scholarly journals Hydration behavior and microstructural evolution of hydratable alumina with different particle size in alumina-spinel castables

2019 ◽  
Vol 127 (4) ◽  
pp. 199-206 ◽  
Author(s):  
Nana XU ◽  
Yuanbing LI ◽  
Sheng FANG ◽  
Shujing LI ◽  
Hailu WANG ◽  
...  
Keyword(s):  
Particle Size ◽  
Microstructural Evolution ◽  
Hydratable Alumina

scholarly journals Simulated Microstructural Evolution and Design of Porous Sintered Wicks

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Karthik K. Bodla ◽  
Suresh V. Garimella
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Transport Properties ◽  
Effective Thermal Conductivity ◽  
Surface Area ◽  
Microstructural Evolution ◽  
Ad Hoc ◽  
Three Dimensions ◽  
Two Phase ◽  
Sintering Kinetics

Porous structures formed by sintering of powders, which involves material-bonding under the application of heat, are commonly employed as capillary wicks in two-phase heat transport devices such as heat pipes. These sintered wicks are often fabricated in an ad hoc manner, and their microstructure is not optimized for fluid and thermal performance. Understanding the role of sintering kinetics—and the resulting microstructural evolution—on wick transport properties is important for fabrication of structures with optimal performance. A cellular automaton model is developed in this work for predicting microstructural evolution during sintering. The model, which determines mass transport during sintering based on curvature gradients in digital images, is first verified against benchmark cases, such as the evolution of a square shape into an area-preserving circle. The model is then employed to predict the sintering dynamics of a side-by-side, two-particle configuration conventionally used for the study of sintering. Results from previously published studies on sintering of cylindrical wires are used for validation. Randomly packed multiparticle configurations are then considered in two and three dimensions. Sintering kinetics are described by the relative change in overall surface area of the compact compared to the initial random packing. The effect of sintering parameters, particle size, and porosity on fundamental transport properties, viz., effective thermal conductivity and permeability, is analyzed. The effective thermal conductivity increases monotonically as either the sintering time or temperature is increased. Permeability is observed to increase with particle size and porosity. As sintering progresses, the slight increase observed in the permeability of the microstructure is attributed to a reduction in the surface area.

Fabrication of Ce-Promoted Ni/Al2O3 Methane Steam Reforming Catalysts by Impregnation

2020 ◽  
Vol 20 (7) ◽  
pp. 4327-4330
Author(s):  
Ye Sol Lim ◽  
Min-Jin Lee ◽  
Kyoung-Jin Lee ◽  
Sangjin Lee ◽  
Haejin Hwang
Keyword(s):  
Particle Size ◽  
Microstructural Evolution ◽  
Steam Reforming ◽  
Carbon Deposition ◽  
Methane Steam Reforming ◽  
Ni Catalysts ◽  
Good Dispersion ◽  
Methane Steam ◽  
Reforming Catalysts ◽  
Steam Reforming Catalysts

CeO2-promoted Ni/Al2O3 catalysts were fabricated by impregnation. The effects of the CeO2 promotion and impregnation order on the microstructural evolution and catalytic durability were investigated for methane steam reforming. The CeO2-promoter nanoparticles resulted in good dispersion and reduced particle size of Ni catalysts. The enhanced durability of CeO2-promoted Ni/Al2O3 catalysts might be associated with the depression of carbon deposition by the presence of CeO2-promoter nanoparticles.

The Microstructural Evolution of Mn3O4 Hausmannite during Autoxidation

2007 ◽  
Vol 280-283 ◽  
pp. 693-698 ◽  
Author(s):  
Ting Fang ◽  
Jenq Gong Duh ◽  
Sue Yueh Tsai
Keyword(s):  
Particle Size ◽  
Low Temperature ◽  
Microstructural Evolution ◽  
Alkaline Solution ◽  
Manganese Oxides ◽  
Tetrahedral Site ◽  
Morphological Transformation ◽  
Particle Size And Morphology ◽  
Normal Spinel ◽  
Size And Morphology

Mn3O4 hausmannite, which is a normal spinel with the Mn2+ in the tetrahedral site and the Mn3+ in the tetrahedral site, is one of the most stable manganese oxides. Variation in the valence of Mn ions (2+, 3+ and 4+) contributes to several different structures of manganese oxides. The autoxidation of precipitated manganese hydroxide in an alkaline solution is a practical approach to synthesize hausmannite (Mn3O4) at low temperature. During the process, the particle size and morphology of derived products were totally different from the precursors even though nanometer-sized Mn(OH)2 crystals were fabricated at first. It was observed that the variation was resulted from the accumulation of produced Mn3O4 crystallites which departed from the original crystals. This study has not only discussed the influence of reactant concentrations on the particle size and morphology of derived powders, but also revealed the morphological transformation of crystals involved in autoxidation with the aid of electron micrographs

Microstructural Evolution and Transport Properties of Sintered Porous Media

2013 ◽  
Author(s):  
Karthik K. Bodla ◽  
Suresh V. Garimella
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Transport Properties ◽  
Effective Thermal Conductivity ◽  
Microstructural Evolution ◽  
Three Dimensions ◽  
Two Phase ◽  
Sintering Kinetics ◽  
Relative Change ◽  
Area Preserving

Sintering is a material-bonding phenomenon that occurs under the application of heat. The porous structures formed by sintering powders are commonly employed as capillary wicks in two-phase heat transport devices such as heat pipes. These sintered wick microstructures are often not truly optimized for fluid and thermal performance. Understanding the role of sintering kinetics, and the resulting microstructural evolution, on wick transport properties is important for fabrication of structures with optimal performance. In this study, a cellular automaton model for predicting microstructural evolution during sintering is developed. The model, which determines mass transport during sintering based on curvature gradients in digital images, is first verified against benchmark cases, such as the evolution of a square into an area-preserving circle. The model is then employed to predict the sintering dynamics of a side-by-side two-particle configuration conventionally used for the study of sintering. Data from previously published studies on sintering of cylindrical wires is used for validation. Randomly packed multi-particle configurations are then considered in two and three dimensions. Sintering kinetics are described by the relative change in overall surface area of the compact compared to the initial random packing. The effect of sintering parameters, particle size, and porosity on fundamental transport properties, viz., effective thermal conductivity and permeability, is analyzed. The effective thermal conductivity increases monotonically as either the sintering time or temperature is increased. Permeability was observed to be largely independent of sintering conditions, but increases with particle size and porosity.

Sintering Studies and Microstructural Evolution of Fe-MoS2 Mixtures

2014 ◽  
Vol 802 ◽  
pp. 415-420 ◽  
Author(s):  
Kaline Pagnan Furlan ◽  
Julia Zimmermann de Assunção ◽  
Gustavo Paz ◽  
Cristiano Binder ◽  
Aloisio Nelmo Klein
Keyword(s):  
Particle Size ◽  
Chemical Composition ◽  
Molybdenum Disulfide ◽  
Microstructural Evolution ◽  
Solid Lubricant ◽  
Particle Sizes ◽  
Iron Sulfides ◽  
Iron And Steel ◽  
The World

The development of dry self-lubricating materials is directly linked to the rising requirements of performance. Iron and steel are the most used metals around the world and molybdenum disulfide (MoS2) one of the most used solid lubricant. Therefore it is expected that one might try to develop self-lubricating steels containing MoS2, however MoS2 reacts with steel matrices during sintering. This work has focused on the study of these reactions; temperatures at which this occurs; the influence of particle sizes and MoS2 content and also MoS2 influence during processing and in the parts properties. The results showed that the reaction occurs at lower temperatures than the predicted and the products are iron-molybdenum and iron sulfides. The sintering studies revealed that MoS2 enhances sintering and the particle size and MoS2 content directly influenced the morphology and chemical composition of the resulting phases.

scholarly journals Microstructure and Thermal Conductivity of Sintered Reaction-Bonded Silicon Nitride: The Particle Size Effects of MgO Additive

2018 ◽  
Vol 2018 ◽  
pp. 1-5 ◽  
Author(s):  
Shin-Il Go ◽  
Yinsheng Li ◽  
Jae-Woong Ko ◽  
Ha-Neul Kim ◽  
Se-Hun Kwon ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Silicon Nitride ◽  
Liquid Phase ◽  
Grain Growth ◽  
Microstructural Evolution ◽  
Size Effects ◽  
Phase Distribution ◽  
Particle Size Effect ◽  
Sintering Additive

The particle size effect of MgO as a sintering additive on the thermal conductivity of sintered reaction-bonded silicon nitride (SRBSN) was investigated. It was revealed that the size of MgO is critical for thermal conductivity with regard to the microstructural evolution process. That is, the abnormal grain growth promoted by an inhomogeneous liquid-phase distribution led to higher thermal conductivity when coarser MgO was added, whereas a relatively homogeneous liquid-phase distribution induced moderate grain growth and lower thermal conductivity when finer MgO was added.

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