Showing papers on "Glass microsphere published in 2002"

Adhesion Forces between Glass and Silicon Surfaces in Air Studied by AFM: Effects of Relative Humidity, Particle Size, Roughness, and Surface Treatment

Abstract: Using the atomic force microscope (AFM), the pull-off forces between flat glass or silicon surfaces and silicon AFM tips or glass microspheres of different sizes have been extensively studied as a function of relative humidity (RH) in the range 5−90%, as model systems for the behavior of cohesive powders. The glass and silicon substrates were treated to render them either hydrophobic or hydrophilic. All the hydrophilic surfaces gave simple force curves and pull-off forces increasing uniformly with RH. Small contacts (R ∼ 20 nm) gave pull-off forces close to values predicted by simple Laplace−Kelvin theory (∼20 nN), but the values with microspheres (R ∼ 20 μm) fell well below predictions for sphere−flat or sphere−sphere geometry, due to roughness and asperity contacts. The hydrophobic silicon surfaces also exhibited simple behavior, with no significant RH dependence. The pull-off force again fell well below predicted values (Johnson−Kendall−Roberts contact mechanics theory) for the larger contacts. Hydroph...

Development and characterization of Ni-NTA-bearing microspheres.

Abstract: Background For ease of purification, proteins are often expressed with a short affinity sequence of five or six adjacent histidine residues (His-tag). This His-tag binds to the metal of metal chelator complexes such as Ni2+-nitrilotriacetic acid (Ni-NTA) or -iminodiacetic acid (Ni-IDA). Chromatography resins bearing covalently attached metal chelator complexes are used widely for the easy affinity purification of His-tagged proteins or peptides. Because Ni-NTA microspheres were not commercially available at the beginning of our studies, we prepared and characterized such microspheres to immobilize His-tagged proteins and study their interactions. Our microspheres are of three types: (a) metal chelator complexes bound covalently to polystyrene microspheres, (b) metal chelator complexes bound covalently to silica microspheres, and (c) lipid-linked metal chelator complexes adsorbed to silica microspheres forming self-assembled bilayer membranes where the metal chelators have lateral mobility. Methods The microspheres bearing covalently attached Ni-chelator were synthesized by reacting a primary amine-bearing Ni-NTA ligand with carboxy-functionalized microspheres and then loading with Ni2+. Microspheres with laterally mobile metal chelator were made by incubating glass microspheres with liposomes containing phosphatidylcholine (PC) and the metal chelating lipid 1,2-dioleoyl-sn-glycero-3-[(N (5-amino-1-carboxypentyl)iminodiacetic acid)succinyl]. Binding of a His-tagged enhanced green fluorescent protein (EGFP) was used to characterize these microspheres by flow cytometry for their specificity, sensitivity, capacity and stability. Results While all micospheres specifically bind His-tagged proteins, the conditions to achieve this are different for the polystyrene- and silica-based spheres. All three types of microspheres bind His-EGFP with saturation occurring at 30–50 nM and an apparent avidity (concentration of half-maximal binding) of approximately 1 to 2 × 10−8 M at pH 7.4. Binding of His-EGFP is inhibited by imidazole or ethylene-diaminetetraacetic acid (EDTA). Polystyrene Ni-NTA microspheres showed significant nonspecific binding as measured by binding in the presence of imidazole or EDTA or by binding of fluorescent proteins lacking a His-tag. This nonspecific binding of proteins to and aggregation of polystyrene spheres could only be prevented by the inclusion of low concentrations of Tween 20, but not by including bovine serum albumin (BSA), polyethylene glycols, or polyvinylpyrrolidones as blocking agents. In contrast, silica-based microspheres with covalently attached Ni-NTA or silica microspheres bearing adsorbed bilayers that contain Ni-NTA-lipid showed little nonspecific binding in the presence of BSA. Our results on the stability of immobilization indicate that washing destabilizes the binding of His-tagged proteins to Ni-NTA microspheres. This binding consists of two interactions of different affinities. We also demonstrate that limited multiplexed analysis with differently sized silica microspheres bearing the Ni-NTA-lipid is feasible. Conclusions The microspheres described are well suited to selectively immobilize His-tagged proteins to analyze their interactions by flow cytometry. The affinity and kinetic stability of the interaction of His-tagged proteins with Ni-NTA are insufficient to use Ni-NTA microspheres in multiplexed analysis formats where different His-tagged proteins are bound to distinct microspheres. Improvements towards this end (improved chelators and/or improved affinity tags) are critical for extending the use of this method. We are currently working on novel chelators to strengthen the stability of immobilization of His-tagged proteins to surfaces. Such improvements would greatly enhance the analysis of interactions of immobilized His-tagged proteins and could make the development of microsphere-based arrays with His-tagged protein/antibody possible. Cytometry 48:136–145, 2002. © 2002 Wiley-Liss, Inc.

Expandable polymeric microspheres, their method of production, and uses and products thereof

Abstract: The present invention is directed to thermo-expandable microspheres and to the expanded microballoons, microcellular foam or foamed composite material that results upon heating the microspheres. The thermo-expandable microsphere of the present invention is characterized by having a polymeric wall surrounding one or more pockets or particles of blowing agent or propellant within the microsphere. The polymeric wall may have reactive functional groups on its surface to give a fusible microsphere. When the microspheres are heated, they expand to form microballoons comprising polymeric shells surrounding one or more internal gaseous voids, and when the microspheres are expanded while in contact with each other, a microcellular foam may be formed. The foam consists of a plurality of microballoons fused together, optionally aided by functional groups present on the surface of the heated microspheres that act to crosslink the material. When microspheres are mixed with a matrix, which can optionally react with functional groups on the microsphere surface, and the resulting combination is heated, the microspheres expand to give a foamed composite material in which the microballoons may be fused or chemically crosslinked to the matrix.

In vitro and in vivo dissolution behavior of a dysprosium lithium borate glass designed for the radiation synovectomy treatment of rheumatoid arthritis.

Abstract: Dysprosium lithium borate (DyLB) glass microspheres were investigated for use in the radiation synovectomy treatment of rheumatoid arthritis. In vitro testing focused on weight loss and cation dissolution from glass microspheres immersed in simulated synovial fluid (SSF) at 37°C for up to 64 days. In vivo testing was performed by injecting glass microspheres into the stifle joints of Sprague-Dawley rats and monitoring the biodegradability of the microspheres and the tissue response within the joints. The DyLB microspheres reacted nonuniformly in SSF with the majority of lithium and boron being dissolved, whereas nearly all of the dysprosium (>99.7%) remained in the reacted microspheres. Because the DyLB glasses released negligible amounts of dysprosium while reacting with SSF, they are considered safe for radiation synovectomy from the standpoint of unwanted radiation release from the joint capsule. Furthermore, the DyLB microspheres fragmented, degraded, and reacted with body fluids while in the joints of rats without histologic evidence of joint damage. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 60: 260–268, 2002; DOI 10.1002/jbm.10047

Fire resistant fabric material

Abstract: A fire resistant fabric material comprising a substrate having an ionic charge which is coated with a coating having essentially the same ionic charge. The coating consists essentially of a filler material comprising clay and a binder material. The substrate is preferably fiberglass, the filler material may further comprise at least one additional filler selected from the group consisting of decabromodiphenyloxide, antimony trioxide, fly ash, charged calcium carbonate, mica, glass microspheres and ceramic microspheres and mixtures thereof and the binder material is preferably acrylic latex.

Method for synthesizing thermo-expandable polymeric microspheres

Abstract: The present invention is directed to thermo-expandable microspheres and to the expanded microballoons, microcellular foam or foamed composite material that results upon heating the microspheres. The thermo-expandable microsphere of the present invention is characterized by having a polymeric wall surrounding one or more pockets or particles of blowing agent or propellant within the microsphere. The polymeric wall may have reactive functional groups on its surface to give a fusible microsphere. When the microspheres are heated, they expand to form microballoons comprising polymeric shells surrounding one or more internal gaseous voids, and when the microspheres are expanded while in contact with each other, a microcellular foam may be formed. The foam consists of a plurality of microballoons fused together, optionally aided by functional groups present on the surface of the heated microspheres that act to crosslink the material. When microspheres are mixed with a matrix, which can optionally react with functional groups on the microsphere surface, and the resulting combination is heated, the microspheres expand to give a foamed composite material in which the microballoons may be fused or chemically crosslinked to the matrix.

Microcellular foams, their method of production, and uses and products thereof

Abstract: The present invention is directed to thermo-expandable microspheres and to the expanded microballoons, microcellular foam or foamed composite material that results upon heating the microspheres. The thermo-expandable microsphere of the present invention is characterized by having a polymeric wall surrounding one or more pockets or particles of blowing agent or propellant within the microsphere. The polymeric wall may have reactive functional groups on its surface to give a fusible microsphere. When the microspheres are heated, they expand to form microballoons comprising polymeric shells surrounding one or more internal gaseous voids, and when the microspheres are expanded while in contact with each other, a microcellular foam may be formed. The foam consists of a plurality of microballoons fused together, optionally aided by functional groups present on the surface of the heated microspheres that act to crosslink the material. When microspheres are mixed with a matrix, which can optionally react with functional groups on the microsphere surface, and the resulting combination is heated, the microspheres expand to give a foamed composite material in which the microballoons may be fused or chemically crosslinked to the matrix.

High purity glass bodies formed by zero shrinkage casting

Abstract: The present invention relates to a method for forming an optical device. The method includes providing a glass aggregate. Typically, the glass aggregate is a mixture of fine glass soot particles and coarser ground or milled glass powder. The glass particles are mixed with a liquid to form a slurry which is cast in a mold to form a porous pre-form. Subsequently, the porous pre-form is consolidated into a glass object by heating the pre-form at a relatively high temperature. The method of the present invention produces optical components having substantially no striae. As a result, scattering is substantially reduced when EUV light is reflected from a component produced from the optical blank.

Electrochemical effects of surface-modified glass microspheres in polyvinylpyridine and polystyrene sulfonate composite electrodes

Abstract: Tailoring the interfacial region of composite modified electrodes has been a topic of discussion for over a decade. This research examines the electrochemical effects of the formation of unique interfacial regions in surface-modified glass microsphere/polyvinylpyridine composite modified electrodes and surface-modified glass microsphere/polystyrene sulfonate composite modified electrodes. The surfaces of the glass microspheres are modified with different organic functional groups by binding organosilanes to the surfaces of the glass microspheres through a siloxane linkage. This research showed that surface-modified glass microspheres can alter the electrochemical flux through both surface-modified glass microsphere/ polyvinylpyridine composites and surface-modified glass microsphere/polystyrene sulfonate composites of hydroquinone, Ru(bpy) 3 2+), and ferricyanide. It was also shown that the polymer itself plays a crucial role in the formation and the properties of the interfacial region. The interfacial region was imaged using fluorescence microscopy, and the microscopy showed that a highly concentrating interfacial region is formed for all of the surface-modified glass microsphere/polymer composites studied regardless of whether there is an electrochemical effect. Further studies with smaller particles are necessary to obtain a large enough interfacial region to be useful for sensor development.

Hollow glass microsphere production for laser direct-driven fusion targets on Shen Guang II

Abstract: A liquid-droplet technique was investigated to fabricate thin wall hollow glass microspheres (HGM) used in laser fusion experiments on Shen Guang II. Glass-forming compositions, operating conditions of the droplet generator and the vertical multiple-zone furnace were optimized. Thin wall HGM with diameters of about 100, 200, and 520 pm were fabricated, whose failure pressures, gas retention properties for D2, and chemical durability were all characterized. The results of the fusion experiments show that the HGM targets are quite satisfactory and the highest neutron yields obtained are 4 × 109.

Microscopic studies of syntactic foams tested under three-point bending conditions

Abstract: Use of syntactic foam as core material in the sandwich structured composites is increasing due to its higher compressive strength, damage tolerance and low moisture absorption compared to the open cell structured foams. Extensive microscopic examination of the syntactic foams tested under compressive and three-point bending conditions is undertaken in this study. The aim of the investigation is to determine the local fracture mode and correlate it with the microscopic structure of the material. Local stress states are identified in the material based on the microscopic fracture features. Syntactic foam tested in the study has resin to microballoons ratio of 1.52 by weight. Compression tests were conducted on the syntactic foam specimens having two different aspect rations, which were 0.4 and 0.91. Three-point bend tests were conducted on the sandwich structures containing syntactic foam as core material and glass fabric as the skin material.Copyright © 2002 by ASME

Behavior of silica particles of different microstructure on RF thermal plasma treatment

Abstract: Hollow ceramic microspheres are facing continuously growing applications as was described by Cochran [1]. Thus, it is not surprising at all that research on them has been extended more recently. Various processing techniques for making ceramic hollow spheres of 5–200 micron diameter have been developed. One promising method is based on sol-gel processing [2–5]. Particular method involves the dispersion of an aqueous colloidal sol of metal oxide in a dehydrating liquid which extracts water from the interior of sol droplets. A second method comprises the coating of a pre-processed polymer or glass microsphere with ceramic gel followed by firing [6]. In other methods, atomized liquid droplets or spray dried powders passing through a furnace or a thermal plasma flame give rise to hollow microspheres [7–9]. Thermal plasma ensures adequately high temperature for melting the ceramic particles. Water vapor or other gases liberated due to the decomposition of binder or blowing agent, which is usually blended to the agglomerates, are supposed to form internal cavity. By controlling the operating conditions, hollow particles can be formed even during the spray drying process [10, 11]. The present report describes the preparation of hollow silica microspheres by inductively coupled RF thermal plasma. The research was initiated and supported by PREMIS Technologies, France. The effect of process gases and the type of the starting materials on the microstructure of the formed particles was studied in the experiments. The experimental apparatus consisted of a TEKNAtype induction plasma torch (PL-035LS) with a quartz confinement tube of 25 mm and a water cooled steel chamber connected to a cyclon. The plasma plate power of 21 kW was provided by a three turn, water cooled induction coil from an RF generator operating at an oscillator frequency of 3 MHz. High purity argon was used both as plasma and sheath gas with flow rates of 20 and 60 l min−1, respectively. Hydrogen was mixed into the sheath gas with a proportion of 10 V/V% to improve the enthalpy and the heat transfer coefficient of argon. In some experiments, air was substituted for argon. The powders were fed with a PRAXAIR powder feeder unit through an injection probe to the top of the plasma flame by argon carrier gas (3 l min−1) with a constant feed rate of 10 g min−1. The outlet of the quartz injection tube has an inner diameter of 2 mm. It was located 10 mm below the top of the induction coil. Three different raw materials were investigated in the experiments. Powder Type 1 of negligible porosity (from Degussa) is made by precipitation of pure silica. Powder Type 2 is an agglomerated sample, in which the diameter of primary silica particles (from SIFRACO) is ∼5 μm. Besides silica, NaNO3 and Na-silicates were also blended into Powder Type 2 for different purposes. Na-silicates were used as binding agent of primary particles, while the blowing agent, NaNO3 was devoted to release different gases (O2, N2) at higher temperatures by decomposition. Powder Type 3 is also an agglomerated silica sample (from SIFRACO). It differs from Powder Type 2 in that it contains only polyvinyl alcohol (PVA) as binder about 1% by weight. Both the raw materials and the produced powders were characterized for density, specific surface area, phase composition (XRD) and microstructure (SEM). Density was determined by means of a helium picnometer (Micromeritics AccuPyc 1300). The specific surface areas were measured with a conventional volumetric instrument by BET method. The microstructural (SEM) investigations were performed on a Jeol JSN50A apparatus. Cross-section images of the particles were made by embedding them in resin media followed by their cutting with diamond blade. During the in-flight process of plasma spraying silica ceramic grains are melted. As a result, one anticipates formation of solid particles of reduced size. It is reasoned by the better space filling of melts as compared to solids. In addition particles can also evaporate to some extent. Spheroidization by plasma flame takes the advantage of this phenomenon [12, 13]. Particles, however, can also become hollow. Formation of hollow particles can be attributed to the release of gases in the interior of particles, if they cannot break through the outer melted layer. The freezing temperature of the

Lens system optically coupled to an image-capture device

Abstract: Simple, inexpensive and durable multi-element lens systems are provided. These lens systems may be optically coupled to digital image-capturing devices, such as those used in digital cameras. Some lens systems of the present invention include a glass microsphere (105) bonded to a planar surface of a glass hemisphere (205). In preferred lens systems, the thickness of the glass hemisphere (205) is selected to form an image plane for transmitted light that is tangent to the surface of the microsphere (105). Accordingly, in digital cameras fabricated with such lens systems, the glass microsphere (105) can be attached directly to a digital image-capturing device (110). These preferred lens systems require no focusing adjustment and are suitable for applications requiring a wide field of view. In some embodiments, the glass microsphere (105) is bonded to the glass hemisphere (205) using a light-absorbing (210) material in order to create an apodized pupil. Some such embodiments are fabricated with a light-absorbing material (210) with an absorption coefficient that varies according to the wavelength of transmitted light.

transparent film with hollow glass microspheres for agriculture.

Abstract: suitable transparent film for use as cover gases comprising one or more homogeneous polymers or two heterogeneous polymers having different molecular structures which are not reactive to each other from a molecular point of view, but that can bind due to their rheological characteristics, characterized in that said polymers, in the amorphous phase, include a quantity of hollow glass microspheres positioned at random in said film, wherein: a. the variable concentration of said hollow glass microspheres ranges from 1% to 99%, b. the density of said hollow glass microspheres ranges from 0, 125-0, 60 g / cm3, with a density range from 0, 10-0, 63 g / cm3 and a bulk density from 0, 05-0, 43 g / cm3, c. said film is a multilayer film comprising a first layer, during the extrusion phase, is combined with at least one second layer, d. said films including dichasmicroesferas hollow glass are produced with a thickness between 10 and 1000 mum.

Syntactic foam articles and related methods

Abstract: A method for making an article of syntactic foam includes spreading a layer of a mixture including particulate resin and microballoons across a surface. At least a portion of the mixture is selectively heated so as to cause the portion to assume a desired shape for at least part of the article. The heating is performed Until the resin flows and wets the microballoons to form a solid mass. The method allows a finished part to be fabricated in a single sintering operation with little or no subsequent machining.

Calculation of glass microsphere compositions

Abstract: An analysis of the compositions and structural criteria of glasses for microspheres is carried out. A system of equations for modeling microsphere compositions is obtained and the applicability bounds of the model are determined. A method for developing glasses for microspheres with low hydrogen permeability and high resistance to atmospheric corrosion is proposed.

Method of manufacturing spherical glass powder

Abstract: PROBLEM TO BE SOLVED: To provide a method which can stably produce fine spherical glass powder, more particularly spherical glass powder below 10 μm in diameter on an industrial scale. SOLUTION: The plasma by a DC (Direct Current) process in place of an RF process is applied in manufacturing of the spherical glass powder by a plasma spheroidization process. More specifically, the method of manufacturing the spherical glass powder comprises introducing the glass raw materials in a gaseous state or atomized state into the plasma formed by the DC process and vitrifying the raw materials, then spheroidizing the formed glass droplets by surface tension and solidifying the solidified glass. COPYRIGHT: (C)2003,JPO

Liquid Droplet Methods Used in Fabrication Techniques of Inertia Confinement Fusion Targets

Abstract: The past,present and future of the liquid droplet methods used in the fabrication of targets for use in inertia confinement fusion experiments are reviewed.The characteristics and shortcomings and remedial solutions thereto for the methods to fabricate hollow glass microspheres,plastic shells,hollow foam spheres,and hollow metal micro-balloons are discussed.

Investigation of fracture of spheroplastics under static and dynamic loading

Abstract: An experimental study of static and dynamic fracture properties of a spheroplastic that has a matrix of polyester resin containing a filler of glass microspheres was conducted Crack propagation was investigated under loading conditions generated by a pulse magnetic field Microstructure features of dynamic fracture were analyzed

Composition and Surface Properties of a Silicon Dioxide Film Deposited by a Plasma-Chemical Technique

Abstract: The molecular composition of plasma-chemical silicon dioxide deposited onto the surface of glass microspheres, which are used in laser fusion experiments on an Iskra-5 facility, was studied by IR spectroscopy. It was found that stoichiometric silica containing organic impurities was deposited on substrates regardless of the glow-discharge working gas composition. The microphotographs of the surface of films deposited in various gas discharge atmospheres were obtained using a JCMA-733 instrument. All films were amorphous, as found by X-ray diffraction analysis.

Signal enhancement in Er3+-doped telluride glass microsphere

Abstract: Microstructure resonators have attracted considerable attention because of their versatility for signal processing applications. We use our Er3+ doped telluride glass to fabricate Er3+ glass microsphere. The excitation of whispering-gallery modes is realized by coupling from an angle-polished single-mode optical fiber tip to an optical microsphere cavity. In the experimental setup, one fiber was used as an input coupler and the other fiber was used as an output coupler. 975nm fiber pigtailed laser diode was used to side pump the microspheres. Very nice whispering-gallery modes (WGM's) near 1.5mm were observed successfully. Signal enhancement was observed in this Er3+ doped telluride glass microsphere with a radius around 50mm. The best enhancement of this Er3+ doped telluride glass microsphere reaches 12dB.

Protection of vertical e.g. traffic signal panels consists of application of e.g. epoxy instant polymerisation two component resin, to increase performance

Abstract: The protection of vertical e.g. traffic signal panels comprises application of epoxy, polyurethane or acrylic branched by peroxide instant-polymerisation two-component resin. The resin makes the panels incorporating metalwork or e.g. glass microspheres resistant to oxidation, humidity and graffiti. EMBODIMENT - The protection can also be retrofitted.

THE PREPARATION OF ZrO_2 MICROBALLOONS AND THE DETERMINATION OF PHYSICAL AND CHEMICAL PARAMETERS.

Abstract: The ZrO 2 microballoons can be synthesized by poly-induction colloidal flocculating method.Through the instruments analysis,it proves that the microballoons possesses the advantages of narrow size distribution,large pore diameter,entire crystal and heat-resistance etc.

Mathematical simulation of the physical process to fabricate hollow glass microspheres by liquid droplet method

Abstract: The physical process to fabricate hollow glass microspheres(HGM) by the Liquid Droplet Method in a 7-meter-high multi-zone high temperature furnace has been modeled mathematically. And the model quantitatively describes the whole process, through which the main parameters of the droplets/membrane spheres/HGM including the velocity, the sizes, the glass-forming oxide mass, the wall-thicknesses, and the inner gas pressures of vapor and air inside can be calculated. Calculation has been done under a series of operation conditions, especially at different purge gas rates, initial concentrations of the blowing agent and those of glass-forming oxides in the glass-forming solutions, and sizes of the initial droplets. The calculated results are to some degree in good agreement with the experiments carried out under the same conditions as the calculation. It is proved that the model can help technicians to select the operation conditions to fabricate HGM in different scales of diameters and wall-thicknesses.

Glass microsphere dose calibration unit for road markings has grooved collection plate

Abstract: A glass microsphere dosing calibration unit is a portable grooved plate (1) with alignment notches (7-11) and graduated collection cavities under a transparent lid (6) with strip width markings (12-16) for direct reading when lifted to the vertical and two retro reflecting strips (4) detected by a photo electric cell (17) temporarily fixed to the dosing machine.

Light scattering plate

Abstract: PROBLEM TO BE SOLVED: To provide a light scattering plate which does not attenuate light of a light source and is excellent in light scattering performance. SOLUTION: The light scattering plate has 5-30 wt.% colorless hollow glass microspheres dispersed uniformly in a platelike body comprising a transparent resin.