Bioceramics calcium phosphate coatings on titanium produced by electrochemical techniques.

Cilj ove doktorske disertacije je dobijanje prahova i prevlaka kalcijum-fosfata na titanu primenom elektrohemijskih metoda, kao i ispitivanje uticaja parametara sinteze (gustina struje, napon, pH vrednost rastvora, vreme taloženja) na fazni sastav, veličinu kristalita i morfologiju dobijenih prahova i prevlaka. Elektrohemijskom sintezom iz rastvora Na2H2EDTA·2H2O, NaH2PO4 i CaCl2 sa odnosom koncentracija Ca/EDTA/PO43− od 0,25/0,25/0,15 M uspešno su dobijeni prahovi monetita i hidroksiapatita. Ispitan je uticaj pH vrednosti polaznog rastvora i gustine struje na vrstu sintetisanog kalcijum-fosfata, morfologiju i termičko ponašanje prahova različitim metodama kao što su rendgenska difrakcija na polikristalnom uzorku, skenirajuća elektronska mikroskopija, diferencijalno termijska i termogravimetrijska analiza i infracrvena spektroskopska analiza. Pri pH vrednosti od 5,0 i gustini struje od 137 mA cm-2 dobijen je nanodimenzioni prah monetita sa veličinom kristalita od 27,1 nm. Sintezom prahova pri pH vrednostima od 9,0 i 12,0 i pri gustinama struje od 137 mA cm-2 i 207 mA cm-2 dobijeni su prahovi hidroksiapatita sa veličinom kristalita u intervalu od 21,6 do 24,3 nm, čime je pokazano da pH vrednost i gustina struje ne utiču značajno na veličinu kristalita. Na morfologiju elektrohemijski sintetisanih prahova hidroksiapatita ne utiče promena gustine struje, ali utiče pH vrednost rastvora. Pri manjoj pH vrednosti od 9,0 se dobijaju prahovi sa sfernim aglomeratima, dok se pri većoj pH vrednosti od 12,0 dobijaju prahovi sa pločastim aglomeratima. Temperatura termičke dekompozicije nanočestičnog praha monetita na kalcijum-pirofosfat i vodu je niža (1260 °C) u odnosu na literaturni podatak (1353 °C), zbog velikog odnosa specifična površina/zapremina nanočestičnog praha. Uslovi elektrohemijske sinteze ne utiču značajno na termičko ponašanje prahova hidroksiapatita. Prevlake monetita dobijene su elektroforetskim taloženjem iz etanolske suspenzije elektrohemijski sintetisanog praha monetita i ispitan je uticaj napona (10-50 V) i vremena taloženja (1-30 min) na masu i morfologiju prevlake. Masa prevlake, srednji prečnik pora, srednja površina pora i poroznost prevlaka zavise...The aim of this PhD thesis was to prepare nanosized calcium-phosphate powders and coatings using electrochemical methods and to investigate the effect of experimental parameters (e.g. applied current density, solution pH value, applied voltage, deposition time) on the phase composition, crystallite domain size, morphology and thermal characteristics of obtained powders and coatings. Electrochemical synthesis of nanosized monetite and hydroxyapatite powders were performed galvanostatically from homogeneous solution of Na2H2EDTA∙2H2O, NaH2PO4 and CaCl2 at a concentration relationship Ca/EDTA/PO43− of 0.25/0.25/0.15M. The influence of the solution pH and applied current density on the phase composition, morphology and thermal behavior was investigated by X-ray diffraction, infrared spectroscopy, size distribution measurements, thermogravimetric and differential thermal analysis, scanning electron microscopy and transmission electron microscopy. At current density of 137 mA cm−2 and pH value of 5.0 monetite powder was synthesized. The crystallite domain size of powder was calculated to be 27.1 nm. At current densities of 137 and 207 mA cm−2 and pH values of 9.0 and 12.0 hydroxyapatite powders were synthesized with crystallite domain size in the range from 21.6 to 24.3 nm, meaning that pH values as well as applied current densities does not affect significantly the crystallite domain size. The morphology of synthesized hydroxyapatite powders were not influenced by current density, but on the other hand are influenced by solution pH. Powders synthesized at lower pH value consist of spherical agglomerates, while powders synthesized at higher pH value have the plate-like structure. The temperature of phase transformation from monetite to calcium pyrophosphate was lower (1260 °C) in comparison with literature data (1353 °C), due to high surface-to-volume ratio of nanosized powder. The parameters of electrochemical synthesis of hydroxypatite powders do not affect significantly the thermal behavior. Monetite coatings were electrophoretically deposited from ethanol suspension of electrochemically synthesized monetite powder, using constant..