Solid State Phenomena Vol. 340

Abstract: The present research work explores the possibility of use of HVOF sprayed cermet coating Stellite-6 on gas turbine material Titanium Alloy (Ti-31). The coating is investigated for their resistance to erosion under laboratory conditions. Solid particle erosion studies were conducted using silica sand as the erodent. Erosion studies were done with impact angles of 30º, 60º and 90º. Stellite-6 coating performs better under sand erosion conditions. Stellite-6 coatings undergo damage by brittle mode. Erosion behavior of the substrate materials is ductile and resistance is better than the coating material. SEM microstructures were used for scar produced by the erodent, at 30º, 60º and 90º. impact angles, also indicates that the material damage is due to ploughing and entrapment of silica particles.

Abstract: It is ended that from past few decades the consumption of fossil fuel as measuring at faster rates in order to satisfy the needs of mankind. Many researches are working in the process of measuring the efficiency of the engine. Thermal coating is a process applying a layer of coated materials on the surface of any metallic part. In this project working of the zirconium di oxide (ZrO₂) is used on coated material and NiCrAl is used on subtract material. A 0.1mm layer of zirconium di oxide is coated on top surface of the piston then the performance of the IC engine is evaluated. The performance parameter of the coated piston is compared with performance parameter of uncoated piston. The material efficiency and Brake power of the coated piston is expected to increase, since the melting point temperature of zirconium di oxide is more than 2500 degree Celsius.

Abstract: Calcium carbonate (CC)-hydroxyapatite (HAP) porous microparticles have gained a lot of popularity as a promising material for clinical applications. The objective of this study is to evaluate the effects of CC-HAP microparticles on osteoblast-like cells to be used as a bone-regeneration biomaterial. In this study, the different concentrations of conditioned media were used to compare the effects of released ions from CC-HAP microparticles. The material’s characteristics demonstrated that the immersion in cell culture medium did not change the crystal phases of CC-HAP. The decrease of calcium ions in cell culture medium is due to the dissolution-precipitation reactions on the material surfaces, which made more crystalline surfaces. The atomic absorption spectroscopy measurement demonstrated that the dissolution-precipitation reactions on the material surfaces in cell culture medium happened in 3 days and were stable between 3 to 5 days. The conditioned media immersed in cell culture medium for 4 days were used for further experiments. Cell evaluations demonstrated that excessive adding of CC -HAP could inhibit cell behaviors such as cell adhesion, proliferation, and differentiation. The cell adhesion indicated by the number of vinculin-positive focal adhesions per cell decreased with the increase of the CC-HAP concentrations. The cells cultured with CC-HAP proliferated at a lower rate than the control without CC-HAP. One of the reasons for the inhibition of cell proliferation was thought to be less formation of focal adhesions with higher concentrations of CC-HAP. The excessive adding of CC-HAP had an inhibitory effect on osteoblast differentiation. The results of this study revealed that the conditioned media prepared by immersion of CC-HAP porous microparticles in cell culture media had effects on the behaviors of osteoblast-like cells such as cell adhesion, proliferation, and differentiation.

Abstract: Bone graft materials are widely used in orthopedic and maxillofacial surgeries. The controlled resorbability of the graft material is essential for bone regeneration. Hydroxyapatite and biphasic calcium phosphate bone grafts have poor resorption and limited bone conductive effects. Histology analyses of bone biopsy from SCPC grafted human extraction sockets showed complete bone regeneration and graft resorption in absence of osteoclasts and macrophages. The hypothesis of the present study is that bioactive SCPC inhibits osteoclast’s activity due to the presence of resorbable silica phase in the material. Our objective is to analyze the effect of SCPC dissolution products on the resorption activity of osteoclasts. The conditioned medium was prepared by immersion of SCPC resorbable bioactive SCPC porous granules (Shefabone, Inc, USA) in cell culture medium at various ratios at 37°C for 3 days. The concentration of Si ions released from the SCPC granules into cell culture medium was measured using ICP-OES. Osteoclast precursors derived from human bone marrow were seeded on bone slices and cultured in the conditioned medium containing 10% FBS and osteoclast induction factors. Osteoclast differentiation and resorption were evaluated by TRAP staining and measurement of the volume of resorption pits on the bone slices. Mature multinuclear giant TRAP-positive osteoclasts were observed on the bone substrates after 14 days incubation in control medium containing osteoclast induction factors. In conditioned medium, the number of multinuclear TRAP-positive cells was significantly decreased as the concentration of SCPC dissolved silica increased. The dissolution of silica from SCPC into the culture medium correlates well with down regulation of osteoclast differentiation and the rapid bone regeneration in human bone defects.

Abstract: The aim of this study was to compare the difference in bone formation between hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) ceramics with similar porous structure. Porous HAp and β-TCP ceramics (total porosity: ~70%) with highly-interconnected structure were fabricated by firing calcium-phosphate fiber mixed with carbon beads (~150 μm). The size of highly-interconnected pores was measured by mercury intrusion technique. Each sample (ϕ4 mm × 8 mm) was implanted into the tibial bone defect (ϕ4.2 mm × 8 mm) of a pig (2 years old, male). After 6 weeks of implantation, undecalcified section was prepared and stained with hematoxylin and eosin (HE) stain. New bone area and remaining material area were evaluated.Interconnection sizes of HAp and β-TCP ceramics were 23.0 µm and 15.6 µm, respectively. New bone area of β-TCP ceramics was significantly higher compared to HAp ceramics. Remaining material ratio was 77.1 ± 3.3% for β-TCP ceramics whereas HAp ceramics remained stable. Bone formation in HAp ceramics was inhomogeneous compared to β-TCP ceramics in HE stained section. Although the β-TCP ceramics interconnection size was smaller, higher resorption may have played a positive role in homogeneous bone formation. According to the result of the study, it is suggested that highly-interconnected porous ceramics made by β-TCP could be a suitable material for bone regeneration.

Abstract: B-type carbonated hydroxyapatite (C_BHA) is potentially an excellent biodegradable bioceramic for bone repair. However, conventional sintering results in formation of undesired phases. Therefore, microwave sintering of C_BHA was investigated to assess the possibility to reduce formation of unwanted phases. Pellets with 0.8 mol% of B-type carbonate were sintered in a multimode instrumented cavity under static air with short thermal cycles. They were prepared from a C_BHA powder alone and from a mixture of C_BHA and carbon powder to generate a local in-situ CO₂ atmosphere. XRD, FT-IR, SEM and BET analyses indicated that C_BHA densification with increase temperature lead to decomposition into apatite. The addition of carbon powder to the C_BHA that generate a CO₂-rich atmosphere around the samples did not prevent the decomposition. Efficient control of temperature and atmosphere composition is required to improve microwave sintering of C_BHA bioceramics.

Abstract: The aim of this work was to identify robust and reproducible signatures characterizing the different steps of bone cell differentiation, from precursors to mature bone cells, using approaches allowing characterization by label-free imaging. Human mesenchymal stromal cells (hMSCs) were cultured either in a growth medium (GM), unable to induce cell differentiation by itself, or in an osteogenic differentiation medium (ODM) on hydroxyapatite ceramics or borosilicate glass. Cell density as well as cell structure, size, and morphology were investigated. A fluorescence microscopy-based approach was followed, using fluorescent labelling of cell features. Some early morphological changes of hMSC during osteogenic differentiation were identified as soon as 48h that were accentuated after 7 days of culture. Cell density was higher when cells were cultured in GM and the cells exhibited significantly smaller nuclei (size ratio about 1.3-1.5) than those cultured in ODM, regardless of the culture support. In ODM, the cells were also of bigger size (1.2 to 1.5 times) and their focal adhesions were reinforcedType I collagen, a gold standard marker of osteogenic differentiation, appeared more intense in ODM. These cell features can be determined using multimodal label-free imaging methods to characterize the differentiation state of hMSCs at the biomaterial surface. They give rise to new cost-effective approaches to investigate cell behavior by suppressing the chemical markers and reducing both the number of needed samples and the requested time to do so.

Abstract: Apatite nanocomposites with graphene (G) or graphene oxide (GO) nanoflakes, as well as with related carbonaceous materials, present promising applications in hard tissue engineering, biomedicine, or drug delivery. Different methodologies have been explored in the last years to prepare apatite-based nanocomposites. Sitting drop vapour diffusion (SDVD) methodology induces the heterogeneous nucleation of biomimetic apatite on the reinforcement material, improving biological properties of the nanocomposites. In this work SDVD was used to prepare G-apatite and GO-apatite nanocomposites. Prior to the SDVD experiments, G flakes were obtained by sonication-assisted liquid-phase exfoliation (LPE) using L-Alanine (L-Aln) as dispersing biomolecule, while a commercial aqueous Graphene Oxide (GO) dispersion was used for the nucleation essays in presence of the same biomolecules. A parallel set of nucleation experiments was performed in presence of Tb³⁺ ions, to endow the nanocomposites of luminescent properties. Characterization by XRD, FTIR, and TEM demonstrated the heterogeneous nucleation of needle-shaped apatite nanocrystals on the surfaces of G and GO flakes. Fluorescence spectroscopy certified the presence of Tb³⁺ ions in the nanocomposites resulting in luminescent materials which can be used in imaging or theragnostic. Finally, in vitro tests with human mesenchymal stem cells revealed excellent cytocompatibility and cell proliferation in presence of the nanocomposites.