Получение наночастиц гидроксиапатита из естественных зубов

Hydroxyapatite is the most important bio ceramic, due to its structure and chemical composition which is similar to bone and teeth. In this study, hydroxyapatite nanoparticles were prepared from natural teeth in two stages. Initially, the nano HA particles was performed by whole tooth and in the second stage, the tooth was divided into dentine and root and HA nanoparticles were prepared from both portions of teeth. At first, freshly extracted human teeth both (whole tooth and dentine and root) were calcined at 850 °C and then, the effects of stirring time, surfactant and different temperatures were investigated. The XRD results confirmed that, the existence of hydroxyapatite phase in all samples. The phosphate bonding groups of PO43- at 1470 cm-1 and 669 cm-1 was confirmed by FTIR results. The FESEM results showed that, hydroxyapatite nano particle with the range of 29–46 nm at stirring time of 36 h with the addition of CTAB as a surfactant at 850 °C was obtained without agglomeration and good dispersion.

BRUCITE-BASED MAGNESIUM PHOSPHATE BONDING AGENT, ITS ANALYSIS AND APPLICATION FOR PERICLASE SINTERING

Some results on magnesium phosphate binder obtained from natural brucite (mainly Mg(OH)2) and H3PO4 were discussed. Hereafter, it was named brucite phosphate (BPB). This binder then was used to the sintering of MgO (periclase). MgO is one of the most high-refractory materials and chemically stable to various aggressive mediums, so the aim was presented as actual. To determine the phase composition data on sample weight loss in different temperature intervals were compared. All weight losses were related to the multistage water moving away. Up to 140 °С it was the removal of crystalline hydrate water. Then monosubstituted magnesium hydrophosphate transformed into MgH2P2O7 and Mg2P4O12, that in principle was in accordance with literature data. Dehydration was accompanied with appropriate endothermal effects. There was a slight exothermal effect which could relate to a structure rearrangement (cyclization) of primary magnesium metaphosphates and/or some crystallization of anhydrous cyclophosphates from primarily obtained amorphous phase non-connected with a weight loss in the interval of 450-575 °С. At 500–1000 °С the phase composition remained constant that was in a good accordance with data obtained by other methods. By means of IR-spectroscopy, it was confirmed the formation of structure cycles composed from oxygen-phosphor tetrahedrons. To determine kinetics parameters of periclase sintering with BPB it was used a model being proposed that took the role of a physical consolidation and a chemical binding in the presence of binder into account under heating. The obtained parameters analysis showed that the forming conglomerate strength was provided with the sintering properly as well as with binder action; an estimated chemical factor contribution was maximal at low temperatures (1100-1200 °C). The activation energy value was practically identical to the activation energy of oxygen diffusion in MgO.

The Preparation of Phosphate Bonding Agent and its Application in Ceramic Coating

A kind of phosphate bonding agent was prepared with H3PO4 and Al(OH)3 as the main raw materials in this paper. Phosphate-metal matrix ceramic coating was prepared on the surface of Q235 steel by using the technology of ambient cure with phosphate bonding agent as main body and CuO and SiC as fillers. The influence of the addition of CuO on curing temperature was studied. Meanwhile, the influence of SiC particle size and content on the abrasion resistance of the coating was studied. The result showed that the amount of friction and wear of phosphate-metal matrix ceramic coating was 5.5mg, when the the molar ratio of P and Al was 3:1.3, SiC particle size was D50=18μm, and its particle content was 40%, 20%wt CuO was added.

Phosphate Bonding: A New Method for Using Large Volume of Fly Ash

Magnesium phosphate cements (MPC) with larger volume of fly ash were studied in the present work. Dead burned magnesia, phosphates and fly ash were the components of MPC. The volume of fly ash in MPC was 70%, 75% and 80%, respectively. Three phosphates, monosodium phosphate (MSP), monopotassium phosphate (MPP) and monoammonium phosphate (MAP) were used. Compressive strength of the three MPC mortars with different fly ash content was determined. Results show that the compressive strength reduced with the proportion increase of fly ash, increased with the curing time. After cured 28 days in the lab air, the compressive strength of cement mortar can reach 14MPa, when the fly ash dosage was 80% by weight of cement. The reaction product is struvite of potassium (KMgPO4•6H2O) in potassium phosphate based MPC, and hydrated sodium phosphate (Na2HPO4•17H2O) in sodium phosphate based MPC. The results indicate that MPC has capacity to bond large volume of fly ash. A new way to utilize fly ash in a large scale can be realized by phosphate bonding.