Ultrasound resonance measurements of the elastic modulus strongly support these theoretical predictions.

Vacancies and atomic processes in intermetallics - From crystals to quasicrystals and bulk metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Schaefer, Hans-Eckhardt [Institute of Theoretical and Applied Physics, Stuttgart University, Pfaffenwaldring 57, 70569 Stuttgart (Germany); Baier, Falko [Voith Turbo Comp., Alexanderstr. 2, 89552 Heidenheim (Germany); Mueller, Markus A. [GFT Technologies A. G., Filderhauptstr. 142, 70599 Stuttgart (Germany); Reichle, Klaus J. [Philipp-Matthaeus-Hahn School, Jakob-Beutter-Str. 15, 72336 Balingen (Germany); Reimann, Klaus [NXP Semiconductors, Central Research and Development, High Tech Campus 4, 5656 AE Eindhoven (Netherlands); Rempel, Andrey A. [Institute of Solid State Chemistry, Russian Academy of Sciences, Ul. Pervomaiskaya 91, 620041 Ekaterinburg (Russian Federation); Sato, Kiminori [Tokyo Gakugei University, Nukuikita 4-1-1, Koganei, Tokyo 184-8501 (Japan); Ye, Feng [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, 30 Xue Yuan Road, Beijing 100083 (China); Zhang, Xiangyi [Yanshan University, Qinhuangdao 066004 (China); Sprengel, Wolfgang [Institute of Materials Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria)

2011-10-15

A review is given on atomic vacancies in intermetallic compounds. The intermetallic compounds cover crystalline, quasicrystalline, and bulk metallic glass (BMG) structures. Vacancies can be specifically characterized by their positron lifetimes, by the coincident measurement of the Doppler broadening of the two quanta emitted by positron-electron annihilation, or by time-differential dilatometry. By these techniques, high concentrations and low mobilities of thermal vacancies were found in open-structured B2 intermetallics such as FeAl or NiAl, whereas the concentrations of vacancies are low and their mobilities high in close-packed structure as, e.g., L1{sub 2}-Ni{sub 3}Al. The activation volumes of vacancy formation and migration are determined by high-pressure experiments. The favorable sublattice for vacancy formation is found to be the majority sublattice in Fe{sub 61}Al{sub 39} and in MoSi{sub 2}. In the icosahedral quasicrystal Al{sub 70}Pd{sub 21}Mn{sub 9} the thermal vacancy concentration is low, whereas in the BMG Zr{sub 57}Cu{sub 15.4}Ni{sub 12.6}Nb{sub 3}Al{sub 10} thermal vacancies are found in high concentrations with low mobilities. This may determine the basic mechanisms of the glass transition. Making use of the experimentally determined vacancy data, the main features of atomic diffusion studies in crystalline intermetallics, in quasicrystals, and in BMGs can be understood. Manfred Faehnle and his group have substantially contributed to the theoretical understanding of vacancies and diffusion mechanisms in intermetallics. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

The effect of adding magnesium oxide on the mechanical properties of the tricalcium phosphate-zirconia composites

Energy Technology Data Exchange (ETDEWEB)

Sallemi, Imen, E-mail: imen.sallemi@hotmail.com; Bouaziz, Jamel; Ben Ayed, Foued

2015-02-01

The effect of magnesium oxide on the mechanical properties of the tricalcium phosphate – 50 wt.% zirconia composites was investigated during a sintering process between 1300 °C and 1400 °C. The characteristics of the samples before and after the sintering process were realized by using the differential thermal analysis, dilatometry, X-ray diffraction, the {sup 31}P magic angle scanning nuclear magnetic resonance, the scanning electron microscope and by considering such mechanical properties as the rupture strength and Vickers hardness. The mechanical performances of the tricalcium phosphate-50 wt.% zirconia composites increased with both the percentage of magnesium oxide and the sintering temperature. At 1400 °C, the mechanical properties of the composites sintered with 10 wt.% magnesium oxide reached their maximum value. Thus, Vickers hardness increased from 554 to 6350 MPa and the rupture strength of the corresponding composites varied from 5.2 to 25 MPa. The increase of the mechanical properties of the samples is due to the formation of both the tetragonal zirconia phase and the liquid phase which helps to fill the pores. The microstructure of needle form is most probably phosphate precipitates which are formed from this liquid phase. Furthermore, the presence of magnesium oxide in the composites prevented the inverse allotropic transformation of zirconia. - Highlights: • We measure the rupture strength and Vickers hardness of bioceramics. • We characterize the effect of MgO on the mechanical properties of the tricalcium phosphate – 50 wt% zirconia composites. • MgO increase the mechanical properties of the composites.

Structural analysis and thermal behavior of diopside-fluorapatite-wollastonite-based glasses and glass-ceramics.

Science.gov (United States)

Kansal, Ishu; Tulyaganov, Dilshat U; Goel, Ashutosh; Pascual, Maria J; Ferreira, José M F

2010-11-01

Glass-ceramics in the diopside (CaMgSi2O6)-fluorapatite (Ca5(PO4)3F)-wollastonite (CaSiO3) system are potential candidates for restorative dental and bone implant materials. The present study describes the influence of varying SiO2/CaO and CaF2/P2O5 molar ratio on the structure and thermal behavior of glass compositions in the CaO-MgO-SiO2-P2O5-Na2O-CaF2 system. The structural features and properties of the glasses were investigated by nuclear magnetic resonance (NMR), infrared spectroscopy, density measurements and dilatometry. Sintering and crystallization behavior of the glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. The microstructure and crystalline phase assemblage in the sintered glass powder compacts were studied under non-isothermal heating conditions at 825 °C. X-ray diffraction studies combined with the Rietveld-reference intensity ratio (R.I.R) method were employed to quantify the amount of amorphous and crystalline phases in the glass-ceramics, while scanning electron microscopy was used to shed some light on the microstructure of resultant glass-ceramics. An increase in CaO/SiO2 ratio degraded the sinterability of the glass powder compacts, resulting in the formation of akermanite as the major crystalline phase. On the other hand, an increase in P2O5/CaF2 ratio improved the sintering behavior of the glass-ceramics, while varying the amount of crystalline phases, i.e. diopside, fluorapatite and wollastonite. Copyright © 2010. Published by Elsevier Ltd.

Influence of molybdenum content on transformation behavior of high performance bridge steel during continuous cooling

International Nuclear Information System (INIS)

Chen, Jun; Tang, Shuai; Liu, Zhenyu; Wang, Guodong

2013-01-01

Highlights: ► The bainite transformation field was refined. ► The empirical equation to estimate the GF s was established. ► Transformation behavior was studied with serially increasing Mo addition. ► The molybdenum content can be lowered as the cooling rate is increased. ► GF transformation field is also shifted to right by increasing Mo content. - Abstract: The continuous-cooling-transformation (CCT) diagrams of high performance bridge steel with different molybdenum content were plotted by means of a combined method of dilatometry and metallography. The results show that the molybdenum addition of 0.17 wt% does not noticeably alter the transformation behavior, whereas 0.38 wt% significantly. In addition, the molybdenum addition of 0.38 wt% completely eliminates the formation of polygonal ferrite (PF) and significantly lower the granular ferrite (GF) transformation starting temperatures throughout the range of cooling rates studied. At lower cooling rates, with the increase of the molybdenum content, the martensite/austenite (M/A) constituents are noticeably refined, whereas the effects are not obvious at higher cooling rates. Moreover, the molybdenum addition of 0.38 wt% can significantly increase the Vickers hardness, but the Vickers hardness increments (by comparison of Mo-0.17wt% steel and Mo-0.38wt% steel) are sharply reduced at the cooling rate of 30 °C/s, indicating that at higher cooling rate, the molybdenum usage can be saved and the higher strengthen can be also gained. It could be found the GF transformation starting temperature is linear with the cooling rate. The empirical equation was established to calculate GF transformation starting temperatures, and the calculated values are in good agreement with measured ones

The role of the native oxide shell on the microwave sintering of copper metal powder compacts

International Nuclear Information System (INIS)

Mahmoud, Morsi M.; Link, Guido; Thumm, Manfred

2015-01-01

Highlights: • Thin oxide native layer had a critical role on microwave sintering of copper. • Explain why microwaves interact with copper powder differently than its bulk. • Abnormal expansion in copper is due to the plastic deformation and crack formation. • In-situ setup gives important insight about the microwave sintering of metals. • Microwave sintering is a promising candidate technology in powder metallurgy. - Abstract: Successful microwave sintering of several metal powders had been reported by many researchers with remarkable improvements in the materials properties and/or in the overall process. However, the concept behind microwave heating of metal powders has not been fully understood till now, as it is well known that bulk metals reflect microwaves. The progress of microwave sintering of copper metal powder compacts was investigated via combining both in-situ electrical resistivity and dilatometry measurements that give important information about microstructural changes with respect to the inter-particle electrical contacts during sintering. The sintering behavior of copper metal powders was depending on the type of the gas used, particle size, the initial green density, the soaking sintering time and the thin oxide layer on the particles surfaces. The thin copper oxide native layer (ceramics) that thermodynamically formed on the particles surfaces under normal handling and ambient environmental conditions had a very critical and important role in the microwave absorption and interaction, the sintering behavior and the microstructural changes. This finding could help to have a fundamental understanding of why MW’s interact with copper metal powder in a different way than its bulk at room temperature, i.e. why a given metal powder could be heated using microwaves while its bulk reflects it

Polymorphism of Bi1-xLnxO1.5 phases (04Ln2O9 (x=0.33; Ln=La, Pr, Nd)

International Nuclear Information System (INIS)

Drache, Michel; Huve, Marielle; Roussel, Pascal; Conflant, Pierre

2003-01-01

The Bi 1-x Ln x O 1.5 solid solutions (Ln=La, Pr, Nd), of the β 2 /β 1 /ε (Bi-Sr-O) structural type, have been investigated in their Ln-rich domains. For Ln=La, Pr, and Nd, the upper limits are 0.35, 0.35 and 0.33, respectively. The Bi 4 Ln 2 O 9 ε phase (x=0.33) appears to be the single definite compound. For Bi 4 La 2 O 9 , Bi 4 Pr 2 O 9 and Bi 4 Nd 2 O 9 , the ε-type cells are respectively: a=9.484(4) A, b=3.982(2) A, c=7.030(3) A, β=104.75(3) deg.; a=9.470(5) A, b=3.945(2) A, c=6.968(4) A, β=104.73(3) deg. and a=9.439(3) A, b=3.944(2) A, c=6.923(2) A, β=105.03(3) deg. . Upon heating, each monoclinic (ε) compound transforms successively into rhombohedral phases (β 2 /β 1 ) and finally into a cubic fluorite-type phase. For La- and Pr-based compounds, all transitions are reversible; for Nd, depending on the thermal treatment, the reversibility of ε→β 2 can be incomplete. These transformations are characterized using X-ray thermodiffractometry, differential thermal analysis, dilatometry and impedance spectroscopy versus temperature. Examination of Bi 4 (Ln, Ln') 2 O 9 samples allows to correlate the evolution of the thermal behavior and of the unit cell parameters, to the lanthanide size. A partial plot of the (Bi 2 O 3 ) 1-x -(La 2 O 3 ) x phase diagram (0≤x≤0.40) is proposed

Metals Processing Laboratory Users (MPLUS) Facility Annual Report FY 2002 (October 1, 2001-September 30, 2002)

Energy Technology Data Exchange (ETDEWEB)

Angelini, P

2004-04-27

The Metals Processing Laboratory Users Facility (MPLUS) is a Department of Energy (DOE), Energy Efficiency and Renewable Energy, Industrial Technologies Program, user facility designated to assist researchers in key industries, universities, and federal laboratories in improving energy efficiency, improving environmental aspects, and increasing competitiveness. The goal of MPLUS is to provide access to the specialized technical expertise and equipment needed to solve metals processing issues that limit the development and implementation of emerging metals processing technologies. The scope of work can also extend to other types of materials. MPLUS has four primary user centers: (1) Processing--casting, powder metallurgy, deformation processing (including extrusion, forging, rolling), melting, thermomechanical processing, and high-density infrared processing; (2) Joining--welding, monitoring and control, solidification, brazing, and bonding; (3) Characterization--corrosion, mechanical properties, fracture mechanics, microstructure, nondestructive examination, computer-controlled dilatometry, and emissivity; and (4) Materials/Process Modeling--mathematical design and analyses, high-performance computing, process modeling, solidification/deformation, microstructure evolution, thermodynamic and kinetic, and materials databases A fully integrated approach provides researchers with unique opportunities to address technologically related issues to solve metals processing problems and probe new technologies. Access is also available to 16 additional Oak Ridge National Laboratory (ORNL) user facilities ranging from state-of-the-art materials characterization capabilities, and high-performance computing to manufacturing technologies. MPLUS can be accessed through a standardized user-submitted proposal and a user agreement. Nonproprietary (open) or proprietary proposals can be submitted. For open research and development, access to capabilities is provided free of charge

Metals Processing Laboratory Users (MPLUS) Facility Annual Report: October 1, 2000 through September 30, 2001

Energy Technology Data Exchange (ETDEWEB)

Angelini, P

2004-04-27

The Metals Processing Laboratory Users Facility (MPLUS) is a Department of Energy (DOE), Energy Efficiency and Renewable Energy, Industrial Technologies Program user facility designated to assist researchers in key industries, universities, and federal laboratories in improving energy efficiency, improving environmental aspects, and increasing competitiveness. The goal of MPLUS is to provide access to the specialized technical expertise and equipment needed to solve metals processing issues that limit the development and implementation of emerging metals processing technologies. The scope of work can also extend to other types of materials. MPLUS has four primary User Centers including: (1) Processing--casting, powder metallurgy, deformation processing including (extrusion, forging, rolling), melting, thermomechanical processing, high density infrared processing; (2) Joining--welding, monitoring and control, solidification, brazing, bonding; (3) Characterization--corrosion, mechanical properties, fracture mechanics, microstructure, nondestructive examination, computer-controlled dilatometry, and emissivity; (4) Materials/Process Modeling--mathematical design and analyses, high performance computing, process modeling, solidification/deformation, microstructure evolution, thermodynamic and kinetic, and materials data bases. A fully integrated approach provides researchers with unique opportunities to address technologically related issues to solve metals processing problems and probe new technologies. Access is also available to 16 additional Oak Ridge National Laboratory (ORNL) user facilities ranging from state of the art materials characterization capabilities, high performance computing, to manufacturing technologies. MPLUS can be accessed through a standardized User-submitted Proposal and a User Agreement. Nonproprietary (open) or proprietary proposals can be submitted. For open research and development, access to capabilities is provides free of charge while

Thermal behavior of GeO{sub 2} doped PbO-B{sub 2}O{sub 3}-ZnO-Bi{sub 2}O{sub 3} glasses

Energy Technology Data Exchange (ETDEWEB)

Cheng Yin [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Xiao Hanning [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China)]. E-mail: hnxiao@hnu.cn; Guo Weiming [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Guo Wenming [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China)

2006-05-15

PbO-B{sub 2}O{sub 3}-ZnO-Bi{sub 2}O{sub 3} glass is a representative system for vacuum and electronic sealing. Effects of GeO{sub 2} on thermal properties of the glass have been investigated in this paper. Activation energy for crystallization, glass structure, the type of crystals were characterized by differential scanning calorimetry, infrared spectroscopy, X-ray diffraction and optical microscopy. Results indicate that the addition of GeO{sub 2} (0.4-2 wt.%) to PbO-B{sub 2}O{sub 3}-ZnO-Bi{sub 2}O{sub 3} glass can suppress crystallization of the glass and decrease the sealing temperature. With the increase of GeO{sub 2} content, germanate crystals were revealed, resulting in a slight increase of sealing temperature. When the content of GeO{sub 2} is 0.7 wt.%, the glass possesses the highest stability and lowest sealing temperature (400 deg. C), which is desirable for low-temperature sealing. The coefficient of thermal expansion of PbO-B{sub 2}O{sub 3}-ZnO-Bi{sub 2}O{sub 3} glass was measured by dilatometry. The result shows that the coefficient of thermal expansion of the glass increases with the content of GeO{sub 2}. The adjustability of the coefficient of thermal expansion would expand the applications of PbO-B{sub 2}O{sub 3}-ZnO-Bi{sub 2}O{sub 3} glass. A flexural strength of 28.3 MPa was obtained at the GeO{sub 2} content of 0.7 wt.%, showing good mechanical property for sealing process.

Some of the properties of plutonium and the aluminium-plutonium alloy; Quelques proprietes du plutonium et de l'alliage aluminium-plutonium

Energy Technology Data Exchange (ETDEWEB)

Abramson, R; Boucher, R; Fabre, R; Monti, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1959-07-01

1- Study of the physical properties of plutonium. 1) Study of the allotropy of plutonium. a) Thermal analysis: the apparatus used and the measurement technique are briefly described. The transition point temperatures and the corresponding heats of transformation have been determined. Finally, the results of the particular study of certain transition points are given. b) Dilatometry. The dilatometric analysis of the phase changes of plutonium has been carried out by means of the Chevenard dilatometer with photographic recording. The testing conditions (heating and cooling speeds, isotherm plateaux) have been varied in order to determine accurately the characteristics of each transition, particularly the {delta} {yields} {gamma} transition on cooling. 2) Micrography of plutonium. For the accurate preparation of metallographic samples the electrolytic polishing must be rapid, which implies a mechanical polishing of excellent quality. Information is given on new attacking reagents which show the structure of the metal very clearly. 2- Study of aluminium-plutonium alloys. Comparative study of Al-Pu and Al-U alloys rich in aluminium. a) Thermal analysis. The liquids and fusion temperatures of the eutectic Al-XAl{sub 4}, have been accurately determined. From the measurement of the heats of fusion the exact composition of the eutectic alloy has been determined. b) Thermal treatments. The eutectic coalescence kinetics have been studied by a micrographic method and by following the evolution of hardness. The results obtained show that the phenomenon is more rapid in Al-Pu alloys than in Al-U alloys. c) Micrographic study of the transition XAl{sub 3} {yields} XAl{sub 4}. The peritectic reaction XAl{sub 3} + liq. {yields} XAl{sub 4} has been suppressed by quenching. The transformation of the XAl{sub 3} phase to the solid phase has been studied as well as the effect of small additions of silicon on the kinetics of this reaction. (author) [French] 1- Etude des proprietes

Study of the low temperature oxidation of uranium powders and its application to the sintering of uranium oxide powders; Etude de l'oxydation des poudres dtranium a basse temperature et son application au frittage de poudres d'uranium oxyde

Energy Technology Data Exchange (ETDEWEB)

Conte-Albert, M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-06-01

The uranium oxygen reaction has been studied with a view to obtaining U-UO{sub 2} samples containing about 20 per cent by weight of UO{sub 2} starting from spherical grain uranium powder (36 {mu} < {phi} < 50 {mu}). The techniques used are micrography, thermogravimetry, sintering under pressure, radio-crystallography. At 170 deg. C in air or argon + oxygen mixtures, the uranium oxide formed is always UO{sub 2} and it is uniformly distributed around the initial uranium spheres. These mixed powders can easily be sintered under pressure in the {gamma}-phase. The density of the samples obtained is 85 to 90 per cent of the theoretical density. The influence of UO{sub 2} on the properties of uranium has been shown by the use of dilatometry and thermal cycling in the {alpha} phase. The temperatures at which the phase changes {alpha} {r_reversible} {beta} and {beta} {r_reversible} {gamma} occur are lowered, the remnant expansion is decreased. High density samples resist well to thermal cycling; the characteristic defects of uranium: high distortion, wrinkled surface, have almost disappeared. Heat treatments in a secondary vacuum at 1050 deg. C cause crystallization of UO{sub 2} in a geometrical form and the appearance of a phase of the F.C.C. crystalline type having the composition U{sub W}C{sub X}O{sub Y}N{sub Z}. This phase causes a new decrease in the {alpha} {r_reversible} {beta}, {beta} {r_reversible} {gamma} transformation temperatures for the uranium. After ten dilatometric cycles the remanent expansion of the sample is about 0.5 per cent. The resistance to thermal cycling of a low density sample which has been heat-treated is similar to that of a high density sample which has not undergone a heat treatment. (author) [French] La reaction uranium-oxygene a ete etudiee pour permettre l'obtention d'echantillons U-UO{sub 2} a 20 pour cent en poids environ d'UO{sub 2}, a partir de billes d'uranium pulverulent (36 {mu} < {phi} < 50 {mu}). Les

Influence of temperature, cold deformation and a constant mechanical load on the microstructural stability of a nitrogen alloyed duplex stainless steel

International Nuclear Information System (INIS)

Weisbrodt-Reisch, A.; Brummer, M.; Hadler, B.; Wolbank, B.; Werner, E.A.

2006-01-01

The influence of temperature, cold deformation and constant mechanical load on the microstructural stability and the kinetics of phase decomposition of a nitrogen-alloyed duplex stainless steel (0.34 wt.% N) was investigated. Calculation of the phase equilibria was done with THERMOCALC using the steel database TCFE3 in order to predict the stability of the phases and to estimate the influence of temperature on the fraction and chemical composition of the phases. Various ageing treatments between 800 deg. C and 1300 deg. C were performed for different time intervals with controlled heating and cooling rates. In order to determine the influence of deformation, annealing at 800 deg. C after cold deformation as well as dilatometry experiments were performed under a constant mechanical compressive load at 800 deg. C and 900 deg. C. Microstructural characterization was carried out by means of light microscopy, electron microscopy and X-ray diffractometry. It was found that the microstructural evolution under a thermal load alone in the temperature range above 950 deg. C concerns mainly the transformation of austenite to ferrite, while below 950 deg. C ferrite decomposition and precipitation of nitrides occur. Since duplex stainless steels possess a microstructure consisting of paramagnetic austenite and ferromagnetic ferrite, the kinetics of ferrite decomposition can be determined easily by magnetic inductive measurements. The results of the microstructural investigations and the measurements of the saturation magnetization show that there is a satisfactory agreement with the theoretical predictions based on THERMOCALC. Ferrite decomposition is significantly accelerated by strain introduced during cold deformation. Furthermore, even under a small mechanical load the kinetics of phase decomposition behaviour at 900 deg. C is drastically changed. Whereas during short annealing times the microstructure remains nearly stable the same annealing conditions under a constant

Pressless process in route of obtaining sintered Nd–Fe–B magnets

Energy Technology Data Exchange (ETDEWEB)

Popov, A.G, E-mail: apopov@imp.uran.ru [Institute of Metal Physics, UB of the RAS, 18, S. Kovalevskoy, Street, 620990 Ekaterinburg (Russian Federation); Golovnia, O.A. [Institute of Metal Physics, UB of the RAS, 18, S. Kovalevskoy, Street, 620990 Ekaterinburg (Russian Federation); Bykov, V.A. [Institute of Metallurgy, UB of the RAS, 101, Amundsena, Street, 620016 Ekaterinburg (Russian Federation)

2015-06-01

A short review on the pressless process (PLP) involved in the manufacture of sintered Nd–Fe–B magnet is given. Two approaches to increasing the degree of powder alignment with a high filling density ρ{sub f} in PLP-containers are proposed. (1) An increase in the pulse duration of applied magnetic field from 3.6 to 6.5 ms enhances the magnetic alignment of magnets prepared from the powder with ρ{sub f}=2.5 g/cm{sup 3} and ρ{sub f}=3 g/cm{sup 3} by 3% and 11%, respectively. (2) Addition of internal lubricants such as zinc stearate or esters reduces friction forces between the powder particles and, when the concentration of lubricants is bellow a critical concentration C{sub cr}, increases B{sub r} and (BH){sub max} by 5–7%. Simulation of the magnetic alignment of uniaxial particles demonstrates that a decrease in the coefficient of friction between the powder particles from 0.9 to 0.6 caused by the lubricant addition enhances the alignment degree. Contact dilatometry was used to study the anisotropy of densification of PLP-powders upon sintering. It has been shown that the anisotropy of the powder shrinkage is formed at the first stage of sintering at the temperature about 800 °C and is caused by the capillary action in the Nd-rich liquid. - Highlights: • A review of the pressless process for NdFeB magnets in the world and Russia is given. • Enhancement of the alignment degree by application of pulsed magnetic field is studied. • Reduction of the friction forces via addition of internal lubricants is proposed. • The simulation of the magnetic alignment of Nd–Fe–B uniaxial particles is presented. • A reason of anisotropic shrinkage of the powder at sintering is suggested.

Study of U - Pu - Fe alloys (Masurca critical experiment)

International Nuclear Information System (INIS)

Barthelemy, P.; Boucher, R.

1965-01-01

Three compositions have been studied: 73.5 U - 25 Pu - 1.5 Fe (weight %) 74 U - 25 Pu - 1 Fe 74.5 U - 25 Pu - 0.5 Fe Elaboration and Casting are easy. After two weeks in air 74.5 U - 25 Pu - 0.5 Fe alloys are reduced in powder. As-cast alloys containing 1 and 1,5% Fe are kept undamaged during several months. A rapid oxidisation of the alloys is however observed when the samples undergo the phase transformation (at 595 deg. C and 590 deg. C respectively). Ignition tests in the presence of air show that the oxidisation starts at about 250 deg. C and that the reaction does not spread. Ignition is not observed during heating from 20 to 660 deg. C. The transformation temperature, the melting temperature and the thermal expansion coefficients have been determined by dilatometry. Below the transformation temperature, the principal phases are U-Pu zeta and (U, Pu) 6 Fe. Thermal conductibility, Young modulus, density and heat of fusion have been measured. Compatibility tests show that between U-Pu-Fe and stainless steel a phase of (U, Pu) 6 Fe type is formed. The 74 U - 25 Pu - 1% Fe alloy seems to behave better than 73.5 U - 25 Pu - 1.5% Fe alloy because the (U, Pu) 6 Fe layer is two or three times smaller. Finally, the thermal stability has been studied with the 74 U - 25 Pu - 1% Fe alloy. A dilatometric anomaly (very weak expansion) occurs when the sample is heated above transformation temperature and cooled. But there is no anomaly by thermal cycling from 50 deg. C to 400 deg. C and there is no deterioration of alloys by heat treatments at 100 deg. C, 200 deg. C, 300 deg. C during 5 months under vacuum. (authors) [fr

In situ X-ray and neutron diffraction of the Ruddlesden–Popper compounds (RE2−xSrx)0.98(Fe0.8Co0.2)1−yMgyO4−δ (RE=La, Pr): Structure and CO2 stability

International Nuclear Information System (INIS)

Chatzichristodoulou, C.; Hauback, B.C.; Hendriksen, P.V.

2013-01-01

The crystal structure of the Ruddlesden–Popper compounds (La 1.0 Sr 1.0 ) 0.98 Fe 0.8 Co 0.2 O 4−δ and (La 1.2 Sr 0.8 ) 0.98 (Fe 0.8 Co 0.2 ) 0.8 Mg 0.2 O 4−δ was investigated at 1000 °C in N 2 (a O2 =1×10 −4 ) by in-situ powder neutron diffraction. In-situ powder X-ray diffraction (PXD) was also employed to investigate the temperature dependence of the lattice parameters of the compounds in air and the oxygen activity dependence of the lattice parameters at 800 °C and 1000 °C. The thermal and chemical expansion coefficients, determined along the two crystallographic directions of the tetragonal unit cell, are highly anisotropic. The equivalent pseudo-cubic thermal and chemical expansion coefficients are in agreement with values determined by dilatometry. The chemical stability in CO 2 containing environments of various Ruddlesden–Popper compounds with chemical formula (RE 2−x Sr x ) 0.98 (Fe 0.8 Co 0.2 ) 1−y Mg y O 4−δ (RE=La, Pr), as well as their stability limit in H 2 /H 2 O=4.5 were also determined by in-situ PXD for x=0.9, 1.0 and y=0, 0.2. - Graphical abstract: Influence of electronic configuration on bond length, lattice parameters and anisotropic thermal and chemical expansion. Highlights: ► The thermal and chemical expansion coefficients are largely anisotropic. ► The expansion of the perovskite layers is constrained along the a direction. ► The studied compositions show remarkable thermodynamic stability upon reduction. ► The thermal and chemical expansion coefficients are lower than related perovskites. ► The investigated materials decompose in CO 2 containing atmospheres

On the Prediction of α-Martensite Temperatures in Medium Manganese Steels

Science.gov (United States)

Field, Daniel M.; Baker, Daniel S.; Van Aken, David C.

2017-05-01

A new composition-based method for calculating the α-martensite start temperature in medium manganese steel is presented and uses a regular solution model to accurately calculate the chemical driving force for α-martensite formation, Δ G_{{Chem}}^{γ \\to α } . In addition, a compositional relationship for the strain energy contribution during martensitic transformation was developed using measured Young's moduli ( E) reported in literature and measured values for steels produced during this investigation. An empirical relationship was developed to calculate Young's modulus using alloy composition and was used where dilatometry literature did not report Young's moduli. A comparison of the Δ G_{{Chem}}^{γ \\to α } normalized by dividing by the product of Young's modulus, unconstrained lattice misfit squared ( δ 2), and molar volume ( Ω) with respect to the measured α-martensite start temperatures, M_{{S}}^{α } , produced a single linear relationship for 42 alloys exhibiting either lath or plate martensite. A temperature-dependent strain energy term was then formulated as Δ G_{{str}}^{γ \\to α } ( {{{J}}/{{mol}}} ) = EΩ δ2 (14.8 - 0.013T) , which opposed the chemical driving force for α-martensite formation. M_{{S}}^{α } was determined at a temperature where Δ G_{{Chem}}^{γ \\to α } + Δ G_{{str}}^{γ \\to α } = 0 . The proposed M_{{S}}^{α } model shows an extended temperature range of prediction from 170 K to 820 K (-103 °C to 547 °C). The model is then shown to corroborate alloy chemistries that exhibit two-stage athermal martensitic transformations and two-stage TRIP behavior in three previously reported medium manganese steels. In addition, the model can be used to predict the retained γ-austenite in twelve alloys, containing ɛ-martensite, using the difference between the calculated M_{{S}}^{ɛ} and M_{{S}}^{α }.

Role of Cu During Sintering of Fe0.96Cu0.04 Nanoparticles

Science.gov (United States)

Sivaprahasam, D.; Sriramamurthy, A. M.; Bysakh, S.; Sundararajan, G.; Chattopadhyay, K.

2018-04-01

Nanoparticle agglomerates of passivated Fe ( n-Fe) and Fe0.96Cu0.04 ( n-Fe0.96Cu0.04), synthesized through the levitational gas condensation (LGC) process, were compacted and sintered using the conventional powder metallurgy method. The n-Fe0.96Cu0.04 agglomerates produced lower green density than n-Fe, and when compacted under pressure beyond 200 MPa, they underwent lateral cracking during ejection attributed to the presence of a passive oxide layer. Sintering under dynamic hydrogen atmosphere can produce a higher density of compact in n-Fe0.96Cu0.04 in comparison to n-Fe. Both the results of dilatometry and thermogravimetric (TG) measurements of the samples under flowing hydrogen revealed enhancement of the sintering process as soon as the reduction of oxide layers could be accomplished. The shrinkage rate of n-Fe0.96Cu0.04 reached a value three times higher than n-Fe at a low temperature of 723 K (450 °C) during heating. This enhanced shrinkage rate was the manifestation of accumulation of Cu at the surface of the particles. The formation of a thin-surface melted layer enriched with copper during heating to isothermal holding facilitated as a medium of transport for diffusion of the elements. The compacts produced by sintering at 773 K (500 °C), with relative density 82 pct, were found to be unstable and oxidized instantly when exposed to ambient atmosphere. The stable compacts of density more than 92 pct with 300- to 450-nm grain size could only be produced when sintering was carried out at 973 K (700 °C) and beyond. The 0.22 wt pct residual oxygen obtained in the sintered compact is similar to what is used for conventional ferrous powder metallurgy products.

Study of flux and mud stone with potential for using in porcelainized stoneware tile compositions; Estudo de fundente e argilito com potencial para uso em formulacoes de porcelanato

Energy Technology Data Exchange (ETDEWEB)

Hoffmann, F.S.; Santos, G. dos; Morelli, M.R., E-mail: felipesh@gmail.com [Departamento de Engenharia de Materiais, Universidade Federal de S. Carlos - UFSCar, S. Carlos, SP (Brazil)

2012-04-15

The porcelain tile is distinguished in the current market for ceramic tiles, with excellent technical and esthetic characteristics. In the present study traditional ceramic raw materials were selected and a standard formulation conventionally reported in the literature was adopted aiming to replace the melting phase (feldspar) of the composition for a raw material that forms liquid phase at high temperature, and replacement of the clay fraction by a mudstone of lower refractoriness. The aim of this study was to evaluate the use of these materials as alternative techniques and lower cost, since, in a mass of porcelain tile, the amount of flux is very large (representing approximately 50% of total raw materials used). The nepheline syenite was the natural raw material selected to replace the feldspar due to the fact that it belongs to the family of feldspathoids, and has similar physicochemical characteristics, therefore, a high fluxing efficiency. To replace the clay fraction was chosen a mudstone naturally occurring, abundant in the region of Santa Gertrudes, SP. Substitutions to the feldspar and clay fraction were completely and/or partially by means of combinations between the flux and mud stones. The masses were processed from the mixing of powders, wet milling, drying, disagglomeration, compaction and firing. In addition to the vitrification curves, techniques such as dilatometry, measurements of porosity, flexure strength test, electron microscopy and X-ray diffraction were used to characterize the material after firing at various temperatures. The results showed that, in principle, it is possible the combination of raw materials such as nepheline and mudstone to replace potassium feldspar and S. Simao clay, as they provide the vitrification at lower temperatures. Compositions with both materials showed lower values of water absorption (<0.1%) and high mechanical strength (> 45 MPa), despite higher pyroplastic strain at 1150 deg C (author)

Modeling of the integrity of machining surfaces: application to the case of 15-5 PH stainless steel finish turning

International Nuclear Information System (INIS)

Mondelin, A.

2012-01-01

During machining, extreme conditions of pressure, temperature and strain appear in the cutting zone. In this thermo-mechanical context, the link between the cutting conditions (cutting speed, lubrication, feed rate, wear, tool coating...) and the machining surface integrity represents a major scientific target. This PhD study is a part of a global project called MIFSU (Modeling of the Integrity and Fatigue resistance of Machining Surfaces) and it focuses on the finish turning of the 15-5PH (a martensitic stainless steel used for parts of helicopter rotor). Firstly, material behavior has been studied in order to provide data for machining simulations. Stress-free dilatometry tests were conducted to obtain the austenitization kinetics of 15-5PH steel for high heating rates (up to 11,000 degrees C/s). Then, parameters of Leblond metallurgical model have been calibrated. In addition, dynamic compression tests (de/dt ranging from 0.01 to 80/s and e ≥ 1) have been performed to calibrate a strain-rate dependent elasto-plasticity model (for high strains). These tests also helped to highlight the dynamic recrystallization phenomena and their influence on the flow stress of the material. Thus, recrystallization model has also been implemented.In parallel, a numerical model for the prediction of machined surface integrity has been constructed. This model is based on a methodology called 'hybrid' (developed during the PhD thesis of Frederic Valiorgue for the AISI 304L steel). The method consists in replacing tool and chip modeling by equivalent loadings (obtained experimentally). A calibration step of these loadings has been carried out using orthogonal cutting and friction tests (with sensitivity studies of machining forces, friction and heat partition coefficients to cutting parameters variations).Finally, numerical simulations predictions of microstructural changes (austenitization and dynamic recrystallization) and residual stresses have been successfully compared with

Estudio y caracterización de vidriados vitrocerámicos basados en piroxeno

Directory of Open Access Journals (Sweden)

Lucas, F.

2004-10-01

Full Text Available A method was proposed to develop pyroxene-based glass-ceramic glazes. First, was studied, by X-ray diffraction and scanning electron microscopy, the effect of several additives in the monophasic crystallization of pyroxene from glasses in the CaO•MgO•Al2O3•SiO2 quaternary system. After, it was determined the sinterization intervals and thermal properties of the glasses, by hot stage microscopy and dilatometry. Finally, some studied glasses were chosen and glazed tiles were developed under fast firing wall- and floor-tile industrial cycles. The results proved the reproducibility of the microstructural characteristics obtained in the previous study with glasses. The measurement of different mechanical properties confirmed their potential application in nowadays industrial processing.

En este trabajo se presenta una metodología para desarrollar vidriados vitrocerámicos basados en piroxeno. En primer lugar se ha estudiado, mediante difracción de rayos X y microscopía electrónica de barrido, el efecto de diferentes aditivos en la cristalización monofásica de piroxeno a partir de vidrios en el sistema CaO•MgO•Al2O3•SiO2. Posteriormente, se han determinado los intervalos de sinterización y características térmicas de los vidrios, mediante microscopía de calefacción y dilatometría. Finalmente, con los vidrios seleccionados se han preparado piezas esmaltadas mediante tratamientos térmicos utilizados habitualmente en la industria de pavimento y revestimiento, comprobando la reproducibilidad de las características microestructurales obtenidas en los estudios iniciales en vidrios. Se han medido sobre las piezas esmaltadas diferentes propiedades que permiten confirmar su potencial aplicación en procesados industriales de monococción y/o bicocción.

Phase transformation in delta Pu alloys at low temperature: in situ dilatometric study

Energy Technology Data Exchange (ETDEWEB)

Texier, G.; Oudot, B.; Platteau, C.; Ravat, B.; Delaunay, F. [CEA Valduc, 21 - Is-sur-Tille (France)

2010-07-01

The purpose of this work is to precisely study the martensitic transformation in a plutonium-gallium alloy. Thus, the thermodynamics and kinetics of the {delta} {yields} {alpha}' + {delta} transformation in a Pu-Ga alloy were studied under isochronal and isothermal conditions. The activation energy of the {delta} {yields} {alpha}' + {delta} phase transformation at a constant cooling rate (0.5 K. min{sup -1}) was determined by using Kissinger and Ozawa models. The average value of the activation energy was found to be at -56 kJ.mol{sup -1}. Dilatometry measurement was also used to trace 'in situ' the entire transformation for several temperatures. The kinetics of the {delta} {yields} {alpha}' + {delta} transformation were modelled under isothermal conditions in the theoretical frame of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. It is proposed that the transformation consists of three stages. The {alpha}' transformation begins with a nucleation of pre-existing embryos. Then, both nucleation and rapid growth of {alpha}' occurs simultaneously and finally, the plates width expend. Apparent activation energies for nucleation and growth transformation were determined from the temperature dependence of the constant K at respectively -34 kJ.mol{sup -1} and -60 kJ.mol{sup -1}. Dler et al. [1] investigated also the thermodynamics and the kinetics of the martensitic transformation in Pu alloys. These nucleation energies were found by modelling of heterogeneous martensitic nucleation via strain interaction with observed superdislocation-like nucleation sites in PuGa alloys. The values obtain by this model was very close to those we find. Investigations in steels alloys indicate that these energies are of the same order for nucleation near dislocation. Then, it could be indicating a strong relationship between these dislocations and martensitic nucleation sites. (authors)

Phase transformation in {delta} Pu alloys at low temperature: In situ dilatometric study

Energy Technology Data Exchange (ETDEWEB)

Texier, G; Oudot, B; Platteau, C; Ravat, B; Delaunay, F, E-mail: gwenael.texier@cea.fr, E-mail: benoit.oudot@cea.fr [CEA, DAM, Valduc, Is sur Tille 21120 (France)

2010-03-15

The purpose of this work is to precisely study the martensitic transformation in a plutonium-gallium alloy. Thus, the thermodynamics and kinetics of the {delta}{yields}{alpha}'+{delta} phase transformation in a Pu-Ga alloy were studied under isochronal and isothermal conditions. The activation energy of the {delta}{yields}{alpha}'+{delta} phase transformation at a constant cooling rate (0.5 K.min{sup -1}) was determined by using Kissinger and Ozawa models. The average value of the activation energy was found to be at -56 kJ.mol{sup -1}. Dilatometry measurement was also used to trace 'in situ' the entire transformation for several temperatures. The kinetics of the {delta}{yields}{alpha}'+{delta} transformation were modelled under isothermal conditions in the theoretical frame of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. It is proposed that the transformation consists of three stages. The {alpha}' transformation begins with a nucleation of pre-existing embryos. Then, both nucleation and rapid growth of {alpha}' occurs simultaneously and finally, the plates width expend. Apparent activation energies for nucleation and growth transformation were determined from the temperature dependence of the constant K at respectively -34 kJ.mol{sup -1} and -60 kJ.mol{sup -1}. Adler et al. [1] investigated also the thermodynamics and the kinetics of the martensitic transformation in Pu alloys. These nucleation energies were found by modelling of heterogeneous martensitic nucleation via strain interaction with observed superdislocation-like nucleation sites in PuGa alloys. The values obtain by this model was very close to those we find. Investigations in steels alloys indicate that these energies are of the same order for nucleation near dislocation. Then, it could be indicating a strong relationship between these dislocations and martensitic nucleation sites.

Extreme conditions magnetostriction study of the Shastry-Sutherland sample SCBO

Science.gov (United States)

Grockowiak, Audrey; Wehinger, BjöRn; Coniglio, William; Ruegg, Chistian; Tozer, Stanley; National High Magnetic Field Laboratory Team; Paul Scherrer Institute Collaboration

The Shasty-Sutherland model, which consists of a set of spin 1/2 dimers on a 2D square lattice, is simple and soluble but captures a central theme of condensed matter physics by sitting precariously on the quantum edge between isolated, gapped excitations and collective, ordered ground states. This model is realized in SrCu2(BO3)2. Recent x-ray diffraction data revealed a direct correlation of the lattice with magnetic susceptibility measurements at low temperatures. The variation of the lattice parameters with temperature is thus directly linked to the spin response of the system. Indeed, scattering intensities from the spin waves, measured by inelastic neutron scattering experiments, decay accordingly. The magnetic correlations can thus be monitored by the lattice parameters and are thus sensitive to magnetostriction. Ambient pressure magnetostriction up to 100.7 T show clear signatures related to the magnetization plateaus at 30, 40 and 80T. Together with total energy calculations these studies revealed a strong magneto elastic coupling driven by the super exchange angle CuOCu. Applying hydrostatic external pressure results in continuous and discontinuous quantum phase transitions. Zero field high pressure neutron spectroscopy measurements have revealed so far three phases : spin dimer from 0 to 2GPa, antiferromagnetic from 4 to 6 GPa, and a 4-spin plaquette singlet state was recently identified in the 2 to 4GPa region. We report here on high pressure (up to 2GPa), high magnetic field (up to 65T) and 3He temperature magnetostriction experiments, using FBGs. Fiber Bragg Grating (FBG) Dilatometry permits to measure the magnetostriction of a sample in function of the response of an optical fiber to applied strain. This work was performed at the NHMFL, supported by the NSF Cooperative Agreement No. DMR-1157490 and the State of Florida, and the DOE NNSA DE-NA0001979 Grant.

Incorporação de resíduo do tratamento de drenagem ácida em massa de cerâmica vermelha Incorporation of acid drainage treatment sludge waste into red ceramic products

Directory of Open Access Journals (Sweden)

S. L. Galatto

2009-03-01

Full Text Available Neste trabalho, apresenta-se o estudo experimental em escala laboratorial e industrial da incorporação de resíduo do tratamento de Drenagem Ácida de Mina (DAM na formulação de massa de cerâmica vermelha, com substituição parcial das argilas. Foram realizados algumas análises e ensaios nas amostras dos blocos cerâmicos: análise dilatométrica a verde, absorção de água, resistência à compressão, eflorescência de sais solúveis e emissões atmosféricas (MP e SOx. Os resultados das análises nos corpos de prova ensaiados indicam aumento de resistência a compressão. Os ensaios de eflorescência de sais solúveis indicam maior intensidade de cristalização de sais solúveis na superfície dos corpos de prova e blocos cerâmicos à medida que se aumenta o percentual de resíduo. As análises realizadas nos blocos cerâmicos ensaiados em escala industrial, recomendam uma proporção de até 2,5% de resíduo na massa cerâmica.An experimental laboratory and industry scale study of the incorporation of residue from Acid Drainage Mine (ADM in the ceramics mass, with partial substitution of clays, is presented. Some analyses and assays of the ceramic blocks were been carried out: dilatometry, water absorption, compressive strength, efflorescence and emissions (MP and SOx. The results show an increase of compressive strength. The efflorescence assays indicate greater intensity of crystallization of soluble salts in the surface of the ceramic blocks for increasing residue content. The analyses in the ceramic blocks in industrial scale recommend a ratio of up to 2.5% of waste in bulk ceramics.

Synthesis and characterization of Al2O3NbC composite and the effect of Y2O3 addition on its sintering

International Nuclear Information System (INIS)

Pasotti, Rosa Maria da Rocha

1999-01-01

Alumina composites containing ceramic particles have been intensively studied because they show improved mechanical properties and some advantages over fibres and whiskers based composites mainly for processing. The embedment of NbC particles in an Al 2 O 3 matrix has been investigated in this work. Composite materials were obtained by the conventional ceramic processing with compositions Al 2 O 3 -x NbC where x=10, 20, and 40 weight %. Materials were sintered in argon at 1650 deg C/30 min, and at 1750 deg C/15min using a graphite resistance furnace. Three sets of samples were processed: containing NbC powder as received; containing NbC powder milled for 30 h; and containing 3 weight % of Y 2 O 3 added to the Al 2 O 3 matrix. After sintering samples were analysed to evaluate the densification grade. Phases were determined by X-ray diffraction, and samples were analysed by optical microscopy, scanning electron microscopy and transmission electron microscopy to observe the microstructure features. Hardness and fracture toughness at room temperature were also determined by the indentation method, and the sintering kinetic was evaluated by dilatometry. The present work shows that Al 2 O 3 -NbC composite can be produced by using pressureless sintering, leading to materials with densities higher than 95% of the theoretical density for all composites containing NbC and sintered at 1750 deg C. The same result can be obtained for composites containing 10 and 20 weight % of NbC, and sintered at temperatures as low as 1650 deg C. Higher concentration of NbC in the Al 2 O 3 matrix promotes an improvement of fracture toughness. Samples with 40-wt % of NbC show K IC equals to 4.5 MPa.m 1/2 . This value is compared to the ones previously determined for Al 2 O 3 - TiC composites, available commercially and used in ceramic cutting-tools. (author)

Preparation and sintering of Zr(C,N,O) phases

International Nuclear Information System (INIS)

Tamborenea, S.; Mazzoni, A.D.; Aglietti, E.F.

2003-01-01

The Zr(C,O,N) compounds form a great mono-phase zone belonging to the pseudoternary ZrO-ZrN-ZrC system.Theses phases have cubic crystalline structure with a o parameter depending on the C, O 2 and N 2 content.These phases have many potential applications in the manufacture of ceramic pieces utilizable as electronic conductors.The Zr (C,O,N) phases can be obtained from ZrO 2 by carbonitriding reactions: that is carbothermal reduction and simultaneous nitriding.In this work a series of experiences of carbonitriding of zirconia under different conditions (temperatures between 1400 and 1600degC, times of 120 min, carbon content between 20 and 40%) in order to obtain suitable powders to be sintered.The XRD analysis shows the Zr(C,O,N) as the main products and β -ZrON as the only secondary product in proportions depending on the obtaining conditions.The variables employed were the C content and the reaction temperature.The Zr(C,O,N) content varies between 40 and 90% and tends to increase with the temperature and the carbon content whereas the β -ZrON phase varies between the 40 and 10 % decreasing its proportion with temperature and the carbon content.The oxidation resistance of these phases was studied by DTA-TG tests in air.Results show complete oxidation reaction at ∼500degC in air.The sintering of these materials was made on disks obtained by pressing of powders of Zr(C,N,O) contents higher than 90%.Sintering was performed in nitrogen atmosphere and temperatures between 1450 and 1620degC.Disks were characterized by pycnometry and Hg volumeter.The densities obtained were between 5 and 6,6g/cm 3 with a tendency to increase with the Zr(C,N,O) phase content, the temperature and the sintering time.Sintered disks were characterized by dilatometry in N 2

Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications

International Nuclear Information System (INIS)

Duarte, Daniel Gomes

2009-01-01

The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning electron

Mechanisms and mechanics of shape loss during supersolidus liquid-phase sintering

Science.gov (United States)

Lal, Anand

Rapid sinter densification of relatively coarse prealloyed powders is possible by exceeding the solidus temperature in an approach termed supersolidus liquid phase sintering (SLPS). However, narrow processing windows for densification without distortion often limit this process. The liquid films at the grain boundaries that are responsible for densification also reduce the structural rigidity of components. Hence, components tend to slump under their own weight. Thus, the present study investigates shape loss during SLPS and rationalizes the processing and material factors with regard to separating densification from distortion. Experiments are performed on various prealloyed powders, including bronze, 316L stainless steel, and T15 tool steel. Differential thermal analysis, dilatometry, and in situ video imaging of sintering compacts are used to follow melting, densification, and distortion, respectively. Further, density and dimensional measurements are performed on sintered compacts. Results indicate a dependence of distortion on the sintering temperature and time, compact size, and melting behavior of the alloy. It is shown that the sintering temperature window, where high-density, precise components are obtained, can be widened for 316L stainless steel by boron addition. For the first time, a beam bending technique is used to measure the macroscopic apparent viscosity of semisolid bronze. The viscosity drops with temperature above the solidus and lies in the range of 108 to 106 Pa-s. Additionally, the in situ transverse rupture strength of bronze is measured to demonstrate the softening above the solidus temperature. Further, microstructural measurements are performed to enable correlation with the slumping behavior and viscosity. A model combining the deformation mechanisms, driving forces, and microstructural characteristics is developed to predict the conditions for densification and distortion onset. The microstructure is also correlated with the magnitude

Isothermal and aniso-thermal creep in the {alpha} phase domain, {beta} phase domain and {alpha}+{beta} two phase domain in a Zr-1%NbO alloy; Fluage isotherme et anisotherme dans les domaines monophases ({alpha} et {beta}) et biphases ({alpha} et {beta}) d'un alliage Zr-1%NbO

Energy Technology Data Exchange (ETDEWEB)

Kaddour, D

2004-12-15

The coupling between phase transformation and mechanical behaviour of a Zr-1%NbO alloy was studied using an original experimental device already used in a previous study devoted to the Zy-4 alloy. The Zr-1%NbO alloy undergoes a phase transformation {alpha} (hc) {r_reversible} (cc) typically between 750 and 1000 C. The transformation temperatures were measured in situ by using the resistivity and dilatometry techniques. The isothermal creep behaviour of fuel cladding tubes was studied, first after heating, in the {alpha} phase domain between 650 and 760 C, in the {beta} phase domain between 960 and 1100 C, as well as in the ({alpha} + {beta}) two phase domain between 800 and 900 C. The results are summarized in Ashby deformation mechanism maps. It is confirmed that the {beta} phase is much more sensitive to creep flow than the {alpha} phase. The effect of microstructure on the isothermal creep flow behaviour was then investigated by first applying a thermal cycle involving either a full or a partial transformation from {alpha} to {beta}. It was investigated both in the {alpha} phase domain, and after direct cooling into the ({alpha} + {beta}) phase domain. The behaviour in aniso-thermal conditions was finally studied at heating and cooling rates of 10 and 200 C/min. In both cases, we showed that there is no significant transformation plasticity in the stress range under investigation ({<=} 5 MPa). A finite element model using Voronoi polyhedra and eventually meshing a film of intergranular {beta} phase was used to describe the behaviour of material in the ({alpha} + {beta}) domain in various microstructural states. The model predictions are in good agreement with the experimental results for the microstructure obtained after cooling, but the model underestimates creep deformation in the as-received state. This difference is probably related to the fact that interface sliding is not taken into account in the model. (author)

Characterization of cure kinetics and physical properties of a high performance, glass fiber-reinforced epoxy prepreg and a novel fluorine-modified, amine-cured commercial epoxy

Science.gov (United States)

Bilyeu, Bryan

Kinetic equation parameters for the curing reaction of a commercial glass fiber reinforced high performance epoxy prepreg composed of the tetrafunctional epoxy tetraglycidyl 4,4-diaminodiphenyl methane (TGDDM), the tetrafunctional amine curing agent 4,4'-diaminodiphenylsulfone (DDS) and an ionic initiator/accelerator, are determined by various thermal analysis techniques and the results compared. The reaction is monitored by heat generated determined by differential scanning calorimetry (DSC) and by high speed DSC when the reaction rate is high. The changes in physical properties indicating increasing conversion are followed by shifts in glass transition temperature determined by DSC, temperature-modulated DSC (TMDSC), step scan DSC and high speed DSC, thermomechanical (TMA) and dynamic mechanical (DMA) analysis and thermally stimulated depolarization (TSD). Changes in viscosity, also indicative of degree of conversion, are monitored by DMA. Thermal stability as a function of degree of cure is monitored by thermogravimetric analysis (TGA). The parameters of the general kinetic equations, including activation energy and rate constant, are explained and used to compare results of various techniques. The utilities of the kinetic descriptions are demonstrated in the construction of a useful time-temperature-transformation (TTT) diagram and a continuous heating transformation (CHT) diagram for rapid determination of processing parameters in the processing of prepregs. Shrinkage due to both resin consolidation and fiber rearrangement is measured as the linear expansion of the piston on a quartz dilatometry cell using TMA. The shrinkage of prepregs was determined to depend on the curing temperature, pressure applied and the fiber orientation. Chemical modification of an epoxy was done by mixing a fluorinated aromatic amine (aniline) with a standard aliphatic amine as a curing agent for a commercial Diglycidylether of Bisphenol-A (DGEBA) epoxy. The resulting cured network

Thermal expansion of superconducting fulleride and borocarbide compounds

International Nuclear Information System (INIS)

Burkhart, G.J.

1995-08-01

In order to detact and analyze thermodynamic phase transitions, the investigation of the thermal expansion via capacitance dilatometry is a powerful experimental technique, due to the extremely high resolution (ΔL/L∝10 -8 -10 -10 ). With respect to the air sensitivity of the fullerides a dilatometer operating under inert atmosphere was designed and the thermal expansion of polycrystalline fulleride (Rb 3 C 60 , K 3 C 60 ) and borocarbide (YNi 2 B 2 C, LuNi 2 B 2 C) compounds was determined in the temperature range 5-320 K. Most effort was focused on a quantitative evaluation of the discontinuity in the thermal expansivity α at the superconducting transition. The results are discussed in the context of the Ehrenfest relation, which connects the jump in the thermal expansivity Δα with the pressure dependence of the superconducting transition temperature dT c /dp and the jump in the specific heat Δc p /T c at the superconducting transition. For Rb 3 C 60 and K 3 C 60 the jump in the specific heat can be derived via the Ehrenfest relation using the results of the thermal expansion measurements and the well-known pressure dependence of the superconducting transition temperature. The derived values for Rb 3 C 60 and K 3 Cu 60 are Δc p /T c ∝75mJ/molK 2 and Δc p /T c ∝64 mJ.molK 2 , respectively. The directly measured specific heat jump of K 3 C 60 gives approximately the same value of Δc p /T c , and, therefore, the use of the Ehrenfest relation on fullerides is justified. The specific heat jumps Δc p /T c , determined from theoretically derived values of the density of states at the Fermi level N(E F ) and the McMillan-parameter λ, exceed the experimental results by a factor of 1.5-2. This finding reflects the uncertainty concerning the superconducting parameters N(E F ) and λ. (orig.)

A study about the contribution of the α-β phase transition of quartz to thermal cycle damage of a refractory used in fluidized catalytic cracking units

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A. H. A. Pereira

2014-09-01

Full Text Available The deterioration of refractories used in fluidized catalytic cracking units (FCC-units is responsible for high costs of maintenance for the petrochemical industry. This is commonly associated with coke deposition during the production of light hydrocarbons. However, other mechanisms responsible for causing damage may also occur, such as the generation of cracks by expansive phase transition. The aim of the work herein was to study the contribution of the a-b phase transition of quartz particles to the deterioration of a commercial aluminosilicate refractory used in a riser by the means of slow thermal cycles. Such damage may occur if the working temperature of the equipment fluctuates around the a-b transition temperature (573 °C. The current study considered the material with and without coke impregnation to evaluate the combined effect of coke presence and phase transition. To evaluate the damage, it was used the Young's modulus as a function of temperature by applying the Impulse Excitation Technique under controlled atmosphere. An equipment recently developed by the authors research group was applied. Specimens were prepared and submitted to slow thermal cycles of temperatures up to 500 °C and up to 700 °C, with a heating rate of 2 °C/min. Part of the specimens was previously impregnated with coke by a reactor using propen. To complete the evaluation, characterization by X-ray diffraction, as well as by dilatometry and scanning electron microscopy were performed. The findings of this study showed that the presence of quartz particles determine the thermo-mechanical behaviour of the material, as well as the thermocycling damage resistance. In spite of the fact that the a-b phase transition stiffens the material during the heating stage, it increases the damage by slow thermal cycling. The coke impregnation increases the resistance to slow thermal cycles, however it decreases the resistance to the damage evolution.

Materiales vitrocerámicos a partir de lodos procedentes de una estación de depuración de aguas residuales urbanas (en la Ciudad de El-Sadat, Egipto

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Garcia-Valles, M.

2011-10-01

Full Text Available Urban wastewater security is a source of significant volumes of sludge which is to be managed. This paper presents the possibility of applying a management process based on vitrification and by which, in addition to inert contaminants in sludge, you get a ceramic material with a significant added value. As a base of different analysis of the sludges, chemical (XRF, mineralogical (XRD and thermal (DTA-TG, we obtain the original glass composition and its energy. By DTATG, dilatometry and SEM, it was determined the temperature of maximum nucleation rate, growth temperature and the morphology and size of developed nuclei, in this case are nanoscale. Briefly, it was found as the management of municipal solid waste by vitrification as an alternative to landfills and incineration.

La depuración de las aguas residuales urbanas es fuente de importantes volúmenes de lodos los cuales es preciso gestionar. En este trabajo se expone la posibilidad de aplicarles un proceso de gestión basado en la vitrificación y mediante el cual, además de inertizar los elementos contaminantes presentes en los lodos, se obtiene un material vitrocerámico con un importante valor añadido. Partiendo de la caracterización química (FRX, mineralógica (DRX y térmica (ATD-TG de estos lodos, se determina la formulación del vidrio original y su poder energético. Mediante ATD-TG, dilatometría y MEB, se ha determinado la temperatura de máxima velocidad de nucleación y la temperatura de crecimiento así como la morfología y tamaño de los núcleos formados que, en este caso, son nanométricos. En definitiva, se ha comprobado como la gestión de los residuos sólidos urbanos mediante la vitrificación es una alternativa a los vertederos y a la incineración.

Strontium chloroapatite based glass-ceramics composites for nuclear waste immobilisation

International Nuclear Information System (INIS)

Jena, Hrudananda; Maji, Binoy Kumar; Asuvathraman, R.; Govindan Kutty, K.V.

2013-01-01

Apatites are naturally occurring minerals with a general formula of M 10 (PO 4 ) 6 X 2 , (M= Ca, Sr, Ba, X= OH, Cl, F) with a hexagonal crystal structure (S.G :P6 3 /m) and can accommodate alkaline earth and various other aliovalent cations and anions into its crystal structure. Apatites are also known to have high resistance to leaching of the constituent elements under geological conditions. It may not often be possible to immobilize the whole spectrum of the radioactive waste in a single phase M 10 (PO 4 ) 6 Cl 2 , then a combination of M-chloroapatite encapsulated in borosilicate glass (BSG) can immobilize most of the radwaste elements in the composite glass-ceramic matrix (glass bonded chloroapatite), thus utilizing the immobilizing efficiency of both the ceramic phase and glass. In the present study, the synthesis, characterization and thermo-physical property measurements of the Sr-chloroapatite (SrApCI) and some glass-bonded composites based on it have been investigated. The Sr-chloroapatite glass-ceramics were prepared by solid state reactions among stoichiometric concentrations of apatite forming reagents, 20 wt. % borosilicate glass (BSG), and known concentrations (10, 13 and 16 wt. %) of a simulated waste in chloride form. The products were characterized by XRD to confirm the formation of Sr 10 (PO 4 ) 6 Cl 2 and glass bonded-chloroapatite composites. The surface morphology and qualitative chemical composition of the powders were examined by SEM and EDX. Thermal expansion and glass transition temperature of the matrices were measured by dilatometry. Glass transition temperature of the glass-bonded composites was also examined by differential scanning calorimetry and differential thermal analysis. The 10-16 wt.% waste loaded matrices showed similar thermal expansion as that of SrApCI, indicating the thermal stability of the matrix to chloride waste immobilization. The glass transition temperature of the waste loaded matrices decreases on increasing the

Silicate melts density, buoyancy relations and the dynamics of magmatic processes in the upper mantle

Science.gov (United States)

Sanchez-Valle, Carmen; Malfait, Wim J.

2016-04-01

Although silicate melts comprise only a minor volume fraction of the present day Earth, they play a critical role on the Earth's geochemical and geodynamical evolution. Their physical properties, namely the density, are a key control on many magmatic processes, including magma chamber dynamics and volcanic eruptions, melt extraction from residual rocks during partial melting, as well as crystal settling and melt migration. However, the quantitative modeling of these processes has been long limited by the scarcity of data on the density and compressibility of volatile-bearing silicate melts at relevant pressure and temperature conditions. In the last decade, new experimental designs namely combining large volume presses and synchrotron-based techniques have opened the possibility for determining in situ the density of a wide range of dry and volatile-bearing (H2O and CO2) silicate melt compositions at high pressure-high temperature conditions. In this contribution we will illustrate some of these progresses with focus on recent results on the density of dry and hydrous felsic and intermediate melt compositions (rhyolite, phonolite and andesite melts) at crustal and upper mantle conditions (up to 4 GPa and 2000 K). The new data on felsic-intermediate melts has been combined with in situ data on (ultra)mafic systems and ambient pressure dilatometry and sound velocity data to calibrate a continuous, predictive density model for hydrous and CO2-bearing silicate melts with applications to magmatic processes down to the conditions of the mantle transition zone (up to 2773 K and 22 GPa). The calibration dataset consist of more than 370 density measurements on high-pressure and/or water-and CO2-bearing melts and it is formulated in terms of the partial molar properties of the oxide components. The model predicts the density of volatile-bearing liquids to within 42 kg/m3 in the calibration interval and the model extrapolations up to 3000 K and 100 GPa are in good agreement

Evaluation of the effect of heavy rare earth elements on the microstructure and mechanical and electrical properties of zirconia - Yttria ceramics

International Nuclear Information System (INIS)

Lazar, Dolores Ribeiro Ricci

2002-01-01

The use of Yttria concentrates for synthesis and processing of zirconia based ceramics, applied as structural and solid electrolyte materials, was investigated in this work. Terbium, dysprosium, holmium, erbium and ytterbium are chemical elements, classified as heavy rare earths, that can be found in those concentrates due to their association with yttrium ores. The ceramic characteristics were compared to zirconia - Yttria and zirconia - Yttria - rare earth oxide systems. The dopant content was 3 and 9 mol%. The raw materials were prepared by the coprecipitation route using solutions from the chemical processing of zircon and monazite ores and obtained by dissolution of high purity rare earth oxides. In the first part of this work, calcination, milling and ceramic processing were studied to produce ceramics with densities up to 95% TD. Samples were prepared in optimized conditions for the evaluation of the effect of each heavy rare earth element. Powders were characterized by chemical analysis. X-ray diffraction, scanning and transmission electron microscopy, gas adsorption (BET) and laser diffraction for the determination of the agglomerate size distributions. Green pellets were characterized by mercury porosimetry and the sintering kinetic was studied by dilatometry. The characterization of the as-sintered pellets was performed by the apparent density measurement (Archimedes method). X-ray diffraction, microstructure analysis by scanning and transmission electron microscopy, Vickers indentation tests for hardness and fracture toughness determination, dynamic mechanical analysis for the elastic modulus measurement, and impedance spectroscopy for electrical resistivity measurement. It was observed that the presence of heavy rare earths in a concentrate containing 85 wt% of Yttria has no significant influence on the properties of zirconia based ceramics. TZP ceramics, containing 3 mol% of dopants, have grain size smaller than 0.4μm, and Vickers hardness and

Incorporação de lama de mármore e granito em massas argilosas Incorporation of marble and granite sludge in clay materials

Directory of Open Access Journals (Sweden)

J. B. Silva

2005-12-01

Full Text Available A utilização de resíduos industriais como aditivos na fabricação de produtos cerâmicos vem despertando um crescente interesse dos pesquisadores nos últimos anos e está se tornando prática comum. Este trabalho descreve a variação do comportamento de uma argila utilizada numa indústria de cerâmica vermelha, resultante de adições de uma lama de mármore e granito, tal como é produzida em uma indústria de beneficiamento de pedras ornamentais do estado do Rio Grande do Norte. Misturas de argila e rejeito (10 - 50% em peso foram compactadas uniaxialmente e sinterizadas a temperaturas entre 950 e 1150 °C. Os resultados obtidos por análise química e mineralógica (DRX e FRX, análises térmicas (DTA, TG e dilatometria, medidas de distribuição granulométrica, porosidade, absorção de água e tensão de ruptura à flexão, revelam que a lama de mármore e granito pode ser incorporada na massa de argila sem perda ou comprometimento das propriedades dos corpos sinterizados de cerâmica vermelha.The use of industrial waste materials as additives in the manufacture of ceramic products has been attracting a growing interest from researchers in recent years and is becoming common practice. This work describes the changes in the behavior of the clay material used in a red-ceramic industry due to additions of a granite and marble sludge, produced in an ornamental stone processing industry in Rio Grande do Norte. Mixtures of clay and waste material (10 - 50 wt.% were uniaxially pressed and sintered at temperatures ranging from 950 to 1150 °C. Results from chemical and mineralogical analysis (XRD and XRF, thermal analysis (DTA, TG and dilatometry, particle size distribution, porosity, water absorption and flexural strength, show that the granite and marble sludge can be added to the clay material with no detrimental effect on the properties of the sintered red-clay products.

Effects of cooling rate, austenitizing temperature and austenite deformation on the transformation behavior of high-strength boron steel

International Nuclear Information System (INIS)

Mun, Dong Jun; Shin, Eun Joo; Choi, Young Won; Lee, Jae Sang; Koo, Yang Mo

2012-01-01

Highlights: ► Non-equilibrium segregation of B in steel depends strongly on the cooling rate. ► A higher austenitization temperature reduced the B hardenability effect. ► An increase in B concentration at γ grain boundaries accelerates the B precipitation. ► The loss of B hardenability effect is due to intragranular borocarbide precipitation. ► The controlled cooling after hot deformation increased the B hardenability effect. - Abstract: The phase transformation behavior of high-strength boron steel was studied considering the segregation and precipitation behavior of boron (B). The effects of cooling rate, austenitizing temperature and austenite deformation on the transformation behavior of B-bearing steel as compared with B-free steel were investigated by using dilatometry, microstructural observations and analysis of B distribution. The effects of these variables on hardenability were discussed in terms of non-equilibrium segregation mechanism and precipitation behavior of B. The retardation of austenite-to-ferrite transformation by B addition depends strongly on cooling rate (CR); this is mainly due to the phenomenon of non-equilibrium grain boundary segregation of B. The hardenability effect of B-bearing steel decreased at higher austenitizing temperature due to the precipitation of borocarbide along austenite grain boundaries. Analysis of B distribution by second ion mass spectroscopy confirmed that the grain boundary segregation of B occurred at low austenitizing temperature of 900 °C, whereas B precipitates were observed along austenite grain boundaries at high austenitizing temperature of 1200 °C. The significant increase in B concentration at austenite grain boundaries due to grain coarsening and a non-equilibrium segregation mechanism may lead to the B precipitation. In contrast, solute B segregated to austenite grain boundaries during cooling after heavy deformation became more stable because the increase in boundary area by grain

High performance dental resin composites with hydrolytically stable monomers.

Science.gov (United States)

Wang, Xiaohong; Huyang, George; Palagummi, Sri Vikram; Liu, Xiaohui; Skrtic, Drago; Beauchamp, Carlos; Bowen, Rafael; Sun, Jirun

2018-02-01

The objectives of this project were to: 1) develop strong and durable dental resin composites by employing new monomers that are hydrolytically stable, and 2) demonstrate that resin composites based on these monomers perform superiorly to the traditional bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) composites under testing conditions relevant to clinical applications. New resins comprising hydrolytically stable, ether-based monomer, i.e., triethylene glycol divinylbenzyl ether (TEG-DVBE), and urethane dimethacrylate (UDMA) were produced via composition-controlled photo-polymerization. Their composites contained 67.5wt% of micro and 7.5wt% of nano-sized filler. The performances of both copolymers and composites were evaluated by a battery of clinically-relevant assessments: degree of vinyl conversion (DC: FTIR and NIR spectroscopy); refractive index (n: optical microscopy); elastic modulus (E), flexural strength (F) and fracture toughness (K IC ) (universal mechanical testing); Knoop hardness (HK; indentation); water sorption (W sp ) and solubility (W su ) (gravimetry); polymerization shrinkage (S v ; mercury dilatometry) and polymerization stress (tensometer). The experimental UDMA/TEG-DVBE composites were compared with the Bis-GMA/TEGDMA composites containing the identical filler contents, and with the commercial micro hybrid flowable composite. UDMA/TEG-DBVE composites exhibited n, E, W sp , W su and S v equivalent to the controls. They outperformed the controls with respect to F (up to 26.8% increase), K IC (up to 27.7% increase), modulus recovery upon water sorption (full recovery vs. 91.9% recovery), and stress formation (up to 52.7% reduction). In addition, new composites showed up to 27.7% increase in attainable DC compared to the traditional composites. Bis-GMA/TEGDMA controls exceeded the experimental composites with respect to only one property, the composite hardness. Significantly, up to 18.1% lower HK values in

Property enhancement by grain refinement of zinc-aluminium foundry alloys

International Nuclear Information System (INIS)

Krajewski, W K; Piwowarski, G; Krajewski, P K; Greer, A L

2016-01-01

Development of cast alloys with good mechanical properties and involving less energy consumption during their melting is one of the key demands of today's industry. Zinc foundry alloys of high and medium Al content, i.e. Zn-(15-30) wt.% Al and Zn-(8-12) wt.% Al, can satisfy these requirements. The present paper summarizes the work [1-9] on improving properties of sand-cast ZnAl10 (Zn-10 wt.% Al) and ZnAl25 (Zn-25 wt. % Al) alloys by melt inoculation. Special attention was devoted to improving ductility, whilst preserving high damping properties at the same time. The composition and structural modification of medium- and high-aluminium zinc alloys influence their strength, tribological properties and structural stability. In a series of studies, Zn - (10-12) wt. % Al and Zn - (25-26) wt.% Al - (1-2.5) wt.% Cu alloys have been doped with different levels of added Ti. The melted alloys were inoculated with ZnTi-based refiners and it was observed that the dendritic structure is significantly finer already after addition of 50 - 100 ppm Ti to the melted alloys. The alloy's structure and mechanical properties have been studied using: SEM (scanning electron microscopy), LM (light microscopy), dilatometry, pin-on-disc wear, and tensile strength measurements. Grain refinement leads to significant improvement of ductility in the binary high-aluminium Zn-(25-27) Al alloys while in the medium-aluminium alloys the effect is rather weak. In the ternary alloys Zn-26Al-Cu, replacing a part of Cu with Ti allows dimensional changes to be reduced while preserving good tribological properties. Furthermore, the high initial damping properties were nearly entirely preserved after inoculation. The results obtained allow us to characterize grain refinement of the examined high-aluminium zinc alloys as a promising process leading to the improvement of their properties. At the same time, using low melting ZnTi-based master alloys makes it possible to avoid the excessive melt

Glass-ceramic coating material for the CO2 laser based sintering of thin films as caries and erosion protection.

Science.gov (United States)

Bilandžić, Marin Dean; Wollgarten, Susanne; Stollenwerk, Jochen; Poprawe, Reinhart; Esteves-Oliveira, Marcella; Fischer, Horst

2017-09-01

The established method of fissure-sealing using polymeric coating materials exhibits limitations on the long-term. Here, we present a novel technique with the potential to protect susceptible teeth against caries and erosion. We hypothesized that a tailored glass-ceramic material could be sprayed onto enamel-like substrates to create superior adhesion properties after sintering by a CO 2 laser beam. A powdered dental glass-ceramic material from the system SiO 2 -Na 2 O-K 2 O-CaO-Al 2 O 3 -MgO was adjusted with individual properties suitable for a spray coating process. The material was characterized using X-ray fluorescence analysis (XRF), heating microscopy, dilatometry, scanning electron microscopy (SEM), grain size analysis, biaxial flexural strength measurements, fourier transform infrared spectroscopy (FTIR), and gas pycnometry. Three different groups of samples (each n=10) where prepared: Group A, powder pressed glass-ceramic coating material; Group B, sintered hydroxyapatite specimens; and Group C, enamel specimens (prepared from bovine teeth). Group B and C where spray coated with glass-ceramic powder. All specimens were heat treated using a CO 2 laser beam process. Cross-sections of the laser-sintered specimens were analyzed using laser scanning microscopy (LSM), energy dispersive X-ray analysis (EDX), and SEM. The developed glass-ceramic material (grain size d50=13.1mm, coefficient of thermal expansion (CTE)=13.310 -6 /K) could be spray coated on all tested substrates (mean thickness=160μm). FTIR analysis confirmed an absorption of the laser energy up to 95%. The powdered glass-ceramic material was successfully densely sintered in all sample groups. The coating interface investigation by SEM and EDX proved atomic diffusion and adhesion of the glass-ceramic material to hydroxyapatite and to dental enamel. A glass-ceramic material with suitable absorption properties was successfully sprayed and laser-sintered in thin films on hydroxyapatite as well as on

Protonation and structural/chemical stability of Ln{sub 2}NiO{sub 4+δ} ceramics vs. H{sub 2}O/CO{sub 2}: High temperature/water pressure ageing tests

Energy Technology Data Exchange (ETDEWEB)

Upasen, S. [Sorbonne Universités, UPMC Univ Paris 06, UMR 8233, MONARIS, 75005 Paris (France); CNRS-IP2CT, UMR 8233, MONARIS, F-75005 Paris (France); Batocchi, P.; Mauvy, F. [ICMCB, ICMCB-CNRS-IUT-Université de Bordeaux, 33608 Pessac Cedex (France); Slodczyk, A. [Sorbonne Universités, UPMC Univ Paris 06, UMR 8233, MONARIS, 75005 Paris (France); CNRS-IP2CT, UMR 8233, MONARIS, F-75005 Paris (France); Colomban, Ph., E-mail: philippe.colomban@upmc.fr [Sorbonne Universités, UPMC Univ Paris 06, UMR 8233, MONARIS, 75005 Paris (France); CNRS-IP2CT, UMR 8233, MONARIS, F-75005 Paris (France)

2015-02-15

Highlights: • High temperature/water pressure autoclave is used to study the reaction/corrosion at SOFC/HTSE electrode. • High stability of Pr{sub 2}NiO{sub 4+δ} (PNO) and Nd{sub 2}NiO{sub 4+δ} (NNO) dense ceramics vs. water pressure is demonstrated. • Protonated rare-earth nickelates retain the perovskite-type structure and their H-content is determined. • Very low laser illumination power is required to avoid RE nickelate phase transition. • Nickelates show increasing stability from La to Pr/Nd vs. CO{sub 2}-rich high temperature water vapor. - Abstract: Mixed ionic-electronic conductors (MIEC) such as rare-earth nickelates with a general formula Ln{sub 2}NiO{sub 4+δ} (Ln = La, Pr, Nd) appear as potential for energy production and storage systems: fuel cells, electrolysers and CO{sub 2} converters. Since a good electrode material should exhibit important stability in operating conditions, the structural and chemical stability of different nickelate-based, well-densified ceramics have been studied using various techniques: TGA, dilatometry, XRD, Raman scattering and IR spectroscopy. Consequently, La{sub 2}NiO{sub 4+δ} (LNO), Pr{sub 2}NiO{sub 4+δ} (PNO) and Nd{sub 2}NiO{sub 4+δ} (NNO) have been exposed during 5 days to high water vapor pressure (40 bar) at intermediate temperature (550 °C) in an autoclave device, the used water being almost free or saturated with CO{sub 2}. Such protonation process offers an accelerating stability test and allows the choice of the most pertinent composition for industrial applications requiring a selected material with important life-time. In order to understand any eventual change of crystal structure, the ceramics were investigated in as-prepared, pristine state as well as after protonation and deprotonation (due to thermal treatment till 1000 °C under dry atmosphere). The results show the presence of traces or second phases originating from undesirable hydroxylation and carbonation, detected in the near

Crystal structure and high-temperature properties of the Ruddlesden–Popper phases Sr3−xYx(Fe1.25Ni0.75)O7−δ (0≤x≤0.75)

International Nuclear Information System (INIS)

Samain, Louise; Amshoff, Philipp; Biendicho, Jordi J.; Tietz, Frank; Mahmoud, Abdelfattah; Hermann, Raphaël P.; Istomin, Sergey Ya.; Grins, Jekabs; Svensson, Gunnar

2015-01-01

Ruddlesden–Popper n=2 member phases Sr 3−x Y x Fe 1.25 Ni 0.75 O 7−δ , 0≤x≤0.75, have been investigated by X-ray and neutron powder diffraction, thermogravimetry and Mössbauer spectroscopy. Both samples as-prepared at 1300 °C under N 2 (g) flow and samples subsequently air-annealed at 900 °C were studied. The as-prepared x=0.75 phase is highly oxygen deficient with δ=1, the O1 atom site being vacant, and the Fe 3+ /Ni 2+ ions having a square pyramidal coordination. For as-prepared phases with lower x values, the Mössbauer spectral data are in good agreement with the presence of both 5- and 4-coordinated Fe 3+ ions, implying in addition a partial occupancy of the O3 atom sites that form the basal plane of the square pyramid. The air-annealed x=0.75 sample has a δ value of 0.61(1) and the structure has Fe/Ni ions in both square pyramids and octahedra. Mössbauer spectroscopy shows the phase to contain only Fe 3+ , implying that all Ni is present as Ni 3+ . Air-annealed phases with lower x values are found to contain both Fe 3+ and Fe 4+ . For both the as-prepared and the air-annealed samples, the Y 3+ cations are found to be mainly located in the perovskite block. The high-temperature thermal expansion of as-prepared and air-annealed x=0.75 phases were investigated by high-temperature X-ray diffraction and dilatometry and the linear thermal expansion coefficient determined to be 14.4 ppm K −1 . Electrical conductivity measurements showed that the air-annealed samples have higher conductivity than the as-prepared ones. - Highlights: • Ruddlesden–Popper, n=2, Sr 3−x Y x Fe 1.25 Ni 0.75 O 7−δ , 0≤x≤0.75, have been synthesised. • The crystal structures of the phases have been determined. • Sr 2.25 Y 0.75 Fe 1.25 Ni 0.75 O 6 , made in N 2 (g) has Fe 3+ /Ni 2+ in square pyramides. • Sr 2.25 Y 0.75 Fe 1.25 Ni 0.75 O 6.4 , made in air has Fe 3+ /Ni 3+ in square pyramides and octahedra. • Air annealed samples have higher electrical

Effects of NiO addition on the densification, microstructure and electrical conductivity of Yttria fully-stabilized zirconia

International Nuclear Information System (INIS)

Batista, Rafael Morgado

2010-01-01

The effects produced by NiO addition to yttria fully-stabilized zirconia were systematically investigated. Commercial zirconia-8 mol% yttria, nickel acetate, nitrate, trihydroxycarbonate and nickel oxide were used as starting materials. The NiO content varied from 0.5 to 5 mol%, and the compositions were prepared by mechanically mixing the starting materials in the stoichiometric proportions. Densification studies carried out by density and dilatometry measurements revealed that the maximum shrinkage (∼16-∼20%) depends on the type of nickel precursor. In the second sintering stage the linear shrinkage increased with increasing NiO content (precursor: nickel trihydroxy-carbonate). In the first sintering stage, the activation energy for grain boundary diffusion changed according to the additive precursor, being lower for the oxide and higher for the trihydroxy-carbonate. In the second stage, when the major part of porosity is eliminated, the maximum shrinkage rate temperatures were found to be independent on the precursor except when nickel acetate is used. The solubility limit at 1350 degree C is 1.48% as determined by X-ray diffraction. Above the solubility limit the excess NiO is retained as a second randomly distributed phase. The main effect of the additive in the ceramic microstructure is to increase the average grain size. The electrical measurements showed that the additive did not produce any significant effect in the grain conductivity irrespective of the sintering time, except when the precursor material was nickel oxide. In this case, the grain conductivity increased with increasing sintering time. This effect is attributed to the crystallite size of the nickel oxide precursor, which is higher than that of 8YSZ, slowing down the formation of solid solution. However, the grain conductivity of samples prepared with nickel trihydroxy-carbonate precursor is slightly lower than those of other samples. The samples sintered for 15 h exhibited an additional

In pursuit of the rhabdophane crystal structure: from the hydrated monoclinic LnPO{sub 4}.0.667H{sub 2}O to the hexagonal LnPO{sub 4} (Ln = Nd, Sm, Gd, Eu and Dy)

Energy Technology Data Exchange (ETDEWEB)

Mesbah, Adel, E-mail: adel.mesbah@cea.fr [ICSM, UMR 5257 CNRS – CEA – ENSCM – Université de Montpellier, Site de Marcoule - Bât 426, BP 17171, 30207 Bagnols/Cèze (France); Clavier, Nicolas [ICSM, UMR 5257 CNRS – CEA – ENSCM – Université de Montpellier, Site de Marcoule - Bât 426, BP 17171, 30207 Bagnols/Cèze (France); Elkaim, Erik [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France); Szenknect, Stéphanie; Dacheux, Nicolas [ICSM, UMR 5257 CNRS – CEA – ENSCM – Université de Montpellier, Site de Marcoule - Bât 426, BP 17171, 30207 Bagnols/Cèze (France)

2017-05-15

The dehydration process of the hydrated rhabdophane LnPO{sub 4}.0.667H{sub 2}O (Ln = La to Dy) was thoroughly studied over the combination of in situ high resolution synchrotron powder diffraction and TGA experiments. In the case of SmPO{sub 4}.0.667H{sub 2}O (monoclinic, C2), a first dehydration step was identified around 80 °C leading to the formation of SmPO{sub 4}.0.5H{sub 2}O (Monoclinic, C2) with Z =12 and a =17.6264(1) Å, b =6.9704(1) Å, c =12.1141(1) Å, β=133.74(1) °, V =1075.33(1) Å{sup 3}. In agreement with the TGA and dilatometry experiments, all the water molecules were evacuated above 220 °C yielding to the anhydrous form, which crystallizes in the hexagonal P3{sub 1}21 space group with a =7.0389(1) Å, c =6.3702(1) Å and V =273.34(1) Å{sup 3}. This study was extended to selected LnPO{sub 4}.0.667H{sub 2}O samples (Ln= Nd, Gd, Eu, Dy) and the obtained results confirmed the existence of two dehydration steps before the stabilization of the anhydrous form, with the transitory formation of LnPO{sub 4}.0.5H{sub 2}O. - Graphical abstract: The dehydration process of the rhabdophane SmPO{sub 4}.0.667H{sub 2}O was studied over combination of in situ high resolution synchrotron powder diffraction and TGA techniques, a first dehydration was identified around 80 °C leading to the formation of SmPO{sub 4}.0.5H{sub 2}O (Monoclinic, C2). Then above 220 °C, the anhydrous form of the rhabdophane SmPO{sub 4} was stabilized and crystallizes in the hexagonal P3{sub 1}21 space group. - Highlights: • In situ synchrotron powder diffraction was carried out during the dehydration of the rhabdopahe LnPO{sub 4}.0.667H{sub 2}O. • The heat of the rhabdophane LnPO{sub 4}.0.667H{sub 2}O leads to LnPO{sub 4}.0.5H{sub 2}O then to anhydrous rhabdophane LnPO{sub 4}. • LnPO{sub 4}.0.5H{sub 2}O (monoclinic, C2) and LnPO{sub 4} (Hexagonal, P3{sub 1}21) were solved over the use of direct methods.

Transient thermal creep of nuclear reactor pressure vessel type concretes

International Nuclear Information System (INIS)

Khoury, G.A.

1983-01-01

The immediate aim of the research was to study the transient thermal strain behaviour of four AGR type nuclear reactor concretes during first time heating in an unsealed condition to 600 deg. C. The work being also relevant to applications of fire exposed concrete structures. The programme was, however, expanded to serve a second more theoretical purpose, namely the further investigation of the strain development of unsealed concrete under constant, transient and cyclic thermal states in particular and the effect of elevated temperatures on concrete in general. The range of materials investigated included seven different concretes and three types of cement paste. Limestone, basalt, gravel and lightweight aggregates were employed as well as OPC and SRC cements. Cement replacements included pfa and slag. Test variables comprised two rates of heating (0.2 and 1 deg. C/minute), three initial moisture contents (moist as cast, air-dry and oven dry at 105 deg. C), two curing regimes (bulk of tests represented mass cured concrete), five stress levels (0, 10, 20, 30 and a few tests at 60% of the cold strength), two thermal cycles and levels of test temperature up to 720 deg. C. Supplementary, dilatometry, TGA and DTA tests were performed at CERL on individual samples of aggregate and cement paste which helped towards explaining the observed trends in the concretes. A simple formula was developed which relates the elastic thermal stresses generated from radial temperature gradients to the solution obtained from the transient heat conduction equation. Thermal stresses can, therefore, be minimized by reductions in the radius of the specimen and the rate of heating The results were confirmed by finite element analysis which indicate( tensile stresses in the central region and compressive stresses near the surf ace during heating which are reversed during cooling. It is shown that the temperature gradients, pore pressures and tensile thermal stresses during both heating and

Electrical properties and thermal expansion of strontium aluminates

Energy Technology Data Exchange (ETDEWEB)

Zakharchuk, K.V. [Department of Materials and Ceramic Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Yaremchenko, A.A., E-mail: ayaremchenko@ua.pt [Department of Materials and Ceramic Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Fagg, D.P. [TEMA-NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro (Portugal)

2014-11-15

Highlights: • Sr{sub 3}Al{sub 2}O{sub 6}, SrAl{sub 2}O{sub 4} and Sr{sub 4}Al{sub 14}O{sub 25} ceramics are semiconductors. • Electrical conductivity is as low as 10{sup −6}−4×10{sup −5} S/cm at 1273 K in dry air. • SrAl{sub 2}O{sub 4} is a mixed conductor with predominant ionic conductivity. • Sr{sub 3}Al{sub 2}O{sub 6} shows significant contribution of protonic transport in wet atmospheres. • Average TECs vary in the range (8.5–11.1)×10{sup −6} K{sup −1} and are p(O{sub 2})-independent. - Abstract: Strontium aluminate ceramics, including Sr{sub 3}Al{sub 2}O{sub 6}, SrAl{sub 2}O{sub 4} and Sr{sub 4}Al{sub 14}O{sub 25}, synthesized by glycine–nitrate combustion and sintered at 1773 K in air, were characterized by thermal analysis, dilatometry and electrical measurements in controlled atmospheres. All studied strontium aluminates are semiconductors with electrical conductivities as low as 10{sup −6}−4×10{sup −5} S/cm at 1273 K in dry air. Electrical measurements in controlled atmospheres in combination with ion transference number determination demonstrated that SrAl{sub 2}O{sub 4} is a mixed conductor with predominant ionic conductivity and increasing n-type and p-type electronic contributions under highly reducing and oxidizing conditions, respectively. While the behavior of electrical conductivity of Sr{sub 3}Al{sub 2}O{sub 6} in dry atmospheres was qualitatively similar to that of SrAl{sub 2}O{sub 4}, a significant increase of conductivity in wet atmospheres was attributed to a protonic contribution to electrical conduction, in correlation with thermogravimetric data and the tendency of this material to form a hydrogarnet at low temperatures. The average thermal expansion coefficients of strontium aluminates, (8.5–11.1)×10{sup −6} K{sup −1} at 333–1373 K, increase with increasing strontium content in the sequence Sr{sub 4}Al{sub 14}O{sub 25} < SrAl{sub 2}O{sub 4} < Sr{sub 3}Al{sub 2}O{sub 6} and are essentially

Synthesis and characterization of Yb and Er based monosilicate powders and durability of plasma sprayed Yb2SiO5 coatings on C/C–SiC composites

International Nuclear Information System (INIS)

Khan, Zuhair S.; Zou Binglin; Huang Wenzhi; Fan Xizhi; Gu Lijian; Chen Xiaolong; Zeng Shuibing; Wang Chunjie; Cao Xueqiang

2012-01-01

Highlights: ► Ultra-pure rare-earth monosilicate powders based on Er and Yb have been fabricated by solid-state reaction. ► Spray-drying treatment results in powders with free flowing characteristics and rounded surface morphologies. ► CTEs are found to be 7.1 ppm/°C for Yb 2 SiO 5 and 7.5 ppm/°C for Er 2 SiO 5 . ► Plasma spraying has been used to deposit Yb 2 SiO 5 coatings on C/C–SiC substrate. ► Coatings remain strongly intact with the substrate on thermal cycling between ∼400 °C and 1500 °C in gas burner rig experiment. - Abstract: Rare-earth silicates such as Yb 2 SiO 5 and Er 2 SiO 5 are promising environmental barrier coating materials for ceramic matrix composites. In this work, Yb 2 SiO 5 and Er 2 SiO 5 ceramic powders have been synthesized by solid-state reaction using Yb 2 O 3 , Er 2 O 3 and SiO 2 as starting materials. The fabricated powders were subjected to spray drying treatment for subsequent synthesis of coatings by plasma spraying. The spray drying resulted in well-dispersed and spherical powder particles with good flowability. Analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry and differential scanning calorimetry (TGA/DSC) and dilatometry were applied to study the microstructural and thermal characteristics of the powders. Ultra-high purity monosilicate powders formed as a result of heating treatments at 1400 °C in a box furnace for 20 h. TG/DSC revealed the genesis temperatures of the silicate formation (low temperature polymorphs) and also showed that the solid-state reactions to form Yb and Er based monosilicates proceeded without any weight-loss in the tested temperature range. The values of coefficients of thermal expansion (CTE) of the fabricated compounds are found to be 7.1 ppm/°C for Yb 2 SiO 5 and 7.5 ppm/°C for Er 2 SiO 5 by dilatometric measurements. Besides these studies, coating formation by plasma spraying of spray-dried Yb 2 SiO 5 powders on the ceramic

Structural properties, deformation behavior and thermal stability of martensitic Ti-Nb alloys

Energy Technology Data Exchange (ETDEWEB)

Boenisch, Matthias

2016-06-10

. Also, experimental evidence indicates a deformation-induced martensite to austenite (α'' → β) conversion. The influence of Nb content on the thermal stability and on the occurrence of decomposition reactions in martensitic Ti-Nb alloys is examined by isochronal differential scanning calorimetry, dilatometry and in-situ synchrotron X-ray diffraction complemented by transmission electron microscopy. The thermal decomposition and transformation behavior exhibits various phase transformation sequences during heating into the β-phase field in dependence of composition. Eventually, the transformation temperatures, interval, hysteresis and heat of the β <-> α'' martensitic transformation are investigated in relation to the Nb content. The results obtained in this study are useful for the development and optimization of β-stabilized Ti-based alloys for structural, Ni-free shape memory and/or superelastic, as well as for biomedical applications.

Materias primas no tradicionales en la industria cerámica

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Caligaris, R.

2000-10-01

Full Text Available The wastes incorporation to the production cycle is an interesting alternative in modern industry. This gives rise to not only an economical profit but to a considerable decrease in environmental impact. Studies made about recycling of several wastes: glass, electric insulators and fly ash are compared in this work. The materials were crushed and separated by particle size distribution in order to prepare representative samples. Different treatment steps were carried out as is usual in the process of ceramic industries. Some of the obtained powders were used without additives while other were mixed in different ratios with other ceramic components in order to improve their final properties. All the compacts, obtained by uniaxial pressing of the powders, received thermal treatments which were adequate to their compositions. They were then characterised by several techniques including dilatometry, X ray diffraction, porosity, microhardness, optical and scanning electron microscopy and energy dispersion analysis (SEM/EDX. From this investigation it was concluded that the studied materials constitute a potential source of raw materials for the ceramic industry.

La incorporación de materiales de desecho en el ciclo productivo es una alternativa de interés en la industria moderna que conduce tanto a un beneficio económico como a una considerable reducción del impacto sobre el medio ambiente. En este trabajo se comparan estudios realizados sobre la reutilización de diversos residuos: vidrio, aisladores eléctricos y cenizas volantes. Estos materiales fueron molidos y clasificados por tamaño de partículas para ser usados en la preparación de muestras representativas. Las diferentes etapas de tratamiento se establecieron según los procesos habituales de producción de la industria cerámica. Algunos de los polvos obtenidos se utilizaron sin aditivos, mientras que otros fueron mezclados en distintas proporciones con diversos componentes

Preparation method and thermal properties of samarium and europium-doped alumino-phosphate glasses

Energy Technology Data Exchange (ETDEWEB)

Sava, B.A., E-mail: savabogdanalexandru@yahoo.com [National Institute of Research and Development for Optoelectronics, Department for Optospintronics, 409 Atomistilor Street, P.O. Box MG – 5, RO-77125 Magurele (Romania); Elisa, M., E-mail: astatin18@yahoo.com [National Institute of Research and Development for Optoelectronics, Department for Optospintronics, 409 Atomistilor Street, P.O. Box MG – 5, RO-77125 Magurele (Romania); Boroica, L., E-mail: boroica_lucica@yahoo.com [National Institute for Lasers, Plasma and Radiation Physics, 77125 Magurele (Romania); Monteiro, R.C.C., E-mail: rcm@fct.unl.pt [Center of Materials Research/Institute for Nanostructures, Nanomodelling and Nanofabrication, (CENIMAT/I3N), Department of Materials Sciences, Faculty of Sciences and Technology, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)

2013-12-01

Highlights: • Improved preparation method of rare-earth-doped phosphate glasses was done. • Working and annealing temperatures were lower than for undoped phosphate glass. • Doped glass viscosity is also lower and has quasi-linear variation with temperature. • Exothermic peak appears at about 555 °C and 685 °C, due to devitrification in glass. -- Abstract: The present work investigates alumino-phosphate glasses from Li{sub 2}O–BaO–Al{sub 2}O{sub 3}–La{sub 2}O{sub 3}–P{sub 2}O{sub 5} system containing Sm{sup 3+} and Eu{sup 3+} ions, prepared by two different ways: a wet raw materials mixing route followed by evaporation and melt-quenching, and by remelting of shards. The linear thermal expansion coefficient measured by dilatometry is identical for both rare-earth-doped phosphate glasses. Comparatively to undoped phosphate glass the linear thermal expansion coefficient increases with 2 × 10{sup −7} K{sup −1} when dopants are added. The characteristic temperatures very slowly decrease but can be considered constant with atomic weight, atomic number and f electrons number of the doping ions in the case of T{sub g} (vitreous transition temperature) and T{sub sr} (high annealing temperature) but slowly increase in the case of T{sub ir} (low annealing temperature–strain point) and very slowly increase, being practically constant in the case of T{sub D} (dilatometric softening temperature). Comparatively to undoped phosphate glass the characteristic temperatures of Sm and Eu-doped glasses present lower values. The higher values of electrical conductance for both doped glasses, comparatively to usual soda-lime-silicate glass, indicate a slightly reduced stability against water. The viscosity measurements, showed a quasi-linear variation with temperature the mean square deviation (R{sup 2}) being ranged between 0.872% and 0.996%. The viscosity of doped glasses comparatively to the undoped one is lower at the same temperature. Thermogravimetric

Modelling and computer simulation for the manufacture by powder HIPing of Blanket Shield components for ITER

International Nuclear Information System (INIS)

Gillia, O.; Bucci, Ph.; Vidotto, F.; Leibold, J.-M.; Boireau, B.; Boudot, C.; Cottin, A.; Lorenzetto, P.; Jacquinot, F.

2006-01-01

In components of blanket modules for ITER, intricate cooling networks are needed in order to evacuate all heat coming from the plasma. Hot Isostatic Pressing (HIPing) technology is a very convenient method to produce near net shape components with complex cooling network through massive stainless steel parts by bonding together tubes inserted in grooves machined in bulk stainless steel. Powder is often included in the process so as to release difficulties arising with gaps closure between tube and solid part or between several solid parts. In the mean time, it releases the machining precision needed on the parts to assemble before HIP. However, inserting powder in the assembly means densification, i.e. volume change of powder during the HIP cycle. This leads to global and local shape changes of HIPed parts. In order to control the deformations, modelling and computer simulation are used. This modelling and computer simulation work has been done in support to the fabrication of a shield prototype for the ITER blanket. Problems such as global bending of the whole part and deformations of tubes in their powder bed are addressed. It is important that the part does not bend too much. It is important as well to have circular tube shape after HIP, firstly in order to avoid their rupture during HIP but also because non destructive ultrasonic examination is needed to check the quality of the densification and bonding between tube and powder or solid parts; the insertions of a probe in the tubes requires a minimal circular tube shape. For simulation purposes, the behaviour of the different materials has to be modelled. Although the modelling of the massive stainless steel behaviour is not neglected, the most critical modelling is about power. For this study, a thorough investigation on the powder behaviour has been performed with some in-situ HIP dilatometry experiments and some interrupted HIP cycles on trial parts. These experiments have allowed the identification of a

Processing, Microstructures and Properties of a Dual Phase Precipitation-Hardening PM Stainless Steel

Science.gov (United States)

Schade, Christopher

To improve the mechanical properties of PM stainless steels in comparison with their wrought counterparts, a PM stainless steel alloy was developed which combines a dual-phase microstructure with precipitation-hardening. The use of a mixed microstructure of martensite and ferrite results in an alloy with a combination of the optimum properties of each phase, namely strength and ductility. The use of precipitation hardening via the addition of copper results in additional strength and hardness. A range of compositions was studied in combination with various sintering conditions to determine the optimal thermal processing to achieve the desired microstructure. The microstructure could be varied from predominately ferrite to one containing a high percentage of martensite by additions of copper and a variation of the sintering temperature before rapid cooling. Mechanical properties (transverse rupture strength (TRS), yield strength, tensile strength, ductility and impact toughness) were measured as a function of the v/o ferrite in the microstructure. A dual phase alloy with the optimal combination of properties served as the base for introducing precipitation hardening. Copper was added to the base alloy at various levels and its effect on the microstructure and mechanical properties was quantified. Processing at various sintering temperatures led to a range of microstructures; dilatometry was used utilized to monitor and understand the transformations and the formation of the two phases. The aging process was studied as a function of temperature and time by measuring TRS, yield strength, tensile strength, ductility, impact toughness and apparent hardness. It was determined that optimum aging was achieved at 538°C for 1h. Aging at slightly lower temperatures led to the formation of carbides, which contributed to reduced hardness and tensile strength. As expected, at the peak aging temperature, an increase in yield strength and ultimate tensile strength as well as

A Mexican kaolin deposit: XANES characterization, mineralogical phase analysis and applications

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Martínez, A.

2009-06-01

Full Text Available A kaolin obtained from Villa de Reyes, a region near to San Luis Potosí (México was characterized by means of X-ray powder diffraction (XRD, optical microscopy (OM, scanning electron microscopy (SEM, X-ray fluorescence (XRF, X-Ray Absorption Near Edge Spectroscopy (XANES, thermal analysis (DTA/TGA, dilatometry (DIL, and chemical analysis. Mineralogical and morphological characteristics of the mineral are presented. The kaolin sample was formed mainly by kaolinite, but other minor phases were also detected such as quartz, cristobalite, tridymite, and dolomite. The high content of volcanic glass detected, by optical microscopy, revealed an incomplete kaolinization process of the raw material. The reddish color of the kaolin was associated with the free iron content in the form of limonite [FeO(OH], which was determined by XANES. The influence of the particle size on the whiteness of kaolin was evaluated. Dilatometric analysis revealed a strong thermal expansion between 110 y 240 °C, which would difficult the use of this material in traditional ceramic applications. On the other hand the presence of glass and high temperature phases of SiO2, such as cristobalite and tridymite will favor its use in the cement industry.El caolín obtenido de Villa de Reyes, una región cercana a San Luis Potosí, México, fue caracterizado por las siguientes técnicas: difracción de rayos-X en polvos (DRX, microscopía óptica (MO, microscopía electrónica de barrido (MEB, fluorescencia de rayos-X (FRX, espectroscopía de absorción de rayos-X (XANES, análisis térmico (DTA/TGA, dilatometría (DIL y análisis químico. Los resultados del análisis mineralógico mediante DRX mostraron un mineral constituido principalmente de caolinita, con una contribución minoritaria de cuarzo, cristobalita, tridimita y dolomita. El análisis por microscopía óptica reveló un alto contenido de material amorfo volcánico, indicando una caolinización incompleta del material v

Crystal structure and high-temperature properties of the Ruddlesden–Popper phases Sr{sub 3−x}Y{sub x}(Fe{sub 1.25}Ni{sub 0.75})O{sub 7−δ} (0≤x≤0.75)

Energy Technology Data Exchange (ETDEWEB)

Samain, Louise; Amshoff, Philipp [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Biendicho, Jordi J. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, Oxfordshire (United Kingdom); Tietz, Frank [Institute of Energy and Climate Research, IEK-1, Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Mahmoud, Abdelfattah [Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Hermann, Raphaël P. [Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Faculty of Science, University of Liège, B-4000 Liège (Belgium); Istomin, Sergey Ya. [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Department of Chemistry, M.V. Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Grins, Jekabs [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden); Svensson, Gunnar, E-mail: gunnar.svensson@mmk.su.se [Department of Materials and Environmental Chemistry, Stockholm University, S-106 91 Stockholm (Sweden)

2015-07-15

Ruddlesden–Popper n=2 member phases Sr{sub 3−x}Y{sub x}Fe{sub 1.25}Ni{sub 0.75}O{sub 7−δ}, 0≤x≤0.75, have been investigated by X-ray and neutron powder diffraction, thermogravimetry and Mössbauer spectroscopy. Both samples as-prepared at 1300 °C under N{sub 2}(g) flow and samples subsequently air-annealed at 900 °C were studied. The as-prepared x=0.75 phase is highly oxygen deficient with δ=1, the O1 atom site being vacant, and the Fe{sup 3+}/Ni{sup 2+} ions having a square pyramidal coordination. For as-prepared phases with lower x values, the Mössbauer spectral data are in good agreement with the presence of both 5- and 4-coordinated Fe{sup 3+} ions, implying in addition a partial occupancy of the O3 atom sites that form the basal plane of the square pyramid. The air-annealed x=0.75 sample has a δ value of 0.61(1) and the structure has Fe/Ni ions in both square pyramids and octahedra. Mössbauer spectroscopy shows the phase to contain only Fe{sup 3+}, implying that all Ni is present as Ni{sup 3+}. Air-annealed phases with lower x values are found to contain both Fe{sup 3+} and Fe{sup 4+}. For both the as-prepared and the air-annealed samples, the Y{sup 3+} cations are found to be mainly located in the perovskite block. The high-temperature thermal expansion of as-prepared and air-annealed x=0.75 phases were investigated by high-temperature X-ray diffraction and dilatometry and the linear thermal expansion coefficient determined to be 14.4 ppm K{sup −1}. Electrical conductivity measurements showed that the air-annealed samples have higher conductivity than the as-prepared ones. - Highlights: • Ruddlesden–Popper, n=2, Sr{sub 3−x}Y{sub x}Fe{sub 1.25}Ni{sub 0.75}O{sub 7−δ}, 0≤x≤0.75, have been synthesised. • The crystal structures of the phases have been determined. • Sr{sub 2.25}Y{sub 0.75}Fe{sub 1.25}Ni{sub 0.75}O{sub 6}, made in N{sub 2}(g) has Fe{sup 3+}/Ni{sup 2+} in square pyramides. • Sr{sub 2.25}Y{sub 0.75}Fe{sub 1.25}Ni

Preparación y propiedades de materiales cerámicos bioinertes en el sistema Al2O3-TiO2-SiO2

Directory of Open Access Journals (Sweden)

Boccaccini, A. R.

1998-12-01

Full Text Available Very fine and sinterable ceramic powders (100-600 nm in the system Al2O3-TiO2-SiO2 were obtained by the method of cohydrolisis from organo-metallic precursors. Isostatically pressed powder compacts could be densified to a relative high density (~ 92 % th. density at relative low temperatures (1320-1380ºC. The technical coefficient of thermal expansion was measured by dilatometry. The value obtained (8.8 10-6 1/ºC corresponds closely to that of Ti, opening the possibility to use Al2O3-TiO2-SiO2 ceramics to fabricate metal/ceramic composite implants. The measured mechanical properties of dense sintered Al2O3-TiO2-SiO2 material: Young´s modulus, flexure strength and compression strength, are higher than those of pure TiO2. Highly porous Al2O3-TiO2-SiO2 ceramics (P~ 65% were obtained by the method of evaporation of hydrogen peroxide. These materials exhibited interconnected porosity and their properties, particularly the Young´s modulus, resulted very similar to those of bone, which is an important pre-requisite for the design of quirurgical implants.Se han obtenido polvos cerámicos muy finos (100- 600 nm y de alta sinterabilidad, en el sistema Al2O3-TiO2-SiO2, por el método de co-hidrólisis controlada a partir de precursores organo-metálicos. Los compactos fabricados a partir del polvo de cohidrólisis calcinado fueron sinterizados en el rango de temperaturas 1320-1380 ºC, obteniéndose densidades elevadas (~ 92% D.T.. El coeficiente de expansión térmica técnico del material cerámico sinterizado fue medido por dilatometría. El valor obtenido, 8.8 10-6 ºC-1, es muy similar al de titanio metálico y por lo tanto el material cerámico Al2O3-TiO2-SiO2 puede ser candidato para la fabricación de implantes compuestos cerámico/metal. Las propiedades mecánicas: módulo de elasticidad, resistencia a la flexión y resistencia a la compresión, del material denso sinterizado, fueron determinadas, resultando muy superiores a las de TiO2 puro

Martensitic transformation, fcc and hcp relative phase stability, and thermal cycling effects in Fe-Mn and Fe-Mn-X Alloys (X = Si, Co)

International Nuclear Information System (INIS)

Baruj, Alberto

1999-01-01

In this Thesis we present a study of the fcc and hcp relative phase stability in the Fe-Mn and Fe-Mn-Co systems. In particular, we have investigated the effect of two main factors affecting the relative phase stability: changes in the chemical composition of the alloys and changes in the density of crystalline defects in the microstructure.In order to analyse the effect of chemical composition, we have performed an experimental study of the fcc/hcp martensitic transformation temperatures in Fe-Mn-Co alloys in the composition range lying between 15% and 34% Mn, and between 1% and 16% Co.We have measured the martensitic transformation temperatures by means of dilatometry and electrical resistivity.We have combined this information with measurements of the fcc/hcp martensitic transformation temperatures in Co-rich alloys to perform a modelling of the Gibbs energy function for the hcp phase in the Fe-Mn-Co and Fe-Co systems.We found that, for alloys in the Mn range between 17% and 25%, Co additions tend to stabilise slightly the fcc phase.In the alloys with Mn contents below that range, increasing the amount of Co stabilise the bcc phase. In alloys with Mn contents above 25% the Neel temperature is depressed by the addition of Co, which stabilise the hcp phase.In order to investigate the effect of changes in the density of crystalline defects, we have performed thermal cycling experiments through the fcc/hcp martensitic transformation in Fe-Mn, Fe-Mn-Co and Fe-Mn-Si alloys.We have applied the thermodynamic description obtained before in order to analyse these experiments.We found in the thermal cycling experiments a first stage where the martensitic transformation is promoted.This stage occurs in all the studied alloys during the first cycle or the two first cycles.Increasing the number of thermal cycles, the promotion stage is replaced by an inhibition of the transformation stage.We propose a possible microstructural interpretation of these phenomena where the plastic

Phase equilibria, crystal structure and properties of complex oxides in the Nd{sub 2}O{sub 3}–SrO–CoO system

Energy Technology Data Exchange (ETDEWEB)

Aksenova, T.V.; Efimova, T.G. [Department of Physical and Inorganic Chemistry, Institute of Natural Science and Mathematics, Ural Federal University, Lenin av., 51, Yekaterinburg 620000 (Russian Federation); Lebedev, O.I. [Laboratoire CRISMAT, ENSICAEN UMR6508, 6 Bd Maréchal Juin, Cedex 4, Caen 14050 (France); Elkalashy, Sh.I.; Urusova, A.S. [Department of Physical and Inorganic Chemistry, Institute of Natural Science and Mathematics, Ural Federal University, Lenin av., 51, Yekaterinburg 620000 (Russian Federation); Cherepanov, V.A., E-mail: v.a.cherepanov@urfu.ru [Department of Physical and Inorganic Chemistry, Institute of Natural Science and Mathematics, Ural Federal University, Lenin av., 51, Yekaterinburg 620000 (Russian Federation)

2017-04-15

The phase equilibria in the ½Nd{sub 2}O{sub 3}–SrO–CoO system were systematically studied at 1373 K in air. The intermediate phases formed in the ½Nd{sub 2}O{sub 3}–SrO–CoO system at 1373 K in air are: Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} (0.0≤x≤0.5 with orthorhombic structure, sp. gr. Pbnm and 0.6≤x≤0.95 whose structure was detected as cubic according to XRD sp. gr. Pm3m, but shown to be tetragonal by TEM due to the oxygen vacancy ordering), Nd{sub 2-y}Sr{sub y}CoO{sub 4-δ} (0.6≤y≤1.1 with tetragonal K{sub 2}NiF{sub 4}-type structure, sp. gr. I4/mmm) and Nd{sub 2-z}Sr{sub z}O{sub 3} (0.0≤z≤0.15 with hexagonal structure, sp. gr. P-3m1). The unit cell parameters for the single phase samples were refined by the Rietveld analysis. The changes of oxygen content in Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} (0.6≤x≤0.95) and Ruddlesden-Popper oxide Nd{sub 2-y}Sr{sub y}CoO{sub 4-δ} were examined by TGA. All were found to be oxygen deficient phases. High-temperature dilatometry allows calculating the thermal expansion coefficient and evaluating the chemical expansion coefficient at high temperature. The projection of isothermal-isobaric phase diagram for the Nd–Sr–Co–O system at 1373 K in air to the compositional triangle of metallic components has been constructed. The phase equilibria in the studied Nd–Sr–Co–O system were compared to La–Sr–Co–O and Nd–M–Co–O (M=Ca and Ba). - Graphical abstract: Crystal structure of vacancy ordered supercell for Nd{sub 0.2}Sr{sub 0.8}CoO{sub 3-δ} and projection of phase diagram for the Nd–Sr–Co–O system onto the triangle edge of metallic components at 1373 K in air. - Highlights: • The diagram for the Nd–Sr–Co–O system at 1373 K in air has been constructed. • The crystal structure of Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} and Nd{sub 2-y}Sr{sub y}CoO{sub 4±δ} was refined. • The formation of superstructure due to the oxygen vacancy ordering was proved. • The changes of oxygen

Effect of solid fission products forming dissolved oxide(Nd) and metallic precipitate(Ru) on the thermophysical properties of MOX fuel

International Nuclear Information System (INIS)

Kim, Dong Joo

2006-02-01

This study experimentally investigated the effect of solid fission products on the thermophysical properties of the mixed oxide fuel and evaluated them on the basis of the analytical theory. Neodymium and ruthenium were selected for the experiments to represent the physical states of the solid fission product as a 'dissolved oxide' and 'metallic precipitate', respectively. The state of the additives, crystal structures, lattice parameters, and theoretical densities were investigated with X-ray diffraction (XRD). Thermal diffusivities and thermal expansion rates were measured with laser flash method and dilatometry, respectively. The thermal expansion data were then fitted to obtain an correlation equation of the density variation as a function of the temperature. The specific heat capacity values were determined using the Neumann-Kopp's rule. The thermal expansion of the 'Nd.added' sample linearly increased with the concentration of the neodymium, which is primarily due to the fact that the melting point of Nd 2 O 3 is lower than that of UO 2 . On the other hand, the thermal expansion of the 'Ru.added' sample hardly changed with increasing ruthenium content. Thermal conductivities of the simulated MOX fuel were determined on the basis of the thermal diffusivities, density variation, and specific heat values measured in this study. The effect of additives on the thermal conductivity of the samples was quantified in the form of the thermal resistance equation, the reciprocal of the phonon conduction equation, which was determined from measured data. For 'dissolved oxide' sample in the UO 2 matrix, the effect is mainly attributed to the increase of lattice point defects caused by U 4+ , Ce 4+ , Nd 3+ and O 2- ions, which play the role of phonon scattering centers, that is, mean free path of phonon scattering decreases with the point defects, thus increase the thermal resistance. Also, the mass difference between the host (U) and the substituted atom (Ce and/or Nd) can

Caracterización de la aleación Ni53.5-Fe19.5-Ga27 con memoria de forma ferromagnética producida por metalurgia de polvos

Directory of Open Access Journals (Sweden)

Olmos, Luis

2015-06-01

Full Text Available The main drawback of ferromagnetic shape memory alloys fabricated through casting methods are its brittleness. In order to overcome this disadvantage, powder metallurgy is an ideal technique for the consolidation of many engineering parts. This paper is focused on the study of the milling and sintering effects of metallic powders over the evolution of the crystalline phases responsibly for the shape memory effect of these materials. To achieve this objective, ferromagnetic shape memory alloy powders (Ni53.5-Fe19.5-Ga27 were prepared from a cast ingot by mechanical milling at two different times of 30 and 60 minutes. The evolution of the phases was investigated through high temperature X-ray diffraction (HTXRD, whereas sintering was analyzed with dilatometry tests. X-ray studies showed that four different phases can be present depending on the particle size and temperature at which the heat treatment was performed. Coarser powders showed a B2 structure along with a γ phase while the finer showed a L21 structure when treated below 1173 K. Furthermore, finer powders had a modulated M14 martensitic structure after sintering at temperatures above 1273 K. The sintering of powders was slow and a mass diffusion mechanism was not clearly observed.La principal desventaja de las aleaciones con memoria de forma ferromagnéticas obtenidas por fundición es su fragilidad. Para superar esta desventaja la metalurgia de polvos es una técnica ideal para la consolidación de las piezas, por lo que este trabajo se orientó a estudiar el efecto generado por los procesos de molienda y sinterizado de polvos sobre la evolución de las fases cristalinas que le confieren la memoria de forma a estos materiales. Para ello se prepararon polvos de la aleación ferromagnética con memoria de forma Ni53.5-Fe19.5-Ga27 a partir de un lingote fundido mediante molienda mecánica, durante dos tiempos diferentes de molienda de 30 y 60 minutos. La evolución de las fases fue

P2O5-doping in waste glasses: evolution of viscosity and crystallization processes

Science.gov (United States)

Tarrago, Mariona; Espuñes, Alex; Garcia-Valles, Maite; Martinez, Salvador

2015-04-01

�C respectively at phosphate contents up to 4%. Subsequent analysis by X-Ray Diffraction has proved that newly formed phases are iron oxides, Ca - Mg silicates and feldspars. Glass transition temperature (Tg; approximately 635°C) obtained by dilatometry remains almost constant until very high phosphate contents; even then, the increase is not large (650°C at 20% P2O5). Hot-Stage microscopy (HSM) has shown the evolution of viscosity with temperature through the analysis of the morphological evolution of cylindrical probes of glass according to German standard DIN 51730. The annealing range (viscosity between 1013.5 and 1012 is reached at temperatures between 600 and 700°C. The temperatures of the lower limit of the working range (viscosity under 103 Pa-s) are between 1325 and 1375°C; decreasing slightly with the addition of P2O5.

Laboratory Testing of Waste Isolation Pilot Plant Surrogate Waste Materials

Science.gov (United States)

Broome, S.; Bronowski, D.; Pfeifle, T.; Herrick, C. G.

2011-12-01

The Waste Isolation Pilot Plant (WIPP) is a U.S. Department of Energy geological repository for the permanent disposal of defense-related transuranic (TRU) waste. The waste is emplaced in rooms excavated in the bedded Salado salt formation at a depth of 655 m below the ground surface. After emplacement of the waste, the repository will be sealed and decommissioned. WIPP Performance Assessment modeling of the underground material response requires a full and accurate understanding of coupled mechanical, hydrological, and geochemical processes and how they evolve with time. This study was part of a broader test program focused on room closure, specifically the compaction behavior of waste and the constitutive relations to model this behavior. The goal of this study was to develop an improved waste constitutive model. The model parameters are developed based on a well designed set of test data. The constitutive model will then be used to realistically model evolution of the underground and to better understand the impacts on repository performance. The present study results are focused on laboratory testing of surrogate waste materials. The surrogate wastes correspond to a conservative estimate of the degraded containers and TRU waste materials after the 10,000 year regulatory period. Testing consists of hydrostatic, uniaxial, and triaxial tests performed on surrogate waste recipes that were previously developed by Hansen et al. (1997). These recipes can be divided into materials that simulate 50% and 100% degraded waste by weight. The percent degradation indicates the anticipated amount of iron corrosion, as well as the decomposition of cellulosics, plastics, and rubbers. Axial, lateral, and volumetric strain and axial and lateral stress measurements were made. Two unique testing techniques were developed during the course of the experimental program. The first involves the use of dilatometry to measure sample volumetric strain under a hydrostatic condition. Bulk

Interactions between impurities and defects created by irradiation in iron; Interactions entre les impuretes et les defauts crees par irradiation dans le fer

Energy Technology Data Exchange (ETDEWEB)

Vigier, P [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1968-07-01

'expose et aux discussions de nouveaux resultats experimentaux. Grace a l'addition d'impurete dans le fer, des experiences de trainage magnetique, energie stockee, resistivite et dilatometrie ont permis d'etablir que le stade I se rattache au modele propose par Granato et Nilan (90): seul le dernier sous-stade I{sub E} provient de la disparition des interstitiels dans les lacunes apres leur libre migration dans le reseau. Divers modeles sont discutes pour le stade II; s'il est probable que les diinterstitiels sont observables apres une irradiation aux electrons, aucune bande de trainage ne semble leur correspondre apres une irradiation aux neutrons. Des phenomenes particuliers apparaissent dans le fer irradie lorsqu'il contient des impuretes telles que nickel ou silicium (apparition de nouvelles bandes de trainage, leur transformation les unes dans les autres); ils refletent la complication successive du defaut elementaire interstitiel de fer-atome d'impurete. Enfin, dans une derniere section, l'auteur decrit quelques experiences effectuees sur des alliages fer-carbone irradies ou non ; elles montrent que le carbone apres avoir precipite a une temperature inferieure a 300 deg. C, se remet en solution lorsque l'alliage est chauffe au-dela de 330 deg. C. (auteur)

Chemical and structural changes in Ln{sub 2}NiO{sub 4+δ} (Ln=La, Pr or Nd) lanthanide nickelates as a function of oxygen partial pressure at high temperature

Energy Technology Data Exchange (ETDEWEB)

Flura, Aurélien; Dru, Sophie; Nicollet, Clément; Vibhu, Vaibhav; Fourcade, Sébastien; Lebraud, Eric; Rougier, Aline; Bassat, Jean-Marc; Grenier, Jean-Claude, E-mail: grenier@icmcb-bordeaux.cnrs.fr

2015-08-15

The chemical stability of lanthanide nickelates Ln{sub 2}NiO{sub 4+δ} (Ln=La, Pr or Nd) has been studied in the temperature range 25–1300 °C, either in air or at low pO{sub 2} (down to 10{sup −4} atm). Thermal gravimetry analysis (TGA) measurements coupled with X-ray diffraction (XRD) characterization have shown that all compounds retain their K{sub 2}NiF{sub 4}-type structure in these conditions, while remaining over-stoichiometric in oxygen up to 1000 °C. Only Nd{sub 2}NiO{sub 4+δ} starts to decompose into Nd{sub 2}O{sub 3} and NiO above 1000 °C, at pO{sub 2}=10{sup −4} atm. In addition, a careful analysis of the lanthanide nickelates structural features has been performed by in situ XRD, as a function of temperature and pO{sub 2}. For all compounds, a structural transition has been always observed in the temperature range 200–400 °C, in air or at pO{sub 2}=10{sup −4} atm. In addition, their cell volume did not vary upon the variation of the oxygen partial pressure. Therefore, these materials do not exhibit a chemical expansion in these conditions, which is beneficial for a fuel cell application as cathode layers. Additional dilatometry measurements have revealed that a temperature as high as 950 °C for Pr{sub 2}NiO{sub 4+δ} or 1100 °C for La{sub 2}NiO{sub 4+δ} and Nd{sub 2}NiO{sub 4+δ} has to be reached in order to begin the sintering of the material particles, which is of primary importance to obtain an efficient electronic/ionic conduction in the corresponding designed cathode layers. Besides, excellent matching was found between the thermal expansion coefficients of lanthanide nickelates and SOFC electrolytes such as 8wt% yttria stabilized zirconia (8YSZ) or Ce{sub 0.8}Gd{sub 0.2}O{sub 2−δ} (GDC), at least from 400 °C up to 1400 °C in air or up to 1200 °C at pO{sub 2}=10{sup −4} atm. - Graphical abstract: This study reports the good chemical stability of oxygen overstoichiometric Ln2NiO4+δ(Ln = La, Pr or Nd) at high temperatures

Synthesis and characterization of sodium cation-conducting Nax(MyL1-yO2 (M = Ni2+, Fe3+; L = Ti4+, Sb5+

Directory of Open Access Journals (Sweden)

Marques, F. M. B.

2004-06-01

Full Text Available The Na+-conducting ceramics of layered Na0.8Ni0.4Ti0.6O2, Na0.8Fe0.8Ti0.2O2, Na0.8Ni0.6Sb0.4O2 (structural type O3 and Na0.68Ni0.34Ti0.66O2 (P2 type with density higher than 91% were prepared via the standard solid-state synthesis route and characterized by the impedance spectroscopy, thermal analysis, scanning electron microscopy, structure refinement using X-ray powder diffraction data, measurements of Na+ concentration cell e.m.f., and dilatometry. The conductivity of antimonate Na0.8Ni0.6Sb0.4O2, synthesized first time, was found lower than that of isostructural Na0.8Ni0.4Ti0.6O2 due to larger ion jump distance between Na+ sites. At temperatures above 420 K, transport properties of sodium cationconducting materials are essentially independent of partial water vapor pressure. In the low-temperature range, the conductivity reversibly increases with water vapor pressure varied in the range from approximately 0 (dry air up to 0.46 atm. The sensitivity to air humidity is influenced by the ceramic microstructure, being favored by increasing boundary area. The average thermal expansion coefficients of layered materials at 300-1173 K are in the range (13.7-16.0×10-6 K-1.Se han preparado cerámicas conductoras conteniendo Na+ de composición Na0.8Ni0.4Ti0.6O2, Na0.8Fe0.8Ti0.2O2, Na0.8Ni0.6Sb0.4O2 (tipo estructural O3 y Na0.68Ni0.34Ti0.66O2 (tipo P2 con densidad mayor del 91%. Las vía de preparación fu la ruta de estandard de síntesis en estado sólido. Las composiciones se caracterizaron mediante espectroscopía de impedancia, análisis térmico, microscopía electrónica de barrido, refinamiento de la estructura usando datos de difracción de rayos X en polvo, medidas de concentración de Na+, f.e.m. de la célula y dilatometría. La conductividad del antimoniate, sintetizado por primera vez, Na0.8Ni0.6Sb0.4O2, era menor que la del compuesto isoestructural Na0.8Ni0.4Ti0.6O2 debido a la mayor distancia de salto iónico entre las posiciones de Na

Atomic structure of radiation damages in FCC-metals after neutron irradiation

International Nuclear Information System (INIS)

Popova, E.V.; Ivchenko, V.A.; Kozlov, A.V.

2005-01-01

Full text: Radiation clusters, formed at a neutron irradiation, are a product of evolution of cascade areas. The quantitative information about clusters can be used for verification of calculations of cascade damage ability, in particular, cascade efficiency. Data about concentration clusters and an average of the vacancies containing in them, allow to receive total of the vacancies reserved in them and to use them for comparison to results of calculations of cascade damage ability. A correctness of such comparison by that above, than below temperature of a neutron irradiation. The purpose of work was experimental studying radiation clusters formed in FCC-metals at a low temperature neutron irradiation methods of dilatometry, field ion (FIM) and transmission electronic microscopy (TEM). Radiation clusters were studied: in industrial austenite steel C0.05Crl6Nil5Mo2Mnl, irradiated in reactor Rw-2a at temperature 310 K up to fluence intermediate and fast neutrons (with E > 0,1 MeV) 6.7·l0 21 m -2 ; in a modelling material - Pt (cleanliness of 99.99 %) with the same - FCC-structure in an initial condition and after an irradiation in reactor RWW-2M at temperature 310 K up to fluence intermediate and fast neutrons (with E > 0.1 MeV) 3.5·10 22 m -2 . As a result of an irradiation of steel and pure Pt, in these materials by methods FIM and TEM many radiation clusters, the accelerated neutrons initiated by interaction with substance was revealed. It is established that these damage areas represent the depleted zones containing separate vacancies, and also small vacancy complexes, with the 'belt' interstitial atoms. The quantitative estimation of the sizes of such radiating defects is lead and their density in volume is experimentally established. So the neutron irradiation of steel at temperature 310 K up to fluence 6.7·10 21 m -2 causes formation radiation clusters which average diameter according to TEM makes 3 nanometers. Observable by methods FIM clusters have the

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

Science.gov (United States)

Wiley, Charles Schenck

2011-12-01

sintering behavior were performed via high-temperature dilatometry in order to measure the in-situ sample contraction and thereby measure the influence of the additives and their amounts on the overall densification rate. Additionally, broad composition and sintering/post-HIPing studies followed by characterization and mechanical testing elucidated the effects of these additives on sample densification, microstructure de- velopment, and mechanical properties such as Vickers hardness and microindentation fracture toughness. Based upon this research, a process has been developed for the sintering of boron carbide that yielded end products with high relative densities (i.e., 100%, or theoretical density), microstructures with a fine (˜2-3 mum) grain size, and high Vickers microindentation hardness values. In addition to possessing these improved physical properties, the costs of producing this material were substantially lower (by a factor of 5 or more) than recently patented work on the pressureless sintering and post-HIPing of phase-pure boron carbide powder. This recently patented work developed out of our laboratory utilized an optimized powder distribution and yielded samples with high relative densities and high hardness values. The current work employed the use of titanium and carbon additives in specific ratios to activate the sintering of boron carbide powder possessing an approximately mono-modal particle size distribution. Upon heating to high temperatures, these additives produced fine-scale TiB2 and graphite inclusions that served to hinder grain growth and substantially improve overall sintered and post-HIPed densities when added in sufficient concentrations. The fine boron carbide grain size manifested as a result of these second phase inclusions caused a substantial increase in hardness; the highest hardness specimen yielded a hardness value (2884.5 kg/mm2) approaching that of phase-pure and theoretically-dense boron carbide (2939 kg/mm2). Additionally, the

Study of U - Pu - Fe alloys (Masurca critical experiment); Etudes d'alliages U-Pu-Fe (experience critique MASURCA)

Energy Technology Data Exchange (ETDEWEB)

Barthelemy, P; Boucher, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1965-07-01

Three compositions have been studied: 73.5 U - 25 Pu - 1.5 Fe (weight %) 74 U - 25 Pu - 1 Fe 74.5 U - 25 Pu - 0.5 Fe Elaboration and Casting are easy. After two weeks in air 74.5 U - 25 Pu - 0.5 Fe alloys are reduced in powder. As-cast alloys containing 1 and 1,5% Fe are kept undamaged during several months. A rapid oxidisation of the alloys is however observed when the samples undergo the phase transformation (at 595 deg. C and 590 deg. C respectively). Ignition tests in the presence of air show that the oxidisation starts at about 250 deg. C and that the reaction does not spread. Ignition is not observed during heating from 20 to 660 deg. C. The transformation temperature, the melting temperature and the thermal expansion coefficients have been determined by dilatometry. Below the transformation temperature, the principal phases are U-Pu zeta and (U, Pu){sub 6}Fe. Thermal conductibility, Young modulus, density and heat of fusion have been measured. Compatibility tests show that between U-Pu-Fe and stainless steel a phase of (U, Pu){sub 6}Fe type is formed. The 74 U - 25 Pu - 1% Fe alloy seems to behave better than 73.5 U - 25 Pu - 1.5% Fe alloy because the (U, Pu){sub 6}Fe layer is two or three times smaller. Finally, the thermal stability has been studied with the 74 U - 25 Pu - 1% Fe alloy. A dilatometric anomaly (very weak expansion) occurs when the sample is heated above transformation temperature and cooled. But there is no anomaly by thermal cycling from 50 deg. C to 400 deg. C and there is no deterioration of alloys by heat treatments at 100 deg. C, 200 deg. C, 300 deg. C during 5 months under vacuum. (authors) [French] Trois compositions ont ete etudiees: 73,5 U - 25 Pu - 1,5 Fe (% ponderaux) 74 U - 25 Pu - 1 Fe 74,5 U - 25 Pu - 0,5 Fe Les elaborations et mises en forme sont-faciles. Les alliages a 0,5% de fer tombent en poudre apres 15 jours d'exposition a l'air. Les alliages a 1 et 1,5% de fer, bruts de coulee, se conservent plusieurs mois. Cependant

Estudo de fundente e argilito com potencial para uso em formulações de porcelanato Study of flux and mudstone with potential for using in porcelainized stoneware tile compositions

Directory of Open Access Journals (Sweden)

F. S. Hoffmann

2012-06-01

baixas. Composições com ambas as matérias-primas apresentaram baixos valores de absorção de água ( 45 MPa, apesar de maior deformação piroplástica a 1150 ºC.The porcelain tile is distinguished in the current market for ceramic tiles, with excellent technical and esthetic characteristics. In the present study traditional ceramic raw materials were selected and a standard formulation conventionally reported in the literature was adopted aiming to replace the melting phase (feldspar of the composition for a raw material that forms liquid phase at high temperature, and replacement of the clay fraction by a mudstone of lower refractoriness. The aim of this study was to evaluate the use of these materials as alternative techniques and lower cost, since, in a mass of porcelain tile, the amount of flux is very large (representing approximately 50% of total raw materials used. The nepheline syenite was the natural raw material selected to replace the feldspar due to the fact that it belongs to the family of feldspathoids, and has similar physicochemical characteristics, therefore, a high fluxing efficiency. To replace the clay fraction was chosen a mudstone naturally occurring, abundant in the region of Santa Gertrudes, SP. Substitutions to the feldspar and clay fraction were completely and/or partially by means of combinations between the flux and mudstones. The masses were processed from the mixing of powders, wet milling, drying, disagglomeration, compaction and firing. In addition to the vitrification curves, techniques such as dilatometry, measurements of porosity, flexure strength test, electron microscopy and X-ray diffraction were used to characterize the material after firing at various temperatures. The results showed that, in principle, it is possible the combination of raw materials such as nepheline and mudstone to replace potassium feldspar and S. Simão clay, as they provide the vitrification at lower temperatures. Compositions with both materials showed

Atom-Probe Tomographic Investigations of a Precipitation-Strengthened HSLA-115 Steel and a Ballistic-Resistant 10 wt. % Ni Steel for Naval Applications

Science.gov (United States)

Jain, Divya

due to overaging of Cu precipitates and tempering of the martensitic matrix. This results in an extended yield strength plateau, compared to alloys relying solely on Cu precipitation strengthening (for example, NUCu-140 steels) and is highly beneficial as impact toughness improves significantly in overaged conditions with respect to Cu precipitates. Optimum mechanical properties (yield strength 141 ksi or 972.1 MPa, elongation to failure 24.8 %, and impact toughness 188.0 J at -18 °C) are attained after 3 h aging at 550 °C. Incorporating finely dispersed M2C carbides with Cu precipitates, thus provides a promising pathway for use of Cu-bearing Naval HSLA-115 steels in higher strength applications, while still meting toughness and ductility requirements. Low-carbon 10 wt. % Ni steels are optimally processed via a multi-step intercritical Quench Lamellarizing Tempering (QLT)-treatment to form a fine dispersion of thermally stable Ni-enriched austenite in a tempered martensitic matrix. Deformation-induced martensitic transformation of this austenite is key to its superior overall mechanical properties, specifically ballistic resistance over HSLA-100 steels. This research elucidates the basic physical principles controlling the thermal stability and kinetics of Ni-stabilized austenite, formed during the QLT-treatment. The role of Ni-enriched austenite and fresh martensitic regions, inherited from the first isothermal intercritical step (L) at 650 °C, in forming thermally stable austenite during the second isothermal intercritical step (T) at 590 °C is highlighted using dilatometry, synchrotron X-ray diffraction, 3-D atom-probe tomography (APT), and thermodynamic and kinetic modeling using ThermoCalc and Dictra. Results indicate the growth of nm-thick austenite layers during T-step tempering (predominantly in the Ni-enriched fresh martensitic regions), with austenite retained from L-step acting as a nucleation template. Thermal stability of austenite is estimated by

Monazite-type ceramics for conditioning of minor actinides. Structural characterization and properties

International Nuclear Information System (INIS)

Babelot, Carole

2013-01-01

and morphological characteristics (using X-ray diffraction (XRD) and scanning electron microscope (SEM)) combined with physical and thermal properties of samples (using thermogravimetry, differential scanning calorimetry (TG-DSC) and dilatometry) are realized in order to study the behavior of monazite-type powder and pellets. The access to short-range-order spectroscopy (time resolved laser fluorescence spectroscopy (TRLFS) and extended X-ray absorption fine structure (EXAFS)) permits to understand the structure of ceramic waste forms at the molecular level. La-monazite matrices being doped with Eu (III) (as a non-radioactive chemical homologue for Am (III)) and Cm (III), TRLFS is used to explore the local structural environment of Eu and Cm within the monazite crystal structure. Eu (III) and Cm (III) are substituted on the La site of LaPO 4 . The single site of Cm (III) is found in four slightly different environments which is assumed to be due to a difference in the four La sites within a LaPO4 unit cell. Structural parameters of the Eu (III) species were also analyzed by EXAFS. The nearest neighbors of Eu (III) are modeled as 9.5 oxygen atoms (N O1 = 4 at r(EuO1) = 2.37 Aa, N O2 = 4 at r(Eu-O2) = 2.53 Aa, and N O3 = 1.5 at r(Eu-O3) = 2.83 Aa). An essential parameter that describes the stability of the host phases is their dissolution rate obtained under conditions of relevance for final repositories. In this context, a set-up is developed and tested on crushed pellets. Normalized weight losses of lanthanumphosphates and europium-doped lanthanum-phosphates, measured in acidic media at 90 C, are interpreted and compared against the previous findings from the literature. The normalized dissolution rate for La and Eu within (La, Eu)PO 4 is between 1.10 -5 and 1.10 -4 g.m -2 .d -1 , whereas the rate of Na, Cs and Sr in phosphate glass at room temperature in deionized water is about 1.10 -2 g.m -2 .d -1 . Another essential parameter is their resistance to radiation. The

Microstructure-property relationship in microalloyed high-strength steel welds

International Nuclear Information System (INIS)

Zhang, Lei

2017-01-01

of steel being joined. In Ti-containing steel, increased heat Input extended the softened zone width, which caused a significant decrease in hardness and then resulted in failure in this area. Therefore, limited heat Input was used to shift failure position to base material. But this was not observed in the other two steels. Hence, small differences in microalloy addition exhibited large variation in tensile properties. Among the three steels, Ti-containing welds were found to have the most pronounced softening, followed by Ti+V-containing welds and finally Nb-containing welds. This varied softening phenomenon was related to two significant processes supported by the results of additional dilatometry simulation: phase transformation and tempering behaviour. In the Ti-containing steel, the phase Transformation product ferrite was large-sized, as a consequence of initial large austenite grains. This led to the decreased corresponding hardness of the Ti-containing steel. Furthermore, lower tempering resistance in Ti-containing steel as compared to Nb-containing steel, resulted in additional softening effect in the softened HAZ. Therefore, steel alloy identification and heat Input during welding were critical, proven by the experimentation within the same S690QL steel grade. This work emphasised the influence of microalloy elements on weld microstructure and mechanical properties in welded joints. Knowledge of this delicate balance between steel alloy design and appropriate welding parameters is critical for the end product. Thus, this work provides specific recommendations and results to ensure proper welding practice and steel design of microalloyed high-strength steels.

Microstructure-property relationship in microalloyed high-strength steel welds

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lei

2017-04-01

of steel being joined. In Ti-containing steel, increased heat Input extended the softened zone width, which caused a significant decrease in hardness and then resulted in failure in this area. Therefore, limited heat Input was used to shift failure position to base material. But this was not observed in the other two steels. Hence, small differences in microalloy addition exhibited large variation in tensile properties. Among the three steels, Ti-containing welds were found to have the most pronounced softening, followed by Ti+V-containing welds and finally Nb-containing welds. This varied softening phenomenon was related to two significant processes supported by the results of additional dilatometry simulation: phase transformation and tempering behaviour. In the Ti-containing steel, the phase Transformation product ferrite was large-sized, as a consequence of initial large austenite grains. This led to the decreased corresponding hardness of the Ti-containing steel. Furthermore, lower tempering resistance in Ti-containing steel as compared to Nb-containing steel, resulted in additional softening effect in the softened HAZ. Therefore, steel alloy identification and heat Input during welding were critical, proven by the experimentation within the same S690QL steel grade. This work emphasised the influence of microalloy elements on weld microstructure and mechanical properties in welded joints. Knowledge of this delicate balance between steel alloy design and appropriate welding parameters is critical for the end product. Thus, this work provides specific recommendations and results to ensure proper welding practice and steel design of microalloyed high-strength steels.

Monazite-type ceramics for conditioning of minor actinides. Structural characterization and properties

Energy Technology Data Exchange (ETDEWEB)

Babelot, Carole

2013-07-01

. Structural and morphological characteristics (using X-ray diffraction (XRD) and scanning electron microscope (SEM)) combined with physical and thermal properties of samples (using thermogravimetry, differential scanning calorimetry (TG-DSC) and dilatometry) are realized in order to study the behavior of monazite-type powder and pellets. The access to short-range-order spectroscopy (time resolved laser fluorescence spectroscopy (TRLFS) and extended X-ray absorption fine structure (EXAFS)) permits to understand the structure of ceramic waste forms at the molecular level. La-monazite matrices being doped with Eu (III) (as a non-radioactive chemical homologue for Am (III)) and Cm (III), TRLFS is used to explore the local structural environment of Eu and Cm within the monazite crystal structure. Eu (III) and Cm (III) are substituted on the La site of LaPO{sub 4}. The single site of Cm (III) is found in four slightly different environments which is assumed to be due to a difference in the four La sites within a LaPO4 unit cell. Structural parameters of the Eu (III) species were also analyzed by EXAFS. The nearest neighbors of Eu (III) are modeled as 9.5 oxygen atoms (N{sub O1} = 4 at r(EuO1) = 2.37 Aa, N{sub O2} = 4 at r(Eu-O2) = 2.53 Aa, and N{sub O3} = 1.5 at r(Eu-O3) = 2.83 Aa). An essential parameter that describes the stability of the host phases is their dissolution rate obtained under conditions of relevance for final repositories. In this context, a set-up is developed and tested on crushed pellets. Normalized weight losses of lanthanumphosphates and europium-doped lanthanum-phosphates, measured in acidic media at 90 C, are interpreted and compared against the previous findings from the literature. The normalized dissolution rate for La and Eu within (La, Eu)PO{sub 4} is between 1.10{sup -5} and 1.10{sup -4} g.m{sup -2}.d{sup -1}, whereas the rate of Na, Cs and Sr in phosphate glass at room temperature in deionized water is about 1.10{sup -2} g.m{sup -2}.d{sup -1}. Another