INVESTIGATION OF SINTERING FEATURES OF CERAMIC MATERIALS BASED ON HYDROXYAPATITE AND ITS SUBSTITUTED FORMS

Порошки стехиометрического и фторзамещенного гидроксиапатита с повышенной активностью к спеканию (температура начала уплотнения составляет 600°С) синтезированы методом осаждения из раствора. Исследованы свойства синтезированных порошков и керамики после обжига. Показано, что введение фторид-ионов позволяет термически стабилизировать фазу апатита до температуры 1000°С, повысить степень дисперсности и площадь удельной поверхности, почти в три раза увеличить микротвердость материала. Сопоставление распределения частиц по размерам в синтезированных порошках и распределения зерен в спеченной керамике подтвердили наследование керамикой наноструктуры исходных порошков. Stoichiometric and fluorsubstituted hydroxyapatite powders with increased sintering activity (the initial compaction temperature is 600°C) were synthesized by precipitation from solutions. Properties of synthesized powders and ceramics after firing were investigated. It is shown that the introduction of fluoride ions can thermally stabilize the apatite phase to a temperature of 1000 °C, increase the degree of dispersion and the specific surface area, and almost three times increase the microhardness of the material. Comparison of the particle size distribution in synthesized powders and the grain distribution in sintered ceramics confirmed that ceramics inherited the nanostructure of the original powders.

Characterization and equilibrium studies for the removal of methylene blue from aqueous solution using activated bone char

The surface characteristics as well as adsorption potential of activated cow bone char for the removal of methylene blue (MB) from aqueous solution were investigated. Physical characteristics of the adsorbent revealed a large surface area, low pore volume, reduced ash and moisture contents, which have been identified as good adsorption characteristics. The surface of the adsorbent was predominated by mesopores with a few microporous structures as well as the presence of carbonates, phosphates, silicates and hydroxyl groups which are characteristic of the apatite phase. Adsorption efficiency for the removal of MB was observed to be influenced by pH, adsorbent dosage as well as initial dye concentrations. Equilibrium adsorption data was best described by the Freundlich isotherm with a good correlation coefficient suggesting multilayer adsorption of the dye molecules on the surface of the adsorbent. Based on the drive for reduced cost, removal efficiency and availability, activated carbon from cow bone could be a promising adsorbent for methylene blue-laden effluent that could be utilized in small and large industrial applications.

Investigation of Bioactive Glass-Ceramic 60SiO2-30CaO-10P2O5 Prepared by Hydrothermal Method

Bioactive glass-ceramics (BGCs) with the composition of 60SiO2-30CaO-10P2O5 (wt. %) have been synthesized by the hydrothermal method. The BGC samples were prepared at two reaction temperatures of 150 and 220°C, named BGC-150 and BGC-220. The XRD and FTIR analyses highlighted that the degree of crystallinity of BGCs increased linearly with hydrothermal reaction temperature. FE-SEM and TEM results indicated that the surface of BGC samples is covered by the nanosized particles which grow into larger sizes as a function of reaction temperature. The bioactivity of BGCs was investigated by the immersion of powder samples in the SBF solution. The results confirmed the dissolution and the interaction of BGC samples in the SBF solution which led to the formation of a new apatite phase on their surface.

Study of Carbonated Calcium Phosphate Precipitation on Collagen

Calcium phosphate biocomposites are candidate materials for bone tissue engineering due to their conductivity and biocompatibility. Calcium phosphate could be grown on collagen by precipitation method in long reaction time. Microwave irradiation is rapid method to assist precipitation by reducing reaction time. In order to study carbonated calcium phosphate precipitation on collagen and investigate the influence of microwave irradiation time, the carbonated calcium phosphate has been grown on collagen by microwave assisted precipitation method. The collagen sheets were soaked in carbonated calcium phosphate suspension prepared by using Ca(NO3)2.4H2O, (NH4)2HPO4, and NaHCO3 as starting materials, then microwave irradiated at 270 Watt for 2 minutes, 8 minutes, and 16 minutes. X-ray powder diffraction (XRD) pattern shows the transformation of dicalcium phosphate dyhydrate to apatite crystal structure. Increase in irradiation time had increased crystallinity of carbonate apatite phase. FTIR spectrum had confirmed presence of collagen, phosphate, and carbonate functional group. Scanning electron micrograph showed the presence of collagen with pore, and the carbonated calcium phosphate could attach and be deposited onto collagen.

Структура и физико-химические механизмы взаимодействия костной ткани с титановыми имплантатами в условиях туберкулезного остита

The structure and physicochemical mechanisms of interaction of bone tissue with titanium implants in tuberculous osteitis have been studied by scanning electron microscopy, X-ray phase analysis, IR spectroscopy and thermal analysis methods. It has been found that the physiological regeneration of bone tissue is accompanied by growth of organic components, embrittlement of the mineral phase of the bone matrix, and its fine disintegration during the treatment of tuberculosis osteitis. The presence of titanium implants during a physiologically normal state contributes to the activation of apatite phase synthesis in the regenerating bone. The main mechanism of implantation osteogenesis in tuberculous osteitis is the formation of the inorganic phase of hydroxyapatite mainly in the areas of destruction of the titanium alloy.

Preparation and characterization of apatite-like compound

Barium–lanthanum britholite solid solutions, Ba10-xLax(PO4)6-x(SiO4)xF2, with 0 ≤ x ≤ 6 were prepared by solid state reaction in the temperature range of 1200–1400 °C. The powders were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES), F-selective electrode, X-ray diffraction (XRD), and Fourier transform infrared (FTIR). In addition, the present study used thermal analysis to follow the apatite formation reaction during the heat treatment. For x ≤ 3, there is formation of a single apatite phase, whereas above this value, the La2SiO5, La2Si2O7, BaSi2O5, and Ba2La2O5 secondary phases were observed. The variation of the lattice parameters of the apatite phase as a function of x confirmed that the solid solution is discontinuous to either side of x = 3.

On the existence of AgM9(VO4)6I (M = Ba, Pb)

Attempts to synthesize “AgM9(VO4)6I” (M = Ba, Pb), potential waste form materials for radioiodine, were unsuccessful, demonstrating that AgI incorporation into an iodine-deficient apatite phase is not feasible under the reported conditions.