Phosphate glasses of composition 48P 2O 5-30CaO-(22 −x)Na 2O-xTiO 2 (with 0 < x ≤ 3, mol%) were prepared by direct melting at 1080 °C ± 20 °C. The chemical durability of these glasses shows an improvement when the Ti O 2 content varies from 0 to 2 mol%. The measurements of differential thermal analysis and density, both, indicate the increase of the glass transition temperature and the density. The increase of Tg leads to an improvement of glass rigidity. X-ray diffraction analysis of the glasses annealed at 650 °C for 48 h, indicates the appearance of a mixture of metaphosphate and pyrophosphate phases when the Ti O 2 content varies from 0 to 2 mol%, the last become majority when the Ti O 2 content rich 2 mol%. Nevertheless, when the Ti O 2 content exceeds 2 mol%, the analysis, both, by infrared spectroscopy and X-ray diffraction, reveals a radical change of structure with the formation of majorities isolated orthophosphate groups. SEM micrographs illustrated that the number of crystallites increased in the glass network when the Ti O 2 content increased at the expense of the Na 2O content. An increase in the TiO 2 content beyond 2 mol% led to the formation of a larger number of crystallites of different sizes, dominated by small crystallite sizes assigned to majority isolated short orthophosphate groups. This phenomenon led to a decrease in chemical durability and seems to be the main cause promoting the bioactivity of glasses. The results of the bioactivity, after a test in an SBF physiological solution within 15 days, shows, both, the formation of hydroxyapatite and tricalcium phosphate layers, in addition to the layer Ca 2P 2O 7, known by its bioactivity, in some samples. The results obtained on the glasses studied make them potential candidates for an application in tissue engineering.
Several studies have been carried out on phosphate-based glasses as promising materials for various applications in all fields. The properties of phosphate glasses such as low melting point, high thermal expansion coefficient, sealing materials and bioactivity, including the concept of the biomaterials degradation, make them potential candidates for many technological applications [
Phosphate glasses are prepared by direct melting of the (NH4)H2PO4, CaCO3, Na2O, TiO2 mixture in suitable proportions. The reagents are intimately crushed then introduced into a porcelain crucible. Then, they are heated initially at 300˚C for 2 h and then at 500˚C for 1h to complete the decomposition. The reaction mixture is then heated at 900˚C. For 40 minutes and finally at 1080˚C. For 30 minutes in order to obtain a homogeneous liquid. Then it is cast in an aluminum plate previously heated to 200˚C to avoid thermal shock. Pellets 5 to 10 mm in diameter and 1 to 3 mm thick are obtained. The samples were then immersed in distilled water at 90˚C for 20 days to determine the dissolution rate evaluated from the mass loss as a function of time. Analysis by IR spectroscopy was done in a frequency range of between 400 and 1600 cm−1 with a resolution of 2 cm−1, using a Fourier transform spectrometer. The vitreous state was first evidenced from the shiny and transparency aspect, which was then confirmed by X-ray diffraction (XRD) patterns. Samples glasses were analyzed by X-ray diffraction after an annealing time of 48 h at 650˚C. Differential thermal analysis (DTA) was performed using a Perkin-Elmer DTA7, at a heating rate of 10˚C/min in a flowing nitrogen atmosphere (30 cm3/mn) with alumina crucibles. The Archimedes method was used to measure the density of glasses using orthophthalate as a floating medium. The microstructures of the sample glasses were characterised by scanning electron microscopy (SEM), equipped with a full system micro-analyser (EDX-EDAX). Glass powder of each sample was soaked in SBF solution at 37˚C for 21 days.
The glass series 48P2O5-30CaO-(22−x)Na2O-xTiO2 (with 0 < x ≤ 3 mol%), was approximated by measuring the dissolution rate (DR) which was defined as the weight loss of the glass expressed in terms g∙cm−2∙mn−1. The DR values reported in
Glass Sample | Starting Oxide mixtures mol % | [O/P] Ratio | log (DR) (g∙cm−2∙min−1) (±0.2) | Tg (˚C) | Tc (˚C) | |||
---|---|---|---|---|---|---|---|---|
P2O5 | CaO | Na2O | TiO2 | (±2) | ||||
48T05 | 48 | 30 | 21.5 | 0.5 | 3046 | −4.9 | 405 | 495 |
48T10 | 48 | 30 | 21 | 1 | 3052 | −5.1 | 449 | 498 |
48T15 | 48 | 30 | 20.5 | 1.5 | 3057 | −5.7 | 473 | 525 |
48T20 | 48 | 30 | 20 | 2 | 3062 | −6.05 | 476 | 540 |
48T25 | 48 | 30 | 19.5 | 2.5 | 3067 | −5.9 | 430 | 490 |
48T30 | 48 | 30 | 19 | 3 | 3072 | −5.5 | 450 | 496 |
of leached pH, for different samples, after 21 days, is represented as a function of the TiO2 content (
The Archimedes principle was used to measure the density of glasses using orthophthalate as a floating medium. The density of the glasses was obtained by using the relation (1),
ρ = [ m air m air + m ortho − m ( ortho + glass ) ] ρ ortho (1)
With: mair: the mass of the sample measured in the area.
mortho: Orthophthalate mass only.
m(ortho+glass): Mass of glass immersed in diethyl orthophthalate.
ρortho: 1.11422 g∙cm−3.
The density variation of composition glasses are represented in
V 0 M = M / ρ N A N 0 ∗ (2)
r c a l ( O = ) = 3 V 0 M / 2 (3)
With M = molar mass, ρ = density, NA = Avogadro number; N 0 ∗ number of oxygen atoms in the molecular formula. The value of the molar volume and the oxygen radius were calculated from the approximate hypothesis of close packing of oxygen anions O2−, having r(O2−) recapitulated for each composition in
Glass sample Code | Chemical compositions (mol%) | Glass compositions inside the ternary diagram |
---|---|---|
48T05 | 48P2O5∙30CaO∙21.5Na2O∙0.5TiO2 | 0.3173(Na2O∙P2O5)∙0.0096(TiO2∙P2O5)∙0.6731(CaO∙P2O5) |
48T10 | 48P2O5∙30CaO∙21Na2O∙1TiO2 | 0.3077 (Na2O∙P2O5)∙0.0192(TiO2∙P2O5)∙0.6731(CaO∙P2O5) |
48T15 | 48P2O5∙30CaO∙20.5Na2O∙1.5TiO2 | 0.2982(Na2O∙P2O5)∙0.02887(TiO2∙P2O5)∙0.6731(CaO∙P2O5) |
48T20 | 48P2O5∙30CaO∙20Na2O∙2TiO2 | 0.2884(Na2O∙P2O5)∙0.0385(TiO2∙P2O5)∙0.6731(CaO∙P2O5) |
48T25 | 48P2O5∙30CaO∙19.5Na2O∙2.5TiO2 | 0.2788(Na2O∙P2O5)∙0.0481(TiO2∙P2O5)∙0.6731(CaO∙P2O5) |
48T30 | 48P2O5∙30CaO∙19Na2O∙3TiO2 | 0.26923(Na2O∙P2O5)∙0.0576(TiO2∙P2O5)∙0.6731(CaO∙P2O5) |
The infrared spectra of 48P2O5-30CaO-(22−x)Na2O-xTiO2 series glasses (with 0 < x ≤ 3) are shown in
of pyrophosphate groups (Q1), while the bands at around 1094 cm−1 and 1267 cm−1 are respectively assigned to the Ѵsym (PO2)/Ѵasy (PO3) of pyrophosphate groups (Q1) and vibration mode Ѵasy (PO2) of metaphosphate groups (Q2) [
Glass sample code | Starting oxide mixtures mol % | ρ (g∙cm−3) (±0.01) | Molar mass (g∙mol−1) | Molar volume (Å3) VoM = M/[ρ NA No*] | Calculated oxygen radius (Å) rcal (O2−) | |||
---|---|---|---|---|---|---|---|---|
P2O5 | CaO | Na2O | TiO2 | |||||
48T05 | 48 | 30 | 21.5 | 0.5 | 2.57 | 98,719 | 21.81 | 1397 |
48T10 | 48 | 30 | 21 | 1 | 2.59 | 98,809 | 21.58 | 1392 |
48T15 | 48 | 30 | 20.5 | 1.5 | 2.60 | 98,898 | 21.52 | 1390 |
48T20 | 48 | 30 | 20 | 2 | 2.61 | 98,988 | 21.40 | 1388 |
48T25 | 48 | 30 | 19.5 | 2.5 | 2.59 | 990,775 | 21.55 | 1391 |
48T30 | 48 | 30 | 19 | 3 | 2.58 | 101,564 | 22.13 | 1403 |
As expected, X-ray crystallography confirmed the vitreous nature of all the investigated glass samples studied. In fact, X-ray diffraction pattern (XRD) recordings show the absence of diffraction peaks. DSC of the glasses (
and finally to orthophosphates phases. When the 48T15 sample was thermally treated at 650˚C, the amorphous phase partially disappeared and majority Ti(PO3)3 [JCPDS files N˚: 01-082-1178], NaCa(PO3)3 [JCPDS files N˚: 00-23-0669], Na4Ca(PO3)6, [JCPDS files N˚: 00-025-0811] and CaP2O6 [JCPDS files N˚: 00-015-0204] (cyclic metaphosphate O/P = 3), with minor Ca2P2O7 [JCDDS files N˚: 00-009-0346] and Na5Ti4(PO4)6 [JCPDS files N˚: 01-081-2420] phases occurred in the sample. When the TiO2 content increased in the glass (48T20), the heat treatment at 650˚C caused the formation of NaTiP2O7 [JCPDS file N˚: 01-084-1137-], Ca2P2O7 [JCPDS file N˚: 00-009-0346] and TiP2O7 [JCPDS file N˚00-052-1470] with some trace of metaphosphate and isolated short orthophosphates phases, and indicated the increase of pyrophosphate phases (O/P = 3.5). However, when the TiO2 content exceeded 2 mol% (48T25), the heat treatment, at the same temperature, indicated the majority formation of Na5Ti (PO4)3 [JCPDS file N˚: 01-081-2421] and CaTi4(PO4)6 [JCPDS file N˚: 00-053-0740] phases to the detriment of the pyrophosphates and metaphosphate phases [
The SEM micrograph shows the existence of two phases, one crystalline and the other glassy (
formation of the predominant cyclic metaphosphate phases. However, when looking at
The study in vitro bioactivity of the prepared glasses was carried out by analyzing X-ray diffraction spectra of the samples after immersion in the simulated body fluid (SBF) for 15 days at 37˚C. The result showed (
A deep analysis of the spectra obtained seems to suggest that the tricalcium phosphate layer is more important than the hydroxyapatite phase when the TiO2 content reaches 3 mol%.
Phosphate glasses of composition 48P2O5-30CaO-(22−x)Na2O-xTiO2 (with 0 < x ≤ 3; mol%) have been investigated. The structure and the chemical durability have been studies using various techniques such IR, XRD, DSC, SEM... Both X-ray diffraction and IR spectroscopy have confirmed the structure change from metaphosphate to olygophosphates when the TiO2 content increases from 0.5 to 2 mol% in the glass. However, beyond 2 mol% of TiO2, the appearance of isolated orthophosphates groups is observed. The scanning electron microscope indicated a morphological changing from one cliche to another as the TiO2 content increased from 0.5 to 2.5 mol%. This change elucidates the passage from cyclic metaphopsphate groups to olygophosphate (mixture meta and pyrophosphate) and finally to isolated short ortho phosphates groups. The variation of transition temperature versus TiO2 content indicated an increase in Tg from 405˚C to 430˚C when the TiO2 content increased from 0.5 to 2 mol%, elucidating an improvement in the rigidity of the glass [
The influence of TiO2 on the glass forming characteristics and properties of Na2O-TiO2-CaO-P2O5 glasses has been investigated. The structure and the chemical durability have been studied using various techniques such IR, XRD, DSC, SEM. The variation of the transition temperature versus TiO2 content indicates an increase in Tg when the TiO2 content increases and indicates an improvement in the rigidity of the glass. SEM micrograph indicates the existence of two phases one crystalline and the other vitreous. The morphological of the phase crystalline change from one micrograph to another as the TiO2 content increases from 0.5 to 2.5 mol% and indicates that the structure moves from cyclic metaphosphate and olygophosphate groups to orthophosphate groups. The chemical reactivity of these materials was evaluated after contacting the different glasses with a synthetic physiological fluid (SBF). The XRD spectra of these glasses, after test in vitro, indicate the formation of a mixture of hydroxyapatite and tricalcium layers with some traces of calcium pyrophosphate phases. The presence of these layers is very interested for an eventual biological application in vivo.
The authors wish to thank National Center for Scientific and Technical Research [Division of Technical Support Unit for Scientific Research (TSUSR) Rabat, Morocco] for their assistance to the realization of this work. We also thank Ms. Pr. R. ELOUATIB (Laboratory physic and chemistry of inorganic materials) for the support that has brought us.
The authors declare no conflicts of interest regarding the publication of this paper.
Er-Rouissi, Y., Aqdim, S., Bouari, A.E., Hmimid, F. and Aqdim, S. (2020) Chemical Durability, Structure Properties and Bioactivity of Glasses 48P2O5-30CaO-(22−x)Na2O-xTiO2 (With 0 < x ≤ 3; mol%). Advances in Materials Physics and Chemistry, 10, 305-318. https://doi.org/10.4236/ampc.2020.1012024