Cerium Pyrophosphate glass is prepared and investigated by different structural techniques. Resin modified glass io n omer cements (RGICs) of pyro cerium phosphate (40CeO2-60P2O s ) composition doped with different concentration s from GaCl Phthalocyanine (C32H16ClGaN8) have been also prepared and studied for the first time. Different techniques have been applied to shed light on the structural changes induced upon addition of GaCl-Phthalocyanine. The corresponding changes in material structure are widely approved by results of 31P magic angle spinning nuclear magnetic resonance (MAS-NMR), X-Ray diffraction and FTIR spectroscopy. The network structure of both base glass and GIC free from C32H16ClGaN8 is confirmed to be amorphous. Doping even with little concentration from GaCl-Phthalocyanine leads to changing the network structure from amorphous to a highly crystalline one. Formulation of GaCl-Phthalocyanine with water soluble acid leads to monocrystalline structure due to monoclinic lattice structure of Phthalocyanine. Carbonated hydroxyl cerium and gallium phosphate structural phases are evidenced to be formed upon GaCl-Phthalocyanine addition. Presence of such bioactive phases can support that the prepared GICs of considerable C32H16ClGaN8 concentration (1 and 1.5 mol%) can be applied as biocompatible materials used in biodental applications. The morphologies of some selected samples were characterized by SEM. The micrographs have revealed that formulating of cerium phosphate powder of the amorphous glass with polymeric acid successfully led to the formation of CePO4-H2O nanofibrous bundles. But formulation with GIC containing GaCl-Phthalocyanine can simply form co-aligned and elongated nanofibers (15 - 40 nm thick and up to ca. 1.2 m long). The formed nanofibers are mainly consisted of hydrated and carbonated CePO4 and GaPO4 nanocrystals. The hardness of the cemented material increases with increasing GaCl-Phthalocyanine concentrations.
There is an increasing interest in metal phosphates composites due to their relevance in biology and materials science [
When the powder of the oxide glass is formulated with some types of weak polymeric acids, the well-formed material is called glass ionomer cement. Expression of a glass-ionomer cement (GIC) is devoted only to a material which involves a proper acid-base reaction as a part of its setting process [
Most of simple and conversional GICs were brittle materials. Therefore several trials have been devoted to enhance the physical properties by the addition of some types of supported materials such as TiO2-Cr2O3-Al2O3, Ag2O, ZrO, SrO, CrF2 [
GICs are considered the most appropriate materials in the field of bio-dental applications [
Several types of GICs modified by specific types of supporting materials have been previously studied [
Binary Cerium phosphate glass with composition 40CeO2∙60P2O5 has been synthesized using analytical grade chemicals using ordinary melt quenching technique. Calculated batches of the starting raw materials were mixed including the appropriate amounts of CeO2 and NH4H2PO4 as a source of P2O5. The mixture was heated in a porcelain crucible at 300˚C for 30 min. in order to evaporate ammonia, water, and nitrogen. Then, the product was melted between 1100 to 1350˚C for an hour. To assure the homogeneity, the previous oxides were added to the melt in the crucibles in small parts and the melts were stirred before each addition. After refining, the melts were quenched on a stainless steel plate. The obtained glasses were homogenous, transparent and there was no sign of devitrification. Because of the phosphate glasses have higher tendency to absorb moisture, the glass samples were sealed with silica gel pellets in sacks of plastic and kept in desiccators until required. GICs were prepared by formulating the glass powder with a polymeric acid of type (Ketac Molar Easymix, Germany). They are mixed und swirled until a homogenous past is obtained.
Infrared absorption spectra of the glasses were recorded in the range of 400 cm−1 to 4000 cm−1 at ambient temperature by a spectrophotometer type (Mattson 5000 FTIR spectrometer). The measurements were carried out on powdered glass samples which is mixed with KBr (1 wt%). The measurement process occurred immediately after the mixture compression with a load of 5 tons/cm2.The distribution of Qn of phosphate units can be obtained from 31P NMR spectra of some selected samples. The measurements were analyzed using a high resolution solid state MAS NMR type (JEOL RESONANCE GSX-500 spectrometer). The obtained spectra were recorded at high external magnetic field (11.747 T), at frequency of 160.47 MHz and spinning rate of 17 KHz. X-ray diffraction pattern was obtained by using X-ray diffractometer type (Philips PW 1729) with a compact analyzer system 1840 and 8203A/02 chart recorder. Surface modification and microstructure of glass samples were examined using a Scanning Electron Microscope (SEM) equipped with EDX unit. Operated and accelerating voltage of 25 KV, with a magnification up 400,000X and resolution for W. (3.5 nm) is the feature of the used SEM. The technique of gold plated samples has been applied. The average grain size of the various specimens was 60 µm.
Very low levels of GaCl-Phthalocyanine (0 - 1.5 mol%) within the glass ionomer cement of the cerium phosphate glass can drastically influence its propensity to crystallize as well as change structure and morphology of the final formed phases.
To understand how these small compositional changes affect the material structure via the doping process, different techniques and spectroscopic tools have been applied. Correlation between data obtained from these techniques can provide a unique insight into the structure of these GICs and how they change during phase separation and crystallization processes. Because of the large differences in molecular weight between the glass constituents, and particularly the significant effects of C32H16ClGaN8, X-Ray diffraction is a highly informative technique for this type of research. In addition, local structural information on the main glass-forming elements of phosphate nuclei was obtained from solid-state NMR spectroscopy.
The addition of GaCl-Phthalocyanine has been shown to be very effective in enhancing the crystallization of GICs, as is shown in
Comparisons between XRD patterns of the studied materials with the Ga(PO3)3 crystal [
The XRD patterns of investigated samples are shown in
(cerium phosphate glass, spectra a), the reference C32H16ClGaN8) GIC (spectra, b) and compares the percentage of the dopant in GICs systems (c, d and e). The spectra of the base glass of composition 40CeO2-60P2O5 are presented by
Then from
process is offered mainly by effect of galliumcholoride since the material containing even limited doping level (0.5 mol%) is crystallized prior to undergoing the second step of crystallization (at 1 and 1.5 mol%). The number of diffraction lines in all doped GIC is the same but change in intensities is the most observed changeable parameter. This means that the type of the formed crystalline phases is similar but the content of the separated phases increases with increasing C32H16ClGaN8 concentrations. There are additional phases are formed by comparing spectra a and b. Besides the hydroxyl-gallium phthalocyanine and chloro-gallium phthalocyanine crystalline phases, GaPO4 or GaCePO4 hydrated and carbonated species are also formed in GICs matrix [
On mixing powder of binary CeO2-P2O5 glass with acid (water-soluble polymer), the acid attacks the matrix of glass and C32H16ClGaN8 resulting in surface degradation. As a result of degradation, release of metal ions such as cerium and gallium cations should occur. The released ions can react with the hydrated or the carbonated phosphate units and the carbonated hydroxyapaptite phases are constructed [
Formation of the above mentioned crystalline phases is highly evidenced also from FTIR spectra of GIC containing different concentrations from GaCl-Phthalocyanine. The appearance of new sharp FTIR absorbance peaks (
a phousphours hydrogel (P-OH) which forces both gallium and cerium cations to link with hydrated phouphor units. Then on mixing powder of glass and liquid, the self cure polymerization reaction begin and setting can be occurred [
More evidences for acid-base reaction can be considered from NMR result of phosphors nuclei. It can be shown from Figures 5 (a)-(b) that the intensity and the fullwidth at half maximum (FWHM) of the NMR resonance peak are highly affected by the acid-base reaction. The intensity of the resonance NMR peak is decreased and FWHM is increased. These changes are considered as good evidences for the degradations processes which are simply produced due to the reaction between the glass and the acid [
By considering FTIR absorbance spectra of doped samples (
while this type of GIC strengthening can assist the formation of mesopores. The most to be noticed from
Results based on both FTIR and XRD spectra have shown sharp peaks in glasses containing GaCl Phthalocyanine. The added agents should act as both stimulator for nucleation and crystallization of cerium phosphate phases which are the essential mineral phase of bone and teeth. Mixing effect of CeO2 and GaCl plays a good role in improvement of hardness and compactness of the material network and consequently high corrosion resistance.
The fast increase of Hv (
simply activate the interaction of organic and the inorganic species which results in decreasing degradations processes that takes place by attacking the acid to the surface of the glass. As a consequence the hardness of the glass shows an effective increasing trend.
Recent investigations have evidenced that the properties of CePO4 nano species depend strongly on, morphology and crystallinity relationships [
The morphology and amorphous structure of CePO4 glass were characterized by Scanning Electron Microscopy. The micrograph of base glass is presented by
fibers are characterized with 10 - 20 nm thick and up to ca. 1.2 m long, as shown in
Given the strong affinity of carboxylate or peptide moieties for cerium phosphate species [
As important advantage, this acid-base reaction can be performed under relatively mild conditions (pH around 4 - 4.5) avoiding the strict requirements of using a great excess amount of phosphates of very low pH values (<1.5). Such conditions, are often necessary to obtain high aspect ratio of elongated CePO4 nanofibers functional gels [
XRD and SEM analysis provides the crystalline nature and the morphology of the metal complexes. Most of the added GaCl molecules exhibited realble improvement in crystallinity, morphological and structural properties. The current studies are seeking to shed light on cerium phosphate based GIC containing small additives from GaCl-Phthalocyanine with unusual properties and different potential applications. For example, GIC-based nanocomposite species, containing GaCl nanocrystals as functional components, were successfully prepared and cross-linked using acid-base reaction between the organic and inorganic constituents of GIC. XRD and SEM showed that cerium phosphate glass and glass ionomer cement retained its amorphous characteristics after and before the reaction between the glass powder and the polymeric acid, while formulating cerium phosphate powder with both polymeric acid and GaCl-Phthalocyanine results in producing nanocrystals which retained crystalline morphology in the nanocomposites after cross-linking, processes. Some crystalline phases are formed in a bundle like shape at low GaCl Phthalocyanine concentration, 0.5 mol%. The bundle morphology is transformed to Co-elongated fiber or wafers like shape at higher concentration. The morphology of crystalline elongated structure recommend the material to be used in different potential applications such as the field of tissue engineering or bio scaffolds applications.
El-Damrawi, G., Behairy, A. and Abdelghany, A.M. (2018) Structural Characterization of Novel Cerium Phosphate Glass Ionomer Cements (GICs) Doped with GaCl (Phthalocyanine). New Journal of Glass and Ceramics, 8, 23-38. https://doi.org/10.4236/njgc.2018.82003