Micromat 2004 villar
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This document summarizes a study on obtaining ultrafine ferritic grains in a 0.16C steel through subcritical torsion. Samples were austenitized at 1100°C, quenched, and tempered for varying times from 0.25 to 48 hours to evaluate the influence of cementite precipitation on grain refinement. After tempering and reheating to 700°C, samples underwent hot torsion testing. Microstructural analysis found finer and more dispersed carbides in samples with lower tempering times. Precipitate size had little influence on ferritic grain refinement. Ultrafine grains below 2 μm were achieved for all tempering times through strains induced by subcritical hot torsion testing.
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This document summarizes a study on the sintering mechanism of silica gel nanoparticles during initial heating stages. Thermogravimetric analysis showed weight loss up to 600°C attributed to removal of absorbed water and hydroxyl groups. Diffuse reflectance infrared spectroscopy revealed bonding changes - bridged hydroxyl groups were replaced by free hydroxyl and water molecules with heating. Heating also increased asymmetric stretching splitting, indicating greater long-range Coulombic forces from increased siloxane bonding between particles. The study concludes initial sintering is driven by dehydration and surface hydroxyl condensation forming siloxane bonds between particles.
The impact of surface hydrogenation on the thermionic electron emission from ...
In this work, thermionic electron emission (TEE) from hot
filament chemical vapour deposition polycrystalline diamond
films deposited on p-type silicon substrates was recorded in
the 25–650 8C temperature range. The studied surfaces were
as deposited, as well as hydrogenated by atomic hydrogen
under ultra-high vacuum conditions. The impact of substrate
temperature during hydrogenation, TH, on TEE was studied.
For TH ¼ 25 8C the TEE was found to display a broad maximum
at substrate temperature around 300 8C followed by an
exponential increase. Annealing at 700 8C results in irreversible
changes in surface conditioning, and drastic reduction of TEE
yield at low temperatures. For samples that underwent
hydrogenation at TH ¼ 300 and 500 8C, the TEE yield is
significant at higher temperatures only. The TEE from these
samples is stable also after 700 8C annealing treatment. We
associate these effects with irreversible thermal induced
physicochemical changes of the hydrogen bonding configuration
adsorbed on the polycrystalline diamond surface resulting
in changes in its surface electronic structure which occur upon
annealing to 300 8C.
Electrophoresis part 3
This document discusses two electrophoresis techniques: capillary electrophoresis and isoelectric focusing. Capillary electrophoresis uses very small volumes of samples and reagents in fused silica capillaries, allowing for high resolution, automation, and detection of low analyte levels. Isoelectric focusing separates proteins based on their isoelectric point, where they have no net charge and become immobilized in a pH gradient gel. Both techniques have various applications in biochemistry including separating proteins, DNA, amino acids, and other biomolecules.
Paul welander cryogenic rf characterization of sc materials at slac with cu...
A second-generation, X-band cryostat has been developed for the characterization of superconducting materials at low temperatures and high powers. The system utilizes two interchangeable hemisperhical cavities that can accommodate 50 mm-diameter samples on the flat surface. Both operate in a TE013-like mode where the magnetic field is strongest on the sample surface, which accounts for about 1/3 of the total cavity loss. The first cavity is a medium-Q copper one, and is utilized for measuring the sample’s critical temperature and magnetic quenching field. The second is a high-Q niobium-coated cavity that is employed for measuring surface resistance in the low-temperature, low-power limit. We will discuss cryostat design, measurement limits, and testing of samples grown both at SLAC and elsewhere.
CAPPILARY ELECTROPHORESIS
Capillary electrophoresis is an analytical technique that separates ions based on their electrophoretic mobility through thin capillary tubes when an electric field is applied. Separation occurs due to differences in electrophoretic mobility which depends on an ion's charge and size. Capillary electrophoresis uses high electric fields in thin capillaries to rapidly separate molecules in minutes versus hours for traditional electrophoresis. It has applications in sequencing DNA/RNA, analyzing pharmaceuticals, and separating proteins, peptides, and other biomolecules.
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More from Karina Mello
Villar cim2011 es
O documento discute o efeito da cementita globular na resistência mecânica e tenacidade de aços ferríticos com grãos ultrafinos. Foi realizado tratamento termomecânico em aço baixo carbono para produzir grãos ultrafinos e cementita finamente dispersa. Ensaios mecânicos mostraram que o material com grãos ultrafinos teve maior resistência e energia de impacto. Microscopia eletrônica revelou que a cementita atua como barreira ao movimento de discordâncias nos grãos, melhorando as propried
Villar ciasem 2007
This document investigates the effect of cementite particles on microstructure refinement and formation of high angle boundaries in low carbon steel. Warm deformation tests were conducted on a 0.16C steel and an ultra-low carbon steel up to a strain of 5 at 685°C and 0.1 s-1 strain rate. Electron backscatter diffraction analysis showed that cementite precipitation and ferrite recrystallization led to the formation of high angle boundaries and grain refinement during subcritical deformation. Flow stress was higher for the 0.16C steel due to cementite particles anchoring grain boundaries.
Trb0807 cobem 2001_villar
1) O documento discute a influência do tratamento térmico de recozimento na microestrutura de um aço inoxidável austenítico com alto teor de nitrogênio utilizado em implantes ortopédicos.
2) Foram realizados tratamentos térmicos de recozimento em 600, 700, 800 e 900°C para estudar a cinética de precipitação e correlacionar o ciclo térmico com a precipitação na matriz e nos contornos de grão.
3) A caracterização microestrutural revelou transformações de fases, fer
Silva neto ov conamet_2007
Este documento discute o efeito da precipitação de cementita na formação de contornos de alto ângulo e no refino de grão ferrítico durante o processamento subcrítico de aços. Experimentos de torção a morno foram realizados em aços com 0,16% C e ultrabaixo carbono após tratamentos térmicos. Os resultados mostraram que a precipitação de cementita e a recristalização dinâmica da ferrita contribuem para o refino de grão e formação de contornos de alto ângulo durante a deformação subcrí
Paineis materiais csbmm_2005
This document provides an agenda for a materials science session taking place on August 29, 2005. It lists 18 presentations covering topics in fatigue fracture analysis, fractographic analysis of welded joints, fracture toughness testing, biocompatibility testing of titanium alloys, and microstructural characterization of biomaterials and ceramics. The presentations involve laboratory testing and characterization of materials including metals, polymers, composites, and ceramics for biomedical and engineering applications.
P083 villar ciasem 2007
Este documento informa al Dr. Villar que su trabajo titulado "EFFECT OF CEMENTITE PARTICLES IN FORMATION OF HIGH ANGLE BOUNDARIES AND OF ULTRAFINE GRAINS IN LOW CARBON STEEL", con O. Villar da Silva Neto y O Balancin como autores, ha sido aceptado para ser presentado oralmente en el 9no Congreso Interamericano de Microscopia Electrónica en Cusco, Perú del 23 al 28 de septiembre. Más detalles sobre la presentación oral, como la fecha, hora y sala, serán notificados posteriormente.
Micromat 2004 simposio_i
The document summarizes a symposium on microanalysis and analytical microscopy of materials. It provides details on the organizers, invited speakers, and oral presentations to be given at the symposium. The symposium will take place from October 10-13, 2004 in Brazil and will include topics such as new applications of electron microscopy in nanotechnology, compositional analysis of interfaces using electron microscopy techniques, and microscopy studies of catalysts and ceramics. Poster sessions will also be held on October 11th and 13th.
Imc17 2010 i4519
This document summarizes a study that investigated the effect of cementite particles on ultra-fine ferrite grain growth in low-carbon steel after subcritical aging. Transmission electron microscopy was used to analyze the microstructure. The aging treatment produced an ultra-fine ferrite grain size of 1.0-1.4 micrometers with both fine globular and rod-shaped cementite particles distributed between the grains. During aging, both the ferrite grains and cementite particles coarsened normally via Ostwald ripening. The cementite particles were found to effectively inhibit ferrite grain growth, matching predictions from Rios' grain growth model.
Csbmm 2007 silva_neto_ebsd_metals and alloys
The document summarizes a study on grain refinement in 0.16C steel through subcritical processing involving heavy deformation. Samples underwent hot torsion deformation at 685°C with strain rates of 1.0, 0.5, and 0.1 s-1. Microstructural analysis found the final microstructure was recrystallized with an average grain size of 1 μm. Three factors were found to contribute to the ultrafine grains: continuous dynamic recrystallization, rotation and breaking of initial boundaries, and cementite particles interfering with subgrain rotation and growth.
Csbmm 2005 villar
This document investigates obtaining ultrafine grains in low carbon steel through thermo-mechanical treatment in the ferrite domain. A low carbon steel with dispersed globular cementite was heavily deformed at 685°C at strain rates from 0.1-1 s-1. Regardless of route to spheroidize carbides, flow stress curves displayed an initial hump then extensive softening and steady state. Microstructural evolution was observed, with ferrite nucleating preferentially at defects. Both heavy deformation and high strain rates increased defects and bands, contributing to dynamic recrystallization and formation of ultrafine ferrite grains less than 2 μm on average. Continuous dynamic recrystallization during deformation led to the
Csbmm 2003 villar
This study investigated grain refinement of ferrite in low-carbon steel through thermomechanical processing near the A1 temperature. Samples underwent spheroidization at 670C followed by torsion straining at 700C, producing ferrite grains less than 2 microns. Both conventional and quenched/strained routes resulted in homogeneous microstructures with fine ferrite grains and cementite precipitates pinning grain boundaries. Increasing strain rate decreased ductility, indicating recrystallization was the dominant refinement mechanism aided by cementite precipitation at boundaries. Sub-critical temperatures were effective for accelerating cementite precipitation and grain refinement.
Csbmm 2002 otavio
This document examines the effect of carbon content on grain refinement in C-Mn and interstitial-free (IF) steels deformed via warm working. Four steels with varying carbon contents were strained at 700°C to 2.3. Dynamic recrystallization resulted in a 2 μm ferrite grain size at the surface for all steels. However, microstructures varied between the center regions based on carbon content, from coarse grains in IF steel to martensite and bainite in the highest carbon steel. Increasing carbon decreased ferrite grain size after deformation but also increased strength, while alloying elements aided additional refinement.
Csbmm 2001 villar
The document studied the effect of nitrogen on precipitation in an austenitic stainless steel used in orthopedic implants. It found that high nitrogen content led to precipitation of niobium nitrides in all annealing temperatures due to nitrogen's higher affinity for niobium than chromium. Two types of nitrides, chromium nitride and niobium nitride, were identified along with intermetallic phases Z and χ containing chromium, niobium, and molybdenum. The significant presence of nitrogen and niobium in the steel composition drove precipitation of these phases.
Conem 2004 villar
1) O documento estuda o efeito do tratamento térmico de envelhecimento na tenacidade do aço inoxidável austenítico ISO 5832-9 usado como biomaterial.
2) Amostras foram tratadas em temperaturas de 600-900°C por 1-24 horas e suas propriedades mecânicas foram avaliadas por ensaios de dureza e impacto Charpy.
3) O tratamento a 900°C por 1-4 horas proporcionou a maior tenacidade, enquanto a 800°C produziu as condições mais
Conamet 2004 villar
Este documento descreve um estudo sobre o refinamento da microestrutura de um aço de baixo carbono durante o processamento termo-mecânico a morno. Amostras foram temperadas, revenidas a 700°C por diferentes tempos e deformadas a 700°C. O revenimento levou à precipitação de cementita e o refino ocorreu durante a deformação, resultando em grãos ferríticos ultrafinos independente do tempo de revenimento.
Conamet 2003 04-421
Este documento descreve o estudo do refino de grão ferrítico em um aço baixo carbono submetido a tratamentos termomecânicos. Dois processos foram comparados: esferoidização convencional a 670°C e esferoidização induzida por deformação a 700°C. Ambos levaram à precipitação de partículas finas de cementita e grãos ferríticos menores que 2μm. A deformação mecânica após esferoidização acelerou o refino de grão, enquanto a quantidade de deformação foi mais
Ciasem 2005 villar
1) The document investigates obtaining ultrafine ferrite grains in a low-carbon steel through hot torsion deformation and tempering at sub-critical temperatures.
2) A steel with 0.16% C and 1.34% Mn containing spheroidized cementite was heavily deformed via hot torsion at 685°C and strain rates from 0.1 to 1 s-1.
3) Microstructural analysis found ultrafine ferrite grains less than 2 μm formed, with dispersed spheroidal cementite, indicating dynamic recrystallization during subcritical deformation was responsible for the grain refinement.
Balancin senafor 2006_villar
Este documento descreve uma pesquisa sobre o refino de grãos em aço baixo carbono através de deformação a quente. A microestrutura inicial consistia de martensita com partículas finas de cementita. Após grandes deformações a quente, observou-se uma microestrutura ferrítica ultrafina com grãos de ~1 μm e partículas de cementita dispersas, indicando refino microestrutural devido à subdivisão de grãos e ancoragem de contornos.
Acta microscopica 2007_silva netoov
Este documento investiga como a precipitação de cementita durante o processamento termomecânico influencia o refino de grão ferrítico e a formação de contornos de alto ângulo em aços de baixo carbono. Os autores deformaram amostras de dois aços (0,16% C e ultrabaixo carbono) a morno e analisaram a evolução da microestrutura usando microscopia eletrônica. Eles concluíram que a precipitação de cementita e a recristalização dinâmica da ferrita são responsáveis pelo ref
Abm 2000 hc9494_villar
Este documento descreve um estudo sobre a microestrutura do metal de solda do aço ASTM-A36 obtido por soldagem a arco submerso variando o insumo de calor. A microestrutura do metal de solda é afetada pelo insumo de calor utilizado durante a soldagem, com altos insumos de calor promovendo uma maior taxa de resfriamento e alterando os constituintes microestruturais como a ferrita acicular. Amostras foram soldadas variando o insumo de calor de 1,27kJ/mm a 1,
More from Karina Mello (20)
Micromat 2004 villar
- 1. ULTRAFINE FERRITIC GRAIN OBTAINMENT THROUGH SUBCRITICAL TORSION OF A 0.16C STEEL Silva Neto, O. V., Balancin, O. Washington Luiz Road, Km 235, 13.565-905, São Carlos - SP, Brazil - pvillar@iris.ufscar.br Department of Engineering of Materials - Federal University of São Carlos - DEMa/UFSCar. ABSTRACT This work presents a study of the ultrafine ferritic grain through thermomechanical treatment of a 0.16C steel in the subcritical range. By varying the subcritical tempering, the influence of cementite precipitation on the grain refinement was evaluated. All samples were austenitizing at 1100°C, quenched on water and tempered under 0.25, 0.5, 1, 12, 24 and 48 hours. The processing routes based on spheroidization tempering at 700°C (just below Ae1) followed the thermomechanical treatment through hot torsion. Before carrying out the torsion tests, the specimens were heated up to 700°C again, maintained by 10 minutes. After each a torsion test the samples were air cooled to environment temperature. The microstructural evolution was observed by optical and scanning electron microscopy. The high resolution electron backscattered diffraction (EBSD) has been used to analyse the boundary misorientations formed during deformation, determining both high and low angle boundaries. As a result after performing torsion tests, finer and dispersive carbides could be verified on samples submitted at lower tempering times. In addition, precipitate size caused little influence on the ferritic grain refinement. Therefore, the ultrafine grains were sufficiently reached with strains under the subcritical range. By this test procedure, it was possible to obtain ferritic grains smaller than 2 μm for all tempering times. Key-words: subcritical tempering, ultrafine grain, cementite, hot torsion, EBSD technique.