Improvement of oxidation resistance of Si3N4 by heat treatment in a wet H2 atmosphere

2002 ◽  
Vol 17 (9) ◽  
pp. 2321-2326
Author(s):  
Young-Hag Koh ◽  
Hae-Won Kim ◽  
Hyoun-Ee Kim
Keyword(s):  
Heat Treatment ◽  
Surface Layer ◽  
Oxidation Resistance ◽  
Silicate Glass ◽  
Continuous Layer ◽  
Heat Treated

To improve the oxidation resistance of Si3N4 material, a dense and continuous layer, composed of small Y2Si2O7 crystallites and silicate glass, was formed on the surface. The surface layer was formed by exposing the specimens in a flowing H2 atmosphere containing 0.1% H2O at 1450 °C for 1 h. For the purpose of comparison, specimens of the same material were heat treated in air at 1450 °C for 1 h. Small equiaxed Y2Si2O7 crystallites were formed when the specimen was heat treated in the wet H2 atmosphere, while relatively large and elongated Y2Si2O7 crystallites developed when the specimens were heat treated in air. The oxidation resistance of Si3N4 material was improved remarkably by the heat treatment in the wet H2, while no improvement in oxidation resistance was observed from the specimen heat treated in air. The improvement was attributed to the retardation of the transport of oxidants through the dense and continuous layer formed on the surface.

Effect of heat treatment on bonding performance of poplar via an insight into dynamic wettability and surface strength transition from outer to inner layers

Holzforschung ◽  
2020 ◽  
Vol 74 (8) ◽  
pp. 777-787 ◽  
Author(s):  
Demiao Chu ◽  
Jun Mu ◽  
Stavros Avramidis ◽  
Sohrab Rahimi ◽  
Zongyuan Lai ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Surface Layer ◽  
Outer Surface ◽  
Near Infrared ◽  
Sessile Drop ◽  
Treated Wood ◽  
Tangential Section ◽  
Surface Strength ◽  
Heat Treated ◽  
Bonding Failure

AbstractHeat treatment (HT) is thought to degrade wood surface wettability and cause gluing problems; this study focused on wettability and surface strength of the surface layer on heat-treated wood. The outer and inner surfaces formed by removing the 1-, 2- and 3-mm surface layers of heat-treated poplar on the tangential section were investigated. Dynamic wetting was analyzed according to the sessile drop method. The bonding failure models on different surfaces were also discussed based on both images of macro- and microscopic fracture interfaces. Using Fourier-transform near-infrared spectroscopy (FT-NIR), the cell wall chemistry on both outer and inner surfaces were analyzed. The results showed that the bonding strength of the outer surface was mainly affected by wettability, whereas the surface strength became the key factor for the inner layers. The removal of the first 1 mm of the surface layer enhanced the wetting process and transferred the failure mode from the glue line to the wood itself. FT-NIR revealed that the intensity of the thermal degradation on inner layers was alleviated with the removal depth; wettability and surface strength were enhanced compared with the outer surface. Surface abrasion and hardness declined, decreasing the surface strength and bonding capacity. This study indicates that the bonding of heat-treated wood is truly affected by the surface strength of the inner layers, in addition to the wettability on the outer surface.

The Heat Treatment of Nanocrystalline Cu2O to Enhance the Catalytic Effect at the Surface Layer

2006 ◽  
Vol 118 ◽  
pp. 635-638 ◽  
Author(s):  
Young Rang Uhm ◽  
Byung Sun Han ◽  
Min Ku Lee ◽  
Chang Kyu Rhee
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Surface Layer ◽  
Catalytic Effect ◽  
Adsorption Ability ◽  
Air Exposure ◽  
Gas Condensation ◽  
Heat Treated ◽  
Temperature Ranges ◽  
Average Size

Cu oxide nano powders were synthesized by the levitational gas condensation (LGC) method, and heated at temperature ranges from 150 to 450 C. The nano powders consist of mainly Cu2O with an average size of 35 nm. The analysis of the IR-spectra of the nanopowders demonstrates that the surface of the sample under an air exposure is coated by hydroxylhydride (-OH, H2O) and hydroxycarbonated [Cu2(OH)2CO3]. The change of the particle size by heat treatment below 450 °C is relatively small. The variation of the adsorption ability is mainly defined under heating at least up to 300 °C, by the surface state of the particles. The catalytic effect was increased at heat treated samples.

The Effect of Heat Treatment on Fe2+/Fe3+ Ratio in Soda-Lime Silicate Glass

2015 ◽  
Vol 659 ◽  
pp. 194-198 ◽  
Author(s):  
Ekarat Meechoowas ◽  
Suwipa Poosrisoma ◽  
Parida Jampeerung ◽  
Tepiwan Jitwatcharakomol
Keyword(s):  
Heat Treatment ◽  
Iron Oxide ◽  
Silicate Glass ◽  
Redox Reaction ◽  
Raw Materials ◽  
Soda Lime ◽  
Annealing Process ◽  
Heat Treated ◽  
Vis Spectroscopy ◽  
Soda Lime Silicate Glass

The redox reaction of a tableware soda-lime silicate glass contained with 0.04 - 1.00 wt% of iron oxide is investigated by UV-Vis spectroscopy. The quality and purity of raw materials, especially sand is required to control the amount of iron oxide as low as possible. Normally tableware glass contains small amount of iron oxide (0.01 - 0.04 wt%) and iron effect (green color) is controlled by adding decolorizing agent. The heat treatment around transition temperature is another method to decolorize iron by redox reaction control. It is believed that the reaction of iron oxide Fe2+(green) « Fe3+(yellow) still occurs in annealing process. In this study, the glasses were prepared by melting in the platinum crucibles. After annealing, they are cut into four pieces and heated at 550 560 570 and 580°C with different times. The results of the transmittance showed no significantly change but the color in CIE L*a*b* system of glasses heat treated at 550 and 560 °C slightly change into whiter shade. According to the result of calculated Fe2+/Fe3+ ratio, the ratio of these glasses were decreased by 5 and 2.5 % respectively. On the contrary, the redox ratio of glass heated at 580 °C increased, due to Fe3+to Fe2+ and the color changed into green. The results proved the kinetic of the redox reaction of Fe2O3 and the possibility to use annealing process as another tool to control flint color of glass.

Effects of Impregnating and Heat Treatment on the Oxidation and Thermal Shock Properties of Pressureless Sintered SiC/Graphite Composites

2012 ◽  
Vol 724 ◽  
pp. 311-314
Author(s):  
Wan Li Yang ◽  
Zhong Qi Shi ◽  
Zhi Hao Jin ◽  
Guan Jun Qiao
Keyword(s):  
Heat Treatment ◽  
Thermal Shock ◽  
Oxidation Resistance ◽  
Vickers Hardness ◽  
Volume Fraction ◽  
Nitrogen Atmosphere ◽  
Silica Sol ◽  
X Ray Diffraction ◽  
Heat Treated ◽  
Before And After

SiC/0~20% graphite (volume fraction) composites were successfully fabricated by pressureless sintering at 1700 °C for 2 h in nitrogen atmosphere. The impregnating and heat treatment process for the samples with silica sol/phenolic impregnant was carried out at 1450 °C for 2 h in nitrogen atmosphere. The Vickers hardness, oxidation resistance and thermal shock property of the composites before and after treatment were tested, and the microstructure and phase composition were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results shown that the Vickers hardness of SiC/20% graphite was increased from 3.35 GPa to 4.90 GPa by heat treatment, and the oxidation resistance and thermal shock property of the heat treated samples were also improved significantly. The SEM and XRD results revealed that the formation of new SiC particles by the reaction of silica sol and phenolic was the main reason for the mechanical properties improvements.

Effect of a Complex Heat Treatment on the Structure of 300M Steel

1981 ◽  
Vol 39 ◽  
pp. 312-313
Author(s):  
R. Padmanabhan ◽  
W. E. Wood
Keyword(s):  
Heat Treatment ◽  
Metal Carbides ◽  
Austenite Grain Size ◽  
300M Steel ◽  
Heat Treated ◽  
Strain Fracture ◽  
Prior Austenite Grain Size ◽  
Short Time ◽  
Final Tempering ◽  
Similar Yield

Intermediate high temperature tempering prior to subsequent reaustenitization has been shown to double the plane strain fracture toughness as compared to conventionally heat treated UHSLA steels, at similar yield strength levels. The precipitation (during tempering) of metal carbides and their subsequent partial redissolution and refinement (during reaustenitization), in addition to the reduction in the prior austenite grain size during the cycling operation have all been suggested to contribute to the observed improvement in the mechanical properties. In this investigation, 300M steel was initially austenitized at 1143°K and then subjected to intermediate tempering at 923°K for 1 hr. before reaustenitizing at 1123°K for a short time and final tempering at 583°K. The changes in the microstructure responsible for the improvement in the properties have been studied and compared with conventionally heat treated steel. Fig. 1 shows interlath films of retained austenite produced during conventionally heat treatment.

“In vitro” and in Animal Model Studies on a Double Virus- Inactivated Factor VIII Concentrate

1995 ◽  
Vol 74 (03) ◽  
pp. 868-873 ◽  
Author(s):  
Silvana Arrighi ◽  
Roberta Rossi ◽  
Maria Giuseppina Borri ◽  
Vladimir Lesnikov ◽  
Marina Lesnikov ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Animal Model ◽  
Factor Viii ◽  
Hepatitis A ◽  
Hepatitis A Virus ◽  
Virus Inactivation ◽  
Enveloped Viruses ◽  
Model Studies ◽  
Heat Treated

SummaryTo improve the safety of plasma derived factor VIII (FVIII) concentrate, we introduced a final super heat treatment (100° C for 30 min) as additional virus inactivation step applied to a lyophilized, highly purified FVIII concentrate (100 IU/mg of proteins) already virus inactivated using the solvent/detergent (SID) method during the manufacturing process.The efficiency of the super heat treatment was demonstrated in inactivating two non-lipid enveloped viruses (Hepatitis A virus and Poliovirus 1). The loss of FVIII procoagulant activity during the super heat treatment was of about 15%, estimated both by clotting and chromogenic assays. No substantial changes were observed in physical, biochemical and immunological characteristics of the heat treated FVIII concentrate in comparison with those of the FVIII before heat treatment.

Vanadium Additions to a High-Cr White Iron and its Effects on the Abrasive Wear Behavior.

MRS Advances ◽  
2020 ◽  
Vol 5 (59-60) ◽  
pp. 3077-3089
Author(s):  
Alexeis Sánchez ◽  
Arnoldo Bedolla-Jacuinde ◽  
Francisco V. Guerra ◽  
I. Mejía
Keyword(s):  
Heat Treatment ◽  
Abrasive Wear ◽  
Volume Fraction ◽  
Wear Behavior ◽  
Wear Behaviour ◽  
White Iron ◽  
Heat Treated ◽  
Bulk Hardness ◽  
Abrasive Wear Behavior ◽  
Vanadium Carbides

AbstractFrom the present study, vanadium additions up to 6.4% were added to a 14%Cr-3%C white iron, and the effect on the microstructure, hardness and abrasive wear were analysed. The experimental irons were melted in an open induction furnace and cast into sand moulds to obtain bars of 18, 25, and 37 mm thickness. The alloys were characterized by optical and electronic microscopy, and X-ray diffraction. Bulk hardness was measured in the as-cast conditions and after a destabilization heat treatment at 900°C for 45 min. Abrasive wear resistance tests were undertaken for the different irons according to the ASTM G65 standard in both as-cast and heat-treated conditions under a load of 60 N for 1500 m. The results show that, vanadium additions caused a decrease in the carbon content in the alloy and that some carbon is also consumed by forming primary vanadium carbides; thus, decreasing the eutectic M7C3 carbide volume fraction (CVF) from 30% for the base iron to 20% for the iron with 6.4%V;but overall CVF content (M7C3 + VC) is constant at 30%. Wear behaviour was better for the heat-treated alloys and mainly for the 6.4%V iron. Such a behaviour is discussed in terms of the CVF, the amount of vanadium carbides, the amount of martensite/austenite in matrix and the amount of secondary carbides precipitated during the destabilization heat treatment.

Heat Treatment Influence on the Corrosion Resistance of a Cu-Al-Fe-Mn Bronze

2018 ◽  
Vol 69 (5) ◽  
pp. 1055-1059 ◽  
Author(s):  
Mariana Ciurdas ◽  
Ioana Arina Gherghescu ◽  
Sorin Ciuca ◽  
Alina Daniela Necsulescu ◽  
Cosmin Cotrut ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Structural Changes ◽  
Heating Temperature ◽  
Galvanic Corrosion ◽  
Cooling Water ◽  
Open Circuit ◽  
Water Quenching ◽  
Heat Treated ◽  
Different Temperatures

Aluminium bronzes are exhibiting good corrosion resistance in saline environments combined with high mechanical properties. Their corrosion resistance is obviously confered by the alloy chemical composition, but it can also be improved by heat treatment structural changes. In the present paper, five Cu-Al-Fe-Mn bronze samples were subjected to annealing heat treatments with furnace cooling, water quenching and water quenching followed by tempering at three different temperatures: 200, 400 and 550�C. The heating temperature on annealing and quenching was 900�C. The structure of the heat treated samples was studied by optical and scanning electron microscopy. Subsequently, the five samples were submitted to corrosion tests. The best resistance to galvanic corrosion was showed by the quenched sample, but it can be said that all samples are characterized by close values of open-circuit potentials and corrosion potentials. Concerning the susceptibility to other types of corrosion (selective leaching, pitting, crevice corrosion), the best corrosion resistant structure consists of a solid solution, g2 and k compounds, corresponding to the quenched and 550�C tempered sample.

Oxidation resistance of TiAl alloy improved by hot-pack rolling and cyclic heat treatment

2021 ◽  
pp. 111196
Author(s):  
Tian Shiwei ◽  
He Anrui ◽  
Liu Jianhua ◽  
Zhang Yefei ◽  
Yang Yonggang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Oxidation Resistance ◽  
Tial Alloy ◽  
Cyclic Heat Treatment ◽  
Pack Rolling ◽  
Cyclic Heat ◽  
Hot Pack

Achieving the synergy of superior damage tolerance and oxidation resistance of 2D Cf/ZrB2-SiC composites via fiber heat treatment

2021 ◽  
Vol 556 ◽  
pp. 149807
Author(s):  
Dongyang Zhang ◽  
Hongying Yu ◽  
Anzhe Wang ◽  
Qi Wang ◽  
Lu Ren ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Oxidation Resistance ◽  
Damage Tolerance ◽  
Sic Composites
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