Effects of hydroxyapatite/Zr and bioglass/Zr coatings on morphology and corrosion behaviour of Rex-734 alloy

Structural, physical, and radiation absorption properties of a significant nuclear power plant component: A comparison between REX-734 and 316L SS austenitic stainless steels

Austenitic stainless steels (SSs) are commonly used as in-core and surrounding structural materials in today’s industrial BWR and PWR systems. Such adaptable steels have also been the primary materials studied and used in several advanced nuclear reactor technologies, such as fast breeding and magnetic fusion reactors. In this study, some critical material properties, such as structural, physical, and radiation-shielding properties of REX-734 and 316L SS, were experimentally evaluated and compared to those of a number of other alloys. In addition to homogeneous element distribution, both alloys exhibit strong crystal orientation. The REX-734 alloy has a tensile strength of 1,259 MPa, whereas the 316L SS alloy has a tensile strength of 495 MPa. Moreover, nitrogen in the REX-734 alloy formed ultra-hard nitrides with Cr, Nb, and Si and precipitated into the structure and increased the strength. According to our findings, the mass attenuation coefficient values of the 316L SS sample were slightly higher than those of the REX-734 sample at all energies. It can be concluded that the REX-734 sample, with its exceptional strength qualities and excellent radiation attenuation capabilities, may be a viable nuclear power plant material for future investigations.

Boron-incorporated biocomposite coatings on 316L and NiTi alloys: Enhanced structural, antibacterial activity, and cell viability performances

Boron doped (5 %, 10%, and 15 wt.%) Hydroxyapatite (B-HA) biocomposites were syntesized and coated on 316L SS and NiTi (Ni-45Ti) metallic substrates by using the electrophoretic deposition process (EPD). The morphological and structural characterization of the coatings was executed using scanning electron microscopy (SEM) and X-ray diffraction devices (XRD). Antibacterial tests were conducted using Escherichia coli ( E. coli, JM103) and Staphylococcus aureus ( S. aureus, ATCC29293) microorganisms. The mitochondrial activity assay (MTT)-[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] was used to examine cell viability and cytotoxicity in Saos-2 osteoblast cells. HA and boron peaks, as well as B-TCP and metallic components, were detected in XRD examinations. Porous morphologies were generated on the surface with boron doped B-HA coatings, as revealed by SEM views. Antibacterial activity studies revealed that both metallic coating groups, notably with boron doping, demonstrated antibacterial activity against gram-negative E. coli and gram-positive S. aureus. The antibacterial activity of the 316L group was shown to be better than that of the NiTi group in comparisonal testing. The syntesized boron-doped biocomposite coatings did not have any detrimental effects on living cells, according to cell viability studies. The cell viability rate was found to be greater in NiTi coatings than in 316 SS coatings, and the impact was amplified by the addition of boron.

Bioactive Glass—An Extensive Study of the Preparation and Coating Methods

Diseases or complications that are caused by bone tissue damage affect millions of patients every year. Orthopedic and dental implants have become important treatment options for replacing and repairing missing or damaged parts of bones and teeth. In order to use a material in the manufacture of implants, the material must meet several requirements, such as mechanical stability, elasticity, biocompatibility, hydrophilicity, corrosion resistance, and non-toxicity. In the 1970s, a biocompatible glassy material called bioactive glass was discovered. At a later time, several glass materials with similar properties were developed. This material has a big potential to be used in formulating medical devices, but its fragility is an important disadvantage. The use of bioactive glasses in the form of coatings on metal substrates allows the combination of the mechanical hardness of the metal and the biocompatibility of the bioactive glass. In this review, an extensive study of the literature was conducted regarding the preparation methods of bioactive glass and the different techniques of coating on various substrates, such as stainless steel, titanium, and their alloys. Furthermore, the main doping agents that can be used to impart special properties to the bioactive glass coatings are described.

Amorphous Silicon Oxynitrophosphide-Coated Implants Boost Angiogenic Activity of Endothelial Cells

Lack of osteointegration is a major cause of aseptic loosening and failure of implants used in bone replacement. Implants coated with angiogenic biomaterials can improve osteointegration and potentially reduce these complications. Silicon- and phosphorus-based materials have been shown to upregulate expression of angiogenic factors and improve endothelial cell functions. In the present study, we hypothesize that implants coated with amorphous silica-based coatings in the form of silicon oxynitrophosphide (SiONP) by using plasma-enhanced chemical vapor deposition (PECVD) technique could enhance human umbilical vein endothelial cell angiogenic properties in vitro. The tested groups were: glass coverslip (GCS), tissue culture plate, SiON, SiONP1 (O: 7.3 at %), and SiONP2 (O: 14.2 at %) implants. The SiONP2 composition demonstrated 3.5-fold more fibronectin deposition than the GCS (p < 0.001). The SiONP2 group also presented a significant improvement in the capillary tubule length and thickness compared with the other groups (p < 0.01). At 24 h, we observed at least a twofold upregulation of vascular endothelial growth factor A, hypoxia-inducible factor-1α, angiopoietin-1, and nesprin-2, more evident in the SiONP1 and SiONP2 groups. In conclusion, the studied amorphous silica-coated implants, especially the SiONP2 composition, could enhance the endothelial cell angiogenic properties in vitro and may induce faster osteointegration and healing. Impact Statement In this study, we report for the first time the significant enhancement of human umbilical vein endothelial cell angiogenic properties (in vitro) by the amorphous silica-based coatings in the form of silicon oxynitrophosphide (SiONP). The SiONP2 demonstrated 3.5-fold more fibronectin deposition than the glass coverslip and presented a significant improvement in the capillary tubule length and thickness. At 24 h, SiONP reported twofold upregulation of vascular endothelial growth factor A, hypoxia-inducible factor-1α, angiopoietin-1, and nesprin-2. The studied amorphous silica-coated implants enhance the endothelial cell angiogenic properties in vitro and may induce faster osteointegration and healing.

Zirconia/Hydroxyapatite Composites Synthesized Via Sol-Gel: Influence of Hydroxyapatite Content and Heating on Their Biological Properties

Zirconia (ZrO₂) and zirconia-based glasses and ceramics are materials proposed for use in the dental and orthopedic fields. In this work, ZrO₂ glass was modified by adding different amounts of bioactive and biocompatible hydroxyapatite (HAp). ZrO₂/HAp composites were synthesized via the sol-gel method and heated to different temperatures to induce modifications of their chemical structure, as ascertained by Fourier transform infrared spectroscopy (FTIR) analysis. The aim was to investigate the effect of both HAp content and heating on the biological performances of ZrO₂. The materials’ bioactivity was studied by soaking samples in a simulated body fluid (SBF). FTIR and scanning electron microscopy (SEM)) analyses carried out after exposure to SBF showed that all materials are bioactive, i.e., they are able to form a hydroxyapatite layer on their surface. Moreover, the samples were soaked in a solution containing bovine serum albumin (BSA). FTIR analysis proved that the synthesized materials are able to adsorb the blood protein, the first step of cell adhesion. WST-8 ([2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt]) assay showed that no cytotoxicity effects were induced by the materials’ extract. However, the results proved that bioactivity increases with both the HAp content and the temperature used for the thermal treatment, whereas biocompatibility increases with heating but is not affected by the HAp content.