Correlation between Chemical Durability Behaviour and Structural Approach of the Vitreous Part of the System 55P2O5-2Cr2O3-(43-x) Na2O-xPbO

Various characterisation techniques were used to study the composition of the glass series 55-P2O5-2Cr2O3-(43-x) Na2O-xPbO (with 8 ≤ x ≤ 38;mole %) in terms of chemical durability, IR spectroscopy and scanning electron microscopy (SEM). The change in the dissolution rate as a function of time when the studied glasses were kept submerged in distilled water at 90°C for 20 days showed an improvement in the chemical durability when Na2O content was substituted to PbO content. IR spectroscopy revealed a structural change from ultraphosphate groups to pyrophosphate, orthophosphate and probably ring metaphosphate groups. SEM revealed the existence of two phases: a vitreous phase and a crystalline phase. The presence of Cr2O3, even in small amounts, seems to play an important role in the formation of crystallites in the glass network. The improved chemical durability is attributed to the replacement of the easily hydrated Na-O-P and P-O-P bonds by covalent and resistant Pb-O-P bands. Both the increase in PbO content and in the Pb + Cr/P ratio causes an increase in the number of covalent Pb-O-P and Cr-O-P bonds, making the glass structure more rigid. The increase of the covalent Pb-O-P bands leads to a clear evolution of the structure and chemical resistance, caused by grain-boundary resistance as a result of glass crystallisation. The IR spectra indicate that the increase in PbO content favours the formation of isolated PO3-4 orthophosphate groups at the expense of pyrophosphate groups. The radical change in the structure from ultraphosphate groups to pyrophosphate and orthophosphate groups seems to be the cause of the formation of crystallites. The existence of crystallites in these glasses results in a marked improvement in their chemical durability. However, when the crystallites exceed a certain limit, the equilibrium between the glass bath and these crystallites is no longer maintained;we notice, once, a decrease in the chemical durability.

CHEMICAL DURABILITY OF WINDOW GLASS IN TALL BUILDING AND ITS EFFECT ON STRENGTH

The window glasses in tall buildings are exposed to rain, polluted air and sunshine, etc. In this paper the rariancc of the surface chemical durability and bending strength of float glass under the influence of acid, alkali, CO2 ,ultra-violet ray are investigated by electron probe X-ray microanalyser, atomic absorption spectrophotometer, FT-IR spectrometer and Materials testing machine. It is found that the concentration of Na ion at glass surface changes after the glass reacts with the media mentioned above and the bending strength of glass is increased with the exception of the glass exposed to UV ray. If the micro-crack at glass surface can be treated properly, the bending strength will be improved.

Chemical Durability, Structure Properties and Bioactivity of Glasses 48P<SUB>2</SUB>O<SUB>5</SUB>-30CaO-(22−x)Na<SUB>2</SUB>O-xTiO<SUB>2</SUB>(With 0 <x ≤ 3;mol%)

Phosphate glasses of composition 48P2O5-30CaO-(22−x)Na2O-xTiO2 (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 TiO2 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 TiO2 content varies from 0 to 2 mol%, the last become majority when the TiO2 content rich 2 mol%. Nevertheless, when the TiO2 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 TiO2 content increased at the expense of the Na2O content. An increase in the TiO2 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 Ca2P2O7, known by its bioactivity, in some samples. The results obtained on the glasses studied make them potential candidates for an application in tissue engineering.

The Effect of Sm_2O_3 on the Chemical Stability of Borosilicate Glass and Glass Ceramics

Sm2O3 containing zinc-borosilicate glass and glass ceramics were prepared by melt quenching method, and the effect of Sm2O3 and micro-crystallization on the chemical stability of borosilicate glass was explored. DTA analysis showed that the endothermic peak and exothermic peak of basic glass changed from 635 ℃ and 834 ℃ to 630 ℃ and 828 ℃ respectively as a result of the doping of Sm2O3. XRD analysis showed the promoting effect of Sm2O3 on crystallization ability of this glass. The cumulative mass loss of base glass, Sm2O3 containing glass, glass ceramic and Sm2O3 containing glass ceramic was 0.289, 0.253, 0.329, 0.269 mg/mm2 respectively after 26 days corrosion in alkali solution, and 1.293, 1.290, 0.999, 1.040 mg/mm2 respectively in acidic erosion medium. Micro-crystallization decreased and improved the alkali and acid resistance of borosilicate glass respectively, the addition of Sm2O3 increased the alkali resistance of base glass and glass ceramics, and the slight effect of Sm2O3 on the acid resistance of borosilicate glass was also observed.

The Mixed-Alkali Effect on The Resistance of Glass to Water

Based on the composition of float glass, the resistance of glassto water, in which a small amount of K_2O(0-1.0 wt/100)wassubstituted for equivalent amount of Na_2O, was investigated by meansof glass grains testing. The components extracted from the glass andtotal alkalinities in extraction solution were de- termined by atomicabsorption spectroscopy and neutralizing method, respectively. Thecomposition of the glass was 14.4 K_2O+ Na_2O, 4.0 MgO, 8.2 CaO, 1.4Al_2O_3, 72.0 SiO, and the minimum extraction radio of oxides(maximum durability)occurred at a K_2O/Na_2O radio of 0.051(byweight)due to the presence of the mixed- alkali effect.

Optimization of Contents of Three Raw Clay Materials in Formulation of a Porcelain

Formulation of traditional hard porcelain generally requires 50% kaolin, 25% silica and 25% feldspar. Four porcelains formulation using the casting method, were prepared with different percentages of kaolinitic clay, sand and pegmatite referenced respectively NONG, SAB and PEG. The physico-chemical, mechanical and mineralogical characteristics were evaluated on specimens formulated and sintered at different temperatures from 1200˚C to 1300˚C. X-ray diffraction has revealed the presence of mullite and quartz as essentially crystalline phases. The specimen formulated with 55% NONG, 25% PEG and 20% SAB and sintered at 1240˚C gives better performance (water absorption: 0.17%, density: 2.42, open porosity: 0.42% and flexural strength: 53.54 MPa).

Structural Features and Properties of the Vitreous Part of the System 50P₂O₅-25CaO-(25-x)Na₂O-xCoO (with 0 ≤ x ≤ 25;mol%)

The glass series 50P2O5-25CaO-(25-x)Na2O-xCoO (with (0 ≤ x ≤ 25;mol%), has been prepared by direct melting at 1080°C ± 20°C. The introduction of cobalt in calcium phosphate glasses is used to compare its effect with calcium in inhibition corrosion. The dissolution rate has been investigated. It indicated an improvement of chemical durability when the cobalt oxide increases in the network glass at the expense of Na2O content. Both, IR spectroscopy and X-ray diffraction have confirmed the structure changes when the CoO content increases in the glass. This change results in the disappearance of isolated orthophosphate groups followed of a polymerizing of the structure from isolated orthophosphate towards pyrophosphate chains (Q1) by promoting the formation of olygophosphates (mixed Q1-Q2) rich in pyrophosphates. Analysis of the density values, showed an increase of density with the increase CoO content. The covalent radius values of oxygen rcal (O2-) indicate a significant decrease and therefore a relatively high reinforcement of the metal-oxygen-phosphorus (Co-O-P) bonds. SEM micrograph confirms the evolution of the glass structural morphology. The sample having a maximum CoO content confirms a homogeneous glass phase with quite crystalline particles. This property is prerequisite for many interesting industrial applications.

In vitro analysis of riboflavin-modified,experimental,two-step etch-and-rinse dentin adhesive:Fourier transform infrared spectroscopy and micro-Raman studies

To modify two-step experimental etch-and-rinse dentin adhesive with different concentrations of riboflavin and to study its effect on the bond strength,degree of conversion,along with resin infiltration within the demineralized dentin substrate,an experimental adhesive-system was modified with different concentrations of riboflavin（mlm,0,1%,3%,5%and 10%）.Dentin surfaces were etched with 37%phosphoric acid,bonded with respective adhesives,restored with restorative composite-resin,and sectioned into resin-dentin slabs and beams to be stored for 24 h or 9 months in artificial saliva.Micro-tensile bond testing was performed with scanning electron microscopy to analyse the failure of debonded beams.The degree of conversion was evaluated with Fourier transform infrared spectroscopy（FTIR） at different time points along with micro-Raman spectroscopy analysis.Data was analyzed with one-way and two-way analysis of variance followed by Tukey＇s for pair-wise comparison.Modification with 1%and 3%riboflavin increased the micro-tensile bond strength compared to the control at 24 h and 9-month storage with no significant differences in degree of conversion（P〈0.05）.The most predominant failure mode was the mixed fracture among all specimens except 10%riboflavin-modified adhesive specimens where cohesive failure was predominant.Raman analysis revealed that 1%and 3%riboflavin adhesives specimens showed relatively higher resin infiltration.The incorporation of riboflavin in the experimental two-step etch-and-rinse adhesive at 3%（mlm） improved the immediate bond strengths and bond durability after 9-month storage in artificial saliva without adversely affecting the degree of conversion of the adhesive monomers and resin infiltration.

Chemical stability of Ce-doped zircon ceramics:Influence of p H,temperature and their coupling effects

Zircon was employed to immobilize simulated tetravalentactinide nuclide（Ce^4＋）. Zr_（1–x）Ce_xSiO_4（0≤x≤0.10） ceramics were synthesized and their chemical durabilities were investigated systematically. The effects of p H and temperature on the chemical durability of the as-prepared compounds were investigated using the MCC-1 static leaching test, and their coupling effects were also explored. It was found that the normalized release rates of Ce in deionized water and alkaline solutions（pH=10） were smaller than those in acid solutions（p H=4）. At a certain p H value, the normalized release rate of Ce（LR Ce） increased with the temperature in the initial period. However, the leaching progress almost reached a balance after 14 days, and both of the p H and the temperature had slight impact on the leaching of Ce element. Moreover, the LR_（Ce） were below 10^（–5）g/m^2/d after 42 days, which was lower than those of other nuclear waste forms in all discussed leachates.

Collagen fiber membrane-derived chemically and mechanically durable superhydrophobic membrane for high- performance emulsion separation

Developing high-performance separation membrane with good durability is a highly desired while challenging issue.Herein,we reported the successful fabrication of chemically and mechanically durable superhydrophobic membrane that was prepared by embedding UiO-66 as size-sieving sites within the supramolecular fiber structure of collagen fiber membrane(CFM),followed by the polydimethylsiloxane(PDMS)coating.The as-prepared CFM/UiO-66(12)/PDMS membrane featured capillary effect-enhanced separation flux and homogeneous porous channels guaranteed high separation efficiency.When utilized as double-layer separation membranes,this new type of composite membranes separated various surfactant stabilized water-in-oil microemulsions and nanoemulsions,with the separation efficiency high up to 99.993%and the flux as high as 973.3 L m−2 h−1.Compared with commercial polytetrafluoro ethylene(PTFE)membrane,the advantage of the double-layer CFM/UiO-66(12)/PDMS membranes in separation flux was evident,which exhibited one order of magnitude higher than that of commercial PTFE membrane.The CFM/UiO-66(12)/PDMS membrane was acid-alkali tolerant,UV-aging resistant and reusable for emulsion separation.Notably,the CFM/UiO-66(12)/PDMS membrane was mechanically durable against strong mechanical abrasion,which was still capable of separating diverse water-in-oil emulsions after the abrasion with sandpaper and assembled as double-layer separation membranes.We anticipate that the combination of CFM and metal organic frameworks(MOFs)is an effective strategy for fabricating high-performance separation membrane with high mechanical and chemical durability.

Tailoring effect of Y_(2)O_(3)on water resistance of Na_(2)O-ZnO-Al_(2)O_(3)-B_(2)O_(3)glasses

To explore the improving effect of Y_(2)O_(3)on the water resistance of xY_(2)O_(3)-(100-x)(0.05 Al_(2)O_(3)-0.15 ZnO-0.15 Na_(2)O-0.65 B_(2)O_(3))(x=0,0.7 mol%,1.4 mol%,2.1 mol%,2.8 mol%)glasses,glass structure and ion migration characteristics were respectively characterized by an infrared spectrometer and an electrochemical workstation.X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive Xray spectroscopy(EDS)and inductively coupled plasm-atomic emission spectrometry(ICP-AES)were used to comprehensively analyze the alteration products.The experimental results show that with the increase of Y_(2)O_(3)content,the mass loss per unit area of the glass is significantly reduced,and pH in leaching solution has the same change trend with mass loss of the glass,which indicates the improving effect of Y_(2)O_(3)addition on the studied glass.The content of[BO_(4)]structural unit and dc conductivity of glass increase firstly and then decrease with the increase of Y_(2)O_(3)content,and reach a maximum at x=0.7 mol%.Although addition of Y_(2)O_(3)plays the role in the changes of glass structure and ion migration characteristics,the more important influence of Y_(2)O_(3)is on the glass surface alteration layer.Y and Zn elements are enriched on the glass surface and finally transformed into an alteration layer,moreover,the adhesion between the alteration layers and the glass matrix is enhanced with the increase of Y_(2)O_(3)content,which effectively blocks the further interdiffusion between the water molecules and the glass matrix.

Er^(3+)/Yb^(3+) Codoped Phosphate Glass for Ion-Exchanged Planar Waveguide Amplifiers

A novel Er3+/Yb3+ codoped phosphate glass was developed, which exhibited good chemical durability in molten salts and excellent spectroscopic properties. Preliminary results of ion exchange at different time and temperature, and with varying melt concentrations indicated that WM4 glass was suitable for ion-exchange experiments and there was no deterioration of surface quality.