WorldWideScience

Sample records for corundum

  1. Corundum-based transparent infrared absorbers

    KAUST Repository

    Schwingenschlögl, Udo

    2009-10-01

    Hypothetical corundum-based compounds are studied by electronic structure calculations. One quarter of the Al atoms in Al2O3 is replaced by a 3d transition metal from the M = Ti, ..., Zn (d1, ..., d9) series. Structure optimisations are performed for all the M-Al2O3 compounds and the electronic states are evaluated. Due to the M substitutes, narrow partially filled bands are formed at the Fermi energy. Beyond, for M = Ni and M = Cu the optical properties of Al2O3 in the visible range are conserved, while for M = Ti, ..., Co the systems form high accuracy optical filters. Since the compounds absorb the infrared radiation, the M = Ni and M = Cu systems are good candidates for heat-protective coatings. © 2009 Elsevier B.V. All rights reserved.

  2. Boronized steels with corundum-baddeleyite coatings

    Directory of Open Access Journals (Sweden)

    P. Pokorny

    2016-07-01

    Full Text Available The paper describes preparation and properties of anti-corrosion and anti-abrasive coatings from corundum-baddeleyite ceramics deposited on surface of low-carbon boronized steel S235JRH-1.0038 (EN 10025-1 by plasma spraying method. Adhesive interlayers Fe2B reaches bond strength of up to 20 MPa in the pull-off tests, the ZrO2 - Al2O3 - SiO2 coatings have a value of fracture adhesion of 4 - 6 MPa. Hardness of these ceramic coatings on steel is as high as 1 800 HV100 and its polarization resistance is 1 600 Ω/cm2 to 4 000 Ω/cm2.

  3. Properties, structure and machnining capabilities sintered corundum abrasives

    Directory of Open Access Journals (Sweden)

    Cz.J. Niżankowski

    2010-07-01

    Full Text Available The diversity of sintered corundum abrasives used in both bonded and in the embankment of abrasive tools currently poses substantialproblems for their choice of technology to specific tasks. Therefore performed a comparative study of ownership structures and capacitiesof elected representatives machnining sintered corundum abrasives of different generations, and this is normal sintered alumina,submicrocrystalline alumina sintered and nanocrystalline alumina sintered. Were studied some properties of a set of abrasive particles,physicochemical properties and structural and mechanical and technological properties. The studies used the method of microscopicmeasurement to determine the shape of abrasive particles, the pycnometer to determine the density of abrasive, a spectrometer todetermine the chemical composition of the magnetic analyzer for determining the magnetic fraction, scanning electron microscope toanalysis of abrasive grains and a special position to designate the machining capacity abrasive grains. The results showed a significantincrease in machining capacity sintered corundum abrasives with increasing degree of fragmentation of the crystallites sintered corundum abrasives and distinctive bands in the emerging microchip. The originality of the development provides a comparative summary ofproperties of sintered corundum abrasives of different generations and functions obtained by the author making the change in value indexof machininhcapacity grit from cutting speeds for different generations of sintered corundum.

  4. LA-ICP-MS U-Pb dating of rutile inclusions within corundum (ruby and sapphire): new constraints on the formation of corundum deposits along the Mozambique belt

    Science.gov (United States)

    Sorokina, Elena S.; Rösel, Delia; Häger, Tobias; Mertz-Kraus, Regina; Saul, John M.

    2017-06-01

    Direct dating of corundum and the establishment of age constraints for corundum crystal growth are restricted due to the absence of a geochronometer. Syngenetic mineral inclusions may help define minimum ages for corundum growth. Here, we present results of in situ LA-ICP-MS U-Pb dating applied to rutile inclusions in corundum from localities along the Mozambique belt. U-Pb dating of rutile inclusions gave ages of 533 ± 11 Ma (2 σ) for the Gitonga pit (John Saul ruby mine) and 526 ± 13 Ma for the Aqua Ruby mine, both in the Mangari area of Kenya, and an age of 499 ± 12 Ma for ruby from the Morogoro area, Tanzania. These ages are interpreted as cooling ages that set a minimum age for corundum growth following metamorphism along the East-African Antarctic Orogen, and might be used for petrogenetic tracing of corundum in placer deposits.

  5. Mullite—corundum Refractories with High Creep Resistance

    Institute of Scientific and Technical Information of China (English)

    LIANGYong-be; LINan; 等

    1996-01-01

    Mullite-corundum bricks and kiln furni-ture with high creep resistance and good thermal shock resistance were fabricated based on low cost raw materials,the approaches of introducing some additives and optimisig,chemical composition and partical size were mployed to produce a high temperature matrix phase with high creep resistance and good thermal shock resistance.

  6. Finding of corundum-bearing rocks in the Lapland granulite belt

    Science.gov (United States)

    Terekhov, E. N.; Shcherbakova, T. F.; Konilov, A. N.

    2016-09-01

    Corundum-bearing rocks are described for the first time in the Kandalaksha structure of the Lapland granulite belt. Corundum is confined to rocks of two types: metagabbro‒anorthosites constituting lenses among metaanarthosites of the Kandalaksha massif and basic granulites. Corundum crystals (up to 200 μm long) occur in plagioclase and garnet and differ from each other depending on the host mineral, which serves as evidence against their xenogenic nature. Some corundum crystals exhibit an axial zone, which may indicate their crystallization from the gaseous phase. Corundum-bearing rocks are accompanied by piclogites (pyroxene‒garnet varieties with olivine). Piclogites and their minerals (clinopyroxene, garnet) are characterized by a positive Eu anomaly, which implies rock reworking by fluids during corundum formation, when deep-seated complexes were subjected to exhumation.

  7. Corundum Based Composite Block Containing Plastic Phase YB/T 4129-2005

    Institute of Scientific and Technical Information of China (English)

    Yu Lingyan; Chai Junlan

    2009-01-01

    @@ 1 Scope This standard specifies the definition, classifica-tion, technical requirements, test methods, inspection rules, packing, marking, transportation and quality certificate of corundum block containing plastic phase.

  8. On the real structure of profiled anion-deficient corundum

    Science.gov (United States)

    Maksimov, V. I.; Sokolov, V. I.; Surdo, A. I.; Abashev, R. M.; Yushkova, E. N.

    2017-02-01

    Profiled Al2O3 single crystals grown by Stepanov’s method to obtain anion-deficient composition were characterized by neutron diffraction at T=300 K for the first time. Whereas the main structure motif of investigated crystals is checked to be of corundum-type, the scattering pictures of as-grown crystal demonstrate pronounced anomalies being probably indications on substructure forming. However, neutron scanning of synthesised crystal taken after annealing under restoring conditions reveals additional effects associated with displacement type superstructure.

  9. Domain walls and ferroelectric reversal in corundum derivatives

    Science.gov (United States)

    Ye, Meng; Vanderbilt, David

    2017-01-01

    Domain walls are the topological defects that mediate polarization reversal in ferroelectrics, and they may exhibit quite different geometric and electronic structures compared to the bulk. Therefore, a detailed atomic-scale understanding of the static and dynamic properties of domain walls is of pressing interest. In this work, we use first-principles methods to study the structures of 180∘ domain walls, both in their relaxed state and along the ferroelectric reversal pathway, in ferroelectrics belonging to the family of corundum derivatives. Our calculations predict their orientation, formation energy, and migration energy and also identify important couplings between polarization, magnetization, and chirality at the domain walls. Finally, we point out a strong empirical correlation between the height of the domain-wall-mediated polarization reversal barrier and the local bonding environment of the mobile A cations as measured by bond-valence sums. Our results thus provide both theoretical and empirical guidance for future searches for ferroelectric candidates in materials of the corundum derivative family.

  10. Corundum-hibonite inclusions and the environments of high temperature processing in the early Solar System

    Science.gov (United States)

    Needham, Andrew W.; Messenger, Scott; Han, Jangmi; Keller, Lindsay P.

    2017-01-01

    Corundum-bearing Ca-Al-rich inclusions (CAIs) are a rare class of high-temperature condensates from the inner regions of the protoplanetary disk. Their mineralogy is intermediate between isolated corundum grains and CAIs where corundum has been replaced by lower-temperature phases. These inclusions sample a critical transitional period of the inner nebula where both the Sun and protoplanetary disk were rapidly evolving. We conducted O isotopic, Al-Mg chronological, petrographic, and crystallographic studies of four corundum-bearing inclusions in the Murchison CM2 and ALHA 77307 CO3.0 carbonaceous chondrites. Within each inclusion, corundum, hibonite, and spinel have indistinguishable 16O-rich compositions. The O isotopic compositions from all inclusions fall within a narrow range of Δ17O = -22.8 ± 3.6‰ that matches values of most previously studied micrometer-sized corundum grains and mineralogically pristine CAIs. These data indicate that, with few exceptions, the most refractory inclusions in carbonaceous chondrites formed from the same O isotopic reservoir. One CAI from ALHA 77307, ALH-61, exhibits a continuous corundum mantle overlying a hibonite core, opposite the equilibrium condensation sequence at typical nebular pressures and dust/gas ratios. Transmission electron microscopy examination of the hibonite-corundum interface suggests that the corundum condensed on the hibonite and was itself then partially overlain with spinel. Additionally, high dust/gas ratios are interpreted from the W- and Mo-depleted composition of a refractory metal nugget within a second corundum-bearing CAI, ALH-160. Together, these observations show that the primary formation conditions of some corundum-bearing CAIs involved non-equilibrium condensation in environments with elevated dust-gas ratios. The corundum-bearing CAIs studied here have inferred initial 26Al/27Al ratios that fall within the roughly bimodal distribution of values observed in most CAIs. ALH-160 retains no

  11. Identification of deposit types of natural corundum by PIXE

    Science.gov (United States)

    Chulapakorn, T.; Intarasiri, S.; Bootkul, D.; Singkarat, S.

    2014-07-01

    Natural corundum, one of the most important exports of Thailand, is a rare, durable and valuable gemstone. The value of these precious stones is determined by their visual appearances, including brilliance, color, fire (light dispersion) and luster. Corundum is an allochromatic mineral whose trace element concentration depends on the origin and has influence on price setting. This work attempts to use an alternative method to identify the geological deposits of rubies and sapphires found in the Thai market which came from various countries, e.g., Africa, Cambodia, Myanmar, Sri Lanka, Thailand and USA. Interrelations between most important major trace elements are the main results of this work. Quantitative analysis of trace elements were performed by particle-induced X-ray emission (PIXE) technique, using 2-MeV proton beam generated and accelerated by the 1.7 MV tandem accelerator at Chiang Mai University. The trace elements of interest are Ti, Cr, Fe and Ga. We have found that the relationships between the ratios of trace element concentration can be used to classify the deposit type. Moreover, this method shows a clear separation between two main types of geological deposits, basaltic and metamorphic deposits, which further helps in determining the gemstone origin. For example, the gemstones from Cambodia, Thailand and the USA can be classified as the basaltic deposits with their high concentration in Fe but low in Ti, while the gemstones from Africa, Myanmar and Sri Lanka are metamorphic deposits because they have low Fe but high Ti concentrations. Both deposits required plots of pairs of trace elements and their ratios in population field appearance in order to distinguish their origins. The advantageous of these methods appear to be a new and a sustainable procedure for determining gemstone origins.

  12. Identification of deposit types of natural corundum by PIXE

    Energy Technology Data Exchange (ETDEWEB)

    Chulapakorn, T. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Intarasiri, S., E-mail: saweat@gmail.com [Science and Technology Research Institute, Chiang Mai University, Chiang Mai 50202 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand); Bootkul, D., E-mail: mo_duangkhae@gmail.com [Department of General Science (Gems and Jewelry), Faculty of Science, Srinakharinwirot University, Sukhumvit 23, Bangkok 10110 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand); Singkarat, S. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand)

    2014-07-15

    Natural corundum, one of the most important exports of Thailand, is a rare, durable and valuable gemstone. The value of these precious stones is determined by their visual appearances, including brilliance, color, fire (light dispersion) and luster. Corundum is an allochromatic mineral whose trace element concentration depends on the origin and has influence on price setting. This work attempts to use an alternative method to identify the geological deposits of rubies and sapphires found in the Thai market which came from various countries, e.g., Africa, Cambodia, Myanmar, Sri Lanka, Thailand and USA. Interrelations between most important major trace elements are the main results of this work. Quantitative analysis of trace elements were performed by particle-induced X-ray emission (PIXE) technique, using 2-MeV proton beam generated and accelerated by the 1.7 MV tandem accelerator at Chiang Mai University. The trace elements of interest are Ti, Cr, Fe and Ga. We have found that the relationships between the ratios of trace element concentration can be used to classify the deposit type. Moreover, this method shows a clear separation between two main types of geological deposits, basaltic and metamorphic deposits, which further helps in determining the gemstone origin. For example, the gemstones from Cambodia, Thailand and the USA can be classified as the basaltic deposits with their high concentration in Fe but low in Ti, while the gemstones from Africa, Myanmar and Sri Lanka are metamorphic deposits because they have low Fe but high Ti concentrations. Both deposits required plots of pairs of trace elements and their ratios in population field appearance in order to distinguish their origins. The advantageous of these methods appear to be a new and a sustainable procedure for determining gemstone origins.

  13. Advances in Trace Element "Fingerprinting" of Gem Corundum, Ruby and Sapphire, Mogok Area, Myanmar

    National Research Council Canada - National Science Library

    F Lin Sutherland; Khin Zaw; Sebastien Meffre; Tzen-Fui Yui; Kyaw Thu

    2015-01-01

    ... corundum area and also identified rare alluvial ruby and sapphire grains characterised by unusually high silicon, calcium and gallium, presence of noticeable boron, tin and niobium and very low iron, titanium and magnesium contents...

  14. Properties and Performances of High Purity Corundum Bricks for Chemical and Petrochemical Industries in China

    Institute of Scientific and Technical Information of China (English)

    CHENRen-pin; LINYu-lian; 等

    1995-01-01

    The properties and performances of high purity corundum bricks for the refractory linings of the gasifiers in the ammonia and ethene synthesis and carbon black reaction furnaces in China are described.The high purity corundum bricks are characterized by high refractoriness,hot strength,dimensional stability and chemical inertness at elevated temperature,Their performances in the gasifiers and carbon black furnaces are very satisfied ,The failure mechansims of the refractory lining are discussed on the basis of the petrographic analysis.

  15. Advances in Trace Element “Fingerprinting” of Gem Corundum, Ruby and Sapphire, Mogok Area, Myanmar

    Directory of Open Access Journals (Sweden)

    F. Lin Sutherland

    2014-12-01

    Full Text Available Mogok gem corundum samples from twelve localities were analyzed for trace element signatures (LA-ICP-MS method and oxygen isotope values (δ18O, by laser fluorination. The study augmented earlier findings on Mogok gem suites that suggested the Mogok tract forms a high vanadium gem corundum area and also identified rare alluvial ruby and sapphire grains characterised by unusually high silicon, calcium and gallium, presence of noticeable boron, tin and niobium and very low iron, titanium and magnesium contents. Oxygen isotope values (δ18O for the ruby and high Si-Ca-Ga corundum (20‰–25‰ and for sapphire (10‰–20‰ indicate typical crustal values, with values >20‰ being typical of carbonate genesis. The high Si-Ca-Ga ruby has high chromium (up to 3.2 wt % Cr and gallium (up to 0. 08 wt % Ga compared to most Mogok ruby (<2 wt % Cr; <0.02 wt % Ga. In trace element ratio plots the Si-Ca-Ga-rich corundum falls into separate fields from the typical Mogok metamorphic fields. The high Ga/Mg ratios (46–521 lie well within the magmatic range (>6, and with other features suggest a potential skarn-like, carbonate-related genesis with a high degree of magmatic fluid input The overall trace element results widen the range of different signatures identified within Mogok gem corundum suites and indicate complex genesis. The expanded geochemical platform, related to a variety of metamorphic, metasomatic and magmatic sources, now provides a wider base for geographic typing of Mogok gem corundum suites. It allows more detailed comparisons with suites from other deposits and will assist identification of Mogok gem corundum sources used in jewelry.

  16. Spectroscopic study of inclusions in gem corundum from Mercaderes, Cauca, Colombia

    Science.gov (United States)

    Zeug, Manuela; Rodríguez Vargas, Andrés Ignacio; Nasdala, Lutz

    2016-10-01

    Mineral inclusions in gem corundum from Mercaderes, Cauca, Colombia, were investigated non-destructively using Raman and photoluminescence spectroscopy, with special focus lying on phases containing radioactive elements. Besides abundant rutile, the minerals zircon, apatite, feldspar, and an epidote-group species, most probably allanite-(Ce), were found. The latter is detected easily from its characteristic Nd3+ emission pattern, which may prove useful in future provenance studies. Zircon inclusions range from well crystalline to moderately radiation damaged [FWHM (full width at half band maximum) of the ν 3(SiO4) Raman band 1.8-10.9 cm-1]. Both the zircon inclusions and their neighbouring host corundum are affected by compressive stress, which is assigned to (1) heterogeneous volume expansion of the host-inclusion couple upon pressure release during the uplift following primary growth and (2) volume expansion of the zircon inclusion due to the accumulation of self-irradiation damage. Internal stress of zircon inclusions averages 1.1 GPa. Heat treatment of corundum leads to structural reconstitution of zircon (narrowed zircon Raman bands with FWHMs in the range 1.8-2.7 cm-1) and accompanying stress release in the adjacent corundum (indicated by downshifts of the R 1 emission of Cr3+). The observation of broadened Raman band of zircon inclusions therefore allows one to exclude high-temperature enhancement of the host corundum.

  17. Absorption and emission spectroscopy in natural and synthetic corundum

    Science.gov (United States)

    Spinolo, G.; Palanza, V.; Ledonne, A.; Paleari, A.

    2009-04-01

    In the frame of an extensive project on the optical characterization of the many varieties of corundum (see:www.gemdata.mater.unimib.it ) we reconsidered the current interpretation of the absorption spectra with particular attention to the bands attributed to the IVCT mechanism Fe2+→ Fe3+ and Fe2+→Ti4+. A detailed study was devoted to natural metamorphic and Verneuil synthetic pale blue sapphires . In that paper (I.Fontana et al 2008) we gave experimental evidence that the band at 17500 cm-1 often attributed to Fe2+→Ti4+ IVCT transitions is in reality due to the 4T2 crystal field transition of Cr3+ partially overlapped by the 2E of Ti3+. The results of radio and photoluminescence excitation experiments obtained there, led us to propose that the color of these sapphires is mainly due to Cr in its two valence states ; Ti 3+ and Fe3+ have a minor role. After those encouraging results, we decided to apply the same approach to the study of deep blue and yellow sapphires of magmatic origin. Evaluation of impurity ion concentration by EDXRF revealed that in all these samples the concentration of Fe is quite high (around 1%) while Cr and Ti are barely detectable. Characteristic of the absorption spectra of deep blue samples is the dominant presence of the 5E spin allowed transition of Fe2+; Fe3+ has a minor role due to the fact that all d5 transitions are spin forbidden and ,consequently, very weak. In yellow sapphires Fe is totally in its 3+ valence state. In these cases, the color from yellow to blue, sometimes even within the same sample, depends. on oxidizing or reducing growth conditions. Even if the concentrations of Cr and Ti are very low, their characteristic emissions are the only ones observable down to 10000 cm-1 in radio and photoluminescence spectra. This piece of evidence suggested us to propose for the absorption bands present in the 14000 to 21000 cm-1 range, often attributed to IVCT, the same attribution given to the analogous bands in metamorphic

  18. Bioaccessibility Of Lead Sequestered To Corundum and Ferrihydrite In A Simulated Gastrointestinal System

    Science.gov (United States)

    Lead (Pb) sorption onto oxide surfaces in soils may strongly influence the risk posed from incidental ingestion of Pb-contaminated soil. Lead was sorbed to model oxide minerals of corundum (α-Al2O3) and ferrihydrite (Fe5HO8•4H2

  19. Wear characteristics of second-phase-reinforced sol-gel corundum abrasives

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Joachim [Central Facility for Electron Microscopy (GFE), RWTH Aachen University, 52056 Aachen (Germany)]. E-mail: mayer@gfe.rwth-aachen.de; Engelhorn, Robert [Laboratory for Machine Tools and Production Engineering (WZL), RWTH Aachen University, 52056 Aachen (Germany); Bot, Rosemarie [Laboratory for Machine Tools and Production Engineering (WZL), RWTH Aachen University, 52056 Aachen (Germany); Weirich, Thomas [Central Facility for Electron Microscopy (GFE), RWTH Aachen University, 52056 Aachen (Germany); Herwartz, Cleo [Central Facility for Electron Microscopy (GFE), RWTH Aachen University, 52056 Aachen (Germany); Klocke, Fritz [Laboratory for Machine Tools and Production Engineering (WZL), RWTH Aachen University, 52056 Aachen (Germany)

    2006-08-15

    The use of sol-gel technologies makes it possible to manufacture new corundum-based abrasives with superior performance in terms of grinding processes. The aim of the present work is to reveal the detailed wear mechanisms on a nanometre scale and relate them to the particular microstructure of these new materials. A commercial sol-gel corundum (Cubitron 321{sup TM}) was used. In the grinding experiments, wheels consisting of four different mixtures with 0%, 30%, 50% and 100% of sol-gel corundum were used to machine a tool steel (100Cr6V) by plane grinding. Changes to the contact zone were studied after controlled abrasion experiments on hard steel substrates using a pin-on-wheel tribometer, in single grit scratch tests and after tests of resistance to heat shock. Cross-sections through contact areas of a sol-gel grain were prepared using a focused ion beam workstation and investigated using conventional and analytical transmission electron microscopy. The results indicate that the combined effect of controlled propagation of subsurface shear cracks and plastic deformation leads to the formation of flat contact zones. On these contact zones, a nanocrystalline FeO debris layer adheres to the alumina. The results of our investigations were verified in grinding experiments and give insight into the physical reasons of the superior tribological properties of the sol-gel corundum abrasives.

  20. Fractal model for evaluating heat transfer of high temperature porous corundum shell in vacuum investment casting

    Directory of Open Access Journals (Sweden)

    WAN Xin

    2006-02-01

    Full Text Available Under vacuum, heat transfer in porous corundum shell of investment casting depends on the characteristics of the solid materials and the spatial arrangement of solids and pores. In this study, we present a modified fractal approach to model the pore structure of corundum shell and to describe its influence on the thermal conductivity. We assumed that there is no heat convection in the shell. A sectioned view of porous corundum shell was studied and used to describe the geometric structure and to calculate the fractal dimension d. Based on the fractal dimension d, we obtained the relationship between volumetric solid content and pore arrangement in different measure scales. A heat transfer model was thus established using a network of resistors in which we applied an equivalent approach to calculate the effective thermal conductivity of real porous corundum shell that include the effects of heat conduction and heat radiation of solid. From the obtained results we discuss these effects on the effective thermal conductivity including the scale of measurement, the structure of pore and the temperature. At last these results were compared with other empirical model, which computed by assuming even porosity in which effect of pore structure was not being considered. Though the thermal conductivity calculated essentially in agreement with that obtained from empirical model, model used in this study is more close to the real heat transfer process.

  1. Corundum-Hibonite Inclusions and the Environments of High Temperature Processing in the Early Solar System

    Science.gov (United States)

    Needham, A. W.; Messenger, S.

    2013-01-01

    Calcium, Aluminum-rich inclusions (CAIs) are composed of the suite of minerals predicted to be the first to condense from a cooling gas of solar composition [1]. Yet, the first phase to condense, corundum, is rare in CAIs, having mostly reacted to form hibonite followed by other phases at lower temperatures. Many CAIs show evidence of complex post-formational histories, including condensation, evaporation, and melting [e.g. 2, 3]. However, the nature of these thermal events and the nebular environments in which they took place are poorly constrained. Some corundum and corundum-hibonite grains appear to have survived or avoided these complex CAI reprocessing events. Such ultra-refractory CAIs may provide a clearer record of the O isotopic composition of the Sun and the evolution of the O isotopic composition of the planet-forming region [4-6]. Here we present in situ O and Mg isotopic analyses of two corundum/hibonite inclusions that record differing formation histories.

  2. Oxygen isotope systematics of gem corundum deposits in Madagascar: relevance for their geological origin

    Science.gov (United States)

    Giuliani, Gaston; Fallick, Anthony; Rakotondrazafy, Michel; Ohnenstetter, Daniel; Andriamamonjy, Alfred; Ralantoarison, Théogène; Rakotosamizanany, Saholy; Razanatseheno, Marie; Offant, Yohann; Garnier, Virginie; Dunaigre, Christian; Schwarz, Dietmar; Mercier, Alain; Ratrimo, Voahangy; Ralison, Bruno

    2007-02-01

    The oxygen isotopic composition of gem corundum was measured from 22 deposits and occurrences in Madagascar to provide a gemstone geological identification and characterization. Primary corundum deposits in Madagascar are hosted in magmatic (syenite and alkali basalt) and metamorphic rocks (gneiss, cordieritite, mafic and ultramafic rocks, marble, and calc-silicate rocks). In both domains the circulation of fluids, especially along shear zones for metamorphic deposits, provoked in situ transformation of the corundum host rocks with the formation of metasomatites such as phlogopite, sakenite, and corundumite. Secondary deposits (placers) are the most important economically and are contained in detrital basins and karsts. The oxygen isotopic ratios (18O/16O) of ruby and sapphire from primary deposits are a good indicator of their geological origin and reveal a wide range of δ18O (Vienna Standard Mean Ocean Water) between 1.3 and 15.6‰. Metamorphic rubies are defined by two groups of δ18O values in the range of 1.7 to 2.9‰ (cordieritite) and 3.8 to 6.1‰ (amphibolite). “Magmatic” rubies from pyroxenitic xenoliths contained in the alkali basalt of Soamiakatra have δ18O values ranging between 1.3 and 4.7‰. Sapphires are classified into two main groups with δ18O in the range of 4.7 to 9.0‰ (pyroxenite and feldspathic gneiss) and 10.7 to 15.6‰ (skarn in marble from Andranondambo). The δ18O values for gem corundum from secondary deposits have a wide spread between -0.3 and 16.5‰. The ruby and sapphire found in placers linked to alkali basalt environments in the northern and central regions of Madagascar have consistent δ18O values between 3.5 and 6.9‰. Ruby from the placers of Vatomandry and Andilamena has δ18O values of 5.9‰, and between 0.5 and 4.0‰, respectively. The placers of the Ilakaka area are characterized by a huge variety of colored sapphires and rubies, with δ18O values between -0.3 and 16.5‰, and their origin is debated. A

  3. Mullite Precursor Gels and as Binder in Corundum-mullite Refractory

    Institute of Scientific and Technical Information of China (English)

    WU Xingrong; LI Liaosha; DONG Yuanchi

    2004-01-01

    Boehmite sol is synthesized via sol-gel process using als,then adding silica sol into boehmite sol to prepare mullite precursor gels. XRD studies are performed to characterize the gels.it is found that the gel can be transformed into mullite when calcined at 1100℃ and completed at 1300℃.Corundum-mullite firebricks with different additions of the mullite precursor gel are made by mixing,semi-dry pressing and then sintering at 1520℃.Apparent porosity,bulk density,flexural strength and thermal shock resistance are measured.Results show that the mullite gel can improve densification and strength of corundum-mullite firebricks,especially enhance the thermal shock resistance.SEM micrographs show that the gel added can be formed into needlelike and elongated mullite in the matrix,whose micromorphology can enhance the strength and thermal shock resistance of the samples.

  4. Improvement of FeO Corrosion Resistance by Addition of β-Sialion in Matrix of Corundum Castable

    Institute of Scientific and Technical Information of China (English)

    LIYawei; CHENFangyu; 等

    2001-01-01

    Silicon aluminum oxynitride (β-Si4Al2O2N6) powder was added into corundum castable and its FeO corrosion resistance was tested in crucible method.It was found that FeO corrosion resistance of sialon containing corundum castables was better than that of no sialon powder added ,The optimum content of the sialon powder in castables was higher than mass of the sialon powder in castables was higher than mass 15%.Moreover,O'-sialon phase,together with β-sialon phase occurred in corundum castables heated in coke bed at 1500℃,although β-sialon powder was initially admixed into the matrix of castables.The EPMA results showed these nitrogen-containing phases located in the matrix of castables were favorable to hinder the penetration of FeO melt at high temperature in comparison with pure corundum castable.However,the flowability of corundum castable became worse originated from the sialon powder added.

  5. Thermal Shock Resistance of Bauxite-based β-Sialon Bonded Corundum Materials

    Institute of Scientific and Technical Information of China (English)

    LIU Zhanjie; ZHANG Haijun; ZHONG Xiangchong

    2005-01-01

    Thermal shock resistant properties of reaction sintered bauxite-based β-Sialon bonded corundum have been investigated, and the results are compared with those of Al2 O3 based counterpart. It is found they all have very good thermal shock resistance. Their residual strength ratios after one thermal shock cycle at △T =1200℃ and △T = 1350℃ are 61% ~73% and 53% ~65% respectively. Their critical temperature difference (TSR) is 600℃~800℃. TSR parameters are calculated based on thermal expansion, modulus of elasticity,and fracture toughness determined. The reasons for improving TSR of these composite materials are discussed.

  6. Evolution of corundum-structured III-oxide semiconductors: Growth, properties, and devices

    Science.gov (United States)

    Fujita, Shizuo; Oda, Masaya; Kaneko, Kentaro; Hitora, Toshimi

    2016-12-01

    The recent progress and development of corundum-structured III-oxide semiconductors are reviewed. They allow bandgap engineering from 3.7 to ∼9 eV and function engineering, leading to highly durable electronic devices and deep ultraviolet optical devices as well as multifunctional devices. Mist chemical vapor deposition can be a simple and safe growth technology and is advantageous for reducing energy and cost for the growth. This is favorable for the wide commercial use of devices at low cost. The III-oxide semiconductors are promising candidates for new devices contributing to sustainable social, economic, and technological development for the future.

  7. Batch sorption and spectroscopic speciation studies of neptunium uptake by montmorillonite and corundum

    Science.gov (United States)

    Elo, O.; Müller, K.; Ikeda-Ohno, A.; Bok, F.; Scheinost, A. C.; Hölttä, P.; Huittinen, N.

    2017-02-01

    Detailed information on neptunium(V) speciation on montmorillonite and corundum surfaces was obtained by batch sorption and desorption studies combined with surface complexation modelling using the Diffuse Double-Layer (DDL) model, in situ time-resolved Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) and X-ray absorption (XAS) spectroscopies. The pH-dependent batch sorption studies and the spectroscopic investigations were conducted under carbonate-free conditions in 10 mM NaClO4 or 10 mM NaCl. Solid concentrations of 0.5 g/l and 5 g/l were used depending on the experiment. The neptunium(V) desorption from the two mineral surfaces was investigated at pH values ranging from 8 to 10, using the replenishment technique. Neptunium(V) was found to desorb from the mineral surface, however, the extent of desorption was dependent on the solution pH. The desorption of neptunium(V) was confirmed in the ATR FT-IR spectroscopic studies at pH 10, where all of the identified inner-sphere complexed neptunium(V), characterized by a vibrational band at 790 cm-1, was desorbed from both mineral surfaces upon flushing the mineral films with a blank electrolyte solution. In XAS investigations of neptunium(V) uptake by corundum, the obtained structural parameters confirm the formation of an inner-sphere complex adsorbed on the surface in a bidentate fashion. As the inner-sphere complexes found in the IR-studies are characterized by identical sorption bands on both corundum and montmorillonite, we tentatively assigned the neptunium(V) inner-sphere complex on montmorillonite to the same bidentate complex found on corundum in the XAS investigations. Finally, the obtained batch sorption and spectroscopic results were modelled with surface complexation modelling to explain the neptunium(V) speciation on montmorillonite over the entire investigated pH range. The modelling results show that cation exchange in the interlayer space as well as two pH-dependent surface complexes

  8. The Effect of Bauxite Substitution on High Temperature Strength Properties of Zirconia—corundum Mullite Material

    Institute of Scientific and Technical Information of China (English)

    ZHONGWei-bin; SUNGeng-chen; 等

    1994-01-01

    Investigations on the effect of bauxite substi-tution for industrial alumina on high temperature strength and thermal shock resistance of reaction-sintered zirconia-corundum-mullite material(ZrO2 15%) have indicated that bauxite substitution would lead to increase in modulus of rupture at 1000-1400℃ as well as improvement in thermal shock resistance,Hot strength value reaches a maximum at 15% buxite addition.The mecha-nism of mechanical behavior at elevated tempera-tures is discussed in association with changes in mi-crostructural characteristics.

  9. Experimental and Analytical Study on the Penetration of Corundum-Rubble Concrete Subjected to Projectile Impact

    Directory of Open Access Journals (Sweden)

    Y. L. Xue

    2017-01-01

    Full Text Available A new type of composite concrete which can be called corundum-rubble concrete (CRC was presented to improve the resistance of protective structure to the projectile impact. Comparative experiments were conducted between CRC and reinforced concrete, and a modified Taylor model was proposed to predict the penetration depth of CRC targets. Experimental results show that CRC is much higher than reinforced concrete in both strength and hardness and shows excellent resistance to the 0.125 m-diameter projectile impact. Theoretical analyses demonstrated that the modified Taylor model’s predicted results were in good agreement with the measured values.

  10. Origin of gem corundum in calcite marble: The Revelstoke occurrence in the Canadian Cordillera of British Columbia

    Science.gov (United States)

    Dzikowski, Tashia J.; Cempírek, Jan; Groat, Lee A.; Dipple, Gregory M.; Giuliani, Gaston

    2014-06-01

    The calcite marble-hosted gem corundum (ruby, sapphire) occurrence near Revelstoke, British Columbia, Canada, occurs in the Monashee Complex of the Omineca Belt of the Canadian Cordillera. Corundum occurs in thin, folded and stretched layers with green muscovite + Ba-bearing K-feldspar + anorthite (An0.85-1) ± phlogopite ± Na-poor scapolite. Other silicate layers within the marble are composed of: (1) diopside + tremolite ± quartz and (2) garnet (Alm0.7-0.5Grs0.2-0.4) + Na-rich scapolite + diopside + tremolite + Na,K-amphiboles. Non-silicate layers in the marble are either magnetite- or graphite-bearing. Predominantly pink (locally red or purple) opaque to transparent corundum crystals have elevated Cr2O3 (≤ 0.21 wt.%) and variable amounts of TiO2; rare blue rims on the corundum crystals contain higher amounts of TiO2 (≤ 0.53 wt.%) and Fe2O3 (≤ 0.07 wt.%). The associated micas have elevated Cr, V, Ti, and Ba contents. Petrography of the silicate layers show that corundum formed from muscovite at the peak of metamorphism (~ 650-700 °C at 8.5-9 kbar). Because the marble is almost pure calcite (dolomite is very rare), the corundum was preserved because it did not react with dolomite to spinel + calcite during decompression. The scapolite-bearing assemblages formed during or after decompression of the rock at ~ 650 °C and 4-6 kbar. Gem-quality corundum crystals formed especially on borders of the mica-feldspar layers in an assemblage with calcite. Whole rock geochemistry data show that the corundum-bearing silicate (mica-feldspar) layers formed by mechanical mixing of carbonate with the host gneiss protolith; the bulk composition of the silicate layers was modified by Si and Fe depletion during prograde metamorphism. High element mobility is supported by the homogenization of δ18O and δ13C values in carbonates and silicates for the marble and silicate layers. The silicate layers and the gneiss contain elevated contents of Cr and V due to the volcanoclastic

  11. Dust in the wind: Crystalline silicates, corundum and periclase in PG 2112+059

    CERN Document Server

    Markwick-Kemper, F; Hines, D C; Bouwman, J

    2007-01-01

    We have determined the mineralogical composition of dust in the Broad Absorption Line (BAL) quasar PG 2112+059 using mid-infrared spectroscopy obtained with the Spitzer Space Telescope. From spectral fitting of the solid state features, we find evidence for Mg-rich amorphous silicates with olivine stoichiometry, as well as the first detection of corundum (Al_2O_3) and periclase (MgO) in quasars. This mixed composition provides the first direct evidence for a clumpy density structure of the grain forming region. The silicates in total encompass 56.5% of the identified dust mass, while corundum takes up 38 wt.%. Depending on the choice of continuum, a range of mass fractions is observed for periclase ranging from 2.7% in the most conservative case to 9% in a less constrained continuum. In addition, we identify a feature at 11.2 micron as the crystalline silicate forsterite, with only a minor contribution from polycyclic aromatic hydrocarbons. The 5% crystalline silicate fraction requires high temperatures such ...

  12. Recovering experimental and theoretical electron densities in corundum using the multipolar model: IUCr Multipole Refinement Project.

    Science.gov (United States)

    Pillet, S; Souhassou, M; Lecomte, C; Schwarz, K; Blaha, P; Rérat, M; Lichanot, A; Roversi, P

    2001-05-01

    This electron-density study on corundum (alpha-Al2O3) is part of the Multipole Refinement Project supported by the IUCr Commission on Charge, Spin and Momentum Densities. For this purpose, eight different data sets (two experimental and six theoretical) were chosen from which the electron density was derived by multipolar refinement (using the MOLLY program). The two experimental data sets were collected on a conventional CAD4 and at ESRF, ID11 with a CCD detector, respectively. The theoretical data sets consist of static, dynamic, static noisy and dynamic noisy moduli of structure factors calculated at the Hartree-Fock (HF) and density functional theory (DFT) levels. Comparisons of deformation and residual densities show that the multipolar analysis works satisfactorily but also indicate some drawbacks in the refinement. Some solutions and improvements during the refinements are proposed like contraction or expansion of the inner atomic shells or increasing the order of the spherical harmonic expansion.

  13. RESEARCH OF PROCESSES ON FORMATION AND TRIBOTECHNICAL PROPERTIES OF WEAR-RESISTANT COMPOSITE GAS THERMAL COATINGS BEING DISPERSIVELY STRENGTHENED BY SYNTHETIC DIAMONDS AND ELECTRO-CORUNDUM

    Directory of Open Access Journals (Sweden)

    O. S. Kobjakov

    2011-01-01

    Full Text Available Formation processes, tribotechnical and wear-resistant properties of composite gas thermal coatings being dispersively strengthened by synthetic diamonds and electro-corundum are investigated in the paper.

  14. Origin of peraluminous minerals (corundum, spinel, and sapphirine) in a highly calcic anorthosite from the Sittampundi Layered Complex, Tamil Nadu, India

    Science.gov (United States)

    Karmakar, Shreya; Mukherjee, Subham; Sanyal, Sanjoy; Sengupta, Pulak

    2017-08-01

    The highly calcic anorthosite (An>95) from the Sittampundi Layered Complex (SLC) develops corundum, spinel and sapphirine that are hitherto not reported from any anorthositic rocks in the world. Petrological observations indicate the following sequence of mineral growth: plagioclasematrix → corundum; clinopyroxene → amphibole; corundum + amphibole → plagioclasecorona + spinel; and spinel + corundum → coronitic sapphirine. Phase relations in the CaO-Na2O-Al2O3-SiO2-H2O (CNASH) system suggest that corundum was presumably developed through vapour present incongruent melting of the highly calcic plagioclase during ultra-high temperature (UHT) metamorphism ( T ≥ 1000 °C, P ≥ 9 kbar). Topological constraints in parts of the Na2O-CaO-MgO-Al2O3-SiO2-H2O (NCMASH) system suggest that subsequent to the UHT metamorphism, aqueous fluid(s) permeated the rock and the assemblage corundum + amphibole + anorthite + clinozoisite was stabilized during high-pressure (HP) metamorphism (11 ± 2 kbar, 750 ± 50 °C). Constraints of the NCMASH topology and thermodynamic and textural modeling study suggest that coronitic plagioclase and spinel formed at the expense of corundum + amphibole during a steeply decompressive retrograde P- T path (7-8 kbar and 700-800 °C) in an open system. Textural modeling studies combined with chemical potential diagrams (μSiO2-μMgO) in the MASH system support the view that sapphirine also formed from due to silica and Mg metasomatism of the precursor spinel ± corundum, on the steeply decompressive retrograde P- T path, prior to onset of significant cooling of the SLC. Extremely channelized fluid flow and large positive solid volume change of the stoichiometrically balanced sapphirine forming reaction explains the localized growth of sapphirine.

  15. Preparation of Al- AlN Bonded Corundum Based Refractories by in-situ Reaction

    Institute of Scientific and Technical Information of China (English)

    ZHU Boquan; FANG Binxiang; ZHANG Wenjie

    2008-01-01

    The Al-AlN bonded corundum based refractories was synthesized with the starting materials of fused alu-mina and metallic aluminium in nitrogen atmosphere through in-situ reaction. The study indicated that with the addition of 14% metallic aluminium (13% of Al powder and 1% of Al fiber) , the material nitridized at 1 100 ℃ for 3 h has excellent physical properties. It is found that a massive quantity of AlN in the forms of both whiskers" and hexagon pellet particles is formed, and a large quantity of Al remained in the matrix. This multiple bonding system resulted in the excellent me-chanical properties of the material. It is also found that the hydration tendency of the prepared material is inhib-ited, and the material exhibited excellent thermal shock resistance. The nature of protective oxidation of the bonding system is characterized. Thus, this material may become a new candidate of carbon-free sliding plate material for continuous casting.

  16. Analysis of volume expansion data for periclase, lime, corundum and spinel at high temperatures

    Indian Academy of Sciences (India)

    B P Singh; H Chandra; R Shyam; A Singh

    2012-08-01

    We have presented an analysis of the volume expansion data for periclase (MgO), lime (CaO), corundum (Al2O3) and spinel (MgAl2O4) determined experimentally by Fiquet et al (1999) from 300K up to 3000K. The thermal equation of state due to Suzuki et al (1979) and Shanker et al (1997) are used to study the relationships between thermal pressure and volume expansion for the entire range of temperatures starting from room temperature up to the melting temperatures of the solids under study. Comparison of the results obtained in the present study with the corresponding experimental data reveal that the thermal pressure changes with temperature almost linearly up to quite high temperatures. At extremely high temperatures close to the melting temperatures thermal pressure deviates significantly from linearity. This prediction is consistent with other recent investigations. A quantitative analysis based on the theory of anharmonic effects has been presented to account for the nonlinear variation of the thermal pressure at high temperatures.

  17. The behavior of mineral inclusions during host decomposition. A SEM-STEM study of rutile inclusions at a natural propagating corundum-spinel interface.

    Science.gov (United States)

    Baldwin, Lisa; Li, Chen; Habler, Gerlinde; Abart, Rainer

    2017-04-01

    When two neighbor phases are not in chemical equilibrium, they may react and produce a reaction rim at their interface, separating the mutually incompatible phases. At constant P-T-X conditions, such a reaction will continue until one of the reactants is completely consumed. Reaction rim growth involves transfer of chemical components across the growing rim by long-range diffusion and localized interface reactions on either side of the growing rim. Consequently, the thickness of the reaction rim will be a function of time. Yet, in order to quantify and interpret such corona structures and to define a reaction rate law, the kinetics and mechanism of rim formation must be well constrained. In particular, the coupling between long-range diffusion, and interface reaction must be known. In this contribution we focus on potential complexities associated with interface reactions. Many natural minerals contain inclusions of other phases, which in turn may influence the reaction interface propagation kinetics during host phase decomposition (Ashby et al. 1969), as a propagating reaction interface dissipates more free energy when bypassing a mineral inclusion, resulting in a locally decelerated reaction rate. Here, we report results of a SEM-STEM study of the interface between natural rutile-bearing corundum and a polycrystalline ferromagnesio-aluminate spinel that grew topotactically with respect to the corundum precursor as a consequence of its reaction with FeO and MgO from basaltic melt. Electron Backscatter Diffraction (EBSD) crystal orientation imaging revealed that the spinel rim is polycrystalline and exhibits (111) twinning that is parallel to the corundum (0001) plane. The rutile inclusions in corundum are elongated perpendicular to the corundum [0001] axis and are randomly oriented in the (0001) plane. Furthermore, they follow an oscillatory grain size distribution zonation with grain sizes being either a few tens of nanometers, or about 500 to 800 nanometers in

  18. Preparation, Microstructure, and Mechanical Properties of Spinel-Corundum-Sialon Composite Materials from Waste Fly Ash and Aluminum Dross

    Directory of Open Access Journals (Sweden)

    Juntong Huang

    2014-01-01

    Full Text Available The solid wastes fly ash and aluminum dross were used to prepare the low cost, high added-value product spinel-corundum-Sialon with an in situ aluminothermic reduction-nitridation reaction. The effects of varying raw material components and heating temperatures on the phase compositions, microstructure, bulk density, apparent porosity, and bending strength of products were investigated. The presence of hazardous or impure elements in the products was also evaluated. The sintered materials mainly consisted of micro-/nanosized plate corundum, octahedral spinel, and hexagonal columnar β-Sialon. The bulk density and bending strength of product samples initially increased and then decreased as Al content increased. Product samples with an Al content exceeding 10 mass% that were sintered at 1450°C exhibited the highest bending strength (288 MPa, the lowest apparent porosity (1.24%, and extremely low linear shrinkage (0.67%. The main impurity present was Fe5Si3 with hazardous elements P, Cr, Mn, and Ni doping. This work could provide a new method to reduce environmental pollution and manufacture low cost high performance refractory materials using the abundant waste materials fly ash and aluminum dross.

  19. The effects of stress concentrations on reaction progress: an example from experimental growth of magnesio-aluminate spinel at corundum - periclase interfaces under uniaxial load

    Science.gov (United States)

    Jerabek, Petr; Abart, Rainer; Rybacki, Erik; Habler, Gerlinde

    2014-05-01

    The study aims to understand the reaction progress and chemical, microstructural and textural evolution of magnesio-aluminate spinel reaction rims formed at varying experimental settings (load, temperature and experiment duration). The spinel rims were grown at the contacts between periclase and corundum at temperatures of 1250°C to 1350°C and dry atmosphere, maintained by a constant argon gas flow, under uniaxial load of 0.026 and 0.26 kN per 9 mm2 of initial contact area. Single crystals of periclase with [100] and of corundum with [0001] perpendicular to the polished reaction interface as well as polycrystalline corundum were used as starting materials. Two loading procedures, immediate application of the load before heating and loading after the desired temperature had been reached, were used. An important byproduct of our experiments stemmed from the immediate application of the load, which led to deformation twinning and fracturing of corundum. This internal deformation of corundum disturbed the reaction interface and introduced loci of concentrated stress due to opening of void spaces in between the reactant crystals. Whenever cracks formed in the initial stages of an experiment, the void space opened immediately and no spinel formed along these interface segments. In the case of deformation twinning, the decreased rim thickness indicates later opening of void spaces. This is because next to twins, the reaction interface is characterized by tight physical contact on the one side and less tight contact on the other side of the twin individual. The tight contacts are characterized by enhanced reaction progress which together with the overall positive volume change of the reaction and limits on plasticity of the studied phases led to the opening of void spaces at places characterized by less tight contacts. The thickness variations are less pronounced in our high load (0.26 kN) experiments where periclase behaves plastically and to some extent reduces the

  20. Heterogeneous distribution of 26Al at the birth of the Solar System: Evidence from corundum-bearing refractory inclusions in carbonaceous chondrites

    Science.gov (United States)

    Makide, Kentaro; Nagashima, Kazuhide; Krot, Alexander N.; Huss, Gary R.; Hutcheon, Ian D.; Hellebrand, Eric; Petaev, Michail I.

    2013-06-01

    We report on the mineralogy, petrology, and in situ oxygen- and magnesium-isotope measurements using secondary ion mass spectrometry of 10 corundum-bearing calcium-aluminum-rich inclusions (CAIs) from the Adelaide (ungrouped), Murray and Murchison (CM) carbonaceous chondrites. We also measured in situ oxygen-isotope compositions of several isolated corundum grains in the matrices of Murray and Murchison. Most of the corundum-bearing objects studied are uniformly 16O-rich [Δ17O values range from -17‰ to -28‰ (2σ = ±2.5‰) (Δ17Oavr = -23 ± 5‰)], suggesting that they formed in a 16O-rich gas of approximately solar composition and largely avoided subsequent thermal processing in an 16O-poor gaseous reservoir. There is a large spread of the initial 26Al/27Al ratio [(26Al/27Al)0] in the corundum-bearing CAIs. Two Adelaide CAIs show no resolvable excess of radiogenic 26Mg (δ26Mg∗): the inferred (26Al/27Al)0 are (0.6 ± 2.0) × 10-6 and (-0.9 ± 1.2) × 10-6, respectively. Slopes of the model 26Al-26Mg isochrons in five CAIs from Murray and Murchison are (4.4 ± 0.2) × 10-5, (3.3 ± 0.3) × 10-5, (4.1 ± 0.3) × 10-5, (3.9 ± 0.4) × 10-5, and (4.0 ± 2.0) × 10-6, respectively. These values are lower than the canonical (26Al/27Al)0 ratio of (5.23 ± 0.13) × 10-5 inferred from the whole-rock magnesium-isotope measurements of the CV CAIs, but similar to the (26Al/27Al)0 ratio of (4.1 ± 0.2) × 10-5 in the corundum-bearing CAI F5 from Murray. Five other previously studied corundum-bearing CAIs from Acfer 094 (ungrouped) and CM carbonaceous chondrites showed no resolvable δ26Mg∗. We conclude that the corundum-bearing CAIs, as well as the solar corundum grains from matrices and acid-resistant residues of unequilibrated ordinary and carbonaceous chondrites, recorded heterogeneous distribution of 26Al in the Solar System during an epoch of CAI formation. The 26Al-rich and 26Al-poor corundum-bearing CAIs and solar corundum grains represent different

  1. High-temperature thermoluminescence of anion-deficient corundum and its connection with intrinsic defects and impurities

    Science.gov (United States)

    Abashev, R. N.; Surdo, A. I.; Milman, I. I.

    2017-05-01

    Anion-deficient corundum and TLD-500 detectors on their basis were studied for a possible correlation between the thermoluminescence (TL) yield in the high-temperature TL peak at 830 K and the transformation of intrinsic defects and contents of impurities. Only 40- 60% of TLD-500 detectors were found to have 830 K TL peak. The efficiency of thermally stimulated direct conversion of F and F+ centers in the 800-930 K region depends on the presence of TL peak at 830 K. Obtained data point to the quenching role of the Ti impurity in the formation of the 830 K TL peak. Also, these data provide indirect evidence of association of the 830 K TL peak with Cr3+ ions.

  2. Synthesis of corundum-type In2O3 nanocrystals via hydro/solvothermal route and their photocatalytic properties

    Science.gov (United States)

    Liu, Guodong; Wu, Weidong; Li, Chengcheng; Shi, Xinjin; Gao, KeKe; Li, Min; Tian, Yuan

    2017-06-01

    The understanding of the polymorphism of In2O3 has evoked recent interest in terms of fundamental scientific and technological aspects. A simple yet effective hydro/solvothermal route was introduced for the preparation of In2O3 nanocrystals with different phases using In(acac)3 as indium source. Through adjusting the systemic amount of water, the hydrolysis reaction of In3+ can be efficiently controlled. Moreover, the phases and morphologies of products can also be regulated. Meanwhile, the photocatalytic property of the prepared corundum-type In2O3 was also measured, which showed superior photocatalytic performance on the decomposition of phenol compared to that of cubic phase In2O3 nanocubes.

  3. Perovskite, LiNbO3, corundum, and hexagonal polymorphs of (In(1-x)M(x))MO3.

    Science.gov (United States)

    Belik, Alexei A; Furubayashi, Takao; Yusa, Hitoshi; Takayama-Muromachi, Eiji

    2011-06-22

    LiNbO(3) (LN), corundum (cor), and hexagonal (hex) phases of (In(1-x)M(x))MO(3) (x = 0.143; M = Fe(0.5)Mn(0.5)) were prepared. Their crystal structures were investigated with synchrotron X-ray powder diffraction, and their properties were studied by differential thermal analysis, magnetic measurements, and Mössbauer spectroscopy. The LN-phase was prepared at high pressure of 6 GPa and 1770 K; it crystallizes in space group R3c with a = 5.25054(7) Å, c = 13.96084(17) Å, and has a long-range antiferromagnetic ordering near T(N) = 270 K. The cor- and hex-phases were obtained at ambient pressure by heating the LN-phase in air up to 870 and 1220 K, respectively. The cor-phase crystallizes in space group R-3c with a = 5.25047(10) Å, c = 14.0750(2) Å, and the hex-phase in space group P6(3)/mmc with a = 3.34340(18) Å, c = 11.8734(5) Å. T(N) of the cor-phase is about 200 K, and T(N) of the hex-phase is about 140 K. During irreversible transformations of LN-(In(1-x)M(x))MO(3) with the (partial) cation ordering, the In(3+), Mn(3+), and Fe(3+) cations become completely disordered in one crystallographic site of the corundum structure, and then they are (partially) ordered again in the hex-phase. LN-(In(1-x)M(x))MO(3) exhibits a reversible transformation to a perovskite GdFeO(3)-type structure (space group Pnma; a = 5.2946(3) Å, b = 7.5339(4) Å, c = 5.0739(2) Å at 10.3 GPa) at room temperature and pressure of about 5 GPa.

  4. Sorption competition of trivalent metals on corundum (α-Al{sub 2}O{sub 3}) studied on the macro- and microscopic scale

    Energy Technology Data Exchange (ETDEWEB)

    Virtanen, S.; Merilaeinen, S.; Lehto, J. [Helsinki Univ. (Finland); Eibl, Manuel; Huittinen, Nina [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Rossberg, Andre [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures; Rabung, T. [Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany)

    2017-06-01

    In this study we investigated the potential competitive influence of Y{sup 3+} on the uptake of trivalent lanthanides and actinides on corundum (α-Al{sub 2}O{sub 3}). Both batch sorption and time-resolved laser fluorescence spectroscopic (TRLFS) data showed a decreased uptake of Eu{sup 3+} or Cm{sup 3+}, respectively, in the presence of Y{sup 3+}, pointing toward sorption competition between the trivalent ions. A change in the actinide speciation on the corundum surface could be observed in the presence of Y{sup 3+}. In extended X-ray absorption fine structure (EXAFS) investigations, the speciation change could be attributed to a systematic transition from a tetradentate Am{sup 3+} surface complex to a tridentate one, when increasing the total metal ion concentration on the mineral surface.

  5. Evidence of colour-modification induced charge and structural disorder in natural corundum: Spectroscopic studies of beryllium treated sapphires and rubies

    Science.gov (United States)

    Sastry, M. D.; Mane, Sandesh N.; Gaonkar, Mahesh P.; Bagla, H.; Panjikar, J.; Ramachandran, K. T.

    2009-07-01

    Corundum α - Al2O3 single crystals is an important gemstone known by different names depending on the colour it exhibits which in turn depends on the impurities that are present. The colour depends on the valence state of the impurity element present in corundum (Cr3+ in ruby, Fe3+ in yellow sapphire and Fe-Ti complex in blue sapphire). There have been a number of reports of diffusion controlled high temperature chemical reactions to influence the colouration in these materials. Present paper deals with the Raman and FT-IR results on Be treated rubies/sapphires and gives evidence of the disorder brought about by such treatments. This can be effectively used for diagnostic purposes for detecting the treated stones.

  6. Evidence of colour-modification induced charge and structural disorder in natural corundum: Spectroscopic studies of beryllium treated sapphires and rubies

    Energy Technology Data Exchange (ETDEWEB)

    Sastry, M D; Mane, Sandesh N; Gaonkar, Mahesh P; Panjikar, J; Ramachandran, K T [Gemmological Institute of India, 304 Sukhsagar Building, N.S.Patkar Marg, Opera House, Mumbai 400 007 (India); Bagla, H, E-mail: mdsastry@yahoo.co.in [Department of Chemistry, KC College, Church gate, Mumbai 400 020 (India)

    2009-07-15

    Corundum {alpha} - Al{sub 2}O{sub 3} single crystals is an important gemstone known by different names depending on the colour it exhibits which in turn depends on the impurities that are present. The colour depends on the valence state of the impurity element present in corundum (Cr{sup 3+} in ruby, Fe{sup 3+} in yellow sapphire and Fe-Ti complex in blue sapphire). There have been a number of reports of diffusion controlled high temperature chemical reactions to influence the colouration in these materials. Present paper deals with the Raman and FT-IR results on Be treated rubies/sapphires and gives evidence of the disorder brought about by such treatments. This can be effectively used for diagnostic purposes for detecting the treated stones.

  7. Effect of Matrix Composition on Physical Properties of Al3CON In-situ Reaction Reinforced Corundum Composite

    Institute of Scientific and Technical Information of China (English)

    YANG Dingao; YUAN Shouqian; JIANG Mingxue; ZHANG Changxi; ZHENG Jianying; LIANG De'an; ZHANG Qiye

    2008-01-01

    60% white corundum used for aggregate.5% aluminium powder for fixed additions and 35% various additives for matrix were prepared for specimens 1#,2#,3#.They were mixed uniformly with the suitable resin as a binder and pressed under pressure of 315 ton forging press,then dried at 200 ℃ for 24 h.Effects of various additives on 1500 ℃×2 h creep properties of Al3CON reinforced corundum composite were researched,The experimenal results show that creep coefficients of specimens 1#,2#,3# at 1500 ℃×2 h are 1.4×10-4,-9.4×10 4,-22.6×10-4 respectively.Crushing strength of the slide plate added with suitable additive A after fired at 1500 ℃×3 h reaches to 225 MPa,the creep rate is positive all the time from 0% to 0.014% at 1500 ℃ for 2 h.The microstructure result analysis shows that reinforced phases of Al3CON fiber composite have been formed after fired with Al powder in coke at high temperatures for specimen 1#,and the strength of the composite is increased.The hot modulus of rupture is up to 59 MPa at 1400 ℃ and the RUL is obviously higher than that at 1700 ℃.Its service life is two times as that of Al2O3-C slide plate when used in the process of pouring steel.The mechanism of creep rate resistance of the composites can be discovered by means of SEM and EDAX analysis.It is concluded that the active Al3CON and Al2O3 multiphases that were formed by N2 in gas,C,Al and Al2O3 inside the matrix of the composites during in-situ reaction,which gives the composites outstanding creep rate resistance for the dense zone resulting from Al3CON oxidation that inhibits contraction at the high temperature.Besides,the matrix will turn into the multiphase with high refractoriness,N content and its Al3CON reinforced fiber will further increase accordingly.In addition,Al3CON formed by Al2O3 and C,Al in the matrix with N2 in gas will inhibit the creep rate and also greatly improve the creep rate resistance of the composites.

  8. High-pressure synthesis and local structure of corundum-type In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.7).

    Science.gov (United States)

    Hoel, Cathleen A; Amores, José Manuel Gallardo; Morán, Emilio; Alario-Franco, Miguel Angel; Gaillard, Jean-François; Poeppelmeier, Kenneth R

    2010-11-24

    The corundum-type In(2-2x)Zn(x)Sn(x)O(3) solid solution (cor-ZITO, x ≤ 0.7) was synthesized at 1000 °C under a high pressure of 70 kbar. cor-ZITO is a high-pressure polymorph of the transparent conducting oxide bixbyite-In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.4). Analysis of the extended X-ray absorption fine structure suggests that significant face-sharing of Zn and Sn octahedra occurs, as expected for the corundum structure type. In contrast to the ideal corundum structure, however, Zn and Sn are displaced and form oxygen bonds with lengths that are similar to those observed in high-pressure ZnSnO(3). Powder X-ray diffraction patterns of cor-ZITO showed the expected unit cell contraction with increased cosubstitution, but no evidence for ilmenite-type ordering of the substituted Zn and Sn. A qualitative second harmonic generation measurement, for the solid solution x = 0.6 and using 1064 nm radiation, showed that Zn and Sn adopt a polar LiNbO(3)-type arrangement.

  9. Quantum chemical study of inner-sphere complexes of trivalent lanthanide and actinide ions on the corundum (110) surface

    Energy Technology Data Exchange (ETDEWEB)

    Polly, R.; Schimmelpfennig, B.; Rabung, T.; Kupcik, T.; Klenze, R.; Geckeis, H. [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Nukleare Entsorgung (INE); Floersheimer, M. [Hochschule RheinMain, Ruesselsheim (Germany). Fachbereich Ingenieurwissenschaften

    2013-11-01

    Sorption plays a major role in the safety assessment of nuclear waste disposal. In the present theoretical study we focused on understanding the interaction of trivalent lanthanides and actinides (La{sup 3+}, Eu{sup 3+} and Cm{sup 3+}) with the corundum (110) surface. Optimization of the structures were carried out using density functional theory with different basis sets. Additionally, Moeller-Plesset perturbation theory of second order was used for single point energy calculations. We studied the structure of different inner-sphere complexes depending on the surface deprotonation and the number of water molecules in the first coordination shell. The most likely structure of the inner-sphere complex (tri- or tetradentate) was predicted. For the calculations we used a cluster model for the surface. By deprotonating the cluster a chemical environment at elevated pH values was mimicked. Our calculations predict the highest stability for a tetradentate inner-sphere surface complexes with five water molecules remaining in the first coordination sphere of the metal ions. The formation of the inner-sphere complexes is favored when a coordination takes place with at most one deprotonated surface aluminol group located beneath the inner-sphere complex. The mutual interaction between sorbing metal ions at the surface is studied as well. The minimal possible distance between two inner-sphere sorbed metal ions at the surface was determined to be 530 pm. (orig.)

  10. Influences of composition of starting powders and sintering temperature on the pore size distribution of porous corundum-mullite ceramics

    Directory of Open Access Journals (Sweden)

    Shujing Li

    2005-01-01

    Full Text Available Porous corundum-mullite ceramics were prepared by an in-situ decomposition pore-forming technique. Starting powders were mixtures of milled Al(OH3 and microsilica and were formed into oblong samples with a length of 100mm and a square cross-section with edge size of 20mm. The samples were heated at 1300°C, 1400°C, 1500°C or 1600°C for 3h in air atmosphere, respectively. Apparent porosity was detected by Archimedes’ Principle with water as a medium. Pore size distribution and the volume percentage of micropores were measured by mercury intrusion porosimetry. The results show that the pore morphology parameters in the samples depend on four factors: particle size distribution of starting powders, decomposition of Al(OH3, the expansion caused by mullite and sintering. The optimum mode which has a higher apparent porosity up to 42.3%, well-distributed pores and more microsize pores up to 16.3% is sample No.3 and the most apposite sintering temperature of this sample is 1500°C.

  11. Mullite-corundum-spinel-cordierite-plagioclase xenoliths in the Skaergaard Marginal Border Group: multi-stage interaction between metasediments and basaltic magma

    Science.gov (United States)

    Markl, Gregor

    2005-04-01

    Metapelitic country rocks were contact- and pyro-metamorphosed by the Tertiary Skaergaard Intrusion, East Greenland. In an initial stage of heating, while they were probably still in place within the host rock contact aureole, they overstepped a range of equilibrium and disequilibrium melting reactions and produced both a granitic melt and very refractory spinel+cordierite+plagioclase±corundum residuals. Parts of these refractory rocks were then subjected to another melting event after being entrained as xenoliths into the Skaergaard Marginal Border Group, where they experienced a temperature of about 1,000°C at a pressure of about 650 bars and at an oxygen fugacity about 0.2-0.5 log units below the FMQ buffer. Here, they underwent bulk melting, but did not mix with the Skaergaard magma, presumably because of the high viscosity contrast. The Al-rich melts crystallized to an assemblage of corundum+mullite+sillimanite+ plagioclase+spinel+rutile±tridymite±cordierite and they reacted with the surrounding basalt producing a strongly cryptically zoned rim of plagioclase (An55 close to the basalt to An90 close to the Al-rich melt). The assemblage in the inner parts of the xenoliths provides textural evidence for disequilibrium growth due to slow diffusivities in the highly viscous, probably water-free Al-rich melt. Later interaction of lower temperature ferrobasaltic to granophyric melts with the xenoliths along their margins and along cracks led to consumption of corundum and mullite and to the stable assemblage of spinel+cordierite+plagioclase+quartz+K-feldspar +magnetite+ilmenite at about 800°C.

  12. Towards the differentiation of non-treated and treated corundum minerals by ion-beam-induced luminescence and other complementary techniques.

    Science.gov (United States)

    Calvo del Castillo, H; Deprez, N; Dupuis, T; Mathis, F; Deneckere, A; Vandenabeele, P; Calderón, T; Strivay, D

    2009-06-01

    Differentiation of treated and non-treated gemstones is a chief concern for major jewellery import companies. Low-quality corundum specimens coming from Asia appear to be often treated with heat, BeO or flux in order to enhance their properties as precious minerals. A set of corundum samples, rubies and sapphires from different origins, both treated and non-treated has been analysed at the Centre Européen d'Archéométrie, with ion-beam-induced luminescence (IBIL) and other complementary techniques such as Raman, proton-induced X-ray emission (PIXE), and proton-induced gamma-ray emission (PIGE). IBIL, also known as ionoluminescence, has been used before to detect impurities or defects inside synthetic materials and natural minerals; its use for the discrimination of gemstone simulants or synthetic analogues has been elsewhere discussed (Cavenago-Bignami Moneta, Gemología, Tomo I Piedras preciosas, perlas, corales, marfil. Ediciones Omega, Barcelona, 1991). PIXE has been frequently applied in the archaeometric field for material characterisation and provenance studies of minerals (Hughes, Ruby & sapphire. RWH Publishing, Fallbrook, 1997; Calvo del Castillo et al., Anal Bioanal Chem 387:869-878, 2007; Calligaro et al., NIM-B 189:320-327, 2002) and PIGE complements the elemental analysis by detecting light elements in these materials such as-and lighter than-sodium that cannot be identified with the PIXE technique (Sanchez et al., NIM-B 130:682-686, 1997; Emmett et al., Gems Gemology 39:84-135, 2003). The micro-Raman technique has also been used complementarily to ion beam analysis techniques for mineral characterisation (Novak et al., Appl Surf Sci 231-232:917-920, 2004). The aim of this study is to provide new means for systematic analysis of corundum gemstone-quality mineral, alternative to the traditional gemmologic methods; for this purpose, a Spanish jewellery import company supplied us with a number of natural corundum samples coming from different places

  13. Theoretical evaluation of the electron paramagnetic resonance spin Hamiltonian parameters for the impurity displacements for Fe3+ and Ru3+ in corundum

    Indian Academy of Sciences (India)

    Q Fu; S Y Wu; J Z Lin; J S Yao

    2007-03-01

    The impurity displacements for Fe3+ and Ru3+ in corundum (Al2O3) are theoretically studied using the perturbation formulas of the spin Hamiltonian parameters (zero-field splitting and anisotropic factors) for a 3d5 (with high spin = 5/2) and a 4d5 (with low spin = 1/2) ion in trigonal symmetry, respectively. According to the investigations, the nd5 ( = 3 and 4) impurity ions may not locate at the ideal Al3+ site but undergo axial displacements by about 0.132 Å and 0.170 Å for Fe3+ and Ru3+, respectively, away from the center of the ligand octahedron along the C3 axis. The calculated spin Hamiltonian parameters based on the above axial displacements show good agreement with the observed values. The validity of the results is discussed.

  14. Microstructure and thermal stability of corundum-type (Al{sub 0.5}Cr{sub 0.5}){sub 2}O{sub 3} solid solution coatings grown by cathodic arc evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Edlmayr, V.; Pohler, M. [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben (Austria); Letofsky-Papst, I. [Institute for Electron Microscopy, University of Technology Graz, Steyrergasse 17, A-8010 Graz (Austria); Mitterer, C., E-mail: christian.mitterer@unileoben.ac.at [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben (Austria)

    2013-05-01

    Corundum-type (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} coatings were grown by reactive cathodic arc evaporation in an oxygen atmosphere using AlCr targets with an Al/Cr atomic ratio of 1. Since the (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} solid solution shows a miscibility gap below 1300 °C, where spinodal decomposition is predicted, the microstructural changes upon annealing were investigated by a combination of transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. The as-deposited coating consists primarily of the corundum-type (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} solid solution, with smaller fractions of cubic (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3}. An additional Al-rich amorphous phase and a Cr-rich crystalline phase stem from the droplets incorporated. The corundum-type (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} solid solution is still present after vacuum annealing at 1050 °C for 2 h, whereas the cubic (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} phase has transformed to corundum-type (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3}. Cr and Cr{sub 2}O{sub 3} have been detected in the annealed coating, the latter most probably originating from the partial oxidation of Cr-rich droplets. Upon crystallization of the amorphous phase fractions present, γ-Al{sub 2}O{sub 3} is formed, which then transforms into α-Al{sub 2}O{sub 3}. No evidence for decomposition of the corundum-type (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} solid solution could be found within the temperature range up to 1400 °C. - Highlights: ► (Al{sub 0.5}Cr{sub 0.5}){sub 2}O{sub 3} hard coatings grown by reactive cathodic evaporation ► Corundum and minor fraction of cubic (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} in the as-deposited state ► No evidence for spinodal decomposition of corundum-type (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} up to 1400 °C ► Cubic (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} transforms into corundum-type (Al{sub x}Cr{sub 1

  15. The specific sorption of Np(V) on the corundum (α-Al2O3) surface in the presence of trivalent lanthanides Eu(III) and Gd(III): A batch sorption and XAS study.

    Science.gov (United States)

    Virtanen, S; Bok, F; Ikeda-Ohno, A; Rossberg, A; Lützenkirchen, J; Rabung, T; Lehto, J; Huittinen, N

    2016-12-01

    The sorption of pentavalent neptunium, Np(V), on corundum (α-Al2O3) was investigated in the absence and presence of trivalent europium or gadolinium as a competing element under CO2-free conditions. The objective of this study was to investigate how a trivalent metal ion with a higher charge than that of the neptunyl(V) ion would affect the sorption of Np(V) when allowed to adsorb on the mineral surface before the addition of Np(V). Batch sorption experiments conducted as a function of pH (pH-edges) and as a function of Np(V) concentration (isotherms) in the absence and presence of 1×10(-5)M Eu(III) showed no sign of Eu being able to block Np sorption sites. Surface complexation modelling using the diffuse double layer model was applied to the batch data to obtain surface complexation constants for the formed Np(V) complexes on corundum. To account for potential changes occurring in the coordination environment of the neptunium ion in the presence of a trivalent lanthanide, X-ray absorption spectroscopy (XAS) measurements were carried out on the samples containing only Np(V) and Np(V)+Gd(III). The results reveal the presence of a bidentate Np(V) edge-sharing complex on the corundum surface in the absence of Gd(III), while the coordination environment of Np(V) on the corundum surface could be changed when Gd(III) is added to the sample before the sorption of Np(V). Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Research on Surface Treatment Process of Corundum Filler for Epoxy Resin Casting Material%环氧浇注用氧化铝填料表面处理工艺研究

    Institute of Scientific and Technical Information of China (English)

    2016-01-01

    The effects of surface treatment processes such as acid pickling, alkali neutralization, and high-temperature calcination on the fused corundum produced in electric arc furnace for abrasive industry were compared, the effect of different surface treatment methods on the physical and chemical properties such as conductivity and pH value of corundum solution, and the effect of different corundums on the rheological properties and mechanical properties of epoxy casting materials were analyzed. The results show that the corundum neutralized by alkali or treated by calcination after acid pickling could adjust the usable time of epoxy casting material and improve the mechanical properties of the cured epoxy resin.%通过比较酸洗、碱处理中和、高温煅烧处理等表面处理工艺对磨料工业电弧炉法熔炼制备电熔刚玉型氧化铝填料的影响,分析了不同表面处理方法对氧化铝填料粉体水洗电导率、pH值等性能的影响及对其环氧浇注料流变性能、固化物力学性能的影响.结果表明:酸洗后通过碱处理或煅烧处理均能有效调节环氧浇注的可使用时间及改善环氧浇注固化物的力学性能.

  17. High-Pressure Synthesis and Local Structure of Corundum-Type In[subscript 2−2x]Zn[subscript x]Sn[subscript x]O[subscript 3] (x ≤ 0.7)

    Energy Technology Data Exchange (ETDEWEB)

    Hoel, Cathleen A.; Amores, Jos Manuel Gallardo; Morn, Emilio; Alario-Franco, Miguel Angel; Gaillard, Jean-Franois; Poeppelmeier, Kenneth R. (UCDM); (NWU)

    2010-12-06

    The corundum-type In{sub 2-2x}Zn{sub x}Sn{sub x}O{sub 3} solid solution (cor-ZITO, x {le} 0.7) was synthesized at 1000 C under a high pressure of 70 kbar. cor-ZITO is a high-pressure polymorph of the transparent conducting oxide bixbyite-In{sub 2-2x}Zn{sub x}Sn{sub x}O{sub 3} (x {le} 0.4). Analysis of the extended X-ray absorption fine structure suggests that significant face-sharing of Zn and Sn octahedra occurs, as expected for the corundum structure type. In contrast to the ideal corundum structure, however, Zn and Sn are displaced and form oxygen bonds with lengths that are similar to those observed in high-pressure ZnSnO{sub 3}. Powder X-ray diffraction patterns of cor-ZITO showed the expected unit cell contraction with increased cosubstitution, but no evidence for ilmenite-type ordering of the substituted Zn and Sn. A qualitative second harmonic generation measurement, for the solid solution x = 0.6 and using 1064 nm radiation, showed that Zn and Sn adopt a polar LiNbO{sub 3}-type arrangement.

  18. High-Pressure Synthesis and Local Structure of Corundum-Type In[subscript 2;#8722;2x]Zn[subscript x]Sn[subscript x]O[subscript 3] (x ;#8804; 0.7)

    Energy Technology Data Exchange (ETDEWEB)

    Hoel, Cathleen A.; Amores, Jose Manuel Gallardo; Moran, Emilio; Alario-Franco, Miguel Angel; Gaillard, Jean-Francois; Poeppelmeier, Kenneth R. (UCDM); (NWU)

    2011-08-09

    The corundum-type In{sub 2-2x}Zn{sub x}Sn{sub x}O{sub 3} solid solution (cor-ZITO, x {<=} 0.7) was synthesized at 1000 C under a high pressure of 70 kbar. cor-ZITO is a high-pressure polymorph of the transparent conducting oxide bixbyite-In{sub 2-2x}Zn{sub x}Sn{sub x}O{sub 3} (x {<=} 0.4). Analysis of the extended X-ray absorption fine structure suggests that significant face-sharing of Zn and Sn octahedra occurs, as expected for the corundum structure type. In contrast to the ideal corundum structure, however, Zn and Sn are displaced and form oxygen bonds with lengths that are similar to those observed in high-pressure ZnSnO{sub 3}. Powder X-ray diffraction patterns of cor-ZITO showed the expected unit cell contraction with increased cosubstitution, but no evidence for ilmenite-type ordering of the substituted Zn and Sn. A qualitative second harmonic generation measurement, for the solid solution x = 0.6 and using 1064 nm radiation, showed that Zn and Sn adopt a polar LiNbO{sub 3}-type arrangement.

  19. Size dependence of structural, magnetic, and electrical properties in corundum-type Ti2O3 nanoparticles showing insulator–metal transition

    Directory of Open Access Journals (Sweden)

    Yoshihiro Tsujimoto

    2015-09-01

    Full Text Available Corundum-type Ti2O3 has been investigated over the last half century because it shows unusual insulator–metal (I-M transition over a broad temperature range (420–550 K. In this work, we successfully synthesized Ti2O3 nanoparticles (20, 70, 300 nm in size by the low-temperature reduction between precursors of rutile-type TiO2 and the reductant CaH2, in a non-topotactic manner. The reaction time required for obtaining the reduced phase increases with increasing the particle size. Synchrotron X-ray powder diffraction and electron microscopy studies reveal that the symmetry of all the present samples remains the same as that of bulk samples. However, the particle-size reduction results in three important features compared with bulk samples as follows, (i color shift from dark brown to bluish black, (ii anisotropic volume contraction involving the shrinkage of Ti–Ti bonds in the ab plane and along the c axis, (iii reduction of the I-M transition temperature from 420 K to 350 K. These suggest that the a1g band broadening caused by the surface strain effects, which favors narrowing of the band gap, may play a critical role in the suppression of IM transition.

  20. Liquid immiscibility recorded in melt inclusions within corundum from alkaline basalt, Changle area,Shandong province, Eastern China%中国山东昌乐地区碱性玄武岩刚玉中记录的岩浆不混溶作用

    Institute of Scientific and Technical Information of China (English)

    刘吉强; 倪培; 沈昆; 丁俊英

    2007-01-01

    Abundant melt- and fluid inclusions occur in corundum megacrysts of alkaline basalt from the Changle area, Shandong province, eastern China. One type of melt inclusions, i.e. multiphase melt inclusions ( glass + bubbles + daughter minerals) were identified ,which occur along growth zones of host corundum megacrysts. Microthermometry and laser Raman microprobe analysis were performed on the melt inclusions. The bubbles within the melt inclusions are confirmed to be CO2-rich phase and the daughter minerals are probably silicates, such as augite and okenite. The results of high temperature homogenization experiment strongly suggest that two immiscible melts, i.e. a H2O- and CO2-rich melt and an anhydrous and CO2-poor melt were trapped by melt inclusions in corundum megacryst.

  1. 刚玉砖抗高磷鲕状赤铁矿还原物料的侵蚀与渗透研究%Corrosion and penetration resistance of corundum bricks to high phosphorus oolitic hematite reducing mate-rials

    Institute of Scientific and Technical Information of China (English)

    范敦城; 张玉燕; 倪文

    2015-01-01

    The paper aims at investigating whether corundum bricks can be used for the bottom of the direct reduction furnace of high phosphorus oolitic hematite.The reducing materials including high phosphorus oolitic hematite,bitumite,Ca(OH)2 and Na2 CO3 at a mass ratio of 1 0.15 0.15 0.03 were mixed and pressed into carbon containing cylindrical specimens with the size of 15 mm ×20 mm.The specimens were placed on the corundum bricks and reduced in a high temperature tube furnace at 1 200 ℃ for 40,60, 80,140 and 220 min,respectively.The corrosion resistance and penetration resistance of corundum bricks to high phosphorus oolitic hematite reducing materials were analyzed with XRD,SEM and EDS.I t shows that the reducing slag formed in the reduction process corrodes the surface of corundum bricks to form a product layer of anorthite and hercynite,retarding the further corrosion of the reducing slag;the reducing slag which has penetrated into the interior of the brick goes through the gaps between the particles and generates anorthite and hercynite,filling the gaps and hindering the reducing slag penetration.%为考察刚玉砖是否适用于高磷鲕状赤铁矿直接还原的炉底,将还原物料高磷鲕状赤铁矿、烟煤、Ca(OH)2和 Na2 CO3按质量比为10.150.150.03混匀后压制成15 mm ×20 mm 的含碳圆柱试样,置于刚玉砖上,一起放入高温管式炉内分别于1200℃保温40、60、80、140和220 min 进行还原试验,采用 XRD、SEM及EDS 研究了刚玉砖抗高磷鲕状赤铁矿还原物料的侵蚀与渗透行为。结果表明:还原物料在还原过程中形成的还原渣侵蚀刚玉砖表面而形成钙长石和铁尖晶石产物层,抑制了还原渣的侵蚀;而已渗透至砖内的还原渣,在向砖内部扩散迁移过程中生成钙长石和铁尖晶石,起到填充与堵塞孔缝的作用,阻碍了还原渣的渗透。

  2. Kinetic control in the synthesis of metastable polymorphs: Bixbyite-to-Rh{sub 2}O{sub 3}(II)-to-corundum transition in In{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Bekheet, Maged F., E-mail: maged.bekheet@ceramics.tu-berlin.de [Fachbereich Material -und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Fachgebiet Keramische Werkstoffe, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany); Schwarz, Marcus R. [Freiberg High Pressure Research Centre, Institut für Anorganische Chemie, Technische Universität-Bergakademie Freiberg, Leipziger Straße 29, 09599 Freiberg (Germany); Kroll, Peter [Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, TX 760019-0065 (United States); Gurlo, Aleksander [Fachbereich Material -und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Fachgebiet Keramische Werkstoffe, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany)

    2015-09-15

    An example for kinetic control of a solid-state phase transformation, in which the system evolves via the path with the lowest activation barrier rather than ending in the thermodynamically most favorable state, has been demonstrated. As a case study, the phase transitions of indium sesquioxide (In{sub 2}O{sub 3}) have been guided by theoretical calculations and followed in situ under high-pressure high-temperature conditions in multi-anvil assemblies. The corundum-type rh-In{sub 2}O{sub 3} has been synthesized from stable bixbyite-type c-In{sub 2}O{sub 3} in two steps: first generating orthorhombic Rh{sub 2}O{sub 3}-II-type o′-In{sub 2}O{sub 3} which is thermodynamically stable at 8.5 GPa/850 °C and, thereafter, exploiting the preferred kinetics in the subsequent transformation to the rh-In{sub 2}O{sub 3} during decompression. This synthesis strategy of rh-In{sub 2}O{sub 3} was confirmed ex situ in a toroid-type high-pressure apparatus at 8 GPa and 1100 °C. The pressure–temperature phase diagrams have been constructed and the stability fields of In{sub 2}O{sub 3} polymorphs and the crystallographic relationship between them have been discussed. - Graphical abstract: In situ energy-dispersive XRD patterns in multi-anvil assemblies show the sequence of phase transition c-In{sub 2}O{sub 3}→o′-In{sub 2}O{sub 3}→rh-In{sub 2}O{sub 3} under particular pressure and temperature conditions. The tick marks refer to the calculated Bragg positions of bixbyite-type (c-In{sub 2}O{sub 3}), Rh{sub 2}O{sub 3}-II-type (o–-In2O{sub 3}) and corundum-type (rh-In{sub 2}O{sub 3}). - Highlights: • The solid-state synthesis methods can be employed for obtaining metastable phases. • The phase transition of In{sub 2}O{sub 3} was guided by DFT calculations. • The phase transition of In{sub 2}O{sub 3} was followed in situ under HP–HT conditions. • Orthorhombic o′-In{sub 2}O{sub 3} polymorph was synthesized from c-In{sub 2}O{sub 3} at 8.5 GPa/850 °C. • Metastable rh

  3. Effect of Magnesium Aluminate Spinel on Microstructure and Performance of Aluminum-corundum Composites%镁铝尖晶石对铝-刚玉复合材料结构和性能的影响

    Institute of Scientific and Technical Information of China (English)

    李勇; 洪炀; 岳丹丹; 马佳佳; 仝尚好; 蒋朋; 薛文东

    2016-01-01

    Al–MgAl2O4–Al2O3 composite was sintered at 1 300℃in N2 made from tabular alumina, fused white corundum,α-Al2O3 fine powder, metal Al powder and MgAl2O4 fine powder (addition with 3%, 6%, 9%, 12%, 15%respectively) and phenolic resin as binder. The results show that the cold crushing strength and the high temperature bending strength of the Al–MgAl2O4–Al2O3 composite was increased with more MgAl2O4 powder added. Besides corundum and some amount of spinel solid solution as the major crystalline phases, new phases such as Al4O4C, AlN–Al2OC solid solution and minor AlxOyNz have been synthesized, with some Al as residue. Although the content of Al added into the Al–MgAl2O4–Al2O3 composite reach 12%, neither independent AlN nor Al4C3 has been detected after sintering. It is the AlN–Al2OC solid solution that exists in the composite. Therefore, the complete disruption of the samples and the performance degradation won’t occur because of the hydration of AlN and Al4C3. The AlxOyNz phase is detected in the samples and the solid solution of generated AlxOyNz in MgAl2O4 can’t realize on account of the low sintered temperature. MgAlON solid solution hasn’t been detected.%以板状刚玉、电熔白刚玉、α-Al2O3微粉、金属Al粉、MgAl2O4微粉[含量分别为3%(质量分数)、6%、9%、12%和15%]为原料,酚醛树脂为结合剂制备Al–MgAl2O4–Al2O3样品。样品经200℃烘干后于1300℃氮气气氛烧成。结果表明:样品常温耐压强度呈增加趋势、样品高温抗折强度增加。样品中除主晶相刚玉和镁铝尖晶石固溶体外,形成新相 Al4O4C、AlN–Al2OC固溶体和少量AlxOyNz等,还有部分金属铝粉剩余。样品中金属铝的含量为12%,但经1300℃氮气气氛烧成后,样品中既无独立AlN,也无独立的Al4C3存在,而是以AlN–Al2OC固溶体形式存在,因此不会出现因AlN或Al4C3水化导致样品性能降低或样品完全散裂的现象。样品中有AlxOyNz

  4. Effect of Aluminium Powder on Microstructure and Property of Corundum-Silicon Nitride Composites%铝粉对刚玉-氮化硅复合材料微观结构和性能的影响

    Institute of Scientific and Technical Information of China (English)

    魏军从; 涂军波

    2011-01-01

    借鉴"过渡塑性相工艺"思想,在刚玉-氮化砖复合材料中引入12.5%(质量分数)的铝粉,研究了铝粉对刚玉-氮化硅复合材料成型性能以及1 600℃空气中烧成后样品的体积密度、显气孔率和耐压强度的影响:利用X射线衍射仪和扫描电镜对材料的物相和微观结构进行了分析.结果表明:在刚玉-氮化硅复合材料中引入铝粉,有利于成型过程中孔隙的填充,坯体显气孔率由21.57%下降为20.42%,坯体致密度提高.样品在空气气氛中烧成后,未加铝粉样品表面形成的致密氧化膜厚度约为3mm,而加入铝粉样品表面氧化膜的厚度约为0.2mm;铝粉先于氮化硅粉发生原位氧化,降低了样品内部的氧分压,残留的铝粉发生氧化或氮化反应生成活性中间产物,促进了样品的烧结.%Corundum-silicon nitride samples were sintered at 1 600 ℃ in air by introduction of 12.5% (in mass) aluminium powder inspired by a transient plastic phase process. Effects of aluminium powder on the forming property as well as bulk density, apparent porosity, and compressive strength of the samples were investigated. The phase composition and microstructure of the reaction products were analysed by X-ray diffractometer and scanning electron microscope. The results indicate that the plasticity of aluminium favors the filling of the interstices during the forming process and improves the densification of the corundum-silicon nitride materials. The apparent porosity decreases from 21.75% to 20.42%. The samples without introduction of any aluminum powder have a compact superficial oxidized film of 3 mm, and the samples with the introduction of aluminum powder have the film of 0.2 mm after fired in air atmosphere. Aluminium precedes silicon nitride to be oxidized in situ, reducing the oxygen partial pressure inside the sample.The residual aluminium is oxidized or nitrided to form the active intermediate products, contributing to the sinter of the

  5. 铝铬渣对用后镁铬砖制备镁铬浇注料性能的影响%Influence of Corundum-chrome Slag on the Property of Magnesite-chrome Castable Prepared with Used Magnesite-chrome Brick

    Institute of Scientific and Technical Information of China (English)

    罗旭东; 张国栋; 曲殿利; 徐延浩; 陈莉莉; 闵振兴

    2012-01-01

    为实现用后镁铬砖的综合利用,本文以用后镁铬砖回收料为主要原料制备镁铬质耐火浇注料,研究了铁合金厂铝铬渣对用后镁铬砖制备镁铬质耐火浇注料体积密度、显气孔率、常温耐压强度、热震稳定性及抗渣性的影响.结果表明:铝铬渣对用后镁铬砖制备镁铬浇注料具有一定的促烧结作用,随着铝铬渣加入量增加,烧后试样常温耐压强度增大.随着浇注料结构中原位尖晶石量增加,试样显气孔率增大,体积密度减小.当铝铬渣加入量为10%时,试样的热震稳定性最好,热震前后试样的常温耐压强度保持率为93.8%,试样具有较好抗渣侵蚀性能,侵蚀层结构稳定均匀.%Based on the comprehensive utilization of used magnesite-chrome brick, magensite-chrome castable were prepared with magnesite-chrome brick. Influence of corundum-chrome slag on the property of magnesite-chrome castable was researched. Bulk density, apparent porosity, cold crushing strength, thermal shock resistance and slag resistance of the magensite-chrome castable were estimated. The experimental result show that sintering performacne of magnesite-chrome castable was promoted by adding corundum-chrome slag. The cold crushing strength of castable specimens will increase with corundum-chrome slag addition. Apparent porosity of castable specimens will increase, and bulk density will decrease with spinel synthesized by situ reaction in the magnesite-chrome castable. The thermal shock resistance of magnesite-chrome castable was the best of all specimens when the corundum-chrome slag addition was 10% , the maintaining rate of cold crushing strength before and after thermal shock was 93. 8%. The slag resistance of magnesite-chrome castalble specimen was attributed to the stable and uniform structure of erosion layer.

  6. 不同碱酸比煤灰在刚玉质耐火材料上的结渣特性%Slagging Characteristics of Coal Ash with Different Alkali/Acid Ratios on Corundum-based Refractory Liner

    Institute of Scientific and Technical Information of China (English)

    陈冬林; 杜洋; 邹婵; 蔡洋

    2013-01-01

    Slagging characteristics of two kinds of coal ash with different alkali/acid ratios were studied on corundum-based refractory liner in Muffle furnace in air at 1 350 ℃ for 40 h, after which the slag morphology and composition were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). Results show that the coal ash with higher alkali metal content has lower viscosity, stronger liquidity and therefore may severely erode the refractory liner; elements in melting ash infiltrate into the liner, distributing in a reducing atomic percentage along the liner depth; the little Cr2O3 contained in refractory liner may penetrate into coal ash and subsequently form there (Al0.9Cr0.1 )2O3 with high melting point and high viscosity, which helps to prevent the liner from erosion by coal ash.%将2种不同碱酸比的煤灰均匀敷设在刚玉质耐火材料上,并将其置于高温马弗炉中在1 350℃空气气氛下煅烧40 h,煅烧完成后采用扫描电子显微镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)等方法对刚玉质耐火材料板上2种结渣倾向对比明显的灰渣形貌和成分进行分析,得到了灰渣的高温烧结特性.结果表明:碱金属含量较高的煤灰黏度较小,流动性较强,对刚玉质耐火材料板的侵蚀较严重;熔融灰渣向刚玉质耐火材料内部渗透侵蚀,各元素原子百分数沿材料板深度方向大致呈下降趋势;在刚玉质耐火材料中加入的少量Cr2O3在高温下会渗透到煤灰中,并生成高熔点、高黏度的铝氧化铬,从而减轻了煤灰对刚玉质耐火材料的侵蚀.

  7. Effect of spinel properties on slag resistance of unfired corundum-spinel brick%尖晶石性质对刚玉-尖晶石不烧砖抗渣性的影响

    Institute of Scientific and Technical Information of China (English)

    方选明; 李楠; 鄢文

    2011-01-01

    Slag resistances of three kinds of unfired corundum-spinel bricks containing different spinels were researched using static crucible method. The effects of grain size and lattice distortion of spinel on slag resistance were investigated by XRD,SEM and EDAX. The results show that: ( 1 )the grain size of spinel remarkably affects the corrosion resistance, and the corrosion resistance increases with grain size increasing; (2)the spinel with higher lattice distortion can absorb more Fe and Mn ions on the interface of slag and refractories; (3)the lattice distortion affects the penetration resistance,the spinel with high lattice distortion can absorb more cations,change the slag composition, make slag with rich silicon and high viscosity,and inhibit the further penetration of slag.%采用静态坩埚法研究了添加3种不同性质尖晶石的刚玉-尖晶石不烧砖的抗渣性能,并通过XRD、SEM和EDAX分析了尖晶石的晶粒尺寸、晶格畸变对试样抗渣性的影响.结果表明:(1.尖晶石的晶粒尺寸影响试样的抗侵蚀能力,晶粒尺寸越大,试样抗侵蚀能力越强;(2.晶格畸变较大时,尖晶石在渣/耐火材料界面处吸收熔渣中Fe、Mn离子能力更强;(3)尖晶石的晶格畸变影响试样的抗渗透性能,当晶格畸变较大时,可吸收渣中更多的阳离子,改变渗透渣的成分,使渣富硅化,黏度增大,阻碍了熔渣进一步渗透.

  8. 昌乐玄武岩内刚玉巨晶(蓝宝石)中发现富碳酸盐和硫酸盐熔融包裹体及其意义%Carbonates and sulfates-bearing melt inclusions in corundum megacrysts from Changle basalts of Shandong Province and their implications

    Institute of Scientific and Technical Information of China (English)

    宋玉财; 胡文瑄

    2009-01-01

    Corundum megacrysts (sapphires) hosted by Changle Cenozoic basalts of Shandong Province contain various melt inclusions, whose compositions are of significance in understanding the mantle metasomatism beneath the North China Craton and the parent magma of the corundum megacrysts. Based on petrographic observation and detailed laser Raman analysis, the authors identified two types of melt inclusions: one is primary melt inclusion rich in carbonates and sulfates and the other is secondary melt inclusion containing sulfates and chloride, with CO2 and H2O existent in both of them. This is the first time that sulfate and carbonate are recognized in fluid/melt inclusions from basalt hosted corudum megacrysts. The compositions, combined with existing isotopic compositons of noble gases and microthermometry of the inclusions, imply that they are a kind of carbonatite that propably originated from metasomatized mantle. The authors thus hold that the mantle beneath the North China Craton might have experienced metasomatism of carbonates and sulfates bearing melts (carbonititic magma) besides silicic melts. The carbonates and sulfates identifed in primary inclusions suggest that they must have played an important role in corundum crystallization. The corundums probably resulted from the interaction between mantle derived carbonatites andsilicic magmas/rocks, and were transported to the surface by subsequent basaltic lava.%山东昌乐新生代玄武岩内的刚玉巨晶(蓝宝石)中含有多种类型熔融包裹体,其成分对了解华北深部地幔交代过程中的流/熔体性质和刚玉母岩浆特点具有重要意义.详细的岩相学和激光拉曼分析鉴定出一类富碳酸盐和硫酸盐成分的原生熔融包裹体以及一类含硫酸盐和氯化物等成分的次生熔融包裹体,二者同时还含有CO2和H2O.碳酸盐和硫酸盐成分在世界范围玄武岩内刚玉巨晶中是首次发现,结合已有的包裹体稀有气体同位素和测温资

  9. 放电等离子烧结制备刚玉-铝酸钙-镁铝尖晶石复相材料%Preparation of corundum-calcium aluminate-magnesium aluminate spinel composites by spark plasma sin-tering

    Institute of Scientific and Technical Information of China (English)

    唐海; 员文杰; 商恒; 樊希安; 邓承继; 祝洪喜

    2016-01-01

    In order to reduce the synthesis temperature of the composite material and maintain its physical properties,corundum-calcium aluminate-magnesium aluminate spinel composites were prepared using 35.16 mass% underburnt dolomite and 64.84 mass% flake alumina as raw materials by spark plasma sin-tering at different temperatures (1 050,1 100,and 1 150 ℃).The effects of the firing temperature on phase composition and strength of corundum-calcium aluminate-magnesium aluminate spinel composites were investigated.The results show that with the temperature increasing the corundum content decreases gradu-ally,while the contents of calcium aluminate and magnesium aluminate spinel gradually increase,the ap-parent porosity of composites slightly increases while the splitting tensile strength improves;flake corun-dum,formed calcium aluminate and magnesium aluminate spinel bond together at high temperatures by spark plasma sintering.The composites with the apparent porosity of 23.2% fired at 1 150 ℃ achieve the splitting tensile strength of 20 MPa.%为了降低复相材料的合成温度并保证其相应的物理性能,以质量分数分别为35.16%的欠烧白云石和64.84%的片状氧化铝为原料,在1050、1100和1150℃下利用放电等离子烧结法(SPS)制备了刚玉-铝酸钙-镁铝尖晶石复相材料,并研究了烧成温度对复相材料的物相组成及强度的影响。结果表明:随着温度的升高,复相材料中刚玉相的含量逐渐降低,而铝酸钙和镁铝尖晶石的含量逐渐上升,材料的显气孔率略有增大,但是其劈裂抗拉强度逐渐增大。放电等离子烧结使复相材料中片状刚玉、生成的铝酸钙和镁铝尖晶石在高温下相互结合。当烧成温度为1150℃时,所制备的复相材料显气孔率为23.2%,劈裂抗拉强度达到20 MPa。

  10. 引入 Y2 O3对刚玉-尖晶石中间包挡渣墙高温强度和抗渣性的影响%Influence of adding Y2O3 on HMOR and slag resistance of corundum-spinel tundish slag barrier

    Institute of Scientific and Technical Information of China (English)

    郭钰龙; 梁永和; 聂建华; 尹玉成

    2015-01-01

    Corundum-spinel tundish slag wall specimens were prepared using special grade bauxite,brown corundum,fused white corundum,magnesium aluminate spinel,α-Al 2 O3 micropowder,ρ-Al 2 O3 ,calcium alu-minate cement as the main raw materials,adding dispersant and other additives like steel fibre.The effect of Y2 O3 addition on hot properties and slag resistance of the specimens was studied.The results show that with Y2 O3 addition increasing,the specimens have higher hot strength and better slag resistance.When the Y2 O3 addition is 2 mass%,the specimen has the best hot strength and slag resistance.The microstructure analysis shows that at high temperatures Y2 O3 reacts with Al 2 O3 forming high melting point phase Y3 Al 5 O12 , which activates the crystal lattice and enhances the density of the specimen effectively.Y2 O3 is active and can form liquid yttrium silicate with silica at high temperatures,bonding spinel and Al 2 O3 in the material tightly,and preventing the further slag penetration.As the addition of Y2 O3 increases,abundant CA6 protec-tion layers are observed at the reaction layer and the penetration layer,restraining the further penetration of slag.Meanwhile,the formed CA6 consumes CaO in the slag,enhancing the slag viscosity and lowering the penetration ability of the slag,and thus stopped slag penetration gradually.%以特级矾土、棕刚玉、电熔白刚玉、镁铝尖晶石、α-Al2 O3微粉、ρ-Al2 O3、铝酸钙水泥为主要原料,添加分散剂和钢纤维等外加剂,研究了加入 Y2 O3对刚玉-尖晶石质中间包挡渣墙高温性能和抗渣性能的影响。结果表明:随着 Y2 O3加入量的增加,试样的高温抗折强度增大,抗渣性能变好,当加入量为2%(w)时其高温强度和抗渣性能均最优。显微结构分析表明:Y2 O3高温下与 Al2 O3反应生成 Y3 Al5 O12高熔点相,活化了晶格,有效提高试样的致密度,Y2 O3活性较大,高温下还能与材料中 SiO2反应形

  11. Mathematical model for corundum single crystal growth by Verneuil method

    Science.gov (United States)

    Grzymkowski, Radosław; Mochnacki, Bohdan; Suchy, Józef

    1983-05-01

    A mathematical model which is an attempt to describe the complex process of monocrystallization by the Verneuil method is presented. The problem has been solved through the method of finite differences and at the same time making use of a certain modification of the mathematical description of Stefan's problem called the the alternating phase truncation method [9]. The elaborated algorithm and the examples of solutions given at the end of the present study point at the usefulness of the presented method of numerical simulation for modern designing and controlling the processes of crystal production.

  12. Effects of Light-burned MA90 Spinel Content on Microstructure and Performance of Corundum-Spinel Castables%轻烧MA90尖晶石加入量对刚玉-尖晶石浇注料显微结构和性能的影响

    Institute of Scientific and Technical Information of China (English)

    陈庆洁; 鄢文; 李楠; 林小丽; 王洛; 王月月

    2016-01-01

    通过固定尖晶石总含量(质量分数23.5%),改变轻烧和死烧MA90尖晶石质量比制备了不同轻烧尖晶石含量的刚玉-尖晶石浇注料,在1600℃下进行了钢包渣侵蚀试验,研究了轻烧尖晶石含量对该浇注料显微结构和抗渣性能的影响.结果表明:随着轻烧尖晶石质量分数从0增加到23.5%,浇注料的线收缩率增大、显气孔率和体积密度基本不变、强度降低;侵蚀后基体中出现裂纹,且轻烧尖晶石含量较高的裂纹较多;随着轻烧尖晶石含量的增加,浇注料的抗渣侵蚀性逐渐降低,抗渣渗透性逐渐增强;当轻烧尖晶石质量分数为17.6%时,其综合性能最好,显气孔率为15.7%,抗折和耐压强度分别为26.9,107.8 MPa,侵蚀指数和渗透指数分别为0.32和0.91.%The corundum-spinel castables with different light-burned spinel content were prepared by fixing total spinel content of 23.5wt% and changing the mass ratio of light-burned and dead-burned MA90 spinel,and then the ladle slag corrosion tests were conducted at 1 600 ℃.The microstructures and slag resistance of the castables were studied.The results show that with the light-burned spinel content increased from 0 to 23.5wt%,the linear shrinkage of the castables increased,the apparent porosity and volume density remained unchanged,and strengths decreased.The cracks were observed in the uncorroded matrix and more cracks were observed in the matrix with a higher content of light-burned spinel after corrosion.With the increase of light-burned spinel content,the slag corrosion resistance of the castables decreased while the slag penetration resistance increased.When the light-burned spinel content was 17.6wt%,the specimen had the optimum performance,which was with the porosity of 15.7%, flexural strength of 26.9 MPa,crushing strength of 107.8 MPa,slag corrosion index of 0.32 and penetration index of 0.91.

  13. BIOACCESSIBILITY OF ARSENIC BOUND TO CORUNDUM USING A SIMULATED GASTROINTESTINAL SYSTEM

    Science.gov (United States)

    Ingestion of soil contaminated with arsenic is an important pathway for human exposure to arsenic. The risk posed by ingestion of arsenic-contaminated soil depends on how much arsenic is dissolved in the gastrointestinal tract. Aluminum oxides are common components in the soil a...

  14. A unique corundum and refractory metal-nugget bearing micrometeorite P117

    Digital Repository Service at National Institute of Oceanography (India)

    Rudraswami, N.G.; Reshma, K.; ShyamPrasad, M.

    , Yada et al. (2004) suggested >60% of unmelted micrometeorites in all size ranges. The micrometeorites widely collected from Polar Regions and from the deep-sea sediments, have sampled diverse parent bodies that generate large quantities of dust during... compared to meteorites will provide understanding relating to diverse parent bodies that generate dust in the solar system. It is well known that carbonaceous chondrites are a major source of cosmic dust on the earth (Kurat et al. 1994; Greshake et al...

  15. Thermal formation of corundum from aluminium hydroxides prepared from various aluminium salts

    Indian Academy of Sciences (India)

    J Temuujin; Ts JADAMBAA; K J D Mackenzie; P Angerer; F Porte; F Riley

    2000-08-01

    Aluminium hydroxides have been precipitated from various aluminium salts and the differences in their thermal behaviour have been investigated. Pseudoboehmite derived from the nitrate, sulfate and chloride all form -Al2O3 at ∼ 400°C but the formation of -Al2O3 at 1200°C occurs more readily in the material derived from the sulfate. This contains a higher concentration of anionic impurities related to differences in the solubility of the original aluminium salts. The sulfate is retained in the gel to higher temperatures at which its eventual decomposition may lead to the formation of a reactive pore structure which facilitates the nucleation of -Al2O3.

  16. Effect of Phenomena Accompanying Wear in Dry Corundum Abrasive on the Properties and Microstructure of Austempered Ductile Iron with Different Chemical Composition

    Directory of Open Access Journals (Sweden)

    Myszka D.

    2015-04-01

    Full Text Available The research described in this article is a fragment in the series of published works trying to determine the applicability of new materials for parts of the mining machinery. Tests were performed on two groups of austempered ductile iron - one of which contained 1.5% Ni and 0.5% Mo, while the other contained 1.9% Ni and 0.9% Cu. Each group has been heat treated according to the three different heat treatment variants and then the material was subjected to detailed testing of mechanical properties and abrasion wear resistance, measuring also hardness and magnetic properties, and conducting microstructural examinations. The results indicated that each of the tested materials was senstive to the surface hardening effect, which resulted in high wear resistance. It has been found that high temperature of austempering, i.e. 370°C, favours high wear resistance of ductile iron containing nickel and molybdenum. Low temperature of austempering, i.e. 270°C, develops high wear resistance in ductile iron containing nickel and copper. Both these materials offer completely different mechanical properties and as such can be used for different and specific applications.

  17. Effect of additives on thermal shock resistance of corundum-mullite load bearing board%添加剂对刚玉-莫来石质承烧板抗热震性的影响

    Institute of Scientific and Technical Information of China (English)

    武杏荣; 曹枫; 田锋; 吴汉章

    2004-01-01

    以电熔莫来石为粗颗粒,α-Al2O3粉、硅线石粉和少量结合粘土等为基质,羧甲基纤维素为结合剂,分别添加钛白粉、锆英石粉及同时添加这两种粉体,经混合,液压成型,在1530℃保温2 h烧成制备了承烧板试样;研究了电熔白刚玉或莫来石中颗粒、钛白粉添加量(4%、6%、8%)、锆英石粉添加量(4%、6%、8%)及同时添加两种粉体(锆英石粉均为6%,钛白粉添加量分别为4%、6%、8%)对承烧板抗热震性能的影响.试验结果表明:以刚玉为中颗粒的试样的抗热震性能优于以莫来石为中颗粒的试样;在此基础上加入锆英石粉或钛白粉制成的试样的抗热震性会明显改善;当两者同时加入时,试样的抗热震性能改善更为显著.SEM分析显示:加入锆英石粉的试样析出锆石相,加入钛白粉的试样有钛酸铝生成,锆英石粉和钛白粉都添加的试样既存在锆石相,又生成钛酸铝晶体,这些相的存在使材料引入微裂纹和沿晶裂纹,有助于抗热震性能的提高.

  18. Development of corundum - spinel castable for outer lining of RH snorkel%RH炉浸渍管外衬刚玉-尖晶石浇注料的研制

    Institute of Scientific and Technical Information of China (English)

    贺巧玲; 李健; 李宏伟; 王玉; 田齐啸

    2000-01-01

    The castable was developed by choosing suitable ultrafine powder addition, magnesite particle size com-position and addition and optimizing matrix composition. The castable is characterized by superior slag re-sistance, spall resistance and proper little expansion.%通过选择合适的超细粉加入量、镁砂粒度组成及加入量,优化基质的组成,利用A12O3与MgO在使用过程中直接生成尖晶石,研制的刚玉-尖晶石浇注料具有优良的抗渣性、耐剥落性以及适度的微膨胀。

  19. Synthesis of LTA zeolite on corundum supports: Preliminary assessment for heavy metal removal from waste water; Sintesis de zeolita LTA sobre soportes de corindon: Evaluacion preliminar para la eliminacion de metales pesados de efluentes acuosos

    Energy Technology Data Exchange (ETDEWEB)

    Jacas, A.; Ortega, P.; Velasco, M. J.; Camblor, M. A.; Rodriguez, M. A.

    2012-11-01

    The effectiveness of materials based on LTA Zeolite as active phase, for their incorporation into systems aimed at the removal of heavy metals on waste water is evaluated in a preliminary way. This type of Zeolite with the main channel of a minimum free diameter of 0,41 nm and a low SiO{sub 2}/Al{sub 2}O{sub 3} ratio is an interesting molecular sieve, which in turn display a high ion exchange capacity. From this point of view, LTA Zeolite crystals were obtained in situ by hydrothermal synthesis and characterized by x ray diffraction (XRD) and scanning electron microscopy (SEM). We have studied the effect of hydrothermal synthesis time at 378 K. Likewise, the removal capacity of heavy metal from the active phase was evaluated in as a first step on diluted solutions of cooper salts at slightly acidic pH ({approx} 4,7). (Author) 28 refs.

  20. Determination of zirconium in zirconia corundum by means of back titration with zirconium oxychloride standard solution%锆液返滴定法测定锆刚玉中锆

    Institute of Scientific and Technical Information of China (English)

    王永双; 张俊安; 余磊

    2003-01-01

    针对[ZrO]2+易水解聚合的特性,提出了在0.18~0.36mol/L HCl介质中加入过量的EDTA络合Zr(Ⅳ),再用氯氧化锆标准溶液作返滴定剂回滴过量的EDTA,从而得出锆量的方法.该方法不用反复煮沸滴定,不需分段标定滴定度,终点敏锐稳定,干扰少,操作简便,用于锆刚玉磨料和锆刚玉耐火材料样品测定,分析时间只需4~6h,RSD(n=5)为0.058%~0.35%,样品加标回收率为99.70%~100.2%,结果满意.

  1. In-Situ Preparation and Thermal Shock Behavior of Corundum-Mullite-Magnesium Aluminate Spinel Composite Ceramic%刚玉–莫来石–镁铝尖晶石复合陶瓷的原位合成及热震行为

    Institute of Scientific and Technical Information of China (English)

    徐晓虹; 马雄华; 吴建锋; 张锋意; 张亚祥; 李坤

    2012-01-01

    以α-Al2O3、苏州土、滑石和石英为主要原料,采用无压烧结制备了刚玉–莫来石–镁铝尖晶石多相复合陶瓷,研究了烧结温度对样品的体积密度、线性收缩率和吸水率等烧结性能以及机械性能的影响。通过X射线衍射和扫描电子显微镜分析了复相陶瓷热震前后的物相组成和显微结构。结果发现:经1480℃烧结的样品吸水率为0.19%,体积密度为3.06g/cm3,抗折强度达99.59MPa,复合材料有较好的热震性能,1100℃空冷热震损失率仅6.9%,可耐受17次热冲击。该复相陶瓷可作为潜在的太阳能热发电材料。%A corundum–mullite–magnesium aluminate spinel composite ceramic as a solar thermal power generation material was fabricated by a pressureless sintering method with alumina(α-Al2O3),Kaolin clay,talc and quartz as main raw materials.The effect of sintering temperature on the sintering properties(i.e.,bulk density(Db),linear shrinkage rate(Sf) and apparent porosity(Pa)) and the mechanical properties were investigated.The phase composition and microstructure of the composite ceramics were analyzed by X-ray diffraction and scanning electron microscopy.The results show that the sample sintered at 1 480 ℃ has water absorption of 0.19%,bulk density of 3.06 g/cm3and bending strength of 99.59 MPa.The composite ceramic has a superior thermal shock resistance.The bending strength loss rate is only 6.9% at 1 100 ℃ by air quenching-strength test,and the sample can endure 17-times thermal shock cycling.This composite ceramic could be used as one of potential solar thermal power materials.

  2. 复合相刚玉颗粒构成对出铁沟浇注料抗热震稳定性的改善%Improvement of Compound Corundum Pellet Ingredient on Tapping Ditch Casting Material Heat-resistant Knocking Stability

    Institute of Scientific and Technical Information of China (English)

    江泓; 童胜利

    2007-01-01

    根据本文中的机理A(引入热膨胀系数失配的第二相)机理B(引进热膨胀系数小的第二相),通过引入热膨胀系数不同的第二、三相形成复合相刚玉颗粒构成,使出铁沟浇注料抗热震稳定性得到改善.

  3. Sintering behavior and microstructure of SiAlON bonded corundum composites in different sintering atmospheres%不同烧结气氛下SiAlON结合刚玉材料的烧结行为和显微结构

    Institute of Scientific and Technical Information of China (English)

    谭清华; 王玺堂

    2006-01-01

    以α-Al2O3微粉和Si3N4粉为主要原料,分别以Al粉、AlN粉、SiO2微粉、Al粉+Ce2O3粉、Al粉+Si粉+Ce2O3粉作添加剂,在空气中裸烧(氧化气氛)和空气中埋炭(还原气氛)的条件下,分别进行1350℃、1450℃、1550℃、1600℃保温6 h的热处理后,制备了SiAlON结合刚玉复相材料,并研究了烧结气氛、烧结温度和添加剂种类对试样烧结行为和显微结构的影响.结果表明:添加稀土氧化物Ce2O3或少量SiO2微粉能促进材料的烧结;在氧化气氛下,以SiO2微粉为添加剂的试样的致密化程度随处理温度的升高而降低,而在埋炭还原气氛下,其致密化程度随温度的升高而提高;SEM观察还表明,含不同添加剂的试样在不同气氛中处理后的显微结构也不同.

  4. Optoelectronic Workshops. Dynamical Instabilities in Homogeneously Broadened Lasers (9th) (23 August 1988)

    Science.gov (United States)

    1988-08-23

    Vision and Electro-Optics Organizer -- Albert Pinto Needs for Broadband Materials and Systems Albert Pinto V4 in Corundum: Crystal Growth and Spectroscopy...too0 00 0 in< Zr 00 (LO 0 H z 1.+ V4+ in Corundum: Crystal Growth and Spectroscopy H. Verdun, U. Brauch, G. de la Fuente, L. Thomas and E. Behrens...of V4+ in this host. V 4+ has been found to be present in small concentrations in corundum crystals grown by the Verneuil method. Annealing under

  5. Programming with Hierarchical Maps

    DEFF Research Database (Denmark)

    Ørbæk, Peter

    This report desribes the hierarchical maps used as a central data structure in the Corundum framework. We describe its most prominent features, ague for its usefulness and briefly describe some of the software prototypes implemented using the technology....

  6. Osteoblast response on Ti- and Zr-based bulk metallic glass surfaces after sand blasting modification.

    Science.gov (United States)

    Li, H F; Wang, Y B; Zheng, Y F; Lin, J P

    2012-10-01

    The present study aimed to evaluate the osteoblast response on Ti- and Zr-based BMG surfaces sand blasted with different grit corundums for implant application, with mechanically polished disks before sand blasting as control groups. The surface properties were characterized by scanning electron microscopy (SEM), contact angle, and roughness measurements. Further evaluation of the surface bioactivity was conducted by MG63 cell attachment, proliferation, morphology, and alkaline phosphatase (ALP) activity on the sample surfaces. It was found that corundum sand blasting surfaces significantly increased the surface wettability and MG63 cell attachment, cell proliferation, and ALP activity in comparison with the control group surfaces. Besides, the sample surface treated by large grit corundum is more favorable for cell attachment, proliferation, and differentiation than samples treated by small grit corundum, indicating that it might be effective for improving implant osseointegration in vivo.

  7. Thermomechanical Properties of Corundum—Mullite—Zirconia Materials

    Institute of Scientific and Technical Information of China (English)

    ZHONGXiangchong; SUNGengcheng

    1998-01-01

    The mechanical properties at elevated tempera-tures of corundum-mullite materials and the effects of zirconia and titania additions have been investi-gated.The results are correlated with changes in microstructure,Based on the results of these investi-gations ,reaction-sintered corundum-mullite-zirco-nia materials with improved hot strength and ther-mal shock resistance have been developed for refractor-ries usage.

  8. Development of Corundum—Mullite—Zirconia Clinkers

    Institute of Scientific and Technical Information of China (English)

    LIUXin-yu; SUNGeng-chen; 等

    1994-01-01

    The properties of corundum-mullite-zirco-nia clinkers made by reaction-sintering have been investigated.It is shown that corundum-mullite-zirconia clinkers exhibit lower sintering tempera-ture as well as better thermal shock resistance and corrosion resistance,The carbon-bonded alu-mina-mullite-zirconia material possesses satis-factory properties and may have prospects for application in severe process environments such as continuous casting.

  9. COMPOSITION AND MICROSTRUCTURE OF MgAl2O4–W COMPOSITE OBTAINED BY ALUMINOTHERMIC REACTION UNDER COKE PROTECTION

    Directory of Open Access Journals (Sweden)

    Han Bingqiang

    2011-12-01

    Full Text Available MgAl2O4–W composite was synthesized by aluminothermic reducing method using Al, WO3, MgO and corundum as raw materials under coke protection. The effects of temperature, content of corundum on the synthesis of MgAl2O4–W composite and lattice parameter of spinel has been discussed. The differential scanning calorimetry (DSC and thermogravimetric (TG analysis indicated that spinel began to form at 1058.2°C without corundum and shifted to 1120.7°C with 0.8 mol of corundum. The XRD analysis confirmed that spinel and tungsten are the main phases under coke protection. Alumina rich spinel with a high solubility of alumina was easily formed because of the high exothermic heats. The solubility limit of Al2O3 in spinel is reached when corundum content is 2.1 mol. Furthermore, the calculated lattice parameter of spinel increases with the increment of added corundum content and rising of temperature. Microstructural observation indicates that cubic tungsten located at grain boundaries of well crystallized spinel. Residual WO3 has needle like morphology.

  10. Preparation of α-Al2O3 base ceramic coating on aluminum alloy via thermo-decomposition of diaspore

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The aim of this work is to describe the possibilities of preparing a corundum coating onaluminum alloy through in-situ chemical reaction at a relative low temperature. The transformationconditions of diaspore (β-AIOOH) to corundum (α-Al2O3 ) are studied using X-ray diffraction analy-sis. Temperature and heating time are two main factors influencing the transformation. Suitableheating parameters can lower the transformation temperature. On this basis, a new process isdeveloped to produce corundum ceramic coating on an aluminum alloy substrate. The phasecomposition and microstructure of the coating are studied using X-ray diffraction analysis andScanning Electron Microscopy. Abrasion properties of the coating are evaluated by ring-block tri-botester. The results show that it is feasible to obtain ceramic coatings on aluminum alloy sub-strates by means of thermo-decomposition of diaspore.

  11. Development and Application of Mullite—Composite Brick for Baths Pool of Blast Furnace

    Institute of Scientific and Technical Information of China (English)

    ZHOULei; LIXian-ming; 等

    1994-01-01

    The paper deals with the development and production of mullite-composite bricks for baths pool of balst furnace,Fused corundum,synthetic mullite ,special grade bauxite and a certain amount of additives were used as raw materials to produce corundum-mullite brick and yellow-corundum brick,All of their physical and chemical properties surpass the designed values.Good results have been obtained from the applic-cation in the baths pool of No.7 blast furnace of Anshan I & S Co.(Angang).The silicon content in pig iron decreases by 0.1%-0.2% while the temperature of the hot metal increases by 20℃,The mineral composition and structure have been studied by means of XRD and SEM.

  12. Sintering Densification Mechanism of Talc on Promoting Thermal Storage Andalusite Ceramics in Solar Thermal Power Generation

    Institute of Scientific and Technical Information of China (English)

    WU Jianfeng; CHENG Hao; XU Xiaohong; LAO Xinbing; ZHANG Yinfeng; RAO Zhengang; DENG Tengfei

    2015-01-01

    Mullite ceramic, as one of high-performance thermal storage ceramics for solar thermal power generation systems, wasin-situ fabricated with talc as a sintering aid via semi-dry pressing and pressureless sintering in air. The mullitization influence of talc as a sintering aid on the formation of andalusite was investigated, and its mechanism to promote the sintering densification of samples was analyzed. The results show that talc reacts with corundum at a low temperature toin-situ produce cordierite. Cordierite reactsin-situ to produce mullite and glass phase, which reduces the sintering temperature sharply when corundum reacts with rich silicon fluid directly and generates secondary mullite. Cordierite resolves and produces magnesium oxide liquid phase, which contains active aluminium oxide lattice capable of reducing reaction activation energy and promoting remaining corundum to react with rich silicon fluid and produces secondary mullite.

  13. Sintering Densification Mechanism of Talc on Promoting Thermal Storage Andalusite Ceramics in Solar Thermal Power Generation

    Institute of Scientific and Technical Information of China (English)

    WU; Jianfeng; CHENG; Hao; XU; Xiaohong; LAO; Xinbing; ZHANG; Yinfeng; RAO; Zhengang; DENG; Tengfei

    2015-01-01

    Mullite ceramic,as one of high-performance thermal storage ceramics for solar thermal power generation systems,was in-situ fabricated with talc as a sintering aid via semi-dry pressing and pressureless sintering in air.The mullitization influence of talc as a sintering aid on the formation of andalusite was investigated,and its mechanism to promote the sintering densification of samples was analyzed.The results show that talc reacts with corundum at a low temperature to in-situ produce cordierite.Cordierite reacts in-situ to produce mullite and glass phase,which reduces the sintering temperature sharply when corundum reacts with rich silicon fluid directly and generates secondary mullite.Cordierite resolves and produces magnesium oxide liquid phase,which contains active aluminium oxide lattice capable of reducing reaction activation energy and promoting remaining corundum to react with rich silicon fluid and produces secondary mullite.

  14. The Improvement of the Slag Resistance of Corundum—Spinel Castable with Addition of Aluminum Oxynitride (AlON)

    Institute of Scientific and Technical Information of China (English)

    LIYawei; LINan; 等

    1999-01-01

    The slag corrosion resisance of corundum-spinel castable has been increased by adding aluminum oxynitride spinel (AlON) powder ,Its results show that corrosion resistance of this castable is remarkably imroved when 3 wt% of the AlON powder added ,It was assumed that solid solution between aluminum oxynitride and magnesium aluminate spinel occurred to prevent the slag penetration into castable and increase the corrosion resistance of the corundum-spinel castable However,the experimental resultsd suggest such castable containing AlON powder be much more appropriate to be used in non-oxidation condition rather than in oxidation atmosphere.

  15. Significance of structure–property relationship in alumina based porcelain insulators to achieve quality

    Indian Academy of Sciences (India)

    Parvati Ramaswamy; S Vynatheya; S Seetharamu

    2005-12-01

    The catastrophic failures of porcelain insulators in power lines can be minimized by understanding the structure–property relationship that governs the performance. A study addressing the materials aspects has been conducted on alumina based porcelain insulators used in 25 kV railway traction lines. This article asserts the controls exercised by chemical composition, crystalline structural phases and microstructure on the functional reliability and durability of the insulators. Influences of the total alumina, -Al2O3 (corundum) and -quartz contents, microstructural features including morphologies of mullite needles, quartz and corundum grains in the alumino silicate glassy matrix, large inhomogeneities in matrix constituents and composition have been highlighted.

  16. Modification of surface morphology of Ti6Al4V alloy manufactured by Laser Sintering

    Science.gov (United States)

    Draganovská, Dagmar; Ižariková, Gabriela; Guzanová, Anna; Brezinová, Janette; Koncz, Juraj

    2016-06-01

    The paper deals with the evaluation of relation between roughness parameters of Ti6Al4V alloy produced by DMLS and modified by abrasive blasting. There were two types of blasting abrasives that were used - white corundum and Zirblast at three levels of air pressure. The effect of pressure on the value of individual roughness parameters and an influence of blasting media on the parameters for samples blasted by white corundum and Zirblast were evaluated by ANOVA. Based on the measured values, the correlation matrix was set and the standard of correlation statistic importance between the monitored parameters was determined from it. The correlation coefficient was also set.

  17. Development of Castables for Gass Tank Bottom

    Institute of Scientific and Technical Information of China (English)

    YUANLin; CHENShengling

    1998-01-01

    The production and use of zircon corundum refractory castables were analyzed.The superior properties and applied effect of castables for glass tank bottom were demonstrated.The results show that those castables have excellent molten glass corrosion resistance (MGCR) and enable glass tank bot-tom to form a seal mass.

  18. Soviet Developments in Material Science No. 1, January - June 1975

    Science.gov (United States)

    1975-11-30

    Lipatov, Yu. S., A. Ye. Nesterov, L. M. Sergeyeva, L. V. Karabanova, and T. D. Ignatova . Thermodynamics of mutually penetrating...sintered corundum versus its porosity. Problemy prochnosti, no. 1, 1975, 94-96. ^51, Ignatova , T. S., L. V. Uzberg and V. A. Perepelitsyn. Effect of a

  19. International Aviation (Selected Articles).

    Science.gov (United States)

    1982-04-12

    abundant and available at low cost, the 2onsum’tion of electrically smelted corundum can be saved drastically. Alumina ccmrcsite is a norous monetite ...according to the monetite formula and then blarks are arecared before calcining for long duration. Then, the blend is processed into -rains, sorted by

  20. Advanced Ceramic Composites for Improved Thermal Management in Molten Aluminum Applications

    Science.gov (United States)

    2009-02-01

    periodic (every one to three days) physical scraping off of the dross and corundum from the TCON plates to simulate refractory cleaning in industrial...applications. Mg content was replenished using solid magnesium metal and the metal line was kept constant by adding additional solid 5083 alloy. Dross

  1. Journal of the Chinese Silicate Society (selected articles)

    Science.gov (United States)

    1985-06-01

    The contents of a Chinese journal are given. The two titles of articles are: (1) The EFG Growth and Application of Small Diameter Sapphire Crystals in Tubular and Rod Shapes; and Study on the Surface Microtopography of Corundums Grown by Verneuil Method; Growing of Excellent Nd:YAG Crystals by Temperature Gradient Technique.

  2. alumina phase transformation from thermal decomposition of ...

    African Journals Online (AJOL)

    HOD

    INTRODUCTION. Alumina is one of the major components used as catalyst support ... used for processing petroleum, gas, petrochemicals and for other ... The extent and total conversion to the corundum ... purification, vegetable glues, porcelain cements, natural deodorant ..... Catalyst in Steam Reforming of Dimethyl ether:.

  3. Low dose effects of fibrous and non-fibrous mineral dusts on the proliferation of mammalian cells in vitro.

    Science.gov (United States)

    Fischer, A B; Kaw, J L; Diemer, K; Eikmann, T

    1998-08-01

    This report presents preliminary results of studies on the growth stimulating properties of mineral dusts. The studies were carried out with Syrian hamster diploid embryonic fibroblasts and Chinese hamster fibroblasts, line B14F28. Toxicity testing was done by the determination of the plating efficiency as a measure of growth and viability. The following dusts were used: the modified UICC asbestos fibres amosite, (AFF) crocidolite (KFF), chrysotile (KFF): in addition glass fibre (GFF), corundum and quartz DQ12. Concentrations > 2 microg/cm2 of AFF, CFF, KFF and GFF depressed the plating efficiency of B14F28 cells in a dose-dependent manner, but all of the fibres and corundum increased colony sizes at concentrations of 0.16-0.33 microg/cm2, in the case of corundum, AFF, KFF, and CFF also at up to 0.66 or 1.32 microg/cm2. DQ12 did not enhance colony growth. The stimulation of proliferation could be demonstrated both in terms of colony size (diameter) and cell numbers. The factor(s) responsible for proliferation stimulation reside in the supernatant, since the medium of dust-treated cell cultures was able to stimulate colony growth after removal of the dusts by filtration. The results indicate the induction of growth factors (cytokines) by low concentrations of the mineral dusts. Experiments concerning the effect of dusts on embryonic golden hamster fibroblasts yielded similar results. The plating efficiency was inhibited by concentrations of GFF and CFF > 0.25 microg cm2 and by AFF, KFF, GFF and corundum at concentrations > 5 microg/cm2, but colony counts were significantly increased by AFF, KFF and corundum at concentrations of 0.25-3 microg/cm2. This biological reaction which was observed in different cell types appears to be especially relevant in the context of environmental exposure where low dust concentrations prevail.

  4. Abundances and distribution of minerals and elements in high-alumina coal fly ash from the Jungar Power Plant, Inner Mongolia, China

    Science.gov (United States)

    Dai, S.; Zhao, L.; Peng, S.; Chou, C.-L.; Wang, X.; Zhang, Y.; Li, D.; Sun, Y.

    2010-01-01

    The fly ash from the Jungar Power Plant, Inner Mongolia, China, is unique because it is highly enriched in alumina (Al2O3>50%). The fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum, quartz, char, calcite, K-feldspar, clay minerals, and Fe-bearing minerals. The mullite content in fly ash is as high as 37.4% because of high boehmite and kaolinite contents in feed coal. Corundum is a characteristic mineral formed during the combustion of boehmite-rich coal.Samples from the economizer were sieved into six size fractions (500 mesh) and separated into magnetic, mullite+corundum+quartz (MCQ) and glass phases for mineralogical and chemical analysis. The corundum content increases but amorphous glass decreases with decreasing particle size. Fractions of small particle sizes are relatively high in mullite, probably because mullite was formed from fine clay mineral particles under high-temperature combustion condition. Similarly, fine corundum crystals formed in the boiler from boehmite in feed coal. The magnetic phase consists of hematite, magnetite, magnesioferrite, and MgFeAlO4 crystals. The MCQ phase is composed of 89% mullite, 6.1% corundum, 4.5% quartz, and 0.5% K-feldspar.Overall, the fly ash from the power plant is significantly enriched in Al2O3 with an average of 51.9%, but poor in SiO2, Fe2O3, CaO, MgO, Na2O, P2O5, and As. Arsenic, TiO2, Th, Al2O3, Bi, La, Ga, Ni, and V are high in mullite, and the magnetic matter is enriched in Fe2O3, CaO, MnO, TiO2, Cs, Co, As, Cd, Ba, Ni, Sb, MgO, Zn, and V. The remaining elements are high in the glass fraction. The concentration of K2O, Na2O, P2O5, Nb, Cr, Ta, U, W, Rb, and Ni do not clearly vary with particle size, while SiO2 and Hg decrease and the remaining elements clearly increase with decreasing particle size. ?? 2009 Elsevier B.V.

  5. Temperature dependence of crystal structure and digestibility of roasted diaspore

    Institute of Scientific and Technical Information of China (English)

    周秋生; 李小斌; 彭志宏; 刘桂华

    2004-01-01

    Through X-ray diffraction patterns and scanning electronic micrographs, temperature dependence of the crystal structure of roasted diasporic bauxite at different temperatures and the digestibility of roasting production were investigated systematically. The lattice parameters of unit cell for chemically purified diaspore and unequilibrium alumina-contained oxide obtained from the diaspore roasted at different temperatures were determined. It is found that, with roasting temperature increasing, the roasting production changes from the original dense and perfect diaspore crystal into imperfect corundum with many microcracks and small pores on its surface and then into perfect corundum with low digestibility. The optimum roasting temperature with best digestibility is approximately 525 ℃ when residence time is about 25 min. It is thought that the change of crystal structure, formation of microcracks and small pores in the temperature field are the main essential reasons for improving digestibility of diasporic bauxite and its roasting production.

  6. Microstructural and Wear Behavior Characterization of Porous Layers Produced by Pulsed Laser Irradiation in Glass-Ceramics Substrates

    Directory of Open Access Journals (Sweden)

    Jose I. Peña

    2013-09-01

    Full Text Available In this work, wear behavior and microstructural characterization of porous layers produced in glass-ceramic substrates by pulsed laser irradiation in the nanosecond range are studied under unidirectional sliding conditions against AISI316 and corundum counterbodies. Depending on the optical configuration of the laser beam and on the working parameters, the local temperature and pressure applied over the interaction zone can generate a porous glass-ceramic layer. Material transference from the ball to the porous glass-ceramic layer was observed in the wear tests carried out against the AISI316 ball counterface whereas, in the case of the corundum ball, the wear volume loss was concentrated in the porous layer. Wear rate and friction coefficient presented higher values than expected for dense glass-ceramics.

  7. Progress and developing trend of purging plug for refining ladle%精炼钢包用透气砖的研究进展与发展方向

    Institute of Scientific and Technical Information of China (English)

    贾全利; 吴然; 孙小改

    2013-01-01

    总结了精炼钢包用透气砖的损毁原因和现用刚玉-尖晶石透气砖在改善抗热震性方面的研究新进展;介绍了非氧化物结合刚玉质透气砖的研究结果和在精炼钢包上的使用情况,提出了透气砖的研究和发展方向.%Damage reasons of purging plug for refining ladle and research progress on thermal shock resistance of corundum-spinel purging plug were summarized. Research achievements and application results of nonoxides bonded corundum purging plug for refining ladle were reviewed. The further research and developing trend of purging plug were proposed.

  8. Effect of Metallic Zn Powder on Oxidation Resistance of Al2O3-C Refractories

    Institute of Scientific and Technical Information of China (English)

    LI Youqi; KE Changming; LI Yousheng; LI Nan

    2006-01-01

    Al2O3-C specimens were prepared by using tabular corundum,flaky graphite,Al,Si,and Zn powder as starting materials and phenolic formaldehyde resin as binder.Keeping the mass ratios of tabular corundum,flaky graphite,Al and Si constant,different contents of ZN(0,0.5%,1%,2%and 3%)were added respectively.The specimens were heat treated at 120-220℃ for 24h,and then fired at 1400℃ .for 3h in air atmosphere. The mass change rate, thickness of decarburization layer, apparent porosity, bulk density and microstructure of the products were determined and observed by means of SEM and EDX.The results show that the specimen with 2% Zn was characterized by minimum in thickness of decarburization layer and in apparent porosity and maximum in bulk density. Consequently, the specimen with 2% metal Zn is supposed to perform the best oxidation resistance.

  9. Effects of Electro-fused Magnesia on Properties of Al2O3 - SiC - C Castable

    Institute of Scientific and Technical Information of China (English)

    NAN Bingqiang; LI Yousheng; LI Nan

    2008-01-01

    Al2O3- SiC - C castables for iron trough with fused magnesia powder (0, 3% , 6% , 9% and 12% ) were prepared with brown fused corundum particles (5 -3 mm, 3-1 mm, ≤1 mm), white fused corundum powder (≤0. 088 mm), SiC particle (≤1 mm) and powder (≤0. 088 mm ) , fused magnesia powder (≤ 0.088 mm ), reactive α-Al2O3 micropowder, ultrafine SiO2, Si powder and sphere pitch as main starting mate-rials and calcium aluminate cement as binder. The spec-imens were fired at 1 100 ℃ and 1 450 ℃ for 3 h after vibrating moulding, curing, demoulding and drying at 110 ℃ for 24 h. Bulk density, apparent porosity, line-ar change rate, modulus of rupture, resistance to blast furnace slag, oxidation resistance, phase composition and microstructure of the specimens were analyzed. The results show that : ( 1 ) With fused magnesia addition increasing, apparent porosity increases, while bulk den-sity, modulus of rupture and oxidation resistance de-cline, slag resistance varies slightly; (2) The main crystal phases in the specimens fired at 1 450 ℃ for 3 h are 3C-SiC, 6H - SiC, corundum, periclase, reac-tion-synthesized spinel and mullite; the quantity of the formed spinel and mullite increases with the increase of fased magnesite addition; (3) Along the corroded side, spinel layer with about 80 μm thickness forms at the co-rundum particles boundary.

  10. A Wealth of Dust Grains in Quasar Winds

    Science.gov (United States)

    2007-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version This plot of data captured by NASA's Spitzer Space Telescope reveals dust entrained in the winds rushing away from a quasar, or growing black hole. The quasar, called PG2112+059, is located deep inside a galaxy 8 billion light-years away. Astronomers believe the dust might have been forged in the winds, which would help explain where dust in the very early universe came from. The data were captured by Spitzer's infrared spectrograph, an instrument that splits apart light from the quasar into a spectrum that reveals telltale signs of different minerals. Each type of mineral, or dust grain, has a unique signature, as can be seen in the graph, or spectrum, above. The strongest features are from the mineral amorphous olivine, or glass (purple); the mineral forsterite found in sand (blue); and the mineral corundum found in rubies (light blue). The detection of forsterite and corundum is highly unusual in galaxies without quasars. Therefore, their presence is a key clue that these grains might have been created in the quasar winds and not by dying stars as they are in our Milky Way galaxy. Forsterite is destroyed quickly in normal galaxies by radiation, so it must be continually produced to be detected by Spitzer. Corundum is hard, and provides a seed that softer, more common minerals usually cover up. As a result, corundum is usually not seen in spectra of galaxies. Since Spitzer did detect the mineral, it is probably forming in a clumpy environment, which is expected in quasar winds. All together, the signatures of the unusual minerals in this spectrum point towards dust grains forming in the winds blowing away from quasars.

  11. Band-gap narrowing in α-(CrxFe1-x)2O3 solid-solution films

    OpenAIRE

    2011-01-01

    We report on structural and optical properties for the (0001)-oriented α-(CrxFe1-x)2O3 (0 ≤ x ≤ 1) epitaxial films prepared on c-sapphire substrates by using pulsed-laser deposition. Pure corundum phase with atomically flat surface was obtained in the entire composition range. Optical absorption spectra for the films with 0.2 

  12. Development of vertical compact ion implanter for gemstones applications

    Energy Technology Data Exchange (ETDEWEB)

    Intarasiri, S., E-mail: saweat@gmail.com [Science and Technology Research Institute, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand); Wijaikhum, A. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Bootkul, D., E-mail: mo_duangkhae@hotmail.com [Department of General Science (Gems and Jewelry), Faculty of Science, Srinakharinwirot University, Bangkok 10110 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand); Suwannakachorn, D.; Tippawan, U.; Yu, L.D.; Singkarat, S. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand)

    2014-08-15

    Ion implantation technique was applied as an effective non-toxic treatment of the local Thai natural corundum including sapphires and rubies for the enhancement of essential qualities of the gemstones. Energetic oxygen and nitrogen ions in keV range of various fluences were implanted into the precious stones. It has been thoroughly proved that ion implantation can definitely modify the gems to desirable colors together with changing their color distribution, transparency and luster properties. These modifications lead to the improvement in quality of the natural corundum and thus its market value. Possible mechanisms of these modifications have been proposed. The main causes could be the changes in oxidation states of impurities of transition metals, induction of charge transfer from one metal cation to another and the production of color centers. For these purposes, an ion implanter of the kind that is traditionally used in semiconductor wafer fabrication had already been successfully applied for the ion beam bombardment of natural corundum. However, it is not practical for implanting the irregular shape and size of gem samples, and too costly to be economically accepted by the gem and jewelry industry. Accordingly, a specialized ion implanter has been requested by the gem traders. We have succeeded in developing a prototype high-current vertical compact ion implanter only 1.36 m long, from ion source to irradiation chamber, for these purposes. It has been proved to be very effective for corundum, for example, color improvement of blue sapphire, induction of violet sapphire from low value pink sapphire, and amelioration of lead-glass-filled rubies. Details of the implanter and recent implantation results are presented.

  13. Improved Osteointegration of Ti-6Al-4V-implants of Different Surface Texture by the Use of Bone Morphogenetic Protein-3 (BMP-3)

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Half of altogether 60 cylindrical implant devices mode of titanium-aluminum-vanadium alloy( Ti-6Al-4 V) were plasma-sprayed with a hydroxyapatite-coating and the other half had a corundum blasted porous surface. 15 implants of each group of the titanium test implants were coated with 230μgporcine, high-purified BMP- 3-precipitate per implant. In each case a BMP- 3-coated and an uncoated control-device were implanted into the femoral part of the patellofemoral joint of the right and left leg of 30 adult giant rabbits. Histomorphological and histomorphometrical we found in both groups with BMP- 3-coated test devices an improved osteointegration. Statistical evaluation using the t-test for matched samples showed 5 weeks after surgery a significant higher volume of new formed bone of the BMP- 3-coated corundum-blasted or hydroxyapatite-coated Ti-6Al-4 V test devices compared to the non-coated controls of the same type (p < 0.01, t-test for matched samples). In both implatt groups with BMP-coating a synergetic effect was verifiable although the bone ongrowth in the hydroxyapatite coated implants was more extensive than in the corundum blasted implants. Light microscopy demonstrated osteointegration without connective tissue membrane around the surface of the implants. Our results indicate that composite metal implants, as used in endoprosthetics and implantology , are suitable carriers for BMP- 3 and improved fixation of the implants can be achieved. The hydroxyapatite surface is superior to the corundum-blasted surface with regards to the observed parameters because of its pronounced bioactivity and its osteoconductive characteristics.

  14. Prevention of burn-on defect on surface of hydroturbine blade casting of ultra-low-carbon refining stainless steel

    Directory of Open Access Journals (Sweden)

    Li Ling

    2008-08-01

    Full Text Available The burn-on sand is common surface defect encountered in CO2-cured silicate-bonded sand casting of hydroturbine blade of ultra-low-carbon martensitic stainless steel, its feature, causes and prevention measures are presented in this paper. Experiments showed that the burn-on defect is caused by oxidization of chromium in the molten steel at high temperature and can be effectively eliminated by using chromium-corundum coating.

  15. Prevention of burn-on defect on surface of hydroturbine blade casting of ultra-low-carbon refining stainless steel

    Institute of Scientific and Technical Information of China (English)

    Li Ling; Xie Huasheng; Huang Danzhong; Li Hankun; Tan Rui; Zhou Jingyi

    2008-01-01

    The burn-on sand is common surface defect encountered in CO2-cured silicate-bonded sand casting of hydroturbine blade of ultra-low-carbon martensitic stainless steel, its feature, causes and prevention measures are presented in this paper. Experiments showed that the bum-on defect is caused by oxidization of chromium in the molten steel at high temperature and can be effectively eliminated by using chromium-corundum coating.

  16. Electronic Structure of High-Pressure Alumina Polymorphs

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-Lei; DUAN Wen-Hui; GU Bing-Lin

    2000-01-01

    Electronic properties are investigated for three alumina polymorphs (corundum, Rb2 O3 (Ⅱ) and Pbnm perovskite),which are predicted as the stable structures under different pressure range, by means of the first-principles molecular dynamics method within local density functional framework. The similarity in electronic properties of the polymorphs of alumina is observed. The effect of possible phase transitions on ruby (Cr+3-doped Al2 O3)fluorescences is discussed.

  17. Seed layer stimulated growth of crystalline high Al containing (Al,Cr){sub 2}O{sub 3} coatings deposited by cathodic arc evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Pohler, M., E-mail: markus.pohler@stud.unileoben.ac.at [Christian Doppler Laboratory for Advanced Hard Coatings at the Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Straße 18, A-8700 Leoben (Austria); Franz, R. [Christian Doppler Laboratory for Advanced Hard Coatings at the Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Straße 18, A-8700 Leoben (Austria); Ramm, J. [OC Oerlikon Balzers AG, Iramali 18, 9469 Balzers (Liechtenstein); Polcik, P. [PLANSEE Composite Materials GmbH, Siebenbürgerstraße 23, 86983 Lechbruck am See (Germany); Mitterer, C. [Christian Doppler Laboratory for Advanced Hard Coatings at the Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Franz-Josef-Straße 18, A-8700 Leoben (Austria)

    2014-01-01

    Single layer and dual layer (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} coatings were synthesised by cathodic arc evaporation with different Al contents to study their growth characteristics. It was demonstrated that variations in the Al content, the energy of incident particles and the coating thickness control the crystallinity and the coating texture. Analysis by X-ray diffraction revealed a distinct (110) out of plane orientation after transition from a fine grained nucleation zone to a columnar growth mode. Furthermore, the impact of (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} seed layers with x = 0.25 and 0.5 on the growth of (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} top layers with x = 0.7 and 0.85 was evaluated in detail. According to X-ray diffraction and transmission electron microscopy, the development of the corundum-type crystal structure of the top layer was promoted by local epitaxy if the low Al containing seed layer exhibited a pronounced columnar structure. In this way, crystalline corundum-type coatings with an Al content up to x = 0.85 were obtained. - Highlights: • Industrial scale cathodic arc deposition of corundum type (Al{sub x}Cr{sub 1−x}){sub 2}O{sub 3} coatings • Discussion of the growth characteristics for different Al/Cr ratios • Characterisation of growth regimes in dual layer coatings • Template stimulated growth of crystalline corundum-type (Al{sub 0.85}Cr{sub 0.15}){sub 2}O{sub 3} coatings • Influence of bias voltage and seed layer thickness on the template effect.

  18. Development of vertical compact ion implanter for gemstones applications

    Science.gov (United States)

    Intarasiri, S.; Wijaikhum, A.; Bootkul, D.; Suwannakachorn, D.; Tippawan, U.; Yu, L. D.; Singkarat, S.

    2014-08-01

    Ion implantation technique was applied as an effective non-toxic treatment of the local Thai natural corundum including sapphires and rubies for the enhancement of essential qualities of the gemstones. Energetic oxygen and nitrogen ions in keV range of various fluences were implanted into the precious stones. It has been thoroughly proved that ion implantation can definitely modify the gems to desirable colors together with changing their color distribution, transparency and luster properties. These modifications lead to the improvement in quality of the natural corundum and thus its market value. Possible mechanisms of these modifications have been proposed. The main causes could be the changes in oxidation states of impurities of transition metals, induction of charge transfer from one metal cation to another and the production of color centers. For these purposes, an ion implanter of the kind that is traditionally used in semiconductor wafer fabrication had already been successfully applied for the ion beam bombardment of natural corundum. However, it is not practical for implanting the irregular shape and size of gem samples, and too costly to be economically accepted by the gem and jewelry industry. Accordingly, a specialized ion implanter has been requested by the gem traders. We have succeeded in developing a prototype high-current vertical compact ion implanter only 1.36 m long, from ion source to irradiation chamber, for these purposes. It has been proved to be very effective for corundum, for example, color improvement of blue sapphire, induction of violet sapphire from low value pink sapphire, and amelioration of lead-glass-filled rubies. Details of the implanter and recent implantation results are presented.

  19. Influence of the post-weld surface treatment on the corrosion resistance of the duplex stainless steel 1.4062

    Science.gov (United States)

    Rosemann, P.; Müller, C.; Baumann, O.; Modersohn, W.; Halle, T.

    2017-03-01

    The duplex stainless steel 1.4062 (X2CrNiN22-2) is used as alternative material to austenitic stainless steels in the construction industry. The corrosion resistance of welded seams is influenced by the base material, the weld filler material, the welding process and also by the final surface treatment. The scale layer next to the weld seam can be removed by grinding, pickling, electro-polished or blasting depending on the application and the requested corrosion resistance. Blasted surfaces are often used in industrial practice due to the easier and cheaper manufacturing process compared to pickled or electro-polished surfaces. Furthermore blasting with corundum-grain is more effective than blasting with glass-beads which also lower the process costs. In recent years, stainless steel surfaces showed an unusually high susceptibility to pitting corrosion after grinding with corundum. For this reason, it is now also questioned critically whether the corrosion resistance is influenced by the applied blasting agent. This question was specifically investigated by comparing grinded, pickled, corundum-grain- and glass-bead-blasted welding seams. Results of the SEM analyses of the blasting agents and the blasted surfaces will be presented and correlated with the different performed corrosion tests (potential measurement, KorroPad-test and pitting potential) on welding seams with different surface treatments.

  20. Structure and catalytic reactivity of Rh oxides

    DEFF Research Database (Denmark)

    Gustafson, J.; Westerström, R.; Resta, A.;

    2009-01-01

    Using a combination of experimental and theoretical techniques, we show that a thin RhO2 surface oxide film forms prior to the bulk Rh2O3 corundum oxide on all close-packed single crystal Rh surfaces. Based on previous reports, we argue that the RhO2 surface oxide also forms on vicinal Rh surfaces...... as well as on Rh nanoparticles. The detailed structure of this film was previously determined using UHV based techniques and density functional theory. In the present paper, we also examine the structure of the bulk Rh2O3 corundum oxide using surface X-ray diffraction. Being armed with this structural...... surface oxide film. In the case of Pt25Rh75(1 0 0), our measurements demonstrate that the formation of bulk Rh2O3 corundum oxide poisons the reaction, and argue that this is also valid for all other Rh surfaces. Our study implies that the CO oxidation reaction over Rh surfaces at realistic conditions...

  1. Microstructure and physical properties of steel-ladle purging plug refractory materials

    Science.gov (United States)

    Long, Bin; Xu, Gui-ying; Andreas, Buhr

    2017-02-01

    Three different castables were prepared as steel-ladle purging-plug refractory materials: corundum-based low-cement castable (C-LCC), corundum-spinel-based low-cement castable (C-S-LCC), and no-cement corundum-spinel castable (C-S-NCC) (hydratable alumina ρ-Al2O3 bonded). The properties of these castables were characterized with regard to water demand/flow ability, cold crushing strength (CCS), cold modulus of rupture (CMoR), permanent linear change (PLC), apparent porosity, and hot modulus of rupture (HMoR). The results show the CCS/CMoR and HMoR of C-LCC and C-S-LCC are greater than those of the castable C-S-NCC. According to the microstructure analysis, the sintering effect and the bonding type of the matrix material differ among the three castables. The calcium hexaluminate (CA6) phase in the matrix of C-LCC enhances the cold and hot mechanical strengths. In the case of C-S-LCC, the CA6 and 2CaO·2MgO·14Al2O3 (C2M2A14) ternary phases generated from the matrix can greatly increase the cold and hot mechanical strengths. In the case of the no-cement castable, sintering becomes difficult, resulting in a lower mechanical strength.

  2. Fracture behavior and microstructure analysis of Al2O3-MgO-CaO castables for steel-ladle purging plugs

    Science.gov (United States)

    Long, Bin; Xu, Gui-ying; Li, Yong; Buhr, Andreas

    2016-11-01

    Three different castables based on the Al2O3-MgO-CaO system were prepared as steel-ladle purging plug refractories: corundum- based low-cement castable (C-LCC), corundum-spinel-based low-cement castable (C-S-LCC), and corundum-spinel no-cement castable (C-S-NCC) (hydratable alumina (ρ-Al2O3) bonded). The fracture behavior at room temperature was tested by the method of "wedge-splitting" on samples pre-fired at different temperatures; the specific fracture energy G f ' and notched tensile strength σNT were obtained from these tests. In addition, the Young's modulus E was measured by the method of resonance frequency of damping analysis (RFDA). The thermal stress resistance parameter R'''' calculated using the values of G f ' , σ NT, and E was used to evaluate the thermal shock resistance of the materials. According to the microstructure analysis results, the sintering effect and the bonding type of the matrix material were different among these three castables, which explains their different fracture behaviors.

  3. Optical constants of refractory oxides at high temperatures

    CERN Document Server

    Zeidler, Simon; Mutschke, Harald; 10.1051/0004-6361/201220459

    2013-01-01

    Many cosmic dust species, among them refractory oxides, form at temperatures higher than 300 K. Nevertheless, most astrophysical studies are based on the room-temperature optical constants of solids, such as corundum and spinel. A more realistic approach is needed for these materials, especially in the context of modeling late-type stars. We aimed at deriving sets of optical constants of selected, astrophysically relevant oxide dust species with high melting points. A high-temperature-high-pressure-cell and a Fourier-transform spectrometer were used to measure reflectance spectra of polished samples. For corundum (alpha-Al$_2$O$_3$), spinel (MgAl$_2$O$_4$), and alpha-quartz (SiO$_2$), temperature-dependent optical constants were measured from 300 K up to more than 900 K. Small particle spectra were also calculated from these data. All three examined oxides show a significant temperature dependence of their mid-IR bands. For the case of corundum, we find that the 13$\\mu$m emission feature - seen in the IR spec...

  4. Characterization of local chemistry and disorder in synthetic and natural {alpha}-Al{sub 2}O{sub 3} materials by X-ray absorption near edge structure spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mottana, A. [Rome, Univ. `Roma Tre` (Italy). Dip. di Scienze Geologiche]|[INFN, Laboratori Nazionali di Frascati, Rome (Italy); Murata, T. [Kyoto, Univ. of Education (Japan). Dept. of Physics; Marcelli, A. [INFN, Laboratori Nazionali di Frascati, Rome (Italy)] [and others

    1997-11-01

    X-ray absorption fine spectra at the Al K-edge were measured experimentally on and calculated theoretically via the multiple-scattering formalism for a chemically pure and physically perfect synthetic {alpha}-Al{sub 2}O{sub 3} ({alpha}-alumina), a natural `ruby/sapphire` (corundum) and a series of artificial `corundum` produced for technical purposes and used as geochemical standards. The Al K-edge spectra differ despite of the identical coordination (short-range arrangement) assumed by O around Al, and vary slightly in relation to the slightly different chemistries of the materials (substitutional defects) as well as on account of the location taken by foreign atoms in the structural lattices (positional defects). A quantitative treatment of the observed changes is made in terms of short-range modification of the coordination polyhedron and of medium- to long-range modifications in the overall structure; both of them induced by substitutions. In some technical `corundums`, the impurities of admixed `{beta}-alumina`, where Al is both in four- and six-fold coordination, produce another small but detectable effect on Al K-edges. Therefore, XAFS spectroscopy proves its potentials for both measuring a light element such as Al, and detecting minor coordination changes and substitutions (ca. 1{approx}3 wt.% as oxide) of the absorber by dilute other atoms, at least under favorable conditions as those occurring in this system are.

  5. Astronomy by mass spectrometry: Interstellar grains in meteorites

    Science.gov (United States)

    Zinner, E.

    1994-07-01

    Primitive meteorites contain small amounts of interstellar dust grains that survived the formation of the solar system. Since these grains formed in stellar atmospheres, their study can provide information on nuclear and chemical processes in stars. To date, diamond, SiC, graphite, TiC, and corundum have been identified. Their circumstellar origin is indicated by their extremely anomalous isotopic compositions, originally of noble gases, but subsequently also of the major and refractory minor and trace elements. While diamond and TiC are too small for single-grain analysis, SiC, graphite, and corundum range up to greater than 1 micron in size and isotopic ratios can be measured for several elements by ion microprobe spectrometry. The correlated isotopic data thus obtained set new constraints on theoretical models of nucleosynthesis and stellar evolution. One type of information to be culled from isotopic measurements of interstellar grains is on the number of stellar sources that contributed material to the solar system. Another type of information is obtained from single-grain isotopic data that either have no counterpart in astronomical observations or that cannot be explained by existing models of nucleosynthesis and thus provide stimulation for further theoretical work. An example are large O-18 depletions in corundum grains from Tieschitz. Another example are large O-18 excesses in graphite grains.

  6. Research of Attrition of Cyclone Walls Made from Different Materials Under the Influence of Various Abbrasive Materials

    Directory of Open Access Journals (Sweden)

    Tomas Gailius

    2016-04-01

    Full Text Available To eliminate particulate pollutants from air cyclones are being used. This article reviews the influence of particulate pollutants on cyclone insert. The stand was designed with possibility to change insert, rotation of engine and abrasive materials. Steel, stainless steel and polyurethane were used for inserts. Sand, glass balls, steel balls and corundum were used as abrasive materials. For the insert the steel balls has the strongest influence, when rotation of engine was 2400 rpm. Stainless steel was the most wearproof material for inserts.

  7. Equation of state of α-Al2O3

    Science.gov (United States)

    Dewaele, A.; Torrent, M.

    2013-08-01

    The ambient temperature equation of state of ruby in the corundum phase (α-Al2O3) has been measured up to 165 GPa in a diamond anvil cell, using a soft pressure transmitting medium. No clear sign of phase transformation or amorphization has been observed in this range, which could affect its luminescence signal. The equation of state of α-Al2O3 has also been calculated within density functional theory, with two different approximations of the exchange-correlation energy (local density and generalized gradient). With suitable correction, these equations of state are predictive within ΔP/P=2.5%.

  8. Direct thermolysis of CO2 into CO and O2.

    Science.gov (United States)

    Jiang, Qingqing; Chen, Zhenpan; Tong, Jinhui; Yang, Min; Jiang, Zongxuan; Li, Can

    2017-01-17

    Most of the solar-driven thermochemical CO2 dissociation reactions have been focused on two-step processes. In this study, a one step CO2 thermolysis process was considered. It was found that direct thermolysis of CO2 obviously occurred at temperatures as low as 1200 °C within a corundum tube. The reaction rate could be enhanced by several times in the presence of metal oxides, which may be attributed to the catalysis of oxygen vacancies in the metal oxides.

  9. Short-lived radioactivity in the early Solar System: the Super-AGB star hypothesis

    OpenAIRE

    Lugaro, Maria; Doherty, Carolyn; Karakas, A. I.; Maddison, S. T.; Liffman, K.; Garc'ia-Hernández, D.A.; Siess, Lionel; Lattanzio, J. C.

    2012-01-01

    The composition of the most primitive solar system condensates, such as calcium-aluminum-rich inclusions (CAIs) and micron-sized corundum grains, show that short-lived radionuclides (SLR), e.g. 26Al, were present in the early solar system. Their abundances require a local or stellar origin, which, however, is far from being understood. We present for the first time the abundances of several SLR up to 60Fe predicted from stars with initial mass in the range approximately 7-11M⊙. These stars ev...

  10. Interaction mechanisms between slurry coatings and solid oxide fuel cell interconnect alloys during high temperature oxidation

    DEFF Research Database (Denmark)

    Persson, Åsa Helen; Mikkelsen, L.; Hendriksen, P.V.;

    2012-01-01

    Six different coatings consisting of fluorite-, corundum-, spinel- or perovskite-type oxides were deposited on a Fe22Cr alloy (Crofer 22APU) and oxidized at 900°C in moisturized air.Five of the coatings prevented break-away oxidation otherwise observed for the uncoated alloy, and the parabolic...... oxidation rate constant was reduced with 50–90% of that for uncoated alloy. One coating consisting of MnCo2O4 did not significantly affect the oxidation rate of the alloy, and just as for uncoated samples break-away oxidation occurred for MnCo2O4 coated samples. The interaction mechanisms between...

  11. Mechanochemical production of nanocomposites of metal/oxide and intermetallic/oxide systems

    Energy Technology Data Exchange (ETDEWEB)

    Grigoryeva, T F; Barinova, A P; Ancharov, A I; Vorsina, I A; Lyakhov, N Z [Institute of Solid State Chemistry and Mechanochemistry, SB RAS, Novosibirsk (Russian Federation); Novakova, A A; Kiseleva, T Yu [M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Talako, T L [Institute of Powder Metallurgy, NAS of Belarus, Minsk (Belarus); Becker, K D; Sepelak, V [Institute of Physical and Theoretical Chemistry, Braunschweig University of Technology, Braunschweig (Germany); Tsybulya, S V; Bulavchenko, O A, E-mail: grig@solid.nsc.r [G.K. Boreskov Institute of Catalysts, SB RAS, Novosibirsk (Russian Federation)

    2009-01-01

    Addition of nanosized intermetallic or metallic phases into corundum considerably raises mechanical behavior of the material. In this work, the nanocomposites of alpha-Al{sup 2}O{sup 3}/intermetallic and alpha-Al{sup 2}O{sup 3}/metal systems were obtained by mechanochemical reduction of alpha-Fe{sup 2}O{sup 3} by Al (and by solid solution of Al in Fe). The mechanochemical reduction process of hematite by various amount of metal-reducer was studied by IR and Moessbauer spectroscopies, and by X-ray synchrotron radiation diffraction technique.

  12. Exploitation of the Sol-Gel Route in Processing Ceramics and Composites

    Science.gov (United States)

    1985-05-01

    zircon gel can be made into vermicular aggregates of zircon particles while the diphasic gel yields equant isolated particles. Ultra-fine corundum and...phase gel aggregated into vermicular morphological entities (Fig. 6A) and shows crystals on the order of -75nm (Fig. 6B) whereas the zircon formed...450C/100l Pa/4 hrs Zircon -- Single phase gel 500C/lOOMPa/12 his Zircon Single phase gel 600OC/IOOMPa/12 hrs Zircon Vermicular aggregates (-75rm

  13. A double cell for X-ray absorption spectrometry of atomic Zn

    CERN Document Server

    Mihelic, A; Arcon, I; Padeznik-Gomilsek, J; Borowski, M

    2002-01-01

    A high-temperature cell with a double wall design has been constructed for X-ray absorption spectrometry of metal vapors. The inner cell, assembled from a corundum tube and thin plates without welding or reshaping, serves as a container of the vapor sample. It is not vacuum tight: instead, the outer tube provides inert atmosphere. Several spectra of K-edge atomic absorption of Zn were obtained in the stationary working regime below the Zn boiling point. The K-edge profile shows an extremely strong resonance and, above the continuum threshold, coexcitations of the outer electrons.

  14. Increasing the reliability and quality of important cast products made of chemically active metals and alloys

    Science.gov (United States)

    Varfolomeev, M. S.; Moiseev, V. S.; Shcherbakova, G. I.

    2017-01-01

    A technology is developed to produce highly thermoresistant ceramic monoxide corundum molds using investment casting and an aluminum-organic binder. This technology is a promising trend in creating ceramic molds for precision complex-shape casting of important ingots made of high-alloy steels, high-temperature and titanium alloys, and refractory metals. The use of the casting molds that have a high thermal and chemical resistance to chemically active metals and alloys under high-temperature casting minimizes the physicochemical interaction and substantially decreases the depth of the hard-to-remove metal oxide layer on important products, which increases their service properties.

  15. Development and Production of High Performances Heavily Bruned Al2O3—C Slicde Plate

    Institute of Scientific and Technical Information of China (English)

    ZHANGChengtian; ZHAOChuanfa; 等

    1998-01-01

    The slide plate,made of sintered tabular corundum,reactive alumina ultr-fine powder with thermoplastic phenolic formaldehyde resin as cemedin and added 4%-6% quality scaled graphite ,special carbon and compound additive (A+B),has excellent performances such as lower thermal expansion,good thermal shock resistance,excellent erosion and corrosion resistance,and high strength,etc.All physical properties can meet the customers' needs,Afer being used in several steel plants in U.S.A.,this kind of slide plate received favorable comments with its easily open and close operation

  16. Temperature distribution and control in liquefied petroleum gas fluidized beds

    Institute of Scientific and Technical Information of China (English)

    Li Wang; Ping Wu; Yanping Zhang; Jing Yang; Lige Tong

    2004-01-01

    Temperature distribution and control have been investigated in a liquefied petroleum gas (LPG) fluidized bed with hollow corundum spheres (A12O3) of 0.867-1.212 mm in diameter at moderately high temperatures (800-1100℃). Experiments were carried out for the air consumption coefficient α in the range of 0.3 to 1.0 and the fluidization number N in the range of 1.3 to 3.0. Particle properties, initial bed height, α and N all affect temperature distribution in the bed. Bed temperature can be adjusted about 200℃ by combined the adjusting of α and N.

  17. Influence of chemical bonding on X-ray spectra of different aluminium compounds

    Energy Technology Data Exchange (ETDEWEB)

    Bonetto, Rita [Centro de Investigacion y Desarrollo en Ciencias Aplicadas Dr. Jorge Ronco, Calle 47 No. 257, CC 59, 1900 La Plata (Argentina) and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina (Argentina)]. E-mail: bonetto@quimica.unlp.edu.ar; Trincavelli, Jorge [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000, Cordoba (Argentina) and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina (Argentina)]. E-mail: jorge@quechua.fis.uncor.edu; Vasconcellos, Marcos [Instituto de Fisica, Universidade Federal de Rio Grande do Sul, Campus do Vale, Av. Bento Goncalves 9500, CEP: 91501-970, Porto Alegre (Brazil)]. E-mail: marcos@if.ufrgs.br

    2005-11-15

    Five minerals containing aluminium in different crystal configurations are studied. The different kinds of chemical bonding between aluminium and oxygen originate molecular orbitals with energy levels and transition probabilities varying from one compound to another. This effect appears as shifts and changes in relative intensities of K{alpha} emission lines and as modifications of the K{beta} characteristic spectrum. In the present work, the aluminium K characteristic spectra obtained by means of an electron microprobe with a wavelength dispersive system are compared for topaz, albite, spodumene, biotite and corundum.

  18. All-Union Conference on the Stepanov Growth of Crystals and Shapes and Their Application in the National Economy, Leningrad, USSR, March 4-6, 1985, Proceedings

    Science.gov (United States)

    Antonov, P. I.

    1985-12-01

    The papers presented in this volume provide an overview of the results of recent theoretical and experimental research in the field of profiled crystal growth from the melt using the Stepanov method. Topics discussed include the Stepanov growth of large germanium single crystals, carbide formation during the Stepanov growth of silicon ribbons, electron properties of gadolinium-alloyed profiled silicon crystals, and the stability of silicon crystal growth on a fabric substrate. Papers are also presented on plastic flow in the surface layers of profiled corundum during diffusion welding, the production fo profiled lithium niobate crystals with a regular domain structure, and profile crystals for optical uses.

  19. Studies on the Structure and Properties of Multiphase Al2O3 Abrasion-resistant Ceramics

    Institute of Scientific and Technical Information of China (English)

    WU Ren-Ping; YU Yan; RUAN Yu-Zhong

    2006-01-01

    The Al2O3 abrasion-resistant ceramics is successfully prepared by using waste aluminum sludge as the main raw material with the addition of a little clay, talc and barium carbonate. The crystal structure and microstructure of ceramic are characterized by means of XRD,SEM, etc., and the physical and mechanical properties are also tested. The results show that besides the phase of corundum, a little mullite, Mg-Al spinel and hyalophane phases also exist in the product. These phases are produced via reaction in-situ, which can inhibit the overgrowth of Al2O3grain in grain boundary, and improve the integral property of the material.

  20. Scientific basis for creation of construction materials based on titanium and alumina minerals

    Science.gov (United States)

    Kotova, O.; Shmakova, A.; Ponaryadov, A.

    2017-02-01

    Currently there is a need in affordable and accessible materials with specific physical and chemical properties. Al- and Ti-minerals are excellent test objects for correlation between structure and physical properties of mineral. For example, corundum and ilmenite are related to the same structural type (rhombohedral lattice R3) and possess various physical properties. With the help of modern equipment we studied titanium- and aluminum-containing concentrates of natural raw and also products of various kinds of influences on them, which showed signs of nanostructuring. We observed methods of directional change of physical and chemical characteristics of Al- and Ti-minerals and creation of new commercial products.

  1. Occurrence of wagnerite in Mg–Al granulites of Sonapahar, Meghalaya

    Indian Academy of Sciences (India)

    S B Dwivedi; K Theunuo

    2017-06-01

    We report for the first time the occurrence of rare phosphate wagnerite as a stable phase from the Mg–Al granulites of Sonapahar. The wagnerite bearing assemblages consist of the spinel, phlogopite, brucite and corundum. The wagnerite appears in the Mg–Al granulites due to the break-down of spinel and fluorapatite. The mineral chemistry of the phases has been discussed from the EPMA data, which reveals that the fluorine content of the wagnerite is relatively low due to the exchange of F to coexisting phases. The major oxide analysis of the rocks show the low content of Ca, which is the requisite for the occurrences of wagnerite.

  2. Formation of a 25 mol% Fe2O3-Al2O3 solid solution prepared by ball milling

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Mørup, Steen; Linderoth, Søren

    1996-01-01

    The phase transformation process of a 25 mol% Fe2O3-Al2O3 powder mixture during high-energy ball milling has been studied by x-ray diffraction and Mossbauer spectroscopy. A metastable solid solution of 25 mol % Fe2O3 in Al2O3 with corundum structure has successfully been prepared after a milling...... time of 122 h. This demonstrates that the high-energy ball milling technique is able to prepare metastable solid solutions with an extended range of compositions in ceramic/ceramic systems with a positive hear of mixing....

  3. Effect of Silica on High-Temperature Interfacial Phenomena of Monolithic Refractories with Al Alloy

    Science.gov (United States)

    Koshy, Pramod; Gupta, Sushil; Sahajwalla, Veena; Edwards, Phil

    2008-04-01

    An experimental study was conducted to study the interfacial phenomena between monolithic refractories and Al alloy at 1250 °C. Dynamic contact angles of monolithic substrates with varying silica levels were measured using the sessile drop technique, while phases present in the preheated monolithic samples and interfacial reaction products were characterized using X-ray diffraction (XRD) and an electron probe microanalyzer (EPMA). The contact angles in the Al alloy/silica system were found to change much more rapidly as compared to that of the alloy/alumina system, clearly demonstrating the high wetting tendency of silica. Under the tested conditions, the corundum phase forms at the interface while Mg was found to vaporize from the alloy and accumulate at the bottom of the monolithic substrate. Both these phenomena are shown to influence the intensity of contact angle variations with time and, thereby, the wetting behavior of monolithic substrates. Based on dynamic contact angles and equilibrium calculations, monolithic refractories are further classified into three groups, such that the wetting characteristics of those with compositions in the ranges of 0 to 25 pct, 25 to 45 pct, and >45 pct silica were shown to be dictated by the presence of corundum, mullite, and free silica, respectively, as the predominant phase.

  4. The influence of composition, cooling rate and atmosphere on the synthesis and thermal stability of aluminum titanate

    Energy Technology Data Exchange (ETDEWEB)

    Naghizadeh, R. [Department of Metallurgical and Materials Engineering, Iran University of Science and Technology (IUST), Tehran (Iran, Islamic Republic of)], E-mail: rnaghizadeh@iust.ac.ir; Rezaie, H.R.; Golestani-fard, F. [Department of Metallurgical and Materials Engineering, Iran University of Science and Technology (IUST), Tehran (Iran, Islamic Republic of)

    2009-02-15

    The formation and stability of tialite (Al{sub 2}TiO{sub 5}) have been studied in equimolar of Al{sub 2}O{sub 3}-TiO{sub 2} (AT) in specimen, mixtures with excess of alumina or rutile and specimen AT with graphite addition. After firing the specimens at 1400 deg. C/3 h in different atmospheres, they were cooled with two routs, slow cooling in the furnace, and special fast cooling. X-ray diffraction of powders showed that in oxidation atmosphere, tialite formed and some of corundum and/or rutile remained. In reduction conditions at slow cooling rate in equimolar and nonequimolar Al{sub 2}O{sub 3}-TiO{sub 2} samples tialite was observed along with corundum, rutile and titanium suboxides but in graphite content specimens tialite was not detected. In fast cooling at AT sample tialite was present but in excess alumina or TiO{sub 2} contents and graphite addition specimens tialite was not present. The mechanism of instability of tialite in reducing condition without annealing process was investigated and microstructures of samples were observed. Results showed that in this condition due to transformation of rutile to titanium suboxides, tialite formation severely decreased and/or established at firing temperature during cooling at 1280-700 deg. C and intensively decomposed to parent oxides or high alumina and titania phases.

  5. In vitro and in vivo evaluation of SLA titanium surfaces with further alkali or hydrogen peroxide and heat treatment.

    Science.gov (United States)

    Zhang, E W; Wang, Y B; Shuai, K G; Gao, F; Bai, Y J; Cheng, Y; Xiong, X L; Zheng, Y F; Wei, S C

    2011-04-01

    The present study aimed to evaluate the bioactivity of titanium surfaces sandblasted with large-grit corundum and acid etched (SLA) plus further alkali or hydrogen peroxide and heat treatment for dental implant application. Pure titanium disks were mechanically polished as control surface (Ti-control) and then sandblasted with large-grit corundum and acid etched (SLA). Further chemical modifications were conducted using alkali and heat treatment (ASLA) and hydrogen peroxide and heat treatment (HSLA) alternatively. The surface properties were characterized by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and contact angle and roughness measurements. Further evaluation of surface bioactivity was conducted by MC3T3-E1 cell attachment, proliferation, morphology, alkaline phosphatase (ALP) activity and calcium deposition on the sample surfaces. After insertion in the beagle's mandibula for a specific period, cylindrical implant samples underwent micro-CT examination and then histological examination. It was found that ASLA and HSLA surfaces significantly increased the surface wettability and MC3T3-E1 cell attachment percentage, ALP activity and the quality of calcium deposition in comparison with simple SLA and Ti-control surfaces. Animal studies showed good osseointegration of ASLA and HSLA surfaces with host bone. In conclusion, ASLA and HSLA surfaces enhanced the bioactivity of the traditional SLA surface by integrating the advantages of surface topography, composition and wettability.

  6. Sand-blasting treatment as a way to improve the adhesion strength of hydroxyapatite coating on titanium implant

    Science.gov (United States)

    Grubova, I.; Priamushko, T.; Surmeneva, M.; Korneva, O.; Epple, M.; Prymak, O.; Surmenev, R.

    2017-05-01

    In the current study, the effect of corundum particle sizes (50 and 250-320 μm) used for sand-blasting on the structure, roughness, wettability, mechanical properties, and adhesion of radio frequency magnetron hydroxyapatite coating deposited on treated titanium substrate is studied. Morphology analysis revealed that pretreatment uniformly deforms the surface and induces the formation of pits, which size depends linearly on the grit size. The deposited coatings (Ca/P was in a range of 1.75-1.79) are homogeneous and repeat the relief of the substrate (mean roughness Ra is 1.9±0.1 (250-320 μm) and 0.8±0.1 μm (50 μm)). Texture coefficient calculations revealed the predominant (002) growth texture of hydroxyapatite coatings. The resistance of the coating to plastic deformation and the surface hardening were significantly higher for coatings formed on sand blasted with particle size of 50 μm. Scratch test have shown the significant improvement of wear resistance and lower friction coefficient of coatings for smoother samples. Dynamic contact angle measurements revealed the hydrophilic properties of the hydroxyapatite coating. Thus, sand-blasting of titanium with corundum powder having the size of 50 μm prior to the deposition of RF magnetron coating is recommended for the medical applications intended to improve the bonding between the substrate and coating.

  7. In vitro and in vivo evaluation of SLA titanium surfaces with further alkali or hydrogen peroxide and heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, E W; Wang, Y B; Zheng, Y F [State Key Laboratory for Turbulence and Complex System, Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871 (China); Shuai, K G; Gao, F; Bai, Y J; Cheng, Y; Xiong, X L [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Wei, S C, E-mail: enwei@pku.edu.cn, E-mail: yanbo.pku@pku.edu.cn, E-mail: shuaikegang@gmail.com, E-mail: soarfgoal@gmail.com, E-mail: norice86@163.com, E-mail: chengyan@pku.edu.cn, E-mail: xxiaoling11@hotmail.com, E-mail: yfzheng@pku.edu.cn, E-mail: weishicheng99@163.com [Department of Oral and Maxillofacial Surgery, School of Stomatology, Peking University, Beijing 100081 (China)

    2011-04-15

    The present study aimed to evaluate the bioactivity of titanium surfaces sandblasted with large-grit corundum and acid etched (SLA) plus further alkali or hydrogen peroxide and heat treatment for dental implant application. Pure titanium disks were mechanically polished as control surface (Ti-control) and then sandblasted with large-grit corundum and acid etched (SLA). Further chemical modifications were conducted using alkali and heat treatment (ASLA) and hydrogen peroxide and heat treatment (HSLA) alternatively. The surface properties were characterized by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and contact angle and roughness measurements. Further evaluation of surface bioactivity was conducted by MC3T3-E1 cell attachment, proliferation, morphology, alkaline phosphatase (ALP) activity and calcium deposition on the sample surfaces. After insertion in the beagle's mandibula for a specific period, cylindrical implant samples underwent micro-CT examination and then histological examination. It was found that ASLA and HSLA surfaces significantly increased the surface wettability and MC3T3-E1 cell attachment percentage, ALP activity and the quality of calcium deposition in comparison with simple SLA and Ti-control surfaces. Animal studies showed good osseointegration of ASLA and HSLA surfaces with host bone. In conclusion, ASLA and HSLA surfaces enhanced the bioactivity of the traditional SLA surface by integrating the advantages of surface topography, composition and wettability.

  8. High Temperature Properties and Microstructure of Boron Nitride—Zirconia/Corundum/Mullite Composites

    Institute of Scientific and Technical Information of China (English)

    ZHAOHailei; ZHONGXiangchong; 等

    1997-01-01

    The high temperature properties and mi-crostructure of boron nitride matrix with addi-tion of 10wt%-30wt% zirconia/corundum/mullite hot-pressing sintered have been studied. The results reveal that addition of zirconia/corundum/mullite to BN-based material results in enhanement of bending strength and frac-ture toughness that may be due to the dispersion strengthening and toughness effects caused by the dispersion of oxide particles in the interwo-ven structure of BN.Furthermore,when oxide addition does not exceed 20wt%,the composite still retains excellent thermal shock resistance characteristic of BN material.The 9Al2O3·2B2O3 formed during the sintering process cre-ate a pull-out effect when the material tends to fracture,which may be beneficial for improve-ment of mechanial properties.The oxidation kinetics model has been worked out,together with formula for activation energy and rate,Thermal fatigue life formula has been derived,and the activation energy for subcritical crack growth and the stress intensity exponent have been calculated.

  9. Fracture behavior and microstructure analysis of Al2O3-MgO-CaO castables for steel-ladle purging plugs

    Institute of Scientific and Technical Information of China (English)

    Bin Long; Gui-ying Xu; Yong Li; Andreas Buhr

    2016-01-01

    Three different castables based on the Al2O3–MgO–CaO system were prepared as steel-ladle purging plug refractories: corun-dum-based low-cement castable (C-LCC), corundum-spinel-based low-cement castable (C-S-LCC), and corundum-spinel no-cement casta-ble (C-S-NCC) (hydratable alumina (ρ-Al2O3) bonded). The fracture behavior at room temperature was tested by the method of “wedge-splitting” on samples pre-fired at different temperatures; the specific fracture energyG′f and notched tensile strengthσNT were ob-tained from these tests. In addition, the Young’s modulusE was measured by the method of resonance frequency of damping analysis (RFDA). The thermal stress resistance parameterR′′ calculated using the values ofG′f,σNT, andE was used to evaluate the thermal shock resistance of the materials. According to the microstructure analysis results, the sintering effect and the bonding type of the matrix material were different among these three castables, which explains their different fracture behaviors.

  10. Origin of sapphires from a lamprophyre dike at Yogo Gulch, Montana, USA: Clues from their melt inclusions

    Science.gov (United States)

    Palke, Aaron C.; Renfro, Nathan D.; Berg, Richard B.

    2016-09-01

    Gem corundum (sapphire) has been mined from an ultramafic lamprophyre dike at Yogo Gulch in central Montana for over 100 years. The sapphires bear signs of corrosion showing that they were not in equilibrium with the lamprophyre that transported them; however, their genesis is poorly understood. We report here the observation of minute glassy melt inclusions in Yogo sapphires. These inclusions are Na- and Ca-rich, Fe-, Mg-, and K-poor silicate glasses with compositions unlike that of the host lamprophyre. Larger, recrystallized melt inclusions contain analcime and calcite drawing a striking resemblance to leucocratic ocelli in the lamprophyre. We suggest here that sapphires formed through partial melting of Al-rich rocks, likely as the lamprophyre pooled at the base of the continental crust. This idea is corroborated by MELTS calculations on a kyanite-eclogite protolith which was presumably derived from a troctolite precursor. These calculations suggest that corundum can form through peritectic melting of kyanite. Linking the melt inclusions petrologically to the lamprophyre represents a significant advancement in our understanding of sapphire genesis and sheds light on how mantle-derived magmas may interact with the continental crust on their ascent to the surface.

  11. Effect of the directional crystallization on microstructure of Ti46Al-5Nb-1W

    Institute of Scientific and Technical Information of China (English)

    Vitezslav; Smishek; Miroslav; Kursa; G.S.; Burkhanov

    2005-01-01

    Ti-Al based intermetallic alloys are promising for various applications in aerospace and automobile industry. Their favorable properties, such as low density and good corrosion resistance, are accompanied on the other hand by low toughness and very difficult metallurgy. One of the possibilities to improve the toughness of Ti-46Al-5Nb-1W (%, at. fraction) alloy consists in change of their microstructure into lamellar microstructure, which can be reached moreover by directional crystallization. This experiment is described in this paper. Samples of the Ti-46Al-5Nb-1W (%, at. fraction) alloy prepared by plasma and vacuum-induction metallurgy were subjected to directional crystallization. Cooling rates were constant and ranged from 5.56 × 10-6 m/s to 1.18 × 10 -4 m/s. Directional crystallization has been accomplished in ceramic tubes made of corundum-Al2O3. The samples were studied by metallographic and chemical analysis.Lamellar microstructure of the samples was found to consist of α2- and γ-phase lamellas. Moreover, ceramic particles Al2O3 were found to be present in the samples. Distribution of the alloying elements in the samples was homogenous.

  12. Effect of impurity on high pressure behavior of nano indium titanate

    Energy Technology Data Exchange (ETDEWEB)

    Chitnis, Abhishek, E-mail: abhishekchitnis87@gmail.com; Garg, Nandini; Mishra, A. K.; Pandey, K. K.; Sharma, Surinder M. [High Pressure & Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai– 400085 (India); Singhal, Anshu [Chemistry Division, Bhabha Atomic Research Centre, Mumbai –400085 (India)

    2015-06-24

    Angle dispersive x-ray diffraction studies were carried out on a mixture of nano particles of indium titanate, indium oxide, and disordered TiO{sub 2} upto pressures of ∼ 45 GPa. Our studies show that indium titanate undergoes a partial decomposition to its constituent high pressure oxides. However, concomitantly a very small fraction of indium titanate transforms to a denser phase at ∼ 27.5 GPa. This transformation to new phase was found to be irreversible. At this pressure even cubic In{sub 2}O{sub 3} transformed to the In{sub 2}O{sub 3} (II) (iso-structural to Rh{sub 2}O{sub 3} (II)) phase, without any signature of the intermediate corundum phase. The high pressure In{sub 2}O{sub 3} (II) phase transforms to the corundum structure on release of pressure. These studies indicate that the presence of a large fraction of seed impurities could have facilitated the decomposition of indium titanate into its constituent oxides at the cost of its incomplete transformation to the high pressure denser phase.

  13. Tu-U-Pb{sub T} ages of monazite and geothermobarometry of high level metapelitic rocks in the orogenic system Itabuna-Salvador-Curaca, state of Bahia, Brazil: a study in electron microprobe; Idades Th-U-Pb{sub T} de monazita e geotermobarometria de rochas metapeliticas de alto grau do sistema orogenico Itabuna-Salvador-Curaca, BA, Brasil: um estudo em microsonda eletronica

    Energy Technology Data Exchange (ETDEWEB)

    Vlach, Silvio Roberto Farias; Lama, Eliane Aparecida del [Sao Paulo Univ., SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica

    2002-12-15

    Electron microprobe Th-U-Pb T dating of monazite was performed on aluminous gneiss samples from the northern Jacurici and southern Ilheus areas of the Itabuna-Salvador-Curuca Orogenic System. Studied samples are spinel-sillimanite-cordierite-garnet gneiss and corundum-spinel-sillimanite-garnet gneiss that equilibrated during a high temperature metamorphism at T-P conditions of about 835 deg C/6,9 kbar and 890 deg C/7.4 kbar, respectively. Microprobe ages of monazite in equilibrium with these mineral associations are interpreted as true crystallization ages and date granulite facies metamorphism. Both samples gave ages of about 2.07 and 2.08 (+-0.02) Ga, in agreement with the known geochronological pattern in this system. The Ilheus sample contain a younger, contrasting monazite generation (e.g., with distinct REE patterns and Th/Gd ratios), dated at ca. 1.97 (+-0.04) Ga. Based on the occurrence of the corundum-sillimanite-quartz association in the sample and information from the literature, we suggest that this age may be related to a regional decompression event and/or a thermal overprint due to late intrusive magmatism (1.9 - 2.0 Ga) in the orogenic system. (author)

  14. The effect of soil mineral phases on the abiotic degradation of selected organic compounds. Final report, June 31, 1990--December 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Sandhu, S.S.

    1994-12-31

    Funds were received from the United States Department of Energy to study the effects of soil mineral phases on the rates of abiotic degradation of tetraphenylborate (TPB) and diphenylboronic acid (DPBA). In addition to kaolinite and montmorillonite clay minerals, the role of goethite, corundum, manganite, and rutile in the degradation of organoborates was also evaluated. The effects of DPBA, argon, molecular dioxygen (O{sub 2}), temperature, and organic matter on the degradation of organoborates were also measured. The results indicated that TPB and DPBA degraded rapidly on the mineral surfaces. The initial products generated from the degradation of TPB were DPBA and biphenyl; however, further degradation resulted in the formation of phenylboric acid and phenol which persisted even after TPB disappeared. The data also showed that the rate of TPB degradation was faster in kaolinite, a 1:1 clay mineral, than in montmorillonite, a double layer mineral. The initial degradation of TPB by corundum was much higher than goethite, manganite and rutile. However, no further degradation by this mineral was observed where as the degradation of TPB continued by goethite and rutile minerals. Over all, the degradation rate of TPB was the highest for goethite as compared to the other metal oxide minerals. The degradation of TPB and DPBA was a redox reaction where metals (Fe, Al, Ti, Mn) acted as Lewis acids. DPBA and argon retarded the TPB degradation where as molecular oxygen organic matter and temperature increased the rate of TPB disappearance.

  15. On the abrasion of heat-treated 2.8C21Cr1Mo white cast iron

    Energy Technology Data Exchange (ETDEWEB)

    Al-Rubaie, Kassim S.; Preti, Orlando [Centro Universitario SOCIESC, Joinville (Brazil). Engenharia Mecanica; Pohl, Michael [Bochum Univ. (Germany). Inst. fuer Werkstoffe

    2016-09-15

    The abrasion behaviour of heat-treated 2.8C21Cr1Mo cast iron was studied. The specimens were destabilised at two temperatures, 980 and 1050 C, for 4 h, air hardened, and then tempered at five temperatures, 220, 320, 400, 500, and 620 C, for 2 h followed by air cooling. Using a pin-on-plate abrasion apparatus, the specimens were abraded on four types of bonded abrasives (silicon carbide, corundum, flint, and glass). The effect of work hardening on the abrasion resistance was investigated. It was found that the increase in alloy hardness produced by heat treatment had little effect on the abrasion resistance against silicon carbide or corundum; the inverse was true against flint or glass. The as-hardened structure containing 40% retained austenite gave the best abrasion resistance, whereas the hardened and tempered at 620 C showed the worst. Both bulk hardness and matrix hardness before wear correlated poorly with the abrasion resistance. Therefore, a general model ''equivalent hardness'' was developed, in which the hardness of the abraded matrix was considered. With this model, the abrasion behaviour can be clearly analysed.

  16. Vanadium-rich ruby and sapphire within Mogok Gemfield, Myanmar: implications for gem color and genesis

    Science.gov (United States)

    Zaw, Khin; Sutherland, Lin; Yui, Tzen-Fu; Meffre, Sebastien; Thu, Kyaw

    2015-01-01

    Rubies and sapphires are of both scientific and commercial interest. These gemstones are corundum colored by transition elements within the alumina crystal lattice: Cr3+ yields red in ruby and Fe2+, Fe3+, and Ti4+ ionic interactions color sapphires. A minor ion, V3+ induces slate to purple colors and color change in some sapphires, but its role in coloring rubies remains enigmatic. Trace element and oxygen isotope composition provide genetic signatures for natural corundum and assist geographic typing. Here, we show that V can dominate chromophore contents in Mogok ruby suites. This raises implications for their color quality, enhancement treatments, geographic origin, exploration and exploitation and their comparison with rubies elsewhere. Precise LA-ICP-MS analysis of ruby and sapphire from Mogok placer and in situ deposits reveal that V can exceed 5,000 ppm, giving V/Cr, V/Fe and V/Ti ratios up to 26, 78, and 97 respectively. Such values significantly exceed those found elsewhere suggesting a localized geological control on V-rich ruby distribution. Our results demonstrate that detailed geochemical studies of ruby suites reveal that V is a potential ruby tracer, encourage comparisons of V/Cr-variation between ruby suites and widen the scope for geographic typing and genesis of ruby. This will allow more precise comparison of Asian and other ruby fields and assist confirmation of Mogok sources for rubies in historical and contemporary gems and jewelry.

  17. NQR Studies of Atomic Arrangements and Chemical Bonding in Glasses

    Science.gov (United States)

    Lee, Donghoon; Gravina, S. J.; Bray, P. J.

    1990-04-01

    A very high sensitivity continuous wave NQR spectrometer was developed to detect pure NQR transitions at low frequencies (down to 200 kHz). A signal-to-noise ratio of more than 100 to 1 has been achieved at about 1.36 MHz for crystalline B 2 0 3 . Two large n B responses have been found in vitreous B 2 0 3 (NMR detected only one site) with linewidths of less than 30 kHz. 27 A1 NQR spectra were obtained for OC-A1203 (Corundum), the mineral andalusite (a form of A1203 • Si0 2), and a glass having the composition of anorthite (CaO • A1203 • 2Si0 2). A very high sensitivity continuous wave NQR spectrometer was developed to detect pure NQR transitions at low frequencies (down to 200 kHz). A signal-to-noise ratio of more than 100 to 1 has been achieved at about 1.36 MHz for crystalline B2O3 . Two large 11 B responses have been found in vitreous B2O3 (NMR detected only one site) with linewidths of less than 30 kHz. 27Al NQR spectra were obtained for α- Al2O3 (Corundum), the mineral andalusite (a form of Al2O3 · SiO2), and a glass having the composition of anorthite (CaO · Al2O3 ·2SiO2).

  18. Marble-hosted ruby deposits of the Morogoro Region, Tanzania

    Science.gov (United States)

    Balmer, Walter A.; Hauzenberger, Christoph A.; Fritz, Harald; Sutthirat, Chakkaphan

    2017-10-01

    The ruby deposits of the Uluguru and Mahenge Mts, Morogoro Region, are related to marbles which represent the cover sequence of the Eastern Granulites in Tanzania. In both localities the cover sequences define a tectonic unit which is present as a nappe structure thrusted onto the gneissic basement in a north-western direction. Based on structural geological observations the ruby deposits are bound to mica-rich boudins in fold hinges where fluids interacted with the marble-host rock in zones of higher permeability. Petrographic observations revealed that the Uluguru Mts deposits occur within calcite-dominated marbles whereas deposits in the Mahenge Mts are found in dolomite-dominated marbles. The mineral assemblage describing the marble-hosted ruby deposit in the Uluguru Mts is characterised by corundum-dolomite-phlogopite ± spinel, calcite, pargasite, scapolite, plagioclase, margarite, chlorite, tourmaline whereas the assemblage corundum-calcite-plagioclase-phlogopite ± dolomite, pargasite, sapphirine, titanite, tourmaline is present in samples from the Mahenge Mts. Although slightly different in mineral assemblage it was possible to draw a similar ruby formation history for both localities. Two ruby forming events were distinguished by textural differences, which could also be modeled by thermodynamic T-XCO2 calculations using non-ideal mixing models of essential minerals. A first formation of ruby appears to have taken place during the prograde path (M1) either by the breakdown of diaspore which was present in the original sedimentary precursor rock or by the breakdown of margarite to corundum and plagioclase. The conditions for M1 metamorphism was estimated at ∼750 °C at 10 kbar, which represents granulite facies conditions. A change in fluid composition towards a CO2 dominated fluid triggered a second ruby generation to form. Subsequently, the examined units underwent a late greenschist facies overprint. In the framework of the East African Orogen we

  19. Garnet-bearing ultramafic rocks from the Dominican Republic: Fossil mantle plume fragments in an ultra high pressure oceanic complex?

    Science.gov (United States)

    Gazel, Esteban; Abbott, Richard N.; Draper, Grenville

    2011-07-01

    Ultra high pressure (UHP) garnet-bearing ultramafic rocks from the Dominican Republic may represent the only known example where such rocks were exhumed at an ocean-ocean convergent plate boundary, and where the protolith crystallized from a UHP magma (> 3.2 GPa, > 1500 °C). This study focuses on the petrology and geochemistry of one of the ultramafic lithologies, the pegmatitic garnet-clinopyroxenite (garnet + clinopyroxene + spinel + corundum + hornblende). Three distinct types of garnet were recognized: Type-1 garnet (low Ca, high Mg) is interpreted as near magmatic (P > 3.2 GPa, > 1500 °C). Type-1‧ garnet (high Ca, low Mg) is interpreted as having formed approximately isochemically from magmatic high-Al clinopyroxene. Type-2 garnet (intermediate Ca, high Mg, and low Fe + Mn) formed together with hornblende as a result of late, low-pressure retrograde hydration. Clinopyroxene is close to diopside-hedenbergite (Mg# ~ 88) and metasomatized by arc-related fluids. Spinel and corundum occur as microinclusions in type-1 and type-1‧ garnets in the only reported natural occurrence of coexisting garnet + spinel + corundum, indicative of very high pressure. Chondrite-normalized REEs (rare earth elements) of the garnets show humped or weakly sinusoidal patterns, typically associated with garnet inclusions in diamond and garnet in kimberlite that crystallized at UHP conditions. These humped to weakly sinusoidal REE patterns developed as the result of interaction with a light REE-enriched metasomatic fluid. Partitioning of REEs between type-1‧ and type-1 garnets is consistent with the former having inherited its REEs from a high-Al clinopyroxene predecessor. The partitioning preserves a record of near-solidus temperatures (~ 1475 °C). Petrology and phase relationships independently suggest near-solidus conditions > 1500 °C (the highest temperature conditions reported in a UHP orogenic setting), providing evidence for an origin in a mantle plume. Therefore, the

  20. Measuring the temperature dependent thermal diffusivity of geomaterials using high-speed differential scanning calorimetry

    Science.gov (United States)

    von Aulock, Felix W.; Wadsworth, Fabian B.; Vasseur, Jeremie; Lavallée, Yan

    2016-04-01

    Heat diffusion in the Earth's crust is critical to fundamental geological processes, such as the cooling of magma, heat dissipation during and following transient heating events (e.g. during frictional heating along faults), and to the timescales of contact metamorphosis. The complex composition and multiphase nature of geomaterials prohibits the accurate modeling of thermal diffusivities and measurements over a range of temperatures are sparse due to the specialized nature of the equipment and lack of instrument availability. We present a novel method to measure the thermal diffusivity of geomaterials such as minerals and rocks with high precision and accuracy using a commercially available differential scanning calorimeter (DSC). A DSC 404 F1 Pegasus® equipped with a Netzsch high-speed furnace was used to apply a step-heating program to corundum single crystal standards of varying thicknesses. The standards were cylindrical discs of 0.25-1 mm thickness with 5.2-6 mm diameter. Heating between each 50 °C temperature interval was conducted at a rate of 100 °C/min over the temperature range 150-1050 °C. Such large heating rates induces temperature disequilibrium in the samples used. However, isothermal segments of 2 minutes were used during which the temperature variably equilibrated with the furnace between the heating segments and thus the directly-measured heat-flow relaxed to a constant value before the next heating step was applied. A finite-difference 2D conductive heat transfer model was used in cylindrical geometry for which the measured furnace temperature was directly applied as the boundary condition on the sample-cylinder surfaces. The model temperature was averaged over the sample volume per unit time and converted to heat-flow using the well constrained thermal properties for corundum single crystals. By adjusting the thermal diffusivity in the model solution and comparing the resultant heat-flow with the measured values, we obtain a model

  1. Metastable Phase Relations in the System Ca(sub O)-Al2(sub O)3-MgO-TiO(sub 2): Applications to Ca- And Al-Rich Inclusions

    Science.gov (United States)

    Keller, L. P.; Han, J.

    2017-01-01

    Introduction: High temperature phases such as corundum, hibonite, grossite, and perovskite are among the earliest phases that condensed in the early solar nebula. Recent work has shown that defect-structured phases occur in some ultrarefractory inclusions as metastable, possibly more kinetically-favored alternatives to the thermodynamically predicted stable phase assemblages [1-4]. For example, Han et al. have shown that non-stoichiometry in hibonite is accommodated by extra "spinel" blocks in the structure instead of the equilibrium assemblages hibonite+corundum or hibonite+spinel. To explore these relations, we have conducted a series of experiments in the system CaO-Al2O3- MgO-TiO2. Here we discuss the compositions and mineralogy of the experimental samples and how they relate to phases in refractory inclusions with a focus on perovskite and spinel. Methods: For the series of annealing studies, a CaO-Al2O3 eutectic melt is allowed to react with a pure alumina crucible at 1,530degC for either 4 hours or 5 days, followed by quenching in air. Later experiments were similar except that additions of 5 wt% MgO, and CaTiO(sub 3) were used to explore the effect of minor elements on the phase assemblages. The experimental conditions resulted in reaction zones approximately 100-300 ?m wide consisting of a hibonite layer immediately adjacent to the corundum, followed by a grossite layer, and finally krotite with residual quenched melt. For the experiments with Mg, spinel is distributed in all layers but is mainly concentrated in the krotite layer. In the Ti-bearing experiments, perovskite precipitated in association with the krotite and residual melt. In addition to the experiments, we also analyzed perovskite grains in the FUN inclusion SHAL [5] and a large compact type A CAI from Allende. The experiments and refractory inclusions were analyzed using a JEOL 7600F SEM and quantitative analyses were obtained using the JEOL 8530F field-emission electron microprobe.

  2. In situ characterization of aluminum-containing mineral-microorganism aqueous suspensions using scanning transmission X-ray microscopy.

    Science.gov (United States)

    Yoon, Tae Hyun; Johnson, Stephen B; Benzerara, Karim; Doyle, Colin S; Tyliszczak, Tolek; Shuh, David K; Brown, Gordon E

    2004-11-23

    In situ characterization of colloidal particles under hydrous conditions is one of the key requirements for understanding their state of aggregation and impact on the transport of pollutants in aqueous environments. Scanning transmission X-ray microscopy (STXM) is one of the few techniques that can satisfy this need by providing element- and chemical-state-specific 2-D maps at a spatial resolution better than 50 nm using soft X-rays from synchrotron radiation wiggler or undulator sources tuned to the absorption edges of different elements. X-ray absorption near-edge structure (XANES) spectra can also be collected simultaneously at a similar spatial resolution and can provide phase identification in many cases. In this study, we report STXM images and XANES spectroscopy measurements at or above the Al K-edge (E = 1559.6 eV) of various Al-containing minerals and synthetic oxides [alpha-Al2O3 (corundum), gamma-Al2O3, gamma-AlOOH (boehmite), alpha-Al(OH)3 (bayerite), KAl2(AlSi3O10)(OH)2 (muscovite), (Al,Mg)8(Si4O10)4(OH)8.nH2O (montmorillonite), and Mg6Al2(OH)16CO3.4H2O (hydrotalcite)] and demonstrate the capability of this spectromicroscopic tool to identify different Al-containing mineral colloids in multiphase mixtures in aqueous solution. We also demonstrate that STXM imaging at or above the C K-edge (E = 284.2 eV) and Al K-edge can provide unique information on the interactions between bacteria and Al-containing nanoparticles in aqueous suspensions. STXM images of a mixture of Caulobacter crescentus and montmorillonite and corundum particles just above the C and Al K-edges show that the mineral particles and bacteria are closely associated in aggregates, which is likely due to the binding of bacteria to clay and corundum particles by extracellular polysaccharides.

  3. Tables of phase functions, opacities, albedos, equilibrium temperatures, and radiative accelerations of dust grains in exoplanets

    CERN Document Server

    Budaj, Jan; Salmeron, Raquel; Hubeny, Ivan

    2015-01-01

    There has been growing observational evidence for the presence of condensates in the atmospheres and/or comet-like tails of extrasolar planets. As a result, systematic and homogeneous tables of dust properties are useful in order to facilitate further observational and theoretical studies. In this paper we present calculations and analysis of non-isotropic phase functions, asymmetry parameter (mean cosine of the scattering angle), absorption and scattering opacities, single scattering albedos, equilibrium temperatures, and radiative accelerations of dust grains relevant for extrasolar planets. Our assumptions include spherical grain shape, Deirmendjian particle size distribution, and Mie theory. We consider several species: corundum/alumina, iron, olivines with 0% and 50% iron content, pyroxenes with 0%, 20% and 60% iron content, carbon at two different temperatures, water ice, liquid water, and ammonia. The presented tables cover the wavelength range of 0.2 to 500 micron and modal particle radii from 0.01 mi...

  4. Growth of ruby and sapphire crystals by the flux method; Crescimento de cristais de rubi e safira pelo metodo do fluxo

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Gislene da Silva [Universidade Federal de Mato Grosso (DRM/UFMT), Cuiaba, MT (Brazil). Dept. de Recuros Minerais; Prado, Rogerio Junqueira, E-mail: rjprado@ufmt.b [Universidade Federal de Mato Grosso (IF/UFMT), Cuiaba, MT (Brazil). Inst. de Fisica

    2010-07-01

    This work reports the growth of corundum crystals by the flux method. The main objective was the evaluation of versatility, effectiveness and real possibilities of the flux method to the synthesis and doping of monocrystals with impurities of particular interest. In this work the chosen impurities were 1) Cr and 2) Fe and Ti, aiming the synthesis of rubies and sapphires, respectively. The crystals were grown by heating a mixture of Al{sub 2}O{sub 3}:Cr or Al{sub 2}O{sub 3}:Fe:Ti and flux (MoO{sub 3}). The maximum crystal size obtained was 1.0 mm, all transparent, presenting well developed faces, bipyramidal hexagonal shape, and showing a typical red (ruby) and/or light blue (sapphire) color. EDX and XPD experiments were performed in order to characterize some of the synthesized crystals. All crystallized specimens presented the a-alumina atomic structure. (author)

  5. Sapphirine-bearing high pressure mafic granulite and its implications in the south Altyn Tagh

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jianxin; MENG Fancong

    2005-01-01

    Sapphirine-bearing high pressure mafic granulites are recognized in the Bashiwake area of the south Altyn Tagh. Mafic granulites and associated peridotites occur as lenses within kyanite-bearing high pressure felsic granulites. Sapphirine occurs as intergrowths with corundum, spinel and Ca-rich plagioclase in symplectite in between garnet and clinopyroxene. Reaction textures and mineral compositions indicate that sapphirine-bearing symplectites formed by reactions consuming kyanite, garnet and clinopyroxene. Therefore, both petrographic observations and the mineral compositions suggest that these quartz-free mafic granulites had an eclogite origin with an assemblage of garnet + clinopyroxene + kyanite, which is estimated to be stable at T = 1000℃ and P≥2.1 Gpa. The sapphirine-bearing symplectites are resulted from isothermal decompression or decompression with slight cooling during exhumation of the host rock.

  6. Influence of sand movement in the Sahara on the erosion of pipeline network

    Directory of Open Access Journals (Sweden)

    Azari Z.

    2010-06-01

    Full Text Available The influence of sandblasting on a surface notched of pipeline with API 5L X52 steel is studied. The purpose of this study is to determine the evolution of static characteristics and lifetime of material in both directions of pipeline (Longitudinal (L and Transverse (T. Specimens were taken from a pipeline and the material damage was made by projecting corundum particles (aluminium oxide. In order to justify the evolution of mechanical properties of material, residual stress analysis was realized by the technique of X-ray diffraction. The observation of damage mode and distribution of residual stress under the notch tip show that the material hardening, the notch radius and the compressive stress, play together an important role in stabilizing the material mechanical properties.

  7. A first principles investigation of electron transfer between Fe(II) and U(VI) on insulating Al- vs. semiconducting Fe-oxide surfaces via the proximity effect

    Science.gov (United States)

    Taylor, S. D.; Marcano, M. C.; Becker, U.

    2017-01-01

    This study investigates how the intrinsic chemical and electronic properties of mineral surfaces and their associated electron transfer (ET) pathways influence the reduction of U(VI) by surface-associated Fe(II). Density functional theory (DFT), including the Hubbard U correction to the exchange-correlation functional, was used to investigate sorption/redox reactions and ET mechanisms between Fe(II) and U(VI) coadsorbed on isostructural, periodic (0 0 1) surfaces of the insulator corundum (α-Al2O3) vs. the semiconductor hematite (α-Fe2O3). Furthermore, the coadsorbed Fe(II) and U(VI) ions are spatially separated from one another on the surfaces (⩾5.9 Å) to observe whether electronic-coupling through the semiconducting hematite surface facilitates ET between the adsorbates, a phenomenon known as the proximity effect. The calculations show that the different chemical and electronic properties between the isostructural corundum and hematite (0 0 1) surfaces lead to considerably different ET mechanisms between Fe(II) and U(VI). ET on the insulating corundum (0 0 1) surface is limited by the adsorbates' structural configuration. When Fe(II) and U(VI) are spatially separated and do not directly interact with one another (e.g. via an inner-sphere complex), U(VI) reduction by Fe(II) cannot occur as there is no physical pathway enabling ET between the adsorbates. In contrast to the insulating corundum (0 0 1) surface, the hematite (0 0 1) surface can potentially participate in ET reactions due to the high number of electron acceptor sites from the Fe d-states near the Fermi level at the hematite surface. The adsorption of Fe(II) also introduces d-states near the Fermi level as well as shifts unoccupied d-states of the Fe cations at the hematite surface to lower energies, making the surface more conductive. In turn, electronic coupling through the surface can link the spatially separated adsorbates to one another and provide distinct ET pathways for an electron from Fe

  8. Interlocked chiral/polar domain walls and large optical rotation in Ni3TeO6

    Directory of Open Access Journals (Sweden)

    Xueyun Wang

    2015-07-01

    Full Text Available Chirality, i.e., handedness, pervades much of modern science from elementary particles, DNA-based biology to molecular chemistry; however, most of the chirality-relevant materials have been based on complex molecules. Here, we report inorganic single-crystalline Ni3TeO6, forming in a corundum-related R3 structure with both chirality and polarity. These chiral Ni3TeO6 single crystals exhibit a large optical specific rotation (α—1355° dm−1 cm3 g−1. We demonstrate, for the first time, that in Ni3TeO6, chiral and polar domains form an intriguing domain pattern, resembling a radiation warning sign, which stems from interlocked chiral and polar domain walls through lowering of the wall energy.

  9. High pressure behavior of Cr2O3 to 62 GPa

    Science.gov (United States)

    Catalli, Krystle; Cynn, Hyunchae; Evans, William J.

    2012-02-01

    Corundum-structured oxides are of interest for a broad range of reasons, including their mineralogical occurrences and technological uses. The high pressure behavior of Cr2O3 is of particular interest due to the widespread use of ruby, (Al,Cr)2O3, as a pressure standard in diamond anvil cells experiments. Although there have been a number of high pressure studies on Cr2O3, discrepancies still exist among the different data sets. Here we present synchrotron X-ray diffraction data on the structure and compressional behavior of Cr2O3 to 62 GPa. Although no change in crystal structure is detected within the resolution of the measurements, a change in compressional behavior occurs near 30 GPa where Cr2O3 changes color from red to orange.

  10. Effect of chemical composition and alumina content on structure and properties of ceramic insulators

    Indian Academy of Sciences (India)

    Arman Sedghi; Nastaran Riahi-Noori; Naser Hamidnezhad; Mohammad Reza Salmani

    2014-04-01

    In the present work, six electrical porcelain compositions with different amount of alumina and silica have been prepared and fired in an industrial furnace at 1300°C. Density, porosity, bending strength and electrical strength were measured in the samples. In order to find a relationship between properties and sample microstructures, samples were analyzed by scanning electron microscope (SEM) and x-ray diffraction (XRD) techniques. The results showed that, with chemical composition of 53.5 wt.% SiO2 and 37.5 wt.% alumina, highest electrical strength of 21.97 kV/mm was achieved in fabricated electrical porcelains. Increasing amount of alumina up to 30 wt.% decreases quartz and cristobalite phases, but increases corundum phase 3 to 5 times. SEM observation revealed that dense particles and uniform distribution of long and thin needle shaped mullite are predominant in sample microstructures with highest electrical strength.

  11. Structural and electronic evolution of Cr[subscript 2]O[subscript 3] on compression to 55 GPa

    Energy Technology Data Exchange (ETDEWEB)

    Dera, Przemyslaw; Lavina, Barbara; Meng, Yue; Prakapenka, Vitali B. (UC); (CIW); (UNLV)

    2016-08-15

    Synchrotron single-crystal x-ray diffraction experiments have been performed on corundum-type Cr{sub 2}O{sub 3} up to a pressure of 55 GPa in Ne and He pressure transmitting media. Diffraction experiments were complemented by measurements of optical absorption spectra with single crystal samples up to 60 GPa. Results of the diffraction data analysis rule out the earlier reported monoclinic distortion at 15-30 GPa, but indicate evidence of two discontinuous transitions of electronic or magnetic nature, most likely associated with a change in magnetic ordering and charge transfer. The compression mechanism established from single crystal refinements indicates much smaller distortion of the Cr{sup 3+} coordination environment than was previously assumed.

  12. Testing of high temperature materials within HTR program in Czech Republic

    Directory of Open Access Journals (Sweden)

    Berka Jan

    2016-01-01

    Full Text Available Research institutes and also industrial companies in Czech Republic are involved in High Temperature Gas Cooled Reactor (HTGR program and activities related to the study of advanced materials and HTGR technologies. These activities are supported by EC (within international projects, e.g. FP7-ARCHER, ALLIANCE, GoFastR can be mentioned and also by Technology Agency of Czech Republic. Within these activities, degradation of metallic and ceramic materials in the high temperature helium atmosphere is investigated, and also new experimental facilities for material testing are built. As examples of tested materials, Alloy 800 H, ferritic steel P91, austenitic steel 316, Inconel 713 and 738 and corundum ceramics could be named. The selected results of exposure experiments in the high temperature helium environment are presented in this paper.

  13. Investigation of thermal processes during test operation of ingot mould with composite surface layer

    Directory of Open Access Journals (Sweden)

    J. Szajnar

    2008-08-01

    Full Text Available The paper presents a method of usable properties of surface layers improvement of grey cast iron EN-GJL-200 ingot mould, by put directly in founding process a composite surface layer on the basis of corundum Al2O3 and quartz sand SiO2. Technology of composite surface layer guarantee mainly increase in hardness and abrasive wear resistance of cast steel and cast iron castings on machine elements. This technology can be competition for generally applied welding technology (surfacing by welding and thermal spraying. The results of studies show, that is positive influence of composite surface layer with ceramic particles on increase in life of cast iron ingot moulds.

  14. Depth concentrations of deuterium ions implanted into some pure metals and alloys

    Science.gov (United States)

    Didyk, A. Yu.; Wiśniewski, R.; Kitowski, K.; Kulikauskas, V.; Wilczynska, T.; Hofman, A.; Shiryaev, A. A.; Zubavichus, Ya. V.

    2012-01-01

    Pure metals (Cu, Ti, Zr, V, Pd) and diluted Pd alloys (Pd-Ag, Pd-Pt, Pd-Ru, Pd-Rh) were implanted by 25-keV deuterium ions at fluences in the range (1.2-2.3) × 1022 m-2. The post-treatment depth distributions of deuterium ions were measured 10 days and three months after the implantation by using Elastic Recoil Detection Analysis (ERDA) and Rutherford Backscattering (RBS). Comparison of the obtained results allowed us to make conclusions about relative stability of deuterium and hydrogen gases in pure metals and diluted Pd alloys. Very high diffusion rates of implanted deuterium ions in V and Pd pure metals and Pd alloys were observed. Small-angle X-ray scattering revealed formation of nanosized defects in implanted corundum and titanium.

  15. Properties of the surface of ceramic formed under laser irradiation of Al2O3-TiO2 compacts

    Science.gov (United States)

    Márquez Aguilar, P. A.; Vlasova, M.; Escobar Martínez, A.; Tomila, T.; Stetsenko, V.

    2014-04-01

    The phase formation in the laser irradiation area from xAl2O3-yTiO2 compacts and the properties of the surface layer have been investigated by the XRD, IR, and SEM methods. Main phases precipitating from eutectic melt are tialite, corundum, and rutile. A high temperature on the surface of specimens leads to the development of dissociation processes of these compounds and molecules of the gaseous medium. As dissociation products fly apart and pass through different temperature zone, there are formed different metal oxides, metal hydroxides, and thermolysis products. When these different oxides are deposited on the surface of the ceramic, they form layers with different adhesion degrees.

  16. Petrography and origin of refractory inclusions from the Murray and Murchison C2 chondrites

    Science.gov (United States)

    Simon, S. B.; Grossman, L.; Hsu, A.

    1993-01-01

    By freeze-thaw disaggregation, we have recovered a total of 47 refractory inclusions. New discoveries include the following: a hibonite-pyroxene spherule from Murray; a CaAl4O7-bearing spherule from Murchison; and a Sc-fassaite-bearing ultrarefractory inclusion from Murchison. Freeze-thaw disaggregation, combined with density separation and hand-picking as described is a proven method for recovering rare objects from carbonaceous chondrites. This method is especially effective on C2's due to their porosity and typically results in the discovery of new types of refractory inclusions. Because few refractory inclusions from Murray have been described, we studied this meteorite, although only a small amount of material (730 mg) was available for disaggregation. Many refractory inclusions from Murchison have been described, and we disaggregated a larger amount (approximately 18 g) of Murchison in an attempt to find new types of refractory inclusions, especially corundum-bearing ones.

  17. TOM - Manufacture and modelling of a demonstration oxide module; TOM, Erstellen und Modellierung eines thermo-elektrischen oxidischen Moduls (TOM) als Demonstrator - Jahresbericht 2007

    Energy Technology Data Exchange (ETDEWEB)

    Tomes, P.; Weidenkaff, A.

    2007-07-01

    This annual report for the Swiss Federal Office of Energy (SFOE) takes a look at the work done at the Swiss Federal Laboratories for Materials Science and Technology EMPA in 2007 on demonstrating the thermoelectric effects of an oxide module. Four-leg oxide-based thermoelectric modules are described which have been produced by combining p and n-type oxide elements. The modules were assembled using a mixture of silver paste along with silver and copper oxide powders. Three types of thermoelectric oxide modules with different thermocouple leg-lengths were examined. In this type of module, p and n-type semiconductor thermocouples are connected electrically in series by highly conducting metal strips using silver with copper oxide and sandwiched between thermally conducting but electrically insulating plates made of corundum. The results obtained are presented in graphical form and discussed.

  18. Plasma boronizing of Ti6AlV4 using solid precursors by double glow plasma alloying technique

    Institute of Scientific and Technical Information of China (English)

    QIN Lin; QU Jun-zhi; LIN Nai-ming; FAN Ai-lan; CHANG Da-qing; TANG Bin

    2006-01-01

    Solid state B-offerings (FeB compound) were used for plasma-assisted boronizing on Ti6Al4V alloy by double glow discharge plasma alloying technique (DGPSA). During all experiment processing there was no harmful and toxic. The thickness and morphology, phase formation, elements concentrations and wear properties of boride layers were examined by means of optical microscopy, Vickers microhardness, X-ray diffraction, glow discharge optical emission spectroscopy and Ball-disk wear tests. The results show that friction coefficient of boride alloying samples versus corundum ball is lower than that of Ti6Al4V samples, as well as wear rate. This indicates that plasma-assisted boronizing of Ti6Al4V alloy has a high potential for industrial applications under tribological conditions.

  19. Interlocked chiral/polar domain walls and large optical rotation in Ni{sub 3}TeO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xueyun; Huang, Fei-Ting [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Yang, Junjie [Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Oh, Yoon Seok [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of); Cheong, Sang-Wook, E-mail: sangc@physics.rutgers.edu [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2015-07-01

    Chirality, i.e., handedness, pervades much of modern science from elementary particles, DNA-based biology to molecular chemistry; however, most of the chirality-relevant materials have been based on complex molecules. Here, we report inorganic single-crystalline Ni{sub 3}TeO{sub 6}, forming in a corundum-related R3 structure with both chirality and polarity. These chiral Ni{sub 3}TeO{sub 6} single crystals exhibit a large optical specific rotation (α)—1355° dm{sup −1} cm{sup 3} g{sup −1}. We demonstrate, for the first time, that in Ni{sub 3}TeO{sub 6}, chiral and polar domains form an intriguing domain pattern, resembling a radiation warning sign, which stems from interlocked chiral and polar domain walls through lowering of the wall energy.

  20. Effect of particle size and particle size distribution on physical characteristics, morphology and crystal structure of explosively compacted high-T(sub c) superconductors

    Science.gov (United States)

    Kotsis, I.; Enisz, M.; Oravetz, D.; Szalay, A.

    1995-01-01

    A superconductor, of composition Y(Ba,K,Na)2Cu3O(x)/F(y) and a composite of composition Y(Ba,K,Na)2Cu3O(x)/F(y) + Ag, with changing K, Na and F content but a constant silver content (Ag = 10 mass%) was prepared using a single heat treatment. the resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 micron, 0-63 micron and 63-900 micron and explosively compacted, using an explosive pressure of 10(exp 4) MPa and a subsequent heat treatment. Best results were obtained with the 63-900 micron fraction of composition Y(Ba(1.95) K(0.01)Cu3O(x)F(0),(05)/Ag: porosity less than 0.01 cu cm/g and current density 2800 A/sq cm at 77K.

  1. A density-functional theory approach to the existence and stability of molybdenum and tungsten sesquioxide polymorphs

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Nils; Dronskowski, Richard [RWTH Aachen Univ. (Germany). Inst. fuer Anorganische Chemie; RWTH Aachen Univ. (Germany). Juelich-Aachen Research Alliance; Reimann, Christoph; Bredow, Thomas [Bonn Univ. (Germany). Inst. fuer Physikalische und Theoretische Chemie; Weber, Dominik; Luedtke, Tobias; Lerch, Martin [Berlin Technische Univ. (Germany). Inst. fuer Chemie

    2017-03-01

    The sesquioxides of molybdenum and tungsten have been reported as thin films or on surfaces as early as 1971, but the preparation of bulk materials and their crystal structures are still unknown up to the present day. We present a systematic ab initio approach to their possible syntheses and crystal structures applying complementary methods and basis-set types. For both compounds, the corundum structure is the most stable and does not display any imaginary frequencies. Calculations targeted at a high-pressure synthesis starting from the stable oxides and metals predict a reaction pressure of 15 GPa for Mo{sub 2}O{sub 3} and over 60 GPa for W{sub 2}O{sub 3}.

  2. Finite-size scaling effect on Néel temperature of antiferromagnetic Cr2O3 (0001) films in exchange-coupled heterostructures

    Science.gov (United States)

    Pati, Satya Prakash; Al-Mahdawi, Muftah; Ye, Shujun; Shiokawa, Yohei; Nozaki, Tomohiro; Sahashi, Masashi

    2016-12-01

    The scaling of antiferromagnetic ordering temperature of corundum-type chromia films has been investigated. Néel temperature TN was determined from the effect of perpendicular exchange bias on the magnetization of a weakly-coupled adjacent ferromagnet. For a thick-film case, the validity of detection is confirmed by a susceptibility measurement. Detection of TN was possible down to 1-nm-thin chromia films. The scaling of ordering temperature with thickness was studied using different buffering materials and compared with Monte-Carlo simulations. The spin-correlation length and the corresponding critical exponent were estimated, and they were consistent between experimental and simulation results. The spin-correlation length is an order of magnitude less than cubic antiferromagnets. We propose that the difference is from the change of number of exchange-coupling links in the two crystal systems.

  3. The analysis of thermal stability of detonation nanodiamond

    Science.gov (United States)

    Efremov, V. P.; Zakatilova, E. I.

    2016-11-01

    The detonation nanodiamond is a new perspective material. Ammunition recycling with use of high explosives and obtaining nanodiamond as the result of the detonation synthesis have given a new motivation for searching of their application areas. In this work nanodiamond powder has been investigated by the method of synchronous thermal analysis. Experiments have been carried out at atmospheric pressure in the environment of argon. Nanodiamond powder has been heated in the closed corundum crucible at the temperature range of 30-1500 °C. The heating rates were varied from 2 K/min to 20 K/min. After the heat treatment, the samples have been studied by the x-ray diffraction and the electron microscopy. As one of the results of this work, it has been found that the detonation nanodiamond has not started the transition into graphite at the temperature below 800 °C.

  4. Crescimento de cristais de rubi e safira pelo método do fluxo Growth of ruby and sapphire crystals by the flux method

    Directory of Open Access Journals (Sweden)

    Gislene da Silva Ribeiro

    2010-01-01

    Full Text Available This work reports the growth of corundum crystals by the flux method. The main objective was the evaluation of versatility, effectiveness and real possibilities of the flux method to the synthesis and doping of monocrystals with impurities of particular interest. In this work the chosen impurities were i Cr and ii Fe and Ti, aiming the synthesis of rubies and sapphires, respectively. The crystals were grown by heating a mixture of Al2O3:Cr or Al2O3:Fe:Ti and flux (MoO3. The maximum crystal size obtained was 1.0 mm, all transparent, presenting well developed faces, bipiramidal hexagonal shape, and showing a typical red (ruby and/or light blue (sapphire color. EDX and XPD experiments were performed in order to characterize some of the synthesized crystals. All crystallized specimens presented the α-alumina atomic structure.

  5. Nanotwin hardening in a cubic chromium oxide thin film

    Directory of Open Access Journals (Sweden)

    Kazuma Suzuki

    2015-09-01

    Full Text Available NaCl-type (B1 chromium oxide (CrO has been expected to have a high hardness value and does not exist as an equilibrium phase. We report a B1-based Cr0.67O thin film with a thickness of 144 nm prepared by pulsed laser deposition as an epitaxial thin film on a MgO single crystal. The thin film contained a number of stacking faults and had a nanotwinned structure composed of B1 with disordered vacancies and corundum structures. The Cr0.67O thin film had a high indentation hardness value of 44 GPa, making it the hardest oxide thin film reported to date.

  6. 高温压电材料的概况及发展趋势%Development of high Tc piezoelectric ceramics

    Institute of Scientific and Technical Information of China (English)

    石维; 冉耀宗; 左江红; 王强; 陶涛; 欧永康

    2011-01-01

    介绍了高温压电材料的研究现状,综述了钙钛矿、钨青铜型、铋层状、碱金属铌酸盐结构体系4种不同压电陶瓷的结构及研究情况,并指出了高居里点压电陶瓷的研究方向和发展趋势。%This paper reviewed the high Curie temperature piezoelectric materials, including tungsten bronze, bismuth layer structured, Perovskite types piezoelectric ceramics and corundum structure ceramics. The research studies on the development of four different structure types high curies piezoelectric ceramics were also reviewed. In addition, the research direction and piezoelectric ceramic development trend were discussed.

  7. Ruby and sapphire from Jegdalek, Afghanistan

    Science.gov (United States)

    Bowersox, G.W.; Foord, E.E.; Laurs, B.M.; Shigley, J.E.; Smith, C.P.

    2000-01-01

    This study provides detailed mining and gemological information on the Jegdalek deposit, in east-central Afghanistan, which is hosted by elongate beds of corundum-bearing marble. Some facet-grade ruby has been recovered, but most of the material consists of semitransparent pink sapphire of cabochon or carving quality. The most common internal features are dense concentrations of healed and nonhealed fracture planes and lamellar twin planes. Color zoning is common, and calcite, apatite, zircon, mica, iron sulfide minerals, graphite, rutile, aluminum hydroxide, and other minerals are also present in some samples. Although the reserves appear to be large, future potential will depend on the establishment of a stable government and the introduction of modern mining and exploration techniques. ?? 2000 Gemological Institute of America.

  8. Concept of a utility scale dispatch able solar thermal electricity plant with an indirect particle receiver in a single tower layout

    Science.gov (United States)

    Schwaiger, Karl; Haider, Markus; Haemmerle, Martin; Steiner, Peter; Obermaier, Michael-Dario

    2016-05-01

    Flexible dispatch able solar thermal electricity plants applying state of the art power cycles have the potential of playing a vital role in modern electricity systems and even participating in the ancillary market. By replacing molten salt via particles, operation temperatures can be increased and plant efficiencies of over 45 % can be reached. In this work the concept for a utility scale plant using corundum as storage/heat transfer material is thermodynamically modeled and its key performance data are cited. A novel indirect fluidized bed particle receiver concept is presented, profiting from a near black body behavior being able to heat up large particle flows by realizing temperature cycles over 500°C. Specialized fluidized bed steam-generators are applied with negligible auxiliary power demand. The performance of the key components is discussed and a rough sketch of the plant is provided.

  9. Synthesis, characterizations, antibacterial and photoluminescence studies of solution combustion-derived α-Al2O3 nanoparticles

    Directory of Open Access Journals (Sweden)

    P.A. Prashanth

    2015-09-01

    Full Text Available In this work, we report a novel, economical, low temperature solution combustion synthesis (SCS method to prepare α-Al2O3 (Corundum nanoparticles. Powder X-ray diffraction (PXRD, field emission scanning electron microscopy (FE-SEM, high-resolution transmission electron microscopy (HR-TEM, Fourier transform infrared spectroscopy (FT-IR, BET surface area and ultraviolet visible spectroscopy (UV–vis measurements were used to characterize the product. Antibacterial studies were examined against gram −ve Klebsiella aerogenes, Escherichia coli, Pseudomonas desmolyticum and gram +ve Staphylococcus aureus bacteria by agar well diffusion method. The α-Al2O3 nanoparticles showed substantial effect on all the four bacterial strains. Photoluminescence (PL measurements under excitation at about 255 nm show that the alumina nanoparticles have emission peaks at 394 and 392 nm.

  10. Heat-Resistant Ceramic Pigments on the Base of Waste Vanadium Catalyst and Alumina

    Directory of Open Access Journals (Sweden)

    M. B. Sedelnikova

    2013-01-01

    Full Text Available Ceramic pigments on the base of technogenic silica-containing material—waste vanadium catalyst were obtained in this work. Corundum is identified along with the predominant mullite phase in the composition of pigments. The ions of nickel, chromium, and iron are embedded in the structure if the concentration of the corresponding oxide in the initial mixture does not exceed 10 wt.%. In this case, the oxide is not identified in a free form according to the results of X-ray diffraction analysis. Spinel CoAl2O4 is formed in cobalt pigments. The developed pigments keep the firing temperature up to 1200°C. The obtained pigments may be recommended for ceramic paints and colored glazes for building materials.

  11. Synthesis of indium tin oxide nanoparticles by a nonhydrolytic sol-gel method

    Directory of Open Access Journals (Sweden)

    Gabriel M. Silva

    2012-01-01

    Full Text Available Indium tin oxide nanoparticles were synthesized in two different sizes by a nonhydrolytic sol-gel method. These powders were then transformed into ITO via an intermediate metastable state at between 300 and 600 ºC. The presence of characteristic O-In-O and O-Sn-O bands at 480 and 670 cm-1 confirmed the formation of ITO. The X-ray diffraction patterns indicated the preferential formation of metastable hexagonal phase ITO (corundum type as opposed to cubic phase ITO when the reflux time was less than 3 h and the heat treatment temperature was below 600 ºC. Particle morphology and crystal size were examined by scanning electron microscopy.

  12. Some geochemical characteristics of alkaline rocks of the Mada Younger Granite complex, Nigeria

    Science.gov (United States)

    Abaa, S. I.

    Some geochemical aspects of the Mada Younger Granite complex are considered. The granites are petrologically classified as A-type, of long time duration, with chemical differences arising from the variation in the A/CNK ratio. The CPW norms show a decrease in anorthite and an increase in corundum in the granites associated with disseminated and vein type cassiterite mineralization. The KRb diagram shows that rocks of the Mada massif crystallized within a pegmatitic-hydrothermal trend. Some chondrite-normalized transition elements indicate that the rocks unaffected by fluid reaction were derived by fractional crystallization. The enhancement of some LIL elements, heavy rare-earths and a decrease in the magnitude of Eu depletion, particularly in the albitized variants of the granites, point to postmagmatic rock-fluid metasomatism and accompanying mineralization.

  13. Morphology of Near- and Semispherical Melted Chips after the Grinding Processes Using Sol-Gel Abrasives Based on SEM-Imaging and Analysis

    Directory of Open Access Journals (Sweden)

    W. Kapłonek

    2016-01-01

    Full Text Available Selected issues related to SEM-imaging and image analysis of spherical melted chips formed during the grinding process are presented and discussed. The general characteristics of this specific group of machining products are given. Chip formation phenomena, as well as their overall morphology, are presented using selected examples of near- and semispherical melted chips occurring singly or concentrated in clusters on the grinding wheel surface after the machining process. Observation of the spherical melted chips and acquisition of their images were carried out for grinding wheel active surfaces with microcrystalline sintered corundum abrasive grains SG™ after the internal cylindrical grinding process of a 100Cr6 steel and Titanium Grade 2® alloy by use of a scanning electron microscope, JEOL JSM-5500LV. Analysis of the obtained SEM micrographs was carried out by Image-Pro® Plus 5.0 software to determine the selected geometrical parameters describing the morphological features of the assessed chips.

  14. Alteration of diaspore by thermal treatment

    Institute of Scientific and Technical Information of China (English)

    杨华明; 胡岳华; 杨武国; 敖伟琴; 邱冠周

    2004-01-01

    Diaspore (α-AlOOH) was heated at various temperatures from 300 to 1000 ℃ for 2 h. The alteration of diaspore by thermal treatment was investigated by differential thermal analysis, thermogravimetric analysis and X-ray diffraction. The mechanism of thermal decomposition of diaspore was discussed according to the Coats-Redfern equation. It is found that after thermal treatment at 500 ℃, diaspore is transformed entirely to corundum (α-Al2O3). Combined with the mass loss ratio obtained from the thermogravimetric analysis data, the activation energies for the thermal treatment of diaspore are calculated as Ea=10.4 kJ/mol below 400 ℃ and Eb=47.5 kJ/mol above 400 ℃, respectively, which is directly related to the structural alteration of diaspore during the thermal treatment. The results indicate that the thermal decomposition of diaspore is conducted primarily by means of an interfacial reaction.

  15. Kinetics of F center annealing and colloid formation in Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kotomin, E.A., E-mail: kotomin@latnet.lv [Institute of Solid State Physics, Kengaraga 8, Riga LV 1063 (Latvia); Kuzovkov, V.N.; Popov, A.I. [Institute of Solid State Physics, Kengaraga 8, Riga LV 1063 (Latvia); Vila, R. [CIEMAT, Madrid (Spain)

    2016-05-01

    The diffusion-controlled kinetics of the F center annealing in Al{sub 2}O{sub 3} (sapphire, corundum) is simulated theoretically for the two regimes: after neutron irradiation when the immobile F centers are annihilated with complementary defects – mobile interstitial oxygen ions, and in thermochemically reduced (additively colored) crystals where mobile F centers aggregate and create the metal colloids. A comparison of the experimental and theoretical kinetics allowed us to estimate the migration energies for the F centers and interstitial oxygen ions. It is obtained that the pre-exponents in diffusion coefficients for defects in different neutron irradiated samples can vary by two orders of magnitude which is attributed by presence of numerous traps for mobile interstitial oxygen ions.

  16. The Ring Monstrance from the Loreto treasury in Prague: handheld Raman spectrometer for identification of gemstones.

    Science.gov (United States)

    Jehlička, Jan; Culka, Adam; Baštová, Markéta; Bašta, Petr; Kuntoš, Jaroslav

    2016-12-13

    A miniature lightweight portable Raman spectrometer and a palm-sized device allow for fast and unambiguous detection of common gemstones mounted in complex jewels. Here, complex religious artefacts and the Ring Monstrance from the Loreto treasury (Prague, Czech Republic; eighteenth century) were investigated. These discriminations are based on the very good correspondence of the wavenumbers of the strongest Raman bands of the minerals. Very short laser illumination times and efficient collection of scattered light were sufficient to obtain strong diagnostic Raman signals. The following minerals were documented: quartz and its varieties, beryl varieties (emerald), corundum varieties (sapphire), garnets (almandine, grossular), diamond as well as aragonite in pearls. Miniature Raman spectrometers can be recommended for common gemmological work as well as for mineralogical investigations of jewels and cultural heritage objects whenever the antiquities cannot be transported to a laboratory.This article is part of the themed issue 'Raman spectroscopy in art and archaeology'.

  17. Strength Properties and Microstructure of Diphase β—Sialon/Al2O3 Composites

    Institute of Scientific and Technical Information of China (English)

    LIYoufen; HONGYanruo; 等

    2000-01-01

    Study on modules of rupture and microstructure of xphase bearing diphase β-Sialon and diphase β-Sialon/Al2O3 composites shows that MOR increases with tempera-ture rise up to a maximum oint and then decreases,For diphase β-Sialon materials,the maximum strength reaches 130 MPa-170 MPa at 1200℃;whereas for diphase β-Sialon/Al2O3 composites,the maximum strength reaches 200MPa-300 MPa at 1000℃,In the microstructure of th composite ,oblong crystals of x-phase and hexagonal prismatic crystals of β-Sialon are interlaced in the skeleton structure of corundum.This struture creates a distinctly intensifying effect on the strength of the composite.

  18. Enhanced properties of MgO-Al2O3 composite materials with Al powder addition under 1300 °C creep test and its mechanism analysis

    Science.gov (United States)

    Jiang, Peng; Ma, Jiajia; Li, Yong; Yue, Dandan; Tong, Shanghao; Xue, Wendong

    2017-04-01

    The Al-MgO-Al2O3 composite samples were prepared with alumina (fused corundum and sintered alumina), high purity sintered magnesia and aluminum powder. Creep test was carried out at 1300 °C and studied. The results show that the creep rate of sample without aluminum addition decreases gradually. The creep properties of the MgO-Al2O3 composite material are improved by aluminum powder addition, with the sample demonstrating an increase creep rate. The physical properties of the samples are enhanced by aluminum powder addition as well. The mechanism of the improvement on the sample is analyzed by different characterization methods and kinetics calculations. Our results indicates that the AlN and MgAl2O4 spinel phases which are formed during the creep test are acting as the reinforcing phases and therefore enhance the creep performance of the samples.

  19. Stability and phase evolution of mullite in reducing atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Naghizadeh, R., E-mail: rnaghizadeh@iust.ac.ir; Golestani-fard, F.; Rezaie, H.R.

    2011-05-15

    The aim of this study is to investigate the stability of mullite and its phase evolution when heated at 1600-1650 deg. C in reducing atmosphere created by a carbon bed. The stoichiometric mullite (3Al{sub 2}O{sub 3}.2SiO{sub 2}) was synthesized by reacting the proper precursors at 1400 deg. C in air atmosphere. Samples containing the primary mullite and graphite or carbon were prepared by pressing the mix and heated at 1600-1650 deg. C. Products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the stoichiometric mullite could decompose to corundum and alumina-rich mullite. During firing under reducing atmosphere, the stoichiometric mullite became richer in Al{sup 3+} cations. The gaseous SiO compound was found to be released from the sample and reacting with C to form SiC phase. Comparison of general mullite solid solution (Al{sub 4+2x}Si{sub 2-2x}O{sub 10-x}) with alumina-rich mullite obtained from decomposition revealed that x would take different values depending on temperature and atmosphere. The ultimate decomposition product was found to be corundum. - Research Highlights: {yields} This method is a new route for investigation of thermochemical stability of stoichimetric mullite under reducing condition which have done by the authors. {yields} This research has got very good results for stability of mullite at different conditions. {yields} This work has also studied the mechanism of stability of mullite under reducing atmosphere.

  20. Characterization of Meteorites by Focused Ion Beam Sectioning: Recent Applications to CAIs and Primitive Meteorite Matrices

    Science.gov (United States)

    Christoffersen, Roy; Keller, Lindsay P.; Han, Jangmi; Rahman, Zia; Berger, Eve L.

    2015-01-01

    Focused ion beam (FIB) sectioning has revolutionized preparation of meteorite samples for characterization by analytical transmission electron microscopy (TEM) and other techniques. Although FIB is not "non-destructive" in the purest sense, each extracted section amounts to no more than nanograms (approximately 500 cubic microns) removed intact from locations precisely controlled by SEM imaging and analysis. Physical alteration of surrounding material by ion damage, fracture or sputter contamination effects is localized to within a few micrometers around the lift-out point. This leaves adjacent material intact for coordinate geochemical analysis by SIMS, microdrill extraction/TIMS and other techniques. After lift out, FIB sections can be quantitatively analyzed by electron microprobe prior to final thinning, synchrotron x-ray techniques, and by the full range of state-of-the-art analytical field-emission scanning transmission electron microscope (FE-STEM) techniques once thinning is complete. Multiple meteorite studies supported by FIB/FE-STEM are currently underway at NASA-JSC, including coordinated analysis of refractory phase assemblages in CAIs and fine-grained matrices in carbonaceous chondrites. FIB sectioning of CAIs has uncovered epitaxial and other overgrowth relations between corundum-hibonite-spinel consistent with hibonite preceding corundum and/or spinel in non-equilibrium condensation sequences at combinations of higher gas pressures, dust-gas enrichments or significant nebular transport. For all of these cases, the ability of FIB to allow for coordination with spatially-associated isotopic data by SIMS provides immense value for constraining the formation scenarios of the particular CAI assemblage. For carbonaceous chondrites matrix material, FIB has allowed us to obtain intact continuous sections of the immediate outer surface of Murchison (CM2) after it has been experimentally ion processed to simulate solar wind space weathering. The surface

  1. Defect compensation by Cr vacancies and oxygen interstitials in Ti4+-doped Cr2O3 epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaspar, Tiffany C.; Sushko, Petr; Bowden, Mark E.; Heald, Steve M.; Papadogianni, Alexandra; Tschammer, Carsten M.; Bierwagen, Oliver; Chambers, Scott A.

    2016-10-07

    Epitaxial thin films of Cr2-xTixO3 were deposited by oxygen-plasma-assisted molecular beam epitaxy (OPA-MBE) for 0.04 ≤ x ≤ 0.26. Ti speciation is verified by both x-ray photoelectron spectroscopy (XPS) and Ti K-edge x-ray absorption near-edge spectroscopy (XANES) to be Ti4+. Substitution of Ti for Cr in the corundum lattice is confirmed by modeling of the Ti K-edge extended x-ray absorption fine structure (EXAFS). Room temperature electrical transport measurements confirm the highly insulating nature of Ti-doped Cr2O3, despite the presence of aliovalent Ti4+. The resistivity of highly pure, undoped Cr2O3 was measured to be three orders of magnitude higher than for Ti-doped Cr2O3. Although the formation of Cr vacancies in Ti-doped Cr2O3 is found by density functional theory (DFT) calculations to be the energetically preferable defect compensation mechanism to maintain charge neutrality, an analysis of the XPS and EXAFS data reveal the presence of both Cr vacancies and oxygen interstitials at intermediate and high Ti concentrations, with a weak trend towards Cr vacancies as the Ti concentration increases. At low Ti concentrations, a strong dependence of the XPS Ti 2p core level peak width on concentration is observed. This dependence is attributed to the presence of widely spaced Ti dopants, which renders compensation of two or three Ti by a single oxygen interstitial or Cr vacancy, respectively, less probable. Instead, defect clusters of unknown type occur, although they may involve Cr vacancies. The defect compensation model developed here provides insight into previous, conflicting reports of n-type versus p-type conductivity in Ti-doped Cr2O3 at high temperature, and will inform future studies to exploit the wide variety of electronic and magnetic properties of corundum-structure oxides.

  2. Structure and electronic properties of AlCrO{sub x}N{sub 1−x} thin films deposited by reactive magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Najafi, H.; Karimi, A. [Institute of Condensed Matter Physics (ICMP), Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Oveisi, E. [Electron Spectrometry and Microscopy Laboratory (LSME-ICMP), Swiss Federal Institute of Technology in Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Morstein, M. [PLATIT AG, Advanced Coating Systems, CH-2545 Selzach (Switzerland)

    2014-12-01

    In this study, the main attempt is devoted to investigating the microstructure and electronic properties of AlCrO{sub x}N{sub 1−x} films in a wide range of oxygen concentrations from 0 to 1. These oxynitride films were deposited by pulsed DC magnetron sputtering from Al{sub 55}Cr{sub 45} targets. Our results showed that films with x = O/(O + N) < 0.6, exhibit a cubic (B1) lattice with a well-developed columnar structure. The incorporation of oxygen into the films without any oxide segregation results in the formation of a substitutional AlCrO{sub x}N{sub 1−x} solid solution and material system behaves like nitrides electronically. In the range of oxygen contents from 0.6 ≤ O/(O + N) < 0.97, coatings with fine columns, diffuse boundaries and high values of metal vacancies were formed. However, the B1 lattice survived despite the large proportion of oxygen. According to the structural and electronic properties of the corresponding layers, we assign this region to the formation of an amorphous phase and metastable monoxides with a B1 structure. Coatings with O/(O + N) ≥ 0.97 are electronically assigned to a solid solution of α-(Al,Cr){sub 2}(O{sub 0.97},N{sub 0.03}){sub 3} with corundum lattice and finer columnar structure. - Highlights: • AlCr(O{sub x}N{sub 1−x}) layers with variable oxygen content 0 < x < 1 were grown. • The layers with the lowest oxygen content, x < 0.6, electronically behave like nitrides. • Coatings with 0.6 ≤ x < 0.97 are assigned to metastable monoxides. • The oxide region consisted of a solid solution of α-phase with a corundum structure.

  3. Effects of Si and Y in structural development of (Al,Cr,Si/Y)O{sub x}N{sub 1−x} thin films deposited by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Najafi, H., E-mail: hossein.najafi@epfl.ch [Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédéraqle de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Karimi, A. [Institute of Condensed Matter Physics (ICMP), Ecole Polytechnique Fédéraqle de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Alexander, D. [Interdisciplinary Center for Electron Microscopy (CIME), Ecole Polytechnique Fédéraqle de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Dessarzin, P.; Morstein, M. [PLATIT AG, Advanced Coating Systems, CH-2545 Selzach (Switzerland)

    2013-12-31

    Silicon (Si) and yttrium (Y) are believed to have a strong influence on functional properties of oxynitrides due to their effects in the growth process and incorporation in solid solution phases. It is worthwhile noting that the presence of these elements is strongly active for controlling structural evolution during the growth. The aim of this work is to systematically study the microstructural development and mechanical properties of (Al,Cr,Si/Y)O{sub x}N{sub 1−x} oxynitride films as a function of Si and Y contents. Our results show that Si and Y have a different mechanism for incorporation into the oxynitride films. According to the TEM, XRD, and XPS results a substitutional role of yttrium is suggested for the investigated coatings, whereas silicon tends to form an amorphous glassy phase. Such oxynitride layers with cubic structure (fcc-B1) meet an enhanced structural stability by the incorporation of both silicon and yttrium. As a result, the nitride growth regime is extended in the range of O/(O + N) ≤ 0.80. On the other hand, they hinder the formation of corundum phase in the predominant oxide regime (O/(O + N) ≥ 0.98) suggesting retarded diffusional processes with the presence of such alloying elements (i.e. Si and Y) in the deposition flux. Additionally, the Y-containing oxynitrides demonstrate a greater nano-hardness for all growth regimes. - Highlights: • Role of Si and Y in oxynitride thin films was studied. • Si and Y have a different mechanism for incorporation into the oxynitride films. • Substitutional role of yttrium is suggested. • Silicon tends to form an amorphous glassy phase. • Si and Y hinder the formation of corundum phase.

  4. Chemistry and origin of the Mayo Kila sapphires, NW region Cameroon (Central Africa): Their possible relationship with the Cameroon volcanic line

    Science.gov (United States)

    Paul Mbih, Kemeng; Meffre, Sebastien; Yongue, Rose Fouateu; Kanouo, Nguo Sylvestre; Jay, Thomson

    2016-06-01

    Mineralogical, chemical and geochronological studies constrained the origin of sapphires from Mayo Kila, Northwest Cameroon. The sapphires are mostly blue, with sizes ranging from 2 to 5 mm. The pale blue grains are transparent, whereas, other corundums are transparent to translucent and/or opaque. The sapphires are dominantly euhedral to sub-hedral with few polished lustrous grains, acquired features during moderate to short distance transport from a proximal source rock. Solid inclusions are limited to rutile and zircon. Trace element analysis of sapphires shows significant concentration (in ppm) in some elements: Fe (2208-14,473), Ti (82-1783), Ga (77-512), Mg (0.9-264.9), Cr (b.d.l -168) and V (1.3-82). The other elements (e.g. Sn, Nb, Ta, Th, Zr, Ni, Ce) are generally below 10 ppm. The calculated ratios for some of the selected elements show an extreme variation: Fe/Mg (43-3043), Fe/Ti (2-76), Ti/Mg (1-328), and Ga/Mg (0.4-363). They are dominantly corundum crystallized in alkaline magma (s) with few from metamorphic source (s). Trace elemental features with Hf (13,354-26,238 ppm), Th (4018-45,584 ppm) and U (7825-17,175 ppm), and Th/U (0.39-2.65) found in zircon inclusions are compatible with quantified values in magmatic crystallized zircons. The Cenozoic age (mean of 30.78 ± 0.28 Ma) obtained for zircon inclusions is close to the age of some igneous rocks found within the Cameroon Volcanic Line (e.g. rocks of the Mount Oku: 31-22 Ma), showing the same period of formation. The most probable source of the zircon host sapphires is the Oku Mountain located SW of Mayo Kila.

  5. Presolar Grains and Their Isotopic Anomalies in Meteorites

    Institute of Scientific and Technical Information of China (English)

    林杨挺; 王世杰

    2001-01-01

    Study on presolar grains including diamond, silicon carbide, graphite, silicon nitrite (Si3N4), corundum and spinel isolated from meteorites is summarized in this paper. Except for nanometer-sized diamond, the other grains are micrometers to submicrometers in size. The presolar grains survived mainly in the fine -grained matrix of primitive chondrites and were isolated by chemical treatments. Diamond contains Xe isotopes (Xe-HL), typically produced in p- and r-processes, probably formed in supernovae. Mainstream silicon carbides are enriched in 29, 30Si and 13C, but depleted in 15N. They also contain various s-process products, consistent with calculations of AGB stars. Other silicon carbides exhibit much larger isotopic anomalies and are classified as groups X, Y, Z and AB. Among them, group X of SiC is characterized by enrichment of 28Si and daughter isotopes of various short-lived nuclides, suggesting an origin from supernovae. Graphite can be divided into four density fractions with distinct isotopic compositions. They may form in AGB stars, novae and supernovae, respectively. Si3N4 is similar to X-SiC in isotopic composition. Corundum is classified as four groups based on their oxygen isotopic compositions. AGB and red giant stars are possible sources for the oxide. More comprehensive study of presolar grains, especially discovery of the other types of oxides and silicates, isotopic analyses of individual submicrometer-sized grains and distribution of presolar grains among various chemical groups and petrographic types of chondrites will provide new information on nucleosynthesis, stellar evolution and formation of the solar nebula.

  6. Composition of breccia matrices from the Manson M-1 drill core

    Science.gov (United States)

    Kracher, A.; Anderson, R. R.; Koeberl, C.

    1994-07-01

    Eleven drill cores were recently recovered from the Manson, Iowa, impact structure. Core M-1, which was drilled at the edge of the large central uplift, contains three major impact rock types: sedimentary clast breccia, melt matrix breccia, and fragmental breccia. Breccia matrices from different depths in the M-1 core were investigated by defocused beam electron probe microanalysis. To obtain average compositions, matrix areas free of lithic and mineral clasts were covered with an orthogonal grid of analyses points. Variations in composition have two main causes: differences in source lithology and postimpact processes. With increasing depth distinct changes in composition can be observed. All compositions are highly feldspathic and surprisingly low in SiO2 for putative source lithologies of mostly granitic composition. Within the lithological units containing melt matrix breccia increasing recrystallization can be observed with depth. Compositions in this interval are marginally corundum normative and not as high in normative feldspar as other matrices. The thoroughly recrystallized matrices from the lowest intervals of the melt matrix breccia are more feldpathic, higher in Na/K ratio, and not corundum normative. Unlike the chemical variation between rock types, we tentatively ascribe the chemical changes within the melt matrix breccia to reaction of matrix with clasts. In particular, quartz clasts in breccias with highly recrystallized matrices develop fringes of K-spar, cpx, and ilmenite. The formation of these minerals is presumably accompanied by complementary changes in matrix composition. Factor analysis on data sets of individual melt matrix analyses provides further clues to the influence of source lithology and post impact processes respectively in the chemical makeup of the breccia matrices. The most significant factors are a mafic component and a plagioclase component.

  7. Monazite Geochronology of Al-Fe Granulites Of Amesmessa Area from In-Ouzzal Terrane (Western Hoggar, Algeria)

    Science.gov (United States)

    Ahmed, Benbatta; Abderrahmane, Bendaoud; Bénédicte, Cenki-Tok; Zohir, Adjerid; Olivier, Bruguier; Jesus, Garrido Marin Carlos; Safouane, Djemai; Khadija, Ouzegane

    2017-04-01

    ABSTRACT: The In Ouzzal terrane in western Hoggar (South Algeria) preserves evidence of ultrahigh-temperature (UHT) crustal metamorphism. It consists in Archean crustal units, composed of orthogneissic domes and green stone belts, strongly remobilized during the Paleoproterozoic orogeny (2000 Ma, Peucat et al., 1996). Ouzegane et al. (2003) summarize this UHT metamorphic history as two granulitic stages of high temperature : a prograde evolution with peak conditions around 9-11 kbar and 950-1050°C, leading to the appearance of exceptional paragenèses with corundum-quartz, sapphirine-quartz and sapphirine-spinel-quartz in Al-Mg granulites, Al-Fe granulites and quartzites; followed by retrograde event characterized by a pressure drop to 5-7 kbar. This retrograde event is marked by intrusive carbonatite bodies and the occurrence of leptynites veins. The present study is interested in Al-Fe granulites which outcrop in a still little known region situated in southeastern part of In-Ouzzal terrane. These granulites are mainly composed by quartz, spinel, garnet, sillimanite, cordierite, biotite, perthitic feldspar, ilmenite, ± corundum. The study consist to dating these Al-Fe granulites by monazites (U-Pb - ICP-MS method) combined with their internal structures revealed by BSE imaging. The primary results suggest two major facts: 1- for the first time, the existence of at least one metamorphism older than 2.5 Ga; 2- a long live paleoproterozoic high temperature metamorphism. These geochronological results completed and combined with a detailed phases relationship study of these Al-Fe granulites will are of major importance as for future discussion on the geodynamic context responsible for this regional UHT metamorphism as well as indicating a record the time of the different stages of granulitic metamorphism. Keywords: UHT metamorphism, Granulites, Paleoproterozoïc, Archaean; Southeastern In Ouzzal terrane; Monazite geochronology; Hoggar

  8. Effects of Mineral Composition on Phase Formation Process of Anorthite-mullite Composite Materials%原料矿物组成对钙长石-莫来石复相材料物相形成过程的影响

    Institute of Scientific and Technical Information of China (English)

    严煌; 王玺堂; 王周福; 刘浩; 马妍

    2016-01-01

    The anorthite-mullite composite materials were in-situ synthesized by using different mineral materials at different sintering temperatures (1 100-1 400 ℃).The effects of mineral composition on the phase formation process of the composite materials were studied by the phase composition and microstructure analysis. The results show that with the quartz (fused quartz or quartz sand),Ca(OH)2 andα-Al2 O3 as the raw materials, the wollastonite and gehlenites were firstly formed,and then the anorthites were produced by the reaction of wollastonite,corundum and quartz.The mullites were obtained by the reaction of corundum and cristobalite at 1 350 ℃.With the wollastonites or grossites,natural Al-Si minerals like kyanites and clays as raw materials,the anorthites were directly produced by the raw materials and mullites were obtained by the secondary mullitization. After sintered at 1 400 ℃,the anorthite-mullite samples prepared with different raw materials all consisted of mullite,anorthite and few corundum phases.The columnar mullite crystals with large sizes existed in the fine anorthite grains.%采用不同矿物原料在不同煅烧温度(1100~1400℃)下原位合成制备了钙长石-莫来石复相材料,通过物相组成和显微结构分析研究了原料矿物组成对复相材料物相形成过程的影响。结果表明:采用石英(熔融石英或天然石英)、Ca(OH)2和α-Al2 O3为原料时,合成过程中首先生成硅灰石和钙黄长石,之后硅灰石再与刚玉和石英反应生成钙长石,莫来石则是在1350℃由方石英和刚玉反应生成;而以硅灰石或铝酸钙,蓝晶石和苏州土天然铝硅系矿物为原料时,部分钙长石相由原料直接反应生成,莫来石通过二次莫来石化生成;1400℃煅烧后不同原料合成的钙长石-莫来石试样中均含有莫来石相、钙长石相和少量刚玉相,尺寸较大的莫来石柱状晶体穿插在较细的钙长石晶粒之中。

  9. Synthesis and Performance Investigation of Mullite Materials by Recycling Waste Fly Ash%粉煤灰资源化合成莫来石材料及其性能研究

    Institute of Scientific and Technical Information of China (English)

    谭丽; 董应超; 孙丽

    2011-01-01

    以天然铝矾土和工业废物粉煤灰为原料,运用反应烧结合成了低成本的莫来石陶瓷材料.结果证明,刚玉与方石英相在1200~1300℃间通过固态反应生成二次莫来石,在温度高于1300℃时,刚玉相熔于短暂玻璃相中.二次莫来石化及莫来石晶体生长所导致的样品体膨胀大于液相烧结所引起的收缩,导致样品出现膨胀现象.1600℃烧结样品的平均热膨胀系数为5.40×10-6℃-1,平均抗弯强度186.19 MPa.莫来石在强酸强碱热溶液中表现出两个阶段:快速阶段(0~5h)和低速阶段(5~20h),这分别对应于样品的表面腐蚀和体腐蚀过程.%Low-cost mullite ceramics were synthesized by reaction-sintering with natural bauxite and industrial waste fly ash as starting materials. The results indicate that secondary mullite was produced at 1200~1300℃ by the solid state reaction of cristobalite and corundum, followed by the dissolution of corundum into transitory glassy phase at higher temperatures (≥ 1300℃). The formation of secondary mullite and its growth resulted in a volume expansion, which was higher than the shrinkage induced by liquid-phase sintering. The samples sintered at 1600℃ had average thermal expansion coefficient of 5.40×10℃-1 and average bending strength of 186.19 Mpa. The sintered mullite exhibited two corrosion stages in hot strong acidic and alkaline solutions: fast stage (0~5h) and low-rate stage (5~20h), which respectively corresponded to the surface corrosion and bulk corrosion processes of the samples.

  10. The Effect of Wasted Magnesia-chrome Fine Powder Addition on Properties of Alumina-magnesia Castable%废镁铬砖细粉对铝镁浇注料性能的影响

    Institute of Scientific and Technical Information of China (English)

    崔庆阳; 黄鹏; 吴林林; 毛晓刚; 李有奇

    2012-01-01

    Alumina-magnesia Castables were prepared using brown corundum (8 ~ lmm), white corundum ( 2) > 94%) as matrix, p-Al2O3 powder for the binder, sodium hexametaphosphate as depersant, to study the waste magnesium-chromium powder equivalent instead of fused magnesia, the mass fraction is (respectively 0,1%, 2%, 3%) on properties of aluminum-magnesium castable. The results showed that: with the increase of waste magnesia-chrome brick powder, the intensity of sample after drying or burning increased, and the volume density, but apparent porosity decreased, the rate of linear change decreasing; but decrease in thermal shock resistance, rupture resistence at high temperature increased slightly, mainly according to the amount of the solid solution formed at high temperature by waste magnesia-chrome brick powder and alumina powder.%以棕刚玉(8~1mm)、白刚玉(≤3mm)为骨料,以白刚玉细粉(≤0.045 mm)、α-Al2O3微粉(≤5μm,d50=2.01 μm)、电熔镁砂细粉(≤ 0.074mm)、硅灰(w(SiO2)>94%)为基质,以ρ-Al2O3微粉为结合剂,以六偏磷酸钠为减水剂制备铝镁质浇注料,采用废镁铬砖细粉等量代替电熔镁砂细粉,研究了废镁铬砖细粉质量分数(分别为0、1%、2%、3%)对铝镁浇注料性能的影响.试验结果表明:随着废镁铬砖细粉加入量的增大,试样的烘后和烧后强度均提高,体积密度增大,显气孔率减小、线变化率先增大后减小;但抗热震性有所降低、高温抗折强度稍有增大,这主要与高温下废镁铬砖细粉和刚玉细粉生成多种固溶体的量有关.

  11. Películas delgadas de Al2O3 sobre silicio preparadas por ablación láser

    Directory of Open Access Journals (Sweden)

    Lamagna, A.

    1998-04-01

    Full Text Available Al2O3 thin films were fabricated by pulsed laser deposition (PLD on Si3N4/Si, to improve the thermal and electrical isolation of gas sensing devices. The microstructure of the films is analyzed as a function of the deposition conditions (laser fluence, oxygen pressure, target-substrate distance and substrate temperature. X-ray analysis shows that only a sharp peak that coincides with the corundum (116 reflection can be observed in all the films. But, when they are annealed at temperatures above 1,200°C, a change in the crystalline structure of some films occurs. The stoichiometry and morphology of the films with and without thermal treatment are compared using environmental scanning electron microscopy (SEM and EDAX analysis.

    Se depositaron películas delgadas de Al2O3 por ablación láser sobre Si3N4/Si para utilizarlas como aislante térmico y eléctrico en dispositivos sensores de gases. Se analiza la microestructura de estas películas en función de las condiciones de la deposición (densidad de energía del láser, presión de oxígeno, distancia blanco-substrato y temperatura del substrato. Los estudios de difracción de rayos X, utilizando geometría de ángulo rasante, muestran que sólo puede observarse la reflexión coincidente con la (116 del corundum. Cuando las películas se tratan térmicamente a temperaturas superiores a 1.200°C sufren un cambio en su cristalinidad que depende de las condiciones de la deposición. Utilizando microscopía electrónica de barrido (SEM y análisis por EDAX, se comparan la estequiometría y la morfología de las películas con y sin tratamiento térmico.

  12. Effect of NiCrAlY Content on Mechanical and Dielectric Properties of NiCrAlY/Al2O3 Composite Coatings%NiCrAlY含量对NiCrAlY/Al2O3涂层机械性能及介电性能的影响

    Institute of Scientific and Technical Information of China (English)

    武志红; 周万城; 罗发; 朱冬梅

    2013-01-01

    采用大气等离子喷涂技术,以镍基合金(NiCrAlY合金)粉为吸收剂、氧化铝(Al2O3)为基体,制备出NiCrAlY/Al2O3(NA)复合涂层.分析了复合涂层的相组成及显微结构,研究了 NiCrAlY含量变化对复合涂层的机械性能及介电性能的影响.结果表明:喷涂后的涂层中出现了刚玉、铬刚玉等非金属相及唯一的金属相Ni.随着NiCrAlY含量的增加,复合涂层的抗弯强度、断裂韧性逐渐增强;在8.2~12.4 GHz频率范围内,涂层的介电常数实部与虚部值都随着NiCrAlY含量的变化而明显变化,且在NiCrAlY含量为25%时达到最高值,这主要与喷涂过程中分离出金属Ni的含量、冷却后的形状及分布状态有关.%NiCrAlY/Al2O3 (NA) composite coatings were fabricated by a plasma spraying method with nickel-based (NiCrAlY) par-tides as an absorber and A12O3 as a matrix. The phase composition and microstructure of these coatings were characterized by X-ray diffraction and scanning electron microscopy, respectively. The mechanical and dielectric properties of the NA composite coatings with different NiCrAlY contents were investigated. The results indicate that the non-metallic phases (i.e., corundum and chromium corundum) and the metal phase nickel generate in the composite coatings. The bending resistance and fracture toughness all increased with increasing NiCrAlY content. The real part and the imaginary part of permittivity both changed in the frequency range of 8.2-12A GHz, and they reached the maximum values at NiCrAlY content of 25% mainly due to various amounts, solidified shapes and distributions of nickel in the composite coatings.

  13. Ruby-sapphire-spinel mineralization in marble of the middle and southern Urals: Geology, mineralogy, and genesis

    Science.gov (United States)

    Kisin, A. Yu.; Murzin, V. V.; Tomilina, A. V.; Pritchin, M. E.

    2016-07-01

    Ruby and spinel occurrences hosted in marble on the eastern slope of the Urals are considered. Ruby- and spinel-bearing marble is a specific rock in granite-gneiss complexes of the East Ural Megazone, which formed at the Late Paleozoic collision stage of the evolution of the Urals. Organogenic marine limestone is the protolith of the marble. No relict sedimentary bedding has been retained in the marble. The observed banding is a secondary phenomenon related to crystallization and is controlled by flow cleavage. Magnesian metasomatism of limestone with the formation of fine-grained dolomite enriched in Cr, V, Ti, Mn, Cu, Zn, Ga, and REE took place at the prograde stage of metamorphism. Dedolomitization of rocks with the formation of background calcite marble also developed at the prograde stage. Mg-calcite marble with spinel and ruby of the first type formed in the metamorphic fluid circulation zone. Magnesian metasomatism with the formation of bicarbonate marble with ruby, pink sapphire, and spinel of the second type developed at the early retrograde stage. The formation of mica-bearing mineralized zones with corundum and spinel of the third type controlled by cleavage fractures is related to the pneumatolytic-hydrothermal stage. The data on ruby-bearing marble in the Urals may be used for forecasting and prospecting of ruby and sapphire deposits hosted in marble worldwide.

  14. Geochemical Characteristics and New Eruption Ages of Ruby-Related Basalts from Southeast Kenya

    Institute of Scientific and Technical Information of China (English)

    Tawatchai Chualaowanich; Chakkaphan Sutthirat; Visut Pisuttha-Arnond; Christoph Hauzenberger; Chinghua Lo; Tongyi Lee; Punya Charusiri

    2014-01-01

    Two ruby-related basaltic fields were recently discovered in the southeast region of Kenya, exposed in the Nguu and Ngulai Hills vicinities. These fields host abundant deep-seated xeno-liths, including corundum-bearing granulites. The basalts are alkaline affinity having compositions from foidrite to basanite. The Ngulai basalts have a wider range of SiO2 (38.2 wt.%-44.8 wt.%) cov-ering those of the Nguu basalts (38.7 wt.%-42.3 wt.%). This overlapping behavior also holds for other major oxides and trace elements, e.g., Al2O3, Na2O, K2O, Cr, Ni, Rb and Ga. The overall OIB-like in-compatible patterns with strong K depletion and slight spike of Ti enrichment signatures imply low degrees of partial melting of the upper mantle region source induced under a mantle plume-related process. The K-depletion signature indicates a residual K-bearing phase still retained in the source domain. Chondrite-normalized REE patterns exhibiting strong LREE enrichment without Eu anoma-lies suggest that plagioclase fractionation is insignificant. New40Ar/39Ar ages indicate eruption events occurred during the Pleistocene times, which are around 2 Ma for the Ngulai basalts and 0.9 to 1.6 Ma for the Nguu basalts. Clinopyroxene-basalt thermobarometric calculations yield the equilibriumP-T ranges of ~8-29 kbar and 1 200-1 450 oC.

  15. Transport properties of polycrystalline TiO{sub 2} and Ti{sub 2}O{sub 3} as semiconducting oxides

    Energy Technology Data Exchange (ETDEWEB)

    Afifi, M.A. [Semiconductor Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Abdel-Aziz, M.M. [Semiconductor Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt)], E-mail: melaziz@link.net; Yahia, I.S.; Fadel, M. [Semiconductor Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Wahab, L.A. [Solid State Laboratory, Physics Department, National Center for Radiation Research and Technology, Naser City, Cairo (Egypt)

    2008-05-08

    The crystal structure, electrical conductivity, Hall effect and thermoelectric power were studied for the titanium oxides (TiO{sub 2} and Ti{sub 2}O{sub 3}). Analytical calculations of the structure using X-ray diffraction showed that TiO{sub 2} crystallizes in tetragonal (rutile) and Ti{sub 2}O{sub 3} in rhombohedral (corundum). Values of the calculated lattice parameters are determined. The dependence of the electrical conductivity versus the inverse of temperature was studied in the temperature range (148-373 K). The activation energy was determined for different domains of temperature. Values of Hall mobility {mu}{sub H} and carrier concentration P of these oxides as a function of temperature were determined and reported. Thermoelectric power was measured for the investigated samples in the same investigated range of temperature. The results of thermoelectric power showed that the conduction can be regarded as p-type in the range from 175 to 299 K for TiO{sub 2} and after that the conduction is n-type. While for Ti{sub 2}O{sub 3}, the negative value of thermo-power within the whole temperature range indicates that electrons are the majority carriers over the investigated range of temperature.

  16. Anvil cell gasket design for high pressure nuclear magnetic resonance experiments beyond 30 GPa.

    Science.gov (United States)

    Meier, Thomas; Haase, Jürgen

    2015-12-01

    Nuclear magnetic resonance (NMR) experiments are reported at up to 30.5 GPa of pressure using radiofrequency (RF) micro-coils with anvil cell designs. These are the highest pressures ever reported with NMR, and are made possible through an improved gasket design based on nano-crystalline powders embedded in epoxy resin. Cubic boron-nitride (c-BN), corundum (α-Al2O3), or diamond based composites have been tested, also in NMR experiments. These composite gaskets lose about 1/2 of their initial height up to 30.5 GPa, allowing for larger sample quantities and preventing damages to the RF micro-coils compared to precipitation hardened CuBe gaskets. It is shown that NMR shift and resolution are less affected by the composite gaskets as compared to the more magnetic CuBe. The sensitivity can be as high as at normal pressure. The new, inexpensive, and simple to engineer gaskets are thus superior for NMR experiments at high pressures.

  17. The possible use of Bayer process cyclone fines for manufacture of abrasives

    Directory of Open Access Journals (Sweden)

    Sancho, J.

    2002-12-01

    Full Text Available This paper deals with the feasibihty of producing synthetic abrasives from a by-product of the Bayer process: the cyclone fines, through synthesis aided by mineralizers addition. The main result has been the production of a low temperature (1200-1300 °C polish by adding fluoride mineralizers, that could be in clear competence with synthetic corundum obtained also in this work by a more traditional way: sodium removal, using of magnesium oxide as mineralizer, and high calcination temperatures (1700 °C.

    En este trabajo se demuestra la posibilidad de producir abrasivos a partir de un subproducto de la fabricación de la alúmina Bayer: los finos de ciclón, mediante la síntesis ayudada por la adición de mineralizantes. Un resultado importante ha sido la obtención de un pulimento a baja temperatura, (1.200-1.300 °C mediante mineralizantes fluorados, que puede competir de forma clara con corindones sintéticos obtenidos, también en este trabajo, de forma tradicional: eliminación de sodio, utilización de óxido de magnesio como mineralizante y elevadas temperaturas de calcinación (1.700 °C.

  18. Recovery of α-Al{sub 2}O{sub 3} from ionizing radiation dosimetric sensors

    Energy Technology Data Exchange (ETDEWEB)

    Sanches, Edgar Aparecido, E-mail: sanches.ufam@gmail.com [Universidade Federal do Amazonas (UFAM), Manaus, AM (Brazil). Dept. de Fisica; Costalonga, Ademir Geraldo Cavallari; Mascarenhas, Yvonne Primerano [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Institute de Fisica; Nascimento, Luana de Freitas [Belgium Nuclear Research Centre, SCK-CEN, Mol (Belgium); Mascarenhas, Yvone Maria [SAPRA S/A Servico de Assessoria e Protecao Radiologica, Sao Carlos, SP, (Brazil)

    2015-01-15

    Corundum, sapphire or α-Al{sub 2}O{sub 3} is an important technological material in many optical and electronic applications such as solid-state lasers, optical windows and, more recently, as a radiation detector. Landauer (Glenwood, IL, USA) accumulated large number of archived and stored Luxel™ dosemeters composed of Al{sub 2}O{sub 3}:C, which were subjected to a recovery process. Due to the importance of this advanced crystalline material in OSL dosimetry, a recovery process was developed based on the dosemeters calcination and Al{sub 2}O{sub 3}:C has been reused in manufacturing of new dosemeters. This paper does not aim to optimize the recovery process, but provides an opportunity to study the involved process parameters and to recover this valuable crystalline material from used dosemeters. To the best of our knowledge no other recovery process involving this dosimetric material was described in scientific literature. Fourier Transform Infrared Spectrometry (FTIR), Thermogravimetry/Differential Thermoanalysis (TG/DTA), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Optically Stimulated Luminescence (OSL) and Rietveld Refinement were used to characterize the recovered material and to check for the stability of its structural and dosimetric properties. (author)

  19. Design and achieving of multicolor upconversion emission based on rare-earth doped tellurite glasses

    Institute of Scientific and Technical Information of China (English)

    邢明铭; 马运北; 罗昔贤; 付姚; 姜涛; 汪红; 段小龙

    2014-01-01

    Yb3+/Tm3+ co-doped and Yb3+/Ho3+/Tm3+ tri-doped tellurite glasses were synthesized by fusing the mixture of TeO2, PbF2, AlF3, BaF2, Yb2O3, Tm2O3 and Ho2O3 in a corundum crucible at 850 ºC for 20 min. The synthesized glasses were characterized by upconversion emission spectra under the excitation of 980 nm laser, and the emission colors were investigated according to the CIE-1931 standards. The results indicated that Yb3+/Tm3+ co-doped tellurite glass exhibited blue upconversion emission with favor-able color coordinates of (0.20, 0.07). Yb3+, Ho3+ and Tm3+ tri-doped tellurite glasses presented white upconversion luminescence under a single 980 nm laser excitation. Moreover, a very wide range of emission colors could be tuned by altering Ho3+ concentration. Combining the contribution of adjusting Ho3+ concentration and pump power, near equal energy white light was obtained.

  20. Electrochemically assisted deposition of strontium modified magnesium phosphate on titanium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Meininger, M. [Department for Functional Materials in Medicine and Dentistry, University of Würzburg, Pleicherwall 2, D-97070 Würzburg (Germany); Wolf-Brandstetter, C. [Max Bergmann Center for Biomaterials, Technical University of Dresden, Budapester Straße 27, D-01069 Dresden (Germany); Zerweck, J.; Wenninger, F.; Gbureck, U.; Groll, J. [Department for Functional Materials in Medicine and Dentistry, University of Würzburg, Pleicherwall 2, D-97070 Würzburg (Germany); Moseke, C., E-mail: claus.moseke@fmz.uni-wuerzburg.de [Department for Functional Materials in Medicine and Dentistry, University of Würzburg, Pleicherwall 2, D-97070 Würzburg (Germany)

    2016-10-01

    Electrochemically assisted deposition was utilized to produce ceramic coatings on the basis of magnesium ammonium phosphate (struvite) on corundum-blasted titanium surfaces. By the addition of defined concentrations of strontium nitrate to the coating electrolyte Sr{sup 2+} ions were successfully incorporated into the struvite matrix. By variation of deposition parameters it was possible to fabricate coatings with different kinetics of Sr{sup 2+} into physiological media, whereas the release of therapeutically relevant strontium doses could be sustained over several weeks. Morphological and crystallographic examinations of the immersed coatings revealed that the degradation of struvite and the release of Sr{sup 2+} ions were accompanied by a transformation of the coating to a calcium phosphate based phase similar to low-crystalline hydroxyapatite. These findings showed that strontium doped struvite coatings may provide a promising degradable coating system for the local application of strontium or other biologically active metal ions in the implant–bone interface. - Highlights: • Sr-doped struvite coatings have been deposited on titanium by electrochemically assisted deposition. • Sr content can be adjusted by means of process time, current density and pulse mode. • Sr-doped coatings release therapeutically relevant Sr doses in physiological media for several weeks. • During immersion in physiological media Sr-doped struvite coatings transform into a low crystalline calcium phosphate phase.

  1. Impact of plasma chemistry versus titanium surface topography on osteoblast orientation.

    Science.gov (United States)

    Rebl, Henrike; Finke, Birgit; Lange, Regina; Weltmann, Klaus-Dieter; Nebe, J Barbara

    2012-10-01

    Topographical and chemical modifications of biomaterial surfaces both influence tissue physiology, but unfortunately little knowledge exists as to their combined effect. There are many indications that rough surfaces positively influence osteoblast behavior. Having determined previously that a positively charged, smooth titanium surface boosts osteoblast adhesion, we wanted to investigate the combined effects of topography and chemistry and elucidate which of these properties is dominant. Polished, machined and corundum-blasted titanium of increasing microroughness was additionally coated with plasma-polymerized allylamine (PPAAm). Collagen I was then immobilized using polyethylene glycol diacid and glutar dialdehyde. On all PPAAm-modified surfaces (i) adhesion of human MG-63 osteoblastic cells increased significantly in combination with roughness, (ii) cells resemble the underlying structure and melt with the surface, and (iii) cells overcome the restrictions of a grooved surface and spread out over a large area as indicated by actin staining. Interestingly, the cellular effects of the plasma-chemical surface modification are predominant over surface topography, especially in the initial phase. Collagen I, although it is the gold standard, does not improve surface adhesion features comparably.

  2. Metamorphism of cordierite gneisses from Eastern Ghat Granulite Terrain, Andhra Pradesh, South India

    Science.gov (United States)

    Murthy, D. S. N.; Charan, S. Nirmal

    1988-01-01

    Cordierite-bearing metapelites of the Eastern Ghat granulite terrain occur in close association of Khondalites, quartzites, calc-silicate rocks and charnockites. Rocks occurring between Bobbili in the north and Guntur in the south of Andhra Pradesh are studied. The association of the mineral and textural relationships suggest the following metamorphic reactions: Garnet + sillimanite + quartz = cordierite, hypersthene + sillimanite + quartz = cordierite, sillimanite + spinel = cordierite + corundum, and biotite + quartz + sillimanite = cordierite + K=feldspar. Generally the minerals are not chemically zoned except garnet-biotite showing zoning when they come in close contact with one another. The potential thermometers are provided by the Fe-Mg distribution of coexisting biotite-garnet and cordierite-garnet. Conflicting interpretation of the P/T dependence of these reactions involving cordierite are due to H2O in the cordierite. The presence of alkali feldspar-quartz assemblage which is common in these gneisses will be constrained from melting only if H2O activity is less than 0.5. The piezometric array inferred is convex towards the temperature array, indicating a rapid and isothermal crustal uplift probably aided by thrust tectonics.

  3. Mineralogy and geochemistry of xenoliths in the Eocene volcanic rocks from southwest of Jandaq

    Directory of Open Access Journals (Sweden)

    Samineh Rajabi

    2013-04-01

    Full Text Available The Eocene volcanic rocks from the southwest of the Jandaq (Kuh-e-Godar-e-Siah, Central-East Iran micro-continent are andesitic basalt and andesite in composition. These rocks contain xenoliths with granulitic mineralogy. Mineral assemblage of these xenoliths is plagioclase + phlogopite + corundum + sillimanite + chlorite + phengite with granublastic, poiklioblastic and foliated textures in the pick metamorphic condition. Thermometry of phlogopite in these xenoliths suggests the average temperature 782oC. The characteristics of the xenoliths are consistent with the granolitic facies metamorphism of the Al-saturated Si-undersaturated crustal sediments at the lower crust condition. Melting of these granulites forms the magma which crystallized the S-type granitoids. Differentiation and crystallization of this magma causes the S-type granite formation. Therefore, the S-type granites in the study area are probably generated from melting of the granulites parts of which brought to the surface as xenoliths by Eocene magmatism in south of the Jandaq (Kuh-e-Godar-e-Siah. S-type granites in the study area are located along the Doruneh, Chupanan and Aeirakan faults in the Aeirakan area and Jandaq ophiolite. These granites are the source of uranium, thorium and uranium ore in southwest of the Aeirakan mountain.

  4. Implant materials modified by colloids

    Directory of Open Access Journals (Sweden)

    Zboromirska-Wnukiewicz Beata

    2016-03-01

    Full Text Available Recent advances in general medicine led to the development of biomaterials. Implant material should be characterized by a high biocompatibility to the tissue and appropriate functionality, i.e. to have high mechanical and electrical strength and be stable in an electrolyte environment – these are the most important properties of bioceramic materials. Considerations of biomaterials design embrace also electrical properties occurring on the implant-body fluid interface and consequently the electrokinetic potential, which can be altered by modifying the surface of the implant. In this work, the surface of the implants was modified to decrease the risk of infection by using metal colloids. Nanocolloids were obtained using different chemical and electrical methods. It was found that the colloids obtained by physical and electrical methods are more stable than colloids obtained by chemical route. In this work the surface of modified corundum implants was investigated. The implant modified by nanosilver, obtained by electrical method was selected. The in vivo research on animals was carried out. Clinical observations showed that the implants with modified surface could be applied to wounds caused by atherosclerotic skeleton, for curing the chronic and bacterial inflammations as well as for skeletal reconstruction surgery.

  5. Upgrading of High-Aluminum Hematite-Limonite Ore by High Temperature Reduction-Wet Magnetic Separation Process

    Directory of Open Access Journals (Sweden)

    Xianlin Zhou

    2016-03-01

    Full Text Available The huge consumption of iron ores in China has attracted much attention to utilizing low grade complex iron resources, such as high-aluminum hematite-limonite ore, which is a refractory resource and difficult to upgrade by traditional physical concentration processes due to the superfine size and close dissemination of iron minerals with gangue minerals. An innovative technology for a high temperature reduction-magnetic separation process was studied to upgrade a high-aluminum iron ore assaying 41.92% Fetotal, 13.74% Al2O3 and 13.96% SiO2. The optimized results show that the final metal iron powder, assaying 90.46% Fetotal, was manufactured at an overall iron recovery of 90.25% under conditions as follows: balling the high aluminum iron ore with 15% coal blended and at 0.3 basicity, reducing the dried pellets at 1350 °C for 25 min with a total C/Fe mass ratio of 1.0, grinding the reduced pellets up to 95%, passing at 0.074 mm and magnetically separating the ground product in a Davis Tube at a 0.10-T magnetic field intensity. The metal iron powder can be used as the burden for an electric arc furnace (EAF. Meanwhile, the nonmagnetic tailing is suitable to produce ceramic, which mainly consists of anorthite and corundum. An efficient way has been found to utilize high-aluminum iron resources.

  6. Determination of the apparent porosity level of refractory concrete during a sintering process using an ultrasonic pulse velocity technique and image analysis

    Directory of Open Access Journals (Sweden)

    LJUBICA M. PAVLOVIĆ

    2010-03-01

    Full Text Available Concrete which undergoes a thermal treatment before (pre-casted concrete blocks and during (concrete embedded in-situ its life-service can be applied in plants operating at high temperature and as thermal insulation. Sintering is a process which occurs within a concrete structure in such conditions. Progression of sintering process can be monitored by the change of the porosity parameters determined with a nondestructive test method - ultrasonic pulse velocity and computer program for image analysis. The experiment has been performed on the samples of corundum and bauxite concrete composites. The apparent porosity of the samples thermally treated at 110, 800, 1000, 1300 and 1500 C was primary investigated with a standard laboratory procedure. Sintering parameters were calculated from the creep testing. The loss of strength and material degradation occurred in concrete when it was subjected to the increased temperature and a compressive load. Mechanical properties indicate and monitor changes within microstructure. The level of surface deterioration after the thermal treatment was determined using Image Pro Plus program. Mechanical strength was estimated using ultrasonic pulse velocity testing. Nondestructive ultrasonic mea¬surement was used as a qualitative description of the porosity change in specimens which is the result of the sintering process. The ultrasonic pulse velocity technique and image analysis proved to be reliable methods for monitoring of micro-structural change during the thermal treatment and service life of refractory concrete.

  7. Effect of CaF2 on Interfacial Phenomena of High Alumina Refractories with Al Alloy

    Science.gov (United States)

    Koshy, Pramod; Gupta, Sushil; Sahajwalla, Veena; Edwards, Phil

    2008-08-01

    An experimental study was conducted to investigate the interfacial phenomena between Al-alloy and industrial grade high alumina refractories containing varying contents of CaF2 at 1250 °C. Interfacial reaction products and phases formed in the heat-treated refractory samples were characterized using electron probe microanalysis (EPMA) and X-ray diffraction (XRD), respectively, while interfacial phenomena including dynamic wetting behavior were analyzed using the sessile drop technique. Refractories containing less than 5 wt pct CaF2 showed good resistance to reactions with the molten alloy, due to the dominance of corundum, and the presence of anorthite at the interface. However, with a further increase in the additive content, a glassy matrix of anorthite with CaF2 was formed. Formation of this phase significantly increased the intensity of reactions resulting in the buildup of an interfacial layer. The study thus revealed the strong catalytic effect of CaF2 on reactions of high alumina refractories with Al-alloy.

  8. A new anode material for oxygen evolution in molten oxide electrolysis.

    Science.gov (United States)

    Allanore, Antoine; Yin, Lan; Sadoway, Donald R

    2013-05-16

    Molten oxide electrolysis (MOE) is an electrometallurgical technique that enables the direct production of metal in the liquid state from oxide feedstock, and compared with traditional methods of extractive metallurgy offers both a substantial simplification of the process and a significant reduction in energy consumption. MOE is also considered a promising route for mitigation of CO2 emissions in steelmaking, production of metals free of carbon, and generation of oxygen for extra-terrestrial exploration. Until now, MOE has been demonstrated using anode materials that are consumable (graphite for use with ferro-alloys and titanium) or unaffordable for terrestrial applications (iridium for use with iron). To enable metal production without process carbon, MOE requires an anode material that resists depletion while sustaining oxygen evolution. The challenges for iron production are threefold. First, the process temperature is in excess of 1,538 degrees Celsius (ref. 10). Second, under anodic polarization most metals inevitably corrode in such conditions. Third, iron oxide undergoes spontaneous reduction on contact with most refractory metals and even carbon. Here we show that anodes comprising chromium-based alloys exhibit limited consumption during iron extraction and oxygen evolution by MOE. The anode stability is due to the formation of an electronically conductive solid solution of chromium(iii) and aluminium oxides in the corundum structure. These findings make practicable larger-scale evaluation of MOE for the production of steel, and potentially provide a key material component enabling mitigation of greenhouse-gas emissions while producing metal of superior metallurgical quality.

  9. Gas-driven filter pressing in magmas: insights into in-situ melt segregation from crystal mushes

    Science.gov (United States)

    Pistone, M.; Arzilli, F.; Dobson, K. J.; Cordonnier, B.; Reusser, E.; Ulmer, P.; Marone, F.; Whittington, A. G.; Mancini, L.; Fife, J.; Blundy, J. D.

    2015-12-01

    Gas-driven filter pressing is the process of melt expulsion from a volatile-saturated crystal mush, induced by the buildup and subsequent release of gas pressure. Filter pressing is inferred to play a major role in magma fractionation at shallow depths (bubbles and crystals (~74 vol%). Above this threshold, the mush tends to fracture and gas escapes via fractures. Therefore, the efficiency of gas-driven filter pressing is promoted close to the percolation threshold and in situations where a mush inflates slowly relative to build-up of pressure and expulsion of melt. Such observations offer a likely explanation for the production of eruptible, crystal-poor magmas within Earth's crust. Figure = Synchrotron X-ray tomographic microscopy 3D renderings of representative haplogranite (A-D) and dacite (E-H) samples, with different crystal (Φ) and bubble fractions (β) at representative temperatures and experimental times (t, in minutes). Black objects are bubbles and fractures; dark gray field is silicic glass/melt; light gray objects are corundum crystals in haplogranite sample, and quartz in dacite sample. White and black arrows indicate representative fractures and directions of melt expulsion during vesiculation, respectively. In H, white contours highlight quartz cluster boundaries and melt channels where melt is driven by gas bubbles. During experiments, gas exsolution mainly consists of (1) bubble nucleation and growth (white circles) and (2) crystal clustering and/or compaction (white rectangles).

  10. Intensifying digestion of diaspore and separation of alumina and silica

    Institute of Scientific and Technical Information of China (English)

    李小斌; 彭志宏; 刘桂华; 周秋生

    2003-01-01

    It was found that there lies a linear relationship among the thermodynamic data of complicate inorganic compounds with similar components. A method for estimating the thermodynamic data of complicate compound and a thermodynamic database involving alumina production were developed. It was found that the alumina digestion rate of activated diasporic bauxite by means of heat field increased much due to the structure aberration, i.e, from perfect structure to unstable corundum. The results from thermodynamic calculation and experiments showed that it was feasible for desilication at atmospheric pressure, and the effects on equilibrium concentration of SiO2 included temperature, mole ratio of Na2O/Al2O3 (αk), caustic and Na+ concentration. The technology of desilication of green liquor at atmosphere and separation of alumina and silica in aluminate solution with high concentration were established. The reaction activity of compounds containing silica and the converting law among compounds were studied, and the prototype technology of desilication products by hydrotreatment was also developed.

  11. Metal-Anion Pairing at Oxide/Water Interfaces: Theoretical and Experimental Investigations from the Nanoscale to the Macroscale

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Heather [The Ohio State Univ., Columbus, OH (United States)

    2016-11-14

    We combine the use of several techniques including bulk adsorption experiments, X-ray absorption, infrared, total internal reflection Raman, and vibrational sum frequencygeneration (XAS, IR, TIR-Raman, VSFG) spectroscopies, and molecular modeling to investigate ion adsorption at mineral surfaces. XAS and TIR-Raman provides data on how the metal binds to the surface (e.g., monodentate, bidentate), IR provides data on bulk anion adsorption at mineral surfaces from aqueous solutions, and VSFG provides surface specific data on anion adsorption at the mineral surface as well as impact of adsorbed metal-anion pairs on water structure at the mineral surface. Molecular modeling is used to guide spectroscopic data interpretation by providing information on water structure around ions in solution and the structure of metal-anion complexes in aqueous solutions. In addition, molecular modeling is used to provide insight into water structure at mineral surfaces, the surface sites involved in ion adsorption, and the distribution of ion pairs between aqueous solution and the mineral surface. Our studies have focused on systems involving alkaline earth metal (Mg2+, Ca2+, Sr2+, Ba2+) and heavy metal (Co2+, Cd2+) cations. The anions we have selected for studyinclude Cl-, NO3-, ClO4-, SO42-, SeO32-, and SeO42-. Ion adsorption and the potential formation ofternary complexes on silica (quartz, amorphous silica), alumina (corundum and gibbsite), and ferric iron oxides (goethite and hematite) are under investigation.

  12. Features of Minerogenic Series Related to Continental Volcanic Rocks in the Southeastern Coastal Area of China-A Case Study of the Daiyunshan-Shiniushan Volcanic Depression in Fujian

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Daiyunshan-Shiniushan volcanic depression in Fujian Province is situated in a volcanic belt of the southeast coastal area in China along the west Pacific Ocean. A new breakthrough has been made in the exploration of gold and silver ore deposits in recent years. The minerogenic series of the Daiyunshan-Shiniushan volcanic depression is discussed in this paper based on the analysis of major metallogenic types and factors. According to the study of enormous ore deposits and occurrences in the study area, two minerogenic series have been recognized: 1. Late Jurassic Au-Ag-Pb-Zn minerogenic series related to intermediate-acid, acid volcanic formations; 2. nonmetallic minerogenic series (pyrophyllite, alunite pearlite, andalusite, zeolite, corundum and so on) related to intermediate and acid volcanic formations. The division and study of the minerogenic series have revealed metallogenic and time-space distribution characteristics of the ore deposits in the volcanic belt of the southeast coastal area in China , which are of economic importance for metallogenic prognosis .

  13. First light of the VLT planet finder SPHERE. IV. Physical and chemical properties of the planets around HR8799

    CERN Document Server

    Bonnefoy, M; Baudino, J L; Lucas, P; Mesa, D; Maire, A -L; Vigan, A; Galicher, R; Homeier, D; Marocco, F; Gratton, R; Chauvin, G; Allard, F; Desidera, S; Kasper, M; Moutou, C; Lagrange, A -M; Baruffolo, A; Baudrand, J; Beuzit, J -L; Boccaletti, A; Cantalloube, F; Carbillet, M; Charton, J; Claudi, R U; Costille, A; Dohlen, K; Dominik, C; Fantinel, D; Feautrier, P; Feldt, M; Fusco, T; Gigan, P; Girard, J H; Gluck, L; Gry, C; Henning, T; Janson, M; Langlois, M; Madec, F; Magnard, Y; Maurel, D; Mawet, D; Meyer, M R; Milli, J; Moeller-Nilsson, O; Mouillet, D; Pavlov, A; Perret, D; Pujet, P; Quanz, S P; Rochat, S; Rousset, G; Roux, A; Salasnich, B; Salter, G; Sauvage, J -F; Schmid, H M; Sevin, A; Soenke, C; Stadler, E; Turatto, M; Udry, S; Vakili, F; Wahhaj, Z; Wildi, F

    2015-01-01

    The system of four planets around HR8799 offers a unique opportunity to probe the physics and chemistry at play in the atmospheres of self-luminous young (~30 Myr) planets. We recently obtained new photometry of the four planets and low-resolution (R~30) spectra of HR8799 d and e with the SPHERE instrument (paper III). In this paper (paper IV), we compare the available spectra and photometry of the planets to known objects and atmospheric models (BT-SETTL14, Cloud-AE60, Exo-REM) to characterize the atmospheric properties of the planets. We find that HR8799d and e properties are well reproduced by those of L6-L8 dusty dwarfs discovered in the field, among which some are candidate members of young nearby associations. No known object reproduces well the properties of planets b and c. Nevertheless, we find that the spectra and WISE photometry of peculiar and/or young early-T dwarfs reddened by submicron grains made of corundum, iron, enstatite, or forsterite successfully reproduce the SED of these two planets. O...

  14. The Application of Thermal Solar Energy to High Temperature Processes: Case Study of the Synthesis of Alumina from Boehmite

    Directory of Open Access Journals (Sweden)

    Isabel Padilla

    2014-01-01

    Full Text Available The aim of this paper is to evaluate the feasibility of obtaining alumina from boehmite using a free, clean, and unlimited power source as the solar energy. Boehmite was obtained by hydrothermal treatment of a hazardous waste coming from aluminum slag milling. The waste is considered as a hazardous substance because of it releasing toxic gases (hydrogen, ammonia, methane, and hydrogen sulfide in the presence of water. The as-obtained boehmite was transformed into alumina, in air atmosphere, using a solar energy concentrator (Fresnel lens. The solar installation provides a power density of 260 W·cm−2 which allows reaching temperatures upper than 1000°C at few minutes of exposure. Tests were performed at different periods of time that ranged between 5 and 90 min. The percentage of transformation of boehmite into alumina was followed by the water content of samples after solar radiation exposure. Samples were characterized by X-ray diffraction, infrared spectroscopy, and thermogravimetry. Metastable aluminas started to appear at 5 min and the crystalline and stable phase corundum at 10 min of solar radiation exposure.

  15. Short-lived radioactivity in the early Solar System: the Super-AGB star hypothesis

    CERN Document Server

    Lugaro, Maria; Karakas, Amanda I; Maddison, Sarah T; Liffman, Kurt; García-Hernández, D A; Siess, Lionel; Lattanzio, John C

    2012-01-01

    The composition of the most primitive Solar System condensates, such as calcium-aluminum-rich inclusions (CAI) and micron-sized corundum grains, show that short-lived radionuclides (SLR), e.g., 26Al, were present in the early Solar System. Their abundances require a local origin, which however is far from being understood. We present for the first time the abundances of several SLR up to 60Fe predicted from stars with initial mass in the range roughly 7-11 Msun. These stars evolve through core H, He, and C burning. After core C burning they go through a "Super"-asymptotic giant branch (Super-AGB) phase, with the H and He shells activated alternately, episodic thermal pulses in the He shell, a very hot temperature at the base of the convective envelope (~ 10^8 K), and strong stellar winds driving the H-rich envelope into the surrounding interstellar medium. The final remnants of the evolution of Super-AGB stars are mostly O-Ne white dwarfs. Our Super-AGB models produce 26Al/27Al yield ratios ~ 0.02 - 0.26. The...

  16. Study of Selected Properties of Thermally Sprayed Coatings Containing WC and WB Hard Particles

    Directory of Open Access Journals (Sweden)

    Brezinová Janette

    2016-12-01

    Full Text Available The paper presents results of research of the essential characteristics of two kinds of advanced coatings applied by HVOF technology. One studied coating: WB-WC-Co (60-30-10% contains two types of hard particles (WC and WB, the second coating is eco-friendly alternative to the previously used WC-based coatings, called “green carbides” with the composition WC-FeCrAl (85-15%. In green carbides coating the heavy metals (Co, Ni, NiCr forming the binding matrix in conventional wear-resistant coatings are replaced by more environmentally friendly matrix based on FeCrAl alloy. On the coatings was carried out: metallographic analysis, measurement of thickness, micro-hardness, adhesion, resistance to thermal cyclic loading and adhesive wear resistance (pin-on-disk test. One thermal cycle consisted of heating the coatings to 600°C, dwell for 10 minutes, and subsequently cooling on the still air. The number of thermal cycles: 10. The base material was stainless steel AISI 316L, pretreatment prior to application of the coating: blasting with white corundum, application device JP-5000.

  17. Combined PIXE/PIGE and IBIL with external beam applied to the analysis of Merovingian glass beads

    Energy Technology Data Exchange (ETDEWEB)

    Mathis, F., E-mail: francois.mathis@ulg.ac.b [Centre Europeen d' Archeometrie, Universite de Liege, Sart Tilman B15 4000 Liege (Belgium); Othmane, G. [Centre Europeen d' Archeometrie, Universite de Liege, Sart Tilman B15 4000 Liege (Belgium); Vrielynck, O. [Service Public de Wallonie Direction de l' Archeologie (Belgium); Calvo del Castillo, H. [Centre Europeen d' Archeometrie, Universite de Liege, Sart Tilman B15 4000 Liege (Belgium); Chene, G.; Dupuis, T. [Centre Europeen d' Archeometrie, Universite de Liege, Sart Tilman B15 4000 Liege (Belgium); Institut de Physique Nucleaire, Atomique et de Spectroscopie, Universite de Liege (Belgium); Strivay, D. [Centre Europeen d' Archeometrie, Universite de Liege, Sart Tilman B15 4000 Liege (Belgium); Service Public de Wallonie Direction de l' Archeologie (Belgium)

    2010-06-15

    New improvements on our archaeometry line at the cyclotron of the Institute of Nuclear and Atomic Physics and of Spectrometry of the University of Liege have allowed the use of PIXE/PIGE and IBIL in-air for the analysis of cultural heritage objects. The extraction is performed through a 100 nm thick Si{sub 3}N{sub 4} window. The detection set-up consists now of two X-ray and one {gamma}-ray detectors, together with a fiber optic UV-visible spectrometer. This set-up has already been tested for the analysis of modern corundum and is now adapted to the analysis of archaeological artefacts. In this work, we have used it to analyse 216 out of the 5000 Merovingian glass beads that come from the necropolis of Bossut-Gottechain (Belgium), one of the most important ever found in Belgium. The IBA analyses confirmed the typological division of different beads groups through chemical composition that gives us new insights on fabrication techniques of glass matrices and colorants.

  18. Mullite phase equilibria in the system: CaO--Al/sub 2/O/sub 3/--SiO/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Draper, V.F.

    1976-10-01

    Sapphire-liquid diffusion couples annealed in sealed molybdenum crucibles in the temperature range of 1602/sup 0/C to 1787/sup 0/C were analyzed by electron beam microprobe. Interfacial compositions across the phase boundaries were used to determine the stable composition range of the mullite phase field and the location of the mullite-corundum boundary. Experiments utilizing quenching methods were also conducted to establish the extent that the metastable nature of the Al/sub 2/O/sub 3/-SiO/sub 2/ system extended into the ternary CaO-Al/sub 2/O/sub 3/-SiO/sub 2/ system and to determine any solid solubility of CaO in mullite. Further evidence was obtained to confirm the recognized value of approximately 82.5 wt percent Al/sub 2/O/sub 3/ as the upper solubility limit for metastable disordered mullite in the binary Al/sub 2/O/sub 3/-SiO/sub 2/ system.

  19. Evaluation of internally consistent parameters for the triple-layer model by the systematic analysis of oxide surface titration data

    Energy Technology Data Exchange (ETDEWEB)

    Sahai, N.; Sverjensky, D.A. [Johns Hopkins Univ., Baltimore, MD (United States)

    1997-07-01

    Systematic analysis of surface titration data from the literature has been performed for ten oxides (anatase, hematite, goethite, rutile, amorphous silica, quartz, magnetite, {delta}-MnO{sub 2}, corundum, and {gamma}-alumina) in ten electrolytes (LiNO{sub 3}, NaNO{sub 3}, KNO{sub 3}, CsNO{sub 3}, LiCl, NaCl, KCl, CsCl, Nal, and NaClO{sub 4}) over a wide range of ionic strengths (0.001 M-2.9 M) to establish adsorption equilibrium constants and capacitances consistent with the triple-layer model of surface complexation. Experimental data for the same mineral in different electrolytes and data for a given mineral/electrolyte system from various investigators have been compared. In this analysis, the surface protonation constants (K{sub s,1} and K{sub s,2}) were calculated by combining predicted values of {Delta}pK(log K{sub s,2} - log K{sub s,1}) with experimental points of zero charge; site-densities were obtained from tritium-exchange experiments reported in the literature, and the outer-layer capacitance (C{sub 2}) was set at 0.2 F {center_dot} m{sup -2}. 98 refs., 8 figs., 27 tabs.

  20. Microstructure, Mechanical and Surface Morphological Properties of Al5Ti5Cr Master Alloy as Friction Material Prepared by Stir Die Casting

    Science.gov (United States)

    Ahmed, Syed Faisal; Srivastava, Sanjay; Agarwal, Alka Bani

    2017-06-01

    Metal matrix composite offers outstanding properties for better performance of disc brakes. In the present study, the composite of AlTiCr master alloy was prepared by stir die casting method. The developed material was reinforced with (0-10 wt%) silicon carbide (SiC) and boron carbide (B4C). The effects of SiC reinforcement from 0 to 10 wt% on mechanical, microstructure and surface morphological properties of Al MMC was investigated and compared with B4C reinforcement. Physical properties like density and micro Vickers hardness number show an increasing trend with an increase in the percentage of SiC and B4C reinforcement. Mechanical properties viz. UTS, yield strength and percentage of elongation are improved with increasing the fraction of reinforcement. The surface morphology and phase were identified from scanning electron microscopy (SEM) and X-ray diffraction analysis and the oxidized product formed during the casting was investigated by Fourier transformation infrared spectroscopy. This confirms the presence of crystallization of corundum (α-Al2O3) in small traces as one of the alumina phases, within casting sample. Micro-structural characterization by SEM depicted that the particles tend to be more agglomerated more and more with the percentage of the reinforcement. The AFM results reveal that the surface roughness value shows a decreasing trend with SiC reinforcement while roughness increases with increase the percentage of B4C.

  1. Effects of alternate fuels. Report No. 6. Analysis of low-alumina castable refractory degraded by residual oil combustion products

    Energy Technology Data Exchange (ETDEWEB)

    Wei, G. C.; Tennery, V. J.

    1978-07-01

    This is the sixth of a series of reports on analyses of several types of refractories used in industrial furnaces with fuels considered alternate to natural gas. Analyses were performed on a low-alumina castable used for only two months in the roof of a residual-oil-fired boiler. The maximum hot-face temperature during operation was about 1530/sup 0/K. The original microstructure of the castable, which consisted of mullite aggregate bonded with iron-containing gehlenite (2 CaO . Al/sub 2/O/sub 3/ . SiO/sub 2/), quartz and cristobalite, was totally altered during service in regions close to the hot face. At room temperature the altered microstructure consisted of corundum and gehlenite in a new oxide glass phase containing the elements Na, K, Ca, Fe, Ti, Al, Ni, and Si. The reactions of the fuel oil impurities Na, Fe, and Ni with mullite, quartz, and cristobalite in the original castable refractory caused the rapid degradation at the hot face during service in the boiler. Increasing the Al/sub 2/O/sub 3/ content of the castable by replacing mullite aggregate with alumina aggregate and using gehlenite with less iron impurity as the bonding material should improve the performance of this castable refractory or retard reactions of the castable with fuel oil combustion products including Na, Fe, and Ni.

  2. Effects of Starch on Properties of Alumina-based Ceramic Cores

    Directory of Open Access Journals (Sweden)

    LI Fengguang

    2016-12-01

    Full Text Available In order to improve the poor leachability of alumina-based ceramic cores, different amount of starch was added to the specimens as pore former. Alumina-based ceramic cores were prepared by hot injection technology using corundum powder as base material, paraffin wax and beeswax as plasticizer, silica powder and magnesium oxide powder as mineralizing agent, wherein the parameters of the hot injection process were as follows:temperature of the slurry was 90℃, hot injection pressure was 0.5 MPa and holding time was 25 s. The effects of starch content on the properties of alumina-based ceramic cores were studied and discussed. The results indicate that during sintering period, the loss of starch in the specimens makes porosity of the alumina-based ceramic cores increase. When starch content increases, the room-temperature flexural strength of the ceramic cores reduces and the apparent porosity increases; the volatile solvent increases and the bulk density decreases. After being sintered at 1560℃ for 2.5 h, room-temperature flexural strength of the alumina-based ceramic cores with starch content of 8%(mass fraction is 24.8 MPa, apparent porosity is 47.98% when the volatile solvent is 1.92 g/h and bulk density is 1.88 g/cm3, the complex properties are optimal.

  3. Boundary magnetization properties of epitaxial C r2 -xA lxO3 thin films

    Science.gov (United States)

    Fallarino, Lorenzo; Binek, Christian; Berger, Andreas

    2015-06-01

    The magnetoelectric antiferromagnet α -C r2O3 (chromia) is known to possess a roughness insensitive net equilibrium magnetization at the (0001) surface, called boundary magnetization (BM), which is coupled to the bulk antiferromagnetic order parameter. In order to verify whether this symmetry sensitive BM persists in alloys, we investigate the impact of diamagnetic dilution on chromia thin films alloyed with the isostructural α -A l2O3 (alumina). Single-crystalline C r2 -xA lxO3 thin films with (0001) surface orientation and varying stoichiometry have been grown by sputter codeposition in the concentration range between x =0 and x =0.6 . For these samples, we find the corundum crystal structure, the antiferromagnetic ordering, and the boundary magnetization to be preserved. We also find that the critical temperature TN can be tuned by alloying with α -A l2O3 , using the BM as a probe to study the magnetic phase transition. Furthermore, we were able to evaluate the critical exponent and the absolute BM values for different samples. Both properties corroborate that the observed magnetic signals originate from the BM rather than the bulk of the samples.

  4. Ferromagnetic boundary magnetization properties of epitaxial Cr(2 - x)Al(x)O3 thin films

    Science.gov (United States)

    Fallarino, Lorenzo; Binek, Christian; Berger, Andreas

    2015-03-01

    The existence of an equilibrium net magnetization at (0001) surfaces is enabled by symmetry constrains for the magnetoelectric antiferromagnet α-Cr2O3. The occurrence of this boundary magnetization (BM) is furthermore roughness insensitive. The BM is hereby fully coupled to the bulk antiferromagnetic order parameter and can be reversed together with it by a combination of E and H fields in bulk materials, or solely by magnetic means for single crystal (0001) oriented thin chromia films. In order to understand whether the BM can be extended to alloys containing different oxide materials, we investigated the effect of Al2O3 doping onto the structural and magnetic properties of α-Cr2O3. We grew, using a hybrid growth procedure, 100 nm thick high-quality epitaxial Cr2-xAlxO3(0001) thin films in the concentration range between x =0 to x =0.6, preserving the original corundum crystal structure and symmetry. Using SQUID magnetometry, we showed that the critical temperature TN can be tuned by alloying with α-Al2O3 using the BM as a probe to study the magnetic transition. Furthermore, we were able to evaluate the critical exponent and the absolute BM values for different samples. Both properties are consistent with the expected values, corroborating the BM nature of the observed magnetic signals.

  5. Improve oxidation resistance at high temperature by nanocrystalline surface layer.

    Science.gov (United States)

    Xia, Z X; Zhang, C; Huang, X F; Liu, W B; Yang, Z G

    2015-08-13

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

  6. Selection of refractory materials for acid tanks at the CSN continuous pickling line; Selecao de materiais refratarios para tanques de acido das linhas de decapagem continua da CSN

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Sidiney Nascimento; Marques, Oscar Rosa; Bueno, Mauricio Chaves [Companhia Siderurgica Nacional, Volta Redonda, RJ (Brazil); Longo, Elson; Silva Pinheiro, Adriano da [Sao Carlos Univ., SP (Brazil). Dept. de Quimica

    1997-12-31

    Aiming at the revamping of the CSN continuous pickling line 4 acid tanks, a Post Mortem study of the refractory lining was carried out. The collected samples were characterized through techniques such as chemical analysis, mercury porosimetry, X-ray diffraction and scanning electronic microscopy. Trying to reproduce the operational conditions closely, laboratorial simulations were carried out. Such simulations lead to the addition of some alterations on the test method proposed by ABNT. Primarily, the sulfuric acid was substituted by hydrochloric acid (30%), containing iron in solution (130g/l). As result, it was concluded that acid resistant refractories containing a smaller alumina and /or corundum and mullite concentrations, presenting a smaller open porosity and average pore diameter, have a better performance face to corrosion due to hydrochloric acid solution. In addition, abrasion wear resistance tests, according to the ASTM-G65-85 standard were carried out in order to select different materials to the acid tanks cells. (author) 3 refs., 5 figs., 12 tabs.

  7. Experimental Study on Specific Heat of Concrete at High Temperatures and Its Influence on Thermal Energy Storage

    Directory of Open Access Journals (Sweden)

    Jianwen Pan

    2016-12-01

    Full Text Available Using concrete as a thermal energy storage (TES material is a promising option for large-scale solar-thermal resource development and utilization. Specific heat is one of the most important characteristics for TES performance. In this paper, the half-open dynamic method based on the mixing principle is proposed and applied to measure concrete-specific heat at temperatures up to 600 °C. Measurement of the specific heat of corundum ceramic (99% Al2O3 is first performed, and the test results illustrate the accuracy and efficiency of the proposed test method. Furthermore, concrete-specific heat tests are carried out at high temperatures. It found that the specific heat increases as the temperature rises, especially, linearly in the range of 300–600 °C, in which the concrete TES module is expected to be in operation. Finally, the effect of concrete-specific heat changes with temperature on its TES capacity is investigated, demonstrating that specific heat is of great significance for concrete TES design for concentrating solar power.

  8. Anvil cell gasket design for high pressure nuclear magnetic resonance experiments beyond 30 GPa

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Thomas; Haase, Jürgen [Faculty of Physics and Earth Sciences, University of Leipzig, Linnéstrasse 5, Leipzig 04103 (Germany)

    2015-12-15

    Nuclear magnetic resonance (NMR) experiments are reported at up to 30.5 GPa of pressure using radiofrequency (RF) micro-coils with anvil cell designs. These are the highest pressures ever reported with NMR, and are made possible through an improved gasket design based on nano-crystalline powders embedded in epoxy resin. Cubic boron-nitride (c-BN), corundum (α-Al{sub 2}O{sub 3}), or diamond based composites have been tested, also in NMR experiments. These composite gaskets lose about 1/2 of their initial height up to 30.5 GPa, allowing for larger sample quantities and preventing damages to the RF micro-coils compared to precipitation hardened CuBe gaskets. It is shown that NMR shift and resolution are less affected by the composite gaskets as compared to the more magnetic CuBe. The sensitivity can be as high as at normal pressure. The new, inexpensive, and simple to engineer gaskets are thus superior for NMR experiments at high pressures.

  9. Dusty tails of evaporating exoplanets. I. Constraints on the dust composition

    CERN Document Server

    van Lieshout, R; Dominik, C

    2014-01-01

    Recently, two exoplanet candidates have been discovered, KIC 12557548b and KOI-2700b, whose transit profiles show evidence for a comet-like tail of dust trailing the planet, thought to be fed by the evaporation of the planet's surface. We aim to put constraints on the composition of the dust ejected by these objects from the shape of their transit light curves. We derive a semi-analytical expression for the attenuation of dust cross-section in the tail, incorporating the sublimation of dust grains as well as their drift away from the planet. This expression shows that the length of the tail is highly sensitive to the sublimation properties of the dust material. We compute tail lengths for several possible dust compositions, and compare these to observational estimates of the tail lengths of KIC 12557548b and KOI-2700b, inferred from their light curves. The observed tail lengths are consistent with dust grains composed of corundum (Al2O3) or iron-rich silicate minerals (e.g., fayalite, Fe2SiO4). Pure iron and ...

  10. Updating of the interpretation of the optical absorption and emission of Verneuil synthetic and natural metamorphic blue sapphire: the role of V{sup 2+}, V{sup 3+} and Cr{sup 2+}

    Energy Technology Data Exchange (ETDEWEB)

    Palanza, V; Chiodini, N; Galli, A; Lorenzi, R; Moretti, F; Paleari, A; Spinolo, G, E-mail: giorgio.spinolo@mater.unimib.it [Department of Materials Science, University of Milano-Bicocca, Via Cozzi 53, Milano 20125 (Italy)

    2010-11-15

    In the blue colored sapphires of metamorphic origin and Verneuil synthetic studied here, the absorption-emission properties in the VIS-NIR range are largely determined by Cr{sup 3+} and Ti{sup 3+}, as we have been able to demonstrate recently. In that work a sharp radio-luminescence band occurring at 870 nm in Verneuil blue sapphires was left unattributed: here we give evidence for the attribution of that band to the {sup 2}E emission transition of V{sup 2+}, and for the existence of such an emission also in natural samples of metamorphic origin. After such a result, we accurately evaluated by EDXRF the V concentrations in various samples and found the ion more ubiquitous than foreseen. We then searched for and found, weak but diagnostic spin forbidden transitions and phonon sequencies in the absorption spectra of samples sufficiently rich in V. The experimental results just mentioned allowed us to discuss the effects of the overlap of V{sup 3+} and Cr{sup 3+} spin-allowed absorption bands on the spectrum of the varieties of corundum under study. To complete the updating of the interpretation, we spent a further effort to strengthen the attribution of the absorption band at 14500 cm{sup -1} (currently interpreted as an IVCT (Fe{sup 2+} {yields} Fe{sup 3+})) to the {sup 5}E{yields}{sup 5}T{sub 2} transitions of Cr{sup 2+}.

  11. Updating of the interpretation of the optical absorption and emission of Verneuil synthetic and natural metamorphic blue sapphire: the role of V2+, V3+ and Cr2+

    Science.gov (United States)

    Palanza, V.; Chiodini, N.; Galli, A.; Lorenzi, R.; Moretti, F.; Paleari, A.; Spinolo, G.

    2010-11-01

    In the blue colored sapphires of metamorphic origin and Verneuil synthetic studied here, the absorption-emission properties in the VIS-NIR range are largely determined by Cr3+ and Ti3+, as we have been able to demonstrate recently. In that work a sharp radio-luminescence band occurring at 870 nm in Verneuil blue sapphires was left unattributed: here we give evidence for the attribution of that band to the 2E emission transition of V2+, and for the existence of such an emission also in natural samples of metamorphic origin. After such a result, we accurately evaluated by EDXRF the V concentrations in various samples and found the ion more ubiquitous than foreseen. We then searched for and found, weak but diagnostic spin forbidden transitions and phonon sequencies in the absorption spectra of samples sufficiently rich in V. The experimental results just mentioned allowed us to discuss the effects of the overlap of V3+ and Cr3+ spin-allowed absorption bands on the spectrum of the varieties of corundum under study. To complete the updating of the interpretation, we spent a further effort to strengthen the attribution of the absorption band at 14500 cm-1 (currently interpreted as an IVCT (Fe2+ → Fe3+)) to the 5E→5T2 transitions of Cr2+.

  12. Test of different measures for the prevention of scaling in the cooling system of Grohnde nuclear power plant; Test verschiedener Massnahmen zur Verhuetung von Kalkablagerungen im Kuehlsystem des Kernkraftwerks Grohnde

    Energy Technology Data Exchange (ETDEWEB)

    Czolkoss, W. [Taprogge GmbH, Wetter (Germany); Jacobi, G.; Schueler, A. [Gemeinschaftskernkraftwerk Grohnde GmbH, Emmerthal (Germany); Fichte, W. [Allianz-Zentrum fuer Technik GmbH (AZT), Ismaning (Germany)

    2002-07-01

    In the cooling system of the Grohnde Nuclear Power Plant, heavy calcium carbonate precipitations have occurred in the turbine condenser and in the cooling tower since 1994. Those precipitations cause performance losses and high cleaning costs. Reasons for the intensified precipitation are apparently the biologically upgraded water quality of the river Weser, as well as specific operational conditions of the cooling system (partial recirculation of cooling water). It was noticed that the formation of calcium carbonate deposits occurred within a limited period of less than two weeks in May. The calcium precipitation was that strong during this time that it could not be stopped despite the immediate application of corundum cleaning balls in the tube cleaning system. (orig.) [German] Im Kuehlsystem des Kernkraftwerks Grohnde kommt es seit 1994 zu starken Kalkausfaellungen im Turbinenkondensator und im Kuehlturm, die Leistungsverluste und hohe Reinigungskosten verursachen. Das Auftreten der Kalkabscheidungen haengt offensichtlich mit der oekologisch verbesserten Wasserqualitaet der Weser und spezifischen Betriebsbedingungen des Kuehlsystems zusammen. Die Auswertung der Betriebsmessdaten des Kuehlwassers zeigt, dass eine der Ursachen der zeitlich begrenzten, extremen Kalkabscheidung im Kuehlsystem offenbar das Wachstum von Mikroorganismen in der Weser ist, aus der das Kuehlsystem gespeist wird. (orig.)

  13. The effect of the regular solution model in the condensation of protoplanetary dust

    CERN Document Server

    Pignatale, Francesco C; Taquet, Vianney; Brooks, Geoffrey; Liffman, Kurt

    2011-01-01

    We utilize a chemical equilibrium code in order to study the condensation process which occurs in protoplanetary discs during the formation of the first solids. The model specifically focuses on the thermodynamic behaviour on the solid species assuming the regular solution model. For each solution, we establish the relationship between the activity of the species, the composition and the temperature using experimental data from the literature. We then apply the Gibbs free energy minimization method and study the resulting condensation sequence for a range of temperatures and pressures within a protoplanetary disc. Our results using the regular solution model show that grains condense over a large temperature range and therefore throughout a large portion of the disc. In the high temperature region (T > 1400 K) Ca-Al compounds dominate and the formation of corundum is sensitive to the pressure. The mid-temperature region is dominated by Fe(s) and silicates such as Mg2SiO4 and MgSiO3 . The chemistry of forsteri...

  14. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    Science.gov (United States)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  15. Spinel formation for stabilizing simulated nickel-laden sludge with aluminum-rich ceramic precursors.

    Science.gov (United States)

    Shih, Kaimin; White, Tim; Leckie, James O

    2006-08-15

    The feasibility of stabilizing nickel-laden sludge from commonly available Al-rich ceramic precursors was investigated and accomplished with high nickel incorporation efficiency. To simulate the process, nickel oxide was mixed alternatively with gamma-alumina, corundum, kaolinite, and mullite and was sintered from 800 to 1480 degrees C. The nickel aluminate spinel (NiAl2O4) was confirmed as the stabilization phase for nickel and crystallized with efficiencies greater than 90% for all precursors above 1250 degrees C and 3-h sintering. The nickel-incorporation reaction pathways with these precursors were identified, and the microstructure and spinel yield were investigated as a function of sintering temperature with fixed sintering time. This study has demonstrated a promising process for forming nickel spinel to stabilize nickel-laden sludge from a wide range of inexpensive ceramic precursors, which may provide an avenue for economically blending waste metal sludges via the building industry processes to reduce the environmental hazards of toxic metals. The correlation of product textures and nickel incorporation efficiencies through selection of different precursors also provides the option of tailoring property-specific products.

  16. Origin and geochemistry of Pan-African granitoid rocks in the Gabal Um Shomer area, Southwestern Sinai, Egypt

    Institute of Scientific and Technical Information of China (English)

    E1-Tokhi M.M.; Musallum A.; Amin B.M.

    2009-01-01

    Geological, petrological and geochemical studies indicated that there are two distinct types of granitoid rocks: older quartz diorites to granodiorite assemblage and younger granitoids, the latter occurring in two phases. The older granitoids have a meta-aluminous chemistry and a calc-alkaline character, with high MgO, Fe2O3, TiO2, CaO, P2O5, Sr and low SiO2, K2O, and Rb. Their major and trace elements data, together with low 87Sr/ 86Sr ratios (0.7029±0.0008) are indicative of I-type affinities. The second- and third-phase granitoids range from calc-alkaline to alkaline, respectively. The second-phase granitoids have a peraluminous chemistry and high Sr, Ba, CaO, MgO, Al2O3 and Ti2O and low SiO2, K2O, Nb, Y and Rb relative to the third-phase granitoids. The corundum normative nature and field observations suggested that it was formed by partial melting of the lower crust. The third-phase granitoids are alkaline in nature and characterized by higher SiO2, Rb, Y, Nb and lower MgO, Sr and Ba values than the younger granitoids (phase II). They are A-type granitoids which were generated from below or within the existing continental crust.

  17. Phase and Micro-Structural Characterization of Sanitary-Ware Fired at Different Temperature

    Directory of Open Access Journals (Sweden)

    ATHER HASSAN

    2017-07-01

    Full Text Available The three main ingredients of sanitary-ware are clay, feldspar and quartz. This ware is being widely used and has therefore, attracted the attention of researchers from time to time. Consequently, it has been extensively investigated. The present study describes the phase and micro-structural analysis of sanitary-ware samples collected from local (Durr Ceramics Peshawar industry. XRD (X-Ray Diffraction of samples fired at 1100oC reveals the presence of ? ? ? ? ?-quartz and primary mullite only. In addition to a-quartz and primary mullite, elongated needles of secondary mullite were also present in samples fired at 1200 and 1300oC. Unlike typical vitreous ceramics bodies, regions containing elongated secondary mullite originating from the clay relict and growing into the feldspar relict were few in number which is consistent with the high clay content in the starting body ingredients of the investigated samples. Another sample investigated for comparison purposes, contained all the phases mentioned above along with some corundum grains which indicated that the composition of sanitary ware varied from manufacturer to manufacturer. EDS (Energy Dispersive Spectroscopy detected high concentration of Fe in some regions in the bulk but the glaze did not contain any Fe.

  18. A influência simultânea do teor de alumina, da porosidade total e da temperatura na condutividade térmica de refratários sílico-aluminosos e aluminosos The simultaneous influence of alumina content, total porosity and temperature on the thermal conductivity of fireclay and alumina refractories

    Directory of Open Access Journals (Sweden)

    M. M. Akiyoshi

    2001-09-01

    Full Text Available A condutividade térmica de materiais refratários sílico-aluminosos e aluminosos com 35,81%-p 0,93 permite concluir que a utilização da razão R pode ser mais significa para a condutividade térmica de cerâmicas refratárias do que a utilização do teor de alumina ou quantidade de coríndon isoladamente. Estas relações são fundamentais no projeto de fornos e equipamentos que empreguem cerâmicas refratárias além de serem dados de entrada adequados para suprir programas de simulação computacional que visem à previsão do comportamento termomecânico destes materiais.Thermal conductivity of high alumina and fireclay refractories with 35.81 wt% 0.93 allows concluding that the use of R ratio is more effective in the thermal conductivity of refractory ceramics than using only the alumina content or the amount of corundum. These relationships obtained in this work are important in the project of furnaces and equipments that uses refractories. They are also suitable data to input computer simulation programs aiming to evaluate the thermomechanical behavior of refractory ceramics.

  19. Anomalous structural disorder and distortion in metal-to-insulator-transition Ti{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, In-Hui; Jin, Zhenlan; Park, Chang-In; Han, Sang-Wook, E-mail: shan@jbnu.ac.kr [Department of Physics Education and Institute of Fusion Science, Jeonbuk(Chonbuk) National University, Jeonju 561-756 (Korea, Republic of); Jiang, Bingzhi [Department of Physics, Yanbian University, Yanji 133002 (China)

    2016-01-07

    Mott proposed that impurity bands in corundum-symmetry Ti{sub 2}O{sub 3} at high temperatures caused a collapse in the bandgap. However, the origin of the impurity bands has not yet been clarified. We examine the local structural properties of metal-to-insulator-transition Ti{sub 2}O{sub 3} using in-situ x-ray absorption fine structure (XAFS) measurements at the Ti K edge in the temperature range from 288 to 739 K. The Ti{sub 2}O{sub 3} powder is synthesized by using a chemical reaction method. X-ray diffraction (XRD) measurements from Ti{sub 2}O{sub 3} with a Rietveld refinement demonstrate a single-phased R-3c symmetry without additional distortion. Extended-XAFS combined with XRD reveals a zigzag patterned Ti position and an anomalous structural disorder in Ti-Ti pairs, accompanied by a bond length expansion of the Ti-Ti pairs along the c-axis for T > 450 K. The local structural distortion and disorder of the Ti atoms would induce impurity levels in the band gap between the Ti 3d a{sub 1g} and e{sub g}{sup π} bands, resulting in a collapse of the band gap for T > 450 K.

  20. Progress in art and science of crystal growth and its impacts on modern society

    Science.gov (United States)

    Nishinaga, Tatau

    2015-05-01

    The impacts of the progress in the art and science of crystal growth on human life are reviewed. Even before the invention of the transistor, quartz and corundum crystals were used as crystal oscillators and jewel bearings, respectively. However, a major impact of crystal growth on society was experienced with the invention of the transistor, which required high-purity and perfect germanium crystals. Once the importance of crystal growth was clearly recognized, the science of crystal growth also extensively developed. The growth of single crystalline silicon allows us to produce integrated circuits, which are used in all the electronic devices in everyday use. The technological developments in the growth of compound semiconductors have also had a large impact on society through the inventions of the laser diode for optical communication and the p-n junction nitride light-emitting diode toward the realization of a less energy-intensive society. The latter invention was awarded the 2014 Nobel Prize in Physics. Finally, future aspects of crystal growth are discussed.

  1. Thermal Stability of NaxCrO2 for Rechargeable Sodium Batteries; Studies by High-Temperature Synchrotron X-ray Diffraction.

    Science.gov (United States)

    Yabuuchi, Naoaki; Ikeuchi, Issei; Kubota, Kei; Komaba, Shinichi

    2016-11-30

    Thermal stability and phase transition processes of NaCrO2 and Na0.5CrO2 are carefully examined by high-temperature synchrotron X-ray diffraction method. O3-type NaCrO2 shows anisotropic thermal expansion on heating, which is a common character as layered materials, without phase transition in the temperature range of 27-527 °C. In contrast, for the desodiated phase, in-plane distorted P3-type layered oxide (P'3 Na0.5CrO2), phase transition occurs in the following order. Monoclinic distortion associated with Na/vacancy ordering is gradually lost on heating, and its symmetry increases and changes to a rhombohedral lattice at 207 °C. On further heating, phase segregation to two P3 layered metastable phases, which have different interlayer distances (17.0 and 13.5 Å, presumably sodium-rich and sodium-free P3 phases, respectively) are observed on heating to 287-477 °C, but oxygen loss is not observed. Oxygen loss is observed at temperatures only above 500 °C, resulting in the formation of corundum-type Cr2O3 and O3 NaCrO2 as thermodynamically stable phases. From these results, possibility of NaxCrO2 as a positive electrode material for safe rechargeable sodium batteries is also discussed.

  2. Combined PIXE/PIGE and IBIL with external beam applied to the analysis of Merovingian glass beads

    Science.gov (United States)

    Mathis, F.; Othmane, G.; Vrielynck, O.; Calvo del Castillo, H.; Chêne, G.; Dupuis, T.; Strivay, D.

    2010-06-01

    New improvements on our archaeometry line at the cyclotron of the Institute of Nuclear and Atomic Physics and of Spectrometry of the University of Liège have allowed the use of PIXE/PIGE and IBIL in-air for the analysis of cultural heritage objects. The extraction is performed through a 100 nm thick Si 3N 4 window. The detection set-up consists now of two X-ray and one γ-ray detectors, together with a fiber optic UV-visible spectrometer. This set-up has already been tested for the analysis of modern corundum [1] and is now adapted to the analysis of archaeological artefacts. In this work, we have used it to analyse 216 out of the 5000 Merovingian glass beads that come from the necropolis of Bossut-Gottechain (Belgium), one of the most important ever found in Belgium. The IBA analyses confirmed the typological division of different beads groups through chemical composition that gives us new insights on fabrication techniques of glass matrices and colorants.

  3. Thermochemical properties of gibbsite, bayerite, boehmite, diaspore, and the aluminate ion between 0 and 350/degree/C

    Energy Technology Data Exchange (ETDEWEB)

    Apps, J.A.; Neil, J.M.; Jun, C.H.

    1989-01-01

    A requirement for modelling the chemical behavior of groundwater in a nuclear waste repository is accurate thermodynamic data pertaining to the participating minerals and aqueous species. In particular, it is important that the thermodynamic properties of the aluminate ion be accurately determined, because most rock forming minerals in the earth's crust are aluminosilicates, and most groundwaters are neutral to slightly alkaline, where the aluminate ion is the predominant aluminum species in solution. Without a precise knowledge of the thermodynamic properties of the aluminate ion aluminosilicate mineral solubilities cannot be determined. The thermochemical properties of the aluminate ion have been determined from the solubilities of the aluminum hydroxides and oxyhydroxides in alkaline solutions between 20 and 350/degree/C. An internally consistent set of thermodynamic properties have been determined for gibbsite, boehmite, diaspore and corundum. The thermodynamic properties of bayerite have been provisionally estimated and a preliminary value for ..delta..G/sub f, 298//sup 0/ of nordstrandite has been determined. 205 refs., 17 figs., 25 tabs.

  4. Gemstones and geosciences in space and time. Digital maps to the "Chessboard classification scheme of mineral deposits"

    Science.gov (United States)

    Dill, Harald G.; Weber, Berthold

    2013-12-01

    The gemstones, covering the spectrum from jeweler's to showcase quality, have been presented in a tripartite subdivision, by country, geology and geomorphology realized in 99 digital maps with more than 2600 mineralized sites. The various maps were designed based on the "Chessboard classification scheme of mineral deposits" proposed by Dill (2010a, 2010b) to reveal the interrelations between gemstone deposits and mineral deposits of other commodities and direct our thoughts to potential new target areas for exploration. A number of 33 categories were used for these digital maps: chromium, nickel, titanium, iron, manganese, copper, tin-tungsten, beryllium, lithium, zinc, calcium, boron, fluorine, strontium, phosphorus, zirconium, silica, feldspar, feldspathoids, zeolite, amphibole (tiger's eye), olivine, pyroxenoid, garnet, epidote, sillimanite-andalusite, corundum-spinel - diaspore, diamond, vermiculite-pagodite, prehnite, sepiolite, jet, and amber. Besides the political base map (gems by country) the mineral deposit is drawn on a geological map, illustrating the main lithologies, stratigraphic units and tectonic structure to unravel the evolution of primary gemstone deposits in time and space. The geomorphological map is to show the control of climate and subaerial and submarine hydrography on the deposition of secondary gemstone deposits. The digital maps are designed so as to be plotted as a paper version of different scale and to upgrade them for an interactive use and link them to gemological databases.

  5. Improving tribological properties of Ti-5Zr-3Sn-5Mo-15Nb alloy by double glow plasma surface alloying

    Science.gov (United States)

    Guo, Lili; Qin, Lin; Kong, Fanyou; Yi, Hong; Tang, Bin

    2016-12-01

    Molybdenum, an alloying element, was deposited and diffused on Ti-5Zr-3Sn-5Mo-15Nb (TLM) substrate by double glow plasma surface alloying technology at 900, 950 and 1000 °C. The microstructure, composition distribution and micro-hardness of the Mo modified layers were analyzed. Contact angles on deionized water and wear behaviors of the samples against corundum balls in simulated human body fluids were investigated. Results show that the surface microhardness is significantly enhanced after alloying and increases with treated temperature rising, and the contact angles are lowered to some extent. More importantly, compared to as-received TLM alloy, the Mo modified samples, especially the one treated at 1000 °C, exhibit the significant improvement of tribological properties in reciprocating wear tests, with lower specific wear rate and friction coefficient. To conclude, Mo alloying treatment is an effective approach to obtain excellent comprehensive properties including optimal wear resistance and improved wettability, which ensure the lasting and safety application for titanium alloys as the biomedical implants.

  6. Growth of ultrathin vanadium oxide films on Ag(100)

    Science.gov (United States)

    Nakamura, Takuya; Sugizaki, Yuichi; Ishida, Shuhei; Edamoto, Kazuyuki; Ozawa, Kenichi

    2016-07-01

    Vanadium oxide films were grown on Ag(100) by vanadium deposition in O2 and subsequent annealing at 450 °C. It was found that at least three types of ordered V oxide films, which showed (1 × 1), hexagonal, and (4 × 1) LEED patterns, were formed on Ag(100) depending on the O2 pressure during deposition and conditions during postannealing. The films with the hexagonal and (1 × 1) periodicities were characterized by photoelectron spectroscopy (PES) and near-edge X-ray absorption fine structure (NEXAFS) analysis. The film with the (1 × 1) periodicity was ascribed to a VO(100) film. On the other hand, the film with the hexagonal periodicity was found to be composed of V2O3, and the analysis of the LEED pattern revealed that the lattice parameter of the hexagonal lattice is 0.50 nm, which is very close to that of corundum V2O3(0001) (0.495 nm).

  7. The Encantada Granite: registration of a peraluminous intrusion in the Rondonian Province - San Ignacio, in SW Amazonic Craton, Mato Grosso, Brazil

    Directory of Open Access Journals (Sweden)

    Brena Verginassi do Nascimento

    2015-06-01

    Full Text Available The Encantada Granite occurs on the extreme southwest of the state of Mato Grosso, SW of the Amazonian Craton, near the border of Brasil/Bolívia. It corresponds to an body oriented to NNW direction that intruded metasedimentary and metavolcanic rocks. It consists of leucogranites with monzo- to sienogranitic composition, marked by prominent schistosity. It is characterized by equigranular to porphyritic inequigranular texture, and composed of quartz, K-feldspar, plagioclase, muscovite and biotite with garnet, zircon, allanite and opaque minerals. Chlorite and epidote are the most common secondary minerals. The geochemical study allows the classification of the magmatism as having acid character, sub-alkaline, high-potassium-calc-alkaline to shoshonitic type. These rocks have alumina index saturation higher than 1, with normative corundum, and thus classified as peraluminous granite. Due to the reflection of the excess of aluminium, they have various aluminous phases, mainly muscovite, biotite and garnet; presents typical pattern of calc-alkaline rocks rich in potassium with enrichment of light ETRs over the heavy ones. The collected data allows to consider that the Encantada Granite rocks were generated from the partial melting of crustal rocks of pelitic composition.

  8. Mineralogical characterization of Greda clays and monitoring of their phase transformations on thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Chavez Panduro, E., E-mail: 04130127@unmsm.edu.pe; Bravo Cabrejos, J., E-mail: jbravoc@unmsm.edu.pe [Universidad Nacional Mayor de San Marcos, Facultad de Ciencias Fisicas (Peru)

    2010-01-15

    The mineralogical characterization of two clay samples from the Central Andean Region of Peru, denominated White Greda and Red Greda, is reported. These clays contain the clay minerals mica and illite respectively. Both clays were treated thermally in an oxidising atmosphere under controlled conditions up to 1,100 deg. C with the purpose of obtaining information about structural changes that may be useful for pottery manufacture. X-ray fluorescence was used for the elemental characterization of the samples and X-ray diffractometry was used to determine the collapse and formation of the mineral phases present in the samples caused by thermal treatment. At temperatures above 1,000 deg. C it is observed the formation of spinel in the case of White Greda and of hematite, corundum and cristobalite in the case of Red Greda. Room temperature transmission Moessbauer spectroscopy allowed the monitoring of the variation of the hyperfine parameters with the thermal treatment temperature; In the case of the evolution of the quadruple splitting of the paramagnetic Fe{sup 3+} sites with temperature, in both clays, the analyses reproduced results such as the 'camel back' curve shape, found by other workers (Wagner and Wagner, Hyperfine Interact 154:35-82, 2004; Wagner and Kyek, Hyperfine Interact 154:5-33, 2004).

  9. Mineralogical characterization of Greda clays and monitoring of their phase transformations on thermal treatment

    Science.gov (United States)

    Panduro, E. Chavez; Cabrejos, J. Bravo

    2010-01-01

    The mineralogical characterization of two clay samples from the Central Andean Region of Peru, denominated White Greda and Red Greda, is reported. These clays contain the clay minerals mica and illite respectively. Both clays were treated thermally in an oxidising atmosphere under controlled conditions up to 1,100°C with the purpose of obtaining information about structural changes that may be useful for pottery manufacture. X-ray fluorescence was used for the elemental characterization of the samples and X-ray diffractometry was used to determine the collapse and formation of the mineral phases present in the samples caused by thermal treatment. At temperatures above 1,000°C it is observed the formation of spinel in the case of White Greda and of hematite, corundum and cristobalite in the case of Red Greda. Room temperature transmission Mössbauer spectroscopy allowed the monitoring of the variation of the hyperfine parameters with the thermal treatment temperature; In the case of the evolution of the quadruple splitting of the paramagnetic Fe3 + sites with temperature, in both clays, the analyses reproduced results such as the “camel back” curve shape, found by other workers (Wagner and Wagner, Hyperfine Interact 154:35-82, 2004; Wagner and Kyek, Hyperfine Interact 154:5-33, 2004).

  10. perovskite up to 55 GPa

    Science.gov (United States)

    Gréaux, Steeve; Andrault, Denis; Gautron, Laurent; Bolfan-Casanova, Nathalie; Mezouar, Mohamed

    2014-06-01

    Compressibility of perovskite-structured Ca3Al2Si3O12 grossular (GrPv) was investigated at high pressure and high temperature by means of angle-dispersive powder X-ray diffraction using a laser-heated diamond anvil cell. We observed the Pbnm orthorhombic distortion for the pure phase above 50 GPa, whereas below this pressure, Al-bearing CaSiO3 perovskite coexists with an excess of corundum. GrPv has a bulk modulus ( K 0 = 229 ± 5 GPa; fixed to 4) almost similar to that reported for pure CaSiO3 perovskite. Its unit-cell volume extrapolated to ambient conditions ( V 0 = 187.1 ± 0.4 Å3) is found to be ~2.5 % larger than for the Al-free phase. We observe an increasing unit-cell anisotropy with increasing pressure, which could have implications for the shear properties of Ca-bearing perovskite in cold slabs subducted into the Earth's mantle.

  11. The geology, mineralogy and rare element geochemistry of the gem deposits of Sri Lanka

    Directory of Open Access Journals (Sweden)

    C. B. Dissanayake

    2000-01-01

    Full Text Available The gem deposits of Sri Lanka are studied from the point of view of their geology, mineralogy and geochemistry. Nearly all the gem formations are located in the central high-grade metamorphic terrain of the Highland Complex. The gem deposits are classified as sedimentary, metamorphic and magmatic; the sedimentary types being the most abundant. The mineralogy of the gem deposits varies widely with, among others, corundum, chrysoberyl, beryl, spinel, topaz,zircon, tourmaline, garnet and sphene being common.Rare element concentrations in sediments from the three main gem fields of Sri Lanka, namely Ratnapura, Elahera and Walawe, were studied. It was found that some sediments are considerably enriched in certain elements compared to their average continental crustal abundances. The Walawe Ganga sediments show anomalous enrichments of the high field strength and associated elements, particularly Zr, Hf, W and Ti. This is attributed to the presence of accessory mineralssuch as zircon, monazite and rutile. Some of these heavy minerals comprise as much as 50 wt% of sediment. The geochemical enrichment of some trace elements compared to their average crustal abundances indicates that highly differentiated granites and associated pegmatites have provided the source materials for enrichment.

  12. The application of thermal solar energy to high temperature processes: case study of the synthesis of alumina from boehmite.

    Science.gov (United States)

    Padilla, Isabel; López-Delgado, Aurora; López-Andrés, Sol; Álvarez, Marta; Galindo, Roberto; Vazquez-Vaamonde, Alfonso J

    2014-01-01

    The aim of this paper is to evaluate the feasibility of obtaining alumina from boehmite using a free, clean, and unlimited power source as the solar energy. Boehmite was obtained by hydrothermal treatment of a hazardous waste coming from aluminum slag milling. The waste is considered as a hazardous substance because of it releasing toxic gases (hydrogen, ammonia, methane, and hydrogen sulfide) in the presence of water. The as-obtained boehmite was transformed into alumina, in air atmosphere, using a solar energy concentrator (Fresnel lens). The solar installation provides a power density of 260 W · cm(-2) which allows reaching temperatures upper than 1000 °C at few minutes of exposure. Tests were performed at different periods of time that ranged between 5 and 90 min. The percentage of transformation of boehmite into alumina was followed by the water content of samples after solar radiation exposure. Samples were characterized by X-ray diffraction, infrared spectroscopy, and thermogravimetry. Metastable aluminas started to appear at 5 min and the crystalline and stable phase corundum at 10 min of solar radiation exposure.

  13. Laboratory Infrared Spectroscopy of Oxide and Carbide Nanoparticles Condensed from the Gas Phase

    Science.gov (United States)

    Mutschke, Harald; Clément, Dominik; Posch, Thomas

    Oxide and carbide dust belong to the first condensates in either oxygen- or carbon-rich stellar outflows. Evidence for their presence in such circumstellar environments comes from infrared spectroscopy (e.g. the 13 micron and 11+ micron bands of M and C stars) and from the study of meteoritic presolar grains (corundum, SiC). We have measured in the laboratory the infrared absorption spectra of oxide and carbide particles produced in condensation experiments. For the production we applied the laser pyrolysis technique in a gas flow reactor as well as laser ablation of metals in reactive atmospheres. The products have been analysed by electron microscopy and other techniques for determination of their chemical composition and structure. They consist of nanoparticles of 5-10 nm size. Silicon carbide particles produced by laser pyrolysis are crystalline (in the cubic SiC structure) whereas oxide nanoparticles produced by laser ablation have a strongly disordered lattice. For the spectroscopic measurement, the particles are extracted from the condensation zone by a molecular beam technique and are deposited on a KBr substrate. At the same time, an Ar ice layer can be grown on the substrate which then incorporates the particles to isolate them from each other. The in-situ measurement also prevents the particles from degradation by environmental influences, e.g. carbonate formation. We discuss the spectra of isolated vs. agglomerated particles and their applicability for comparison with infrared observations of AGB star outflows.

  14. Wear mechanism of castable for RH furnace snorkel and its long service life practice%RH炉浸渍管用浇注料的蚀损机理及其长寿化实践

    Institute of Scientific and Technical Information of China (English)

    刘黎; 徐国涛; 陈希来; 邹龙

    2012-01-01

    研究了RH真空精炼炉浸渍管用刚玉尖晶石质浇注料的蚀损机理:熔渣及钢液通过浇注料表面缺陷渗入其内部,与浇注料发生反应生成低熔点化合物;炉温频繁的波动,导致浇注料内部应力过大,使其产生裂纹;在钢液及熔渣的冲刷作用下,造成浇注料剥落。还探讨了提高浸渍管用浇注料使用寿命的途径。%The wear mechanism of corundum spinel castable used for the snorkel of RH vacuum refining furnace is studied. The smelting slag and molten steel penetrate into the inside of the castable through its surface defect and they react with castable to form low melting point compound. The temperature of the furnace fluctuates frequently to cause the generations of extra stress and cracks in castable. Under the scouring action of slag and molten steel, the castable is peeled off. And the ways for improving the service life of the castable for the snorkel are discussed.

  15. Petrography, geochemistry and regional significance of crystalline klippen in the Garhwal Lesser Himalaya, India

    Indian Academy of Sciences (India)

    R Islam; S K Ghosh; S Vyshnavi; Y P Sundriya

    2011-06-01

    Uphalda gneisses (UG) is a crystalline klippe located near Srinagar in Garhwal Himalaya. These gneisses are compared with Debguru porphyroids (DP) (≈ Ramgarh group) of Garhwal–Kumaun Himalaya and Baragaon mylonitic gneisses (BMG) of Himachal Himalaya. Petrographic study reveals that the deformation of UG was initiated at higher temperature (above 350°C) and continued till lowering of temperature and deformation led to the mylonitization. Geochemically, these granitic gneisses (UG, DP and BMG) exhibit similar composition. Features such as high molecular A/CNK value (< 1), presence of normative corundum and absence of normative diopside, enhanced Rb/Sr, Rb/Zr ratios, enrichment of Th and containing rounded zircons support their crustally-derived S-type granitic nature. The linear plot in major oxides is interpreted in terms of fractional crystallization processes. Mantle normalized multi-element spider diagram of UG illustrates depletion of Ba, Nb, Sr, P and Ti and enrichment of Th and show similarities with DP and BMG. Similarities were observed in lithology, petrographic characters and chemical composition of UG, DP, BMG and Ulleri augen gneisses (Nepal). Comparison with the rocks of Higher Himalayan crystallines (≈ Vaikrita), suggests that these rocks (UG) are not transported from Higher Himalaya as understood earlier. This study however proposes that, these gneissic bodies represent an older basement occurring as a tectonic sliver which emplaced within the cover sequence as wedges at different structural levels. This is a regional phenomena observed throughout the Lesser Himalayan region.

  16. INTENSITY AND QUALITY IMPROVEMENT OF HARD AND SUPER-HARD MATERIAL SAWING BY TRANSFERRING PLANE CIRCULAR MOTION TO BLANK

    Directory of Open Access Journals (Sweden)

    M. G. Kiselev

    2011-01-01

    Full Text Available The paper considers an experimental evaluation of the influence of a plane periodic circular motion which is transferred to a blank on the intensity of its sawing and quality of its machined surface. Description of a modernized industrial sawing section has been given in the paper. The section is used for sawing various types of specimens (jasper, quartz glass, corundum as under conventional machining conditions so while transferring them a circular motion along a closed path with a shape being like an ellipse. It has been established that in comparison with machining under conventional conditions transfer of such motion to a blank makes it possible significantly (by 2.5-3.9-fold to improve sawing intensity and simultaneously to reduce Ra value of their sawed surfaces by 1.9-3.0-fold. The obtained results have allowed to make a qualitative description of a mechanism which reveals an influence of a blank circular motion on higher intensity of its sawing and quality of the machined surface.

  17. Gibbs energy of formation of cobalt divanadium tetroxide

    Science.gov (United States)

    Jacob, K. T.; Pandit, S. Shashidhara

    1985-11-01

    The Gibbs energy of formation of V 2O 3-saturated spinel CoV 2O 4 has been measured in the temperature range 900-1700 K using a solid state galvanic cell, which can be represented as Pt, Co + CoV 2O 4 + {V2O3}/{(CaO)}{ZrO2}/{Co} + CoO, Pt. The standard free energy of formation of cobalt vanadite from component oxides can be represented as CoO (rs) + V 2O 3 (cor) → CoV 2O 4 (sp), ΔG° = -30,125 - 5.06 T (± 150) J mole -1. Cation mixing on crystallographically nonequivalent sites of the spinel is responsible for the decrease in free energy with increasing temperature. A correlation between "second law" entropies of formation of cubic 2-3 spinels from component oxides with rock salt and corundum structures and cation distribution is presented. Based on the information obtained in this study and trends in the stability of aluminate and chromite spinels, it can be deduced that copper vanadite is unstable.

  18. Mineralogy, textures, and whole-rock geochemistry of advanced argillic alteration: Hugo Dummett porphyry Cu-Au deposit, Oyu Tolgoi mineral district, Mongolia

    Science.gov (United States)

    Khashgerel, Bat-Erdene; Kavalieris, Imants; Hayashi, Ken-Ichiro

    2008-11-01

    Advanced argillic (AA) alteration is developed over a vertical interval of 500 m, above (and enclosing) Late Devonian quartz monzodiorite intrusions that accompany porphyry-style Cu-Au mineralization at the Hugo Dummett deposit. The AA alteration is mainly in basaltic rocks and locally extends into the overlying dacitic ash-flow tuff for about 100 m. The AA zone overprints porphyry-style quartz veins associated with quartz monzodiorite intrusions, but at least partly precedes high-grade porphyry-style bornite mineralization. Mineralogically, it consists of andalusite, corundum, residual quartz, titanium oxides, diaspore, alunite, aluminum phosphate-sulfate (APS) minerals, zunyite, pyrophyllite, topaz, kaolinite, and dickite, as well as anhydrite and gypsum, but is dominated by residual quartz and pyrophyllite. Alteration zonation is not apparent, except for an alunite-bearing zone that occurs approximately at the limit of strong quartz veining. Whole-rock geochemistry shows that the AA alteration removes most major elements except Si, Al, Ti, and P, and removes the trace elements Sc, Cs, and Rb. V, Zr, Hf, Nb, Ta, U, and Th are relatively immobile, whilst light REEs (La to Nd), Sr, Ba, and Ga can be enriched. Middle REEs (Sm to Gd) are moderately depleted; Y and heavy REEs (Tb to Lu) are strongly depleted except in two unusual samples where middle to heavy REEs are enriched.

  19. Dermoelectroporation, lipofilling, and pulsed light: a protocol after 2 years of experience

    Science.gov (United States)

    Bacci, Pier A.; Mancini, Sergio

    2005-11-01

    The enourmus boost from adopting biomolecular startegies associated to a better understanding of genetic phenomena opened the way to new methodologies. Among those we can surely locate dermoelectroporation, a methodology that uses the transdermal absorption capacity by means of an apparatus that delivers controlled electrical pulses able to open some "electrical doors". This methodology allows us a protocol of treatment suitable in subjects exhibiting the effects of acne, initial stages of skin ageing without tissue yield. and upkeep of aesthetic surgery. With the term "Biolifting" we signifie a treatment procedure aimed at rejuvenating the face by non-surgical, "soft" and out-patient treatment means. This treatment requires bi-monthly or monthly sessions, a total of four to eight, of a procedure consisting first in superficial microdermabrasion performed with corundum crystals, intended for the removal of the corneus layer and for vascularization. Immediately afterwards, active substances are introduced by means of the Dermoelectroporation treatment, characterized by the possibility of creating the opening of "intercellular gates" that allow the passage of the molecules. The session can be concluded with the application of pulsating light which introduces energy and stimulates the regenerating properties of connective tissues. A home treatment with moisturizing and regenerating creams ends the treatment which is used, with interesting results, also for the aesthetic therapy of stretch marks or hypertrophic scars.

  20. Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

    Science.gov (United States)

    Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Karim, Saniah Ab; Zaman, Rosyaini Afindi; Ain, Mohd Fadzil; Ahmad, Zainal Arifin; Mohamed, Julie Juliewatty

    2016-07-01

    (1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al2O3 was reduced both dielectric loss and permittivity at least for an order of magnitude.

  1. On the Enclathration of NaB(OH)4 in the β-Cages of Sodalite: Crystallization Kinetics and Crystal Structure

    Science.gov (United States)

    Buhl, J.-Ch.; Mundus, C.; Löns, J.; Hoffmann, W.

    1994-12-01

    The hydrothermal formation of sodium hydroxyborate enclathrated sodalite synthesized from an initial ternary mixture of mullite, cristobalite and corundum has been investigated. Depending on temperature and pressure the compound Na7.5[AlSiO4]6[B(OH)4]1.5 · 2H2O could be synthesized in form of polycrystalline powder as well as in form of single crystals. The kinetics of the sodalite growth could be determined at 423 K and 473 K. 29Si-and 27Al MAS NMR was shown to be the preferred method to describe the conversion into sodalite quantitatively. Evidence for the first formation of polycrystalline sodalite has been found after the total dissolution of mullite and cristobalite. Single crystal X-ray diffraction data were used for the structure determination and refinement. The position and orientation of the hydroxyborate anions within the sodalite's /β-cages could only be found in the course of a "rigid body" refinement with constraints for the B(OH)4 tetrahedron. The boron atoms are located in an off-centre position within the sodalite cages. One out of the four oxygen atoms of the hydroxyborate group is positioned near the centre of a face of the sodium tetrahedron, whereas the three remaining oxygen atoms are near to the middle of its edges.

  2. New insights into the multiferroic properties of Mn3TeO6

    Science.gov (United States)

    Ivanov, S. A.; Ritter, C.; Nordblad, P.; Tellgren, R.; Weil, M.; Carolus, V.; Lottermoser, Th; Fiebig, M.; Mathieu, R.

    2017-03-01

    Mn3TeO6 has a trigonal corundum related structure (space group R\\overline{3} ), and orders in an incommensurate antiferromagnetic (AFM) structure at T N ≈ 24 K. A weak ferroelectric order below T  * ~ 21 K has recently been reported. In order to investigate possible structural changes below T N leading to the observed dipole order, we have performed a detailed study of the crystal and magnetic structures of Mn3TeO6 using neutron powder diffraction (NPD) in the temperature range of 5–40 K. Complementary low-temperature second harmonic generation (SHG) measurements were performed in order to confirm the reported dipole order at T  *. No change in the rhombohedral symmetry associated with a possible displacive phase transition at T  * was observed in the long-range structural correlations, and it appears that Mn3TeO6 keeps the same incommensurately modulated magnetic spin structure with the propagation vector k  =  (0 0; 0.43) in the whole temperature range from 5 to 24 K.

  3. Progress in Research and Development of Refractory Oxide-Nonoxide Composites

    Institute of Scientific and Technical Information of China (English)

    ZHONG Xiangchong

    2008-01-01

    Some of the progress made in our laboratories in collaboration with industry in research and development work on high performance oxide-nonoxide composites for metallurgical applications has been reviewed. (1) SiAlON bonded corundum composites for blast furnace usage have been produced by reduction-nitridation sintering at high temperature, using bauxite instead of alumina in the matrix. (2) Low carbon Al2O3-SiAlON slide plate materials successfully used in high quality steel continuous casting have been developed in which most or all of the graphite in Al2O3-C brick is replaced by bauxite-based β-SiAlON. (3) Al/Si metal bonded Al2O3-C material characterized by low carbon content, low firing temperature and in-situ formation of carbides and nitrides at high temperature during service are found to possess very high hot strength and very good thermal shock resistance and have also been successfully used as slide plates in ladles and tundishes for high quality steel casting.

  4. Geology and Genesis of Peraluminous Granites in East Tianshan Upper Paleozoic Island Arc Belt

    Institute of Scientific and Technical Information of China (English)

    顾连兴; 严正富; 等

    1996-01-01

    A peraluminous granite belt occurs along the connecting zone between the Turpan Hami Precambrian block and the Upper Paleozoic island arc belt.Muscovite granite and twomica granite are the essential lithological components of that belt.All the potassium feldspars in these granites are microcline.Heavy minerals are dominated by magnetite,SiO2 contents of these granites are greater than 73% with most of the A/NKC values greater than 1,1,norma tive corundum values greater than 1 Plots of CIPW norms in the (Al-K-Na) Ca(Fe2++Mg) diagran are mostly situated in the plagioclase cordierite-muscovite region.The rocks are characterized by very low contents of minor elements and ∑REE with strong Eu depletion δ18 O values between 6.6‰and 7.0‰,Rb-Sr isochron age of 260.2±6.2Ma and an initial 87Sr/86 Sr ration of 0.7052,These granites might have been produced by partial melting of moderately acidic volcanites and low-maturity sediments in the basement sequences and could be genetically connected with the southware A-type subduction of the Turpan-Hami block following the closure of the Middle Carboniferous back-arc basin.

  5. Effect of particle size and particle size distribution on physical characteristics, morphology and crystal strucutre of explosively compacted high-Tc superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kotsis, I.; Enisz, M.; Oravetz, D. [Univ. of Veszprem (Hungary)] [and others

    1994-12-31

    A superconductor, of composition Y(Ba,K,Na){sub 2}Cu{sub 3}O{sub x}/F{sub y} and a composite, of composition Y(Ba,K,Na){sub 2}Cu{sub 3}O{sub x}/F{sub y}+Ag, with changing K, Na and F content, but a constant silver content (Ag=10 mass per cent) was prepared using a single heat treatment. The resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 {mu}m, 0-63 {mu}m and 63-900 {mu}m and explosively compacted, using an explosive pressure of 10{sup 4} MPa and a subsequent heat treatment. Best results were obtained with the 63-900 {mu}m fraction of composition Y(Ba{sub 1,95}K{sub 0,01})Cu{sub 3}O{sub x}F{sub 0,05}/Ag: porosity <0.01 cm{sup 3}/g and current density 2800 A/cm{sup 2} at 77 K.

  6. Ultra Sodic gedrite and micro-scale metasomatic processes in granulitised kyanite eclogites from the Rhodope UHPM Province, Greece

    Science.gov (United States)

    Moulas, Evangelos; Kostopoulos, Dimitrios K.; Connolly, James A. D.; Burg, Jean-Pierre

    2010-05-01

    The Rhodope Massif occupies most of northeastern Greece and southern Bulgaria and comprises high-grade metamorphic rocks such as metapelites with microdiamond inclusions. The (U)HP mineral paragenesis underwent extensive metamorphic overprint at granulite-facies followed by amphibolite-facies retrograde metamorphism. A kyanite-eclogite that occurs as lenses in orthogneisses from Thermes village was used to unravel the pressure-temperature-time path of the (U)HP rocks from the Rhodope. The peak-pressure mineral assemblage is omphacite, garnet, kyanite, phengite, rutile, apatite and zircon. Quartz is absent from the matrix and it can be found either as inclusions in garnet or as post-peak veins. This late quartz contains primary and secondary fluid inclusions implying the presence of a fluid phase during post high-pressure metamorphism. Kyanite is never observed in direct contact with quartz being armoured by an intervening stripe of plagioclase which itself shows zoning, becoming increasingly albitic towards quartz. Plagioclase formation at the Ky-Qtz interface requires certain Na and Ca influx that was provided by matrix omphacite. Two types of symplectites were formed by reaction between omphacite and kyanite. Firstly, corundum+plagioclase symplectites were formed at the expense of the jadeitic component of omphacite during decompression. Subsequently, the residual diopsidic component of omphacite reacted with the already formed corundum to give rise to spinel+plagioclase symplectites. The previous mechanisms demonstrate metasomatism in the micro-scale by diffusion controlled processes. During decompression matrix omphacite was decomposed to amphibole+plagioclase symplectites which reacted with garnet to form coronas consisting of two amphiboles (ortho- and clino-), plagioclase, ilmenite and magnetite. Biotite and plagioclase are also found as symplectites replacing phengite during decompression. Thermodynamic modelling of the symplectitic domains that replace

  7. Stabilization of nickel by aluminum- and iron-rich ceramic materials: Reaction pathways and product leaching behavior

    Science.gov (United States)

    Shih, Kaimin

    The feasibility of stabilizing nickel-laden sludge with commonly available ceramic precursors was investigated. Nickel aluminate spinel (NiAl2O 4) was the immobilization phase produced when NiO was sintered with aluminum-rich precursors, including gamma-Al2O3, corundum, kaolinite and mullite. Analogously, nickel ferrite spinel (NiFe2O 4) was the stable phase produced by firing NiO with hematite, as an iron-rich precursor. By using gamma-Al2O3 as the precursor, the NiAl2O4 formation mechanism was a reaction between NiO and gamma-Al2O3 at lower temperatures (990°C), while the reaction was between NiO and corundum at higher temperatures. When sintering NiO with kaolinite, nickel can be efficiently incorporated in NiAl2O4 by two mechanisms: (i) a low temperature reaction with a defect spinel, and (ii) a high temperature reaction with mullite. Nickel-incorporation efficiency was quantitatively estimated by powder X-ray Diffraction (XRD) analysis. With 3-hours sintering, NiFe2O 4 (trevorite) formation took place above 600°C with more than 95% nickel incorporation efficiency achieved above 1000°C; while NiAl 2O4 crystallized above 1000°C with an efficiency >90% above 1250°C. In using kaolinite and mullite as precursors, nickel is not incorporated in any silicon-containing phase. The kinetic factors responsible for nickel incorporation efficiency from different precursors were revealed through investigation of product microstructures. Moreover, four raw material mixing procedures were compared, with the ball-milled slurries demonstrating the highest nickel incorporation efficiency. Prolonged leach tests of NiO, NiAl2O4, NiFe 2O4 and sintered kaolinite + NiO samples were carried out using the TCLP extraction fluids #1 and #2 to evaluate the durability of sintered products. Over longer leaching periods, spinel proved superior to NiO for immobilization of nickel, although NiFe2O4 appears slightly more leachable than NiAl2O4. With TCLP extraction fluid #1 (pH 4.9), the

  8. First light of the VLT planet finder SPHERE. IV. Physical and chemical properties of the planets around HR8799

    Science.gov (United States)

    Bonnefoy, M.; Zurlo, A.; Baudino, J. L.; Lucas, P.; Mesa, D.; Maire, A.-L.; Vigan, A.; Galicher, R.; Homeier, D.; Marocco, F.; Gratton, R.; Chauvin, G.; Allard, F.; Desidera, S.; Kasper, M.; Moutou, C.; Lagrange, A.-M.; Antichi, J.; Baruffolo, A.; Baudrand, J.; Beuzit, J.-L.; Boccaletti, A.; Cantalloube, F.; Carbillet, M.; Charton, J.; Claudi, R. U.; Costille, A.; Dohlen, K.; Dominik, C.; Fantinel, D.; Feautrier, P.; Feldt, M.; Fusco, T.; Gigan, P.; Girard, J. H.; Gluck, L.; Gry, C.; Henning, T.; Janson, M.; Langlois, M.; Madec, F.; Magnard, Y.; Maurel, D.; Mawet, D.; Meyer, M. R.; Milli, J.; Moeller-Nilsson, O.; Mouillet, D.; Pavlov, A.; Perret, D.; Pujet, P.; Quanz, S. P.; Rochat, S.; Rousset, G.; Roux, A.; Salasnich, B.; Salter, G.; Sauvage, J.-F.; Schmid, H. M.; Sevin, A.; Soenke, C.; Stadler, E.; Turatto, M.; Udry, S.; Vakili, F.; Wahhaj, Z.; Wildi, F.

    2016-03-01

    Context. The system of fourplanets discovered around the intermediate-mass star HR8799 offers a unique opportunity to test planet formation theories at large orbital radii and to probe the physics and chemistry at play in the atmospheres of self-luminous young (~30 Myr) planets. We recently obtained new photometry of the four planets and low-resolution (R ~ 30) spectra of HR8799 d and e with the SPHERE instrument (Paper III). Aims: In this paper (Paper IV), we aim to use these spectra and available photometry to determine how they compare to known objects, what the planet physical properties are, and how their atmospheres work. Methods: We compare the available spectra, photometry, and spectral energy distribution (SED) of the planets to field dwarfs and young companions. In addition, we use the extinction from corundum, silicate (enstatite and forsterite), or iron grains likely to form in the atmosphere of the planets to try to better understand empirically the peculiarity of their spectrophotometric properties. To conclude, we use three sets of atmospheric models (BT-SETTL14, Cloud-AE60, Exo-REM) to determine which ingredients are critically needed in the models to represent the SED of the objects, and to constrain their atmospheric parameters (Teff, log g, M/H). Results: We find that HR8799d and e properties are well reproduced by those of L6-L8 dusty dwarfs discovered in the field, among which some are candidate members of young nearby associations. No known object reproduces well the properties of planets b and c. Nevertheless, we find that the spectra and WISE photometry of peculiar and/or young early-T dwarfs reddened by submicron grains made of corundum, iron, enstatite, or forsterite successfully reproduce the SED of these planets. Our analysis confirms that only the Exo-REM models with thick clouds fit (within 2σ) the whole set of spectrophotometric datapoints available for HR8799 d and e for Teff = 1200 K, log g in the range 3.0-4.5, and M/H = +0.5. The

  9. SINTESIS BAHAN UBAHAN GRADUAL ALUMINUM TITANAT/KORUNDUM DARI ALUMINA TRANSISI DENGAN PENAMBAHAN MgO

    Directory of Open Access Journals (Sweden)

    Achmad Sulhan Fauzi

    2013-03-01

    Full Text Available This article describes the results of research on the use of transition alumina for improving the performance of ceramics. Synthesis has been made of gradual changes materials (Functionally Graded Materials, FGM aluminum titanate (AT / corundum based on transition alumina powders with the addition of MgO as a stabilizer of AT as much as 2 wt.%. Samples without the addition of MgO was also made for comparison. Transition alumina with and without the addition of MgO were calcined at a temperature of 1100C for 1 hour to become ?-alumina. The powder mixture was compacted at a pressure of 49.3 MPa and then prasintered at a temperature of 1100C for 1 hour, then repeatedly infiltrated with infiltrator TiCl3 solution (20% which prepared by dissolving the Ti metal powders into HCl. Furthermore, the material sintered at temperatures of 1500C with a holding time for 3 hours. Physical character of materials showed an increase in density and decrease in porosity of the material due to the addition of MgO. Phase identification results obtained from the content of AT and corundum phases which gradual in depth, indicating that FGM has been formed. These results were supported by analysis of x-ray diffraction pattern showing the formation of a solid solution Al2 (1-x + MgxTi1 xO5 which marked by the shifting of the peak of AT phase in FGM samples with the addition of MgO. Tulisan ini menjelaskan hasil penelitian tentang penggunaan alumina transisi untuk meningkatkan performa keramik. Telah dilakukan sintesis bahan ubahan gradual (Functionally Graded Material, FGM aluminum titanat (AT/korundum berbahan dasar serbuk alumina transisi dengan penambahan MgO sebagai penstabil AT sebanyak 2 wt.%. Sampel tanpa tambahan MgO juga dibuat sebagai pembanding. Alumina transisi dengan dan tanpa penambahan MgO dikalsinasi pada temperatur 1100C selama 1 jam sehingga menjadi ?-alumina. Serbuk campuran dikompaksi pada tekanan 49,3 MPa lalu diprasinter pada temperatur 1100C selama

  10. Interferences in determination of free silica in dust of workplaces with pyrophosphoric acid method%工作场所粉尘中游离二氧化硅含量焦磷酸测定法的影响因素

    Institute of Scientific and Technical Information of China (English)

    徐彦; 于会明; 于冬雪; 顾竹琳; 马岩; 孙玉凤; 王静; 苏红

    2012-01-01

    目的 准确测定工作场所粉尘中游离二氧化硅含量,为评价粉尘危害提供可靠依据.方法 用改进后的焦磷酸法对普通玻璃、硬质玻璃、石英玻璃、硅胶、硅藻土、焦磷酸难溶矿物,包括黄玉、刚玉、锆英石、绿柱石、电气石、碳化硅以及方石英和鳞石英进行实验分析,研究其在焦磷酸和氢氟酸中的溶解对游离二氧化硅定量测定的影响,以及石英在焦磷酸中的损失对游离二氧化硅定量测定的影响.结果 粉尘中含有普通玻璃、硅胶、黄玉、刚玉、锆英石时,不影响粉尘中游离二氧化硅含量的测定,而硬质玻璃、石英玻璃、硅藻土、绿柱石、电气石、碳化硅的存在则影响游离二氧化硅的测定结果,方石英和磷石英在焦磷酸中的溶解损失影响耐火材料和陶瓷生产等工业粉尘中游离二氧化硅含量的测定,石英溶解损失也对游离二氧化硅测定存在影响.结论 明确某些物质对工作场所粉尘中游离二氧化硅含量测定的影响,从而对游离二氧化硅在工作场所粉尘中的存在状况做出正确判断.%Objective To accurately determine the free silica content in settled dust of workplaces so as to provide reliable criteria for assessing the dust hazard. Methods Ordinary glass, hard glass, quartz glass, silica gel, diatomaceous earth, and pyrophosphoric acid slightly or hardly soluble minerals including topaz, corundum, zircon, beryl, tourmaline, silicon carbide, cristobalite and tridymite were analyzed by modified pyrophosphoric acid method. The impact of their solution in pyrophosphoric acid and hydrofluoric acid on the determination of free silica was studied. The impact of quartz loss in pyrophosphoric acid on the determination of free silica was also studied. Results Results showed that ordinary glass, silica gel, topaz, corundum, and zircon did not affect the determination of free silica content, whereas hard glass, quartz glass

  11. LF渣和ρ-Al2 O3结合铝镁质浇注料的相互作用%Interaction of LF slag and ρ-Al2O3 bonded alumina-magnesia castables

    Institute of Scientific and Technical Information of China (English)

    李艳华; 韩兵强; 贺恒星; 刘延山; 李楠

    2014-01-01

    以5~3 mm棕刚玉和3~1、≤1 mm板状刚玉为骨料,以0.074 mm电熔白刚玉、0.088 mm电熔镁砂和0.061 mm尖晶石为细粉,以ρ-Al2O3微粉为结合剂,研究了加入质量分数8%的90尖晶石和加入质量分数7%的97电熔镁砂细粉的铝镁质浇注料常温物理性能、抗LF渣的侵蚀和渗透性能。采用SEM对侵蚀后试样进行了显微结构分析,并利用热力学软件Factsage 6.2对侵蚀过程进行了模拟。结果表明:加入质量分数8%的90尖晶石的铝镁浇注料比加入质量分数7%的97电熔镁砂的铝镁浇注料在各温度处理后的常温强度高,显气孔率低,体积密度大,抗LF渣渗透性能优异。铝镁浇注料中引入较多MgO在高温下大量形成原位尖晶石,易造成较大的体积膨胀,对抗渣渗透性能不利,但有利于吸收渣中FeO、MnO,提高渣的黏度,对抗渣侵蚀性能有利。试验结果与热力学软件模拟结果吻合。%Two batches of alumina-magnesia castables were prepared by using brown corundum (5 -3 mm)and tabular corundum (3-1 and ≤1 mm)as aggregates,fused white alumina (0.074 mm),fused magnesia (0.088 mm)and spinel powder (0.061 mm)as matrix,ρ-Al2O3 as binder,and adding 8 mass%90 spinel and 7 mass%97 fused magnesia,respectively.Cold physical properties,corrosion and penetra-tion resistance to LF slag of the two castables were compared.Microstructures of the two kinds of corroded specimens were investigated with SEM and the corrosion process was thermodynamically simulated by software Factsage 6.2.The results show that:compared with the castable with 7 mass%97 fused magne-sia,the alumina-magnesia castable containing 8 mass%90 spinel has a higher cold strength,a higher bulk density,a lower apparent porosity,and a better penetration resistance to LF slag at all temperatures;high MgO content in alumina-magnesia castables results in more in-situ formed spinel during firing,expanding the volume,which is

  12. Quantitative comparisons of analogue models of brittle wedge dynamics

    Science.gov (United States)

    Schreurs, Guido

    2010-05-01

    Analogue model experiments are widely used to gain insights into the evolution of geological structures. In this study, we present a direct comparison of experimental results of 14 analogue modelling laboratories using prescribed set-ups. A quantitative analysis of the results will document the variability among models and will allow an appraisal of reproducibility and limits of interpretation. This has direct implications for comparisons between structures in analogue models and natural field examples. All laboratories used the same frictional analogue materials (quartz and corundum sand) and prescribed model-building techniques (sieving and levelling). Although each laboratory used its own experimental apparatus, the same type of self-adhesive foil was used to cover the base and all the walls of the experimental apparatus in order to guarantee identical boundary conditions (i.e. identical shear stresses at the base and walls). Three experimental set-ups using only brittle frictional materials were examined. In each of the three set-ups the model was shortened by a vertical wall, which moved with respect to the fixed base and the three remaining sidewalls. The minimum width of the model (dimension parallel to mobile wall) was also prescribed. In the first experimental set-up, a quartz sand wedge with a surface slope of ˜20° was pushed by a mobile wall. All models conformed to the critical taper theory, maintained a stable surface slope and did not show internal deformation. In the next two experimental set-ups, a horizontal sand pack consisting of alternating quartz sand and corundum sand layers was shortened from one side by the mobile wall. In one of the set-ups a thin rigid sheet covered part of the model base and was attached to the mobile wall (i.e. a basal velocity discontinuity distant from the mobile wall). In the other set-up a basal rigid sheet was absent and the basal velocity discontinuity was located at the mobile wall. In both types of experiments

  13. 镍基高温合金上双层搪瓷-陶瓷复合涂层1000℃氧化机理%Oxidation Behavior of Bilayered Ceramic Particle-reinforced Enamel Composite Coating on Nickel-based Superalloy K38G at 1000 ℃

    Institute of Scientific and Technical Information of China (English)

    沈明礼; 朱圣龙; 王福会

    2012-01-01

    A bilayered enamel-ceramic composite coating, consisted of an inner layer of enamel-50 mass% corundum and an outer layer of enamel-50 mass% quartz, was prepared on nickel-based superalloy K38G by spray-sintering technique. The coating is dense with glaze surface and has good adhesion to the substrate. Its oxidation behavior at 1000 ℃ for 120 h was studied by means of thermogravimetry, SEM, EDS and XRD. Cristobalite, a high-temperature polymorph of quartz, and zircon and albite precipitates were detected in the as-prepared enamel-ceramic composite coating. In addition, Ni, Co and Cr were present in the inner layer of enamel-corundum. The mass gain of the coated alloy after 120 h oxidation was about 0.2 mg/cm2, quite lower than those of NiCrA1Y coatings. Most of the quartz particles in the coating transformed into cristobalite after oxidation tests. Besides, orthoelase was detected too. Ni-enrichment was observed in the outermost region of the outer layer, while Cr-enrichment was found in the inner layer close to the inner/outer interface. And Ni-, Cr-, Al-enrichment were found in the inner layer near the substrate either of the as-prepared samples or of the samples after oxidation tests.%在镍基高温合金K38G基体上制备了双层搪瓷-陶瓷复合涂层,其中面层为搪瓷-50mass%石英,底层为搪瓷-50mass%刚玉层.涂层结合力良好,表面均匀致密,有釉面光泽.1000℃、120h氧化结果表明,涂层试样的氧化增重仅为0.2mg/cm^2左右,比文献中报道的NiCrAlY涂层的氧化速率低数倍(Ni-22Cr-10Al-1Y(mass%)1000℃100h氧化增重已达1.2mg/cm^2).刚制备出的搪瓷-陶瓷复合涂层中的部分石英颗粒已转变为方石英相,并析出少量的锆英石相和钠长石相.氧化后的涂层中大部分石英颗粒转变成方石英,并析出少量的钾长石相.氧化后的涂层试样中Ni,Cr富集分别出现在涂层的外层靠近空气区域和内层靠近外层

  14. Densification and dielectric properties of SrO–Al2O3–B2O3 ceramic bodies

    Indian Academy of Sciences (India)

    Doaa A Abdel Aziz; Shama E Ahmed

    2011-02-01

    The influence of SrO (0.0–5.0 wt%) on partial substitution of alpha alumina (corundum) in ceramic composition (95 Al2O3–5B2O3) have been studied by co-precipitated process and their phase composition, microstructure, microchemistry and microwave dielectric properties were studied. Phase composition was revealed by XRD, while microstructure andmicrochemistry were investigated by electron-probe microanalysis (EPMA). The dielectric properties by means of dielectric constant (r), quality factor ( × ) and temperature coefficient of resonant frequency (f) were measured in the microwave frequency region using a network analyser by the resonance method. The addition of B2O3 and SrO significantly reduced the sintering temperature of alumina ceramic bodies to 1600°C with optimum density (∼ 4 g/cm3) as compared with pure alumina powders recycled from Al dross (3.55 g/cm3 sintered at 1700°C). The sintered ceramic bodies show different ranges for the dielectric properties. Dielectric constant exists between 24 and 29, quality factor ( × ) is ranging between 15,236 and 22,020 GHz with a slight increase than those recorded with commercial alumina (10,000 – 20,000 GHz) and temperature coefficient of resonant frequency (f) in the –69 to –83 ppm/°C range. The addition of SrO up to 5 wt% leads to a maximum (r) value (29) due to relatively higher ionic polarizability of Sr2+ than that of the Al3+ and B3+ ions. On the other hand, changing chemical and phase composition with the formation of platelets of Sr-hexaluminate phase (SrAl12O19) results in maximizing value of ( × ) up to 22,020 GHz at ≈ 8 GHz and large negative charge of (f) to –83 ppm/°C.

  15. Analysis and modification of blue sapphires from Rwanda by ion beam techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bootkul, D., E-mail: mo_duangkhae@hotmail.com [Department of General Science - Gems & Jewelry, Faculty of Science, Srinakharinwirot University, Bangkok 10110 (Thailand); Chaiwai, C.; Tippawan, U. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Wanthanachaisaeng, B. [Gems Enhancement Research Unit, Faculty of Gems, Burapha University, Chanthaburi Campus, Chanthaburi 22170 (Thailand); Intarasiri, S., E-mail: saweat@gmail.com [Science and Technology Research Institute, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2015-12-15

    Highlights: • Ion beam analysis is an effective method for detecting trace elements. • Ion beam treatment is able to improve optical and color appearances of the blue sapphire from Rwanda. • These alternative methods can be extended to jewelry industry for large scale application. - Abstract: Blue sapphire is categorised in a corundum (Al{sub 2}O{sub 3}) group. The gems of this group are always amazed by their beauties and thus having high value. In this study, blue sapphires from Rwanda, recently came to Thai gemstone industry, are chosen for investigations. On one hand, we have applied Particle Induced X-ray Emission (PIXE), which is a highly sensitive and precise analytical technique that can be used to identify and quantify trace elements, for chemical analysis of the sapphires. Here we have found that the major element of blue sapphires from Rwanda is Al with trace elements such as Fe, Ti, Cr, Ga and Mg as are commonly found in normal blue sapphire. On the other hand, we have applied low and medium ion implantations for color improvement of the sapphire. It seems that a high amount of energy transferring during cascade collisions have altered the gems properties. We have clearly seen that the blue color of the sapphires have been intensified after nitrogen ion bombardment. In addition, the gems were also having more transparent and luster. The UV–Vis–NIR measurement detected the modification of their absorption properties, implying of the blue color increasing. Here the mechanism of these modifications is postulated and reported. In any point of view, the bombardment by using nitrogen ion beam is a promising technique for quality improvement of the blue sapphire from Rwanda.

  16. Retrieval of atmospheric properties of cloudy L dwarfs

    Science.gov (United States)

    Burningham, Ben; Marley, M. S.; Line, M. R.; Lupu, R.; Visscher, C.; Morley, C. V.; Saumon, D.; Freedman, R.

    2017-09-01

    We present the first results from applying the spectral inversion technique in the cloudy L dwarf regime. Our new framework provides a flexible approach to modelling cloud opacity which can be built incrementally as the data require and improves upon previous retrieval experiments in the brown dwarf regime by allowing for scattering in two-stream radiative transfer. Our first application of the tool to two mid-L dwarfs is able to reproduce their near-infrared spectra far more closely than grid models. Our retrieved thermal, chemical and cloud profiles allow us to estimate T_eff = 1796^{+23}_{-25} K and log g = 5.21^{+0.05}_{-0.08} for 2MASS J05002100+0330501, and for 2MASSW J2224438-015852 we find T_eff = 1723^{+18}_{-19} K and log g = 5.31^{+0.04}_{-0.08}, in close agreement with previous empirical estimates. Our best model for both objects includes an optically thick cloud deck which passes τcloud ≥ 1 (looking down) at a pressure of around 5 bar. The temperature at this pressure is too high for silicate species to condense, and we argue that corundum and/or iron clouds are responsible for this cloud opacity. Our retrieved profiles are cooler at depth and warmer at altitude than the forward grid models that we compare, and we argue that some form of heating mechanism may be at work in the upper atmospheres of these L dwarfs. We also identify anomalously high CO abundance in both targets, which does not correlate with the warmth of our upper atmospheres or our choice of cloud model, and find similarly anomalous alkali abundance for one of our targets. These anomalies may reflect unrecognized shortcomings in our retrieval model or inaccuracies in our gas phase opacities.

  17. SUBSTITUTED IRON OXIDES FOR THE GRANT ENTITLED LASER PROCESSING OF ADVANCED MAGNETIC MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    Monica Sorescu

    2004-03-01

    Structural and morphological characteristics of (1-x){alpha}-Fe{sub 2}O{sub 3}-xSnO{sub 2} (x = 0.0-1.0) nanoparticles obtained under hydrothermal conditions have been investigated by X-ray diffraction (XRD), transmission Moessbauer spectroscopy, scanning (SEM) and transmission electron microscopy (TEM) as well as energy dispersive X-ray analysis (EDX). On the basis of the Rietveld structure refinements of the XRD spectra at low tin concentrations, it was found that Sn{sup 4+} ions partially substitute for Fe{sup 3+} at the octahedral sites and also occupy the interstitial octahedral sites which are vacant in {alpha}-Fe{sub 2}O{sub 3} corundum structure. A phase separation of {alpha}-Fe{sub 2}O{sub 3} and SnO{sub 2} was observed for x {ge} 0.4: the {alpha}-Fe{sub 2}O{sub 3} structure containing tin decreases simultaneously with the increase of the SnO{sub 2} phase containing substitutional iron ions. The mean particle dimension decreases from 70 nm to 6 nm, as the molar fraction x increases up to x = 1.0. The estimated solubility limits in the nanoparticle system (1-x){alpha}-Fe{sub 2}O{sub 3}-xSnO{sub 2} synthesized under hydrothermal conditions are: x {le} 0.2 for Sn{sup 4+} in {alpha}-Fe{sub 2}O{sub 3} and x {ge} 0.7 for Fe{sup 3+} in SnO{sub 2}. These findings are in press in the Journal of Physics and Chemistry of Solids.

  18. Challenge to Electron Microprobe Analysis by Nano-features in Geo-materials

    Science.gov (United States)

    Ma, C.; Rossman, G. R.

    2007-12-01

    With current high-resolution analytical scanning electron microscope and transmission electron microscope technology, nano-features (i.e., inclusions, exsolutions, pores) are being discovered in many common geo- materials routinely analyzed by EPMA. Most EPMA instruments have a thermionic electron gun with a tungsten "hairpin" type filament and operate at such high probe currents that they do not produce the high resolution imaging that field emission SEMs do. Such nano-features present difficulties to electron microprobe analysis of the host materials. It is an accuracy issue. Presented here are a few examples. Nano-inclusions like magnetite or pyroxene are common in volcanic glass. Massive rose quartz contains nano-fibers of a dumortierite-related phase that is pink, which is the cause of rose color and optical star effects. Blue quartz has nano-inclusions of ilmenite. Nano-exsolutions and nano-inclusions occur in some feldspars (moonstone and sunstone). Nano- pores in corundum and opals are observed. Thin coatings of nanocrystals on grains of hematite bring Al and P (or As) into the analytical picture. In each of these cases, electron microprobe analyses of host materials were contaminated or affected by the nano-features. For a complete analytical description of a geo-material it is necessary to first examine probe samples under an optical microscope (400× minimum) and a FE-SEM. If the sample contains nano-features, it would then be necessary to combine FIB and TEM-EDS-EELS to comprehensively analyze the host composition.

  19. The roles of fractional crystallization, magma mixing, crystal mush remobilization and volatile-melt interactions in the genesis of a young basalt-peralkaline rhyolite suite, the greater Olkaria volcanic complex, Kenya Rift valley

    Science.gov (United States)

    Macdonald, R.; Belkin, H.E.; Fitton, J.G.; Rogers, N.W.; Nejbert, K.; Tindle, A.G.; Marshall, A.S.

    2008-01-01

    The Greater Olkaria Volcanic Complex is a young (???20 ka) multi-centred lava and dome field dominated by the eruption of peralkaline rhyolites. Basaltic and trachytic magmas have been erupted peripherally to the complex and also form, with mugearites and benmoreites, an extensive suite of magmatic inclusions in the rhyolites. The eruptive rocks commonly represent mixed magmas and the magmatic inclusions are themselves two-, three- or four-component mixes. All rock types may carry xenocrysts of alkali feldspar, and less commonly plagioclase, derived from magma mixing and by remobilization of crystal mushes and/or plutonic rocks. Xenoliths in the range gabbro-syenite are common in the lavas and magmatic inclusions, the more salic varieties sometimes containing silicic glass representing partial melts and ranging in composition from anorthite ?? corundum- to acmite-normative. The peralkaline varieties are broadly similar, in major element terms, to the eruptive peralkaline rhyolites. The basalt-trachyte suite formed by a combination of fractional crystallization, magma mixing and resorption of earlier-formed crystals. Matrix glass in metaluminous trachytes has a peralkaline rhyolitic composition, indicating that the eruptive rhyolites may have formed by fractional crystallization of trachyte. Anomalous trace element enrichments (e.g. ??? 2000 ppm Y in a benmoreite) and negative Ce anomalies may have resulted from various Na- and K-enriched fluids evolving from melts of intermediate composition and either being lost from the system or enriched in other parts of the reservoirs. A small group of nepheline-normative, usually peralkaline, magmatic inclusions was formed by fluid transfer between peralkaline rhyolitic and benmoreitic magmas. The plumbing system of the complex consists of several independent reservoirs and conduits, repeatedly recharged by batches of mafic magma, with ubiquitous magma mixing. ?? The Author 2008. Published by Oxford University Press. All

  20. Evolution of crystalline target rocks and impactites in the chesapeake bay impact structure, ICDP-USGS eyreville B core

    Science.gov (United States)

    Horton, J.W.; Kunk, M.J.; Belkin, H.E.; Aleinikoff, J.N.; Jackson, J.C.; Chou, I.-Ming

    2009-01-01

    The 1766-m-deep Eyreville B core from the late Eocene Chesapeake Bay impact structure includes, in ascending order, a lower basement-derived section of schist and pegmatitic granite with impact breccia dikes, polymict impact breccias, and cataclas tic gneiss blocks overlain by suevites and clast-rich impact melt rocks, sand with an amphibolite block and lithic boulders, and a 275-m-thick granite slab overlain by crater-fill sediments and postimpact strata. Graphite-rich cataclasite marks a detachment fault atop the lower basement-derived section. Overlying impactites consist mainly of basement-derived clasts and impact melt particles, and coastalplain sediment clasts are underrepresented. Shocked quartz is common, and coesite and reidite are confirmed by Raman spectra. Silicate glasses have textures indicating immiscible melts at quench, and they are partly altered to smectite. Chrome spinel, baddeleyite, and corundum in silicate glass indicate high-temperature crystallization under silica undersaturation. Clast-rich impact melt rocks contain ??- cristobalite and monoclinic tridymite. The impactites record an upward transition from slumped ground surge to melt-rich fallback from the ejecta plume. Basement-derived rocks include amphibolite-facies schists, greenschist(?)-facies quartz-feldspar gneiss blocks and subgreenschist-facies shale and siltstone clasts in polymict impact breccias, the amphibolite block, and the granite slab. The granite slab, underlying sand, and amphibolite block represent rock avalanches from inward collapse of unshocked bedrock around the transient crater rim. Gneissic and massive granites in the slab yield U-Pb sensitive high-resolution ion microprobe (SHRIMP) zircon dates of 615 ?? 7 Ma and 254 ?? 3 Ma, respectively. Postimpact heating was 7lt;~350 ??C in the lower basementderived section based on undisturbed 40Ar/ 39Ar plateau ages of muscovite and <~150

  1. Reduced Activity and Large Particles from the Disintegrating Planet Candidate KIC 12557548b

    Science.gov (United States)

    Schlawin, E.; Herter, T.; Zhao, M.; Teske, J. K.; Chen, H.

    2016-08-01

    The intriguing exoplanet candidate KIC 12557548b is believed to have a comet-like tail of dusty debris trailing a small rocky planet. The tail of debris scatters up to 1.3% of the stellar light in the Kepler observatory’s bandpass (0.42-0.9 μm). Observing the tail’s transit depth at multiple wavelengths can reveal the composition and particle size of the debris, constraining the makeup and lifetime of the sub-Mercury planet. Early dust particle size predictions from the scattering of the comet-like tail pointed toward a dust size of ˜0.1 μm for silicate compositions. These small particles would produce a much deeper optical transit depth than near-infrared transit depth. We measure a transmission spectrum for KIC 12557548b using the SpeX spectrograph (covering 0.8-2.4 μm) simultaneously with the MORIS imager taking r‧ (0.63 μm) photometry on the Infrared Telescope Facility for eight nights and one night in H band (1.63 μm) using the Wide-field IR Camera at the Palomar 200 inch telescope. The infrared spectra are plagued by systematic errors, but we argue that sufficient precision is obtained when using differential spectroscopic calibration when combining multiple nights. The average differential transmission spectrum is flat, supporting findings that KIC 12557548b’s debris is likely composed of larger particles ≳0.5 μm for pyroxene and olivine and ≳0.2 μm for iron and corundum. The r‧ photometric transit depths are all below the average Kepler value, suggesting that the observations occurred during a weak period or that the mechanisms producing optical broadband transit depths are suppressed.

  2. ADVANCED 3D LASER MICROSCOPY FOR MEASUREMENTS AND ANALYSIS OF VITRIFIED BONDED ABRASIVE TOOLS

    Directory of Open Access Journals (Sweden)

    WOJCIECH KAPLONEK

    2012-12-01

    Full Text Available In many applications, when a precise non-contact assessment of an abrasive tools’ surface is required, alternative measurement methods are often used. Their use offers numerous advantages (referential method as they introduce new qualities into routinely realized measurements. Over the past few years there has been a dynamic increase in the interest for using new types of classical confocal microscopy. These new types are often defined as 3D laser microscopy. This paper presents select aspects of one such method’s application – confocal laser scanning microscopy – for diagnostic analysis of abrasive tools. In addition this paper also looks at the basis for operation, the origins and the development of this measurement technique.The experimental part of this paper presents the select results of tests carried out on grinding wheel active surfaces with sintered microcrystalline corundum grains SG™ bound with glass-crystalline bond. The 3D laser measuring microscopes LEXT OLS3100 and LEXT OLS4000 by Olympus were used in the experiments. Analysis of the obtained measurement data was carried out in dedicated OLS 5.0.9 and OLS4100 2.1 programs, supported by specialist TalyMap Platinum 5.0 software. The realized experiments confirmed the possibility of using the offered measurement method. This concerns both the assessment of grinding wheel active surfaces and their defects, as well as the internal structures of the tools (grain-bond connections. The method presented is an interesting alternative to the typical methods used in the diagnostics of abrasive tools.

  3. Effect of the metal concentration on the structural, mechanical and tribological properties of self-organized a-C:Cu hard nanocomposite coatings

    Science.gov (United States)

    Pardo, A.; Buijnsters, J. G.; Endrino, J. L.; Gómez-Aleixandre, C.; Abrasonis, G.; Bonet, R.; Caro, J.

    2013-09-01

    The influence of the metal content (Cu: 0-28 at.%) on the structural, mechanical and tribological properties of amorphous carbon films grown by pulsed filtered cathodic vacuum arc deposition is investigated. Silicon and AISI 301 stainless steel have been used as substrate materials. The microstructure, composition and bonding structure have been determined by scanning electron microscopy, combined Rutherford backscattered spectroscopy-nuclear reaction analysis, and Raman spectroscopy, respectively. The mechanical and tribological properties have been assessed using nanoindentation and reciprocating sliding (fretting tests) and these have been correlated with the elemental composition of the films. A self-organized multilayered structure consisting of alternating carbon and copper metal nanolayers (thickness in the 25-50 nm range), whose formation is enhanced by the Cu content, is detected. The nanohardness and Young’s modulus decrease monotonically with increasing Cu content. A maximum value of the Young’s modulus of about 255 GPa is obtained for the metal-free film, whereas it drops to about 174 GPa for the film with a Cu content of 28 at.%. In parallel, a 50% drop in the nanohardness from about 28 GPa towards 14 GPa is observed for these coatings. An increase in the Cu content also produces an increment of the coefficient of friction in reciprocating sliding tests performed against a corundum ball counterbody. As compared to the metal free film, a nearly four times higher coefficient of friction value is detected in the case of a Cu content of 28 at.%. Nevertheless, the carbon-copper composite coatings produced a clear surface protection of the substrate despite an overall increase in wear loss with increasing Cu content in the range 3-28 at.%.

  4. Effect of the metal concentration on the structural, mechanical and tribological properties of self-organized a-C:Cu hard nanocomposite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Pardo, A., E-mail: ainhoa.pardo@ctm.com.es [Fundació CTM Centre Tecnològic, Manresa (Spain); Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC) (Spain); Buijnsters, J.G., E-mail: Ivan.Buijnsters@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, KU Leuven, Leuven (Belgium); Endrino, J.L., E-mail: jose.endrino@research.abengoa.com [Abengoa Research, Sevilla (Spain); Gómez-Aleixandre, C., E-mail: cgaleix@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC) (Spain); Abrasonis, G., E-mail: g.abrasonis@hzdr.de [Institute of Ion Beam Physics and Materials Research, Dresden (Germany); Bonet, R., E-mail: raul.bonet@ctm.com.es [Fundació CTM Centre Tecnològic, Manresa (Spain); Caro, J., E-mail: jaume.caro@ctm.com.es [Fundació CTM Centre Tecnològic, Manresa (Spain)

    2013-09-01

    The influence of the metal content (Cu: 0–28 at.%) on the structural, mechanical and tribological properties of amorphous carbon films grown by pulsed filtered cathodic vacuum arc deposition is investigated. Silicon and AISI 301 stainless steel have been used as substrate materials. The microstructure, composition and bonding structure have been determined by scanning electron microscopy, combined Rutherford backscattered spectroscopy-nuclear reaction analysis, and Raman spectroscopy, respectively. The mechanical and tribological properties have been assessed using nanoindentation and reciprocating sliding (fretting tests) and these have been correlated with the elemental composition of the films. A self-organized multilayered structure consisting of alternating carbon and copper metal nanolayers (thickness in the 25–50 nm range), whose formation is enhanced by the Cu content, is detected. The nanohardness and Young’s modulus decrease monotonically with increasing Cu content. A maximum value of the Young’s modulus of about 255 GPa is obtained for the metal-free film, whereas it drops to about 174 GPa for the film with a Cu content of 28 at.%. In parallel, a 50% drop in the nanohardness from about 28 GPa towards 14 GPa is observed for these coatings. An increase in the Cu content also produces an increment of the coefficient of friction in reciprocating sliding tests performed against a corundum ball counterbody. As compared to the metal free film, a nearly four times higher coefficient of friction value is detected in the case of a Cu content of 28 at.%. Nevertheless, the carbon–copper composite coatings produced a clear surface protection of the substrate despite an overall increase in wear loss with increasing Cu content in the range 3–28 at.%.

  5. Single Crystal Structure Determination of Alumina to 1 Mbar

    Science.gov (United States)

    Dong, H.; Zhang, L.; Prakapenka, V.; Mao, H.

    2014-12-01

    Aluminum oxide (Al2O3) is an important ceramic material and a major oxide in the earth. Additionally, alumina is a widely used pressure standard in static high-pressure experiments (Cr3+-bearing corundum, ruby). The changes of its crystal structure with pressure (P) and temperature (T) are important for its applications and understanding its physical properties in the deep Earth. There have been numerous reports on the high P-T polymorphs of alumina. Previous theoretical calculations and experiments suggest that the crystal structure of Al2O3 evolves greatly at high P-T. In this study, we used the newly developed multigrain crystallography method combined with single-crystal x-ray diffraction analysis technique for the structure determination of alumina at high P-T to provide single-crystal structure refinement for high-pressure phases of Al2O3. Alumina powder was mixed with ~10% Pt and Ne was used as both pressure transmitting media and thermal insulating layers during laser-heating. Coarse-grained aggregates of Al2O3 were synthesized in a laser-heated diamond anvil cell. The structure change of Al2O3 was monitored by in situ x-ray diffraction at ~1 Mbar and 2700 K. The results allow us to distinguish the structural differences between the Rh2O3 (II) structure (space group Pbcn) and perovskite structure (space group Pbnm) for the first high-pressure phase of Al2O3. More detailed results will be discussed in the later work.

  6. An investigation of the feasibility of applying Raman microscopy for exploring stained glass.

    Science.gov (United States)

    Bouchard, Michel; Smith, David C; Carabatos-Nédelec, Constantin

    2007-12-15

    Raman microscopy (RM) is widely used in archaeometrical studies of pigments, geomaterials and biomaterials in the Cultural Heritage, but one domain has received relatively less attention: the colouring of stained glass. This feasibility study investigates the advantages and disadvantages of employing RM alone in this field by means of a study of modern commercial glasses, modern commercial pigments, and a few archaeological stained glasses, but especially by an experimental project whereby the authors created stained glass. The different kinds of possible unreacted or reacted material are rigorously established. The distinction between Na, K, Ca glasses was explored, as well as the red colouring of an industrial glass which was proved to be due to the presence of (Zn, Cd)S(x)Se(1-x). Yellow, green, blue and maroon pigments were studied before and after an initial firing and then after heating on glass. The quality of the Raman spectra varied enormously and was sometimes disappointing. Nevertheless RM successfully identified various coloured products such as bindheimite, crocoite, cobalt aluminate, haematite; relict reactants such as corundum, eskolaite and oxides of Co or Pb; and provided indications of other phases such as maghemite or Co-olivine. One conclusion is that the amount of chemical reaction between the pigments and the glass is small compared to the amount in between the pigments. Comments are made on the potential for dating archaeological glass from the known age of synthesis of the pigments, and of the dangers of this approach. Overall it has been shown that RM can be useful for studying stained glass, especially for remote in situ analytical operations with mobile RM, but one must expect some problems either with fluorescence or weak spectra.

  7. Insight into the Consolidation Mechanism of Oxidized Pellets Made from the Mixture of Magnetite and Chromite Concentrates

    Science.gov (United States)

    Zhu, Deqing; Yang, Congcong; Pan, Jian; Zhang, Qiang; Shi, Benjing; Zhang, Feng

    2016-04-01

    To produce more competitive stainless steel products, the utilization of low-cost chromite concentrate is of great importance. In a previous study, a high-quality product pellet (CMP) for blast furnace smelting process made from a mixture of 40 wt pct chromite and 60 wt pct magnetite concentrates was manufactured by a high-pressure grinding rollers pretreatment. In this work, an insight into the consolidation mechanism of CMP is taken in comparison with the oxidized pellets (MP) made from 100 pct magnetite concentrate by adopting the scanning electron microscopy, energy-dispersive spectrometer, and X-ray diffractometer. The mineralogy of the pellets and the morphology of the preheated and roasted mineral particles are demonstrated. To gain better understanding of the consolidation mechanism of CMP, the thermodynamics of chromite-magnetite spinel system and hematite-sesquioxide corundum system in air are considered by using FactSage software. It can be found that the solid-state bonding is the dominant form in the consolidation of CMP, which mainly depends on the recrystallization of hematite, the solid solution bonding in adjacent areas of both magnetite-chromite particles and chromite-chromite particles. The latter two bonds rely on the formation of the miscible sesquioxide and spinel solid solution at the contact areas of particles, which is largely affected by the oxidizability of magnetite and chromite spinels. When more chromite concentrate is blended, the weak bonding among the chromite particles gradually becomes the dominant factor, which will lead to the decrease of the mechanical strength of fired pellets. The presence of a small quantity of siliceous liquid phase in CMP is believed to be beneficial to the hardening by accelerating the ion diffusion rate and forming slag bonds.

  8. Properties of the surface of ceramic formed under laser irradiation of Al{sub 2}O{sub 3}–TiO{sub 2} compacts

    Energy Technology Data Exchange (ETDEWEB)

    Márquez Aguilar, P.A., E-mail: pmarquez@uaem.mx [Center of Investigation in Engineering and Applied Sciences of the Autonomous University of the State of Morelos (CIICAp-UAEMor) (Mexico); Vlasova, M.; Escobar Martínez, A. [Center of Investigation in Engineering and Applied Sciences of the Autonomous University of the State of Morelos (CIICAp-UAEMor) (Mexico); Tomila, T.; Stetsenko, V. [Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3, Krzhyzhanovsky St., Kiev 252680 (Ukraine)

    2014-04-01

    Highlights: • At directed laser treatment of x% Al{sub 2}O{sub 3}–y% TiO{sub 2} powder compacts in air the composite ceramics x% Al{sub 2}TiO{sub 5}–y% Al{sub 2}O{sub 3}–z% TiO{sub 2} are forming. • Due to formation of high temperature on the ceramic surface the processes dissociation of compounds take place. • Simultaneously dissociate components of the gas medium (and CO{sub 2} and H{sub 2}O vapor). • At scattering the dissociation products turn out in different temperature zones and form new compounds. • Parts of the newly formed compounds are deposited on the surface of the ceramics and form a porous layer of complex composition. - Abstract: The phase formation in the laser irradiation area from xAl{sub 2}O{sub 3}–yTiO{sub 2} compacts and the properties of the surface layer have been investigated by the XRD, IR, and SEM methods. Main phases precipitating from eutectic melt are tialite, corundum, and rutile. A high temperature on the surface of specimens leads to the development of dissociation processes of these compounds and molecules of the gaseous medium. As dissociation products fly apart and pass through different temperature zone, there are formed different metal oxides, metal hydroxides, and thermolysis products. When these different oxides are deposited on the surface of the ceramic, they form layers with different adhesion degrees.

  9. Aging effects of plasma polymerized ethylenediamine (PPEDA) thin films on cell-adhesive implant coatings

    Energy Technology Data Exchange (ETDEWEB)

    Testrich, H., E-mail: holger.testrich@uni-greifswald.de [University of Greifswald, Institute of Physics, Felix-Hausdorff Str. 6, 17489 Greifswald (Germany); Rebl, H. [University of Rostock, Biomedical Research Center, Department of Cell Biology, Schillingallee 69, 18057 Rostock (Germany); Finke, B.; Hempel, F. [Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff Str. 2, 17489 Greifswald (Germany); Nebe, B. [University of Rostock, Biomedical Research Center, Department of Cell Biology, Schillingallee 69, 18057 Rostock (Germany); Meichsner, J. [University of Greifswald, Institute of Physics, Felix-Hausdorff Str. 6, 17489 Greifswald (Germany)

    2013-10-15

    Thin plasma polymer films from ethylenediamine were deposited on planar substrates placed on the powered electrode of a low pressure capacitively coupled 13.56 MHz discharge. The chemical composition of the plasma polymer films was analyzed by Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRRAS) as well as by X-ray photoelectron spectroscopy (XPS) after derivatization of the primary amino groups. The PPEDA films undergo an alteration during the storage in ambient air, particularly, due to reactions with oxygen. The molecular changes in PPEDA films were studied over a long-time period of 360 days. Simultaneously, the adhesion of human osteoblast-like cells MG-63 (ATCC) was investigated on PPEDA coated corundum blasted titanium alloy (Ti-6Al-4V), which is applied as implant material in orthopedic surgery. The cell adhesion was determined by flow cytometry and the cell shape was analyzed by scanning electron microscopy. Compared to uncoated reference samples a significantly enhanced cell adhesion and proliferation were measured for PPEDA coated samples, which have been maintained after long-time storage in ambient air and additional sterilization by γ−irradiation. - Highlights: • Development of cell-adhesive nitrogen-rich coatings for biomedical applications. • Plasma polymer films from low pressure 13.56 MHz discharge in argon-ethylenediamine. • Enhanced osteoblast adhesion/proliferation on coated implant material (Ti-6Al-4V). • Despite film aging over 360 days the enhanced cell adhesion of the coating remains. • No influence of additional y-sterilization on the enhanced cell adhesion.

  10. Effects of Grit Blasting and Annealing on the High-Temperature Oxidation Behavior of Austenitic and Ferritic Fe-Cr Alloys

    Science.gov (United States)

    Proy, M.; Utrilla, M. V.; Otero, E.; Bouchaud, B.; Pedraza, F.

    2014-08-01

    Grit blasting (corundum) of an austenitic AISI 304 stainless steel (18Cr-8Ni) and of a low-alloy SA213 T22 ferritic steel (2.25Cr-1Mo) followed by annealing in argon resulted in enhanced outward diffusion of Cr, Mn, and Fe. Whereas 3 bar of blasting pressure allowed to grow more Cr2O3 and Mn x Cr3- x O4 spinel-rich scales, higher pressures gave rise to Fe2O3-enriched layers and were therefore disregarded. The effect of annealing pre-oxidation treatment on the isothermal oxidation resistance was subsequently evaluated for 48 h for both steels and the results were compared with their polished counterparts. The change of oxidation kinetics of the pre-oxidized 18Cr-8Ni samples at 850 °C was ascribed to the growth of a duplex Cr2O3/Mn x Cr3- x O4 scale that remained adherent to the substrate. Such a positive effect was less marked when considering the oxidation kinetics of the 2.25Cr-1Mo steel but a more compact and thinner Fe x Cr3- x O4 subscale grew at 650 °C compared to that of the polished samples. It appeared that the beneficial effect is very sensitive to the experimental blasting conditions. The input of Raman micro-spectroscopy was shown to be of ground importance in the precise identification of multiple oxide phases grown under the different conditions investigated in this study.

  11. Enclaves con espinela-corindon·sillimanita en rocas andesítico-dacíticas (Noguera, sierra de Albarracin. Teruel

    Directory of Open Access Journals (Sweden)

    Aparicio, A.

    1987-08-01

    Full Text Available In intrusive dacitic-andesitic rocks, near Noguera de Albarracín, Iberian Mountains (Spain, there exist metamorphic inclusions with spinel, corundum, sillimanite, biotite and other interesting minerals, many of them indicating high T-P conditions (above 800° C and 5 Kb. The petrological studies indicate that such enclaves were built through a poliphasic process where various prograde and retrograde minerals were formed. A possible relationship between the metamorphic and the volcanic processes and both, metamorphic and volcanic, with the swelling-uplifting phenomenon, securely related with intrusive granitoids that took place in Albarracin area during last Hercynian times, is considered here.En un afloramiento intrusivo, constituído por rocas dacítico-andesíticas, al W de Noguera de Albarracín, existen enclaves de rocas metamórficas con espinela, corindón, sillimanita y otros minerales. Los estudios petrológicos indican que estos enclaves fueron originados en un proceso polifásico donde varias secuencias mineralógicas prógradas y retrógradas son reconocidas. Muchas de la paragénesis indican condiciones físicas de formación alrededor de los 800° C y los 5 Kb. Se plantea la posibilidad de la existencia de una relación entre el proceso metamórfico y el volcánico, y ambos asociados con el abombamiento cortical, posiblemente en relación con granitoides, que tuvo lugar en la Sierra de Albarracín durante el Paleozoico Superior.

  12. Thermodynamic database development-modeling and phase diagram calculations in oxide systems

    Institute of Scientific and Technical Information of China (English)

    Arthur D. Pelton

    2006-01-01

    The databases of the FactSage thermodynamic computer system have been under development for 30 years. These databases contain critically evaluated and optimized data for thousands of compounds and hundreds of multicomponent solutions of solid and liquid metals, oxides, salts, sulfides, etc. The databases are automatically accessed by user-friendly software that calculates complex multiphase equilibria in large multicomponent systems for a wide variety of possible input/output constraints. The databases for solutions have been developed by critical evaluation/optimization of all available phase equilibrium and thermodynamic data. The databases contain parameters of models specifically developed for different types of solutions involving sublattices, ordering, etc. Through the optimization process, model parameters are found which reproduce all thermodynamic and phase equilibrium data within experimental error limits and permit extrapolation into regions of temperature and composition where data are unavailable. The present article focuses on the databases for solid and liquid oxide phases involving 25 elements. A short review of the available databases is presented along with the models used for the molten slag and the solid solutions such as spinel, pyroxene, olivine, monoxide, corundum, etc. The critical evaluation/optimization procedure is outlined using examples from the A12O3-SiO2-CaO-FeO-Fe2O3 system. Sample calculations are presented in which the oxide databases are used in conjunction with the FactSage databases for metallic and other phases. In particular, the use of the FactSage module for the calculation of multicomponent phase diagrams is illustrated.

  13. Mineralogy and geochemistry of Bobov Dol coals, Bulgaria

    Energy Technology Data Exchange (ETDEWEB)

    Vassilev, S.V.; Yossifova, M.G.; Vassileva, C.G. (Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. of Applied Mineralogy)

    1994-10-01

    The mineralogy, elemental composition and modes of occurrence of 49 elements in nine composite samples of Bobov Dol high-ash coals were studied by optical microscopy, scanning and transmission electron microscopy, X-ray diffractometry and chemical analysis. The major minerals were quartz, kaolinite, illite, plagioclase and K-feldspar and the minor minerals and phases were pyrite, marcasite, siderite, calcite, dolomite, gypsum, muscovite, montmorillonite and volcanic glass. The accessory minerals include a wide variety of minerals, such as galena, pyrrhotite, magnetite, hematite, goethite, chromite, rutile, anatase, corundum, gibbsite, biotite, chlorite, zircon, enstatite, garnet, jarosite, alunite, barite, polyhalite, aragonite, ankerite, witherite, apatite, halite and sylvite. The modes of occurrence and some genetic peculiarities of the above-mentioned minerals are described. Thirty-three elements occurred in concentrations higher than the respective Clarke values; especially S, Rb, Nb, Hf, Zn, Cu, Pb, Mn, Ti and U. The concentration trends and modes of occurrence of the trace elements are also discussed. In decreasing order of significance, the trace elements probably occur as element-organic compounds, as impurities in the mineral constituents, as major components in the minerals, as major and impurity components in the inorganic amorphous constituents, and in the fluid constituents. The Bobov Dol coals have undergone complex syngetenic, diagenetic and epigenetic mineralization processes associated with hydrothermal and volcanic activities. These processes were also accompanied by intensive tectonic movements, and possibly, by a later change from continental to marine sedimentation in the area after burial of the coal. 38 refs., 1 fig., 6 tabs., 5 plates.

  14. Dust in the Quasar Wind (Artist Concept)

    Science.gov (United States)

    2007-01-01

    Dusty grains -- including tiny specks of the minerals found in the gemstones peridot, sapphires and rubies -- can be seen blowing in the winds of a quasar, or active black hole, in this artist's concept. The quasar is at the center of a distant galaxy. Astronomers using NASA's Spitzer Space Telescope found evidence that such quasar winds might have forged these dusty particles in the very early universe. The findings are another clue in an ongoing cosmic mystery: where did all the dust in our young universe come from? Dust is crucial for efficient star formation as it allows the giant clouds where stars are born to cool quickly and collapse into new stars. Once a star has formed, dust is also needed to make planets and living creatures. Dust has been seen as far back as when the universe was less than a tenth of its current age, but how did it get there? Most dust in our current epoch forms in the winds of evolved stars that did not exist when the universe was young. Theorists had predicted that winds from quasars growing in the centers of distant galaxies might be a source of this dust. While the environment close to a quasar is too hot for large molecules like dust grains to survive, dust has been found in the cooler, outer regions. Astronomers now have evidence that dust is created in these outer winds. Using Spitzer's infrared spectrograph instrument, scientists found a wealth of dust grains in a quasar called PG2112+059 located at the center of a galaxy 8 billion light-years away. The grains - including corundum (sapphires and rubies); forsterite (peridot); and periclase (naturally occurring in marble) - are not typically found in galaxies without quasars, suggesting they might have been freshly formed in the quasar's winds.

  15. Formation of crystalline Zn-Al layered double hydroxide precipitates on γ-alumina: the role of mineral dissolution.

    Science.gov (United States)

    Li, Wei; Livi, Kenneth J T; Xu, Wenqian; Siebecker, Matthew G; Wang, Yujun; Phillips, Brian L; Sparks, Donald L

    2012-11-06

    To better understand the sequestration of toxic metals such as nickel (Ni), zinc (Zn), and cobalt (Co) as layered double hydroxide (LDH) phases in soils, we systematically examined the presence of Al and the role of mineral dissolution during Zn sorption/precipitation on γ-Al(2)O(3) (γ-alumina) at pH 7.5 using extended X-ray absorption fine structure spectroscopy (EXAFS), high-resolution transmission electron microscopy (HR-TEM), synchrotron-radiation powder X-ray diffraction (SR-XRD), and (27)Al solid-state NMR. The EXAFS analysis indicates the formation of Zn-Al LDH precipitates at Zn concentration ≥0.4 mM, and both HR-TEM and SR-XRD reveal that these precipitates are crystalline. These precipitates yield a small shoulder at δ(Al-27) = +12.5 ppm in the (27)Al solid-state NMR spectra, consistent with the mixed octahedral Al/Zn chemical environment in typical Zn-Al LDHs. The NMR analysis provides direct evidence for the existence of Al in the precipitates and the migration from the dissolution of γ-alumina substrate. To further address this issue, we compared the Zn sorption mechanism on a series of Al (hydr)oxides with similar chemical composition but differing dissolubility using EXAFS and TEM. These results suggest that, under the same experimental conditions, Zn-Al LDH precipitates formed on γ-alumina and corundum but not on less soluble minerals such as bayerite, boehmite, and gibbsite, which point outs that substrate mineral surface dissolution plays an important role in the formation of Zn-Al LDH precipitates.

  16. Synchronistic preparation of fibre-like SiC and cubic-ZrO{sub 2}/SiC composite from zircon via carbothermal reduction process

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Youguo; Liu, Yangai [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Huang, Zhaohui, E-mail: huang118@cugb.edu.cn [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Fang, Minghao [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Hu, Xiaozhi [School of Mechanical and Chemical Engineering, University of Western Australia, Perth, WA 6009 (Australia); Yin, Li; Huang, Juntong [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China)

    2013-01-15

    Graphical abstract: Display Omitted Highlights: ► Zircon carbothermal reduction was carried out in a tailor-made device at high-temperature air atmosphere. ► Fibre-like SiC and cubic-ZrO{sub 2}/SiC composite were obtained synchronically. ► Zirconium and silicon in zircon ore was initial separated. ► [SiO{sub 4}] was mutated to fibre-like SiC, while [ZrO{sub 8}] was transformed to cubic ZrO{sub 2}. ► The SiC were surprisingly enriched in the reducing atmosphere charred coal particles layers by gas–solid reaction. -- Abstract: Fibre-like SiC and cubic-ZrO{sub 2}/SiC composite were prepared respectively from zircon with yttrium oxide addition via carbothermal reduction process at 1600 °C for 4 h in an air atmosphere furnace, where the green samples were immerged in charred coal particles inside a high-temperature enclosed corundum crucible. The reaction products were characterized by XRD, XRF, XPS and SEM. The results indicate that ZrO{sub 2} in the products was mainly existed in the form of cubic phase. The reacted samples mainly contain cubic ZrO{sub 2}, β-SiC and trace amounts of zircon, with the SiC accounting for 14.8 wt%. Furthermore, a large quantity of fibre-like SiC was surprisingly found to concentrate in the charred coal particles layers around the samples. This study obtains fibre-like SiC and cubic-ZrO{sub 2}/SiC composite synchronically from zircon via carbothermal reduction process, which also bring a value-added high-performance application for natural zircon.

  17. In situ hydration of sulphoaluminate cement mixtures monitored by synchrotron x-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Turrillas, X. [Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Barcelona (Spain); Martinez, L.G.; Carvalho, A.M.; Carezzato, G.L. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Rossetto, C.M. [Faculdade de Tecnologia de Sao Paulo (FATEC), SP (Brazil)

    2016-07-01

    Full text: The hydration of calcium sulpho-aluminate cement mixtures was studied in situ by synchrotron X-ray diffraction at the XRD1 beamline of the Laboratorio Nacional de Luz Sincrotron (LNLS) in Campinas, SP. The powder specimens were introduced in borosilicate glass capillary tubes of 0.7 mm of internal diameter and imbued with deionized water. As the hydration reaction is very fast the capillaries were placed on the goniometer and the data collection was started after two minutes of mixing with water. The X-ray energy chosen to get an adequate flux for these short time acquisitions was 12 keV or more precisely 1.033258 Å, determined with polycrystalline corundum standard. Diffraction patterns were collected sequentially every 35 seconds for several hours at temperatures ranging from 40 degC to 55 degC with an accuracy better than 0.1 degC attained with the help of a hot air blower. The diffracted signal was collected with an array of twenty-four Mythen detectors at 760 mm from the capillary tube. The diffraction patterns had appropriate statistics to determine the kinetics of the reaction either by quantitative Rietveld analysis or by fitting isolated diffraction peaks to Gaussian curves as a function of time. The most important phases involved in the hydration are Klein´s salt, also known as Ye’elimite, Ca4(AlO2)6SO4, and gypsum, CaSO4.2H2O to yield Ettringite, Ca6Al2(SO4)3(OH)12 - 26H2O, phase responsible for the mechanical properties. (author)

  18. Theoretical modeling of charge trapping in crystalline and amorphous Al2O3

    Science.gov (United States)

    Dicks, Oliver A.; Shluger, Alexander L.

    2017-08-01

    The characteristics of intrinsic electron and hole trapping in crystalline and amorphous Al2O3 have been studied using density functional theory (DFT). Special attention was paid to enforcing the piece-wise linearity of the total energy with respect to electron number through the use of a range separated, hybrid functional PBE0-TC-LRC (Guidon et al 2009 J. Chem. Theory Comput. 5 3010) in order to accurately model the behaviour of localized states. The tuned functional is shown to reproduce the geometric and electronic structures of the perfect crystal as well as the spectroscopic characteristics of MgAl hole centre in corundum α-Al2O3. An ensemble of ten amorphous Al2O3 structures was generated using classical molecular dynamics and a melt and quench method and their structural characteristics compared with the experimental data. The electronic structure of amorphous systems was characterized using the inverse participation ratio method. Electrons and holes were then introduced into both crystalline and amorphous alumina structures and their properties calculated. Holes are shown to trap spontaneously in both crystalline and amorphous alumina. In the crystalline phase they localize on single O ion with the trapping energy of 0.38 eV. In amorphous phase, holes localize on two nearest neighbour oxygen sites with an average trapping energy of 1.26 eV, with hole trapping sites separated on average by about 8.0 Å. No electron trapping is observed in the material. Our results suggest that trapping of positive charge can be much more severe and stable in amorphous alumina rather than in crystalline samples.

  19. Rheological principles of development hetero-modulus and hetero-viscous complex materials with extreme dynamic strength

    Science.gov (United States)

    Gömze, L. A.; Gömze, L. N.

    2017-02-01

    Materials with different crystalline and morphological compositions have different chemical, physical, mechanical and rheological properties, including wear protection, melting temperature, module of elasticity and viscosity. Examining the material structures and behaviors of differentceramic bodies and CMCs under high speed collisions in several years the authors have understood the advantages of hetero-modulus and hetero-viscous complex material systems to absorb and dissipate the kinetic energy of objects during high speed collisions. Applying the rheo-mechanical principles the authors successfully developed a new family of hetero-modulus and hetero-viscous alumina matrix composite materials with extreme mechanical properties including dynamic strength. These new corundum-matrix composite materials reinforced with Si2ON 2, Si3N4 , SiAlON and AlN submicron and nanoparticles have excellent dynamic strength during collisions with high density metallic bodies with speeds about 1000 m/sec or more. At the same time in the alumina matrix composites can be observed a phase transformation of submicron and nanoparticles of alpha and beta silicone-nitride crystals into cubicc-Si3N4 diamond-like particles can be observed, when the high speed collision processes are taken place in vacuum or oxygen-free atmosphere. Using the rheological principles and the energy engorgement by fractures, heating and melting of components the authors successfully developed several new hetero-modulus, hetero-viscous and hetero-plastic complex materials. These materials generally are based on ceramic matrixes and components having different melting temperatures and modules of elasticity from low values like carbon and light metals (Mg, Al, Ti, Si) up to very high values like boride, nitride and carbide ceramics. Analytical methods applied in this research were scanning electron microscopy, X-ray diffractions and energy dispersive spectrometry. Digital image analysis was applied to microscopy

  20. Acid Sulfate Weathering on Mars: Results from the Mars Exploration Rover Mission

    Science.gov (United States)

    Ming, Douglas W.; Morris, R. V.; Golden, D. C.

    2006-01-01

    Sulfur has played a major role in the formation and alteration of outcrops, rocks, and soils at the Mars Exploration Rover landing sites on Meridiani Planum and in Gusev crater. Jarosite, hematite, and evaporite sulfates (e.g., Mg and Ca sulfates) occur along with siliciclastic sediments in outcrops at Meridiani Planum. The occurrence of jarosite is a strong indicator for an acid sulfate weathering environment at Meridiani Planum. Some outcrops and rocks in the Columbia Hills in Gusev crater appear to be extensively altered as suggested by their relative softness as compared to crater floor basalts, high Fe(3+)/FeT, iron mineralogy dominated by nanophase Fe(3+) oxides, hematite and/or goethite, corundum-normative mineralogies, and the presence of Mg- and Casulfates. One scenario for aqueous alteration of these rocks and outcrops is that vapors and/or fluids rich in SO2 (volcanic source) and water interacted with rocks that were basaltic in bulk composition. Ferric-, Mg-, and Ca-sulfates, phosphates, and amorphous Si occur in several high albedo soils disturbed by the rover's wheels in the Columbia Hills. The mineralogy of these materials suggests the movement of liquid water within the host material and the subsequent evaporation of solutions rich in Fe, Mg, Ca, S, P, and Si. The presence of ferric sulfates suggests that these phases precipitated from highly oxidized, low-pH solutions. Several hypotheses that invoke acid sulfate weathering environments have been suggested for the aqueous formation of sulfate-bearing phases on the surface of Mars including (1) the oxidative weathering of ultramafic igneous rocks containing sulfides; (2) sulfuric acid weathering of basaltic materials by solutions enriched by volcanic gases (e.g., SO2); and (3) acid fog (i.e., vapors rich in H2SO4) weathering of basaltic or basaltic-derived materials.

  1. Benchmarking analogue models of brittle thrust wedges

    Science.gov (United States)

    Schreurs, Guido; Buiter, Susanne J. H.; Boutelier, Jennifer; Burberry, Caroline; Callot, Jean-Paul; Cavozzi, Cristian; Cerca, Mariano; Chen, Jian-Hong; Cristallini, Ernesto; Cruden, Alexander R.; Cruz, Leonardo; Daniel, Jean-Marc; Da Poian, Gabriela; Garcia, Victor H.; Gomes, Caroline J. S.; Grall, Céline; Guillot, Yannick; Guzmán, Cecilia; Hidayah, Triyani Nur; Hilley, George; Klinkmüller, Matthias; Koyi, Hemin A.; Lu, Chia-Yu; Maillot, Bertrand; Meriaux, Catherine; Nilfouroushan, Faramarz; Pan, Chang-Chih; Pillot, Daniel; Portillo, Rodrigo; Rosenau, Matthias; Schellart, Wouter P.; Schlische, Roy W.; Take, Andy; Vendeville, Bruno; Vergnaud, Marine; Vettori, Matteo; Wang, Shih-Hsien; Withjack, Martha O.; Yagupsky, Daniel; Yamada, Yasuhiro

    2016-11-01

    We performed a quantitative comparison of brittle thrust wedge experiments to evaluate the variability among analogue models and to appraise the reproducibility and limits of model interpretation. Fifteen analogue modeling laboratories participated in this benchmark initiative. Each laboratory received a shipment of the same type of quartz and corundum sand and all laboratories adhered to a stringent model building protocol and used the same type of foil to cover base and sidewalls of the sandbox. Sieve structure, sifting height, filling rate, and details on off-scraping of excess sand followed prescribed procedures. Our analogue benchmark shows that even for simple plane-strain experiments with prescribed stringent model construction techniques, quantitative model results show variability, most notably for surface slope, thrust spacing and number of forward and backthrusts. One of the sources of the variability in model results is related to slight variations in how sand is deposited in the sandbox. Small changes in sifting height, sifting rate, and scraping will result in slightly heterogeneous material bulk densities, which will affect the mechanical properties of the sand, and will result in lateral and vertical differences in peak and boundary friction angles, as well as cohesion values once the model is constructed. Initial variations in basal friction are inferred to play the most important role in causing model variability. Our comparison shows that the human factor plays a decisive role, and even when one modeler repeats the same experiment, quantitative model results still show variability. Our observations highlight the limits of up-scaling quantitative analogue model results to nature or for making comparisons with numerical models. The frictional behavior of sand is highly sensitive to small variations in material state or experimental set-up, and hence, it will remain difficult to scale quantitative results such as number of thrusts, thrust spacing

  2. Direct Metal Laser Sintering of Ti6Al4V for Biomedical Applications: Microstructure, Corrosion Properties, and Mechanical Treatment of Implants

    Directory of Open Access Journals (Sweden)

    Janette Brezinová

    2016-07-01

    Full Text Available Ti6Al4V samples have been prepared by Direct Metal Laser Sintering (DMLS with varied laser power. Some of the samples were stress-relief annealed. The microstructure of materials was investigated using a light microscopy. Columnar grains of martensite dominate in as-made microstructure. Stress-relief annealing led to the white acicular phase growth in the structure with a fishbone arrangement on the boundary of some original martensitic needles. Mechanical properties of materials were characterized through hardness measurement in two directions relating to the sample building direction. It was found that the hardness of materials increased with a laser power and values varied from 370 to 415 HV 0.3/30. After stress-relief annealing, the structure of materials being homogenized, pattern spacing dissolved and the hardness in both directions became stabilized at values of 350–370 HV 0.3/30. The laser power affects the corrosion rate of the material. The lowest corrosion rate was recorded at the maximum laser power (190 W. Heat treatment does not affect the corrosion rate remarkably, however it leads to stabilization of corrosion potential of materials Ecorr. The surface of the samples was modified by an abrasive blasting using spherical (zirblast and sharp-edged (white corundum blasting abrasives and three levels of air pressure. The abrasive blasting of sintered materials led to a decrease of the surface roughness of materials with air pressure increasing. Blasting with zirblast led to a more significant decrease of roughness parameters compared with surfaces blasted with sharp-edged white aluminum. Different shapes of abrasives caused characteristic surface morphology.

  3. Structural transformations and wear resistance of abrasive-affected amorphous Fe- and Co-based alloys

    Science.gov (United States)

    Korshunov, L. G.; Chernenko, N. L.

    2008-12-01

    The abrasive wear resistance of the Fe64Co30Si3B3, Fe82.6Nb5Cu3Si8B1.4, Co86.5Cr4Si7B2.5, and Fe81Si4B13C2 amorphous alloys (ribbon 30 μm thick) has been investigated upon sliding over fixed abrasives (corundum and silicon carbide). The character of fracture of the surface and structural transformations initiated in these materials by the abrasive action have been studied by the metallographic, X-ray diffraction, and electron-microscopic methods. It has been shown that the abrasive wear resistance of the amorphous alloys is smaller by a factor of 1.6-2.9 than that of the Kh12M and U8 tool steels possessing approximately the same level of hardness. A pronounced softening of the surface layer of the amorphous alloys in the process of wear, which is characterized by a decrease in their microhardness reaching 12.5%, has been found. It has been shown that in the surface layer of these amorphous alloys upon wear there arises a small amount (on the order of several volume percent) of the nanocrystalline structure, which does not exert a marked effect on the microhardness and wear resistance of the alloys. In the alloys under study, the main factor that is responsible for their comparatively low abrasive wear resistance is their local softening in the process of wear caused by specific features of deformation processes occurring heterogeneously under the action of high shear contact stresses.

  4. Helium and neon diffusion in pure hematite (α-Fe2O3) crystal lattice

    Science.gov (United States)

    Balout, Hilal; Roques, Jérôme; Gautheron, Cécile; Tassan-Got, Laurent

    2016-04-01

    Hematite (α-Fe2O3) has the corundum-type structure and is relatively present on Earth and Mars surface associated to ore mineral precipitation or as a weathering phase. He and Ne retention in such mineral has been intensively investigated experimentally because of the potential use of (U-Th-Sm)/(He-Ne) chronometer and thermochronometer. Therefore, the He/Ne diffusion in hematite crystal is an important issue for the interpretation of (U-Th)/(He-Ne) thermochronometric ages. For this purpose an accurate investigation of helium and neon diffusion in hematite crystal lattice has been achieved by computational multi-scale approach. Different insertion sites and diffusion pathways are first characterized where the spin polarized density functional theory (sp-DFT) approach coupled to the nudged elastic band (NEB) method is used to determine the migration energies between the insertion sites. Then, a statistical method, based on transition state theory (TST), is used to compute the jump probability between sites. The previous results are used as input data in a 3D random walk simulation, which permits to determine the effective activation energy and diffusion coefficient. Using the He/Ne diffusion coefficients, the closure temperature Tc has been calculated. For typical grain size of 100 microns, Tc will be of 116° C and 297° C for He and Ne atoms, respectively. These results Show that He and Ne atoms are highly retained in the crystal lattice at surface temperature. The obtained diffusion coefficients confirm that He/Ne retentively power in hematite lattice is very important, allowing a large range of different geological applications such the measurement of hematite crystallization ages on Earth and Mars.

  5. Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago.

    Science.gov (United States)

    Bunch, Ted E; Hermes, Robert E; Moore, Andrew M T; Kennett, Douglas J; Weaver, James C; Wittke, James H; DeCarli, Paul S; Bischoff, James L; Hillman, Gordon C; Howard, George A; Kimbel, David R; Kletetschka, Gunther; Lipo, Carl P; Sakai, Sachiko; Revay, Zsolt; West, Allen; Firestone, Richard B; Kennett, James P

    2012-07-10

    It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica- and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because some groups have failed to do so. We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically. We compared YDB objects with melt products from a known cosmic impact (Meteor Crater, Arizona) and from the 1945 Trinity nuclear airburst in Socorro, New Mexico, and found that all of these high-energy events produced material that is geochemically and morphologically comparable, including: (i) high-temperature, rapidly quenched microspherules and SLOs; (ii) corundum, mullite, and suessite (Fe(3)Si), a rare meteoritic mineral that forms under high temperatures; (iii) melted SiO(2) glass, or lechatelierite, with flow textures (or schlieren) that form at > 2,200 °C; and (iv) particles with features indicative of high-energy interparticle collisions. These results are inconsistent with anthropogenic, volcanic, authigenic, and cosmic materials, yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago. The wide geographic distribution of SLOs is consistent with multiple impactors.

  6. Microwave dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12}-Al{sub 2}O{sub 3} composite

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Zaman, Rosyaini Afindi; Ahmad, Zainal Arifin [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Karim, Saniah Ab; Mohamed, Julie Juliewatty, E-mail: juliewatty.m@umk.edu.my [Advance Materials Research Cluster, Faculty of Earth Sciences, Universiti Malaysia Kelantan, Jeli Campus, 17600 Jeli, Kelantan (Malaysia); Ain, Mohd Fadzil [School of Electrical and Electronic Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

    2016-07-19

    (1-x)CaCu{sub 3}Ti{sub 4}O{sub 12} + (x)Al{sub 2}O{sub 3} composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO{sub 3}, CuO and TiO{sub 2} powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al{sub 2}O{sub 3} were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl{sub 2}O{sub 4} and Corundum (Al{sub 2}O{sub 3}) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al{sub 2}O{sub 3} (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al{sub 2}O{sub 3} (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al{sub 2}O{sub 3} was reduced both dielectric loss and permittivity at least for an order of magnitude.

  7. Microstructure of Al2O3 scales formed on NiCrAl alloys. Ph.D. Thesis - Case Western Reserve Univ.

    Science.gov (United States)

    Smialek, J. L.

    1981-01-01

    The structure of transient scales formed on pure and Y or Zr-doped Ni-15Cr-13Al alloys oxidized for 0.1 hr at 1100 C was studied by the use of transmission electron microscopy. Crystallographically oriented scales were found on all three alloys, but especially for the Zr-doped NiCrAl. The oriented scales consisted of alpha-(Al,Cr)2O3, Ni(Al,Cr)2O4 and gamma-Al2O3. They were often found in intimate contact with each other such that the close-packed planes and directions of one oxide phase were aligned with those of another. The prominent structural features of the oriented scales were approximately equal to micrometer subgrains; voids, antiphase domain boundaries and aligned precipitates were also prevalent. Randomly oriented alpha-Al2O3 was also found and was the only oxide ever observed at the immediate oxide metal interface. These approximately 0.15 micrometer grains were populated by intragranular voids which decreased in size and number towards the oxide metal interface. A sequence of oxidation was proposed in which the composition of the growing scale changed from oriented oxides rich in Ni and Cr to oriented oxides rich in Al. At the same time the structure changed from cubic spinels to hexagonal corundums with apparent precipitates of one phase in the matrix of the other. Eventually randomly oriented pure alpha-Al2O3 formed as the stable oxide with an abrupt transition: there was no gradual loss of orientation, no gradual compositional change or no gradual decrease in precipitate density.

  8. Copper stabilization via spinel formation during the sintering of simulated copper-laden sludge with aluminum-rich ceramic precursors.

    Science.gov (United States)

    Tang, Yuanyuan; Chui, Stephen Sin-Yin; Shih, Kaimin; Zhang, Lingru

    2011-04-15

    The feasibility of incorporating copper-laden sludge into low-cost ceramic products, such as construction ceramics, was investigated by sintering simulated copper-laden sludge with four aluminum-rich ceramic precursors. The results indicated that all of these precursors (γ-Al(2)O(3), corundum, kaolinite, mullite) could crystallochemically stabilize the hazardous copper in the more durable copper aluminate spinel (CuAl(2)O(4)) structure. To simulate the process of copper transformation into a spinel structure, CuO was mixed with the four aluminum-rich precursors, and fired at 650-1150 °C for 3 h. The products were examined using powder X-ray diffraction (XRD) and scanning electron microscopic techniques. The efficiency of copper transformation among crystalline phases was quantitatively determined through Rietveld refinement analysis of the XRD data. The sintering experiment revealed that the optimal sintering temperature for CuAl(2)O(4) formation was around 1000 °C and that the efficiency of copper incorporation into the crystalline CuAl(2)O(4) structure after 3 h of sintering ranged from 40 to 95%, depending on the type of aluminum precursor used. Prolonged leaching tests were carried out by using acetic acid with an initial pH value of 2.9 to leach CuO and CuAl(2)O(4) samples for 22 d. The sample leachability analysis revealed that the CuAl(2)O(4) spinel structure was more superior to stabilize copper, and suggested a promising and reliable technique for incorporating copper-laden sludge or its incineration ash into usable ceramic products. Such results also demonstrated the potential of a waste-to-resource strategy by using waste materials as part of the raw materials with the attainable temperature range used in the production of ceramics.

  9. Resistencia a la corrosión y desgaste de recubrinnientos deTiN obtenidos por PVD

    Directory of Open Access Journals (Sweden)

    Conde, A.

    2005-12-01

    Full Text Available Surface hardening techniques for metallic alloys are widely used to achieve layers of very high hardness and corrosion and wear resistance. In the present paper TiN coatings are obtained by PVD on a tool steel. The films are characterized by SEM, X-ray diffraction and XPS. Corrosion behaviour in NaCl solution showed the importance of the presence of defects on the PVD coating due to the different electrochemical behaviour of the steel base. Pin-on-disk measurements at approximately 40% RH against a corundum (Al2O3 ball showed a significant decrease in the wear rate compared with the results for the standard tool steel.

    Los tratamientos de endurecimiento superficial de aleaciones metálicas se utilizan para lograr capas de muy elevada dureza, resistencia a la corrosión y desgaste. En este trabajo, se estudia el comportamiento de recubrimientos de TiN obtenidos mediante PVD sobre aceros de herramientas. Las capas obtenidas se caracterizan mediante microscopía electrónica de barrido, difracción de rayos X y XPS. Se analiza el comportamiento frente a la corrosión de las capas protectoras, así como la influencia del substrato en su comportamiento en soluciones de NaCl. Finalmente, se realizan ensayos de desgaste por deslizamiento en seco mediante la técnica de pin-on-disk, comprobándose la mayor resistencia de estas capas.

  10. Correlation and prediction of thermodynamic properties of nonelectrolytes at infinite dilution in water over very wide temperature and pressure ranges (2000 K and 10 GPa)

    Science.gov (United States)

    Plyasunov, Andrey V.

    2015-11-01

    Thermodynamic modeling of natural processes involving deep aqueous fluids requires the knowledge of the values of chemical potentials (the Gibbs energy) of aqueous species. An accurate prediction of thermodynamic properties at high T and P is a strong challenge. It is shown that geochemical models, including the well-known HKF-model, cannot be recommended for an indiscriminate use at supercritical temperatures to predict chemical potentials of nonelectrolytes at infinite dilution in water. Nevertheless, sufficiently accurate predictions of ϕ2∞ (the fugacity coefficients at infinite dilution in water) of aqueous nonelectrolytes up to 2000 K and water densities up to 1500 kg m-3, i.e. pressure up to 10-12 GPa, can be made relying on known theoretical relations valid at various parts of the phase diagram of water. In essence, the method, proposed in this work, consists in the interpolation of properties between two known limits: the first one, at low water densities, is defined by the values of the second virial coefficients for water-solute interactions, and the second, at high water densities - by predictions of the theory of a mixture of hard spheres. The interpolation at moderate temperatures (700-1300 K) and water densities (500-900 kg m-3) is simplified by sufficiently accurate predictions of properties using a semiempirical variant of a corresponding-states principle. Presented examples of the prediction of fugacity coefficients of "gases" at infinite dilution in water and of an aqueous solubility of corundum over very wide ranges of water densities/pressures demonstrate the potential and generality of the proposed methods of evaluating the thermodynamic properties of aqueous neutral compounds.

  11. Precise Dating and Geological Significance of the Caledonian Shangyou Pluton in South Jiangxi Province

    Institute of Scientific and Technical Information of China (English)

    MAO Jianren; ZENG Qingtao; LI Zilong; HU Qing; ZHAO Xilin; YE Haimin

    2008-01-01

    The zircon SHRIMP dating age for the Shangyou granites is 464+11 Ma. The geological feature of the pluton is consistent with the isotopic age, which shows that it is a product of Caledonian orogenesis. The Shangyou granites are regarded as peraluminous crust-derived granites to possess the typical geochemical characteristics of calc-alkaline rocks on the active continental margin with enriched Si, K, AI (A/CNK = 1.11 on average), HREE, Rb, U, Th and heavily depleted V, Cr, Co, Ni, as well as Ti-Y, Nb-Ta, Zr, St, P and Ba, to be commonly corundum normative (av C = 1.44). The Shangyou granites with higher 87Sr/86Sr ratios (0.707126-0.712186),εNd(t) values (-7.29 to-10.22) and (tDM) values (1.52-1.63 Ga), which are considered to result from partial melting of continental crust metamorphic sedimentary rocks with relatively low of crust maturation degree corresponding to the Middle Proterozoic, to have some possible contributions of mantle-derived components. The Shangyou granites are regarded as post-collision granites, which were formed in a transitional tectonic setting from compression to extension in the Middle Ordovician period after the Yangtze plate was subducted beneath the Cathaysian plate. The Ar-Ar total ages of K-feldspar and biotite are 292.1 Ma and 295.5 Ma respectively, which have recorded information of a late-stage thermal alteration event.

  12. Analysis on used bauxite based brick in torpedo ladle of Pangang,%攀钢铁水罐用后高铝残砖分析

    Institute of Scientific and Technical Information of China (English)

    韩兵强; 王长民; 杨强; 高钦; 李楠

    2011-01-01

    利用化学分析、X射线衍射仪、电子探针以及热力学等方法对攀钢铁水罐用后高铝残砖进行了分析.结果表明:残砖几乎没有挂渣层.舍钒钛渣由于表面张力小,黏度低,在高铝砖中的渗透很深;渣中的V2O5、TiO2、MnO、FeO等与高铝砖中组分反应生成的固溶体和化合物(如尖晶石、刚玉、钙长石等)中均发现固溶有V2O5;变质层的形成导致了致密化热震剥落;而较高的气孔率也是高铝砖损毁严重的另一重要原因.%Used bauxite based brick in torpedo ladle of Pangang Group Co., Ltd.was analyzed by means of ICPAES,XRD,EPMA,and thermodynamics.The results show that: (1)there is hardly any slag layer adhering on the used brick; (2)the vanadium and titanium containing slag penetrates into the bauxite based brick deeply because of low surface tension and viscosity;(3)V2O5 is found in the solid solution and compounds (such as spinel,corundum,and anorthite) formed by the reactions of V2O5,TiO2,MnO,and FeO in slag with the components of bauxite based brick; (4)the formation of deteriorated layer leads to the densification thermal shock spalling; (5)high porosity is another key reason for the serious damage of bauxite based brick.

  13. Two anionically derivatized scandium oxoselenates(IV): ScF[SeO3] and Sc2O2[SeO3

    Science.gov (United States)

    Greiner, Stefan; Chou, Sheng-Chun; Schleid, Thomas

    2017-02-01

    Scandium fluoride oxoselenate(IV) ScF[SeO3] and scandium oxide oxoselenate(IV) Sc2O2[SeO3] could be synthesized through solid-state reactions. ScF[SeO3] was obtained phase-pure, by reacting mixtures of Sc2O3, ScF3 and SeO2 (molar ratio: 1:1:3) together with CsBr as fluxing agent in corundum crucibles embedded into evacuated glassy silica ampoules after firing at 700 °C for seven days. Sc2O2[SeO3] first emerged as by-product during the attempts to synthesize ScCl[SeO3] following aforementioned synthesis route and could later be reproduced from appropriate Sc2O3/SeO3 mixtures. ScF[SeO3] crystallizes monoclinically in space group P21/m with a=406.43(2), b =661.09(4), c=632.35(4) pm, β=93.298(3)° and Z=2. Sc2O2[SeO3] also crystallizes in the monoclinic system, but in space group P21/n with a=786.02(6), b=527.98(4), c=1086.11(8) pm, β=108.672(3)° for Z=4. The crystal structures of both compounds are strongly influenced by the stereochemically active lone pairs of the ψ1-tetrahedral [SeO3]2- anions. They also show partial structures, where the derivatizing F- or O2- anions play an important role. For ScF[SeO3] chains of the composition 2+ ∞ 1[FSc2/2] form from connected [FSc2]5+ dumbbells, while [OSc3]7+ pyramids and [OSc4]10+ tetrahedra units are condensed to layers according to 2+ ∞ 2[O2Sc2 ] in Sc2O2[SeO3].

  14. Dusty tails of evaporating exoplanets. II. Physical modelling of the KIC 12557548b light curve

    Science.gov (United States)

    van Lieshout, R.; Min, M.; Dominik, C.; Brogi, M.; de Graaff, T.; Hekker, S.; Kama, M.; Keller, C. U.; Ridden-Harper, A.; van Werkhoven, T. I. M.

    2016-11-01

    Context. Evaporating rocky exoplanets, such as KIC 12557548b, eject large amounts of dust, which can trail the planet in a comet-like tail. When such objects occult their host star, the resulting transit signal contains information about the dust in the tail. Aims: We aim to use the detailed shape of the Kepler light curve of KIC 12557548b to constrain the size and composition of the dust grains that make up the tail, as well as the mass loss rate of the planet. Methods: Using a self-consistent numerical model of the dust dynamics and sublimation, we calculated the shape of the tail by following dust grains from their ejection from the planet to their destruction due to sublimation. From this dust cloud shape, we generated synthetic light curves (incorporating the effects of extinction and angle-dependent scattering), which were then compared with the phase-folded Kepler light curve. We explored the free-parameter space thoroughly using a Markov chain Monte Carlo method. Results: Our physics-based model is capable of reproducing the observed light curve in detail. Good fits are found for initial grain sizes between 0.2 and 5.6 μm and dust mass loss rates of 0.6 to 15.6 M⊕ Gyr-1 (2σ ranges). We find that only certain combinations of material parameters yield the correct tail length. These constraints are consistent with dust made of corundum (Al2O3), but do not agree with a range of carbonaceous, silicate, or iron compositions. Conclusions: Using a detailed, physically motivated model, it is possible to constrain the composition of the dust in the tails of evaporating rocky exoplanets. This provides a unique opportunity to probe to interior composition of the smallest known exoplanets.

  15. Presolar Grains and Their Isotopic Anomalies in Meteorites

    Institute of Scientific and Technical Information of China (English)

    林杨挺; 王世杰

    2001-01-01

    Study on presolar grains including diamond,silicon carbide,graphite,silicon nitrite(Si3N4),coundum and spinel isolated from meteorites is summarized in this paper.Except for nanometer-sized diamond,the other grains are micrometers to submicrometers in size.The presolar grains survived mainly in the fine-grained matrix of primitive chondrites and were isolated by chemical treatments.Diamond contains Xe isotopes(Xe-HL),typically produced in p-and r-processes,probably formed in supernovae.Mainstream silicon carbides are enriched in 29,30Si and 13C,but depleted in 15N.They also contain various s-process products,consistent with calculations of AGB stars.Other silicon carbides exhibit much larger isotopic anomalies and are classified as groups X,Y,Z and AB.Among them,group X of SiC is characterized by enrichment of 28Si and daughter isotopes of various short-lived nuclides,suggesting an origin from supernovae.Graphite can be divided into four density fractions with distince isotopic compositions.They may form in AGB stars,novae and supernovae,respctively,Si3N4 is similar to X-SiC in isotopic composition.Corundum is classified as four groups based on theid oxygen isotopic compositions.AGB and red giang stare are possible sources for the oxide.More comprehensive study of presolar grains,especially discovery of the other types of oxides and silicates,isotopic analyses of individual submicrometer-sized grains and distribution of presolar grains among various chemical groups and petropaphic types of chondrites will provide new information on nucleosynthesis,stellar evolution and formation of the solar nebula.

  16. The Petrology and Diagenetic History of the Phacoides Sandstone, Temblor Formation at the McKittrick Oil Field, California

    Science.gov (United States)

    Kaess, A. B.; Horton, R. A.

    2015-12-01

    The McKittrick oil field is located near the western edge of the San Joaquin Basin, California. The oil field is currently in production with 480 wells producing from the Tulare, San Joaquin, Reef Ridge, Monterey, Temblor, Tumey, and Kreyenhagen formations. Within the Temblor Formation production is mainly from the Miocene Carneros and the Phacoides sandstones. Eighty-two samples from the Phacoides sandstone (2403 - 3045 m below surface) were obtained from the California Well Sample Repository to characterize and understand the diagenetic history and its influence on its reservoir properties. Petrographic thin sections were analyzed by quantitative optical petrography, energy dispersive X-ray spectrometry, and imaging with back-scatter electron and cathodoluminescence. The Phacoides sandstone consists of fine to very coarse, poorly to well-sorted, arkosic arenites, and wackes with detrital framework grains including sub-angular quartz, K-feldspar (microcline and orthoclase), plagioclase, and lithic fragments. Ba-free, Ba-rich, and perthitic K-feldspars are present. Accessory minerals include glauconite, biotite, muscovite, magnetite, titanomagnetite, sphene, zircon, apatite, corundum, and rutile. Diagenetic alteration includes: (1) compaction, (2) mineral dissolution, (3) albitization of feldspars, alteration of biotite to pyrite and chlorite, replacement of framework grains by calcite, (4) alteration of volcanic rock fragments, (5) cementation by kaolinite, calcite and dolomite, and (6) precipitation of K-feldspar and quartz overgrowths. Early-formed fractures were healed by authigenic quartz, albite, and K-feldspars. Precipitation of carbonates and clays, rearranging of broken grains, and formation of pseudomatrix reduced primary porosity. Secondary porosity is common and formed initially by the dissolution of plagioclase (excluding albite) and volcanic fragments, and later by dissolution of calcite, dolomite, and detrital K-feldspars. Hydrocarbon emplacement was

  17. The stabilities of gibbsite, boehmite, aluminous goethites and aluminous hematites in bauxites, ferricretes and laterites as a function of water activity, temperature and particle size

    Science.gov (United States)

    Trolard, Fabienne; Tardy, Yves

    1987-04-01

    Stability relationships between Al-goethite, Al-hematite, boehmite and gibbsite are presented in terms of water activity [H 2O], temperature ( T), grain size and bulk-composition in the system Fe 2O 3-Al 2O 3-H 2O at a total pressure of 1 bar. Al-goethite and Al-hematite are treated as ideal solid solutions, the former of the end-members FeOOH (goethite) and AlOOH (diaspore) and the latter of the end-members Fe 2O 3 (hematite) and Al 2O 3 (corundum). Using log K sp provided by the literature for the various phases involved, the common associations observed in laterites, bauxites and ferricretes do not have stability fields over geologically reasonable intervals of [H 2O] and T. Consequently a new internally consistent set of log Ksp values is proposed and used, and allows such associations to have actual stability fields in the appropriate diagrams. The new log Ksp values used in the calculations are such that the solubilities of the end members are greater than those commonly listed. This is in agreement with natural observations which show that such minerals, are generally poorly crystallized and of very small size. The assumption of an ideal solid solution in aluminous goethite and aluminous hematite combined with the new log Ksp values leads to prediction of composition limits for these two minerals which agree well with observed values. The fact that an ideal solid solution must extend continuously from one end-member to the other is masked by the appearance of other stability fields ( e.g. gibbsite or boehmite) which cross and overlap a part of the solid solution stability fields of AlOOH-FeOOH and Fe 2O 3-Al 2O 3.

  18. Preparation of Mullite from Low-grade Kaolin%低品位高岭土制备莫来石的研究

    Institute of Scientific and Technical Information of China (English)

    周华梅; 乔秀臣; 于建国

    2011-01-01

    以苏州低品位高岭土为原料,分剐研究了直接煅烧和添加氢氧化铝煅烧制备3:2型莫来石.通过XRF、DTA、XRD,IR等测试手段,研究了样品分别经1 000~1 500℃煅烧1 h后的相转变过程.结果表明:高岭土直接煅烧在1 500℃可生成不舍方石英的3:2型莫来石产品.添加Al(OH)3可以降低3:2型莫来石的合成温度至1 300℃,但结晶度较低,提高煅烧温度虽然可提高结晶度,但刚玉相的出现降低了莫来石的氧化铝含量.%This research investigated the preparation of mullite with an Al2O3 ∶ SiO2 ratio of 3 ∶2 from Suzhou low-grade kaolin by direct calcination and the calcination with the addition of Al(OH)3.The phase transformations of samples calcined between 1 000 ℃ and 1 500 ℃ for an hour were investigated using XRF, DTA, XRD and IR measurements.The results showed that a 3∶ 2 type mullite without the presence of cristobalite was formed in kaolin calcined at 1 500 ℃.The formation temperature of mullite was lowered down to 1 300 ℃ after adding Al(OH)3, however, the crystalline degree of mullite formed was lower.Although the increase in calcination temperature can increase the crystalline degree of mullite, the alumina content of mullite decreased due to the formation of corundum.

  19. Oxygen Isotopes in Meteorites

    Science.gov (United States)

    Clayton, R. N.

    2003-12-01

    samples of oxygen-rich mineral grains that have formed in stellar atmospheres and have recorded the nucleosynthetic processes in individual stars. Similar samples are already available for carbon-rich grains, in the form of SiC and graphite, primarily from asymptotic giant branch (AGB) stars and supernovae (Anders and Zinner, 1993). These presolar grains have provided a wealth of detailed information concerning nucleosynthesis of carbon, nitrogen, silicon, calcium, titanium, and heavier elements (see Chapter 1.02). It is thought that such carbon-rich minerals should form only in environments with C/O>1, as in the late stages of AGB evolution, or in carbon-rich layers of supernovae. By analogy, one would expect to form oxide and silicate minerals in environments with C/O<1, as is common for most stars. Indeed there is evidence in infrared spectra for the formation of Al2O3 (corundum) and silicates, such as olivine (Speck et al., 2000) around evolved oxygen-rich stars. However, searches for such grains in meteorites have yielded only a very small population of corundum grains, a few grains of spinel and hibonite, and no silicates ( Nittler et al., 1997). The observed oxygen isotopic compositions of presolar corundum grains show clear evidence of nuclear processes in red-giant stars, and have had significant impact on the theory of these stars ( Boothroyd and Sackmann, 1999).There are several possible reasons for the failure to recognize and analyze large populations of oxygen-rich presolar grains:(i) they may not exist: oxygen ejected in supernova explosions may not condense into mineral grains on the short timescale available;(ii) they may be smaller in size than can be detected by applicable techniques (˜0.1 μm); and(iii) they may be destroyed in the laboratory procedures used to isolate other types of presolar grains.

  20. Application of Scanning-Imaging X-Ray Microscopy to Fluid Inclusion Candidates in Carbonates of Carbonaceous Chondrites

    Science.gov (United States)

    Tsuchiyama, Akira; Nakano, Tsukasa; Miyake, Akira; Akihisa, Takeuchi; Uesugi, Kentaro; Suzuki, Yoshio; Kitayama, Akira; Matsuno, Junya; Zolensky, Michael E.

    2016-01-01

    In order to search for such fluid inclusions in carbonaceous chondrites, a nondestructive technique using x-ray micro-absorption tomography combined with FIB sampling was developed and applied to a carbonaceous chondrite. They found fluid inclusion candidates in calcite grains, which were formed by aqueous alteration. However, they could not determine whether they are really aqueous fluids or merely voids. Phase and absorption contrast images can be simultaneously obtained in 3D by using scanning-imaging x-ray microscopy (SIXM). In refractive index, n=1-sigma+i(beta), in the real part, 1-sigma is the refractive index with decrement, sigma, which is nearly proportional to the density, and the imaginary part, beta, is the extinction coefficient, which is related to the liner attenuation coefficient, mu. Many phases, including water and organic materials as well as minerals, can be identified by SIXM, and this technique has potential availability for Hayabusa-2 sample analysis too. In this study, we examined quantitative performance of d and m values and the spatial resolution in SIXM by using standard materials, and applied this technique to carbonaceous chondrite samples. We used POM ([CH2O]n), silicon, quartz, forsterite, corundum, magnetite and nickel as standard materials for examining the sigma and mu values. A fluid inclusion in terrestrial quartz and bi-valve shell (Atrina vexillum), which are composed of calcite and organic layers with different thickness, were also used for examining the spatial resolution. The Ivuna (CI) and Sutter's Mill (CM) meteorites were used as carbonaceous chondrite samples. Rod- or cube-shaped samples 20-30 micron in size were extracted by using FIB from cross-sectional surfaces of the standard materials or polished thin sections of the chondrites, which was previously observed with SEM. Then, the sample was attached to a thin W-needle and imaged by SIXM system at beamline BL47XU, SPring-8, Japan. The slice thickness was 109.3 nm

  1. Characterization of feed coal and coal combustion products from power plants in Indiana and Kentucky

    Energy Technology Data Exchange (ETDEWEB)

    Brownfield, M.E.; Affolter, R.H.; Cathcart, J.D.; O' Connor, J.T.; Brownfield, I.K.

    1999-07-01

    The US Geological Survey, Kentucky Geological Survey, and the University of Kentucky Center for Applied Energy Research are collaborating with Indiana and Kentucky utilities to determine the physical and chemical properties of feed coal and coal combustion products (CCP) from three coal-fired power plants. These three plants are designated as Units K1, K2, and I1 and burn high-, moderate-, and low-sulfur coals, respectively. Over 200 samples of feed coal and CCP were analyzed by various chemical and mineralogical methods to determine mode of occurrence and distribution of trace elements in the CCP. Generally, feed coals from all 3 Units contain mostly well-crystallized kaolinite and quartz. Comparatively, Unit K1 feed coals have higher amounts of carbonates, pyrite and sphalerite. Unit K2 feed coals contain higher kaolinite and illite/muscovite when compared to Unit K1 coals. Unit I1 feed coals contain beta-form quartz and alumino-phosphates with minor amounts of calcite, micas, anatase, and zircon when compared to K1 and K2 feed coals. Mineralogy of feed coals indicate that the coal sources for Units K1 and K2 are highly variable, with Unit K1 displaying the greatest mineralogic variability; Unit I1 feed coal however, displayed little mineralogic variation supporting a single source. Similarly, element contents of Units K1 and K2 feed coals show more variability than those of Unit I1. Fly ash samples from Units K1 and K2 consist mostly of glass, mullite, quartz, and spines group minerals. Minor amounts of illite/muscovite, sulfates, hematite, and corundum are also present. Spinel group minerals identified include magnetite, franklinite, magnesioferrite, trevorite, jacobisite, and zincochromite. Scanning Electron Microscope analysis reveals that most of the spinel minerals are dendritic intergrowths within aluminum silicate glass. Unit I1 fly ash samples contain glass, quartz, perovskite, lime, gehlenite, and apatite with minor amounts of periclase, anhydrite

  2. Photo-catalytic hydrogen production over Fe{sub 2}O{sub 3} based catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Boudjemaa, A. [Technical and Scientific Research Centre of Physico-chemistry Analysis (CRAPC), BP 248, RP 16004, Algiers (Algeria); Laboratory of Chemistry of Natural Gas, Faculty of Chemistry (USTHB) BP 32, 16111 Algiers (Algeria); Trari, M. [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB) BP 32, 16111 Algiers (Algeria)

    2010-08-15

    The hydrogen photo-evolution was successfully achieved in aqueous (Fe{sub 1-x}Cr{sub x}){sub 2}O{sub 3} suspensions (0 {<=} x {<=} 1). The solid solution has been prepared by incipient wetness impregnation and characterized by X-ray diffraction, BET, transport properties and photo-electrochemistry. The oxides crystallize in the corundum structure, they exhibit n-type conductivity with activation energy of {proportional_to}0.1 eV and the conduction occurs via adiabatic polaron hops. The characterization of the band edges has been studied by the Mott Schottky plots. The onset potential of the photo-current is {proportional_to}0.2 V cathodic with respect to the flat band potential, implying a small existence of surface states within the gap region. The absorption of visible light promotes electrons into (Fe{sub 1-x}Cr{sub x}){sub 2}O{sub 3}-CB with a potential ({proportional_to}-0.5 V{sub SCE}) sufficient to reduce water into hydrogen. As expected, the quantum yield increases with decreasing the electro affinity through the substitution of iron by the more electropositive chromium which increases the band bending at the interface and favours the charge separation. The generated photo-voltage was sufficient to promote simultaneously H{sub 2}O reduction and SO{sub 3}{sup 2-} oxidation in the energetically downhill reaction (H{sub 2}O + SO{sub 3}{sup 2-} {yields} H{sub 2} + SO{sub 4}{sup 2-}, {delta}G = -17.68 kJ mol{sup -1}). The best activity occurs over Fe{sub 1.2}Cr{sub 0.8}O{sub 3} in SO{sub 3}{sup 2-} (0.1 M) solution with H{sub 2} liberation rate of 21.7 {mu}mol g{sup -1} min{sup -1} and a quantum yield 0.06% under polychromatic light. Over time, a pronounced deceleration occurs, due to the competitive reduction of the end product S{sub 2}O{sub 6}{sup 2-}. (author)

  3. Geochemical constraints on the presence of clay minerals in the Burns formation, Meridiani Planum, Mars

    Science.gov (United States)

    Cino, C. D.; Dehouck, E.; McLennan, S. M.

    2017-01-01

    Burns formation sandstones, deposited by aeolian processes and preserved at Meridiani Planum, Mars, contain abundant sulfate minerals. These sedimentary rocks are thought to be representative of a sulfate-rich geological epoch during late Noachian - early Hesperian time that followed an earlier clay-rich epoch. Twenty Burns formation targets, abraded by the Rock Abrasion Tool (RAT) and for which alpha-particle X-ray spectrometry (APXS) and Mössbauer spectroscopy data are available, were selected for geochemical modeling. A linear unmixing modeling approach was employed. Mineralogical constituents quantitatively constrained by Mössbauer and Mini-TES spectroscopy and interpreted to be chemically precipitated from aqueous fluids during deposition and/or early diagenesis were subtracted from the bulk chemistry. Resulting residual chemical compositions, interpreted to be dominated by detrital siliciclastic components and representing ∼21-35% of the rocks, were then geochemically evaluated to constrain the potential for the presence of clay minerals or their poorly-crystalline or non-crystalline precursors/chemical equivalents. Calculations incorporated a robust estimate of the uncertainties in mineral abundances. On Al2O3 - (CaO+Na2O) - K2O (A-CN-K) and Al2O3 - (CaO+Na2O+K2O) - (FeOtotal+MgO) (A-CNK-FM) molar ternary diagrams, removal of chemical constituents resulted in a shift from igneous-like compositions to compositions consistent with secondary mineral assemblages containing significant aluminous clay mineral components. All of the residual compositions are corundum-normative, further supportive of the presence of highly aluminous phases. On the A-CNK-FM diagram, clay minerals plotting closest to the residual field are natural montmorillonites but could also represent mixtures of various Mg/Fe-rich phyllosilicates, such as nontronite or saponite, and other more Al-rich minerals such as Al-montmorillonite, kaolinite or illite. Depending on the age of clay

  4. Novel highly ordered core–shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Dey, Sonal; Hossain, Mohammad D.; Mayanovic, Robert A.; Wirth, Richard; Gordon, Robert A.

    2016-10-26

    Core–shell nanoparticles have potential for a wide range of applications due to the tunability of their magnetic, catalytic, electronic, optical, and other physicochemical properties. A frequent drawback in the design of core–shell nanoparticles and nanocrystals is the lack of control over an extensive, disordered, and compositionally distinct interface that occurs due to the dissimilarity of structural and compositional phases of the core and shell. In this work, we demonstrate a new hydrothermal nanophase epitaxy (HNE) technique to synthesize highly structurally ordered α-Cr2O3@α-Co0.38Cr1.62O2.92 inverted core–shell nanoparticles (CSNs) with evidence for the nanoscale growth of corundum structure beginning from the core and extending completely into the shell of the CSNs with minimal defects at the interface. The high-resolution TEM results show a sharp interface exhibiting epitaxial atomic registry of shell atoms over highly ordered core atoms. The XPS and Co K-edge XANES analyses indicate the +2 oxidation state of cobalt is incorporated in the shell of the CSNs. Our XPS and EXAFS results are consistent with oxygen vacancy formation in order to maintain charge neutrality upon substitution of the Co2+ ion for the Cr3+ ion in the α-Co0.38Cr1.62O2.92 shell. Furthermore, the CSNs exhibit the magnetic exchange bias effect, which is attributed to the exchange anisotropy at the interface made possible by the nanophase epitaxial growth of the α-Co0.38Cr1.62O2.92 shell on the α-Cr2O3 core of the nanoparticles. The combination of a well-structured, sharp interface and novel nanophase characteristics is highly desirable for nanostructures having enhanced magnetic properties.

  5. Development of waste-based ceramic pigments

    Directory of Open Access Journals (Sweden)

    Costa, G.

    2007-02-01

    Full Text Available We report the preparation of ceramic pigments using industrial wastes as primary sources. In this context, the use of Al-rich sludge generated in the wastewater treatment unit of an anodising or surface coating industrial plant, and a galvanizing sludge from the Cr/Ni plating process, will be detailed. The ceramic pigments reported here were prepared using typical solid state reactions involving the metal rich sludge. The main focus will be on the synthesis of chrome-tin orchid cassiterite (Sn,CrO2, chrome-tin red malayaite Ca(Cr,SnSiO5, victoria green garnet Ca3Cr2Si3O12, and chrome alumina pink/green corundum (Cr,Al2O3 pigments. The pigments were fully characterised and then were tested in a standard ceramic glaze after. Typical working conditions and colour development will be reported.

    Se presenta la preparación de pigmentos cerámicos empleando residuos industriales como fuente de materias primas. Se detallan el uso de barros ricos en aluminio obtenidos en los tratamientos de depuración de aguas de plantas industriales de anodizado y barros de galvanizados de chapados de Cr/Ni. Los pigmentos cerámicos se prepararon empleando reacción en estados sólido a partir del barro rico en metal. Los principales pigmentos estudiados son orquídea casiterita de cromo-estaño (Sn,CrO2, malayita rojo de cromo-estaño Ca(Sn,CrSiO3, granate verde victoria Ca3Cr2Si3O12, y corindón rosa/verde de cromo alúmina (Cr,Al2O3. Los pigmentos fueron caracterizados y ensayados después de ser vidriados en cerámicas estándares. Se presentan las condiciones de trabajo y el desarrollo de color.

  6. Preparation and Characterization of Zeolite Membrane for Bioethanol Purification

    Directory of Open Access Journals (Sweden)

    Aprilina Purbasari

    2013-06-01

    Full Text Available The use of bioethanol as an alternative fuel with a purity of more than 99.5% wt has prompted research on bioethanol purification. One of the promising methods used for bioethanol purification is pervaporation membrane. This research is aimed to prepare and characterize zeolite membranes for pervaporation membrane. The membrane preparation consisted of two stages, namely support preparation and zeolite deposition on the support. In support preparation, α- alumina and kaolin with specific composition (50:30; 40:40; 50:30 was mixed with additives and water. After pugging and aging process, the mixture became paste and extruded into tubular shape. The tube was then calcined at temperature of 1250 °C for 3 hours. After that, zeolite 4A was deposited on the tubes using clear solution made of 10 %wt zeolite and 90 %wt water and heated at temperature of 80 °C for 3 hours. Furthermore, the resulting zeolite membranes was washed with deionized water for 5 minutes and dried in oven at temperature of 100 °C for 24 hours. Characterization of zeolite membranes included mechanical strength test, XRD, and SEM. In the mechanical strength test, the membrane sample with α- alumina:kaolin = 50:30 (membrane A has the highest mechanical strength of 46.65 N/mm2. Result of XRD analysis for the membrane A indicated that mullite and corundum phases were formed, which mullite phase was more dominant. Meanwhile the result of SEM analysis shows that zeolite crystals have been formed and covered the pores support, but the deposition of zeolite has not been optimal yet. The performance examination for bioethanol purification showed that the membrane could increase the purity of bioethanol from 95% to 98.5% wt. © 2013 BCREC UNDIP. All rights reservedReceived: 23rd October 2012; Revised: 15th February 2013; Accepted: 16th February 2013[How to Cite: Purbasari, A., Istirokhatun, T., Devi, A.M., Mahsunnah, L. , Susanto, H. (2013. Preparation and Characterization of Zeolite

  7. An integrated geochemical, geophysical and mineralogical study of river sediments in alpine area and soil samples near steel plant, in Austria

    Science.gov (United States)

    Irfan, M. I.; Meisel, T.

    2012-04-01

    , ankerite, corundum (anthropogenic), garnet, chlorite, titanium oxide minerals (ilmenite, rutile, titanite) and amphibole etc. The observed significant increase in heavy metal content from the source region of the Vordernberger Bach at 1500 m above sea level to the confluence of the Vordernberger Bach with the Mur River at 540 m AMSL can be attributed to anthropogenic influence. As expected, the anthropogenic input is more pronounced in the vicinity of historic and current iron and steel production.

  8. The sub-arcsecond dusty environment of Eta Carinae

    Science.gov (United States)

    Chesneau, O.; Min, M.; Herbst, T.; Waters, L. B. F. M.; Leinert, Ch.; Hillier, D. J.

    2005-09-01

    The core of the nebula surrounding Eta Carinae was observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to spatially and spectrally isolate the warm dusty environment and the central object. Narrow-band images at 3.74 μm and 4.05 μm reveal a butterfly shaped dusty environment close to the central star with unprecedented spatial resolution. Fringes have been obtained in the Mid-IR and a correlated flux of about 100 Jy situated 0.3 arcsec south-east from the photocenter of the nebula at 8.7 μm is detected. This flux is partly attributed to the central object and provides an upper limit for the SED of the central source from 3.8 μm to 13.5 μm. We have been able to spectrally disperse the signal from the nebula itself at PA=318 degree, i.e. in the direction of the bipolar nebula (˜310°) within the MIDI field of view of 3 arcsec. A large amount of corundum (Al2O3) is discovered, peaking at 0.6-1.2 arcsec south-east from the star, whereas the dust content of the Weigelt blobs, in the equatorial plane, is dominated by silicates. We propose a geometry for the Butterfly nebulae assuming a similar axis for the large and little Homunculus. We suggest that the Butterfly nebulae is a consequence of the 1890 outburst and is embedded in the Little Homonculus its geometry is, mostly shaped by the local dust formation conditions which are directly affected by the latitudinal dependance of the ejection and the present wind. The dust is mostly formed in the bright rims of the Butterfly nebula. The dust condenses closer to the poles of the star owing to the larger mass-loss rate and the relative velocity between the stellar wind and the ejecta at these latitudes. In this geometry, the bright southern clump directly sees the southern pole of the central object. At intermediate latitudes, the mass-loss rate and the relative velocity of the wind are decreased and dust forms further out. We suggest that the survival and the large mass of the

  9. Radiation-Induced Topological Disorder in Irradiated Network Structures

    Energy Technology Data Exchange (ETDEWEB)

    Hobbs, Linn W.

    2002-12-21

    This report summarizes results of a research program investigating the fundamental principles underlying the phenomenon of topological disordering in a radiation environment. This phenomenon is known popularly as amorphization, but is more formally described as a process of radiation-induced structural arrangement that leads in crystals to loss of long-range translational and orientational correlations and in glasses to analogous alteration of connectivity topologies. The program focus has been on a set compound ceramic solids with directed bonding exhibiting structures that can be described as networks. Such solids include SiO2, Si3N4, SiC, which are of interest to applications in fusion energy production, nuclear waste storage, and device manufacture involving ion implantation or use in radiation fields. The principal investigative tools comprise a combination of experimental diffraction-based techniques, topological modeling, and molecular-dynamics simulations that have proven a rich source of information in the preceding support period. The results from the present support period fall into three task areas. The first comprises enumeration of the rigidity constraints applying to (1) more complex ceramic structures (such as rutile, corundum, spinel and olivine structures) that exhibit multiply polytopic coordination units or multiple modes of connecting such units, (2) elemental solids (such as graphite, silicon and diamond) for which a correct choice of polytope is necessary to achieve correct representation of the constraints, and (3) compounds (such as spinel and silicon carbide) that exhibit chemical disorder on one or several sublattices. With correct identification of the topological constraints, a unique correlation is shown to exist between constraint and amorphizability which demonstrates that amorphization occurs at a critical constraint loss. The second task involves the application of molecular dynamics (MD) methods to topologically-generated models

  10. Geology, Petrology and O and H isotope geochemistry of remarkably 18O depleted Paleoproterozoic rocks of the Belomorian Belt, Karelia, Russia, attributed to global glaciation 2.4 Ga

    Science.gov (United States)

    Bindeman, I. N.; Serebryakov, N. S.

    2011-06-01

    This paper deals with strongly 18O-depleted (down to - 27.3‰ VSMOW) 1.9Ga Paleoproterozoic mid-grade metamorphic rocks found in the Belomorian Belt of Karelia (E. Baltic Shield). The protolith of these rocks is attributed to have been altered by glacial meltwaters during the world's first 2.4-2.3 Ga Paleoproterozoic "Slushball" glaciation, when Karelia was located near equatorial latitudes. We describe in detail three and report seven new localities with unusually depleted 18O signatures that now span 220 km across the Belomorian Belt. Hydrogen isotope ratios measured in amphibole, biotite and staurolite also display remarkably low values of - 212 to - 235‰. Isotope mapping in the three best exposed localities has allowed us to identify the world's most 18O depleted rock, located at Khitostrov with a δ 18O value - 27‰. In Khitostrov samples, zircons have normal δ 18O detrital cores and low-δ 18O metamorphic rims. Mapping demonstrates that zones of δ 18O depletion occur in a concentric pattern 100-400 m in dimension, and each locality displays significant δ 18O and δD heterogeneity on a meter to centimeter scale, characteristic of meteoric-hydrothermal systems worldwide. The zone of maximum δ 18O depletions usually has the highest concentration of metamorphic corundum, rutile, and zircon and also display doubled concentrations of insoluble trace elements (Zr, Ti, Cr, HREE). These results are explained by elemental enrichment upon mass loss during hydrothermal dissolution in pH-neutral meteoric fluid. Remarkably low-δ 18O and δD values suggest that alteration could have only happened by glacial meltwaters in a subglacial rift zone. Many localities with δ 18O depletions occur inside metamorphozed 2.4 Ga gabbro-noritic intrusions, or near their contact with Belomorian gneisses, implying that the intrusions were driving meteoric hydrothermal systems during the known 2.4 Ga episode of Belomorian rifting. Given that the isotopically-depleted localities now

  11. Automotive crankshaft" axis linkage cut point tracking" servo grinding and its key technology%汽车曲轴的"三轴联动切点跟踪"随动磨床及其关键技术研究

    Institute of Scientific and Technical Information of China (English)

    黄兴红; 潘旭华; 吴兴; 黄文广

    2011-01-01

    在分析两轴联动切点跟踪曲轴随动磨削方法的技术缺陷基础上,系统地介绍了"三轴联动切点跟踪"磨削原理,给出了"三轴联动切点跟踪"曲轴随动磨削运动模型,概括了该原理在曲轴连杆颈和主轴颈磨削中的技术优势.并且通过高精度液体静压导轨、高刚性直线驱动技术和在线测量与误差补偿等关键技术的综合运用,成功地解决了超精密磨削加工中各运动部件动态性能及其对加工精度的影响,攻克了用普通刚玉砂轮高效率、高精度磨削曲轴主轴颈和连杆颈的技术难题.%Based on the analysis of two-axis servo cut point trackina crankshaft grinding method on the basis of technical defects, systematic introduction to the "axis linkage cut point tracking" grinding principle,gives the "cut point tracking axis linkage" with the crankshaft activity grinding motion model, summarizes the principles of the neck and the connecting rod in the crankshaft main journal grinding technology advantage. And by high-precision hydrostatic guideway, high rigidity straight line drive technology and online measurement and error compensation of the integrated use of key technologies, successfully resolves the ultra-precision grinding dynamic performance of the various moving parts and its impact on the machining accuracy, to capture a corundum wheel with ordinary high-effieiency, high precision grinding of the crankshaft main journal and connecting rod neck of technical problems.

  12. First solar system solids to proto-planets: A Rapid growth in a few million years

    Science.gov (United States)

    Goswami, Jitendranath

    2016-07-01

    First solar system solids to proto-planets: A Rapid growth in a few million years J. N. Goswami Physical Research Laboratory Ahmedabad-380009, India Collapse of a dense molecular cloud led to the formation of the proto-Sun surrounded by a high temperature gaseous nebula. The nebula settled down to the mid-plane and formation of the first solar system solids, refractory oxides and silicates, such as Corundum, Perovskite, Melilite took place, that was followed by formation of more common silicate minerals. Laboratory studies of primitive meteorites support this scenario and also provide evidence for correlated presence of several now-extinct short-lived nuclides (e.g. 41Ca, 26Al, 60Fe) at the time of formation of the first solar system solids. Presence of 60Fe in early solar system solids suggests injection of freshly synthesized nuclides from a stellar source (a supernova) into the proto-solar cloud that also triggered its collapse and led to formation of our solar system. Presence of 41Ca (half-life: 0.1Ma) in early solar system solids suggest a time scale of less than a million years for the collapse of the proto-solar cloud and formation of proto-Sun and the first solar system solids. The gradual evolution of larger solar system objects, up to planetesimals (represented by the asteroids), took place at a rapid pace within a time scale of a few million years. Some of the asteroids retain their pristine nature (e.g. parent bodies of carbonaceous chondrite), while others, underwent melting and differentiation due to internal heating. Harold Urey proposed radioactive 26Al as a possible heat source that was confirmed by experiment only in 1999. Irons and stony iron meteorites are fragments from core regions of differentiated asteroids. Extensive computer simulation studies suggest that an explosive stellar event (e.g. supernova) can indeed trigger the collapse of the proto-solar cloud and also inject freshly synthesized short-lived nuclides into it within a relatively

  13. Rubi e safiras de Minas Gerais, Brasil

    Directory of Open Access Journals (Sweden)

    Antonio Liccardo

    2005-09-01

    gems. Inclusions of an Al2SiO5 polimorph and field evidences suggest that the origin of corundum might be due to regional metamorphic processes, thus expanding the possibilities for the discovery of new occurrences of ruby and sapphires in the high grade metamorphic terrain in eastern Minas Gerais.

  14. Chemical thermodynamic data. 1. The concept of links to the chemical elements and the historical development of key thermodynamic data

    Science.gov (United States)

    Wolery, Thomas J.; Jové Colón, Carlos F.

    2017-09-01

    links to the same elemental reference form in a thermodynamic database will result in an inconsistency in the database. Thus, in constructing a database, it is important to establish a set of reliable links (generally resulting in a set of primary reference data) and then correct all data adopted subsequently for consistency with that set. Recommended values of key data have not been constant through history. We review some of this history through the lens of major compilations and other influential reports, and note a number of problem areas. Finally, we illustrate the concepts developed in this paper by applying them to some key species of geochemical interest, including liquid water; quartz and aqueous silica; and gibbsite, corundum, and the aqueous aluminum ion.

  15. Records of near-isothermal decompression and clockwise P-T history from the Paleoproterozoic Mahakoshal Belt, Central Indian Tectonic Zone: Constraints from pseudosection modelling and monazite geochronology

    Science.gov (United States)

    Deshmukh, Tanzil; Naraga, Prabhakar; Bhattacharya, Abhijit; Kaliappan, Madhavan

    2017-04-01

    The Mahakoshal Belt (MB) is regarded as the oldest subunit along the northern collar of the Central Indian Tectonic Zone (CITZ) arguably representing the zone of accretion between the North India Block and the South India Block. The following study focuses on deciphering the structural and metamorphic P-T-t history of the schists/phyllites from the eastern part of the belt, and provides insights into the Paleoproterozoic tectonic development in the CITZ. The schists comprise phengite, quartz, andalusite, biotite, muscovite and margarite, and are associated with veins of rare andalusite + corundum + quartz assemblage. The field relations combined with deformation microtextures in the MB schists suggests three episodes of metamorphism, M1, M2 and M3, corresponding with D1, D2 and D3 deformation events respectively. Inclusion trails (S1) of phengite + biotite + quartz ± chlorite in syn/post-S2 andalusite porphyroblasts constrain the M1 metamorphic event in pelitic schists. The application of pseudosection modelling estimated peak metamorphic conditions at ˜8 kbar and 520 ˚ C. Near isothermal decompression (populations at 1.8-1.9 Ga, and rim populations at 1.7-1.8 Ga and 1.5-1.6 Ga. Thus, the peak metamorphism in MB schists was Paleoproterozoic in age, 1.8-1.9 Ga, and the clockwise P-T path was recorded at 1.7-1.8 Ga, which overlaps with the emplacement of blastoporphyritic granitoids along southern margin of the MB. The results obtained in this study combined with the existing structural-metamorphic-chronological information demonstrate the CITZ to be a composite of desperately-evolved crustal domains. With some major omissions, the tectono-thermal events identified in the CITZ partly overlap with those observed in the Capricorn Orogen (Western Australia) and the Trans North China Orogen. Therefore, these global correlations possibly corroborate new configurations on the assembly and fragmentation of Columbia Supercontinent, but await further studies and robust age

  16. Optimization of the Arc Spraying Process Parameters of the Fe–Base Mn-Si-Cr-Mo-Ni Coatings for the Best Wear Performance

    Directory of Open Access Journals (Sweden)

    Justinas GARGASAS

    2016-05-01

    Full Text Available In this paper, the use of Fe–base Mn-Si-Cr-Mo-Ni and Fe–base Mn-Si-Cr wires for thermal arc spraying is presented. For this purpose the mechanical and physical properties of coatings were evaluated. The quality of the coating’s was dependent on the selected equipment, spray materials, technological parameters of the spray and spray technology. The aim was to qualify and optimize the parameters for spray coating to get the best coatings properties with good tribological properties. All coatings were deposited on mild steel S235JR substrates. Two experimental cored wires of unique chemical composition – STEIN-MESYFIL 932 V and STEIN-MESYFIL 954 V – were used for thermal arc spraying. The wires of 1.6 mm diameter were used for the surfacing material. Hardness, porosity and oxide measurements were used to verify the spray parameters and analyze the coatings. Rubber wheel test, which is based on the standard ASTM G65, was used. Dry-sand, rubber-wheel procedure according ASTM G65 was used to investigate low stress abrasion, whereas for high stress abrasion investigations a rubber wheel was used. This experiment was carried out by changing the speed of disc friction, travel distance and measuring the mass loss of surface friction. Miller Test according to ASTM G75-95 Standard was carried out in experiment with friction. The samples were immersed in water with corundum and polished with 22 N load, for 8 hours. Furthermore a correlation was performed between the spraying current and voltage parameter. The coatings’ cross sections were examined using scanning electron microscope (SEM and optical microscopy. The influence of the composite components of the coatings’ microstructure, such as porosity, microhardness, oxide inclusions, on the tribological properties of thermal sprayed coatings is discussed in this paper. DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7339

  17. Recycling of used Al2O3-SiC-C bricks%用后Al2O3-SiC-C砖的回收再利用

    Institute of Scientific and Technical Information of China (English)

    王落霞; 沈明科; 高斌

    2011-01-01

    对铁水包和混铁车用后的Al2O3-SiC-C(简称ASC)砖进行再生处理,然后以高铝矾土熟料、电熔刚玉、叶蜡石、SiC粉和鳞片石墨为原料,分别掺加质量分数为10%、20%、30%的Al2O3-SiC-C再生料制备了铁水包用和混铁车用再生Al2O3-SiC-C砖.与原砖相比,再生砖的体积密度和常温耐压强度较高,显气孔率较低,而高温抗折强度、抗氧化性、抗渣性与原砖的差距不大.过多添加ASC再生料对再生Al2O3-SiC-C砖的高温抗折强度和抗渣侵蚀性能不利,以统料形式添加时,混铁车用Al2O3-SiC-C衬砖中ASC再生料的添加量(w)不宜超过30%.%Recycled AI2O3-SiC-C bricks for iron ladle and torpedo ladle were prepared using high alumina bauxite clinker,fused corundum,pyrauxite,SiC powder and flake graphite as starting materials,adding 10%,20% and 30% (mass percent) of recycled materials made from used AI2O3-SiC-C bricks,respectively. Compared with the original bricks,the recycled bricks have high bulk density and cold crushing strength,low apparent porosity,but similar hot modulus of rupture,oxidation resistance and slag corrosion resistance. The excessive recycled AI2O3-SiC-C material is harmful to hot modulus of rupture and slag corrosion resistance of the recycled bricks,and its proper addition in working lining bricks of torpedo ladle should not exceed 30%.

  18. Interaction of rat alveolar macrophages with dental composite dust.

    Science.gov (United States)

    Van Landuyt, K L; Cokic, S M; Asbach, C; Hoet, P; Godderis, L; Reichl, F X; Van Meerbeek, B; Vennemann, A; Wiemann, M

    2016-11-26

    Dental composites have become the standard filling material to restore teeth, but during the placement of these restorations, high amounts of respirable composite dust (composite particles for their cytotoxic effect using an alveolar macrophage model system. ​METHODS: Composite dust was generated following a clinical protocol, and the dust particles were collected under sterile circumstances. Dust was dispersed in fluid, and 5-μm-filtered to enrich the respirable fractions. Quartz DQ12 and corundum were used as positive and negative control, respectively. Four concentrations (22.5 μg/ml, 45 μg/ml, 90 μg/ml and 180 μg/ml) were applied to NR8383 alveolar macrophages. Light and electron microscopy were used for subcellular localization of particles. Culture supernatants were tested for release of lactate dehydrogenase, glucuronidase, TNF-α, and H2O2. Characterization of the suspended particles revealed numerous nano-sized particles but also many high volume particles, most of which could be removed by filtering. Even at the highest concentration (180 μg/ml), cells completely cleared settled particles from the bottom of the culture vessel. Accordingly, a mixture of nano- and micron-scaled particles was observed inside cells where they were confined to phagolysosomes. The filtered particle fractions elicited largely uniform dose-dependent responses, which were elevated compared to the control only at the highest concentration, which equaled a mean cellular dose of 120 pg/cell. A low inflammatory potential was identified due to dose-dependent release of H2O2 and TNF-α. However, compared to the positive control, the released levels of H2O2 and TNF-α were still moderate, but their release profiles depended on the type of composite. Alveolar macrophages are able to phagocytize respirable composite dust particle inclusive nanoparticles. Since NR8383 cells tolerate a comparatively high cell burden (60 pg/cell) of each of the five materials with minimal signs

  19. Preparation and its properties of cordierite-mullite refractory material used in microwave metallurgy%微波冶金用堇青石莫来石耐火材料制备及性能

    Institute of Scientific and Technical Information of China (English)

    孟彬; 彭金辉; 刘永鹤; 郭胜惠

    2011-01-01

    To develop a kind of refractory material suitable for microwave metallurgy,cordierite-mullite refractory materials with different mixture ratios were synthesized by sintering at normal atmosphere and different temperatures.The effects of sintering temperature and mixture ratio on phase composition,bending strength,thermal shock resistance and dielectric properties were analyzed.The results show that the content of remnant corundum phase after sintering decreases with the increase of temperature from 1400 ℃ to 1450 ℃,the volumetric density,the bending strength and the relative dielectric constants increase,the water-absorbing capacity,the apparatus porosity and the dielectric dissipation decreases.The loss of bending strength after 4 times and 8 times of thermal shocks from 1100 ℃ to room temperature in flowing water is 30% and 50%,respectively.Considering the integrated requirements of bending strength,dielectric property and thermal shock resistance,the optimal sintering temperature of this refractory material is 1450 ℃ and the optimal ratio of cordierite and mullite is 1∶ 1.%为探索适合于微波冶金高温反应过程使用的耐高温、抗热震、低微波吸收率耐火材料,采用常压烧结法在不同温度合成了不同配比的堇青石-莫来石质耐火材料.采用XRD分析、三点弯曲法及Angilent阻抗分析等测试了烧结温度及配比对耐火材料物相组成、抗弯强度、抗热震性能及介电性能的影响规律.结果表明,随烧结温度由1400℃提高至1450℃,烧结样品中残留的刚玉相明显减少,耐火材料的体积密度、抗弯强度显著增大,吸水率和显气孔率数值则显著降低;1100℃保温后急速水冷4次和8次热震循环后,耐火材料的抗弯强度损失率分别为30

  20. Study on the Properties of Microwave Thermal Effect Ceramics%微波热效应陶瓷材料性能研究

    Institute of Scientific and Technical Information of China (English)

    王彬彬; 刘秉国; 彭金辉; 许磊; 张世敏

    2012-01-01

    采用常压烧结法合成了Fe2O3-莫来石微波热效应陶瓷材料,并对材料的抗弯强度、抗热震性能及介电性能进行了研究.结果表明,随烧结温度由1250℃升高至1350℃,烧结样品中残留的刚玉相减少,微波热效应陶瓷材料的体积密度、抗弯强度显著增大,相对介电常数随Fe2O3含量增加而增大,气孔率适中.在最佳烧结温度1350℃,氧化铁含量为30%,莫来石理论含量为70%条件下,制备的微波热效应陶瓷材料的体积密度为2.185g/cm3,抗压强度为77MPa,相对介电常数适中,满足微波热效应陶瓷性能要求.%The Fe2O3-molanstone microwave thermal effect ceramics were synthesized by sintering at normal atmosphere, and bending strength, thermal shock resistance and dielectric properties of the ceramics are studied. The results show that the content of remnant corundum phase after sintering decreases with the increase of temperature from 1250°C to 1350°C,the bulk density and the bending strength of microwave thermal effect ceramic materials increase significantly, the relative dielectric constants are significantly higher with the increase of Fe2O3 content, and the porosity is moderate. While the content of ferric oxide is 30% and the theory content of mullite is 70%, with the best sintering temperature of 1350℃ , the microwave thermal effect ceramic volume density is 2. 185 g/cm3, the bending strength is 77MPa, the relative dielectric constant is moderate, which can meet the requirements of microwave thermal effect ceramic performance.

  1. Rhyolites contaminated with metapelite and gabbro, Lipari, Aeolian Islands, Italy: products of lower crustal fusion or of assimilation plus fractional crystallization?

    Science.gov (United States)

    Barker, Daniel S.

    1987-12-01

    Pleistocene lavas from Monte S. Angelo and Chiesa Vecchia volcanoes on Lipari contain two suites of inclusions. A metapelitic suite consists of gneisses and granulites with combinations of cordierite, garnet, corundum, hercynite, andalusite, sillimanite, orthopyroxene, ilmenite, magnetite, biotite, plagioclase, and quartz. A gabbroic suite has cumulus texture and contains plagioclase, orthopyroxene, clinopyroxene, and magnetite. All megacryst phases in the lavas appear to be derived from rock fragments, with the exception of euhedral strongly zoned calcic plagioclase, and none has grown by homogeneous nucleation from liquid represented by the groundmass, which is peraluminous rhyolite (>70 wt% SiO2, >6 wt% K2O). Ground-mass microcrysts were nearly all derived from disaggregated metapelites; overgrowths of alkali feldspar on plagioclase and of orthopyroxene on clinopyroxene, and quartz intergrown with alkali feldspar, are the only phases that grew from the rhyolitic liquid. Euhedral cordierite, hercynite, and plagioclase at the margins of some rock fragments grew by reaction of metapelite with liquid. For grains in contact within metapelite inclusions, geothermometers and geobarometers yield estimates of equilibration conditions in the range of 800±100° C and 5±1 kbar. Compositions of phases in the same thin section, but not in the same inclusion, yield broadly erratic P and T estimates indicating disequilibrium among metapelite inclusions. Pyroxene thermometry in the gabbro suite indicates a crystallization temperature of 1020±50° C and a lack of subsequent thermal equilibration with the rhyolitic liquid. The metapelite suite may partly be restite, but much is xenolithic, derived from a vertical interval of perhaps several kilometers, and may have undergone a much earlier episode of melting. The gabbro fragments are accidental xenoliths incorporated as the magma rose. Contaminants (metapelite and gabbro) account for 50 vol.% of the lavas, and cause them to be

  2. Optimization of the Arc Spraying Process Parameters of the Fe–Base Mn-Si-Cr-Mo-Ni Coatings for the Best Wear Performance

    Directory of Open Access Journals (Sweden)

    Justinas GARGASAS

    2016-05-01

    Full Text Available In this paper, the use of Fe–base Mn-Si-Cr-Mo-Ni and Fe–base Mn-Si-Cr wires for thermal arc spraying is presented. For this purpose the mechanical and physical properties of coatings were evaluated. The quality of the coating’s was dependent on the selected equipment, spray materials, technological parameters of the spray and spray technology. The aim was to qualify and optimize the parameters for spray coating to get the best coatings properties with good tribological properties. All coatings were deposited on mild steel S235JR substrates. Two experimental cored wires of unique chemical composition – STEIN-MESYFIL 932 V and STEIN-MESYFIL 954 V – were used for thermal arc spraying. The wires of 1.6 mm diameter were used for the surfacing material. Hardness, porosity and oxide measurements were used to verify the spray parameters and analyze the coatings. Rubber wheel test, which is based on the standard ASTM G65, was used. Dry-sand, rubber-wheel procedure according ASTM G65 was used to investigate low stress abrasion, whereas for high stress abrasion investigations a rubber wheel was used. This experiment was carried out by changing the speed of disc friction, travel distance and measuring the mass loss of surface friction. Miller Test according to ASTM G75-95 Standard was carried out in experiment with friction. The samples were immersed in water with corundum and polished with 22 N load, for 8 hours. Furthermore a correlation was performed between the spraying current and voltage parameter. The coatings’ cross sections were examined using scanning electron microscope (SEM and optical microscopy. The influence of the composite components of the coatings’ microstructure, such as porosity, microhardness, oxide inclusions, on the tribological properties of thermal sprayed coatings is discussed in this paper. DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7339

  3. Adsorption of dissolved aluminum on sapphire-c and kaolinite: implications for points of zero charge of clay minerals.

    Science.gov (United States)

    Lützenkirchen, Johannes; Abdelmonem, Ahmed; Weerasooriya, Rohan; Heberling, Frank; Metz, Volker; Marsac, Remi

    2014-01-01

    We have studied the impact of dissolved aluminum on interfacial properties of two aluminum bearing minerals, corundum and kaolinite. The effect of intentionally adding dissolved aluminum on electrokinetic potential of basal plane surfaces of sapphire was studied by streaming potential measurements as a function of pH and was complemented by a second harmonic generation (SHG) study at pH 6. The electrokinetic data show a similar trend as the SHG data, suggesting that the SHG electric field correlates to zeta-potential. A comparable study was carried out on kaolinite particles. In this case electrophoretic mobility was measured as a function of pH. In both systems the addition of dissolved aluminum caused significant changes in the charging behavior. The isoelectric point consistently shifted to higher pH values, the extent of the shift depending on the amount of aluminum present or added. The experimental results imply that published isoelectric points of clay minerals may have been affected by this phenomenon. The presence of dissolved aluminum in experimental studies may be caused by particular pre-treatment methods (such as washing in acids and subsequent adsorption of dissolved aluminum) or even simply by starting a series of measurements from extreme pH (causing dissolution), and subsequently varying the pH in the very same batch. This results in interactions of dissolved aluminum with the target surface. A possible interpretation of the experimental results could be that at low aluminum concentrations adatoms of aluminum (we will refer to adsorbed mineral constituents as adatoms) can form at the sapphire basal plane, which can be rather easily removed. Simultaneously, once the surface has been exposed to sufficiently high aluminum concentration, a visible change of the surface is seen by AFM which is attributed to a surface precipitate that cannot be removed under the conditions employed in the current study. In conclusion, whenever pre-treatment or the

  4. Biomolecule-Mineral Interactions in the Geochemical Environment on Early Earth and in the Human Body

    Science.gov (United States)

    Sahai, N.

    2011-12-01

    We worked on four projects consistent with the broad goals of the grant to investigate (i) the potential impacts of mineral surface chemistry and particle size on the stability and viability of cell membranes, bacteria and human cells and (ii) the influence of biomolecules on mineral nucleation and growth. The projects are of relevance to the origin and early evolution of life, biomineralization, medical mineralogy, and environmental biogeochemistry. The freedom enabled by the five-year grant to explore high-risk scientific areas, and the resulting high impact outcomes, cannot be overstated. We developed an almost entirely new field of Medical Mineralogyy and extended our concepts and knowledge-base to the potential roles of mineral surfaces in the evolution of protocells and the earliest cells. These exciting connections to medical mineralogy, and to the origin and evolution of life on early Earth are fascinating topics to the general public and even to other scientists, especially when the links to mineralogy and geochemistry are highlighted. In brief, we examined the stability of lipid bilayers representing model protocell membranes comprised of phospholipid bilayers with mineral surfaces. We found that the stability of lipid bilayers depends on mineral surface charge and increases as silica glass ~ quartz human either inadvertently as inhaled dusts or are inserted by design such as in components of orthopedic implants. It is important to know how the mineral surface properties affect the body's immune system response. We found that adhesion/detachment force of the Jurkat -line of T-lymphocytes increased as SiO2 glass ~ quartz < rutile (100) ~ mica (001) < polycrystalline corundum, and was related to the unraveling of cell surface glycoproteins, and to mineral surface charge. The studies described above have resulted in 23 peer-reviewed publications to date (published or in review or in prep.); one MSA volume and one Elements issue edited by the P.I.; trained

  5. The Influence of Phenocrysts on Magma Degassing in Rhyolitic Systems

    Science.gov (United States)

    deGraffenried, R.; Larsen, J. F.; Lindoo, A. N.

    2016-12-01

    The kinetics of volatile exsolution and magma degassing control volcanic eruption styles, but the role of phenocrysts in the degassing process is poorly understood. The focus of this study is two series of decompression experiments examining how phenocrysts may or may not influence vesicle structures leading to permeability development and degassing in magmas with rhyolitic matrix melts. Powdered rhyolite obsidian (75 SiO2 wt. %; Mono Craters, CA) was seeded with 20 and 40 vol. % euhedral corundum crystals (350 μm) to approximate phenocrysts. Experiments were run using TZM (Ti-Zr-Mo alloy) vessels fitted with a water-cooled rapid quench top in a vertical Deltech furnace. Each run was held at 110 MPa and 900OC for 24 hours then decompressed continuously at a rate of 0.25 MPa/s to a final pressure (Pf) between 75 and 15 MPa. Permeability was measured using a bench-top permeameter constructed for the small experimental samples. Porosity was obtained from reflected light images using NIH Image J. The porosity of the samples increased from 11.0±1.7 to 73.3±3.1 vol % at Pf of 75 to 15 MPa for crystal free samples, 30.1±6.9 to 62.2±2.6 vol % at Pf of of 75 to 25 MPa for 20 vol % crystal samples, and 13.3±2.5 to 41.2±9.6 vol % at Pf of 75 to 50 MPa for 40 vol % crystal samples. The 20 vol % samples are impermeable up to at least 50 MPa Pf. The 40 vol % samples are impermeable up to 25 MPa Pf, with one sample having a measured Darcian permeability of -13.93±0.05 m2 at 25 MPa Pf. Comparatively, the crystal free samples were mostly impermeable up to 15 MPa, with one sample having a measured Darcian permeability of -14.41±0.04 m2 at 15 MPa Pf and 73.3 vol % porosity. Although preliminary, our permeable 40 vol % experiment suggests the phenocrysts help the samples develop permeability at a higher ending pressure and potentially lower porosity. Differences in the porosity curve as a function of pressure between the 20 and 40 vol % series indicate phenocrysts influence

  6. Geochemistry and petrogenesis of Neoproterozoic Mylliem granitoids, Meghalaya Plateau, northeastern India

    Indian Academy of Sciences (India)

    Jyotisankar Ray; Abhishek Saha; Sohini Ganguly; V Balaram; A Keshav Krishna; Sampa Hazra

    2011-06-01

    -type nature of the Mylliem granitoids. The peraluminous, S-type character is further supported by geochemical parameters such as Fe* and MALI (modified alkali lime index). Normative corundum < 1.0 wt.% is suggestive of the S-type nature of Mylliem granitoids. This is indicative of parent melt-extraction from metasedimentary source rocks by partial melting. Distinct geochemical parameters suggest a post-orogenic tectonic environment for the Mylliem granitoids. The peraluminous, calc-alkalic to alkali-calcic, post-orogenic Mylliem granitoids are geochemically correlatable with the post-orogenic Caledonian granitoids of Ireland and Britain.

  7. Nano or micro grained alumina powder? A choose before sintering

    Directory of Open Access Journals (Sweden)

    Román, R.

    2008-12-01

    Full Text Available Two different wet routes have been used to synthesize alumina powders in order to compare the characteristics of the final product and its behaviour during sintering. The Homogeneous Precipitation (HP gives rise to nanoparticulated powders of about 2 nm. However, such particles quickly aggregate and grow with calcination temperature. The Polymerized Organic-Inorganic Synthesis (POI produces homogeneous particle size powders (about 1 micron after resin charring. The characterization of the powder surface is the basis of an efficient process control. Particle characterization parameters (morphology, crystallinity and degree of aggregation are characterized by different techniques, such as DTA/TG, IR, XRD, SEM and TEM, and compared between these synthesis methods. The results show the evolution from the amorphous to the corundum alumina phase for both processes and their ability for sintering, as well discuses the beneficial of nanoparticles obtained by HP during sintering.

    Se han utilizado dos diferentes síntesis por vía húmeda para la preparación de polvos de alúmina con el fin de comparar las características de los productos finales y su comportamiento durante la sinterización. La Precipitación Homogénea (HP da lugar a polvos nanoparticulados de unos 2nm. Se observa sin embargo, como estas partículas se agregan rápidamente y crecen con la temperatura de calcinación. La Síntesis por Polimerización Orgánica-Inorgánica (POI produce polvos de tamaño de partícula homogéneo (en torno a 1 micra después de la descomposión de la resina. La caracterización de la superficie de los polvos es la base de un control eficiente del proceso. Los parámetros de caracterización de las partículas obtenidas (morfología, cristalinidad y grado de agregación se obtienen por diferentes técnicas como DTA/TG, IR, XRD, SEM y TEM, y se comparan entre estos métodos de síntesis. Los resultados muestran la evolución desde el amorfo a la fase

  8. Laboratory Investigations of the High Temperature Corrosion of Various Materials in Simulated oxy-fuel and Conventional Coal Firing

    Energy Technology Data Exchange (ETDEWEB)

    Folkeson, N.; Pettersson, J.; Svensson, J.E. [Chalmers Univ. of Technology (Sweden); Hjornhede, A. [Vattenfall Power Consultant AB (Sweden); Montgomery, M. [Vattenfall Heat Nordic/DTU Mekanik (Denmark); Bjurman, M. [Vattenfall Research and Development AB (Sweden)

    2009-07-01

    Laboratory exposures in horizontal tube furnaces were conducted to test various materials for corrosion resistance in simulated oxy-fuel firing and conventional coal firing environments. Two different exposures were done at 630 C for 672 hours. The reaction atmosphere, consisting of CO{sub 2}, H{sub 2}O, O{sub 2}, N{sub 2} and SO{sub 2}, was mixed to resemble that of oxy-fuel firing in the first exposure and that of conventional coal firing in the second exposure (N{sub 2} was added during the second exposure only). Four different materials were tested in the first exposure; Sanicro 63, Alloy 800HT, 304L and 304HCu. In the second exposure four different materials were tested; 304L, Alloy 800HT, Kanthal APMT and NiCrAl. Apart from cleaned sample coupons, some samples pre-exposed in a test rig under oxy-fuel conditions with lignite as fuel and some pre-exposed with bituminous coal as fuel were investigated in the first exposure. In the second exposure some samples were pre-exposed in a rig under conventional firing conditions with lignite as fuel. The corrosion attack on the investigated samples was analysed by gravimetry, x-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive x-ray (EDX). The SEM/EDX analysis was made on both the sample envelope and metallographic cross sections of the samples. The results show that there is small difference in the corrosion attack between the two environments. There was also little difference in oxide morphology and composition between cleaned samples and pre-exposed samples of the same material. The austenitic chromia former 304HCu suffered the most extensive corrosion attack in the oxy-fuel environment. In the conventional air firing environment 304L showed the highest mass gain. Chromia formers with higher chromium concentrations performed better, especially the super austenitic Alloy 800HT, with its high chromium concentration, formed a thin and protective corundum type oxide. The nickel based

  9. Differences in granular materials for analogue modelling: Insights from repeated compression tests analyzed with X-ray Computed Tomography and image analysis software

    Science.gov (United States)

    Klinkmueller, M.; Schreurs, G.

    2009-12-01

    Six different granular materials for analogue modelling have been investigated using a sandbox with a compressional set-up and X-ray computed tomography (XRCT). The evolving structures were evaluated with image analysis software. The sandbox has one movable sidewall that is driven by a computer-controlled servomotor at 20 cm/h. A 12 cm wide and 20 cm long sheet of hard cardboard was placed on the base of the sandbox and attached to the moving sidewall creating a velocity discontinuity. The whole sandbox was covered on the inside with Alkor foil to reduce sidewall friction. Computed Tomography was used to scan the whole volume in 3 mm increments of shortening until 15 mm maximum deformation was reached. The second approach was a scanning procedure to a maximum deformation of 80 mm in 2 mm increments of shortening for the first 10 mm and in 5 mm increments for the last 70 mm. The short deformation scans were repeated three times to investigate reproducibility. The long deformation scans were performed twice. The physical properties of the materials (table 1) have been described in a previous material benchmark. Four natural quartz sands and two artificial granular materials, corundum brown sand and glass beads, have been used. The two artificial materials were used for this experimental series as examples for very angular and very rounded sands in contrast to the sub-rounded to angular natural quartz sands. The short deformation experiments show partly large differences in thrust angles of both front and back-thrust, in timing of thrust initiation, and in the degree of undulation of thrusts. The coarse-grained sands show smooth and low undulating thrusts that are only affected by the sidewall friction whereas the thrusts in fine-grained sands undulate significantly and partly divide and merge in an anastomosing fashion. The coarse-grained sand thrusts are clearer visualized by XRCT, which indicates a wider shear zone where the material dilates. Furthermore, the

  10. Study on Process of Preparing Fe-Al2O3 Magnetic Abrasive by High Energy Ball Milling%高能球磨法制备Al2O3/Fe磁性磨粒的工艺研究

    Institute of Scientific and Technical Information of China (English)

    王晓峰; 李文辉

    2013-01-01

    Magnetic abrasive finishing machining technology is a new technology to use the magnetic field force produced by permanent magnetic or electromagnetic device asthe driving force of magnetic abrasive finishing machining of parts surface,which can realize the surface polishing,deburring,eliminating the micro crack,and reducing the surface roughness of parts.4 new technology of preparing magnetic abrasives used high energy ball milling was put forward and the working principle was analyzed in the ball milling.Pure iron powder was used as the magnetic phase,corundum powder as the abrasive,and three different times Fe-Al2O3 magnetic abrasives were prepared by high energy ball milling method.X-ray diffraction and SEM were used to analyze the morphology and phase components of the magnetic abrasives.Magnetic flux density of the magnetic abrasives were tested by the instrument.It finds that the process is easy and low cost,so it would have great hope to accomplish large-scale industrialized production.%磁性磨粒光整加工技术是利用永磁或者电磁发生装置产生的磁场力作为磁性磨粒的源动力对零件表面进行光整加工的一种新技术,它可以实现对零件进行表面抛光、去除毛刺、消除微观裂纹、降低表面粗糙度等加工.提出应用高能球磨法制备磁性磨粒的新工艺,分析了球磨过程中的工作原理.用纯铁粉作为磁性体,三氧化二铝粉作为磨料相,采用高能球磨法制备了三种不同时间的Fe-Al2O3磁性磨粒.采用X射线衍射仪和扫描电子显微镜分析了该磁性磨粒的物相组成和外观形貌,用特斯拉仪测试了磁性磨粒的磁感应强度.发现了该工艺简单,成本低,且有望进行大规模工业化生产.

  11. In-situ study of ferric iron distribution in synthetic spinels by electron microprobe analysis

    Science.gov (United States)

    Goncharov, Alexey; Olga, Sinelshikova; Rustam, Lukmanov

    2017-04-01

    The iron oxidation state in mantle minerals is a key value in oxygen fugacity calculation and the most widely used analytical approach for Fe3+/ΣFe determination is Mössbauer spectroscopy, which is a bulk method and there is a lack of information on Fe3+/ΣFe zonation in individual mineral grains and Fe3+/ΣFe in inclusions. Here we present application of the flank method using the electron microprobe by analysing the FeLα and FeLβ X-ray emission spectra to a suite of 20 synthetic MgAl2O2-Cr2O3-Fe2O3(FeO) spinels. Materials were done with 5 - 25 FeO wt.%, and 2-70 Cr2O3 wt.% and Fe3+/ΣFe = 0.10 to 0.80, where Fe3+/ΣFe was determined independently using Mössbauer spectroscopy on the same grains used for the flank method measurements. Synthesis of the samples produced using a pyrolysis method of organic salt compositions in MgAl2O2-Cr2O3-Fe2O3(FeO) system with following heating in corundum crucibles at 1300 ° C for 5 -10 hours under controlled oxygen fugacity. All synthetic materials were investigated by X-ray and Mössbauer spectroscopy to examine a phase and iron oxidation state features. In terms of chemical composition and Fe3+/ΣFe resulting synthetic material covers a whole range of spinels derived in mantle peridotites and pyroxenites. These synthetic products were used as a standard sample to investigate co-variations of ratios of intensities measured on the flanks of FeLα and Lβ peaks and Fe3+/ΣFe, FeO content and Cr#. The obtained correlations can be used to perform in-situ studies of ferric iron distribution in natural mantle spinels. The presented approach will allow investigating the difference in mantle spinel Fe3+/ΣFe at a microscale from core to rim in individual grain, inclusion, melting pocket and in intergrows with other mantle mineral assemblage. The reported study was funded by RFBR according to the research project № 16-35-60076 mol_a_dk.

  12. Preparation and Healing of Cracks in Al2O3-MgAION Composite

    Institute of Scientific and Technical Information of China (English)

    YANG Daoyuan; ZHU Kai; WU Juan

    2009-01-01

    The Al2O3-MgAION specimens with dimensions of φ20 mm×10 mm and 3 mm×4 mm×36 mm were pre-pared using corundum grains ( w( Al2O3) >98% , par-ticle size: 3-1 mm, ≤1 mm, ≤85 μm and ≤3 μm, respectively) and MgAION (particle size ≤ 2 μm ) as starting materials, PVA as binder, designing 3 formula-tions containing aggregate and 4 special formulations without aggregate, pressing under 150 Mpa and keep-ing for 5 s, firing at 1 500 ℃ for 2 h in nitrogen under normal pressure, and the cracks were prepared on the specimens by thermal shock method (air cooling at 1 100 ℃ for 10 cycles) and by Vickers method (29.4, 49.0 and 98.0 N, keeping for 25 s) , then holding at 1 100 ℃ and 1 550 ℃ for 6 h in nitrogen atmosphere for cracks healing, respectively. The influences of crack prefabricated method, grain composition, pressure of Vickers and pressure holding time on the shape and di-mension of cracks were studied. Effects of healing tem-perature on healing degree and MOR of specimens were investigated and the crack healing rate was calculated. The results showed that: (1) the cracks of MgAION specimens prepared by thermal shock method under nor-real pressure were of irregular shape and uncertain length; (2) the cracks prepared by Vickers method was approximate diamond-shape without slender cracks emit-ting from every vertex angle; but if composite specimens were fabricated by particles of several microns, the crack size, shape and its site, especially that obtained under 98.0 N for 25 s, could be controlled exactly under a Vickers hardometer, which made the crack healing re-search easy to conduct; (3) after healing treatment at 1 100 ℃ or 1 500 ℃, the cracks became shallower and smaller even disappeared, the strength of the specimen was recovered finally; (4) a formulation for crack heal-ing rate expressed by the cracked capacity was: V/ t = 1/3 C2v(1+ctg θ) Cv/ t.

  13. La interacción de materiales del sistema sílice-alúmina con productos fluorados aluminosos

    Directory of Open Access Journals (Sweden)

    Verdeja, L. F.

    1998-05-01

    Full Text Available The aim of this paper is to get a first approximation of the systematic study of the corrosion mechanisms of the silica-alumina, alumina and rich-alumina refractory by fluoride compounds and molten aluminum. The thermodynamic results support the main role of the chemical attack and the erosive mechanisms in the wear of the silica-alumina materials. The influence of the composition of the crystalline phases in the degree of the ceramic lining attack is also studied. The results suggest not to use either oxide or nitride high-value materials for the lining of furnaces and transport recipients containing molten aluminum, because of the chemical corrosion by compounds such as cryolite or aluminum fluoride and also, because of the avidity of aluminum towards oxygen. The study of corundum-based materials like the best refractory used in order to react with fluoride compounds and molten aluminum is an alternative to be considered. The study of the crusts adhesion like a protection mechanism of the refractory lining is also a possible approach.

    Este trabajo pretende contribuir al estudio sistemático de los mecanismos de corrosión que experimentan los refractarios sílico-aluminosos, aluminosos y de alta alúmina con productos fluorados y aluminio en estado líquido. Se aportan datos termodinámicos que confirman el papel preponderante del ataque químico y de los mecanismos erosivos en el desgaste de materiales del sistema sílice-alúmina. Se discute, asimismo, la influencia de la composición de las fases cristalinas encontradas en el grado de agresión a los revestimientos cerámicos. Se propone, ante la agresividad de agentes químicamente activos, como la criolita o el fluoruro de aluminio, y la gran afinidad del aluminio por el oxígeno, no aconsejar la utilización de materiales oxídicos y nitrurados de alto valor para el revestimiento de hornos y bolsas de transporte de aluminio. Se propone, como línea de trabajo a seguir, la

  14. Effects of Cement Addition on the Slag Resistance of Alumina-spinel Castables%水泥对刚玉-尖晶石浇注料抗侵蚀性影响研究

    Institute of Scientific and Technical Information of China (English)

    贾全利; 叶方保; 钟香崇

    2011-01-01

    以板状刚玉为骨料,电熔白刚玉、电熔尖晶石、Al2O3微粉和纯铝酸钙水泥为基质,研究了纯铝酸钙水泥加入量对刚玉-尖晶石浇注料抗侵蚀性能的影响.结果表明:纯铝酸钙水泥加入量为4%时,浇注料的侵蚀、渗透指数最大,抗渣侵蚀性能最差;水泥含量≥6%时抗渣侵蚀、渗透指数明显下降,抗渣性逐渐改善.水泥加入量影响浇注料的抗侵蚀性能主要与基质中的物相组成和显微结构有关.随水泥加入量的增加,水泥中的CaO与Al2O3反应形成六铝酸钙,基质中刚玉的含量减少;渣中的CaO与刚玉颗粒反应形成六铝酸钙,产生体积膨胀堵塞气孔,抑制了渣的渗透,使得抗渣侵蚀性能得到改善.%Alumina-spinel castables were prepared by using tabular alumina as aggregates, fused white corundum, fused spinel, ultra-fine alumina and calcium aluminate cement (CAC) as matrix. Effect of calcium aluminate cement on the slag resistance of alumina-spinel castables was investigated. The results show that the penetration and corrosion index of specimens increase with increas in CAC content from 2% to 4% ,indicating that slag resistance of specimens deteriorated. Slag resistance of castables is improved with increase in GAG content from 4% to 10%. The influence of CAC on the slag resistance of specimens is mainly correlated to the phase compositions and mierostructure of matrix in castables. The calcium hexaluminate(CA6) formed by CaO reacting with Al203 ,which leads to decrease the content of alumina in the matrix; CaO in slag reacts with alumina aggregates to form GA6, which results in volume expansion and pore size reduction, and consequently prevent slag penetration into the matrix.

  15. Effect of microstructure on slag resistance of Al2 O3-Cr2 O3 bricks%Al2O3-Cr2O3砖显微结构对抗渣性能的影响

    Institute of Scientific and Technical Information of China (English)

    孙红刚; 李鹏涛; 付建莹; 闫双志; 王刚; 耿可明

    2014-01-01

    The slag resistance of two Al2 O3-Cr2 O3 bricks (with 10 mass%Cr2 O3 )A and B were researched using static crucible method and rotary slag method,respectively.The results show that,two Al2 O3-Cr2 O3 bricks have similar properties such as apparent porosity,bulk density,thermal shock resistance,and chem-ical compositions.Brick B has higher strength than brick A.Compared with brick B:brick A has smaller in-ner pores,because the white corundum aggregates in brick A are smoother and denser with continuous particle size distribution;Al2 O3-Cr2 O3 solid solution in brick A is smaller,crossing and forming net structure with small gaps,which reduces the penetration and wear of slag to refractories,meaning that brick A has better slag resistance than brick B.It’s obvious that optimizing microstructure is an effective way to im-prove the slag resistance of Al2 O3-Cr2 O3 materials.%分别采用静态坩埚抗渣法和回转抗渣法,对w(Cr2 O3)=10%的A和B两种Al2 O3-Cr2 O3砖进行了抗渣性能对比。结果发现:两种砖的化学组成、显气孔率、体积密度和抗热震性相近,B砖强度优于A砖的。但由于与B砖相比,A砖内部气孔尺寸更小,所用电熔白刚玉骨料形貌平滑,较为致密,粒度呈连续式分布,且A砖中Al2 O3-Cr2 O3固溶体发育较小,相互交错,形成了孔隙较小的空间网状结构,这种显微结构显著降低了熔渣对耐火材料的渗透和破坏,使A砖的抗渣性优于B砖的。因此,制备微气孔化结构的制品是提高Al2 O3-Cr2 O3材料抗渣性能的有效途径。

  16. 大型不锈钢铸件粘砂及表面烧结机理研究与改进%Mechanisum and Prevention of Surface Burnning-on of Large Sized Stainness Steel Casting

    Institute of Scientific and Technical Information of China (English)

    扈广麒; 王培; 彭凡; 肖纳敏

    2011-01-01

    对采用呋喃树脂自硬铬矿砂生产高铬不锈钢水轮机叶片铸件表面易出现"釉化"涂料层、界面型砂"釉化"烧结和粘砂缺陷进行了研究,并提出了解决措施.铸件粘砂的主要原因为钢液透过涂料层渗入铬矿砂,在界面发生氧化还原反应,将铬铁矿砂的铁还原出来,还原出的铁和砂粒形成致密混合物,并附着在铸件表面形成"釉化"烧结层.还原出的铁和铬渣以及砂粒中的未反应物,形成了致密的机械混合物,和铸件金属直接相连,附着在铸件的表面,形成粘砂.锆英粉涂料本身也和高铬钢发生微弱的化学反应.用新型添加剂及复合涂料改进型砂和替代锆英粉涂料,提高了钢液和铬矿砂界面涂料层的致密度、化学稳定性和耐火性,可以有效地解决这类问题.%Some defects such as coating glazing, interface sand glazing and sintering and sand fusion always appear on surface of cast high-chromium stainless steel hydraulic turbine blade castings when using furan resin chromite sand. The main reason for these defects is the infiltration of liquid steel through the coating to chromite and the redox reaction took place which reduces iron out of chromite sand. First, the iron and sand are mixed together and become dense mixture, and then iron, sand and the un-reacted material in sand are mixed together to form dense mechanical mixtures attached to the surface of casting causing the sand burning. Second, a weak chemical reaction occurs between zircon powder coating and the high-chromium steel. According to the analyses, the powder coating with higher chemical stability and fire resistance was chosen instead of zircon powder coating. Additionally, the corundum powder coating can improve the coasting density at the interface of the molten steel and chromite sand. And this method is useful for solving such kind of problems.

  17. Microstructures, mineral chemistry, noble gases and nitrogen in the recent fall, Bhuka iron (IAB) meteorite

    Science.gov (United States)

    Murty, S. V. S.; Ranjith, P. M.; Ray, Dwijesh; Ghosh, S.; Chattopadhyay, Basab; Shrivastava, K. L.

    2016-10-01

    We report some chemical, petrological and isotopic studies of the Bhuka iron meteorite that fell in Rajasthan, India in 2005. Numerous silicate and graphite inclusions are visible on the surface of the hand specimen. In the polished and etched surface studied, irregular patches of graphite are found as the most dominant inclusion and commonly associated with pure corundum (95 wt% Al2O3), spinel, feldspar and Si-rich phases. Apart from typical lamellar intergrowth with kamacite (i.e. the Widmänstatten pattern), taenites are also commonly found to occur as a rim of the graphite inclusions. P-rich (up to 10 wt%) taenites are also found locally within the recrystallised kamacite matrix. Based on mineralogy, texture and bulk composition, Bhuka resembles the low-Ni IAB subgroup (ungrouped). Noble gas isotope studies suggest He, Ne and Ar are mostly of cosmogenic origin, while Kr and Xe are a mixture of cosmogenic, radiogenic and trapped components. A pre-atmospheric radius of 10±1 cm and a cosmic ray exposure age of 346±52 Ma are derived based on depth dependant (3He/4He)c and 38Arc respectively, as per the production systematics of cosmogenic noble gas isotopes (Ammon et al., 2009). Cosmogenic 83Kr and 126Xe yield production rates of 12 and 0.335 (in 10-15ccSTP/g Ma) for 83Kr and 126Xe respectively. Presence of trapped Kr and Xe, with (84Kr/132Xe)t=2 and radiogenic 129Xe=120×10-12 ccSTP/g are due to presence of graphite/silicate inclusions in the analysed sample. Over ~150% excess 131Xec than expected from spallation suggests contribution from (n,ɤ) reactions from Ba from inclusions and suggests irradiation of pre-atmospheric object in a larger body, indicative of complex irradiation. Trapped N of 24 ppm, with δ15N=-10.7±0.8‰ observed in Bhuka, is heavier than the range observed hither to in IAB irons.

  18. Mineralogy and geochemistry of granitoids from Kinnaur region, Himachal Higher Himalaya, India: Implication on the nature of felsic magmatism in the collision tectonics

    Indian Academy of Sciences (India)

    Brajesh Singh; Santosh Kumar; Masao Ban; Kazuo Nakashima

    2016-10-01

    Felsic magmatism in the southern part of Himachal Higher Himalaya is constituted by Neoproterozoic granite gneiss (GGn), Early Palaeozoic granitoids (EPG) and Tertiary tourmaline-bearing leucogranite (TLg). Magnetic susceptibility values ($\\lt$3 ×10$^{−3}$ SI), molar Al$_2$O$^3$/(CaO+Na$_2$O+K$_2$O) ($\\geq$1.1), mineral assemblage (bt–ms–pl–kf–qtz ± tur ± ap), and the presence of normative corundum relate these granitoids to peraluminous S-type, ilmenite series (reduced type) granites formed in a syncollisional tectonic setting. Plagioclase from GGn (An$_{10}$–An$_{31}$) and EPG (An$_{15}$–An$_{33}$) represents oligoclase to andesine and TLg (An$_2$–An$_{15}$) represents albite to oligoclase, whereas compositional ranges of K-feldspar are more or less similar (Or$_{88}$ to Or$_{95}$ in GGn, Or$_{86}$ to Or$_{97}$ in EPG and Or$_{87}$ to Or$_{94}$ in TLg). Biotites in GGn (Mg/Mg+Fe$^t$ = 0.34–0.45), EPG (Mg/Mg+Fe$^t$ = 0.27–0.47), and TLg (Mg/Mg+Fe$^t$ = 0.25–0.30) are ferribiotites enriched in siderophyllite, which stabilised between FMQ and HM buffers and are characterised by dominant 3Fe$\\rightleftarrows$2Al, 3Mg$\\rightleftarrows$2Al substitutions typical of peraluminous (S-type), reducing felsic melts. Muscovite in GGn (Mg/Mg+Fe$^t$ = 0.58–0.66), EPG (Mg/Mg+Fe$^t$ = 0.31−0.59), and TLg (Mg/Mg+Fet = 0.29–0.42) represent celadonite and paragonite solid solutions, and the tourmaline fromEPG and TLg belongs to the schorl-elbaite series, which are characteristics of peraluminous, Li-poor, biotite-tourmaline granites. Geochemical features reveal that the GGn and EPG precursor melts were most likely derived from melting of biotite-rich metapelite and metagraywacke sources, whereas TLg melt appears to have formed from biotite-muscovite rich metapelite and metagraywacke sources. Major and trace elements modelling suggest that the GGn, EPG and TLg parental melts have experienced low degrees (∼13, ∼17 and ∼13%, respectively) of kf

  19. Extreme extension across Seram and Ambon, eastern Indonesia: evidence for Banda slab rollback

    Science.gov (United States)

    Pownall, J. M.; Hall, R.; Watkinson, I. M.

    2013-09-01

    The island of Seram, which lies in the northern part of the 180°-curved Banda Arc, has previously been interpreted as a fold-and-thrust belt formed during arc-continent collision, which incorporates ophiolites intruded by granites thought to have been produced by anatexis within a metamorphic sole. However, new geological mapping and a re-examination of the field relations cause us to question this model. We instead propose that there is evidence for recent and rapid N-S extension that has caused the high-temperature exhumation of lherzolites beneath low-angle lithospheric detachment faults that induced high-temperature metamorphism and melting in overlying crustal rocks. These "Kobipoto Complex" migmatites include highly residual Al-Mg-rich garnet + cordierite + sillimanite + spinel + corundum granulites (exposed in the Kobipoto Mountains) which contain coexisting spinel + quartz, indicating that peak metamorphic temperatures likely approached 900 °C. Associated with these residual granulites are voluminous Mio-Pliocene granitic diatexites, or "cordierite granites", which crop out on Ambon, western Seram, and in the Kobipoto Mountains and incorporate abundant schlieren of spinel- and sillimanite-bearing residuum. Quaternary "ambonites" (cordierite + garnet dacites) emplaced on Ambon were also evidently sourced from the Kobipoto Complex migmatites as demonstrated by granulite-inherited xenoliths. Exhumation of the hot peridotites and granulite-facies Kobipoto Complex migmatites to shallower structural levels caused greenschist- to lower-amphibolite facies metapelites and amphibolites of the Tehoru Formation to be overprinted by sillimanite-grade metamorphism, migmatisation, and limited localised anatexis to form the Taunusa Complex. The extreme extension required to have driven Kobipoto Complex exhumation evidently occurred throughout Seram and along much of the northern Banda Arc. The lherzolites must have been juxtaposed against the crust at typical

  20. Stabilities of gibbsite, boehmite, aluminous goethites and aluminous hematites in bauxites, ferricretes and laterites as a function of water activity, temperature and particle size

    Energy Technology Data Exchange (ETDEWEB)

    Trolard, F.; Tardy, Y.

    1987-04-01

    Stability relationships between Al-goethite, Al-hematite, boehmite and gibbsite are presented in terms of water activity (H/sub 2/O), temperature (T), grain size and bulk-composition in the system Fe/sub 2/O/sub 3/-Al/sub 2/O/sub 3/-H/sub 2/O at a total pressure of 1 bar. Al-goethite and Al-hematite are treated as ideal solid solutions, the former of the end-members FeOOH and AlOOH and the latter of the end-members Fe/sub 2/O/sub 3/ (hematite) and Al/sub 2/O/sub 3/ (corundum). Using log K/sub sp/ provided by the literature for the various phases involved, the common associations observed in laterites, bauxites and ferricretes do not have stability fields over geologically reasonable intervals of (H/sub 2/O) and T. Consequently a new internally consistent set of log K/sub sp/ values is proposed and used, and allows such associations to have actual stability fields in the appropriate diagrams. The new log K/sub sp/ values used in the calculations are such that the solubilities of the end members are greater than those commonly listed. This is in agreement with natural observations which show that such minerals, are generally poorly crystallized and of very small size. The assumption of an ideal solid solution in aluminous goethite and aluminous hematite combined with the new log K/sub sp/ values leads to prediction of composition limits for these two minerals which agree well with observed values. The fact than an ideal solid solution must extend continuously from one end-member to the other is masked by the appearance of other stability fields which cross and overlap a part of the solid solution stability fields of AlOOH-FeOOH and Fe/sub 2/O/sub 3/-Al/sub 2/O/sub 3/.

  1. Physical incorporation of particles in a porous media: a path to a smart wood

    Science.gov (United States)

    Zerriaa, Azza; El Ganaoui, Mohammed; Gerardin, Christine; Tazibt, Abdel; Gabsi, Slimane

    2016-05-01

    The aim of this work is to develop a functional wood incorporating, in its surface, physical and chemical properties that meet society demand. For instance: fire resistance, magnetic electrical conduction (metal-wood particles), antibacterial reaction (copper-wood), anti-pollution (zeolite-wood), dry coloring, reflective effects (minerals-wood). As part of the research on wooden materials, the technique of "JAZOLTHOP1" driving micrometric particles before combining them and moving in supersonic speeds was used in the framework of enriching a wooden substrate. Various tests were conducted on two wooden materials (fir and ash tree) submitted to four typologies of particles (steel shot, garnet, corundum and glass beads). The surfaces of the test samples were machined beforehand for a use of conventional smooth quality, thus defining a reference surface before incorporation. The enriched samples were characterized by using two optical techniques; firstly a surface technique through macroscopy Leica 110X ZP, then a volume technique through tomography2. Subsequently, volume simulations (wood-inclusions) were implemented to study the thermal transfer. The obtained results showcase the existence of certain set conditions to reach the critical fluency of incorporation and to localize the enrichment on a parallel plan to the sample surface. The results show also the influence of particles concentration and the kind of the chosen wood on the final composite matrix/particle media. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui http:// http:// http:// http:// http:// http://Nunzihttp:// http://Jean-Michelhttp:// http:// http:// http:// http:// http://Bennacerhttp:// http://Rachidhttp:// http:// http:// http:// http:// http://El Ganaouihttp:// http://Mohammedhttp:// http:// http:// http://Guest editorshttp:// http:// http:// http

  2. About LTCC materials in the substance system of CaO-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}; Ueber LTCC-Werkstoffe aus dem Stoffsystem CaO-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Gemeinert, Marion

    2009-09-01

    Glass ceramic composites made of glassy and crystalline powders offer numerous possibilities for modifying materials properties e.g. sintering behaviour, thermal expansion coefficient, mechanical behaviour, chemical durability, dielectric properties and surface quality for special use. Glass ceramic composite powders can be used for the production of ceramic green tapes which are processed by LTCC (Low Temperature Co-fired Ceramics)- technology to form ceramic multilayers for electronic packaging in microsystems. During free sintering of LTCC-multilayers a lateral shrinkage occurs which is connected with a comparatively high shrinkage tolerance. Different sintering technologies are used to avoid the lateral shrinkage. A new possibility to achieve a zero lateral shrinkage is given by use of a self-constrained laminate. Therefore a multilayer is produced of two different materials for inner and outer layers, showing different sintering temperatures ({delta}T>50 K). Object of this dissertation was the development of LTCC-materials, which can be used for inner layers of a self-constrained laminate to reduce the lateral shrinkage nearly to zero. Therefore LTCC-materials in the field of CaO-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}, which can be sintered below 800 C, were investigated. Starting from the development of adapted glasses based on calcium lanthanium borate- and calcium lanthanium alumoborate glasses glass ceramic composites were produced by the addition of corundum powder. The composites crystallize during the sintering process almost completely. Lanthanum borate crystallizes from the glassy phase and calcium alumoborate and calcium alumoborate oxide respectively is formed by a chemical solid state reaction of the residual glassy phase, which is enriched by calcium borate, and the corundum. The proportional relation of the new crystalline phases determines the thermal and dielectric properties of the material. The most important formed new

  3. 越南西北部大象山超高温变质岩的发现及其区域构造意义%The discovery and tectonic implication of ultrahigh-temperature metamorphic rocks in the Day Nui Con Voi, northwestern Vietnam

    Institute of Scientific and Technical Information of China (English)

    吴虎峻; 刘俊来; TRANMy Dung; NGUYEN QuangLuat; PHAMBinh; 吴文彬; 陈文; 张招崇

    2011-01-01

    越南西北部大象山群孔兹岩系中发育一套含刚玉+尖晶石+石榴石+夕线石组合的富铝岩石块体,它们呈透镜状包体形式赋存于孔兹岩系内.岩石中刚玉+尖晶石+石榴石+夕线石组合的发育指示岩石经历了超高温变质作用的改造.其中尖晶石和石英的共生组合表明了变质温度高于900℃,而利用岩石退变质矿物组合中的黑云母-石榴石温度计,黑云母-斜长石-石榴石-石英组合温度-压力计估算的变质温度压力条件分别为879 ~917℃、0.90 ~0.94GPa.岩石中的早期刚玉+夕线石的组合的存在说明岩石变质作用已经从高角闪岩相进入到了麻粒岩相;而峰期变质矿物组合尖晶石+石英的出现,指示了变质温度高于900℃的超高温变质作用.另一方面,退变质过程中钛铁矿的发育表明岩石经历了快速抬升降压的过程.变质作用的P-T轨迹分析揭示出岩石经历了早期同步升温增压后的快速增温达到峰期条件,后经历快速等温减压过程.这种温压条件的变化与板块会聚过程中由于俯冲板片的断离而使软流圈上涌造成热异常的温压条件变化基本一致.通过对超高温变质岩石进行锆石SIMS U-Pb测年获得的结果大于58Ma,推测这次超高温变质与喜马拉雅运动中印度与欧亚大陆的初期会聚-碰撞作用相关.%There is a pile of rock blocks which contain corundum + spinel + garnet + fibrolite association in the form of lenticular enclaves in khondalite series along the Day Nui Con Voi, northwestern Vietnam. The mineral association is resulted from ultrahigh-temperature metamorphism. The coexistence of spinel and quartz indicates that the metamorphic temperature is higher than 900℃. Meanwhile, the biotite-garnet thermometer and biotite-plagioclase-garnet-quartz association thermobarometer for the mineral associations during retrogressive metamorphism gave temperature and pressure ranges of 879 ~917℃ and 0

  4. Wagnerite-MA5BC From Granulite-Facies Paragneiss, Larsemann Hills, Prydz Bay, East Antarctica

    Science.gov (United States)

    Ren, L.; Grew, E. S.; Xiong, M.; Ma, Z.

    2003-04-01

    Wagnerite-Ma5bc, which is one of three new polytypes of (Mg,Fe)_2(PO_4)(F,OH) (Chopin, Armbruster &Leyx, this conference), occurs in paragneiss associated with banded cordierite-prismatine gneiss. It forms anhedral to euhedral grains mostly 0.5-2 mm across, some with a tabular habit. Textures are consistent with a primary assemblage wagnerite-Ma5bc + plagioclase + apatite + magnetite + ilmenite-hematite that crystallized under granulite-facies conditions (750 - ˜860^oC, 6-7 kbar). Also present are biotite, quartz, K-feldspar, monazite, xenotime, corundum, hercynite, sulfide. Electron microprobe analyses give P_2O_5 41.39, SiO_2 0.06, TiO_2 0.88, FeO 4.16, MnO 0.09, MgO 44.54, CaO 0.09, F 6.87, H_2O (calculated for OH + F = 1) 2.04, O=F -2.89, total 97.22 wt%, corresponding to (Mg1.88Fe0.10Ti0.02)(P0.99O_4)(F0.61OH0.39). Space group is Ia. Lattice parameters a = 9.645(2)Å, b = 31.659(6) Å , c = 11.914(2) Å, â=108.26 (3)^o, V= 3455(1) Å^3 for Z=40, Dcalc = 3.18(1) g/cm^3. The crystal structure has been solved by direct methods and refined to R_1=0.0413 for the independent 4521 reflections [I>2σ(I)] using MoKα radiation. The primary difference among the wagnerite polytypes is ordering of the (F,OH) positions. F can occupy one of two positions resulting in two distinct configurations along the a direction. In magniotriplite the sequence of configurations in the b direction is disordered, whereas in wagnerite-Ma2bc the sequence is ordered 121212... and in wagnerite-Ma5bc, 12112... Magniotriplite and the wagnerite polytypes do not overlap in composition: minerals richer in Fe and Mn (average ionic radius >= 0.76 Å) crystallize as the disordered minerals in the triplite group, whereas highly magnesian minerals (average ionic radius = 86% of the Mg end member) crystallize as the ordered wagnerite polytypes. Magniotriplite formed at moderate temperatures (e.g., amphibolite-facies), whereas wagnerite-Ma2bc is found in rocks formed under a wide range of P

  5. Subduction recycling of continental sediments and the origin of geochemically enriched reservoirs in the deep mantle

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, R.P.; Irifune, T.; Shimizu, N.; Nishiyama, N.; Norman, M.D.; Inoue, T. (Ehime U); (WHOI); (UC); (ANU)

    2008-10-08

    the product of melting of deeply recycled (subducted) Archean-age metasediments in the mantle transition zone [Murphy, D.T., Collerson, K.D., Kamber, B.S., 2002. Lamproites from Gaussberg, Antartica: possible transition zone melts of Archaean subducted sediments. J. Petrol. 43, 981-1001]. Here we report the results of phase equilibria experiments on two different natural sedimentary compositions (a high-grade metapelite with < 1 wt.% H{sub 2}O, and a marine 'mud' with 8 wt.% H{sub O}) at 16-23 GPa. In both materials, the high-pressure mineral assemblages contain {approx} 15-30 wt.% K-hollandite (KAlSi{sub 3}O{sub 8}), in addition to stishovite, garnet, an Al-silicate phase (kyanite or phase egg), and a Fe-Ti spinel (corundum). Ion microprobe analyses of K-hollandite for a range of trace elements reveal that this phase controls a significant proportion of the whole-rock budget of incompatible, large-ion lithophile elements (LILEs, e.g., Rb, Ba, Sr, K, Pb, La, Ce and Th). Comparisons between the abundances and ratios of these elements in K-hollandite with those in EM-I type ocean-island basalts from Pitcairn Island and related seamounts, and with the Gaussberg lamproites, indicate the presence of deeply recycled, continent-derived sediments in these lavas sources. Our results suggest that the incompatible trace-element signature of EM-I OIB reservoirs in general and of the Gaussberg lamproites in particular can be attributed to recycling of K-hollandite-bearing continental sediments to transition zone depths.

  6. 淀粉对氧化铝基陶瓷型芯性能的影响%Effects of Starch on Properties of Alumina-based Ceramic Cores

    Institute of Scientific and Technical Information of China (English)

    李风光; 唐世艳; 刘富初; 樊自田

    2016-01-01

    In order to improve the poor leachability of alumina-based ceramic cores, different amount of starch was added to the speci-mens as pore former. Alumina-based ceramic cores were prepared by hot injection technology using corundum powder as base material, paraffin wax and beeswax as plasticizer, silica powder and magnesium oxide powder as mineralizing agent, wherein the parameters of the hot injection process were as follows:temperature of the slurry was 90℃, hot injection pressure was 0. 5 MPa and holding time was 25 s. The effects of starch content on the properties of alumina-based ceramic cores were studied and discussed. The results indicate that during sintering period, the loss of starch in the specimens makes porosity of the alumina-based ceramic cores increase. When starch content increases, the room-temperature flexural strength of the ceramic cores reduces and the apparent porosity increases; the volatile solvent increases and the bulk density decreases. After being sintered at 1560 ℃ for 2. 5 h, room-temperature flexural strength of the alumina-based ceramic cores with starch content of 8%(mass fraction) is 24. 8 MPa, apparent porosity is 47. 98% when the vol-atile solvent is 1. 92 g/h and bulk density is 1. 88 g /cm3 , the complex properties are optimal.%为了解决氧化铝基陶瓷型芯不易脱芯的难题,加入一定量的淀粉作为成孔剂。以白刚玉粉为基体材料、石蜡和蜂蜡为增塑剂、二氧化硅粉和氧化镁粉为矿化剂,采用热压注法制备氧化铝基陶瓷型芯;制备工艺参数如下:浆料温度为90℃、热压注压力为0.5 MPa、保压时间为25 s;研究不同淀粉加入量对氧化铝基陶瓷型芯性能的影响。结果表明:在烧结过程中,样品中淀粉的烧失,增大了氧化铝基陶瓷型芯内部的孔隙率;随着淀粉加入量的增加,氧化铝基陶瓷型芯的室温抗弯强度降低、显气孔率增大、溶失性增大、体积密度减小;经1560

  7. Wagnerite-Ma5bc, a new polytype of Mg{sub 2}(PO{sub 4})(F,OH), from granulite-facies paragneiss, Larsemann Hills, Prydz Bay, East Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Ren, L. [Inst. of Geology, Chinese Academy of Geological Sciences, Beijing (China); Grew, E.S. [Univ. of Maine, Dept. of Geological Sciences, Maine (United States); Xiong, M.; Ma, Z. [China Univ. of Geosciences, Beijing (China)

    2003-04-01

    Wagnerite-Ma5bc, a new polytype, occurs in paragneiss associated with banded cordierite-prismatine gneiss in the Larsemann Hills. East Antarctica. It forms anhedral to euhedral grains mostly 0.5-2 mm across, some with a tabular habit. Textures are consistent with a primary assemblage wagnerite-Ma5bc + plagioclase + apatite + magnetite + ilmenite-hematite that crystallized under granulite-facies conditions (750 - {approx}860{sup o}C, 6-7 kbar). Also present are biotite, quartz, K-feldspar, minerals of the monazite and xenotime groups, corundum, hercynite, and sulfide. Electron-microprobe analyses give P{sub 2}O{sub 5} 41.39, SiO{sub 2} 0.06, TiO{sub 2} 0.88, FeO 4.16, MnO 0.09, MgO 44.54, CaO 0.09, F 6.87, H{sub 2}O (calculated for OH + F = 1) 2.04, O=F -2.89, total 97.22 wt%, corresponding to (Mg{sub 1.88}Fe{sub 0.10}Ti{sub 0.02})(P{sub 0.99}O{sub 4})(F{sub 0.6}){sub 1}OH{sub 0.39}). The space group is Ia. Lattice parameters: a 9.645(2), b 31.659(6), c 11.914(2) A, {beta} 108.26(3){sup o}, V 3455(1) A{sup 3} for Z = 40. The crystal structure has been solved by direct methods and refined to R{sub 1} = 0.0413 for the independent 4521 reflections [I > 2{sigma}(l)] using MoK{alpha} radiation. The primary difference between the wagnerite-Ma5bc and wagnerite-Ma2bc (e.g., type locality) is ordering of the (F,OH) positions. F can occupy one of two positions, resulting in two distinct configurations along the a direction. In magniotriplite, the sequence of configurations in the b direction is disordered, whereas in wagnerite-Ma2bc, the sequence is ordered 121212... and in wagnerite-Ma5bc, 12112... Magniotriplite and the wagnerite polytypes do not overlap in composition: minerals richer in Fe and Mn (average ionic radius {>=}0.76 A) crystallize as the disordered minerals in the triplite group, whereas highly magnesian minerals (average ionic radius {<=}0.73 A or {>=}86% of the Mg end member) crystallize as the ordered polytypes of wagnerite. Magniotriplite formed at moderate

  8. Raman spectroscopic study of alunite occurrences in the Sapes porphyry-epithermal deposit, NE Greece

    Science.gov (United States)

    Papazotos, Panagiotis; Perraki, Maria; Voudouris, Panagiotis; Skliros, Vasilios

    2017-04-01

    as to identify the differences and similarities in their structural and chemical features reflecting the geological, geochemical and depositional environment. References Breitinger D., Krieglstein R., Bogner A., Schwab R., Pimpl T, Mohr, J., Schukow H. (1997). Vibrational spectra of synthetic minerals of the alunite and crandallite type. Journal of Molecular Structure, 408/409, 287-290 Frost R., Wills R., Weier M., Maertens W., Kloprogge J. (2006). A Raman spectroscopic study of alunites. Journal of Molecular Structure, 785, 123-132. Maubec N., Lahfid A., Lerouge C., Wille G., Michel K. (2012). Characterization of alunite supergroup minerals by Raman spectroscopy. Spectrochim. Acta A, 96, 925-939. Voudouris P. (2014). Hydrothermal corundum, topaz, diaspore and alunite supergroup minerals in the advanced argillic alteration lithocap of the Kassiteres-Sapes porphyry-epithermal system, western Thrace, Greece. Neues Jahrbuch für Mineralogie, 191/2, 117-136.

  9. Theoretical modeling of zircon's crystal morphology according to data of atomistic calculations

    Science.gov (United States)

    Gromalova, Natalia; Nikishaeva, Nadezhda; Eremin, Nikolay

    2017-04-01

    potential. The other sets of interatomic potentials («Zircon 2, Zircon 3») differed from the first in that parameters was found with the help of quantum-chemical calculations of the structure «ab initio».The surface energies for different faces of zircon were calculated using Metadise code (Watson et al., 1996) at P4-3000 personal computer with Windows XP operating system. The computation time for one simple form was from 30 minutes to 12 hours. Calculations have shown that depending on the chosen model the surface energy of zircons faces several changes. For example, Esurf of face (331) obtained using models of potentials «Zircon 2», «Zircon 3» sufficiently similar (2.82 and 3.01 J/mol2 respectively). Meaning of Esurf of this face, calculated on the basis of set «Zircon 1» significantly lower (1,54 J/mol2). With regard to the face (100), it has low surface energies when selecting all three models, with a minimum value (1,14 J/mol2) in the model «Zircon 1». References: Gromalova N.A., Eremin N.N., Urusov V.S. Atomistic computer modeling of the crystal-morpology of corundum group minerals // Zapiski RMO. V. 144. №4. 2015. p. 84-92. Watson G.W., Kelsey E.T., de Leeuw N.H., Harris D.J, Parker S.C. Atomistic simulation of dislocations, surfaces and interfaces in MgO. Journal of the Chemical Society Faraday Transactions. 1996. V.92 P. 433-438.

  10. Origin and significance of the 2011 El Hierro xeno-pumice

    Science.gov (United States)

    Zaczek-Pedroza, Kirsten; Troll, Valentin R.; Deegan, Frances M.; Meade, Fiona C.; Burchardt, Steffi; Carracedo, Juan C.; Klügel, Andreas; Harris, Chris; Wiesmaier, Sebastian; Berg, Sylvia E.; Barker, Abigail K.

    2014-05-01

    samples to be Si-oversaturated, partly corundum-normative, but with not magmatic mineral components in the norm. 5) Trace element concentrations of xeno-pumice are unlike any magmatic rocks from El Hierro and La Palma, but similar to known sedimentary rocks from the region. 6) A distinct Eu anomaly, typical for continentally derived sediment, is present in xeno-pumice but absent in El Hierro and La Palma magmatic rocks. Lastly, 7) Oxygen isotope values range from 9.1 to 11.6 o (n=6), which are elevated with respect to magmatic rocks from the Canaries (5.2 to ~ 7 o), but are characteristic for sediment derived from a mixture of continental (S- and I-type) granite sources. The combined datasets allow for a more thorough discussion on the origin of El Hierro xeno-pumice and we conclude that xeno-pumice is compositionally akin to sedimentary rocks from the region, but strikingly dissimilar to magmatic rocks from El Hierro and La Palma. We suggest a dominantly sedimentary origin for xeno-pumice. Xeno-pumice is therefore not an indicator for explosive felsic magma within volcanic plumbing systems, but a reflection of magma-crust interaction during ascent and emplacement. The occurrence of similar frothy sedimentary xenoliths in recent and historical eruptions on Lanzarote, Gran Canaria, Tenerife and La Palma make a case for xeno-pumice being a common phenomenon in the region.

  11. Preparation of Al-Al2O3 Composite Sliding Gate by Transient Plastic Phase Process%用塑性金属工艺制备Al-Al2O3复合无碳滑板

    Institute of Scientific and Technical Information of China (English)

    李勇; 张军杰; 李进宝; 薛文东; 陈俊红; 孙加林

    2013-01-01

    以板状刚玉、电熔白刚玉、α-Al2O3微粉、金属Al粉为原料、热固性酚醛树脂为结合剂,利用过渡塑性相工艺在埋炭条件下于1 450℃保温6h烧成制备Al-Al2O3复合无碳滑板.当Al含量为9%(质量分数)时,复合滑板的综合物理性能最佳,其显气孔率为4.1%,体积密度为3.27 g/cm3,常温耐压强度为410MPa,1 400℃保温30min后复合滑板的高温抗折强度为60.7 MPa.通过设计化学反应并控制烧结气氛制备的复合滑板中,部分过渡相Al与材料中的C和气氛中的CO、N2反应生成Al4C3和AlN复合相,AhC3进一步与材料中的Al2O3反应生成Al4O4C、Al2OC增强相,剩余的游离态Al仍为金属塑性相.Al-Al2O3复合滑板化学稳定性高、氧含量低,不含碳且不易水化,用于洁净钢时不会产生二次C、O、H及其它杂质的污染.%A high performance A1-A12O3 metal and oxide composite carbon-free sliding gate was prepared under carbon burial at 1450 ℃ for 6 h via a transient plastic phase process using tabular alumina, fused white corundum, Α-A12O3 fine powder and a fine Al powder as raw materials and phenolic resin as binder. The composite samples with Al content of 9% in mass had the optimum comprehensive physical properties. The apparent porosity, bulk density, cold crushing strength and hot bending strength of the samples heated at 1400 ℃ for 30min were 4.1%, 3.27 g/cm3, 410 MPa and 60.7 MPa, respectively. The performance of the composite sliding gate prepared via the control of chemical reaction and calcining atmosphere was superior. Al reacted with both C and CO mixed with N2 could form Al4C3 and AJN, and Al4C3 continuously reacted with Al2O3 to form Al4O4C, A12OC reinforcement phase and the remaining free Al as a metal plastic phase. The A1-A12O3 composite sliding gate had a high chemical stability and a low oxygen potentiality, without any free C and hydrated Al4C3, which could be applied to clean steel production process, and the secondary C

  12. Hyper-Raman spectroscopy of Earth related materials

    Science.gov (United States)

    Hellwig, H.

    2004-12-01

    conventional Raman and hyper-Raman are complimentary. In many cases the combined information of both techniques can reveal all the vibrational information of a material. This information can be used to calculate thermodynamic properties, to identify mineral phases ('finger-printing'), or to investigate the dynamics related to phase transitions ('soft-modes'). First results on planetary materials will be presented, including MgO and stichovite. Corundum as another possible high pressure transmitting material is characterized as well. Further measurements are underway, including MgSiO3 and CaSiO3 perovskite. [1] A. M. Hofmeister, in: Infrared Spectroscopy in Geochemistry, Exploration Geochemistry, and Remote Sensing, Vol. 33 (ed. P. K. King, M. S. Ramsey, and G. A. Swayze), Mineralogical Society of Canada (2004) [2] P. F. McMillan, R. J. Hemley, and P. Gillet, in : Mineral Spectroscopy: A Tribute to Roger G. Burns, Vol. 5 (ed. D. Dyar, C. McCammon, and M. W. Schaefer), The Geochemical Society Special Publication (1996). [3] H. Vogt, in: Topics in Applied Physics, Vol. 50, Light scattering in solids II (ed. M. Cardonna and G. Guentherodt), Springer-Verlag, Heidelberg, New York (1982).

  13. Fractional ultrabasic-basic evolution of upper-mantle magmatism: Evidence from xenoliths in kimberlites, inclusions in diamonds and experiments

    Science.gov (United States)

    Litvin, Yuriy; Kuzyura, Anastasia

    2017-04-01

    Ultrabasic peridotites and pyroxenites together with basic eclogites are the upper-mantle in situ rocks among xenoliths in kimberlites. Occasionally their diamond-bearing varieties have revealed within the xenoliths. Therewith the compositions of rock-forming minerals demonstrate features characteristic for primary diamond-included minerals of peridotite and eclogite parageneses (the elevated contents of Cr-component in peridotitic garnets and Na-jadeitic component in eclogitic clinopyroxenes). High-pressure experimental study of melting equilibria on the multicomponent peridotie-pyroxenite system olivine Ol - orthopyroxene Opx - clinopyroxene Cpx - garnet Grt showed that Opx disappeared in the peritectic reaction Opx+L→Cpx (Litvin, 1991). As a result, the invariant peritectic equilibrium Ol+Opx+Cpx+Grt+L of the ultrabasic system was found to transform into the univariant cotectic assemblage Ol+Cpx+Grt+L. Further experimental investigation showed that olivine reacts with jadeitic component (Jd) with formation of garnet at higher 4.5 GPa (Gasparik, Litvin, 1997). Study of melting relations in the multicomponent system Ol - Cpx - Jd permits to discover the peritectic point Ol+Omph+Grt+L (where Omph - omphacitic clinopyroxene) at concentration 3-4 wt.% Jd-component in the system. The reactionary loss of Opx and Ol makes it possible to transform the 4-phase garnet lherzolite ultrabasic association into the bimineral eclogite assemblage. The regime of fractional Ol, Cpx and Grt crystallization must be accompanied by increasing content of jadeitic component in residual melts that causes the complete "garnetization of olivine". In the subsequent evolution, the melts would have to fractionate for basic SiO2-saturated compositions responsible for petrogenesis of eclogite varieties marked with accessory corundum Crn, kyanite Ky and coesite Coe. Both the peritectic mechanisms occur in regime of fractional crystallization. The sequence of the upper-mantle fractional

  14. [The preparation and characterization of fine dusts carried out in the Clinica del Lavoro di Milano in support of experimental studies].

    Science.gov (United States)

    Occella, E; Maddalon, G; Peruzzo, G F; Foà, V

    1999-01-01

    This paper aims to illustrate the conditions selected at the Clinica del Lavoro of the University of Milan to prepare and analyze a large number of fine dust samples produced over a period of about 50 years, that were initially used for studies within the Clinic performed in its own facilities, and since 1956 were sent to other Italian and overseas laboratories (Luxembourg, UK, Germany, Norway, Sweden, South Korea, USA). The total quantity of material distributed (with maximum size 7-10 microns) was about 2 kg and consisted of the following mineral and artificial compounds: quartz, HF-treated quartz, tridymite, HF-treated tridymite, cristobalite, chromite, anthracite, quartz sand for foundry moulds, sand from the Lybian desert, vitreous silica, pumice, cement, as well small quantities of metallic oxides, organic resins, chrysotile, crocidolite, fibres (vitreous, cotton and polyamidic). About half of the entire quantity of dusts produced consisted of partially HF-treated tridymite. Initially, research on the etiology of silicosis used quartz dust samples, simply sieved or ventilated (consisting of classes finer than 0.04 mm, containing a 15-20% respirable fraction). From 1956 to 1960 the dusts were produced by manual grinding in an agate mortar, below about 10 microns, starting from quartz from Quincinetto (near Ivrea, Province of Turin), containing about 99.5% quartz: particle size and composition were checked using an optical-petrographic technique, with identification of the free and total silica content. Subsequently, the dusts used for biological research were obtained by grinding coarse material with a cast iron pestle and planetary mills, agate and corundum jars. The grinding products were sized by means of centrifugal classification, using the selector developed by N. Zurlo, ensuring control of dust size both optically and by means of wet levigators and hydraulic classifiers (in cooperation with the Institute of Mines of Turin Polytechnic School). After 1990

  15. Brittle-ductile deformation effects on zircon crystal-chemistry and U-Pb ages: an example from the Finero Mafic Complex (Ivrea-Verbano Zone, western Alps)

    Science.gov (United States)

    Langone, Antonio; José Alberto, Padrón-Navarta; Zanetti, Alberto; Mazzucchelli, Maurizio; Tiepolo, Massimo; Giovanardi, Tommaso; Bonazzi, Mattia

    2016-04-01

    A detailed structural, geochemical and geochronological survey was performed on zircon grains from a leucocratic dioritic dyke discordantly intruded within meta-diorites/gabbros forming the External Gabbro unit of the Finero Mafic Complex. This latter is nowadays exposed as part of a near complete crustal section spanning from mantle rocks to upper crustal metasediments (Val Cannobina, Ivrea-Verbano Zone, Italy). The leucocratic dyke consists mainly of plagioclase (An18-24Ab79-82Or0.3-0.7) with subordinate amounts of biotite, spinel, zircon and corundum. Both the leucocratic dyke and the surrounding meta-diorites show evidence of ductile deformation occurred under amphibolite-facies conditions. Zircon grains (up to 2 mm in length) occur mainly as euhedral grains surrounded by fine grained plagioclase-dominated matrix and pressure shadows, typically filled by oxides. Fractures and cracks within zircon are common and can be associated with grain displacement or they can be filled by secondary minerals (oxides and chlorite). Cathodoluminescence (CL) images show that zircon grains have internal features typical of magmatic growth, but with local disturbances. However EBSD maps on two selected zircon grains revealed a profuse mosaic texture resulting in an internal misorientation of ca. 10o. The majority of the domains of the mosaic texture are related to parting and fractures, but some domains show no clear relation with brittle features. Rotation angles related to the mosaic texture are not crystallographically controlled. In addition, one of the analysed zircons shows clear evidence of plastic deformation at one of its corners due to indentation. Plastic deformation results in gradual misorientations of up to 12o, which are crystallographically controlled. Trace elements and U-Pb analyses were carried out by LA-ICP-MS directly on petrographic thin sections and designed to cover the entire exposed surface of selected grains. Such investigations revealed a strong

  16. Osbornite (TiN) and boron nitride nanoinclusions in coesite from Tibet: a first record of nitrogen in a terrestrial ultrahigh pressure environment

    Science.gov (United States)

    Dobrzhinetskaya, L.; Wirth, R.; Yang, J.; Hutcheon, I.; Weber, P.; Green, H. W.

    2007-12-01

    We report here discovery of nitrides in podiform chromitite of the Luobusa ophiolite, Tibet, representing the mantle section of a ¡°fossil¡± fragment of oceanic crust which marks the Early Tertiary (~65Ma) suture zone between Asia and India. Nanometric crystals of TiN and BN are included in coesite which, together with kyanite, TiO2-II and several other still unidentified phases rim a FeTi-alloy pellet; this sample, together with an OsIr alloy pellet containing microdiamond were extracted from the massive chromitite (Yang et al., Geology, 2007). Both TiN and BN form bright-grey-contrast particles in secondary-electron scanning electron microscope imaging. Several focused ion beam foils were prepared for a transmission electron microscope (TEM) and a nano secondary ion mass spectrometry (nanoSIMS) studies. Because energy dispersive X-ray spectra (EDS) of boron and nitrogen K-lines have overlaps with each other and with Ti L-lines, we have used electron energy loss spectroscopy (EELS) in TEM to determine the presence of boron and nitrogen K-edges and to separate them from Ti L-lines. Electron diffraction patterns identify the cubic boron nitride (c-BN) structure. TiN is stoichiometric (Ti=77.20wt%; N=22.80wt%) and is also cubic. Both phases contain trace carbon. Osbornite, is usually found only in meteorites, although it also has been reported as inclusions in carbonado diamonds and as inclusion in a corundum grain from lamproitic breccia in the Asov block, Eastern-European platform, Ukraine. Until now, boron nitride was known only as an industrial compound, with both hexagonal and cubic structures. With the nanoSIMS Cameca-50 using the Cs beam we have measured nitrogen and carbon isotopes in both the TiN and c-BN inclusions: δ 15N= +(6-10) ‰ and δ 13C= (+1) ¨C (-10) ‰. The results show that both minerals are characterized by δ 15N similar to crustal rocks involved in the subduction process and their δ 13C values suggest mixture of heavy (mantle) and

  17. Hematite solubility in NaCl- and CaSiO3-bearing aqueous fluids at 10 kbar and 800 C

    Science.gov (United States)

    Wykes, J. L.; Manning, C. E.

    2005-12-01

    ~0.0105 molal total Fe at 72 wt% NaCl. The solubility enhancement of approximately an order of magnitude is comparable to the enhancement seen for wollastonite and corundum following the addition of NaCl. Experiments to determine the effect of hematite solubility in pure H2O as a function of fO2 are ongoing. Additional experiments were performed wollastonite undersaturated H2O-NaCl-CaSiO3 fluids. At a fixed NaCl mole fraction of 0.1, increasing CaSiO3 content of the fluid results in an increase in hematite solubility. At 0.089 molal CaSiO3, fractionally below andradite saturation, hematite solubility is 0.01 molal total Fe, which is approximately double that in the CaSiO3-free system (0.005 molal). This enhancement in solubility could either be due to an increase in solution pH or the formation of silicate complexes in solution, presumably an andradite-like molecule. Given the ubiquity of garnets in eclogite facies rocks, fluids equilibrated with andradite-component-bearing garnets represent a more realistic analogue of ferric iron-bearing fluids than those equilibrated with hematite alone. The important roles of pH and silicate complexing indicates that experimental characterization of the ferrous/ferric ratio of slab fluids should concentrate on complex mineral assemblages (eg. cpx-garnet) rather than single mineral systems.

  18. Effects of α-Al2 O3 and SiO2 composite micropowders on properties of self-flowing andalusite castables%α-Al2O3微粉和SiO2微粉复合引入对红柱石质自流浇注料性能的影响

    Institute of Scientific and Technical Information of China (English)

    闫光辉; 刘百宽; 尹洪峰; 李君霞; 王文学

    2014-01-01

    采用特级高铝矾土熟料、红柱石、SiO2微粉及α-Al2 O3微粉为主要原料,以Secar71水泥为结合剂,固定骨料与细粉质量比为6535,且固定粉料中SiO2微粉与α-Al2 O3微粉的总加入量(w)为8%,研究了仅改变两种微粉的加入比例(α-Al2O3微粉的加入量(w)分别为8%、6%、4%、2%、0,SiO2微粉相应为0、2%、4%、6%、8%)对试样的流动性、高温强度、物相组成和显微结构的影响。结果表明:当α-Al2 O3微粉、SiO2微粉加入量(w)各为4%时,其流动性最佳,此时体系在高温下生成了大量的一次莫来石相,针状莫来石晶体穿插在刚玉骨架之间,使材料的常温抗折强度以及抗热震性最优。%The specimens were prepared using special grade bauxite clinker,andalusite,SiO2 micropowder and α-Al2O3 micropowder as main starting materials and Secar71 cement as binder.The mass ratio of ag-gregate to fines was 65 35 and the total addition of SiO2 micropowder and α-Al2 O3 micropowder was fixed at 8% (in mass,the same hereinafter),addition of α-Al2 O3 micropowder was 8%,6%,4%,2% and 0,re-spectively.Effects of adjusting additions of the two micropowders on the flowability,hot strength,phase composition and microstructure were researched.The results show that:when the additions of SiO2 mi-cropowder and α-Al2 O3 micropowder are both 4%,the specimen performs the best flowability;a lot of nee-dle like mullite crystals form at high temperatures,crossing into the corundum skeleton,endowing the mate-rials with the optimal cold modulus of rupture and thermal shock resistance.

  19. 低品位菱镁矿与工业铝灰制备镁铝尖晶石%Preparation of magnesium aluminate spinel from low-grade magnesite and industrial alumina ash

    Institute of Scientific and Technical Information of China (English)

    钟鑫宇; 罗旭东; 张国栋; 曲殿利; 王闯

    2012-01-01

    Magnesium aluminate spinel material was prepared by solid reaction with low-grade magnesite and industrial alumina ash as raw materials.The effect of sintering temperature on composition and microstructure of industrial alumina ash was discussed firstly.For further study,the effects of sintering temperature on composition,crystal cell parameters,and microstructure of magnesium aluminate spinel material were studied.Crystalline phases and microstructure of the sintered sample were determined by XRD and SEM respectively .The lattice parameters of main crystalline phase and crystallinity of the samples sintered at different temperatures were calculated and compared by X'Pert plus software.Results showed that lattice parameters of hexagonal corundum that is main crystalline phase in the industrial alumina ash presented a nonisotropic variation tendency with the increase of sintering temperature.Magnesium aluminate spinel material could be prepared by solid reaction of low-grade magnesite and industrial alumina ash at 1 400℃.The cell parameter of main crystalline phase of the magnesium aluminate spinel material prepared at this temperature reached maximum, and relatively well-distributed grains in the material and relatively compact microstructure were both observed.%以低品位菱镁矿与工业铝灰为原料制备镁铝尖晶石材料.分析讨论了不同煅烧温度对工业铝灰材料组成与微观结构的影响,并进一步研究了煅烧温度对制备镁铝尖晶石材料的组成、镁铝尖晶石相晶胞常数及材料微观结构的影响.用X射线衍射(XRD)和扫描电镜(SEM)对煅烧后试样的物相和显微结构进行研究.利用X′ pert plus软件对试样中主晶相的品格常数进行计算,比较不同温度煅烧试样的相对结晶度.结果表明:随着工业铝灰煅烧温度的升高1材料中主晶相六方晶型的刚玉相晶胞常数呈现各向异性的变化趋势.低品位菱镁矿与工业铝灰经1 400℃高温煅烧

  20. Effect of tin oxide on properties of magnesium aluminate spinel castables%氧化锡加入量对镁铝尖晶石浇注料性能的影响

    Institute of Scientific and Technical Information of China (English)

    员文杰; 商恒; 朱青友; 邓承继; 祝洪喜

    2015-01-01

    Effects of tin oxide additions (5%,7.5% and 10% by mass)on the properties and microstructure of magnesium aluminate spinel castables adopting tabular corundum T60 or reactive alumina CL370 as the matrix were researched in order to improve the properties of magnesium aluminate spinel castables.The results show that with the tin oxide addition increasing,the apparent porosity and linear change on heating of castables made from tabular alumina decrease,and the cold modulus of rupture increases;the apparent porosity and linear change on heating of castables made from reactive alumina with 7.5% SnO2 addition is the lowest,and the cold modulus of rupture reaches the maximum value;the main reaction products include Mg2 SnO4 ,CaSnO3 and Ca2 SnO4 in castables after calcined at 1 450 ℃ for 5 h;tin oxide addition can strengthen the bonding between the components of castables by in-situ reactions,and promote the sintering.%为了提高镁铝尖晶石浇注料的性能,研究了氧化锡加入量(质量分数分别为5%、7.5%和10%)对基质中分别采用板状刚玉 T60和活性氧化铝 CL370的镁铝尖晶石浇注料性能和显微结构的影响。结果表明:在镁铝尖晶石浇注料中添加氧化锡,随着氧化锡添加量的增加,采用板状刚玉试样的显气孔率和烧后线变化率减小,常温抗折强度增大;而采用活性氧化铝试样则以氧化锡添加量为7.5%(w)时显气孔率和烧后线变化率最小,常温抗折强度最大。添加氧化锡的镁铝尖晶石浇注料在1450℃煅烧5 h 后均含有 Mg2 SnO4、CaSnO3和Ca2 SnO4。可见,氧化锡在高温下与镁砂和铝酸钙水泥发生一系列原位反应提高组分之间的结合,并促进浇注料的烧结。

  1. Characterization and modes of occurrence of elements in feed coal and coal combustion products from a power plant utilizing low-sulfur coal from the Powder River Basin, Wyoming

    Science.gov (United States)

    Brownfield, Michael E.; Cathcart, James D.; Affolter, Ronald H.; Brownfield, Isabelle K.; Rice, Cynthia A.; O'Connor, Joseph T.; Zielinski, Robert A.; Bullock, John H.; Hower, James C.; Meeker, Gregory P.

    2005-01-01

    The U.S. Geological Survey and the University of Kentucky Center for Applied Energy Research are collaborating with an Indiana utility company to determine the physical and chemical properties of feed coal and coal combustion products from a coal-fired power plant. The Indiana power plant utilizes a low-sulfur (0.23 to 0.47 weight percent S) and lowash (4.9 to 6.3 weight percent ash) subbituminous coal from the Wyodak-Anderson coal zone in the Tongue River Member of the Paleocene Fort Union Formation, Powder River Basin, Wyoming. Based on scanning electron microscope and X-ray diffraction analyses of feed coal samples, two mineral suites were identified: (1) a primary or detrital suite consisting of quartz (including beta-form grains), biotite, feldspar, and minor zircon; and (2) a secondary authigenic mineral suite containing alumino-phosphates (crandallite and gorceixite), kaolinite, carbonates (calcite and dolomite), quartz, anatase, barite, and pyrite. The primary mineral suite is interpreted, in part, to be of volcanic origin, whereas the authigenic mineral suite is interpreted, in part, to be the result of the alteration of the volcanic minerals. The mineral suites have contributed to the higher amounts of barium, calcium, magnesium, phosphorus, sodium, strontium, and titanium in the Powder River Basin feed coals in comparison to eastern coals. X-ray diffraction analysis indicates that (1) fly ash is mostly aluminate glass, perovskite, lime, gehlenite, quartz, and phosphates with minor amounts of periclase, anhydrite, hematite, and spinel group minerals; and (2) bottom ash is predominantly quartz, plagioclase (albite and anorthite), pyroxene (augite and fassaite), rhodonite, and akermanite, and spinel group minerals. Microprobe and scanning electron microscope analyses of fly ash samples revealed quartz, zircon, and monazite, euhedral laths of corundum with merrillite, hematite, dendritic spinels/ferrites, wollastonite, and periclase. The abundant calcium and

  2. Effects of Temperature, Oxygen Partial Pressure, and Materials Selection on Slag Infiltration into Porous Refractories for Entrained-Flow Gasifiers

    Science.gov (United States)

    Kaneko, Tetsuya Kenneth

    partial pressure of the operating atmosphere regulates the penetration of slag into refractory. The viscosity of the slag, which dictates its penetration rate, is influenced by the oxidation state of the Fe cation. Slag penetrations are shallower in oxidizing conditions than they are in reducing conditions because the iron-oxide from the slag solutions into the corundum-structured refractory and the slag is depleted of iron-oxide, increasing the viscosity of slags. Equally, the chemistries of both the refractory and slag materials dictate the course of penetration. Cr2O3-Al2O3 refractory limits mixed feedstock slag penetration through formation of a chromium spinel layer that functions as a physical obstacle against fluid flow. Al2O 3-SiO2 refractory limits eastern coal feedstock slag penetration as a result of refractory dissolution of SiO2, which increases the viscosity of slags. A physical model, which considers unidirectional fluid flow of slag through each pore of the porous microstructure of the refractory, sufficiently approximates the penetration depth of the slag into the refractory. Agreement between experiments and the physical model demonstrates that the slag is driven into the refractory by capillary pressure. Since the viscosity of the slag continuously changes as the slag travels through the inherent temperature gradient of the refractory lining, the model incorporates dynamic viscosities that are dependent on both temperature and composition to project depths that are unique to the experimental parameters. The significantly different length scales of the radial and penetration directions of the pores allows for the application of a lubrication approximation onto the momentum equation. This process produces an analytical solution that effectively envelopes the variable viscosity into a single term.

  3. Geochemistry of Coesite-Bearing Pyrope Quartzites and Related Rocks From the Dora Maira Massif, Western Alps: New Results and the Enigma of the Jadeite-Rocks

    Science.gov (United States)

    Schertl, H.

    2008-12-01

    In contrast to the extensive petrological and geochronological work on the various ultrahigh-pressure (UHP) metamorphic rocks of the coesite-bearing unit of the Dora Maira Massif, there is still a deficiency of basic geochemical data. A complete suite of geochemical data for pyrope quartzites, various intercalations of phengite-schists and jadeite-bearing rocks, as well as country rock gneisses from different localities within the southern Dora Maira Massiv is now available, which was studied in detail in order to establish the nature of the different protoliths and their primary relationships (Schertl and Schreyer, 2008; see also Chopin, 1984 and Compagnoni and Hirajima, 2001). Typically, the pyrope quartzites are high in Mg and strongly depleted in Na, Ca, Fe, Cu, P, Rb, Ba, Sr against their country rock gneisses which essentially exhibit a granitic bulk composition. The country rocks have a peraluminous chemistry; they generally are corundum normative and best attributed to S-type granites. Trace element contents of phengite-schist inclusions in pyrope quartzite confirm their close relationship to the granitic country rocks. Internal variations of Na, Ca versus K, Mg are matched by Rb, Ba and Sr, which is in line with some phengite-schists to contain higher amounts of phengite or higher amounts of jadeite-pseudomorphs, respectively. The origin of the jadeite-rich rocks is still a matter of debate. Jadeite-bearing layers and jadeite quartzite forming conformable bands and boudins within pyrope quartzite differ generally by their lower contents in K, Mg, Rb and higher contents in Na, Fe, Ca, Mn, P and Zn. Earlier suggestions that these layers represent former melts seem unlikely in the view of their almost constant mass behaviour for SiO2 and Al2O3 relative to the surrounding pyrope quartzites. The present study indicates that the pyrope quartzites were formed metasomatically whereas an evaporitic nature of the protolith can be ruled out. Discrimination plots

  4. Ductile-brittle deformation effects on crystal-chemistry and U-Pb ages of magmatic and metasomatic zircons from a dyke of the Finero Mafic Complex (Ivrea-Verbano Zone, Italian Alps)

    Science.gov (United States)

    Langone, Antonio; Padrón-Navarta José, Alberto; Ji, Wei-Qiang; Zanetti, Alberto; Mazzucchelli, Maurizio; Tiepolo, Massimo; Giovanardi, Tommaso; Bonazzi, Mattia

    2017-07-01

    A detailed microstructural, geochemical and geochronological study was performed on zircon grains from plagioclase-rich dioritic dykes discordantly intruded within meta-diorites/gabbros forming the External Gabbro unit of the Finero Mafic Complex (Italian Alps). This unit is exposed as part of a near complete crustal section spanning from mantle rocks to upper crustal metasediments (Val Cannobina, Ivrea-Verbano Zone, Italy). The leucocratic dykes consist mainly of plagioclase (An18-24Ab79-82Or0.3-0.7) with subordinate amounts of biotite and spinel defining melanocratic layers. Zircon and corundum are common accessory phases. Both the dykes and the surrounding meta-diorites/gabbros show evidence of ductile deformation under amphibolite-facies conditions. Zircon grains/fragments (up to 2 mm in length) occur as porphyroclasts surrounded by fine-grained plagioclase within the leucocratic domains and may occur within the melanocratic layers completely or partially surrounded by biotite and spinels. Fractures are common within zircon, define networks and have associated displacements occasionally and/or they can be filled by secondary minerals. Cathodoluminescence (CL) images reveal that zircon grains from the leucocratic layers show relicts of primary magmatic (i.e. oscillatory and or sector) zoning generally related with the crystal shapes or crystallographic orientation, whereas those from the melanocratic domains do not. In both cases, zircon shows secondary CL features, i.e. mosaic-like textures, due to deformation. EBSD maps confirmed a profuse mosaic texture, resulting in an internal misorientation of ca. 10°, generally associated with fractures. Locally, zircon shows clear evidence of crystal-plastic deformation at the edges, with a gradual misorientations of up to 12°, suggesting an origin prior fragmentation. Trace elements and U-Pb analyses were carried out by LA-ICP-MS directly on petrographic thin sections. Such in situ investigations revealed a strong

  5. Study of the Flow and Heat Transfer Characters in the Tube Sheet Cooling Chamber of a Fire Tube Waste Heat Boiler%火管式余热锅炉管板冷却室内流动传热研究

    Institute of Scientific and Technical Information of China (English)

    李超; 黄波; 代正华; 杨骥; 于广锁; 王辅臣

    2015-01-01

    cooling of syngas tube and generating more uniform distributions of velocity and temperature. To the 2 inlets type, the optimized mass flow of cooling water is 200t/h. Furthermore, with the addition of corundum tube in entrance of the syngas, the syngas tube can be efficiently protected by reducing the hotspot temperature by 106K.

  6. New volcanogenic-eruptive genetic type of diamond occurrence (based on studying the 2012-2013 Fissure Tolbachik Eruption in Kamchatka)

    Science.gov (United States)

    Karpov, Gennady; Anikin, Leonid; Filatov, Stanislav; Silaev, Valery; Petrovsky, Vitaly; Zolotarev, Andrey; Dunin-Barkovsky, Romuald; Volynets, Anna

    2014-05-01

    the instance considered. The above can indicate that Tolbachik diamonds were never affected by mantle anneal. Generally, by their spectroscopic properties, Kamchatka diamonds correspond to the Ib-type whose occurrence among natural diamonds does not exceed 2%. Reported are isolated twinned crystals. Tiny grains of blue moissanite, single grains of pink garnet and pink and blue corundum were found within the association accompanying diamonds (commonly in basalt pores). Often found are thin laminae and filaments of native elements (Fe, Al, Cu), blades or lumpy grains of Cu-Sn (Zn) alloy. Tolbachik diamonds bear no evidence of magmatic corrosion. Data obtained allow us to state the discovery of a new genetic type of diamond occurrence that we suggest to call "volcanogenic-eruptive", or Tolbachik type.

  7. Effects of Heterogeneous Adsorption Affinity on Natural Organic Matter (NOM) Transport in Laboratory Sand Columns

    Science.gov (United States)

    McInnis, D. P.; Bolster, D.; Maurice, P. A.

    2012-12-01

    Transport of reactive sorbing solutes through porous media is commonly quantified by implementing an effective retardation coefficient in the advection-dispersion equation (ADE), which describes dispersion in accordance with Fick's law. However, anomalous (non-Fickian) transport behavior can be observed in systems with heterogeneous retardation coefficients (Dentz & Castro, 2009). In such systems, the ADE is unable to reproduce the non-Fickian nature of plume shapes and breakthrough curves, motivating the development and application of alternative solute transport theories, such as the continuous time random walk (CTRW) or multi-rate mass transfer (MRMT). Heterogeneity in retardation coefficients in practice arises from variability in the geochemical properties controlling sorption-desorption kinetics between the solute and mineral surfaces. These distributions have been described in the context of heterogeneity of the porous medium, but to date little attention has been given to the potential role of a geochemically heterogeneous solute. In this work, we consider a system in which anomalous transport arises during the passage of natural organic matter (NOM), a polydisperse mixture of compounds derived from the breakdown of plants and microorganisms in the environment, through homogeneous laboratory sand columns. NOM solutions were passed through columns containing either hematite, corundum, or a naturally-coated quartz sand at a variety of pH and ionic strength conditions. Influent and effluent NOM concentration was measured as UV absorbance at 254 nm. The resulting breakthrough curves are non-Fickian, displaying power-law tailing at late times. Such curves cannot be predicted by the ADE model. Reactivity of NOM components is known to be related to their molecular weight (MW), which tends to be log-normally distributed in aquatic NOM isolates (Cabaniss et al., 2000). Low-MW compounds are more water-soluble, have a higher diffusion coefficient, and due to their

  8. Geochemical characteristics and their implications of peraluminous granite in the Jiama deposit, Tibet%西藏甲玛过铝质花岗岩的地球化学特征及成因意义

    Institute of Scientific and Technical Information of China (English)

    秦志鹏; 汪雄武; 唐菊兴; 唐晓倩; 周云; 彭慧娟

    2011-01-01

    探讨了西藏甲玛中新世花岗斑岩的地球化学特征及意义.通过对岩体(脉)进行的野外地质调查、岩相学研究、全岩地球化学分析及同位素分析,结果表明甲玛花岗斑岩表现过铝质花岗岩的特征,整体表现为:Na2O/K2O1.1,刚玉标准分子(w(C-norm))>1%;轻稀土元素富集,重稀土元素亏损,负Eu、Ce异常不明显,高Sr,低Y、Yb,但Sr/Y值相对较低,不具有埃达克岩的地球化学特征;此外,富集大离子亲石元素,尤其是Rb、Cs、Th、U、K等元素,而高场强元素,尤其是Sc、Ti则强烈亏损;Pb-Sr-Nd同位素均显示其下地壳的物质来源,并受到地幔物质(EMⅡ)的混染.甲玛过铝质花岗斑岩形成于亚洲-印度大陆"后碰撞"造山运动早期阶段的构造活动.%This paper studies the geochemical characteristics and their implications of the Miocene granite porphyry in the Jiama deposit, Tibet. The results are obtained by means of field geological investigations, petrographic study, bulk rock analysis and isotopic analysis. These results indicate that the Jiama granite porphyry has the characteristics of peraluminous granite. Na2O/K2O is less than 1 and A/CNK is more than 1. 1. Corundum standard molecule(w(C-norm)) is more than 1%. Light REE are rich, while heavy REE are scarce. Negative Eu and Ce are extremely inconspicuous. Sr is high, Y and Yb are low, and Sr/Y value is relatively low. It doesnot possess the geochemical characteristics of adakite rock. It is rich in LILE, especially Rb, Cs, Th, U and K, while its HFSE are scarce, especially Sc and Ti. The Pb-Sr-Nd isotopes reveal about the source of materials from the lower crust, which is mixed with the mantle materials (EM Ⅱ ). It is concluded that the Jiama peraluminous granite porphyry is a product of tectonic movements in the early period of the “post-collision” orogenesis of Asia-India Continent.

  9. Composition and Thermal History of the Lower Crust Beneath the Tanzania Craton and the Adjacent Mozambique Belt

    Science.gov (United States)

    Mansur, A. T.; Manya, S.; Rudnick, R. L.

    2006-05-01

    The Tanzanian craton has undergone little deformation since its formation 2.6 Ga ago, but Archaean crust of the adjacent Mozambique Belt (MB) has been reworked by at least two high-grade metamorphic events. An old, thick (~~200-km) lithospheric keel appears to have stabilized the craton during these deformational events. Although a thick keel appears to be absent beneath the MB today, ancient mantle lithosphere is preserved beneath much of the MB and the original thickness of this lithosphere is uncertain. Studies of the present-day lower crust can help to constrain the compositional and thermal evolution of this region. Granulite xenoliths from the Labait volcano (craton margin) are exclusively mafic and are mostly two pyroxene granulites, but also include gt-opx granulites and a gt-cpx-spinel-corundum anorthosite. Most samples also have orthoclase as a major phase. Two-pyroxene thermometry yields temperatures of 710 to 810°C for an estimated lower crustal pressure of 1 GPa; whereas the anorthosite appears to have equilibrated at a somewhat hotter temperature (gt-cpx T = 970°C). All Labait xenoliths exhibit high K2O (0.8 to 2.6 wt., excluding the anorthosite), Ba (530 to 6730 ppm), Sr (440 to 1040 ppm) and Ni contents (100 to 400 ppm) and relatively high Mg# (47 to 63). The combined high Ni, Mg# and alkali and alkaline-earth elements may reflect an unusual igneous protolith (e.g., adakitic magma) or mafic cumulates that have been metasomatically enriched in the lower crust. Granulite xenoliths from Lashaine (MB) are also exclusively mafic and form two groups: 1) anorthositic, high Al2O3 (17 to 23 wt. %) and Mg#, plag-ky-cpx-gt granulites, which are enriched in Sr and have positive Eu anomalies and 2) lower Al2O3 (13 wt. %), two pyroxene ± gt granulites, which are enriched in Ti, K, P and Ni. The latter may be meta-cumulates from alkaline magmas. Temperatures for Lashaine granulites range from 770 to 980°C. Unlike Labait and Lashaine, the Naibor Soito

  10. 高铝粉煤灰中Al2O3与SiO2在碱溶液中的反应行为%Reaction behaviour of Al2O3 and SiO2 in high alumina coal fly ash during alkali hydrothermal process

    Institute of Scientific and Technical Information of China (English)

    蒋周青; 杨静; 马鸿文; 王乐; 马玺

    2015-01-01

    The reaction behaviours of Al2O3 and SiO2 in high alumina coal fly ash under various alkali hydrothermal conditions were studied. The means of XRD, XRF, FTIR and SEM were used to measure the mineral phase and morphology of the solid samples obtained by different alkali hydrothermal treatments as well as the leaching ratio of SiO2 to Al2O3 in alkali solution. The results showed that with the increase of the hydrothermal treating temperature from 75 to 160 °C, phillipsite-Na, zeolite A, zeolite P, and hydroxysodalite were produced sequentially while the mullite and corundum phase still remained. Zeolite P was massively formed at low-alkali concentration and the hydroxysodalite was predominantly obtained at high-alkali concentration. By the dissolution of aluminosilicate glass and the formation of zeolites together, the leaching efficiency of SiO2 can reach 42.13% with the mass ratio of Al2O3/SiO2 up to 2.19:1.%研究高铝粉煤灰中Al2O3与SiO2组分在NaOH碱液中不同水热条件下的反应行为。采用XRD、XRF、SEM、FTIR等测试方法对高铝粉煤灰碱溶液处理前后的物相组成和形貌变化进行表征,得到粉煤灰Al2O3和SiO2组分的溶出率变化规律。结果表明,高铝粉煤灰经75°C到160°C不同温度碱溶液处理后,颗粒表面硅铝玻璃相消失,依次生成钠型沸石、A型沸石、P型沸石及羟基方钠石,所含刚玉及莫来石相未被完全溶解。在低碱浓度溶液中P型沸石为主要生成相,高碱浓度下羟基方钠石为稳定的相。在铝硅玻璃体溶解和沸石相生成两种反应的共同作用下,粉煤灰中SiO2的溶出率可达42.13%,滤渣中Al2O3/SiO2质量比提高到2.19:1.

  11. 中国辽宁金刚石中高硅钙铁榴石(Majorite)等超高压矿物包裹体的发现及地质意义%Discovery and Geological Significance of Majorite Inclusion in Diamond from Liaoning Province, China

    Institute of Scientific and Technical Information of China (English)

    陆琦; 刘惠芳; 肖平; 施倪承; 李国武; 汤中道

    2012-01-01

    The high calcium silicate iron garnet (Majorite) in diamond from Liaoning of China is the inclusion of single crystal fragments with coexistence corundum, titanium carbide, red diamond fragments, per-ovskite and silica inclusions. The composition of the Majorite was displayed ultra-silicon high calcium and magnesium deficiency by electron probe microanalysis and its mineral formula based on 8 analysis points is (Ca2 35Fe0.49Mn0.15Mg0.02)3.01 (Al1.08Fe0.48Si0.44) 2.00(SiO4)3, X-ray diffraction peaks is obtained from single crystal diffractometer demonstrated that the crystal structure of the Majorite is a = l. 195 15(4) nm, and using I> 2Σ(I) ,got R1=0. 077 9,WR2=0. 141 6, Goodness-of-fit(F2) = 1. 382. Micron silica and iron oxide exist in the Majorite inclusion and may be the Sri Lankan quartz and square iron ore. According to Kenneth proposing the calculation formula of pressure, the formation pressure of the Majorite was of 14 GPa and depth of 400 km. The presence of Majorite inclusion as ultra-high pressure mineral in diamond may be exemplified the view of geophysical Tanlu fault cut through the upper mantle into the asthenosphere.%在中国辽宁金刚石中获得的高硅钙铁榴石(Majorite)为一单晶碎片包裹体,与其共存的金刚石包裹体还有刚玉、碳化钛、红色金刚石碎片、钙钛矿、二氧化硅等.通过电子探针成分分析,确定该高硅钙铁榴石(Majorite)成分超硅高钙缺镁,8个分析点平均值计算的矿物分子式为(Ca2.35 Fe049Mn0.15Mg0.02)3.01 (Al1.08 Fe0.48Si0.44)2.00(SiO4)3,根据Kenneth等(2000)提出的计算压力的公式得到该包裹体高硅钙铁榴石(Majorite)形成的压力为14 Gpa,估算形成深度达400 km.用四圆单晶衍射仪测定了该石榴石的晶体结构,α=1.195 15(4) nm,求得了各原子的座标、占位度和各向异性温度因子,用Ⅰ> 2σ(Ⅰ),计算得到R1=0.077 9,WR2 =0.141 6,Goodness-of-fit(F2) =1.382.在该高硅钙铁榴石包裹体中还存在微米级

  12. 玄武岩熔液对耐火材料的侵蚀%Erosion of basalt melt to refractories

    Institute of Scientific and Technical Information of China (English)

    马旭峰; 张涛; 王群伟; 石鹏坤; 吕艳华

    2012-01-01

    in order to get a thorough understanding ot erosion ot Dasait melt to retractones,the erosion experiments of dense chrome oxide brick,dense zircon brick and fused cast zirconia-corundum brick (AZS -33) in basalt melt at 1 500 °C for 72 h were carried out according to ASTM C621-1984(2001) and the mi-crostructure of the eroded specimens was analyzed. The results show that the sequence of erosion resistance to basalt melt from good to poor is dense chrome oxide brick,dense zircon brick,and AZS-33;and the severe spalling occurs in liquid level line of AZS-33. The microstructure analysis shows dense chrome oxide brick has uniform structure and less reaction with basalt melt,and can form a dense spinel layer with the components in basalt slag to prevent the further slag penetration;the surface of dense zircon brick reacts with basalt melt forming a thin de-zirconia layer and glass phase,whose dense and uniform structure also prevents the further slag penetration;AZS-33 has low apparent porosity and good penetration resistance to basalt melt,but much liquid results in poor erosion resistance.%为深入了解玄武岩高温熔体对耐火材料的侵蚀行为,参照ASTM C621-1984(2001)分别对致密氧化铬砖、致密锆英石砖和熔铸锆刚玉砖(AZS-33)进行了1 500℃72 h的玄武岩熔液侵蚀试验,并对侵蚀后试样进行了显微结构对比分析.侵蚀试验结果表明,致密氧化铬砖的抗熔融玄武岩侵蚀性最好,其次是致密锆英石砖,最差的是熔铸AZS-33砖,其在液面线处出现严重剥落现象.显微结构分析表明:致密氧化铬砖结构均匀,与玄武岩熔液反应性小,同时与玄武岩渣中的成分形成尖晶石致密层阻止了渣的进一步渗透;致密锆英石砖表面与玄武岩熔液反应产生很薄的脱锆层和玻璃相,并且其致密均匀的结构也阻止了渣的进一步渗透;熔铸锆刚玉砖的显气孔率虽然很低,对玄武岩熔液有较好的抗渗透性,但其液相量较

  13. 不同碱度渣对铝镁浇注料的侵蚀行为%Corrosion behavior of slags with different basicities to alumina-magnesia castables

    Institute of Scientific and Technical Information of China (English)

    张巧燕; 朱伯铨; 李享成

    2012-01-01

    Alumina-magnesia castable crucible specimens were prepared using tabular corundum (≤ 5 mm) ,fused magnesia powder (≤0.088 mm),fused spinel powder ( ≤0.044 mm) ,and α-AI2O3 micropow-der (d50≤0.7 μm) as main starting materials,batching,mixing,shaping,and drying. Slag resistance was determined by static crucible method at 1 600 ℃ for 3 h adopting two ladle slags with different basicities (3.40 and 1.03). The corrosion and penetration indexes and microstructure characteristics of the specimens after slag resistance test were analyzed to study the corrosion behaviors of the two slags to alumina -magnesia castables. The results show that the corrosion of the low-basicity slag to alumina-magnesia castables is much more serious than that of the high-basicity slag for that their reactions with castables form different products:for the low-basicity slag,the multi-phases coexistence of CA6 and compounds of CaO-AI2O3-SiO2 in the materials together with volume expansion caused by the formation of CA6 intensify the slag corrosion and penetration:for the high-basicity slag,the reaction between slag and castables generates a CA2 dense layer and a large amount of in-situ MA in the interface, reducing the slag corrosion to the materials effectively.%以板状刚玉颗粒(≤5 mm)、电熔镁砂粉(≤0.088 mm)、电熔尖晶石粉(≤0.044 mm)、α-Al2O3微粉(d50≤0.7 μm)为主要原料,经配料、混料、成型、烘干后制备了铝镁质坩埚试样,采用2种不同碱度的钢包渣(碱度分别为3.40和1.03),通过静态坩埚法对铝镁浇注料进行抗渣试验(1600℃3h),分析了抗渣试验后试样的渣蚀指数和显微结构,以研究不同碱度渣对铝镁浇注料试样的侵蚀行为.结果表明,低碱度渣对铝镁浇注料的侵蚀和渗透比高碱度渣严重,这主要是因为不同碱度渣与浇注料反应生成的产物不同.低碱度渣对铝镁浇注料侵蚀时,材料内部CA6和钙铝硅系化合物多相共存的组织以及CA6

  14. Geology and reconnaissance stable isotope study of the Oyu Tolgoi porphyry Cu-Au system, South Gobi, Mongolia

    Science.gov (United States)

    Khashgerel, B.-E.; Rye, R.O.; Hedenquist, J.W.; Kavalieris, I.

    2006-01-01

    The Oyu Tolgoi porphyry Cu-Au system in the South Gobi desert, Mongolia, comprises five deposits that extend over 6 km in a north-northeast-oriented zone. They occur in a middle to late Paleozoic are terrane and are related to Late Devonian quartz monzodiorite intrusions. The Hugo Dummett deposits are the northernmost and deepest, with up to 1,000 m of premineral sedimentary and volcanic cover rock remaining. They are the largest deposits discovered to date and characterized by high-grade copper (>2.5% Cu) and gold (0.5-2 g/t) mineralization associated with intense quartz veining and several phases of quartz monzodiorite intruded into basaltic volcanic host rocks. Sulfide minerals in these deposits are zoned outward from a bornite-dominated core to chalcopyrite, upward to pyrite ?? enargite and covellite at shallower depth. The latter high-sulfidation-state sulfides are hosted by advanced argillic alteration mineral associations. This alteration is restricted mainly to dacitic ash-flow tuff that overlies the basaltic volcanic rock and includes ubiquitous quartz and pyrophyllite, kaolinite, plus late dickite veins, as well as K alunite, Al phosphate-sulfate minerals, zunyite, diaspore, topaz, corundum, and andalusite. A reconnaissance oxygen-hydrogen and sulfur isotope study was undertaken to investigate the origin of several characteristic alteration minerals in the Oyu Tolgoi system, with particular emphasis on the Hugo Dummett deposits. Based on the isotopic composition of O, H, and S (??18O(SO4) = 8.8-20.1???, ??D = -73 to -43???, ??34S = 9.8-17.9???), the alunite formed from condensation of magmatic vapor that ascended to the upper parts of the porphyry hydrothermal system, without involvement of significant amounts of meteoric water. The isotopic data indicate that pyrophyllite (??18O = 6.5-10.9???, ??D = -90 to -106???) formed from a magmatic fluid with a component of meteoric water. Muscovite associated with quartz monzodiorite intrusions occurs in the core

  15. Geochemistry and petrogenesis of Mashhad granitoids: An insight into the geodynamic history of the Paleo-Tethys in northeast of Iran

    Science.gov (United States)

    Mirnejad, H.; Lalonde, A. E.; Obeid, M.; Hassanzadeh, J.

    2013-06-01

    hybridized in the mantle wedge with peridotite melt. The quartz diorite-tonalite-granodiorite stock and granodiorite batholith could be considered as arc-related granitoid intrusions, which were emplaced during the northward subduction of Paleo-Tethys Ocean crust beneath the Turan micro-continent. The monzogranite is strongly peraluminous (Al2O3/(CaO + Na2O + K2O) Mol. = 1.07-1.17), alkali-rich with normative corundum ranging between 1.19% and 2.37%, has high initial 87Sr/86Sr ratios (0.707457-0.709710) and low initial 143Nd/144Nd ratios (0.512042-0.512111) and ɛNd(t) values (- 5.3 to - 6.6) that substantiate with geochemical attributes of S-type granites formed by dehydration-melting of heterogeneous metasedimentary assemblages in thickened lower continental crust. The monzogranite was emplaced as a consequence of high-temperature metamorphism during the final integration of Turan and Iran plates. The ages found in the Mashhad granites show that the subduction of Paleo-Tethys under the Turan plate that led to the generation of arc-related Mashhad granites in late-Triassic, finally ceased due to the collision of Iran and Turan micro-plates in early Jurassic.

  16. Extreme extension across Seram and Ambon, eastern Indonesia: Evidence for Banda slab rollback

    Directory of Open Access Journals (Sweden)

    J. M. Pownall

    2013-04-01

    Full Text Available The island of Seram, which lies in the northern part of the 180°-curved Banda Arc, has previously been interpreted as a fold-and-thrust belt formed during arc-continent collision, which incorporates ophiolites intruded by granites thought to have been produced by anatexis within a metamorphic "sole". However, new geological mapping and a re-examination of the field relations cause us to question this model. We instead propose that there is evidence for recent N–S extension that has caused the high-temperature exhumation of hot mantle peridotites, granites, and granulites (the "Kobipoto Complex" beneath low-angle lithospheric detachment faults. Greenschist- to lower-amphibolite facies metapelites and amphibolites of the Tehoru Formation, which comprise the hanging wall above the detachment faults, were overprinted by sillimanite-grade metamorphism, migmatisation and limited localised diatexis to form the Taunusa Complex. Highly aluminous metapelitic garnet + cordierite + sillimanite + spinel + corundum + quartz granulites exposed in the Kobipoto Mountains (central Seram are intimately associated with the peridotites. Spinel + quartz inclusions in garnet, which indicate that peak metamorphic temperatures for the granulites likely approached 900 °C, confirm that peridotite was juxtaposed against the crust at typical lithospheric mantle temperatures and could not have been part of a cooled ophiolite. Some granulites experienced slight metatexis, but the majority underwent more advanced in situ anatexis to produce widespread granitic diatexites characterised by abundant cordierite and garnet xenocrysts and numerous restitic sillimanite + spinel "clots". These Mio-Pliocene "cordierite granites", which are present throughout Ambon, western Seram, and the Kobipoto Mountains in direct association with peridotites, demonstrate that the extreme extension required to have driven Kobipoto Complex exhumation must have occurred along much of the northern

  17. Origin of pegmatites and fluids at Ponta Negra (RJ, Brazil) during late- to post-collisional stages of the Gondwana Assembly

    Science.gov (United States)

    Bongiolo, Everton Marques; Renac, Christophe; Piza, Patricia d'Almeida de Toledo; Schmitt, Renata da Silva; Mexias, André Sampaio

    2016-01-01

    the pegmatites. A linear trend of decreasing CO2 content and δ13CCO2 is consistent with mixtures between (i) carbon derived from organic matter or volatilization of skarns and (ii) inorganic carbon (carbonate). Based on the data obtained, we propose that the pegmatites of Ponta Negra are close to an LCT-type geochemical signature (highly peraluminous magmas with normative corundum), and originated by partial melting of the metasedimentary Palmital succession at depth, during the waning stages of the Búzios Orogeny. The primary melts of the PNP cross-cut both the Neoproterozoic supracrustals and the Paleoproterozoic orthogneissic basement during its ascent and emplacement at higher crustal levels. Variable melt sources explain the slight differences in geochemical compositions among the studied rocks within the metasedimentary succession, which probably include Mn-bearing exhalites, as well as differentiation processes. The 454 ± 5 Ma U-Pb (zircon) age of the Cajú syenogranite overlaps previous geochronological data of 440 ± 11 Ma obtained on a pegmatite dyke at Ponta Negra, bracketing and extending the time interval for the Gondwana assembly collapse magmatism in the region. The heat that triggered this magmatic event could still be a consequence of the collisional orogeny, increasing contents of heat-producing elements, or, a large intraplate extension that followed the Gondwana amalgamation and initiated the formation of Paleozoic basins.

  18. Comportamiento térmico de los minerales no metálicos de Cayo Guan, Cuba

    Directory of Open Access Journals (Sweden)

    Barba, F.

    2009-06-01

    Full Text Available The present work shows the chemical (ICP-OES, flame emission, physical, mineralogical (DRX and microstructural (SEM+EDX characterization and the evolution with the temperature of clays from the deposit of Cayo Guan, Moa, Cuba to determine its possible applications as a raw ceramic material. The particle size distribution is typically bimodal, separated by a fraction, between 125 and 45 μm, which is always < 10 % in weight. The kaolinite is the majority phase, being its content specially high in one of the samples with a relation SiO2/Al2O3 (1.16 coincident with the theoretical kaolinite (1.17; the rest of the samples show a considerable excess of Al2O3 (gibbsite or gels. This high content of alumina and iron compounds (12-21% wt Fe2O3 as hematites, goethite or gels and low alkali and silica percentages lead to high refractoriness of these clays. This property together with the phases of iron at high temperatures that evolve to spinel FeAl2O4, iron in solid solution in mullite and corundum and mainly magnetite, suggests that it is possible the application of the studied clays in the field of ceramic materials, such as heat accumulators.

    En el macizo de Moa se encuentran lateritas ricas en cobalto y níquel que están siendo explotadas por las compañías mineras debido a su gran interés económico. Pero existen también grandes volúmenes de minerales no metálicos, que no han sido estudiados. En este trabajo se aborda la evolución de las fases a alta temperatura de estos materiales que presentan diferentes relaciones gibsita/caolinita para su posterior aplicación en la industria cerámica. Se ha realizado su caracterización granulométrica, química (ICP-OES, fotometría de llama, mineralógica (DRX y microestructural (MEB-EDS. La caolinita es la fase arcillosa mayoritaria, especialmente en una de las muestras con una relación Si

  19. Physico-chemical transition from peridotite assemblage to the eclogite one (experimental data at 7.0 GPa).

    Science.gov (United States)

    Butvina, Valentina; Litvin, Yurii

    2010-05-01

    this problem. Physico-chemical transition from peridotite assemblage to the eclogite one can be only ensured by the processes of fractional crystallization of mantle magmatic melts. The primary melting and magmatic evolution of mantle garnet lerzolite (or the Ringwood pyrolite) is controlled by a five-phase peritectics 'p' Ol+Opx+Cpx+Grt+L and four cotectic curves conjugated to it (Litvin, 1991). In melting and evolution of melts of both olivine eclogites and coesite and corundum eclogites the corresponding five-phase eutectics are of a dominant importance. A general ridge for all elementary tetrahedrons (simplexes) is a line of compositions diopside-pyrope (clinopyroxene-garnet) which bimineral eclogite assemblages belong to. The internal section En-Di-Cor of the general tetrahendric diagram (symplex complex) separates olivine-saturated and silica-saturated compositions. 'Eclogite' thermal barrier is 'thermal barrier' on (O'Hara, 1968), on the cotectic line Opx+Cpx+Grt+L, connecting 'peridotite' peritectic and 'eclogite' eutectic points. Meanwhile, at equilibrium (and fractional) crystallization of peridotite system in the peritectic point 'p' orthopyroxene vanishes as a result of the peritectic reaction 'orthopyroxene + melt - clinopyroxene' (Davis, 1963; Litvin, 1991). With further temperature decrease the composition of the remnant melt is controlled by the nonorthopyroxene cotectics Ol+Cpx+Grt+L first, in the limits of the peridotite 'simplex', but then mechanism of fractional crystallization is also realized in the limits of the olivine-eclogite 'simplex' up to the corresponding nonvariant eutectics. The considered cotectics Ol+Cpx+Grt+L is of the greatest interest from the viewpoint of a possible change of compositions of remnant melts from olivine-normative to silica-normative ones. One can assume that under the conditions of fractional melt crystallization along the cotectic curve Ol+Cpx+Grt+L together with olivine jigging accumulation of incorehent elements

  20. Petrología de la aureola metamórfica de la granodiorita de Barcelona en la Sierra de Collcerola (Tibidabo

    Directory of Open Access Journals (Sweden)

    Julivert, M.

    1988-12-01

    only locally corundum, spinel, sillimanite and scapolite were developed. An important feature of most of the studied rocks is the existence in them of local equilibria; this must be Iikely the result of minor variations in the composition of the vapor phase and/or bulk rock system. The changes in the chemical composition of the tluids could be due to the existence of numerous millimetric to metric altemances of contrasting lithologies (e. g. pelites-earbonates or pelites-basic rocks, although they could also greatly be due to the intlux of tluids proceeding from the emplacement of the granodiorite. In effect, most rocks of the aureole present mineral associations of the homblendehomfels facies, nevertheless, locally, in places situated at 200 m of the contact, associations of the pyroxene-hornfels facies developed (corundum-spinel-sillimanite, etc., which suggests that besides normal heating by thermal conduction, there must exist and additional heat supply, Iikely related to convecting tluids, induced by the intrusion of the granodiorite. Although under such circurnstances estimation of P-T conditions of the contact metamorphism is very difficult, on the basis of the chemical composition of analyzed minerals, and taking into account stratigraphic considerations for the situation previous to the emplacement of the granodiorite, it may be suggested that the maximum P-T conditions reached during the contact metamorphism were around 1.5 kbar and 700°C.Los materiales Paleozoicos que afloran en la Sierra de Collcerola (Tibidabo van desde términos altos del Ordovíco hasta el Carbonífero. Estos Materiales se disponen aproximadamente en una estructura sinclinal con pliegues menores vergentes al SE o SSE desarrollándose una esquistosidad de flujo muy marcada. Las estructuras de dirección WNW-ESE están cortadas en las proximidades de Barcelona por la intrusión de un cuerpo granodiorítico (granodiorita de Barcelona. Esta intrusión no muestra ningún signo de deformaci

  1. 空位缺陷和相变对冲击压缩下蓝宝石光学性质的影响∗%Effects of vacancy p oint defects and phase transitions on optical properties of shocked Al2O3

    Institute of Scientific and Technical Information of China (English)

    唐士惠; 操秀霞; 何林; 祝文军

    2016-01-01

    this behavior. On the basis of these results, we may judge that 1) the transparency loss explanation for shocked Al2O3 in the view of vacancy point defects is reasonable; 2) the absorption extinction should dominate the extinction phenomenon observed in shocked Al2O3. Our calculations find that high-pressure structural transition in Al2O3 causes an obvious enhancement of its refractive index. The refractive index decreases with increasing shock pressure in corundum and Rh2O3 regions, and decreases slightly below 172 GPa and increases slowly above 172 GPa with increasing shock pressure in CalrO3 region. The V+2O and V−3Al defects in Al2O3 have apparent influences on the shock pressure dependence of its refractive index. These results mean that the information about Al2O3 refractive index under strong shock loading cannot be obtained simply by extrapolating its low pressure data. Our prediction could be of importance for future experimental study and new window-material development.%为了探究冲击压缩下蓝宝石光学性质的变化行为,本文采用第一性原理方法,在180 GPa的压力范围内计算了蓝宝石理想晶体和含空位点缺陷晶体的光学性质。吸收光谱数据表明,仅考虑压力和温度因素不能解释冲击消光实验的结果,而冲击诱导的氧离子空位点缺陷应该是导致该结果的一个重要原因。波长在532 nm处的折射率数据表明:1)蓝宝石的两个高压结构相变将导致其折射率明显上升;在Corundum和Rh2O3相区,其折射率将随冲击压力增大而降低;在CalrO3相区,压力小于172 GPa时,其折射率随冲击压力增大而缓慢地降低,但172 GPa以上时折射率却随冲击压力增大而逐渐增大;2)空位点缺陷对折射率随冲击压力的变化规律有明显的影响。本文结果不仅有助于增强用空位点缺陷的物理机理来解释蓝宝石冲击透明性损伤现象的可靠性,而且对未来进一步的实验研究以

  2. The influence of boron on the crystal structure and properties of mullite. Investigations at ambient, high-pressure, and high-temperature conditions

    Energy Technology Data Exchange (ETDEWEB)

    Luehrs, Hanna

    2013-11-21

    800 C was proved for B-mullite, whereas on the other hand, complete decomposition into boron-free mullite and corundum is observed at 1400 C. Furthermore, the incorporation of boron into the crystal structure reduces the mean metric thermal expansion coefficient by 15% in comparison to boron-free mullite. Such a reduction by chemical substitution makes B-mullites a potential candidate for technical applications in the temperature range below 1000 C. Boron incorporation is associated with the formation of additional oxygen vacancies which reduces the mechanical stability of the mullite structure at high-pressure. Moreover, a slight increase of the overall (volume) compressibility of B-mullite compared to boron-free mullite is observed. The compressibility in mullite is anisotropic with the a-axis being the most and the c-axis being the least compressible one. The increasing divergence with pressure between the compressibilities in a- and b-direction can be explained by a rotation of the octahedra and the increasing inclination angle ω. One major outcome of this thesis is the crystal structure of B-mullite, synthesized at 1200 C and ambient pressure. The refinements in space group Pbam based on neutron diffraction and {sup 11}B MAS NMR data clearly confirm the suggested silicon-boron substitution mechanism and yield a composition of Al{sub 4.64}Si{sub 1.16}B{sub 0.2}O{sub 9.58}. Boron resides in planar BO{sub 3} groups crosslinking the mullite-type AlO{sub 4} octahedral chains perpendicular to the c-axis. The position and the intrinsic rigidity of the BO{sub 3} group imposes local distortion of the AlO{sub 6} octahedra. As a consequence split positions of the oxygen atoms are required in the first coordination sphere of boron, which in turn lead to significantly shortened oxygen-oxygen distances in c-direction and only minor shortenings in the a- and b-directions. Herewith, the crystallographic model provides an explanation for the anisotropic behavior of lattice

  3. 替代燃料对水泥窑用方镁石-复合尖晶石材料的侵蚀%Corrosion of alternative fuels to periclase-compound spinel bricks for cement rotary kilns

    Institute of Scientific and Technical Information of China (English)

    陈树江; 刘耀闻; 李国华; 张国栋; 郝明选; 袁林

    2015-01-01

    This paper aims at researching the produced atmosphere corrosion during the calcination of ce-ment clinker using combustible wastes as substitute fuels to periclase-compound spinel bricks for burning zone of cement kilns.Firstly,chemical reactions between V2 O5 and high purity magnesia or magnesium alu-minate spinel at 1 500 ℃ were researched.Secondly,periclase-compound spinel crucible specimens were prepared at 1 600 ℃ using high purity magnesia,ferruginous magnesia,and hercynite as raw materials;the corrosion medium was prepared using 50% cement clinker,25% rubber tyre and 25% petroleum coke;the static crucible corrosion tests were carried out at 1 450 ℃ for 3 h.The microstructure and phase composition of the corroded specimens were analyzed by SEMand XRD,respectively.It is found that (1)V2 O5 reacts with MgO from spinel forming corundum and magnesium vanadate accompanied by a large volume expansion, deteriorating the spinel structure,thus damaging the brick structure,so when the substitute fuels are used for cement kilns,magnesium aluminate spinel is not a suitable raw material for periclase-compound spinel bricks;(2)the produced acid gases such as SO3 and V2 O5 during the combustion of alternative fuels pene-trate into the bricks along pores and crystal interfaces,gather in pores and crystal interfaces,react with CaO and MgO from periclase-compound spinel bricks forming Ca3 (VO4 )2 ,Mg3 (VO4 )2 ,CaSO4 and MgSO4 ac-companied by volume effect,which is disadvantage to the brick stability;additionally,the acid gases react with C2 S forming low melting phases and CaSO4 ,which goes against the stability of kiln coating.%为了解采用可燃性废弃物作为替代燃料煅烧水泥熟料时产生的气氛对水泥窑烧成带用方镁石-复合尖晶石砖的侵蚀情况,首先进行了化学试剂 V2 O5分别与高纯镁砂和镁铝尖晶石砂在1500℃下的反应试验;然后以高纯镁砂、高铁镁砂、铁铝尖晶石砂为原料,于1600℃

  4. Review on the Application of X-ray Diffraction in Gem Identification, Synthesis and Crystal Structure Research%X 射线衍射技术应用于宝石鉴定-合成及晶体结构研究进展

    Institute of Scientific and Technical Information of China (English)

    张妮; 林春明

    2016-01-01

    Due to the nondestructive requirements of gem testing,evaluation of precious stones shows characteristics of science and uncertainty.Gemological application of X-ray Diffraction (XRD)is specialized,with its application mainly concentrated in three aspects:① Gemstone identification:phase identification of the monocrystalline gemstones and polycrystalline gemstones;origin of the gemstones;classification of the pleomorphic gem minerals.For example,according to the XRD patterns of microcrystalline cryptocrystalline quartz variants,different silica mineral phases of the chalcedony can be distinguished accurately;types of ‘Di’in bloodstone can be distinguished through the composition and content of clay mineral.②Research on crystal structure of the gem minerals:analysis of crystal chemistry of the monocrystalline gems with complex composition;situation of the substitution of mineral isomorphism;quality of the gem by using the degree of crystallinity.For example,through the c/a ratio in lattice parameters of beryl,aluminium octahedral isomorphism and the beryllium tetrahedral isomorphism can be distinguished.The relationship between the crystallinity calculated from XRD data and the quality of nephrite is close.③Development of gemological research technology:to monitor the process of gemstone optimization;to inspect the mineral crystal size, crystalline quality and internal stress during the synthetic process of gemstones;to research the artificial breeding technology based on the crystal structure of organic gemstones.Take the heat treatment process of spinel as example:magnesium irons moved from octahedral M—O to tetrahedral T—O,resulting in the bond length of M—O and T—O changing upon temperature and being reflected in the spinel color.During the synthesis process of topaz,XRD data shows that the structure of the formed fluorine topaz is similar to natural topaz at 770 -800℃.At 950℃ and 1000℃, the fluorine topaz is decomposed to corundum and

  5. 泡沫胶凝法制备轻质钙长石耐火材料的工艺研究%Preparation of lightweight anorthitic refractories by foaming-gel method

    Institute of Scientific and Technical Information of China (English)

    夏光华; 谢穗; 何婵

    2011-01-01

    Lightweight anorthitic was prepared by foaming-gel method using calcined bauxite, calcined kaolin, wollastonite,protein foaming agent, gelatin, polyvinyl alcohol, silica sol, and polymeric aluminum sulfate as starting materials. The influences of protein foaming agent addition, gelatin addition, adding occasions of silica sol and polymeric aluminum sulfate as well as the silica sol addition on the foam-gel shaping were discussed,and the chemical composition, microstructure, and properties of the fired lightweight anorthitic were analyzed. The results show that: ( 1 ) when volume content of protein foaming agent in protein foaming agent-water system is 15% ,the foaming multiple of the system is the biggest; when adding 1.2 g gelatin in 100 mL protein foaming agent-water system,the subsidence rate of bubble is the lowest and its stability is the best;when spreading polymeric aluminum sulfate coagulant to sticky mud to prepare foamed mud,stirring at high speed,slowly adding silica sol in proportion of 137 mL silica sol in 1 L slurry bubble,15 min after stirring,the system begins to have the gelation ;2)the lightweight anorthite material shaping by the optimum technology and firing at 1 280 ℃ for 0.5 h,consists of anorthitic as principal crystalline phase and a small amount of corundum phase; the fired anorthite lightweight material has porous structure,and its pores are mostly closed with average size of about 200 μm and distribute uniformly; performance parameters of fired anorthite lightweight materials have achieved or even surpassed those of Germany's Jm23 brick.%以煅烧矾土、煅烧高岭土、硅灰石、蛋白质发泡剂、明胶、聚乙烯醇、硅溶胶和聚合硫酸铝为原料,采用泡沫胶凝法制备了轻质钙长石材料,主要研究了蛋白质发泡剂加入量、明胶加入量、硅溶胶和聚合硫酸铝的加入时机以及硅溶胶加入量等对泡沫胶凝成型工艺的影响,并分析了烧成后轻质钙长石材料的物相