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.

scholarly journals Modulation of Lithium Disilicate Translucency through Heat Treatment

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2094
Author(s):  
Seok-Ki Jung ◽  
Dae Woon Kim ◽  
Jeongyol Lee ◽  
Selvaponpriya Ramasamy ◽  
Hyun Sik Kim ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Light Scattering ◽  
Flexural Strength ◽  
Control Method ◽  
Light Transmission ◽  
Lithium Disilicate ◽  
Lower Heat ◽  
Average Size ◽  
Ball Test

The aim of this study was to present a control method for modulating the translucency of lithium disilicate ceramics through thermal refinement. Identical lithium disilicate blocks were thermally refined using four different heat treatment schedules, and the microstructure, translucency, and flexural strength of the ceramics were investigated in detail by SEM, spectroscopy, and a piston-on-three-ball test. The results showed that ceramics treated under higher heat had larger grains, with an average size between 240 and 1080 nm. In addition, a higher transmittance of all wavelengths was observed in ceramics treated under lower heat, and the transmittance in the 550 nm wavelength ranged from 27 to 34%. The results suggest that the translucency of ceramics can be modified through thermal refinement under two conditions: (1) the particle size of the ceramic is small enough to achieve minimal grain-boundary light scattering, and (2) the percentage of particles allowing visible light transmission is altered by the heat treatment.

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.

scholarly journals Synthesis of Photochromic AgCl-Urethane Resin Composite Films

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
Hidetoshi Miyazaki ◽  
Hirochi Shimoguchi ◽  
Hisao Suzuki ◽  
Toshitaka Ota
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Composite Film ◽  
Liquid State ◽  
Resin Composite ◽  
Composite Films ◽  
Photochromic Property ◽  
Heat Treated ◽  
Fading Rate ◽  
20 Nm

AgCl-resin photochromic composite films were prepared using AgNO3, HCl-EtOH, CuCl2solution, and a liquid-state urethane resin as starting materials. The obtained composite films showed a photochromic property. The rate of darkening of the composite film increased after mixing with CuCl2. The AgCl particle size in the film without heat treatment was 6–20 nm, and that of the heat-treated film was 25–80 nm; these results were confirmed using TEM observations. The fading rate of the film without heat treatment was higher than that of the heat-treated films.

Effect of Heat Treatment on Properties of Mineral Attapulgite

2008 ◽  
Vol 58 ◽  
pp. 41-46 ◽  
Author(s):  
Qing Guo Tang ◽  
Jin Sheng Liang ◽  
Jun Ping Meng ◽  
Fei Wang ◽  
Li Wei Li ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Free Energy ◽  
Surface Free Energy ◽  
Water Vapor Adsorption ◽  
Heat Temperature ◽  
Heat Treated ◽  
Dispersion Component ◽  
Medium Particle ◽  
Medium Particle Size

Mineral attapulgite powders were heat treated at different temperature from 100°C to 800°C. The effect of heat treatment on properties of attapulgite were studied by particle size distribution, surface free energy, and water vapor adsorption performance. The results show that the medium particle size and surface free energy of attapulgite increase and hygroscopic capacity promptly reduce with the increase of heat temperature .The medium particle size of the raw palygorskite is 3.09 μm, and it becomes 14.12 μm after heat treatment at 800 °C. The surface free energy, polarity component and dispersion component of the natural attapulgite are 45.16mN•m-1, 13.92mN•m-1, 31.24mN•m-1, respectively, and they become 116.22 mN•m-1，116.22 mN•m-1，0.0 mN•m-1 after heat treatment at 800°C. Moreover, the hygroscopic capacity of attapulgite in 24h decreases from 17.1 % to 5.6% after heat treatment at 800°C.

scholarly journals Phase Transitions in the α–γ–β Spodumene Thermodynamic System and Impact of γ-Spodumene on the Efficiency of Lithium Extraction by Acid Leaching

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 519
Author(s):  
Colin Dessemond ◽  
Gervais Soucy ◽  
Jean-Philippe Harvey ◽  
Philippe Ouzilleau
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Extraction Efficiency ◽  
Mechanical Energy ◽  
Acid Leaching ◽  
Thermodynamic System ◽  
Coarse Fraction ◽  
X Ray ◽  
Heat Treated ◽  
Lower Heat

Heat-treatment of spodumene concentrate at 1323 K (1050 °C) for 30 min in a rotary kiln yielded a successful decrepitation. Particle size decreased from 2 cm to less than 425 µm for 80% of the initial mass. X-ray analysis of both fractions did not reveal the presence of α-spodumene or γ-spodumene. The coarse fraction was ground to less than 425 µm with minimal mechanical energy and mixed with the finer fraction to perform lithium extraction. The lithium extraction efficiency reached 98 wt% without the need for flotation. Some aspects of the thermodynamic behavior of the spodumene system were assessed. Results show that metastable γ-spodumene may hinder the formation of β-spodumene at lower heat treatment temperatures. Some heat-treated samples presented non-negligible γ-spodumene content and lithium extraction efficiency decreases as the γ content increases. Finally, the assumed irreversibility of the transformations was studied by analyzing heat-treated samples following long controlled-storage periods. The results show that concentrate composition is not static over the studied time. This suggests that the β formation is not as irreversible as claimed. It is recommended to avoid long periods between heat-treatment and extraction to avoid the slow conversion of β-spodumene to other allotropes, which are less susceptible to lithium extraction.

scholarly journals Synthesis by Microwaves of Bimetallic Nano-Rhodium-Palladium

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
M. Ugalde ◽  
E. Chavira ◽  
M. T. Ochoa-Lara ◽  
I. A. Figueroa ◽  
C. Quintanar ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Sol Gel ◽  
Inert Atmosphere ◽  
Microwave Oven ◽  
Microwave Assisted ◽  
Gel Technique ◽  
Pd Clusters ◽  
Average Size ◽  
By Products

An improved acrylamide sol-gel technique using a microwave oven in order to synthesize bimetallic Rh-Pd particles is reported and discussed. The synthesis of Pd and Rh nanoparticles was carried out separately. The polymerization to form the gel of both Rh and Pd was carried out at 80°C under constant agitations. The method chosen to prepare the Rh and Pd xerogels involved the decomposition of both gels. The process begins by steadily increasing the temperature of the gel inside a microwave oven (from 80°C to 170°C). In order to eliminate the by-products generated during the sol-gel reaction, a heat treatment at a temperature of 1000°C for 2 h in inert atmosphere was carried out. After the heat treatment, the particle size increased from 50 nm to 200 nm, producing the bimetallic Rh-Pd clusters. It can be concluded that the reported microwave-assisted, sol-gel method was able to obtain nano-bimetallic Rh-Pd particles with an average size of 75 nm.

Effect of Heat Treatment on Chemical Structure of a Bio-Filler from Vetiver Grass

2011 ◽  
Vol 410 ◽  
pp. 71-74 ◽  
Author(s):  
Wimonlak Sutapun ◽  
Yupaporn Ruksakulpiwat ◽  
Nitinat Suppakarn
Keyword(s):  
Heat Treatment ◽  
Thermal Decomposition ◽  
Particle Size ◽  
Crystalline Structure ◽  
Chemical Structure ◽  
Fiber Surface ◽  
Thermogravimetric Analyzer ◽  
Heat Treated ◽  
Particle Size Analyzer ◽  
Ftir Spectrometer

In this work, the effect of heat treatment on chemical and crystalline structure of vetiver powder was studied. The vetiver powder was heat treated at 170°C, the temperature below thermal decomposition of hemicellulose, for 2-6 hours. The chemical structure, crystalline structure, and thermal decomposition of untreated and heat-treated vetiver were examined via FTIR spectrometer X-ray diffractometer, and thermogravimetric analyzer, respectively. In addition, the particle size and size distribution, fiber surface, and specific surface area were investigated by particle size analyzer, scanning electron microscope, and BET surface analyzer, repectively. It was founded that some waxes, lignin, and hemicellulose were removed by the thermal treatment. This resulted in smaller particle size of heat-treated vetivers. In addition, moisture content was minimized from 7 to 4 wt% by the treatment. However, removal of those compositions did not influence crystal structure of cellulose and surface functional groups of heat-treated vetiver.

scholarly journals Synthesise β-tricalcium phosphate (β-TCP) ceramic powder by 2 reaction steps: hydrothermaland calcination reaction toward bone tissue regeneration

2021 ◽  
Vol 63 (1) ◽  
pp. 39-41
Author(s):  
Huynh Quoc Huy Nguyen ◽  
◽  
Dai Phu Huynh ◽  
Van Thang Le ◽  
Dai Phong Lam ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Bone Tissue ◽  
Tissue Regeneration ◽  
Tricalcium Phosphate ◽  
Ceramic Powder ◽  
Treatment Temperature ◽  
Bone Tissue Regeneration ◽  
Molar Ratio ◽  
Heat Treated

This research presents the effect of heat treatment temperature on the forming ability of β-tricalcium phosphate (β-TCP) bioceramic materials toward the bone tissue regeneration application. Ca(OH)2 and H3PO4 were mixed with a Ca/P molar ratio of 1.5, followed by hydrothermal treatment at 180oC for 24 hours to obtain the calcium phosphate hydrate (CPH) with phase composition similar to hydroxyapatite (HA). The CPH mineral was heat-treated at 700 and 1000oC for 3 hours to evaluate the ability to obtain β-TCP. The result showed that β-TCP can be obtained by the CPH calcined at 1000oC for 3 hours, with the particle size of 1~2 μm, suitable for bone tissue regeneration application.

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