Papers by Keyword: Al₂O₃

Abstract: The paper presents a systematic approach to optimize the HVOF deposition technology of Al₂O₃ 40 TiO₂ coatings for the protection of components in the energy industry. Key performance factors evaluated include scratch resistance, surface roughness, and friction coefficient, given their importance for the intended applications. By means of a comprehensive experimental program using the Design of Experiment (DOE) method, the main HVOF process parameters were investigated, such as Fuel-to-Oxygen ratio (F/O), Stand-off Distance (SOD), and Powder Feed Rate (PFR), to identify optimal deposition conditions. Scratch resistance tests revealed that increasing the F/O and reducing the SOD significantly improved the tribological properties of the coatings. Surface morphology analysis through optical and electron microscopy confirmed that optimized HVOF parameters lead to dense coatings with low roughness and minimal defects, essential characteristics for components subjected to wear and severe friction. Additionally, tribological measurements demonstrated a significant reduction in the coefficient of friction for the optimized coatings. The obtained results demonstrate the HVOF technology’s capability to produce Al₂O₃ 40 TiO₂ coatings with superior properties for protecting energy industry components operating under severe conditions. The presented optimization approach can serve as a guide for best practices in developing new coating systems with enhanced performance.

Abstract: Resistance spot welding (RSW) is a key body-in-white welding technique. The copper alloy (CA) electrode cap (EC) is the most important factor that affects the quality and cost of welding. It is difficult for the existing CrZr EC to meet the high quality and low cost of welding new materials, such as thermoformed steel (TFS) plates. The microstructural and physicochemical characteristics and electrode cap service life of Al₂O₃ and rare earth (RE) copper alloy ECs under welding heat-pressure cycle during their service life were studied to find new EC materials to solve the problems mentioned above. The results show that the Al₂O₃ EC has high hardness, and Al₂O₃ is distributed in the form of spherical or elliptical particles. Under the action of heat-pressure cycle, they are constantly broken and refined, which further improves the creep resistance at high temperature and the life of the EC. Under the same conditions, the microstructures of the RE EC gradually changed from regular twins to fine grid-shaped twins, which played an active role in preventing dislocation movement and improving creep resistance. Al₂O₃ and RE can change the microstructures and interfacial behaviors via different mechanisms to improve the high-temperature creep resistance. Al₂O₃ EC is suitable for welding AlSi-coated plates, such as TFS plate, and prevents further erosion of the surface owing to its ceramic properties. RE EC is suitable for welding galvanized plates because of its special twin microstructures, which can change the properties and structure of the erosion layer and reduce the interfacial tension. The study of the microstructures and interface layer characteristics of the two ECs provided a theoretical basis and research direction for the development and life improvement of ECs.

Abstract: This bibliographic research explores the field of renewable energy by exploiting the potential of the High Velocity Oxygen Fuel Deposition (HVOF) method, an advanced thermal spray coating technology. HVOF involves propelling powder particles at remarkable speeds onto material surfaces, providing a means of applying protective coatings. This study explores the versatility of HVOF in creating protective coatings tailored for renewable energy applications. Specifically, the main coating targeted is the infrared reflective coating, made using alumina powders renowned for their exceptional attributes such as high strength, hardness, corrosion resistance and heat resistance, making them ideal for various components used in the renewable energy sector.

Abstract: Ceramic/ metal functionally graded materials (FGMs) have been promising to sustain coating structures working under super high temperature as well as high temperature gradient conditions. Compositional gradients in the FGMs can be engineered according to functional performance requirements. This study aims to fabricate Al₂O₃/ZrO₂/SUS304 hybrid FGMs with continuous compositional gradient manners using a combination of centrifugal slurry methods and spark plasma sintering (SPS). The compositional gradients in the FGMs were investigated on microstructures with elemental distributions and hardness on the cross sections of the FGMs. It was demonstrated that the compositions of ZrO₂ and SUS304 continuously varied in the FGMs, while Al₂O₃ resided only on ZrO₂-rich sides, which can effectively enhance the fracture toughness of the ZrO₂-rich layer. Ball milling treatments can make the Al₂O₃ layer more formed in the ZrO₂-rich layer. With increasing the amount of Al₂O₃, the Al₂O₃ layer resided closer to the top of the ZrO₂ surfaces in the FGMs subject to ball milling treatments, which can prevent the crack propagation from the ZrO₂ top surfaces.

Abstract: In this paper a combination of colloidal silica and different gelling agents are studied in order to observe the effect of gelation rate on the formed sol-gel structure. Proper ratios of sol matrix materials and gelation agents were determined. Sets of samples based on these recipes were prepared with added filling material and tested for mechanical properties. Samples with added solution of NaCl gelling agent showed the highest flexural strength observed and also lower doses of this gelling agent are required for one of the studied sols which can positively effect the final price of product.

Abstract: In this work, an aluminum oxide nanocoating was prepared using the pulsed laser deposition technique to study the properties of the coating and to find the optimal conditions to achieve the highest quality of the aluminum oxide nanocoating. The structural properties were studied using X-ray diffraction. The results showed that the aluminum oxide nanocoatings were alpha phase polycrystalline structures. The surface topography was studied using atomic force microscopy. The surface topography showed that the average surface roughness ranged from 1.26 nm to 7 nm. The optical properties were studied using a UV-VIS spectrometer. It showed the energy gap within the range 4.09 eV to 3.98 eV. The hardness of the aluminum oxide nanocoatings were calculated using the nanoindentation technique and found within the range of 32.79 GPa to 10.41 GPa. According to the present work, the effect of the input parameters represented by the pulse energy and the number of pulses on the responses represented by the energy gap, hardness, and surface roughness were studied. The experiments were designed based on the L9 orthogonal array with the Taguchi approach. A multiple responsive optimizations of Takeuchi's design was done using the desirability function.

Abstract: The purpose of this study was the research for a non-standardized method of measuring the shear bond strength at constant compression force and compare with the shear testing methods on cylindrical and prismatic samples, like DIN 50161:1977-10, DIN EN15340-2007. The conducted comparative analysis showed a significant shortcoming of the well-known methods for assessing the shear bond strength on samples for industrial application. The main one is an inability to measure the “actual/real” adhesion shear strength of thermal spray coatings for industrial parts. The shear bond strength of plasma-sprayed coating MgAl₂O₄ with thickness 0.30-has been investigated by applying the prismatic samples (linear dimensions of shear area 1.5-), using Nanovea scratch tester at compression forces ranging from 1 to 70 N. Shear force-displacement curves get essential information about adhesion/cohesion, delamination and cracking properties of thermal spray coating. An increase of shear forces is primarily associated with a rise in friction forces at the coating delamination boundary. Applying for parts of the ITER blanket modules, this research has demonstrated the importance of practical application of the shear testing results at compressive loads for ensuring product life.

Abstract: Metal matrix composites are the novel engineering materials finding applications in several extreme environmental and industrial requirements leading to the developments of numerous types of its kind in recent decades. Powder metallurgical techniques is one among the promising methods of producing intricate shaped end products out of the MMCs. Essentially the uniformity in distribution of the reinforcements and the accuracy in employing the percentile addition of the reinforcements decide the tailor made properties of these composites. There are several techniques to evaluate the reinforcement percentage and uniformity. This work concentrates on the analysis of effectiveness of volume fraction determination methods namely Archimedes test and acid dissolution test for 7075 Al/Al₂O₃ composite. Using the two methods the volume fraction of 7075Al/ Al₂O₃ composite prepared by powder metallurgy technique is determined. Advantages and disadvantages of both methods were analyzed using the result analysis and the observation indicated that the acid dissolution test produces more accurate results than the Archimedes test. In addition, the randomized selection of the specimens out of the end products leads to the corroboration of reinforcement uniformity in the composite matrix.

Abstract: The synthesis of acid-activated Al₂O₃-pillared bentonite as a solid acid catalyst has been completed. The pillarization process was carried out using the varying pf calcination time, mole OH/Al ratio, and mmol of Keggin/bentonite to determine the optimum total acidity. The higher the calcination time, (OH/Al) ratio, and suspension concentration, the greater the acidity of ​​the Al₂O₃-pillared bentonite. The optimum conditions were achieved at a calcination time of 20 minutes, a mol of (OH/Al) ratio of 2.2, and Keggin/bentonite of 10 mmol with a total acidity of 11.76 mmol gram ammonia and 2.44 mmol/gram pyridine. The pillared bentonite had a surface area of ​​154.64 m²/g and a pore diameter of 3.38 nm. The pillaring process was successfully increasing the basal spacing of natural bentonite from 14.77 to 17.78.

Abstract: Composite materials were applied to meet the demands of production efficiency on industrial because they offered the superior properties both of aspects on mechanical and physical properties were constantly being refined and developed with several methods. Composite technology with aluminum as a matrix as well as ceramic materials as reinforcement was very dependent on a result of the perfection of the manufacturing process on the matrix material and reinforcement was used. Aluminum currently still dominates as a matrix because of its ductility, while reinforcing materials that are widely used are ceramic elements such as silicon carbide (SiC) and alumina (Al₂O₃). Using of SiC/Al₂O₃ has been widely studied because of the remarkable improvement of the mechanical properties it produces. The addition of number of SiC particles to Al₂O₃ was able to significantly increase the hardness properties. In this study, a number of composite manufacturing methods were compared from the results of properties by accumulative press bonding (APB), accumulative roll bonding (ARB), and repetitive press roll forming (RPRF). The mechanical properties of RPRF results are known to produce better properties, especially mechanical properties. Mechanical properties were observed from tensile and hardness tests. The finer grain size is produced by increasing the compression cycle and increasing the mechanical properties when adding double reinforcement of the SiC/Al₂O₃, which causes the strength and hardness of the RPRF results to increase. Whereas other methods such as APB and ARB it is not compatible with composite materials, this proves that the RPRF method was very suitable for processing composite materials compared to APB and ARB methods.