Glasses In Acid Solutions Research Articles

Formation of nano-porous Pd(Ni) structure produced by dealloying Zr-Al-Ni-Pd base glassy alloys and their electrochemical properties

In this work bulk metallic glasses of Zr55Al10Ni10Pd25, Zr50Al10Ni15Pd25 and Zr40Al10Ni25Pd25 in rod forms were prepared by copper mold casting technique. The glass-forming ability, thermal stability and corrosion behavior were examined with the aim to investigate the possibility of synthesizing nanoporous Pd(Ni) alloy structure which are exhibiting good electrochemical characteristics by the dealloying treatment of Zr-Al-Ni-Pd bulk metallic glasses in acid solution. After chemical treatments, the glassy rods exhibit open, three-dimensional, and separated nanopores structure. The size of nanopores (NP) is increased with increasing Zr content due to the enhanced dealloying kinetics.

Structural characterization and calorimetric dissolution behavior of Na2O[sbnd]CuO[sbnd]P2O5 glasses

Two series of glasses belonging to the ternary system Na2O - CuO - P2O5 where copper is introduced differently were synthesized by the conventional melt-quenching technique. Both series start from meta-phosphate composition NaPO3 (50Na2O-50P2O5). In the first series, the Na2O/P2O5 ratio is constant (Na2O/P2O5=1) and both Na2O and P2O5 oxides were replaced by copper oxide CuO: (50-x/2) Na2O - xCuO - (50-x/2) P2O5, 0≤x≤40. In the second series, the molar percentage of P2O5 is kept constant at 50mol% and Na2O is replaced by CuO: (50-x)Na2O – xCuO – 50P2O5, 0≤x≤50. The glasses of these two series belong respectively to NaPO3-CuO and NaPO3-Cu(PO3)2 lines of the ternary system. These materials were characterized by density measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), Raman, diffuse reflectance and dissolution heat measurements carried out with micro-calorimetry technique. Introduction of copper in meta-phosphate glass induces a blue/green color, and strengthens the vitreous network, as shown by the decrease of the molar volume (VM) and the increase of the glass transition temperature (Tg) when the content of CuO rises. The crystallization of the glasses, followed by XRD, leads to the formation of NaPO3, Na2CuP2O7 or Na2Cu(PO3)4 depending on the composition. Raman spectroscopy shows the conservation of the metaphosphate chains for NaPO3-Cu(PO3)2 glasses characterized by a constant O/P ratio (O/P=3) and the depolymerization of these chains for NaPO3-CuO glasses where O/P ratio varies from 0 to 3.67. UV - visible study showed that the optical energy gap decreases by increasing the CuO concentration. Calorimetric study of the dissolution of glasses in acid solution shows a decrease of the dissolution enthalpy, for both series, when the CuO content increases. The dissolution phenomenon is endothermic for glasses with low content in CuO (x<30) and exothermic for glasses rich in CuO.

Effects of barium oxide on structure and properties of calcium iron phosphate glasses

In order to study the effects of barium oxide on the structure and properties of glasses from the glass system of xBaO-(20-x)CaO-32Fe2O3-48P2O5 (x=2,4,6,8,10,12,14,16,18mol%), several methods are applied to the investigation, including XRD, FTIR, DSC and chemical durability tests. Results from FTIR spectra shows that BaO loosens the glass network, with some sorts of crystals forming in the two glass groups depicted in the XRD spectra. However, the glass transition temperature (Tg) and glass crystalline temperature (Tc), as well as the difference between the two(ΔT=Tc-Tg), rise with the addition of BaO. All densities of glasses level up with larger concentration of barium oxide; fluctuations occur in the glass system with the formation of different crystals. When CaO is replaced by BaO, the dissolution rate moves to high level in alkali solution when compared with the basic glass (20CaO-32Fe2O3-48P2O5), while glasses in acid solution possess the inferior resistance than glasses in alkaline solution. It turns out that crystals in these glasses did improve resistance to acid and alkaline ions when they are compared with their base glasses.

Structure and thermochemical study of strontium sodium phosphate glasses

Phosphate glasses having the general formula (100-x) NaPO3-x SrO with an O/P ratio varying between 3 and 3.25 were synthesized by melt quenching technique. The glasses are studied in order to determine the influence of SrO addition on the structural and physical-chemical properties. Density, glass transition and crystallization temperatures increase with SrO content, showing the shrinking and reticulation of phosphate network. The chemical durability of the glass series is enhanced by the substitution of Na2O and P2O5 by SrO. Fourier Transform Infrared Spectroscopy and 31P Magic Angle Spinning Nuclear Magnetic Resonance spectroscopies revealed the depolymerisation of the glass network by the decrease of middle chain units to create end chain units species. Calorimetric study of the dissolution of glasses in acid solution shows a decrease of the dissolution enthalpy when the SrO is added.

Hydrolysis kinetics of lead silicate glass in acid solution

Hydrolysis kinetics of the lead silicate glass (LSG) with 40 mol% PbO in 0.5 N HNO 3 aqueous acid solution was investigated. The surface morphology and the gel layer thickness were studied by scanning electron microscopy (SEM) micrographs. Energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma spectroscopy (ICP) were used to determine the composition of the gel layer and the aqueous solution, respectively. The silicon content of the dissolution products was determined by using weight-loss data and compositions of the gel layer and the solution. The kinetic parameters were determined using the shrinking-core-model (SCM) for rate controlling step. The activation energy obtained for hydrolysis reaction was Q che = 56.07 kJ/mole. The diffusion coefficient of the Pb ions from the gel layer was determined by using its concentration in solution and in LSG. The shrinkage of the sample and the gel layer thickness during dissolution process were determined.

Optical properties of porous glasses doped with ZnS

The paper presents a new preparation method to form semiconductor nanoclusters inside silica porous glasses as matrices and describes investigations of the luminescence properties of the samples loaded repeatedly with ZnS nanoparticles. Silica porous glasses were obtained by leaching the two-phase sodium borosilicate glasses in acid solution. The samples consisting of two types of glasses with different pore sizes and immobilized nanosized ZnS in these matrices by a chemical deposition process were used. EDS measurements confirmed purity of the samples. The recorded absorption and photoluminescence spectra exhibit the quantum size effect due to the increasing number of the chemical deposition cycles.

Etching Mechanism of Pb-Free Glasses in Acid Solution for Barrier Ribs in Plasma Display Panel

We present the preliminary results of our research on the behavior of lead free glasses in the acid etching process, which is used for the formation of barrier ribs in plasma display panel. The glasses (BaO-B2O3-ZnO system) were etched in HNO3 solution (0.1-1.0% HNO3) at 50°C. The structure and surface of the etched bulk glass were investigated by using inductively coupled plasma and X-ray photoelectron spectroscopy. As a result, Ba (3-35ppm/min) and Zn (2- 27ppm/min) ions as major components were leached in the solution. A decrease of the bridge oxygen and a relative increase of non bridge oxygen in the etched glass were found by X-ray photoelectron spectroscopy.

Leaching Behavior of Sodium from Fine Particles of Soda–Lime–Silicate Glass in Acid Solution

The leaching behavior of Na from soda–lime–silicate glass was investigated by preparing glass powders with average particle diameters of 53 and 19 μm, and leaching in HNO3 at 90°−140°C. A new theoretical equation for Na leaching from a spherical particle is proposed based on the assumption that a rate‐determining process is the three‐dimensional self‐diffusion of Na in glass. The diffusion constant (D) of Na in glass was obtained by fitting the experimental data to a theoretical equation. The values of D and activation energy obtained are comparable to those obtained in other studies on larger particles.

Kinetics of corrosion of the alkali borosilicate glasses in acid solutions

The data from an investigation of acid solution corrosion of single-phase alkali borosilicate glasses were analyzed in terms of ion interdiffusion enhanced by network hydrolysis. Glasses under study are identical to an equilibrium composition of the chemically unstable phase of the phase-separated glasses, which are usually used to produce a porous glass. Corrosion of a single-phase glass (or an unstable phase of two-phase glass) can be conceived of as chemical dissolution of its components with the precipitation of the low-soluble products as an intermediate stage.

Leaching mechanism of PbOSiO 2 glasses in acid solution

The leaching mechanism of xPbO(100- x)SiO 2 glasses ( x=35, 40, 50, 55, 60 mol%) in a nitric acid has been investigated by solution analysis and surface analysis. It was observed that the removal of Pb depended on PbO content in a complicated way. For short periods of leaching, the removal of Pb increases gradually with the PbO content up to 50 mol% and remains at a nearly constant value at more than 50 mol%. For longer periods, it increases gradually with the PbO content in all concentration regions. This result is well explained by the combination of two types of mechanisms. One is the selective leaching of Pb and the other is the dissolution of the glass surface or the leached layer with residual Pb. The selective leaching of Pb is considered to be controlled by the interdiffusion of Pb 2+ and H + ions. The diffusion coefficients of Pb 2+ and H + ions were determined by a numerical analysis from the Pb in-depth profiles in the leached layer.

Chemical durability of Na 2OCaOSiO 2 glasses in acid solutions

The resistance of Na 2OCaOSiO 2 glasses to acid solutions has been studied. The compositions studied were Na 2O · 4SiO 2, Na 2O · x CaO · (4− x) SiO 2 and a common electrode glass containing 22.63Na 2O and 5.58 CaO, mol%. The reaction was made at 40°C for about 3 h in 1N solutions of HCl, HNO 3 and H 2SO 4. Powdered glass samples were used and the reaction was followed by analyzing the solution for soda, lime and silica. The extraction rates of each constituent were measured. The effect of acid concentration was also studied for each glass using 10 −3–10N solutions of the three acids for a fixed time. The quantity of calcium extracted increased slowly at first with increasing calcium content in the glass, but rapidly when the lime content exceeded ≈10 mol%. Above this concentration, both calcium and sodium appears to pass into solution in the same proportion in which they are present in the glass. The extraction rate was found to depend on the type and concentration of the acid used, being least in H 2SO 4 and much higher and almost equal in both HCl and HNO 3. An attempt was made to correlate the results of decomposition of the soda-lime-silica glasses to their membrane potentials in acidic solutions.

Reaction of vitreous sodium silicates and aluminosilicates with aqueous solutions. Communication 3. Effect of the addition of silica and alumina to sodium silicates on the instability of the latter to acids

1. The chemical stability of vitreous sodium aluminosilicates can be characterized by the depth of the attacked layer of glass (8), which is a measure of the breakdown of electrovalent O-Na bonds, and by the degree of breakdown suffered by the aluminum-silicon-oxygen of the glass, expressed by the proportions of the Al2O3 and SiO2 originally present in the residual surface layer that have passed into the solution, 2. With increased additions of SiO2 to sodium silicates, the depth of the attacked layer of glass falls and the silica skeleton is strengthened, 3. When alumina is introduced into sodium silicates, on the one hand there is an increase in the number of silicon-oxygen groups that become united owing to the neutralization by sodium ions of the extra negative charge of the aluminum-oxygen tetrahedra, and on the other hand, owing to the formation of Si-O-Al linkages, depolymerization of silica in the glass increases, with the result that the instability of aluminosilicate glasses In acid solutions Increases greatly when the amount of aluminum oxide added to sodium disilicate exceeds 0.3 mole. 4. The mechanism of the interaction of sodium aluminosilicates with solutions of acids may be regarded as the combination of processes of ion exchange between sodium and aluminum in the glass and hydrogen in the solution, followed by the passage into the solution of small isolated aggregates of silicon-oxygen groups.