Surface degradation behaviour of sodium borophosphate glass in aqueous media: Some studies

Abstract

The degradation behaviour of phosphate glass with nominal composition, 40Na 2 O-10BaO-xB 2 O 3 -(50-x)P 2 O 5 , where 0 ≤ x ≤ 20 mol%, was studied in water, HCl and NaOH solutions at room temperature to 60°C for different periods extending up to 300 h. These glasses were synthesized by conventional melt-quench technique. Dissolution rates were found to increase with B 2 O 3 content in the glass. The dissolution rates for the glass having 10 mol% B 2 O 3 were found to be 0⋅002 g/cm 2 and 0⋅015 g/cm 2 in distilled water and 5% NaOH solution, respectively, at room temperature after 225 h of total immersion period, whereas it increased considerably to 0⋅32 g/cm 2 in 5% NaOH at 60°C after 225 h. However, glass samples with x = 15 and 20 mol% B 2 O 3 were dissolved in 5% HCl solution after 5 h immersion. The degradation behaviour has been correlated with the structural features present in the glass. The optical microscopy of the corroded surface revealed that the corrosion mechanism were different in acid and alkali media.

Bioactive glasses prepared from organic-mediated BOP bonded materials

“…As it is known that quantification of ultra-light elements is a challenge for EDS and generally gives unreliable results [32]; the nominal compositions given in Table 1 were found by using the EDS Na/P ratios and assuming that all boron contents in the precursor materials were converted to B 2 O 3 in the glass. Bulk densities of the glasses were found to vary between 2.57 and 3.87 g cm −3 and comparable to those of the alkaline borophosphate glasses showing a non-linear behavior with boron addition [14,33].…”

“…The presence of B\O\P bonds and B\OH groups in the glass precursors facilitates the nucleation of these phases. The pattern for G6 showed a single broad diffraction maximum around 30°as noted for sodium borophosphate glasses [14].…”

“…The spectra generally consist of broad absorption peaks due to the overlap of the characteristic borate and phosphate bands. The broad shoulder at 1500-1400 cm −1 in the spectrum of G1 indicates the presence of trigonal borate groups [14]. Other peaks in the 1100-500 cm − 1 region were assigned as ν a (P\O\P) of pyrophosphate groups (Q 1 : PO 3 2 − ) at~1100 cm − 1 , ν a (P\O\P) of metaphosphate groups (Q 2 : PO 2 − ) at 1000-860 cm −1 , ν s (P\O\P) at 830-715 cm − 1 and strong bending vibrations (ν 4 ) of the phosphate groups at 550-500 cm − 1 [16,39].…”

“…However, simple phosphate glasses are hygroscopic and have poor chemical durabilities. The addition of trivalent ions (Al 3+ , B 3+ , Bi 3+ , …) into the phosphate network improves physical properties and enhances chemical stability by forming cross-linking M 3+ \O\P bonds [10][11][12][13][14][15][16]. Recent studies have shown that addition of B 2 O 3 not only increases the mechanical properties but also allows a more rapid conversion to HA over the glass surface [3,[17][18][19][20][21].…”

Samarium-doped oxyfluoride borophosphate glasses for x-ray dosimetry in Microbeam Radiation Therapy

“…Borophosphate glasses can provide a high amount of non-bridging oxygens that are apparently necessary to stabilize Sm 2+ , brought by tetrahedral boron and phosphorus species. Furthermore, borophosphate glasses are able to provide good chemical durability [11][12][13][14][15][16]. Given the above observations, we have decided to synthesize four types of Sm-doped oxyfluoride glasses that can potentially allow the conversion of Sm 3+ to Sm 2+ upon irradiation with x-rays.…”