Microporous Glass Research Articles

A microporous glass-polymer composite as a new material for solid-state dye lasers: II. Lasing properties

The conversion efficiency and service life of the laser elements based on a polymer-filled microporous glass (PFMPG) composite doped with organic dyes are studied. It is shown that both the conversion efficiency and the service life of the laser elements achieve the values obtained for the same dyes in bulk polymer elements. Good lasing characteristics of the elements studied are advantageously combined with the high mechanical strength and high laser damage resistance and excellent thermooptical properties of the PFMPG composite.

Control of various morphological changes of poly(meth)acrylate microspheres and their swelling degrees by SPG emulsification

Crosslinked poly(meth)acrylate polymers with a variety of morphologies were synthesized with two steps. In the first step, a microporous glass membrane (Shirasu Porous Glass, SPG) was employed to prepare uniform emulsion droplets by applying an adequate pressure to the monomer phase, which was composed of the ADVN initiator, solvent of toluene or heptane or their mixture, and a mixture of (meth)acrylate monomers. The droplets were formed continuously through the membrane and suspended in the aqueous solution, which contained a PVA-127 suspending agent, SLS emulsifier, and NaNO2 inhibitor to suppress the nucleation of secondary particles. SPG pore sizes of 0.90, 5.25, and 9.25 μm were used. Then the emulsion droplets were polymerized at 343 K with a rotation rate 160 rpm for 24 h. The (meth)acrylate monomers 2-ethylhexyl acrylate (2-EHA), 2-ethylhexyl methacrylate (2-EHMA), cyclohexyl acrylate (CHA), methyl methacrylate (MMA), lauryl acrylate (LA), and lauryl methacrylate (LMA) were used in this research. The influences of the ratios of the monomer and crosslinking agent EGDMA, the amount of diluents, the monomer type on the polymer particle morphology, the swelling degree, and the polymer particle size were investigated. It was found that an increase in the concentrations of EGDMA and heptane resulted in higher coarse porous spheres and smaller polymer particle sizes. A coefficient with a variation close to 10%, or a standard deviation of about 4, was obtained. The capacity of these spheres as solvent absorption materials was examined. The highest swelling degrees of heptane and toluene were obtained when LA was employed as the monomer with 30% (by weight) of EGDMA and 70% (by weight) of heptane as an inert solvent. The highest capacity of the solvent absorption was obtained when using a polymer particle size of 4.81 μm, as prepared by SPG pore size 0.9 μm. The polymer particles were able to absorb aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, and a mix of aliphatic hydrocarbon solvents and aromatic hydrocarbon solvents, such as toluene and heptane. The capacity of solvent absorption for the aromatic hydrocarbon solvents was higher than for the aliphatic hydrocarbon solvents. In addition, the particles did not rupture or collapse after absorption in solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4038–4056, 2000

Morphological changes (including filamentation) in Escherichia coli grown under starvation conditions on silicon wafers and other surfaces.

Using a scanning electron microscope, pleomorphism (notably filamentation) was seen when Escherichia coli was grown under starvation conditions for 14 d on microporous silicon wafers, titanium, glass and plastic discs. Under these conditions, the 'standard', rod shaped cell (1-3 microns) failed to separate after division and filaments developed, some as long as 50 microns, with many showing bulbous tips. Filamentation began to occur 5 d after the imposition of starvation conditions. Dumbbell shaped cells were also observed, although apparent 'Y' and 'V'-shaped cells proved to be artefacts, caused by overlapping rods. The implications of the appearance of pleomorphism in E. coli, when grown under starvation conditions, is discussed in relation to its pathogenicity and growth in the environment.

Anomalous surface diffusion of water compared to aprotic liquids in nanopores.

1H nuclear magnetic relaxation dispersion experiments show remarkable differences between water and acetone in contact with microporous glass surfaces containing trace paramagnetic impurities. Analyzed with surface relaxation theory on a model porous system, the data obtained for water show that proton surface diffusion limited by chemical exchange with the bulk phase permits long-range effectively one-dimensional exploration along the pores. This magnetic-field dependence coupled with the anomalous temperature dependence of the relaxation rates permits a direct interpretation in terms of the proton translational diffusion coefficient at the surface of the pores. A universal rescaling applied to these data collected for different pore sizes and on a large variety of frequencies and temperatures, supports this interpretation. The analysis demonstrates that acetone diffuses more slowly, which increases the apparent confinement and results in a two-dimensional model for the molecular dynamics close to surface relaxation sinks. Surface-enhanced water proton diffusion, however, permits the proton to explore a greater spatial extent of the pore, which results in an apparent one-dimensional model for the diffusive motions of the water that dominate nuclear spin relaxation.

Photoorientation of Polymer Fragments in a System Azo-Polymer-Microporous Glass

Anisotropy induction in the azo-polymer introduced into microporous glass under irradiation with polarised UV light is investigated. Practically pure “angular hole burning” mechanism is realised. Influence of the porous matrix on the life-time of cis-isomers, dipol-dipol interaction of polymer side chains, main-chain ordering was established.

Viscosity change in oil/water food emulsions prepared using a membrane emulsification system

This paper reports viscosity measurements of oil/water (O/W) monodispersed emulsions of different droplet diameters obtained in a membrane emulsification system. Hydrophilic microporous glass membranes of different pore diameters were used to prepare O/W emulsions. The results showed that the droplet diameter of the emulsions varied with the average pore diameter of the membrane. The average droplet diameter was found to be about five times greater than the average membrane pore diameter. A correlation was found for the relationship between the average droplet diameter and the emulsion viscosity. As the dispersed droplet size became smaller, the total surface area of the droplets increased. Therefore, the emulsion viscosity and the relative viscosity increased. Few studies have reported the viscosity of O/W emulsions with droplet diameter of 5 μm or more and an oil phase concentration of 10 vol% or less. In the present study a correlation between the droplet diameter and the emulsion viscosity was statistically established. ©

Investigation of Mechanisms Contributing to Slow Desorption of Hydrophobic Organic Compounds from Mineral Solids

This research investigates the mechanisms contributing to the slow desorption of hydrophobic organic compounds from water-saturated mineral solids. The mechanisms investigated were adsorption-retarded aqueous diffusion, micropore diffusion, high-energy micropore adsorption, and micropore blockage by precipitated minerals. To reduce the potential confounding effects of adsorbent heterogeneity, a set of homogeneous silica gel and glass bead adsorbents were used in the investigation. Desorption rates for the slow-desorbing fractions of chloroform (CF), trichloroethylene (TCE), and perchloroethylene (PCE) from silica gel did not conform to the pore-diffusion model for adsorption-retarded aqueous diffusion. This indicated that diffusion through adsorbent mesopores was not responsible for slow desorption from silica gel. Micropore-diffusion modeling of TCE desorption from three silica gels and microporous glass beads indicated that pores less than 2 nm in diameter were responsible for slow desorption. Desorptio...

Dense Palladium and Perovskite Membranes and Membrane Reactors

The development of high-temperature processes and tighter environmental regulations requires utilization of efficient gas-separation processes that will provide high fluxes, high selectivity of separation, and the ability to operate at elevated temperatures. Dense inorganic membranes and membrane reactors are especially well suited for high-temperature reactions and separations, due in part to their thermal stability and high separation selectivity (in theory, infinite). Furthermore, membrane reactors offer an inherent advantage of combining reaction, product concentration, and separation in a single-unit operation for the improvement of process economics and waste minimization.The classification of membrane reactors can either be by membrane material and geometry or by the configuration of the reactor. Porous and dense membranes in both tubular and disk forms have been used for membrane reactors. The membrane can either be catalytically active (catalytic membrane reactor [CMR]) or simply act as a separation medium. In the latter case, the catalyst is packed in the reactor, whose walls are formed by the membrane (packed-bed membrane reactor [PBMR]). In addition, if the membrane is also catalytically active, the reactor is called a packed-bed catalytic membrane reactor (PBCMR).The principal materials from which porous inorganic (ceramic) membranes are made are alumina, zirconia, and glass. Alumina and zirconia membranes are usually asymmetric and composite, with a porous support (0.5–2.0 mm thick) for mechanical strength and one or more thin layers for carrying out separations.On the other hand, glass membranes, such as Vycor and microporous glass, have symmetric pores. Materials commonly used as the porous support are alumina, granular carbon, sintered metal, and silicon carbide.

Water/Oil Emulsions Prepared by the Membrane Emulsification Method and Their Stability

ABSTRACTWe developed and tested a simple method to measure dispersed droplet size of W/O emulsions. Then, using a microporous glass membrane treated with oil phase, we produced a W/O emulsion with high water content (40% w/w) at a high emulsification rate by the membrane emulsification method, and assessed its stability. In comparison with emulsions by the stirring methods, variations in dispersed droplet size and viscosity of emulsions by membrane method were small and the emulsions were more stable. Droplet size was not related to the stability of the W/O emulsion prepared by membrane emulsification.

Emulsification using micro porous glass (MPG): surface behaviour of milk proteins

To investigate the emulsifying properties and adsorption behaviour of high molecular amphiphilic substances such as proteins, it is important to maintain the native status of the used samples. The new method of micro porous glass (MPG) emulsification could offer an opportunity to do this because of the low shear forces. The oil-in-water emulsions were produced by dispersing the hydrophobic phase (liquid butter fat or sunflower oil) through the MPG of different average pore diameters ( d p=0.2 or 0.5 μm) into the flowing continuous phase containing the milk proteins (from reconstituted skim milk and buttermilk). The emulsions were characterised by particle size distribution, creaming behaviour and protein adsorption at the hydrophobic phase. The particle size distribution of protein-stabilised MPG emulsions is determined by the pore size of MPG, the velocity of continuous phase (or wall shear stress σ w) and the transmembrane pressure. A high velocity of v =2 m s −1 ( σ w=13.4 Pa) and low pressure (pressure of disperse phase slightly exceeded the critical pressure Δ p TM=4.5 bar of 0.2 μm-MPG) led to the smallest droplet diameter. As a consequence of average droplet diameters of d 43>3.5 μm creaming was observed without centrifugation in all MPG emulsions after 24 h, but no coalescence of the oil droplets occurred. The study of protein adsorption showed that the MPG emulsification at low shear forces resulted in lower protein load values (2.5±0.5 mg m −2) than pressure emulsification (11.5±1.0 mg m −2). In addition, the various emulsification conditions (MPG or pressure homogenization) led to differences in the relative proportions of casein fractions, whey proteins and milk fat globule membranes (MFGM) at the fat globule surfaces.

Personal ammonia sensor for industrial environments

The realisation of an opto-chemical ammonia sensor suitable for personal monitoring tasks is described, comprising a cyanine dye immobilised in a microporous glass thin film. The fabrication of sensor platforms incorporating embossed grating couplers provides a compact optical design with effective waveguiding characteristics, resulting in reversible ammonia sensitivity in the 5-100 ppm range in under 2 min. Cross-sensitivity of sensor response with water and other potential interferents is considered.

The preparation of a sol–gel glass oxygen sensor incorporating a covalently bound fluorescent dye

The synthesis of a novel ruthenium(II) polypyridyl complex incorporating silane pendant moieties is described. This fluorescent material was covalently bound to an organically modified silica glass precursor to give thin films suitable for optical oxygen sensing. These films showed good oxygen sensitivity characteristics, and possess the distinct advantage over physically entrapped dyes of being chemically attached to the support membrane. This approach to the preparation of luminescent micro-porous glass films provides sensitive membranes suitable for applications where zero dye leaching is a requirement.

Structural features of solid gallium in microporous glass

An experimental Debye-Scherrer study of structural features of gallium in porous glass with pore diameter d=4 nm is reported. Gallium structures different from the known bulk modifications have been discovered.

Translational diffusion of liquids at surface of microporous materials: new theoretical analysis of field cycling magnetic relaxation measurements

1H spin-lattice relaxation rates of several aprotic polar liquids on calibrated microporous chromatographic glass beads that have paramagnetic ion impurities are recorded over magnetic field strengths using a field-switched magnetic relaxation dispersion spectrometer. The typical bilogarithmic magnetic field dependence of these rates supports quantitatively our theory of nuclear paramagnetic relaxation and gives the translational diffusion at the surface of nanopores. Our results demonstrate that magnetic relaxation dispersion at low magnetic field strengths in high surface area heterogeneous systems may be quantitatively understood in terms of the parameters of the spatial confinement and the local translational dynamics.

Preparation of monodisperse poly(acrylamide-co-acrylic acid) hydrogel microspheres by a membrane emulsification technique and their size-dependent surface properties

Monodisperse poly(acrylamide-co-acrylic acid) hydrogel microspheres with different polymer compositions (0–10 mol% acrylic acid and 90–100 mol% acrylamide) and with different sizes have been prepared from w/o emulsion using microporous glass membranes with average pore sizes of 0.33, 0.73, 1.15, and 1.70 μm. The broader size distribution was observed in the microspheres composed of hydrogel containing more acrylic acid. The size distribution was not affected by the membrane pore size. The microsphere size on the other hand was dependent on both the membrane pore size and the polymer composition. As the membrane with a larger pore size was used, larger microspheres were obtained. When the membrane with a pore size of 1.70 μm was used, the microsphere size clearly increased as the acrylic acid concentration in the monomer mixture increased, while it decreased as the acrylic acid concentration increased when the membranes with smaller pore sizes were used. The surface properties of the microspheres have been studied from their electrophoretic mobility values. The electrophoretic mobility values of poly(acrylamide-co-acrylic acid) microspheres were negative at pH 7.4 with ionic strengths between 0.005 and 0.154 at 25°C, although those of poly(acrylamide) microspheres were almost zero. The electrophoretic mobility of the microspheres became more negative as the acrylic acid concentration increased, with two exceptions. Only two types of poly(acrylamide-co-acrylic acid) microspheres prepared with the membrane of the largest pore size (1.70 μm) showed the same electrophoretic mobility values at all ionic strengths, although they were composed of hydrogels of different acrylic acid concentrations (5 and 10 mol%). The electrophoretic mobility values of the microspheres were also size dependent. More negative mobility values were obtained with smaller microspheres than larger ones. By analyzing the data with an electrokinetic theory for “soft” surfaces, it was found that the microsphere surface becomes softer by the addition of acrylic acid. It was also suggested that the microspheres with smaller sizes have higher surface charge density than those with larger sizes, although the microspheres were prepared from solutions with the same monomer composition. From this, it is found that copolymerization of acrylamide monomers and acrylic acid monomers does not proceed homogeneously within a single microsphere. The density of polymer networks composed of both monomers is higher in the core region than in the surface layer of the microspheres. The accumulation of polymers in the core region of a microsphere explains the decrease in microsphere size with the increase in acrylic acid concentration observed in smaller microspheres. When microspheres are relatively large, enough volume is available for 10 mol% acrylic acid inside a microsphere and the polymer networks are looser than in smaller microspheres, which causes the increase in microsphere size depending on the acrylic acid concentration. This volume increase explains the same electrophoretic mobility values observed in two types of large microspheres containing different concentrations of acrylic acid (5 and 10 mol%).

Field cycling magnetic relaxation study of translational diffusion at surfaces of nanopores

1 H spin-lattice relaxation rates of several aprotic polar liquids on microporous chromatographic glass beads that have paramagnetic ion impurities are recorded over magnetic field strengths using a field-switched magnetic relaxation dispersion spectrometer. The data support quantitatively our theory of nuclear paramagnetic relaxation and give the translational diffusion at the surface of nanopores.

膜乳化法による高水分Ｗ／Ｏ食品エマルションの調製及びその安定性評価

High-water-content (40% (w/w)) W/O emulsions from substances containing fats and oils were prepared at a high emulsification rate by use of a microporous glass membrane, and the stability of emulsions prepared by the membrane emulsification method was assessed. As the indices of stability, variations in dispersed droplet diameter, viscosity, and oil separation rate over time were used. Even under the experimental conditions employed, by changing the pore diameter of the membrane, it was possible to control dispersed droplet diameter for the most part. From the standpoint of stability, when compared to the stirring emulsification method, variations in dispersed droplet diameter and viscosity of W/O emulsions were confirmed to be more stable, which is an advantage of using the membrane emulsification method. As an additional advantage, the stability of W/O emulsions prepared by the membrane emulsification method was not related to the dispersed droplet diameter size. In addition, with regard to the emulsification rate in this experiment,the dispersion phase flow rate through the membrane pores resulted in relatively little O/W interfacial tension, and a theory of flow through the membrane was understood. These results indicate that using the membrane emulsification method, it is possible to prepare at a practical level (high emulsification rate), a more stable, high-water-content W/O emulsion than is possible by means of the existing (stirring emulsification) method.

Anomalous Surface Diffusion of Water in Nanopores

AbstractProton nuclear magnetic relaxation dispersion experiments show remarkable differences between water and aprotic liquids in contact with microporous glass surfaces containing trace paramagnetic impurities. Proton surface diffusion permits long range effectively 1-dimensional exploration along the pores for water. This gives a direct measurement of the translational diffusion coefficient at the pore surface.

Effects of preparation conditions on the monodispersity of albumin microspheres

Monodisperse albumin microspheres were successfully prepared by both chemical or thermal hardening methods via membrane emulsification using microporous glass membranes with uniform pore sizes. The monodispersity of the microspheres was found to depend strongly on parameters such as albumin concentration, emulsifier concentration, and volume ratio of the internal aqueous phase (albumin solution) to the dispersion medium (organic solvent). The optimum conditions for obtaining monodisperse albumin microspheres are described.

Laboratory-scale bioremediation of oil-contaminated soil of Kuwait with soil amendment materials

A huge amount of oil-contaminated soil remains unremediated in the Kuwait desert. The contaminated oil has the potentiality to cause pollution of underground water and to effect the health of people in the neighborhood. In this study, laboratory scale bioremediation experiments were carried out.Hyponex (Hyponex, Inc.) and bark manure were added as basic nutrients for microorganisms, and twelve kinds of materials (baked diatomite, microporous glass, coconut charcoal, an oil-decomposing bacterial mixture (Formula X from Oppenheimer, Inc.), and eight kinds of surfactants) were applied to accelerate the biodegradation of oil hydrocarbons.15% to 33% of the contaminated oil was decomposed during 43 weeks' incubation. Among the materials tested, coconut charcoal enhanced the biodegradation. On the contrary, the addition of an oildecomposing bacterial mixture impeded the biodegradation. The effects of the other materials were very slight.The toxicity of the biodegraded compounds was estimated by the Ames test and the tea pollen tube growth test. Both of the hydrophobic (dichloromethane extracts) and hydrophilic (methanol extracts) fractions showed a very slight toxicity in the Ames test. In the tea pollen tube growth test, the hydrophobic fraction was not toxic and enhanced the growth of pollen tubes.