3 research outputs found
Development and study of cement and a phosphocalciques ceramic as medical use
The hydroxyapatite (Ca(PO(OH) has a structure and a chemical
composition very close to those of the mineral phase of calcified tissues.
It is thus used for a long time in orthopedic and odontological surgery. In
the past few years, cements which evolve toward the hydroxyapatite have been
the object of several studies. This communication reports the synthesis and
the study of new phosphocalcic cement, which evolves after hardening,
towards a hydroxyapatite. The cement is composed of tricalcium phosphate a
type (-Ca(PO, calcium hydroxide (Ca(OH)
and phosphoric acid (HPO. The sintering of hardened cement,
leads to ceramics having a structure and chemical composition close to those
of the bone's mineral phase. The trisodium phosphate is used as melting
agent to increase the hardness of ceramics and to decrease the sintering
temperature, without affecting the physicochemical properties of ceramics
Investigation by infrared absorption spectroscopy into the chemical mechanisms of the wet process synthesis of some calcium phosphates
The present work describes the reactions of wet
process synthesis, of some calcium phosphates, such as tricalcium phosphate
(Ca(PO and hydroxyapatite
(Ca(PO(OH). These reactions of synthesis are
acido-basic reactions between the phosphoric acid (HPO and
calcium carbonates (CaCO.The evolution of these reactions (and the
concerned chemical mechanisms) were followed by mid infrared spectroscopy
absorption. Indeed, in the first stage of these three reactions in which the
medium is strongly acidic, favours the formation of a stable intermediate
compound, which is the brushite.During the reaction, the concentration of
phosphoric acid decreases, the pH increases and the brushite becomes
unstable, thus it evolves to a more stable calcium phosphate under these new
pH conditions. This later product was either the tricalcium phosphate or
hydroxyapatite, according to the pH solution
Study of the chemical mechanisms of the reaction of neutralization of calcium hydroxide by phosphoric acid
Calcium phosphates reported in this study, are prepared following
an acido-basic reaction between phosphoric acid and calcium hydroxide. These
phosphates are the brushite, tricalcium phosphate, hydroxyapatite and
oxygenated apatite. The follow-up of the reaction by infra-red spectroscopy
of absorption showed that the alkaline pH of calcium hydroxide solution,
favours the formation of carbonated apatite, at the start of the reaction.
Following the addition of phosphoric acid, the pH becomes increasingly
favourable to the formation of the desired phase. The insertion of molecular
oxygen in the apatitic tunnel is carried out by the use of hydrogen
peroxide. The molecular oxygen rate in the apatite is then determined by
volumetric analysis