Glass Solution Research Articles

Fluid flow effects in levitated droplets

Levitation techniques have been applied to a staggering range of materials, from liquid helium to aqueous solutions of proteins, to metals, ceramics, glasses and semiconductors. These experiments have encompassed temperatures from cryogenic to greater than 2500 °C, and samples from micrograms to tens of kilograms. It should come as no surprise that a wide variety of levitation principles have been employed for processing these samples, including electromagnetic (EML), electrostatic (ESL), aerodynamic and gas film, acoustic and dia- or paramagnetic levitation, as well as combinations of these and others. All of these containerless techniques share one key feature: internal flow in liquid samples. The flow may be driven directly by the positioning force, as in EML and aerodynamic levitation, or by temperature gradients through Marangoni convection and/or natural buoyancy, as in ESL. It is possible to reduce the positioning-driven and buoyancy flows by performing the experiments in microgravity; however, often even the reduced levels are important. For some experiments, such as viscosity measurements, only whether the flow is laminar or turbulent must be established. For other experiments, however, quantitative assessments of velocity, shear stress or shear strain rate are required. In most cases, it is difficult or impossible to measure the internal flow in levitated droplets directly. The samples are usually small, and often opaque, reactive, high-temperature, metastable, or all of the above. Furthermore, recirculating flow limits the utility of tracking surface particles, since they tend to collect in stagnation points rather than following the flow. Most research groups have chosen mathematical modelling to assess the internal flow in levitated droplets. Several different classes of experiments are examined in terms of the effect of fluid flow and the impact of flow modelling. This paper focuses on EML and ESL, although the techniques and many of the results are applicable to other levitation methods.

New development of inorganic ion exchanger: Synthesis and Ion Uptake Properties of Ternary Mixed Hydrous Oxides as Environmentally Harmonious Material

Twenty-one Si-AI-Mg mixed hydrous oxide (MHO) samples, in which the atomic fraction of the constituents differ within 0.125-0.750, were synthesized by the neutralization and precipitation method for development of new inorganic ion adsorbent as environmentally harmonious material. Their ion uptake properties were as well examined. The present study synthesizes Si-Al-Mg MHOs for the first time and investigates ion uptake properties of products to verify expected composite effect.Samples with desired chemical compositions were synthesized easily and reproducibly by mixing an acidic solution of water glass, aluminum and magnesium chloride into aqueous ammonia. Constituent phases recognized in the sam-ples by XRD measurement were gibbsite, bayerite, boehmite, low crystalline trioctahedral smectite-like phase, and serpentine-hydrotalcite intermediate phase, respectively. The XRD peak intensity of these component phases changes depending on chemical compositions of the samples. All samples were mesoporous materials with average pore diameter of 3.3 to 11.5 nm.All the samples showed ion uptake properties which were remarkably different in terms of their chemical compositions. The uptake of some ions on the samples reached equilibrium within 1 day. Selectivity of ion uptake was strongly controlled by atomic ratios of Si and Mg; those with high atomic ratio of Si show cation selectivity, and those with high atomic ratio of Mg conversely showed anion selectivity. All the samples sorbed arsenate [As (III) ] and arsenate [As (V) ] species and the existence of the domain with extremely high separation factor (αAs (V) /As (III) ) values over 100 in equimolar composition area of Si-AI-Mg ternary system was found. The relationship between the uptake amounts of K+and phosphate ions and the chemical compositions of the samples were expressed by the following two multiple regression equations:QP= -0.279CSi+0.088CMg+0.195 (R2=0.745)QK= 0.445CSi- 0.384CMg+ 0.280 (R2=0.828)whereQPandQKare the uptake amount (mmol g-1) of phosphate (H2PO4- +HPO42-) and K+ions, CSiand CMgare the atomic ratio of silicon and magnesium present in the samples andRis multiple correlation coefficient. It was shown that the values calculated according to the above equations were considerably close to the observed ones.

Towards chemosensing phosphorescent conjugated polymers: cyclometalated platinum(ii) poly(phenylene)s

The synthesis and optical properties of several phosphorescent conjugated poly(phenylene)s containing cyclometalated square-planar platinum (II) complexes are reported. These electronic polymers were synthesized via Suzuki cross-coupling of a dibromophenylpyridine-ligated Pt(II) complex with a fluorene diboronic ester. Their optical properties are characterized by relatively strong orange room-temperature phosphorescence with well-resolved vibronic structure in both frozen 2-methyltetrahydrofuran glass and room-temperature fluid solution. Time-resolved phosphorescence spectroscopy has shown that the polymers have excited state lifetimes of approximately 14 μs. These optical properties of the oligomers and polymers are contrasted with those of small model complexes, the optical properties of which have a strong dependence on the identity of the β-diketonate ligand used. The potential utility of phosphorescent conjugated polymers is illustrated by examination of the diffusive quenching due to oxygen as a function of molecular structure.

A Spin-on Dielectric Material for High Aspect Ratio Gap Fill

AbstractThis communication describes the results of a potential spin-on glass (SOG) solution for narrow and high aspect ratio trench fill in both shallow trench isolation (STI) and premetal dielectric (PMD) applications. We have focused our development work on a hydrogen silsesquioxane (HSQ, (HSiO3/2)n) material, which offers the advantage of a carbon free gap fill solution. The main challenge for carbon-free SOG materials is to achieve material densification in the nano-scale gaps during thermal processing that of the gap filled material during the wet cleaning steps. This paper reports some approaches and findings on material densification in the nano-scale gaps and the results of subsequent wet etch tests.

Silica gel with continuous macropores prepared from water glass in the presence of poly(acrylic acid)

Monolithic silica gel with macropores was prepared in the solution of water glass and polyacrylic acid (HPAA) by freezing transitional structures of phase separation. In the system, phase separation proceeds between silica polymers and HPAA, so that the porous morphology varies from closed macropores to particle aggregates through bicontinuous morphology, where both macropores and silica skeleton are three-dimensionally interconnected, with increasing HPAA/silica ratio. In addition, we can control the macropore size in bicontinuous morphology by varying the concentration of both silica and HPAA, or by changing the molecular weight of HPAA. The pore size distribution is quite sharp indicating the presence of pores with the same size all through the monolithic samples.

The effect of fluoride on the dissolution rates of natural glasses at pH 4 and 25°C

Far-from-equilibrium, steady-state dissolution rates at pH 4 of a suite of natural glasses, ranging from basaltic to rhyolitic in composition, have been determined as a function of aqueous fluoride concentrations up to 1.8 × 10 −4 mol/kg in mixed-flow reactors. Dissolution rates of each of these glasses increase monotonically with increasing aqueous fluoride concentration. Measured dissolution rates are found to be consistent with both the Furrer and Stumm (1986) surface coordination model and the Oelkers (2001) multi-oxide dissolution model. Application of the latter model yields the following equation that can describe all measured rates as a function of both glass and aqueous solution composition: log ( r + , geo / ( mol / m 2 / s ) ) = [ − 0.086 ⋅ SiO 2 ( wt % ) − 2.23 ] + [ − 0.0067 ⋅ SiO 2 ( wt % ) + 0.683 ] ⋅ log ( a H + 3 / a A 1 3 + ) where r +,geo represents the far-from-equilibrium dissolution rate, normalized to geometric surface area, SiO 2(wt.%) refers to weight percent of SiO 2 in the glass, and a i denotes the activity of the subscripted aqueous species. Computed glass dissolution rates increase with increasing aqueous fluoride concentration due to the formation of aqueous Al-fluoride complexes, which decrease a Al 3+ . This rate expression can be used to predict far-from-equilibrium dissolution rates of natural glasses in a variety of natural environments. Comparison of rate predictions with the composition of natural fluids suggests that the presence of aqueous fluoride can enhance natural glass dissolution rates by an order of magnitude or more in a variety of geochemical systems.

Rutherford backscattering spectroscopy of amorphous films of Ag–As–S system prepared by spin-coating technique

A new class amorphous chalcogenide films of the system Ag–As–S prepared by standard spin-coating technique from organic solutions of chalcogenide glasses were studied. Rutherford backscattering spectroscopy (RBS) has been proved as an important non-destructive tool for establishing composition and depth distribution of the elements within prepared films. Elastic recoil detection analysis (ERDA) allowed us to study H presence in addition to the basic constituent atoms (Ag, As, S) in films. The μ-XRF spectroscopy and SEM with EDX analysis showed that the films were stoichiometric with a composition of AgAsS 2. Differential scanning calorimetry (DSC) has proven the similarities of thermal parameters such as glass transition temperature, T g, and crystallization temperature T c between spin-coated films and bulk glass of AgAsS 2.

Phase separation in the solution of water glass and poly(vinyl alcohol)

Silica gel samples with macropores were prepared from solutions of silicate and poly(vinyl alcohol) (PVA), where macropores were formed by fixing a transitional structure of phase separation. Among the silica sources tested, tetraethoxysilane (TEOS), colloidal silica and water glass, only the system with water glass shows phase separation and forms macroporous silica gel. In the system with TEOS, ethanol formed during hydrolysis of TEOS becomes good solution and stabilizes the system not to induce phase separation. In the system with colloidal silica, dense structure of silica is probably not suitable for controlling phase separation and gelation. In the system with water glass, driving force of phase separation is considered to be a repulsive interaction between solvent molecules and PVA interacting with silica surface and the solution separates into a phase rich in solvent and that rich in silica and PVA. One of the features in the water glass–PVA system is insensitivity of macropore size against compositional change in the solution, i.e. macroporous morphology in the resultant silica gel hardly changes by changing the composition ratio in the solution. This would be an advantage in the preparation of well-defined macroporous silica from water glass, whose composition varies among the product lot number, because reproducibility in macroporous morphology is ensured regardless of the lot number of the water glass.

Calculation of the Kinetics of Interaction of Alkali Borosilicate Glasses with Aqueous Solutions

The mass transfer inertia in the course of interaction of single- and two-phase sodium borosilicate glasses with aqueous solutions of acids (leaching) is investigated. The kinetics of mass transfer in glass–solution systems is calculated from the hyperbolic equation of wave diffusion with due regard for the delay of diffusion fluxes. The calculated time dependences of the integrated characteristic of the process adequately describe the experimental data. The parameters of the attainment of a quasi-stationary regime of the process and the apparent activation energies for diffusion and relaxation are determined.

Porous Material from Solidified Paper Sludge with Water Glass Solution by Alkali Hydrothermal Treatment

Porous Material from Solidified Paper Sludge with Water Glass Solution by Alkali Hydrothermal Treatment

Laser‐Induced Direct Lithography for Patterning of Carbon with sp3 and sp2 Hybridization

AbstractA new method of laser‐induced lithography for direct writing of carbon on a glass surface is described, in which deposition occurs from a transparent precursor solution. At the glass–solution interface where the laser spot is focused, a micro‐explosion process takes place, leading to the deposition of pure carbon on the glass surface. Transmission electron microscopy (TEM) analysis shows two distinct co‐existing phases. The dominant one shows a mottled morphology with diffraction typical of cubic (sp3) diamond. The other region shows an ordered array of graphene sheets with diffraction pattern typical of sp2‐bonded carbon. The sp3 crystallites range in size from 9 to 30 Å and are scattered randomly throughout the sample. A UV Raman spectrum shows a broad band at the location of the expected diamond peak, together with a peak corresponding to the graphite region. We conclude that the patterned carbon is composed of a mixture of nanocrystalline sp3 and sp2 carbon forms.

Practical improvements in CaO-swelling cements

Calcium oxide-swelling cement expansion behaviour was studied to improve results of annular sealing during well cementing and underground gas storage. Calcium oxide cement compositions expand during hardening. Cement slurry expansion, resistance to flow (to assess pumpability downhole) and thickening time, shear and compressive strengths, and system permeability, which are properties of autoclave-cured hardened cement paste, are discussed in detail. The objective was to avoid calcium oxide sedimentation and reduced swelling tendency that could be anticipated using the calcium oxide-swelling cement. Slurries were initially prepared according to API standards, as quick-look tests to help choose appropriate parameters for further investigations. Expansion and consistency (resistance to flow) tests were conducted in high pressure–high temperature (HPHT) devices at 60, 80, 90 and 120 °C, and 120 MPa. Repeat experiments were conducted by adding sodium silicate solution (water–glass) and the results were compared. As high as 30–40% water–glass solution improves gelation tendency and expansion of the cement slurry from 3.5% to 6.2%. The investigation examines the results obtained, in some test cases, and shows that the influence of about 13% CaO by weight of cement becomes significant when the temperature is between 65 and 80 °C. Calcium oxide-swelling cements composed of 13% calcium oxide, improve tightness of cemented boreholes against gas leakage. Workover and cementing operators could extend the applications of CaO to carbonate formations, where the traditional cementing jobs are difficult because of vugs and secondary porosities.

Time-resolved spectroscopic study of Eu(TTA) 3(TPPO) 2 chelate in situ synthesized in vinyltriethoxysilane-derived sol–gel-processed glass

Homogeneous transparent monolithic samples doped with Eu(TTA) 3(TPPO) 2 chelate have been prepared by using the in situ synthesis technique. The time-resolved spectra of Eu(TTA) 3(TPPO) 2 chelate dispersed in both vinyltriethoxysilane-derived sol–gel glass and ethanol solution were measured at room temperature. The possible mechanisms responsible for the electronic transitions and excitation energy migration of the chelate in the sol–gel glass were discussed. The decay curves of the 5D 0 level of the europium ions in Eu(TTA) 3(TPPO) 2 chelate in above two matrices were also obtained in the temperature range from 13 to 300 K and the temperature dependence of the lifetime of the 5D 0 level was studied.

Thermodynamics of dissolution of glassy polymers

A parametric semi-empirical thermodynamic theory for the dissolution of glassy polymers in liquids is formulated based on the experimental results on Gibbs energy, enthalpy and entropy of mixing in isothermal conditions for a large number of systems. The values of these thermodynamic functions include the contribution from the glassy structure of the polymer, which depends on the volume fraction of metastable voids, the cohesion energy of polymer, and the entropy depression parameter. The glassy-state contribution to the enthalpy and entropy of mixing is large and negative, which provides sufficient difference from the same functions for the elastic polymers. However, this also leads to the enthalpy/entropy compensation, and the values of Gibbs energy of mixing only weakly depend on the glassy nature of the polymer. The theory is shown to provide adequate explanation for all specific features of the concentration dependences of different thermodynamic functions found in experiment at constant temperature. The parameters of the model are tabulated for a large variety of solutions of polymer glasses.

The Wall Potential in the Pores of Vycor Glass Experienced by 3He Quasiparticles in a Dilute 3He-4He Solution

We have studied the Fermi fluid, 3He in 3He-4He solution, confined within the narrow channels of Vycor glass. Continuous wave NMR signals were observed in two almost identical coils, one containing bulk solution and the other the solution in Vycor glass. Three different solutions (0.1, 1.6, and 6%) have been studied over the temperature range 3mK to above 1K. The measurements relate to two exclusion effects of 3He from Vycor glass. One concerns potential energy, and we demonstrate the partial exclusion of 3He independent of concentration as the temperature is lowered from high temperatures down to around 200mK, thus giving an experimental measure of the van der Waals forces between the wall and the helium. The second effect is the additional quantum exclusion which arises from the influence of quantum wire confinement on the kinetic energy, as the temperature is progressively lowered below 50mK in the very dilute (0.1%) solution.

Preparation of ultrafine silica powders

Numerous processes have been used for the preparation of ultrafine silica powders, which include the flame or plasma hydrolysis of silicon tetrachloride vapor at high temperatures [1, 2] and the hydrolytic polycondensation of organosilicates or silicon tetrachloride in liquid solvents [3, 4]. Silica powders produced by the above methods have unique properties such as fine particle size, large surface area and good dispersibility. However, their high production costs have limited the powders’ large-scale commercial applications [5]. Development of alternative cheaper routes to produce ultrafine silica powders with desirable characteristics is therefore of considerable interest. In this letter, we report the preparation of ultrafine silica powders by sol-gel process from water glass using ethyl acetate as a latent acid reagent. The interaction of ethyl acetate with water glass solution and the gelling characteristic of water glass in the presence of ethyl acetate were examined and the effect of calcination on the properties of the silica powders was studied. Water glass (technical grade) with SiO2 content of 26.4% and SiO2/Na2O mole ratio of 3.3 was used as a starting material, which was diluted with distilled water and vacuum filtered before use. Ethyl acetate (analytical grade) was added to water glass solution in a given mole ratio of CH3COOC2H5 to SiO2 under stirring at 25 ± 1◦C. After reaction for a period of time and appearance of silica gels, the resulting slurry was kept reacting for 40 min, and then acidified by HCl and stirred for another 1 h at 80 ◦C. It was filtered at the pump and thoroughly washed with distilled water to eliminate Cl− and Na+ ions. The wet gels obtained after filtration were stirred with n-butanol and distilled to remove water as azeotrope. Ultrafine silica powders can be obtained after azeotropic distillation and drying at 120 ◦C for 2 h. The calcination of the powders was carried out at 300 to 1200 ◦C for 2 h with an air atmosphere. The pH of the reaction system was monitored by using a pH meter (Model pHS2, Shanghai, China). The hydrolysis ratio of ethyl acetate was obtained by determining the content of alcohol generated in the process of gelling reaction via gas chromatography (Model BF3400, Beijing, China). The conditions were as follow: column, GDX-103, 2.6 mm × 2 m, 60–80 mesh; detector, TCD; carrier gas, He, volume rate, 45 mL/min; column temperature, 120 ◦C; inject and detection temperature, 210 ◦C. A series of sols and gels were prepared to examine the change in gelation time with the mole ratio of CH3COOC2H5 to SiO2. The gelation time of the reaction system was defined as the time when a visible solid phase was detected either in the form of a gel or precipitate. In this system gels were only formed at low ethyl acetate contents, whereas at higher contents phase separation of the solid and liquid phase occurred. This gelation time was a useful qualitative measure of the stability of the reaction system. The particle morphology and size of the silica sols and silica powders were observed by transmission electronic microscopy (TEM) (Model H-600, Hitachi, Tokyo, Japan). Specimens were made by dropping the silica sols and the prepared water suspension, including silica powders, onto carbon filmed copper grids. The phase structure of the silica powders was determined by X-ray diffractometry (Model D/MAX-III B, Rigaku Co., Tokyo, Japan) with Cu Kα radiation. The specific surface areas of the as-synthesized and calcined powders were measured via the Brunauer-Emmett-Teller (BET) method with nitrogen absorption using an automated volumetric analyzer (Model ASAP 2000, Micromeritics). In the solution of water glass, silica is present as monomeric, oligomeric and polymeric colloidal silicate ions. The colloidal species, with particles in the range 1 to 2 nm, are in equilibrium with monomeric and oligomeric species [6]. The behavior of silicates in solution is governed by the two following interdependent sets of equilibria [7]:

Replica Symmetric Solutions of Random Field Tunneling Model for Proton Glasses

We investigate for the replica-symmetric solutions of the tunneling model proton glass with longitudinal random field of Gaussian distribution. From the replica-symmetric solutions we obtain phase diagrams for each random field distribution, especially the de Almeida-Thouless stability lines in the temperature ( T ) - average interaction strength ( J 0 ) plane and also in the temperature ( T ) - external longitudinal field ( H ) plane.

Analysis of the composition of CuI-As2Se3 and CuI-PbI2-As2Se3 chalcogenide films by X-ray fluorescence spectroscopy

The chalcogenide films As2Se3, CuI–As2Se3, and CuI–PbI2–As2Se3 are prepared through chemical deposition from an organic solvent and investigated by X-ray fluorescence spectroscopy. The contents of the main components of the chalcogenide films are compared by analyzing the intensity ratios for the AsKα, SeKα, and CuKα lines. It is found that the content of the main components (As, Se, and Cu) is virtually the same in binary chalcogenide, pseudobinary, and multicomponent chalcogenide systems, no matter what the technique used for preparing the materials (films deposited from solutions of chalcogenide glasses in n-butylamine and bulk glasses). This result is consistent with a model of dissolution of vitreous semiconductors in organic bases (amine) according to which the fundamental properties of bulk glasses remain unchanged upon formation of the films. The experimental data indicate an analogy between the properties of the multicomponent chalcogenide glasses CuI–As2Se3 and CuI–PbI2–As2Se3 and the chalcogenide glass–based films.

Replica Symmetric Solutions of Random Field Tunneling Model for Proton Glasses

We investigate for the replica-symmetric solutions of the tunneling model proton glass with longitudinal random field of Gaussian distribution. From the replica-symmetric solutions we obtain phase diagrams for each random field distribution, especially the de Almeida-Thouless stability lines in the temperature ( T ) - average interaction strength ( J 0 ) plane and also in the temperature ( T ) - external longitudinal field ( H ) plane.

Analysis and Prediction of Absorption Behavior for Theophylline Orally Administered as Powders Based on Gastrointestinal-transit-Absorption (Gita) Model

Absorption behavior of theophylline, categorized into Class I of Biopharmaceutics Classification System, orally administered as powders in rats was analyzed and predicted by Gastrointestinal-Transit-Absorption (GITA) model, which was modified to describe GI-transit kinetics and dissolution of powders orally administered. First of all, GI-transit kinetics of glass beads was examined to describe the transit kinetics of powders through GI tract in rats. The results showed that the gastric emptying of glass beads was slower than that of solution, but that there was not much difference in the transit rate constants through the small intestine and cecum between glass beads and solution. Furthermore, to introduce the dissolution process of theophylline powders into GITA model, an in-vitro dissolution test was examined for theophylline powders according to the Japanese Pharmacopoeia paddle method. The dissolution rate constants calculated based on the mean dissolution time were not so different in the range of pH from 1.2 to 6.5. Using the parameters for GI transit, dissolution and absorption obtained, the plasma concentration-time profile of theophylline after oral administration as powders to rats was predicted based on GITA model. The profile calculated was significantly correlated with the observed time course of plasma concentration for theophylline, and the parameters such as C(max) and AUC based on the predicted curve coincided with those on the observed data, showing that GITA model is useful for the prediction of the absorption behavior of drugs administered as powders. The simulation studies showed that about 80% of orally administered theophylline powders dissolved in the stomach and that the remaining powders rapidly moved to the lower jejunum and ileum, where they dissolved. Furthermore, it was suggested that theophylline is absorbed mostly in the upper small intestine, duodenum, upper jejunum and lower jejunum, after its oral administration as powders.