Metastable
Mostrando 1-12 de 287 artigos, teses e dissertações.
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1. Simultaneous Quantification of Amorphous and Crystalline Valsartan in Tablets Using Raman Spectroscopy and Chemometrics Tools
Valsartan is an antihypertensive active pharmaceutical ingredient (API), it is used in the amorphous state in the commercial products. As amorphous materials are metastable, amorphous valsartan can crystallize to valsartan E, promoting changes in the dissolution and bioavailability of the drug. Tablets containing metastable forms of APIs need special conditi
Journal of the Brazilian Chemical Society. Publicado em: 2022
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2. Microstructure and diametral fracture strength of spark plasma sintered WC-6Co-0.2B and WC-6Co-0.5B ceramic composites from nanosized and metastable WC powders
Abstract The present work aimed at evaluating the microstructures and mechanical properties of spark plasma sintered WC-6 wt% Co ceramic composites doped with boron (0.2 and 0.5 wt%). W-50 at% C (W-6.13 wt% C) powders produced under different milling times (20, 60, 180, and 600 min) were used as starting materials and subsequently mixed with Co (6 wt%) and B
Cerâmica. Publicado em: 2022
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3. First-Principles Calculations of a New Semi-Conductive Carbon Allotrope Named ABF-Carbon
Carbon is an extremely versatile element and can generate a plethora of structures with distinct properties. Proposing new possible metastable allotropic structures for carbon has been the subject of increasing interest over the past few years. In this contribution, we present a new carbon allotrope, named ABF-Carbon, based on the connection of spiropentadie
J. Braz. Chem. Soc.. Publicado em: 2021-04
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4. Effect of Squeeze Casting on Microhardness and Microstructure of Al-3Cu-xSi Alloy
Aluminum alloys of the ANSI series 319 present Si and Cu as the main alloying elements and the mechanical strength of these alloys can be improved by the precipitation of the metastable Al2Cu phase. Squeeze Casting is a casting process in which the cast metal is deposited in a metal mold and solidified under certain pressure exerted by a punch. This process
Mat. Res.. Publicado em: 30/09/2019
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5. Effects of Macrosegregation and Microstructure on the Corrosion Resistance and Hardness of a Directionally Solidified Zn-5.0wt.%Mg Alloy
This study aims to analyze the influence of macrosegregation on microstructure evolution, and of microstructure length scale on the corrosion resistance of a Zn-5.0wt.%Mg alloy casting. The analyzed samples were taken along the length of castings unidirectionally solidified in unsteady state conditions of heat extraction. Microstructure characterization, mic
Mat. Res.. Publicado em: 05/09/2019
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6. Effects of composition on transformation temperatures and microstructure of Ni-Ti-Hf shape memory alloys
Abstract High transformation temperature shape-memory alloys (HTSMA) usually present a martensitic transformation temperature (Ms) starting at 100 ºC. That is the case of high nickel Ni-Ti-Hf alloys. This article presents experimental results obtained from arc melting of Ni50Ti50-XHfX .at% (X = 8, 11, 14, 17 and 20 .at%) alloys. This process homogenized eve
REM, Int. Eng. J.. Publicado em: 2019-06
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7. Dependence of Wear and Mechanical Behavior of Nitrocarburized/CrN/DLC Layer on Film Thickness
Diamond-like carbon (DLC) films are amorphous metastable carbon form that provide interesting mechanical and tribological properties. The role of film thickness influence upon wear and mechanical properties is of interest and not yet fully reported. In this study, two samples of previously plasma nitrocarburized, quenched and tempered H13 steel were duplex t
Mat. Res.. Publicado em: 31/01/2019
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8. Effect of sol-gel processing parameters on structure of zirconia
Abstract The present study reports the experimental results regarding the effect of molar ratio of hydrolysis water used in the sol-gel synthesis upon the structure of zirconia. The ZrO2 materials were synthesized via simple metal-chelate route using zirconium n-propoxide [Zr(OCH2CH2CH3)4], n-propanol, acetic acid, and deionized water. Thermogravimetric anal
Cerâmica. Publicado em: 2019-01
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9. Selection between LTA or FAU phases by manipulating the synthesis gel composition, crystallization time and temperature
Resumo Zeólitas LTA e FAU foram sintetizadas com brometo de cetiltrimetilamônio (CTAB) visando avaliar os efeitos das razões Si/Al, Na/Al e H2O/Al, do tempo e da temperatura no rendimento de cada estrutura. A significância de cada variável foi determinada através de planejamentos experimentais, cujas variáveis resposta foram as áreas de picos de difr
Cerâmica. Publicado em: 2019-01
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10. Controlling sintering and grain growth of nanoceramics
Resumo Sinterização e crescimento de grão são processos fundamentais que afetam a evolução microestrutural das cerâmicas. Os modelos fenomenológicos que descrevem esses processos, conforme encontrados nos livros didáticos, são simplificações do conjunto altamente dinâmico de parâmetros do sistema, o que leva à previsibilidade limitada e à nec
Cerâmica. Publicado em: 2019-01
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11. Effect of Thermo-Mechanical Treatments on the Microstructure and Mechanical Properties of the Metastable β-type Ti-35Nb-7Zr-5Ta Alloy
In this work, theoretical composition design and thermo-mechanical treatments were combined in order to improve the mechanical compatibility of a biomedical β-type titanium alloy. By applying a composition design theory, cold rolling and low temperature aging, a metastable β-type Ti-35Nb-7Zr-5Ta (wt%) alloy with an elastic modulus of 47 GPa and a yield str
Mat. Res.. Publicado em: 29/10/2018
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12. Efecto del tratamiento sub-cero sobre la microestructura y dureza de fundiciones blancas alto cromo
ABSTRACT The effect of the sub-zero treatment temperature on the transformation of retained austenite to martensite in two high chromium white cast irons (ASTM A532 Class II Type B) was studied. The sub-zero treatment applied to each alloy in the as cast condition was performed at -40, -65 and -180 ° C for 10 minutes; after the holding time was completed th
Matéria (Rio J.). Publicado em: 19/07/2018