Papers by Keyword: Hydrothermal Treatment

Abstract: In this study, carbonate apatite [Ca_10-x(PO₄)_6-y(CO₃)_z(OH)_2-x-y-z, CHAp], a bone substitute material, was coated on roughened titanium through a sol-gel hydrothermal method. The sol-gel process was used to prepare calcium tartaric complexes, which were then subsequently hydrothermally treated on titanium in the presence of sodium hydroxide, and sodium hydrogen phosphate. The results showed that carbonate apatite, composed of nanosized fibers, was evenly deposited across the titanium surface. This coating resulted in a lower surface roughness (Ra) value of 1.31 μm compared to 3.98 μm for uncoated titanium. Additionally, the carbonate apatite coating decreased the contact angles of the titanium surface, thereby significantly enhancing cell attachment and migration compared to the uncoated surface. These results could be valuable for further evaluation of this coating in biomedical applications.

Abstract: Preparation conditions of titanium oxide (TiO₂) powders were examined by the hydrolysis of titanium potassium oxalate (K₂TiO(C₂O₄)₂), through the homogeneous precipitation method (80oC for 24 h) and hydrothermal treatment (160 or 170oC for 1 h). According to the Rietveld analysis, almost a single phase of anatase TiO₂ could be obtained by the hydrothermal treatment at 160oC for 1 h, followed by the heating at 900oC for 10 min in air. The molar ratio of anatase to rutile TiO₂ was found to be controlled by optimizing the hydrothermal conditions in the solution and the heating conditions in air for the photocatalytic activity.

Abstract: The article considers a method of recycling citrogypsum – the сіtric acid production waste. A modified gypsum binder was obtained by means of dehydration of citrogypsum suspension and adding a modifier - polyacrylamide (PAA) - to it in conditions of autoclave treatment. The application of PAA as a modifying admixture causes the necessity to reduce the water-gypsum ratio (W/G) of the mix in order to prevent lamination at the molding product forming; at the same time, to provide the necessary flowability of the mix the introduction of plasticizing admixtures is needed, or the application of the harsher moulding mixtures or pressing technologies. For cylindrical samples, obtained by the compaction method at W/G=0.25 and the specific compacting pressure 20МPа, the optimal content of polyacrylamide as a modifying admixture amounts to 2% of the initial citrogypsum weight. This allows increasing the compression strength of the ready samples by more than 5 times. The samples, produced on the basis of modified gypsum binders, are characterized with high water resistance – the softening coefficient amounted to over 0.8.

Abstract: Thermal spraying is commercially used to produce hydroxyapatite coatings, but the high temperature depletes hydroxyl ions in the structure. To return hydroxyapatite to its original state, it is necessary to restore the hydroxyl ion content in the structure. In this work, the effect of hydrothermal treatment on the hydroxyl ions was investigated in hydroxyapatite powder and thermally sprayed hydroxyapatite coatings. Samples were hydrothermally treated at 200 °C for 24 h and 48 h. Chemical phases were determined by X-ray diffraction, functional groups and hydroxyl ion concentration was examined by Fourier transform infra-red spectroscopy. Results showed that hydrothermal processing of hydroxyapatite coatings at 200 °C for 48 hours produced the greatest increase in the hydroxyl ion concentration by 29%.

Abstract: Raw coal fly ash and acid pretreated fly ash were used to synthesize A-type zeolite by hydrothermal treatment. In order to synthesize zeolite A an aqueous gel having a molar batch composition of Na₂O:Al₂O₃:1.926SiO₂:128H₂O was utilized. Fly ash and zeolitic products were characterized by SEM, XRF, XRD and cation exchange capacity (CEC). After hydrothermal treatment, several types of zeolites were formed: zeolite A, analcime, faujasite and hydroxy-sodalite. The highest content of zeolite A was formed in the mixture treated at 80°C for 8 hours. CEC values of the zeolitic products were 28-38 times higher than that of in raw fly ash. Acid pretreatment which leads to low calcium and iron content is preferable method for processing of fly ash for the zeolite synthesis. Synthesized zeolite can be used for ion exchangers for water treatment.

Abstract: SUS 304 stainless steel is known to be a biocompatible material and is widely used as screws or plates. However, issues regarding iron ion release after implantation become a concern which limits the application of SUS304. Therefore, to overcome these shortcomings, surface modification on SUS304 by forming calcium layer is needed to disable iron release from the substrate and also to encourage cell attachment. In this study, initially SUS 304 substrate are subjected to electrolysis process in sodium chloride solution to form pitting corrosion. These pitting corrosion will give the anchoring effect for the calcium ions to attach. Then the substrate are subjected to hydrothermal treatment at 200°C in calcium phosphate solution for 24, 36, 48, and 60 hours for deposition of calcium ions on the pitted SUS304 surface. Surface morphology observed by scanning electron microscope (SEM) shows that the calcium ions were deposited on the surface of the SUS304 substrate regardless hydrothermal treatment time. Rockwell hardness values shows that as hydrothermal treatment time increased the hardness value decreases. Therefore, hydrothermal treatment method enables the deposition of calcium ions layer on the surface of SUS304 which will inhibit the release of iron ions and enhanced bone attachment with the implant due to the bonding of the calcium ions with the bone.

Abstract: Carbonate apatite would be ideal for bone substitute due to its composition of 4-8% carbonate similar to bone mineral. The purpose of the present study was to produce carbonate apatite scaffold by using hydrothermal treatment of β-TCP scaffold as a precursor. The effect of different solutions on hydrothermal treatment was studied. The microstructure of scaffold before and after hydrothermal were characterized by scanning electron microscopy (SEM). It is observed that surface characteristics are governed by the types of immersion solution. The typical smooth surface of the β-TCP scaffold was observed before hydrothermal. Different morphology was observed after hydrothermal in different solutions. X-Ray Diffraction (XRD) pattern indicates that the peak of apatite with low intensities present after hydrothermal treatment in sodium hydrogen carbonate solution.

Abstract: Milling and hydrothermal treatment of alumina powders in aqueous medium can result in surface transformations generating aluminum hydroxides. The aim of this work was to advance the understanding on these transformations. A α-alumina powder was ball milled in water at different pHs for 10 h, and then autoclaved (150 °C, 3 atm, 3 h). The powders were analyzed by transmission electron microscopy, differential scanning calorimetry simultaneously with thermogravimetry, X-ray diffraction, and infrared spectroscopy. It was observed that milling in basic medium caused the formation of doyleite [Al (OH₃)] nanoparticles, which were fully converted to boehmite (AlOOH) by hydrothermal treatment. The boehmite fraction determined by thermal analysis was 1.7 wt%. The powder milled in acid medium had no mechanochemical and hydrothermal transformations.

Abstract: Surface hydrophilicity is considered to have a strong influence on the biological reactions of bone-substituting materials. However, the influence of a hydrophilic or hydrophobic surface on the osteoconductivity is not completely clear. In this study, we produced super-hydrophilic and hydrophobic surface on Ti-and Zr-alloys. Hydrothermal treatment at 180 ^oC for 180 min. in the distilled water and immersion in x5 PBS(-) brought the super-hydrophilic surface (water contact angle < 10 (deg.)) and heat treatment of as-hydrothermaled the hydrophobic surface. The osteoconductivity of the surface treated samples with several water contact angle was evaluated by in vivo testing. The surface properties, especially water contact angle, strongly affected the osteoconductivity and protein adsorbability, and not the surface substance.

Abstract: Protein adsorption is considered to have a strong influence on the biological reactions of bone-substituting materials. However, the osteoconductivity of protein adsorbed Ti surface is not completely clear. In this study, we produced the protein adsorbed Ti implants using hydro-processing. The hydrothermal treatment in the distilled water gave the super-hydrophilic Ti surface and they had much protein adsorbability. Fibronectin or albumin was picked up as a protein, which was cell adhesive protein and not cell adhesive, respectively. And also, the content of the adsorbed protein was evaluated by FT-IR (ATR) analysis. The water contact angle influenced the amount of the adsorption of the protein and the osteoconductivity of the samples were evaluated by in vivo testing.