R. A. Condrate

Sol–gel processing of hydroxyapatite

Hydroxyapatite, a calcium phosphate-based compound with numerous applications in the biological field was synthesized using the sol–gel processing route. The formation of hydroxyapatite and other compounds during the heat-treatment cycle were identified and characterized using thermal analyses and X-ray diffraction together with infrared and Raman spectroscopy. The influence of the addition of various organic alcohols (R–OH, R=CH3–, C2H5– and C3H8–) on the reaction results was studied.

The Infrared and Raman Spectra of β-and α-Tricalcium Phosphate (Ca3(Po4)2)

Abstract Factor group analysis was applied to interpret the vibrational spectra of β-and α-tricalcium phosphate (Ca3(PO4)2). The analysis predicts the number of bands formed due to the splitting of the fundamental vibrational modes of the PO4 3-ion. The number of the infrared and Raman bands predicted by this analysis for the two phases are drastically different and can be ascribed to the difference in atomic arrangements in the two phases resulting in greater shielding of the PO4 3-ions in the β-phase than in the α-phase. Discrepancies in the number of predicted and experimentally-observed bands can be attributed to the weak intensities of some vibrational modes or the convolution of vibrations and limited spectral resolution.

An FTIR spectral investigation of the structural species found on alumina surfaces

Abstract The diffuse reflectance infrared Fourier transform (DRIFT) spectra of several alumina powders indicate a mixture of bayerite and gibbsite as well as a dawsonite-like species on the surface. These latter surface species were formed by the reaction of surface sodium ion impurity along with water vapor and carbon dioxide adsorbed on the surface. The presence of sodium ions on the alumina surface enhanced the adsorption of carbon dioxide by the formation of a dawsonite-like species. The spectral results for this study can also be related to earlier results for carbon dioxide adsorption on γ-alumina (catalyst), and provide a new approach to interpret the infrared bands at 1520–1570 cm −1 and 1350–1410 cm −1 which are related to carbonate ions.

Vibrational spectra of structural units in glass

Abstract This paper contains a discussion of structural models that are used to analyze the infrared and Raman spectra of glasses. Good examples are given for each model. An example is given in which the structure of a glass composition (SiP2O7) is completely different from the structure of all related crystalline phases with the same stoichiometry. Finally, an example of B2O3GeO2 glass is presented where large changes in the concentrations of structural units occur with changes in temperature.

Structures, spectra and related properties of group IVB-doped vitreous silica☆

Abstract Vibrational spectra and related physical properties were analyzed for titanium-, zirconium- and hafnium-containing vitreous silicas on the basis of glass structure. Linear functional relationhips were found between both partial molar volume and refractivity, and the dopant concentration throughout the dopant range examined. Analysis of the data suggested four-fold coordination with oxygen atoms by titanium atoms with greater coordination by zirconium and hafnium atoms. Raman and difference infrared spectra for these glasses showed an intensity decrease of the v3 (F2) band at 1068 cm−1 accompanied by the emergence of a band at circa 950cm−1 whose exact wavenumber was defined by the dopant species ( gv Hf > gv Zr > gv Ti ) and, in the case of TiO2- containing glasses, a band at 1110 cm−1. The intensities of these bands were proportional to the dopant concentration. Empirical spectral analysis suggested that upon TiO2 addition Ti-atoms bonded to a single oxygen atom of a SiO4-unit, while upon zirconia and hafnia addition each metal atom bonded to two oxygen atoms of a SiO4-unit. These structural models were consistent with ion coordination predictions based upon the physical property measurements.

Graded coating of hydroxyapatite and titanium by atmospheric plasma spraying

Abstract Graded coating of hydroxyapatite and titanium by plasma spraying was attempted as an alternative means to direct deposition of hydroxiapatite on titanium. The application of multiple layers of hydroxyapatite and titanium mixtures ensured a gradual change in composition across the interface. As a result, the microstructure of the area near the coating-substrate interface showed a good adhesion between the coating and substrate. The oxidation of the Ti substrate and powders was found to be effectively reduced by selecting the appropriate particle sizes and protective atmosphere. The major reaction phase, TiO x ( x ≈1.04), rather than TiO 2 , was observed in the graded coating layers and is believed to play an important role in promoting bonding between hydroxyapatite and titanium.

The Vibrational Spectra of VPO5 Crystal Phases and Related Glasses

Infrared and Raman spectra were measured and interpreted for two crystalline VPO5 phases (α- and β-VPO5) and several related vanadium phosphate glasses. The spectral results for the crystalline phases were consistent with those predicted by factor group analysis using the previously determined space groups. Empirical band assignments were made for the observed bands on the basis of the bands observed earlier for related phosphate and oxyvanadium compounds. Also, the band assignments made for the infrared spectra of the glasses were consistent with the assignments for crystalline V2O5 and the two crystalline VPO5 phases. No Raman spectra were observed for the glasses because processes involving adsorption and Rayleigh scattering dominated over Raman scattering. The infrared spectra of vanadium phosphate glasses with high P2O5 concentrations possessed many features resembling those observed in the infrared spectra of α-VPO5, suggesting similarities in the short range order for the two materials. Analyses of the vibrational spectra of hydrated α-VPO5 samples suggests that the water molecules are adsorbed in the interlamellar spaces of the crystals, complexing to vanadium ions. Initial steps in the hydration of vanadium phosphate glasses apparently involve physical adsorption of water on their surfaces. No water adsorption could be detected for β-VPO5 under normal conditions from its infrared and Raman spectra.

Vibrational spectral/structural changes from the hydrolysis/polycondensation of methyl-modified silicates. I: Comparisons for single monomer condensates

Abstract Comparisons were made for the structures of condensates of tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMS) and diethoxydimethylsilane (DEDMS) upon hydrolysis/polycondensation using infrared and Raman spectra. Vibrational spectral data indicated that all of the amorphous condensates generated from single monomer precursors possessed four-membered (Si-O) 4 rings as structural units within their structures. Three-membered rings appeared at lower concentrations for the DEDMS-derived condensate.

Infrared spectral studies of various metal polyacrylates

A new process for the production of high surface area, high reactivity ceramic oxide powders involves the bonding of metal cations to polymeric polyacrylate chains. This process results in the formation of a gelatinous metal polyacrylate precipitate which can be easily removed from the mother liquor, and then calcined to form a high density ceramic oxide. Using FTIR spectroscopy, the nature of the structural arrangements has been studied for metal complexes in the yttrium, lanthanum, aluminum, cerium, copper, and iron polyacrylates. Interpretation of the infrared spectra indicates that two types of metal complex formation occur in these precipitates, involving bidentate or bridging interactions. The type that is observed for a particular metal ion is dependent on its metal ion size.

The Difference Infrared Spectra of Titanium-Containing Vitreous Silica

Vitreous silicas containing up to 10% titania are of significant commercial importance because of their low thermal expansions. Instrumental techniques are being developed to determine the structure of the titanium groups in these glasses in order to relate their reduced thermal expansitivities with structural properties. Amosov, Zakharov, and Yudin have investigated both the ESR and optical spectra of titanium-containing quartz glasses. Tobin and Baak have observed the Raman spectra of these glasses and noted several bands that were assigned to the titanium-containing groups. Bobovich has also looked at the Raman spectra of titaniferous silicate glasses containing sodium. Very little investigation has been carried out with the infrared spectra of titania groups in vitreous silica. Tarte has observed the spectra of titanium groups in silicate glasses containing sodium and calcium. Manghani, Ferraro, and Basile have investigated Na2O-TiO2-SiO2 glasses by infrared spectroscopy. A major problem in the infrared investigation of these glasses is that the normal infrared spectra of the bulk silica matrix overshadows the spectra of the added components. This problem can be minimized by the use of a difference infrared (DIR) spectral technique that involves placing extremely thin plates of the titanium-containing vitreous silica and high purity silica in the sample and reference beams, respectively. In this note we will describe our technique for preparation of extremely thin glass plates (down to 8 μ thickness) and discuss the observed DIR bands for titanium-containing vitreous silica.