Recession Behaviour of Oxides under High Velocity Steam Jet | Chapter 7 | New Horizons of Science, Technology and Culture Vol. 6

 

This review summarises the results of a collaborative research project between the Advanced Manufacturing Research Institute (AIST) and Oak Ridge National Laboratory (ORNL) from 2002 to 2005, conducted as part of the “US-Japan High-Level Consultation on Climate Change Science and Technology Working Group.” The focus was on water vapour as a corrosion species. The oxide was exposed to the same temperature and high-velocity steam jet conditions as those in gas turbines, and its corrosion behaviour was evaluated. The investigation targeted oxides with good corrosion resistance in preliminary tests and low coefficients of thermal expansion. Specifically, rare earth silicates, eutectic materials, and zircon were examined. The polycrystalline rare earth silicate phase developed a porous surface due to selective corrosion of the intergranular glass phase. The crystalline phase is also partially decomposed, resulting in a silica-deficient phase. In the corrosion of rare earth silicate phases, the presence of grain boundary glass phases significantly affected the stability of the crystalline phase itself. The Lu2Si2O7/Al6Si2O13 eutectic material, prepared through solidification, lacked glass phases at the grain boundaries, which prevented the formation of porous structures due to corrosion. The Al6Si2O13 phase was fully corroded. Tests on the zircon phase showed that the silica component leached from the crystalline structure. Generally, when double oxides containing silica are exposed to gas turbine conditions, phase decomposition occurs, leading to corrosion of the silica components. This results in the formation of a silica-deficient phase at the bulk surface. For many oxides, exposure tests conducted under gas turbine conditions have demonstrated that Lu2Si2O7 exhibits the highest corrosion resistance. Therefore, controlling the microstructure of the EBC layer containing this phase or the overall structure of the coating is significant for further enhancing corrosion resistance.

 

 

Author(s) Details

Shunkichi Ueno
College of Engineering, Nihon University, Koriyama, Fukushima 963-8642, Japan.

 

Hua Tay Lin
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006, China.

 

Please see the book here :- https://doi.org/10.9734/bpi/nhstc/v6/6762

Recession Behaviour of Oxides under High Velocity Steam Jet | Chapter 7 | New Horizons of Science, Technology and Culture Vol. 6

 

This review summarises the results of a collaborative research project between the Advanced Manufacturing Research Institute (AIST) and Oak Ridge National Laboratory (ORNL) from 2002 to 2005, conducted as part of the “US-Japan High-Level Consultation on Climate Change Science and Technology Working Group.” The focus was on water vapour as a corrosion species. The oxide was exposed to the same temperature and high-velocity steam jet conditions as those in gas turbines, and its corrosion behaviour was evaluated. The investigation targeted oxides with good corrosion resistance in preliminary tests and low coefficients of thermal expansion. Specifically, rare earth silicates, eutectic materials, and zircon were examined. The polycrystalline rare earth silicate phase developed a porous surface due to selective corrosion of the intergranular glass phase. The crystalline phase is also partially decomposed, resulting in a silica-deficient phase. In the corrosion of rare earth silicate phases, the presence of grain boundary glass phases significantly affected the stability of the crystalline phase itself. The Lu2Si2O7/Al6Si2O13 eutectic material, prepared through solidification, lacked glass phases at the grain boundaries, which prevented the formation of porous structures due to corrosion. The Al6Si2O13 phase was fully corroded. Tests on the zircon phase showed that the silica component leached from the crystalline structure. Generally, when double oxides containing silica are exposed to gas turbine conditions, phase decomposition occurs, leading to corrosion of the silica components. This results in the formation of a silica-deficient phase at the bulk surface. For many oxides, exposure tests conducted under gas turbine conditions have demonstrated that Lu2Si2O7 exhibits the highest corrosion resistance. Therefore, controlling the microstructure of the EBC layer containing this phase or the overall structure of the coating is significant for further enhancing corrosion resistance.

 

 

Author(s) Details

Shunkichi Ueno
College of Engineering, Nihon University, Koriyama, Fukushima 963-8642, Japan.

 

Hua Tay Lin
School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510006, China.

 

Please see the book here :- https://doi.org/10.9734/bpi/nhstc/v6/6762

Geopolymer Composite Materials from Mining and Agricultural Residues for Engineering Applications: Red Mud and Rice Husk Ash | Chapter 7 | Current Research on Geography, Earth Science and Environment Vol. 3

 

The transformation of raw materials into finished products generates residues and waste, whose management has become an environmental concern. With industrialisation and increasing material complexity, human activities have led to the exponential generation of waste. The more diverse and synthetic the materials involved, the more challenging it becomes to manage waste in ways that fulfil the dual objectives of protecting human health and the environment while conserving natural resources. In the Bayer process, the reaction of bauxite with sodium hydroxide to produce alumina results in the generation of red mud (RM), a highly alkaline waste that occupies land and poses environmental risks. In Guinea, rice is a staple food, and its processing produces large quantities of rice husk (RH), which also presents disposal challenges. RH contains about 20% silica, which becomes approximately 90% silica after combustion, forming rice husk ash (RHA) — a valuable material for various applications. Geopolymer technology offers a sustainable route for the valorisation of industrial residues. This study aimed to develop and analyse geopolymer composite materials using red mud and rice husk ash as alternatives to conventional construction materials. In this study, a composite geopolymer (GP) was synthesised using RM from a local alumina plant, RH from a local rice mill in Guinea, and water glass solution (WGS). For mechanical and microstructural characterisation, the geopolymer specimens were categorised into three main groups—GPA, GPB, and GPC—based on varying RM and RHA ratios while keeping the water glass solution (WGS) constant at 15%. Various mix ratios of RM, RHA, and WGS were tested. The resulting specimens were evaluated for compressive strength at different curing temperatures. Microstructural characterisation was conducted using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The results revealed that the final product is predominantly composed of amorphous geopolymeric phases and that higher temperatures enhance the compressive strength of the material. The XRD of RM is characterised by the presence of sharp peaks mainly caused by hematite (Fe₂O₃), gibbsite (Al(OH)₃), akdalaite (4Al₂O₃·H₂O), lepidocrocite (FeO(OH)), and calcite (CaCO₃). There are no broad humps in the pattern; hence, amorphous phases are not present in large quantities. The greatest value of compressive strength was developed by the GPB1 specimen exhibited a strength:  36,31 MPa at ambient temperature and 66,97 MPa at 1000°C. Through geopolymerization, RM and RH are not stored in piles or dumped into nature; this is a considerable achievement for the circular economy and the zero waste principle.

 

 

Author(s) Details

D. Sidibé
Higher Institute of Mines and Geology of Boké, ISMGB, Guinea.

 

D. Keita
Higher Institute of Mines and Geology of Boké, ISMGB, Guinea.

 

A. A. Konaté
Higher Institute of Mines and Geology of Boké, ISMGB, Guinea.

 

O. B. Kaba
Higher Institute of Mines and Geology of Boké, ISMGB, Guinea.

 

M. Cissé
Higher Institute of Mines and Geology of Boké, ISMGB, Guinea.

 

S. Traoré
Polytechnic Institute, University of Conakry, UGANC, Guinea.

 

Please see the book here :- https://doi.org/10.9734/bpi/crgese/v3/6247