Advanced Ceramics Progress
Volume:6 Issue: 3, Summer 2020

This study investigates the effect of carbide particle size on the microstructure, mechanical properties, and abrasive wear resistance of WC-17%Co HVOF-sprayed coatings. The characteristics of WC-1, WC-2, and WC-3 coatings with carbide sizes of 1 µm, 0.9 µm, and 0.5 µm, respectively, were also investigated. WC-1 coating experienced the maximum carbon loss of 42%, while WC-2 and WC-3 coatings underwent lower carbon losses of 30% and 29%, respectively. The XRD pattern revealed W2C/WC peak ratios of 15.58, 9.14, and 14.96% for WC-1, WC-2, and WC-3 coatings, respectively. The Vickers microhardness of WC-1, WC-2, and WC-3 coatings was measured as 1418 ± 61, 1306 ± 71, and 1203 ± 57 kgf/mm2, respectively. The WC-2 coating showed the maximum fracture toughness of 5.9 MPa.m1/2, after which WC-3 and WC-1 coatings were characterized by 5.6 and 5.4 MPa.m1/2, respectively. The wear rate of the coatings abraded by alumina 60 was 1.2-7.8 times higher than that of the coatings abraded by silica 70 almost over the whole range of applied loads (19.6-127.5 N). The WC-3 coating exhibited lower abrasive wear resistance against alumina 60 than WC-1 and WC-2 coatings. The worn surfaces produced by alumina 60 abrasive showed indications of grooving, pitting, and cutting of the coatings’ surfaces. For all coatings abraded by silica 70, removal of the matrix, micro-grooving, carbide particles fragmentation, and voids formation through carbide pullout were detected. For WC-3 coating, in contrast to WC-2 and WC-3, the indications of sub-surface cracking were identified when abraded by both alumina 60 and silica 70.

In this research, the SiC-matrix composite with different amounts of TiC (0, 2.5, 5, 7.5, and 10 wt%) supplemented with additives including 4.3 wt% Al2O3 and 5.7 wt% Y2O3 were utilized to initiate the required liquid phase. The sintering process was performed using pressureless sintering at      1900 °C for 1.5 hours under argon atmosphere. The composition and microstructure of the obtained composites were analyzed using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and Energy-Dispersive X-ray Spectroscopy (EDX). The results showed that TiC additives improved the densification of samples and impeded the growth of SiC grains. According to the phase analysis, the SiC was the main phase, while the TiC and YAG were characterized as partial phases. Additionally, due to the reaction of TiC and Al2O3, the composition of the liquid phase contained YAG and YAM. Assessments revealed that the microstructure and the final properties of composites were affected by density, produced phases and their distribution in the matrix, and grain size. According to the results, upon increasing the TiC up to 5 wt%, all the measured properties including density, hardness, elastic modulus, and fracture toughness improved and reached 97.40%, 26.73 GPa, 392 GPa, and 5.80 MPa.m1/2, respectively. However, with increasing the additives to more than 5 wt%, these properties deteriorated. Microscopic evaluations revealed that crack deflection and crack bridging mechanisms contributed to the fracture toughness of SiC ceramics.

In this study, barium aluminosilicate glass sealant was synthesizedand characterized for Solid Oxide Fuel Cell (SOFC) applications. First, the stoichiometric amounts of powder were mixed and melted at 1330°C for 2h, followed by quenching in water. They were then pressed into cylindrical specimens under load of 200 MPa, followed by sintering at different temperatures. The phase content and microstructure of the samples were analyzed by X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) methods, respectively. Microhardness and toughness of the sintered samples were investigated by means of Vickers micro-hardness test. Young’s modulus and nano-hardness of the glass sealant were measured by nano-indentation method. The thermal expansion coefficient of the specimens was estimated by a dilatometer. The results showed that after sintering at 750°C, sealants with homogeneous microstructure and high density were obtained. The sealants were characterized by mechanical and thermal properties appropriate for SOFC applications with a very low leak rate.

One of the popular orthopedic implants is utilizing fixation screws to fix Anterior Cruciate Ligament (ACL) grafts and secure the graft into femur and tibia. Currently, these screws are made of titanium or bioabsorbable materials. In this respect, bioabsorbable screws were generated in order to overcome some of the potential problems caused by metallic screws. Although the bioabsorbable screws are susceptible to some drawbacks includingbone ingrowth features as well as good in vitro and in vivo mechanical properties. The biomechanical results of ACL screws showed that the ultimate failure loads and yield point loads varied from 800-1500 N and 600-1000 N, respectively. Moreover, the evaluations of in vivo degradation behaviorshowed the almost complete or fully complete resorption of ACL screws from 6 month to 2 years. However, it was proved that the addition of bone mineral phases such as Hydroxyapatite (HA), β-Tricalcium Phosphate (β-TCP), and Calcium Carbonate (CC) could enhance this degradation rate. Incorporation of biceramics into pure polymeric ACL screws may contribute to enhancing the osteogenesity of bone after full resoprption of screws,function as buffering agents that decrease the acidity of screw adjacents resulting from degradation of products, andimprovee the mechanical properties of ACL screws. In this paper, the latest bioabsorbable ACL screws which are currently available for graft fixation in orthopedic markets are discussed. A brief review of the literature regarding the physical, biological, and mechanical properties of bioabsorbable ACL screws was made. Besides,the insertion technique, various manufactured sizes, and in vitro and in vivo mechanical properties for each screw were addressed.

Bioactive glass-ceramics play an important role in bone tissue regeneration. In the present research, the crystallization of glasses and scaffold fabrication were investigated. After choosing the appropriate composition in the SiO2-CaO-Na2O-p 2O5 system, raw materials were melted at 1400  and then, quenched in water. Subsequently, the crystallization of synthesized glass samples was studied. Fourier Transfer infrared (FT-IR) spectroscopy was carried out to study the structural changes of the samples. XRD patterns showed that fluorapatite Ca10(PO4)6(O,F2) was the only precipitated crystalline phase. The template synthesis method was applied for the fabrication of the scaffold and starch as a porogen material. The optimized scaffold structure was chosen with the appropriate size of pores, interconnectivity, and strength behavior through investigating the porosity, SEM images, and mechanical properties. ICP, SEM, and EDX analyses were used to determine the in vitro bioactivity of the samples after immersion for 14 days in SBF.

In the present study, the Ni-P-GO nanocomposite coating was applied to the surface of AZ31D alloy through electroless plating process. To achieve the nanocomposite coating, 5 g/L Graphene Oxide (GO) was added to the plating bath. By changing the pH of the bath, coatings were created in three ranges of low, medium, and high phosphorus on the surface of AZ31D. According to the results, by increasing the phosphorus content, the amount of graphene oxide absorbed in the coating increased. Microstructural examination by Scanning Electron Microscopy (SEM) showed that all coatings formed on the substrate had the cauliflower morphology. Phase analsis of the coating by X-Ray Diffraction (XRD) showed that at a low phosphorus level, the coating is semi-amorphous; however, with increasing phosphorus content, the coating becomes completely crystalline. The highest hardness value of the specimen was observed with the lowest amount of phosphorus. The microhardness measurments showed that the hardness decreased with increasing the amount of phosphorus so that the minimum hardness of the specimen containing 14.97 wt.% phosphorus was measured at 521 Hv50. Contrary to the morphology, phosphorus levels have a significant effect on the structure and hardness of Ni-P-GO nanocomposite coatings. As the amount of phosphorus increased, the corrosion resistance of the coating increased. This is attributed to the reduction of the current of corrosion and more positive potential values.